A method for green and sustainable preparation of fluorine-free water and oil repellent pulp molding and application thereof

Abstract

The present application relates to a kind of green sustainable preparation fluorine-free water and oil repellent pulp molding method and application, water and oil repellent agent in the present application has excellent water and oil repellent effect, for the surface coating of pulp molding product can meet its water and oil repellent demand, while 95±5 ℃ hot water and hot oil also have very strong water and oil repellent effect and good durability.Performance.The raw materials required by the method are simple and easy to obtain, the preparation method is simple and easy to operate, the cost is low and environmentally friendly, and it is non-toxic to human body, while the water and oil repellent effect is excellent, suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of functional materials, and specifically relates to a green and sustainable method for preparing fluorine-free water- and oil-repellent pulp molding and its application. Background Technology

[0002] With over 30 countries and regions worldwide enacting legislation or policies to restrict the production, sale, and use of plastics, and prohibiting their production, sale, and use in certain sectors, at least 76 countries globally restrict the use of single-use plastic products. Global plastic restriction and bans have become an unstoppable trend. my country first issued the "Notice on Restricting the Production, Sale, and Use of Plastic Shopping Bags" in January 2008, restricting the production, sale, and use of plastic products. The restrictions and bans on single-use plastic products worldwide are only increasing. Under these circumstances, pulp molding, due to its low cost and biodegradability, has become a suitable alternative to plastics.

[0003] Pulp molding is a three-dimensional papermaking technology. It uses waste paper as raw material, shaping it into specific paper products using special molds on a molding machine. It has four major advantages: the raw material is waste paper, including cardboard, waste corrugated paper, and waste white paper, making it widely available; its production process involves pulping, adsorption molding, drying, and setting, which is environmentally friendly; it can be recycled and reused; and it is smaller in volume than foamed plastics, can be stacked, and is convenient for transportation, making it a typical green and environmentally friendly packaging product. However, due to the large number of pores inside pulp molding, it suffers from drawbacks such as easy absorption of water and oil, and high air permeability, significantly limiting the application areas of pulp molded products. Although certain chemical agents such as rosin are added during the pulp molding process, their effect on improving the water and oil repellency and air barrier properties of pulp molding is still very limited. Coating the surface of paper with a continuous, dense plastic film made of polyethylene, polypropylene, polyvinyl alcohol, etc., using a casting machine is an effective method to give molded pulp products good water and oil repellency. However, the plastic layer and the base layer are difficult to separate, and the coated plastic film cannot degrade in nature, so it still cannot completely solve the problem of plastic pollution. Currently, C8-type fluorinated water and oil repellents are mainly used to solve the problem of molded pulp products not being water and oil repellent. Because C8-type fluorinated long-chain water and oil repellents produce perfluorooctanoic acid (PFOA) and perfluorooctane sulfonyl compounds (PFOS) during production and use, these two substances are bioaccumulative and difficult to degrade. Even low doses can cause various serious diseases in organisms. Therefore, the EU, the US, Canada, and other countries have restricted the use of C8-type water and oil repellents. In recent years, companies such as 3M, Daikin, and Asahi Glass have switched from producing C8 water and oil repellents to C6 and even C4 water and oil repellents. However, this only reduces the harm; they are still essentially fluorinated water and oil repellents. Currently, the market for completely fluorine-free water and oil repellent agents is almost entirely lacking, especially at high temperatures where achieving fluorine-free water and oil repellency is even more difficult, significantly limiting industrial applications. Many leading global companies are dedicated to the research and development of completely fluorine-free water and oil repellent products. Mastering the key technologies for fluorine-free water and oil repellency will give them a leading position in the global paper and plastics industry in the future. Coated plastic layers and fluorine-containing water and oil repellent agents are difficult to degrade and pose hazards to the environment and human health. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a green and sustainable method for preparing fluorine-free water- and oil-repellent pulp molding and its application, so as to overcome the defects of poor water and oil repellency of pulp molding in the prior art.

[0005] The present invention discloses a fluorine-free water- and oil-repellent composition, the composition comprising an oil-repellent agent and a water-repellent agent; wherein, by weight percentage, the oil-repellent agent comprises: 3-4% chitosan, 2-3% acetic acid, and 94-95% water; and by weight percentage, the water-repellent agent comprises: 2.5-10% stearic acid and 90-97.5% ethanol.

[0006] The degree of deacetylation of the chitosan is above 95%.

[0007] The present invention provides a fluorine-free water- and oil-repellent material, wherein the material is loaded with the fluorine-free water- and oil-repellent composition of claim 1.

[0008] A method for preparing the fluorine-free water- and oil-repellent material of the present invention includes:

[0009] (1) Mix acetic acid and water to obtain an acetic acid solution, then dissolve chitosan in the acetic acid solution to obtain an oil repellent;

[0010] (2) Stearic acid is dissolved in ethanol to obtain a water-repellent agent;

[0011] (3) Substrate surface coating step (1) Oil repellent agent, dry, to obtain oil repellent material;

[0012] (4) Coat the surface of the oil-repellent material from step (3) with the water-repellent agent from step (2), and dry to obtain a fluorine-free water-repellent and oil-repellent material.

[0013] The preferred embodiment of the above preparation method is as follows:

[0014] The oil-repellent agent in step (1) consists of 3-4% chitosan, 2-3% acetic acid, and 94-95% water by mass percentage.

[0015] In step (1), the mass percentage concentration of acetic acid is ≥99.5%.

[0016] In step (2), the water-repellent agent contains, by mass percentage: stearic acid 2.5-10%, ethanol 90-97.5%.

[0017] In step (2), the mass percentage concentration of stearic acid is ≥98% and the mass percentage concentration of ethanol is ≥95%.

[0018] In step (2), stearic acid dissolves in ethanol at a temperature above 70°C.

[0019] Furthermore, in step (2), the temperature at which stearic acid dissolves in ethanol is 70℃-80℃.

[0020] In step (3), the substrate material is paperboard; the paperboard is molded pulp; the coating is applied by spraying; and the coating amount is 4.5-6.2 g / m³. 2 .

[0021] In step (3), the drying process involves drying at 20-80℃ for 2-3 hours.

[0022] In step (4), the coating is applied by immersion; the coating amount is 6.1-7.9 g / m³. 2 .

[0023] The coating temperature in step (4) is above 75°C; the drying temperature is 20-80°C for 1-2 hours.

[0024] Furthermore, the coating temperature in step (4) is 75℃±5℃.

[0025] The present invention relates to the application of the fluorine-free water- and oil-repellent material in disposable food packaging.

[0026] A single-layer chitosan coating effectively improves the water and oil repellency of pulp molding. While it provides good barrier properties against grease, it doesn't maintain 100% stable hot water repellency, even when it repels cold water, and its performance is affected by thickness. This invention utilizes a chitosan-stearic acid bilayer coating to enhance the water and oil barrier properties of the original food container. A chitosan solution is applied to the original container to fill / cover the pores between the cellulose fibers and utilize its oil-repellent properties to improve the oil repellency of the pulp molding. A stearic acid solution is applied as the second layer, forming a protective film on the outermost layer to improve the hot water repellency and stability of the coated container. Both chitosan and stearic acid are biodegradable, biocompatible, and inexpensive, making them excellent alternatives to fluorinated water and oil repellents in food packaging.

[0027] Beneficial effects

[0028] (1) The method for preparing the fluorine-free water- and oil-repellent coating provided by the present invention uses a double-layer coating method to coat the oil-repellent agent and the water-repellent agent onto the material respectively, thereby preparing a material with tighter internal bonding and better water- and oil-repellent effect.

[0029] (2) The present invention fills and coats the prepared chitosan solution and stearic acid solution into the interior and surface of pulp molded products by spraying and high temperature immersion, which can better promote the combination of water and oil repellent agents and the paper-plastic products themselves, allowing the oil and water repellent agents to fill the pores on the surface and interior of the paper-plastic products and form a dense film on the fiber surface, preventing the penetration of oil and water, thereby simultaneously enhancing the water and oil repellency of pulp molded products.

[0030] (3) This invention can meet the water and oil repellency requirements of pulp molded products in daily production and life. After being treated with the water and oil repellent agent of this invention, the water repellency of pulp molded products is greatly improved, and the oil repellency is also greatly improved. The oil resistance level of untreated pulp molded products is less than level 1, while the highest oil resistance level after treatment can reach level 12, which has a very superior oil repellency effect. Untreated pulp molded products have no waterproof ability at all, with a contact angle of 0°. The treated products can be waterproof, with a water contact angle of up to 116.4°.

[0031] (4) The present invention can improve the hot water and oil resistance and stability of pulp molded products. After the pulp molded products are treated with the water and oil repellent agent of the present invention, their hot water and oil resistance is greatly improved. After being soaked in hot water and oil for 30 minutes, they still remain without leakage, and after repeated tests on multiple samples, none of them failed.

[0032] (5) The raw materials of the fluorine-free water and oil repellent agent prepared by the present invention are simple, readily available, green, pollution-free, and biodegradable, meeting the requirements of the food industry. It will not cause harm to the human body and the environment, ensuring the health of consumers and the sustainable development of the environment. Attached Figure Description

[0033] Figure 1 SEM images of the original pulp molded lunch box and the fluorine-free water- and oil-repellent lunch box prepared in Example 1; wherein (a) the surface of the original lunch box, (b) the cross-section of the original lunch box, (c) the surface of Example 1, and (d) the cross-section of Example 1;

[0034] Figure 2 Infrared spectrum comparison of the original lunch box and the fluorine-free water-repellent and oil-repellent lunch box prepared in Example 1;

[0035] Figure 3 The 30s water contact angle (a) and 300s water contact angle (b) of the fluorine-free water-repellent and oil-repellent lunchbox prepared in Example 1;

[0036] Figure 4 The image shows a comparison of the fluorine-free water- and oil-repellent lunchbox prepared in Example 1 after being dripped with hot water for 30 seconds (a), hot water for 30 minutes (b), hot oil for 30 seconds (c), and hot oil for 30 minutes (d). Detailed Implementation

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] Acetic acid: mass percentage concentration ≥99.5%, purchased from Sinopharm Group, CAS: 64-19-7;

[0039] Pulp molding products: Pulp molding disposable food containers, sourced from Greensoc New Materials (Yunnan) Co., Ltd.;

[0040] Chitosan: The viscosity of chitosan is 100-200 mPa·s, the degree of deacetylation is >95%, purchased from Aladdin, CAS: 9012-76-4;

[0041] Ethanol: mass percentage concentration >95%, purchased from Sinopharm Group, CAS: 64-17-5;

[0042] Stearic acid: >98% by mass, purchased from Maclean's, CAS: 57-11-4

[0043] Example 1

[0044] Weigh 2g of acetic acid and pour it into 94ml of deionized water. Stir until fully dissolved to obtain an acetic acid solution. Weigh 4g of chitosan and add it to the acetic acid solution. Stir for 5 hours to obtain an oil repellent. Spray the oil repellent onto the pulp molded product with a coating amount of 5g / m². 2 Place in an 80℃ oven and dry for 3 hours.

[0045] Weigh 10g of stearic acid and pour it into 90g of ethanol while heating at 70℃. Stir until fully dissolved to prepare a water-repellent agent. Immerse the sample in the stearic acid solution at 75℃ for 30 minutes. The coating amount is 7g / m². 2 Place in an 80℃ oven and dry for 2 hours.

[0046] Example 2

[0047] Weigh 2g of acetic acid and pour it into 94ml of deionized water. Stir until fully dissolved to obtain an acetic acid solution. Weigh 4g of chitosan and add it to the acetic acid solution. Stir for 5 hours to obtain an oil repellent. Spray the oil repellent onto the pulp molded product with a coating amount of 5g / m². 2 Place in an 80℃ oven and dry for 3 hours.

[0048] Weigh 5g of stearic acid and pour it into 95g of ethanol while heating at 70℃. Stir until fully dissolved to prepare a water-repellent agent. Immerse the sample in the stearic acid solution at 75℃ for 30 minutes. The coating amount is 7g / m². 2 Place in an 80℃ oven and dry for 2 hours.

[0049] Example 3

[0050] Weigh 2g of acetic acid and pour it into 94ml of deionized water. Stir until fully dissolved to obtain an acetic acid solution. Weigh 4g of chitosan and add it to the acetic acid solution. Stir for 5 hours to obtain an oil repellent. Spray the oil repellent onto the pulp molded product with a coating amount of 5g / m². 2 Place in an 80℃ oven and dry for 3 hours.

[0051] Weigh 2.5g of stearic acid and pour it into 97.5g of ethanol while heating at 70℃. Stir until fully dissolved to prepare a water-repellent agent. Immerse the sample in the stearic acid solution at 75℃ for 30 minutes. The coating amount is 7g / m². 2 Place in an 80℃ oven and dry for 2 hours.

[0052] Example 4

[0053] Weigh 2g of acetic acid and pour it into 95ml of deionized water. Stir until fully dissolved to obtain an acetic acid solution. Weigh 3g of chitosan and add it to the acetic acid solution. Stir for 5 hours to obtain an oil repellent. Spray the oil repellent onto the pulp molded product with a coating amount of 5g / m². 2 Place in an 80℃ oven and dry for 3 hours.

[0054] Weigh 10g of stearic acid and pour it into 90g of ethanol while heating at 70℃. Stir until fully dissolved to prepare a water-repellent agent. Immerse the sample in the stearic acid solution at 75℃ for 30 minutes. The coating amount is 7g / m². 2 Place in an 80℃ oven and dry for 2 hours.

[0055] Example 5

[0056] Weigh 2g of acetic acid and pour it into 95ml of deionized water. Stir until fully dissolved to obtain an acetic acid solution. Weigh 3g of chitosan and add it to the acetic acid solution. Stir for 5 hours to obtain an oil repellent. Spray the oil repellent onto the pulp molded product with a coating amount of 5g / m². 2 Place in an 80℃ oven and dry for 3 hours.

[0057] Weigh 5g of stearic acid and pour it into 95g of ethanol while heating at 70℃. Stir until fully dissolved to prepare a water-repellent agent. Immerse the sample in the stearic acid solution at 75℃ for 30 minutes. The coating amount is 7g / m². 2 Place in an 80℃ oven and dry for 2 hours.

[0058] Example 6

[0059] Weigh 2g of acetic acid and pour it into 95ml of deionized water. Stir until fully dissolved to obtain an acetic acid solution. Weigh 3g of chitosan and add it to the acetic acid solution. Stir for 5 hours to obtain an oil repellent. Spray the oil repellent onto the pulp molded product with a coating amount of 5g / m². 2 Place in an 80℃ oven and dry for 3 hours.

[0060] Weigh 2.5g of stearic acid and pour it into 97.5g of ethanol while heating at 70℃. Stir until fully dissolved to prepare a water-repellent agent. Immerse the sample in the stearic acid solution at 75℃ for 30 minutes. The coating amount is 7g / m². 2 Place in an 80℃ oven and dry for 2 hours.

[0061] Performance testing:

[0062] 1. Oil Repellency Test: The oil repellency rating was determined using the TAPPI T559 pm-96 standard. Specifically, castor oil, toluene, and n-heptane were mixed in different proportions to prepare 12 solutions of different grades (Table 1), numbered 1-12, representing oil repellency from poorest to best. In each test, a solution of grade one was added to the sample for 15 seconds, then wiped off. If no oil stain remained on the paper surface after 15 seconds, the oil repellency test for that grade of solution was considered passed. Then, solutions with higher oil repellency grades were tested until the surface test failed. The average of three sets of experimental data was taken for each sample. If a grade 1 test was failed, the oil repellency rating was 0. The higher the oil repellency rating, the stronger the oil repellency of the sample and the better its practicality.

[0063] Table 1. Determination of grease resistance of coated paper samples according to TAPPI T559 pm-96 standard.

[0064]

[0065]

[0066] 2. Heat-resistant oil test: The heat-resistant oil test mainly adopts the GB / T 36787—2018 test standard. Specifically, the paper lunch box is placed on a dry glass plate, and edible oil and water at 95℃±5℃ are poured in to a depth of 6mm from the opening of the paper lunch box. After covering and standing for 30 minutes, observe whether the sample is deformed, cracked, peeled, or wrinkled, and observe whether there is any oil or water seepage or leakage from the bottom and sides of the sample.

[0067] 3. Hot Water Resistance Test: The hot water resistance test mainly adopts the GB / T 36787—2018 test standard. Specifically, the sample is placed on a dry glass plate or flat plate lined with filter paper, filled with water at 95℃±5℃, and allowed to stand for 30 minutes. The sample is then observed for deformation, seepage, or leakage at the bottom. Three samples are tested for each sample. If no seepage, leakage, or deformation is observed in any of the three samples, the sample is considered to have no seepage, leakage, or deformation. (Note: Water vapor condensation at the bottom due to the temperature difference between the inside and outside of the sample during the test is not considered seepage or leakage.)

[0068] Where √ indicates no leakage; ○ indicates only slight leakage; △ indicates leakage, but no seepage; X indicates most leakage. The performance of the prepared fluorine-free water and oil repellent was tested, and the test results are listed in Table 2.

[0069] Table 2 Performance Test Table of Fluorine-Free Water and Oil Repellent Agents

[0070] Example Oil resistance rating Heat-resistant oil properties 30s water contact angle Hot water resistance Original lunch box 0 X 0 X Example 1 12 √ 116.4° √ Example 2 12 √ 108.7° √ Example 3 11 √ 103.5° ○ Example 4 5 △ 100.3° ○ Example 5 4 X 96.9° ○ Example 6 4 X 93.4° △

[0071] 4. Hot water and heat-resistant oil resistance test stability: Five parallel samples were used for hot water and heat-resistant oil resistance tests for each example. Where: √: All samples passed the test, 0% defect rate; ○: Some samples passed the test, some leaked, resulting in a defect rate; X: All samples failed the test, all defective.

[0072] Table 3. Stability of Fluorine-Free Water and Oil Repellents in Hot Water and Oil

[0073]

[0074]

[0075] Product characteristics:

[0076] Specifically, such as Figure 1 , 2 As shown in Figures 3 and 4.

[0077] The original lunchbox and the fluorine-free water- and oil-repellent sample prepared in Example 1 were scanned using a scanning electron microscope (SEM) for surface and cross-section analysis. The comparison results are as follows: Figure 1 As shown, the original lunchbox had relatively large fiber pores and a loose cross-section. After spraying with the fluorine-free water and oil repellent agent, the fiber pores were filled, the surface became smooth and flat, and the cross-section became more compact, indicating that the oil and water repellent agents successfully filled the fiber interior and surface. The cross-section of the coated lunchbox changed from loose and dispersed to very compact, indicating that the filling of the lunchbox pores by the oil and water repellent agents was not limited to the surface layer, but acted on the entire lunchbox.

[0078] The original lunchbox and the fluorine-free water- and oil-repellent sample prepared in Example 1 were tested using a Fourier transform infrared spectrometer equipped with an attenuated total reflectance accessory (ATR). The comparison results are as follows: Figure 2 As shown. At 3300cm -1 There is a broad peak at 3300 cm⁻¹, representing the -OH vibrations in cellulose and chitosan, and the -NH vibrations in chitosan. This is compared to the original food container at 3300 cm⁻¹. -1 The peak area at 1702 cm⁻¹ decreased somewhat after coating, indicating that some hydroxyl groups on the surface of the coated food container were masked and formed hydrogen bonds with the cellulose fibers inside the container, thus consuming the hydroxyl groups and significantly improving water repellency. -1 The sharp absorption peak at 1540 cm⁻¹ represents the presence of the -COOH group in stearic acid, while the peak at 1540 cm⁻¹ represents the presence of the -COOH group in stearic acid. -1 The absorption peak at that point is attributed to the stretching amide vibrations of chitosan C=O and NH.

[0079] The 30s water contact angle (a) and 300s water contact angle (b) of the original lunchbox and the fluorine-free water-repellent and oil-repellent sample prepared in Example 1 were measured using a contact angle meter. The results are as follows: Figure 3 As shown in the figure. Since the original lunch box was immediately penetrated by water and oil within 30 seconds with a contact angle of 0°, no figure is attached. However, the water repellency of the lunch box coated with chitosan / stearic acid was greatly improved, with the contact angle increasing to 116.4° after 30 seconds, and the water contact angle still remaining at 104.1° after 300 seconds.

[0080] like Figure 4 As shown, the coated lunch box underwent a hot water and hot oil resistance test. The original lunch box was found to be unresistant to hot water and hot oil, therefore no figure is attached. Figure 4 This indicates that the double-coated lunchbox has good resistance to hot water and hot oil, and still retains its barrier properties against hot water and hot oil after 30 minutes, demonstrating good durability in resisting hot water and hot oil.

Claims

1. A method for preparing a fluorine-free water- and oil-repellent material, comprising: (1) Mix acetic acid and water to obtain an acetic acid solution, and then dissolve chitosan in the acetic acid solution to obtain an oil repellent; wherein, by mass percentage, the oil repellent components are: chitosan 4%, acetic acid 2-3%, and water 94-95%; (2) Stearic acid is dissolved in ethanol to obtain a water repellent; wherein, by mass percentage, the water repellent components are: stearic acid 5-10%, ethanol 90-95%; (3) Substrate surface coating step (1) Oil repellent agent, drying, to obtain oil repellent material; wherein the drying is at 80℃ for 2-3 hours; The base material is paperboard; the paperboard is molded from pulp. (4) Coat the surface of the oil-repellent material from step (3) with the water-repellent agent from step (2), and dry to obtain a fluorine-free water-repellent and oil-repellent material; wherein the coating temperature is above 75°C.

2. The preparation method according to claim 1, characterized in that, In step (1), the degree of deacetylation of chitosan is above 95%.

3. The preparation method according to claim 1, characterized in that, In step (2), stearic acid dissolves in ethanol at a temperature above 70°C.

4. The preparation method according to claim 1, characterized in that, The coating in step (3) is applied by spraying; the coating amount is 4.5-6.2 g / m³. 2 .

5. The preparation method according to claim 1, characterized in that, In step (4), the coating is applied by immersion; the coating amount is 6.1-7.9 g / m³. 2 .

6. The preparation method according to claim 1, characterized in that, In step (4), the drying process involves drying at 20-80℃ for 1-2 hours.

7. A fluorine-free water- and oil-repellent material prepared by the method of claim 1.

8. The application of the fluorine-free water- and oil-repellent material of claim 7 in disposable food packaging.

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