A fluorine-free oil and water repellent agent for plant fiber molded tableware pulp and preparation method thereof

Abstract

The present invention relates to the field of waterproof and oil-proof plant fiber molded tableware, and particularly to a fluorine-free oil and water-proof agent for plant fiber molded tableware slurry. The fluorine-free oil and water-proof agent comprises the following components by weight: 5-11 parts of starch, 8-15 parts of gelatin, 1.5-2.5 parts of binder, 1.2-2.2 parts of modified nano silicon dioxide, 0.8-1.5 parts of nano titanium dioxide, 2-2.8 parts of modified chitosan, 10-20 parts of anti-seepage filler, and 40-60 parts of deionized water. The fluorine-free oil and water-proof agent of the present invention is directly added into the plant fiber molded tableware slurry, can improve the water and oil resistance of the plant fiber tableware, and is pollution-free to the environment and harmless to the human body.

Description

Technical Field

[0001] The invention relates to the field of water and oil resistance of plant fiber molded tableware, in particular to a fluorine-free oil and water repellent used in plant fiber molded tableware slurry. Background Art

[0002] Pulp molded tableware has the advantages of being environmentally friendly and safe, so it has been used more and more widely in recent years. The main component of this product is natural plant fiber, which has a loose and porous structure and contains a large amount of hydroxyl groups, and has poor protection against water and oil. There are currently two commonly used protection methods, coating a protective layer on the surface of the tableware, or directly adding oil and water repellents to the pulp during the production process. At present, fluorine-containing oil and water repellents have the best effect and are the most widely used, but they are highly toxic and can cause pollution to human health and the ecological environment. Therefore, fluorine-free oil and water repellents have become a research hotspot.

[0003] Fluorine-free oil and water repellents often use starch, chitosan and other substances to form a dense protective film on the surface of tableware to play a role in water and oil repellency, while adding an appropriate amount of nanoparticles such as silica can increase the roughness of the surface of tableware, thereby improving its hydrophobic and oleophobic ability. Studies have reported that modifying the surface of silica nanoparticles with hydrophobic alkyl chains can reduce its hydrophilicity, thereby further improving its waterproof performance, but its oleophobic performance is limited and needs to be further enhanced.

[0004] Patent CN202310699922.5 discloses a non-coated fluorine-free waterproof and oil-proof functional paper for food packaging. The waterproof and oil-proof packaging paper prepared in this application adds nano-silica pretreated with stearic acid, which reduces the hydrophilicity of silica and improves the waterproof performance of the packaging paper, but it does not solve the problem of its limited oleophobic ability; Patent CN202011066406.1 discloses a fluorine-free waterproof and oil-proof agent and a preparation method thereof. The waterproof and oil-proof agent prepared in this application adds nano-silica, nano-alumina and other particles, which can improve the surface roughness and improve the hydrophobic and oleophobic properties to a certain extent, but the improvement in its oleophobic ability is limited.

[0005] Therefore, there is an urgent need on the market for a fluorine-free oil and water repellent agent for preparing plant fiber tableware with good water and oil resistance. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a fluorine-free oil and water repellent for plant fiber molded tableware slurry and a preparation method thereof. The fluorine-free oil and water repellent of the present invention is composed of starch, gelatin, a binder, modified nano silicon dioxide, nano titanium dioxide, modified chitosan, an anti-seepage filler and deionized water, and has good hydrophobic and oleophobic capabilities.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides a fluorine-free oil and water repellent for plant fiber molded tableware slurry, which comprises the following components in parts by weight: 5-11 parts of starch, 8-15 parts of gelatin, 1.5-2.5 parts of binder, 1.2-2.2 parts of modified nano silicon dioxide, 0.8-1.5 parts of nano titanium dioxide, 2-2.8 parts of modified chitosan, 10-20 parts of anti-seepage filler, and 40-60 parts of deionized water.

[0009] In some embodiments of the present invention, the binder is sodium carboxymethyl cellulose or sodium alginate.

[0010] Sodium carboxymethyl cellulose or sodium alginate can react with starch and gelatin through hydrogen bonds and cross-linking reactions to make the protective film formed by starch and gelatin macromolecules tighter, reduce the gaps between molecules, and thus improve the waterproof and oil-proof properties of plant fiber tableware.

[0011] In some embodiments of the present invention, the method for preparing the modified nano-silicon dioxide comprises the following steps:

[0012] S1: Add silane coupling agent KH550 and succinic anhydride to an organic solvent, react at a temperature of 45-58°C for 2.2-3.5 hours, add silica nanoparticles, continue to react for 4.5-5.5 hours, centrifuge after the reaction, wash, and dry to obtain carboxylated silica nanoparticles;

[0013] S2: Add sulfuric acid solution, carboxylated silica nanoparticles prepared in step S1 and the compound shown in formula I into toluene

[0014]

[0015] The mixture is heated to reflux at a temperature of 109-114° C. for 9-10 hours, filtered, washed and dried to obtain modified nano-silicon dioxide.

[0016] Adding silica nanoparticles to water and oil repellents can increase the surface roughness and the actual contact area between solid and liquid, thereby increasing the energy required for the liquid to completely wet the surface of plant fiber tableware and improving the liquid-repellent ability of the tableware material. Modifying the surface of silica with hydrophobic alkyl chains can reduce the hydrophilicity of silica, thereby further improving its waterproof ability, but its oleophobic ability still needs to be improved. The applicant first modifies the surface of silica with carboxyl groups, and then uses the compound shown in formula I to modify the carboxyl-modified silica. The hydroxyl groups in the compound shown in formula I can undergo esterification reaction with the carboxyl groups on the surface of silica, and the ortho-steric hindrance of the hydroxyl groups can be reduced by adjusting the reaction time. The obtained modified nano-silica, on the one hand, introduces a lactone ring on the surface of the nanoparticle. Under neutral and weakly alkaline conditions, the lactone ring may open and react with the hydroxyl groups on the plant fiber to form an ester bond, thereby blocking the gaps in the plant fiber structure and hindering the penetration of water droplets and oil droplets, thereby further improving the waterproof and oil-proof properties of the plant fiber tableware; on the other hand, the modified nano-silica introduces some ester groups and carbonyl groups, which can form hydrogen bonds with other components in the system, thereby enhancing the interaction between molecules, improving the tightness between molecules, making the protective film denser, and also improving the waterproof and oil-proof properties of the plant fiber tableware.

[0017] The CAS number of the compound represented by formula I in the present invention is 60866-47-9.

[0018] In some embodiments of the present invention, the mass ratio of the carboxylated silica nanoparticles to the compound represented by formula I in step S2 is 1:(0.2-0.4).

[0019] Preferably, in step S2, the mass ratio of the carboxylated silica nanoparticles to the compound represented by formula I is 1:0.3.

[0020] The present invention does not impose any special restrictions on the source of the silicon dioxide nanoparticles, which can be purchased commercially, including but not limited to the silicon dioxide nanoparticles purchased from Bohuasi Nanotechnology Co., Ltd.

[0021] In some embodiments of the present invention, the particle size of the silicon dioxide nanoparticles in step S1 is 30-50 nm.

[0022] In some embodiments of the present invention, the particle size of the nano titanium dioxide is 10-20 nm.

[0023] Nano-silicon dioxide and nano-titanium dioxide can both improve the hydrophobic and oleophobic properties of the material surface by increasing the roughness. The applicant has found that adding modified nano-silicon dioxide with a larger particle size and nano-titanium dioxide with a smaller particle size in a certain mass ratio can further improve the water and oil resistance of the material. This may be because when nanoparticles of different particle sizes are gathered together, a more complex and rougher multi-scale hierarchical structure can be formed.

[0024] The present invention does not impose any special restrictions on the source of the nano titanium dioxide, which can be purchased commercially, including but not limited to the nano titanium dioxide purchased from Bohuasi Nanotechnology Co., Ltd.

[0025] In some embodiments of the present invention, the method for preparing the modified chitosan comprises the following steps:

[0026] Add chitosan and glacial acetic acid into ethanol, heat and stir, add methyl allyl ketone, heat and reflux at a temperature of 77-82° C., react for 9.5-10.5 hours, spin dry, wash, and dry to obtain modified chitosan.

[0027] Chitosan is a commonly used waterproof and oil-proof additive that can form a dense protective film to block water droplets and oil droplets. However, its structure contains amino groups, which will react with the ketocarbonyl groups on the modified nano-silica nanoparticles to form Schiff bases. The combination of the two affects their respective effects. The applicant modified chitosan by using methyl allyl ketone. On the one hand, the ketocarbonyl groups in the methyl allyl ketone structure will react with the amino groups on the chitosan to occupy the reaction sites, effectively preventing the reaction between the modified nano-silica and the amino groups of chitosan; on the other hand, the applicant unexpectedly discovered that the modification reaction increased the service life of the material. This may be because methyl allyl ketone introduces a carbon-carbon double bond in the modified chitosan structure, which has a strong reducing property and can act as an antioxidant and be oxidized first, thereby increasing the service life of the plant fiber tableware.

[0028] The present invention does not impose any special restrictions on the source of the chitosan, which can be purchased commercially, including but not limited to the chitosan purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0029] In some embodiments of the present invention, the mass ratio of chitosan to methyl allyl ketone is 1:(0.5-0.8).

[0030] Preferably, the mass ratio of chitosan to methyl allyl ketone is 1:0.65.

[0031] The applicant selected chitosan and methyl allyl ketone in a specific mass ratio so that most of the amino groups on the chitosan were reacted, thereby preventing it from reacting with modified nano-silica and thus reducing the waterproof and oil-proof performance of the oil-proof and water-proof agent for plant fiber tableware.

[0032] In some embodiments of the present invention, the anti-seepage filler is bentonite or kaolin.

[0033] Bentonite and kaolin can form a tight protective layer with high viscosity and low water permeability coefficient, thereby improving the protective performance of the oil and water repellent of plant fiber tableware.

[0034] The present invention does not impose any special restrictions on the sources of the bentonite and kaolin, which can be purchased commercially, including but not limited to the bentonite purchased from Guangzhou Chaoshun Chemical Co., Ltd.; including but not limited to the kaolin purchased from Jiangyin Guangyuan Superfine Powder Co., Ltd.

[0035] Another aspect of the present invention provides a method for preparing a fluorine-free oil and water repellent agent for use in plant fiber molded tableware slurry, comprising the following steps:

[0036] Ⅰ. Add starch, gelatin, binder and modified chitosan into deionized water and stir to obtain a mixed solution;

[0037] Ⅱ. Add modified nano-silicon dioxide, nano-titanium dioxide and anti-seepage filler to the mixed solution prepared in step Ⅰ, stir, and ultrasonicate for 20-30 minutes to obtain the fluorine-free oil and water repellent agent for plant fiber molded tableware slurry.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention uses starch, gelatin, a binder, modified nano-silicon dioxide, nano-titanium dioxide, modified chitosan, an anti-seepage filler and deionized water to prepare a fluorine-free oil and water repellent agent. The product is green and environmentally friendly, and the tableware prepared by mixing it with plant fiber tableware slurry has relatively excellent water and oil resistance.

[0040] (2) The present invention utilizes the compound shown in Formula I to modify the silica nanoparticles. The hydrophobic structure can reduce the hydrophilicity of silica. In addition, the modification reaction introduces a lactone ring structure, which is easily opened under neutral and weakly alkaline conditions and reacts with the hydroxyl groups of the plant fiber to form an ester bond, thereby blocking the gaps in the plant fiber structure, thereby further improving the waterproof and oil-proof properties of the plant fiber tableware. On the other hand, the modified nano-silica introduces some ester groups and carbonyl groups, which can form hydrogen bonds with other components in the system, thereby improving the interaction between molecules, increasing the tightness between molecules, making the protective film denser, and also improving the waterproof and oil-proof properties of the plant fiber tableware.

[0041] (3) The present invention utilizes methyl allyl ketone to modify chitosan. On the one hand, methyl allyl ketone reacts with the amino group in the chitosan structure, effectively preventing the ketone carbonyl group on the modified silica from reacting with chitosan, thereby reducing the waterproof and oil-proof properties of the plant fiber tableware. On the other hand, the applicant unexpectedly discovered that the modification reaction introduced carbon-carbon double bonds into chitosan, which can be preferentially oxidized and act as an antioxidant, thereby increasing the service life of the plant fiber tableware. DETAILED DESCRIPTION

[0042] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0043] In the following examples, except for modified nano-silicon dioxide and modified chitosan, the other compound monomers and related reagents used can be purchased from the market. Among them, starch was purchased from Jinan Jinhao Chemical Co., Ltd.; gelatin was purchased from Hefei Tianjian Chemical Co., Ltd.; silicon dioxide nanoparticles were purchased from Bohuasi Nanotechnology Co., Ltd.; nano-titanium dioxide was purchased from Bohuasi Nanotechnology Co., Ltd.; chitosan was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; bentonite was purchased from Guangzhou Chaoshun Chemical Co., Ltd.; kaolin was purchased from Jiangyin Guangyuan Superfine Powder Co., Ltd.

[0044] Preparation Example 1

[0045] The preparation method of modified nano-silicon dioxide A comprises the following steps:

[0046] S1: Add 0.3 ml of silane coupling agent KH550 and 0.14 g of succinic anhydride to 25 ml of N,N-dimethylformamide, react at 52°C for 3 h, add 1 g of silica nanoparticles, continue to react for 5 h, centrifuge after the reaction, wash with anhydrous ethanol, and dry to obtain carboxylated silica nanoparticles;

[0047] S2: Add 0.4 ml of 78 wt% sulfuric acid solution, 1 g of carboxylated silica nanoparticles prepared in step S1 and 0.3 g of the compound represented by formula I into 22 ml of toluene.

[0048]

[0049] The mixture was heated under reflux at 113° C. for 10 h, filtered, washed with acetone, and dried to obtain modified nano-silica A.

[0050] Preparation Example 2

[0051] The preparation method of modified nano-silica B is the same as that of modified nano-silica A, except that the mass of the compound represented by formula I added in step S2 is 0.1 g.

[0052] Preparation Example 3

[0053] The preparation method of modified nano-silicon dioxide C comprises the following steps:

[0054] 1 g of silica nanoparticles and 0.3 ml of dodecyltrimethoxysilane were added to 30 ml of anhydrous ethanol, reacted at 40° C. for 5 h, filtered, washed with acetone, and dried to obtain modified nano-silica C.

[0055] Preparation Example 4

[0056] The preparation method of modified chitosan A comprises the following steps:

[0057] Add 0.5 g of chitosan and 0.8 ml of glacial acetic acid to 28 ml of anhydrous ethanol, heat and stir at 48°C for 40 min, add 0.33 g of methyl allyl ketone, heat and reflux at 78°C, react for 10.5 h, spin dry, wash with deionized water, and dry to obtain modified chitosan A.

[0058] Preparation Example 5

[0059] Modified chitosan B is prepared in the same manner as modified chitosan A, except that the mass of methyl allyl ketone added in step (1) is 0.2 g.

[0060] Example 1

[0061] A fluorine-free oil and water repellent for plant fiber molded tableware slurry comprises the following components by weight: 8 parts of starch, 12 parts of gelatin, 2 parts of sodium carboxymethyl cellulose, 1.7 parts of modified nano silicon dioxide A, 1.2 parts of nano titanium dioxide, 2.4 parts of modified chitosan A, 15 parts of bentonite and 50 parts of deionized water.

[0062] Among them, the modified nano-silica A is prepared by Preparation Example 1, and the modified chitosan A is prepared by Preparation Example 4.

[0063] The preparation method of the fluorine-free oil and water repellent agent for plant fiber molded tableware slurry in this embodiment comprises the following steps:

[0064] Ⅰ. Add starch, gelatin, sodium carboxymethyl cellulose and modified chitosan A into deionized water and stir for 20 minutes to obtain a mixed solution;

[0065] Ⅱ. Add modified nano-silica A, nano-titanium dioxide and bentonite to the mixed solution prepared in step Ⅰ, stir for 20 minutes, and ultrasonicate for 25 minutes to obtain the fluorine-free oil and water repellent agent for use in the plant fiber molded tableware slurry.

[0066] Example 2

[0067] A fluorine-free oil and water repellent for plant fiber molded tableware slurry comprises the following components by weight: 5 parts of starch, 8 parts of gelatin, 1.5 parts of sodium alginate, 1.7 parts of modified nano silicon dioxide A, 0.8 parts of nano titanium dioxide, 2.4 parts of modified chitosan A, 10 parts of kaolin and 40 parts of deionized water.

[0068] Among them, the modified nano-silica A is prepared by Preparation Example 1, and the modified chitosan A is prepared by Preparation Example 4.

[0069] The preparation method of the fluorine-free oil and water repellent agent for plant fiber molded tableware slurry in this embodiment comprises the following steps:

[0070] Ⅰ. Add starch, gelatin, sodium alginate and modified chitosan A into deionized water and stir for 20 minutes to obtain a mixed solution;

[0071] Ⅱ. Add modified nano-silica A, nano-titanium dioxide and kaolin to the mixed solution prepared in step Ⅰ, stir for 20 minutes, and ultrasonicate for 20 minutes to obtain the fluorine-free oil and water repellent agent for the plant fiber molded tableware slurry.

[0072] Example 3

[0073] A fluorine-free oil and water repellent for plant fiber molded tableware slurry comprises the following components by weight: 11 parts of starch, 15 parts of gelatin, 2.5 parts of sodium alginate, 1.7 parts of modified nano silicon dioxide A, 1.5 parts of nano titanium dioxide, 2.4 parts of modified chitosan A, 20 parts of kaolin and 60 parts of deionized water.

[0074] Among them, the modified nano-silica A is prepared by Preparation Example 1, and the modified chitosan A is prepared by Preparation Example 4.

[0075] The preparation method of the fluorine-free oil and water repellent agent for plant fiber molded tableware slurry in this embodiment comprises the following steps:

[0076] Ⅰ. Add starch, gelatin, sodium alginate and modified chitosan A into deionized water and stir for 20 minutes to obtain a mixed solution;

[0077] Ⅱ. Add modified nano-silica A, nano-titanium dioxide and kaolin to the mixed solution prepared in step Ⅰ, stir for 20 minutes, and ultrasonicate for 30 minutes to obtain the fluorine-free oil and water repellent agent for the plant fiber molded tableware slurry.

[0078] Example 4

[0079] A fluorine-free oil and water repellent for plant fiber molded tableware slurry comprises the following components by weight: 7 parts of starch, 11 parts of gelatin, 2.3 parts of sodium carboxymethyl cellulose, 1.2 parts of modified nano silicon dioxide A, 1.1 parts of nano titanium dioxide, 2.8 parts of modified chitosan A, 12 parts of bentonite and 45 parts of deionized water.

[0080] Among them, the modified nano-silica A is prepared by Preparation Example 1, and the modified chitosan A is prepared by Preparation Example 4.

[0081] The preparation method of the fluorine-free oil and water repellent for plant fiber molded tableware slurry in this embodiment is the same as that in Example 1.

[0082] Example 5

[0083] A fluorine-free oil and water repellent for plant fiber molded tableware slurry comprises the following components by weight: 9 parts of starch, 13 parts of gelatin, 1.7 parts of sodium carboxymethyl cellulose, 2.2 parts of modified nano silicon dioxide A, 1.3 parts of nano titanium dioxide, 2 parts of modified chitosan A, 14 parts of bentonite and 55 parts of deionized water.

[0084] Among them, the modified nano-silica A is prepared by Preparation Example 1, and the modified chitosan A is prepared by Preparation Example 4.

[0085] The preparation method of the fluorine-free oil and water repellent for plant fiber molded tableware slurry in this embodiment is the same as that in Example 1.

[0086] Example 6

[0087] A fluorine-free oil and water repellent for plant fiber molded tableware slurry and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that modified nano-silica B replaces modified nano-silica A in equal amounts, wherein modified nano-silica B is prepared by Preparation Example 2.

[0088] Example 7

[0089] A fluorine-free oil and water repellent for plant fiber molded tableware slurry and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that modified chitosan A is replaced by modified chitosan B in equal amounts, wherein modified chitosan B is prepared by Preparation Example 5.

[0090] Example 8

[0091] A fluorine-free oil and water repellent for plant fiber molded tableware slurry and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that modified nano-silica C replaces modified nano-silica A in equal amounts, wherein modified nano-silica C is prepared by Preparation Example 3.

[0092] Comparative Example 1

[0093] A fluorine-free oil and water repellent and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified nano-silica A is replaced by an equal amount of commercially available conventional nano-silica.

[0094] Comparative Example 2

[0095] A fluorine-free oil and water repellent and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified chitosan A is replaced by an equal amount of commercially available conventional chitosan.

[0096] Performance Testing

[0097] (1) Water resistance

[0098] When preparing plant fiber tableware according to the patent application number CN201110421315.X, 3% of the weight of fluorine-free oil and water repellent is added, and the water repellency of the prepared tableware is measured by measuring the contact angle between the prepared tableware and deionized water. The larger the contact angle, the better the water repellency.

[0099] (2) Oil resistance

[0100] When preparing plant fiber tableware according to the patent application number CN201110421315.X, 3% of the weight of fluorine-free oil and water repellent is added, and the oil repellency of the prepared tableware is measured by measuring the contact angle between the prepared tableware and soybean oil. The larger the contact angle, the better the oil repellency.

[0101] The water resistance and oil resistance of the fluorine-free oil and water repellents prepared in Examples 1-8 and Comparative Examples 1-2 were tested according to the above test method. The test results are shown in Table 1.

[0102] Table 1

[0103] Group Contact angle between tableware and deionized water (°) Contact angle between tableware and soybean oil (°) Example 1 145 124 Example 2 143 122 Example 3 144 123 Example 4 142 121 Example 5 143 122 Example 6 133 114 Example 7 135 115 Example 8 130 111 Comparative Example 1 121 105 Comparative Example 2 126 108

[0104] As can be seen from Table 1, the fluorine-free oil and water repellent used in the plant fiber molded tableware slurry in Examples 1-5 of the present invention has the advantage of good water and oil resistance. Among them, Example 6 reduces the amount of the compound shown in Formula I, so that the density of the lactone ring and hydrophobic chain modified on the surface of the nanoparticles is reduced, resulting in the modified nano-silica and the plant fiber not being tightly bound, exposing more intermolecular gaps, and the hydrophilicity of the particles themselves not being reduced enough, thereby reducing the water and oil resistance of the plant fiber tableware; Example 7 reduces the amount of methyl allyl ketone, so that more amino functional groups remain in the chitosan, which will react with the ketone carbonyl on the modified nano-silica, affecting the functions of both, thereby reducing the water and oil resistance of the plant fiber tableware; Example 8 uses dodecyltrimethoxysilane to modify the nano-silica, modifies the hydrophobic chain on the surface of the nanoparticles, and reduces the hydrophilicity of the nano-silica. The particles themselves are hydrophilic, but due to the lack of a lactone ring structure, they cannot open the ring with the hydroxyl groups of the plant fibers to form ester bonds, resulting in the inability to block the gaps between the plant fiber molecules, thereby reducing the water resistance and oil resistance of the plant fiber tableware; Comparative Example 1 uses commercially available conventional nano-silica to replace modified nano-silica. Although it can improve the surface roughness of the material, the particles have strong hydrophilicity, thereby reducing the water resistance and oil resistance of the plant fiber tableware; Comparative Example 2 uses commercially available conventional chitosan to replace modified chitosan. A large number of amino groups on the surface of chitosan combine with modified nano-silica, which affects the formation of a protective layer by chitosan itself, and also affects the combination of nano-silica and plant fibers, thereby reducing the water resistance and oil resistance of the plant fiber tableware.

[0105] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A fluorine-free oil and water repellent for use in plant fiber molded tableware slurry, characterized in that: The composition comprises the following components by weight: 5-11 parts of starch, 8-15 parts of gelatin, 1.5-2.5 parts of binder, 1.2-2.2 parts of modified nano silicon dioxide, 0.8-1.5 parts of nano titanium dioxide, 2-2.8 parts of modified chitosan, 10-20 parts of anti-seepage filler, and 40-60 parts of deionized water; The preparation method of the modified nano-silicon dioxide comprises the following steps: S1: Add silane coupling agent KH550 and succinic anhydride to an organic solvent, react at a temperature of 45-58°C for 2.2-3.5 hours, add silica nanoparticles, continue to react for 4.5-5.5 hours, centrifuge after the reaction, wash, and dry to obtain carboxylated silica nanoparticles; S2: Add sulfuric acid solution, carboxylated silica nanoparticles prepared in step S1 and the compound shown in formula I into toluene （Ⅰ）， Heating and reflux at a temperature of 109-114° C. for 9-10 hours, filtering, washing, and drying to obtain modified nano-silica; wherein the mass ratio of the carboxylated silica nanoparticles to the compound represented by formula I in step S2 is 1:(0.2-0.4); and the particle size of the silica nanoparticles in step S1 is 30-40 nm; The preparation method of the modified chitosan comprises the following steps: Add chitosan and glacial acetic acid into ethanol, heat and stir, add methyl allyl ketone, heat and reflux at a temperature of 77-82°C, react for 9.5-10.5 hours, spin dry, wash, and dry to obtain modified chitosan; wherein the mass ratio of chitosan to methyl allyl ketone is 1:(0.5-0.8).

2. The fluorine-free oil and water repellent agent for plant fiber molded tableware slurry according to claim 1, characterized in that: The binder is sodium carboxymethyl cellulose or sodium alginate.

3. The fluorine-free oil and water repellent agent for plant fiber molded tableware slurry according to claim 1, characterized in that: The particle size of the nano titanium dioxide is 10-20 nm.

4. The fluorine-free oil and water repellent agent for plant fiber molded tableware slurry according to claim 1, characterized in that: The anti-seepage filler is bentonite or kaolin.

5. A method for preparing the fluorine-free oil and water repellent for use in plant fiber molded tableware slurry according to any one of claims 1 to 4, characterized in that: The steps include: Ⅰ. Add starch, gelatin, binder and modified chitosan into deionized water and stir to obtain a mixed solution; Ⅱ. Add modified nano-silicon dioxide, nano-titanium dioxide and anti-seepage filler to the mixed solution prepared in step Ⅰ, stir, and ultrasonicate for 20-30 minutes to obtain the fluorine-free oil and water repellent agent for plant fiber molded tableware slurry.

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