Degradable environment-friendly paper cup interior coating and preparation method thereof

Abstract

The present application relates to the field of environment-friendly materials and its preparation technology, and particularly relates to a degradable environment-friendly paper cup interior coating and a preparation method thereof. The method comprises the following steps: firstly, synthesizing polymerizable quaternary ammonium salt surfactant (RPKO-X), and then introducing the polymerizable quaternary ammonium salt surfactant and a bio-based polymer solution into a polyacrylate molecular chain by a redox initiation polymerization method, so as to obtain a degradable acrylate emulsion for paper cup interior coating. By introducing the hydrophobic monomer RPKO-X with emulsifier characteristics, a stronger crosslinking network is formed, which can significantly improve the water resistance and oil resistance of the coating. Meanwhile, by introducing the bio-based material polyvinyl alcohol 2688, the environmental friendliness of the coating is enhanced, and the rapid degradation of the coating after use is promoted. By using the redox initiation polymerization system, the method is simple to prepare, can be prepared under mild conditions, and the emulsion particle size is uniform and stable.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly materials and their preparation technology, specifically to a biodegradable environmentally friendly paper cup internal coating and its preparation method. Background Technology

[0002] Paper cups, made from paper, are lightweight and portable, making them widely used in restaurants, fast food outlets, and popular bubble tea shops for serving both hot and cold drinks. The inner wall of these paper cups is typically coated with a polyethylene (PE) plastic film. This PE coating technology evenly distributes the PE material onto the inner wall to achieve waterproofing and leak-proof properties, ensuring the cup doesn't easily leak when filled with liquids and maintaining its structural strength. However, with increasing global awareness of environmental protection, plastic pollution is becoming increasingly serious. Traditional PE coatings are not only difficult to degrade, but also can have long-term negative impacts on soil, water sources, and organisms after plastic waste accumulates.

[0003] To address the aforementioned issues, research on biodegradable materials as coatings for the interior of paper cups has gradually gained attention, especially coatings based on bio-based materials, which are favored due to their wide availability and environmental friendliness. Biodegradable materials such as polylactic acid (PLA), polyhydroxyalkanoates (PHA), and starch-based materials have demonstrated promising application prospects in multiple fields.

[0004] Application No. 202280086854.9 discloses "a bio-based coating and its formation and application method," which is a biodegradable bio-based coating that can be used, for example, in packaging and food containers or as a sacrificial layer. The bio-based coating can be formed on the outer surface of a substrate, including paper or pulp starch, corrugated cardboard, mushrooms (including mycelium), seaweed, fabrics, concrete, or metal. However, the high cost of raw materials leads to high production costs for bio-based materials; and under some extreme environmental conditions, the performance of bio-based coatings (such as temperature resistance and chemical resistance) is not ideal, limiting their application range.

[0005] Therefore, it is particularly important to develop a high-performance and environmentally friendly biodegradable coating for the inside of paper cups. Summary of the Invention

[0006] The purpose of this invention is to provide a novel method for preparing a biodegradable and environmentally friendly coating for the interior of paper cups, in order to solve the problems in the prior art where the high cost of raw materials leads to high production costs of bio-based materials, and the unsatisfactory performance of bio-based coatings under some extreme environmental conditions, which limits their application range.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, comprising the following steps:

[0008] Step 1: Mix 12-18 parts of long-chain amide dimethyl tertiary amine and 24-36 parts of anhydrous ethanol in a water bath under nitrogen protection. Slowly add 3-5 parts of halopropylene and 6-10 parts of anhydrous ethanol, and then heat the mixture to react. Remove the anhydrous ethanol and unreacted halopropylene, and allow it to stand to obtain an aqueous layer. After removing the water, recrystallize and separate and purify to obtain the polymerizable quaternary ammonium salt surfactant RPKO-X, where X is 16, 18 or 21.

[0009] Step 2: Mix 70-80 parts of methacrylate monomers, 2-4 parts of silane coupling agent and 1-3 parts of acrylic monomers containing hydrophilic groups evenly to obtain solution A;

[0010] Step 3: Weigh 1-2 parts of anionic emulsifier, 1-2 parts of nonionic emulsifier, 0.5-1 part of polymerizable quaternary ammonium salt surfactant, 10-20 parts of 5% polyvinyl alcohol 2688 solution, 2-4 parts of reducing agent and 100 parts of water, mix and dissolve to obtain solution B;

[0011] Step 4: Weigh 2-4 portions of oxidizing agent, add water to dissolve and obtain solution C;

[0012] Step 5: Add component A to component B and pre-emulsify to obtain a uniform acrylic resin pre-emulsion;

[0013] Step 6: After purging nitrogen gas into the pre-emulsion for 1-1.5 hours, slowly add solution C dropwise using a micro-injection pump, and then control the temperature to react, thus obtaining a biodegradable acrylic emulsion for coating the inside of paper cups.

[0014] Furthermore, in step one above, the water bath temperature is 40-50℃, and the stirring speed is constant at 500-800 r / min.

[0015] Furthermore, in step one above, the mixture is slowly added dropwise over 3-4 hours, and then the temperature is increased by 5-10°C for 24-30 hours.

[0016] Furthermore, in step five above, the pre-emulsification is carried out by stirring with a high-speed mixer at 10,000-12,000 r / min for 10-15 min.

[0017] Furthermore, in step six above, solution C is slowly added dropwise over a period of 1-2 hours, followed by maintaining the temperature at 40-50°C for 4-5 hours.

[0018] Furthermore, the halogenated propylene in step one above is chloropropylene or bromopropylene.

[0019] Furthermore, in step two above, the acrylic monomer containing hydrophilic groups is one, two, or a mixture of two or more of the following in any proportion: hydroxyethyl acrylate, hydroxypropyl acrylate, dihydroxyethyl acrylate, polyethylene glycol acrylate, acetamide acrylate, and formamide acrylate.

[0020] Furthermore, the reducing agent mentioned above is one, two or more of sodium bisulfite, sodium sulfite, sodium thiosulfate, and sodium metabisulfite in any proportion.

[0021] Furthermore, the aforementioned oxidant is one, two, or a mixture of two or more of potassium persulfate, ammonium persulfate, sodium persulfate, and tert-butanol peroxide in any proportion.

[0022] Furthermore, the above preparation method yields a biodegradable and environmentally friendly paper cup interior coating.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) The intermediate product of the present invention, the functional monomer, can polymerize the quaternary ammonium salt surfactant RPKO-X. In the subsequent synthesis of emulsion, it can be introduced as both an emulsifier and a hydrophobic monomer. During the polymerization process, a stronger cross-linking network can be formed, which enhances the degree of cross-linking of the film and reduces the permeability of the film to water and oil, thereby effectively improving its water resistance, oil resistance and heat resistance.

[0025] (2) This invention introduces bio-based polymer materials during the synthesis process to improve the degradation rate of the coating after use, enabling it to biodegrade under natural conditions, reducing environmental pollution and impact, which aligns with the requirements of sustainable development. Simultaneously, the cross-linked structure formed by the polymerizable quaternary ammonium salt surfactant RPKO-X during the polymerization reaction, combined with the bio-based polymer, can significantly enhance the mechanical strength and toughness of the coating. Furthermore, the bio-based polymer, as a supplement to the cross-linking points, can also enhance the crack resistance and abrasion resistance of the coating, extending the product's service life.

[0026] (3) The polymerizable quaternary ammonium salt surfactant RPKO-X provides hydrophobicity, while the bio-based polymer polyvinyl alcohol 2688 provides hydrophilicity. The two interact to form a dynamic hydrophilic-hydrophobic interface. The formation of this interface enables the coating not only to resist water penetration but also to maintain stability in oily environments, significantly improving the coating's chemical resistance.

[0027] (4) The preparation process of the present invention is simple. The redox-initiated polymerization system is used in the emulsion synthesis process, so that the reaction can be carried out under mild conditions. The polymerization rate and the molecular weight of the polymer are controlled by adjusting the dripping rate of the oxidant solution C by using a micro-injection pump. Therefore, the prepared emulsion particles are uniform and stable. Attached Figure Description

[0028] Figure 1 This is a particle size distribution diagram of the emulsion;

[0029] Figure 2 SEM images of the paper samples before and after coating:

[0030] (A) Surface morphology of blank paper sample without surface coating (500x magnification), (B) SEM image of coating prepared in Comparative Example 1 uniformly coated on paper (500x magnification), (C) SEM image of coating prepared in Comparative Example 2 uniformly coated on paper (500x magnification), (D) SEM image of coating prepared in Example 6 uniformly coated on paper (500x magnification).

[0031] Figure 3 The diagram shows the water and salt resistance test results.

[0032] 90°C hot water: (A) Comparative Example 1, (B) Comparative Example 2 and (C) Example 6;

[0033] White oil: (D) Comparative Example 1, (E) Comparative Example 2 and (F) Example 6;

[0034] Coffee: (G) Comparative Example 1, (H) Comparative Example 2 and (J) Example 6;

[0035] Figure 4 The static contact angle of water on the coated paper. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0037] The present invention provides a method for preparing a biodegradable and environmentally friendly paper cup interior coating. The design concept is as follows: firstly, a polymerizable quaternary ammonium salt surfactant (RPKO-X) is synthesized, and then, through redox-initiated polymerization, the polymerizable quaternary ammonium salt surfactant and a bio-based polymer solution are simultaneously introduced into the polyacrylate molecular chain to obtain a biodegradable acrylic emulsion for coating the interior of paper cups.

[0038] Example 1: A method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, comprising the following steps:

[0039] Step 1: Place 15 parts of oleic acid amide dimethyl tertiary amine and 30 parts of ethanol in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Place the flask in a 40℃ water bath and stir at a constant speed of 500 rpm under nitrogen protection. Add 5 parts of a mixture of allyl chloride and 10 parts of ethanol dropwise over 3 hours. Raise the temperature to 50℃ and maintain the reaction for 24 hours. Remove the solvent anhydrous ethanol by rotary evaporation. Wash away any unreacted allyl chloride with water. Let the mixture stand in a separatory funnel to separate the oil layer, obtaining the aqueous layer. Remove the water by vacuum distillation. Recrystallize with ethyl acetate / ethanol to obtain the polymerizable quaternary ammonium salt surfactant RPKO-O (X = 18).

[0040] Step 2: Mix 75 parts of methyl methacrylate, 2 parts of KH-550 and 2 parts of hydroxyethyl acrylate evenly to obtain solution A;

[0041] Step 3: Weigh 2 parts SDS, 2 parts OP-10, 1 part RPKO-O, 10 parts of 5% polyvinyl alcohol 2688 solution, 3 parts sodium bisulfite and 100 parts water and mix them to obtain solution B;

[0042] Step 4: Weigh 3 parts of potassium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0043] Step 5: Add component A to component B and pre-emulsify using a high-speed mixer at 11000 r / min for 10 min to obtain a uniform acrylic resin pre-emulsion.

[0044] Step 6: After purging nitrogen into the pre-emulsion for 1 hour, add solution C dropwise using a micro-injection pump, control the temperature at 50°C, and continue the reaction for 4 hours to obtain a biodegradable acrylic emulsion for coating the inside of paper cups.

[0045] Example 2, a method for preparing a biodegradable and environmentally friendly coating for the inside of a paper cup, comprising the following steps:

[0046] Step 1: Place 18 parts of erucamide dimethyl tertiary amine and 36 parts of ethanol in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Place the flask in a 40°C water bath and stir at a constant speed of 500 rpm under nitrogen protection. Add 4 parts of a mixture of allyl chloride and 8 parts of ethanol dropwise over 3 hours. Raise the temperature to 50°C and maintain the reaction temperature for 24 hours. Remove the solvent anhydrous ethanol by rotary evaporation. Wash away any unreacted allyl chloride with water. Let the mixture stand in a separatory funnel, separate the oil layer to obtain the aqueous layer, remove the water by vacuum distillation, recrystallize with ethyl acetate / ethanol, and separate and purify to obtain the polymerizable quaternary ammonium salt surfactant RPKO-O (X = 18).

[0047] Step 2: Mix 80 parts of methyl methacrylate, 2 parts of KH-550, 2 parts of hydroxypropyl acrylate and 1 part of diethyl acrylate evenly to obtain solution A;

[0048] Step 3: Weigh 2 parts SDS, 2 parts OP-10, 1 part RPKO-O, 10 parts of 5% polyvinyl alcohol 2688 solution, 3 parts sodium bisulfite and 100 parts water and mix them to obtain solution B;

[0049] Step 4: Weigh 3 parts of potassium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0050] Step 5: Same as step 5 in Example 1;

[0051] Step six is ​​the same as step six in Example 1.

[0052] Example 3: A method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, comprising the following steps:

[0053] Step 1: Place 12 parts of palm kernel oleamide dimethyl tertiary amine and 24 parts of ethanol in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen protection device. Place the flask in a 40℃ water bath and stir at a constant speed of 500 rpm under nitrogen protection. Add 3 parts of a mixture of allyl chloride and 6 parts of ethanol dropwise over 3 hours. Raise the temperature to 50℃ and maintain the reaction for 24 hours. Remove the solvent anhydrous ethanol by rotary evaporation. Wash away any unreacted allyl chloride with water. Let the mixture stand in a separatory funnel to separate the oil layer, obtaining the aqueous layer. Remove the water by vacuum distillation. Recrystallize with ethyl acetate / ethanol to obtain the polymerizable quaternary ammonium salt surfactant RPKO-H (X = 16).

[0054] Step 2: Mix 70 parts of methyl methacrylate, 2 parts of KH-550, 1 part of hydroxyethyl acrylate and 2 parts of acetamide acrylate evenly to obtain solution A;

[0055] Step 3: Weigh 2 parts SDS, 2 parts OP-10, 1 part RPKO-H, 10 parts 5% polyvinyl alcohol 2688 solution, 3 parts sodium bisulfite and 100 parts water and mix them to obtain solution B;

[0056] Step 4: Weigh 3 parts of potassium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0057] Step 5: Same as step 5 in Example 1;

[0058] Step six is ​​the same as step six in Example 1.

[0059] Example 4: A method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, comprising the following steps:

[0060] Step 1: Same as Example 1;

[0061] Step 2: Mix 40 parts of methyl methacrylate and 40 parts of butyl acrylate monomer, 3 parts of KH-560 agent and 1 part of hydroxypropyl acrylate evenly to obtain solution A;

[0062] Step 3: Weigh 1.5 parts SDS, 1.5 parts OP-10, 1 part RPKO-O, 20 parts 5% (w / w) polyethylene glycol 2688 solution, 3 parts sodium bisulfite and 100 parts water and mix them to obtain solution B;

[0063] Step 4: Weigh 3 parts of potassium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0064] Step 5: Same as step 5 in Example 1;

[0065] Step six is ​​the same as step six in Example 1.

[0066] Example 5: A method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, comprising the following steps:

[0067] Step 1: Same as Example 2;

[0068] Step 2: Mix 40 parts of methyl methacrylate, 30 parts of butyl acrylate, 2 parts of KH-570 agent and 1 part of hydroxypropyl acrylate evenly to prepare solution A;

[0069] Step 3: Weigh 1.5 parts SDS, 1.5 parts OP-10, 1 part RPKO-E, 20 parts 5% (w / w) polyethylene glycol 2688 solution, 2 parts sodium bisulfite and 100 parts water and mix them to obtain solution B;

[0070] Step 4: Weigh 2 parts of ammonium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0071] Step 5: Same as step 5 in Example 1;

[0072] Step six is ​​the same as step six in Example 1.

[0073] Example 6: A method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, comprising the following steps:

[0074] Step 1: Same as Example 1;

[0075] Step 2: Mix 40 parts of methyl methacrylate, 40 parts of butyl acrylate, 2 parts of KH-570 agent and 1 part of hydroxypropyl acrylate evenly to prepare solution A;

[0076] Step 3: Weigh 1.5 parts SDS, 1.5 parts OP-10, 1 part RPKO-O, 15 parts 5% polyvinyl alcohol 2688, 2-4 parts sodium bisulfite and 100 parts water and mix them to obtain solution B.

[0077] Step 4: Weigh 4 parts of ammonium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0078] Step 5: Same as step 5 in Example 1;

[0079] Step six is ​​the same as step six in Example 1.

[0080] Example 7, a method for preparing a biodegradable and environmentally friendly coating for the inside of a paper cup, comprising the following steps:

[0081] Step 1: Same as Example 3;

[0082] Step 2: Mix 30 parts methyl methacrylate, 40 parts butyl acrylate, 2 parts KH-570 agent and 1 part hydroxypropyl acrylate evenly to prepare solution A;

[0083] Step 3: Weigh 1.5 parts SDS, 1.5 parts OP-10, 1 part RPKO-H, 15 parts hydroxypropyl cellulose with a mass concentration of 5%, 2-4 parts sodium bisulfite, and 100 parts water, mix and dissolve to obtain solution B;

[0084] Step 4: Weigh 3 parts of ammonium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0085] Step 5: Same as step 5 in Example 1;

[0086] Step six is ​​the same as step six in Example 1.

[0087] Comparative Example 1

[0088] Step 1: Same as Example 6;

[0089] Step 2: Mix 40 parts of methyl methacrylate, 40 parts of butyl acrylate, 2 parts of KH-570 agent and 1 part of hydroxypropyl acrylate evenly to prepare solution A;

[0090] Step 3: Weigh 1.5 parts SDS, 1.5 parts OP-10, 1 part RPKO-O, 2-4 parts sodium bisulfite, and 100 parts water, mix and dissolve to obtain solution B; the difference from Example 6 is that no bio-based polymer solution was used.

[0091] Step 4: Weigh 4 parts of ammonium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0092] Step 5: Add component A to component B and pre-emulsify using a high-speed mixer at 11000 r / min for 10 min to obtain a uniform acrylic resin pre-emulsion.

[0093] Step 6: After purging nitrogen into the pre-emulsion for 1 hour, add solution C dropwise using a micro-injection pump, control the temperature at 50°C, and continue the reaction for 4 hours to obtain a biodegradable acrylic emulsion for coating the inside of paper cups.

[0094] Comparative Example 2

[0095] Step 1: Mix 40 parts methyl methacrylate, 40 parts butyl acrylate, 2 parts KH-570 agent and 1 part hydroxypropyl acrylate evenly to prepare solution A;

[0096] Step 2: Weigh 1.5 parts SDS, 1.5 parts OP-10, 15 parts polyvinyl alcohol 2688 with a mass concentration of 5%, 2-4 parts sodium bisulfite, and 100 parts water, mix and dissolve to obtain solution B; the difference from Example 6 is that the polymerizable quaternary ammonium salt surfactant (RPKO-O) prepared in Step 1 of the method provided by the present invention was not used.

[0097] Step 3: Weigh 4 parts of ammonium persulfate and dissolve it in 30 parts of water to obtain solution C;

[0098] Step 4: Add component A to component B and pre-emulsify using a high-speed mixer at 11000 r / min for 10 min to obtain a uniform acrylic resin pre-emulsion.

[0099] Step 5: After purging nitrogen into the pre-emulsion for 1 hour, add solution C dropwise using a micro-injection pump, control the temperature at 50°C, and continue the reaction for 4 hours to obtain a biodegradable acrylic emulsion for coating the inside of paper cups.

[0100] Taking Example 6 as the preferred embodiment, its performance was tested:

[0101] Experimental Example 1

[0102] The emulsions prepared in Comparative Examples 1, 2, and 6 were diluted to a mass fraction of 1%, and the particle size distribution and zeta potential of the composite emulsions were determined using a Mastersizer 2000 Malvern laser particle size analyzer. Specific test results are as follows: Figure 1 ,from Figure 1 It can be seen that introducing both polyvinyl alcohol (PVA) and RPKO-O into the synthesis of polyacrylic acid resin emulsions narrows the particle size distribution. This is because PVA molecules have relatively long chains, and their entanglement and extension in the emulsion system are complex and uneven. Some emulsion particles may be wrapped by a large number of PVA chains, resulting in strong steric hindrance and relative dispersion. PVA provides good steric hindrance, while the alkyl carbon chains in the polymerizable quaternary ammonium salt surfactant RPKO-O maintain stable electrostatic repulsion between particles through a suitable charge distribution. The combined effect of both makes the emulsion particles more uniformly dispersed, effectively limiting particle aggregation and size inhomogeneity, thus potentially narrowing the particle size distribution.

[0103] Experiment Example 2

[0104] The emulsions prepared in Comparative Examples 1, 2, and 6 were uniformly coated onto paper and dried in a 40°C oven for 24 hours. The samples were then laid flat on conductive adhesive, sputtered with gold, and fixed onto a stage. Their surface morphology was analyzed and observed using a FEIQ45+EDXOctane Prime scanning electron microscope (SEM) from FEI and EDAX (USA), with a scanning voltage of 15 kV. Specific test results are as follows: Figure 2 ,from Figure 2 As can be seen, the paper is relatively rough before surface coating, but becomes smooth after coating. The paper surface treated with the coating prepared by this invention is the smoothest. This is because the alkyl chain of the polymerizable quaternary ammonium salt surfactant RPKO-O used in this invention can form a stronger cross-linking network during polymerization, thereby giving the emulsion coated on the paper a higher cross-linking density, resulting in a denser film with superior smoothness.

[0105] Experimental Example 3

[0106] The emulsions prepared in Comparative Example 1, Comparative Example 2, and Example 6 were uniformly coated onto paper and dried in a 40°C oven for 24 hours. The paper's water and oil resistance were then tested by dripping dyed 90°C hot water, white oil, and coffee onto the paper surface. Specific test results are as follows: Figure 3 ,from Figure 3 It can be seen that the emulsion prepared by the present invention has excellent water and oil resistance when coated on paper. The water and oil resistance of Comparative Example 1 and Example 6 are better than that of Example 2. This is because during the synthesis of polyacrylic acid emulsion, polymerizable quaternary ammonium salt surfactant RPKO-O was added as an emulsifier and hydrophobic monomer, thereby forming a stronger cross-linking network, which significantly improves the water and oil resistance of the coating.

[0107] like Figure 4 As shown, the contact angle of the coated paper with water reaches 126°, indicating that the paper cup surface has excellent waterproof performance.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a biodegradable and environmentally friendly coating for the interior of a paper cup, characterized in that: Includes the following steps: Step 1: Mix 12-18 parts of long-chain amide dimethyl tertiary amine and 24-36 parts of anhydrous ethanol in a water bath under nitrogen protection. Slowly add a mixture of 3-5 parts of halopropylene and 6-10 parts of anhydrous ethanol, and then heat the mixture to react. Remove the anhydrous ethanol and unreacted halopropylene, and allow it to stand to obtain an aqueous layer. After removing the water, recrystallize and separate and purify to obtain a polymerizable quaternary ammonium salt surfactant. Step 2: Mix 70-80 parts of methacrylate monomers, 2-4 parts of silane coupling agent and 1-3 parts of acrylic monomers containing hydrophilic groups evenly to obtain solution A; Step 3: Weigh 1-2 parts of anionic emulsifier, 1-2 parts of nonionic emulsifier, 0.5-1 part of polymerizable quaternary ammonium salt surfactant, 10-20 parts of 5% polyvinyl alcohol 2688 solution, 2-4 parts of reducing agent and 100 parts of water, mix and dissolve to obtain solution B; Step 4: Weigh 2-4 portions of oxidizing agent, add water to dissolve and obtain solution C; Step 5: Add component A to component B and pre-emulsify to obtain a uniform acrylic resin pre-emulsion; Step 6: After purging nitrogen into the pre-emulsion for 1-1.5 h, slowly add solution C dropwise using a micro-injection pump, and then control the temperature to react, to obtain a biodegradable acrylic emulsion for coating the inside of paper cups. In step six, solution C is slowly added dropwise over a period of 1-2 hours, followed by maintaining the temperature at 40-50 °C for 4-5 hours. The long-chain amide dimethyl tertiary amine is oleamide dimethyl tertiary amine, erucamide dimethyl tertiary amine, or palm kernel oleamide dimethyl tertiary amine; The methacrylate monomer is methyl methacrylate; The acrylic monomer containing hydrophilic groups is one or both of hydroxyethyl acrylate and hydroxypropyl acrylate.

2. The method for preparing a biodegradable and environmentally friendly paper cup interior coating according to claim 1, characterized in that: In step one, the water bath temperature is 40-50℃, and the stirring speed is constant at 500-800 r / min; The mixture is added slowly over 3-4 hours, then the temperature is increased by 5-10 °C, and the reaction is allowed to proceed for 24-30 hours.

3. The method for preparing a biodegradable and environmentally friendly paper cup interior coating according to claim 2, characterized in that: The halogenated propylene in step one is chloropropylene or bromopropylene.

4. The method for preparing a biodegradable and environmentally friendly paper cup interior coating according to claim 3, characterized in that... In step five, the pre-emulsification is performed by stirring with a high-speed mixer at 10,000-12,000 r / min for 10-15 min.

5. The method for preparing a biodegradable and environmentally friendly paper cup interior coating according to claim 4, characterized in that: The reducing agent is one, two, or a mixture of two or more of sodium bisulfite, sodium sulfite, sodium thiosulfate, and sodium metabisulfite in any proportion.

6. The method for preparing a biodegradable and environmentally friendly paper cup interior coating according to claim 5, characterized in that: The oxidant is one, two, or a mixture of two or more of potassium persulfate, ammonium persulfate, sodium persulfate, and tert-butanol peroxide in any proportion.

7. A biodegradable and environmentally friendly paper cup interior coating prepared by the method described in claim 1.

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