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

Abstract

The invention relates to the technical field of environment-friendly materials and preparation thereof, in particular to a degradable environment-friendly paper cup interior coating and a preparation method thereof. The method comprises the following steps: firstly synthesizing a polymerizable quaternary ammonium salt surfactant (RPKO-X), and then simultaneously introducing the polymerizable quaternary ammonium salt surfactant and a bio-based polymer solution into a polyacrylate molecular chain in a redox-initiated polymerization manner, so as to obtain the degradable acrylate emulsion for coating the interior of the paper cup. The hydrophobic monomer RPKO-X with the characteristics of an emulsifier is introduced to form a stronger cross-linked network, so that the water resistance and oil resistance of the coating can be remarkably improved, and meanwhile, the environment friendliness of the coating is enhanced and the rapid degradation of the coating after use is promoted by utilizing the introduction of the bio-based material polyvinyl alcohol 2688. A polymerization system is initiated through redox, the method is simple in preparation and can be prepared under mild conditions, and the emulsion is uniform and stable in particle size.

Description

Technical Field

[0001] The invention relates to the technical field of environmentally friendly materials and preparation thereof, and in particular to a degradable environmentally friendly paper cup inner coating and a preparation method thereof. Background Art

[0002] Paper cups are made of paper and are lightweight and easy to carry. They are widely used in restaurants, fast food restaurants, and popular tea shops to hold cold and hot drinks. The inner wall of these paper cups is usually coated with a layer of polyethylene (PE) plastic film. The PE material is evenly coated on the inner wall of the paper cup through PE coating technology to achieve waterproof and leak-proof functions, thereby ensuring that the paper cup is not easy to leak when holding liquids and maintains its structural strength. However, with the increasing global awareness of environmental protection, the problem of plastic pollution has become more serious. Traditional PE coatings are not only difficult to degrade, but also may have long-term negative effects on soil, water sources and organisms after the accumulation of plastic waste.

[0003] In view of the above problems, the research on biodegradable materials as internal coatings for paper cups has gradually attracted attention, especially coatings based on bio-based materials, which are favored because of their wide sources and environmental friendliness. Biodegradable materials such as polylactic acid (PLA), polyhydroxyalkanoates (PHA), and starch-based materials have shown good application prospects in many fields.

[0004] The document with application number "202280086854.9" discloses "a bio-based coating and a method for forming and using the same", which is a degradable bio-based coating that can be used, for example, for 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, fabric, concrete or metal. However, due to the high cost of raw materials, the production cost of bio-based materials is high; under some extreme environmental conditions, the performance of bio-based coatings (such as temperature resistance, chemical resistance, etc.) is not ideal, which limits its application range.

[0005] Therefore, it is particularly important to develop a biodegradable and environmentally friendly paper cup interior coating with excellent performance and strong environmental adaptability. Summary of the invention

[0006] The purpose of the present invention is to provide a novel method for preparing a novel degradable and environmentally friendly paper cup internal coating, so as to solve the problems in the prior art that the production cost of bio-based materials is high due to the high cost of raw materials; and under some extreme environmental conditions, the performance of the bio-based coating is not ideal, which limits its application scope.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing a degradable and environmentally friendly paper cup internal coating, comprising the following steps:

[0008] Step 1, 12-18 parts of long carbon chain amido dimethyl tertiary amine and 24-36 parts of anhydrous ethanol, stirring in a water bath, passing nitrogen protection, slowly dropwise adding a mixture of 3-5 parts of halogenated propylene and 6-10 parts of anhydrous ethanol, and then heating to react; removing anhydrous ethanol and unreacted halogenated propylene, standing to obtain a water layer; after removing water, recrystallizing, separating and purifying to obtain a polymerizable quaternary ammonium salt surfactant RPKO-X, wherein X is 16, 18 or 21;

[0009] Step 2: 70-80 parts of methacrylate monomer, 2-4 parts of silane coupling agent and 1-3 parts of acrylic monomer containing hydrophilic group are mixed uniformly to prepare solution A;

[0010] Step 3, weigh 1-2 parts of anionic emulsifier, 1-2 parts of nonionic emulsifier, 0.5-1 parts 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 to mix and dissolve to obtain solution B;

[0011] Step 4: Weigh 2-4 parts of oxidant and dissolve it in water to obtain solution C;

[0012] Step 5, adding component A to component B, pre-emulsifying to obtain a uniform acrylic resin pre-emulsion;

[0013] Step 6: After nitrogen is introduced into the pre-emulsion for 1-1.5 hours, solution C is slowly added dropwise using a micro-injection pump, and then the temperature is controlled to react to obtain a degradable acrylic emulsion for coating the inside of a paper cup.

[0014] Furthermore, in the above step 1, the water bath temperature is 40-50° C., and the stirring speed is constant at 500-800 r / min.

[0015] Furthermore, in the above step 1, the mixed solution is slowly added dropwise for 3-4 hours, and then the temperature is raised by 5-10° C. and the reaction is carried out for 24-30 hours.

[0016] Furthermore, in the above step 5, the pre-emulsification is carried out by stirring with a high-speed stirrer at 10000-12000 r / min for 10-15 min.

[0017] Furthermore, in the above step six, the time for slowly adding solution C is 1-2 hours, and then the temperature is controlled to 40-50° C. and the reaction is kept warm for 4-5 hours.

[0018] Furthermore, the halogenated propene in the above step 1 is allyl chloride or allyl bromide.

[0019] Furthermore, in the above step 2, the acrylic monomer containing a hydrophilic group is one of hydroxyethyl acrylate, hydroxypropyl acrylate, dihydroxyethyl acrylate, polyethylene glycol acrylate, acetamide acrylate, and formamide acrylate, or a mixture of two or more of them in any ratio.

[0020] Furthermore, the reducing agent is one of sodium bisulfite, sodium sulfite, sodium thiosulfate, and sodium metabisulfite, or a mixture of two or more of them in any ratio.

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

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

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The intermediate product of the present invention, the functional monomer polymerizable quaternary ammonium salt surfactant RPKO-X, can be introduced into the subsequent process of synthesizing the emulsion as both an emulsifier and a hydrophobic monomer, and can form a stronger cross-linked network during the polymerization process, thereby enhancing the cross-linking degree of the film and reducing the permeability of the film to water and oil, thereby effectively improving its water resistance, oil resistance and heat resistance.

[0025] (2) The present invention increases the degradation rate of the coating after use by introducing bio-based polymer materials during the synthesis process, and can be biodegraded under natural conditions, reducing environmental pollution and reducing the impact on the environment, which meets the requirements of sustainable development. At the same time, the cross-linked structure formed by the polymerizable quaternary ammonium salt surfactant RPKO-X in the polymerization reaction, combined with the bio-based polymer, can significantly enhance the mechanical strength and toughness of the coating; the bio-based polymer, as a supplement to the cross-linking point, can also enhance the crack resistance and wear resistance of the coating and extend the service life of the product.

[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 to not only resist water penetration, but also maintain stability in an oily environment, significantly improving the chemical resistance of the coating.

[0027] (4) The preparation process of the present invention is simple. A 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 speed of the oxidant solution C using a microinjection pump, so that the prepared emulsion particles are uniform and stable. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0030] (A) Surface morphology of a blank paper sample without surface coating (500 times), (B) SEM image of the coating prepared in Comparative Example 1 evenly coated on paper (500 times), (C) SEM image of the coating prepared in Comparative Example 2 evenly coated on paper (500 times), (D) SEM image of the coating prepared in Example 6 evenly coated on paper (500 times);

[0031] Figure 3 This is the water and salt resistance test diagram:

[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 It is the static contact angle of water on the coated paper. DETAILED DESCRIPTION

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

[0037] The invention provides a method for preparing a degradable and environment-friendly paper cup interior coating. The design idea is: firstly, a polymerizable quaternary ammonium salt surfactant (RPKO-X) is synthesized, and then the polymerizable quaternary ammonium salt surfactant and a bio-based polymer solution are simultaneously introduced into a polyacrylate molecular chain by redox-initiated polymerization, thereby obtaining a degradable acrylic emulsion for coating the interior of a paper cup.

[0038] Embodiment 1, a method for preparing a degradable and environmentally friendly paper cup inner coating, 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, a thermometer, a reflux condenser and a nitrogen protection device, place it in a 40°C water bath and stir at a constant speed of 500r / min, pass nitrogen protection, drop 5 parts of a mixture of propylene chloride and 10 parts of ethanol, the drop time is 3h, heat to 50°C, and keep warm for 24h. Remove the solvent anhydrous ethanol by rotary evaporation, add water to wash away a small amount of unreacted propylene chloride, let it stand in a separatory funnel, separate the oil layer, obtain the water layer, remove the water by vacuum distillation, recrystallize with ethyl acetate / ethanol, separate and purify to obtain the polymerizable quaternary ammonium salt surfactant RPKO-O (X is 18);

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

[0041] Step 3, weigh 2 parts of SDS, 2 parts of OP-10, 1 part of RPKO-O, 10 parts of 5% polyvinyl alcohol 2688 solution, 3 parts of sodium bisulfite and 100 parts of water, and mix and dissolve 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 with a high-speed stirrer at 11000 r / min for 10 minutes to obtain a uniform acrylic resin pre-emulsion;

[0044] Step 6: After nitrogen is introduced into the pre-emulsion for 1 hour, solution C is added dropwise using a microinjection pump, the temperature is controlled at 50° C., and the reaction is continued for 4 hours to obtain a degradable acrylic emulsion for coating the inside of paper cups.

[0045] Embodiment 2, a method for preparing a degradable and environmentally friendly paper cup inner coating, comprising the following steps:

[0046] Step 1: Place 18 parts of erucic acid amide dimethyl tertiary amine and 36 parts of ethanol in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen protection device, place it in a 40°C water bath and stir at a constant speed of 500r / min, pass nitrogen protection, drop 4 parts of propylene chloride and 8 parts of ethanol mixed solution, the drop time is 3h, heat to 50°C, and keep warm for 24h. Remove the solvent anhydrous ethanol by rotary evaporation, add water to wash away a small amount of unreacted propylene chloride, let it stand in a separatory funnel, separate the oil layer, obtain the water layer, remove the water by vacuum distillation, recrystallize with ethyl acetate / ethanol, separate and purify to obtain the polymerizable quaternary ammonium salt surfactant RPKO-O (X is 18);

[0047] Step 2: 80 parts of methyl methacrylate, 2 parts of KH-550, 2 parts of hydroxypropyl acrylate and 1 part of dihydroxyethyl acrylate are mixed uniformly to prepare solution A;

[0048] Step 3, weigh 2 parts of SDS, 2 parts of OP-10, 1 part of RPKO-O, 10 parts of 5% polyvinyl alcohol 2688 solution, 3 parts of sodium bisulfite and 100 parts of water, and mix and dissolve 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 of Example 1;

[0051] Step 6: Same as step 6 of embodiment 1.

[0052] Embodiment 3, a method for preparing a degradable and environmentally friendly paper cup inner coating, 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, a thermometer, a reflux condenser and a nitrogen protection device, place in a 40°C water bath and stir at a constant speed of 500r / min, pass nitrogen protection, drop 3 parts of a mixture of propylene chloride and 6 parts of ethanol, the drop time is 3h, heat to 50°C, and keep warm for 24h. Remove the solvent anhydrous ethanol by rotary evaporation, add water to wash off a small amount of unreacted propylene chloride, let it stand in a separatory funnel, separate the oil layer, obtain the water layer, remove the water by vacuum distillation, recrystallize with ethyl acetate / ethanol, separate and purify to obtain the polymerizable quaternary ammonium salt surfactant RPKO-H (X is 16);

[0054] Step 2: 70 parts of methyl methacrylate, 2 parts of KH-550, 1 part of hydroxyethyl acrylate and 2 parts of acetamide acrylate were mixed uniformly to prepare solution A;

[0055] Step 3, weigh 2 parts of SDS, 2 parts of OP-10, 1 part of RPKO-H, 10 parts of 5% polyvinyl alcohol 2688 solution, 3 parts of sodium bisulfite and 100 parts of water, and mix and dissolve 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 of Example 1;

[0058] Step 6: Same as step 6 of embodiment 1.

[0059] Embodiment 4, a method for preparing a degradable and environmentally friendly paper cup inner coating, comprising the following steps:

[0060] Step 1, same as in Example 1;

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

[0062] Step 3, weigh 1.5 parts of SDS, 1.5 parts of OP-10, 1 part of RPKO-O, 20 parts of 5% polyethanol 2688 solution, 3 parts of sodium bisulfite and 100 parts of water, and mix and dissolve 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 of Example 1;

[0065] Step 6: Same as step 6 of embodiment 1.

[0066] Embodiment 5, a method for preparing a degradable and environmentally friendly paper cup inner coating, comprising the following steps:

[0067] Step 1, same as in Example 2;

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

[0069] Step 3, weigh 1.5 parts of SDS, 1.5 parts of OP-10, 1 part of RPKO-E, 20 parts of 5% polyethanol 2688 solution, 2 parts of sodium bisulfite and 100 parts of water, and mix and dissolve 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 of Example 1;

[0072] Step 6: Same as step 6 of embodiment 1.

[0073] Example 6, a method for preparing a degradable and environmentally friendly paper cup inner coating, comprising the following steps:

[0074] Step 1, same as in Example 1;

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

[0076] Step 3, weigh 1.5 parts of SDS, 1.5 parts of OP-10, 1 part of RPKO-O, 15 parts of 5% polyvinyl alcohol 2688, 2-4 parts of sodium bisulfite and 100 parts of water, and mix and dissolve 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 of Example 1;

[0079] Step 6: Same as step 6 of embodiment 1.

[0080] Embodiment 7, a method for preparing a degradable and environmentally friendly paper cup inner coating, comprising the following steps:

[0081] Step 1, same as in Example 3;

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

[0083] Step 3, weigh 1.5 parts of SDS, 1.5 parts of OP-10, 1 part of RPKO-H, 15 parts of 5% hydroxypropyl cellulose, 2-4 parts of sodium bisulfite and 100 parts of water, and mix and dissolve them 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 of Example 1;

[0086] Step 6: Same as step 6 of embodiment 1.

[0087] Comparative Example 1

[0088] Step 1, same as Example 6;

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

[0090] Step 3: Weigh 1.5 parts of SDS, 1.5 parts of OP-10, 1 part of RPKO-O, 2-4 parts of sodium bisulfite and 100 parts of water, mix and dissolve to obtain solution B; the difference from Example 6 is that no bio-based polymer solution is 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 with a high-speed stirrer at 11000 r / min for 10 minutes to obtain a uniform acrylic resin pre-emulsion;

[0093] Step 6: After nitrogen is introduced into the pre-emulsion for 1 hour, solution C is added dropwise using a microinjection pump, the temperature is controlled at 50° C., and the reaction is continued for 4 hours to obtain a degradable acrylic emulsion for coating the inside of paper cups.

[0094] Comparative Example 2

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

[0096] Step 2: weigh 1.5 parts of SDS, 1.5 parts of OP-10, 15 parts of polyvinyl alcohol 2688 with a mass concentration of 5%, 2-4 parts of sodium bisulfite and 100 parts of water, and mix and dissolve them 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 is not used;

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

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

[0099] Step 5: After nitrogen is introduced into the pre-emulsion for 1 hour, solution C is added dropwise using a microinjection pump, the temperature is controlled at 50° C., and the reaction is continued for 4 hours to obtain a degradable acrylic emulsion for coating the inside of paper cups.

[0100] Taking Example 6 as the best embodiment, performance test was performed on it:

[0101] Experimental Example 1

[0102] The emulsions prepared in Comparative Example 1, Comparative Example 2 and Example 6 were diluted to a mass fraction of 1%, and the particle size distribution and Zeta potential of the composite emulsions were measured using a Mastersizer 2000 Malvern laser particle size analyzer. Figure 1 ,from Figure 1 It can be seen that when polyacrylic acid resin emulsion is synthesized, the particle size distribution becomes narrower when polyvinyl alcohol and RPKO-O are introduced into it at the same time. This is because the molecular chain of polyvinyl alcohol is relatively long, and the winding and stretching of its molecular chain in the emulsion system are complex and uneven. Some emulsion particles may be wrapped by more polyvinyl alcohol chains, and the steric hindrance is strong and relatively dispersed. Polyvinyl alcohol provides good steric hindrance, and the alkyl carbon chain in the polymerizable quaternary ammonium salt surfactant RPKO-O maintains a stable electrostatic repulsion between particles through appropriate charge distribution. The combined effect of the two makes the emulsion particles more evenly dispersed, effectively limiting the agglomeration of particles and the uneven size, which may narrow the particle size distribution.

[0103] Experimental Example 2

[0104] The emulsions prepared in Comparative Example 1, Comparative Example 2 and Example 6 were evenly coated on paper and placed in a 40°C oven for drying for 24 hours. The samples were then laid flat on the conductive adhesive, sprayed with gold, and fixed on a stage. The surface morphology was analyzed and observed using a FEIQ45+EDXOctane Prime scanning electron microscope (SEM) from FEI and EDAX of the United States. The scanning voltage was selected to be 15 kV. The specific test results are shown in the figure. Figure 2 ,from Figure 2 It can be seen that the paper is relatively rough before the surface is coated, but becomes smooth after coating. The surface of the paper treated with the coating prepared by the present invention is the smoothest. This is because the alkyl chain of the polymerizable quaternary ammonium salt surfactant RPKO-O used in the present invention can form a stronger cross-linking network during the polymerization process, so that the emulsion coated on the paper has a higher cross-linking density, and the film finally formed is denser and exhibits better smoothness.

[0105] Experimental Example 3

[0106] The emulsions prepared in Comparative Example 1, Comparative Example 2 and Example 6 were evenly coated on paper and placed in a 40°C oven for drying for 24 hours. Dyed 90°C hot water, white oil and coffee were dripped on the surface of the paper to test its water and oil resistance. The 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, and the water and oil resistance of Comparative Example 1 and Example 6 are better than that of Example 2. This is because in the process of synthesizing the polyacrylic acid emulsion, the polymerizable quaternary ammonium salt surfactant RPKO-O is added as an emulsifier and a hydrophobic monomer, thereby forming a stronger cross-linked network, which significantly improves the water resistance and oil resistance of the coating.

[0107] like Figure 4 As shown in the figure, the contact angle of the paper treated with the coating to water is up to 126°, indicating that the surface of the paper cup has excellent waterproof performance.

[0108] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a degradable and environmentally friendly paper cup internal coating, characterized in that: The following steps are involved: Step 1, 12-18 parts of long carbon chain amido dimethyl tertiary amine and 24-36 parts of anhydrous ethanol, stirring in a water bath, passing nitrogen protection, slowly dropwise adding a mixture of 3-5 parts of halogenated propylene and 6-10 parts of anhydrous ethanol, and then heating to react; removing anhydrous ethanol and unreacted halogenated propylene, standing to obtain a water layer; after removing water, recrystallizing, separating and purifying to obtain a polymerizable quaternary ammonium salt surfactant RPKO-X, wherein X is 16, 18 or 21; Step 2: 70-80 parts of methacrylate monomer, 2-4 parts of silane coupling agent and 1-3 parts of acrylic monomer containing hydrophilic group are mixed uniformly to prepare solution A; Step 3, weigh 1-2 parts of anionic emulsifier, 1-2 parts of nonionic emulsifier, 0.5-1 parts 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, and mix and dissolve to obtain solution B; Step 4: Weigh 2-4 parts of oxidant and dissolve it in water to obtain solution C; Step 5, adding component A to component B, pre-emulsifying to obtain a uniform acrylic resin pre-emulsion; Step 6: After nitrogen is introduced into the pre-emulsion for 1-1.5 h, solution C is slowly added dropwise using a micro-injection pump, and then the temperature is controlled to react to obtain a degradable acrylic emulsion for coating the inside of a paper cup.

2. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 1, characterized in that: In the step 1, the water bath temperature is 40-50° C., and the stirring speed is constant at 500-800 r / min.

3. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 1, characterized in that: In the step 1, the mixed solution is slowly added dropwise for 3-4 hours, and then the temperature is raised by 5-10°C and the reaction is carried out for 24-30 hours.

4. A method for preparing a degradable and environmentally friendly paper cup internal coating according to any one of claims 1 to 3, characterized in that: In the step 5, the pre-emulsification is carried out by stirring with a high-speed stirrer at 10000-12000 r / min for 10-15 min.

5. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 4, characterized in that: In the step six, the time for slowly adding solution C is 1-2 hours, and then the temperature is controlled at 40-50° C. and the reaction is kept warm for 4-5 hours.

6. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 5, characterized in that: The halogenated propene in step 1 is allyl chloride or allyl bromide.

7. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 6, characterized in that: In the step 2, the acrylic monomer containing a hydrophilic group is one of hydroxyethyl acrylate, hydroxypropyl acrylate, dihydroxyethyl acrylate, polyethylene glycol acrylate, acetamide acrylate, and formamide acrylate, or a mixture of two or more of them in any ratio.

8. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 7, characterized in that: The reducing agent is one of sodium bisulfite, sodium sulfite, sodium thiosulfate and sodium metabisulfite, or a mixture of two or more of them in any proportion.

9. The method for preparing a degradable and environmentally friendly paper cup internal coating according to claim 8, characterized in that: The oxidant is one of potassium persulfate, ammonium persulfate, sodium persulfate, and tert-butyl peroxide, or a mixture of two or more of them in any proportion.

10. A degradable and environmentally friendly paper cup interior coating prepared according to the preparation method of claim 1.

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