Degradable food container and preparation method therefor

Abstract

The present application relates to the technical field of degradable packaging. Particularly disclosed are a degradable food container and a preparation method therefor. The degradable food container comprises a paper food container base body and a degradable coating applied on the paper food container base body, wherein the degradable coating is prepared from the following raw materials in parts by weight: 40-50 parts of polylactic acid; 10-15 parts of polybutylene succinate; 15-20 parts of polyglycolic acid; 10-20 parts of cassava starch; 5-8 parts of an external additive; 1.2-1.8 parts of montmorillonite; 0.2-0.8 parts of boron nitride nanotubes; and 1.5-2.5 parts of modified hemp fibers. The preparation method therefor comprises: heating polylactic acid, polybutylene succinate and polyglycolic acid to a molten state, then adding cassava starch and an external additive thereto, finally adding montmorillonite, boron nitride nanotubes and modified hemp fibers thereto, performing extrusion granulation, melting and then coating same on the surface of the paper food container base body, cooling same, and then cutting and forming same into a container to obtain the degradable food container. The degradable food container of the present application can exhibit excellent temperature change resistance when being subjected to temperature change caused by an external environment.

Description

Degradable meal box and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of degradable packaging, more specifically, it relates to a degradable meal box and a preparation method thereof. BACKGROUND

[0002] Meal boxes are a kind of convenient and fast food containers, commonly used in take-out, outdoor picnic, office meal and other scenes; among them, paper meal boxes refer to meal boxes made of paper materials, usually made of paper pulp. This material is very environmentally friendly and degradable. It is usually a disposable paper lunch box, which is convenient to use, low in cost, and has been widely used in the catering industry.

[0003] However, the use of paper meal boxes also has its limitations, such as not suitable for loading liquid food, poor water and oil resistance, so a thin coating is plated on the surface of the paper meal box to play the role of water and oil resistance and high temperature resistance; the coating on the surface of the paper meal box is usually synthetic plastic. As a kind of non-natural petroleum-based plastic, although it can withstand high temperature and is waterproof and oil-proof, it has no problem in packing food, dealing with cold drinks and hot drinks, but the monomers of plastic are often combined by very strong covalent bonds such as C-C bonds. It is very difficult to break this high molecular polymer chain, and the microbial degradation process and efficiency are extremely slow, so it is difficult for these high molecular polymers to be degraded by microorganisms after entering the environment.

[0004] With the continuous strengthening of environmental awareness, more and more enterprises have begun to develop environmentally friendly coating materials, among which the oil-proof paper water-based biobased degradable coating is a representative environmentally friendly coating material. The oil-proof paper water-based biobased degradable coating is processed by one or more biobased materials through a suitable method, and the main components are starch and polylactic acid and other biodegradable materials. The coating can be uniformly and firmly attached to the surface of paper, paperboard and other substrates, and can form a waterproof and oil-proof coating on the surface of paper, paperboard and other substrates. The advantages are environmentally friendly, degradable, and the impact of biodegradable substances on the environment is small, and the preparation cost is relatively low.

[0005] For the related technology in the above, the inventors believe that although the above environmentally friendly coating material has the advantages of water resistance, oil resistance, environmental protection, degradability, etc., the overall temperature resistance is poor. In the process of cooling hot food in the meal box and heating the meal box together with the food, the environmentally friendly coating material and the paper substrate are difficult to maintain stable combination, and are prone to debonding, thereby causing the application experience of the meal box to be poor.

[0006] Therefore, there is an urgent need to propose a scheme to solve the above technical problems. SUMMARY

[0007] In order to improve the temperature change resistance of the environment-friendly coating material, keep stable combination between the coating material and the paper substrate, and further improve the application quality of the meal box, the application provides a degradable meal box and a preparation method thereof.

[0008] In a first aspect, the application provides a degradable meal box, which adopts the following technical scheme:

[0009] A degradable meal box comprises a paper meal box substrate and a degradable coating layer arranged on the paper meal box substrate, wherein the degradable coating layer is made of raw materials in the following proportions by weight:

[0010] 40-50 parts of polylactic acid;

[0011] 10-15 parts of polybutylene succinate;

[0012] 15-20 parts of polyglycolic acid;

[0013] 10-20 parts of cassava starch;

[0014] 5-8 parts of an external additive;

[0015] 1.2-1.8 parts of montmorillonite;

[0016] 0.2-0.8 parts of boron nitride nanotubes;

[0017] 1.5-2.5 parts of modified hemp fibers;

[0018] The modified hemp fibers are prepared through the following modification steps:

[0019] S1, hemp fiber raw materials are immersed in deionized water at a weight ratio of 1:(25-35), and 0.8-1.5% by weight of a silane coupling agent is added to the deionized water, and after 20-30 min of immersion treatment, the pretreated hemp fibers are obtained by taking out and drying;

[0020] S2, N-acetylated acetanilide, malononitrile and potassium tert-butoxide are stirred in a DFM solvent at a molar ratio of 1:(1.1-1.3):(0.9-1.1), and after the reaction is completed, the precipitated solid is prepared into an 8-12% ethanol solution, and finally the pretreated hemp fibers are immersed in the prepared solution at a weight ratio of 1:(18-20), and after 4-6 h of immersion, the modified hemp fibers are obtained by taking out, washing with water and drying.

[0021] By adopting the technical scheme, the polylactic acid is made of lactic acid as raw material, and traditional lactic acid fermentation mostly uses starchy raw materials; the polybutylene succinate is formed by condensation polymerization of succinic acid and 1,4-butanediol, and the raw material is derived from petroleum or biological resources fermentation; the polyglycolic acid is a thermoplastic linear polyglycolic acid with good biodegradability and biocompatibility; the cassava starch not only has excellent degradability, but also contains a large amount of amylopectin, so that the cassava starch can provide stable viscosity after dispersion for the combination of each component raw material; the combination of polylactic acid, polybutylene succinate, polyglycolic acid and cassava starch can obtain a stable degradable matrix, and when other raw materials are introduced, they can form stable combination and play excellent corresponding effect.

[0022] The hemp fibers can be quickly degraded into harmless substances in the natural environment, and are natural and environmentally friendly materials. Modifying the hemp fibers can not only improve the interfacial adhesion of the hemp fibers, but also improve the thermal stability of the hemp fibers. The boron nitride nanotubes can not only improve the structural toughness of the degradable coating, but also have rapid heat conduction capacity. The montmorillonite acts as a physical crosslinking point in the degradable coating, which can inhibit the movement of molecular chains to some extent, thereby improving the thermal stability. When the montmorillonite, boron nitride nanotubes and modified hemp fibers are used in combination, they can bring excellent cooperation effect. By containing part of the boron nitride nanotubes and montmorillonite in the hollow structure of the modified hemp fibers, a stable gradient heat conduction path is formed, and the combination of the above-mentioned montmorillonite, boron nitride nanotubes and modified hemp fibers is rooted in the paper lunch box matrix by capillary action. When the temperature changes caused by the external environment, the combination of the above-mentioned montmorillonite, boron nitride nanotubes and modified hemp fibers can greatly avoid the damage of the degradable coating caused by thermal stress changes, and keep the degradable coating and the paper lunch box matrix in relatively stable combination, thereby making the degradable lunch box have excellent temperature change resistance and excellent application quality.

[0023] Preferably, the weight ratio of the montmorillonite, boron nitride nanotubes and modified hemp fibers is 1.5:0.5:2.

[0024] By adopting the above technical scheme, the montmorillonite, boron nitride nanotubes and modified hemp fibers with the above weight ratio can not only stably exert their own functions, but also form a stable combination. The combination of the montmorillonite, boron nitride nanotubes and modified hemp fibers can be uniformly dispersed in the degradable coating and fully exert its function, thereby bringing excellent and stable compounding effect, making the temperature change resistance of the degradable lunch box better, and the overall quality more excellent.

[0025] Preferably, the particle size of the montmorillonite is 50-100 nm; the diameter of the boron nitride nanotube is 45-55 nm, the length is 10-20 μm, and the specific surface area is 40-50 m 2 / g; and the single fiber fineness of the modified hemp fiber is 15-30 μm.

[0026] By using the above technical solutions, the montmorillonite, boron nitride nanotube and modified hemp fiber of the above specifications are used in combination to form a combination of montmorillonite, boron nitride nanotube and modified hemp fiber, which is uniformly dispersed in the degradable coating to exhibit better temperature change resistance. Meanwhile, in the hollow structure of the modified hemp fiber, a more uniform and clear boron nitride nanotube staggered distribution structure with montmorillonite as the staggered connection point is formed, which has better gradient thermal conduction path effect, and the combination stability of the modified hemp fiber and the paper lunch box substrate is also better, thereby making the combination between the degradable coating and the paper lunch box substrate exhibit excellent temperature change resistance, and the application quality of the degradable lunch box is better.

[0027] Preferably, the cassava starch is modified before use, and the modification treatment steps are as follows:

[0028] The cassava starch and deionized water are mixed in a ratio of 1 g:(8-10) ml, heated to 90-95℃, then cellulose is added, and after constant temperature treatment for 8-10 min, the temperature is lowered to 35-40℃, then calcium carbonate and polyvinyl alcohol are added and stirred, and finally after roller mixing, the sheet is cut into particles to obtain modified cassava starch.

[0029] In the above operation, the weight ratio of the cassava starch, cellulose, calcium carbonate and polyvinyl alcohol used is (4.5-6):(3.5-4):(2-3):1.

[0030] By using the above technical solutions, calcium carbonate can improve the stability of the modified cassava starch mixture system; cellulose has strong mechanical strength and chemical stability, and acts as a skeleton in the modified cassava starch mixture system; polyvinyl alcohol can significantly improve the viscosity and heat resistance of the modified cassava starch mixture system; and the combination of cellulose, calcium carbonate and polyvinyl alcohol for modifying cassava starch greatly improves the compatibility between modified cassava starch and other component raw materials, and to some extent, improves the combination stability between the degradable coating and the paper lunch box substrate. At the same time, the affinity and combination between modified cassava starch and modified hemp fiber are more prominent, so that the corresponding effects of the combination of montmorillonite, boron nitride nanotube and modified hemp fiber are more easily and stably achieved, thereby further improving the temperature change resistance of the degradable lunch box and further improving the overall application quality.

[0031] Preferably, the weight ratio of the cassava starch, cellulose, calcium carbonate and polyvinyl alcohol is 5.5:3.5:2.5:1.

[0032] By adopting the above technical solution, the modified cassava starch prepared by the above amount ratio of cassava starch, cellulose, calcium carbonate and polyvinyl alcohol can be closely combined with other component raw materials and fully play a role in actual application, thereby also playing a better promotion effect on the improvement of the temperature change resistance of the degradable meal box, and the overall application quality of the degradable meal box is also better.

[0033] Preferably, the external additive is one or a combination of several of fillers, thickeners and antibacterial and mildew-proof agents.

[0034] By adopting the above technical solution, the filler can improve the dimensional stability and surface finish of the degradable coating, and different fillers can also improve the overall performance of the degradable coating according to their own characteristics; the thickener can increase the viscosity and consistency of the substance, thereby improving the texture, stability and use experience of the product; the antibacterial and mildew-proof agent can inhibit or kill the growth of bacteria and mold through the dispersion of antibacterial ion antibacterial additive powder, thereby prolonging the service life of the degradable coating; and the above raw materials used as external additives can be uniformly dispersed among other component raw materials and form a stable mixed state, and can play an excellent self-effect.

[0035] Preferably, the filler is one or a combination of several of talc powder, silica powder, mica powder, whisker silicon, whisker calcium, glass fiber, titanium dioxide and glass microbeads.

[0036] Preferably, the thickener is one or a combination of several of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, sodium alginate and polyacrylamide.

[0037] Preferably, the antibacterial and mildew-proof agent is polyhexamethylene guanidine hydrochloride.

[0038] By adopting the above technical solution, the above types of fillers, thickeners and antibacterial and mildew-proof agents can be stably dispersed among other component raw materials and fully play their own roles in the mixed system of the degradable coating. At the same time, according to the actual application scene needs of the degradable meal box, a plurality of them can be selected for combination, which can further improve the product diversity of the degradable meal box.

[0039] In a second aspect, the present application provides a preparation method of a degradable meal box, which adopts the following technical solution:

[0040] A preparation method of a degradable meal box, comprising the following steps:

[0041] (1) Prepare raw materials containing polylactic acid, polybutylene succinate, polyglycolic acid, cassava starch, external additives, montmorillonite, boron nitride nanotubes and modified hemp fibers according to the proportion;

[0042] (2) Heat the polylactic acid, polybutylene succinate and polyglycolic acid in step (1) to a molten state and mix uniformly, then add cassava starch and external additives for mixing, and finally add montmorillonite, boron nitride nanotubes and modified hemp fibers for mixing, and extrude and granulate to obtain degradable coating particles;

[0043] (3) Put the paper lunch box base into the film coating machine, melt the degradable coating particles and coat them on the surface of the paper lunch box base, and then cool to form a degradable coating to obtain a coated paper;

[0044] (4) After cutting and forming the coated paper into a box, a degradable lunch box is obtained.

[0045] By using the above technical scheme, the preparation method is simple to operate, and each raw material is added step by step, which is convenient for quality control during the process, and is conducive to obtaining a degradable lunch box with stable and excellent quality, which is suitable for large-scale industrial production. At the same time, in the preparation of degradable coating particles, the polylactic acid, polybutylene succinate and polyglycolic acid are first heated and melted and mixed, then the cassava starch and external additives are added, which is conducive to obtaining a uniform and stable degradable substrate, and then the montmorillonite, boron nitride nanotubes and modified hemp fibers are added, so that the three raw materials can fully disperse and play their own roles, and also can partially combine with each other to play an excellent compounding effect, ensuring that the degradable coating and the paper lunch box base can be stably combined in a temperature change environment, thereby helping to obtain a degradable lunch box with excellent temperature change resistance.

[0046] In summary, the present application has the following advantages:

[0047] 1. The present application modifies hemp fibers and uses montmorillonite, boron nitride nanotubes and modified hemp fibers in combination, which can greatly avoid the damage of the degradable coating caused by thermal stress changes, and can maintain a relatively stable combination between the degradable coating and the paper lunch box base, thereby making the degradable lunch box exhibit excellent temperature change resistance;

[0048] 2. The present application uses cellulose, calcium carbonate and polyvinyl alcohol to modify cassava starch, which has high affinity and binding property with modified hemp fibers, so that the corresponding effect of montmorillonite, boron nitride nanotubes and modified hemp fibers can be more easily and stably achieved, and the combination stability between the degradable coating and the paper lunch box base can be further improved, thereby further improving the temperature change resistance of the degradable lunch box and improving the overall application quality. DETAILED DESCRIPTION

[0049] The present application is further described in detail below in connection with the preparation examples, examples and comparative examples.

[0050] The raw materials used in the preparation examples and examples of the present application are commercially available, except for special instructions:

[0051] The polylactic acid is purchased from Dongguan Hesheng Plastic Co., Ltd., and the model is Fengyuan FY201;

[0052] The polybutylene succinate is purchased from Shanghai Yilun Plastic Co., Ltd., and the model is PBAT ECOFLEX C1200;

[0053] The polyglycolic acid is purchased from Wuhan Shur Biological Technology Co., Ltd., and the model is XH6240MOKQ05;

[0054] The cassava starch is purchased from Dongying Huayuan Biological Technology Co., Ltd., and the model is hx-05;

[0055] The montmorillonite is purchased from Lingshou Jinfan Mineral Product Processing Factory, and the model is coating industry grade;

[0056] The boron nitride nanotube is purchased from Zhongke Leiming (Beijing) Technology Co., Ltd., and the model is BNNT-50;

[0057] The hemp fiber is purchased from Tongxiang Shangde Textile Co., Ltd., and the model is bleached hemp fiber;

[0058] The cellulose is purchased from Lingshou Yuanda Mica Factory, and the model is Yuanda Mining 01-2011;

[0059] The calcium carbonate is purchased from Lingshou Yongshun Mineral Product Processing Factory, and the model is light calcium carbonate with a specification of 800 mesh;

[0060] The polyvinyl alcohol is purchased from Shandong Yueyang New Material Co., Ltd., and the model is PVA20-99;

[0061] The paper lunch box base is purchased from Dongguan Gala Industrial Investment Co., Ltd., and the model is Russian white face cow cardboard with a thickness of 0.35 mm;

[0062] The talc powder is purchased from Lingshou Yehui Mineral Product Co., Ltd., and the model is industrial grade with a specification of 325 mesh;

[0063] The hydroxyethyl cellulose is Clariant cellulose, and the model is HS30000;

[0064] The polyhexamethylene guanidine hydrochloride is purchased from Shandong Duoli Chemical Co., Ltd., and the CAS number is 57028-96-3.

[0065] Preparation examples of raw materials and / or intermediates

[0066] Preparation example 1

[0067] A modified hemp fiber is prepared by the following modification steps:

[0068] S1, hemp fiber raw materials are immersed in deionized water at a ratio of 1:30 by weight, and 1.2% by weight of silane coupling agent is added to the deionized water, after 25 min of immersion treatment, the hemp fiber is taken out and dried to obtain pretreated hemp fiber;

[0069] S2, N-acetylaniline, malononitrile and potassium tert-butoxide are stirred in 4 times the mass of DFM solvent at a molar ratio of 1:1.2:1 for 4 h, after the reaction is completed, pour into saturated sodium chloride solution, the precipitated solid is prepared into 10% concentration ethanol solution, finally the pretreated hemp fiber is immersed in the prepared solution at a ratio of 1:19 by weight, after 5 h of immersion, take out, wash with water and dry to obtain modified hemp fiber.

[0070] Note: the silane coupling agent used is KH550 silane coupling agent.

[0071] Preparation Example 2

[0072] A modified hemp fiber is prepared by the following modification steps, which is different from Preparation Example 1:

[0073] S1, hemp fiber raw materials are immersed in deionized water at a ratio of 1:25 by weight, and 0.8% by weight of silane coupling agent is added to the deionized water, after 20 min of immersion treatment, the hemp fiber is taken out and dried to obtain pretreated hemp fiber;

[0074] S2, N-acetylaniline, malononitrile and potassium tert-butoxide are stirred in 4 times the mass of DFM solvent at a molar ratio of 1:1.1:0.9 for 4 h, after the reaction is completed, pour into saturated sodium chloride solution, the precipitated solid is prepared into 8% concentration ethanol solution, finally the pretreated hemp fiber is immersed in the prepared solution at a ratio of 1:18 by weight, after 4 h of immersion, take out, wash with water and dry to obtain modified hemp fiber.

[0075] Preparation Example 3

[0076] A modified hemp fiber is prepared by the following modification steps, which is different from Preparation Example 1:

[0077] S1, hemp fiber raw materials are immersed in deionized water at a ratio of 1:35 by weight, and 1.5% by weight of silane coupling agent is added to the deionized water, after 30 min of immersion treatment, the hemp fiber is taken out and dried to obtain pretreated hemp fiber;

[0078] S2, N-acetyacetanilide, malononitrile and potassium tert-butoxide were stirred in 4 times mass of DFM solvent at a molar ratio of 1:1.3:1.1 for 4 hours, and then poured into a saturated sodium chloride solution. The precipitated solid was prepared into a 12% ethanol solution. Finally, the pretreated hemp fibers were immersed in the prepared solution at a weight ratio of 1:20, and then taken out after 6 hours of immersion. After washing with water and drying, the modified hemp fibers were obtained.

[0079] Preparation Example 4

[0080] A modified cassava starch was prepared by the following modification steps:

[0081] Cassava starch and deionized water were mixed at a ratio of 1g:9ml, heated to 92.5℃, and then cellulose was added. After constant temperature treatment for 9 minutes, the temperature was lowered to 37.5℃, and then calcium carbonate and polyvinyl alcohol were added and stirred. Finally, after roller mixing and extrusion, the modified cassava starch was obtained.

[0082] Note: In the above operation, the weight ratio of cassava starch, cellulose, calcium carbonate and polyvinyl alcohol used was 5.5:3.5:2.5:1.

[0083] Preparation Example 5

[0084] A modified cassava starch was prepared by the following modification steps, which was different from Preparation Example 4:

[0085] Cassava starch and deionized water were mixed at a ratio of 1g:8ml, heated to 90℃, and then cellulose was added. After constant temperature treatment for 8 minutes, the temperature was lowered to 35℃, and then calcium carbonate and polyvinyl alcohol were added and stirred. Finally, after roller mixing and extrusion, the modified cassava starch was obtained.

[0086] Preparation Example 6

[0087] A modified cassava starch was prepared by the following modification steps, which was different from Preparation Example 4:

[0088] Cassava starch and deionized water were mixed at a ratio of 1g:10ml, heated to 95℃, and then cellulose was added. After constant temperature treatment for 10 minutes, the temperature was lowered to 40℃, and then calcium carbonate and polyvinyl alcohol were added and stirred. Finally, after roller mixing and extrusion, the modified cassava starch was obtained.

[0089] Preparation Example 7

[0090] A modified cassava starch was prepared by the following modification steps, which was different from Preparation Example 4:

[0091] Preparation Example 8

[0092] A modified tapioca starch, which is different from Preparation Example 4 in that the weight ratio of tapioca starch, cellulose, calcium carbonate, and polyvinyl alcohol is 6:4:3:1.

[0093] Preparation Example 9

[0094] A modified tapioca starch, which is different from Preparation Example 4 in that the weight ratio of tapioca starch, cellulose, calcium carbonate, and polyvinyl alcohol is 5.25:4.25:2.5:1.

[0095] Example 1

[0096] A degradable meal box, comprising a paper meal box base body and a degradable coating layer disposed on the paper meal box base body, the raw materials used for preparing the degradable coating layer and their respective weights are shown in Table 1, and the degradable meal box is prepared by the following steps:

[0097] (1) Prepare raw materials including polylactic acid, polybutylene succinate, polyglycolic acid, tapioca starch, external additives, montmorillonite, boron nitride nanotubes, and modified hemp fibers according to the proportion;

[0098] (2) Put the polylactic acid, polybutylene succinate, and polyglycolic acid in step (1) into a banbury mixer, heat to a molten state, and mix uniformly, then add tapioca starch and external additives for banbury mixing for 10 minutes, and finally add montmorillonite, boron nitride nanotubes, and modified hemp fibers for banbury mixing for 20 minutes, and then extrude and granulate to obtain degradable coating particles;

[0099] (3) Put the paper meal box base body into a film coating machine, melt the degradable coating particles, and coat them on the surface of the paper meal box base body, the coating temperature is 150°C, and after cooling, a degradable coating layer is formed to obtain a coated paper;

[0100] (4) After cutting and forming the coated paper into a box, a degradable meal box is obtained.

[0101] Note: The modified hemp fibers used are obtained from Preparation Example 1; the particle size of the montmorillonite is 75 nm; the diameter of the boron nitride nanotubes is 50 nm, the length is 15 μm, and the specific surface area is 45 m 2 / g; the single fiber fineness of the modified hemp fibers is 22.5 μm; the external additives are a combination of fillers, thickeners, and antibacterial and mildew-proof agents in a weight ratio of 8:3:1, the fillers are talc, the thickeners are hydroxyethyl cellulose, and the antibacterial and mildew-proof agent is polyhexamethylene guanidine hydrochloride.

[0102] Examples 2-3

[0103] A degradable meal box, which differs from example 1 in that the raw materials used for its preparation and their corresponding weights are shown in table 1, Table 1 Raw materials used for degradability and their corresponding weights (kg / portion) in examples 1-3

[0104]

[0105] Example 4

[0106] A degradable meal box, which differs from example 1 in that the particle size of the montmorillonite is 50 nm; the diameter of the boron nitride nanotube is 45 nm, the length is 10 μm, and the specific surface area is 40 m 2 / g; the single fiber fineness of the modified hemp fiber is 15 μm.

[0107] Example 5

[0108] A degradable meal box, which differs from example 1 in that the particle size of the montmorillonite is 100 nm; the diameter of the boron nitride nanotube is 55 nm, the length is 20 μm, and the specific surface area is 50 m 2 / g; the single fiber fineness of the modified hemp fiber is 30 μm.

[0109] Example 6

[0110] A degradable meal box, which differs from example 1 in that the total amount of montmorillonite, boron nitride nanotube and modified hemp fiber is unchanged, and the weight ratio of the three is adjusted to 1.5:0.5:2.

[0111] Example 7

[0112] A degradable meal box, which differs from example 1 in that the modified hemp fiber is obtained from preparation example 2.

[0113] Example 8

[0114] A degradable meal box, which differs from example 1 in that the modified hemp fiber is obtained from preparation example 3.

[0115] Example 9

[0116] A degradable meal box, which differs from example 1 in that the cassava starch is replaced with modified cassava starch, and the modified cassava starch is obtained from preparation example 4.

[0117] Example 10

[0118] A degradable meal box, which differs from example 9 in that the modified cassava starch is obtained from preparation example 5.

[0119] Example 11

[0120] A degradable meal box, which is different from Example 9 in that the modified tapioca starch is obtained from Preparation Example 6.

[0121] Example 12

[0122] A degradable meal box, which is different from Example 9 in that the modified tapioca starch is obtained from Preparation Example 7.

[0123] Example 13

[0124] A degradable meal box, which is different from Example 9 in that the modified tapioca starch is obtained from Preparation Example 9.

[0125] Example 14

[0126] A degradable meal box, which is different from Example 9 in that the modified tapioca starch is obtained from Preparation Example 9.

[0127] Example 15

[0128] A degradable meal box, which is different from Example 1 in that the particle size of the montmorillonite is 45 nm; the diameter of the boron nitride nanotube is 40 nm, the length is 8 μm, and the specific surface area is 38 m 2 / g; the single fiber fineness of the modified hemp fiber is 13 μm.

[0129] Example 16

[0130] A degradable meal box, which is different from Example 1 in that the particle size of the montmorillonite is 1.5 nm; the diameter of the boron nitride nanotube is 60 nm, the length is 22 μm, and the specific surface area is 52 m 2 / g; the single fiber fineness of the modified hemp fiber is 32 μm.

[0131] Comparative Example

[0132] Comparative Example 1

[0133] A degradable meal box, which is different from Example 1 in that the montmorillonite and the boron nitride nanotube are not used in the degradable coating.

[0134] Comparative Example 2

[0135] A degradable meal box, which is different from Example 1 in that the montmorillonite and the modified hemp fiber are not used in the degradable coating.

[0136] Comparative Example 3

[0137] A degradable meal box, which is different from Example 1 in that the boron nitride nanotube and the modified hemp fiber are not used in the degradable coating.

[0138] Comparative Example 4

[0139] A degradable meal box, which is different from Example 1 in that montmorillonite is not used in the degradable coating.

[0140] Comparative Example 5

[0141] A degradable meal box, which is different from Example 1 in that boron nitride nanotubes are not used in the degradable coating.

[0142] Comparative Example 6

[0143] A degradable meal box, which is different from Example 1 in that modified hemp fibers are not used in the degradable coating.

[0144] Comparative Example 7

[0145] A degradable meal box, which is different from Example 1 in that montmorillonite, boron nitride nanotubes and modified hemp fibers are not used in the degradable coating.

[0146] Performance detection test

[0147] Test samples: The degradable meal boxes obtained in Examples 1-16 and Comparative Examples 1-7 were used as test samples 1-16 and control samples 1-7, and the thickness of the paper meal box substrate was 0.35 mm, and the thickness of the degradable coating was 0.08 mm.

[0148] Test method: The test samples 1-16 and control samples 1-7 were taken, and the MK-B-90X electric peel strength tester was used to test the peel strength, and the test standard of the peel strength should refer to GB / T8808-1988 "Peel test method for soft composite plastic materials", each sample was tested three times, and the average value was recorded as A;

[0149] The test samples 1-16 and control samples 1-7 were placed in a temperature alternating test box, first heated to 100°C at 5°C / min, then cooled to 10°C at 2°C / min, and after 3 cycles, the peel strength test was performed after natural recovery to room temperature, and the test standard of the peel strength should refer to GB / T8808-1988 "Peel test method for soft composite plastic materials", each sample was tested three times, and the average value was recorded as B;

[0150] The peel strength loss rate of each sample was calculated, the peel strength loss rate (%) = (A-B) / A, and then the test samples 1-16 and control samples 1-7 were recorded in Table 2.

[0151]

[0152]

[0153] It can be seen from the combination of embodiments 1-3 and comparative examples 1-7 and table 2 that the combination of montmorillonite, boron nitride nanotubes and modified hemp fibers in the degradable coating can make the degradable coating exhibit strong temperature change resistance, maintain stable adhesion with the paper lunch box substrate, and is not prone to large peel strength loss. The peel strength loss rate obtained by testing is also relatively small. At the same time, if only any one or two of montmorillonite, boron nitride nanotubes and modified hemp fibers are used in the degradable coating, the improvement of the temperature change resistance of the degradable coating is limited, and the combination of any two can only bring simple addition of the improvement effect, and only when the three are used together, a significant improvement effect of 1+1>2 can be brought.

[0154] It can be seen from the combination of embodiments 1 and 4-5 and table 2 that the particle size of montmorillonite is 50-100 nm; the diameter of boron nitride nanotubes is 45-55 nm, the length is 10-20 pm, and the specific surface area is 40-50 m 2 / g; the single fiber fineness of the modified hemp fiber is 15-30 pm; all of which can ensure that montmorillonite, boron nitride nanotubes and modified hemp fiber cooperate stably and exert excellent corresponding effects, so that the combination between the degradable coating and the paper lunch box substrate exhibits excellent temperature change resistance. In combination with embodiments 15-16 and table 2, it can be seen that if the montmorillonite, boron nitride nanotubes and modified hemp fiber exceed the above specification range, the peel strength loss rate obtained by testing will be significantly increased.

[0155] It can be seen from the combination of embodiments 1 and 9-11 and table 2 that the use of cellulose, calcium carbonate and polyvinyl alcohol to modify cassava starch in combination can further improve the stability of the combination between the degradable coating and the paper lunch box substrate, so that the temperature change resistance of the degradable lunch box is further improved. In combination with embodiments 12-14 and table 2, it can be seen that when the weight ratio of cassava starch, cellulose, calcium carbonate and polyvinyl alcohol is 5.5:3.5:2.5:1 in the preparation of modified cassava starch, the improvement of the temperature change resistance of the degradable lunch box can exert a better improvement effect, and the peel strength loss rate measured is also relatively small.

[0156] This specific embodiment is only an explanation of the application, and is not a limitation of the application. Those skilled in the art can make modifications to the embodiment without creative contribution after reading the specification, but as long as it is within the scope of the claims of the application, it is protected by the patent law.

Claims

1. A degradable meal box, characterized in that, The paper lunch box base and the degradable coating placed on the paper lunch box base are prepared from the following raw materials by weight: Polylactic acid 40-50 parts; Polybutylene succinate 10-15 parts; Polyglycolic acid 15-20 parts; Cassava starch 10-20 parts; External additives 5-8 parts; Montmorillonite 1.2-1.8 parts; Boron nitride nanotube 0.2-0.8 parts; Modified hemp fiber 1.5-2.5 parts; The modified hemp fiber is prepared by the following modification steps: S1, the hemp fiber raw material is immersed in deionized water at a weight ratio of 1:(25-35), and 0.8-1.5% by weight of silane coupling agent is added to the deionized water, after 20-30min of immersion treatment, take out and dry, get pretreated hemp fiber; S2, take N-acetylacetanilide, malononitrile and potassium tert-butoxide according to the molar ratio of 1:(1.1-1.3):(0.9-1.1) in DFM solvent Stirring reaction, after the reaction is completed, pour into saturated sodium chloride solution, the solid precipitated is prepared into 8-12% concentration ethanol solution, finally the pretreated hemp fiber is immersed in the prepared solution at a weight ratio of 1:(18-20), after 4-6h of immersion, take out, wash with water and dry, get modified hemp fiber; The external additives are a combination of fillers, thickeners and antibacterial and mildew-proof agents at a weight ratio of 8:3:1, the fillers are talc, the thickeners are hydroxyethyl cellulose, and the antibacterial and mildew-proof agents are polyhexamethylene guanidine hydrochloride.

2. The degradable meal box according to claim 1, characterized in that: The weight ratio of the montmorillonite, boron nitride nanotube and modified hemp fiber is 1.5:0.5:

2.

3. The degradable meal box according to claim 1, characterized in that: The particle size of the montmorillonite is 50-100 nm; the diameter of the boron nitride nanotube is 45-55 nm, the length is 10-20 μm, and the specific surface area is 40-50 m 2 / g; and the single fiber fineness of the modified hemp fiber is 15-30 μm.

4. The degradable meal box according to claim 1, characterized in that: The cassava starch is modified before use, and the modification steps are as follows: Take cassava starch and deionized water at a ratio of 1g:(8-10)ml, heat to 90-95℃, then add cellulose, constant temperature treatment for 8-10min, then cool to 35-40℃, then add calcium carbonate and polyvinyl alcohol and stir, finally roll and mix, sheet and cut, get modified cassava starch; In the above modification process, the weight ratio of the cassava starch, cellulose, calcium carbonate and polyvinyl alcohol used is (4.5-6):(3.5-4):(2-3):

1.

5. The degradable meal box according to claim 4, characterized in that: The weight ratio of the cassava starch, cellulose, calcium carbonate and polyvinyl alcohol is 5.5:3.5:2.5:

1.

6. The degradable meal box according to claim 1, characterized in that: The external additives are a combination of one or more of fillers, thickeners and antibacterial and mildew-proof agents.

7. The degradable meal box according to claim 6, characterized in that: The fillers are a combination of one or more of talc, silica powder, mica powder, whisker silicon, whisker calcium, glass fiber, titanium dioxide and glass beads.

8. The degradable meal box according to claim 6, characterized in that: The thickeners are a combination of one or more of carboxymethyl cellulose sodium, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, sodium alginate and polyacrylamide.

9. The degradable meal box according to claim 6, characterized in that: The antibacterial and mildew-proof agent is polyhexamethylene guanidine hydrochloride.

10. The method of claim 1, wherein: The following steps are included: (1) Prepare raw materials including polylactic acid, polybutylene succinate, polyglycolic acid, cassava starch, external additives, montmorillonite, boron nitride nanotube and modified hemp fiber according to the proportion; (2) The polylactic acid, polybutylene succinate and polyglycolic acid in step (1) are heated to a molten state and mixed uniformly, then cassava starch and an external additive are added and mixed, and finally montmorillonite, boron nitride nanotubes and modified hemp fibers are added and mixed, and the degradable coating particles are prepared by extrusion granulation; (3) The paper lunch box substrate is sent into a film laminating machine, and the degradable coating particles are melted and laminated on the surface of the paper lunch box substrate, and after cooling, a degradable coating is formed to obtain a coated paper; (4) After cutting and forming into a box, a degradable lunch box is obtained.

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