Temperature-resistant and oil-resistant degradable meal box film, meal box and preparation method

Abstract

The application relates to the technical field of composite films, and provides a temperature-resistant and oil-resistant degradable meal box film, a meal box and a preparation method. The preparation raw materials of the three layers in the degradable meal box film are strictly controlled, so that the obtained meal box film has good temperature resistance and oil resistance, high mechanical properties and low haze; meanwhile, the degradable master batch is added in the outer layer, the middle layer and the inner layer, so that the traditional plastics, polypropylene and ethylene-vinyl acetate copolymer, are converted into a new generation of biodegradable plastics which are non-toxic and harmless to nature, the obtained degradable meal box film can be completely degraded into carbon dioxide and water, microplastics are not generated, meanwhile, the performance of the plastic film is not changed, the meal box film is applied to the degradable meal box, and after use, the meal box and the film do not need to be separated, and can be synchronously degraded in an integrated mode.

Description

Technical Field

[0001] This invention relates to the field of composite film technology, and in particular to a temperature- and oil-resistant biodegradable lunchbox film, a lunchbox, and a preparation method thereof. Background Technology

[0002] Traditional plastic lunch boxes are non-biodegradable and can only be discarded after use, resulting in a large amount of plastic waste. Currently, with the global increase in plastic consumption, the pressure of plastic waste generation is becoming increasingly heavy. Environmental protection and social responsibility require the world to shift towards sustainable development. At present, the plastics industry has three major development directions: weight reduction and thinning, recyclability, and biodegradability.

[0003] Eco-friendly lunch boxes, also known as plant fiber lunch boxes or eco-friendly pulp lunch boxes, are generally made of plant fibers, mainly sugarcane bagasse and straw. They are a pure natural, biodegradable, and safe food packaging material. However, these lunch boxes are permeable to water and not oil-resistant, so they cannot be used to hold foods with soup or broth; they can only be used with a thin film over them.

[0004] Currently, traditional biodegradable films have low softening points, are not heat-resistant, oil-resistant, or impact-resistant, and cannot meet the requirements for food containers. Therefore, current technology can only laminate traditional non-biodegradable plastics onto biodegradable food containers. After use, the film needs to be separated from the food container, with the food container degrading and the film being recycled. However, the consumer base is relatively dispersed, making this approach difficult to implement, leading to incineration and landfill as the only options, polluting the environment. Summary of the Invention

[0005] In view of this, the present invention provides a temperature- and oil-resistant biodegradable lunch box film, a lunch box, and a preparation method thereof. The biodegradable lunch box film provided by the present invention has good temperature and oil resistance and is biodegradable. When applied to a biodegradable lunch box, it does not require separation of the lunch box and the film after use, as they can degrade together simultaneously.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A temperature- and oil-resistant biodegradable lunchbox film is made of three layers: outer layer, middle layer, and inner layer, through co-extrusion blown film.

[0008] The outer layer is prepared from the following raw materials by mass: 10-40 parts of a first ethylene-vinyl acetate copolymer, 30-85 parts of a second ethylene-vinyl acetate copolymer, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids; the first ethylene-vinyl acetate copolymer has a melt index of 0.2-1.0 g / 10 min and a density of 0.925-0.940 g / cm³. 3 The melt index of the second ethylene-vinyl acetate copolymer is 1.2–2.5 g / 10 min, and its density is 0.930–0.945 g / cm³. 3 ;

[0009] The raw materials for preparing the middle layer, by mass parts, include: 15-45 parts of block copolymer polypropylene, 25-85 parts of random copolymer polypropylene, 10-20 parts of modified toughening material, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids.

[0010] The raw materials for preparing the inner layer, by mass parts, include: 15-40 parts of random copolymer polypropylene, 30-85 parts of block copolymer polypropylene, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids.

[0011] Preferably, the block copolymer polypropylene used in the middle layer has a melt index of 1.8–3.0 g / 10 min and a density of 0.898–0.910 g / cm³. 3 The random copolymer polypropylene used in the middle layer has a melt index of 7.0–9.0 g / 10 min and a density of 0.895–0.910 g / cm³. 3 The modified toughening material used in the intermediate layer has a melt index of 3.0–4.0 g / 10 min and a density of 0.870–0.90 g / cm³. 3 ;

[0012] The inner layer uses random copolymer polypropylene with a melt index of 1.0–2.0 g / 10 min and a density of 0.890–0.910 g / cm³. 3 The inner layer uses block copolymer polypropylene with a melt index of 4–8 g / 10 min and a density of 0.90–0.920 g / cm³. 3 .

[0013] Preferably, the degradation masterbatch used in the outer layer has a melt index of 46–55 g / 10 min and a density of 0.920–0.940 g / cm³. 3 The processing aid used in the outer layer has a melt index of 1–8 g / 10 min and a density of 0.910–0.925 g / cm³. 3 ;

[0014] The degradation masterbatch used in the middle and inner layers has a melt index of 85–95 g / 10 min and a density of 0.885–0.910 g / cm³. 3 The processing aids used in the middle and inner layers have a melt index of 5–8 g / 10 min and a density of 0.890–0.910 g / cm³. 3 .

[0015] Preferably, the first ethylene-vinyl acetate copolymer is of type FL00112; the second ethylene-vinyl acetate copolymer is of type 7350F and / or 18F3; the degradation masterbatch used in the outer layer is of type TRF-57; and the additives used in the outer layer are of type PA0895LD and / or PPA-3.

[0016] Preferably, the block copolymer polypropylene used in the middle layer is of type J351F; the random copolymer polypropylene used in the middle layer is of type RP271M; and the modified toughening material used in the middle layer is of type A4085S.

[0017] The random copolymer polypropylene used in the inner layer is of type R301; the block copolymer polypropylene used in the inner layer is of type CF309 and / or PPR-F08E.

[0018] The degradation masterbatch used in the middle and inner layers is PLMV3.3; the processing aids used in the middle and inner layers are PA0833PPR and / or PPA-3.

[0019] Preferably, based on the total mass of the outer layer, middle layer and inner layer as 100%, the mass fraction of the outer layer is 12.5-25%, the mass fraction of the middle layer is 40-75%, and the mass fraction of the inner layer is 12.5-40%; the thickness of the high-strength biodegradable express bag film is 50-100 μm.

[0020] The present invention also provides a method for preparing the temperature-resistant, oil-resistant, and biodegradable lunch box film described above, comprising the following steps:

[0021] The raw materials for the outer, middle, and inner layers are co-extruded and blown into a film to obtain the temperature-resistant, oil-resistant, and biodegradable lunchbox film.

[0022] Preferably, the process of the three-layer co-extrusion blown film specifically includes: feeding the raw materials for the preparation of the outer layer, middle layer and inner layer into the outer layer, middle layer and inner layer extruders respectively for melt plasticization, conveying the obtained adhesive liquid to the die head, extruding and blowing film to obtain film bubbles, and after the film bubbles are cooled, they are sequentially dried, corona treated, trimmed, lowered and wound to obtain the temperature-resistant, oil-resistant and biodegradable lunch box film.

[0023] Preferably, the outer extruder, middle extruder, and inner extruder are each equipped with five heating zones, which are sequentially designated as zones 1 to 5 according to the order in which the raw materials pass through. The temperature of zone 1 in the outer extruder is 140±5℃, zone 2 is 150±5℃, zone 3 is 158±5℃, zone 4 is 165±5℃, and zone 5 is 160±5℃. The temperature of zone 1 in the middle extruder is 180±5℃, zone 2 is 188±5℃, zone 3 is 192±5℃, zone 4 is 186±5℃, and zone 5 is 180±5℃. The temperature of zone 1 in the inner extruder is 190±5℃, zone 2 is 195±5℃, zone 3 is 200±5℃, zone 4 is 200±5℃, and zone 5 is 190±5℃.

[0024] The mold head is divided into 4 heating zones, which are numbered 1 to 4 according to the order in which the adhesive passes through. The temperature of zone 1 is 200±5℃, zone 2 is 203±5℃, zone 3 is 210±5℃, and zone 4 is 200±5℃.

[0025] The present invention also provides a temperature- and oil-resistant biodegradable lunch box, comprising a biodegradable lunch box and a lunch box film disposed on the surface of the biodegradable lunch box; the lunch box film is the temperature- and oil-resistant biodegradable lunch box film described in the above scheme or the temperature- and oil-resistant biodegradable lunch box film prepared by the preparation method described in the above scheme.

[0026] This invention provides a temperature- and oil-resistant biodegradable lunchbox film, which is made of three layers: an outer layer, a middle layer, and an inner layer, through co-extrusion blown film production. By weight, the outer layer comprises: 10-40 parts of a first ethylene-vinyl acetate copolymer, 30-85 parts of a second ethylene-vinyl acetate copolymer, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids. The first ethylene-vinyl acetate copolymer has a melt index of 0.2-1.0 g / 10 min and a density of 0.925-0.940 g / cm³. 3 The melt index of the second ethylene-vinyl acetate copolymer is 1.2–2.5 g / 10 min, and its density is 0.930–0.945 g / cm³. 3The raw materials for the preparation of the middle layer, by weight, include: 15-45 parts of block copolymer polypropylene, 25-85 parts of random copolymer polypropylene, 10-20 parts of modified toughening material, 1.5-2.5 parts of biodegradable masterbatch, and 0.3-1.5 parts of processing aids. The raw materials for the preparation of the inner layer, by weight, include: 15-40 parts of random copolymer polypropylene, 30-85 parts of block copolymer polypropylene, 1.5-2.5 parts of biodegradable masterbatch, and 0.3-1.5 parts of processing aids. This invention strictly controls the raw materials for the preparation of the three layers of the biodegradable lunchbox film, ensuring that the resulting lunchbox film has good temperature and oil resistance, high mechanical properties, and low haze. Simultaneously, by adding biodegradable masterbatch to the outer, middle, and inner layers, this invention can transform traditional plastics such as polypropylene and ethylene-vinyl acetate copolymer into a new generation of biodegradable plastics that are non-toxic and harmless to nature. The resulting biodegradable lunchbox film can be completely degraded into carbon dioxide and water, without producing microplastics, and without altering the properties of the plastic film. The results of the examples show that the biodegradable lunch box film provided by the present invention does not exhibit stratification or bubble formation when treated with hot oil at 100°C for 30 minutes, and can achieve effective degradation under light, heat, oxygen, and composting conditions; when the lunch box film of the present invention is applied to biodegradable lunch boxes, there is no need to separate the lunch box and the film after use, as they can degrade simultaneously as a whole. Detailed Implementation

[0027] This invention provides a temperature- and oil-resistant biodegradable lunchbox film, which is made of three layers: an outer layer, a middle layer, and an inner layer, through co-extrusion blown film.

[0028] The outer layer is prepared from the following raw materials by mass: 10-40 parts of a first ethylene-vinyl acetate copolymer, 30-85 parts of a second ethylene-vinyl acetate copolymer, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids; the first ethylene-vinyl acetate copolymer has a melt index of 0.2-1.0 g / 10 min and a density of 0.925-0.940 g / cm³. 3 The melt index of the second ethylene-vinyl acetate copolymer is 1.2–2.5 g / 10 min, and its density is 0.930–0.945 g / cm³. 3 ;

[0029] The raw materials for preparing the middle layer, by mass parts, include: 15-45 parts of block copolymer polypropylene, 25-85 parts of random copolymer polypropylene, 10-20 parts of modified toughening material, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids.

[0030] The raw materials for preparing the inner layer, by mass parts, include: 15-40 parts of random copolymer polypropylene, 30-85 parts of block copolymer polypropylene, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids.

[0031] Unless otherwise specified, all raw materials used in this invention are preferably commercially available products.

[0032] The outer layer is prepared from 10 to 40 parts, preferably 20 to 30 parts, of a first ethylene-vinyl acetate copolymer (EVA) by mass. The melt index of the first ethylene-vinyl acetate copolymer is 0.2 to 1.0 g / 10 min, preferably 0.5 to 0.8 g / 10 min, and the density is 0.925 to 0.940 g / cm³. 3 The preferred value is 0.930–0.934 g / cm³. 3 In a specific embodiment of the present invention, the first ethylene-vinyl acetate copolymer is preferably FL00112, manufactured by ExxonMobil, with a melt index of 0.5 g / 10 min and a density of 0.934 g / cm³. 3 It has characteristics such as high polarity, good thermal adhesion, good compatibility with polypropylene, and easy processing.

[0033] Based on the mass fraction of the first ethylene-vinyl acetate copolymer used in the outer layer, the raw materials for preparing the outer layer include 30 to 85 parts of a second ethylene-vinyl acetate copolymer, preferably 40 to 70 parts; the melt index of the second ethylene-vinyl acetate copolymer is 1.2 to 2.5 g / 10 min, preferably 1.8 to 2.5 g / 10 min, and the density is 0.930 to 0.945 g / cm³. 3 The preferred value is 0.938–0.94 g / cm³. 3 In a specific embodiment of the present invention, the second ethylene-vinyl acetate copolymer is preferably of type 7350F and / or 18F3, wherein the manufacturer of the second ethylene-vinyl acetate copolymer of type 7350F is Taiwan Plastics Industry Co., Ltd., with a melt index of 1.8 g / 10 min and a density of 0.938 g / cm³. 3 The manufacturer of the second ethylene-vinyl acetate copolymer, model 18F3, is Yanshan Petrochemical. Its melt index is 2.5 g / 10 min, and its density is 0.94 g / cm³. 3 The second ethylene-vinyl acetate copolymer used in this invention has characteristics such as high polarity, good hot adhesion, good compatibility with polypropylene, and easy processing.

[0034] Based on the mass fraction of the first ethylene-vinyl acetate copolymer used in the outer layer, the raw materials for preparing the outer layer include 1.5 to 2.5 parts of degradation masterbatch, preferably 1.8 to 2.2 parts; the melt index of the degradation masterbatch used in the outer layer is preferably 46 to 55 g / 10 min, more preferably 48 to 51.6 g / 10 min, and the density is preferably 0.920 to 0.940 g / cm³. 3 More preferably, it is 0.925–0.930 g / cm³. 3In a specific embodiment of the present invention, the degradation masterbatch used in the outer layer is model TRF-57, manufactured by Polymateria Ltd. (UK), with a melt index of 51.6 g / min and a density of 0.930 g / cm³. 3 The degradation masterbatch used in the outer layer of this invention has the following advantages: An advanced catalytic system can convert ethylene, propylene, and copolymer materials into bioavailable waxes, which can be easily assimilated by naturally occurring microorganisms without requiring a specific environment; the degradation time of this masterbatch can be adjusted according to different usage conditions and cycles, making the degradation time controllable; no microplastics or toxic substances are left after degradation, making it harmless to nature; the physical properties of the film after adding the degradation masterbatch are no different from traditional plastics, and it does not reduce the physical properties of the product. Compared with other degradation films, it has a wider range of applications and lower costs; adding the degradation masterbatch does not require changes to the original process equipment, saving upgrade costs and meeting the requirements of green and sustainable development; it can be recycled and granulated together with ordinary plastics without affecting physical properties. Under the catalytic action of this degradation masterbatch, the plastic undergoes the following three chemical reactions: 1. Free radical initiation: When exposed to energy such as light and heat, the carbon chain of the polyethylene molecule breaks, generating highly reactive free radicals; 2. Free radical propagation: Under aerobic conditions, the highly reactive free radicals rapidly react to generate intermediate products such as peroxy free radicals or hydroperoxy free radicals; 3. Chain termination: Compounds containing unstable peroxy free radicals or hydroperoxy free radicals undergo molecular bond breakage and a series of chemical reactions to generate small molecule compounds with carbon, hydrogen, and oxygen structures, ultimately becoming carbon dioxide, water, and wax. This process is non-toxic and harmless to nature. The wax undergoes biotransformation through naturally occurring bacteria and fungi in the soil and mineralization under open environmental temperature conditions. The resulting temperature- and oil-resistant biodegradable food container film meets the degradation requirements of ASTM6954, GB / T20197, and BSI PAS 9017.

[0035] Based on the mass fraction of the first ethylene-vinyl acetate copolymer used in the outer layer, the raw materials for preparing the outer layer include 0.3 to 1.5 parts of processing aids, preferably 0.5 to 1 part; the melt index of the processing aids used in the outer layer is preferably 1 to 8 g / 10 min, more preferably 2.1 to 8 g / 10 min, and the density is preferably 0.910 to 0.925 g / cm³. 3 More preferably, it is 0.915–0.920 g / cm³. 3 The processing aid is preferably a functional masterbatch prepared from fluoropolymer and polyolefin resin; in a specific embodiment of the present invention, the processing aid is preferably PA0895LD and / or PPA-3, wherein the processing aid of type PA0895LD has a melt index of 2.1 g / min and a density of 0.915 g / cm³. 3The manufacturer is Suzhou Constance Engineering Plastics Co., Ltd., and the processing aid, model PPA-3, has a melt index of 8 g / min and a density of 0.92 g / cm³. 3 The manufacturer is Huayi Technology Development Co., Ltd.; in a specific embodiment of the present invention, when using processing aid PA0895LD, the preferred mass fraction of the processing aid in the outer layer is 0.3 to 1.5 parts; when using processing aid PPA-3, the preferred mass fraction of the processing aid in the outer layer is 0.5 to 1 part. The processing aid used in the present invention can effectively reduce die accumulation, reduce crystal points, lower extrusion pressure, and improve production efficiency.

[0036] The raw materials for preparing the middle layer, by mass parts, include 15-45 parts of block copolymer polypropylene, preferably 20-40 parts; the melt index of the block copolymer polypropylene used in the middle layer is preferably 1.8-3.0 g / 10 min, more preferably 2.5-2.8 g / 10 min, and the density is preferably 0.898-0.910 g / cm³. 3 More preferably, it is 0.90–0.905 g / cm³. 3 In a specific embodiment of the present invention, the block copolymer polypropylene used in the middle layer is preferably J351F and / or R520F, wherein the block copolymer polypropylene of type J351F is manufactured by Hyosung of South Korea, and has a melt index of 2.5 g / 10 min and a density of 0.90 g / cm³. 3 The block copolymer polypropylene, model R520F, is manufactured by SK Chemicals, with a melt index of 1.8 g / 10 min and a density of 0.90 g / cm³. 3 The block copolymer polypropylene used in this invention has characteristics such as high stiffness, high transparency, and easy processing.

[0037] Based on the mass fraction of block copolymer polypropylene used in the middle layer, the raw materials for preparing the middle layer include 25-85 parts of random copolymer polypropylene, preferably 30-80 parts, and more preferably 40-60 parts; the melt index of the random copolymer polypropylene used in the middle layer is preferably 7.0-9.0 g / 10 min, more preferably 7.0-9.0 g / 10 min, and the density is preferably 0.895-0.910 g / cm³. 3 More preferably, it is 0.90–0.905 g / cm³. 3 In a specific embodiment of the present invention, the block copolymer polypropylene is preferably RP271M, manufactured by LyondellBasell, with a melt index of 8.0 g / 10 min and a density of 0.90 g / cm³. 3 It has the characteristics of high stiffness, high transparency, and easy processing.

[0038] Based on the mass fraction of block copolymer polypropylene used in the middle layer, the raw materials for preparing the middle layer include 10-20 parts of modified toughening material, preferably 13-18 parts; the melt index of the modified toughening material is preferably 3.0-4.0 g / 10 min, more preferably 3.2-3.6 g / 10 min, and the density is preferably 0.870-0.90 g / cm³. 3 More preferably, it is 0.875–0.885 g / cm³. 3 In a specific embodiment of the present invention, the modified toughening material is preferably A4085S, manufactured by Mitsui Chemicals, with a melt index of 3.6 g / 10 min and a density of 0.885 g / cm³. 3 It has the characteristics of high toughness, impact resistance, and easy processing.

[0039] Based on the mass fraction of block copolymer polypropylene used in the middle layer, the raw materials for preparing the middle layer include 1.5 to 2.5 parts of degraded masterbatch, preferably 1.8 to 2.2 parts; the melt index of the degraded masterbatch used in the middle layer is preferably 85 to 95 g / 10 min, more preferably 90 to 92 g / 10 min, and the density is preferably 0.885 to 0.910 g / cm³. 3 More preferably, it is 0.890–0.900 g / cm³. 3 In a specific embodiment of the present invention, the degradation masterbatch used in the middle layer is preferably PLMV3.3, manufactured by Polymateria Ltd. (UK), with a melt index of 90 g / min and a density of 0.900 g / cm³. 3In this invention, the degradation masterbatch used in the middle layer has the following advantages: the advanced catalytic system of the masterbatch can convert polypropylene material into bioavailable wax, which can be easily assimilated by naturally occurring microorganisms without requiring a specific environment; the degradation time can be adjusted according to different usage conditions and cycles, and the degradation time is controllable; no microplastics or toxic substances are left after degradation, making it harmless to nature; the physical properties of the film after adding the degradation masterbatch are no different from those of traditional plastics, and the physical properties of the product are not reduced; compared with other degradation films, it has a wider range of applications and lower costs; adding the degradation masterbatch does not require changing the original process equipment, saving upgrade costs and meeting the requirements of green and sustainable development; it can be recycled and granulated together with ordinary plastics without affecting physical properties. Under the catalytic action of the degradation masterbatch, the plastic undergoes the following three chemical reactions: 1. Free radical initiation: When exposed to energy such as light and heat, the carbon chain of the polyethylene molecule breaks, generating highly reactive free radicals; 2. Free radical propagation: Under aerobic conditions, the highly reactive free radicals rapidly react to generate intermediate products such as peroxy free radicals or hydroperoxy free radicals; 3. Chain termination: Compounds containing unstable peroxy free radicals or hydroperoxy free radicals undergo molecular bond breakage and a series of chemical reactions to generate small molecule compounds with carbon, hydrogen, and oxygen structures, ultimately becoming carbon dioxide, water, and wax. This process is non-toxic and harmless to nature. The wax undergoes biotransformation through naturally occurring bacteria and fungi in the soil and mineralization under open environmental temperature conditions. The resulting temperature- and oil-resistant biodegradable food container film meets the degradation requirements of ASTM6954, GB / T20197, and BSIPAS 9017.

[0040] Based on the mass fraction of block copolymer polypropylene used in the middle layer, the raw materials for preparing the middle layer include 0.3 to 1.5 parts of processing aids, preferably 0.5 to 1 part; the melt index of the processing aids used in the middle layer is preferably 5.0 to 8.0 g / 10 min, more preferably 6.0 to 7.5 g / 10 min, and the density is preferably 0.890 to 0.910 g / cm³. 3 More preferably, it is 0.895–0.90 g / cm³. 3 In a specific embodiment of the present invention, the block copolymer polypropylene used in the middle layer is preferably PA0833PPR and / or PPA-3, wherein PA0833PPR is manufactured by Suzhou Constance Engineering Plastics Co., Ltd., and has a melt index of 6.0 g / min and a density of 0.90 g / cm³. 3 The processing aid, model PPA-3, has a melt index of 8 g / min and a density of 0.92 g / cm³. 3The manufacturer is Huayi Technology Development Co., Ltd.; in a specific embodiment of the present invention, when using processing aid PA0833PPR, the preferred mass fraction of the processing aid in the intermediate layer is 0.3 to 1.5 parts; when using processing aid PPA-3, the preferred mass fraction of the processing aid in the intermediate layer is 0.5 to 1 part. The processing aid used in this invention has good high-temperature resistance, which can effectively reduce die accumulation, reduce crystal points, lower extrusion pressure, and improve production efficiency.

[0041] The raw materials for preparing the inner layer, by mass parts, include 15-40 parts of random copolymer polypropylene, preferably 20-35 parts; the melt index of the random copolymer polypropylene used in the inner layer is preferably 1.0-2.0 g / 10 min, more preferably 1.5-1.8 g / 10 min, and the density is preferably 0.890-0.910 g / cm³. 3 More preferably, it is 0.895–0.900 g / cm³. 3 In a specific embodiment of the present invention, the random copolymer polypropylene used in the inner layer is preferably R301, manufactured by Hyosung of South Korea, with a melt index of 1.5 g / 10 min and a density of 0.900 g / cm³. 3 It has properties such as high transparency, high strength, high temperature resistance, and easy processing.

[0042] Based on the mass fraction of random copolymer polypropylene used in the inner layer, the raw materials for preparing the inner layer include 30-85 parts of block copolymer polypropylene, preferably 40-80 parts; the melt index of the block copolymer polypropylene used in the inner layer is preferably 4-8 g / 10 min, more preferably 5-8 g / 10 min, and the density is preferably 0.90-0.920 g / cm³. 3 More preferably, it is 0.910–0.915 g / cm³. 3 In a specific embodiment of the present invention, the block copolymer polypropylene used in the inner layer is preferably CF309 and / or PPR-F08E, wherein the block copolymer polypropylene of type CF309 is manufactured by Samsung Total, and has a melt index of 5.0 g / 10 min and a density of 0.910 g / cm³. 3 The block copolymer polypropylene, model PPR-F08E, is manufactured by Sinopec Refining & Chemical Co., Ltd., with a melt index of 8 g / 10 min and a density of 0.9 g / cm³. 3 The block copolymer polypropylene used in this invention has properties such as high transparency, high gloss, high temperature resistance, high impact strength, and resistance to stress whitening.

[0043] Based on the mass fraction of random copolymer polypropylene used in the inner layer, the raw materials for preparing the inner layer include 1.5 to 2.5 parts of degradation masterbatch, preferably 1.8 to 2.0 parts; the melt index, density and specific grade of the degradation masterbatch used in the inner layer are preferably the same as those of the degradation masterbatch used in the middle layer, and will not be repeated here.

[0044] Based on the mass fraction of random copolymer polypropylene used in the inner layer, the raw materials for preparing the inner layer include 0.3 to 1.5 parts of processing aids, preferably 0.5 to 1 part. The melt index, density, and specific grade of the processing aids used in the inner layer are preferably the same as those used in the middle layer, and will not be repeated here. In a specific embodiment of the present invention, when using processing aid of type PA0833PPR, the mass fraction of the processing aid in the inner layer is preferably 0.3 to 1.5 parts; when using processing aid of type PPA-3, the mass fraction of the processing aid in the inner layer is preferably 0.5 to 1 part.

[0045] In this invention, taking the total mass of the outer layer, middle layer and inner layer as 100%, the mass fraction of the outer layer is preferably 12.5-25%, more preferably 15%, 20% or 25%; the mass fraction of the middle layer is preferably 40-75%, more preferably 40%, 50% or 60%; and the mass fraction of the inner layer is preferably 12.5-40%, more preferably 15%, 25% or 40%. The thickness of the high-strength biodegradable express bag film is preferably 50-100 μm, more preferably 60-80 μm.

[0046] In this invention, the longitudinal tensile strength of the heat-resistant and oil-resistant biodegradable lunchbox film is preferably 42.9–44.2 MPa, the transverse tensile strength is preferably 37.2–40.1 MPa, the longitudinal elongation at break is preferably 610%–625%, the transverse elongation at break is preferably 715%–730%, the wetting tension is preferably 40–45 mN / 15 mm, and the haze is preferably less than 10%, more preferably 9.1%–9.8%. The heat-resistant and oil-resistant biodegradable lunchbox film does not exhibit delamination or bubbling after being treated with hot oil at 100°C for 30 minutes, and it can effectively degrade under natural environmental, photodegradation, thermo-oxidative degradation, and composting conditions.

[0047] The present invention also provides a method for preparing the temperature-resistant, oil-resistant, and biodegradable lunch box film described above, comprising the following steps:

[0048] The raw materials for the outer, middle, and inner layers are co-extruded and blown into a film to obtain the temperature-resistant, oil-resistant, and biodegradable lunchbox film.

[0049] In this invention, the process of three-layer co-extrusion blown film specifically includes: feeding the raw materials for the preparation of the outer layer, middle layer and inner layer into the outer layer, middle layer and inner layer extruders respectively for melt plasticization, conveying the obtained adhesive liquid to the die head, extruding and blowing film to obtain film bubbles, and after the film bubbles are cooled, they are sequentially dried, corona treated, trimmed, lowered and wound to obtain the temperature-resistant, oil-resistant and biodegradable lunch box film.

[0050] In this invention, the outer extruder, middle extruder, and inner extruder are preferably each provided with five heating zones, which are sequentially designated as zones 1 to 5 according to the order in which the raw materials pass through. The preferred temperatures for zones 1 and 5 of the outer extruder are: zone 1: 140±5℃; zone 2: 150±5℃; zone 3: 158±5℃; zone 4: 165±5℃; and zone 5: 160±5℃. For the middle extruder, the preferred temperatures for zones 1 and 5 are: zone 1: 180±5℃; zone 2: 188±5℃; zone 3: 192±5℃; zone 4: 186±5℃; and zone 5: 180±5℃. For the inner extruder, the preferred temperatures for zones 1 and 5 are: zone 1: 190±5℃; zone 2: 195±5℃; zone 3: 200±5℃; zone 4: 200±5℃; and zone 5: 190±5℃.

[0051] In this invention, the extrusion pressure of the outer extruder is preferably 175-230 bar, the extrusion pressure of the middle extruder is preferably 195-215 bar, and the extrusion pressure of the inner extruder is preferably 185-235 bar.

[0052] In this invention, the mold head is preferably divided into 4 heating zones, which are numbered 1 to 4 in the order in which the adhesive passes through. The temperature of zone 1 of the mold head is preferably 200±5℃, the temperature of zone 2 is preferably 203±5℃, the temperature of zone 3 is preferably 210±5℃, and the temperature of zone 4 is preferably 200±5℃.

[0053] In this invention, the cooling temperature is preferably 15-20°C, and the cooling device is preferably a cooling water ring; the cooled membrane bubble enters the dryer through a herringbone pattern for drying, and the drying temperature is preferably 45±5°C.

[0054] This invention also provides a heat- and oil-resistant biodegradable lunch box, comprising a biodegradable lunch box and a lunch box film disposed on the surface of the biodegradable lunch box; the lunch box film is the heat- and oil-resistant biodegradable lunch box film described in the above-described scheme or a heat- and oil-resistant biodegradable lunch box film prepared by the preparation method described in the above-described scheme; this invention does not have special requirements for the biodegradable lunch box, and any material well known to those skilled in the art can be used, such as a biodegradable lunch box made of plant fibers, preferably including sugarcane bagasse or straw. The heat- and oil-resistant biodegradable lunch box of this invention does not require separation of the film and the lunch box after use, and can degrade simultaneously as a whole, making it convenient to use.

[0055] The present invention does not have any special requirements for the preparation method of the heat-resistant and oil-resistant biodegradable lunch box. Any method known to those skilled in the art can be used. In a specific embodiment of the present invention, conventional film-coating equipment is used to coat the heat-resistant and oil-resistant biodegradable lunch box film onto the biodegradable lunch box.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] The sources of raw materials and performance parameters used in the examples are shown in Table 1.

[0058] Table 1. Raw material sources and performance parameters

[0059]

[0060] Example 1

[0061] The temperature- and oil-resistant biodegradable lunchbox film of this embodiment is made of three layers: outer layer, middle layer and inner layer, by co-extrusion blown film. The weight percentage of each layer is as follows: outer layer 20%, middle layer 40%, and inner layer 40%.

[0062] The amount of raw materials used in each layer is shown in Table 2. The total thickness of the temperature- and oil-resistant biodegradable lunch box film is 80 μm. The preparation method is as follows:

[0063] The raw materials for the outer, middle, and inner layers are mixed in proportion by an automatic batching system and then fed into the outer, middle, and inner layer extruders. After the raw materials are melted and plasticized, they are fed into the die head and extruded downwards. The film is then cooled by a cooling water ring at a temperature controlled between 15 and 20°C. After passing through a herringbone pattern, the film enters a dryer for drying at a temperature of 45°C ± 5°C. The film then passes through a guide roller into a corona treatment device for corona treatment. Finally, the edges are trimmed and the film passes through a lower traction clamping roller into a front and rear winding device for front and rear winding. This process yields a temperature-resistant, oil-resistant, and biodegradable lunchbox film with a thickness of 80 μm.

[0064] The temperatures of each zone of the outer, middle, and inner layer extruders and the die head, as well as the pressures of the outer, middle, and inner layer extruders, are shown in Table 3.

[0065] Table 2 shows the raw material amounts (by mass) for Examples 1-3 and Comparative Example 2.

[0066]

[0067]

[0068] Table 3 Temperature and pressure of extruder and die head

[0069] temperature Zone 1 / ℃ Zone 2 / ℃ Zone 3 / ℃ 4 zones / ℃ 5 zones / ℃ Pressure / bar outer layer 140 150 158 165 160 210 Middle layer 180 188 192 186 180 205 Inner layer 190 195 200 200 190 215 mold head 200 203 210 200 / /

[0070] A heat- and oil-resistant biodegradable lunch box film is applied to a biodegradable lunch box made of sugarcane bagasse using a film coating equipment to obtain a heat- and oil-resistant biodegradable lunch box.

[0071] Example 2

[0072] The temperature- and oil-resistant biodegradable lunchbox film of this embodiment is made of three layers: an outer layer, a middle layer, and an inner layer, which are co-extruded and blown together. The weight percentages of the materials in each layer are as follows: outer layer 15%, middle layer 60%, and inner layer 25%. The amount of raw materials used in each layer is shown in Table 2. The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0073] The obtained heat-resistant and oil-resistant biodegradable lunch box film is coated onto a biodegradable lunch box made of sugarcane bagasse using a film coating equipment to obtain a heat-resistant and oil-resistant biodegradable lunch box.

[0074] Example 3

[0075] The temperature- and oil-resistant biodegradable lunchbox film of this embodiment is made of three layers: an outer layer, a middle layer, and an inner layer, which are co-extruded and blown together. The weight percentages of the materials in each layer are as follows: outer layer 25%, middle layer 50%, and inner layer 25%. The amount of raw materials used in each layer is shown in Table 2. The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0076] The obtained heat-resistant and oil-resistant biodegradable lunch box film is coated onto a biodegradable lunch box made of sugarcane bagasse using a film coating equipment to obtain a heat-resistant and oil-resistant biodegradable lunch box.

[0077] Example 4

[0078] The temperature- and oil-resistant biodegradable lunchbox film of this embodiment is made of three layers: an outer layer, a middle layer, and an inner layer, which are co-extruded and blown together. The weight percentages of the materials in each layer are as follows: outer layer 17%, middle layer 50%, and inner layer 33%. The amount of raw materials used in each layer is shown in Table 2. The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0079] The obtained heat-resistant and oil-resistant biodegradable lunch box film is coated onto a biodegradable lunch box made of sugarcane bagasse using a film coating equipment to obtain a heat-resistant and oil-resistant biodegradable lunch box.

[0080] Example 5

[0081] The temperature- and oil-resistant biodegradable lunchbox film of this embodiment is made of three layers: an outer layer, a middle layer, and an inner layer, which are co-extruded and blown together. The weight percentages of the materials in each layer are as follows: outer layer 15%, middle layer 55%, and inner layer 30%. The amount of raw materials used in each layer is shown in Table 2. The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0082] The obtained heat-resistant and oil-resistant biodegradable lunch box film is coated onto a biodegradable lunch box made of sugarcane bagasse using a film coating equipment to obtain a heat-resistant and oil-resistant biodegradable lunch box.

[0083] Example 6

[0084] The temperature- and oil-resistant biodegradable lunchbox film of this embodiment is made of three layers: an outer layer, a middle layer, and an inner layer, co-extruded blown film. The weight percentages of the materials in each layer are as follows: outer layer 20%, middle layer 55%, and inner layer 25%. The raw material usage for each layer is shown in Table 2. The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0085] The obtained heat-resistant and oil-resistant biodegradable lunch box film is coated onto a biodegradable lunch box made of sugarcane bagasse using a film coating equipment to obtain a heat-resistant and oil-resistant biodegradable lunch box.

[0086] Comparative Example 1

[0087] The temperature- and oil-resistant biodegradable lunch box film of this comparative example is made of three layers: outer layer, middle layer and inner layer, by co-extrusion blown film. The weight percentage of each layer is as follows: outer layer 20%, middle layer 50%, and inner layer 30%.

[0088] The outer layer uses Exxon's FL00112 EVA and Suzhou Constance Engineering Plastics Co., Ltd.'s PA0895LD processing aid. The middle layer uses Borouge's RB707CF copolymer polypropylene, and the inner layer uses Hyosung's J310F block copolymer polypropylene. The processing aid used in both the middle and inner layers is Suzhou Constance's PA0833PPR. The properties and amounts of the raw materials are shown in Table 4.

[0089] Table 4. Raw material usage for Comparative Example 1 (by parts by mass)

[0090]

[0091] The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0092] Comparative Example 2

[0093] The temperature- and oil-resistant biodegradable lunchbox film of this comparative example is made by co-extrusion blown film of three layers: outer layer, middle layer and inner layer. The weight percentage of each layer is as follows: outer layer 20%, middle layer 40%, and inner layer 40%. The raw material usage of each layer is shown in Table 2. The preparation method is the same as in Example 1, and the film thickness is 80 μm.

[0094] Performance testing:

[0095] The mechanical properties, wetting tension, haze, heat resistance to oil and degradation properties of the films prepared in Examples 1-6 and Comparative Examples 1-2 were tested. The standards used for the tests and the test results are shown in Table 5.

[0096] Table 5 Performance Test Results

[0097]

[0098] According to the data in Table 5, the temperature- and oil-resistant biodegradable lunch box film has good mechanical properties, high wetting tension, low haze, and good transparency. It can also be effectively degraded under light, heat, oxygen, and composting conditions. In Comparative Example 1, the raw material formula of the three layers was changed, and in Comparative Example 2, the amount of degradation masterbatch in the outer, middle, and inner layers was reduced. The degradation performance of the resulting films under light, heat, oxygen, and composting conditions was unqualified.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A temperature- and oil-resistant biodegradable lunchbox film, characterized in that, It is made of three layers: outer layer, middle layer, and inner layer, through co-extrusion blown film. The raw materials for preparing the outer layer, by mass parts, include: 10-40 parts of a first ethylene-vinyl acetate copolymer, 30-85 parts of a second ethylene-vinyl acetate copolymer, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids; the melt index of the first ethylene-vinyl acetate copolymer is 0.2-1.0 g / 10 min, and the density is 0.925-0.940 g / cm³. 3 The melt index of the second ethylene-vinyl acetate copolymer is 1.2~2.5 g / 10 min, and the density is 0.930~0.945 g / cm³. 3 ; The raw materials for preparing the middle layer, by mass parts, include: 15-45 parts of block copolymer polypropylene, 25-85 parts of random copolymer polypropylene, 10-20 parts of modified toughening material, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids. The raw materials for preparing the inner layer, by mass parts, include: 15-40 parts of random copolymer polypropylene, 30-85 parts of block copolymer polypropylene, 1.5-2.5 parts of degradation masterbatch, and 0.3-1.5 parts of processing aids. The block copolymer polypropylene used in the middle layer has a melt index of 1.8~3.0 g / 10min and a density of 0.898~0.910 g / cm³. 3 The random copolymer polypropylene used in the middle layer has a melt index of 7.0~9.0 g / 10min and a density of 0.895~0.910 g / cm³. 3 The modified toughening material used in the intermediate layer has a melt index of 3.0~4.0 g / 10min and a density of 0.870~0.90 g / cm³. 3 ; The inner layer uses random copolymer polypropylene with a melt index of 1.0~2.0 g / 10min and a density of 0.890~0.910 g / cm³. 3 The inner layer uses block copolymer polypropylene with a melt index of 4-8 g / 10 min and a density of 0.90-0.920 g / cm³. 3 ; The processing aid used in the outer layer has a melt index of 1.0~8.0 g / 10 min and a density of 0.910~0.925 g / cm³. 3 ; The processing aids used in the middle and inner layers have a melt index of 5-8 g / 10 min and a density of 0.890-0.910 g / cm³. 3 ; The degradation masterbatch used in the outer layer is manufactured by Polymateria, with a melt index of 51.6 g / 10 min and a density of 0.930 g / cm³. 3 The model number is TRF-57; the model number of the degradation masterbatch used in the middle and inner layers is PLMV3.

3.

2. The temperature-resistant, oil-resistant, and biodegradable lunchbox film according to claim 1, characterized in that, The first ethylene-vinyl acetate copolymer is of type FL00112; the second ethylene-vinyl acetate copolymer is of type 7350F and / or 18F3; and the processing aid used in the outer layer is of type PA0895LD and / or PPA-3.

3. The temperature-resistant and oil-resistant biodegradable lunchbox film according to any one of claims 1 to 2, characterized in that, The block copolymer polypropylene used in the middle layer is of type J351F and / or R520F; the random copolymer polypropylene used in the middle layer is of type RP271M; the modified toughening material used in the middle layer is of type A4085S. The random copolymer polypropylene used in the inner layer is of type R301; the block copolymer polypropylene used in the inner layer is of type CF309 and / or PPR-F08E. The processing aids used in the middle and inner layers are PA0833PPR and / or PPA-3.

4. The temperature-resistant, oil-resistant, and biodegradable lunchbox film according to claim 1, characterized in that, With the total mass of the outer layer, middle layer and inner layer as 100%, the mass fraction of the outer layer is 12.5~25%, the mass fraction of the middle layer is 40~75%, and the mass fraction of the inner layer is 12.5~40%; the thickness of the temperature-resistant, oil-resistant and biodegradable lunch box film is 50~100μm.

5. The method for preparing the temperature-resistant and oil-resistant biodegradable lunchbox film according to any one of claims 1 to 4, characterized in that, Includes the following steps: The raw materials for the outer, middle, and inner layers are co-extruded and blown into a film to obtain the temperature-resistant, oil-resistant, and biodegradable lunchbox film.

6. The preparation method according to claim 5, characterized in that, The process of the three-layer co-extrusion blown film specifically includes: feeding the raw materials for the preparation of the outer layer, middle layer and inner layer into the outer layer, middle layer and inner layer extruders respectively for melt plasticization, conveying the obtained adhesive liquid to the die head, extruding and blowing film to obtain film bubbles, and after the film bubbles are cooled, they are sequentially dried, corona treated, trimmed, lowered and wound up to obtain the temperature-resistant, oil-resistant and biodegradable lunch box film.

7. The preparation method according to claim 6, characterized in that, The outer, middle, and inner extruders are each equipped with five heating zones, numbered 1 to 5 according to the order in which the raw materials pass through. The temperatures of the outer extruder are as follows: Zone 1: 140±5℃; Zone 2: 150±5℃; Zone 3: 158±5℃; Zone 4: 165±5℃; Zone 5: 160±5℃. The temperatures of the middle extruder are as follows: Zone 1: 180±5℃; Zone 2: 188±5℃; Zone 3: 192±5℃; Zone 4: 186±5℃; Zone 5: 180±5℃. The temperatures of the inner extruder are as follows: Zone 1: 190±5℃; Zone 2: 195±5℃; Zone 3: 200±5℃; Zone 4: 200±5℃; Zone 5: 190±5℃. The mold head is divided into 4 heating zones, which are numbered 1 to 4 according to the order in which the adhesive passes through. The temperature of zone 1 is 200±5℃, zone 2 is 203±5℃, zone 3 is 210±5℃, and zone 4 is 200±5℃.

8. A temperature- and oil-resistant, biodegradable lunch box, characterized in that, It includes a biodegradable lunch box and a lunch box film disposed on the surface of the biodegradable lunch box; the lunch box film is the temperature-resistant and oil-resistant biodegradable lunch box film according to any one of claims 1 to 4 or the temperature-resistant and oil-resistant biodegradable lunch box film prepared by the preparation method according to any one of claims 5 to 7.

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