A surface-printed fully degradable PE film, bag, and preparation method

Abstract

This invention relates to the field of composite film technology, providing a surface-printed fully degradable PE film, bag, and preparation method. This invention strictly controls the raw materials and proportions used in the outer, middle, and inner layers of the PE film, and adds degradation masterbatch to these layers, enabling the transformation of traditional polyethylene plastic into a new generation of biodegradable plastic that is harmless to nature, without affecting the film's performance. The resulting surface-printed degradable PE film can degrade under light, heat, oxygen, and composting conditions, and can completely degrade into carbon dioxide and water without producing microplastics, exhibiting excellent environmental friendliness. Furthermore, the film has high transparency, high strength, is not prone to leaching, and is resistant to ink smudging during printing, meeting the requirements of various industries and broadening the application fields of degradable films.

Description

Technical Field

[0001] This invention relates to the field of composite film technology, and in particular to a surface-printed fully degradable PE film, bag, and preparation method. Background Technology

[0002] PE film is widely used in various industries, bringing significant economic and social benefits. However, due to its high stability and resistance to decomposition, waste PE film is difficult to dispose of effectively. With the increasing global consumption of plastics, the pressure from plastic waste is mounting, and the environmental pollution caused by discarded plastics is drawing growing attention. Environmental protection and social responsibility are demanding a global shift towards sustainable development.

[0003] Biodegradable films are thin films that can be completely degraded into harmless substances under certain conditions. Currently, they are usually prepared using biodegradable materials. However, current biodegradable films have low strength, poor transparency, and ink smudges when printed, making them difficult to use widely. They can only be used in areas with low requirements, such as shopping bags and garbage bags. Furthermore, current biodegradable films can usually only degrade under composting conditions. Summary of the Invention

[0004] In view of this, the present invention provides a surface-printable fully degradable PE film, a bag, and a preparation method. The surface-printable fully degradable PE film provided by the present invention not only has good degradability, but also high strength and high transparency, and is not easy to smudge during printing, making it suitable for surface printing and meeting the application requirements of various fields.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A surface-printed fully degradable PE film is made by three-layer co-extrusion blown film preparation raw materials of outer layer, middle layer and inner layer;

[0007] The outer layer is prepared by mass fractions of 10-30 parts of low-density polyethylene, 30-85 parts of metallocene medium-density polyethylene, 20-45 parts of linear low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids.

[0008] The raw materials for preparing the middle layer, by mass parts, include 10-30 parts of low-density polyethylene, 15-40 parts of linear low-density polyethylene, 30-80 parts of first metallocene low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids.

[0009] The raw materials for preparing the inner layer, by mass parts, include 10-30 parts of low-density polyethylene, 25-50 parts of second metallocene low-density polyethylene, 30-70 parts of third metallocene low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids.

[0010] The melt index of the first metallocene low-density ethylene and the second metallocene low-density polyethylene are independently 0.5–1.5 g / 10 min, and their densities are independently 0.912–0.925 g / cm³. 3 The third metallocene low-density polyethylene has a melt index of 0.5–1.5 g / 10 min and a density of 0.908–0.920 g / cm³. 3 ;

[0011] The outer, middle, and inner layers use degradation masterbatches with a melt index of 46–55 g / 10 min and a density of 0.920–0.940 g / cm³. 3 .

[0012] Preferably, the low-density polyethylene used in the outer, middle, and inner layers has a melt index of 1.5–2.5 g / 10 min and a density of 0.920–0.925 g / cm³. 3 ;

[0013] The outer layer uses metallocene medium-density polyethylene with a melt index of 0.8–1.8 g / 10 min and a density of 0.920–0.935 g / cm³. 3 ;

[0014] The outer layer uses linear low-density polyethylene with a melt index of 0.2–1.0 g / 10 min and a density of 0.920–0.930 g / cm³. 3 .

[0015] Preferably, the middle layer uses linear low-density polyethylene with a melt index of 1.5–2.5 g / 10 min and a density of 0.912–0.925 g / cm³. 3 .

[0016] Preferably, the processing aids used in the outer, middle, and inner layers have a melt index of 1.5–2.8 g / min and a density of 0.910–0.920 g / cm³. 3 .

[0017] Preferably, the low-density polyethylene used in the outer and middle layers is grade 2420H; the metallocene medium-density polyethylene used in the outer layer is grade 1327MA; and the linear low-density polyethylene used in the outer layer is grade 2505H.

[0018] The linear low-density polyethylene used in the middle layer is grade 7402; the first metallocene low-density polyethylene is grade 1018BN.

[0019] The inner layer uses low-density polyethylene of grade 2426H; the second metallocene low-density polyethylene is grade 1018BM; and the third metallocene low-density polyethylene is grade 1012MK.

[0020] The degradation masterbatch used in the outer, middle and inner layers is of the brand name TRF-57;

[0021] The processing aids used in the outer, middle, and inner layers are designated PA0895LD.

[0022] Preferably, when the total mass of the outer layer, middle layer and inner layer is 100%, the mass fraction of the outer layer is 20-30%, the mass fraction of the middle layer is 40-60%, and the mass fraction of the inner layer is 20-30%.

[0023] This invention also provides a method for preparing the surface-printed fully degradable PE film described above, comprising the following steps:

[0024] The raw materials for preparing the outer, middle, and inner layers are co-extruded and blown into a three-layer film to obtain the surface-printed fully degradable PE film.

[0025] 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, performing bubble stabilization, upper traction, corona treatment, edge trimming, lower traction and winding in sequence to obtain the surface-printed fully degradable PE film.

[0026] The present invention also provides a surface-printed fully degradable PE bag, which is prepared from a surface-printed fully degradable PE film; the surface-printed fully degradable PE film is the surface-printed fully degradable PE film described in the above scheme or the surface-printed fully degradable PE film prepared by the preparation method described in the above scheme.

[0027] The present invention also provides a method for preparing the surface-printed fully degradable PE bag described above, comprising the following steps: printing on the surface of the surface-printed fully degradable PE film and then making the bag to obtain the surface-printed fully degradable PE bag.

[0028] This invention provides a surface-printed fully degradable PE film, which is made by co-extrusion blown film of three layers: an outer layer, a middle layer, and an inner layer. By weight, the outer layer comprises 10-30 parts of low-density polyethylene, 30-85 parts of metallocene medium-density polyethylene, 20-45 parts of linear low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 part of processing aids. By weight, the middle layer comprises 10-30 parts of low-density polyethylene, 15-40 parts of linear low-density polyethylene, and 30-45 parts of first metallocene low-density polyethylene. The inner layer comprises 80 parts by weight, 1.5–2.5 parts by weight of degradation masterbatch, and 0.5–1 part by weight of processing aid; the raw materials for preparing the inner layer include 10–30 parts by weight of low-density polyethylene, 25–50 parts by weight of second metallocene low-density polyethylene, 30–70 parts by weight of third metallocene low-density polyethylene, 1.5–2.5 parts by weight of degradation masterbatch, and 0.5–1 part by weight of processing aid; the melt index of the first metallocene low-density polyethylene and the second metallocene low-density polyethylene are independently 0.5–1.5 g / 10 min, and the density is independently 0.912–0.925 g / cm³. 3 The third metallocene low-density polyethylene has a melt index of 0.5–1.5 g / 10 min and a density of 0.908–0.920 g / cm³. 3 The outer, middle, and inner layers utilize degradation masterbatches with a melt index of 46–55 g / 10 min and a density of 0.920–0.940 g / cm³. 3 This invention strictly controls the raw materials and proportions used in the outer, middle, and inner layers of the PE film. Simultaneously, it adds degradable masterbatch to these layers, enabling the transformation of traditional polyethylene into a new generation of biodegradable plastic that is harmless to nature, without affecting the film's performance. The resulting biodegradable PE film can degrade under light, heat, oxygen, and composting conditions, completely degrading into carbon dioxide and water without producing microplastics. It is environmentally friendly, and the film boasts high transparency, high strength, and is not prone to leaching. Furthermore, printing is not prone to ink smudging, meeting the requirements of various industries and broadening the application fields of biodegradable films. Detailed Implementation

[0029] This invention provides a surface-printed fully degradable PE film, which is made by three-layer co-extrusion blown film preparation raw materials of outer layer, middle layer and inner layer;

[0030] The outer layer is prepared by mass fractions of 10-30 parts of low-density polyethylene, 30-85 parts of metallocene medium-density polyethylene, 20-45 parts of linear low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids.

[0031] The raw materials for preparing the middle layer, by mass parts, include 10-30 parts of low-density polyethylene, 15-40 parts of linear low-density polyethylene, 30-80 parts of first metallocene low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids.

[0032] The raw materials for preparing the inner layer, by mass parts, include 10-30 parts of low-density polyethylene, 25-50 parts of second metallocene low-density polyethylene, 30-70 parts of third metallocene low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids.

[0033] The melt index of the first metallocene low-density ethylene and the second metallocene low-density polyethylene are independently 0.5–1.5 g / 10 min, and their densities are independently 0.912–0.925 g / cm³. 3 The third metallocene low-density polyethylene has a melt index of 0.5–1.5 g / 10 min and a density of 0.908–0.920 g / cm³. 3 .

[0034] The outer layer is prepared from 10 to 30 parts by weight, preferably 15, 22, or 30 parts of low-density polyethylene; the melt index of the low-density polyethylene is preferably 1.5 to 2.5 g / 10 min, more preferably 1.8 to 2.2 g / 10 min, and the density is preferably 0.920 to 0.925 g / cm³. 3 More preferably, it is 0.922–0.924 g / cm³. 3 In a specific embodiment of the present invention, the low-density polyethylene used in the outer layer is preferably grade 2420H, with a melt index of 2.0 g / 10 min and a density of 0.924 g / cm³. 3 The manufacturer is BASF Yangtze. The low-density polyethylene used in the outer layer of this invention has the characteristics of high cleanliness, good transparency and easy processing.

[0035] Based on the mass fraction of low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 30 to 85 parts of metallocene medium-density polyethylene, preferably 35, 65, or 80 parts; the melt index of the metallocene medium-density polyethylene used in the outer layer is preferably 0.8 to 1.8 g / 10 min, more preferably 1 to 1.5 g / 10 min, and the density is preferably 0.920 to 0.935 g / cm³. 3 More preferably, it is 0.926–0.928 g / cm³. 3 In a specific embodiment of the present invention, the metallocene medium-density polyethylene used in the outer layer is preferably grade 1327MA, with a melt index of 1.3 g / 10 min and a density of 0.928 g / cm³. 3The manufacturer is ExxonMobil; the metallocene medium-density polyethylene used in this invention has the characteristics of high strength, high gloss, high transparency, and good temperature resistance.

[0036] Based on the mass fraction of low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 20 to 45 parts of linear low-density polyethylene, preferably 22, 30, or 42 parts; the melt index of the linear low-density polyethylene used in the outer layer is preferably 0.2 to 1.0 g / 10 min, preferably 0.3 to 0.5 g / 10 min, and the density is preferably 0.920 to 0.930 g / cm³. 3 More preferably, it is 0.922–0.925 g / cm³. 3 In a specific embodiment of the present invention, the linear low-density polyethylene is preferably grade 2505H, with a melt index of 0.5 g / 10 min and a density of 0.925 g / cm³. 3 The manufacturer is CNOOC Shell; the linear low-density polyethylene used in this invention has the characteristics of high strength, good temperature resistance, and easy processing.

[0037] Based on the mass fraction of low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 1.5 to 2.5 parts of degraded masterbatch, preferably 2 parts; the melt index of the degraded masterbatch used in the outer, middle, and inner layers is preferably 46 to 55 g / 10 min, more preferably 50 to 52 g / 10 min, and the density is preferably 0.920 to 0.940 g / cm³. 3 More preferably, it is 0.925–0.935 g / cm³. 3 In a specific embodiment of the present invention, the preferred grade of the degradation masterbatch is TRF-57, which has a melt index of 51 g / 10 min and a density of 0.93 g / cm³. 3The manufacturer is Polymateria, UK. The biodegradable masterbatch used in this invention can convert polyethylene into bioavailable wax without requiring a specific environment for degradation. After degradation, it leaves no microplastics or toxic substances and is harmless to nature. Furthermore, the physical properties of the film do not change after adding the biodegradable masterbatch. Compared with other biodegradable films, it has a wider range of applications and lower costs. Adding the biodegradable masterbatch does not require changing the original process equipment and can be recycled and granulated together with ordinary plastics without affecting the physical properties. Specifically, under the catalytic action of the degradation masterbatch, polyethylene can undergo the following three chemical reactions: 1. 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 growth: 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 under open environmental temperature conditions. The resulting fully degradable PE film meets the degradation requirements of ASTM6954, GB / T20197, and BSIPAS 9017.

[0038] Based on the mass fraction of low-density polyethylene used in the outer layer, the raw materials for preparing the outer layer include 0.5 to 1 part of processing aids, preferably 0.8 to 1 part; the melt index of the processing aids used in the outer layer is preferably 1.5 to 2.8 g / min, more preferably 1.8 to 2.5 g / min, and the density is preferably 0.910 to 0.920 g / cm³. 3 More preferably, it is 0.912–0.915 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 used in the outer layer is preferably PA0895LD, with a melt index of 2.1 g / min and a density of 0.915 g / cm³. 3 The manufacturer is Suzhou Constance Engineering Plastics Co., Ltd. The processing aids used in this invention can effectively reduce die buildup, reduce crystal points, lower extrusion pressure, and improve production efficiency.

[0039] The raw materials for preparing the middle layer, by mass, include 10 to 30 parts of low-density polyethylene, preferably 10, 20, and 25 parts; the melt index, density, and specific grade of the low-density polyethylene used in the middle layer are preferably the same as those used in the outer layer, and will not be repeated here.

[0040] Based on the mass fraction of low-density polyethylene used in the middle layer, the raw materials for preparing the middle layer include 15 to 40 parts of linear low-density polyethylene, preferably 15, 25, or 38 parts; the melt index of the linear low-density polyethylene used in the middle layer is preferably 1.5 to 2.5 g / 10 min, more preferably 1.8 to 2.2 g / 10 min, and the density is preferably 0.912 to 0.925 g / cm³. 3 More preferably, it is 0.915–0.920 g / cm³. 3 In a specific embodiment of the present invention, the linear low-density polyethylene used in the middle layer is preferably grade 7402, with a melt index of 2 g / 10 min and a density of 0.918 g / cm³. 3 The manufacturer is Maoming Petrochemical; the linear low-density polyethylene used in this invention has good transparency, few crystal points, and is easy to process.

[0041] Based on the mass fraction of low-density polyethylene used in the middle layer, the raw materials for preparing the middle layer include 30 to 80 parts of first metallocene low-density polyethylene, preferably 32, 55, or 75 parts; the melt index of the first metallocene low-density polyethylene is 0.5 to 1.5 g / 10 min, preferably 0.8 to 1.2 g / 10 min, and the density is preferably 0.912 to 0.925 g / cm³. 3 More preferably, it is 0.915–0.920 g / cm³. 3 In a specific embodiment of the present invention, the first metallocene low-density polyethylene is preferably grade 1018BN, with a melt index of 1 g / 10 min and a density of 0.918 g / cm³. 3 The manufacturer is LG Chem of South Korea; the first metallocene low-density polyethylene used in this invention has the properties of high strength, good transparency, few crystal points and easy processing.

[0042] Based on the mass fraction of low-density polyethylene used in the middle layer, the raw materials for preparing the middle layer include 1.5 to 2.5 parts of degradation masterbatch, preferably 2 parts. The melt index, density, and specific grade of the degradation masterbatch used in the middle layer are preferably the same as those of the degradation masterbatch used in the outer layer, which will not be elaborated here.

[0043] Based on the mass fraction of low-density polyethylene used in the middle layer, the raw materials for preparing the middle layer include 0.5 to 1 part of processing aids, preferably 0.5 to 0.6 parts; the melt index, density and specific grade of the processing aids used in the middle layer are preferably the same as those used in the outer layer, and will not be repeated here.

[0044] The raw materials for preparing the inner layer, by weight, include 10-30 parts, 15 parts, 20 parts, or 25 parts of low-density polyethylene; the melt index of the low-density polyethylene used in the inner layer is preferably 1.5-2.5 g / 10 min, more preferably 1.8-2.2 g / 10 min, and the density is preferably 0.920-0.925 g / cm³. 3 More preferably, it is 0.922–0.924 g / cm³. 3 In a specific embodiment of the present invention, the low-density polyethylene used in the inner layer is preferably grade 2426H, with a melt index of 2.0 g / 10 min and a density of 0.924 g / cm³. 3 The manufacturer is LyondellBasell. The inner layer of this invention uses low-density polyethylene, which has the characteristics of high cleanliness, good transparency, good openness, and easy processing.

[0045] Based on the mass fraction of low-density polyethylene used in the inner layer, the raw materials for preparing the inner layer include 25 to 50 parts of second metallocene low-density polyethylene, preferably 30, 40, or 45 parts; the melt index of the second metallocene low-density polyethylene is 0.5 to 1.5 g / 10 min, preferably 0.8 to 1.2 g / 10 min, and the density is 0.912 to 0.925 g / cm³. 3 Preferably, it is 0.915–0.920 g / cm³. 3 In a specific embodiment of the present invention, the second metallocene low-density polyethylene is preferably grade 1018BM, with a melt index of 1 g / 10 min and a density of 0.918 g / cm³. 3 The manufacturer is LG Chem of South Korea; the second metallocene low-density polyethylene used in this invention has the properties of high strength, good opening properties, few crystal points and easy processing.

[0046] Based on the mass fraction of low-density polyethylene used in the inner layer, the raw materials for preparing the inner layer include 30 to 70 parts of third metallocene low-density polyethylene, preferably 38, 50, or 65 parts; the melt index of the third metallocene low-density polyethylene is 0.5 to 1.5 g / 10 min, preferably 0.8 to 1.2 g / 10 min, and the density is 0.908 to 0.920 g / cm³. 3 Preferably, it is 0.910–0.915 g / cm³. 3 In a specific embodiment of the present invention, the third metallocene low-density polyethylene is preferably grade 1012MK, with a melt index of 1 g / 10 min and a density of 0.912 g / cm³. 3 The manufacturer is Exxon; the third metallocene low-density polyethylene used in this invention has characteristics such as high cleanliness, good transparency, good open-cell properties, and easy processing.

[0047] Based on the mass fraction of low-density polyethylene used in the inner layer, the raw materials for preparing the inner layer include 1.5 to 2.5 parts of degradation masterbatch, preferably 2 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 outer layer, which will not be elaborated here.

[0048] Based on the mass fraction of low-density polyethylene used in the inner layer, the raw materials for preparing the inner layer include 0.5 to 1 part of processing aids, preferably 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 outer layer, and will not be repeated here.

[0049] In this invention, the total mass of the outer layer, middle layer, and inner layer is taken as 100%. The mass fraction of the outer layer is preferably 20-30%, the mass fraction of the middle layer is preferably 40-60%, and the mass fraction of the inner layer is preferably 20-30%. In this invention, the thickness of the surface-printed biodegradable PE film is preferably 30-100 μm, more preferably 30-90 μm.

[0050] In this invention, the longitudinal tensile strength of the surface-printed biodegradable PE film is preferably 32-34 MPa, the transverse tensile strength is preferably 30-33 MPa, the longitudinal elongation at break is preferably 550-600%, the transverse elongation at break is preferably 730-760%, the haze is preferably ≤11%, more preferably ≤10.6%, and the heat-sealing strength is preferably 15.5-16.5 N / 15 mm. The surface-printed biodegradable PE film can be effectively degraded under natural environment, photodegradation, thermo-oxidative degradation, and composting conditions.

[0051] This invention also provides a method for preparing the surface-printed fully degradable PE film described above, comprising the following steps:

[0052] The raw materials for preparing the outer, middle, and inner layers are co-extruded and blown into a three-layer film to obtain the surface-printed fully degradable PE film.

[0053] 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 blown film to obtain film bubbles, and after the film bubbles are cooled, performing bubble stabilization, upper traction, corona treatment, edge trimming, lower traction and winding in sequence to obtain the surface-printed fully degradable PE film.

[0054] In this invention, the outer extruder, the middle extruder, and the inner extruder are preferably each provided with 5 heating zones, which are numbered 1 to 5 according to the order in which the raw materials pass through; the die head is provided with 4 heating zones, which are numbered 1 to 4 according to the order in which the raw materials pass through.

[0055] In this invention, the extrusion temperatures of the outer extruder, middle extruder, inner extruder, and each zone of the die are shown in Table 1:

[0056] Table 1. Extrusion temperatures of various zones in the outer, middle, and inner layer extruders and die.

[0057] temperature Zone 1 Zone 2 Zone 3 4th District 5th District outer layer 172±5℃ 178±5℃ 175±5℃ 170±5℃ 165±5℃ Middle layer 165±5℃ 168±5℃ 170±5℃ 165±5℃ 160±5℃ Inner layer 162±5℃ 165±5℃ 168±5℃ 163±5℃ 158±5℃ mold head 180±5℃ 185±5℃ 188±5℃ 183±5℃

[0058] In this invention, the extrusion pressure of the outer extruder is preferably 215-325 bar, the extrusion pressure of the middle extruder is preferably 205-315 bar, and the extrusion pressure of the inner extruder is preferably 220-285 bar.

[0059] The present invention also provides a surface-printed fully degradable PE bag, which is prepared from a surface-printed fully degradable PE film; the surface-printed fully degradable PE film is the surface-printed fully degradable PE film described in the above scheme or the surface-printed fully degradable PE film prepared by the preparation method described in the above scheme.

[0060] This invention also provides a method for preparing the surface-printed fully degradable PE bag described above, comprising the following steps: printing on the surface of the surface-printed fully degradable PE film and then forming the bag to obtain the surface-printed fully degradable PE bag. In this invention, the printing method is preferably gravure printing, and preferably the outer layer of the surface-printed fully degradable PE film is printed; this invention does not have special requirements for the bag-making process, and methods well known to those skilled in the art can be used; in a specific embodiment of this invention, during bag making, the inner layer of the fully degradable PE film is heat-sealed, and the heat-sealing conditions include: a side sealing temperature of 160°C, a bottom sealing temperature of 185°C, a heat-sealing pressure of 4.5N, and a bag-making speed preferably of 120 bags / min.

[0061] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof, but this should not be construed as limiting the scope of protection of the present invention.

[0062] The sources of raw materials and performance parameters used in the examples are shown in Table 2.

[0063] Table 2 shows the source of raw materials and performance parameters used in the examples.

[0064]

[0065] Example 1

[0066] This embodiment has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentage of the materials in each layer is as follows: outer layer 30%, middle layer 40%, and inner layer 30%.

[0067] The amount of raw materials used in each layer is shown in Table 5. The total thickness of the biodegradable PE film is 60 μm. The preparation method is as follows:

[0068] 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 for extrusion and blown film production. After being cooled by air, the film passes through a stabilizing ring and a herringbone pattern to the upper traction rotation to flatten the cylinder. The cylinder then enters the corona treatment device for corona treatment via guide rollers. After being trimmed, the film passes through the lower traction clamping rollers to the front and rear winding devices for front and rear winding, thus obtaining a 60μm surface-printed fully degradable PE film.

[0069] The temperatures and pressures of the outer, middle, and inner layer extruders and dies are shown in Table 3.

[0070] Table 3 Extruder Temperature and Pressure

[0071] temperature Zone 1 Zone 2 Zone 3 4th District 5th District Pressure (bar) outer layer 172℃ 178℃ 175℃ 170℃ 165℃ 238 Middle layer 165℃ 168℃ 170℃ 165℃ 160℃ 256 Inner layer 162℃ 165℃ 168℃ 163℃ 158℃ 245 mold head 180℃ 185℃ 188℃ 183℃

[0072] Bag making using the above-mentioned surface-printed fully degradable PE film: According to customer requirements, gravure printing is used to print on the surface-printed fully degradable PE film. After printing, the surface-printed fully degradable PE film is made into bags according to the required bag shape. Bag making process parameters: side sealing temperature is 160℃, bottom sealing temperature is 185℃, heat sealing pressure is 4.5N, and bag making speed is 120 bags / min.

[0073] Example 2

[0074] This embodiment features a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each layer are as follows: outer layer 25%, middle layer 50%, and inner layer 25%. The raw material amounts for each layer are shown in Table 5. The total thickness of the surface-printed fully degradable PE film is 60 μm. The preparation method is the same as in Example 1, resulting in a surface-printed fully degradable PE film and bag.

[0075] Example 3

[0076] This embodiment has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each layer are as follows: outer layer 20%, middle layer 60%, and inner layer 20%. The raw material usage and layer thickness ratio of each layer are shown in Table 5. The total thickness of the surface-printed fully degradable PE film is 60 μm. The preparation method is the same as in Example 1, resulting in a surface-printed fully degradable PE film and bag.

[0077] Comparative Example 1

[0078] This comparative example has a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each layer are as follows: 30% for the outer layer, 40% for the middle layer, and 30% for the inner layer. The total thickness of the film is 60 μm.

[0079] The outer, middle, and inner layers all use biodegradable resin BDR-F1320CD 100, with a melt index of 4 g / 10 min and a density of 1.3 g / cm³. 3The manufacturer is Foshan Pangding New Material Technology Co., Ltd.

[0080] The preparation method is the same as in Example 1. The temperatures and pressures of the extruders and dies for the outer, middle, and inner layers are shown in Table 4.

[0081] Table 4 Extruder Temperature and Pressure

[0082] temperature Zone 1 Zone 2 Zone 3 4th District 5th District Pressure (bar) outer layer 125 130 135 125 120 172 Middle layer 120 135 140 130 125 195 Inner layer 123 130 136 132 120 170 mold head 120 125 130 125

[0083] Comparative Example 2

[0084] This embodiment features a three-layer structure: an outer layer, a middle layer, and an inner layer. The weight percentages of the materials in each layer are as follows: outer layer 25%, middle layer 50%, and inner layer 25%. The raw material amounts for each layer are shown in Table 5. The total thickness of the surface-printed fully degradable PE film is 60 μm. The preparation method is the same as in Example 1, resulting in a surface-printed fully degradable PE film and bag.

[0085] Table 5. Raw material usage (parts by mass) for Examples 1-3 and Comparative Example 2

[0086]

[0087]

[0088] Performance testing:

[0089] The mechanical properties, wetting tension and haze, degradation performance, ink layer adhesion strength and heat sealing strength of the PE films prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 6.

[0090] Table 6 Performance Test Results

[0091]

[0092] As can be seen from the data in Table 6, the biodegradable PE film prepared by this invention has good mechanical properties, low haze, strong adhesion to the ink layer, and suitable heat-sealing strength. Furthermore, it can degrade under light, heat-oxidation, and composting conditions. In Comparative Example 1, the film prepared using degradable materials had poor mechanical properties, high haze, weak adhesion to the ink layer, low heat-sealing strength, and could not degrade under light and heat-oxidation conditions. In Comparative Example 2, the addition of degradable masterbatch was omitted. Although the mechanical properties, transparency, adhesion to the ink layer, and heat-sealing strength of the film met the requirements, it could not degrade, and its degradation performance under light, heat-oxidation, and composting conditions was unqualified.

[0093] 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 surface-printed fully degradable PE film, characterized in that, It is made from the raw materials for the outer, middle and inner layers through a three-layer co-extrusion blown film process; The outer layer is prepared by mass fractions of 10-30 parts of low-density polyethylene, 30-85 parts of metallocene medium-density polyethylene, 20-45 parts of linear low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids. The raw materials for preparing the middle layer, by mass parts, include 10-30 parts of low-density polyethylene, 15-40 parts of linear low-density polyethylene, 30-80 parts of first metallocene low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids. The raw materials for preparing the inner layer, by mass parts, include 10-30 parts of low-density polyethylene, 25-50 parts of second metallocene low-density polyethylene, 30-70 parts of third metallocene low-density polyethylene, 1.5-2.5 parts of degradation masterbatch, and 0.5-1 parts of processing aids. The melt index of the first metallocene low-density ethylene and the second metallocene low-density polyethylene are independently 0.5–1.5 g / 10 min, and their densities are independently 0.912–0.925 g / cm³. 3 The third metallocene low-density polyethylene has a melt index of 0.5–1.5 g / 10 min and a density of 0.908–0.920 g / cm³. 3 ; The outer, middle, and inner layers use degradation masterbatches with a melt index of 46–55 g / 10 min and a density of 0.920–0.940 g / cm³. 3 .

2. The surface-printed fully degradable PE film according to claim 1, characterized in that, The low-density polyethylene used in the outer, middle, and inner layers has a melt index of 1.5–2.5 g / 10 min and a density of 0.920–0.925 g / cm³. 3 ; The outer layer uses metallocene medium-density polyethylene with a melt index of 0.8–1.8 g / 10 min and a density of 0.920–0.935 g / cm³. 3 ; The outer layer uses linear low-density polyethylene with a melt index of 0.2–1.0 g / 10 min and a density of 0.920–0.930 g / cm³. 3 .

3. The surface-printed fully degradable PE film according to claim 1, characterized in that, The middle layer uses linear low-density polyethylene with a melt index of 1.5–2.5 g / 10 min and a density of 0.912–0.925 g / cm³. 3 .

4. The surface-printed fully degradable PE film according to claim 1, characterized in that, The processing aids used in the outer, middle, and inner layers have a melt index of 1.5–2.8 g / min and a density of 0.910–0.920 g / cm³. 3 .

5. The surface-printed fully degradable PE film according to any one of claims 1 to 4, characterized in that, The outer and middle layers use low-density polyethylene grade 2420H; the outer layer uses metallocene medium-density polyethylene grade 1327MA; and the outer layer uses linear low-density polyethylene grade 2505H. The linear low-density polyethylene used in the middle layer is grade 7402; the first metallocene low-density polyethylene is grade 1018BN. The inner layer uses low-density polyethylene of grade 2426H; the second metallocene low-density polyethylene is grade 1018BM; and the third metallocene low-density polyethylene is grade 1012MK. The processing aids used in the outer, middle, and inner layers are designated PA0895LD.

6. The surface-printed fully degradable PE film according to any one of claims 1 to 4, characterized in that, The total mass of the outer, middle, and inner layers is 100%, with the outer layer having a mass fraction of 20-30%, the middle layer having a mass fraction of 40-60%, and the inner layer having a mass fraction of 20-30%.

7. The method for preparing the surface-printed fully degradable PE film according to any one of claims 1 to 6, characterized in that, Includes the following steps: The raw materials for preparing the outer, middle, and inner layers are co-extruded and blown into a three-layer film to obtain the surface-printed fully degradable PE film.

8. The preparation method according to claim 7, 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, performing bubble stabilization, upper traction, corona treatment, edge trimming, lower traction and winding in sequence to obtain the surface-printed fully degradable PE film.

9. A surface-printed fully degradable PE bag, characterized in that, It is prepared from a surface-printed fully degradable PE film; the surface-printed fully degradable PE film is the surface-printed fully degradable PE film according to any one of claims 1 to 6 or the surface-printed fully degradable PE film prepared by the preparation method according to any one of claims 7 to 8.

10. The method for preparing the surface-printed fully degradable PE bag according to claim 9, characterized in that, Includes the following steps: After printing on the surface of the surface-printed fully degradable PE film, the bag is made to obtain the surface-printed fully degradable PE bag.

Images