Black and white PETG shrink film and preparation system

Abstract

The utility model discloses a black and white PETG (polyethylene terephthalate glycol) shrink film, which comprises five layers of co-extrusion composite structures, namely a buffer layer D positioned in the middle, a white layer B close to the outer side of the buffer layer D, a black layer C close to the inner side of the buffer layer D, a printing layer A on the outer side of the white layer B, and a self-repairing layer E on the inner side of the black layer C. The utility model further discloses a special preparation system for the black and white PETG shrink film, which can be used for uninterruptedly producing the black and white PETG shrink film in batches. According to the black and white PETG shrink film with the five-layer co-extrusion composite structure disclosed by the utility model, the problems of microcrack propagation and barrier attenuation of the traditional PETG shrink film are solved by utilizing the elastic body structure of the D layer to dissipate stress and the self-repairing and forced closing of microcracks of the E layer through an interlayer synergistic effect, and the isolation service life of the film is prolonged.

Description

Technical Field

[0001] This utility model relates to a black and white PETG shrink film and its preparation system. Background Technology

[0002] Black and white shrink film is commonly used in the packaging industry. It can be used for packaging products that are sensitive to light, such as certain flavorings in food and active ingredients in pharmaceuticals, where light can cause spoilage, decomposition, or reduced efficacy. The black layer of the shrink film effectively blocks light, protecting the product's quality and stability. The white portion provides excellent contrast, facilitating the printing of markings. The sharp contrast between white and black background makes printed text, patterns, trademarks, or barcodes more clearly legible. This is crucial for product identification, inventory management, and providing consumers with product information. Furthermore, because black and white shrink film uses fewer pigments, it may be easier to comply with certain environmental regulations while meeting packaging requirements.

[0003] CN 113211921 A discloses a PETG black-and-white composite film with light-shielding properties, employing an ABC structure, where layer A is a printed layer, layer B is a white structural layer, and layer C is a black structural layer. However, due to differences in additives, the white and black layers of existing black-and-white shrink films exhibit microcrack channels formed at the interface during shrinkage due to disordered crystallization. These microcracks cause a significant drop in the barrier properties of the shrink film. Actual measurements show that the water and oxygen barrier properties of the black-and-white shrink film used for packaging spoiled products are more than 30% lower than the factory test values. Microscopic grain boundaries are identified as the preferred pathway for water and oxygen penetration. Furthermore, the difference between the transverse and longitudinal tensile strengths of black-and-white shrink films with grain boundary cracks exceeds 50%, and the shrinkage rate fluctuates by more than 10%, severely affecting packaging sealing. Existing black-and-white shrink films rarely address this microcrack phenomenon at the interlayer interface and lack corresponding preventative measures. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a black and white PETG shrink film to reduce or avoid the problems mentioned above.

[0005] To solve the above-mentioned technical problems, this utility model proposes a black and white PETG shrink film, comprising a five-layer co-extruded composite structure. The five-layer co-extruded composite structure consists of a buffer layer D in the middle, a white layer B on the outside adjacent to the buffer layer D, a black layer C on the inside, a printing layer A on the outside of the white layer B, and a self-healing layer E on the inside of the black layer C. The total thickness of the black and white PETG shrink film is 50-150 μm, the thickness of the printing layer A accounts for 10-15% of the total thickness, the thickness of the white layer B accounts for 15-20% of the total thickness, the thickness of the black layer C accounts for 25-30% of the total thickness, the thickness of the buffer layer D accounts for 20-25% of the total thickness, and the remaining thickness is the self-healing layer E.

[0006] This invention also proposes a preparation system for the aforementioned black and white PETG shrink film, comprising five independent extruders: a first extruder corresponding to the printed layer A, a second extruder corresponding to the white layer B, a third extruder corresponding to the buffer layer D, a fourth extruder corresponding to the black layer C, and a fifth extruder corresponding to the self-healing layer E; the outlets of the five independent extruders are connected to the inlet of a multi-layer co-extrusion die via pipes, and the thick sheet extruded by the multi-layer co-extrusion die is fed into a cooling water tank; the thick sheet fed into the cooling water tank is conveyed to a biaxial stretching mechanism, and the film formed by the biaxial stretching mechanism is fed into a hot air circulating oven, the outlet of the hot air circulating oven is connected to the inlet of an air-cooling mechanism, and the outlet of the air-cooling mechanism is connected to a slitting and winding mechanism.

[0007] Preferably, the outlets of the five extruders are each connected to the outlet of a vacuum drying oven via pipes.

[0008] Preferably, a weighing scale is installed in each pipe connecting the five extruders and the vacuum drying oven.

[0009] This invention presents a five-layer co-extruded composite black and white PETG shrink film. Through interlayer synergy, utilizing the stress dissipation of the D-layer elastomer structure and the self-repairing and forced closure of microcracks in the E-layer, it solves the problems of microcrack propagation and barrier attenuation in traditional PETG shrink films, thereby improving the film's barrier life. Furthermore, the preparation system proposed in this invention can be used for continuous mass production of this film, overcoming the deficiency of existing technologies that lack corresponding preparation systems. Attached Figure Description

[0010] The accompanying drawings are intended only to illustrate and explain this application and do not limit the scope of this utility model.

[0011] Figure 1 The diagram shown is a structural schematic of a black and white PETG shrink film according to a specific embodiment of the present invention.

[0012] Figure 2The diagram shown is a structural schematic of a black and white PETG shrink film preparation system according to another specific embodiment of the present invention. Detailed Implementation

[0013] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, specific embodiments are now described with reference to the accompanying drawings. Identical components are denoted by the same reference numerals.

[0014] To address the microcrack problem at the interlayer interface of black and white shrink films caused by differences in raw material crystallization kinetics, this invention proposes a black and white PETG shrink film, such as... Figure 1 As shown, the black and white PETG shrink film proposed in this invention comprises a five-layer co-extruded composite structure. This five-layer co-extruded composite structure consists of a buffer layer D in the middle, a white layer B on the outer side immediately adjacent to the buffer layer D, a black layer C on the inner side, a printing layer A on the outer side of the white layer B, and a self-healing layer E on the inner side of the black layer C. The significant difference between the black and white PETG shrink film of this invention and the black and white composite films mentioned in the background art is that a buffer layer D is inserted between the white layer B and the black layer C, and a self-healing layer E is provided on the inner side of the black layer C. The main function of the newly added buffer layer D is to reduce stress concentration, inhibit the propagation of microcracks, and improve interlayer bonding. The main function of the self-healing layer E is to provide self-repair for cracks while enhancing barrier properties. This will be further explained in detail later.

[0015] The printing layer A, white layer B, and black layer C can use the same components, functions, and effects as in existing technologies. However, considering the structure has changed from three layers to five layers, the thickness of each layer has been adjusted accordingly. In a preferred embodiment, the thickness of the printing layer A accounts for 10-15% of the total thickness, the white layer B accounts for 15-20%, the black layer C accounts for 25-30%, the buffer layer D accounts for 20-25%, and the remaining thickness is the self-healing layer E. In another specific embodiment, the total thickness of the black and white PETG shrink film of this invention is preferably 50-150 μm. The thickness of each layer in the black and white PETG shrink film of this invention has been optimized compared to existing technologies. The thickness percentage of the white layer B is significantly reduced, while the thickness percentage of the black layer C is slightly increased. The buffer layer D compensates for the reduced reflectivity of the white layer B, and the self-healing layer E significantly improves the barrier properties of the black layer C.

[0016] Since the printed layer A, white layer B, and black layer C can use the same components as existing technologies, the newly added buffer layer D and self-healing layer E will be described in detail below.

[0017] In one specific embodiment, the buffer layer D may be composed of the following components in parts by weight: 85-88 parts by weight of PETG chips, 8-10 parts by weight of hydrogenated SEBS elastomer, 2-3 parts by weight of siloxane coupling agent, and 1-2 parts by weight of nano-calcium carbonate (particle size 200-300nm).

[0018] Among them, the preferred domestic substitute for hydrogenated SEBS elastomer is Baling Petrochemical's YH-688, or Kraton's G1645. SEBS elastomer is used to improve interlayer peel strength and control the elastic modulus gradient of the shrinkage film. Siloxane coupling agents, such as conventional polydimethylsiloxane coupling agents, or vinyltriethoxysilane and vinyltrimethoxysilane, are used to form thioether bonds (CSC) and ether bonds (COC) at the interface between the D layer and the B / C layer, improving interlayer peel strength and blocking crack propagation along the interface. Nano-calcium carbonate acts as a heterogeneous nucleating agent, regulating the crystallization rate of PETG and reducing shrinkage anisotropy.

[0019] In another specific embodiment, the self-healing layer E may be composed of the following components in parts by weight: 65-70 parts by weight of PETG chips, 15-18 parts by weight of EVOH, 8-12 parts by weight of DCPD repair agent, 2-3 parts by weight of catalyst, and 3-5 parts by weight of nano-montmorillonite (100-200nm).

[0020] EVOH, an ethylene-vinyl alcohol copolymer, can be selected from products such as EVAL H173B from Kuraray (Japan) or FP104B from Soarnol (Japan). It generates reverse shrinkage stress during high-temperature shrinkage of the film, forcing microcracks to close and reducing oxygen permeability. DCPD repair agent is a self-healing material based on dicyclopentadiene (DCPD). Domestic products such as Hengda New Materials or Huarun Chemical's DCPD hydrogenated resin can be selected. It undergoes ring-opening polymerization upon contact with the catalyst during crack propagation to achieve self-repair. The preferred catalyst is a Grubbs organometallic catalyst (1,3-bis(2,4,6-trimethylphenyl)-2-(imidazolidinedimethyl))(dichlorobenzylmethyl)(tricyclohexylphosphine)ruthenium (CAS No.: 246047-72-3)), such as Merck's second-generation Grubbs catalyst (Germany), or Aladdin's Grubbs catalyst (USA). Domestic alternatives include Shanghai Jizhi Biochemical's second-generation Grubbs catalyst. Nano-montmorillonite can be used to block oxygen and water vapor permeation pathways.

[0021] The black and white PETG shrink film with a five-layer co-extruded composite structure of this invention solves the problems of microcrack propagation and barrier attenuation in traditional PETG shrink films by utilizing the interlayer synergy, the stress dissipation of the D layer elastomer structure, and the self-repair and forced closure of microcracks in the E layer, thereby improving the film's barrier life.

[0022] Furthermore, the black and white PETG shrink film of this invention can be prepared by the following method.

[0023] First, PETG chips with an intrinsic viscosity of 0.75-0.85 dL / g were placed in a vacuum drying oven and dried at 80°C for 4 hours until the moisture content was ≤50 ppm. The dried PETG chips were then weighed and packaged as PETG base material.

[0024] Five independent extruders are set up, with multi-layer co-extrusion dies installed at the end of each extruder. The components other than PETG that make up the printing layer A, white layer B, buffer layer D, black layer C, and self-healing layer E are mixed with the PETG base material in proportion and fed into the corresponding extruders.

[0025] The thickness of each layer is controlled according to the proportion of material input. For example, as mentioned above, the thickness ratio of the five layers is controlled as follows: layer A accounts for 10-15%, layer B accounts for 15-20%, layer C accounts for 25-30%, layer D accounts for 20-25%, and layer E accounts for 12-18%.

[0026] Set the extruder temperature, screw speed, and melt pressure values ​​for each layer, as shown in the table below.

[0027] Layer name Extruder section temperature (°C) Screw speed (rpm) Melt pressure (MPa) A floor 230-235-240-230 45 12-14 Floor B 235-240-245-235 35 15-18 D layer 240-245-250-240 40 18-20 C layer 230-235-240-230 38 14-16 E layer 225-230-235-225 42 10-12

[0028] Five independent extruders feed the melt of each layer of material into a multi-layer co-extrusion die, which then extrudes the material into a thick sheet. The extruded sheet is then rapidly cooled and shaped by a cooling water tank (water temperature 12℃).

[0029] Next, the thick sheet was subjected to biaxial stretching. First, it was stretched laterally, preheated at 85°C for 15 seconds, and then stretched laterally at 100°C with a stretching ratio of 3.5:1; then it was stretched longitudinally at 95°C with a stretching ratio of 2.8:1.

[0030] Finally, it undergoes heat setting in a hot air circulating oven at 70℃ for 30 seconds. After setting, it is cooled, slit, and rolled up.

[0031] Corresponding to the above preparation method, this application also proposes a preparation system for black and white PETG shrink film specifically for this utility model, which can be used for uninterrupted mass production of black and white PETG shrink film.

[0032] like Figure 2 As shown, the black and white PETG shrink film preparation system of this application includes five independent extruders, namely the first extruder 100 corresponding to the printed layer A, the second extruder 200 corresponding to the white layer B, the third extruder 300 corresponding to the buffer layer D, the fourth extruder 400 corresponding to the black layer C, and the fifth extruder corresponding to the self-healing layer E.

[0033] The outlets of the five extruders are each connected to the outlet of a vacuum drying chamber 10 via pipes. The vacuum drying chamber 10 is used to dry PETG chips for use as PETG base material. Each pipe connecting the five extruders and the vacuum drying chamber 10 is equipped with a weighing scale 11, which is used to weigh and transport the PETG base material to the corresponding extruder, while other materials are fed into the corresponding extruder through the extruder opening and mixed with the PETG base material.

[0034] The outlets of five independent extruders are connected to the inlet of a multi-layer co-extrusion die 501 via pipes. The extruded sheets from the multi-layer co-extrusion die 501 are fed into a cooling water tank 502 for rapid cooling and forming. The sheets passing through the cooling water tank 502 are then conveyed to a biaxial stretching mechanism 503. The film formed by the biaxial stretching mechanism 503 is fed into a hot air circulating oven 504 for heat setting. The outlet of the hot air circulating oven 504 is connected to the inlet of an air-cooling mechanism 505 for cooling the heat-set film. The outlet of the air-cooling mechanism 505 is connected to a slitting and winding mechanism 506.

[0035] Example 1

[0036] Layer A is 5 μm thick, layer B is 7.5 μm thick, and layer C is 12.5 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 10 μm thick. Layer E is 15 μm thick. The total thickness is 50 μm.

[0037] Layer D: 85 parts by weight of PETG chips, 8 parts by weight of SEBS elastomer, 2 parts by weight of siloxane coupling agent, and 1 part by weight of nano-calcium carbonate (200nm).

[0038] E layer: 65 parts by weight of PETG slices, 15 parts by weight of EVOH, 8 parts by weight of DCPD repair agent, 2 parts by weight of catalyst, and 3 parts by weight of nano-montmorillonite (100nm).

[0039] Example 2

[0040] Layer A is 5 μm thick, layer B is 7.5 μm thick, and layer C is 12.5 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 10 μm thick. Layer E is 15 μm thick. The total thickness is 50 μm.

[0041] Layer D: 88 parts by weight of PETG chips, 10 parts by weight of SEBS elastomer, 3 parts by weight of siloxane coupling agent, and 2 parts by weight of nano-calcium carbonate (200nm).

[0042] E layer: 65 parts by weight of PETG slices, 15 parts by weight of EVOH, 8 parts by weight of DCPD repair agent, 2 parts by weight of catalyst, and 3 parts by weight of nano-montmorillonite (100nm).

[0043] Example 3

[0044] Layer A is 5 μm thick, layer B is 7.5 μm thick, and layer C is 12.5 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 10 μm thick. Layer E is 15 μm thick. The total thickness is 50 μm.

[0045] Layer D: 86.5 parts by weight of PETG chips, 9 parts by weight of SEBS elastomer, 2.5 parts by weight of siloxane coupling agent, and 1.5 parts by weight of nano-calcium carbonate (200nm).

[0046] E layer: 65 parts by weight of PETG slices, 15 parts by weight of EVOH, 8 parts by weight of DCPD repair agent, 2 parts by weight of catalyst, and 3 parts by weight of nano-montmorillonite (100nm).

[0047] In Examples 1-3, the components of layer E remain unchanged, only the component content of layer D is changed.

[0048] Example Lateral shrinkage rate (100℃) interlayer peeling force oxygen transmission rate <![CDATA[Microcrack density (number / mm 2 )]]> 1 77％ 4.0 N / mm <![CDATA[4.2cc / m 2 ·d]]> 3.5 2 78％ 4.3 N / mm <![CDATA[3.9cc / m 2 ·d]]> 3.1 3 78％ 4.6 N / mm <![CDATA[3.8cc / m 2 ·d]]> 2.8

[0049] Example 4

[0050] Layer A is 15 μm thick, layer B is 20 μm thick, and layer C is 30 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 25 μm thick. Layer E is 10 μm thick. The total thickness is 108 μm.

[0051] Layer D: 85 parts by weight of PETG chips, 8 parts by weight of SEBS elastomer, 2 parts by weight of siloxane coupling agent, and 1 part by weight of nano-calcium carbonate (300nm).

[0052] E layer: 65 parts by weight of PETG slices, 15 parts by weight of EVOH, 8 parts by weight of DCPD repair agent, 2 parts by weight of catalyst, and 3 parts by weight of nano-montmorillonite (200nm).

[0053] Example 5

[0054] Layer A is 15 μm thick, layer B is 20 μm thick, and layer C is 30 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 25 μm thick. Layer E is 10 μm thick. The total thickness is 108 μm.

[0055] Layer D: 85 parts by weight of PETG chips, 8 parts by weight of SEBS elastomer, 2 parts by weight of siloxane coupling agent, and 1 part by weight of nano-calcium carbonate (300nm).

[0056] E layer: 70 parts by weight of PETG slices, 18 parts by weight of EVOH, 12 parts by weight of DCPD repair agent, 3 parts by weight of catalyst, and 5 parts by weight of nano-montmorillonite (200nm).

[0057] Example 6

[0058] Layer A is 15 μm thick, layer B is 20 μm thick, and layer C is 30 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 25 μm thick. Layer E is 10 μm thick. The total thickness is 108 μm.

[0059] Layer D: 85 parts by weight of PETG chips, 8 parts by weight of SEBS elastomer, 2 parts by weight of siloxane coupling agent, and 1 part by weight of nano-calcium carbonate (300nm).

[0060] E layer: 67.5 parts by weight of PETG slices, 16.5 parts by weight of EVOH, 10 parts by weight of DCPD repair agent, 2.5 parts by weight of catalyst, and 4 parts by weight of nano-montmorillonite (200nm).

[0061] In Examples 4-6, the components of layer D remained unchanged, only the component content of layer E was changed.

[0062]

[0063]

[0064] Example 7

[0065] Layer A is 5 μm thick, layer B is 7.5 μm thick, and layer C is 12.5 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 10 μm thick. Layer E is 15 μm thick. The total thickness is 50 μm.

[0066] Layer D: 86.5 parts by weight of PETG chips, 9 parts by weight of SEBS elastomer, 2.5 parts by weight of siloxane coupling agent, and 1.5 parts by weight of nano-calcium carbonate (250nm).

[0067] E layer: 67.5 parts by weight of PETG slices, 16.5 parts by weight of EVOH, 10 parts by weight of DCPD repair agent, 2.5 parts by weight of catalyst, and 4 parts by weight of nano-montmorillonite (150nm).

[0068] Example 8

[0069] Layer A is 15 μm thick, layer B is 20 μm thick, and layer C is 30 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 25 μm thick. Layer E is 10 μm thick. The total thickness is 100 μm.

[0070] Layer D: 86.5 parts by weight of PETG chips, 9 parts by weight of SEBS elastomer, 2.5 parts by weight of siloxane coupling agent, and 1.5 parts by weight of nano-calcium carbonate (250nm).

[0071] E layer: 67.5 parts by weight of PETG slices, 16.5 parts by weight of EVOH, 10 parts by weight of DCPD repair agent, 2.5 parts by weight of catalyst, and 4 parts by weight of nano-montmorillonite (150nm).

[0072] Example 9

[0073] Layer A is 20 μm thick, layer B is 27.5 μm thick, and layer C is 42.5 μm thick. These three layers are prepared using the same composition as in existing technologies. Layer D is 35 μm thick. Layer E is 25 μm thick. The total thickness is 150 μm.

[0074] Layer D: 86.5 parts by weight of PETG chips, 9 parts by weight of SEBS elastomer, 2.5 parts by weight of siloxane coupling agent, and 1.5 parts by weight of nano-calcium carbonate (250nm).

[0075] E layer: 67.5 parts by weight of PETG slices, 16.5 parts by weight of EVOH, 10 parts by weight of DCPD repair agent, 2.5 parts by weight of catalyst, and 4 parts by weight of nano-montmorillonite (150nm).

[0076] Examples 7-9 show that the components of layer D and layer E remain unchanged, but the thickness of the five-layer structure is altered.

[0077] Example Lateral shrinkage rate (100℃) interlayer peeling force oxygen transmission rate <![CDATA[Microcrack density (number / mm 2 )]]> 7 75％ 4.4 N / mm <![CDATA[4.1cc / m 2 ·d]]> 4.2 8 76％ 4.5 N / mm <![CDATA[3.7cc / m 2 ·d]]> 3.5 9 77％ 4.6 N / mm <![CDATA[3.5cc / m 2 ·d]]> 3.0

[0078] Comparative Example 1

[0079] Referring to Example 1, the SEBS elastomer was removed from the D layer component, while the other parameters remained unchanged.

[0080] Layer D: 93 parts by weight of PETG slices, 2 parts by weight of siloxane coupling agent, and 1 part by weight of nano-calcium carbonate (200nm).

[0081] Comparative Example 2

[0082] Referring to Example 2, nano-calcium carbonate was removed from the D layer component, while the other parameters remained unchanged.

[0083] Layer D: 90 parts by weight of PETG chips, 10 parts by weight of SEBS elastomer, and 3 parts by weight of siloxane coupling agent.

[0084] Comparative Example 3

[0085] Referring to Example 3, the siloxane coupling agent was removed from the D layer component, while the other parameters remained unchanged.

[0086] Layer D: 89 parts by weight of PETG slices, 9 parts by weight of SEBS elastomer, and 1.5 parts by weight of nano-calcium carbonate (200nm).

[0087] Comparative Example Lateral shrinkage rate (100℃) interlayer peeling force oxygen transmission rate <![CDATA[Microcrack density (number / mm 2 )]]> 1 65％ 2.4N / mm <![CDATA[19.5cc / m 2 ·d]]> 105 2 69％ 3.5N / mm <![CDATA[17.3cc / m 2 ·d]]> 113 3 70％ 3.7 N / mm <![CDATA[16.6cc / m 2 ·d]]> 98

[0088] Comparative Example 4

[0089] Referring to Example 4, EVOH was removed from the E layer component, while the other parameters remained unchanged.

[0090] E layer: 80 parts by weight of PETG slices, 8 parts by weight of DCPD repair agent, 2 parts by weight of catalyst, and 3 parts by weight of nano-montmorillonite (200nm).

[0091] Comparative Example 5

[0092] Referring to Example 5, DCPD was removed from the E layer component, while the other parameters remained unchanged.

[0093] E layer: 82 parts by weight of PETG chips, 18 parts by weight of EVOH, 3 parts by weight of catalyst, and 5 parts by weight of nano-montmorillonite (200nm).

[0094] Comparative Example 6

[0095] Referring to Example 6, the catalyst was removed from the E layer component, while the other parameters remained unchanged.

[0096] E layer: 70 parts by weight of PETG slices, 16.5 parts by weight of EVOH, 10 parts by weight of DCPD repair agent, and 4 parts by weight of nano-montmorillonite (200nm).

[0097] Comparative Example 7

[0098] Referring to Example 7, nano-montmorillonite was removed from the E layer component, while the other parameters remained unchanged.

[0099] E layer: 71 parts by weight of PETG slices, 17 parts by weight of EVOH, 10 parts by weight of DCPD repair agent, and 2.5 parts by weight of catalyst.

[0100]

[0101]

[0102] By comparison, embodiments 1-9 of this utility model all meet the design requirements in key indicators with minimal fluctuations: transverse heat shrinkage rate (100℃): 76-78% (design requirement ≥75%); oxygen permeability: 3.5-5.0cc / m 2 •d (design requirement ≤5cc); Microcrack density: 2.8-4.2 cracks / mm 2 (Design requirements ≤ 5 items)

[0103] Performance indicators Fluctuation range of 9 examples Traditional products Design Requirements lateral shrinkage rate 75-78％ 70％ ≥75％ interlayer peeling force 4.0-4.7 2.0 ≥4.0 oxygen transmission rate <![CDATA[3.5-4.5cc / m 2 ·d]]> 25cc ≤5cc Microcrack density <![CDATA[2.8 - 4.2 lines / mm 2 > 120 ≤5

[0104] Conclusion: When the key components of each layer change within the recommended range, the performance index fluctuation is less than 5%, demonstrating the strong robustness of the formulation system. Even with adjustments to a single layer component, other layers compensate through mechanisms such as interface strengthening (layer D) and dynamic repair (layer E), maintaining overall performance stability. This novel PETG black and white shrink film, through a multi-layer cascade compensation mechanism, ensures excellent and consistent product performance within a reasonable range of component fluctuations, significantly outperforming traditional optimization schemes.

[0105] Those skilled in the art should understand that although the present invention has been described with reference to multiple embodiments, not every embodiment contains only one independent technical solution. This description is provided merely for clarity; those skilled in the art should understand the specification as a whole and consider the technical solutions involved in each embodiment as being able to be combined with each other to form different embodiments to understand the scope of protection of the present invention.

[0106] The above description is merely an illustrative embodiment of this utility model and is not intended to limit the scope of this utility model. Any equivalent changes, modifications, and combinations made by those skilled in the art without departing from the concept and principles of this utility model should fall within the protection scope of this utility model.

Claims

1. A black and white PETG shrink film characterized in that, The five-layer co-extrusion composite structure includes a middle buffer layer D, a white layer B next to the outer side of the buffer layer D, a black layer C next to the inner side of the buffer layer D, a printing layer A next to the outer side of the white layer B, and a self-repairing layer E next to the inner side of the black layer C; wherein the total thickness of the black and white PETG shrink film is 50-150μm, the thickness of the printing layer A accounts for 10-15% of the total thickness, the thickness of the white layer B accounts for 15-20% of the total thickness, the thickness of the black layer C accounts for 25-30% of the total thickness, the thickness of the buffer layer D accounts for 20-25% of the total thickness, and the remaining thickness is the self-repairing layer E.

2. A system for the preparation of the black and white PETG shrink film according to claim 1, characterized by, The five independent extruders are respectively a first extruder (100) corresponding to the printing layer A, a second extruder (200) corresponding to the white layer B, a third extruder (300) corresponding to the buffer layer D, a fourth extruder (400) corresponding to the black layer C, and a fifth extruder (500) corresponding to the self-repairing layer E; the outlets of the five independent extruders are connected to the inlet of a multi-layer co-extrusion die (501) through pipelines, the thick sheet extruded by the multi-layer co-extrusion die (501) is input to a cooling water tank (502); the thick sheet passing through the cooling water tank (502) is transported to a bidirectional stretching mechanism (503), the film formed by the bidirectional stretching mechanism (503) is input to a hot air circulating oven (504), the outlet of the hot air circulating oven (504) is connected to the inlet of an air cooling mechanism (505), and the outlet of the air cooling mechanism (505) is connected to a slitting and winding mechanism (506).

3. The preparation system of claim 2, wherein, The outlets of the five extruders are respectively connected to the outlet of a vacuum drying box (10) through pipelines.

4. The preparation system of claim 3, wherein, A metering scale (11) is arranged in each pipeline connecting the five extruders and the vacuum drying box (10).

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