A recyclable POF heat shrinkable film and its preparation method

Abstract

The present application relates to the technical field of POF heat shrinkable film, and specifically discloses a recyclable POF heat shrinkable film and its preparation method. A recyclable POF heat shrinkable film includes an intermediate core layer and a surface layer, wherein the surface layer is located on the upper and lower sides of the intermediate core layer, and the surface layer is made of the following raw materials: 25-32 parts of PP, 2-5 parts of recycled masterbatch, 0.5-2 parts of opening agent, 1-4 parts of slip agent, and 1-2 parts of anti-fogging agent; the recycled masterbatch contains the following components: 65-73 parts of LLDPE new material, 3-40 parts of LLDPE recycled material, and 21-30 parts of active ingredient; the active ingredient contains the following components: 45-55 parts of P34HB, 12-15 parts of seaweed fiber, and 4-5 parts of nucleating agent. Its preparation method is as follows: after mixing PP and recycled masterbatch, the opening agent, slip agent, and anti-fogging agent are added and mixed, the intermediate core layer raw material is mixed, and then a sheet is obtained by three-layer co-extrusion using an extruder, and then stretched and shaped. The present application can improve the conflict between the anti-fog function and the processing performance, so that the POF heat shrinkable film has excellent anti-fog performance while also having better overall structural strength.

Description

Technical Field

[0001] The present application relates to the technical field of POF heat shrinkable films, and more specifically, to a recyclable POF heat shrinkable film and a preparation method thereof. Background Art

[0002] POF heat shrink film is the full name of multi-layer co-extruded polyolefin heat shrink film. Its main raw materials include linear low-density polyethylene (LLDPE) and co-polypropylene (PP). It is a new type of environmentally friendly shrink film. The product adopts advanced biaxially oriented three-layer and five-layer melt co-extrusion special process.

[0003] POF heat shrink film is mainly used for packaging products with regular and irregular shapes. Due to its non-toxic and environmentally friendly, high transparency, high shrinkage rate, good heat sealing performance, high gloss, strong toughness, tear resistance, uniform heat shrinkage and suitability for fully automatic high-speed packaging, it is widely used in automotive products, plastic products, stationery, books, electronics, circuit boards, headphones, handicrafts, photo frames and other wooden products, toys, pesticides, daily necessities, food, cosmetics, canned beverages, dairy products, medicine, cassettes and videotapes, etc.

[0004] POF heat shrink film can be recycled for resource reuse through specialized recycling processes. This process involves cleaning, crushing, and melting the film, transforming it into new plastic products. This reduces the exploitation of natural resources, lowers energy consumption and carbon emissions, and promotes sustainable development. Recycling POF heat shrink film can also save costs and improve economic efficiency for businesses. Furthermore, because POF heat shrink film is made from polyolefins, which do not contain chlorine, it does not produce toxic gases during the recycling process, minimizing the impact on the environment and making it highly sought after in the market.

[0005] POF heat shrink film requires anti-fog properties in certain applications. For example, in humid environments or those with large temperature fluctuations, it needs to effectively prevent fog or water droplets from forming on the inner surface of the film, ensuring that the contents inside the film are clearly visible. The anti-fog property primarily relies on the addition of specific anti-fog agents, but the addition of these agents increases viscosity, making it more susceptible to adhesion during processing. This can lead to uneven pulling, wrinkling, or tearing of the film, resulting in poor overall structural strength of the POF heat shrink film. Therefore, a solution to this technical problem is urgently needed. Summary of the Invention

[0006] In order to improve the conflict between anti-fog function and processing performance, so that the POF heat shrinkable film has excellent anti-fog performance while also having better overall structural strength, the present application provides a recyclable POF heat shrinkable film and a preparation method thereof.

[0007] In a first aspect, the present application provides a recyclable POF heat shrinkable film, which adopts the following technical solution:

[0008] A recyclable POF heat shrinkable film comprises an intermediate core layer and surface layers, wherein the surface layers are located on the upper and lower sides of the intermediate core layer, and the surface layers are made of raw materials comprising the following parts by weight:

[0009] PP 25-32 copies;

[0010] Recycle 2-5 parts of masterbatch;

[0011] 0.5-2 parts of opening agent;

[0012] 1-4 parts of lubricant;

[0013] 1-2 parts of anti-fog agent;

[0014] The recycled masterbatch comprises the following components in parts by weight:

[0015] 65-73 parts of LLDPE new material;

[0016] 3-40 parts of LLDPE recycled material;

[0017] 21-30 parts of active ingredient;

[0018] The active ingredient comprises the following components in parts by weight:

[0019] P34HB 45-55 copies;

[0020] 12-15 parts of seaweed fiber;

[0021] 4-5 parts of nucleating agent;

[0022] The LLDPE recycled material is obtained by recycling consumer waste sources.

[0023] By adopting the above technical solution, the surface layer is primarily composed of PP, which has excellent transparency. This gives the POF heat-shrink film high transparency, allowing it to clearly display the packaged items and enhance the product's appearance. PP also has excellent heat-sealing properties, enabling it to quickly seal when heated, ensuring the tightness and integrity of the package. The anti-fog agent used in the surface layer primarily creates tiny bumps or depressions in the heat-shrink film, reducing the contact area between films and lowering friction, making the film easier to remove. The lubricant reduces shrinkage resistance by lowering the coefficient of friction, allowing the film to respond more quickly to the heat shrink process. This lubrication helps reduce resistance and stress concentration generated during shrinkage, thereby increasing shrinkage rate and uniformity. The use of an anti-fog agent effectively prevents the formation of fog or water droplets on the inner surface of the film in humid environments or environments with large temperature fluctuations, ensuring that the items within the film are clearly visible.

[0024] At the same time, recycled masterbatch is also used in the surface layer, which can reduce costs and bring about environmental protection and energy saving effects. The recycled masterbatch is mainly composed of LLDPE new material, LLDPE recycled material and active components. Among them, the purity of LLDPE new material is selected to be 99.9%, and LLDPE recycled material is recycled from consumer waste sources. The active components mainly use P34HB, seaweed fiber and nucleating agent. P34HB is a fully degradable polymer material with high strength, good ductility and controllable mechanical properties. However, the crystallization performance of P34HB is poor, and a nucleating agent needs to be added to accelerate the crystallization of the material and improve the grain structure, shortening the molding time while improving the thermal and mechanical properties. Seaweed fiber does not have a certain surface area and pore structure, which not only improves strength, stiffness and toughness, but can also be combined with P34HB to form a structural system with high crystallinity and a developed three-dimensional layered structure under the action of a nucleating agent. In this way, the application of the recycled masterbatch can significantly improve the processing viscosity caused by the use of the anti-fog agent, making it less likely for the surface layer to be pulled unevenly, wrinkled or torn during the processing and molding process, and the overall structure is relatively stable, ultimately obtaining a POF heat shrinkable film with excellent anti-fog performance and good overall structural strength.

[0025] Preferably, the nucleating agent is boron nitride.

[0026] By adopting this technical solution, boron nitride, a crystal composed of nitrogen and boron atoms, acts as a nucleating agent, improving the material's crystallization process and promoting the orderly arrangement of crystals during growth, thereby enhancing the material's crystal quality and purity. Furthermore, boron nitride exhibits excellent high-temperature stability and lubricity, enabling it to achieve optimal synergy with P34HB and seaweed fiber, further enhancing the effectiveness of the recycled masterbatch.

[0027] Preferably, the anti-blocking agent is one or a combination of erucamide, oleamide, talc, diatomaceous earth and silicon dioxide.

[0028] By adopting the above technical solution, the above types of opening agents have little effect on the transparency, glossiness and mechanical strength of the film when used, and can be dispersed among the various raw material mixing systems on the surface, and can exert excellent and stable effects, thereby obtaining the expected surface structure.

[0029] Preferably, the lubricant is one or a combination of amide lubricants, soap lubricants and silicone lubricants.

[0030] By adopting the above technical solution, the above-mentioned types of lubricants can be evenly dispersed among the raw materials in the surface layer and can stably exert their corresponding functions, thereby forming a surface structure with better quality.

[0031] Preferably, the anti-fog agent is one or a combination of xylitol ester, glycerol monooleate, glycerol monolaurate, glycerol monostearate, sorbitan monopalmitate, sorbitan monostearate and polyethylene oxide glycerol monostearate.

[0032] By adopting the above technical solutions, the above types of anti-fog agents can provide a long-lasting anti-fog effect when applied in the surface layer, especially in an environment with large temperature differences or in a humid environment. They can effectively prevent the formation of fog or water droplets on the inner surface of the film, keeping the items in the film clearly visible, and the overall application effect is relatively stable and excellent.

[0033] Preferably, the middle core layer is composed of a mixture of LLDPE-1 and LLDPE-2, and the density of LLDPE-1 is 0.918 g / cm 3 , the melt index is 2g / 10min, and the density of the LLDPE-2 is 0.903g / cm 3 , the melt index is 1.8g / 10min.

[0034] By adopting the above technical solution and selecting LLDPE as the intermediate core layer, it can provide good shrinkage performance and elasticity, so that the recyclable POF heat shrink film can tightly wrap the items after heating, playing a role of stability and protection; at the same time, when the above two specifications of LLDPE-1 and LLDPE-2 are used in combination, it can not only improve the processing performance of the intermediate core layer, but also make the molecular structure formed by the combination more regular, bringing about better corresponding effects, which is conducive to obtaining high-quality recyclable POF heat shrink film.

[0035] Preferably, the weight mixing ratio of the LLDPE-1 and LLDPE-2 is 1:(1.2-1.3).

[0036] By adopting the above technical solution, when the LLDPE-1 and LLDPE-2 of the above mixing ratio are used, the corresponding quality of the obtained intermediate core layer is better and can form a stable bond with the surface layer, and the corresponding quality of the recyclable POF heat shrinkable film finally obtained is also better.

[0037] Preferably, the thickness of the intermediate core layer is 65-75% of the overall thickness of the recyclable POF heat shrinkable film.

[0038] By adopting the above technical solution, since the middle core layer can provide better physical protection, such as tear resistance, puncture resistance and impact resistance, the thickness ratio of the middle core layer will directly affect the protective performance of the recyclable POF heat shrinkable film, but the thickness of the middle layer will also have a direct impact on the overall application heat shrinkage of the recyclable POF heat shrinkable film; and the thickness of the middle core layer is 65-75% of the overall thickness of the recyclable POF heat shrinkable film, which can achieve a more adaptable balance in application heat shrinkage and protective performance, thereby obtaining a recyclable POF heat shrinkable film with better overall application quality.

[0039] In a second aspect, the present application provides a method for preparing a recyclable POF heat shrinkable film, which adopts the following technical solution:

[0040] A method for preparing a recyclable POF heat shrinkable film comprises the following steps:

[0041] (1) Prepare the raw materials including the middle core layer raw material and the surface layer PP, recycled masterbatch, anti-blocking agent, lubricant and anti-fogging agent according to the ratio;

[0042] (2) After mixing the PP and the recycled masterbatch in step (1), an anti-blocking agent, a slip agent and an anti-fogging agent are added and kneaded to obtain a surface layer material; the intermediate core layer raw material is kneaded to obtain an intermediate core layer material;

[0043] (3) The surface layer material and the middle core layer material in step (2) are co-extruded into a sheet by using an extruder;

[0044] (4) The sheet obtained in step (3) is preheated and then stretched and shaped to obtain a recyclable POF heat shrinkable film.

[0045] By adopting the above technical solution, the corresponding raw materials are mixed and then a multi-layer co-extrusion method is used to obtain a sheet, which is then further stretched and shaped to obtain the final recyclable POF heat shrinkable film product. The overall operation of the process is relatively simple and efficient, and the matching performance of each raw material is fully utilized, ensuring the uniformity and high quality of the product. The overall process is also in line with large-scale industrial and efficient production.

[0046] Preferably, in step (2), the melt blending temperature of the surface layer material is 150-160°C; and in step (3), the extrusion temperature of the surface layer material is 170-200°C.

[0047] By adopting the above technical solution, in the preparation of the surface layer, the setting of the above melt blending temperature can enable the raw materials required for the preparation of the surface layer to be fully mixed and exert excellent corresponding coordination effects; and the setting of the above extrusion temperature can enable the surface layer material to form a uniform and stable structure during the extrusion process, ensuring the excellent performance of the surface layer's own characteristics; in this way, the formed surface layer can enable the recyclable POF heat shrinkable film to have excellent anti-fog properties while also having good overall structural strength.

[0048] In summary, this application has the following beneficial effects:

[0049] The present application uses recycled masterbatch in the surface layer, combines P34HB in the recycled masterbatch with seaweed fiber, and under the action of a nucleating agent, forms a structural system with high crystallinity and a developed three-dimensional layered structure in the surface structure, thereby significantly improving the processing viscosity phenomenon caused by the use of anti-fog agents, making it less likely for the surface layer to be pulled unevenly, wrinkled or torn during the processing and molding process, and the overall structure is relatively uniform and stable, ultimately obtaining a POF heat shrinkable film with excellent anti-fog performance and good overall structural strength. DETAILED DESCRIPTION

[0050] The present application is further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0051] Unless otherwise specified, the raw materials used in the preparation examples, embodiments and comparative examples of the present application are all commercially available.

[0052] PP was purchased from Formosa Plastics 5020 in Taiwan, China;

[0053] The opening agent is erucamide;

[0054] The slip agent is an organosilicon slip agent, purchased from Shenzhen Xiangrun New Materials Co., Ltd. as organosilicon slip agent X-86;

[0055] The antifog agent is sorbitan monopalmitate;

[0056] Seaweed fiber was purchased from Qingdao Hailan Biological Products Co., Ltd.

[0057] The nucleating agent is boron nitride, which was purchased from Suzhou Napu Material Technology Co., Ltd.

[0058] Example 1

[0059] A recyclable POF heat shrinkable film comprises an intermediate core layer and surface layers, wherein the surface layers are located on the upper and lower sides of the intermediate core layer. The components required for preparing the surface layers and their corresponding weights are shown in Table 1, the components of the recycled masterbatch in the surface layers and their corresponding weights are shown in Table 2, and the components of the active components of the recycled masterbatch and their corresponding weights are shown in Table 3. The recyclable POF heat shrinkable film is prepared by the following steps:

[0060] (1) Prepare the raw materials including the middle core layer raw material and the surface layer PP, recycled masterbatch, anti-blocking agent, lubricant and anti-fogging agent according to the ratio;

[0061] (2) After mixing the PP and the recycled masterbatch in step (1), an anti-blocking agent, a slip agent and an anti-fogging agent are added and kneaded to obtain a surface layer material; the intermediate core layer raw material is kneaded to obtain an intermediate core layer material;

[0062] (3) The surface layer material and the middle core layer material in step (2) are co-extruded into a sheet by using an extruder;

[0063] (4) The sheet obtained in step (3) is preheated and then stretched and shaped to obtain a recyclable POF heat shrinkable film.

[0064] Note: In the above operation, the LLDPE new material in the recycled masterbatch was purchased from Sinopec M2320. The LLDPE recycled material was obtained by recycling consumer waste sources and provided by Wenzhou Ruian Waste Plastic City. The middle core layer is composed of a mixture of LLDPE-1 and LLDPE-2. The density of LLDPE-1 is 0.918g / cm 3 , the melt index is 2g / 10min, and the density of the LLDPE-2 is 0.903g / cm 3 , the melt index is 1.8g / 10min, and the weight mixing ratio of LLDPE-1 and LLDPE-2 is 1:1.25. The thickness of the recyclable POF heat shrinkable film is 15μm, the thickness of the middle core layer is 70% of the overall thickness of the recyclable POF heat shrinkable film, and the thickness of the surface layers on the upper and lower sides of the middle core layer are the same. The recycled masterbatch is obtained by mixing LLDPE recycled material with LLDPE new material and P34HB, seaweed fiber, and nucleating agent in the active components, and then melting, extruding and granulating. The melting temperature is 170℃, the extrusion temperature of the extruder is 165℃, and the screw speed is 250r / min. In step (2), the melt blending temperature of the surface layer material is 155℃, and the mixing temperature of the middle core layer raw material is 160℃; in step (3), the extrusion temperature of the surface layer material is 185℃, and the extrusion temperature of the middle core layer material is 165℃.

[0065] Example 2-3

[0066] A recyclable POF heat shrinkable film is different from Example 1 in that the components required for preparing the surface layer and their corresponding weights are shown in Table 1.

[0067] Table 1 Components and weight portions (kg / portion) required for preparing the surface layer of Examples 1-3

[0068]

[0069] Examples 4-5

[0070] A recyclable POF heat shrinkable film is different from Example 1 in that the components of the recycled masterbatch in the surface layer and their corresponding weights are shown in Table 2.

[0071] Table 2 Components and weight portions of recycled masterbatch of Examples 1, 4-5 (kg / portion)

[0072]

[0073] Examples 6-7

[0074] A recyclable POF heat shrinkable film, which is different from Example 1 in that the components of the active components of the recycled masterbatch and their corresponding weights are shown in Table 3.

[0075] Table 3 Components and weight portions (kg / portion) of active components in recovered masterbatches of Examples 1, 6-7

[0076]

[0077] Example 8

[0078] A recyclable POF heat shrinkable film is different from Example 1 in that the weight mixing ratio of LLDPE-1 and LLDPE-2 in the middle core layer is 1:1.2.

[0079] Example 9

[0080] A recyclable POF heat shrinkable film is different from Example 1 in that the weight mixing ratio of LLDPE-1 and LLDPE-2 in the middle core layer is 1:1.3.

[0081] Example 10

[0082] A recyclable POF heat shrinkable film is different from Example 1 in that LLDPE-1 is not used in the middle core layer.

[0083] Example 11

[0084] A recyclable POF heat shrinkable film is different from Example 1 in that LLDPE-2 is not used in the middle core layer.

[0085] Example 12

[0086] A recyclable POF heat shrinkable film, which is different from Example 1 in that the thickness of the middle core layer is 65% of the overall thickness of the recyclable POF heat shrinkable film.

[0087] Example 13

[0088] A recyclable POF heat shrinkable film, which is different from Example 1 in that the thickness of the middle core layer is 75% of the overall thickness of the recyclable POF heat shrinkable film.

[0089] Example 14

[0090] A recyclable POF heat shrinkable film is different from Example 1 in that, in step (2), the melt blending temperature of the surface layer material is 150°C; and in step (3), the extrusion temperature of the surface layer material is 170°C.

[0091] Example 15

[0092] A recyclable POF heat shrinkable film is different from Example 1 in that, in step (2), the melt blending temperature of the surface layer material is 160°C; and in step (3), the extrusion temperature of the surface layer material is 200°C.

[0093] Comparative Example 1

[0094] A recyclable POF heat shrinkable film is different from Example 1 in that no recycled masterbatch is used in the raw materials for preparing the surface layer.

[0095] Comparative Example 2

[0096] A recyclable POF heat shrinkable film is different from Example 1 in that P34HB and nucleating agent are not used in the active components of the recycled masterbatch.

[0097] Comparative Example 3

[0098] A recyclable POF heat shrinkable film is different from Example 1 in that no seaweed fiber is used in the active components of the recycled masterbatch.

[0099] Performance testing

[0100] Test samples: The recyclable POF heat shrinkable films obtained in Examples 1-15 were used as test samples 1-15, and the recyclable POF heat shrinkable films obtained in Comparative Examples 1-3 were used as control samples 1-3.

[0101] Test method: ASTM tests were performed on test samples 1-15 and control samples 1-3. The test items included optical properties, shrinkage properties, tensile properties, and tear strength. The optical properties were evaluated by haze (%), transparency (%), and gloss @45°C (%) tests, and the test results are shown in Table 4. The shrinkage properties were evaluated by shrinkage rate @120°C (%) MD and shrinkage rate @120°C (%) TD tests, and the test results are shown in Table 5. The tensile properties were evaluated by tensile strength (N / mm2) MD, tensile strength (N / mm2) TD, elongation at break (%) MD, and elongation at break (%) TD tests, and the test results are shown in Table 6. The tear strength was evaluated by testing in the D direction and TD direction, and the test results are shown in Table 7.

[0102] Table 4 Test results of test samples 1-15 and control samples 1-3

[0103]

[0104] Table 5 Test results of test samples 1-15 and control samples 1-3

[0105]

[0106] Table 6 Test results of test samples 1-15 and control samples 1-3

[0107]

[0108] Table 7 Test results of test samples 1-15 and control samples 1-3

[0109]

[0110] Combining Example 1 and Comparative Examples 1-3 and Tables 4, 5, 6, and 7, it can be seen that the present application, by using recycled masterbatch in the surface layer, can make the recyclable POF heat shrinkable film less prone to uneven pulling, wrinkling, or tearing during the processing and molding process, and the overall optical properties, shrinkage properties, tensile properties, and tear strength are significantly improved and enhanced. At the same time, it was found that if P34HB and nucleating agent are used as active components alone, or seaweed fiber is used as an active component alone, the improvement and enhancement of optical properties, shrinkage properties, tensile properties, and tear strength after the recycled masterbatch is applied are not good, and the improvement is limited. The sum of the effects brought by each as an active component is far less than the excellent effect brought by the combined use. It can be seen that P34HB, seaweed fiber, and nucleating agent are used together as active components in the recycled masterbatch, which can bring a significant improvement effect of 1+1>2, thereby obtaining a recyclable POF heat shrinkable film with significantly excellent quality.

[0111] Combining Examples 1 and 8-9 with Tables 4, 5, 6, and 7, it can be seen that using LLDPE as the intermediate core layer and combining two specifications of LLDPE-1 and LLDPE-2 can result in recyclable POF heat-shrinkable films that exhibit excellent optical properties, shrinkage properties, tensile properties, and tear strength. Specifically, when the weight ratio of LLDPE-1 to LLDPE-2 is 1:(1.2-1.3), excellent and stable application results are achieved. Furthermore, combining Examples 10-11 with Tables 4, 5, 6, and 7, it can be seen that using only either LLDPE-1 or LLDPE-2 results in a significant loss in optical properties, shrinkage properties, tensile properties, and tear strength.

[0112] Combining Example 1 and Examples 12-13 with Tables 4, 5, 6, and 7, it can be seen that the thickness of the intermediate core layer is 65-75% of the overall thickness of the recyclable POF heat shrinkable film, which can achieve a more adaptable balance between application heat shrinkage and protection performance, thereby obtaining a recyclable POF heat shrinkable film with better overall application quality.

[0113] From Example 1 and Examples 14-15 and Tables 4, 5, 6, and 7, it can be seen that the melt blending temperature of the surface layer material is 150-160°C, and the extrusion temperature is 170-200°C, both of which can enable the surface layer material to obtain a uniform and stable structure and ensure the excellent performance of the surface layer's own characteristics, thereby ultimately obtaining a recyclable POF heat shrinkable film with excellent quality and stability.

[0114] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A recyclable POF heat shrinkable film, characterized in that: The invention comprises a middle core layer and a surface layer, wherein the surface layer is located on the upper and lower sides of the middle core layer, and the surface layer is made of the following raw materials in parts by weight: PP 25-32 copies; Recycle 2-5 parts of masterbatch; 0.5-2 parts of opening agent; 1-4 parts of lubricant; 1-2 parts of anti-fog agent; The recycled masterbatch comprises the following components in parts by weight: 65-73 parts of LLDPE new material; 3-10 parts of LLDPE recycled material; 21-30 parts of active ingredient; The active ingredient comprises the following components in parts by weight: P34HB 45-55 copies; 12-15 parts of seaweed fiber; 4-5 parts of nucleating agent; The LLDPE recycled material is obtained by recycling consumer waste sources.

2. The recyclable POF heat shrinkable film according to claim 1, characterized in that: The nucleating agent is boron nitride.

3. The recyclable POF heat shrinkable film according to claim 1, characterized in that: The opener is one or a combination of erucamide, oleamide, talcum powder, diatomaceous earth and silicon dioxide.

4. The recyclable POF heat shrinkable film according to claim 1, characterized in that: The lubricant is one or a combination of amide lubricants, soap lubricants and silicone lubricants.

5. The recyclable POF heat shrinkable film according to claim 1, characterized in that: The anti-fog agent is one or a combination of xylitol ester, glycerol monooleate, glycerol monolaurate, glycerol monostearate, sorbitan monopalmitate, sorbitan monostearate and polyethylene oxide glycerol monostearate.

6. The recyclable POF heat shrinkable film according to claim 1, characterized in that: The middle core layer is composed of a mixture of LLDPE-1 and LLDPE-2, and the density of the LLDPE-1 is 0.918 g / cm 3 , the melt index is 2g / 10min, and the density of the LLDPE-2 is 0.903g / cm 3 , the melt index is 1.8g / 10min.

7. The recyclable POF heat shrinkable film according to claim 6, characterized in that: The weight mixing ratio of the LLDPE-1 and LLDPE-2 is 1:(1.2-1.3).

8. The recyclable POF heat shrinkable film according to claim 1, characterized in that: The thickness of the intermediate core layer is 65-75% of the overall thickness of the recyclable POF heat shrinkable film.

9. The method for preparing the recyclable POF heat shrinkable film according to claim 1, wherein: The following steps are involved: (1) Prepare the raw materials including the middle core layer raw material and the surface layer PP, recycled masterbatch, anti-blocking agent, lubricant and anti-fogging agent according to the ratio; (2) After mixing the PP and the recycled masterbatch in step (1), an anti-blocking agent, a slip agent and an anti-fogging agent are added and kneaded to obtain a surface layer material; the intermediate core layer raw material is kneaded to obtain an intermediate core layer material; (3) The surface layer material and the middle core layer material in step (2) are co-extruded into a sheet by using an extruder; (4) The sheet obtained in step (3) is preheated and then stretched and shaped to obtain a recyclable POF heat shrinkable film.

10. The method for preparing a recyclable POF heat shrinkable film according to claim 9, wherein: In step (2), the melt blending temperature of the surface layer material is 150-160°C; and in step (3), the extrusion temperature of the surface layer material is 170-200°C.

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