Preservative film

Abstract

The invention discloses a preservative film. In the section structure of the preservative film, the preservative film is provided with an inner layer area and a surface layer area, and the surface layer area completely covers the inner layer area. The total weight of the inner layer area is 100 weight percent, and the inner layer area contains 40 weight percent to 60 weight percent of ethylene elastomer, 35 weight percent to 55 weight percent of propylene random copolymer and 1 weight percent to 10 weight percent of hydrogenated petroleum resin. And the surface layer region contains ethylene vinyl acetate.

Description

Technical Field

[0001] The present application relates to a cling film, and in particular to a cling film suitable for a fully automatic packaging machine. Background Art

[0002] Compared with other polymer cling films, polyvinyl chloride (PVC) cling film has better tensile properties and can be widely used in automatic packaging machinery. However, polyvinyl chloride cling film contains chlorine, which is easy to affect the environment.

[0003] In order to avoid environmental pollution, countries have successively proposed corresponding policies. For example, Australia is expected to ban polyvinyl chloride cling film in 2025. Unfortunately, although non-PVC cling film (such as polyethylene cling film) on the market does not contain chlorine, it cannot be used in fully automatic packaging machinery.

[0004] Take polyethylene cling film as an example. Polyethylene has high crystallinity and may produce crystal deformation after being stretched. On the fully automatic packaging machine, after the cling film is stretched by the fully automatic packaging machine, horizontal lines or obvious wrinkles will appear on the surface of the cling film. As a result, the product packaging appearance is not good and cannot be accepted by consumers.

[0005] Therefore, how to improve the tensile properties of polyethylene cling film by improving the material to replace polyvinyl chloride cling film has become one of the important issues that this business wants to solve. Summary of the invention

[0006] The technical problem to be solved by the present application is to provide a fresh-keeping film to address the deficiencies of the prior art.

[0007] In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a cling film. In the cross-sectional structure of the cling film, the cling film has an inner layer region and a surface layer region, and the surface layer region completely covers the inner layer region. Taking the total weight of the inner layer region as 100 weight percent, the inner layer region contains 40 weight percent to 60 weight percent of ethylene elastomer, 35 weight percent to 55 weight percent of propylene random copolymer and 1 weight percent to 10 weight percent of hydrogenated petroleum resin. The surface layer region contains ethylene vinyl acetate.

[0008] Furthermore, the ethylene elastomer, the propylene random copolymer and the hydrogenated petroleum resin in the inner layer region are uniformly mixed in a continuous phase.

[0009] Furthermore, the propylene random copolymer has a melting point of 130°C to 150°C.

[0010] Furthermore, the propylene random copolymer has a melt index of 1 g / 10 mm to 10 g / 10 mm.

[0011] Furthermore, the propylene random copolymer is copolymerized by propylene monomer and ethylene monomer.

[0012] Furthermore, the hydrogenated petroleum resin is a hydrogenated petroleum resin polymerized with a monomer having 5 carbon atoms or a hydrogenated petroleum resin polymerized with a monomer having 9 carbon atoms.

[0013] Furthermore, taking the total weight of the inner layer region as 100 weight percent, the inner layer region further contains 4 weight percent to 8 weight percent of an anti-fogging agent.

[0014] Furthermore, taking the total weight of the surface region as 100 weight percent, the surface region further contains 2 weight percent to 5 weight percent of an anti-fogging agent.

[0015] Furthermore, taking the total thickness of the cling film as 100%, the inner layer area accounts for 50% to 70% of the total thickness of the cling film.

[0016] Furthermore, the Young's modulus of the plastic wrap is 3.5 MPa to 5.6 MPa.

[0017] One of the beneficial effects of the present invention is that the cling film provided by the present invention can improve the tensile properties of the cling film through the technical solution of "the inner layer region contains 40 weight percent to 60 weight percent of ethylene elastomer, 35 weight percent to 55 weight percent of propylene random copolymer and 1 weight percent to 10 weight percent of hydrogenated petroleum resin".

[0018] To further understand the features and technical contents of the present application, please refer to the following detailed description and drawings of the present application. However, the drawings provided are only for reference and illustration and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a three-dimensional schematic diagram of the cling film of this application.

[0020] Figure 2 for Figure 1 Schematic cross-sectional view of the II-II section line. DETAILED DESCRIPTION

[0021] The following is an explanation of the implementation methods of the "preservative film" disclosed in the present invention through specific examples. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted in actual size. It is stated in advance. The following implementation methods will further describe the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention. In addition, the term "or" used in this article may include any one or more combinations of the associated listed items depending on the actual situation.

[0022] In order to solve the problem of poor ductility and stretched appearance of existing polyethylene cling film, the present invention provides a cling film, which has good ductility and stretched appearance (i.e., appropriate stretching properties) and can be applied to fully automated packaging machinery. Therefore, the cling film of the present invention can replace the polyvinyl chloride cling film currently on the market.

[0023] Generally speaking, the tensile properties are positively correlated with the Young's modulus. Therefore, the Young's modulus is used in this specification to quantify the tensile properties of the cling film. Specifically, the Young's modulus of the cling film is measured according to the standard test method of ASTM D638, and the Young's modulus of the cling film of the present invention can reach 3.5 MPa to 5.6 MPa.

[0024] Under the premise of having appropriate stretching properties, the cling film of the present invention can also maintain the property of low haze, and the transparency of the cling film will not be affected by the change of the stretching properties. Specifically, the haze of the cling film can be less than 5%, preferably, the haze of the cling film can be less than 2%.

[0025] Please refer to the combined Figure 1 and Figure 2 As shown, the cling film Z of the present invention has an inner layer region 1 and a surface layer region 2 in the cross-sectional structure, and the surface layer region 2 completely covers the inner layer region 1 .

[0026] In terms of product appearance, the inner layer region 1 and the surface layer region 2 are formed as one piece, but when actually analyzing the ingredients contained, the cling film Z can be divided into the inner layer region 1 and the surface layer region 2.

[0027] For example, the cling film Z can be formed by laminating a three-layer film structure. The three-layer film structure includes two surface films and an inner film disposed between the two surface films. After lamination, the inner film forms the inner layer region 1, and the two surface films constitute the surface region 2 and cover the inner layer region 1. However, the present invention is not limited thereto.

[0028] By adjusting the composition of the inner layer area 1 and the surface layer area 2, the cling film Z of the present invention has functional properties similar to those of general cling films, so that the cling film Z of the present invention can have appropriate stretching properties and can be used in fully automated packaging machines, and the cling film Z will not produce transverse stripes during the stretching process.

[0029] That is to say, by dividing the cling film Z into an inner layer region 1 and a surface layer region 2 by using materials, the cling film Z can replace the polyvinyl chloride cling film currently on the market while maintaining the original functional properties.

[0030] The cling film of the present invention is specially improved on polyethylene cling film. In order to improve the problem of poor appearance of the existing polyethylene cling film after stretching, the present invention selects ethylene elastomer as one of the materials of the inner layer region 1.

[0031] The ethylene elastomer includes a soft segment part and a hard segment part. Therefore, compared with the ethylene polymer, the ethylene elastomer can make the fresh-keeping film Z have better tensile properties and elastic recovery force.

[0032] However, ethylene elastomer itself is hard, and if the content of ethylene elastomer is too high, the film is easily broken during the process of manufacturing the film (film below 15 microns). Therefore, in the inner layer region 1 of the cling film Z (the total weight of the inner layer region is 100 weight percent), the content of ethylene elastomer needs to be less than 65 weight percent, preferably, the content of ethylene elastomer is less than or equal to 60 weight percent.

[0033] Specifically, in the inner layer region 1 of the cling film Z, the content of the ethylene elastomer is 40 weight percent to 60 weight percent. Preferably, the content of the ethylene elastomer is 40 weight percent to 50 weight percent. For example, the content of the ethylene elastomer can be 42 weight percent, 44 weight percent, 46 weight percent or 48 weight percent.

[0034] In addition, in order to strike a balance between the tensile properties and the texture of the cling film Z, the melt flow index (MI) of the ethylene elastomer is 0.5 g / 10 mm to 10 g / 10 mm. Preferably, the melt flow index of the ethylene elastomer is 1 g / 10 mm to 3 g / 10 mm.

[0035] As mentioned above, the content of ethylene elastomer has an upper limit, so it is impossible to use a single material of ethylene elastomer to manufacture a film. Therefore, the present invention selects a propylene random copolymer mixed with an ethylene elastomer as the material for forming the inner layer region 1.

[0036] The addition of the propylene random copolymer can maintain the tensile properties improved by the ethylene elastomer without making the material forming the inner layer region 1 too hard and brittle, thereby preventing the material from breaking during the film forming process.

[0037] Compared to other polymer structures (e.g. alternating copolymers or block copolymers), random copolymers have more amorphous phases, thus avoiding the occurrence of crystal deformation. Therefore, the addition of propylene random copolymers can also avoid the generation of transverse stripes.

[0038] Specifically, in the inner layer region 1 of the cling film Z (the total weight of the inner layer region is 100 weight percent), the content of the propylene random copolymer is 35 weight percent to 55 weight percent. Preferably, the content of the propylene random copolymer is 40 weight percent to 50 weight percent. For example, the content of the propylene random copolymer can be 42 weight percent, 44 weight percent, 46 weight percent or 48 weight percent.

[0039] In a preferred embodiment, the propylene random copolymer is synthesized from ethylene monomer and propylene monomer. Since a portion of the propylene random copolymer is synthesized from ethylene monomer, it has better compatibility with ethylene elastomer, thereby reducing the probability of forming transverse stripes on the cling film after stretching.

[0040] If the total weight of the monomers for synthesizing the propylene random copolymer is 100 weight percent, the content of the ethylene monomer is 1 weight percent to 5 weight percent, and the content of the propylene monomer is 95 weight percent to 99 weight percent. An appropriate amount of ethylene monomer can improve the compatibility of the propylene random copolymer and the ethylene elastomer. If the content of the ethylene monomer is too high, the texture of the cling film will be soft.

[0041] In addition, the present invention also controls the melting point of the propylene random copolymer to be less than 150° C. Preferably, the melting point of the propylene random copolymer is 130° C. to 150° C. More preferably, the melting point of the propylene random copolymer is 130° C. to 135° C.

[0042] Generally speaking, the melting point is positively correlated with the crystallinity. If the crystallinity of the material is high, the cling film Z may form horizontal lines when subjected to high-intensity stretching, which will negatively affect the appearance of the packaging. Therefore, by adjusting the melting point of the propylene random copolymer, a balance can be achieved between the tensile properties and texture of the cling film Z.

[0043] In addition to the melting point, the melt flow index (MI) of the propylene random copolymer can also be controlled to be 1 g / 10 mm to 10 g / 10 mm. The melt flow index of the propylene random copolymer is related to the fluidity of the material to facilitate the production of the film.

[0044] In order to achieve a balance between the elastic recovery force, Young's modulus, appropriate hardness and appropriate crystallinity of the cling film Z, the present invention further controls the weight ratio of the ethylene elastomer to the propylene random copolymer to be 0.9 to 1.1 to ensure the complementary effect of the properties between the ethylene elastomer and the propylene random copolymer. If the content of the ethylene elastomer is too high, the texture of the cling film will be too hard, which is not conducive to film formation. If the content of the random copolymer is too high, the tensile properties of the cling film will be reduced, and it cannot be applied to fully automated packaging machinery.

[0045] In addition, a hydrogenated petroleum resin can be added to the inner layer region 1. The addition of the hydrogenated petroleum resin can improve the elastic recovery of the cling film Z and improve the compatibility between the ethylene elastomer and the propylene random copolymer. When the compatibility is improved, it is less likely to form transverse stripes when the cling film is stretched. Moreover, when the compatibility is improved, the cling film can maintain a certain degree of transparency, thereby achieving the effect of maintaining the haze of the cling film less than 2%.

[0046] After being used for a period of time, the hydrogenated petroleum resin may migrate to the surface of the cling film Z. Therefore, the addition of hydrogenated petroleum resin also has the effect of improving the surface adhesion of the cling film Z.

[0047] However, the amount of hydrogenated petroleum resin added should not be too much, otherwise the viscosity of the material will be too high, which is not conducive to film processing. Therefore, in the inner layer area 1 of the cling film Z, the content of hydrogenated petroleum resin must be less than 10 weight percent.

[0048] Specifically, in the inner layer region 1 of the cling film Z (the total weight of the inner layer region is 100 weight percent), the content of hydrogenated petroleum resin is 1 weight percent to 10 weight percent. Preferably, the content of hydrogenated petroleum resin is 3 weight percent to 7 weight percent. For example, the content of hydrogenated petroleum resin can be 4 weight percent, 5 weight percent or 6 weight percent.

[0049] In an exemplary embodiment, the hydrogenated petroleum resin may be a hydrogenated petroleum resin polymerized with a monomer having 5 carbon atoms or a hydrogenated petroleum resin polymerized with a monomer having 9 carbon atoms.

[0050] For example, the hydrogenated petroleum resin may be piperylene hydrogenated resin or dicyclopentadiene (DCPD) hydrogenated resin, or the hydrogenated petroleum resin may be a water-white thermoplastic resin obtained by polymerization and hydrogenation of a C9 fraction, a byproduct of ethylene cracking. However, the present invention is not limited thereto.

[0051] It is worth noting that after the above-mentioned ethylene elastomer, propylene random copolymer and hydrogenated petroleum resin are uniformly mixed, a uniform continuous phase is formed in the inner layer region 1, so that the inner layer region 1 has better tensile properties. Therefore, the cling film Z of the present invention can replace the existing polyvinyl chloride cling film and be applied to fully automatic packaging machinery.

[0052] The inner region 1 plays a major supporting role in the cling film Z, so the inner region 1 has a larger thickness proportion in the overall cling film Z. If the total thickness of the cling film Z is taken as 100%, the thickness of the inner region 1 is 50% to 70%, and the total thickness of the surface region 2 (located above and below the inner region 1) is 30% to 50%.

[0053] In an exemplary embodiment, the total thickness of the cling film Z is 8 to 12 microns, preferably 9 to 11 microns. That is, the thickness of the inner layer region 1 can be 4 to 8.4 microns, and the total thickness of the surface layer region 2 is 2.4 to 6 microns.

[0054] The surface area 2 of the cling film Z is mainly composed of ethylene-vinyl acetate (EVA). Ethylene-vinyl acetate makes the surface of the cling film Z have a slight adhesive force, thereby improving the packaging performance when used as a packaging material. In an exemplary embodiment, the melt index of ethylene-vinyl acetate is 1 g / 10 mm to 5 g / 10 mm.

[0055] In order to meet the application requirements, some functional additives can also be added to the cling film Z so that the cling film Z can have good transparency, anti-fogging and packaging properties (hereinafter referred to as functional properties).

[0056] In an exemplary embodiment, the inner layer region 1 and the surface layer region 2 of the cling film Z may contain an anti-fogging agent, which prevents the cling film Z from generating fog in a low temperature environment (refrigerated state). Taking the total weight of the cling film Z as 100 weight percent, the cling film Z contains 3 weight percent to 5 weight percent of the anti-fogging agent.

[0057] Preferably, both the inner region 1 and the surface region 2 contain anti-fogging agents. After long-term use, the anti-fogging agents will migrate to the surface of the cling film and lose the anti-fogging effect. Therefore, if both the inner region 1 and the surface region 2 contain anti-fogging agents, even if the anti-fogging agents in the surface region 2 have migrated to the surface of the cling film, the anti-fogging agents in the inner region 1 are still there, so the anti-fogging effect of the cling film Z can be prolonged.

[0058] The anti-fogging agent added to the inner layer region 1 and the surface layer region 2 may be the same or different.

[0059] For example, the anti-fogging agent added to the inner layer region 1 may be a glyceride compound, and the glyceride compound may be sorbitan monooleate.

[0060] Preferably, the molecular weight of the glyceride compound can be 350 g / mol to 450 g / mol, for example, the molecular weight of the glyceride compound can be 375 g / mol, 400 g / mol or 425 g / mol. By controlling the molecular weight of the glyceride compound, the time for the glyceride compound to migrate to the surface of the plastic wrap Z can be extended.

[0061] The antifogging agent added in the surface region 2 can be a glyceride compound or an ether compound. The types and characteristics of the glyceride compound are as described above, so they are not repeated. The molecular weight of the ether compound can be 150 g / mol to 250 g / mol. For example, the molecular weight of the ether compound can be 175 g / mol, 200 g / mol or 225 g / mol. By controlling the molecular weight of the antifogging agent, the time for the antifogging agent to migrate to the surface of the plastic wrap Z can be extended.

[0062] Due to the difference in position, the antifogging agent in the inner layer region 1 can exist in the cling film Z for a longer time than the antifogging agent in the surface layer region 2. In addition, by controlling the molecular weight, the antifogging agent in the inner layer region 1 and the antifogging agent in the surface layer region 2 can jointly maintain the antifogging property of the cling film Z.

[0063] In this exemplary embodiment, even if the anti-fog agent in the surface region 2 has moved to the surface of the cling film Z, the cling film Z still has the anti-fog agent in the inner region 1. Therefore, by adding the anti-fog agent to different regions of the cling film Z (the inner region 1 and the surface region 2), the anti-fog effect of the cling film Z can be extended.

[0064] In an exemplary embodiment, the total weight of the inner layer region 1 is 100 weight percent, and the content of the anti-fogging agent in the inner layer region 1 is 4 weight percent to 8 weight percent, for example, 5 weight percent, 6 weight percent, or 7 weight percent. The total weight of the surface layer region 2 is 100 weight percent, and the content of the anti-fogging agent in the surface layer region 2 is 2 weight percent to 5 weight percent, for example, 3 weight percent or 4 weight percent.

[0065] [Experimental data]

[0066] In order to prove that the cling film of the present invention has good tensile properties, can be used in fully automatic packaging machinery, and does not produce transverse lines due to stretching, the cling films of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared by cast extrusion according to the component ratios in Table 1, and a commercially available polyethylene cling film (Miaojie cling film) was used as Comparative Example 4.

[0067] In Table 1, propylene random copolymer purchased from Formosa Plastics (model 5050), propylene random copolymer purchased from DOW (model ENGAGE TM 8100), hydrogenated petroleum resin purchased from Idemitsu (model P-125), glycerol ester compound (anti-fogging agent) purchased from RIKEN (model EAR-770), and ethylene vinyl acetate purchased from Tosoh (model 630). It should be noted that the anti-fogging agent used in the inner layer area is the same as that used in the surface layer area.

[0068] In Examples 1 to 3 and Comparative Examples 1 to 3, a specific content (as shown in Table 1) of ethylene elastomer, propylene random copolymer, hydrogenated petroleum resin and antifogging agent was weighed using a lost in weight feeder, and melt-mixed using a mixer as the inner layer material. A specific content (as shown in Table 1) of ethylene vinyl acetate and antifogging agent was weighed using a lost in weight feeder, and melt-mixed using a mixer as the surface layer material.

[0069] Next, the inner layer material and the surface layer material are respectively melted by single screw extrusion, and formed into an inner layer film and a surface layer film after passing through a Tdie molding die. The thickness of the inner layer film and the surface layer film is measured and listed in Table 2.

[0070] After the inner film and the surface film are made, the inner film is placed between the two surface films to form a three-layer film structure, and then laminated by co-extrusion to obtain the cling film Z. Specifically, after co-extrusion, the inner film and the two surface films are integrated, and the inner film is wrapped between the two surface films. The inner film constitutes the inner layer region 1, and the two outer films are combined to form the surface region 2.

[0071] The physical properties of the cling films Z of Examples 1 to 3 and Comparative Examples 1 to 4 were measured, and the measurement results are listed in Table 2.

[0072] In Table 2, the Young's modulus of the cling film is measured according to the ASTM-D638 standard test method.

[0073] The automatic packaging performance of the cling film was evaluated after packaging using a packaging machine purchased from Teraoka (model AW4600). If the appearance after packaging was smooth, without transverse lines or obvious wrinkles, it was indicated by "○". If the appearance after packaging had obvious transverse lines and wrinkles, it was indicated by "×".

[0074] The anti-fogging property of plastic wrap is measured by weighing 100 ml of water in a 250 ml beaker, covering the beaker with plastic wrap, and placing it in a 4°C refrigerator for ten minutes. After taking it out, observe the water droplets on the surface of the plastic wrap. If the water vapor forms a water film on the surface of the plastic wrap, but there is no fog, it is indicated by "○". If the water vapor forms water droplets on the surface of the plastic wrap and cannot be seen through, it is indicated by "×".

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079]

[0080] According to the results of Table 1 and Table 2, it can be seen that the cling film of the present invention has an appropriate Young's modulus. The Young's modulus of the cling film in the machine direction (machine direction, MD) is 4.8MPa to 5.6MPa, and the Young's modulus in the cross direction (cross direction, CD) is 3.5MPa to 4.5MPa. Preferably, the Young's modulus of the cling film in the machine direction is 4.9MPa to 5.5MPa, and the Young's modulus in the cross direction (cross direction, CD) is 3.8MPa to 4.2MPa.

[0081] From the content of Comparative Example 1, it can be seen that the addition of hydrogenated petroleum resin can prevent the cling film from forming transverse lines or obvious wrinkles when stretched. From the contents of Comparative Examples 2 and 3, it can be seen that adding antifogging agents to the inner layer area and the surface layer area at the same time can achieve a better antifogging effect. From the content of Comparative Example 4, it can be seen that the cling film of the present invention can solve the problem that the existing polyethylene cling film will form transverse lines or obvious wrinkles when stretched.

[0082] [Beneficial Effects of Embodiments]

[0083] One of the beneficial effects of the present invention is that the cling film provided by the present invention can improve the tensile properties of the cling film through the technical solution of "the inner layer region contains 40 weight percent to 60 weight percent of ethylene elastomer, 35 weight percent to 55 weight percent of propylene random copolymer and 1 weight percent to 10 weight percent of hydrogenated petroleum resin".

[0084] Furthermore, by selecting ethylene elastomer, propylene random copolymer and hydrogenated petroleum resin and uniformly mixing them to form the inner layer material, the cling film of the present invention can have appropriate stretching properties and have a good appearance after being stretched by a fully automatic packaging machine. Therefore, the existing polyvinyl chloride cling film can be replaced.

[0085] The present invention also controls the properties of ethylene elastomer, propylene random copolymer and hydrogenated petroleum resin respectively to optimize the overall properties of the inner layer material. For example, the content and weight average molecular weight of the synthetic ethylene elastomer are controlled, the synthetic monomer, melting point and melt index of the propylene random copolymer are controlled, and the synthetic monomer of the hydrogenated petroleum resin is controlled.

[0086] In addition, the present invention contains anti-fogging agents in both the inner layer and the surface layer, and by selecting a specific type of anti-fogging agent, the anti-fogging effect can be improved without increasing the haze of the cling film. Moreover, the molecular weight range of the anti-fogging agent can be further controlled, so that the cling film has a long-lasting anti-fogging effect.

[0087] The contents disclosed above are only preferred feasible embodiments of the present application, and are not intended to limit the protection scope of the claims of the present application. Therefore, all equivalent technical changes made using the contents of the present application specification and drawings are included in the protection scope of the claims of the present application.

Claims

1. A cling film, characterized in that: In the cross-sectional structure of the cling film, the cling film has an inner layer region and a surface layer region, and the surface layer region completely covers the inner layer region; wherein, taking the total weight of the inner layer region as 100 weight percent, the inner layer region contains 40 weight percent to 60 weight percent of ethylene elastomer, 35 weight percent to 55 weight percent of propylene random copolymer, and 1 weight percent to 10 weight percent of hydrogenated petroleum resin; and the surface layer region contains ethylene vinyl acetate.

2. The cling film according to claim 1, characterized in that: The ethylene elastomer, the propylene random copolymer and the hydrogenated petroleum resin in the inner layer region are uniformly mixed to form a continuous phase.

3. The cling film according to claim 1, characterized in that: The melting point of the propylene random copolymer is 130°C to 150°C.

4. The cling film according to claim 1, characterized in that: The propylene random copolymer has a melt index of 1 g / 10 mm to 10 g / 10 mm.

5. The cling film according to claim 1, characterized in that: The propylene random copolymer is prepared by copolymerizing propylene monomer and ethylene monomer.

6. The cling film according to claim 1, characterized in that: The hydrogenated petroleum resin is a hydrogenated petroleum resin polymerized from a monomer having 5 carbon atoms or a hydrogenated petroleum resin polymerized from a monomer having 9 carbon atoms.

7. The cling film according to claim 1, characterized in that: Taking the total weight of the inner layer region as 100 weight percent, the inner layer region further contains 4 weight percent to 8 weight percent of an anti-fogging agent.

8. The cling film according to claim 1, characterized in that: Taking the total weight of the surface layer region as 100 weight percent, the surface layer region further contains 2 weight percent to 5 weight percent of an anti-fogging agent.

9. The cling film according to claim 1, characterized in that: Taking the total thickness of the cling film as 100%, the inner layer area accounts for 50% to 70% of the total thickness of the cling film.

10. The cling film according to claim 1, characterized in that: The Young's modulus of the fresh-keeping film is 3.5 MPa to 5.6 MPa.

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