Polypropylene film and method for producing the same, method for producing polypropylene decorative film

Abstract

The application discloses a polypropylene film and a preparation method thereof, and a preparation method of a polypropylene decorative film. The polypropylene film comprises a primer layer, a printing surface layer, an intermediate layer and a composite surface layer. The primer layer is prepared from a main body resin. The printing surface layer is located on one side of the primer layer and is prepared from polypropylene, grafted polypropylene, ethylene-vinyl acetate copolymer and alpha olefin copolymer. The intermediate layer is located on the side, away from the primer layer, of the printing surface layer and is prepared from polyolefin. The composite surface layer is located on the side, away from the printing surface layer, of the intermediate layer and is prepared from polyolefin. Thus, the ink adhesion of the polypropylene film after heat bonding and wet heat aging treatment is improved by arranging the primer layer on the surface of the polypropylene film. A printing surface layer is developed, the components of which are designed to have high cohesion and reduce the tearing of the printing surface layer. The components of the intermediate layer are further designed to improve the adhesion strength between the intermediate layer and the printing surface layer.

Description

Technical Field

[0001] This application relates to the field of polypropylene films, specifically to polypropylene films and their preparation methods, and to methods for preparing polypropylene decorative films. Background Technology

[0002] With increasing societal focus on environmental safety and public health, decorative panels and their raw materials are shifting towards green, environmentally friendly, and high-performance products. Polypropylene, as one of the preferred materials for environmentally friendly decorative films, has also seen some development. To print ink on the substrate surface and improve ink adhesion after high-temperature lamination of the transparent film, a common practice is to add polar components to the polypropylene material to enhance ink adhesion. However, the polar components added to improve ink adhesion often have poor compatibility with non-polar polypropylene, easily leading to low film cohesion and increased tearing, further affecting ink adhesion.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0004] In a first aspect of this application, a polypropylene film is provided, comprising: a base coating layer, the raw material of which includes a host resin; a printed surface layer, the printed surface layer being located on one side of the base coating layer, the raw material of which includes polypropylene, grafted polypropylene, ethylene-vinyl acetate copolymer, and α-olefin copolymer; an intermediate layer, the intermediate layer being located on the side of the printed surface layer away from the base coating layer, the raw material of which includes polyolefin; and a composite surface layer, the composite surface layer being located on the side of the intermediate layer away from the printed surface layer, the raw material of which includes polyolefin.

[0005] Therefore, by applying a base coating to the surface of a polypropylene film and utilizing the similarity-miscibility property of the base coating and the ink, the ink adhesion of the polypropylene film after heat lamination and damp heat aging is improved. A printing surface layer has also been developed, in which an ethylene-vinyl acetate copolymer serves as a polar component, compatible with the base coating. Grafted polypropylene and α-olefin copolymers act as compatibilizers, enhancing the system's compatibility and resulting in a printing surface layer with high cohesive strength, making it less prone to tearing after heat lamination. Simultaneously, the application of polyolefins to the intermediate layer utilizes the principle of similarity-miscibility to improve the adhesion strength between the intermediate layer and the printing surface layer, reducing the likelihood of tearing between them.

[0006] In some embodiments, the host resin includes one or more of polyurethane resin and acrylic resin; and / or, the raw material of the base coating further includes a curing agent, wherein the curing agent includes one or more of isocyanate, aziridine, and carbodiimide.

[0007] Therefore, by utilizing the non-polar and polar groups contained in polyurethane and acrylic molecules, they can be compatible with the polar and non-polar components in the printing surface layer, promoting the compatibility between the printing surface layer and the base layer. Furthermore, the main resin of printing inks is usually polyurethane or acrylic resin, so the property of "like dissolves like" can be used to improve the adhesion of the ink to the base layer. The curing agent added to the base layer can increase the cross-linking degree of the base layer, so the active functional groups on the surface of the base layer can form strong chemical bonds with ink molecules, thereby further improving the adhesion of the ink to the base layer.

[0008] In some embodiments, the printed surface layer comprises, based on its total mass, 55%-78% ternary copolymer polypropylene, 4%-10% grafted polypropylene, 10%-20% ethylene-vinyl acetate copolymer, 8%-15% α-olefin copolymer, and 0.05%-3% anti-aging agent.

[0009] Therefore, the third monomer, polyethylene, in ternary copolymer polypropylene can exhibit a similar compatibility phenomenon with the ethylene segments on the molecular chain of the ethylene-vinyl acetate copolymer. Thus, compared to binary copolymer polypropylene and homopolymer polypropylene, ternary copolymer polypropylene is more easily mixed with ethylene-vinyl acetate copolymer. By selecting an appropriate mass ratio of ethylene-vinyl acetate copolymer, the printed surface layer can maintain a certain polarity to enhance adhesion to the base coat, while reducing the possibility of tearing due to the introduction of excessive ethylene chain components. By controlling the mass ratio of grafted polypropylene and α-olefin copolymer, the printed surface layer can maintain a certain polarity while exhibiting better compatibility and higher cohesive strength.

[0010] In some embodiments, the melting point of the ternary copolymer polypropylene is 130°C-140°C.

[0011] Therefore, in the high-temperature environment of the subsequent multi-layer co-extrusion process, the ternary copolymer polypropylene exhibits a viscous flow state due to the ambient temperature being higher than the melting point, and has good fluidity in the multi-layer co-extrusion process, which promotes the one-time molding of polypropylene film.

[0012] In some embodiments, the grafting rate of the grafted polypropylene is 0.8%-1.4%.

[0013] Therefore, maleic anhydride, as a graft monomer with high polarity containing carbonyl functional groups, allows for easier intermolecular forces to form between the printed surface layer and the base coating layer containing polar groups after grafting maleic anhydride onto polypropylene, thereby increasing the adhesion of the base coating layer to the printed surface layer. Furthermore, the polar groups of the grafted polypropylene can interact strongly with the polar groups of the ethylene-vinyl acetate copolymer, thus improving the compatibility of polypropylene and ethylene-vinyl acetate copolymer and enhancing the cohesive force of the printed surface layer.

[0014] In some embodiments, the melt index of the grafted polypropylene at 2.16 kg and 230 °C is 3 g / 10 min to 12 g / 10 min.

[0015] Therefore, by limiting the melt flow index of grafted polypropylene, the problem of phase separation in the system can be effectively reduced.

[0016] In some embodiments, the mass fraction of vinyl acetate in the ethylene-vinyl acetate copolymer is 8.5%-19%.

[0017] Therefore, by controlling the mass fraction of vinyl acetate, the problems of low polarity of the ethylene-vinyl acetate copolymer and poor compatibility between the printed surface layer and the base layer caused by excessively low vinyl acetate content can be reduced. Conversely, excessively high vinyl acetate content introduces too much polyethylene component, thus reducing the decrease in cohesion of the printed surface layer caused by excessive vinyl acetate content.

[0018] In some embodiments, the melting point of the α-olefin copolymer is 60°C-80°C.

[0019] Therefore, the α-olefin copolymer exhibits a viscous flow state in the high-temperature environment of the subsequent multilayer co-extrusion process because the ambient temperature is higher than the melting point, and has good fluidity. It can work with other components to promote the one-time molding of polypropylene film.

[0020] In some embodiments, the α-olefin copolymer includes one or more of ethylene-α-olefin copolymer and propylene-α-olefin copolymer.

[0021] Therefore, by selecting α-olefin copolymers with more branches, and taking advantage of the good compatibility between α-olefin copolymers and polypropylene and polar ethylene copolymers, the α-olefin copolymer can be used as a good compatibilizer, thereby improving the cohesion of the printed surface layer.

[0022] In some embodiments, the intermediate layer comprises 74%-90% polyolefin, 9%-25% filler, and 0.05%-3% anti-aging agent, based on the total mass of the intermediate layer.

[0023] Therefore, by adding a certain amount of polyolefin to the intermediate layer, the intermediate layer adheres more firmly to the printed surface layer due to the property of "like dissolves like". Adding a certain amount of filler to the intermediate layer can improve the opacity and UV shielding effect of the polypropylene film, thereby increasing its service life. At the same time, filler raw materials are widely available and can reduce costs; controlling the filler content can reduce the dispersion problems caused by excessive filler. Adding a certain amount of anti-aging agent to the intermediate layer can reduce the damage caused by the external natural environment to the polypropylene film.

[0024] In some embodiments, the composite surface layer comprises 97%-100% polyolefin and 0.05%-3% anti-aging agent, based on the total mass of the composite surface layer.

[0025] Therefore, by adding a certain amount of polyolefin to the composite surface layer, the composite surface layer adheres more firmly to the intermediate layer through the property of similar solubility. By adding a certain amount of anti-aging agent to the composite surface layer, the damage of the external natural environment to the polypropylene film can be reduced.

[0026] In some embodiments, the polyolefin comprises polypropylene and polyethylene, wherein the polypropylene comprises one or more of homopolymer polypropylene, block polypropylene, and atactic polypropylene, wherein the polyethylene comprises one or more of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene; and / or, based on the total mass of the polyolefin, it comprises not less than 85% polypropylene.

[0027] Therefore, by adding polypropylene and polyethylene to the intermediate layer and composite surface layer and controlling the content of polypropylene, the printed surface layer, intermediate layer and composite surface layer can achieve a stronger bond in the multi-layer co-extrusion process, and the phenomenon of easy tearing of polypropylene film can be improved.

[0028] In some embodiments, the thickness ratio of the printed surface layer, intermediate layer, and composite surface layer is 1:6:1 to 1:9:1; and / or, the thickness of the printed surface layer is 9 μm to 37.5 μm; and / or, the thickness of the intermediate layer is 75 μm to 245 μm; and / or, the thickness of the composite surface layer is 9 μm to 37.5 μm; and / or, the thickness of the base coating is 0.3 μm to 1 μm; and / or, the thickness of the polypropylene film is 100 μm to 300 μm.

[0029] Therefore, by controlling the thickness of each functional layer, it is possible to better leverage the synergistic effect of each layer, thereby constructing a polypropylene film with strong cohesion, resistance to tearing, and excellent ink adaptability.

[0030] In a second aspect of this application, a method for preparing the aforementioned polypropylene film is proposed, comprising: molding raw materials for a printed surface layer, an intermediate layer, and a composite surface layer in a single step using a multi-layer co-extrusion process to obtain a polypropylene film intermediate, wherein the polypropylene film intermediate comprises a printed surface layer, an intermediate layer, and a composite surface layer stacked sequentially; and forming a base coating layer on the side of the polypropylene film intermediate where the printed surface layer is disposed to obtain a polypropylene film.

[0031] Therefore, the aforementioned polyolefin film can be effectively prepared through a simple, convenient, and easily implemented multilayer co-extrusion process, and this multilayer co-extrusion process is easily applied to industrial production.

[0032] In some embodiments, the temperature of the multilayer co-extrusion process is 150°C-230°C.

[0033] Therefore, by setting the temperature of the multi-layer co-extrusion process, each layer can have a certain viscosity and fluidity in the molten state, thereby achieving stable co-extrusion and firm bonding of each layer.

[0034] In a third aspect of this application, a method for preparing a polypropylene decorative film using the aforementioned polypropylene film is proposed, comprising: performing a printing process on one side of the polypropylene film having a base coating layer to form a printed pattern layer; and forming a protective layer on the side of the printed pattern layer away from the base coating layer to form a polypropylene decorative film.

[0035] Therefore, by setting a printed pattern layer and a protective layer on the bottom coating side of a polypropylene film, a polypropylene decorative film can be prepared, enabling the effective application of polypropylene film.

[0036] In some embodiments, the formation of the protective layer includes one or more of coating processes and heat-applied mask processes.

[0037] Therefore, by setting a protective layer on the polypropylene decorative film, the printed pattern layer can be physically protected and chemically isolated, thus extending the service life of the polypropylene decorative film. Attached Figure Description

[0038] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of the polypropylene film of this application.

[0039] Explanation of reference numerals in the attached figures: 1- Primer layer, 2- Printed top layer, 3- Intermediate layer, 4- Composite top layer. Detailed Implementation

[0040] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0041] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0042] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0043] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0044] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] In the description of this application, it should be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0046] In the description of this application, "multiple" means two or more.

[0047] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0048] In this application, the order in which the steps are written does not imply a strict execution order and does not limit the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0051] During the use of decorative films, it is necessary to pay attention to the ink adhesion after the film material has aged. Existing technologies mostly focus on improving the printability and ink adhesion of polypropylene films before aging, while research on the ink adhesion of polypropylene films after aging is lacking. Therefore, the technical challenge that needs to be studied is to prepare a polypropylene film product that maintains good ink adhesion and is not easily torn after high-temperature lamination of a transparent film and ink onto the polypropylene film, following the aging process.

[0052] In this application, a polypropylene film is constructed with a base coating, a printed surface layer, an intermediate layer, and a composite surface layer arranged sequentially from the outside to the inside. The base coating includes a main resin, the printed surface layer includes polypropylene, grafted polypropylene, ethylene-vinyl acetate copolymer, and α-olefin copolymer, and the intermediate layer and composite surface layer include polyolefins. This invention achieves good adhesion of printing ink to the polypropylene film after high-temperature bonding and damp heat aging treatment, and the polypropylene film is not easily torn and has high cohesive strength.

[0053] In a first aspect of this application, a polypropylene film is provided, with reference to Figure 1 The system includes: a base layer 1, the raw material of which includes a main resin; a printed surface layer 2, the printed surface layer being located on one side of the base layer, the raw material of which includes polypropylene, grafted polypropylene, ethylene-vinyl acetate copolymer, and α-olefin copolymer; an intermediate layer 3, the intermediate layer being located on the side of the printed surface layer away from the base layer, the raw material of which includes polyolefin; and a composite surface layer 4, the composite surface layer being located on the side of the intermediate layer away from the printed surface layer, the raw material of which includes polyolefin.

[0054] Therefore, by applying a base coating to the surface of the polypropylene film and utilizing the similar compatibility between the base coating and the ink, the ink adhesion of the polypropylene film after heat lamination and damp heat aging is improved. A printing surface layer has also been developed, in which an ethylene-vinyl acetate copolymer serves as a polar component, compatible with the base coating, and grafted polypropylene and α-olefin copolymers act as compatibilizers, enhancing the system's compatibility and resulting in a printing surface layer with high cohesive strength, making it less prone to tearing after heat lamination. Furthermore, by applying polyolefins to both the printing surface layer and the intermediate layer, the adhesive strength between the two layers is improved, reducing the likelihood of tearing between the printing surface layer and the intermediate layer.

[0055] In some embodiments, the host resin includes one or more of polyurethane resin and acrylic resin. Thus, by utilizing the non-polar and polar groups contained in polyurethane and acrylic molecules, compatibility with the polar and non-polar components in the printed surface layer can be achieved, promoting the compatibility between the printed surface layer and the base layer. Furthermore, the host resin of the printing ink is typically made of polyurethane resin or acrylic resin; therefore, the property of "like dissolves like" can be used to improve the adhesion of the ink to the base layer.

[0056] In some embodiments, the raw materials of the primer layer further include a curing agent, wherein the curing agent includes one or more of isocyanate, aziridine, and carbodiimide. Thus, the curing agent added to the primer layer can increase the crosslinking degree of the primer layer, allowing the active functional groups on the surface of the primer layer to form strong chemical bonds with ink molecules, thereby further improving the adhesion of the ink to the primer layer.

[0057] In some embodiments, the base coating comprises 10%-35% of a main resin, based on the total mass of the base coating. For example, the mass fraction of the main resin, based on the total mass of the base coating, can be any one of 10%, 15%, 20%, 25%, 30%, or 35%, or a range between any two. It also comprises 60%-85% water, for example, based on the total mass of the base coating, the mass fraction of water can be any one of 60%, 65%, 70%, 75%, 80%, or 85%, or a range between any two. Finally, it comprises 5%-15% solvent, for example, based on the total mass of the base coating, the mass fraction of the solvent can be any one of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or a range between any two. Includes 0.1%-1% of additives. For example, based on the total mass of the primer coating, the mass fraction of the additives can be any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any range between two values.

[0058] In some embodiments, the solvent includes one or more of ethanol, isopropanol, n-propanol, and methanol. Thus, the addition of a solvent allows the main resin to dissolve or disperse into a flowable liquid, facilitating the application of the base coat.

[0059] In some embodiments, the additives include one or more of aziridine, isocyanate, carbodiimide, defoamer, and leveling agent.

[0060] Therefore, the addition of additives can help solve specific process or performance problems and promote the base coating to maintain high ink adhesion.

[0061] In some embodiments, based on the total mass of the printed surface layer, it includes 55%-78% ternary copolymer polypropylene. For example, based on the total mass of the printed surface layer, the mass fraction of the ternary copolymer polypropylene can be any one of 55%, 57%, 59%, 61%, 63%, 65%, 67%, 70%, 73%, and 78%, or a range between any two. It also includes 4%-10% grafted polypropylene. For example, based on the total mass of the printed surface layer, the mass fraction of the grafted polypropylene can be any one of 4%, 5%, 6%, 7%, 8%, 9%, and 10%, or a range between any two. Finally, it includes 10%-20% ethylene-vinyl acetate copolymer. For example, based on the total mass of the printed surface layer, the ethylene-vinyl acetate copolymer... The mass fraction of the vinyl acetate copolymer can be any one of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any range between two; it includes 8%-15% of α-olefin copolymer. As an example, based on the total mass of the printed surface layer, the mass fraction of the α-olefin copolymer can be any one of 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any range between two; it includes 0.05%-3% of anti-aging agent. As an example, based on the total mass of the printed surface layer, the mass fraction of the anti-aging agent can be any one of 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, or any range between two.

[0062] Therefore, the third monomer, polyethylene, in ternary copolymer polypropylene can exhibit a similar compatibility phenomenon with the ethylene segments on the molecular chain of the ethylene-vinyl acetate copolymer. Thus, compared to binary copolymer polypropylene and homopolymer polypropylene, ternary copolymer polypropylene is more easily mixed with ethylene-vinyl acetate copolymer. Consequently, by selecting an appropriate mass ratio of ethylene-vinyl acetate copolymer, the polypropylene film can maintain a certain polarity to enhance adhesion to the base coating, while reducing the risk of tearing of the printed surface due to excessive content. By controlling the mass ratio of grafted polypropylene and α-olefin copolymer, the printed surface can maintain a certain polarity while exhibiting better compatibility and higher cohesive strength.

[0063] In some embodiments, the melting point of the ternary copolymer polypropylene is 130°C-140°C.

[0064] Therefore, in the high-temperature environment of the subsequent multi-layer co-extrusion process, the ternary copolymer polypropylene exhibits a viscous flow state due to the ambient temperature being higher than the melting point, and has good fluidity in the multi-layer co-extrusion process, which promotes the one-time molding of polypropylene film.

[0065] As an example, the melting point of the ternary copolymer polypropylene can be any one of 130℃, 131℃, 132℃, 133℃, 134℃, 135℃, 136℃, 137℃, 138℃, 139℃, 140℃, or a range between any two.

[0066] In some embodiments, the grafting rate of the grafted polypropylene is 0.8%-1.4%.

[0067] Therefore, maleic anhydride, as a graft monomer with high polarity containing carbonyl functional groups, allows for easier intermolecular forces to form between the printed surface layer and the base coating layer containing polar groups after grafting maleic anhydride onto polypropylene, thereby increasing the adhesion of the base coating layer to the printed surface layer. Furthermore, the polar groups of the grafted polypropylene can interact strongly with the polar groups of the ethylene-vinyl acetate copolymer, thus improving the compatibility of polypropylene and ethylene-vinyl acetate copolymer and enhancing the cohesive force of the printed surface layer.

[0068] As an example, the grafting rate of the grafted polypropylene can be any one of 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or a range between any two.

[0069] In some embodiments, the melt index of the grafted polypropylene at 2.16 kg and 230 °C is 3 g / 10 min to 12 g / 10 min.

[0070] Therefore, by limiting the melt flow index of grafted polypropylene, the problem of phase separation in the system can be effectively reduced.

[0071] As an example, the melt index of the grafted polypropylene at 2.16 kg and 230 °C can be any one of the following values ​​or a range between any two: 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 11 g / 10 min, and 12 g / 10 min.

[0072] In some embodiments, the mass fraction of vinyl acetate in the ethylene-vinyl acetate copolymer is 8.5%-19%.

[0073] Therefore, by controlling the mass fraction of vinyl acetate, the problems of low polarity of the ethylene-vinyl acetate copolymer and poor compatibility between the printed surface layer and the base layer caused by excessively low vinyl acetate content can be reduced. Conversely, excessively high vinyl acetate content introduces too much polyethylene component, thus reducing the decrease in cohesion of the printed surface layer caused by excessive vinyl acetate content.

[0074] As an example, the mass fraction of vinyl acetate in the ethylene-vinyl acetate copolymer can be any one of 8.5%, 9.5%, 10.5%, 11.5%, 12.5%, 13.5%, 14.5%, 15.5%, 16.5%, 17.5%, 18.5%, or 19%, or a range between any two.

[0075] In some embodiments, the melting point of the α-olefin copolymer is 60°C-80°C.

[0076] Therefore, α-olefin copolymers also have good flowability in the high-temperature environment of subsequent multilayer co-extrusion processes, and can work with other components to promote the one-time molding of polypropylene films.

[0077] As an example, the melting point of the α-olefin copolymer can be any one of 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, or 80°C, or a range between any two.

[0078] In some embodiments, the α-olefin copolymer includes one or more of ethylene-α-olefin copolymer and propylene-α-olefin copolymer.

[0079] Therefore, by selecting α-olefin copolymers with more branches, and taking advantage of the good compatibility between α-olefin copolymers and polypropylene and polar ethylene copolymers, the α-olefin copolymer can be used as a good compatibilizer, thereby improving the cohesion of the printed surface layer.

[0080] In some embodiments, the intermediate layer comprises 74%-90% polyolefin based on its total mass. Thus, by adding a certain amount of polyolefin to the intermediate layer, the intermediate layer adheres more firmly to the printed surface layer due to the property of similarity dissolving in each other.

[0081] As an example, based on the total mass of the intermediate layer, the mass fraction of the polyolefin can be any one of 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, or a range between any two.

[0082] In some embodiments, the intermediate layer comprises 9%-25% filler based on its total mass. Thus, by adding a certain amount of filler, the opacity and UV shielding effect of the polypropylene film can be improved, thereby increasing the service life of the polypropylene film. At the same time, the filler raw materials are widely available and easy to obtain, which can reduce costs. Controlling the filler content can reduce the problem of poor dispersion caused by excessive filler content.

[0083] As an example, based on the total mass of the intermediate layer, the mass fraction of the filler can be any one of 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, or a range between any two.

[0084] In some embodiments, based on the total mass of the intermediate layer, 0.05%-3% of an anti-aging agent is included, thereby reducing the damage to the polypropylene film caused by the external natural environment by adding a certain amount of anti-aging agent.

[0085] As an example, based on the total mass of the intermediate layer, the mass fraction of the anti-aging agent can be any one of 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, or a range between any two.

[0086] In some embodiments, the composite surface comprises 97%-100% polyolefin based on the total mass of the composite surface.

[0087] Therefore, by adding a certain amount of polyolefin to the composite surface layer, the composite surface layer adheres more firmly to the intermediate layer due to the property of similar solubility.

[0088] As an example, based on the total mass of the composite surface layer, the mass fraction of polyolefin can be any one of 97%, 98%, 99%, 100%, or a range between any two.

[0089] In some embodiments, the composite surface layer comprises 0.05%-3% of an anti-aging agent based on its total mass.

[0090] Therefore, by adding a certain amount of anti-aging agent, the damage caused by the external natural environment to polypropylene film can be reduced.

[0091] As an example, based on the total mass of the composite surface layer, the mass fraction of the anti-aging agent can be any one of 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, or a range between any two.

[0092] In some embodiments, the polyolefin includes polypropylene and polyethylene, wherein the polypropylene includes one or more of homopolymer polypropylene, block polypropylene, and atactic polypropylene, and wherein the polyethylene includes one or more of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene.

[0093] In some embodiments, the polyolefin comprises not less than 85% polypropylene based on the total mass of the polyolefin.

[0094] As an example, based on the total mass of the polyolefin, the mass fraction of polypropylene can be any one of 85%, 90%, 95%, 99%, or a range between any two.

[0095] Therefore, by adding polypropylene and polyethylene to the intermediate layer and composite surface layer and controlling the content of polypropylene, the printed surface layer, intermediate layer and composite surface layer can achieve a stronger bond in the multi-layer co-extrusion process, and the phenomenon of easy tearing of polypropylene film can be improved.

[0096] In some embodiments, the filler includes one or more of alumina, calcium carbonate, magnesium carbonate, aluminum sulfate, barium sulfate, aluminum silicate, magnesium silicate, titanium dioxide, and silicon dioxide.

[0097] In some embodiments, the anti-aging agent includes one or more of antioxidants, ultraviolet absorbers, light stabilizers, and free radical quenchers.

[0098] In some embodiments, the anti-aging agents are all conventional anti-aging agents, such as antioxidant 1010, or a mixture of antioxidant 1010 and other types of anti-aging agents in a conventional proportion.

[0099] In some embodiments, the thickness ratio of the printed surface layer, intermediate layer, and composite surface layer is (1:6:1) to (1:9:1). As an example, the thickness ratio of the printed surface layer, intermediate layer, and composite surface layer can be any one of 1:6:1, 1:7:1, 1:8:1, or 1:9:1, or a range between any two.

[0100] In some embodiments, the thickness of the printed surface layer is 9μm-37.5μm. As an example, the thickness of the printed surface layer can be any one of 9μm, 10μm, 15μm, 20μm, 25μm, 30μm, 37μm, 37.5μm or a range between any two.

[0101] In some embodiments, the thickness of the intermediate layer is 75μm-245μm. As an example, the thickness of the intermediate layer can be any one of 75μm, 100μm, 130μm, 160μm, 190μm, 215μm, 230μm, and 245μm, or a range between any two.

[0102] In some embodiments, the thickness of the composite surface layer is 9μm-37.5μm. As an example, the thickness of the composite surface layer can be any one of 9μm, 10μm, 15μm, 20μm, 25μm, 30μm, 37μm, 37.5μm or a range between any two.

[0103] In some embodiments, the thickness of the base coating is 0.3 μm-1 μm. As an example, the thickness of the base coating can be any one of 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm or a range between any two.

[0104] In some embodiments, the thickness of the polypropylene film is 100μm-300μm. As an example, the thickness of the polypropylene film can be any one of 100μm, 120μm, 140μm, 160μm, 180μm, 200μm, 220μm, 240μm, 260μm, 280μm, and 300μm, or a range between any two.

[0105] Therefore, by controlling the thickness of each functional layer, it is possible to better leverage the synergistic effect of each layer, thereby constructing a polypropylene film with strong cohesion, tear resistance, and excellent ink adaptability.

[0106] In a second aspect, this application provides a method for preparing the aforementioned polypropylene film, comprising: S1: The raw materials of the printed surface layer, intermediate layer and composite surface layer are formed in one step through a multi-layer co-extrusion process to obtain a polypropylene film intermediate, wherein the polypropylene film intermediate includes a printed surface layer, an intermediate layer and a composite surface layer stacked in sequence.

[0107] In some embodiments, the temperature of the multilayer co-extrusion process is 150°C-230°C.

[0108] Therefore, by setting the temperature of the multi-layer co-extrusion process, each layer can have a certain viscosity and fluidity in the molten state, thereby achieving stable co-extrusion and firm bonding of each layer.

[0109] As an example, the temperature of the multilayer co-extrusion process can be any one of 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃ or a range between any two.

[0110] In some embodiments, the multilayer co-extrusion process includes: each layer is melt-extruded through different extruders, each layer of material is cast onto a shaping roller through a T-die, and then the polypropylene film is prepared by corona treatment, edge trimming, and winding.

[0111] In some embodiments, the specific process conditions and parameters of the multilayer co-extrusion process can be the process conditions and parameters of conventional multilayer co-extrusion processing, as long as they meet the requirements of film flatness, uniformity and good appearance properties.

[0112] Therefore, the aforementioned polyolefin film can be effectively prepared through a simple, convenient, and easily implemented multilayer co-extrusion process, which is readily applicable to industrial production.

[0113] S2: A base coating is formed on the side of the polypropylene film intermediate where the printed surface layer is located to obtain a polypropylene film.

[0114] In some embodiments, the formation of the base coating includes one or more of gravure coating or screen coating.

[0115] In a third aspect, this application proposes a method for preparing a polypropylene decorative film using the aforementioned polypropylene film, comprising: S10: Printing is performed on the side of the polypropylene film with the base coating to form a printed pattern layer.

[0116] In some embodiments, the printing process can be performed using a multi-color gravure printing machine to print patterns and obtain a polypropylene decorative film. The printing process is adjusted according to the characteristics of the printing machine and the adaptability of the polypropylene film to the printing process, thereby improving the overprinting effect and production efficiency.

[0117] S20: A protective layer is formed on the side of the printed pattern layer away from the base layer to form a polypropylene decorative film.

[0118] In some embodiments, the formation of the protective layer includes one or more of coating treatment and heat-bonding film treatment. The coating treatment can be performed using a gravure coating machine, and the heat-bonding film treatment can be performed using a multi-roller heat laminator. The lamination temperature and production speed can be adjusted according to the process adaptability of the polypropylene film.

[0119] Therefore, by setting a printed pattern layer and a protective layer on one side of the base coating of a polypropylene film, a polypropylene decorative film can be prepared, enabling the effective application of polypropylene film. The protective layer of the polypropylene decorative film provides physical protection and chemical isolation for the printed pattern layer, thus extending the service life of the polypropylene decorative film.

[0120] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0121] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0122] The raw materials used in the embodiments of this application are as follows:

[0123] Example 1 1. Raw material preparation: Based on the total mass of the printed surface layer, it includes 64% ternary copolymer polypropylene① (melting point 130℃), 5% grafted polypropylene① (grafting rate 1.0%, melt index 3g / 10min), 20% ethylene-vinyl acetate copolymer① (vinyl acetate mass fraction 8.5%), 10% α-olefin copolymer①, and 1% antioxidant 1010. Based on the total mass of the intermediate layer, it includes 80% polyolefin (homopolymer polypropylene 100%), 18% filler (titanium dioxide), and 2% antioxidant 1010. Based on the total mass of the composite surface layer, it includes 99.5% polyolefin (block polypropylene 85%, low-density polyethylene 15%) and 0.5% antioxidant 1010.

[0124] 2. Multi-layer co-extrusion process: After the raw materials of each layer are fully mixed in the mixer, they are loaded into different screw extruders and extruded through a multi-channel T-die at a layer thickness ratio of 1:6:1 for the printed surface layer: intermediate layer: composite surface layer to form a composite film. The film is then subjected to double-sided corona treatment to obtain a polypropylene film intermediate with a thickness of 120μm.

[0125] 3. Applying the primer coating: Based on the total mass of the primer coating, it includes 30% acrylic resin①, 60% water, 9% solvent (isopropanol and ethanol in a mass ratio of 1:1), and 1% additives (including 1% aziridine). Finally, a 1μm dry-thickness primer coating is applied to the printed surface side of the polypropylene film intermediate to obtain the polypropylene film.

[0126] Example 2 Example 2 is the same as Example 1, except that the ternary copolymer polypropylene ① (melting point 130℃) is replaced with ternary copolymer polypropylene ② (melting point 140℃).

[0127] Example 3 Example 3 is the same as Example 1, except that the ternary copolymer polypropylene ① (melting point 130℃) is replaced with ternary copolymer polypropylene ② (melting point 140℃), and the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min).

[0128] Example 4 Example 4 is consistent with Example 1, except that 64% of ternary copolymer polypropylene ① (melting point 130℃) is replaced with 74% of ternary copolymer polypropylene ② (melting point 140℃), grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and 20% of ethylene-vinyl acetate copolymer ① is replaced with 10% of ethylene-vinyl acetate copolymer ①.

[0129] Example 5 Example 5 is consistent with Example 1, except that 64% of ternary copolymer polypropylene ① (melting point 130℃) is replaced with 74% of ternary copolymer polypropylene ② (melting point 140℃), grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and 20% of ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) is replaced with 10% ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%).

[0130] Example 6 Example 6 is consistent with Example 1, except that the ternary copolymer polypropylene ① (melting point 130℃) is replaced with ternary copolymer polypropylene ② (melting point 140℃), the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and the ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) is replaced with ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%).

[0131] Example 7 Example 7 is consistent with Example 1, except that 64% of the ternary copolymer polypropylene ① (melting point 130℃) was replaced with 59% of the ternary copolymer polypropylene ② (melting point 140℃), 5% of the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) was replaced with 10% of the grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) was replaced with ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%). The 1μm dry thickness base coat was replaced with a 0.3μm dry thickness base coat.

[0132] Example 8 Example 8 is consistent with Example 1, except that 64% of the ternary copolymer polypropylene ① (melting point 130℃) is replaced with 59% of the ternary copolymer polypropylene ② (melting point 140℃), 5% of the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with 10% of the grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) is replaced with ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%). Based on the total mass of the primer coating, 30% of the acrylic resin ① is replaced with 30% of the polyurethane resin ①, and the 1μm dry thickness primer coating is replaced with a 0.3μm dry thickness primer coating.

[0133] Example 9 Example 9 is consistent with Example 1, except that 64% of the ternary copolymer polypropylene ① (melting point 130℃) is replaced with 59% of the ternary copolymer polypropylene ② (melting point 140℃), 5% of the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with 10% of the grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) is replaced with ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%). Based on the total mass of the primer coating, 30% of the acrylic resin ① is replaced with 30% of the polyurethane resin ① based on the total mass of the primer coating.

[0134] Example 10 Example 10 is consistent with Example 1, except that 64% of the ternary copolymer polypropylene ① (melting point 130℃) is replaced with 59% of the ternary copolymer polypropylene ② (melting point 140℃), 5% of the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with 10% of the grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) is replaced with ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%). Based on the total mass of the primer coating, 30% of the acrylic resin ① is replaced with 30% of the resin (polyurethane resin ② to acrylic resin ① mass ratio 1:1), and the 1μm dry thickness primer coating is replaced with a 0.5μm dry thickness primer coating.

[0135] Example 11 Example 11 is the same as Example 1, except that the α-olefin copolymer ① (melting point 60°C) is replaced with α-olefin copolymer ② (melting point 77°C).

[0136] Example 12 Example 12 is the same as Example 1, except that aziridine is replaced with isocyanate.

[0137] Example 13 Example 13 is the same as Example 1, except that aziridine is replaced with carbodiimide.

[0138] Example 14 Example 14 is the same as Example 1, except that 64% of the ternary copolymer polypropylene① is replaced with 54% of the ternary copolymer polypropylene①, and 20% of the ethylene-vinyl acetate copolymer① is replaced with 30% of the ethylene-vinyl acetate copolymer①.

[0139] Example 15 Example 15 is the same as Example 1, except that 64% of ternary copolymer polypropylene① is replaced with 74% of ternary copolymer polypropylene①, and 20% of ethylene-vinyl acetate copolymer① is replaced with 10% of ethylene-vinyl acetate copolymer③.

[0140] Example 16 Example 16 is the same as Example 1, except that the ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction of 8.5%) is replaced with ethylene-vinyl acetate copolymer ④ (vinyl acetate mass fraction of 28%).

[0141] Example 17 Example 17 is consistent with Example 1, except that 64% of the ternary copolymer polypropylene ① (melting point 130℃) is replaced with 59% of the ternary copolymer polypropylene ② (melting point 140℃), 5% of the grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min) is replaced with 10% of the grafted polypropylene ② (grafting rate 0.8%, melt index 12g / 10min), and ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%) is replaced with ethylene-vinyl acetate copolymer ② (vinyl acetate mass fraction 19%). Based on the total mass of the primer coating, 30% acrylic resin ① and 60% water are replaced with 10% acrylic resin ② and 80% water, and the 1μm dry thickness primer coating is replaced with a 0.1μm dry thickness primer coating.

[0142] Comparative Example 1 Comparative Example 1 is the same as Example 1, except that the polypropylene film does not contain a base coating.

[0143] Comparative Example 2 Comparative Example 2 is consistent with Example 1, except that, based on the total mass of the printed surface layer, the following components were replaced: 64% ternary copolymer polypropylene ① (melting point 130°C), 5% grafted polypropylene ① (grafting rate 1.0%, melt index 3g / 10min), 20% ethylene-vinyl acetate copolymer ① (vinyl acetate mass fraction 8.5%), 10% α-olefin copolymer ①, and 1% antioxidant 1010.

[0144] Test method: The polypropylene film is printed with ink using a printing press. After printing, the transparent film and the polypropylene film containing the printing ink are heat-bonded at 130°C to complete the preparation of the polypropylene decorative film.

[0145] Initial peel performance test method: After peeling off the attached decorative film, the test is carried out in accordance with item 6.7 of GB / T 31034-2014, using a universal tensile testing machine of model ETM-104B.

[0146] Peeling performance test method after damp heat aging treatment: The bonded sample is placed in an environmental aging chamber at 85℃ and 85% relative humidity. After 5 days, it is taken out and restored in an open environment at 23℃ and less than 75% relative humidity for 24 hours. After peeling off the bonded decorative film, the test is carried out in accordance with item 6.7 of GB / T 31034-2014 using a universal tensile testing machine of model ETM-104B.

[0147] Printing ink adhesion: evaluated according to ASTM D3359.

[0148] Test results:

[0149] The test results show that the polypropylene films prepared using experimental parameters within the preferred range in Examples 1-13 exhibit high peel strength in both the initial and humid heat-aged states, and no tearing of the printed surface or ink detachment occurs. This demonstrates that the polypropylene films possess high cohesive strength and high ink adhesion in both the initial state and after humid heat aging, exhibiting excellent peel performance. The non-preferred examples are polypropylene films prepared using experimental parameters outside the preferred range. In Example 14, the amount of ethylene-vinyl acetate copolymer added exceeded the specified weight, introducing excessive ethylene chain components into the resin system. In Example 16, the specified vinyl acetate content ratio was exceeded. In Example 15, the content of the polar component ethylene-vinyl acetate copolymer was insufficient. In Example 17, the base coating thickness was insufficient. The peel strength values ​​of the non-preferred examples are lower than those of the preferred examples, and tearing of the printed surface and ink detachment are more likely to occur. Therefore, although the non-preferred examples can maintain a certain level of cohesive strength and ink adhesion, their initial state and state after humid heat aging are inferior to those of the preferred examples. Comparative Example 1 showed ink peeling in both the initial state and after humid heat aging, indicating that the lack of a base coating resulted in poor ink adhesion. In Comparative Example 2, the absence of grafted polypropylene led to insufficient cohesion in the printed surface, causing tearing of the printed surface.

[0150] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A polypropylene film, characterized in that, include: The base coating material includes the main resin; A printed surface layer, located on one side of the base layer, wherein the raw materials of the printed surface layer include polypropylene, grafted polypropylene, ethylene-vinyl acetate copolymer, and α-olefin copolymer. An intermediate layer, located on the side of the printed surface layer away from the base layer, wherein the raw material of the intermediate layer includes polyolefin; A composite surface layer, located on the side of the intermediate layer away from the printed surface layer, wherein the raw material of the composite surface layer includes polyolefin.

2. The polypropylene film according to claim 1, characterized in that, The main resin includes one or more of polyurethane resin and acrylic resin; and / or, The raw materials of the base coating also include a curing agent, wherein the curing agent includes one or more of isocyanate, aziridine, and carbodiimide.

3. The polypropylene film according to claim 1 or 2, characterized in that, Based on the total mass of the printed surface layer, it comprises 55%-78% ternary copolymer polypropylene, 4%-10% grafted polypropylene, 10%-20% ethylene-vinyl acetate copolymer, 8%-15% α-olefin copolymer, and 0.05%-3% anti-aging agent; wherein, The melting point of the ternary copolymer polypropylene is 130℃-140℃; and / or, The grafting rate of the grafted polypropylene is 0.8%-1.4%; and / or, The grafted polypropylene has a melt index of 3 g / 10 min to 12 g / 10 min at 2.16 kg and 230 °C; and / or, The ethylene-vinyl acetate copolymer contains 8.5%-19% vinyl acetate by mass; and / or, The melting point of the α-olefin copolymer is 60℃-80℃; and / or, The α-olefin copolymer includes one or more of ethylene-α-olefin copolymer and propylene-α-olefin copolymer.

4. The polypropylene film according to claim 1 or 2, characterized in that, Based on the total mass of the intermediate layer, it comprises 74%-90% polyolefin, 9%-25% filler, and 0.05%-3% anti-aging agent; and / or, Based on the total mass of the composite surface layer, it includes 97%-100% polyolefin and 0.05%-3% anti-aging agent.

5. The polypropylene film according to claim 4, characterized in that, The polyolefin includes polypropylene and polyethylene, wherein the polypropylene includes one or more of homopolymer polypropylene, block polypropylene, and atactic polypropylene. The polyethylene includes one or more of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene; and / or, Based on the total mass of the polyolefin, it includes not less than 85% polypropylene.

6. The polypropylene film according to claim 4, characterized in that, The thickness ratio of the printed surface layer, intermediate layer, and composite surface layer is (1:6:1) to (1:9:1); and / or, The thickness of the printed surface layer is 9μm-37.5μm; and / or, The thickness of the intermediate layer is 75μm-245μm; and / or, The thickness of the composite surface layer is 9μm-37.5μm; and / or, The thickness of the base coating is 0.3 μm-1 μm; and / or, The thickness of the polypropylene film is 100μm-300μm.

7. A method for preparing the polypropylene film according to any one of claims 1-6, characterized in that, include: The raw materials for the printed surface layer, intermediate layer and composite surface layer are formed in one step through a multi-layer co-extrusion process to obtain a polypropylene film intermediate, which includes a printed surface layer, intermediate layer and composite surface layer stacked in sequence. A base coating is formed on the side of the polypropylene film intermediate where the printed surface layer is located to obtain a polypropylene film.

8. The method according to claim 7, characterized in that, The temperature of the multi-layer co-extrusion process is 150℃-230℃.

9. A method for preparing a polypropylene decorative film using the polypropylene film according to any one of claims 1-6, characterized in that, include: Printing is performed on the side of the polypropylene film with the base coating to form a printed pattern layer; A protective layer is formed on the side of the printed pattern layer away from the base layer to form a polypropylene decorative film.

10. The method according to claim 9, characterized in that, The formation of the protective layer includes one or more of coating treatment and heat-applied mask treatment.

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