Casting polypropylene film and composite packaging film

Abstract

The invention relates to the technical field of materials, in particular to a casting polypropylene film and a composite packaging film. The casting polypropylene film comprises a corona layer, a core layer and a packaging layer which are sequentially stacked, wherein the core layer is prepared from the following materials in parts by weight: 65 to 95 parts of block co-polypropylene, 5 to 20 parts of first elastomer and 0 to 5 parts of first aid; the block co-polypropylene comprises a rubber phase, and the average size of the rubber phase is 0-0.2 [mu] m and is not 0. The casting polypropylene film has better interlayer stability, so that the casting polypropylene film does not generate self-layering when being stripped from a base material, and the reliability of a corresponding composite film is improved.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a cast polypropylene film and a composite packaging film. Background Art

[0002] Cast polypropylene film (CPP film) has the characteristics of high transparency, good stiffness, low heat sealing temperature, heat resistance, moisture resistance, good barrier properties, strong printing and lamination adaptability, smooth surface, uniform molding thickness and balanced performance. Due to its excellent comprehensive performance and broad application prospects, it occupies an important position in the field of packaging materials.

[0003] Especially in recent years, with the increasing development of pre-prepared food packaging materials, high-end barrier packaging materials, soft-pack lithium-ion batteries and solid-state battery packaging materials, the demand for related packaging materials has also increased significantly, and the requirements for the packaging materials themselves have also increased. Common composite packaging materials may have an outer protective layer (the material may be nylon or polyethylene terephthalate PET) / barrier layer (the material may be aluminum foil, high barrier PET, other films or sheets with barrier effects) / encapsulation layer (materials include polypropylene PP film or polyethylene PE film), and each layer of material is usually bonded and composited with a corresponding adhesive. The encapsulation layer will use PP film or PE film due to different packaging requirements. For composite materials with high packaging strength requirements and harsh application environments, CPP film is generally used as the inner packaging material.

[0004] Although PP film plays an important role in packaging materials, performance differences may bring many problems. CPP has excellent heat resistance. Since the softening point of PP is about 140°C, it can be used in hot filling, cooking bags, aseptic packaging and other fields. It has excellent acid, alkali and grease resistance, high transparency, good flexibility, high barrier properties, high strength and tear resistance, and easy processing. For example, the cooking type CPP film is generally compounded with printed biaxially oriented polypropylene film (BOPP) and biaxially oriented polyester film (BOPET) to make two or more layers of cooking film, which requires the CPP film to have good composite properties, high heat sealing strength and peel strength, impact resistance and tear strength.

[0005] However, CPP films with poor interlayer stability may indeed cause delamination problems during use. In the aluminum-plastic film used as the packaging material for lithium-ion batteries, if the interlayer stability of the CPP film is poor, the electrolyte may penetrate through the interlayer gap, causing safety problems such as fire. Traditional aluminum-plastic films are generally layered structures, and the structures are generally polyamide (PA) / aluminum (Al) / CPP and PET / PA / aluminum (Al) / CPP. Each layer is bonded with an adhesive, but the most fatal weakness of multi-layer composite aluminum-plastic films in application is the delamination problem, that is, the separation between CPP and CPP, between CPP and Al layer, and between aluminum-plastic film and lug layer.

[0006] The delamination of CPP film may also occur during the test of the peeling force performance between CPP film and substrate. For example, when BOPP / CPP is compounded without solvent, sometimes the peeling strength is low. One common situation is that the CPP film delaminates itself during the peeling process. When the bonding strength between BOPP and CPP is greater than the bonding strength between the different layers of the CPP film itself, the film separates at the weaker place. In addition, the delamination of the sealing part after heat sealing of the composite film packaging may also be related to the CPP film.

[0007] The improvement of interlayer stability of CPP films can be mainly achieved through raw material selection, formulation optimization and production process improvement in existing literature, as follows:

[0008] (1) Selecting the right polymer material: In the production of CPP film, it is key to select a polypropylene resin with good compatibility. For example, homopolymer polypropylene and copolymer polypropylene with different melt indexes can be used for matching. Homopolymer polypropylene can provide better rigidity and barrier properties, while copolymer polypropylene can increase toughness and softness. By mixing in a reasonable ratio, such as mixing homopolymer polypropylene and copolymer polypropylene in a ratio of 7:3, the overall performance of the film can be improved, the bonding between the layers can be made tighter, and the interlayer stability can be improved;

[0009] (2) Adding compatibilizers: Compatibilizers can enhance the affinity between different polymers. For example, in a multi-layer CPP film structure, when there are polypropylene layers with different properties, maleic anhydride grafted polypropylene is added as a compatibilizer. The molecular chain of this compatibilizer contains active groups that can react with polypropylene. It can form chemical bonds or physical entanglements between different polypropylene layers, effectively improving the adhesion between the layers. Generally speaking, the amount of compatibilizer added can be controlled at around 3-5% according to actual conditions;

[0010] (3) Optimize the extrusion process: During the cast extrusion process, controlling parameters such as extrusion temperature, screw speed and pulling speed is crucial for interlayer stability. Extrusion temperature that is too high will cause excessive degradation of polypropylene resin and affect its performance; too low temperature will cause incomplete plasticization of the resin. For example, for commonly used CPP film extrusion equipment, controlling the extrusion temperature between 200-230°C, the screw speed at 50-80r / min, and the pulling speed at 10-15m / min can make the resin evenly extruded and form a continuous and stable film layer, reduce interlayer stress, and improve interlayer stability;

[0011] (4) Optimization of multi-layer co-extrusion technology: When using multi-layer co-extrusion technology to produce CPP film, it is necessary to ensure that the layers fit closely together. During the co-extrusion process, it is key to adjust the extrusion thickness and extrusion speed of each layer. For example, for a three-layer CPP film structure, the middle layer is a barrier layer and the outer layer is a heat-sealing layer. During extrusion, the extrusion speed of the barrier layer should be slightly slower than that of the heat-sealing layer, so that the barrier layer can be better wrapped by the heat-sealing layer after extrusion, thereby enhancing the bonding force between the layers. At the same time, the ratio of the extrusion thickness of each layer should be adjusted according to the specific requirements of the product, such as the heat-sealing layer: barrier layer: heat-sealing layer can adopt a thickness ratio of 1:2:1.

[0012] The above technical means can be applied to conventional CPP film products. For application environments requiring higher impact strength, the core layer generally uses impact-resistant polypropylene, and homopolymer polypropylene cannot be used. The addition of compatibilizers will increase costs. The process technology improvement is the optimization of the basic processing technology and cannot fundamentally solve the problem. Summary of the invention

[0013] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the present invention provides a cast polypropylene film and a composite packaging film, wherein the cast polypropylene film has good interlayer stability, so that the cast polypropylene film does not produce self-delamination when it is peeled off from a substrate, thereby improving the reliability of the corresponding composite film.

[0014] To this end, the first aspect of the present invention provides a cast polypropylene film, the cast polypropylene film comprising a corona layer, a core layer and an encapsulation layer stacked in sequence;

[0015] The material forming the core layer includes 65-95 parts by weight of block copolymer polypropylene, 5-20 parts by weight of a first elastomer, and 0-5 parts by weight of a first auxiliary agent;

[0016] The block copolymer polypropylene comprises a rubber phase, and an average size of the rubber phase in the block copolymer polypropylene is 0-0.2 μm and is not zero.

[0017] In view of the problem that cast polypropylene film has poor packaging performance due to low interlayer stability when used as packaging material, the present invention limits the rubber phase size of block copolymerized polypropylene in the core layer of cast polypropylene film, increases the bonding points of the internal interface between the layers of cast polypropylene film, forms a "micro-crosslinking" effect, thereby enhancing the interlayer stability of cast polypropylene film and solving the problem of cast polypropylene film packaging delamination. At the same time, the cast polypropylene film does not produce self-delamination when peeling from the substrate, thereby improving the reliability of the corresponding composite film.

[0018] According to an embodiment of the present invention, the content of the rubber phase in the block copolymerized polypropylene is 20wt%-30wt%.

[0019] According to an embodiment of the present invention, the average size of the rubber phase in the block copolymer polypropylene is 0-0.15 μm, and is not 0.

[0020] According to an embodiment of the present invention, the material constituting the core layer further comprises random copolymer polypropylene.

[0021] According to an embodiment of the present invention, the block copolymer polypropylene is ethylene-propylene block polypropylene with a melting point of 160° C.-170° C. and a melt index of 1-4 g / 10 min.

[0022] According to an embodiment of the present invention, the first elastomer includes at least one of propylene-based elastomer, ethylene-based elastomer, ethylene-acrylic acid copolymer or styrene-based elastomer.

[0023] According to an embodiment of the present invention, the first auxiliary agent includes at least one of a polymer processing aid, an antioxidant, an antistatic agent or a slip and opening agent.

[0024] According to an embodiment of the present invention, the material forming the corona layer includes 70-98 parts by weight of random copolymer polypropylene, 10-20 parts by weight of a second elastomer, and 0-2 parts by weight of a second auxiliary agent.

[0025] According to an embodiment of the present invention, the second elastomer includes at least one of propylene-based elastomer, ethylene-based elastomer, ethylene-acrylic acid copolymer or styrene-based elastomer.

[0026] According to an embodiment of the present invention, the second auxiliary agent includes at least one of a polymer processing aid, an antioxidant, an antistatic agent or a slip and opening agent.

[0027] According to an embodiment of the present invention, the material forming the heat-sealing layer includes 70-98 parts by weight of random copolymer polypropylene, 10-20 parts by weight of a third elastomer, and 0-2 parts by weight of a third auxiliary agent.

[0028] According to an embodiment of the present invention, the third elastomer includes at least one of propylene-based elastomer, ethylene-based elastomer, ethylene-acrylic acid copolymer or styrene-based elastomer.

[0029] According to an embodiment of the present invention, the third auxiliary agent includes at least one of a polymer processing aid, an antioxidant, an antistatic agent or a slip and opening agent.

[0030] According to an embodiment of the present invention, the sealing temperature of the encapsulation layer is 120-135°C.

[0031] According to an embodiment of the present invention, the thickness ratio of the corona layer, the core layer and the encapsulation layer is 1:(3-9):1.

[0032] The second aspect of the present invention provides a composite packaging film, wherein the composite packaging film comprises the cast polypropylene film of the first aspect, so that the composite packaging film has good interlayer stability and reliability.

[0033] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0035] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0036] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0037] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0038] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0039] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0040] According to an embodiment of the present invention, a first aspect of the present invention provides a cast polypropylene film, the cast polypropylene film comprising a corona layer, a core layer and an encapsulation layer stacked in sequence;

[0041] The material forming the core layer includes 65-95 parts by weight of block copolymer polypropylene, 5-20 parts by weight of a first elastomer, and 0-5 parts by weight of a first auxiliary agent;

[0042] The block copolymer polypropylene comprises a rubber phase, and an average size of the rubber phase in the block copolymer polypropylene is 0-0.2 μm and is not zero.

[0043] In view of the problem that cast polypropylene film has poor packaging performance due to low interlayer stability when used as packaging material, the present invention limits the rubber phase size of block copolymerized polypropylene in the core layer of cast polypropylene film, increases the bonding points of the internal interface between the layers of cast polypropylene film, forms a "micro-crosslinking" effect, thereby enhancing the interlayer stability of cast polypropylene film and solving the problem of cast polypropylene film packaging delamination. At the same time, the cast polypropylene film does not produce self-delamination when peeling from the substrate, thereby improving the reliability of the corresponding composite film.

[0044] Specifically, there is a close relationship between the size of the block copolymer polypropylene rubber phase and the interlayer stability. When the rubber phase size is small, it has a positive effect on the interlayer stability. When the rubber phase size is small and evenly dispersed in the polypropylene matrix, it can play a role similar to "micro cross-linking points", enhancing the connection and interaction between polymer molecular chains. In this case, the interlayer structure of the film is tighter and the interlayer bonding force is stronger. When subjected to external forces or in complex environmental conditions, the layers are not easily separated or delaminated, so that the cast polypropylene film has good interlayer stability. For example, in some application scenarios where the interlayer stability of packaging materials is required to be high, such as pharmaceutical packaging and food packaging, a smaller rubber phase can better ensure the integrity and safety of the packaging. When the rubber phase size is large, the negative effect on the interlayer stability will form larger agglomerates or phase separation areas in the polypropylene matrix. The interfacial bonding between these larger rubber phase areas and the polypropylene matrix is ​​weak. When affected by external forces, temperature changes or chemical erosion, stress concentration is easily generated at the interface, resulting in interlayer separation or delamination, thereby reducing the interlayer stability of the cast polypropylene film. For example, in a high temperature or high humidity environment, a cast polypropylene film with a large rubber phase may have interlayer delamination problems, affecting its performance. Therefore, the size of the block copolymerized polypropylene rubber phase in the cast polypropylene film is limited to obtain a cast polypropylene film with good interlayer stability and comprehensive performance.

[0045] Among them, the "size of the rubber phase" can be obtained by injection molding block copolymer polypropylene into a strip, first putting it into liquid nitrogen for brittle fracture, and then putting it into m-xylene and soaking it at room temperature for 72 hours. At this time, the non-crystallized rubber phase will dissolve in m-xylene, and only crystalline polypropylene will remain in the casting. Since the rubber phase is removed and holes are left, the hole position in the figure is the original rubber phase. The mass proportion of the rubber phase can be calculated by the mass difference, and the size of the rubber phase can be calculated using the IPP software.

[0046] According to a specific embodiment of the present invention, the content of the rubber phase in the block copolymerized polypropylene is 20wt%-30wt%, thereby making the cast polypropylene film have sufficient toughness.

[0047] According to a specific embodiment of the present invention, the average size of the rubber phase in the block copolymer polypropylene is 0-0.15 μm, and is not 0, thereby further achieving better interlayer stability.

[0048] According to a specific embodiment of the present invention, the material constituting the core layer also includes random copolymer polypropylene, which can adjust the fluidity of the core layer and further improve the interlayer stability, while replacing part of the impact-resistant polypropylene to reduce the probability of crystal point generation.

[0049] According to a specific embodiment of the present invention, the block copolymer polypropylene is ethylene-propylene block polypropylene, with a melting point of 160°C-170°C and a melt index of 1-4 g / 10 min. Here, "melt index" should be understood as the melt flow rate of the block copolymer polypropylene at a temperature of 230°C and a load of 2.16 kg of 1-4 g / 10 min.

[0050] According to a specific embodiment of the present invention, the types of the first elastomer and the first auxiliary agent are not particularly limited, and the first elastomer includes but is not limited to propylene-based elastomer, vinyl elastomer, ethylene-acrylic acid copolymer, and styrene-based elastomer. The first auxiliary agent includes but is not limited to polymer processing aids, antioxidants, antistatic agents, and smooth opening agents. The first auxiliary agent can be added according to the situation during the formation of the core layer.

[0051] According to a specific embodiment of the present invention, the material forming the corona layer includes 70-98 parts by weight of random copolymer polypropylene, 10-20 parts by weight of a second elastomer, and 0-2 parts by weight of a second auxiliary agent.

[0052] The types of the random copolymer polypropylene, the second elastomer and the second auxiliary agent are not particularly limited, and the second elastomer includes but is not limited to propylene-based elastomer, vinyl elastomer, ethylene-acrylic acid copolymer, and styrene elastomer. The second auxiliary agent includes but is not limited to polymer processing aids, antioxidants, antistatic agents, and smooth opening agents. The second auxiliary agent can be added according to the situation during the formation of the corona layer.

[0053] According to a specific embodiment of the present invention, the material forming the encapsulation layer includes 70-98 parts by weight of random copolymer polypropylene, 10-20 parts by weight of a third elastomer, and 0-2 parts by weight of a third auxiliary agent.

[0054] The types of the random copolymer polypropylene, the third elastomer and the third auxiliary agent are not particularly limited, and the third elastomer includes but is not limited to propylene-based elastomer, vinyl elastomer, ethylene-acrylic acid copolymer, and styrene-based elastomer. The third auxiliary agent includes but is not limited to polymer processing aids, antioxidants, antistatic agents, and smooth opening agents. The third auxiliary agent can be added according to the situation during the formation of the encapsulation layer.

[0055] According to a specific embodiment of the present invention, the sealing start temperature of the encapsulation layer is 120-135° C. As some examples, the sealing start temperature of the encapsulation layer may be 120° C., 125° C., 130° C., 135° C., etc.

[0056] According to a specific embodiment of the present invention, the thickness ratio of the corona layer, the core layer and the encapsulation layer is 1:(3-9):1.

[0057] According to a specific embodiment of the present invention, the preparation method of the cast polypropylene film is not particularly limited. The raw materials of each layer are mixed respectively, and then formed into a film through a casting process, and the corona layer is coronaed to obtain the final product.

[0058] According to an embodiment of the present invention, a second aspect of the present invention provides a composite packaging film, which includes the cast polypropylene film described in the first aspect.

[0059] Specifically, the composite packaging film may further include a PA / Al composite film, and the cast polypropylene film corona layer is composited with the aluminum foil surface of the composite film.

[0060] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0061] Example 1

[0062] The materials forming the core layer are:

[0063] Block copolymer polypropylene (rubber phase average size 0.15 μm, content 25 wt%; melting point 165°C, melt index 1.8 g / 10 min) 89.5 parts by weight

[0064] Propylene-based elastomer 3980FL 10 parts by weight

[0065] Antioxidant 168 0.5 parts by weight.

[0066] The materials forming the corona layer are:

[0067] Random copolymer polypropylene 84.5 parts by weight

[0068] Styrene-based elastomer TAIPOL 6014 15 parts by weight

[0069] Antioxidant 168 0.5 parts by weight.

[0070] The materials forming the encapsulation layer are:

[0071] Random copolymer polypropylene 84.5 parts by weight

[0072] Vinyl elastomer LC175 15 parts by weight

[0073] Antioxidant 168 0.5 parts by weight.

[0074] Example 2

[0075] The materials forming the core layer are:

[0076] Block copolymer polypropylene (rubber phase average size 0.2 μm, content 28 wt%; melting point 163°C, melt index 2.0 g / 10 min) 89.5 parts by weight

[0077] Propylene-based elastomer 3980FL 10 parts by weight

[0078] Antioxidant 168 0.5 parts by weight.

[0079] The materials forming the corona layer are:

[0080] Random copolymer polypropylene 84.5 parts by weight

[0081] Propylene elastomer 3980FL 15 parts by weight

[0082] Antioxidant 168 0.5 parts by weight.

[0083] The materials forming the encapsulation layer are:

[0084] Random copolymer polypropylene 84.5 parts by weight

[0085] Propylene elastomer 3980FL 15 parts by weight

[0086] Antioxidant 168 0.5 parts by weight.

[0087] Example 3

[0088] The materials forming the core layer are:

[0089] Block copolymer polypropylene (rubber phase average size 0.1 μm, content 20 wt%; melting point 167°C, melt index 1.0 g / 10 min) 89.5 parts by weight

[0090] Styrene-based elastomer TAIPOL 6014 10 parts by weight

[0091] Antioxidant 168 0.5 parts by weight.

[0092] The materials forming the corona layer are:

[0093] Random copolymer polypropylene 84.5 parts by weight

[0094] Styrene-based elastomer TAIPOL 6014 15 parts by weight

[0095] Antioxidant 168 0.5 parts by weight.

[0096] The materials forming the encapsulation layer are:

[0097] Random copolymer polypropylene 84.5 parts by weight

[0098] Propylene elastomer 3980FL 15 parts by weight

[0099] Antioxidant 168 0.5 parts by weight.

[0100] Comparative Example 1

[0101] The materials forming the core layer are:

[0102] Block copolymer polypropylene (rubber phase average size 0.3 μm, content 20 wt%; melting point 167°C, melt index 1.5 g / 10 min) 89.5 parts by weight

[0103] Propylene-based elastomer 3980FL 10 parts by weight

[0104] Antioxidant 168 0.5 parts by weight.

[0105] The materials forming the corona layer are:

[0106] Random copolymer polypropylene 84.5 parts by weight

[0107] Propylene elastomer 3980FL 15 parts by weight

[0108] Antioxidant 168 0.5 parts by weight.

[0109] The materials forming the encapsulation layer are:

[0110] Random copolymer polypropylene 84.5 parts by weight

[0111] Propylene elastomer 3980FL 15 parts by weight

[0112] Antioxidant 168 0.5 parts by weight.

[0113] Comparative Example 2

[0114] The materials forming the core layer are:

[0115] Block copolymer polypropylene (rubber phase average size 0.4 μm, content 28 wt%; melting point 165°C, melt index 3.0 g / 10 min) 89.5 parts by weight

[0116] Styrene-based elastomer TAIPOL 6014 10 parts by weight

[0117] Antioxidant 168 0.5 parts by weight.

[0118] The materials forming the corona layer are:

[0119] Random copolymer polypropylene 84.5 parts by weight

[0120] Propylene elastomer 3980FL 15 parts by weight

[0121] Antioxidant 168 0.5 parts by weight.

[0122] The materials forming the encapsulation layer are:

[0123] Random copolymer polypropylene 84.5 parts by weight

[0124] Vinyl elastomer LC175 15 parts by weight

[0125] Antioxidant 168 0.5 parts by weight.

[0126] Test Case

[0127] In Example 1-3 and Comparative Example 1-2, the raw materials for forming the corona layer, core layer and encapsulation layer are mixed respectively according to the above weight ratio and put into the corresponding hopper of the three-layer co-extrusion casting machine, and the thickness ratio of the three layers is set to 1:4:1. A 50μm cast polypropylene film is made by co-extrusion casting process, and the corona layer is corona-coated.

[0128] The cast polypropylene films of Examples 1-3 and Comparative Examples 1-2 were laminated onto the aluminum foil surface of PA / Al. After the adhesive was matured, the peeling force (tested at a speed of 100 mm / min) and peeling appearance between the cast polypropylene films and the aluminum foil were tested at 25°C and 85°C, respectively. The results are shown in Table 1.

[0129] The results show that, compared with Comparative Examples 1-2, Examples 1-3 limit the size of the rubber phase in the block copolymer polypropylene used in the core layer. The smaller rubber phase size can play a role similar to "micro-crosslinking points", thereby enhancing the connection and interaction between polymer molecular chains and the formation of hydrogen bonds and effective bonding with other molecular chains, thereby improving the interlayer bonding strength between the core layer and the corona layer and the encapsulation layer. Therefore, the prepared cast polypropylene film has better interlayer stability, so that it does not produce self-delamination when it is peeled off from the substrate.

[0130] Table 1

[0131]

[0132] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0133] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A cast polypropylene film, characterized in that It comprises a corona layer, a core layer and an encapsulation layer which are stacked in sequence; The material forming the core layer includes 65-95 parts by weight of block copolymer polypropylene, 5-20 parts by weight of a first elastomer, and 0-5 parts by weight of a first auxiliary agent; The block copolymer polypropylene comprises a rubber phase, and an average size of the rubber phase in the block copolymer polypropylene is 0-0.2 μm and is not zero.

2. The cast polypropylene film according to claim 1, characterized in that The content of the rubber phase in the block copolymer polypropylene is 20wt%-30wt%; Optionally, the average size of the rubber phase in the block copolymerized polypropylene is 0-0.15 μm, and is not 0.

3. The cast polypropylene film according to claim 1, characterized in that The material constituting the core layer also includes random copolymer polypropylene.

4. The cast polypropylene film according to claim 1, characterized in that The block copolymer polypropylene is ethylene-propylene block polypropylene, with a melting point of 160° C.-170° C. and a melt index of 1-4 g / 10 min.

5. The cast polypropylene film according to claim 1, characterized in that The first elastomer comprises at least one of a propylene-based elastomer, a vinyl elastomer, an ethylene-acrylic acid copolymer, or a styrene-based elastomer; Optionally, the first auxiliary agent includes at least one of a polymer processing aid, an antioxidant, an antistatic agent or a slip and opening agent.

6. The cast polypropylene film according to claim 1, characterized in that The material forming the corona layer includes 70-98 parts by weight of random copolymer polypropylene, 10-20 parts by weight of a second elastomer, and 0-2 parts by weight of a second auxiliary agent; Optionally, the second elastomer comprises at least one of a propylene-based elastomer, a vinyl-based elastomer, an ethylene-acrylic acid copolymer, or a styrene-based elastomer; Optionally, the second auxiliary agent includes at least one of a polymer processing aid, an antioxidant, an antistatic agent or a slip and opening agent.

7. The cast polypropylene film according to claim 1, characterized in that The material forming the encapsulation layer includes 70-98 parts by weight of random copolymer polypropylene, 10-20 parts by weight of a third elastomer, and 0-2 parts by weight of a third auxiliary agent; Optionally, the third elastomer comprises at least one of a propylene-based elastomer, a vinyl elastomer, an ethylene-acrylic acid copolymer, or a styrene-based elastomer; Optionally, the third auxiliary agent includes at least one of a polymer processing aid, an antioxidant, an antistatic agent or a slip and opening agent.

8. The cast polypropylene film according to claim 1, characterized in that The sealing temperature of the encapsulation layer is 120-135°C.

9. The cast polypropylene film according to claim 1, characterized in that The thickness ratio of the corona layer, the core layer and the encapsulation layer is 1:(3-9):

1.

10. A composite packaging film, characterized in that: The invention comprises the cast polypropylene film according to any one of claims 1 to 9.

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