Cooking CPP film and preparation method and application thereof

Abstract

The invention provides a cooked CPP film and a preparation method and application thereof. The structure of the cooked CPP film sequentially comprises a heat sealing layer, a first core layer, a second core layer, a middle layer, a third core layer, a fourth core layer and a corona layer from inside to outside, wherein the heat sealing layer is prepared from the following components in percentage by weight: 17 to 47 weight percent of ternary co-polypropylene, 50 to 80 weight percent of polyolefin elastomer and 1 to 3 weight percent of anti-sticking master batch. Compared with a conventional cooking film, the cooking CPP film has the advantages that the temperature resistance can reach 121 DEG C, meanwhile, the cooking CPP film has a wider heat sealing interval and a lower sealing starting temperature, and the heat sealing interval is 74-140 DEG C. Therefore, the film has certain heat sealing performance during cooking, and the films around the cooked contents can be bonded together to fix the contents. The food safety is ensured, the production efficiency and output are further improved, the energy consumption is reduced, and the cost is reduced.

Description

Technical Field

[0001] The present application relates to the field of material technology, and particularly to a steamed CPP film, a preparation method thereof, and an application thereof. Background Art

[0002] Cast polypropylene is an unstretched polypropylene film (CPP) produced by a casting process. Because of its advantages such as light weight, high transparency, excellent mechanical adaptability, good stiffness, moisture resistance, heat resistance, and easy heat sealing, it is widely used in the fields of food, medicine, daily commodities, clothing, and industry. In the field of food packaging, due to its good heat resistance, the cooking-grade CPP is widely used as a base material in the field of composite packaging materials. The high-temperature cooking-grade CPP film, after being compounded with other film materials to form a bag, can withstand cooking and sterilization at a temperature above 120 °C, and can remain stable and unbroken during the high-temperature cooking process, and at the same time has good barrier properties and sealing properties.

[0003] However, in the production process of heat-resistant packaging, heat sealing is the most commonly used sealing packaging method. The heat sealing effect is generally related to the heat sealing temperature, heat sealing pressure, and heat sealing time. Among them, the starting sealing temperature and heat sealing strength are the key factors affecting the packaging efficiency and cost. At present, the starting sealing temperature of the cooking-grade CPP on the market is usually above 100 °C. The relatively high starting sealing temperature will lead to an increase in energy consumption and a decrease in production efficiency. With the development of food packaging technology, the demand for ultra-low temperature heat-sealing materials has increased significantly. The heat sealing temperature of a film is usually closely related to its own characteristics. Polymers do not have a definite melting point. The more flexible the molecular chain is, the shorter the chain segment is, and the melting temperature and heat sealing temperature will also decrease accordingly.

[0004] In the prior art, the heat sealing range of a conventional 121 °C cooking film is small, and the starting sealing temperature is relatively high, generally above 100 °C. The long-term high-temperature environment is likely to cause equipment aging, and the processing procedure is complex, and the required energy consumption and production cost are relatively high. Secondly, the sealing performance and barrier performance of the conventional 121 °C cooking film are poor. During the cooking process, there will be a large amount of water vapor between the cooking film and the contents, which is likely to cause the contents to slide or the package to rupture, affecting the product quality and aesthetics. Moreover, in order to reduce the heat sealing temperature of the film, some copolymers with good flexibility are usually added to the formula of the conventional product, resulting in problems such as stickiness and a decrease in mechanical properties of the film, and it is impossible to ensure the stability of its mechanical properties while reducing the heat sealing temperature of the film. Finally, the existing cooking-grade CPP is usually produced by a three-layer coextrusion technology, and the product has a single nature and cannot meet the multi-functional requirements.

[0005] Therefore, in the current production process of preparing retort packaging films, some copolymers with good flexibility are usually added to the film formulation, such as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-vinyl acetate copolymer (EEA), and polyolefin elastomer (POE), so as to reduce the heat sealing temperature of the film. However, excessive addition may lead to a decrease in the mechanical strength of the material.

[0006] Based on this, in the prior art, the CPP film either has poor mechanical properties or a low heat sealing temperature. Based on this, there is an urgent need to provide a retort CPP film and its preparation method to improve the above problems. Summary of the Invention

[0007] The main purpose of the present invention is to provide a retort CPP film, its preparation method and application, so as to solve the technical problems that the CPP film in the prior art either has poor mechanical properties or a low heat sealing temperature.

[0008] To achieve the above object, according to one aspect of the present invention, a retort CPP film is provided. The structure of the retort CPP film includes, from inside to outside in sequence: a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer, and a corona layer; wherein, the components in the heat-sealing layer by weight include: 17-47 wt% of terpolymerized polypropylene, 50-80 wt% of polyolefin elastomer, and 1-3 wt% of anti-sticking masterbatch.

[0009] Further, the melt index of the terpolymerized polypropylene is 7.5-8.5 g / 10 min, and the density is 0.89-0.93 g / cm 3 ; preferably, the melt index of the polyolefin elastomer is 7.5-8.5 g / 10 min, and the density is 0.86-0.91 g / cm 3 ; preferably, the melt index of the anti-sticking masterbatch is 7.0-8.0 g / 10 min, and the density is 0.89-0.93 g / cm 3 .

[0010] Further, the components in the first core layer by weight include: 70-90 wt% of binary random copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; preferably, the material of the second core layer is selected from one or more of binary random copolymerized polypropylene, ethylene-propylene copolymer, or polyolefin elastomer.

[0011] Further, the components in the second core layer by weight include: 70-90 wt% of binary random copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; preferably, the components in the second core layer by weight include: 55-75 wt% of binary random copolymerized polypropylene, 20-40 wt% of polyolefin elastomer, and 5-10 wt% of ethylene-propylene copolymer.

[0012] Further, the middle layer includes one or more of random binary copolymerized polypropylene, ethylene-propylene copolymer or polyolefin elastomer; preferably, the weight of each component in the middle layer includes: 70-90 wt% of random binary copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; preferably, the weight of each component in the middle layer includes: 55-75 wt% of random binary copolymerized polypropylene, 20-40 wt% of polyolefin elastomer and 5-10 wt% of ethylene-propylene copolymer.

[0013] Further, the third core layer includes one or more of random binary copolymerized polypropylene, ethylene-propylene copolymer or polyolefin elastomer; preferably, the weight of each component in the third core layer includes: 70-90 wt% of random binary copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; preferably, the weight of each component in the third core layer includes: 55-75 wt% of random binary copolymerized polypropylene, 20-40 wt% of polyolefin elastomer and 5-10 wt% of ethylene-propylene copolymer.

[0014] Further, the weight of each component in the fourth core layer includes: 70-90 wt% of random binary copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; preferably, the weight of each component in the corona layer includes: 70-90 wt% of random terpolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer.

[0015] Further, the melt index of the random binary copolymerized polypropylene is 7.5-8.5 g / 10 min, and the density is 0.89-0.93 g / cm 3 ; preferably, the melt index of the ethylene-propylene copolymer is 2.7-3.3 g / 10 min, and the density is 0.83-0.89 g / cm 3 ; preferably, the thickness of the retort CPP film is 30-100 μm.

[0016] To achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a retort CPP film, which uses a multi-layer coextrusion casting method to form a heat-sealing layer, a first core layer, a second core layer, a middle layer, a third core layer, a fourth core layer and a corona layer that are sequentially stacked.

[0017] According to another aspect of the present invention, there is provided an application of the retort CPP film obtained by the method for preparing a retort CPP film in the fields of food, medicine and biomedical technology.

[0018] The cooked CPP film obtained by applying the technical solution of the present invention has a heat resistance performance of up to 121 °C compared with the conventional cooked film, and has a wider heat-sealing range and a lower starting heat-sealing temperature. The heat-sealing range is 74-140 °C. It has a certain heat-sealing performance during cooking, and the film around the content after cooking can be bonded together to fix the content. While ensuring food safety, it further improves production efficiency and output, reduces energy consumption, and lowers costs. Detailed implementation manners

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0020] As described in the background art section of the present invention, the CPP films in the prior art may have technical problems such as poor mechanical properties or low heat-sealing temperature. Based on this, the present invention provides a cooked CPP film, and the structure of the cooked CPP film sequentially includes from the inside to the outside: a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer, and a corona layer; wherein, the components in the heat-sealing layer by weight include: 17-47 wt% of terpolypropylene, 50-80 wt% of polyolefin elastomer, and 1-3 wt% of anti-sticking masterbatch.

[0021] In the heat-sealing layer of the CPP film provided by the present invention, a polyolefin elastomer (POE) is introduced to significantly reduce the heat-sealing temperature. The combination of it and the anti-sticking masterbatch can effectively avoid the possible film adhesion, wrinkles, and uneven stress during the heat-sealing process caused by the addition of POE. The addition of ethylene-propylene copolymer in other layers can further enhance the comprehensive performance of the film, making the film have a wider heat-sealing range, high heat-sealing strength, and excellent high-temperature cooking resistance.

[0022] Moreover, the above-mentioned cooked CPP film in the present invention has a heat resistance performance of up to 121 °C compared with the conventional cooked film, and has a wider heat-sealing range and a lower starting heat-sealing temperature. The heat-sealing range is 74-140 °C. The extremely low starting heat-sealing temperature enables it to have a certain heat-sealing performance during cooking, and the film around the content after cooking can be bonded together to fix the content. While ensuring food safety, it can improve the efficiency and output of packaging production, reduce energy consumption, and lower costs.

[0023] Moreover, in the present invention, by adding different polymers to the formulation, the product simultaneously possesses the flexibility, impact resistance, low heat-sealing performance, and easy processing properties of terpolymers, copolymers, and polyolefin elastomer materials. During subsequent applications, after it is compounded into bags, it can withstand high-temperature cooking, is durable, not easily torn or leaked, and has comprehensive packaging performance.

[0024] In addition, the CPP film in the present invention has a seven-layer structure, with good interlayer adhesion and high film stability compared to conventional cooking film products. While reducing the heat-sealing temperature of the film, it can ensure the stability of its mechanical properties. The seven-layer co-extrusion design allows the use of various layer configurations and materials, making the product formulation design more flexible. By adding different masterbatches between different layers, multifunctional cooking films can be produced, which have a wider range of applications.

[0025] In a preferred embodiment, the melt index of the terpolymerized polypropylene is 7.5 - 8.5 g / 10 min, and the density is 0.89 - 0.93 g / cm 3 ; to improve the thermal stability of the CPP film. More preferably, the melt index of the polyolefin elastomer is 7.5 - 8.5 g / 10 min, and the density is 0.86 - 0.91 g / cm 3 ; the melt index of the anti-sticking masterbatch is 7.0 - 8.0 g / 10 min, and the density is 0.89 - 0.93 g / cm 3 .

[0026] To further enhance the comprehensive performance of the CPP film, make its structure more stable, and its mechanical properties better, it is preferred that the weight of each component in the first core layer includes: 70 - 90 wt% of binary random copolymerized polypropylene and 10 - 30 wt% of ethylene-propylene copolymer; the material of the second core layer is selected from one or more of binary random copolymerized polypropylene, ethylene-propylene copolymer, or polyolefin elastomer. More preferably, the weight of each component in the second core layer includes: 70 - 90 wt% of binary random copolymerized polypropylene and 10 - 30 wt% of ethylene-propylene copolymer; the weight of each component in the second core layer includes: 55 - 75 wt% of binary random copolymerized polypropylene, 20 - 40 wt% of polyolefin elastomer, and 5 - 10 wt% of ethylene-propylene copolymer.

[0027] In a preferred embodiment, the intermediate layer includes one or more of binary random copolymerized polypropylene, ethylene-propylene copolymer, or polyolefin elastomer; more preferably, the weight of each component in the intermediate layer includes: 70 - 90 wt% of binary random copolymerized polypropylene and 10 - 30 wt% of ethylene-propylene copolymer; the weight of each component in the intermediate layer includes: 55 - 75 wt% of binary random copolymerized polypropylene, 20 - 40 wt% of polyolefin elastomer, and 5 - 10 wt% of ethylene-propylene copolymer.

[0028] In order to further endow the CPP film with a wider heat-sealing range, high heat-sealing strength, and excellent high-temperature cooking resistance, it is preferred that the third core layer comprises one or more of random binary copolymerized polypropylene, ethylene-propylene copolymer, or polyolefin elastomer; more preferably, the weight percentages of the components in the third core layer are as follows: 70-90 wt% of random binary copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; the weight percentages of the components in the third core layer are as follows: 55-75 wt% of random binary copolymerized polypropylene, 20-40 wt% of polyolefin elastomer, and 5-10 wt% of ethylene-propylene copolymer. It is preferred that the weight percentages of the components in the fourth core layer are as follows: 70-90 wt% of random binary copolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer; the weight percentages of the components in the corona layer are as follows: 70-90 wt% of random terpolymerized polypropylene and 10-30 wt% of ethylene-propylene copolymer.

[0029] In a preferred embodiment, the melt index of the random binary copolymerized polypropylene is 7.5-8.5 g / 10 min, and the density is 0.89-0.93 g / cm 3 ; preferably, the melt index of the ethylene-propylene copolymer is 2.7-3.3 g / 10 min, and the density is 0.83-0.89 g / cm 3 ; preferably, the thickness of the cooked CPP film is 30-100 μm.

[0030] On the other hand, the present invention also provides a method for preparing a steamed CPP film, which uses the multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer and a corona layer that are sequentially stacked. Among them, the preparation method of the multi-layer co-extrusion casting method includes the following steps: First, suck the raw materials into the hoppers of each extruder according to the requirements of the formula sheet; Second, weigh and mix the materials of each layer and then flow them into the extruder for high-temperature melting and plasticizing, pass through filtration, be transported to the connection port, distributor, and extruded through a T-die; Finally, carry out casting cooling and shaping, thickness measurement, corona treatment, and winding and traction in sequence. The important parameters involved are as follows: the processing temperature of the extruder corresponding to the heat-sealing layer is 230-255°C; the processing temperatures of the extruders corresponding to the first and fourth core layers are 230-255°C; the processing temperatures of the extruders corresponding to the second and third core layers are 230-255°C; the processing temperature of the extruder corresponding to the intermediate layer is 230-255°C; the processing temperature of the extruder corresponding to the corona layer is 230-255°C; the processing temperature corresponding to the filter screen is 230-255°C; the processing temperature corresponding to the connection port is 230-255°C; the processing temperature corresponding to the distributor is 230-255°C; the processing temperature corresponding to the die is 230-255°C. The casting cooling and shaping unit forms a film by cooling and shaping the melt; the main cooling roll of the casting cooling and shaping unit has a water temperature of 25-28°C, the secondary cooling roll has a temperature of 25-28°C, the air knife power is 40-60%, the vacuum box power is 40-60%, and the electrostatic edge locking power is 15-25KW. The standard thickness of the thickness measurement unit is 40-60μm, and the compensation coefficient of the thickness gauge is 3.5-5.5; the power of the corona treatment machine is 30-60%, and the corona value when leaving the machine is ≥42 dynes; the winding and traction tension is 80-90N, the pressing force is 25-30N, and the back pressure is 1.5-2.3Bar; After winding treatment, it also includes aging treatment of the wound film.

[0031] On the other hand, the present invention also provides an application of the steamed CPP film obtained by the above-mentioned method for preparing a steamed CPP film in the fields of food, medicine, and biomedical technology.

[0032] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0033] Example 1

[0034] The weight ratios of the components in the CPP film are shown in Table 1.

[0035] Table 1

[0036] Thickness / μm Weight ratio of each component Heat-sealing layer 8.00 70% Polyolefin elastomer + 27% Terpolymerized polypropylene + 3% Anti-sticking masterbatch First core layer 9.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Second core layer 3.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Intermediate layer 7.50 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Third core layer 3.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Fourth core layer 9.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Corona layer 7.50 85% Random terpolymerized polypropylene + 15% Ethylene-propylene copolymer

[0037] Among them, the melt index of the terpolymerized polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3; The melt index of the polyolefin elastomer is 8.0 g / 10 min, and the density is 0.88 g / cm 3 ; The melt index of the anti-sticking masterbatch is 7.0 g / 10 min, and the density is 0.91 g / cm 3 , The melt index of the binary random copolymerized polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer and a corona layer which are sequentially stacked.

[0038] Example 2

[0039] The weight ratios of the components in the CPP film are shown in Table 2.

[0040] Table 2

[0041] Thickness / μm Weight ratio of each component Heat-sealing layer 8.00 50% Polyolefin elastomer + 47% Terpolymerized polypropylene + 3% Anti-sticking masterbatch First core layer 9.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Second core layer 3.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Intermediate layer 7.50 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Third core layer 3.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Fourth core layer 9.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Corona layer 7.50 85% Random terpolymerized polypropylene + 15% Ethylene-propylene copolymer

[0042] Among them, the melt index of the terpolymerized polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3 ; The melt index of the polyolefin elastomer is 8.0 g / 10 min, and the density is 0.88 g / cm 3 ; The melt index of the anti-sticking masterbatch is 7.0 g / 10 min, and the density is 0.91 g / cm 3 , The melt index of the binary random copolymerized polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer and a corona layer which are sequentially stacked.

[0043] Example 3

[0044] The weight ratios of the components in the CPP film are shown in Table 3.

[0045] Table 3

[0046]

[0047]

[0048] Among them, the melt index of the terpolymerized polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3; The melt index of the polyolefin elastomer is 8.0 g / 10 min, and the density is 0.88 g / cm 3 ; The melt index of the anti-sticking masterbatch is 7.0 g / 10 min, and the density is 0.91 g / cm 3 , The melt index of the binary random copolymer polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer, and a corona layer that are sequentially stacked.

[0049] Example 4

[0050] The weight ratios of the components in the CPP film are shown in Table 4.

[0051] Table 4

[0052] Thickness / μm Weight ratio of each component Heat-sealing layer 8.00 50% Polyolefin elastomer + 47% Terpolymerized polypropylene + 3% Anti-sticking masterbatch First core layer 9.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Second core layer 3.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Intermediate layer 7.50 75% Random binary copolymerized polypropylene + 20% Polyolefin elastomer + 5% Ethylene-propylene copolymer Third core layer 3.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Fourth core layer 9.75 85% Random binary copolymerized polypropylene + 15% Ethylene-propylene copolymer Corona layer 7.50 85% Random terpolymerized polypropylene + 15% Ethylene-propylene copolymer

[0053] Among them, the melt index of the terpolymer polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3 ; The melt index of the polyolefin elastomer is 8.0 g / 10 min, and the density is 0.88 g / cm 3 ; The melt index of the anti-sticking masterbatch is 7.0 g / 10 min, and the density is 0.91 g / cm 3 , The melt index of the binary random copolymer polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer, and a corona layer that are sequentially stacked.

[0054] Example 5

[0055] The weight ratios of the components in the CPP film are shown in Table 5.

[0056] Table 5

[0057]

[0058]

[0059] Among them, the melt index of the terpolymer polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3; The melt index of the polyolefin elastomer is 8.0 g / 10 min, and the density is 0.88 g / cm 3 ; The melt index of the anti-sticking masterbatch is 7.0 g / 10 min, and the density is 0.91 g / cm 3 , The melt index of the binary random copolymer polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer and a corona layer which are sequentially stacked.

[0060] Example 6

[0061] The weight ratios of the components in the CPP film are shown in Table 6.

[0062] Table 6

[0063] Thickness / μm Weight ratio of each component Heat-sealing layer 8.00 80% Polyolefin elastomer + 17% Terpolymerized polypropylene + 3% Anti-sticking masterbatch First core layer 9.75 85% Random terpolymerized polypropylene + 15% Ethylene-propylene copolymer Second core layer 3.75 60% Random binary copolymerized polypropylene + 30% Polyolefin elastomer + 10% Ethylene-propylene copolymer Intermediate layer 7.50 60% Random binary copolymerized polypropylene + 30% Polyolefin elastomer + 10% Ethylene-propylene copolymer Third core layer 3.75 60% Random binary copolymerized polypropylene + 30% Polyolefin elastomer + 10% Ethylene-propylene copolymer Fourth core layer 9.75 85% Random terpolymerized polypropylene + 15% Ethylene-propylene copolymer Corona layer 7.50 85% Random terpolymerized polypropylene + 15% Ethylene-propylene copolymer

[0064] Among them, the melt index of the terpolymer polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3 ; The melt index of the polyolefin elastomer is 8.0 g / 10 min, and the density is 0.88 g / cm 3 ; The melt index of the anti-sticking masterbatch is 7.0 g / 10 min, and the density is 0.91 g / cm 3 , The melt index of the binary random copolymer polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer and a corona layer which are sequentially stacked.

[0065] Comparative Example 1

[0066] The weight ratios of the components in the CPP film are shown in Table 7.

[0067] Table 7

[0068]

[0069]

[0070] Among them, the melt index of the terpolymer polypropylene is 8.0 g / 10 min, and the density is 0.90 g / cm 3; The melt index of the binary random copolymer polypropylene is 8 g / 10 min, and the density is 0.9 g / cm 3 ; The melt index of the ethylene-propylene copolymer is 3 g / 10 min, and the density is 0.86 g / cm 3 ; The CPP film is formed by a multi-layer co-extrusion casting method technology to form a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer, and a corona layer arranged in sequential laminations.

[0071] Performance test:

[0072] Take the cooked CPP films prepared in the above-mentioned examples and comparative examples, and use the heat-sealing tester of Jinan Labthink to conduct performance tests. The heat-sealing pressure is 200 kPa, the time is 1 s, the lower sealing knife is 80 °C. Among them, the actual adjusted temperature of the upper sealing knife with a silicone pad is used, and no high-temperature adhesive tape is padded. Use the national standard for cooked films GB / T 27740-2011 to conduct performance tests on the above-mentioned cooked CPP films, and the test results are shown in Table 8.

[0073] Table 8

[0074]

[0075] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects:

[0076] The cooked CPP film provided by the present invention has a seven-layer co-extrusion structure and a carefully formulated material composition, so that the composite film has a low starting sealing temperature, a wide heat-sealing range, high heat-sealing strength, and excellent processing performance. During the production process, the processing procedures can be simplified, energy consumption can be reduced, and costs can be lowered.

[0077] Among them, the addition of polyolefin elastomer and anti-sticking masterbatch in the heat-sealing layer significantly improves the low-temperature heat-sealing performance and processing performance of the film. The combination of the random terpolymer polypropylene and the ethylene-propylene copolymer further enhances the flexibility, impact resistance, and heat-sealing performance of the material while ensuring good mechanical properties, enabling a faster packaging production line speed, and improving the efficiency and output of the packaging production line. The extremely low starting sealing temperature enables the film to have a certain heat-sealing performance during cooking. After cooking, the film around the contents adheres together to fix the contents, which is beneficial to improving the airtightness of the product, preventing the contents from sliding, and making the packaging more stable, beautiful, safe.

[0078] Moreover, this product is produced by a seven-layer co-extrusion device. Compared with conventional cooked film products, it has good interlayer adhesion and high stability. The multi-layer co-extrusion technology can effectively avoid problems such as the decrease in the mechanical strength of the film caused by the reduction of the heat-sealing temperature. The formula design is more flexible, and high-barrier, double-sided color, and other multi-functional cooked film products can be produced.

[0079] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of any invention or the scope of what is claimed, but rather as mainly describing the features of specific embodiments of a particular invention. Certain features described in multiple embodiments in this specification can also be implemented in combination in a single embodiment. On the other hand, the various features described in a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. In addition, although features may operate in certain combinations as described above and even be initially claimed as such, one or more features from the claimed combination can in some cases be removed from that combination, and the claimed combination can be directed to a sub-combination or a variation of a sub-combination.

[0080] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve the desired result.

[0081] The above description is only a specific implementation manner of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A steamed CPP film, characterized in that, The structure of the cooked CPP film from the inside to the outside in sequence includes: a heat-sealing layer, a first core layer, a second core layer, an intermediate layer, a third core layer, a fourth core layer, and a corona layer; wherein, the weight of each component in the heat-sealing layer includes: 17-47wt% of a terpolymerized polypropylene, 50-80wt% of a polyolefin elastomer, and 1-3wt% of an anti-sticking masterbatch.

2. The steamed CPP film according to claim 1, wherein The melt index of the terpolymerized polypropylene is 7.5 to 8.5 g / 10 min, and the density is 0.89 to 0.93 g / cm 3 ; Preferably, the melt index of the polyolefin elastomer is 7.5 to 8.5 g / 10 min, and the density is 0.86 to 0.91 g / cm 3 ; Preferably, the melt index of the anti-sticking masterbatch is 7.0 to 8.0 g / 10 min, and the density is 0.89 to 0.93 g / cm 3 .

3. The steamed CPP film according to claim 1, wherein The weight of each component in the first core layer includes: 70-90wt% of a binary random copolymerized polypropylene and 10-30wt% of an ethylene-propylene copolymer; Preferably, the material of the second core layer is selected from one or more of a binary random copolymerized polypropylene, an ethylene-propylene copolymer, or a polyolefin elastomer.

4. The steamed CPP film according to claim 3, characterized in that, The weight of each component in the second core layer includes: 70-90wt% of the binary random copolymerized polypropylene and 10-30wt% of the ethylene-propylene copolymer; Preferably, the weight of each component in the second core layer includes: 55-75wt% of the binary random copolymerized polypropylene, 20-40wt% of the polyolefin elastomer, and 5-10wt% of the ethylene-propylene copolymer.

5. The steamed CPP film according to claim 1, wherein The intermediate layer includes one or more of a binary random copolymerized polypropylene, an ethylene-propylene copolymer, or a polyolefin elastomer; Preferably, the weight of each component in the intermediate layer includes: 70-90wt% of the binary random copolymerized polypropylene and 10-30wt% of the ethylene-propylene copolymer; Preferably, the weight of each component in the intermediate layer includes: 55-75wt% of the binary random copolymerized polypropylene, 20-40wt% of the polyolefin elastomer, and 5-10wt% of the ethylene-propylene copolymer.

6. The steamed CPP film according to claim 1, wherein The third core layer includes one or more of a binary random copolymerized polypropylene, an ethylene-propylene copolymer, or a polyolefin elastomer; Preferably, the weight of each component in the third core layer includes: 70-90wt% of the binary random copolymerized polypropylene and 10-30wt% of the ethylene-propylene copolymer; Preferably, the weight of each component in the third core layer includes: 55-75wt% of the binary random copolymerized polypropylene, 20-40wt% of the polyolefin elastomer, and 5-10wt% of the ethylene-propylene copolymer.

7. The steamed CPP film according to claim 1, wherein, The weight of each component in the fourth core layer includes: 70-90wt% of the binary random copolymerized polypropylene and 10-30wt% of the ethylene-propylene copolymer; Preferably, the weight of each component in the corona layer includes: 70-90wt% of the ternary random copolymerized polypropylene and 10-30wt% of the ethylene-propylene copolymer.

8. The steamed CPP film according to claim 1 or 7, characterized in that, The melt index of the binary random copolymer polypropylene is 7.5 to 8.5 g / 10 min, and the density is 0.89 to 0.93 g / cm 3 ; Preferably, the ethylene-propylene copolymer has a melt index of 2.7 to 3.3 g / 10 min and a density of 0.83 to 0.89 g / cm 3 ; Preferably, the thickness of the cooked CPP film is 30-100μm.

9. A method for preparing a steamed CPP film according to any one of claims 1 to 8, characterized in that, The heat-sealing layer, the first core layer, the second core layer, the intermediate layer, the third core layer, the fourth core layer, and the corona layer are formed by a multi-layer co-extrusion casting method technology and are sequentially stacked.

10. The application of a cooked CPP film obtained by the preparation method of the cooked CPP film according to claim 9 in the fields of food, medicine, and biomedicine.

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