Impact resistant cpp cast film and method of making the same

Abstract

The application relates to the technical field of cast film, and discloses an impact-resistant CPP cast film and a preparation method thereof. The impact-resistant CPP cast film comprises an outer layer, a core layer and an inner layer arranged in sequence from top to bottom. The outer layer comprises the following raw materials in parts by weight: 20-30 parts of first polypropylene and 10-15 parts of second polypropylene. The core layer comprises the following raw materials in parts by weight: 5-10 parts of first polypropylene, 30-35 parts of second polypropylene and 5-8 parts of filling. The inner layer comprises the following raw materials in parts by weight: 20-40 parts of third polypropylene and 0.1-0.3 parts of a slip agent. The mineral filling contents of the first polypropylene and the second polypropylene are different. The technical scheme solves the problem of poor impact resistance of CPP cast film in the related art.

Description

Technical Field

[0001] This invention relates to the field of cast film technology, specifically to an impact-resistant CPP cast film and its preparation method. Background Technology

[0002] CPP cast film, or cast polypropylene film, is a polypropylene film produced through a casting extrusion process. It is a non-oriented film, exhibiting orientation only in the longitudinal direction. Depending on its properties and applications, cast film can be categorized into general-purpose CPP film, aluminized CPP film, and retort grade CPP film, among others. Due to its excellent transparency, moisture barrier properties, heat resistance, stiffness, and gloss, it is widely used in various fields such as optical and electronic products, food packaging, and pharmaceuticals. In food packaging, it can be used to produce various types of packaging bags; in pharmaceutical packaging, its excellent barrier properties effectively protect medicines from external environmental influences.

[0003] As industries increasingly demand higher standards for packaging materials, research on the performance of CPP cast film continues to deepen. However, in many application scenarios, the impact resistance of CPP cast film remains insufficient. During packaging operations, such as filling and sealing, cast film with poor impact resistance may break due to slight mechanical impact, leading to incomplete packaging or substandard packaging quality. During product transportation, products are inevitably subjected to bumps, collisions, and other external forces. CPP cast film packaging with poor impact resistance is prone to breakage, leaving the internal products unprotected and potentially causing damage or spoilage. Therefore, developing a CPP cast film with good impact resistance is essential. Summary of the Invention

[0004] This invention proposes an impact-resistant CPP cast film and its preparation method, which solves the problem of poor impact resistance of CPP cast films in related technologies.

[0005] The technical solution of the present invention is as follows: The present invention proposes an impact-resistant CPP cast film, comprising an outer layer, a core layer and an inner layer arranged sequentially from top to bottom. The outer layer comprises the following raw materials in parts by weight: 20-30 parts of first polypropylene and 10-15 parts of second polypropylene. The core layer comprises the following raw materials in parts by weight: 5-10 parts of first polypropylene, 30-35 parts of second polypropylene and 5-8 parts of filler. The inner layer comprises the following raw materials in parts by weight: 20-40 parts of third polypropylene and 0.1-0.3 parts of slip agent. The mineral filler content of the first polypropylene and the second polypropylene is different.

[0006] As a further technical solution, the mineral filler content of the first polypropylene is 5 wt%, and the mineral filler content of the second polypropylene is 30 wt%.

[0007] As a further technical solution, in the outer layer raw materials, the mass ratio of the first polypropylene and the second polypropylene is 2:1.

[0008] As a further technical solution, in the core layer raw material, the mass ratio of the first polypropylene and the second polypropylene is 1:3.5.

[0009] In this invention, the mineral filler content of the first polypropylene is 5 wt%, and the mineral filler content of the second polypropylene is 30 wt%. The first polypropylene provides good flexibility and basic mechanical properties, while the higher mineral filler content in the second polypropylene gives the material a certain rigidity and hardness.

[0010] As a further technical solution, the third polypropylene is a copolymer polypropylene.

[0011] In this invention, copolymer polypropylene is used as the raw material for the inner layer. Copolymer polypropylene has excellent processing performance and good fluidity in the molten state, which can be more uniformly distributed during the preparation of the cast film, thus ensuring the molding quality of the inner layer.

[0012] As a further technical solution, the mass ratio of the raw materials of the outer layer, the core layer, and the inner layer is 1:2 to 3:1.

[0013] In this invention, the raw material weights of the outer layer, core layer, and inner layer are rationally configured. The core layer, with a larger weight ratio, can provide sufficient support and buffering capacity for the cast film. When subjected to impact, the core layer can effectively disperse and absorb energy, preventing it from being easily penetrated. The outer and inner layers, with relatively smaller and equal weight ratios, can ensure that the cast film has certain surface properties and can work synergistically with the core layer to jointly resist impact. This structural design allows the cast film to fully utilize the advantages of each layer when facing impact, significantly improving its impact resistance.

[0014] As a further technical solution, the filler includes one or more of calcium carbonate, talc, and mica powder.

[0015] In this invention, fillers such as calcium carbonate, talc, and mica powder are added to the core layer. These fillers have high hardness and rigidity. When added to the core layer of the impact-resistant CPP cast film, they can effectively improve the overall rigidity and hardness of the cast film. When facing the impact of external pressure, these fillers can enhance the film's ability to resist deformation, making the cast film less susceptible to impact damage, thereby greatly improving the impact resistance of the cast film.

[0016] As a further technical solution, the slip agent includes one or both of erucamide and oleamide.

[0017] In this invention, a lubricant is added to the inner layer. Erucamide and oleamide have excellent surface migration properties and can quickly migrate to the film surface to form a uniform lubricating film. This lubricating film greatly reduces the coefficient of friction of the film surface, enabling the film to exhibit good slip properties during production, processing and subsequent use. It effectively reduces the resistance caused by friction, significantly improves production efficiency, and reduces equipment wear and energy consumption.

[0018] The present invention also proposes a method for preparing an impact-resistant CPP cast film, characterized by the following steps: mixing the raw materials of the outer layer, the core layer, and the inner layer respectively, extruding and plasticizing them, co-extruding and casting them after passing them through a distributor, cooling and shaping them, and then subjecting them to corona treatment to obtain the impact-resistant CPP cast film.

[0019] As a further technical solution, the cooling and molding temperature is 25~30℃.

[0020] In this invention, the cooling temperature is limited to 25~30℃, which allows the polypropylene molecular chains sufficient time to arrange themselves in an orderly manner, forming a suitable degree of crystallinity and crystal structure. If the cooling temperature is too high, the crystallization rate will be too fast, which may lead to coarse crystals and reduce the mechanical and optical properties of the film. If the cooling temperature is too low, the crystallinity may be insufficient, affecting the rigidity and impact resistance of the film.

[0021] As a further technical solution, the corona value is 40~42 dynes.

[0022] In this invention, the CPP cast film is subjected to corona treatment. Corona treatment can generate free radicals on the film surface and introduce polar groups, thereby improving the polarity and wettability of the film surface.

[0023] The working principle and beneficial effects of this invention are as follows: In this invention, the CPP cast film is a layered structure composed of an outer layer, a core layer, and an inner layer. Different amounts of a first polypropylene and a second polypropylene are added to the outer and core layers. In the outer layer, the amount of the first polypropylene is greater than that of the second polypropylene, giving the outer layer good flexibility and a certain buffering capacity. In the core layer, the amount of the first polypropylene is less than that of the second polypropylene. This ratio fully utilizes the advantages of the two polypropylenes. The higher mineral filler content of the second polypropylene gives it higher rigidity and strength, serving as the main supporting structure in the core layer, enabling it to withstand greater external forces. The presence of the first polypropylene ensures that the core layer has a certain degree of toughness, preventing it from becoming brittle due to excessive rigidity. Simultaneously, the addition of fillers synergistically enhances the strength and stability of the core layer with the two polypropylenes. When an impact force penetrates the outer layer, the core layer can effectively buffer and disperse the remaining impact force, greatly improving the overall impact resistance of the cast film. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In the following examples and comparative examples: First polypropylene: mineral filler content is 5wt%, model number is EE056AEC; Second polypropylene: mineral filler content is 30wt%, model is FSC65T30; Third polypropylene: Model B4101; Polyethylene: Model 1I60A; Polytetrafluoroethylene: Polytetrafluoroethylene micro powder with an average particle size of 3μm; Polyvinyl chloride trifluoroethylene-vinylidene fluoride copolymer: fluorine content 25wt%, purchased from Maclean's reagents; Polyvinylidene fluoride: Product number 768739, purchased from Maclean's Reagents.

[0026] Example 1 A method for preparing an impact-resistant CPP cast film includes the following steps: 20 parts by weight of first polypropylene and 10 parts by weight of second polypropylene are mixed and extruded and plasticized to obtain an outer layer mixture; 5 parts by weight of first polypropylene, 30 parts by weight of second polypropylene and 5 parts by weight of calcium carbonate are mixed and extruded and plasticized to obtain a core layer mixture; 20 parts by weight of third polypropylene and 0.1 parts by weight of erucamide are mixed and extruded and plasticized to obtain an inner layer mixture; the outer layer mixture, core layer mixture and inner layer mixture are co-extruded and cast in a mass ratio of 1:2:1 using a distributor; after cooling and molding at 25°C, the film is corona treated with a corona value of 40 dynes to obtain the impact-resistant CPP cast film.

[0027] Example 2 A method for preparing an impact-resistant CPP cast film includes the following steps: 25 parts by weight of first polypropylene and 12 parts by weight of second polypropylene are mixed and extruded and plasticized to obtain an outer layer mixture; 8 parts by weight of first polypropylene, 32 parts by weight of second polypropylene and 6 parts by weight of talc are mixed and extruded and plasticized to obtain a core layer mixture; 30 parts by weight of third polypropylene and 0.2 parts by weight of oleamide are mixed and extruded and plasticized to obtain an inner layer mixture; the outer layer mixture, core layer mixture and inner layer mixture are co-extruded and cast in a mass ratio of 1:2:1 through a distributor; after cooling and molding at 28°C, the film is corona treated with a corona value of 41 dynes to obtain the impact-resistant CPP cast film.

[0028] Example 3 A method for preparing an impact-resistant CPP cast film includes the following steps: 30 parts by weight of first polypropylene and 15 parts by weight of second polypropylene are mixed and extruded and plasticized to obtain an outer layer mixture; 10 parts by weight of first polypropylene, 35 parts by weight of second polypropylene and 8 parts by weight of mica powder are mixed and extruded and plasticized to obtain a core layer mixture; 40 parts by weight of third polypropylene and 0.3 parts by weight of oleamide are mixed and extruded and plasticized to obtain an inner layer mixture; the outer layer mixture, core layer mixture and inner layer mixture are co-extruded and cast in a mass ratio of 1:3:1 through a distributor; after cooling and molding at 30°C, the film is corona treated with a corona value of 42 dynes to obtain the impact-resistant CPP cast film.

[0029] Example 4 Compared with Example 3, Example 4 differs in that the second polypropylene in the outer layer and the core layer is replaced with an equal amount of polypropylene (model MD232UBC) with a mineral filler content of 20wt%.

[0030] Example 5 Compared with Example 3, Example 5 differs in that the second polypropylene in the outer layer and the core layer is replaced with an equal amount of polypropylene (model MD442UBC) with a mineral filler content of 40wt%.

[0031] Example 6 Compared with Example 3, Example 6 differs in that the first polypropylene in the outer layer and the core layer is replaced with an equal amount of polypropylene (model MD232UBC) with a mineral filler content of 20wt%.

[0032] Comparative Example 1 Compared with Example 3, Comparative Example 1 differs in that the second polypropylene in the outer layer and the core layer is replaced with an equal amount of the first polypropylene.

[0033] Comparative Example 2 Compared with Example 3, Comparative Example 2 differs in that the first polypropylene in the outer layer and the core layer is replaced with an equal amount of second polypropylene.

[0034] Comparative Example 3 Compared with Example 3, Comparative Example 3 differs in that the first polypropylene and the second polypropylene in the outer layer mixture are 22.5 parts each.

[0035] Comparative Example 4 Compared with Example 3, Comparative Example 4 differs in that the first polypropylene in the outer layer mixture is 15 parts and the second polypropylene is 30 parts.

[0036] Comparative Example 5 Compared with Example 3, Comparative Example 5 differs in that the first polypropylene in the core layer mixture is 22.5 parts and the second polypropylene is 22.5 parts.

[0037] Comparative Example 6 Compared with Example 3, Comparative Example 6 differs in that the first polypropylene in the core layer mixture is 35 parts and the second polypropylene is 10 parts.

[0038] Experimental Example 1 The CPP cast films prepared in Examples 1-6 and Comparative Examples 1-6 were tested for impact fracture mass according to the test method specified in GB / T 9639.1-2008 "Test Methods for Impact Resistance of Plastic Films and Sheets - Free Falling Scale Method - Part 1: Step Method". The sample thickness was 70 μm.

[0039] The test results are shown in Table 1: Table 1 Performance test results of CPP cast films prepared in Examples 1-6 and Comparative Examples 1-6

[0040] As shown in Table 1, the impact breakage quality of Example 3 is higher than that of Examples 4-6 and Comparative Examples 1-2, indicating that the impact resistance of CPP cast film can be improved when the mineral filler content of the first polypropylene and the second polypropylene is different.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An impact-resistant CPP cast film, characterized in that, The material comprises, from top to bottom, an outer layer, a core layer, and an inner layer. The outer layer comprises the following raw materials in parts by weight: 20-30 parts of first polypropylene and 10-15 parts of second polypropylene. The core layer comprises the following raw materials in parts by weight: 5-10 parts of first polypropylene, 30-35 parts of second polypropylene, and 5-8 parts of filler. The inner layer comprises the following raw materials in parts by weight: 20-40 parts of third polypropylene and 0.1-0.3 parts of slip agent. The mineral filler content of the first polypropylene and the second polypropylene is different. The first polypropylene has a mineral filler content of 5 wt%, and the second polypropylene has a mineral filler content of 30 wt%.

2. The impact-resistant CPP cast film according to claim 1, characterized in that, The third polypropylene is a copolymer polypropylene.

3. The impact-resistant CPP cast film according to claim 1, characterized in that, The mass ratio of the raw materials for the outer layer, the core layer, and the inner layer is 1:2 to 3:

1.

4. The impact-resistant CPP cast film according to claim 1, characterized in that, The filler includes one or more of calcium carbonate, talc, and mica powder.

5. The impact-resistant CPP cast film according to claim 1, characterized in that, The slip agent includes one or both of erucamide and oleamide.

6. A method for preparing an impact-resistant CPP cast film according to any one of claims 1 to 5, characterized in that, Includes the following steps: The raw materials for the outer layer, the core layer, and the inner layer are mixed separately, extruded and plasticized, co-extruded and cast after passing through a distributor, cooled and shaped, and then corona treated to obtain an impact-resistant CPP cast film.

7. The method for preparing an impact-resistant CPP cast film according to claim 6, characterized in that, The cooling and molding temperature is 25~30℃.

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