Impact-resistant CPP cast film and preparation method thereof

Abstract

The invention relates to the technical field of cast films, and provides an anti-impact 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 which are sequentially arranged from top to bottom, the outer layer is prepared from, by weight, 20-30 parts of first polypropylene and 10-15 parts of second polypropylene, the core layer is prepared from, by weight, 5-10 parts of first polypropylene, 30-35 parts of second polypropylene and 5-8 parts of filler, and the inner layer is prepared from, by weight, 20-40 parts of third polypropylene and 0.1-0.3 part of slipping agent; the mineral filling contents of the first polypropylene and the second polypropylene are different. According to the technical scheme, the problem of poor impact resistance of the CPP cast film in related technologies is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of cast films, and specifically, to an impact-resistant CPP cast film and a preparation method thereof. Background Art

[0002] CPP cast film, that is, cast polypropylene film, is a polypropylene film produced by the cast extrusion process. It is a non-oriented film and has some orientation only in the longitudinal direction. According to different characteristics and uses, cast films can be divided into general-purpose CPP films, aluminized CPP films, cooking-grade CPP films, etc. Because of its excellent transparency, moisture barrier property, heat resistance, stiffness, and glossiness, it is widely used in many fields such as optoelectronic products, food packaging, and medical supplies. In the field of food packaging, it can be used for the production of various packaging bags; in the packaging of medical supplies, its good barrier property can effectively protect drugs from the external environment.

[0003] With the continuous improvement of the requirements for packaging materials in various industries, the research on the performance of CPP cast films is also continuously deepening. However, in many application scenarios, the impact resistance of CPP cast films still has deficiencies. During packaging operations, such as filling and sealing processes, a cast film with poor impact resistance may rupture due to slight mechanical external force impacts, resulting in the inability to complete packaging or unqualified packaging quality; during the transportation of products, it will inevitably be subjected to external forces such as jolts and collisions, and the packaging of CPP cast films with poor impact resistance is prone to rupture, causing the internal products to lose protection and possibly resulting in product damage and deterioration. Therefore, it is necessary to develop a CPP cast film with good impact resistance. Summary of the Invention

[0004] The present invention provides an impact-resistant CPP cast film and a preparation method thereof, which solve the problem of poor impact resistance of CPP cast films in the related art.

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

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

[0007] As a further technical solution, in the outer layer raw material, the mass ratio of the first polypropylene to 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 to the second polypropylene is 1:3.5.

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

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

[0011] In the present invention, copolymerized polypropylene is used as a raw material in the inner layer. Copolymerized polypropylene has excellent processing performance and good fluidity in a molten state, and can be more evenly distributed in the preparation process of the cast film, thereby ensuring the molding quality of the inner layer.

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

[0013] In the present invention, the raw material masses of the outer layer, core layer and inner layer are reasonably configured. The core layer with a larger mass proportion can provide sufficient support and buffering capacity for the cast film. When impacted, the core layer can effectively disperse and absorb energy to prevent it from being easily penetrated. The mass proportions of the outer layer and the inner layer are relatively small and equal, which can not only ensure that the cast film has certain surface properties, but also cooperate with the core layer to resist impact together. This structural design enables the cast film to give full play to the advantages of each layer when facing impact and significantly improve the impact resistance.

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

[0015] In the present invention, fillers are added to the core layer. Calcium carbonate, talcum powder and mica powder are used as fillers, which have high hardness and rigidity. When they are added to the core layer of the impact-resistant CPP cast film, the overall rigidity and hardness of the cast film can be effectively improved. When facing the impact of external pressure, these fillers can enhance the ability of the film to resist deformation, making the cast film less likely to be damaged by impact, thereby greatly improving the impact resistance of the cast film.

[0016] As a further technical solution, the raw material of the outer layer further includes polyethylene and fluorine-containing polymer, and the mass ratio of the first polypropylene, polyethylene and fluorine-containing polymer is 10:2:1~2.

[0017] In the present invention, polypropylene containing mineral fillers is used as the raw material for the outer layer. The mineral fillers may change the crystalline structure and morphology of polypropylene, affecting the physical and chemical properties of the film surface, and further leading to a decrease in wetting tension. Therefore, polyethylene and fluoropolymer are added to the outer layer of the present invention to adjust the energy state of the outer layer surface and further improve the wetting tension of the cast film.

[0018] As a further technical solution, the fluoropolymer is composed of a poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer and polytetrafluoroethylene with a mass ratio of 2 - 3:1.

[0019] In the present invention, by coordinating the mass ratio of polytetrafluoroethylene and poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer, the synergistic effect of the two is exerted, and by regulating the surface energy of the cast film, the wetting tension of the cast film is further optimized.

[0020] As a further technical solution, the slip agent includes one or both of erucamide and oleamide.

[0021] In the present invention, a slip agent is added to the inner layer. Erucamide and oleamide have excellent surface migration properties and can quickly migrate to the film surface and form a uniform lubricating film. This lubricating film greatly reduces the friction coefficient of the film surface, enabling the film to exhibit good slip properties during production, processing, and subsequent use, effectively reducing the resistance caused by friction, significantly improving production efficiency, and reducing equipment wear and energy consumption.

[0022] The present invention also provides a method for preparing an impact - resistant CPP cast film, which is characterized by including the following steps: After separately mixing the raw materials of the outer layer, the core layer, and the inner layer, extruding and plasticizing, co - extruding and casting through a diverter, cooling and forming, and corona treatment to obtain the impact - resistant CPP cast film.

[0023] As a further technical solution, the temperature of the cooling and forming is 25 - 30 °C.

[0024] In the present invention, by defining the temperature of the cooling and forming as 25 - 30 °C, it can enable the polypropylene molecular chains to have sufficient time for orderly arrangement, forming a suitable degree of crystallinity and crystal structure. If the cooling temperature is too high, the crystallization rate is too fast, which may lead to coarse crystals and reduce the mechanical and optical properties of the film; while if the cooling temperature is too low, the degree of crystallinity may be insufficient, affecting the rigidity and impact resistance of the film.

[0025] As a further technical solution, the corona value of the corona treatment is 40 - 42 dynes.

[0026] In the present invention, corona treatment is carried out on the CPP cast film. Corona treatment can generate free radicals on the film surface and introduce polar groups, thereby improving the polarity and wettability of the film surface.

[0027] The working principle and beneficial effects of the present invention are as follows: In the present invention, the CPP cast film is a layered structure composed of an outer layer, a core layer, and an inner layer. Different amounts of the first polypropylene and the second polypropylene are added to the outer layer and the core layer. In the outer layer, the amount of the first polypropylene is greater than that of the second polypropylene, making the outer layer have good flexibility and certain buffering ability. In the core layer, the amount of the first polypropylene is less than that of the second polypropylene. This ratio gives full play to the advantages of the two polypropylenes. The higher mineral filling content of the second polypropylene makes it have higher rigidity and strength, and it serves as the main supporting structure in the core layer and can withstand greater external forces. The presence of the first polypropylene ensures that the core layer has a certain toughness and avoids the core layer being easily brittle due to excessive rigidity. At the same time, the addition of the filler has a synergistic effect with the two polypropylenes, further enhancing the strength and stability of the core layer. When the impact force breaks through 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. Specific embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0029] In the following examples and comparative examples: The first polypropylene: the mineral filling content is 5wt%, and the model is EE056AEC; The second polypropylene: the mineral filling content is 30wt%, and the model is FSC65T30; The third polypropylene: the model is B4101; Polyethylene: the model is 1I60A; Polytetrafluoroethylene: polytetrafluoroethylene micropowder, with an average particle size of 3μm; Poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer: the fluorine content is 25wt%, purchased from Macklin Reagent; Polyvinylidene fluoride: the product number is 768739, purchased from Macklin Reagent.

[0030] Example 1 A preparation method of an impact-resistant CPP cast film comprises the following steps: By weight, 20 parts of a first polypropylene and 10 parts of a second polypropylene are weighed and mixed, then extruded and plasticized to obtain an outer layer mixture. 5 parts of the first polypropylene, 30 parts of the second polypropylene, and 5 parts of calcium carbonate are weighed and mixed, then extruded and plasticized to obtain a core layer mixture. 20 parts of a third polypropylene and 0.1 part of erucamide are weighed and mixed, then extruded and plasticized to obtain an inner layer mixture. The outer layer mixture, the core layer mixture, and the inner layer mixture are co-extruded and cast through a diverter in a mass ratio of 1:2:1. After cooling and forming at 25°C, corona treatment is performed with a corona value of 40 dynes, and thus the impact-resistant CPP cast film is obtained.

[0031] Example 2 A preparation method of an impact-resistant CPP cast film comprises the following steps: By weight, 25 parts of a first polypropylene and 12 parts of a second polypropylene are weighed and mixed, then extruded and plasticized to obtain an outer layer mixture. 8 parts of the first polypropylene, 32 parts of the second polypropylene, and 6 parts of talcum powder are weighed and mixed, then extruded and plasticized to obtain a core layer mixture. 30 parts of a third polypropylene and 0.2 part of oleic acid amide are weighed and mixed, then extruded and plasticized to obtain an inner layer mixture. The outer layer mixture, the core layer mixture, and the inner layer mixture are co-extruded and cast through a diverter in a mass ratio of 1:2:1. After cooling and forming at 28°C, corona treatment is performed with a corona value of 41 dynes, and thus the impact-resistant CPP cast film is obtained.

[0032] Example 3 A preparation method of an impact-resistant CPP cast film comprises the following steps: By weight, 30 parts of a first polypropylene and 15 parts of a second polypropylene are weighed and mixed, then extruded and plasticized to obtain an outer layer mixture. 10 parts of the first polypropylene, 35 parts of the second polypropylene, and 8 parts of mica powder are weighed and mixed, then extruded and plasticized to obtain a core layer mixture. 40 parts of a third polypropylene and 0.3 part of oleic acid amide are weighed and mixed, then extruded and plasticized to obtain an inner layer mixture. The outer layer mixture, the core layer mixture, and the inner layer mixture are co-extruded and cast through a diverter in a mass ratio of 1:3:1. After cooling and forming at 30°C, corona treatment is performed with a corona value of 42 dynes, and thus the impact-resistant CPP cast film is obtained.

[0033] Example 4 Compared with Example 3, the difference in Example 4 is 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 filling content of 20 wt%.

[0034] Example 5 Compared with Example 3, the difference in Example 5 is 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 filling content of 40 wt%.

[0035] Example 6 Compared with Example 3, Example 6 is different in that the first polypropylene in the outer layer and the core layer is replaced with an equal amount of polypropylene with a mineral filling content of 20 wt% (model MD232UBC).

[0036] Example 7 Compared with Example 3, Example 7 is different in that 6 parts of polyethylene and 3 parts of polytetrafluoroethylene are further added to the core layer mixture.

[0037] Example 8 Compared with Example 3, Example 8 is different in that 6 parts of polyethylene and 6 parts of polytetrafluoroethylene are further added to the core layer mixture.

[0038] Example 9 Compared with Example 8, Example 9 is different in that the polytetrafluoroethylene is replaced with an equal amount of poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer.

[0039] Example 10 Compared with Example 8, Example 10 is different in that the polytetrafluoroethylene is replaced with a mixture of polytetrafluoroethylene and poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer with a mass ratio of 1:2.

[0040] Example 11 Compared with Example 8, Example 11 is different in that the polytetrafluoroethylene is replaced with a mixture of polytetrafluoroethylene and poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer with a mass ratio of 1:3.

[0041] Example 12 Compared with Example 11, Example 12 is different in that the poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer is replaced with an equal amount of polyvinylidene fluoride.

[0042] Comparative Example 1 Compared with Example 3, Comparative Example 1 is different in that the second polypropylene in the outer layer and the core layer is replaced with an equal amount of the first polypropylene.

[0043] Comparative Example 2 Compared with Example 3, Comparative Example 2 is different in that the first polypropylene in the outer layer and the core layer is replaced with an equal amount of the second polypropylene.

[0044] Comparative Example 3 Compared with Example 3, Comparative Example 3 is different in that there are 22.5 parts of the first polypropylene and 22.5 parts of the second polypropylene in the outer layer mixture.

[0045] Comparative Example 4 Compared with Example 3, Comparative Example 4 is different in that there are 15 parts of the first polypropylene and 30 parts of the second polypropylene in the outer layer mixture.

[0046] Comparative Example 5 Compared with Example 3, the difference in Comparative Example 5 is that in the core layer mixture, the first polypropylene is 22.5 parts and the second polypropylene is 22.5 parts.

[0047] Comparative Example 6 Compared with Example 3, the difference in Comparative Example 6 is that in the core layer mixture, the first polypropylene is 35 parts and the second polypropylene is 10 parts.

[0048] Experimental Example 1 For the CPP cast films prepared in Examples 1 to 6 and Comparative Examples 1 to 6, according to the test method specified in GB / T 9639.1-2008 "Plastics - Films and Sheeting - Methods of Test for Impact Resistance - Free Falling Dart Method - Part 1: Staircase Method", the impact breakage mass of the samples was tested, and the sample thickness was 70 μm.

[0049] The test results are shown in Table 1: Table 1 Performance test results of CPP cast films prepared in Examples 1 to 6 and Comparative Examples 1 to 6

[0050] As can be seen from Table 1, the impact breakage mass of Example 3 is higher than that of Examples 4 to 6 and Comparative Examples 1 to 2, indicating that when the mineral filling contents of the first polypropylene and the second polypropylene are different, the impact resistance of the CPP cast film can be improved.

[0051] Experimental Example 2 For the CPP cast films prepared in Example 3 and Examples 7 to 12, according to the test method specified in GB / T 14216-2008 "Plastics - Determination of the wetting tension of films and sheets", the wetting tension of the samples was tested.

[0052] The test results are shown in Table 2: Table 2 Performance test results of CPP cast films prepared in Example 3 and Examples 7 to 12

[0053] As can be seen from Table 2, the wetting tension of Examples 7 to 12 is higher than that of Example 3, indicating that adding polyethylene and fluoropolymer can improve the wetting tension of the CPP cast film. Among Examples 7 to 12, the wetting tension of Examples 10 and 11 is higher than that of Examples 7 to 9 and Example 12, indicating that there is a synergistic effect between polytetrafluoroethylene and poly(chlorotrifluoroethylene - vinylidene fluoride) copolymer, which can further improve the wetting tension of the CPP cast film.

[0054] The above are only the 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 principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An impact-resistant CPP cast film, characterized in that: It includes an outer layer, a core layer and an inner layer which are arranged in sequence from top to bottom. The outer layer includes the following raw materials in parts by weight: 20-30 parts of a first polypropylene and 10-15 parts of a second polypropylene. The core layer includes the following raw materials in parts by weight: 5-10 parts of a first polypropylene, 30-35 parts of a second polypropylene and 5-8 parts of a filler. The inner layer includes the following raw materials in parts by weight: 20-40 parts of a third polypropylene and 0.1-0.3 parts of a lubricant. The first polypropylene and the second polypropylene have different mineral filling contents.

2. The impact-resistant CPP cast film according to claim 1, characterized in that: The mineral filling content of the first polypropylene is 5 wt %, and the mineral filling content of the second polypropylene is 30 wt %.

3. The impact-resistant CPP cast film according to claim 1, characterized in that: The third polypropylene is copolymerized polypropylene.

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

1.

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

6. The impact-resistant CPP cast film according to claim 1, characterized in that: The raw materials of the outer layer also include polyethylene and fluorine-containing polymer, and the mass ratio of the first polypropylene, polyethylene and fluorine-containing polymer is 10:2:1-2.

7. The impact-resistant CPP cast film according to claim 6, characterized in that: The fluorine-containing polymer is composed of polychlorotrifluoroethylene-vinylidene fluoride copolymer and polytetrafluoroethylene in a mass ratio of 2 to 3:

1.

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

9. The method for preparing an impact-resistant CPP cast film according to any one of claims 1 to 8, characterized in that: The following steps are involved: The raw materials of the outer layer, the core layer and the inner layer are mixed respectively, extruded and plasticized, co-extruded and cast after passing through a diverter, cooled and formed, and subjected to corona treatment to obtain an impact-resistant CPP cast film.

10. The impact-resistant CPP cast film according to claim 9, characterized in that: The cooling molding temperature is 25-30°C.

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