A tear and impact resistant cpp film and a method for making the same

Abstract

The application relates to the technical field of film materials, and discloses a kind of tear-resistant and impact-resistant CPP film and a preparation method thereof.The CPP film is prepared by mixing, extruding and cooling and shaping processes using polypropylene as a base material and maleic anhydride grafted polypropylene and functional fiber additives as auxiliary materials.The functional fiber additives are prepared by modifying dendritic macromolecules on the surface of bamboo fibers.The macromolecules can form an interwoven network structure with polypropylene molecular chains, and the bamboo fibers can exist in the CPP film in the form of a crosslinked core.On the one hand, the bamboo fibers can be efficiently utilized to enhance the tear resistance of the CPP film by pulling and stretching, and on the other hand, the crosslinked network structure can effectively improve the density of the CPP film, and the macromolecule structure also contains a rigid fluorene ring, which can make the crosslinked network molecular chain more stable, thereby effectively improving the impact resistance of the CPP film.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, specifically to a tear-resistant and impact-resistant CPP membrane and its preparation method. Background Technology

[0002] Cast polypropylene film (CPP) is a non-stretched, non-oriented polypropylene film produced through a T-die melt casting and rapid cooling process. It features uniform thickness, high transparency, and excellent heat-sealing performance. As a core substrate in the packaging industry, CPP film is widely used in the food, pharmaceutical, daily chemical, and electronics sectors. However, with the increasing application of CPP film, its shortcomings have become apparent. Poor tear strength and impact resistance are significant factors limiting its further development. This is because many neutral products in industrial packaging and other fields require high strength in their packaging films. In particular, tear strength and impact strength have a decisive impact on the performance of heavy-duty packaging films. Therefore, improving the mechanical strength of CPP film has become a research hotspot.

[0003] Currently, it is common to use fiber and other additives to reinforce and modify CPP membranes. However, the interfacial compatibility between fiber and other additives and polypropylene is poor, which prevents them from fully exerting their advantages. Furthermore, adding large amounts of these additives not only fails to achieve the purpose of reinforcement and modification but also has a negative impact on the material. Based on this, the present invention provides a CPP membrane with good comprehensive performance, which can solve the problems existing in the prior art. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a tear-resistant and impact-resistant CPP film and its preparation method.

[0006] (II) Technical Solution

[0007] A tear-resistant and impact-resistant CPP film, comprising the following raw materials by weight:

[0008] Polypropylene 65-80 parts, maleic anhydride grafted polypropylene 15-25 parts, functional fiber additives 2-5.5 parts, elastomer 3-6 parts, lubricant 0.5-2 parts, antioxidant 0.5-1.5 parts;

[0009] The functional fiber additive is bamboo fiber with a surface modified with dendritic macromolecular polymers.

[0010] As a further aspect of the present invention, the preparation method of the functional fiber additive includes the following steps:

[0011] Step 1: Pre-treatment of bamboo fiber

[0012] Bamboo fibers are immersed in a 10-20% sodium hydroxide aqueous solution, then the temperature is raised to 60-70℃, and the mixture is kept warm and stirred for 2-4 hours. The fibers are then removed, separated, washed until neutral, and dried.

[0013] Step 2: Surface modification of bamboo fiber

[0014] Pretreated bamboo fibers are added to an ethanol aqueous solution and ultrasonically dispersed evenly. Then, the temperature is raised to 60-70℃, and epichlorohydrin and a phase transfer catalyst are added. After the addition is complete, the mixture is stirred for 3-6 hours. Then, sodium hydroxide aqueous solution is added. After the addition is complete, the mixture is stirred for 1-2 hours. Then, the heating is stopped, the material is cooled and discharged to obtain epoxidized modified bamboo fibers.

[0015] Step 3: Preparation of functional fiber additives

[0016] Epoxidized bamboo fibers are dispersed in toluene. Then, 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene and an alkaline catalyst are added to the resulting dispersion. After the addition is complete, stirring is started and nitrogen gas is introduced for protection. The temperature is then raised to 70-80℃ and kept at this temperature for 2-4 hours. Then, 2,3-dithio(2-mercapto)-1-propanethiol is added. After the addition is complete, the temperature is raised to 90-100℃ and stirred continuously for 12-18 hours. Finally, the material is cooled and discharged to obtain the functional fiber additive.

[0017] As a further aspect of the present invention, in step two, the volume fraction of the ethanol aqueous solution is 60-75%.

[0018] As a further aspect of the present invention, in step two, the phase transfer catalyst is any one of tetrabutylammonium bromide, tetramethylammonium bromide, tetramethylammonium chloride, or tetrabutylammonium chloride.

[0019] As a further aspect of the present invention, in step two, the mass fraction of the sodium hydroxide aqueous solution is 5-15%.

[0020] As a further aspect of the present invention, in step two, the mass ratio of the pretreated bamboo fiber to epichlorohydrin is 1:0.3-0.6.

[0021] As a further aspect of the present invention, in step three, the mass ratio of the epoxidized modified bamboo fiber, 2,3-dithio(2-mercapto)-1-propanethiol and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene is 1:0.6-1.2:1.5-2.5.

[0022] As a further aspect of the present invention, in step three, the alkaline catalyst is triethylamine.

[0023] In the above technical solution, bamboo fibers are first treated with sodium hydroxide to fully expose oxygen-containing functional groups such as hydroxyl groups on their surface. Then, under the action of a phase transfer catalyst, the epoxy groups in the epichlorohydrin structure can undergo ring-opening addition with the hydroxyl groups of the alkali-treated bamboo fibers. Next, under the action of sodium hydroxide, the hydroxyl substituents generated by the ring-opening reaction form a closed ring with the halogen substituents of epichlorohydrin, thereby modifying the surface of the bamboo fibers with epoxy groups to obtain epoxidized modified bamboo fibers. Finally, 2,3-dithio(2-mercapto)-1-propanethiol is used as a chain extender, and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene is used as a chain extender. Under the action of an alkaline catalyst, the epoxy groups and active mercapto groups in their structures undergo continuous ring-opening addition polymerization, thereby modifying the surface of the bamboo fibers with dendritic macromolecular polymers, i.e., functional fiber additives.

[0024] As a further aspect of the present invention, the elastomer is at least one of TPU, SBS or SEBS; the lubricant is polyethylene wax or paraffin wax; and the antioxidant is at least one of antioxidant 1010, antioxidant 168 or antioxidant 1076.

[0025] A method for preparing a tear-resistant and impact-resistant CPP film includes the following steps:

[0026] Step 1: Weigh and prepare all the raw materials according to their weight proportions;

[0027] The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, functional fiber additives, elastomers, lubricants, and antioxidants to a high-speed mixer. After mechanically mixing the mixture evenly, the mixture is fed into an extruder and extruded through a flat die to form a molten sheet.

[0028] The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

[0029] (III) Beneficial Technical Effects

[0030] This invention utilizes bamboo fibers with a surface-modified dendritic macromolecular polymer as an additive. Because the macromolecular polymer structure contains numerous hydroxyl functional groups generated by ring-opening polymerization, it can interact with the maleic anhydride groups in the compatibilizer structure during subsequent melting. Due to the dendritic structure of the macromolecular polymer, it can form an interwoven network structure with the polypropylene molecular chains. This structure allows the bamboo fibers to exist in the CPP membrane as cross-linked cores. On one hand, it efficiently utilizes the tensile and stretching properties of the bamboo fibers, effectively enhancing the tear resistance of the CPP membrane. On the other hand, the cross-linked network structure effectively improves the density of the CPP membrane. Furthermore, the presence of rigid fluorene rings in the macromolecular polymer structure further enhances the stability of the cross-linked network molecular chains, thereby effectively improving the impact resistance of the CPP membrane. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be provided below. Preferred embodiments of the invention are given below. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0032] Preparation Example

[0033] Preparation of functional fiber additives:

[0034] Step 1: Pre-treatment of bamboo fiber

[0035] Immerse 5g of bamboo fiber in 100mL of 15% sodium hydroxide aqueous solution, then raise the temperature to 65℃, keep it warm and stir for 3 hours, take it out, separate the fiber material, wash it until neutral, and then dry it.

[0036] Step 2: Surface modification of bamboo fiber

[0037] 2.8g of pretreated bamboo fiber was added to a 70% ethanol aqueous solution and ultrasonically dispersed. The temperature was then raised to 65℃, followed by the addition of 1.5g epichlorohydrin and 0.1g tetrabutylammonium bromide. After the addition was complete, the mixture was stirred for 4 hours. Then, 20mL of a 10% sodium hydroxide aqueous solution was added. After the addition was complete, the mixture was stirred for 1 hour. The heating was then stopped, the mixture was cooled, and the material was discharged to obtain epoxidized bamboo fiber.

[0038] Step 3: Preparation of functional fiber additives

[0039] 1.5g of epoxidized bamboo fiber was dispersed in toluene. Then, 1.2g of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene and triethylamine were added to the resulting dispersion. After the addition was complete, stirring was started and nitrogen gas was introduced for protection. The temperature was then raised to 75℃ and kept at that temperature for 3 hours. Then, 3g of 2,3-dithio(2-mercapto)-1-propanethiol was added. After the addition was complete, the temperature was raised to 95℃ and stirred continuously for 16 hours. The mixture was then cooled and discharged to obtain the functional fiber additive.

[0040] Example 1

[0041] A tear-resistant and impact-resistant CPP film, comprising the following raw materials by weight:

[0042] 65 parts polypropylene, 15 parts maleic anhydride-grafted polypropylene, 2 parts functional fiber additives, 3 parts TPU elastomer, 0.5 parts polyethylene wax lubricant, and 0.5 parts antioxidant 1010.

[0043] The method for preparing the CPP membrane includes the following steps:

[0044] Step 1: Weigh and prepare all the raw materials according to their weight proportions;

[0045] The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, functional fiber additives, TPU elastomer, polyethylene wax lubricant, and antioxidant 1010 into a high-speed mixer. After mechanically mixing the mixture evenly, it is fed into an extruder and extruded through a flat die to form a molten sheet.

[0046] The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

[0047] The preparation method for the functional fiber additives is shown in the preparation example, and the same applies to the following examples.

[0048] Example 2

[0049] A tear-resistant and impact-resistant CPP film, comprising the following raw materials by weight:

[0050] 70 parts polypropylene, 20 parts maleic anhydride-grafted polypropylene, 5 parts functional fiber additives, 4 parts SBS elastomer, 1 part paraffin lubricant, and 1681 parts antioxidant.

[0051] The method for preparing the CPP membrane includes the following steps:

[0052] Step 1: Weigh and prepare all the raw materials according to their weight proportions;

[0053] The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, functional fiber additives, SBS elastomer, paraffin lubricant, and antioxidant 168 to a high-speed mixer. After mechanically mixing the mixture evenly, the mixture is fed into an extruder and extruded through a flat die to form a molten sheet.

[0054] The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

[0055] Example 3

[0056] A tear-resistant and impact-resistant CPP film, comprising the following raw materials by weight:

[0057] 80 parts polypropylene, 25 parts maleic anhydride-grafted polypropylene, 5.5 parts functional fiber additives, 6 parts SEBS elastomer, 2 parts paraffin lubricant, and 1.5 parts antioxidant 1076.

[0058] The method for preparing the CPP membrane includes the following steps:

[0059] Step 1: Weigh and prepare all the raw materials according to their weight proportions;

[0060] The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, functional fiber additives, elastomer SEBS, lubricant paraffin, and antioxidant 1076 to a high-speed mixer. After mechanically mixing the mixture evenly, the mixture is fed into an extruder and extruded through a flat die to form a molten sheet.

[0061] The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

[0062] Comparative Example 1

[0063] A tear-resistant and impact-resistant CPP film, comprising the following raw materials by weight:

[0064] 70 parts polypropylene, 20 parts maleic anhydride-grafted polypropylene, 5 parts bamboo fiber, 4 parts SBS elastomer, 1 part paraffin wax lubricant, and 1681 parts antioxidant.

[0065] The method for preparing the CPP membrane includes the following steps:

[0066] Step 1: Weigh and prepare all the raw materials according to their weight proportions;

[0067] The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, bamboo fiber, SBS elastomer, paraffin lubricant, and antioxidant 168 to a high-speed mixer. After mechanically mixing the mixture evenly, the mixture is fed into an extruder and extruded through a flat die to form a molten sheet.

[0068] The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

[0069] Comparative Example 2

[0070] A tear-resistant and impact-resistant CPP film, comprising the following raw materials by weight:

[0071] 70 parts polypropylene, 20 parts maleic anhydride-grafted polypropylene, 4 parts SBS elastomer, 1 part paraffin wax lubricant, and 1681 parts antioxidant.

[0072] The method for preparing the CPP membrane includes the following steps:

[0073] Step 1: Weigh and prepare all the raw materials according to their weight proportions;

[0074] The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, SBS elastomer, paraffin lubricant, and antioxidant 168 to a high-speed mixer. After mechanically mixing the mixture evenly, the mixture is fed into an extruder and extruded through a flat die to form a molten sheet.

[0075] The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

[0076] Performance testing

[0077] The CPP membranes from the examples and comparative examples were prepared into test samples that met various specifications, and various performance tests were conducted. The results are recorded in the table below:

[0078] Table 1 - Test Results

[0079]

[0080]

[0081] The right-angle tear strength was tested according to standard QB / T 1130-1991.

[0082] Impact strength was tested in accordance with standard GB / T 9639.1-2008.

[0083] Analysis of the test results shows that the CPP membrane prepared in the embodiments of the present invention has good tear resistance and impact resistance. After replacing the functional fiber additive with bamboo fiber, due to the interface problem, the reinforcing effect of bamboo fiber itself cannot be fully exerted, and it is also impossible to form a cross-linked network structure, resulting in a significant reduction in the various properties of the membrane.

[0084] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including implementing any combination of methods. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

[0085] Based on the preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A tear-resistant and impact-resistant CPP film, characterized in that, By weight, it includes the following ingredients: Polypropylene 65-80 parts, maleic anhydride grafted polypropylene 15-25 parts, functional fiber additives 2-5.5 parts, elastomer 3-6 parts, lubricant 0.5-2 parts, antioxidant 0.5-1.5 parts; The functional fiber additive is bamboo fiber with a surface modified with dendritic macromolecular polymers; The preparation method of the functional fiber additive includes the following steps: Step 1: Pre-treatment of bamboo fiber Bamboo fibers are immersed in a 10-20% sodium hydroxide aqueous solution, then the temperature is raised to 60-70℃, and the mixture is kept warm and stirred for 2-4 hours. The fibers are then removed, separated, washed until neutral, and dried. Step 2: Surface modification of bamboo fiber Pretreated bamboo fibers are added to an ethanol aqueous solution and ultrasonically dispersed evenly. Then, the temperature is raised to 60-70℃, and epichlorohydrin and a phase transfer catalyst are added. After the addition is complete, the mixture is stirred for 3-6 hours. Then, sodium hydroxide aqueous solution is added. After the addition is complete, the mixture is stirred for 1-2 hours. Then, the heating is stopped, the material is cooled and discharged to obtain epoxidized modified bamboo fibers. Step 3: Preparation of functional fiber additives Epoxidized bamboo fibers are dispersed in toluene. Then, 2,3-dithio(2-mercapto)-1-propanethiol and an alkaline catalyst are added to the resulting dispersion. After the addition is complete, stirring is started and nitrogen gas is introduced for protection. The temperature is then raised to 70-80℃ and kept at that temperature for 2-4 hours. Then, 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene is added. After the addition is complete, the temperature is raised to 90-100℃ and stirred continuously for 12-18 hours. Finally, the material is cooled and discharged to obtain the functional fiber additive.

2. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, In step two, the volume fraction of the ethanol-water solution is 60-75%.

3. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, In step two, the phase transfer catalyst is any one of tetrabutylammonium bromide, tetramethylammonium bromide, tetramethylammonium chloride, or tetrabutylammonium chloride.

4. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, In step two, the mass fraction of the sodium hydroxide aqueous solution is 5-15%.

5. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, In step two, the mass ratio of the pretreated bamboo fiber to epichlorohydrin is 1:0.3-0.

6.

6. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, In step three, the mass ratio of the epoxidized modified bamboo fiber, 2,3-dithio(2-mercapto)-1-propanethiol and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene is 1:0.6-1.2:1.5-2.

5.

7. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, In step three, the alkaline catalyst is triethylamine.

8. The tear-resistant and impact-resistant CPP film according to claim 1, characterized in that, The elastomer is at least one of TPU, SBS, or SEBS; the lubricant is polyethylene wax or paraffin wax; and the antioxidant is at least one of antioxidant 1010, antioxidant 168, or antioxidant 1076.

9. A method for preparing a tear-resistant and impact-resistant CPP film as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh and prepare all the raw materials according to their weight proportions; The second step involves adding polypropylene, maleic anhydride-grafted polypropylene, functional fiber additives, elastomers, lubricants, and antioxidants to a high-speed mixer. After mechanically mixing the mixture evenly, the mixture is fed into an extruder and extruded through a flat die to form a molten sheet. The third step is to attach the molten sheet onto the cooling roller, cool it, and then cool and shape it through a water bath.

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