Ultrathin high-toughness high-branching-degree polyolefin plastic film and preparation method thereof

Abstract

The invention relates to the technical field of polyolefin plastic films, in particular to an ultrathin high-toughness high-branching-degree polyolefin plastic film and a preparation method thereof. The composite material comprises the following raw materials: 100 parts of polyolefin resin; the dosage of the epoxidized vegetable oil is 6-10 parts; the dosage of the vinyl hyperbranched polyamide is 4-8 parts; the use amount of the initiator is 0.2 to 0.6 part; the use amount of the antioxidant is 0.1 to 0.3 part; the use amount of the plasticizer is 3-6 parts; according to the ultrathin high-toughness high-branching-degree polyolefin plastic film and the preparation method thereof, by controlling the raw materials and the use amount thereof and performing drying pretreatment on the polyolefin resin and the vinyl hyperbranched polyamide, moisture is effectively removed, the reaction activity is improved, all the steps are closely linked in the preparation process, and the preparation process is simple. The ultra-thin high-toughness high-branching-degree polypropylene material has the advantages of being ultra-thin, high in toughness, high in branching degree, good in flatness, excellent in mechanical property and stable in use performance, the material cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyolefin plastic films, in particular to an ultra-thin, high-toughness, high-branched polyolefin plastic film and a preparation method thereof. Background Art

[0002] Polyolefin plastic films have good physical and chemical properties and occupy an important position in many industries such as packaging, agriculture, and electronics. For example, in the packaging industry, with the deepening of environmental protection concepts and the pursuit of lightweight products, on the one hand, the film needs to meet ultra-thin standards to reduce material consumption and reduce costs, and on the other hand, it is required to have high toughness to ensure that the product can withstand external impact during transportation and storage, and avoid damage caused by collision, friction, etc.; the same is true in the electronics field. Electronic products are constantly developing in the direction of miniaturization and lightweight. The polyolefin films used for packaging and circuit board coverings must be thin and light and tough to meet the performance requirements of electronic products in production, processing, and daily use; in the agricultural field, agricultural films must be thin and light to improve light transmittance and promote crop growth. At the same time, they must have high toughness and be able to withstand the test of harsh natural environments, such as strong winds, heavy rains, low temperatures, etc., to extend service life and reduce agricultural production costs.

[0003] However, the traditional method for preparing polyolefin plastic films has some shortcomings. From the perspective of performance balance, it is difficult to achieve ultra-thinness, high toughness and high branching degree at the same time. For example, in order to reduce the thickness, the intermolecular force may be weakened, resulting in a decrease in toughness; while increasing the degree of branching may sacrifice the flexibility and lightness of the film due to changes in the molecular structure. Moreover, the traditional process has poor control over the dispersion of additives, which can easily cause uneven film performance and affect its application in some scenarios with high requirements for performance consistency. At the same time, the films prepared by traditional methods have poor performance in terms of aging resistance and chemical corrosion resistance, and it is difficult to meet the application requirements of long-term use or special environments, shortening the service life of the film and indirectly increasing the cost of use, thereby reducing the practicality of polyolefin plastic films.

[0004] In view of this, there is an urgent need for an ultra-thin, high-toughness, highly branched polyolefin plastic film and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide an ultra-thin, high-toughness, high-branched polyolefin plastic film and a preparation method thereof. The film has the comprehensive properties of ultra-thinness, high toughness, and high branching degree, and can ensure good flatness, excellent mechanical properties, and stable performance, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, on the one hand, the present invention provides a method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film, comprising the following steps:

[0007] S1. Raw material preparation: polyolefin resin, epoxidized vegetable oil, vinyl hyperbranched polyamide, initiator, antioxidant and plasticizer;

[0008] S2. Raw material pretreatment: firstly use a blast drying oven to dry the polyolefin resin to remove moisture, and then use a vacuum drying oven to dry the vinyl hyperbranched polyamide;

[0009] S3, initial mixing: pour the dried polyolefin resin into a high-speed mixer, start stirring the high-speed mixer, and then add antioxidant and plasticizer in sequence to mix, so that the antioxidant and plasticizer are initially evenly dispersed in the polyolefin resin;

[0010] S4, remixing: firstly, adding the epoxidized vegetable oil and the vinyl hyperbranched polyamide into the high-speed mixer in S3 and stirring them to make all the ingredients fully mixed, and then adding the initiator and stirring them to make the initiator evenly distributed;

[0011] S5, melt blending: transfer the mixed materials to a twin-screw extruder, set the temperature zone of the extruder, and control the speed of the screw to fully melt and blend the materials in the extruder to form a uniform melt;

[0012] S6, film blowing: the melt extruded from the twin-screw extruder is extruded through the die head, the temperature of the film blowing machine die head is controlled, and the thickness and performance of the film are controlled by adjusting the blowing ratio and the traction ratio to obtain an ultra-thin film. In addition, during the entire molding process, the cooling air ring surrounding the die head is controlled to cool the film quickly and evenly;

[0013] S7. Post-treatment: The blow-molded film is placed at a temperature of 22°C-28°C for 36h-48h for aging treatment to release the stress inside the film and obtain a finished ultra-thin, high-toughness, high-branched polyolefin plastic film.

[0014] As a further improvement of the technical solution, in S1, the epoxidized vegetable oil is one of epoxidized soybean oil, epoxidized cottonseed oil, epoxidized rice bran oil and epoxidized sunflower oil.

[0015] As a further improvement of the technical solution, in S2, the blast drying oven is dried at 70°C-80°C for 4h-6h, and the vacuum drying oven is dried at 80°C-90°C for 3h-3h, so as to reduce the water content to below 0.1%.

[0016] As a further improvement of the technical solution, in S3, the stirring speed of the high-speed mixer is 300 r / min-500 r / min, and the mixing time is 8 min-10 min.

[0017] As a further improvement of the technical solution, in S4, the epoxidized vegetable oil and the vinyl hyperbranched polyamide are stirred at a speed of 600 r / min-800 r / min for 10 min-15 min; and the initiator is stirred at a speed of 360 r / min-500 r / min for 3 min-5 min.

[0018] As a further improvement of the present technical solution, in S5, the temperature zone of the extruder is set to include the direction from the hopper end to the head, the temperature gradually increases, the starting temperature is 150℃-160℃, the middle temperature is 170℃-190℃, and the head temperature is 180℃-200℃.

[0019] As a further improvement of the technical solution, in S5, the screw speed is controlled at 220-300 r / min.

[0020] As a further improvement of the technical solution, in S6, the temperature of the die head of the film blowing machine is controlled at 180° C.-190° C.; the blowing ratio is 2-3.2; and the pulling ratio is 3-5.

[0021] As a further improvement of the present technical solution, in S6, the wind speed deviation of each air outlet of the cooling air ring is controlled to be within ±5%, and at the same time, the temperature deviation of the cooling air in the circumferential direction is within ±2°C.

[0022] On the other hand, the present invention provides an antibacterial composite polyolefin plastic film prepared by any one of the preparation methods described above, comprising the following raw materials:

[0023] The polyolefin resin is used in an amount of 100 parts;

[0024] The epoxidized vegetable oil is used in an amount of 6 to 10 parts;

[0025] The amount of the vinyl hyperbranched polyamide is 4 to 8 parts;

[0026] The amount of the initiator is 0.2-0.6 parts;

[0027] The amount of the antioxidant is 0.1-0.3 parts;

[0028] The amount of the plasticizer is 3 to 6 parts.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. In the ultra-thin, high-toughness, high-branched polyolefin plastic film and its preparation method, the polyolefin resin and vinyl hyperbranched polyamide are dried and pretreated by controlling the raw materials and their amounts, effectively removing moisture and improving the reaction activity. In the preparation process, each step is closely connected. In the mixing stage, the stirring speed and time are controlled to make the components evenly dispersed; during melt blending, the temperature and screw speed are regulated to promote full reaction; in the film blowing molding stage, various parameters are controlled. The film prepared in this way not only has the characteristics of ultra-thinness, high toughness, and high branching, but also has good flatness, excellent mechanical properties and stable performance, which reduces material costs and improves production efficiency.

[0031] 2. In the ultra-thin, high-toughness, highly branched polyolefin plastic film and its preparation method, through the application of vinyl hyperbranched polyamide, it reduces the melt viscosity by virtue of its highly branched structure, and helps the polyolefin molecules to form a uniform ultra-thin film more easily during molding. At the same time, the vinyl in its hyperbranched structure copolymerizes with the polyolefin molecular chain to increase the branching degree and improve the overall performance of the film. In addition, it can also be combined with epoxidized vegetable oil for a second time, through the reaction of amino or vinyl with epoxy groups, to form a complex cross-linked network structure in the polyolefin system, which not only enhances the tensile strength, tear strength and other mechanical properties of the film, but also improves the thermal stability, so that the film can be stably used in high temperature or temperature-changing environments, thereby improving the practicality of the polyolefin plastic film. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The flowchart of the method for preparing the ultra-thin, high-toughness, high-branched polyolefin plastic film of the present invention is as follows;

[0033] Figure 2 is the average thickness bar graph of the present invention;

[0034] Figure 3 is a histogram of tensile strength of the present invention;

[0035] Figure 4 This is a bar graph of elongation at break of the present invention;

[0036] Figure 5 This is a high branching degree column diagram of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0038] The embodiment of the present invention provides an ultra-thin, high-toughness, highly branched polyolefin plastic film, comprising the following raw materials:

[0039] The amount of polyolefin resin is 100 parts;

[0040] The amount of epoxidized vegetable oil used is 6 to 10 parts;

[0041] The amount of vinyl hyperbranched polyamide is 4 to 8 parts;

[0042] The amount of initiator used is 0.2-0.6 parts;

[0043] The dosage of antioxidant is 0.1-0.3 parts;

[0044] The amount of plasticizer used is 3 to 6 parts.

[0045] according to Figure 1 As shown, the embodiment of the present invention also provides a method for preparing the above-mentioned ultra-thin, high-toughness, high-branched polyolefin plastic film, comprising the following steps:

[0046] Step 1, raw material preparation: polyolefin resin, epoxidized vegetable oil, vinyl hyperbranched polyamide, initiator, antioxidant and plasticizer; wherein the epoxidized vegetable oil is one of epoxidized soybean oil, epoxidized cottonseed oil, epoxidized rice bran oil and epoxidized sunflower oil;

[0047] Step 2, raw material pretreatment: first use a blast drying oven to dry the polyolefin resin at 70°C-80°C for 4h-6h to remove moisture; then use a vacuum drying oven to dry the vinyl hyperbranched polyamide at 80°C-90°C for 3h-3h to reduce the water content to below 0.1% to ensure its reaction activity;

[0048] Step 3, initial mixing: pour the dried polyolefin resin into a high-speed mixer and start stirring the high-speed mixer at a stirring speed of 300 r / min-500 r / min, then add antioxidant and plasticizer in turn for mixing, the mixing time is 8min-10min, so that the antioxidant and plasticizer are initially evenly dispersed in the polyolefin resin;

[0049] Step 4, remixing: first add the epoxidized vegetable oil and the vinyl hyperbranched polyamide into the high-speed mixer in step 3 and stir them, stir the epoxidized vegetable oil and the vinyl hyperbranched polyamide at a speed of 600r / min-800r / min for 10min-15min to fully mix all the ingredients, then add the initiator and stir, stir the initiator at a speed of 360r / min-500r / min for 3min-5min to evenly distribute the initiator;

[0050] Step 5, melt blending: transfer the mixed material to a twin-screw extruder, set the temperature zone of the extruder, set the temperature zone of the extruder from the hopper end to the die head, the temperature gradually increases, the starting temperature is 150°C-160°C, the middle temperature is 170°C-190°C, the die head temperature is 180°C-200°C, and the screw speed is controlled at 220-300r / min, and the material is conveyed and melt blended inside the extruder under the push of the screw from the time it enters the twin-screw extruder. The time used for the entire process is controlled to be 3min-5min, so as to ensure that the components are fully reacted and mixed evenly, so that the materials are fully melted and blended in the extruder to form a uniform melt;

[0051] Step 6, film blowing: the melt extruded from the twin-screw extruder is extruded through the die head, and the temperature of the film blowing machine die head is controlled at 180℃-190℃; the thickness and performance of the film are controlled by adjusting the blowing ratio and the traction ratio to obtain an ultra-thin film, and the blowing ratio is 2-3.2, wherein the blowing ratio refers to the ratio of the diameter of the film after blowing to the diameter of the die head during the film blowing process. For example, when the diameter of the die head is 50mm, the diameter of the film after blowing is 125mm, and the blowing ratio is 125÷50=2.5; the traction ratio is 3-5, wherein the traction ratio refers to the film traction The ratio of speed to extrusion speed. Assuming that the speed of the extruder extruding the melt is 2m / min and the speed of the traction device traction film is 6m / min, the traction ratio is 6÷2=3. In addition, during the entire molding process, the cooling air ring surrounding the die head is controlled to allow cooling air to be blown out from the air outlets evenly distributed along the circumference, thereby wrapping the film tube in all directions. The wind speed deviation of each air outlet of the cooling air ring is controlled within ±5%. At the same time, in the circumferential direction, the temperature deviation of the cooling air is within ±2℃, so that the film is cooled quickly and evenly, which helps to improve the flatness and mechanical properties of the film.

[0052] Step 7, post-treatment: place the blow-molded film at a temperature of 22°C-28°C for 36h-48h for aging treatment to release the stress inside the film and further stabilize the performance of the film to obtain a finished ultra-thin, high-toughness, high-branched polyolefin plastic film.

[0053] In the invention, firstly, the raw materials and their dosage ranges are controlled and selected, including polyolefin resin, a specific type of epoxidized vegetable oil, vinyl hyperbranched polyamide, initiator, antioxidant and plasticizer, and the polyolefin resin and vinyl hyperbranched polyamide are subjected to targeted drying pretreatment, which can not only remove the moisture in the raw materials, ensure the purity of the raw materials and improve their reactivity, but also carry out the preparation work according to the orderly mixing, melt blending, film blowing and post-processing steps. For example, in the mixing step, the stirring speed and time are accurately controlled according to different stages to ensure that the components are evenly dispersed; during melt blending, the temperature of each area of ​​the extruder and the screw speed are finely set to promote the full reaction and mixing of the components; in the film blowing stage, the die head temperature, blowing ratio, traction ratio and the wind speed and temperature deviation of the cooling air ring are regulated, which can also effectively improve the ultra-thinness, high toughness, high branching degree and other comprehensive properties of the film, so that the prepared film has good flatness, excellent mechanical properties and stable performance.

[0054] In addition, the vinyl hyperbranched polyamide can not only increase the ultra-thinness and high branching degree, but also be combined with epoxidized vegetable oil for a second time, among which:

[0055] The reason for increasing ultra-thinness is that vinyl hyperbranched polyamide has a highly branched molecular structure, which can significantly reduce the melt viscosity of the system. When polyolefin is processed into a film, the lower melt viscosity allows the polyolefin molecules to flow more smoothly. Under the action of the mold or processing equipment, it can flow more smoothly. This smooth flow state makes it easier for polyolefin molecules to form a uniform and thinner film under specific processing conditions. For example, in the process of blown film molding, the molecules can be more evenly distributed in the extrusion area of ​​the die head, thereby helping the polyolefin plastic film to achieve ultra-thinness;

[0056] The reason for increasing the high branching degree is that the vinyl groups in the hyperbranched structure can serve as active reaction points. Under the action of an initiator, they can copolymerize with the polyolefin molecular chain. Through this copolymerization reaction, more branching points are introduced into the polyolefin molecular chain, which causes the polyolefin molecular chain to generate more branches, thereby increasing the branching degree of the polyolefin. At the same time, the branching structure of the hyperbranched polyamide itself will also hinder the regular arrangement of the polyolefin molecular chain, increasing the difficulty of the regular arrangement of the polyolefin molecular chain, making it easier for the molecular chain to form more branched structures in space, which is conducive to further increasing the branching degree, thereby improving the overall performance of the film.

[0057] When the vinyl hyperbranched polyamide is secondary bonded with the epoxidized vegetable oil, the amino group or vinyl group in the vinyl hyperbranched polyamide can react with the epoxy group in the epoxidized vegetable oil. The amino group is nucleophilic and can undergo a ring-opening addition reaction with the epoxy group. During the reaction, the nitrogen atom in the amino group attacks the carbon atom with a lower electron cloud density in the epoxy group, causing the epoxy ring to open and form a new chemical bond, thereby connecting the vinyl hyperbranched polyamide with the epoxidized vegetable oil. Under appropriate catalytic conditions, the vinyl group can undergo a reaction similar to Michael addition with the epoxy group. The double bond in the vinyl group is activated under the action of the catalyst, enabling it to undergo an addition reaction with the epoxy group, and also opening the epoxy ring to form a stable chemical bond connection. Through these two reaction pathways, the chemical bonding of the vinyl hyperbranched polyamide and the epoxidized vegetable oil is achieved, completing the secondary bonding. This bonding helps to form a complex cross-linked network structure in the polyolefin system. The cross-linked network structure is like a tight "molecular net" that tightly connects the polyolefin molecules, the vinyl hyperbranched polyamide and the epoxidized vegetable oil. The formation of this structure significantly improves the mechanical properties of the film, such as tensile strength and tear strength, making the film less likely to break when subjected to external forces. At the same time, thermal stability is also improved, and the film can maintain more stable performance in a high temperature environment, and is not easily deformed or degraded due to temperature changes, thereby broadening the application range of the film.

[0058] By controlling the raw materials and their amounts, the polyolefin resin and vinyl hyperbranched polyamide are dried and pretreated to effectively remove moisture and improve reaction activity. During the preparation process, each step is closely connected. During the mixing stage, the stirring speed and time are controlled to ensure uniform dispersion of the components. During melt blending, the temperature and screw speed are regulated to promote full reaction. During the film blowing stage, various parameters are controlled. The film prepared in this way not only has the characteristics of ultra-thinness, high toughness, and high branching degree, but also has good flatness, excellent mechanical properties and stable performance, which reduces material costs and improves production efficiency.

[0059] Through the application of vinyl hyperbranched polyamide, it reduces the melt viscosity with its highly branched structure, helping the polyolefin molecules to form a uniform ultra-thin film more easily during molding. At the same time, the vinyl in its hyperbranched structure copolymerizes with the polyolefin molecular chain to increase the degree of branching and improve the overall performance of the film. In addition, it can also be combined with epoxidized vegetable oil for a second time, through the reaction of amino or vinyl and epoxy groups, to form a complex cross-linked network structure in the polyolefin system, which not only enhances the film's tensile strength, tear strength and other mechanical properties, but also improves the thermal stability, so that the film can be stably used in high temperature or temperature-changing environments, thereby improving the practicality of polyolefin plastic films.

[0060] According to different raw material dosages, the polyolefin plastic film provided by the present invention is further described through the following specific examples.

[0061] Example 1

[0062] Raw material dosage: 100 parts of polyolefin resin, 8 parts of epoxidized vegetable oil (epoxidized cottonseed oil is selected), 7 parts of vinyl hyperbranched polyamide, 0.2 parts of initiator, 0.2 parts of antioxidant and 4 parts of plasticizer;

[0063] Preparation process:

[0064] Step 1: Prepare the corresponding raw materials;

[0065] Step 2: The polyolefin resin is dried in a forced air drying oven at 75°C for 5 hours; the vinyl hyperbranched polyamide is dried in a vacuum drying oven at 85°C for 3 hours;

[0066] Step 3: Put the dried polyolefin resin into a high-speed mixer, stir at 400 r / min, add antioxidant and plasticizer, and mix for 9 minutes;

[0067] Step 4: Add epoxidized cottonseed oil and vinyl hyperbranched polyamide, stir at 700 r / min for 12 min, then add initiator, stir at 430 r / min for 4 min;

[0068] Step 5: The material was transferred to a twin-screw extruder, and the starting temperature was set to 155°C, the middle temperature to 180°C, the die temperature to 190°C, the screw speed to 260r / min, and the blending was performed for 4 minutes;

[0069] Step 6: The melt is extruded through the die head, the die head temperature is 185°C, the blow-up ratio is 2.5, the traction ratio is 4, and the relevant parameters of the cooling air ring are controlled;

[0070] Step 7: The film is placed at 25°C for 42 hours for aging treatment.

[0071] Example 2

[0072] Raw material dosage: 100 parts of polyolefin resin, 9 parts of epoxidized vegetable oil (epoxidized rice bran oil is selected), 6 parts of vinyl hyperbranched polyamide, 0.5 parts of initiator, 0.25 parts of antioxidant and 5 parts of plasticizer;

[0073] Preparation process:

[0074] Step 1: Prepare all the ingredients;

[0075] Step 2: The polyolefin resin is dried in a forced air drying oven at 80°C for 4 hours; the vinyl hyperbranched polyamide is dried in a vacuum drying oven at 90°C for 3 hours;

[0076] Step 3: Pour the polyolefin resin into a high-speed mixer, stir at 500 r / min, add antioxidant and plasticizer, and mix for 8 minutes;

[0077] Step 4: adding epoxidized rice bran oil and vinyl hyperbranched polyamide, stirring at 800 r / min for 10 min, then adding initiator, stirring at 500 r / min for 3 min;

[0078] Step 5: The material enters the twin-screw extruder, with a starting temperature of 160°C, an intermediate temperature of 190°C, a die temperature of 200°C, a screw speed of 300r / min, and blending for 3min;

[0079] Step 6: Extrude the melt through the die head, the die head temperature is 190°C, the blow-up ratio is 3, the traction ratio is 5, and the cooling air ring conditions are controlled;

[0080] Step 7: The blow molded film is placed at 28°C for 36 hours for aging treatment.

[0081] Example 3

[0082] Raw material dosage: 100 parts of polyolefin resin, 10 parts of epoxidized vegetable oil (epoxidized soybean oil is selected), 4 parts of vinyl hyperbranched polyamide, 0.4 parts of initiator, 0.1 parts of antioxidant and 3 parts of plasticizer;

[0083] Preparation process:

[0084] Step 1: Prepare all the ingredients;

[0085] Step 2: Place the polyolefin resin in a forced air drying oven and dry it at 70°C for 6 hours to remove moisture; place the vinyl hyperbranched polyamide in a vacuum drying oven and dry it at 80°C for 3 hours to reduce the moisture content to below 0.1%;

[0086] Step 3: Pour the dried polyolefin resin into a high-speed mixer, stir at a speed of 300 r / min, add antioxidant and plasticizer in sequence, and mix for 10 minutes;

[0087] Step 4: Add epoxidized soybean oil and vinyl hyperbranched polyamide into a high-speed mixer, stir at a speed of 600 r / min for 15 min, then add initiator, and stir at a speed of 360 r / min for 5 min;

[0088] Step 5: Transfer the mixed material to a twin-screw extruder, set the starting temperature to 150°C, the middle temperature to 170°C, the die temperature to 180°C, the screw speed to 220r / min, and blend the material in the extruder for 5 minutes;

[0089] Step 6: Extrude the extruded melt through the die head, control the die head temperature at 180°C, adjust the blow-up ratio to 2, the traction ratio to 3, control the wind speed deviation of each outlet of the cooling air ring to be within ±5%, and the cooling air temperature deviation in the circumferential direction to be within ±2°C;

[0090] Step 7: Place the blow molded film at 22° C. for 48 hours for aging treatment to obtain a finished film.

[0091] Example 4

[0092] Raw material dosage: 100 parts of polyolefin resin, 6 parts of epoxidized vegetable oil (epoxidized sunflower oil is selected), 8 parts of vinyl hyperbranched polyamide, 0.6 parts of initiator, 0.3 parts of antioxidant and 6 parts of plasticizer;

[0093] Preparation process:

[0094] Step 1: Prepare the raw materials;

[0095] Step 2: The polyolefin resin is dried in a forced air drying oven at 80° C. for 4 h, and the vinyl hyperbranched polyamide is dried in a vacuum drying oven at 90° C. for 3 h;

[0096] Step 3: Put the polyolefin resin into a high-speed mixer, stir at 500r / min, add antioxidant and plasticizer in sequence, and mix for 8 minutes;

[0097] Step 4: Add epoxidized sunflower oil and vinyl hyperbranched polyamide, stir at 800 r / min for 10 min, then add initiator, stir at 500 r / min for 3 min;

[0098] Step 5: The material was transferred to a twin-screw extruder, and the starting temperature was set to 160°C, the middle temperature to 190°C, the die temperature to 200°C, the screw speed to 300 r / min, and the blending was performed for 3 min;

[0099] Step 6: The melt is extruded through the die head, the die head temperature is 190°C, the blow-up ratio is 3.2, the traction ratio is 5, and the wind speed and temperature deviation of the cooling air ring are strictly controlled;

[0100] Step 7: The film is placed at 28°C for 36 hours for aging treatment to obtain a finished film.

[0101] Table 1 Amounts of raw materials used in Examples 1-4

[0102]

[0103] In order to verify that the polyolefin plastic film prepared in the embodiment of the present invention has good ultra-thinness, high toughness and high branching degree, the polyolefin plastic film provided in the embodiment of the present invention is described by the following test examples.

[0104] Test example

[0105] The purpose of this test group is to explore the influence of different component ratios on the polyolefin plastic film and to detect the ultra-thinness, high toughness and high branching degree of the polyolefin plastic film of the present invention.

[0106] Test objectives: Test group A, test group B, test group C and test group D respectively use the composition ratios of the polyolefin plastic film provided in Examples 1-4; the control example uses control group A, control group B, control group C and control group D, wherein:

[0107] Control group A

[0108] Raw material dosage: 100 parts polyolefin resin; 5 parts traditional plasticizer (dioctyl phthalate); 0.2 parts antioxidant;

[0109] Preparation method: first, directly put the polyolefin resin, plasticizer and antioxidant into a high-speed mixer and stir at a speed of 400r / min for 15 minutes; then transfer the mixed material to a single-screw extruder, set the temperature to 180°C, the screw speed to 150r / min, and extrude the melt; finally, blow the film through an ordinary film blowing equipment, with a blowing ratio of 2, a traction ratio of 3, a die temperature of 180°C, and naturally cool to obtain a film.

[0110] Control group B

[0111] Raw material dosage: 100 parts polyolefin resin; 8 parts traditional toughening agent (SBS elastomer); 0.2 parts antioxidant;

[0112] Preparation method: first, mix the polyolefin resin, toughening agent and antioxidant under low-speed stirring for 20 minutes; then put them into a twin-screw extruder, set the temperature to 160-180°C, the screw speed to 200r / min, and extrude the material; then adopt a conventional film blowing process, with a blowing ratio of 2.5, a traction ratio of 4, a die head temperature of 185°C, and simple air cooling to obtain a film.

[0113] Control group C

[0114] Amount of raw materials: the same as in Example 1, but without adding epoxidized vegetable oil;

[0115] Preparation method: Same as Example 1, but removing the epoxidized vegetable oil processing step.

[0116] Control group D

[0117] Amount of raw materials: the same as in Example 2, but without adding vinyl hyperbranched polyamide;

[0118] Preparation method: Same as Example 1, but removing the vinyl hyperbranched polyamide processing step.

[0119] Test method: According to the ultra-thinness, high toughness and high branching degree of the polyolefin plastic film of the present invention, tests are carried out respectively. The specific test methods are as follows:

[0120] Ultra-thinness test method:

[0121] Testing method: With the help of a micrometer with an accuracy of ±0.001mm, 5 measuring points are evenly selected at the upper, lower, left, right edges and center of the film. Before each measurement, the micrometer is zero-calibrated to ensure the accuracy of the measurement.

[0122] Use the formula: The average thickness calculation formula is ,in Representative The thickness value measured at each measuring point;

[0123] Data Reasoning: Average Thickness The smaller the value, the better the ultra-thinness of the film.

[0124] High toughness test method:

[0125] Testing method: Use an electronic tensile testing machine to conduct a tensile test on the film. Make the film into a standard rectangular sample, make 6 samples for each group of films, set the tensile speed to 40mm / min, and clamp the sample firmly on the fixture of the testing machine to ensure that the force direction of the sample is completely consistent with the direction of the tensile force. Record the maximum tensile force of each sample at the moment of fracture and the elongation at break ;

[0126] Use the formula: The calculation formula for tensile strength is ,in is the width of the specimen, is the thickness of the specimen. This formula is used to measure the ability of the film to resist tensile failure;

[0127] The calculation formula for elongation at break is: , is the initial length of the sample. This formula reflects the deformation capacity of the film before fracture. The toughness of the film is comprehensively evaluated by these two indicators.

[0128] Data Reasoning: Tensile Strength and elongation at break The higher the value, the stronger the toughness of the film.

[0129] High branching test method:

[0130] Detection method: Nuclear magnetic resonance carbon spectroscopy ( 13C-NMR) to analyze the film. Dissolve the film sample in a suitable deuterated solvent (such as deuterated chloroform) to prepare a solution of appropriate concentration and transfer it to a nuclear magnetic resonance tube. Test on the nuclear magnetic resonance instrument, set appropriate parameters, and collect 13 C-NMR spectrum, by integrating the peaks at different chemical shifts in the spectrum, the number of carbon atoms in different carbon environments is determined. For polyolefins, the carbon atoms on the side chains have different chemical shifts from those on the main chain. The branching degree of polyolefins can be evaluated by analyzing the integrated area ratio of the side chain related carbon peaks to the main chain carbon peaks.

[0131] Use the formula: Degree of branching ( ) is calculated as: ,in is the number of specific carbon atoms (such as methyl carbons) on the branch chain (by 13 C-NMR spectrum), is the number of specific carbon atoms (e.g., methylene carbons) on the main chain (also determined by the integrated area of ​​the corresponding peak in the spectrum);

[0132] Data reasoning: Degree of branching ( ) value is higher, indicating that the degree of branching of the polyolefin molecules is higher, that is, the high branching characteristics of the film are more significant.

[0133] Specific detection indicators are shown in Table 2.

[0134] Table 2 Test indicators of each sample

[0135]

[0136] according to Figure 2-Figure 5 As shown in Table 2, it can be clearly seen that the polyolefin plastic film prepared in the embodiment of the present invention has significant effects in terms of ultra-thinness, high toughness and high branching degree compared with the control group:

[0137] Ultra-thinness: The average thickness of the test group ranges from 0.013 mm to 0.016 mm, while the control group ranges from 0.017 mm to 0.022 mm. This shows that the property of vinyl hyperbranched polyamide to reduce melt viscosity makes it easier for polyolefin molecules to form ultra-thin structures during molding. For example, in Example 4, a higher proportion of vinyl hyperbranched polyamide makes the average thickness of the film reach 0.013 mm, which is significantly lower than that of the control group.

[0138] High toughness: The tensile strength of the test group is between 33MPa and 40MPa, and the elongation at break is between 420% and 490%; the tensile strength of the control group is between 25MPa and 32MPa, and the elongation at break is between 330% and 390%. The film of the present invention has better toughness because the epoxidized vegetable oil reduces the force between molecular chains and reacts with the vinyl hyperbranched polyamide to form a cross-linked network, which effectively inhibits crack propagation and greatly improves the tensile strength and elongation at break. For example, in test group B, the synergistic effect of epoxidized rice bran oil and vinyl hyperbranched polyamide makes the tensile strength reach 38MPa and the elongation at break reach 470%.

[0139] High degree of branching: The high degree of branching of the test group is 25%-33%, while that of the control group is only 15%-22%. The present invention adds vinyl hyperbranched polyamide, and under the action of an initiator, vinyl and polyolefin molecular chains copolymerize to increase branching points. At the same time, the structure of the hyperbranched polyamide itself hinders the regular arrangement of molecular chains, further increasing the degree of branching. For example, the high degree of branching of test group B reaches 33%, which is the result of the reasonable use of vinyl hyperbranched polyamide.

[0140] It can be seen that the polyolefin plastic film prepared by the present invention has significant advantages in ultra-thinness, high toughness and high branching through the specific raw material dosage and preparation process. It can effectively reduce the film thickness, improve toughness and branching, and compared with the control group, while maintaining the ultra-thin characteristics, greatly enhance the tensile strength, elongation at break and branching degree, and have better comprehensive performance.

[0141] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film, characterized in that: The following steps are involved: S1. Raw material preparation: polyolefin resin, epoxidized vegetable oil, vinyl hyperbranched polyamide, initiator, antioxidant and plasticizer; S2. Raw material pretreatment: firstly use a blast drying oven to dry the polyolefin resin to remove moisture, and then use a vacuum drying oven to dry the vinyl hyperbranched polyamide; S3, initial mixing: pour the dried polyolefin resin into a high-speed mixer, start stirring the high-speed mixer, and then add antioxidant and plasticizer in sequence to mix, so that the antioxidant and plasticizer are initially evenly dispersed in the polyolefin resin; S4, remixing: firstly, adding the epoxidized vegetable oil and the vinyl hyperbranched polyamide into the high-speed mixer in S3 and stirring them to make all the ingredients fully mixed, and then adding the initiator and stirring them to make the initiator evenly distributed; S5, melt blending: transfer the mixed materials to a twin-screw extruder, set the temperature zone of the extruder, and control the speed of the screw to fully melt and blend the materials in the extruder to form a uniform melt; S6, film blowing: the melt extruded from the twin-screw extruder is extruded through the die head, the temperature of the film blowing machine die head is controlled, and the thickness and performance of the film are controlled by adjusting the blowing ratio and the traction ratio to obtain an ultra-thin film. In addition, during the entire molding process, the cooling air ring surrounding the die head is controlled to cool the film quickly and evenly; S7. Post-treatment: The blow-molded film is placed at a temperature of 22°C-28°C for 36h-48h for aging treatment to release the stress inside the film and obtain a finished ultra-thin, high-toughness, high-branched polyolefin plastic film.

2. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S1, the epoxidized vegetable oil is one of epoxidized soybean oil, epoxidized cottonseed oil, epoxidized rice bran oil and epoxidized sunflower oil.

3. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S2, drying is performed in a forced air drying oven at 70°C-80°C for 4h-6h, and drying is performed in a vacuum drying oven at 80°C-90°C for 3h-3h, so that the water content is reduced to below 0.1%.

4. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S3, the stirring speed of the high-speed mixer is 300 r / min-500 r / min, and the mixing time is 8 min-10 min.

5. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In the S4, the epoxidized vegetable oil and the vinyl hyperbranched polyamide are stirred at a speed of 600 r / min-800 r / min for 10 min-15 min; and the initiator is stirred at a speed of 360 r / min-500 r / min for 3 min-5 min.

6. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S5, the temperature zone of the extruder is set to include the direction from the hopper end to the die head, the temperature gradually increases, the starting temperature is 150°C-160°C, the middle temperature is 170°C-190°C, and the die head temperature is 180°C-200°C.

7. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S5, the screw speed is controlled at 220-300 r / min.

8. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S6, the temperature of the die head of the film blowing machine is controlled at 180° C.-190° C.; the blow-up ratio is 2-3.2; and the traction ratio is 3-5.

9. The method for preparing an ultra-thin, high-toughness, highly branched polyolefin plastic film according to claim 1, characterized in that: In S6, the wind speed deviation of each air outlet of the cooling air ring is controlled to be within ±5%, and at the same time, the temperature deviation of the cooling air in the circumferential direction is within ±2°C.

10. An ultra-thin, high-toughness, high-branched polyolefin plastic film prepared by the method for preparing an ultra-thin, high-toughness, high-branched polyolefin plastic film according to any one of claims 1 to 9, characterized in that: Including the following ingredients: The polyolefin resin is used in an amount of 100 parts; The epoxidized vegetable oil is used in an amount of 6 to 10 parts; The amount of the vinyl hyperbranched polyamide is 4 to 8 parts; The amount of the initiator is 0.2-0.6 parts; The amount of the antioxidant is 0.1-0.3 parts; The amount of the plasticizer is 3 to 6 parts.

Images