Recycling method of FEP cast film offcut, recycled FEP cast film and application of recycled FEP cast film

Abstract

The invention provides a recycling method of FEP cast film offcut, a recycled FEP cast film and application of the recycled FEP cast film, the recycling method comprises the steps that firstly, the FEP cast film offcut is granulated to obtain recycled material particles, then the obtained recycled material particles, FEP resin and color master batch are blended to obtain a blended raw material, and the blended raw material is extruded to obtain the FEP cast film offcut. And finally, carrying out melt extrusion, calendaring, cooling and molding, traction and flattening, trimming and rolling on the obtained blended raw material to obtain the recycled FEP cast film, thereby completing the recycling of the FEP cast film offcut. According to the recycling method, the utilization rate of the FEP resin can be effectively increased, the problem of reuse of the FEP cast film offcut at the same grade is solved to a great extent, and it can be guaranteed that the prepared recycled FEP cast film has excellent tensile property and puncture resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of cast films, and in particular relates to a method for recycling FEP cast film edge material, recycled FEP cast film and application thereof. Background Art

[0002] In recent years, the aviation industry has developed very rapidly. With the smooth delivery and expansion of large aircraft, the use of high-temperature isolation membranes has gradually increased. FEP is the abbreviation of Fluorinated ethylene propylene, and its Chinese name is perfluoroethylene propylene copolymer, commonly known as F46. As we all know, FEP is the main raw material for the production of high-temperature isolation membranes. Its price remains high and the supply is in short supply.

[0003] FEP cast film is a kind of film formed by casting process with FEP resin as the main raw material. The advantages of cast process technology are its high efficiency, economy and sustainability. The plastic film prepared by cast process technology has high transparency, flexibility and mechanical strength, and can be widely used in aerospace and electronic materials. However, cast film products need to be trimmed and rolled up, and its finished product utilization rate is difficult to reach 100%. Especially in the field of FEP cast film, the finished product utilization rate is less than 75%, and the edge material accounts for more than 25%, resulting in a large waste of raw materials. In addition, due to its high specific gravity and thin finished product thickness, the finished film is generally between 10 and 50 microns. It is easy to cause blockage of the feed port when it is crushed at room temperature and then fed, which affects the production and causes film breakage, and creates great difficulties for recycling.

[0004] Therefore, in view of the above technical problems, developing a method for recycling FEP cast film edge materials and improving the utilization rate of FEP are technical problems that urgently need to be solved in this field. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for recycling FEP cast film scraps, recycled FEP cast film and its application. The recycling method can effectively improve the utilization rate of FEP resin, greatly solve the problem of reuse of FEP cast film scraps of the same grade, and can also ensure that the recycled FEP finished film has excellent tensile properties and puncture resistance.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for recycling FEP cast film scraps, the recycling method comprising the following steps:

[0008] (1) Granulation: Granulate the FEP cast film edge material to obtain recycled material particles;

[0009] (2) Blending: blending the recycled material particles obtained in step (1), FEP resin and masterbatch to obtain a blended raw material;

[0010] (3) Film making: The blended raw material obtained in step (2) is melt-extruded, calendered, cooled, stretched, trimmed and rolled to obtain a recycled FEP cast film, thereby completing the recycling of the FEP cast film edge material.

[0011] The recycling method of FEP cast film scraps provided by the present invention comprises the following steps: firstly, the FEP cast film scraps are directly granulated without any pre-treatment to obtain recycled material particles; then, the obtained recycled material particles are blended with FEP resin and masterbatch to obtain blended raw materials; finally, the obtained blended raw materials are melt-extruded, calendered, cooled and formed, pulled and flattened, trimmed and rolled to obtain recycled FEP cast film, thereby completing the recycling of the FEP cast film scraps. The recycling method of FEP cast film scraps provided by the present invention is not only simple to operate, but also solves the problem of reusing the same grade of FEP cast film scraps to a great extent, so that the utilization rate of FEP resin reaches 100%, and at the same time, the performance of the finally produced recycled FEP cast film does not show a significant decline, and has excellent tensile properties and puncture resistance, indicating that the scraps can be fully utilized.

[0012] In the present invention, the edge material produced in the trimming process using FEP resin and masterbatch as the blending raw materials is defined as FEP cast film edge material recycled once, recorded as F1; the edge material produced by trimming the FEP cast film edge material (F1) recycled once and the FEP resin and masterbatch as the blending raw materials is defined as FEP cast film edge material recycled twice, recorded as F2, and so on.

[0013] Preferably, the FEP cast film scraps include scraps (F1) produced in the trimming process using new FEP resin and masterbatch as blending raw materials,

[0014] And / or, the scraps (denoted as F2, F3, F4 or F5) generated in the trimming process by using FEP cast film scraps that have been recycled ≤ 5 times (e.g., 5, 4, 3 or 2, etc.), FEP resin and masterbatch as blending raw materials.

[0015] Preferably, the granulation in step (1) is carried out in a single screw granulator.

[0016] Preferably, the single screw aspect ratio of the single screw granulator is above 1:20 (for example, 1:21, 1:22, 1:24, 1:26, 1:28 or 1:30, etc.), and the temperature from the feeding port to each zone is as follows: the feeding port is 200-400°C (for example, 200°C, 250°C, 300°C, 350°C or 400°C, etc.), zone 1 is 200-400°C (for example, 200°C, 250°C, 300°C, 350°C or 400°C, etc.), zone 2 is 200-400°C (for example, 200°C, 250°C, 300°C, 350°C or 400°C, etc.), zone 3 is 200-400°C (for example, 200°C, 250°C, 300°C, 350°C or 400°C, etc.). ), the temperature of the four zones is 200-400°C (for example, 200°C, 250°C, 300°C, 350°C or 400°C, etc.), and the length of each zone is independently 10-20 cm (for example, 10 cm, 12 cm, 14 cm, 16 cm, 18 cm or 20 cm, etc.), the temperature of the screen changer is 250-370°C (for example, 250°C, 270°C, 290°C, 310°C, 350°C or 370°C, etc.), the filter has at least three layers of filtration, and the accuracy of each layer of filtration is at least 80 meshes (for example, 80 meshes, 100 meshes or 120 meshes, etc.), and the temperature of the die head is 250-370°C (for example, 250°C, 270°C, 290°C, 310°C, 350°C or 370°C, etc.).

[0017] Preferably, the single screw aspect ratio of the single screw granulator is above 1:20, and the temperatures from the feed port to each zone are as follows: the feed port is 240-260°C, zone 1 is 240-260°C, zone 2 is 260-280°C, zone 3 is 260-280°C, zone 4 is 260-280°C, and the length of each zone is independently 10-20 cm, the screen changer temperature is 260-280°C, the filter screen is at least five layers of filtration, stacked according to 80 mesh / 80 mesh / 100 mesh / 100 mesh / 120 mesh, and the temperature of the die head is 260-280°C.

[0018] Preferably, in the granulation process of step (1), the entire heating time from feeding to discharging is controlled to be 30 to 180 s (for example, 30 s, 40 s, 60 s, 80 s, 100 s, 120 s, 140 s, 160 s or 180 s, etc.), the cold blowing compressed air is turned on, the die head is turned on for rotary slicing, and the cutter speed is appropriately adjusted according to the size of the particles, and the cutter speed is not less than 25 Hz (for example, 25 Hz, 26 Hz, 27 Hz, 29 Hz, 31 Hz, 33 Hz, 35 Hz, 37 Hz, 39 Hz or 40 Hz, etc.).

[0019] Preferably, based on the total mass of the raw materials in step (2) as 100%, the mass percentage of the recycled material particles is 25-40% (for example, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39% or 40%, etc.), the mass percentage of the FEP resin is 50-75% (for example, 50%, 55%, 60%, 65%, 70% or 75%, etc.), and the mass percentage of the masterbatch is 1-10% (for example, 1%, 2%, 4%, 6%, 8% or 10%, etc.).

[0020] Preferably, the melt index of the FEP resin is 1 to 20 g / 10 min, for example, 1 g / 10 min, 2 g / 10 min, 4 g / 10 min, 6 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 14 g / 10 min, 16 g / 10 min, 18 g / 10 min or 20 g / 10 min, and the test temperature of the melt index is 375 ° C and the load is 5 kg.

[0021] Preferably, the melt extrusion process in step (3) specifically includes: adding the raw materials into the extruder for melting, extruding from the T-die of the casting machine, blowing it up evenly with an air knife and attaching it to the casting cooling roller to obtain an extruded blank film, thereby completing the melt extrusion.

[0022] Preferably, the melting temperature is 330-380°C (for example, 330°C, 340°C, 350°C, 360°C, 370°C or 380°C, etc.), the lip gap of the die is 0.02-0.07mm (for example, 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm or 0.07mm, etc.), the extrusion temperature of the die is 350-380°C (for example, 350°C, 355°C, 360°C, 370°C or 380°C, etc.), and the air pressure of the air knife is 0.2-0.7MPa (for example, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa or 0.7MPa, etc.).

[0023] Preferably, the calendering and cooling molding process in step (3) specifically includes: shaping the extruded blank film through a cooling roller to obtain a FEP film.

[0024] Preferably, the cooling roller is cooled by heat transfer oil, and the temperature of the cooling roller is controlled at 120-180°C (for example, 120°C, 140°C, 160°C or 180°C, etc.) after passing through a heat exchanger inside the cooling roller, and the rotation speed of the cooling roller is 1-10m / min (for example, 1m / min, 2m / min, 4m / min, 6m / min, 8m / min or 10m / min, etc.).

[0025] In a second aspect, the present invention provides a recycled FEP cast film, wherein the recycled FEP cast film is prepared by the recycling method described in the first aspect.

[0026] Preferably, the tensile strength in MD of the recycled FEP cast film is not less than 43 MPa (for example, 43 MPa, 43.5 MPa, 44 MPa, 44.5 MPa, 45 MPa, 46 MPa, 48 MPa or 50 MPa, etc.), and the tensile strength in TD is not less than 37 MPa (for example, 37 MPa, 38 MPa, 39 MPa, 40 MPa, 41 MPa, 42 MPa, 43 MPa, 44 MPa or 45 MPa, etc.).

[0027] In a third aspect, the present invention provides an application of the recycled FEP cast film as described in the second aspect in a composite material molding process.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The recycling method of FEP cast film provided by the present invention first granulates FEP cast film scraps to obtain recycled material particles, then blends the obtained recycled material particles, FEP resin and masterbatch to obtain blended raw materials, and finally melt-extrudes, calenders, cools and forms, pulls and flattens, trims and rolls the obtained blended raw materials to obtain recycled FEP cast film, thereby completing the recycling of the FEP cast film scraps; the recycling method can effectively improve the utilization rate of FEP resin, greatly solves the problem of reusing the same grade of FEP cast film scraps, and can also ensure that the manufactured recycled FEP cast film has excellent tensile properties and puncture resistance. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0031] The following specific implementation methods involve some raw material information as follows:

[0032] (1) FEP resin A: melt index is 6 g / 10 min (375°C / 5 kg), purchased from Daikin, brand NP-20;

[0033] (2) FEP resin B: melt index is 18 g / 10 min (375°C / 5 kg), purchased from Dongyue, brand 618B;

[0034] (3) Masterbatch: Kolan FEP Masterbatch 198.8.

[0035] Preparation Example 1

[0036] A method for preparing a FEP cast film specifically comprises the following steps:

[0037] (1) Blending: 95% by weight of FEP resin A and 5% by weight of masterbatch are blended to obtain a blending raw material;

[0038] (2) Melt extrusion: The obtained blended raw materials are added to an extruder for melting, extruded from a T-die head of a casting machine, and evenly blown up by an air knife to fit onto a casting cooling roller to obtain an extruded blank film;

[0039] Among them, the melting temperature is 350°C, the lip gap of the die is 0.05mm, the extrusion temperature of the die is 370°C, and the air pressure of the air knife is 0.3MPa;

[0040] (3) Calendering and cooling molding: The obtained extruded blank film is shaped by cooling rollers to obtain a FEP film;

[0041] The cooling roller is cooled by heat transfer oil. After passing through the heat exchanger inside the cooling roller, the temperature of the cooling roller is controlled at 150°C, and the speed of the cooling roller is 5m / min.

[0042] (4) Pulling, flattening, trimming and winding: The obtained FEP film is pulled, flattened, trimmed and wound to obtain the FEP cast film.

[0043] The edge material produced in the trimming process of step (3) of the above-mentioned Preparation Example 1 is defined as the FEP cast film edge material which has been recycled once, and is denoted as F1.

[0044] Example 1

[0045] A method for recycling FEP cast film scraps comprises the following steps:

[0046] (1) Granulation: FEP cast film edge material F1 (from Preparation Example 1) was granulated using a single screw granulator to obtain recycled material granules;

[0047] Among them, the single screw aspect ratio of the single screw granulator is 1:22, and the temperature from the feed port to each zone is as follows: the feed port (220°C, zone 1 is 250°C, zone 2 is 270°C, zone 3 is 270°C, zone 4 is 270°C, the length of each zone is 10 cm, the screen changer temperature is 270°C, the filter screen is five-layer filtration, stacked according to 80 mesh / 80 mesh / 100 mesh / 100 mesh / 120 mesh, the temperature of the die head is 270°C, and in the granulation process, it is necessary to control the entire heating time from feeding to discharging to 70s, turn on the cold blowing compressed air, turn on the die head to rotate and slice, and adjust the cutter speed appropriately according to the size of the particles. The cutter speed is not less than 25Hz;

[0048] (2) Blending: 30% by weight of recycled material particles, 65% by weight of FEP resin A, and 5% by weight of masterbatch are blended to obtain a blended raw material;

[0049] (3) Melt extrusion: The obtained blended raw materials are added to an extruder for melting, extruded from a T-die head of a casting machine, and evenly blown up by an air knife to fit onto a casting cooling roller to obtain an extruded blank film;

[0050] Among them, the melting temperature is 350°C, the lip gap of the die is 0.05mm, the extrusion temperature of the die is 370°C, and the air pressure of the air knife is 0.3MPa;

[0051] (4) Calendering and cooling molding: The obtained extruded blank film is shaped by cooling rollers to obtain a FEP film;

[0052] The cooling roller is cooled by heat transfer oil. After passing through the heat exchanger inside the cooling roller, the temperature of the cooling roller is controlled at 150°C, and the speed of the cooling roller is 5m / min.

[0053] (5) Pulling, flattening and trimming and winding: The obtained FEP film is pulled, flattened and trimmed and wound to obtain a recycled FEP cast film, thereby completing the recycling of the FEP cast film edge material.

[0054] The edge material generated in the trimming process of step (5) of the above-mentioned embodiment 1 is defined as the FEP cast film edge material which has been recycled twice, and is denoted as F2.

[0055] Example 2

[0056] A method for recycling FEP cast film scraps, which differs from Example 1 in that the FEP cast film scraps F2 from Example 1 replaces the FEP cast film scraps F1 from Preparation Example 1, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0057] The edge material generated in the trimming process of the above-mentioned Example 2 is defined as the FEP cast film edge material which has been recycled three times, and is recorded as F3.

[0058] Example 3

[0059] A method for recycling FEP cast film scraps, which differs from Example 1 in that FEP cast film scraps F3 from Example 2 are used to replace FEP cast film scraps F1 from Preparation Example 1, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0060] The edge material generated in the trimming process of the above-mentioned Example 3 is defined as the FEP cast film edge material which has been recycled 4 times, and is recorded as F4.

[0061] Example 4

[0062] A method for recycling FEP cast film scraps, which differs from Example 1 in that FEP cast film scraps F4 from Example 3 are used to replace FEP cast film scraps F1 from Preparation Example 1, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0063] The edge material generated in the trimming process of the above-mentioned Example 4 is defined as the FEP cast film edge material which has been recycled 5 times, and is recorded as F5.

[0064] Example 5

[0065] A method for recycling FEP cast film scraps, which differs from Example 1 in that FEP cast film scraps F5 from Example 4 are used to replace FEP cast film scraps F1 from Preparation Example 1, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0066] Example 6

[0067] A method for recycling FEP cast film scraps, which differs from Example 1 only in that FEP resin B is used to replace FEP resin A, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0068] Example 7

[0069] A method for recycling FEP cast film scraps, which differs from Example 1 only in that the mass percentage of recycled material particles is 40%, the mass percentage of FEP resin A is 55%, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0070] Example 8

[0071] A method for recycling FEP cast film scraps, which differs from Example 1 only in that the mass percentage of recycled material particles is 45%, the mass percentage of FEP resin A is 50%, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0072] Comparative Example 1

[0073] A method for recycling FEP cast film scraps, which differs from Example 1 only in that the mass percentage of the recycled material particles is 95%, the mass percentage of the FEP resin A is 0%, and other substances, amounts, steps and parameters are the same as those in Example 1.

[0074] Performance Test:

[0075] (1) Tensile strength and elongation at break: tested according to the method provided in ASTM D 882-10;

[0076] (2) Puncture force: Tested according to the method provided in ASTM F1306-16.

[0077] The FEP cast films prepared in Preparation Example 1, Examples 1 to 8 and Comparative Example 1 were tested according to the above test method. The test results are shown in Table 1:

[0078] Table 1

[0079]

[0080]

[0081] From the data in Table 1, we can see that:

[0082] (1) The recycling method provided by the present invention can realize the recycling of FEP cast film edge materials, and after at least five cycles of recycling, the tensile properties and puncture resistance of the recycled FEP cast film are still very good.

[0083] (2) Since the granulation and cast film are carried out by melt extrusion, part of the raw materials will decompose in a high temperature environment. Therefore, the proportion of recycled material particles should not be too high, otherwise the performance of the recycled FEP cast film will be reduced. If the addition ratio is too low, the output side material will be larger than the recycled material particles, which is of little significance to actual production.

[0084] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate a method for recycling FEP cast film scraps, recycling FEP cast film and its application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling FEP cast film scraps, characterized in that: The recycling method comprises the following steps: (1) Granulation: Granulate the FEP cast film edge material to obtain recycled material particles; (2) Blending: blending the recycled material particles obtained in step (1), FEP resin and masterbatch to obtain a blended raw material; (3) Film making: The blended raw material obtained in step (2) is melt-extruded, calendered, cooled, stretched, trimmed and rolled to obtain a recycled FEP cast film, thereby completing the recycling of the FEP cast film edge material.

2. The recycling method according to claim 1, characterized in that: The FEP cast film scraps include scraps produced in the trimming process using FEP resin and masterbatch as blending raw materials. And / or, the scraps generated in the trimming process of using FEP cast film scraps that have been recycled ≤5 times, FEP resin and masterbatch as blending raw materials.

3. The recycling method according to claim 1 or 2, characterized in that: The granulation in step (1) is carried out in a single screw granulator; Preferably, the single screw aspect ratio of the single screw granulator is above 1:20, and the temperature from the feed port to each zone is as follows: the feed port is 200-400°C, zone 1 is 200-400°C, zone 2 is 200-400°C, zone 3 is 200-400°C, zone 4 is 200-400°C, the length of each zone is independently 10-20 cm, the screen changer temperature is 250-370°C, the filter screen is at least three layers of filtration, and the filtration accuracy of each layer is at least 80 meshes, and the temperature of the die head is 250-370°C; Preferably, during the granulation process of step (1), the entire heating time from feeding to discharging is controlled to be 30 to 180 seconds, and the cold blowing compressed air is turned on, the die head is turned on for rotary slicing, and the cutter speed is appropriately adjusted according to the size of the particles, and the cutter speed is not less than 25 Hz.

4. The recycling method according to any one of claims 1 to 3, characterized in that: Taking the total mass of the blended raw materials in step (2) as 100%, the mass percentage of the recycled material particles is 25-40%, the mass percentage of the FEP resin is 50-75%, and the mass percentage of the masterbatch is 1-10%.

5. The recycling method according to any one of claims 1 to 4, characterized in that: The melt index of the FEP resin in step (2) is 1 to 20 g / 10 min.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The melt extrusion process of step (3) specifically comprises: adding the blended raw material obtained in step (2) into an extruder to melt, extruding from a T-die head of a casting machine, and evenly blowing it up with an air knife to fit it to a casting cooling roller to obtain an extruded blank film, thereby completing the melt extrusion; Preferably, the melting temperature is 330-380° C., the lip gap of the die is 0.02-0.07 mm, the extrusion temperature of the die is 350-380° C., and the air pressure of the air knife is 0.2-0.7 MPa.

7. The recycling method according to any one of claims 1 to 6, characterized in that: The calendering and cooling molding process in step (3) specifically includes: passing the extruded blank film obtained by melt extrusion through a cooling roller for shaping to obtain a FEP film; Preferably, the cooling roller is cooled by heat transfer oil, and after passing through a heat exchanger inside the cooling roller, the temperature of the cooling roller is controlled at 120-180° C., and the rotation speed of the cooling roller is 1-10 m / min.

8. A recycled FEP cast film, characterized in that: The recycled FEP cast film is prepared by the recycling method according to any one of claims 1 to 7.

9. The recycled FEP cast film according to claim 8, characterized in that The tensile strength of the recycled FEP cast film in MD direction is not less than 43 MPa, and the tensile strength in TD direction is not less than 37 MPa.

10. Use of the recycled FEP cast film as claimed in claim 8 or 9 in a composite material forming process.

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