A three-layer co-extruded transparent PPSU film and its preparation method

Abstract

This invention discloses a three-layer co-extruded transparent PPSU film and its preparation method, relating to the technical field of polymer film materials. The three-layer co-extruded transparent PPSU film comprises a three-layer sandwich structure consisting of an outer layer, an inner layer, and an outer layer. The outer layers are modified PPSU resin layers, and the inner layer is a regular PPSU resin layer. The modified PPSU resin layer is composed of 89-92 parts PPSU resin, 2.2-4 parts modified nano-silica, 5-6 parts chopped glass fiber, and 0.8-1 parts antioxidant. The regular PPSU resin layer is made of PPSU resin. By using two layers of modified PPSU resin to coat the regular PPSU resin layer, forming an outer-inner-outer layer sandwich structure, not only can the tensile strength of the film be improved while retaining its good toughness, resulting in better mechanical properties, but the influence of modified fillers on the film's light transmittance can also be reduced, leading to better appearance and light transmittance.

Description

Technical Field

[0001] This invention relates to the technical field of polymer films, and in particular to a three-layer co-extruded transparent PPSU film and its preparation method. Background Technology

[0002] Polysulfone resin is an amorphous thermoplastic engineering plastic characterized by high temperature resistance, high strength, creep resistance, self-flame retardancy, and high transparency. PPSU (polyphenylene sulfone resin), as one of the important varieties of polysulfone resin, not only possesses stronger impact toughness, chemical stability, and hydrolysis resistance compared to PSU, but also exhibits good thermal stability and insulation properties. It can operate continuously at temperatures up to 180℃ and maintains extremely high notched impact toughness even after prolonged high-temperature treatment. Therefore, PPSU resin is widely used in the electronics, medical, food, and various high-precision fields.

[0003] Currently, PPSU membranes with good toughness can be produced using existing formulations and processes, and the manufacturing process is mature. However, in applications, it has been found that the tensile strength of these PPSU membranes is slightly poor and cannot meet the requirements of special engineering plastics. Summary of the Invention

[0004] In order to improve the tensile strength and overall performance of PPSU film while maintaining its good toughness, this application provides a three-layer co-extruded transparent PPSU film and its preparation method.

[0005] Firstly, the three-layer co-extruded transparent PPSU film provided in this application adopts the following technical solution:

[0006] A three-layer co-extruded transparent PPSU film is composed of a three-layer sandwich structure of outer layer-inner layer-outer layer, wherein the outer layers on both sides are modified PPSU resin layers and the inner layer is a common PPSU resin layer.

[0007] The modified PPSU resin layer is made from the following raw materials in parts by weight: 89-92 parts PPSU resin, 2.2-4 parts modified nano silica, 5-6 parts chopped glass fiber, and 0.8-1 parts antioxidant;

[0008] The ordinary PPSU resin layer is made of PPSU resin.

[0009] By adopting the above technical solution, the film is composed of a three-layer sandwich structure of outer layer-inner layer-outer layer. The inner ordinary PPSU resin layer, which is the main body, can maintain the high toughness of PPSU resin, while the outer modified PPSU resin layer can play a certain reinforcing role. By reasonably matching the outer and inner layers, the mechanical properties of the film can be improved by the filler, while the influence of the modified filler on the overall toughness and light transmittance of the film can be reduced to a certain extent. Thus, the tensile strength of the film can be improved while retaining its own good toughness, and the film can also maintain good appearance performance and light transmittance.

[0010] Optionally, the modified nano-silica is silane-modified nano-silica gel particles, and the preparation of the silane-modified nano-silica gel particles includes the following steps:

[0011] A1. First, add tetraethyl orthosilicate to a 30%-35% aqueous ethanol solution and mix thoroughly. Heat the solution in an oil bath to 35-40°C, then slowly add saturated ammonia water, maintain the temperature and stir continuously for 25-40 minutes. Add an appropriate amount of γ-methacryloyloxypropyltrimethoxysilane and stir to mix. Then let it stand for 10-12 hours to obtain modified silica gel.

[0012] A2. The modified silica gel obtained in step A1 is repeatedly soaked and washed with deionized water until the soaking solution is neutral. Then, it is heated to 95-120℃ and the surface of the gel is thoroughly dried. Then, it is ground and crushed to obtain silane-modified nano silica gel particles.

[0013] By employing the above-mentioned technical solution, nano-silica gel particles are prepared using a sol-gel process. During the preparation process, surface modification with γ-methacryloxypropyltrimethoxysilane effectively increases the specific surface area and porosity of the modified nano-silica, thereby enhancing the modification effect of γ-methacryloxypropyltrimethoxysilane. Furthermore, the prepared gel particles possess excellent optical transparency and low refractive index, which helps reduce the impact of modified nano-silica on the transparency of the modified PPSU resin layer, thus improving the overall transparency of the film.

[0014] Optionally, in step S1, the volume ratio of anhydrous ethanol to tetraethyl orthosilicate is 100:(1-2), and the volume ratio of tetraethyl orthosilicate, saturated ammonia, and γ-methacryloyloxypropyltrimethoxysilane is 1:(20-25):(5-10).

[0015] By adopting the above technical solution, it is beneficial to prepare nano-silica gel with smaller particle size, thereby improving the dispersibility of nano-silica gel in PPSU resin.

[0016] Optionally, the chopped glass fiber is also subjected to silane coupling treatment, which includes the following steps: B1, first immerse the glass fiber in an acidic solution, heat it to 50-60°C, immerse it for 30-40 minutes, take it out and soak and clean the surface of the glass fiber with deionized water until the cleaning solution is neutral to obtain acid-treated glass fiber;

[0017] B2. Immerse the acid-treated glass fiber obtained in step B1 in γ-methacryloxypropyltrimethoxysilane for 30-40 minutes. After immersion, remove and dry the fiber, then cut it into short fibers with an average length of 3-5 mm to obtain silane-coupled chopped glass fibers.

[0018] By adopting the above technical solution, not only can the compatibility and dispersibility of chopped glass fibers in PPSU resin be improved, allowing the chopped glass fibers to be uniformly dispersed in the PPSU resin, but the light transmittance of the modified PPSU resin layer is also improved, thereby increasing the overall light transmittance of the film. Furthermore, the glass fiber surface, which has undergone acid treatment, has numerous grooves and depressions, which facilitates the full penetration of PPSU resin and the formation of an anchoring structure with the chopped glass fibers. This improves the overall strength of the modified PPSU resin layer, thereby increasing the overall tensile strength of the film.

[0019] Optionally, the antioxidant may be any one or a mixture of antioxidant 1024 and antioxidant DLTP.

[0020] By adopting the above technical solutions, antioxidant 1024 or antioxidant DLTP can improve the antioxidant properties and thermal stability of PPSU resin, thereby improving the surface properties of the modified PPSU resin layer and enhancing the overall light transmittance of the film.

[0021] Optionally, the antioxidant is a mixture of antioxidant 1024 and antioxidant DLTP, and the weight ratio of antioxidant 1024 to antioxidant DLTP is 1:(1-1.5).

[0022] By adopting the above technical solution, the combined use of antioxidant 1024 and antioxidant DLTP can produce a synergistic effect, which not only helps to improve the antioxidant performance and thermal stability of the modified PPSU resin layer, but also helps to improve the overall light transmittance of the film.

[0023] Optionally, the thickness ratio of each layer of the film is (1-1.5):(7-8):(1-1.5).

[0024] By adopting the above technical solution, when the thickness ratio of each layer of the film is in the range of (1-1.5):(7-8):(1-1.5), the influence of the modified PPSU resin layer on the overall toughness and light transmittance of the film can be reduced to a certain extent. Under the premise of maintaining the overall good toughness and light transmittance of the film, the tensile strength of the film can be improved and the thermal shrinkage rate can be reduced, which is conducive to improving the comprehensive performance of the film.

[0025] Secondly, the preparation method of a three-layer co-extruded transparent PPSU film provided in this application adopts the following technical solution:

[0026] A method for preparing a three-layer co-extruded transparent PPSU film includes the following steps:

[0027] S1. First, thoroughly mix PPSU resin with modified nano-silica, heat to 130-145℃ and dry for 4-6 hours. Then, mix the dried PPSU resin, modified nano-silica, chopped glass fiber and antioxidant in proportion, granulate, extrude, and then heat to 130-145℃ again and dry for 4-6 hours to obtain modified PPSU resin granules.

[0028] S2. Modified PPSU resin granules are fed into extruder A, and PPSU resin is fed into extruder B. Extruder A and extruder B are extruded simultaneously. Then, extruder A distributes the modified PPSU resin granule melt evenly into the upper and lower flow channels according to the thickness ratio through the die distributor. Extruder B distributes the PPSU resin melt into the middle flow channel through the die distributor. The three layers of melt are simultaneously extruded through the co-extrusion die and cast into a film to obtain a three-layer co-extruded PPSU film.

[0029] S3. Measure the film thickness uniformity online. After the film cools and sets, it is wound up to obtain a three-layer co-extruded PPSU film roll with uniform thickness.

[0030] By employing the above technical solution, heating and drying the modified nano-silica before mixing effectively removes residual moisture from its surface, further improving its dispersibility in PPSU resin. Secondly, uniformly distributing the melt using a die distributor helps ensure the thickness of each layer and reduces thickness errors.

[0031] Optionally, in step S1, during the extrusion granulation process of the modified PPSU resin particles, a twin-screw extruder is selected, the temperature of zone one of the extruder is set to 330-345℃, the temperature of zones two to five is set to 335-345℃, the die temperature is set to 340-345℃, and the extruder speed is 40-45 r / min.

[0032] By adopting the above technical solution, reasonably setting the temperature of each zone of the twin-screw extruder, and coordinating with a suitable extrusion rate, it is beneficial to fully mix PPSU resin with other additives and fillers and extrude it uniformly.

[0033] Optionally, in step S2, during the process of the three-layer melt being compoundly extruded through a co-extrusion die and cast into a film, the melt is cast to a first casting roller and a second casting roller after being extruded through the co-extrusion die for traction and stretching to form a film. The temperature of the co-extrusion die is 345-355°C, the temperature of the first casting roller is 140-145°C, the temperature of the second casting roller is 135-145°C, and the rotational speed ratio of the first casting roller to the second casting roller is 1:(1.025-1.03).

[0034] By adopting the above technical solution, the temperature difference between the first and second casting rollers and the co-extrusion die head is significant, which is beneficial for accelerating melt cooling and enabling rapid film setting. The high temperature of 135-145℃ for the first and second casting rollers not only helps maintain the uniformity and stability of the film during cooling and setting, reducing problems such as bubbles or perforations, but also improves the gloss and transparency of the film surface to a certain extent. Secondly, when the speed ratio of the first and second casting rollers is 1:(1.025-1.03), combined with the higher temperature of the casting rollers, it facilitates uniform longitudinal stretching of the film and reduces the internal stress generated during stretching. This not only helps prevent film breakage during stretching but also helps reduce the film's thermal shrinkage rate.

[0035] In summary, the technical solution of this application includes at least one of the following beneficial effects:

[0036] 1. By using two layers of modified PPSU resin to coat the ordinary PPSU resin layer, forming a three-layer sandwich structure of outer layer-inner layer-outer layer, the tensile strength of the film can be improved while retaining the good toughness of the film itself, which is conducive to giving the film better mechanical properties. Moreover, the influence of modified fillers on the light transmittance of the film can be reduced, which is conducive to giving the film better appearance and light transmittance.

[0037] 2. Modifying PPSU resin with modified nano-silica gel particles helps reduce the impact of modified nano-silica on the transparency of the modified PPSU resin layer, thereby improving the overall transparency of the film.

[0038] 3. Modifying PPSU resin with silane-coupled chopped glass fibers not only improves the compatibility and dispersibility of chopped glass fibers in PPSU resin, enabling them to be uniformly dispersed in the PPSU resin, but also reduces the impact of chopped glass fibers on the light transmittance of the modified PPSU resin layer, thereby improving the overall light transmittance of the film. Detailed Implementation

[0039] The present application will be further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0040] The glass fiber was purchased from Jiujiang Lianfeng Glass Fiber Co., Ltd., specifically 100g alkali-free glass fiber of model 2116.

[0041] Preparation Example

[0042]

Preparation Example 1-1

[0043] A modified nano-silica, comprising the following preparation steps:

[0044] First, 0.5 kg of nano-silica was vacuum dried. Then, the dried nano-silica was placed in toluene and stirred thoroughly. The temperature was gradually increased to 60°C. Then, an excess of γ-methacryloyloxypropyltrimethoxysilane was added. The temperature was maintained and the reaction was continued with stirring for 5 hours. The obtained product was filtered, washed several times, and then vacuum dried to finally obtain modified nano-silica.

[0045]

Preparation Examples 1-2

[0046] A modified nano-silica, comprising the following preparation steps:

[0047] A1. First, add 0.6L of tetraethyl orthosilicate to 60L of 30% ethanol aqueous solution and mix thoroughly. Heat the solution in an oil bath to 35℃, then slowly add 15L of saturated ammonia water, maintain the temperature and stir continuously for 25min. Add 3L of γ-methacryloyloxypropyltrimethoxysilane and stir to mix. Then let it stand for 10h to obtain modified silica gel.

[0048] A2. The modified silica gel obtained in step A1 is repeatedly soaked and washed with deionized water until the soaking solution is neutral. Then, it is heated to 115°C and the surface of the gel is thoroughly dried. Then, it is ground and crushed to obtain silane-modified nano silica gel particles.

[0049]

Preparation Examples 1-3

[0050] A modified nano-silica, comprising the following preparation steps:

[0051] A1. First, add 1.2L of tetraethyl orthosilicate to 60L of 35% ethanol aqueous solution and mix thoroughly. Heat in an oil bath to 38℃, then slowly add 24L of saturated ammonia water, maintain the temperature and stir continuously for 40min. Add 12L of γ-methacryloyloxypropyltrimethoxysilane and stir to mix. Then let stand for 12h to obtain modified silica gel.

[0052] A2. The modified silica gel obtained in step A1 is repeatedly soaked and washed with deionized water until the soaking solution is neutral. Then, it is heated to 130°C and the surface of the gel is thoroughly dried. Then, it is ground and crushed to obtain silane-modified nano silica gel particles.

[0053]

Preparation Example 2-1

[0054] A chopped glass fiber, comprising the following preparation steps:

[0055] Glass fibers are directly cut into short fibers with an average length of 3-5mm using a yarn cutter.

[0056]

Preparation Example 2-2

[0057] A silane-coupled chopped glass fiber, comprising the following processing steps:

[0058] B1. First, immerse the glass fiber in a 10% sulfuric acid solution, heat it to 50°C, and fully immerse and react for 30 minutes. Then, remove the glass fiber and soak and clean the surface of the glass fiber with deionized water until the cleaning solution is neutral to obtain acid-treated glass fiber.

[0059] B2. The acid-treated glass fiber obtained in step B1 is immersed in γ-methacryloxypropyltrimethoxysilane for 30 minutes. After immersion, it is dried and then cut into short fibers with an average length of 3-5 mm to obtain silane-coupled chopped glass fibers.

[0060] Example

[0061]

Example 1

[0062] A three-layer co-extruded PPSU film is composed of an outer-inner-outer layer composite structure, with both outer layers being modified PPSU resin layers and the inner layer being a regular PPSU resin layer.

[0063] Specifically, the modified PPSU resin layer comprises raw materials in the following weight proportions: 9.1 kg PPSU resin, 0.3 kg modified nano-silica, 0.5 kg chopped glass fibers, and 0.1 kg antioxidant. In this embodiment, the modified nano-silica is the modified nano-silica prepared in [Preparation Example 1-1], the chopped glass fibers are the chopped glass fibers prepared in [Preparation Example 2-1], and the antioxidant is antioxidant 1024.

[0064] The standard PPSU resin layer is made by melt extrusion of PPSU resin.

[0065] A method for preparing a three-layer co-extruded PPSU film includes the following steps:

[0066] S1. First, mix 9.1 kg of PPSU resin with 0.3 kg of modified nano silica thoroughly, heat to 140°C and dry for 4 hours. Then, put the dried PPSU resin, modified nano silica, 0.5 kg of chopped glass fiber and 0.1 kg of antioxidant into a high-speed mixer and mix evenly. Then, extrude and granulate the mixture, and then heat to 140°C again and dry for 4 hours to obtain modified PPSU resin granules.

[0067] In this embodiment, a twin-screw extruder is selected for extrusion granulation. The temperature of the first zone of the twin-screw extruder is 330°C, the temperature of the second to fifth zones is 335°C, the die temperature is 340°C, and the rotation speed is set to 40 r / min.

[0068] S2. The modified PPSU resin granules obtained in step S1 are fed into extruder A, and 40 kg of PPSU resin is fed into extruder B. Extruder A and extruder B are extruded simultaneously. Then, extruder A distributes the modified PPSU resin granule melt evenly into the upper and lower flow channels according to the thickness ratio through the die distributor. Extruder B distributes the PPSU resin melt into the middle flow channel through the die distributor. The three layers of melt are simultaneously co-extruded through the die and cast into a film to obtain a three-layer co-extruded PPSU film.

[0069] In this embodiment, both extruder A and extruder B are single-screw extruders. The temperature of single-screw extruder A is set to 350°C and the rotation speed is 10 r / min, while the temperature of single-screw extruder B is set to 330°C and the rotation speed is 40 r / min.

[0070] In addition, during the process of three-layer melt being co-extruded and cast into a film through a die, the thickness ratio of each layer is 1:8:1. After the melt is co-extruded through the die, it is cast onto the first casting roller and the second casting roller for traction and stretching. The temperature of the die is 350°C, the temperature of the first casting roller is 140°C, the temperature of the second casting roller is 135°C, and the speed ratio between the first casting roller and the second casting roller is 1:1.025.

[0071] S3. Measure the film thickness uniformity online. After the film cools and sets, it is wound up to obtain a three-layer co-extruded PPSU film roll with an average thickness of 100μm.

[0072]

Example 2

[0073] A three-layer co-extruded PPSU film is composed of an outer-inner-outer layer composite structure, with both outer layers being modified PPSU resin layers and the inner layer being a regular PPSU resin layer.

[0074] Specifically, the modified PPSU resin layer comprises raw materials in the following weight proportions: 9.2 kg PPSU resin, 0.22 kg modified nano-silica, 0.5 kg chopped glass fiber, and 0.08 kg antioxidant. In this embodiment, the modified nano-silica is the modified nano-silica prepared in [Preparation Examples 1-2], the chopped glass fiber is the chopped glass fiber prepared in [Preparation Example 2-1], and the antioxidant is DLTP.

[0075] The standard PPSU resin layer is made by melt extrusion of PPSU resin.

[0076] A method for preparing a three-layer co-extruded PPSU film includes the following steps:

[0077] S1. First, mix 9.2 kg of PPSU resin with 0.22 kg of modified nano silica thoroughly, heat to 140°C and dry for 4 hours. Then, put the dried PPSU resin, modified nano silica, 0.5 kg of chopped glass fiber and 0.08 kg of antioxidant into a high-speed mixer and mix evenly. Then, extrude and granulate the mixture, and then heat to 145°C again and dry for 4 hours to obtain modified PPSU resin granules.

[0078] In this embodiment, a twin-screw extruder is selected for extrusion granulation. The temperature of the first zone of the twin-screw extruder is 335°C, the temperature of the second to fifth zones is 340°C, the die temperature is 345°C, and the rotation speed is set to 45 r / min.

[0079] S2. The modified PPSU resin granules obtained in step S1 are fed into extruder A, and 40 kg of PPSU resin is fed into extruder B. Extruder A and extruder B are extruded simultaneously. Then, extruder A distributes the modified PPSU resin granule melt evenly into the upper and lower flow channels according to the thickness ratio through the die distributor. Extruder B distributes the PPSU resin melt into the middle flow channel through the die distributor. The three layers of melt are simultaneously co-extruded through the die and cast into a film to obtain a three-layer co-extruded PPSU film.

[0080] In this embodiment, both extruder A and extruder B are single-screw extruders. The temperature of single-screw extruder A is set to 345°C and the rotation speed is 10 r / min, while the temperature of single-screw extruder B is set to 345°C and the rotation speed is 40 r / min.

[0081] In addition, during the process of the three-layer melt being compoundly extruded through a co-extrusion die and cast into a film, the thickness ratio of each layer is 1.5:7:1.5. After the melt is compoundly extruded through the co-extrusion die, it is cast to the first casting roller and the second casting roller for traction and stretching. The temperature of the co-extrusion die is 350°C, the temperature of the first casting roller is 145°C, the temperature of the second casting roller is 140°C, and the speed ratio between the first casting roller and the second casting roller is 1:1.03.

[0082] S3. Measure the film thickness uniformity online. After the film cools and sets, it is wound up to obtain a three-layer co-extruded PPSU film roll with an average thickness of 100μm.

[0083]

Example 3

[0084] A three-layer co-extruded PPSU film is composed of an outer-inner-outer layer composite structure, with both outer layers being modified PPSU resin layers and the inner layer being a regular PPSU resin layer.

[0085] Specifically, the modified PPSU resin layer comprises raw materials in the following weight proportions: 8.9 kg PPSU resin, 0.4 kg modified nano-silica, 0.6 kg chopped glass fiber, and 0.1 kg antioxidant. In this embodiment, the modified nano-silica is the modified nano-silica prepared in [Preparation Example 1-1], the chopped glass fiber is the chopped glass fiber prepared in [Preparation Example 2-1], and the antioxidant is a mixture of antioxidant 1024 and antioxidant DLTP, with a mixing ratio of 1:1, i.e., the amount of antioxidant 1024 added is 0.05 kg, and the amount of antioxidant DLTP added is 0.05 kg.

[0086] The standard PPSU resin layer is made by melt extrusion of PPSU resin.

[0087] A method for preparing a three-layer co-extruded PPSU film includes the following steps:

[0088] S1. First, mix 8.9 kg of PPSU resin with 0.4 kg of modified nano silica thoroughly, heat to 130°C and dry for 6 hours. Then, put the dried PPSU resin, modified nano silica, 0.5 kg of chopped glass fiber, 0.04 kg of antioxidant 1024 and 0.06 kg of antioxidant DLTP into a high-speed mixer and mix evenly. Then, extrude and granulate the mixture, and then heat to 130°C again and dry for 6 hours to obtain modified PPSU resin granules.

[0089] In this embodiment, a twin-screw extruder is selected for extrusion granulation. The temperature of the first zone of the twin-screw extruder is 340°C, the temperature of the second to fifth zones is 345°C, the die temperature is 345°C, and the rotation speed is set to 40 r / min.

[0090] S2. The modified PPSU resin granules obtained in step S1 are fed into extruder A, and 40 kg of PPSU resin is fed into extruder B. Extruder A and extruder B are extruded simultaneously. Then, extruder A distributes the modified PPSU resin granule melt evenly into the upper and lower flow channels according to the thickness ratio through the die distributor. Extruder B distributes the PPSU resin melt into the middle flow channel through the die distributor. The three layers of melt are simultaneously co-extruded through the die and cast into a film to obtain a three-layer co-extruded PPSU film.

[0091] In this embodiment, both extruder A and extruder B are single-screw extruders. The temperature of single-screw extruder A is set to 350°C and the rotation speed is 10 r / min, while the temperature of single-screw extruder B is set to 350°C and the rotation speed is 40 r / min.

[0092] In addition, during the process of the three-layer melt being compoundly extruded through a co-extrusion die and cast into a film, the thickness ratio of each layer is 1.2:7.6:1.2. After the melt is compoundly extruded through the co-extrusion die, it is cast to the first casting roller and the second casting roller for traction and stretching. The temperature of the co-extrusion die is 350°C, the temperature of the first casting roller is 145°C, the temperature of the second casting roller is 145°C, and the speed ratio between the first casting roller and the co-extrusion second casting roller is 1:1.025.

[0093] S3. Measure the film thickness uniformity online. After the film cools and sets, it is wound up to obtain a three-layer co-extruded PPSU film roll with an average thickness of 100μm.

[0094]

Example 4

[0095] A three-layer co-extruded PPSU film, which differs from [Example 1] in that it uses different modified nano-silica.

[0096] In this embodiment, the modified nano-silica added to the modified PPSU resin layer is the modified nano-silica prepared in Examples 1-3.

[0097]

Example 5

[0098] A three-layer co-extruded PPSU film, which differs from [Example 4] in that it uses different short-cut glass fibers.

[0099] In this embodiment, the chopped glass fiber is selected from the chopped glass fiber prepared in [Preparation Example 2-2].

[0100]

Example 6

[0101] A three-layer co-extruded PPSU film, which differs from [Example 5] in that it uses a different antioxidant.

[0102] In this embodiment, the antioxidant is replaced with an equal amount of the antioxidant DLTP.

[0103]

Example 7

[0104] A three-layer co-extruded PPSU film, which differs from [Example 5] in that it uses a different antioxidant.

[0105] In this embodiment, the antioxidant is replaced by an equal amount of a mixture of antioxidant 1024 and antioxidant DLTP, and the weight ratio of antioxidant 1024 to antioxidant DLTP is 1:1.5, that is, the amount of antioxidant 1024 added is 0.04 kg and the amount of antioxidant DLTP added is 0.06 kg.

[0106] Comparative Example

[0107] Comparative Example 1

[0108] A PPSU film, which differs from [Example 1] in that the film has a single-layer structure.

[0109] In this comparative example, the outer modified PPSU resin layer was replaced with the inner ordinary resin layer of equal thickness.

[0110] Comparative Example 2

[0111] A PPSU film, which differs from [Example 1] in that the film has a single-layer structure.

[0112] In this comparative example, the inner ordinary resin layer of equal thickness was replaced with the outer modified PPSU resin layer.

[0113] Comparative Example 3

[0114] A PPSU film, which differs from [Example 1] in that the material used for the outer layer of the film is different.

[0115] In this comparative example, the modified nano-silica in the outer modified PPSU resin layer was replaced with an equal amount of ordinary nano-silica.

[0116] Performance test data

[0117] (1) Film tensile properties test: The test was conducted in accordance with GB / T 1040.3-2006 Determination of tensile properties of plastics Part 3: Test conditions for films and sheets, and the tensile strength (MPa) and elongation at break (%) of the films prepared in each example and comparative example were recorded. Among them, the sample shape was selected as type 2 sample, and the tensile speed was 50 mm / min.

[0118] (2) Thermal stability of film: The film was cut into strips with a width of 20 mm and a length of 100 mm. The strips were then placed in an oven at 200 °C and baked for 30 min. After taking them out, the longitudinal shrinkage rate (%) of the films prepared in each example and comparative example was measured and recorded.

[0119] (3) Light transmittance: The light transmittance of the films prepared in each example and comparative example was tested in accordance with GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics" and recorded.

[0120] Table 1 Performance test data of the thin film

[0121] Tensile strength (MPa) Elongation at break % Longitudinal shrinkage rate % Light transmittance Example 1 82 52 0.5 83 Example 2 84 54 0.4 82 Example 3 81 51 0.5 84 Example 4 85 56 0.4 85 Example 5 87 57 0.3 86 Example 6 88 57 0.3 83 Example 7 87 58 0.3 87 Comparative Example 1 70 62 1.1 87 Comparative Example 2 93 21 0.2 78 Comparative Example 3 76 44 0.6 80

[0122] Based on the data from Examples 1 and Comparative Examples 1-2, and in conjunction with Table 1, it can be seen that the film composed of a three-layer sandwich structure (outer layer-inner layer-outer layer) exhibits a tensile strength increased from 70 MPa to 82 MPa compared to the film with only a single ordinary PPSU resin layer, while still maintaining a high elongation at break (>50%). Furthermore, the film also possesses good light transmittance. Based on the data from Comparative Examples 1 and 2, and in conjunction with Table 1, it can be seen that although the film made solely of modified PPSU resin layers has higher tensile strength and lower longitudinal thermal shrinkage, its elongation at break and light transmittance are both inferior to those of films made solely of ordinary PPSU resin layers. This indicates that directly adding fillers to modify the PPSU resin significantly impacts the toughness and light transmittance of the film. Therefore, by combining the modified PPSU resin layer with the ordinary PPSU resin layer in a certain proportion to form a three-layer sandwich structure of outer layer-inner layer-outer layer, the influence of the modified filler in the modified PPSU resin layer on the overall toughness and light transmittance of the film can be reduced to a certain extent. It can also improve the tensile strength and reduce the thermal shrinkage rate of the film while maintaining good toughness and light transmittance, which is beneficial to improving the overall performance of the film.

[0123] Based on the data from Examples 1, 4, and Comparative Example 3, and referring to Table 1, it is evident that surface modification of nano-silica with γ-methacryloxypropyltrimethoxysilane significantly improves the tensile strength and elongation at break of the prepared film, while also markedly improving the overall light transmittance. This is likely because surface modification of nano-silica with γ-methacryloxypropyltrimethoxysilane further enhances its hydrophobicity and improves its compatibility and dispersibility in PPSU resin, allowing for uniform dispersion of nano-silica within the modified PPSU resin layer. This not only helps reduce stress concentration during film stretching, improving the toughness and strength of the modified PPSU resin layer, but also reduces the agglomeration of nano-silica within the PPSU resin, thus improving the light transmittance of the modified PPSU resin layer.

[0124] Secondly, nano-silica gel particles were prepared using a sol-gel process, and surface modification was performed using γ-methacryloxypropyltrimethoxysilane during the preparation process. Compared with direct immersion modification of nano-silica, the mechanical properties and light transmittance of the resulting film were further improved. This may be because the nano-silica gel itself has a high specific surface area and porosity, which allows it to be fully modified by γ-methacryloxypropyltrimethoxysilane, improving its modification effect. Moreover, the modified nano-silica gel particles also have excellent optical transparency and low refractive index, which reduces the impact on the transparency of the modified PPSU resin layer compared with ordinary nano-silica particles, thereby improving the overall transparency of the film.

[0125] Based on Examples 4 and 5 and the data in Table 1, it can be seen that by first modifying the surface of the glass fiber and then cutting it into short fibers, compared with unmodified chopped glass fibers, the resulting film can maintain a certain elongation at break and slightly increase its tensile strength, thus further improving the overall mechanical properties of the film. Furthermore, the overall light transmittance of the film is also slightly improved. This may be because when the glass fiber is immersed in sulfuric acid solution, the impurities and oxides on the surface of the glass fiber react with the sulfuric acid and are removed, leaving grooves or depressions on the surface of the glass fiber. Then, when the glass fiber is immersed in γ-methacryloyloxypropyltrimethoxysilane, active chemical groups can be fully introduced into the grooves or depressions on the surface of the glass fiber, further improving the hydrophobicity of the glass fiber surface. This not only improves the compatibility and dispersibility of the chopped glass fiber in PPSU resin, allowing the chopped glass fiber to be uniformly dispersed in the PPSU resin, but also improves the light transmittance of the modified PPSU resin layer, thereby increasing the overall light transmittance of the film. Moreover, PPSU resin can fully penetrate into the grooves or depressions on the surface of chopped glass fibers and form an anchoring structure with the chopped glass fibers, which is beneficial to improving the overall strength of the modified PPSU resin layer, thereby improving the overall tensile strength of the film.

[0126] Based on the data from Examples 5, 6, and 7, and in conjunction with Table 1, it can be seen that when antioxidant 1024 is used alone in the outer modified PPSU resin layer, the overall transparency of the resulting film increases slightly compared to using antioxidant DLTP alone. Furthermore, when antioxidant 1024 and antioxidant DLTP are mixed in a 1:1.5 ratio, the transparency of the outer layer of the film is further improved, thus further increasing the overall transparency of the film. This may be because antioxidant DLTP, as a commonly used auxiliary antioxidant, does not produce good antioxidant and thermal stability effects when used alone, and is therefore often used in combination with other primary antioxidants. Antioxidant 1024, as a hindered phenolic antioxidant with a dual structure of acylhydrazine, can produce a synergistic effect when used in combination with antioxidant DLTP, further improving the antioxidant performance and thermal stability of the modified PPSU resin layer. DLTP can also more effectively neutralize free radicals in the system, slowing down or inhibiting the thermal oxidation of PPSU resin and other additives during processing, thereby improving the overall light transmittance of the film.

[0127] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A three-layer co-extruded transparent PPSU film, characterized in that: It is composed of a three-layer sandwich structure of outer layer-inner layer-outer layer, with the outer layers on both sides being modified PPSU resin layers and the inner layer being a common PPSU resin layer; The modified PPSU resin layer is made from the following raw materials in parts by weight: 89-92 parts PPSU resin, 2.2-4 parts modified nano silica, 5-6 parts chopped glass fiber, and 0.8-1 parts antioxidant. The ordinary PPSU resin layer is made of PPSU resin; The modified nano-silica is silane-modified nano-silica gel particles, and the preparation of the silane-modified nano-silica gel particles includes the following steps: A1. First, add tetraethyl orthosilicate to a 30%-35% ethanol aqueous solution and mix thoroughly. Heat in an oil bath to 35-40℃, then slowly add saturated ammonia water, maintain the temperature and continue stirring for 25-40 minutes. Add an appropriate amount of γ-methacryloyloxypropyltrimethoxysilane and stir to mix. Then let stand for 10-12 hours to obtain modified silica gel. A2. The modified silica gel obtained in step A1 is repeatedly soaked and washed with deionized water until the soaking solution is neutral. Then, it is heated to 95-120℃ and the surface of the gel is thoroughly dried. Then, it is ground and crushed to obtain silane-modified nano silica gel particles. The chopped glass fibers also undergo silane coupling treatment, which includes the following steps: B1. First, immerse the glass fiber in an acidic solution, heat it to 50-60°C, and immerse it for 30-40 minutes. After taking it out, immerse and clean the surface of the glass fiber with deionized water until the cleaning solution is neutral to obtain acid-treated glass fiber. B2. Immerse the acid-treated glass fiber obtained in step B1 in γ-methacryloxypropyltrimethoxysilane for 30-40 minutes. After immersion, remove and dry the fiber, then cut it into short fibers with an average length of 3-5 mm to obtain silane-coupled chopped glass fibers.

2. The three-layer co-extruded transparent PPSU film according to claim 1, characterized in that: In step A1, the volume ratio of the aqueous ethanol solution to the tetraethyl orthosilicate is 100:(1-2), and the volume ratio of the tetraethyl orthosilicate, the saturated ammonia solution, and the γ-methacryloyloxypropyltrimethoxysilane is 1:(20-25):(5-10).

3. The three-layer co-extruded transparent PPSU film according to claim 1, characterized in that: The antioxidants selected are any one or more of antioxidant 1024 and antioxidant DLTP.

4. The three-layer co-extruded transparent PPSU film according to claim 3, characterized in that: The antioxidant is a mixture of antioxidant 1024 and antioxidant DLTP, and the weight ratio of antioxidant 1024 to antioxidant DLTP is 1:(1-1.5).

5. The three-layer co-extruded transparent PPSU film according to claim 1, characterized in that: The thickness ratio of the outer layer, inner layer, and outer layer of the film is (1-1.5):(7-8):(1-1.5).

6. A method for preparing a three-layer co-extruded transparent PPSU film, used to prepare the three-layer co-extruded transparent PPSU film according to any one of claims 1-5, characterized in that: S1. First, thoroughly mix PPSU resin with modified nano-silica, heat to 130-145℃ and dry for 4-6 hours. Then, mix the dried PPSU resin, modified nano-silica, chopped glass fiber and antioxidant in proportion, granulate, extrude, and then heat to 130-145℃ again and dry for 4-6 hours to obtain modified PPSU resin granules. S2. Modified PPSU resin granules are fed into extruder A, and PPSU resin is fed into extruder B. Extruder A and extruder B are extruded simultaneously. Then, extruder A distributes the modified PPSU resin granule melt evenly into the upper and lower flow channels according to the thickness ratio through the die distributor. Extruder B distributes the PPSU resin melt into the middle flow channel through the die distributor. The three layers of melt are simultaneously extruded through the co-extrusion die and cast into a film to obtain a three-layer co-extruded PPSU film. S3. Measure the film thickness uniformity online. After the film cools and sets, it is wound up to obtain a three-layer co-extruded PPSU film roll with uniform thickness.

7. The method for preparing a three-layer co-extruded transparent PPSU film according to claim 6, characterized in that: In S1, during the extrusion granulation process of the modified PPSU resin particles, a twin-screw extruder is selected. The temperature of the first zone of the extruder is set to 330-345℃, the temperature of the second to fifth zones is set to 335-345℃, the die temperature is set to 340-345℃, and the extruder speed is 40-45 r / min.

8. The method for preparing a three-layer co-extruded transparent PPSU film according to claim 6, characterized in that: In step S2, during the process of the three-layer melt being compoundly extruded through a co-extrusion die and cast into a film, the melt is cast to the first casting roller and the second casting roller after being extruded through the co-extrusion die for traction and stretching to form a film. The temperature of the co-extrusion die is 345-355°C, the temperature of the first casting roller is 140-145°C, the temperature of the second casting roller is 135-145°C, and the rotational speed ratio of the first casting roller to the second casting roller is 1:(1.025-1.03).