ETFE films formed by blown film forming, their preparation methods and applications

Abstract

This invention belongs to the field of ETFE film technology, specifically relating to a blown ETFE film for the front panel of a thin-film battery and its preparation method. The raw materials include the following components: ETFE, silane coupling agent-modified nano-silica, and aluminum oxide. The silane coupling agent-modified nano-silica is added to the other materials after being mixed in a twin-screw extruder, then extruded using a single-screw extruder, and finally formed by a blown film machine. The technical solution provided by this invention controls the moisture content and bubble generation in the material during blown film production by adding different hygroscopic agents in stages and by venting the mixture again using a single-screw extruder after mixing, thus ensuring the surface smoothness of the product and improving the film's light transmittance.

Description

Technical Field

[0001] This invention belongs to the field of ETFE thin film technology, specifically relating to a blown ETFE thin film for the front panel of a thin-film battery and its preparation method. Background Technology

[0002] The weight of photovoltaic modules is a major challenge. The main challenge in lightweight photovoltaic modules is how to replace the glass front panel while maintaining mechanical stability and weather resistance. Compared to crystalline silicon cells, thin-film cells are lighter and thinner, and their lightweight modules typically use flexible substrates and polymer front panels as durable insulating materials.

[0003] As the outer layer material that is directly in contact with solar radiation in thin-film batteries, it needs to meet numerous performance requirements, including durability, UV resistance, high light transmittance, long-lasting UV blocking, mechanical toughness, abrasion resistance, chemical resistance, excellent adhesion, easy cleaning, lightweight, and flexibility.

[0004] ETFE (ethylene-tetrafluoroethylene copolymer) film material has excellent light transmittance and is known as "soft glass". It is lightweight, only 1% of the weight of glass of the same size; it has good toughness, high tensile strength, and is not easily torn, with an elongation of more than 400%; it has a relatively high fluorine content, so it has strong weather resistance, chemical corrosion resistance and self-cleaning properties, which makes it particularly suitable for the requirements of thin-film battery front panel materials.

[0005] However, ETFE film materials require relatively high processing temperatures and are currently mainly obtained by melting ETFE particles at high temperatures and then extruding them. They can be used for building roofing or wall materials. If ETFE is used as the front panel of a thin-film battery, it needs to undergo biaxial stretching and other processes after extrusion, making parameter control difficult. Therefore, blown film forming, which has higher production efficiency, is more ideal. Moisture in the material easily forms bubbles during blown film forming, affecting the film's flatness and thus reducing light transmittance. Summary of the Invention

[0006] This invention provides a blown ETFE film, its preparation method, and its application, in order to solve the problem of air bubbles easily generated during the blown ETFE film process.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: the ETFE film formed by blown film formation includes the following components in its raw materials: ETFE, silane coupling agent modified nano-silica and aluminum oxide; the silane coupling agent modified nano-silica is added to other materials after being mixed in a twin-screw extruder, then extruded by a single-screw extruder, and finally formed by a blown film machine.

[0008] In the composition, alumina and silane coupling agent-modified nano-silica can effectively absorb moisture from the material, minimizing the formation of bubbles during film formation. During mixing in the twin-screw extruder, the relatively stable nano-alumina at high temperatures absorbs moisture and removes water. However, the silane coupling agent-modified nano-silica is prone to decomposition and inactivation upon prolonged heating; therefore, it is not added during the initial mixing stage. The material is then added during the single-screw extruder process, where the relatively stable alumina absorbs moisture and removes water. The single-screw extruder can simultaneously mix the silane coupling agent-modified nano-silica with the material and expel as much gas as possible from the material, preventing bubble formation during film blowing.

[0009] Optionally, the silane coupling agent in the silane coupling agent modified nano-silica is KH550 (γ-aminopropyltriethoxysilane).

[0010] Optionally, the aluminum oxide is nano-aluminum oxide prepared by gas-phase synthesis.

[0011] Vaporized nano-alumina can reduce polymer crystallinity and improve chain mobility, which is beneficial to the light transmittance and film-forming properties of the membrane.

[0012] Optionally, the raw materials also include UV absorbers and antioxidants.

[0013] Optionally, the UV absorber is a triazine UV absorber, and the antioxidant is a hindered phenolic antioxidant.

[0014] The present invention also provides a method for preparing the above-mentioned blown film ETFE film, which includes the following steps:

[0015] S1: Weigh the components of the raw material according to the following mass ratio and set aside:

[0016] ETFE 70-90 units

[0017] 1-2 parts of silane coupling agent modified nano-silica

[0018] 1-2 parts of aluminum oxide;

[0019] S2: Mix all components except for the silane coupling agent-modified nano-silica in a twin-screw extruder;

[0020] S3: The product after mixing in the twin-screw extruder is introduced into the single-screw extruder for exhaust, and the silane coupling agent modified nano-silica is fed into the single-screw extruder;

[0021] S4: The product exported from the single screw extruder is pumped into the blown film machine via a high-pressure metering pump for blown film extrusion.

[0022] Optionally, the temperature settings of zones 1-9 in the twin-screw extruder are 200℃, 220℃, 320℃, 325℃, 330℃, 335℃, 340℃, 350℃, and 350℃, respectively.

[0023] Optionally, the temperatures in each zone of the single-screw extruder are 200-220℃, 240-270℃, 270-290℃, 290-310℃, 300-320℃, and 280-300℃, respectively, and the screw speed is 50-120 rpm.

[0024] Optionally, after the film bubble is formed, it is sequentially pulled and wound by multiple sets of rollers. During the pulling process, the temperature of the multiple sets of rollers is controlled to decrease in a gradient between 40-200℃.

[0025] The present invention also provides a solar thin-film battery, which includes a front panel layer, an encapsulation film layer, a metallized circuit layer, a thin-film battery substrate layer, an encapsulation film layer and a flexible substrate layer bonded together in sequence, wherein the front panel layer is the ETFE film formed by the above-mentioned blown film.

[0026] The technical solution provided by this invention controls the moisture content and bubble generation in the material during blown film production by adding different hygroscopic agents in stages and venting the mixture again through a single-screw extruder after mixing. This ensures the smoothness of the product surface and improves the light transmittance of the film. Detailed Implementation

[0027] For ease of understanding, the blown film ETFE film, its preparation method, and its application are described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] A solar thin-film battery includes a front panel layer, an encapsulating film layer, a metallized circuit layer, a thin-film battery substrate layer, an encapsulating film layer, and a flexible substrate layer, which are sequentially bonded together. The front panel layer is an ETFE film formed by blown film.

[0029] The blown ETFE film is prepared using the following method:

[0030] S1: Weigh the components of the raw material according to the following mass ratio and set aside:

[0031] ETFE 75-90 units

[0032] 1-2 parts of KH550 modified micronized silica

[0033] 3-5 parts organic UV absorber;

[0034] 1-2 parts of vapor-phase nano-alumina;

[0035] Antioxidant 0.1-1 part.

[0036] Among them, ETFE is 3M Dyneon's ET 6235Z, abbreviated as ETFE; KH550 modified micron silica (Chenguang KH550), abbreviated as KH-S; organic UV absorber is BASF TINUVIN 405, abbreviated as 405; fumed nano alumina is Degussa AEROXIDE Alu C, abbreviated as Alu C; and antioxidant is BASF Irganox 1076, abbreviated as 1076.

[0037] S2: ETFE, 405, Alu C and 1076 are fed into a twin-screw extruder for mixing. The temperature settings of zones 1-9 in the twin-screw extruder are 200℃, 220℃, 320℃, 325℃, 330℃, 335℃, 340℃, 350℃ and 350℃ respectively.

[0038] S3: The product after mixing in the twin-screw extruder is introduced into the exhaust gas of the single-screw extruder, and the silane coupling agent modified nano-silica is added into the single-screw extruder. The temperatures of each zone in the single-screw extruder are 200℃, 250℃, 280℃, 300℃, 310℃, and 290℃ respectively, and the screw speed is 65 rpm.

[0039] S4: The product exported from the single-screw extruder is pumped into a blown film extruder via a metering pump. The metering pump is a high-pressure metering pump, with pressure controlled at 6-12 MPa. The die head temperature of the blown film extruder is controlled at approximately 320°C. The die core is integrally formed, avoiding gaps and air bubbles between multiple segments that could reduce flatness. More importantly, after the film bubble is formed, it is sequentially drawn and wound by multiple sets of rollers. The drawing process includes at least three sets of temperature-controlled rollers, each set including rollers rotating in opposite directions. The film passes between two rollers. The medium temperature of the first set of rollers is controlled at 180-200°C, the second set at 100-120°C, and the third set below 100°C, preferably 50-70°C. Gradient cooling ensures smooth film drawing and, more importantly, uniform temperature. Rapid cooling also reduces the crystallinity of ETFE, ensuring light transmittance.

[0040] Examples 1-5

[0041] The preparation process is the same, the main difference lies in the specific amount of each component raw material used. For details of each component by weight, please refer to Table 1.

[0042] Table 1

[0043]

[0044] Comparative Example 1

[0045] The difference from Example 1 is that the KH-S is added at the beginning along with other components, and there is no single-screw extruder venting stage.

[0046] Comparative Example 2

[0047] The difference from Example 1 is that Alu C is replaced with ordinary ultrafine alumina 1344-28-1 produced by Shanghai Yuanjiang Chemical.

[0048] Comparative Example 3

[0049] The difference from Example 1 is that KH-S was not added and there was no single-screw extruder venting stage.

[0050] Performance testing

[0051] 1. Elongation at break: 911 kWh / m 2 The elongation at break in the TD direction was tested under ultraviolet light irradiation.

[0052] 2. Transmittance: Measured using a spectrophotometer.

[0053] 3. Haze: Detected by Sansi 3nh HG60

[0054] 4. Appearance: The appearance of the material was observed after 2000 hours at 85℃ and 85% humidity.

[0055] The films prepared in Examples 1-5 and Comparative Examples 1-3 were tested for elongation at break, transmittance, haze, and appearance, respectively. The test results are shown in Table 2.

[0056] Table 2

[0057]

[0058] By using the same components and processes in Examples 1-5, but with different component contents, the test data shows that the thin film in the above examples can meet the performance requirements as a solar front panel.

[0059] In Comparative Example 1, the KH550 modified micron silica was compounded by a twin-screw extruder, which led to decomposition and failure. As a result, air bubbles were present in the blown film, the light transmittance was reduced and small molecules were precipitated.

[0060] In Comparative Example 2, ordinary ultrafine alumina was used. Although it also has the function of absorbing moisture, the light transmittance was still reduced. It is speculated that the crystallinity of the film was higher after the addition compared with fumed alumina.

[0061] In Comparative Example 3, no KH550 modified micronized silica was added, and the exhaust gas was not vented by single-screw extrusion after twin-screw extrusion. Therefore, the light transmittance was reduced, which is presumably due to the residual moisture and gas causing a decrease in smoothness.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ETFE film produced by blown film forming, characterized in that, The method for preparing the blown ETFE film includes the following steps: S1: Weigh the components of the raw material according to the following mass ratio and set aside: ETFE 70-90 units 1-2 parts of silane coupling agent modified nano-silica 1-2 parts of aluminum oxide; S2: Mix all components except for the silane coupling agent-modified nano-silica in a twin-screw extruder; S3: The product after mixing in the twin-screw extruder is introduced into the single-screw extruder for exhaust, and the silane coupling agent modified nano-silica is fed into the single-screw extruder; S4: The product discharged from the single screw extruder is pumped into the blown film machine via a high-pressure metering pump for blown film extrusion; The aluminum oxide is nano-aluminum oxide prepared by gas-phase synthesis. The temperatures in each zone of the single-screw extruder are 200-220℃, 240-270℃, 270-290℃, 290-310℃, 300-320℃, and 280-300℃, respectively, and the screw speed is 50-120 rpm. After the film bubble is formed, it is pulled and wound up by multiple sets of rollers in sequence. During the pulling process, the temperature of the multiple sets of rollers is controlled to decrease in a gradient between 40-200℃.

2. The blown ETFE film according to claim 1, characterized in that, The silane coupling agent in the silane coupling agent modified nano-silica is KH550.

3. The blown ETFE film according to claim 1, characterized in that, The raw materials also include UV absorbers and antioxidants.

4. The blown ETFE film according to claim 3, characterized in that, The UV absorber is a triazine UV absorber, and the antioxidant is a hindered phenolic antioxidant.

5. A method for preparing the blown ETFE film according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Weigh the components of the raw material according to the following mass ratio and set aside: ETFE 70-90 units 1-2 parts of silane coupling agent modified nano-silica 1-2 parts of aluminum oxide; S2: Mix all components except for the silane coupling agent-modified nano-silica in a twin-screw extruder; S3: The product after mixing in the twin-screw extruder is introduced into the single-screw extruder for exhaust, and the silane coupling agent modified nano-silica is fed into the single-screw extruder; S4: The product exported from the single screw extruder is pumped into the blown film machine via a high-pressure metering pump for blown film production.

6. The preparation method according to claim 5, characterized in that, The temperature settings for zones 1-9 of the twin-screw extruder are 200℃, 220℃, 320℃, 325℃, 330℃, 335℃, 340℃, 350℃, and 350℃, respectively.

7. A solar thin-film battery, characterized in that, It includes a front panel layer, an encapsulating film layer, a metallized circuit layer, a thin-film battery substrate layer, an encapsulating film layer, and a flexible substrate layer, which are sequentially bonded together. The front panel layer is an ETFE film formed by blown film forming as described in any of claims 1-4.

Images