EVA-based encapsulation adhesive film and preparation method thereof

Abstract

The application belongs to the technical field of high polymer materials, and discloses an EVA packaging adhesive film and a preparation method thereof. The EVA packaging adhesive film has an EVA resin as a base and contains 0.05-0.4wt% of an anti-hydrolysis agent. The preparation method comprises the following steps: melting and blending the EVA resin and the anti-hydrolysis agent to obtain an anti-hydrolysis master batch, mixing the anti-hydrolysis master batch, the EVA resin and other components in the EVA packaging adhesive film except the EVA resin and the anti-hydrolysis agent uniformly, and processing into a film to obtain the EVA packaging adhesive film. The application selects a cyclic multi-carbodiimide with a specific structure and applies it to the EVA packaging adhesive film, so that the EVA packaging adhesive film has more excellent anti-hydrolysis performance than other cyclic multi-carbodiimides, monomeric carbodiimides and polymeric carbodiimides, and can effectively solve the PID phenomenon of the EVA packaging adhesive film in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials and relates to an EVA-type packaging film and a preparation method thereof. Background Art

[0002] During actual use, moisture easily enters the edge of the photovoltaic module, causing the EVA (ethylene vinyl acetate copolymer) encapsulation film to hydrolyze and generate acetic acid. The free H + Will be with glass type Na + Substitution generates a large amount of freely mobile Na + , the Na on the glass surface + Gradually migrate to the surface of the silicon wafer, Na + The presence of concentrated potential reduces the mobility of photogenerated carriers in the silicon wafer, increases the series resistance of the module, and causes a rapid decline in the module's power output. This significant drop in power generation is known as potential-induced degradation (PID), a phenomenon that photovoltaic encapsulation film companies are continuously working to address.

[0003] The current mainstream technologies mainly adopt the following methods:

[0004] (1) Multilayer co-extruded films composed of EVA and POE are designed to reduce the occurrence of PID and its negative impact. POE itself has a low polarity, which makes most areas of this multilayer co-extruded film have better water and vapor barrier properties, thereby reducing the occurrence of PID. However, PID is still prone to occur at the frame of the component, causing corrosion to the solder strip and silver grid. In addition, POE has a low polarity and a lower degree of cross-linking than EVA, which causes the bonding strength to drop rapidly under extreme conditions, reducing the life of the component.

[0005] (2) Neutralizing the acetic acid produced by EVA hydrolysis by filling weakly alkaline inorganic oxides and inorganic hydroxides to form salts. However, this method has great limitations, mainly because inorganic oxides and inorganic hydroxides have poor compatibility with EVA resins. The occurrence of powder agglomeration will significantly affect the transmittance of EVA-type encapsulation films, and thus affect the power generation efficiency. Therefore, a good dispersion process is required to evenly disperse these inorganic powders in EVA-type encapsulation films. Since inorganic substances cannot melt during processing and have a large difference in refractive index with the resin, nano-scale inorganic powders need to be selected for filling to reduce the impact on the transmittance of the film. However, the dispersion of these nanopowders is difficult, resulting in a limited amount of their addition to the film. They exist in the EVA-type encapsulation film in the form of solid fillers and cannot neutralize the acetic acid produced by the hydrolysis of EVA resin in a timely and complete manner. In addition, in order to improve dispersibility, it is usually necessary to surface modify the inorganic oxides and hydroxides, but this will further reduce the reaction sites of the surface active groups of the nanopowders with acetic acid, thereby reducing the neutralization reaction rate. Furthermore, the dispersion properties and neutralization efficiency of these inorganic powders are closely related to their morphology, particle size, and crystal form. Therefore, batch-to-batch performance fluctuations are inevitable, posing a serious challenge to the stability of EVA encapsulation films, which require extremely high optical properties. Furthermore, the water molecules generated by the neutralization of inorganic oxides and hydroxides with acetic acid cannot be effectively removed from the film system, which in turn triggers subsequent hydrolysis.

[0006] (3) Add ion scavengers to reduce Na + One method is to add inorganic nanomaterials with layered structures and use the holes in the layered structure to embed and capture Na + At the same time, the steric effect between the sheets limits the ion transport channel, thereby reducing Na + Aggregation on the surface of the cell. However, this method has the same problems as the method of adding inorganic oxides and hydroxides. Another method is to add organic ion capture materials with complexing and adsorption capabilities to circumvent the problems of inorganic materials. However, due to the low electronegativity of the Na element itself, Na + It is difficult to be fixed by strong chemical bonds. Therefore, this type of complexing and adsorption materials rely more on charge effects to fix Na + , which is relatively weak and non-specific (for example, electrostatic adsorption generated by anions and cations can also be used to adsorb H + effect), which also makes them effective in delaying Na + The effect on migration rate is relatively limited.

[0007] (4) Adding an organic anti-hydrolysis agent. The fundamental cause of the PID phenomenon is the subsequent chain reaction caused by water vapor breaking the EVA ester bond. Therefore, from the source, the component side must solve the problem of water vapor permeation at the edge of the EVA encapsulation film, while the film side needs to avoid or inhibit the hydrolysis of the ester bond.

[0008] (5) Others. Some people have also tried to adjust the formula and dope EVA resin with low VA content as an encapsulation material in order to reduce the total amount of acetic acid groups in the film substrate. However, this approach will obviously reduce the bonding strength of the film. Because when the VA content of EVA resin is low, its main polymer unit becomes PE, and this type of resin is generally considered to be non-photovoltaic grade material. If a large amount of replacement is made, significant performance degradation will occur; and if a small amount is replaced, its anti-PID effect is not obvious.

[0009] Among them, the advantages of method (4) are obvious. The fundamental reason for the PID phenomenon is that water vapor causes the EVA ester bond to break. Adding an organic anti-hydrolysis agent can avoid or inhibit the hydrolysis of the ester bond from the source, thereby effectively reducing the occurrence of the PID phenomenon. The organic anti-hydrolysis agent has better dispersion uniformity and can be evenly dispersed in the EVA encapsulation film, avoiding the adverse effects on the transmittance, and also avoiding the defects that may be caused by inorganic additives.

[0010] Carbodiimide materials, as anti-hydrolysis agents for ester-bonded polymers, have extensively demonstrated their anti-hydrolysis mechanism and effectiveness. These organic anti-hydrolysis agents offer improved dispersion uniformity and minimal impact on light transmittance, thus avoiding the potential drawbacks of inorganic additives. Carbodiimide materials are categorized as monomeric, polymeric, and polycarbodiimides.

[0011] However, while previous attempts have been made to use monomeric and polymeric carbodiimides in EVA encapsulation films, the results have been unsatisfactory, as exemplified by patent CN118185503B. Monomeric carbodiimides, due to their low molecular weight, are prone to migration and, in hot and humid environments, can aggregate within the film, forming agglomerates that affect its appearance. This migration issue limits the upper limit of monomeric carbodiimide addition, preventing its high reactivity from being fully realized in film products and failing to meet product requirements. Polymeric carbodiimides, however, are difficult to control during polymerization due to their high reactivity, resulting in a broad molecular weight distribution. High-molecular-weight polymeric carbodiimides are insufficiently reactive and lack anti-hydrolysis properties. Low-molecular-weight polymeric carbodiimides, due to their already established degree of crosslinking, are prone to excessive crosslinking when used according to normal production processes, rendering them unusable. Furthermore, polymeric carbodiimides with a broad molecular weight distribution are difficult to uniformly distribute within the resin, significantly impacting the light transmittance of EVA encapsulation films and causing unacceptable product quality fluctuations.

[0012] Polycarbodiimides include cyclic, linear, and branched polycarbodiimides. Cyclic polycarbodiimides are characterized by virtually no toxic byproducts, high thermal stability, and high reactivity. However, existing technologies often apply cyclic polycarbodiimides to materials with high processing temperatures, such as polyethylene terephthalate, based on their high thermal stability, or to easily degradable materials, such as polylactic acid, based on their high reactivity. Examples include patent CN102245703B, patent application CN102825773A, patent JP7459998B1, and patent CN113461925B. EVA encapsulation film is an optical device that focuses on the optical effects of the product. The processing temperature of EVA is not high, so no additives are required and it has the characteristics of high thermal stability. The additives have non-toxic by-products that do not affect the suppression of PID phenomena, so no additives are required and it has the characteristics of almost no toxic by-products. This has led to the existing technology never applying cyclic polycarbodiimide to EVA (a different genus from polyethylene terephthalate and polylactic acid) encapsulation film.

[0013] It would be of great practical significance if a cyclic polycarbodiimide with a specific structure could be selected and applied to EVA encapsulation films to overcome the problems existing in the application of monomeric carbodiimides and polymeric carbodiimides in EVA encapsulation films. Summary of the Invention

[0014] The purpose of the present invention is to solve the problems existing in the prior art and to provide an EVA-type encapsulating film and a preparation method thereof.

[0015] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0016] An EVA encapsulation film, the matrix of which is EVA resin, contains 0.05-0.4wt% of an anti-hydrolysis agent, the structural formula of which is as follows:

[0017] .

[0018] The cyclic polycarbodiimide with a specific structure selected in the present invention has achieved unexpected technical effects when applied to EVA encapsulation films, which are specifically reflected in:

[0019] ① When the cyclic polycarbodiimide with a specific structure selected in the present invention is applied to EVA-based encapsulation films, it exhibits better hydrolysis resistance than cyclic polycarbodiimides with other structures.

[0020] ② When the cyclic polycarbodiimide with a specific structure selected in the present invention is applied to EVA-based encapsulation films, it exhibits better hydrolysis resistance than monomeric carbodiimide and polymeric carbodiimide.

[0021] Prior art indicates that, when used to prevent hydrolysis in polyesters, monomeric carbodiimides significantly outperform polycarbodiimides, which in turn outperform polymeric carbodiimides at the same active group concentration. When used to prevent hydrolysis in ultra-high-temperature engineering plastics, due to thermal stability, polymeric carbodiimides significantly outperform polycarbodiimides at the same active group concentration, which in turn outperform monomeric carbodiimides. Based on prior art, it was unexpected that polycarbodiimides (the cyclic polycarbodiimides of a specific structure selected in the present invention) would significantly outperform both monomeric and polymeric carbodiimides at the same active group concentration in preventing hydrolysis in EVA-based encapsulating films.

[0022] ③ When the cyclic polycarbodiimide with a specific structure selected in the present invention is applied to EVA-type encapsulation films, the migration problem existing in monomeric carbodiimide when applied to EVA-type encapsulation films is overcome, because the cyclic polycarbodiimide with a specific structure selected in the present invention has a molecular weight more than doubled compared to monomeric carbodiimide.

[0023] ④ When the cyclic polycarbodiimide with a specific structure selected in the present invention is applied to EVA type encapsulation film, it overcomes the problem that the polymeric carbodiimide has poor anti-hydrolysis effect and affects the transmittance of the EVA type encapsulation film when applied to the EVA type encapsulation film.

[0024] As the preferred technical solution:

[0025] For the EVA encapsulation film as described above, the VA content of the EVA resin is ≥28wt%.

[0026] In the EVA encapsulation film as described above, the content of the anti-hydrolysis agent is 0.1-0.2 wt %.

[0027] The EVA encapsulation film described above further contains 0.05-0.2 wt % of an antioxidant, 0.1-0.4 wt % of a light stabilizer, 0.01-0.2 wt % of an initiator, 0.1-2 wt % of a cross-linking agent, and 0.1-1 wt % of an auxiliary cross-linking agent.

[0028] The EVA encapsulation film as described above, wherein the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate, or mono(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate; the initiator is 2-ethylhexyl tert-butyl peroxycarbonate, tetramethylbutyl 1,1,3,3-peroxyneodecanoate, or dicumyl peroxide; the crosslinker is triallyl isocyanurate, triallyl cyanurate, or trimethyl isocyanurate; and the co-crosslinker is γ-methacryloyloxypropyltrimethoxysilane.

[0029] An EVA encapsulation film as described in any of the above items, the EVA encapsulation film has a thickness of 300-550 mm, a PID attenuation power of 0.75-3.52%, a light transmittance of 90.20-91.96%, a light transmittance of 87.50-90.34% after 2000 hours of humidity and heat aging test, and a yellowness index △YI of 0.23-3.46.

[0030] The present invention also provides a method for preparing an EVA-type encapsulating adhesive film as described in any of the above items, comprising melt-blending an EVA resin and an anti-hydrolysis agent to obtain an anti-hydrolysis masterbatch, uniformly mixing the anti-hydrolysis masterbatch, the EVA resin, and the components of the EVA-type encapsulating adhesive film other than the EVA resin and the anti-hydrolysis agent, and processing the mixture into a film to obtain the EVA-type encapsulating adhesive film.

[0031] The present invention uses a masterbatch method to first prepare an anti-hydrolysis masterbatch, which is then added to form an EVA encapsulating film. The anti-hydrolysis agent selected in the present invention has high activity, a low addition level, and a high melting point. Pre-dispersion through the masterbatch method ensures uniform dispersion of the anti-hydrolysis agent in the EVA resin, effectively suppressing the subsequent hydrolysis chain reaction of the EVA resin. Using a masterbatch to prepare the encapsulating film also reduces dust in the production environment, making it suitable for large-scale continuous processing of encapsulating films and the high requirements for a dust-free environment.

[0032] As the preferred technical solution:

[0033] In the method described above, the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1-20 wt %.

[0034] The process flow of the film-forming method as described above is: mixing and plasticizing in a single-screw extruder → melt extrusion → cast film → winding.

[0035] Beneficial effects:

[0036] (1) The present invention selects a cyclic polycarbodiimide with a specific structure and applies it to EVA type encapsulating adhesive films, which shows better anti-hydrolysis performance than cyclic polycarbodiimides with other structures, monomeric carbodiimides and polymeric carbodiimides, thereby overcoming the migration problem existing in monomeric carbodiimides when applied to EVA type encapsulating adhesive films, as well as the problem that polymeric carbodiimides have poor anti-hydrolysis effect and affect the transmittance of EVA type encapsulating adhesive films when applied to EVA type encapsulating adhesive films.

[0037] (2) The cyclic polycarbodiimide of a specific structure selected in the present invention has a cyclic end-capping structure. When the residue is hydrolyzed, an isocyanate lactone product is generated. The product is non-volatile and therefore does not generate small molecule toxic gases during use, thereby ensuring the stability of the EVA encapsulation film and the reliability of the production environment.

[0038] In existing technologies, both monomeric and polymeric carbodiimides have end-capped structures. During the synthesis process, small amounts of precursors containing isocyanate groups remain. While exerting their hydrolysis resistance, these residues can generate toxic and odorous small volatile isocyanates. This is particularly noticeable during thermal processing, negatively impacting the on-site work environment.

[0039] (3) The cyclic polycarbodiimide of a specific structure selected in the present invention has a fixed molecular formula (amount) and a fixed percentage content of carbodiimide groups equivalent to that of monomeric carbodiimide, which ensures product stability and efficiency during actual use and avoids the problem of removing reaction water caused by the simple use of an alkaline neutralizer.

[0040] (4) The cyclic polycarbodiimide of a specific structure selected in the present invention has a high reaction rate (activity) and a large reaction capacity (carbodiimide content) compared to other carbodiimide anti-hydrolysis agents, so the addition amount is low.

[0041] (5) The cyclic polycarbodiimide with a specific structure selected in the present invention does not produce cross-linking during the process of anti-hydrolysis, and does not affect the pre-cross-linking degree of the EVA encapsulation film.

[0042] (6) The cyclic polycarbodiimide of the specific structure selected in the present invention has a cyclic structure. Based on the molecular tension effect of the cyclic compound, the carbodiimide group in the anti-hydrolysis agent has higher reactivity, and the distribution of reactive sites in the molecular structure is more uniform.

[0043] (7) The present invention uses a cyclic polycarbodiimide of a specific structure as an organic additive, which avoids the problem of product stability fluctuation that occurs when inorganic additives are used in EVA encapsulation films.

[0044] (8) The present invention uses a cyclic polycarbodiimide with a specific structure to inhibit the PID phenomenon of EVA encapsulation films. It is an active protection type. It is based on the internal cause of the PID phenomenon and avoids or inhibits the occurrence of hydrolysis of ester bonds at the end of the EVA encapsulation film. At the same time, it can also be used in combination with passive protection measures such as ion capture agents and alkaline neutralizers in actual production to balance the comprehensive cost and performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Graphs showing appearance defects of the EVA encapsulation film prepared in Example 1 of the present invention before and after aging;

[0046] Figure 2 Graphs showing appearance defects of the EVA encapsulation film prepared in Example 2 of the present invention before and after aging;

[0047] Figure 3 Graphs showing appearance defects of the EVA encapsulation film prepared in Comparative Example 5 of the present invention before and after aging;

[0048] Figure 4 Graphs showing appearance defects of the EVA encapsulation film prepared in Comparative Example 6 of the present invention before and after aging; Figures 1 to 4 In the figure, a is the appearance defect test picture of EVA type encapsulation film before 2000h of humidity and heat aging test, b is the appearance defect test picture of EVA type encapsulation film after 1000h of humidity and heat aging test, and c is the appearance defect test picture of EVA type encapsulation film after 2000h of humidity and heat aging test. DETAILED DESCRIPTION

[0049] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0050] In order to ensure that the properties of the materials used in each embodiment and comparative example are fully disclosed, the manufacturers and brands of the materials are indicated. Products of other manufacturers and brands that meet the requirements of the present invention are also feasible.

[0051] The testing methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0052] Melt index: The hydrolysis-resistant masterbatch prepared in each embodiment and each comparative example was used as a sample, and then the melt index of the sample was measured according to ASTM D1238 standard. The test temperature was 190° C. and the test load was 2.16 kg.

[0053] PID attenuation power: The EVA-based encapsulation films prepared in each embodiment and each comparative example were respectively used as samples, and then the PID attenuation power of the samples was measured with reference to the IEC TS 62804-1 2015 standard.

[0054] Light transmittance: The EVA encapsulation films prepared in each embodiment and each comparative example were used as samples, and the light transmittance of the samples was measured with reference to GB / T 29848-2013 standard.

[0055] Light transmittance after 2000 hours of heat and humidity aging test: The EVA encapsulation films prepared in each embodiment and comparative example were used as samples. The samples were then placed in an environment with a temperature of 85°C and a relative humidity of 85% for 2000 hours. The light transmittance of the aged samples was then measured in accordance with GB / T 29848-2013.

[0056] Yellowness index ΔYI: The EVA encapsulating films prepared in each embodiment and each comparative example were used as samples, and the yellowness index ΔYI of the samples was measured according to GB / T 2409-1980.

[0057] Example 1

[0058] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0059] (1) Preparation of raw materials;

[0060] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0061] EVA resin: manufactured by LG Chem of South Korea, brand EP28025, VA content 28wt%;

[0062] Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0063] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate;

[0064] Initiator: tert-butyl peroxycarbonate-2-ethylhexyl ester;

[0065] Crosslinking agent: triallyl isocyanurate;

[0066] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0067] (2) EVA resin and anti-hydrolysis agent are added to a twin-screw extruder, and after melt extrusion, drawing and pelletizing, an anti-hydrolysis masterbatch with a melt index of 31g / 10min is obtained; wherein the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 20wt%, and the temperature of the first zone of the twin-screw extruder is 70℃, the temperature of the second zone is 155℃, the temperature of the third zone is 155℃, the temperature of the fourth zone is 130℃, the temperature of the fifth zone is 100℃, the temperature of the sixth zone is 100℃, the temperature of the seventh zone is 110℃, and the temperature of the eighth zone is 120℃;

[0068] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0069] The final EVA encapsulation film is composed of an EVA resin as the matrix, and the EVA encapsulation film is composed of 0.2 wt% of an anti-hydrolysis agent, 0.1 wt% of an antioxidant, 0.2 wt% of a light stabilizer, 0.1 wt% of an initiator, 0.5 wt% of a cross-linking agent, 0.3 wt% of a co-cross-linking agent, and the balance of EVA resin.

[0070] The thickness of the EVA encapsulation film is 380mm, the PID attenuation power is 0.75%, the transmittance is 91.84%, the transmittance after 2000h of the humidity and heat aging test is 90.34%, and the yellowness index △YI is 0.23.

[0071] Comparative Example 1

[0072] A method for preparing an EVA encapsulating film is basically the same as that of Example 1, except that the anti-hydrolysis agent in step (1) is replaced by an anti-hydrolysis agent (monomeric carbodiimide, manufactured by Suzhou Keshengtong New Material Technology Co., Ltd., with the brand name Bio-SAH 362);

[0073] Since monomeric carbodiimide volatilizes severely during extrusion granulation, it is impossible to produce hydrolysis-resistant masterbatch, which also makes steps (2) and (3) impossible to carry out.

[0074] Comparative Example 2

[0075] A method for preparing an EVA encapsulating film is basically the same as that of Example 1, except that the anti-hydrolysis agent in step (1) is replaced by an anti-hydrolysis agent (polymeric carbodiimide, manufactured by Shanghai Langyi Functional Materials Co., Ltd., with the brand name Hymax 213);

[0076] Since the polymeric carbodiimide is severely cross-linked during extrusion granulation, it is impossible to produce a hydrolysis-resistant masterbatch, which also makes steps (2) and (3) impossible to carry out.

[0077] Comparative Example 3

[0078] A method for preparing an EVA encapsulating film is basically the same as that in Example 1, except that the anti-hydrolysis agent in step (1) is replaced by an anti-hydrolysis agent (linear biscarbodiimide, manufactured by Shanghai Langyi Functional Materials Co., Ltd., with a structural formula of ); The anti-hydrolysis agent in steps (2) and (3) adopts the anti-hydrolysis agent of this comparative example;

[0079] The melt index of the hydrolysis-resistant masterbatch obtained in step (2) is 23 g / 10 min;

[0080] The anti-hydrolysis masterbatch in step (3) adopts the anti-hydrolysis masterbatch prepared in this comparative example.

[0081] The final EVA encapsulation film is basically the same as Example 1, except that the PID attenuation power of the EVA encapsulation film is 4.52%, the transmittance is 91.29%, the transmittance after 2000h of the wet heat aging test is 87.89%, and the yellowness index △YI is 2.62.

[0082] Comparing Comparative Example 3 with Example 1, it can be seen that the PID attenuation power of the EVA-based encapsulation film prepared in this comparative example is significantly improved. The transmittance after 2000 hours of the damp heat aging test decreases more significantly than the transmittance before aging, and the yellowness index ΔYI increases. This is because the linear biscarbodiimide, while having comparable reactivity and being well dispersed in the film, has a smaller molecular weight than the cyclic carbodiimide of the present invention, and its linear structure is more easily migrated during the aging test, resulting in a significant decrease in the PID attenuation power and transmittance after aging, and a decrease in anti-yellowing performance.

[0083] Comparative Example 4

[0084] A method for preparing an EVA encapsulating film is basically the same as that in Example 1, except that the anti-hydrolysis agent in step (1) is replaced by an anti-hydrolysis agent (cyclic biscarbodiimide, manufactured by Shanghai Langyi Functional Materials Co., Ltd., with a structural formula of ); The anti-hydrolysis agent in steps (2) and (3) adopts the anti-hydrolysis agent of this comparative example;

[0085] The melt index of the hydrolysis-resistant masterbatch obtained in step (2) is 27 g / 10 min;

[0086] The anti-hydrolysis masterbatch in step (3) adopts the anti-hydrolysis masterbatch prepared in this comparative example.

[0087] The final EVA encapsulation film is basically the same as Example 1, except that the PID attenuation power of the EVA encapsulation film is 7.63%, the transmittance is 90.70%, the transmittance after 2000h of the wet heat aging test is 85.82%, and the yellowness index △YI is 16.74.

[0088] By comparing Comparative Example 4 with Example 1, it can be seen that the PID attenuation power of the EVA-based encapsulation film prepared in this comparative example is greatly improved, the transmittance attenuation after 2000 hours of the damp heat aging test is also greater, and the yellowness index △YI is greatly improved. This is because the cyclic biscarbodiimide selected in this comparative example has a larger molecular weight, a large amount of benzene ring conjugated structure, and poor compatibility with the EVA resin. It is easy to agglomerate in EVA, resulting in low reaction activity in the EVA system, resulting in an increase in the PID attenuation power, a greater transmittance attenuation after 2000 hours of the damp heat aging test, and a significant increase in the yellowness index △YI.

[0089] Example 2

[0090] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0091] (1) Preparation of raw materials;

[0092] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0093] EVA resin: manufactured by LG Chem of South Korea, brand EP28025, VA content 28wt%;

[0094] Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0095] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate;

[0096] Initiator: tert-butyl peroxycarbonate-2-ethylhexyl ester;

[0097] Crosslinking agent: triallyl isocyanurate;

[0098] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0099] (2) EVA resin and anti-hydrolysis agent are added to a twin-screw extruder, and after melt extrusion, drawing and pelletizing, an anti-hydrolysis masterbatch with a melt index of 28g / 10min is obtained; wherein the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1wt%, and the temperature of the first zone of the twin-screw extruder is 70°C, the temperature of the second zone is 155°C, the temperature of the third zone is 155°C, the temperature of the fourth zone is 130°C, the temperature of the fifth zone is 100°C, the temperature of the sixth zone is 100°C, the temperature of the seventh zone is 110°C, and the temperature of the eighth zone is 120°C;

[0100] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0101] The final EVA encapsulation film is composed of an EVA resin as the matrix, and the EVA encapsulation film is composed of 0.05 wt% of an anti-hydrolysis agent, 0.1 wt% of an antioxidant, 0.2 wt% of a light stabilizer, 0.1 wt% of an initiator, 0.5 wt% of a cross-linking agent, 0.3 wt% of a co-cross-linking agent, and the balance of EVA resin.

[0102] The thickness of the EVA encapsulation film is 380mm, the PID attenuation power is 0.92%, the transmittance is 91.96%, the transmittance after 2000h of the humidity and heat aging test is 89.71%, and the yellowness index △YI is 0.69.

[0103] Comparative Example 5

[0104] A method for preparing an EVA encapsulating film is basically the same as that in Example 2, except that the anti-hydrolysis agent in step (1) is replaced by an anti-hydrolysis agent (monomeric carbodiimide, manufactured by Suzhou Keshengtong New Material Technology Co., Ltd., with the brand name Bio-SAH 362); and the anti-hydrolysis agent in steps (2) and (3) is the anti-hydrolysis agent of this comparative example.

[0105] The melt index of the hydrolysis-resistant masterbatch obtained in step (2) is 28 g / 10 min;

[0106] The anti-hydrolysis masterbatch in step (3) adopts the anti-hydrolysis masterbatch prepared in this comparative example.

[0107] The final EVA encapsulation film is basically the same as Example 2, except that the PID attenuation power of the EVA encapsulation film is 5.68%, the transmittance is 93.01%, the transmittance after 2000h of the wet heat aging test is 86.17%, and the yellowness index △YI is 5.86.

[0108] Comparing Comparative Example 5 with Example 2, it can be seen that the PID attenuation power of the EVA-type encapsulation film prepared in this comparative example is significantly improved. Although the initial transmittance is high, the transmittance after 2000 hours of the wet heat aging test decreases significantly compared to the initial transmittance, and the yellowness index △YI changes even more. This is because the monomeric anti-hydrolysis agent content in this comparative example is low, and its high reactivity also allows it to be well dispersed in the film. However, its small molecular weight makes it easy to migrate. In a wet heat environment, it will gather in the film to form agglomerates, which also causes its migration and agglomeration to be serious in the aging test, resulting in an increase in PID attenuation power and poor performance such as transmittance and yellowing after aging.

[0109] Comparative Example 6

[0110] A method for preparing an EVA encapsulating film is basically the same as that in Example 2, except that the anti-hydrolysis agent in step (1) is replaced by an anti-hydrolysis agent (polymeric carbodiimide, manufactured by Shanghai Langyi Functional Materials Co., Ltd., with the brand name Hymax 213); and the anti-hydrolysis agent in steps (2) and (3) uses the anti-hydrolysis agent of this comparative example.

[0111] The melt index of the hydrolysis-resistant masterbatch obtained in step (2) is 22 g / 10 min;

[0112] The anti-hydrolysis masterbatch in step (3) adopts the anti-hydrolysis masterbatch prepared in this comparative example.

[0113] The final EVA encapsulation film is basically the same as Example 2, except that the PID attenuation power of the EVA encapsulation film is 15.36%, the transmittance is 90.20%, the transmittance after 2000h of the wet heat aging test is 86.64%, and the yellowness index △YI is 6.57.

[0114] By comparing Comparative Example 6 with Example 2, it can be seen that the PID attenuation power of the EVA-based encapsulation film prepared in this comparative example is significantly improved, the transmittance after 2000 hours of the wet heat aging test is more reduced than the transmittance before aging, and the yellow index △YI changes more. This is because the polymeric anti-hydrolysis agent will undergo thermal cross-linking, resulting in the formation of a partial cross-linked structure when preparing the anti-hydrolysis masterbatch, causing the loss of reactive groups. At the same time, the molecular weight is larger after cross-linking, and the polymeric anti-hydrolysis agent has poor compatibility with EVA and lower reaction activity, which ultimately leads to an increase in PID attenuation power, a decrease in transmittance after 2000 hours of the wet heat aging test, and an increase in the yellow index △YI.

[0115] The EVA packaging films prepared in Example 1, Example 2, Comparative Example 5 and Comparative Example 6 were placed in an environment with a temperature of 85°C and a relative humidity of 85% for 2000 hours, and then the appearance defects of the aged EVA packaging films were checked by an EL detector. The results are as follows: Figures 1 to 4 As shown in the figure, it can be seen that compared with the EVA encapsulation films of Example 1 and Example 2, the EVA encapsulation films in Comparative Examples 5 and 6 have more black defects after 2000h of the wet heat aging test. The more defects there are, the more failed parts there are, the hydrolysis resistance is significantly reduced, and the yellowness index △YI increases.

[0116] Example 3

[0117] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0118] (1) Preparation of raw materials;

[0119] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0120] EVA resin: manufactured by LG Chem of South Korea, brand EP28025, VA content 28wt%;

[0121] Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0122] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate;

[0123] Initiator: tert-butyl peroxycarbonate-2-ethylhexyl ester;

[0124] Crosslinking agent: triallyl isocyanurate;

[0125] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0126] (2) EVA resin and anti-hydrolysis agent are added to a twin-screw extruder, and after melt extrusion, drawing and pelletizing, an anti-hydrolysis masterbatch with a melt index of 28g / 10min is obtained; wherein the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1wt%, and the temperature of the first zone of the twin-screw extruder is 70°C, the temperature of the second zone is 155°C, the temperature of the third zone is 155°C, the temperature of the fourth zone is 130°C, the temperature of the fifth zone is 100°C, the temperature of the sixth zone is 100°C, the temperature of the seventh zone is 110°C, and the temperature of the eighth zone is 120°C;

[0127] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0128] The final EVA encapsulation film is composed of an EVA resin as the matrix, and the EVA encapsulation film is composed of 0.05wt% of an anti-hydrolysis agent, 0.05wt% of an antioxidant, 0.4wt% of a light stabilizer, 0.05wt% of an initiator, 0.6wt% of a cross-linking agent, 0.1wt% of a co-cross-linking agent, and the balance of EVA resin.

[0129] The thickness of the EVA encapsulation film is 380mm, the PID attenuation power is 1.84%, the transmittance is 91.56%, the transmittance after 2000h of the heat and humidity aging test is 87.56%, and the yellowness index △YI is 2.07.

[0130] Example 4

[0131] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0132] (1) Preparation of raw materials;

[0133] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0134] EVA resin: manufactured by LG Chem of South Korea, brand EP28025, VA content 28wt%;

[0135] Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0136] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate;

[0137] Initiator: tert-butyl peroxycarbonate-2-ethylhexyl ester;

[0138] Crosslinking agent: triallyl isocyanurate;

[0139] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0140] (2) EVA resin and anti-hydrolysis agent are added to a twin-screw extruder, and after melt extrusion, drawing and pelletizing, an anti-hydrolysis masterbatch with a melt index of 28g / 10min is obtained; wherein the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1wt%, and the temperature of the first zone of the twin-screw extruder is 70°C, the temperature of the second zone is 155°C, the temperature of the third zone is 155°C, the temperature of the fourth zone is 130°C, the temperature of the fifth zone is 100°C, the temperature of the sixth zone is 100°C, the temperature of the seventh zone is 110°C, and the temperature of the eighth zone is 120°C;

[0141] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0142] The final EVA encapsulation film is composed of an EVA resin matrix, 0.05 wt% of an anti-hydrolysis agent, 0.1 wt% of an antioxidant, 0.1 wt% of a light stabilizer, 0.1 wt% of an initiator, 0.4 wt% of a cross-linking agent, 0.5 wt% of a co-cross-linking agent, and the balance of EVA resin.

[0143] The thickness of the EVA encapsulation film is 380mm, the PID attenuation power is 2.19%, the transmittance is 91.37%, the transmittance after 2000h of the heat and humidity aging test is 89.24%, and the yellowness index △YI is 1.6.

[0144] Example 5

[0145] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0146] (1) Preparation of raw materials;

[0147] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0148] EVA resin: manufacturer is LG Chem, brand name is EA33045, VA content is 33wt%;

[0149] Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0150] Light stabilizer: bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate;

[0151] Initiator: tert-butyl peroxycarbonate-2-ethylhexyl ester;

[0152] Crosslinking agent: triallyl isocyanurate;

[0153] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0154] (2) EVA resin and anti-hydrolysis agent are added to a twin-screw extruder, and after melt extrusion, drawing and pelletizing, an anti-hydrolysis masterbatch with a melt index of 28g / 10min is obtained; wherein the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1wt%, and the temperature of the first zone of the twin-screw extruder is 70°C, the temperature of the second zone is 155°C, the temperature of the third zone is 155°C, the temperature of the fourth zone is 130°C, the temperature of the fifth zone is 100°C, the temperature of the sixth zone is 100°C, the temperature of the seventh zone is 110°C, and the temperature of the eighth zone is 120°C;

[0155] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0156] The final EVA encapsulation film is composed of an EVA resin as the matrix, and the EVA encapsulation film is composed of 0.05 wt% of an anti-hydrolysis agent, 0.1 wt% of an antioxidant, 0.2 wt% of a light stabilizer, 0.1 wt% of an initiator, 0.5 wt% of a cross-linking agent, 0.3 wt% of a co-cross-linking agent, and the balance of EVA resin.

[0157] The thickness of the EVA encapsulation film is 380mm, the PID attenuation power is 3.18%, the transmittance is 91.46%, the transmittance after 2000h of the heat and humidity aging test is 87.5%, and the yellowness index △YI is 1.53.

[0158] Example 6

[0159] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0160] (1) Preparation of raw materials;

[0161] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0162] EVA resin: manufactured by LG Chem of South Korea, brand EP28025, VA content 28wt%;

[0163] Antioxidant: β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate;

[0164] Light stabilizer: bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate;

[0165] Initiator: 1,1,3,3-tetramethylbutyl peroxyneodecanoate;

[0166] Cross-linking agent: triallyl cyanurate;

[0167] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0168] (2) Adding EVA resin and anti-hydrolysis agent into a twin-screw extruder, and obtaining anti-hydrolysis masterbatch with a melt index of 30g / 10min after melt extrusion, drawing and pelletizing; wherein the content of anti-hydrolysis agent in the anti-hydrolysis masterbatch is 10wt%, and the temperature of the first zone of the twin-screw extruder is 70℃, the temperature of the second zone is 155℃, the temperature of the third zone is 155℃, the temperature of the fourth zone is 130℃, the temperature of the fifth zone is 100℃, the temperature of the sixth zone is 100℃, the temperature of the seventh zone is 110℃, and the temperature of the eighth zone is 120℃;

[0169] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0170] The final EVA encapsulation film is composed of an EVA resin matrix, 0.4 wt% of an anti-hydrolysis agent, 0.2 wt% of an antioxidant, 0.4 wt% of a light stabilizer, 0.2 wt% of an initiator, 2 wt% of a cross-linking agent, 1 wt% of a co-cross-linking agent, and the balance of EVA resin.

[0171] The thickness of the EVA encapsulation film is 300mm, the PID attenuation power is 3.52%, the transmittance is 90.25%, the transmittance after 2000h of the wet heat aging test is 88.52%, and the yellowness index △YI is 3.46.

[0172] Example 7

[0173] A method for preparing an EVA-based encapsulation film comprises the following steps:

[0174] (1) Preparation of raw materials;

[0175] Anti-hydrolysis agent: cyclic biscarbodiimide (manufacturer: Teijin Limited, Japan, brand: TCC FP10M), structural formula: ;

[0176] EVA resin: manufactured by LG Chem of South Korea, brand EP28025, VA content 28wt%;

[0177] Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;

[0178] Light stabilizer: mono(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate;

[0179] Initiator: dicumyl peroxide;

[0180] Cross-linking agent: trimethyl isocyanurate;

[0181] Cross-linking agent: γ-methacryloxypropyltrimethoxysilane;

[0182] (2) EVA resin and anti-hydrolysis agent are added to a twin-screw extruder, and after melt extrusion, drawing and pelletizing, an anti-hydrolysis masterbatch with a melt index of 28g / 10min is obtained; wherein the content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1wt%, and the temperature of the first zone of the twin-screw extruder is 70°C, the temperature of the second zone is 155°C, the temperature of the third zone is 155°C, the temperature of the fourth zone is 130°C, the temperature of the fifth zone is 100°C, the temperature of the sixth zone is 100°C, the temperature of the seventh zone is 110°C, and the temperature of the eighth zone is 120°C;

[0183] (3) After the anti-hydrolysis masterbatch, EVA resin, anti-hydrolysis agent, antioxidant, light stabilizer, initiator, cross-linking agent and auxiliary cross-linking agent are uniformly mixed, they are processed into films in accordance with the process flow of "single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding" to obtain EVA encapsulation film; wherein, the temperature of the first zone of the single-screw extruder is 80°C, the temperature of the second zone is 88°C, the temperature of the third zone is 85°C, the temperature of the fourth zone is 85°C, and the temperature of the fifth zone is 85°C.

[0184] The final EVA encapsulation film is composed of 0.1 wt% of an anti-hydrolysis agent, 0.1 wt% of an antioxidant, 0.1 wt% of a light stabilizer, 0.01 wt% of an initiator, 0.1 wt% of a cross-linking agent, 0.3 wt% of a co-cross-linking agent, and the balance of EVA resin.

[0185] The thickness of the EVA encapsulation film is 550mm, the PID attenuation power is 0.84%, the transmittance is 90.2%, the transmittance after 2000h of the humidity and heat aging test is 87.52%, and the yellowness index △YI is 2.95.

Claims

1. An EVA-based encapsulation film, the matrix of which is EVA resin, characterized in that: Contains 0.05-0.4wt% of an anti-hydrolysis agent, the structural formula of the anti-hydrolysis agent is as follows: 。 2. An EVA-based encapsulation film according to claim 1, characterized in that: The VA content of EVA resin is ≥28wt%.

3. The EVA encapsulation film according to claim 1, characterized in that: The content of the anti-hydrolysis agent is 0.1-0.2wt%.

4. The EVA encapsulation film according to claim 1, characterized in that: The invention also contains 0.05-0.2 wt % of an antioxidant, 0.1-0.4 wt % of a light stabilizer, 0.01-0.2 wt % of an initiator, 0.1-2 wt % of a cross-linking agent and 0.1-1 wt % of an auxiliary cross-linking agent.

5. The EVA encapsulation film according to claim 4, characterized in that: The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate or mono(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate; the initiator is 2-ethylhexyl tert-butyl peroxycarbonate, tetramethylbutyl 1,1,3,3-peroxyneodecanoate or diisopropylbenzene peroxide; the crosslinking agent is triallyl isocyanurate, triallyl cyanurate or trimethyl isocyanurate; and the auxiliary crosslinking agent is γ-methacryloyloxypropyltrimethoxysilane.

6. The EVA encapsulation film according to any one of claims 1 to 5, characterized in that: The thickness of EVA encapsulation film is 300-550mm, the PID attenuation power is 0.75-3.52%, the transmittance is 90.20-91.96%, the transmittance after 2000h of humidity and heat aging test is 87.50-90.34%, and the yellowness index △YI is 0.23-3.

46.

7. A method for preparing an EVA-based encapsulating film according to any one of claims 1 to 6, characterized in that: After melt-blending the EVA resin and the anti-hydrolysis agent to obtain the anti-hydrolysis masterbatch, the anti-hydrolysis masterbatch, the EVA resin and the components of the EVA type encapsulation film except the EVA resin and the anti-hydrolysis agent are uniformly mixed and processed into a film to obtain the EVA type encapsulation film.

8. The method according to claim 7, characterized in that The content of the anti-hydrolysis agent in the anti-hydrolysis masterbatch is 1-20wt%.

9. The method according to claim 7, characterized in that The process flow of film processing is: single-screw extruder mixing and plasticizing → melt extrusion → cast film → winding.

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