Disclosure of Invention
Aiming at the problems and defects existing in the prior art, the invention provides a modified PVDF film, a preparation method and a solar cell backboard.
According to the invention, the EVOH is introduced into the polyvinylidene fluoride matrix, and a certain compatilizer is added to increase the compatibility of the polyvinylidene fluoride and the EVOH so as to obtain better mechanical strength, the hydroxyl in the EVOH polymer can be subjected to chemical reaction with the organic groups in the EVA to enhance the adhesion force, and the EVOH has good water vapor barrier property and can be widely applied to the fields of solar back plates and the like.
In order to achieve the above object, the preparation method of the modified polyvinylidene fluoride film according to the present invention is characterized by comprising the steps of:
The preparation method of the modified PVDF film comprises the following steps:
s1, uniformly mixing dry polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles, a compatilizer, an antioxidant and an ultraviolet light absorber in a high-speed mixer, and performing melt granulation in a double-screw extruder to obtain a modified polyvinylidene fluoride special material;
S2, forming and processing the special modified polyvinylidene fluoride material into a modified polyvinylidene fluoride thick film;
and S3, carrying out biaxial stretching on the modified polyvinylidene fluoride thick film to obtain the modified PVDF film.
Further, the mass ratio of the polyvinylidene fluoride particles to the ethylene-vinyl alcohol copolymer particles is 9-7:1-3.
Further, the compatilizer is polyvinylidene fluoride grafted by irradiation and acrylic acid or maleic anhydride, and the addition proportion of the acrylic acid or the maleic anhydride is 5-10 wt% of the polyvinylidene fluoride.
Further, the antioxidant is antioxidant 1010 or antioxidant 168, and the ultraviolet light absorber is 2-hydroxy-4-n-octoxybenzophenone, 2- (2-hydroxy-5-benzyl) benzotriazole, resorcinol monobenzoate.
Further, the proportion of the antioxidant and the ultraviolet light absorber is 1-2 wt% of the total mass of the polyvinylidene fluoride particles and the ethylene-vinyl alcohol copolymer particles.
Further, the forming processing mode of the polyvinylidene fluoride thick film is hot press film forming and tape casting forming by a flat vulcanizing machine, and the thickness of the thick film is not less than 0.05mm.
Further, the biaxial stretching is synchronous biaxial stretching, the synchronous biaxial stretching temperature is 100-120 ℃, the stretching speed is 30-50 mm/s, and the stretching ratio is 1.5-4.
Further, the compatilizer is polyvinylidene fluoride grafted glycidyl methacrylate or polyvinylidene fluoride grafted maleic anhydride special material, and the adding proportion of the compatilizer is 5-10 wt% of the polyvinylidene fluoride particles.
Further, before S1, the step of preparing the compatibilizer includes:
Putting the dried polyvinylidene fluoride particles, glycidyl methacrylate, benzoyl peroxide and 9-vinyl anthracene into a double-screw extruder for melt reaction, extrusion and granulation to obtain the special material for grafting the polyvinylidene fluoride and the glycidyl methacrylate, wherein the adding proportion of the benzoyl peroxide and the 9-vinyl anthracene is 0.025-0.15% of the total mass of the glycidyl methacrylate and the polyvinylidene fluoride, and the mass ratio of the polyvinylidene fluoride to the glycidyl methacrylate is 90-97:3-10;
Or the special material for grafting the polyvinylidene fluoride is prepared by carrying out melt reaction extrusion granulation on dry polyvinylidene fluoride particles, maleic anhydride, benzoyl peroxide, 9-vinyl anthracene and a double-screw extruder, wherein the adding proportion of the benzoyl peroxide and the 9-vinyl anthracene is 0.025% -0.15% of the total mass of the Maleic Anhydride (MAH) and the polyvinylidene fluoride, and the mass ratio of the polyvinylidene fluoride to the maleic anhydride is 90-97:3-10.
According to another aspect of the invention, the invention provides a polyvinylidene fluoride film prepared by the method and a solar cell backboard prepared by the film.
Compared with the prior art, the hydrophilic performance of PVDF and the adhesive force of an EVA adhesive film are improved, the surface energy of a PVDF film can be obviously reduced by blending the PVDF and the EVOH, the hydroxyl of the EVOH molecular chain can be subjected to alcoholysis reaction with the organic groups of the EVA adhesive film, the adhesive force of the PVDF and the EVA adhesive film can be obviously improved, and the EVOH is used as a three-high barrier molecular material, so that the barrier performance is excellent, and the water vapor barrier capability of the PVDF can be obviously improved by blending the PVDF. But PVDF and EVOH are poor in compatibility, and the mechanical properties of the material are improved by adding melt grafted glycidyl methacrylate or maleic anhydride for reactive compatibility. The invention further improves the water vapor barrier property and the mechanical property of the PVDF film through a synchronous biaxial stretching process, and the modified PVDF film with high water vapor barrier property and excellent mechanical property can be widely applied to the adhesion of the inner layer of the solar cell backboard and the EVA adhesive film through optimization of the stretching ratio, the stretching temperature and the stretching speed.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent.
The preparation method of the modified PVDF film comprises the following steps:
s1, uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles, a compatilizer, an antioxidant and an ultraviolet light absorber in a high-speed mixer, and carrying out melt granulation in a double-screw extruder to obtain the modified polyvinylidene fluoride special material.
S2, forming and processing the special modified polyvinylidene fluoride material into a modified polyvinylidene fluoride thick film;
and S3, carrying out biaxial stretching on the modified polyvinylidene fluoride thick film to obtain the modified PVDF film.
Further, the mass ratio of the polyvinylidene fluoride particles to the ethylene-vinyl alcohol copolymer particles is 9-7:1-3.
The principle that the mass ratio of polyvinylidene fluoride to ethylene-vinyl alcohol copolymer is 9-7:1-3 is as follows:
Since polyvinylidene fluoride and ethylene-vinyl alcohol copolymer are incompatible, the higher the proportion of ethylene-vinyl alcohol copolymer to be added, the higher the proportion of the compatibilizer to be added, the lower the corresponding stretching ratio, and the higher the mass ratio, the higher the stretching ratio, the film will be broken. The higher the mass ratio, the higher the draw ratio and the corresponding tensile strength and water vapor barrier properties.
Further, the compatilizer is polyvinylidene fluoride grafted by irradiation and acrylic acid or maleic anhydride, and the addition proportion of the acrylic acid or the maleic anhydride is 5-10 wt% of the polyvinylidene fluoride.
Further, the antioxidant is antioxidant 1010 or antioxidant 168, and the ultraviolet light absorber comprises 2-hydroxy-4-n-octoxybenzophenone, 2- (2-hydroxy-5-benzyl) benzotriazole and resorcinol monobenzoate.
Further, the proportion of the antioxidant and the ultraviolet light absorber is 1-2 wt% of the total mass of the polyvinylidene fluoride particles and the ethylene-vinyl alcohol copolymer particles.
Further, the forming processing mode of the polyvinylidene fluoride thick film is hot press film forming and tape casting forming by a flat vulcanizing machine, and the thickness of the thick film is not less than 0.05mm.
Further, the biaxial stretching is synchronous biaxial stretching, the synchronous biaxial stretching temperature is 100-120 ℃, the stretching speed is 30-50 mm/s, and the stretching ratio is 1.5-4.
Further, the compatilizer is polyvinylidene fluoride grafted glycidyl methacrylate or polyvinylidene fluoride grafted maleic anhydride special material, and the adding proportion of the compatilizer is 5-10 wt% of the polyvinylidene fluoride particles.
Further, before S1, the step of preparing the compatibilizer includes:
Putting the dried polyvinylidene fluoride particles, glycidyl methacrylate, benzoyl peroxide and 9-vinyl anthracene into a double-screw extruder for melt reaction, extrusion and granulation to obtain the special material for grafting the polyvinylidene fluoride and the glycidyl methacrylate, wherein the adding proportion of the benzoyl peroxide and the 9-vinyl anthracene is 0.025-0.15% of the total mass of the glycidyl methacrylate and the polyvinylidene fluoride, and the mass ratio of the polyvinylidene fluoride to the glycidyl methacrylate is 90-97:3-10;
Or the special material for grafting the polyvinylidene fluoride is prepared by carrying out melt reaction extrusion granulation on dry polyvinylidene fluoride particles, maleic anhydride, benzoyl peroxide, 9-vinyl anthracene and a double-screw extruder, wherein the adding proportion of the benzoyl peroxide and the 9-vinyl anthracene is 0.025% -0.15% of the total mass of the Maleic Anhydride (MAH) and the polyvinylidene fluoride, and the mass ratio of the polyvinylidene fluoride to the maleic anhydride is 90-97:3-10.
According to another aspect of the invention, the invention provides a polyvinylidene fluoride film prepared by the method and a solar cell backboard prepared by the film.
Compared with the prior art, the hydrophilic performance of PVDF and the adhesive force of an EVA adhesive film are improved, the surface energy of a PVDF film can be obviously reduced by blending the PVDF and the EVOH, the hydroxyl of the EVOH molecular chain can be subjected to alcoholysis reaction with the organic groups of the EVA adhesive film, the adhesive force of the PVDF and the EVA adhesive film can be obviously improved, and the EVOH is used as a three-high barrier molecular material, so that the barrier performance is excellent, and the water vapor barrier capability of the PVDF can be obviously improved by blending the PVDF. But PVDF and EVOH are poor in compatibility, and the mechanical properties of the material are improved by adding melt grafted glycidyl methacrylate or maleic anhydride for reactive compatibility. The invention further improves the water vapor barrier property and the mechanical property of the PVDF film through a synchronous biaxial stretching process, and the modified PVDF film with high water vapor barrier property and excellent mechanical property can be widely applied to the adhesion of the inner layer of the solar cell backboard and the EVA adhesive film through optimization of the stretching ratio, the stretching temperature and the stretching speed.
The present invention will be described in further detail with reference to examples.
Example 1:
the modified polyvinylidene fluoride film is prepared according to the following steps:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles and polyvinylidene fluoride with a compatilizer of melt grafted glycidyl methacrylate, an antioxidant 1010 and an ultraviolet light absorbent resorcinol monobenzoate in a high-speed mixer, and performing melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 90:10, the compatilizer is 5wt% of the polyvinylidene fluoride, and the antioxidant 1010 and the ultraviolet light absorber resorcinol monobenzoate are 1wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) Preparing the modified polyvinylidene fluoride particles obtained in the step (1) into a thick film with the thickness of 0.4mm by adopting a tape casting molding method;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 120 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 50mm/s, and the stretching ratio is 4.0.
Example 2:
the modified polyvinylidene fluoride film is prepared according to the following steps:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles and polyvinylidene fluoride with a compatilizer of melt grafted glycidyl methacrylate, an antioxidant 1010 and an ultraviolet light absorbent resorcinol monobenzoate in a high-speed mixer, and performing melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 70:30, the compatilizer is 10wt% of the polyvinylidene fluoride, and the antioxidant 1010 and the ultraviolet light absorber resorcinol monobenzoate are 1wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) Casting the modified polyvinylidene fluoride particles obtained in the step (1) into a thick film with the thickness of 0.4 mm;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 120 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 50mm/s, and the stretching ratio is 4.0.
Example 3:
the modified polyvinylidene fluoride film is prepared according to the following steps:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles and polyvinylidene fluoride with a compatilizer of melt grafted maleic anhydride, an antioxidant 1010 and an ultraviolet light absorbent resorcinol monobenzoate in a high-speed mixer, and performing melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 90:10, the compatilizer is 5wt% of the polyvinylidene fluoride, and the antioxidant 1010 and the ultraviolet light absorber resorcinol monobenzoate are 1wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) Preparing a thick film with the thickness of 0.4mm from the modified polyvinylidene fluoride particles obtained in the step (1) by adopting a hot pressing film forming method of a flat vulcanizing machine;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 120 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 50mm/s, and the stretching ratio is 4.0.
Example 4:
the modified polyvinylidene fluoride film is prepared according to the following steps:
(1) The dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles, polyvinylidene fluoride with a compatilizer of melt grafted glycidyl methacrylate, an antioxidant 168 and resorcinol monobenzoate as an ultraviolet light absorber are uniformly mixed in a high-speed mixer, and are melt granulated in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 70:30, the compatilizer is 10wt% of the polyvinylidene fluoride, and the antioxidant 168 and the ultraviolet light absorber resorcinol monobenzoate are 2wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) Preparing the modified polyvinylidene fluoride particles obtained in the step (1) into a thick film with the thickness of 0.05mm by adopting a hot press film forming method of a flat vulcanizing machine;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 120 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 50mm/s, and the stretching ratio is 1.5.
Example 5:
the modified polyvinylidene fluoride film is prepared according to the following steps:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles, polyvinylidene fluoride with a compatilizer of melt grafted maleic anhydride, an antioxidant 1010 and an ultraviolet light absorber 2- (2-hydroxy-5-benzyl) benzotriazole in a high-speed mixer, and performing melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 80:20, the compatilizer is 5wt% of the polyvinylidene fluoride, and the antioxidant 1010 and the ultraviolet light absorber 2- (2-hydroxy-5-benzyl) benzotriazole are 1wt% of the polyvinylidene fluoride;
(2) Preparing the modified polyvinylidene fluoride particles obtained in the step (1) into a thick film with the thickness of 0.3mm by adopting a tape casting molding method;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 110 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 30mm/s, and the stretching ratio is 3.0.
Example 6:
the modified polyvinylidene fluoride film is prepared according to the following steps:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles and polyvinylidene fluoride with a compatilizer of melt grafted maleic anhydride, an antioxidant 1010 and an ultraviolet light absorber 2-hydroxy-4-n-octoxybenzophenone in a high-speed mixer, and performing melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 80:20, the compatilizer is 10wt% of the polyvinylidene fluoride, and the antioxidant 1010 and the ultraviolet light absorber 2-hydroxy-4-n-octoxybenzophenone are 1wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) Preparing a thick film of 0.2mm from the modified polyvinylidene fluoride particles obtained in the step (1) by adopting a hot pressing film forming method of a flat vulcanizing machine;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 120 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 50mm/s, and the stretching ratio is 4.0.
Comparative example 1:
A polyvinylidene fluoride film was prepared as a comparative sample according to the following procedure:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, polymethyl methacrylate particles, an antioxidant 1010 and resorcinol monobenzoate serving as an ultraviolet light absorber in a high-speed mixer, and carrying out melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 70:30, and the antioxidant 1010 and the ultraviolet light absorber resorcinol monobenzoate are 1wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) And (3) preparing the modified polyvinylidene fluoride particles obtained in the step (1) into a film with the thickness of 25 mu m by adopting a tape casting molding method.
Comparative example 2:
A polyvinylidene fluoride film was prepared as a comparative sample according to the following procedure:
(1) Uniformly mixing the dried polyvinylidene fluoride particles, ethylene-vinyl alcohol copolymer particles, an antioxidant 1010 and resorcinol monobenzoate serving as an ultraviolet light absorber in a high-speed mixer, and carrying out melt granulation in a double-screw extruder. The mass ratio of the polyvinylidene fluoride to the ethylene-vinyl alcohol copolymer is 70:30, and the antioxidant 1010 and the ultraviolet light absorber resorcinol monobenzoate are 1wt% of the total mass of the polyvinylidene fluoride and the ethylene-vinyl alcohol copolymer;
(2) Preparing a thick film with the thickness of 0.1mm from the modified polyvinylidene fluoride particles obtained in the step (1) by adopting a hot pressing film forming method of a flat vulcanizing machine;
(3) And (3) synchronously biaxially stretching the modified polyvinylidene fluoride thick film obtained in the step (2) at 120 ℃ to prepare a biaxially oriented polyvinylidene fluoride thin film, wherein the stretching speed is 50mm/s, and the stretching ratio is 2.
The preparation of the example and comparative solar cell back sheets was performed as follows:
the middle is a PET supporting layer, the outer layer is a PVDF film, the inner layer is a modified PVDF film or a comparative PVDF film prepared by the invention, and the bonding thickness of the PVDF film and the PET adhesive is (300+/-10 mu m).
The PVDF films of the examples and comparative examples (thickness about 25 μm) were subjected to tensile properties, tensile properties tests according to GBT1040-1992, at a tensile rate of 25 mm/min.
The test method is to cut a strip with the width of 1cm from the back plate and the EVA by a knife, and ensure that the strip is cut thoroughly, pull and peel the separation layer by a pull testing machine at the speed of 100mm/min in the 180-degree direction, take the point when the material is peeled off at a uniform speed, take the minimum value, and judge that the peeling strength between the EVA and the back plate is 40N/cm as qualified.
And (3) testing the water vapor transmittance, namely testing by adopting a W3/330 water vapor transmittance testing system according to the GB/T21529-2008 standard, wherein the testing area is 108mm multiplied by 108mm, the testing temperature is 40 ℃, the testing humidity is 90%, and each solar cell backboard is used for testing three samples and taking an average value.
The tensile properties of the films were measured, and the water vapor transmittance and EVA adhesion of the solar cell back sheet were measured as shown in table 1:
TABLE 1
From the table, it can be seen that the modified PVDF film prepared by the embodiment has good mechanical properties, and the solar cell backboard and EVA adhesive film prepared by the modified PVDF film have good adhesion capability and good water vapor barrier property.
It should be noted that the above-mentioned embodiments are merely preferred embodiments of the present invention, and the present invention is not limited thereto, but may be modified or substituted for some of the technical features thereof by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.