KR20130006410A - Mono-layer pvdf film and preparation method thereof - Google Patents

Abstract

PURPOSE: A manufacturing method of a polyvinylidene fluoride film is provided to provide a polyvinylidene fluoride film with excellent weatherability, heat resistance, scratch resistance and dimensional stability. CONSTITUTION: A manufacturing method of a polyvinylidene fluoride film comprises: a step of manufacturing a master batch by compounding a polymethylmethacrylate homopolymer resin or a copolymer resin thereof, and titanium oxide(TiO2); and a step of melting and rolling the master batch, and a polyvinylidene fluoride homopolymer resin or a copolymer resin thereof and extruding the same to a sheet. The concentration of the polymethylmethacrylate homopolymer resin or copolymer resin thereof, the polyvinylidene fluoride single resin or copolymer resin thereof, and titanium oxide are 50-90 weight%, 5-25 weight% and 5-25 weight%, respectively.

Description

MONO-LAYER PVdF FILM AND PREPARATION METHOD THEREOF BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a method for producing a polyvinylidene fluoride (PVdF) film which can be used as a back sheet of a solar cell.

Solar cells are attracting attention as clean energy because they are less concerned about energy source depletion and environmental pollution. Since the solar cell is mainly used in an external environment, it is common to coat the surface of the solar cell with a polymer material having glass or light transmitting property in order to enhance the environmental resistance. Thin-film crystalline silicon solar cells, amorphous solar cells, and compound semiconductor solar cells have been under active research because of their relatively low cost and large area. Particularly, the amorphous silicon thin film type solar cell in which silicon is bonded onto the conductive metal substrate of the intermediate layer and the transparent conductive layer is formed is promising as a form of future solar cell module because of its light weight, thin film property and flexibility. In such a thin film battery, it is necessary to cover the light incidence side surface with a transparent covering material and protect the solar cell.

Japanese Laid-Open Patent Application No. 62-273780 discloses a polyester film layer containing an ultraviolet absorber as a light receiving surface material of a solar cell module and a protective layer of the same type or PVdF film on the back surface thereof, A solar cell module having a plurality of solar cells encapsulated with an adhesive resin such as EVA is disclosed.

Japanese Unexamined Patent Application Publication No. 06-318718 discloses a laminate comprising an EVA sheet in which a crosslinking agent, an ultraviolet absorber and an antioxidant are added in advance, and a polyester film having a thin film layer of silicon oxide, and the adhesion surface of the organic polymer is subjected to corona- Discloses a solar cell module in which a light receiving surface layer of a photovoltaic device is constituted by a tetrafluoroethylene (ETFE) film.

However, the solar cell protected by such a multi-layer film is insufficient in heat resistance to the heat treatment temperature and the actually used temperature when the solar cell main body (photovoltaic device) is packed with the protective film, The light amount decreases and the output decreases. Therefore, a solar cell module in which a solar cell is coated with a polymer film is required to have a coating material that is transparent and has enhanced scratch resistance without being deformed by heat.

PVdF single film is excellent in weather resistance, radiation resistance and chemical resistance and is used as a coating material for protecting a product or a material. The PVdF film is excellent in gloss, appearance, and scratch resistance, and thus can be used as various types of substrates. However, since the PVdF film generally has insufficient adhesion with the support, it is necessary to arrange the adhesive composition layer in the middle.

In general, when a layer of an adhesive composition is included, a method of coextruding the adhesive composition layer with a PVdF film to form a two-layer film, and then attaching the film to the support by hot pressing. Further, after the two-layer film is placed in the mold so that the PVdF layer contacts the wall of the mold, the support may be injected into the mold in a molten state. Depending on the nature of the support, PVdF and the layer of adhesive composition may be co-extruded to form a multi-layer PVdF film in which the adhesive composition is disposed between the PVdF and the support.

US Patent No. 4,226,904 discloses a polymethylmethacrylate (PMMA) film coated with a PVdF film. In order to improve the adhesion, PMMA is mixed with a dimethylformamide (DMF) solvent and cast on a PVdF film And the PVdF film layer is pressed onto the PMMA resin layer after evaporating the solvent.

U.S. Patent No. 4,415,519 discloses an ABS or PVC support coated with a PVdF film layer through an adhesive layer, wherein the adhesive is made of PMMA or a PMMA / PVDdF / ABS mixture (weight ratio 40:30:30) Or PMMA / polyacrylic derivative / ABS mixture (weight ratio 30:40:30).

U.S. Patent No. 5,242,976 describes a composition capable of bonding PVdF to a support by coextrusion, wherein the composition comprises 27-50 wt% of PMMA, 17.5-36.5 wt% of PVdF, and 25-47.45 wt% of PVDF By weight based on the total weight of the composition.

PVdF resin is widely used as a surface protective film for a structure exposed to the outside because it is melt-moldable and has excellent corrosion resistance, solvent resistance and ultraviolet ray resistance. Since such a surface protective film is used by adhering to the outer surface of various substrates, it is necessary to have adhesion and thickness uniformity which do not cause peeling even in long-term use.

In order to solve the problem that the PVdF resin is incompatible with the other resins other than the fluorine-based resin, Japanese Unexamined Patent Application Publication Nos. 55-044898 and 61-008350 disclose a PVdF resin having excellent compatibility with PVdF resin, A three-layer extruded sheet in which a PMMA resin having good compatibility is interposed between a vinyl chloride resin layer and an adhesive resin layer, and a PVdF / PMMA mixed layer are laminated between the PVdF resin layer and the PMMA resin layer as the adhesive resin layer And an extrusion sheet in which the interlaminar adhesive strength is improved is disposed.

However, these methods may deteriorate adhesive force or compatibility due to different resin properties, and therefore, when applied to a battery for a photovoltaic back sheet, the thickness and appearance may be defective.

Further, in order to be used as a surface protective film, a film having a matte surface may be used in order to enhance the quality and design. In order to form a matte surface, a method of applying a physical treatment such as sandblasting or polishing to the surface of the film after molding the fluorine resin film, a method of coating a matte agent on the surface of the film after molding the fluorine resin film, a method of embossing the fluorine resin film (Japanese Unexamined Patent Application, First Publication No. Hei 2-28239) or a method of adding an inorganic or organic material to a fluorine resin with a matting agent and the like have been developed. Among these methods, the method of using the embossing roll and the method of adding the matting agent are simple and inexpensive in comparison with other methods.

However, such a conventional method may cause a problem that gloss is formed on the surface during the thermal lamination process, and problems such as poor appearance and poor mechanical strength due to deterioration of the dispersibility of the matting agent may occur.

Japanese Patent Application Laid-Open No. 62-273780 Japanese Laid-Open Patent Publication No. 06-318718 U.S. Patent No. 4,226,904 U.S. Patent No. 4,415,519 U.S. Patent No. 5,242,976 Japanese Patent Application Laid-Open No. 55-044898 Japanese Patent Application Laid-Open No. 61-008350

Accordingly, an object of the present invention is to provide a method for producing a PVdF film which is excellent in weather resistance, heat resistance, scratch resistance, dimensional stability, and transparency and excellent in adhesion to a support.

According to the above object, the present invention provides a resin composition comprising 50 to 90% by weight of a polyvinylidene fluoride (PVdF) single resin or copolymer resin thereof; 5 to 25% by weight of polymethyl methacrylate (PMMA) single resin or copolymer resin thereof; And 5 to 25% by weight of titanium oxide (TiO ₂ ), based on the total weight of the polyvinylidene fluoride film.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: (A) preparing a master batch by compounding a polymethyl methacrylate (PMMA) single resin or a copolymer resin thereof with titanium oxide (TiO ₂ ); And (B) melt-kneading the masterbatch and polyvinylidene fluoride (PVdF) single resin or copolymerized resin thereof and extruding it into a sheet, wherein the PMMA single resin or copolymerized resin thereof, PVdF single resin or copolymerized thereof The content of the resin and the titanium oxide is 50 to 90% by weight, 5 to 25% by weight, and 5 to 25% by weight based on the total weight of the film provides a method for producing a polyvinylidene fluoride film.

The PVdF film produced by the production method of the present invention is excellent in weather resistance, heat resistance, scratch resistance and dimensional stability, and is transparent and excellent in adhesion to a support. Therefore, the PVdF film can be used for protection of articles or materials, It can be applied stably in terms of process and quality.

Hereinafter, the present invention will be described in more detail.

In the film of the present invention, the main component, PVdF, may be a homopolymer of a vinylidene fluoride (VF2) monomer or may be in the form of a copolymer.

When PVdF is a copolymer resin, it is preferable that vinylidene fluoride (VF2) and a comonomer are resins copolymerized in a weight ratio of 50:50 to 99: 1,

The comonomer which can be copolymerized is preferably a fluorinated monomer such as vinyl fluoride; Trifluoroethylene (VF3); Chlorofluoroethylene (CTFE); 1,2-difluoroethylene; Tetrafluoroethylene (TFE); Hexafluoropropylene (HFP); Perfluoro (alkyl vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE) and perfluoro (propyl vinyl) ether (PPVE); Perfluoro (1,3-dioxol); And perfluoro (2,2-dimethyl-1,3-dioxole) (PDD). Among these, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3), or tetrafluoroethylene (TFE) are preferable.

In order to be suitable for extrusion and injection molding, PVdF preferably has a viscosity measured by a capillary flow meter under the conditions of a shear rate of 100 s ^-1 and 230 캜 of 100 to 2,500 Pa · s, preferably 500 to 2,000 Pa · s More preferable.

The content of PVdF is preferably 50 to 90% by weight, particularly 60 to 80% by weight, based on the total film weight. When the content of PVdF is less than 50% by weight, sufficient weathering resistance may be limited. When the content is more than 90% by weight, physical properties more than necessary may be produced or the manufacturing cost may increase.

In the film of the present invention, PMMA, which is another major constituent, may be a single resin of a methyl methacrylate monomer or a copolymer resin with other comonomers.

When PMMA is a copolymer resin, it is preferable that methyl methacrylate (MMA) and a comonomer are resins copolymerized in a weight ratio of 50:50 to 99: 1.

Examples of comonomers which can be copolymerized include alkyl (meth) acrylate, acrylonitrile, butadiene, styrene, isoprene, and mixtures thereof. The alkyl (meth) acrylate is described in Kirk-Othmer Encyclopedia of Chemical Techology, 4 ^th Edition, Vol. 1, p. 292-293 & 16, p. 475-478.

Preferably, the copolymer resin may be copolymerized with methyl acrylate and / or ethyl acrylate comonomers in an amount of 1 to 20% by weight, especially 5 to 15% by weight.

PMMA can be functionalized, for example, containing an acid, acid chloride, alcohol or anhydride functionality, and these functional groups can be introduced by graft or copolymerization. Among these, an acid functional group provided by an acrylic acid copolymer resin is preferable. The content of the functional group may be 0 to 15% by weight based on the weight of the PMMA containing the functional group.

Two adjacent acrylic acid functional groups lose water and form anhydrides such as the following formula (1) or (2). These anhydrides can act to enhance the soft impact structure of PMMA, or to soften the soft structure by alleviating the crystalline behavior of PVdF after blending with PVdF:

The MVI (melt volume index) of PMMA can be 4 to 6 cm < 3 > / 10 min when measured at 230 DEG C under a load of 3.8 kg.

The content of PMMA is preferably 5 to 25% by weight, especially 10 to 25% by weight, based on the total film weight. When the content of PMMA is less than 5% by weight, adhesion to the substrate may be lowered during lamination. When the content of PMMA is more than 25% by weight, it is difficult to ensure sufficient weatherability.

In the film of the present invention, TiO ₂ , another main component, controls the optical characteristics such as light transmittance, reflectance and color, and controls the friction coefficient, the surface roughness and the fine touch.

The TiO ₂ is preferably added in a compounding manner, and the particle diameter is preferably 0.1 to 0.7 탆, and more preferably 0.2 to 0.35 탆. If the size of the TiO ₂ particles is less than 0.1 탆, the optical characteristics and the surface characteristics may be insignificantly affected. If the size exceeds 0.7 탆, the optical characteristics and the surface roughness of the film may deteriorate, A phenomenon that a small hole or the like is formed on the surface of the film) may occur.

The content of TiO ₂ is preferably 5 to 25% by weight, particularly 10 to 15% by weight, based on the total film weight. If the content of TiO ₂ particles is less than 5 wt%, the effect of addition may be insufficient. If the content of TiO ₂ particles is more than 25 wt%, the particles may aggregate and clog the filter during the film production process. In this case, Life, production efficiency, dispersibility, weatherability, and lightness.

Hereinafter, the physical properties and properties of the film according to the present invention will be described.

It is preferable that the film of the present invention has an elongation change rate in the longitudinal direction [(elongation after initial elongation-elongation after aging) / initial elongation x 100] of 50% or less with respect to the aging treatment under the conditions of 120 ° C and 60 minutes.

It is also preferable that the film of the present invention does not exhibit the endothermic peak melting crystallization temperature (Tmc) during the measurement of differential scanning calorimetry (DSC) under the condition of N ₂ air flow and temperature raising rate of 10 ° C / min.

Further, the film of the present invention exhibited a rate of change of YI (Yellow Index) against PCT (Pressure Cooker Test) at 2 atm, 120 ° C, 100% relative humidity and 75 hours [ PCT total YI) / PCT total YI x 100] is preferably 70% or less.

It is also preferable that the film of the present invention is composed of a heterogeneous surface having a surface roughness (Ra) of 0.3 mu m or more on one surface and a surface roughness of less than 0.3 mu m on the opposite surface.

The film of the present invention preferably has a reflectance of 75% or more at a wavelength of 550 nm.

The film of the present invention preferably has shrinkage ratios of 5% or less in the longitudinal direction (MD) and the transverse direction (TD) with respect to the heat treatment at 150 占 폚 and 30 minutes, respectively.

The film of the present invention preferably has tensile strengths of 3 kgf / mm 2 or more and elongations of 100% or more in the longitudinal direction (MD) and the transverse direction (TD), respectively.

Such a PVdF film of the present invention can be manufactured by a method including the following detailed steps:

(A) preparing a master batch by compounding polymethyl methacrylate (PMMA) single resin or its copolymer resin with titanium oxide (TiO ₂ ); And

(B) A step of melt-kneading the master batch and a polyvinylidene fluoride (PVdF) single resin or a copolymer resin thereof and extruding the mixture into a sheet.

Further, the method of the present invention may include a step (C) after the step (B), a step of winding the extruded sheet between a heating roll and embossed sewing rolls to obtain a final film.

In the step (B), the extrusion may be performed by a method in which the set resin temperature of the extruder is preferably set to 180 to 240 DEG C and extruded into a single layer through a conduit to a T die of the same temperature,

In the step (c), the surface temperature of the heating roll may be 70 to 110 ° C. In the step of obtaining the final film, the heating roll may be placed on a heated roll, passed through the squeezing roll on the opposite side, Can be accomplished by winding it on the base.

The use of the above-mentioned squeezing roll improves the folding force between the extruded single-layer sheet and the heating roll, thereby facilitating winding, and can control the surface roughness and gloss of the final film by controlling the embossing of the surface of the squeezing roll .

The thickness of the produced single-layer PVdF film is preferably 10 to 200 탆, more preferably 20 to 150 탆.

The PVdF film of the present invention exhibits excellent dimensional stability and mechanical properties, particularly, less change in physical properties with respect to aging treatment and pressure resistance test (PCT), and excellent processability. In addition, excellent adhesion is exhibited in the thermal lamination process depending on the surface roughness of the two-sided heterogeneous property, and since there is no melting crystal temperature (Tmc) in the film state, there is little surface change of the product roll due to long-term storage.

Accordingly, it can be stably applied in terms of process and quality owing to its excellent physical properties when used as a back sheet of a solar cell, particularly for protection of articles or materials.

Example

Hereinafter, the present invention will be described in more detail by way of examples, which are presented as preferred examples and are not intended to limit the scope of the present invention.

Example  1 to 9 and Comparative example  1 to 6

Each of the following ingredients was prepared:

- PVdF: single resin, MVI 24 g / 10 min (ASTM D1238, 230 캜, 5 kg load)

- PMMA: single resin, MVI 5.0 g / 10 min (ASTM D1238, 230 캜, 3.8 kg load), LGMMA

- TiO ₂ : particle size 230 nm,

At this time, the respective components were used together with the weight ratios listed in Table 1 below.

First, PMMA and TiO ₂ were compounded in a biaxial kneader at a temperature of 240 ° C to prepare a master batch. The prepared masterbatch and PVdF were melted as raw materials at a temperature of 210 DEG C in an extruder having a screw diameter of 130 mm and a screw L / D 32. This was extruded at the same temperature with a T-die having a die width of 2,800 mm, and was wound around a heating roll of 90 DEG C and an embossing roll of embossing treatment. As a result, a single-layer, monolayer PVdF film having a thickness of 25 mu m was obtained.

Test Example

The properties of each of the films prepared in Examples and Comparative Examples were measured as described below and shown in Table 1 below.

(1) Surface roughness

Surface roughness tester (Rough Surface Tester, RST-Plus, Veeco / Wyko).

(2) Tensile strength and elongation

The strength and elongation in the longitudinal and transverse directions were measured according to ASTM D882.

(3) thermal shrinkage

The extent of change in length after heat treatment at 150 占 폚 for 30 minutes was measured.

(4) Elongation change rate (? E)

The rate of change in elongation after aging treatment (120 DEG C, 60 minutes) was determined by the following equation:

ΔE (%) = (initial elongation-elongation after aging) / initial elongation x 100

(5) Melting crystallization temperature (Tmc)

(DSC, Q-100, TA Instrument, USA) at a heating rate of 10 ° C / min in a N ₂ gas flow.

(6) Yellow index change rate (? Y)

The yellow index (YI) change rate before and after the pressure resistance test (PCT, Pressure Cooker Test, 2atm, 120 ° C, 100% RH, 75 hours)

ΔY (%) = (YI after PCT - YI before PCT) / PCT YI x 100

(7) Reflectance

And measured with a light source having a wavelength of 550 nm using a color difference meter (UltraScan ^TM Pro, HunterLab).

(8) Filter pressure change rate (? P)

The rate of change of filter pressure for 6 hour extrusion was obtained by the following equation:

ΔP (%) = (pressure after extrusion-initial pressure) / initial pressure x 100

As can be seen from the above Table 1, the films of the examples produced according to the preferred composition ranges of the present invention are excellent in surface roughness, strength, elongation, heat shrinkage, elongation change rate, yellow index change rate, reflectance, filter pressure change rate, While the comparative films prepared according to the compositions outside the scope of the present invention exhibited poor physical properties.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

Claims (11)

(A) preparing a master batch by compounding polymethyl methacrylate (PMMA) single resin or its copolymer resin with titanium oxide (TiO ₂ ); And
(B) a step of melt kneading the master batch and a polyvinylidene fluoride (PVdF) single resin or a copolymer resin thereof, and extruding the resultant into a sheet,
The content of the PMMA mono- or copolymer thereof, PVdF mono- or copolymer thereof and titanium oxide is 50 to 90% by weight, 5 to 25% by weight, and 5 to 25% by weight of polyvinylidene based on the total weight of the film Method for producing fluoride film.
The method of claim 1,
After the step (B), (C) a step of winding the extruded sheet while passing through a heating roll and embossed rolls of the embossed roll to obtain a final film .
The method of claim 1,
Wherein in the step (B), the temperature of the melt kneading is 180 to 240 占 폚.
The method of claim 2,
Wherein in the step (C), the temperature of the heating roll is 70 to 110 占 폚.
The method of claim 1,
The copolymer resin of PVdF is a resin obtained by copolymerizing vinylidene fluoride (VF2) and a comonomer in a weight ratio of 50:50 to 99: 1, and the comonomer is vinyl fluoride, trifluoroethylene (VF3), chlorofluoro (Meth) acrylates such as ethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro ), Perfluoro (2,2-dimethyl-1,3-dioxol) (PDD) or a mixture thereof.
The method of claim 1,
The copolymer resin of PMMA is a resin in which methyl methacrylate (MMA) and a comonomer are copolymerized in a weight ratio of 50:50 to 99: 1, and the comonomer is an alkyl (meth) acrylate, acrylonitrile, butadiene, Styrene, isoprene, or a mixture thereof.
The method of claim 1,
Wherein the film has a surface roughness (Ra) of 0.3 mu m or more on one surface and a surface roughness of 0.3 mu m or less on the opposite surface.
The method of claim 1,
Wherein the film has a reflectance of 75% or more at a wavelength of 550 nm.
The method of claim 1,
Wherein the film has a shrinkage ratio in the longitudinal direction and in the transverse direction of 5% or less with respect to the heat treatment under the conditions of 150 占 폚 and 30 minutes, respectively.
The method of claim 1,
Wherein the film has a tensile strength in the longitudinal direction and the transverse direction of 3 kgf / mm < 2 > or more and an elongation of 100% or more, respectively.
A back sheet for a solar cell comprising a polyvinylidene fluoride film produced by the method of claim 1.