KR20170141170A - Multi layer film having improved weatherability and preparation method thereof - Google Patents

Abstract

The present invention relates to a multilayer film having weather resistance and a preparation method thereof. The multilayer film having weather resistance comprises: an A layer including 50-100 wt% of polyvinylidene fluoride (PVdF), 0-50 wt% of thermoplastic polyester elastomer (TPEE) and 0-30 wt% of titanium dioxide (TiO_2); and a B layer including 0-80 wt% of PVdF, 20-100 wt% of TPEE and 5-50 wt% of TiO_2. The film of the present invention has excellent durability, weather resistance and chemical resistance, thereby being useful as a back sheet for a photovoltaic module.

Description

TECHNICAL FIELD [0001] The present invention relates to a weather-resistant multi-layer film,

The present invention relates to a weather-resistant multilayer film useful as a back sheet of a solar cell.

Due to environmental problems such as air pollution due to mass consumption of fossil fuels, abnormal weather due to warming, and energy problems due to rising oil prices, environment-friendly energy such as hydrogen battery, fuel cell, solar energy, bio energy, wind energy and marine energy There is a surge in demand for. Dual solar energy is considered to be suitable as next generation renewable energy because it can supply infinite energy and is easy to develop.

Since the solar module using sunlight is used outdoors for a long time, it is essential to have functions such as durability, heat resistance and weather resistance. A vinylidene fluoride film is mainly used as a film for protecting the solar module. Japanese Laid-Open Patent Publication Nos. 2008-85270, 2002-26354 and 2002-134770 disclose a method of laminating a polyethylene terephthalate (PET) film between polyvinyl fluoride (PVF) films or replacing PVF Discloses a film produced by co-extruding a film by adding an inorganic substance to the film to increase the reflectance.

Japanese Patent Application Laid-Open No. 62-273780 discloses a method for producing a solar cell module, which comprises a polyester film layer containing an ultraviolet absorber as a light receiving surface material of a solar cell module and a protective film of a homologous film or polyvinylidene fluoride (PVdF) Discloses a solar cell module having a plurality of solar cells encapsulated with an adhesive resin such as ethylene vinyl acetate (EVA).

PVdF resin is widely used as a surface protective film for a structure exposed to the outside because it can be melt-molded and has excellent corrosion resistance, solvent resistance and ultraviolet ray resistance. Since the surface protective film is used in a bonded state on the surface of various substrates, adhesion and thickness uniformity are required to prevent peeling during use for a long period of time.

PVdF resins have poor compatibility with other resins other than the fluorine-based resin. Therefore, in JP-A-55-44898 and JP-A-61-8350, it is preferable to use a polymethylmethacrylate (PMMA) resin having relatively high compatibility A three-layer extruded sheet made of an adhesive resin layer interposed between the PVdF resin layer and the vinyl chloride resin layer, and a PVdF resin layer and a PVdF and PMMA mixed resin layer disposed between the PMMA resin layer as the adhesive resin layer And an extruded sheet produced therefrom. However, when the sheet produced by the above method is used as a solar cell backing sheet, the adhesive strength may be lowered due to different resin properties, or the compatibility may be insufficient, resulting in poor appearance and thickness uniformity. Further, as a result of performing the weathering test for 100 hours with respect to these films, there was a disadvantage that the rate of change of elongation was drastically reduced.

Accordingly, an object of the present invention is to provide a weather-resistant multilayer film which is excellent in durability, weather resistance, and chemical resistance and is useful as a back sheet of a solar module.

It is another object of the present invention to provide a method for producing the weather resistant multilayer film.

In order to achieve the above object,

Polyvinylidene fluoride (PVdF) resin 50-100% by weight of a thermoplastic polyester elastomer (TPEE) 0 ~ 50% by weight and titanium oxide (TiO ₂₎ A layer made of a 0-30 wt.%; And a B layer composed of 0 to 80 wt% of PVdF, 20 to 100 wt% of TPEE and 5 to 50 wt% of TiO ₂ .

According to another aspect of the present invention,

1) A raw material A obtained by mixing and pelletizing 50 to 100 parts by weight of a polyvinylidene fluoride (PVdF) resin, 0 to 50 parts by weight of a thermoplastic polyester elastomer (TPEE) and 0 to 30 parts by weight of titanium oxide (TiO ₂ ) ;

2) preparing raw material B in which 0 to 80 parts by weight of PVdF, 20 to 100 parts by weight of TPEE and 5 to 50 parts by weight of TiO ₂ are mixed and pelletized;

3) feeding the prepared raw materials A and B into a feed block, alternately stacking them, and pneumatically delivering them; And

4) passing the extruded sheet through a casting roll to obtain a final film.

Since the weather-resistant multilayered film of the present invention is excellent in durability, weather resistance, and chemical resistance, it can be applied stably in terms of process and quality when used as a back sheet for solar cells.

Hereinafter, the present invention will be described more specifically.

The present invention, polyvinylidene fluoride (PVdF) resin 50-100% by weight of a thermoplastic polyester elastomer (TPEE) 0 ~ 50% by weight and titanium oxide (TiO ₂₎ A layer made of a 0-30 wt.%; And a B layer composed of 0 to 80 wt% of PVdF, 20 to 100 wt% of TPEE and 5 to 50 wt% of TiO ₂ .

The film of the present invention is a multilayer film of two or more layers, and can satisfy required physical properties regardless of the number of layers.

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

When PVdF is a copolymer resin, a resin in which 50 wt% or more of VF2 and another comonomer copolymerizable with VF2 are copolymerized is preferable.

As the comonomer which can be copolymerized, a fluorinated monomer is preferable, for example, vinyltrifluoroethylene (VF3); Chlorotrifluoroethylene (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 MFI (melt flow index) of PVdF may be from 1 to 11 g / 10 min and preferably from 1 to 9 g / 10 min when measured at 230 ° C under a load of 2.16 kg.

In the film of the present invention, the thermoplastic polyester elastomer (TPEE), which is another major constituent, is a polybutylene terephthalate (PBT), a polyethylene naphthalate (PEN), a polycyclohexylenedimethylene terephthalate (PCT) Methylene terephthalate (PTT), and polybutylene terephthalate (PBT) having a similar extrusion processing temperature to polyvinylidene fluoride (PVdF) is most preferred.

TPEE is a linear polymer and can be injection molded or extruded with molding material in the form of a pellet, and has excellent moldability and physical properties such as excellent heat resistance, heat aging resistance, fatigue resistance, impact resistance, weather resistance and chemical resistance .

The MFI (melt flow index) of TPEE may be from 5 to 14 g / 10 min and preferably 14 g / 10 min when measured at 230 ° C under a load of 2.16 kg.

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.

TiO ₂ is preferably added in a compounding manner, and the average particle diameter is preferably 0.1 to 0.7 탆, particularly preferably 0.2 to 0.4 탆. When the size of the TiO ₂ particles is less than 0.1 탆, the optical characteristics and the surface characteristics may be insignificant. When the size exceeds 0.7 탆, the optical characteristics and the surface roughness of the film may decrease, A phenomenon that a small hole or the like is formed on the surface of the film) may occur.

The TiO ₂ particles may be used in an amount of 0 to 20 wt% for the A layer of the film, 30 to 50 wt% for the B layer of the film, and 5 to 50 wt% for the entire multilayer film.

In the present invention, if the content of the TiO ₂ particles is less than 5% by weight based on the total weight of the entire multilayer film, the addition effect may be insignificant. If the content exceeds 50% by weight, the light shielding and reflectance effects are not improved, It may become difficult to form the film.

The present invention also relates to a method for producing a polyvinylidene fluoride resin composition, comprising the steps of: ₁ ) mixing 50 to 100 parts by weight of a polyvinylidene fluoride (PVdF) resin, 0 to 50 parts by weight of a thermoplastic polyester elastomer (TPEE) and 0 to 30 parts by weight of titanium oxide Preparing a raw material A; 2) preparing a raw material B in which 0 to 80 parts by weight of PVdF, 20 to 100 parts by weight of TPEE and 0 to 50 parts by weight of TiO ₂ are mixed and pelletized; 3) feeding the prepared raw materials A and B into a feed block, alternately stacking them, and pneumatically delivering them; And 4) passing the extruded sheet through a casting roll to obtain a final film.

In the production process of the present invention, the components of the raw materials A and B can be pelletized by blending or compounding at a temperature of 200 to 260 DEG C, preferably 240 DEG C, in a biaxial kneader.

The raw materials A and B thus prepared are added to two extruders so as to have a layer ratio of 1: 1 to 1: 4, preferably 1: 3, melted at a temperature of 200 to 260 DEG C, preferably 210 DEG C, And then co-extruded. The co-extrusion may be performed by a co-extrusion process generally performed in the art, wherein each layer adjusts the inter-layer ratio by appropriately adjusting the capacity of the extruder.

The sheet thus extruded can be passed through a casting roll at an electric power of 1 to 10 kv, preferably 5 kv, to produce the weatherable multi-layer film of the present invention having a uniform thickness and surface.

In the weather-resistant multilayer film according to the present invention, each of the thicknesses of the A layer and the B layer is preferably from 30 nm to 5 占 퐉, and the total thickness is preferably from 20 占 퐉 to 100 占 퐉.

The film of the present invention has a tensile strength in the longitudinal direction (MD) and a tensile strength in the width direction (TD) of not less than 3.8 kgf / mm 2, an elongation of not less than 350% (△ YI, Yellow Index) for a pressure test (PCT, Pressure Cooker Test) under the conditions of 2 atm, 120 캜, 100% relative humidity and 75 hours in the width direction (TD) Is 25% or less and the reflectance at a wavelength of 550 nm is 81% or more.

Example

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

≪ Preparation of weatherable multi-layer film &

Each of the following ingredients was prepared.

1) Polyvinylidene fluoride (PVdF): MFI 9 g / 10 min (ASTM D1238, 230 캜, 2.16 kg load), Solvay's PVDF Chip

2) Thermoplastic polyester elastomer (TPEE): MFI 14 g / 10 min (ASTM D1238, 230 캜, 2.16 kg load), LG Chem TPEE Chip

3) TiO ₂ : Particle size 230 nm,

Example  One

A PVdF resin alone raw material was extruded into an A layer, and TPEE / TiO ₂ = 50/50 in a biaxial kneader at a temperature of 240 ° C to extrude the pelletized raw material into the B layer.

And melted at 210 DEG C in two extruders having a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio of the PVdF A layer and the TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Example  2

PVdF / TPEE = 90/10 to content extruding the pelletized raw materials are blended at a temperature of 240 ℃ in group A twin-screw kneading the layer, and TPEE / TiO ₂ = 50/50 in a biaxial kneader at a temperature of 240 ° C to form a pelletized raw material.

And melted at 210 DEG C in two extruders having a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio between the PVdF / TPEE A layer and the TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Example  3

PVdF / TPEE = 80/20 to content extruding the pelletized raw materials are blended at a temperature of 240 ℃ in group A twin-screw kneading the layer, and TPEE / TiO ₂ = 50/50 in a biaxial kneader at a temperature of 240 ° C to form a pelletized raw material.

And melted at 210 DEG C in two extruders having a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio between the PVdF / TPEE A layer and the TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Example  4

PVdF / TPEE / TiO ₂ = 90/5/5 in a biaxial kneader at a temperature of 240 ° C to form a pelletized raw material, which was extruded into a layer A, and PVdF / TPEE / TiO ₂ = 10/45/45 in a biaxial kneader at a temperature of 240 ° C to form a pelletized raw material.

And melted at 210 ° C in two extruders of a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio between the PVdF / TPEE / TiO ₂ A layer and the PVdF / TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Example  5

PVdF / TPEE / TiO ₂ = By compounding at a temperature of 240 ℃ in the group with twin-screw kneading 80/10/10 content extruding a pelletized material with the layer A, and PVdF / TPEE / TiO ₂ = 20/40/40 in a biaxial kneader at a temperature of 240 ° C to form a pelletized raw material.

And melted at 210 ° C in two extruders of a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio between the PVdF / TPEE / TiO ₂ A layer and the PVdF / TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Example  6

PVdF / TPEE / TiO ₂ = By compounding at a temperature of 240 ℃ in the group with twin-screw kneading 70/15/15 content extruding a pelletized material with the layer A, and PVdF / TPEE / TiO ₂ = 30/35/35 in a twin-screw kneader at a temperature of 240 ° C to form a pelletized raw material, which was then extruded into a B layer.

And melted at 210 ° C in two extruders of a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio between the PVdF / TPEE / TiO ₂ A layer and the PVdF / TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Example  7

PVdF / TPEE / TiO ₂ = By compounding at a temperature of 240 ℃ in the group with twin-screw kneading 60/20/20 content extruding a pelletized material with the layer A, and PVdF / TPEE / TiO ₂ = 40/30/30 in a biaxial kneader at a temperature of 240 ° C to form a pelletized raw material.

And melted at 210 ° C in two extruders of a screw diameter of 130 mm and a screw L / D 32 so that the weight ratio between the PVdF / TPEE / TiO ₂ A layer and the PVdF / TPEE / TiO ₂ B layer was 1: 3. Then, a 45-layer film having a thickness of 30 [micro] m was produced using a T-die having a die width of 2800 mm by feed block coextrusion.

Comparative Example  One

A film having a thickness of 30 탆 was prepared in the same manner as in Example 1 except that the weight ratio of the A layer and the B layer was co-extruded so as to be 1: 5.

Comparative Example  2

A film having a thickness of 30 탆 was prepared in the same manner as in Example 2 except that the weight ratio of the A layer and the B layer was co-extruded so as to be 1: 5.

Comparative Example  3

A film having a thickness of 30 탆 was prepared in the same manner as in Example 3 except that the weight ratio of the A layer and the B layer was co-extruded so as to be 1: 5.

Comparative Example  4

A film having a thickness of 30 탆 was prepared in the same manner as in Example 4 except that the weight ratio of the A layer and the B layer was 1: 5 and co-extruded.

Comparative Example  5

A film having a thickness of 30 탆 was prepared in the same manner as in Example 5, except that the weight ratio of the A layer and the B layer was co-extruded so as to be 1: 5.

Comparative Example  6

Except that the weight ratio of the A layer and the B layer was 1: 5 in Example 6, to thereby produce a film having a thickness of 30 탆.

Comparative Example  7

A film having a thickness of 30 탆 was prepared in the same manner as in Example 7, except that the weight ratio of the A layer and the B layer was co-extruded at a ratio of 1: 5.

Test Example

The properties of the weather-resistant films prepared in Examples 1 to 7 and Comparative Examples 1 to 7 were evaluated by the following methods, and the results are shown in Table 1 below.

1) Tensile strength

The tensile strengths in the longitudinal direction (MD) and the transverse direction (TD) were measured according to ASTM D882.

2) Shindo

The elongation in the longitudinal direction (MD) and in the transverse direction (TD) was measured according to ASTM D882.

3) Heat shrinkage

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

4) Yellow Index Change Rate (ΔYI)

The rate of change in yellow index (ΔYI, Yellow Index) before and after the pressure resistance test (PCT, Pressure Cooker Test, 2 atm, 120 ° C., 100% relative humidity and 75 hours)

? YI (%) = (YI before PCT - YI before PCT / YI before PCT) x 100

5) Reflectance

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

Properties Strength (Kgf / mm ² ) Shinto (%) Heat Shrinkage (%) △ YI reflectivity(%) MD TD MD TD MD TD Example 1 4.5 4.5 350 350 0.1 0 25 82 Example 2 4.4 4.5 360 370 0.5 0 23 83 Example 3 4.2 4.2 400 420 1.2 1.0 20 83 Example 4 4.4 4.4 370 350 1.0 0 22 81 Example 5 4.0 4.1 450 455 1.0 1.0 20 83 Example 6 3.9 4.0 460 470 1.5 1.0 17 82 Example 7 3.8 4.0 480 500 2.0 1.5 15 82 Comparative Example 1 4.2 4.3 500 500 0.5 0.5 24 78 Comparative Example 2 4.1 4.2 510 520 1.0 0.5 22 79 Comparative Example 3 4.1 4.1 550 565 1.4 1.5 19 79 Comparative Example 4 4.1 3.9 525 520 1.5 1.0 21 77 Comparative Example 5 3.7 3.6 580 580 1.3 1.3 20 79 Comparative Example 6 3.6 3.5 600 590 1.5 1.5 17 78 Comparative Example 7 3.5 3.5 620 630 2.6 2.0 14 78

As can be seen from Table 1, the film of the present invention using TPEE exhibited excellent effects in terms of physical properties such as strength, elongation, heat shrinkage, rate of yellow index change, and reflectance.

Claims (10)

Polyvinylidene fluoride (PVdF) resin 50-100% by weight of a thermoplastic polyester elastomer (TPEE) 0 ~ 50% by weight and titanium oxide (TiO ₂₎ A layer made of a 0-30 wt.%; And a B layer composed of 0 to 40% by weight of PVdF, 20 to 50% by weight of TPEE and 30 to 50% by weight of TiO ₂ , wherein the A layer and the B layer are co-extruded,
And an average particle diameter of the titanium oxide is 0.1 to 0.7㎛, the content of the TiO _2, based on the total weight of the film of 5 to 50% by weight,
(MD) and width direction (TD) for a heat treatment at 150 占 폚 and 30 minutes, and tensile strengths in a longitudinal direction (MD) and a width direction (TD) of at least 3.8 kgf / TD) is not more than 2.0%, the rate of change of the yellowness index (DELTA YI) with respect to pressure cooker test at 2 atm, 120 DEG C, 100% relative humidity and 75 hours is not more than 25% Wherein the reflectance at a wavelength of 80% or more is 80% or more. The method according to claim 1,
Wherein the film is a two-layer or more film. The method according to claim 1,
Wherein the PVdF resin is a PVdF single resin or a PVdF copolymer resin. The method of claim 3,
Wherein the PVdF copolymer resin is a resin obtained by copolymerizing 50 wt% or more of vinylidene fluoride (VF2) and a comonomer copolymerizable with VF2, wherein the comonomer is selected from the group consisting of vinyl fluoride, trifluoroethylene (VF3), chlorotrifluoro But are not limited to, ethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro (alkylvinyl) , Perfluoro (2,2-dimethyl-1,3-dioxole) (PDD), and mixtures thereof. The method according to claim 1,
Characterized in that the TPEE resin is selected from the group consisting of polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polycyclohexylenedimethylene terephthalate (PCT) and polytrimethylene terephthalate (PTT) Resistant, weather-resistant multilayer film. The method according to claim 1,
Wherein the MFI (melt flow index) of the PVdF copolymer resin is 1 to 11 g / 10 min as measured at 230 캜 under a load of 2.16 kg. The method according to claim 1,
Wherein the MFI (melt flow index) of the TPEE resin is 5 to 14 g / 10 minutes as measured at 230 占 폚 under a load of 2.16 kg. The method according to claim 1,
Wherein the TiO _{2 has} an average particle diameter of 0.1 to 0.7 μm. The method according to claim 1,
Wherein the thickness of the A layer and the B layer is 30 nm to 5 占 퐉, respectively, and the total thickness of the film is 20 占 퐉 to 100 占 퐉. A back sheet for a solar cell comprising a weather-resistant multilayer film according to any one of claims 1 to 9.