KR20140042957A - Fluoropolymer coating compositions and fluoropolymer coated films useful for backsheets with high durability in photovoltaic modules - Google Patents

Abstract

Provided in the present invention is a fluoropolymer coating composition comprising: a fluorinate polymer selected among a homopolymer of a vinylidene fluoride monomer, and a copolymer comprising a vinylidene fluoride monomer and one or more comonomer; an acrylic polymer containing a hydroxyl group; and polyisocyanate containing a perfluoroalkyl group, and by using the composition, a backsheet with high durability and high weatherability in a photovoltaic module can be manufactured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluoropolymer coating composition and a fluoropolymer coating film for producing a highly durable back sheet for a solar cell module. 2. Description of the Related Art Fluoropolymer Coating Compositions and Fluoropolymer Coated Films for High Durability in Photovoltaic Modules

The present invention relates to a fluoropolymer coating composition capable of producing a highly durable back sheet for a solar cell module, and a fluoropolymer coating film produced using the same.

The solar cell module consists of an outer glass material, typically a solar cell encapsulated in a transparent protective package, and a backsheet on the backside. Solar cells are made of materials that contain silicon for photovoltaic collection, cadmium indium selenide (CIS), cadmium indium galliumselenide (CIGS), and quantum dots.

Since the solar cell module is used outdoors, high durability and weather resistance are required in its structure and material structure. In particular, since the back sheet on the back surface of the solar cell module exposed to the environment plays a role in maintaining the long-term characteristics of the solar cell for more than 25 years even in harsh environments, it not only has excellent weather resistance and durability, And UV resistance. The backsheet plays an important role in protecting against degradation of the silicon wafer caused by reaction with water, oxygen, or UV rays.

Generally, the backsheet is used in the form of a film laminated with three functional layers. The polymer base film having excellent water vapor and oxygen barrier properties is a fluoropolymer film excellent in weather resistance and encapsulated in both sides. Polyethylene terephthalate (PET) has been mainly used as a polymer base film, and Tedlar (trade name) (United States Patent 6,646,196), a polyvinyl fluoride (PVF) film produced by DuPont, USA, has been mainly used as a weather resistant fluoropolymer film. The polyethylene terephthalate is excellent in water vapor barrier property and relatively inexpensive, but the performance is easily deteriorated due to exposure to environmental influences such as UV light, IR light and ozone. Therefore, it is possible to protect PET with weather resistant Tedlar (PVF). However, the back sheet on which the Tedlar film is adhered is relatively expensive and resistant to moisture.

A typical solar cell backsheet is made of a laminate film of a PVF / PET / PVF layer. In this structure, the adhesion of PVF to PET has a disadvantageous point. Generally, the polymer surface is treated with a corona discharge or a similar technique, or an adhesive is applied on PET to improve adhesion.

Such PVF / PET / PVF laminate film composites have conventionally been produced from fluoropolymers adhered to polyester substrates, particularly pre-made laminate films of PVF. However, the lamination process of bonding a preliminarily prepared fluoropolymer laminate film to a polymer substrate using an adhesive has a complicated manufacturing process, and there is a problem that the fluoropolymer laminate is separated again after outdoor exposure for several years.

Further, the prior art is required to form at least one adhesive layer or one adhesive layer with one primer layer prior to the lamination process step, and a laminate film using a fluoropolymer film prepared in advance and requiring heat and pressure in the lamination process step It is expensive to manufacture and requires a lot of investment. In addition, the previously prepared fluoropolymer laminate film must have a sufficient thickness to impart the required strength in the manufacturing process and the subsequent process. As a result, the fluoropolymer laminate film is required to have an effective protective layer, . This increases the price of the solar cell module back sheet.

In order to solve the problems of the conventional technology, a technique for manufacturing a back sheet by coating a fluorine polymer on a polymer substrate has been developed. U.S. Patent Application Publication No. 2007-0154704, 2009-0260677 discloses a back sheet for a solar cell on which a fluoropolymer is coated on a polymer base film, and a mixture of the fluoropolymer and the adhesive polymer is disclosed in U.S. Patent Nos. 2010-0247789, 2011-0086172 Discloses a method for producing a back sheet for a solar cell coated with a fluoropolymer containing a substrate having a functional group capable of interacting with an adhesive polymer contained in a fluoropolymer coating composition. Korean Unexamined Patent Publication Nos. 2010-0105505, 2011-0030857, and 2011-0010386 disclose a back sheet for a solar cell comprising a fluoropolymer and an acrylic resin, or a coating layer including a polyamide resin or a urethane adhesive layer on a substrate, Lt; / RTI > However, they have a problem that the bonding strength between the fluoropolymer coating layer and the polymer substrate is insufficient, or the bonding layer is deteriorated when used for a long period of time in a high temperature and high humidity environment, and the bonding force is lost.

Accordingly, there is an increasing need for a backsheet material for a new solar cell module, which can reduce manufacturing cost while having excellent weatherability and durability while maintaining excellent adhesion even in a high temperature and high humidity environment in accordance with the rapid growth of solar cell demand .

U.S. Published Patent Application No. 2007-0154704 (2007.07.05) U.S. Published Patent Application No. 2009-0260677 (Oct. 22, 2009) Korean Patent Publication No. 2010-0105505 (September 29, 2010)

The present invention was conceived to overcome the problem that the adhesive force between the fluoropolymer coating layer and the polymer substrate is insufficient and the adhesive layer is deteriorated when used for a long time in a high temperature and high humidity environment to lose bonding force. The fluorine polymer composition is superior in durability and weatherability even in a high temperature and high humidity environment by preventing deterioration of the adhesive layer due to moisture penetration during long-term use, and the fluorine polymer composition is coated on the polymer base material And a back sheet of a solar cell module using the fluorine polymer coating film.

In addition, since it is not necessary to previously form an adhesive layer on a substrate, the present invention can dramatically shorten the manufacturing process steps, and even when the thickness of the fluoropolymer coating layer is adjusted as thin as possible, Which is capable of significantly reducing the size of the solar cell module back sheet.

The present inventors have used a fluoropolymer coating composition comprising a crosslinking agent of a polyisocyanate having an acrylic adhesive polymer binder resin and a perfluoroalkyl group which are compatible with a fluoropolymer and a fluoropolymer and have a functional group capable of crosslinking When a fluorine polymer is coated on a polymer base material such as polyester terephthalate (PET), the adhesion between the fluorine polymer coating layer and the polymer base material is remarkably improved to provide a film having excellent weather resistance and water resistance. The present inventors have found that a back sheet for a solar cell module manufactured using the same can exhibit high weather resistance and durability.

The present invention relates to a fluoropolymer selected from a homopolymer of a vinylidene fluoride monomer and a copolymer comprising a vinylidene fluoride monomer and at least one comonomer; An acrylic polymer containing a hydroxy group; And a polyisocyanate containing a perfluoroalkyl group can be provided.

The polymer coating composition according to one embodiment of the present invention includes a fluorinated polymer containing 60 mole% or more of vinylidene fluoride.

The polymer coating composition according to an embodiment of the present invention is any one or more monomers selected from alkyl acrylate and alkyl methacrylate having 1 to 18 carbon atoms in the alkyl group, and hydroxy alkyl having 1 to 4 carbon atoms in the alkyl group. It includes an acrylic polymer prepared by polymerizing any one or more monomers selected from acrylate and methacrylate.

The fluorine-based polymer and the hydroxyl group-containing acrylic polymer according to one embodiment of the present invention may be included in the solid content of the total composition of 60 to 90% by weight and 10 to 40% by weight, respectively.

Polyisocyanate containing a perfluoroalkyl group according to an embodiment of the present invention may be included 0.1 to 10% by weight based on the solids content of the total composition.

The perfluoroalkyl group-containing polyisocyanate according to an embodiment of the present invention may be obtained by reacting perfluoroalkyl group-containing alcohol represented by the following general formula (1) and an organic polyisocyanate.

[Chemical Formula 1]

F (CF ₂ ) _n (CH ₂ ) ₂ OH (n = an integer of 4 to 20)

The perfluoroalkyl group-containing polyisocyanate according to an embodiment of the present invention may be obtained by reacting perfluoroalkyl group-containing alcohol represented by the following general formula (2) with an organic polyisocyanate.

(2)

_{H (CF 2 CF 2) n} CH 2 OH (n = integer of 1 to 6)

The present invention relates to a fluoropolymer coating film comprising a polyester polymer base material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalene and mixtures thereof, and a coating layer containing the fluoropolymer coating composition according to the present invention on the polymer base, .

The present invention can provide a back sheet for a solar cell module comprising the fluoropolymer coating film.

In addition, the present invention can provide a solar cell module including the back sheet.

The fluoropolymer coating composition according to the present invention dramatically improves the adhesion of the adhesive layer between the coating layer and the substrate and has excellent water resistance. The back sheet for a solar cell module containing the fluoropolymer coating film using the fluoropolymer coating composition has a high temperature Deterioration of the adhesive layer due to moisture penetration can be prevented even when used for a long time in a high humidity environment.

In addition, when the fluoropolymer coating composition according to the present invention is used, it is not necessary to previously form an adhesive layer on a substrate as compared with a back sheet having a conventional laminated film structure, so that the manufacturing process can be shortened, It is possible to provide a back sheet having a high durability and weather resistance, thereby reducing the cost of the raw material.

The present invention relates to a fluoropolymer selected from a homopolymer of a vinylidene fluoride monomer and a copolymer comprising a vinylidene fluoride monomer and at least one comonomer; An acrylic polymer containing a hydroxy group; And a polyisocyanate containing a perfluoroalkyl group can be provided.

The fluorine-based polymer according to an embodiment of the present invention may be selected from a homopolymer of vinylidene fluoride monomer, and a copolymer comprising vinylidene fluoride monomer and at least one comonomer.

The fluorine-based polymer according to one embodiment of the present invention is selected from homopolymers and copolymers of vinylidene fluoride (VDF), preferably contains 60 mole% or more of vinylidene fluoride, and preferably contains 80 mole% or more of VDF ≪ RTI ID = 0.0 > VDF. ≪ / RTI > If the vinylidene fluoride content is less than 60 mole%, the weather resistance of the back sheet may be lowered.

The vinylidene fluoride copolymer is preferably vinylidene fluoride includes a comonomer selected from the group consisting of fluoroolefins, fluorovinyl ethers and fluorodioxoles, specifically, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorothyrifluoroethylene (CTFE), trifluoroethylene, hexafluoroisobutylene, perfluorobutyl ethylene, perfluoro propyl vinyl ether (PPVE), Perfluoro ethylvinyl ether (PEVE), perfluoro methyl vinyl ether (PMVE), perfluoro-2,2-dimethyl-1,3-diosol (PDD), perfluoro-2-methylene-4- Any one or more selected from methyl-1,3-dioxolane can be used.

The crosslinkable adhesive acrylic polymer binder resin according to an embodiment of the present invention is mostly oriented between the polymer substrate and the fluoropolymer coating layer to form an adhesive layer in the course of coating and curing and the polyisocyanate having a perfluoroalkyl group is a polymer Crosslinking with the polymeric binder resin not only improves the adhesion between the fluoropolymer coating layer and the polymer substrate but also enhances the mechanical strength.

The polyisocyanate containing a perfluoroalkyl group according to an embodiment of the present invention has a perfluoroalkyl group having a critical surface tension of about 8 dynes / cm and excellent in hydrophobicity, so that a polyisocyanate having a perfluoroalkyl group As a crosslinking agent is capable of exhibiting excellent water resistance and is further selected from a homopolymer of a vinylidene fluoride monomer according to the present invention and a copolymer comprising a vinylidene fluoride monomer and at least one comonomer When used in combination with an acrylic polymer containing a fluorine-based polymer and a hydroxy group, an unpredictable effect of improving weatherability and durability can be obtained. Particularly, a fluorine polymer film to which a fluorine polymer coating composition containing such a composition is applied and a fluorine- For battery modules Has excellent long-term weathering using durable advantage in hot and humid conditions.

The crosslinkable adhesive acrylic polymer according to one embodiment of the present invention is a (meth) acrylic monomer, a hydroxyl group-containing acrylic monomer, a polymerization initiator and a solvent are added to a polymerization reactor for reaction at 60 to 120 ° C. for 1 to 8 hours. It is preferable that the weight average polymerization degree of an acrylic polymer is 1,000-20,000.

The polymerizable monomer capable of forming an adhesive acrylic polymer according to an embodiment of the present invention is any one or more monomers selected from alkyl acrylate and alkyl methacrylate having 1 to 18 carbon atoms in the alkyl group, and 1 It can be prepared by polymerizing any one or more monomers selected from hydroxy alkylacrylate and methacrylate having ˜4 carbon atoms.

The alkyl acrylate and alkyl methacrylate having 1 to 18 carbon atoms in the alkyl group according to an embodiment of the present invention may be selected from the group consisting of methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, iso Propyl methacrylate, butyl acrylate, isobutyl methacrylate, butyl methacrylate, t-butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl Methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate; Styrene, alpha methyl styrene, acrylamide, methacrylamide, acrylonitrile, hydroxy methacrylamide, and mixtures thereof.

In order to give a hydroxy group that is a crosslinking functional group to the adhesive acrylic polymer according to an embodiment of the present invention, at least one monomer selected from hydroxy alkylacrylate and methacrylate having 1 to 4 carbon atoms in the alkyl group is an alkyl group. It can be used together with any one monomer selected from alkyl acrylate and alkyl methacrylate having 1 to 18 carbon atoms in.

According to an embodiment of the present invention, at least one monomer selected from the group consisting of hydroxyalkyl acrylates and methacrylates having 1 to 4 carbon atoms in the alkyl group may be hydroxymethyl acrylate, hydroxymethyl methacrylate, hydroxyethyl Acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, and mixtures thereof may be used. More preferably, the acrylic polymer is an alkyl methacrylate having 2 to 6 carbon atoms in the alkyl group or an alkyl acrylate having 2-8 carbon atoms in the alkyl group and a hydroxyalkyl (meth) acrylate having 2-4 carbon atoms in the alkyl group Can be selected from monomers.

The polymerization initiator according to an embodiment of the present invention may be an azo-containing compound, a peroxy-containing compound or a benzoic acid compound, and examples thereof include azo-bis-isobutyronitrile, But are not limited to, 1,1'-azo-bis (cyanocyclohexane), t-butyl peracetate, peroxy acetate, di- Butyl peroxide and the like can be used.

The solvent according to an embodiment of the present invention may include ketone compounds such as methyl ether ketone, methyl isobutyl ketone and methyl amyl ketone, aromatic hydrocarbon compounds such as toluene and xylene, propyl carbonate, n-methyl pyrrolidone, Acetate, dimethylformamide, isophorone, and mixtures thereof.

The fluoropolymer coating composition according to one embodiment of the present invention comprises a fluorinated organic polyisocyanate crosslinking agent obtained by reacting a perfluoroalkyl group-containing alcohol with an organic polyisocyanate in an amount of about 0.1 to 10 wt% , And about 0.1 to 50 mol% of the active isocyanate group of the organic polyisocyanate may be reacted with the perfluoroalkyl group-containing alcohol at a temperature of about 50-120 DEG C in the presence of a catalyst to form the fluorinated organic polyisocyanate.

When the amount of the active isocyanate is less than 0.1 mol%, the effect of improving the water resistance (hydrophobicity) of the adhesive layer is hardly expected. When the amount is more than 50 mol%, the water resistance is not improved any more, The alcohol-containing alcohol is unnecessarily used, which is uneconomical.

As the organic polyisocyanate, aromatic, aliphatic, cycloaliphatic 2 and 3-functional polyisocyanates can be used. Specific usable diisocyanates include 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'- Examples of the diisocyanate include bisphenylene diisocyanate, toluene diisocyanate, biscyclohexyl diisocyanate, tetramethylene xylene diisocyanate, ethylethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1-methyltrimethylene diisocyanate, 1,4-cyclohexyldiisocyanate, 1,3-phenylene diisocyanate, 1,5-naphthalene diisocyanate, bis- (4-isocyanatocyclohexyl) -methane, 4,4 ' - diisocyanatodiphenyl ether, and the like. Examples of the trifunctional isocyanate include triphenylmethane triisocyanate, 1,3,5-benzene triisocyanate, 2,4,5-toluene triisocyanate and the like. And oligomers of diisocyanate such as hexamethylene diisocyanate trimmer.

The perfluoroalkyl group-containing polyisocyanate according to an embodiment of the present invention may be obtained by reacting perfluoroalkyl group-containing alcohol represented by the following general formula (1) and an organic polyisocyanate.

[Chemical Formula 1]

F (CF ₂ ) _n (CH ₂ ) ₂ OH (n = an integer of 4 to 20)

The perfluoroalkyl group-containing polyisocyanate according to an embodiment of the present invention may be obtained by reacting perfluoroalkyl group-containing alcohol represented by the following general formula (2) with an organic polyisocyanate.

(2)

_{H (CF 2 CF 2) n} CH 2 OH (n = integer of 1 to 6)

The fluoropolymer coating composition according to an embodiment of the present invention may use a catalyst for curing reaction. The amount of the catalyst used is preferably 0.01 to 1.0 wt% based on the solids content of the fluoropolymer coating composition.

The catalyst may be any one or more selected from dibutyltin dilaurate, dibutyltin diacetate and tertiary amine, preferably dibutyltin dilaurate.

Adhesive acrylic polymer binder component according to an embodiment of the present invention may contain about 10 to 40% by weight based on the solids content of the fluoropolymer coating composition. If the content is less than 10% by weight, the bonding force between the fluoropolymer coating layer and the polymer substrate is not sufficient. If the content is more than 40% by weight, the physical properties of the fluoropolymer coating layer may be deteriorated and durability and weatherability may be deteriorated.

The present invention may include additives such as pigments, fillers, light stabilizers, etc., or barrier particles in order to improve the barrier properties of oxygen and moisture to the fluoropolymer coating composition as needed in the back sheet production process.

The polymeric base film according to one embodiment of the present invention is a polyester, and specifically, polyethylene terephthalate, polyethylene naphthalene, polyethylene terephthalate / polyethylene naphthalate, and mixtures thereof may be used. The polyester is excellent in electrical insulating property and moisture barrier property, and is inexpensive because it is economical.

The polymeric substrate film according to an embodiment of the present invention contains a functional group that interacts with the compatible adhesive polymer in order to promote adhesion of the fluoropolymer coating to the substrate film on the surface. At this time, the polymer base film may be coated with a fluorine polymer on both sides to impart excellent strength, weather resistance, UV resistance and moisture barrier property, and preferably form a sandwich type structure.

The polymer base film according to an embodiment of the present invention may be coated with a primer layer. The primer layer promotes adhesion of the fluoropolymer coating to the substrate film by providing a functional group that interacts with the compatible adhesive polymer in the fluoropolymer coating composition. As the primer, a polyamine, a polyamide, an acrylamide polymer, a polyethyleneimine, an acrylate polymer, a polyester, a polyurethane, an epoxy polymer, and a mixture thereof may be used.

The fluoropolymer coating composition according to an embodiment of the present invention includes a solution or a dispersion. In this case, the solvent may be a solution or a dispersion having a boiling point that is high enough to avoid bubbling during the film forming / drying process. The polymer present in the form of a dispersion requires a solvent to help coalescence of the fluoropolymer.

The concentration of the polymer in the coating composition according to an embodiment of the present invention can improve the workability by controlling the viscosity, which depends on the specific polymer, the other components of the composition, and the processing apparatus and conditions to be used.

The fluorine polymer coating composition according to an embodiment of the present invention preferably contains 10 to 50 wt% of the fluorine polymer based on the total weight of the composition.

The polymer form in the fluoropolymer coating composition according to an embodiment of the present invention is present in the form of a dispersion or a solution depending on the type of the fluoropolymer and the solvent to be used and the solvent is acetone, methyl ethyl ketone, tetrahydrofuran, isophorone, dimethylacetate Amide, propylene carbonate, y-butylolactone, N-methylpyrrolidone, dimethylsulfoxide, and mixtures thereof.

In order to produce the fluoropolymer coating film according to an embodiment of the present invention, the fluoropolymer composition can be directly applied to the polymer substrate in a liquid state by a conventional coating method without preparing a preformed film. The coating method may be, but not limited to, casting, dipping, spraying, coating or roll, knife, curtain coating, and the like.

The liquid dispersion after the liquid coating according to one embodiment of the present invention removes the solvent to form a fluoropolymer coating on the substrate film. The removal can be performed by a method of thermally condensing after drying. At this time, the temperature is preferably 200 ℃ at room temperature (25 ℃), the temperature of the film is lower than the temperature. The curing temperature of the coating should be sufficient to allow the functional groups of the crosslinkable adhesive acrylic polymer and the functional groups and cross-linking agent of the polymer-based film to interact so that the fluoropolymer coating fully adheres to the substrate film.

It is preferable to heat the polymer substrate to 120 DEG C to 250 DEG C so that the fluoropolymer composition is coated on the polymer substrate, the solvent is removed, and the fluorine polymer particles coalesce into a continuous film. The temperature is preferably set to be higher than the temperature of the fluoropolymer coating. At this time, the solvent helps the condensation to be performed at a lower temperature than when the solvent is not used. Therefore, the conditions for coagulating the polymer can be controlled depending on the type of the fluorine polymer used, the operating conditions such as the casting dispersion and the thickness of the base film.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. Various modifications and variations are possible in light of the above teachings.

A fluoropolymer coating film according to an embodiment of the present invention is formed by forming a fluoropolymer coating layer on a polyester (SKC skyrol SG00L, thickness 250 탆) substrate and evaluating the adhesive strength between the polyester substrate and the fluoropolymer coating layer according to ASTM D1876- Peel Strength was measured by a < 01 > method.

(evaluation)

(1) Peel Strength (180 T-Peel Strength) Evaluation: Adhesive strength evaluation

The peel strength was measured with an Instron Model 4482 (Instron Model 4482), and the highest value was recorded and the three samples were averaged. (ASTM D1876-01 T-Peel Test). A maximum value of 0 is recorded when the sample is easily hand-peeled at the initial stage of peeling.

(2) Temperature and humidity test (Damp Heat Test)

Evaluate whether deformation, alteration, pinhole and layer separation occurs after exposure to a damp heat test for 1000 hours in a chamber maintained at 85 ° C / 85% relative humidity.

Production Example 1  : Fluorine polymer  Produce

The homopolymers and copolymers of vinylidene fluoride according to one embodiment of the present invention were prepared as follows.

<Fluorine Polymer (A)>

620 ml of deionized water was added to a 1000 ml pressure reactor equipped with a stirrer, and the mixture was depressurized at 5 atm with nitrogen gas and then degassed five times to remove air, and then 20% by weight of perfluorooctanoic acid 6.3 ml of aqueous solution of sodium chloride and 1.0 ml of chloroform were added. The temperature of the reactor was raised to 80 DEG C and the pressure was increased to 300 psig by adding vinylidene fluoride (VDF). Thereafter, 10 ml of an aqueous solution of 2 g / L ammonium ascorbate (APS) was added. After a 5 psi pressure drop occurred at the beginning of the reaction, the initiator aqueous solution was started to be supplied at a rate of 0.6 ml / min while maintaining the pressure in the reactor at 300 psig. After the initiation of the reaction, 205 g of VDF was added, the supply of all the raw materials was stopped, and the pressure of the reactor was lowered to recover the product. The solids content of the product dispersion was 25.0%. The product dispersion was diluted with the same amount of deionized water and then coagulated by freezing. The aggregated fluoropolymer solids were collected by filtration, washed three times with 1000 ml of deionized water, and dried at 50 ° C.

<Fluorine polymer (I)>

Except that a vinylidene fluoride / chlorotetrafluoroethyl (VDF / CTFE = 80: 20 weight ratio) was used in place of the vinylidene fluoride (VDF).

<Fluorine polymer (c)>

Except that a vinylidene fluoride / hexafluoropropylene (VDF / HFP = 70: 30 weight ratio) was used in place of the vinylidene fluoride (VDF).

Manufacturing example  2 : Perfluoroalkyl  contain Polyisocyanate  synthesis

&Lt; Perfluoroalkyl-containing polyisocyanate a >

300 g of hexamethylene diisocyanate (HMDI; MW = 168.19), 30 g of dimethylformamide, perfluoroalkyl alcohol (F (CF ₂ ) _n (CH ₂ ) ₂ OH, n = 6; MW = 364) and 0.05 g of dibutyltin dilaurate (2% ethyl acetate) were charged and replaced with nitrogen. The reaction mixture was heated to 75 DEG C and reacted at this temperature for 6 hours.

<Perfluoroalkyl-containing polyisocyanate b>

Stirrer, hexamethylene diisocyanate (HMDI; MW = 250.25) in 500 ml reactor equipped with a condenser and a temperature indicator 300g, dimethylformamide 30g, perfluoroalkyl alcohol _{(F (CF 2) n (} CH 2) 2 OH; n = Average 8; MW = 464) and 0.05 g of dibutyltin dilaurate (2% ethyl acetate) were charged and replaced with nitrogen. The reaction mixture was heated to 75 DEG C and reacted at this temperature for 6 hours.

<Perfluoroalkyl-containing polyisocyanate c>

300 g of toluene isocyanate (TDI; MW = 174.16), 50 g of dimethylformamide, perfluoroalkyl alcohol (F (CF ₂ ) _n (CH ₂ ) ₂ OH; n = 8; MW = 464) and 0.05 g of dibutyltin dilaurate (2% ethyl acetate) were charged and replaced with nitrogen. The reaction mixture was heated to 75 DEG C and reacted at this temperature for 6 hours.

<Perfluoroalkyl-containing polyisocyanate d>

300 g of hexamethylene diisocyanate trimmers (Desmodur N-3390; MW = 504.58), 60 g of dimethylformamide, 60 g of perfluoroalkyl alcohol (F (CF ₂ ) _n (CH ₂ ) ₂ OH; n = 8; MW = 464) and 0.05 g of dibutyltin dilaurate (2% ethyl acetate) were charged and replaced with nitrogen. The reaction mixture was heated to 75 DEG C and reacted at this temperature for 6 hours.

Production Example 3  : Acrylic polymer synthesis

<Acrylic Polymer A>

After dissolving 0.5 g of sodium dodecyl sulfate and 0.3 g of sodium bicarbonate in 190 g of distilled water, it is transferred to a 500 mL 4-neck flask equipped with a stirrer, a condenser and a thermometer, and then heated to 80 ° C. After adding 0.5 g of sodium persulfate initiator dissolved in 10 g of distilled water, 50 g of an acrylate monomer mixture (methyl methacrylate / ethyl acrylate / 2-hydroxymethylacrylate = 42.5 / 5 / 2.5) Octanethiol (0.5 g) was introduced into the reactor at a flow rate of 20 mL / h using a syringe pump. After the addition of the acrylate monomer mixture was completed, the reaction was continued for 3 hours to synthesize a hydroxyl group-containing acrylic polymer. The reaction product, polymer water dispersion, was dried and then washed with 500 ml of distilled water five times to remove inorganic substances and surfactants. This was dried to obtain a hydroxyl group-containing acrylic polymer in powder form.

<Acrylic polymers B, C, D, E, F>

The hydroxyl group-containing acrylic polymer as shown in Table 1 below was synthesized by changing the kind and content of the acrylate monomer in the same manner as in < Hydroxy group-containing acrylic polymer A &gt;.

(Example 1)

21 g of the powdery solid of <Fluoropolymer 1> (VDF homopolymer) prepared by the above-mentioned method and 0.4 g of <Perfluoroalkyl-containing polyisocyanate a>, which was synthesized by the above-mentioned method, were mixed in a dimethylformamide solvent And then uniformly mixed using a ball mill containing 4 mm glass beads for 30 minutes to prepare a fluoropolymer coating composition. This composition was coated on SKC's PET film (SKC skyrol SG00L, 250 탆 thick) substrate using a draw knife of 0.125 mm thickness. This was allowed to evaporate in air for 5 minutes and then cured in an oven. Peel strength (adhesion) between the fluoropolymer coating and the PET substrate of the coating film was measured using the T-Peel Test method (Damp Heat Test) was conducted for 80 days, and then deformation, deterioration, pinhole and layer separation, etc. were observed. Did not occur.

(Examples 2 to 14)

A fluoropolymer coating composition was prepared in the same manner as in Example 1, except for the kind and amount of the fluoropolymer, the acrylic polymer, and the perfluoroalkyl group-containing polyisocyanate prepared in the fluoropolymer, and the same procedure as in Example 1 was carried out. The results of the peeling strength measurement and the temperature and humidity test (Damp Heat Test) on the coating layer formed by coating the fluorine polymer on the film are shown in Table 2 below. As shown in Table 2, the fluoropolymer coated film prepared using the fluoropolymer coating composition according to an embodiment of the present invention has excellent adhesion and durability.

Claims (10)

Fluorine-based polymers selected from homopolymers of vinylidene fluoride monomers and copolymers comprising vinylidene fluoride monomers and one or more comonomers; An acrylic polymer containing a hydroxy group; And a polyisocyanate containing a perfluoroalkyl group. The method of claim 1,
Wherein the fluorine-based polymer contains vinylidene fluoride in an amount of 60 mole% or more. The method of claim 1,
The acrylic polymer is selected from any one or more monomers selected from alkyl acrylate and alkyl methacrylate having 1 to 18 carbon atoms in the alkyl group, and hydroxy alkyl acrylate and methacrylate having 1 to 4 carbon atoms in the alkyl group. Fluoropolymer coating composition prepared by polymerizing any one or more monomers. The method of claim 1,
The fluorine-based polymer and the hydroxy group-containing acrylic polymer are 60 to 90% by weight and 10 to 40% by weight, respectively, based on the solids content of the total composition. The method of claim 1,
Polyisocyanate containing a perfluoroalkyl group is a fluoropolymer coating composition containing 0.1 to 10% by weight based on the solids content of the total composition. The method of claim 1,
Wherein the polyisocyanate containing a perfluoroalkyl group is obtained by reacting a perfluoroalkyl group-containing alcohol represented by the following formula (1) and an organic polyisocyanate.
[Chemical Formula 1]
F (CF ₂ ) _n (CH ₂ ) ₂ OH (n = an integer of 4 to 20) The method of claim 1,
Wherein the polyisocyanate containing a perfluoroalkyl group is obtained by reacting a perfluoroalkyl group-containing alcohol represented by the following formula (2) and an organic polyisocyanate.
(2)
_{H (CF 2 CF 2) n} CH 2 OH (n = integer of 1 to 6) Based polymer substrate selected from the group consisting of polyethylene terephthalate, polyethylene naphthalene, and mixtures thereof, and a fluoropolymer containing a coating layer containing any one of the compositions selected from the group consisting of the first to seventh layers on the polymer substrate Coating film. A back sheet for a solar cell module comprising the fluoropolymer coating film of claim 8. A solar cell module comprising the back sheet of claim 9.