KR20190055853A - ethylene vinyl acetate copolymer composite for solar cell encapsulant and solar cell encapsulant thereby - Google Patents

Abstract

The present invention relates to an ethylene vinyl acetate copolymer composition for a solar cell encapsulant. More specifically, the present invention relates to: an ethylene vinyl acetate copolymer composition for the solar cell encapsulant, which contains 0.05 to 2 parts by mass of surface-modified silicon dioxide, is capable of effectively bonding with EVA without damaging a solar light transmittance, and is capable of effectively increasing a volume resistivity value and sustainability of effects thereof to inhibit Na ion dissociation and migration to cells, thereby being able to effectively exhibit anti-PID performance. Also, the present invention relates to a manufacturing method thereof.

Description

The present invention relates to an ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant and a solar cell encapsulant using the same,

The present invention relates to an ethylene vinyl acetate (EVA) resin composition for use in a solar cell encapsulant, which protects a cell of a solar cell from external impact when used in a solar cell module and satisfies the required solar transmittance To an EVA sheet for a solar cell encapsulant for securing electrical insulation.

 EVA has been widely used for many years as a bar material for photovoltaic modules due to its high transparency and ease of processing, long-term durability and cost advantages. However, in recent years, some cell types are found to be vulnerable to PID phenomenon when EVA encapsulant is used, and improvement is required.

PID (Potential Induced Degradation) is a phenomenon of deterioration of power generation efficiency. When the solar module is exposed to high temperature and high humidity environment, high voltage current (High Potential) is applied to the module, . In order to overcome this PID phenomenon, efforts are being made to develop an anti-PID cell and improve the sealing material.

The photovoltaic module consists of a cell that produces electricity, an encapsulating material on both sides, a front glass part that receives sunlight, and a back sheet that has moisture and gas barrier function. In order to prevent the loss of sunlight transmittance, the encapsulant should be made as transparent as possible. To this end, EVA uses a product with the highest VA (Vinyl acetate) content. However, the increase in transparency with increasing VA content does not show any significant difference from 30%. The higher the VA content, the deteriorated electrical insulation and the viscosity increase, which makes processing difficult. Particularly, there is a disadvantage that acetic acid is generated due to decomposition by heat and moisture. On the other hand, when the content of vinyl acetate is small, blocking of the sheet, low water vapor permeability, and excellent electrical insulation are poor, but transparency and adhesiveness are poor. In order to compensate for the disadvantages thereof, there is a problem that various additives are excessively prescribed. Meanwhile, PID phenomenon, which is a problem in recent years, is considered to be related to the electrical characteristics and degradation characteristics of EVA. PID phenomenon is caused by leakage of current from the module to the outside due to the high voltage generated by the module, resulting in polarization in the cell or shunt resistance in the emitter layer due to migration of Na ions separated from the glass to the cell surface. Of the total population. Therefore, efforts are being made to increase the insulation property of the EVA sheet, particularly the volume resistivity.

Korean Patent Laid-Open Publication No. 10-2014-0090340 discloses that the leakage current is related to the insulation property of the EVA encapsulant, which is responsible for the electrical insulation of the cell. As a method for solving the problem in this respect, improvement of the EVA encapsulant To increase the electrical insulation resistance of EVA. Japanese Laid-Open Patent Application No. 2014-150246 also discloses a method for inhibiting the movement of Na. To this end, methods for prescribing additives containing Na capture function have been proposed. On the other hand, it is known that EVA decomposes vinyl acetate groups under high temperature by moisture to generate acetic acid. It is known that acetic acid generated in the EVA induces corrosion of glass to assist in the generation of Na ion and also helps the liberation of Na ion. Chinese Patent Publication No. 2012-10235124P A method of adding an acetic acid reactive additive as a means for suppressing the generation of acetic acid in EVA has been proposed. However, in the case of an increase or addition of such additives, problems such as discoloration of color (YI: increase in yellow index) due to deterioration of additive itself are caused, and inorganic additives having Na absorption ability cause problems of sunlight scattering There is a problem of reducing sunlight reaching the cell.

On the other hand, research results on the improvement of the insulation property by the inorganic additives presented recently have been shown to be effective at an initial value measured after production of the resin composition or the sealing material sheet. However, after the PID test with a high voltage or after the Damp Heat Test to reproduce the actual long-term conditions with high temperature and high humidity, it seems that this initial value fails to be maintained.

Accordingly, development of an EVA material for a solar cell encapsulant that can continuously prevent the PID phenomenon by securing the sustainability and the improvement of the insulation property value without deteriorating the long-term performance and the light transmittance of the solar module and member is required.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a solar cell module and a solar cell module in which the electrical insulation property and the anti-PID characteristic are continuously maintained And an ethylene vinyl acetate copolymer resin composition.

In order to achieve the above object, an aspect of the present invention is an ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant comprising a surface-modified silicon dioxide, wherein the surface-modified silicon dioxide is contained in 100 parts by mass of the ethylene vinyl acetate copolymer resin composition Wherein the silicon dioxide has an average particle size of 1 to 10 탆 and the silicon dioxide is spherical silicon dioxide. The present invention also provides an ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant.

According to an embodiment of the present invention, the surface area of the silicon dioxide is 200 to 500 m ² / g.

Modification of the silicon dioxide is performed by an alkoxysilane compound having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, and more preferably 3 to 6 carbon atoms, and the weight ratio of the alkoxysilane compound to the silicon dioxide is 0.1: 1 to 4 : 1.

The alkoxysilane to be used herein is at least one member selected from the group consisting of vinyltrichlorosilane, vinyltris (? Methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane,? -Methacryloxypropyltrimethoxysilane, (Aminoethyl) gamma -aminopropyltrimethoxysilane, N-beta (aminoethyl) gamma -aminopropyltrimethoxysilane, N- One kind selected from the group consisting of methyldimethoxysilane,? -Aminopropyltriethoxysilane, N-phenyl-? -Aminopropyltrimethoxysilane,? -Mercaptopropyltrimethoxysilane, and? -Chloropropyltrimethoxysilane Or more.

The silicon dioxide used in the present invention is preferably spherical silicon dioxide, and the average particle diameter is 1 to 10 mu m. This is because it prevents scattering of silicon dioxide and improves the dispersion effect when the resin is mixed. Therefore, it is preferable that the silicon dioxide used is not the aggregated form of silicon dioxide but is used as individual spherical silica.

As a method of modifying silicon dioxide, it is possible to provide soaking, solvent dilution mixing, drying, and spray spray drying. In the present invention, however, silicon dioxide is mixed with a solvent in which alkoxysilane is dissolved, followed by spray drying desirable.

According to an embodiment of the present invention, the ethylene vinyl acetate resin has a vinyl acetate content of 23 to 29% by weight and a melt index of 5 to 30 g / 10 min (190 ° C, 2.16 kg of ASTM D 1238).

Another aspect of the present invention is to provide a sealing material for a solar cell using the ethylene vinyl acetate copolymer resin composition.

Wherein the sheet for a solar cell encapsulant comprises 0.3 to 1.0 parts by weight of a crosslinking agent relative to 100 parts by weight of the ethylene vinyl acetate copolymer resin composition; 0.3 to 1.0 part by weight of a crosslinking auxiliary; 0.3 to 1.0 part by weight of a silane coupling agent; And a control unit.

The ethylene vinyl acetate copolymer resin composition using the above method has a volume resistivity of 5 * 10 15 Ω · cm or more.

The volume resistivity of the encapsulant for solar cell using the ethylene vinyl acetate copolymer resin composition after crosslinking is 5 * 10 < 15 > OMEGA cm or more. Also, it maintains the volume resistivity value more than 1 * 10 ^ 15 even after 1000 hours of Damp heat test.

INDUSTRIAL APPLICABILITY The ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant of the present invention increases the volume resistivity of the resin composition itself and reduces the amount of leakage current, thereby effectively preventing migration and deposition of Na ions into the cell, which is a cause of the PID phenomenon.

In addition, the surface modification improves the bonding strength between the silicon dioxide and the ethylene vinyl acetate copolymer, and the effect of improving the insulation property is maintained, and the amount of the alkoxysilane compound used therein is effectively reduced, It is possible to eliminate the side effect that occurs when the alkoxysilane compound is directly used in the resin in order to prevent the loss of transmittance and to strengthen the interfacial adhesion strength between the silicon dioxide and the resin. According to the present invention, the PID phenomenon is effectively prevented and the long-term durability of the solar module is maintained.

Further, the solar cell encapsulant according to the present invention can maintain physical properties even after a long period of time, for example, 1000 hours.

FIG. 1 is a graph showing the relationship between the initial volume resistivity after crosslinking of the solar cell encapsulating material sheet prepared using the ethylene vinyl acetate composition for solar cell according to the present invention and the Damp Heat Chamber having a relative humidity of 85 ° C / 85 after 500 hours and 1000 hours A graph of volume resistivity value measurement.
FIG. 2 is a graph comparing solar transmittance after 500 hours in a Damp Heat Chamber at a relative humidity of 85.degree. C./85 with respect to a glass / EVA sheet / glass specimen made of the solar cell sealing sheet.

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

The present invention relates to an ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant comprising a surface-modified silicon dioxide, wherein the surface-modified silicon dioxide is contained in an amount of 0.01 to 4 parts by mass Preferably 0.05 to 2 parts by mass, and the silicon dioxide has an average particle size of 1 to 10 μm, and the silicon dioxide is spherical silicon dioxide. The present invention also provides an ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant.

If the amount of the surface-modified silicon dioxide is less than 0.05 part by mass, it is difficult to expect a desired volume resistivity increasing effect. If the amount of the surface-modified silicon dioxide is more than 2 parts by mass, the light scattering increases and the cell efficiency is lowered.

The silicon dioxide used for the surface modification preferably has an average particle size of 0.1 to 30 mu m, more preferably 1 to 10 mu m. If it is less than 1 탆, the dispersibility when mixed with ethylene vinyl acetate deteriorates, and if it is more than 10 탆, light scattering increases and the light transmittance becomes poor.

The surface area of the silicon dioxide used for the surface modification is preferably 50 to 1000 m ² / g, more preferably 200 to 500 m ² / g. If the volume resistivity is less than 200 m ² / g, the effect of increasing the volume resistivity is low. If the volume resistivity is more than 500 m ² / g, the increase of pore size in the particle prevents the effective use of alkoxysilane.

The weight ratio of the alkoxysilane compound and the silicon dioxide used for the surface modification is preferably 0.1: 1 to 4: 1. When the ratio of the alkoxysilane compound is less than 0.1, adhesion between the silicon dioxide and the ethylene vinyl acetate copolymer is lowered, The adsorption effect of ions is lowered. If the ratio is 4 or more, there is a problem that YI is increased due to the side effect due to the moisture absorption characteristics of the alkoxysilane.

The alkoxysilane compound having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms, and more preferably 3 to 6 carbon atoms used for the surface modification may be vinyltrichlorosilane, vinyltris (? Methoxyethoxy) silane, (3,4-epoxycyclohexyl) ethyltrimethoxysilane,? -Glycidoxypropylmethyldiethoxysilane, N- (methacryloxypropyltrimethoxysilane), vinyltrimethoxysilane, vinyltrimethoxysilane, aminopropyltrimethoxysilane,? - aminopropyltrimethoxysilane,? - aminopropyltrimethoxysilane,? - aminopropyltrimethoxysilane,? - aminopropyltrimethoxysilane, N- Silane,? -Mercaptopropyltrimethoxysilane, and? -Chloropropyltrimethoxysilane can be used.

Examples of the method for modifying silicon dioxide include a soaking method in which an alkoxysilane is directly added dropwise, a method in which an alkoxysilane is diluted with a solvent of an alcohol, followed by stirring with a silicon dioxide, and then a solvent is removed by a usual drying method, And the like can be used.

In the present invention, it is preferable that silicon dioxide is mixed with a solvent in which an alkoxysilane is mixed, followed by spray drying. For example, when a general method of diluting an alkoxysilane in a solvent and washing after a simple mixing reaction at room temperature is applied, the reaction must be proceeded at room temperature to prevent gelation of the alkoxysilane itself, The silane actually bonded to the surface OH group of the silicon dioxide becomes very small and mostly disappears in the washing process, so that the amount of the alkoxysilane remaining in the silicon dioxide becomes very small. As a result, On the other hand, in the spray drying method after the mixing reaction, which is preferably used in the present invention, only the solvent is effectively removed, and the silane compound remaining bonded at the room temperature to the surface hydroxyl group becomes the majority of the injected silane compound. , And then mixed with EVA, and at high temperature during high-temperature extrusion, effectively binds silicon dioxide and EVA. If the mixed silicon dioxide does not properly bond with the EVA through the silane compound, voids are generated at the interface, which acts as a defect causing light scattering, thereby lowering the light transmittance. In addition, such defects serve as a cause of deterioration of long-term property, and it becomes impossible to maintain the initial increased electrical insulation property.

The surface-modified silicon dioxide is a master batch type (ASTM D1238, 190 DEG C, 2.16 kg) mixed with an ethylene vinyl acetate resin and having a melt index of 5 to 30 g / 10 min. type resin is added to the ethylene vinyl acetate copolymer resin production process to ensure a uniform dispersibility. In another embodiment, the master batch of the surface-modified silicon dioxide is mixed with the ethylene vinyl acetate copolymer resin Can be mixed and used.

The ethylene vinyl acetate copolymer resin composition of the present invention may contain an ethylene vinyl acetate resin having a vinyl acetate content of 23 to 29% by weight and a melt index of 5 to 30 g / 10 min (190 ° C, 2.16 kg of ASTM D 1238) have. If the content of the vinyl acetate is less than 23% by weight, transparency lowers, the transmittance of the sunlight decreases, and the adhesive strength decreases. When the content of the vinyl acetate exceeds 29% by weight, the decomposition of the vinyl acetate functional group is accelerated and the content of free acetic acid increases sharply not. If the melt index of the ethylene vinyl acetate resin is less than 5 g / 10 min, the productivity of the extruder is increased due to an increase in the pressure of the extruder during sheet processing. If the melt index is more than 30 g / 10 min, The flowability of the solar cell is increased, and the leakage of the solar cell to the outside of the module or the movement of the solar cell is undesirable.

The present invention provides a process for producing an ethylene vinyl acetate copolymer resin composition.

The method for producing an ethylene vinyl acetate copolymer resin composition of the present invention comprises the steps of: injecting an ethylene monomer and a vinyl acetate monomer into a tubular reactor; Adding 100 to 3,000 ppm of a radical generating catalyst; A polymerization pressure of 2500 to 3000 kg / cm ² , a polymerization temperature of 200 to 300 ° C, and a polymerization time of 5 to 20 minutes; And 500 to 1500 ppm of a metal ion adsorbent after the polymerization step; And 500 to 1500 ppm of a nitric decomposition inhibitor into an extruder; . ≪ / RTI >

The ethylene vinyl acetate copolymer resin composition may include an ethylene vinyl acetate resin having a vinyl acetate monomer content of 23 to 29% by weight. When the content is less than 23% by weight, the transparency is lowered to lower the solar light transmittance, . When it exceeds 29% by weight, decomposition of the vinyl acetate coordination group is promoted, and the content of free acetic acid increases rapidly, which is not preferable.

The radical-generating catalyst is preferably a peroxide-based mixture, and may be contained at 100 to 3,000 ppm.

If the amount of the radical generating catalyst is less than 100 ppm, the reaction temperature during polymerization is low and the conversion to EVA is low and the molecular weight is not easily controlled. If the amount is more than 3,000 ppm, the reaction temperature during polymerization tends to be high.

Specific examples of the dialkyl peroxydicarbonate-based compound that can be used as the peroxide-based mixture include Di (2-ethylhexyl) peroxy-dicarbonate, Di-butylperoxy- Specific examples of the oxypivalate-based compound include t-amyl peroxypivalate, t-butyl peroxypivalate, and specific examples of the alkyl peroxyalkylhexanoate-based compound include t-amyl Butyl peroxy-2-ethyl hexanoate, tert-butyl peroxy-2-ethyl hexanoate, and tert-butyl peroxy-3,5,5-trimethyl hexanoate. The dialkyl peroxide type Specific examples of the compound include Dt-butyl peroxide, Di-t-amyl peroxide, and the like.

The polymerization pressure is preferably 2500 to 3000 kg / cm ² , and the polymerization temperature is preferably 200 to 300 ° C. The polymerization is preferably carried out for 3 to 10 minutes.

In the present invention, a photovoltaic ethylene vinyl acetate copolymer resin sheet (hereinafter referred to as EVA sheet) using the ethylene vinyl acetate copolymer resin composition can be provided.

The ethylene vinyl acetate copolymer resin sheet may further contain additives for crosslinking and adhesion at the time of lamination for module manufacture and crosslinking agents and crosslinking aids for processing EVA sheet for long term stability.

The crosslinking agent used in the EVA sheet is a peroxyketal having a half-life of 1 hour at 110 to 120 ° C, a peroxycarbonate having a half-hour of half-life at 90 to 130 ° C and a dialkyl peroxide having a half- More than species are preferred. The peroxyketals may be selected from the group consisting of 1,1-di (tert-amylperoxy) cyclohexane, 1,1-di (tert-butylperoxy) -3,3,5-trimethylcyclohexane, -Butylperoxy) cyclohexane, and the peroxycarbonate is 2,5-dimethyl-2,5-di- (2-ethylhexanonylperoxy) hexane, tert-amylperoxy-2-ethylhexanoate, tert- Butyl peroxy-2-ethyl hexanoate, tert-amyl (2-ethylhexyl) monoperoxycarbonate, tert-butyl isopropyl monoperoxycarbonate, 2,5-dimethyl- ) Hexane, tert-butyl- (2-ethylhexyl) monoperoxycarbonate, tert-amyl peroxybenzoate, tert-butyl peroxyacetate, tert-butylperoxy-3,5,5-trimethylhexanoate, butyl peroxybenzoate.

Also, the dialkyl peroxide may be at least one selected from the group consisting of dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, α, α'-di (tert- butylperoxy) Tert-butylperoxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3.

If the content of the crosslinking agent is less than 0.1 part by weight, sufficient crosslinking can not be attained. When the amount of the crosslinking agent is more than 1.5 parts by weight, bubbles may be formed at the time of lamination Unreacted cross-linking agent remains and may affect long-term properties, which is not preferable.

The EVA sheet using the ethylene vinyl acetate copolymer resin composition of the present invention may include a crosslinking aid together with a crosslinking agent.

The crosslinking aid may be selected from polyallyl compounds such as triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate and diallyl maleate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, Trimethylolpropane trimethacrylate, and trimethylolpropane trimethacrylate.

The content of the crosslinking aid is preferably 0.1 to 3 parts by weight based on 100 parts by weight of the total composition.

If the amount of the crosslinking aid is less than 0.1 parts by weight, the target crosslinking degree will not be satisfied. If the amount is more than 3 parts by weight, the crosslinking degree is too high, so that the stress applied to the cell may not be effectively removed. .

The EVA sheet for a solar cell using the ethylene vinyl acetate copolymer resin composition of the present invention may further contain various other additives as necessary.

Specific examples of the additives include ultraviolet absorbers, ultraviolet stabilizers, silane coupling agents, hindered phenol-based or phosphite-based antioxidants, hindered amine-based UV stabilizers, UV absorbers, flame retardants and discoloration inhibitors.

Examples of the ultraviolet absorber include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy- 4-n-dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2- Sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy- 4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, and the content of the ultraviolet absorber is 0.05 to 0.5 By weight.

Examples of the ultraviolet stabilizer include bis-2,2,6,6-tetramethyl-4-piperidinyl sebacate, bis-1-methyl-2,2,6,6-tetramethyl-4-piperidinyl Benzotriazole, 2- (2-hydroxy-3,5-di-tert-amylphenyl) -2H-benzotriazole Sol, polymethylpropyl-3-oxo- (4 (2,2,6,6-tetramethyl-4-piperidinyl) siloxane, and the content of the ultraviolet stabilizer is 100 wt% 0.05 to 0.5 parts by weight based on 100 parts by weight of the resin.

The silane coupling agent can be used to improve the adhesion between the EVA sheet and the glass or the cell. Specifically, the silane coupling agent may have a functional group such as a vinyl group, an acryloxy group and a methacryloxy group, and a hydrolyzable functional group such as an alkoxy group / RTI > For example, vinyltrichlorosilane, vinyltris (? Methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane,? -Methacryloxypropyltrimethoxysilane,? - (3,4-epoxy (Aminoethyl) gamma -aminopropyltrimethoxysilane, N-beta (aminoethyl) gamma -aminopropylmethyldimethoxysilane, N- Silane,? -Aminopropyltriethoxysilane, N-phenyl-? -Aminopropyltrimethoxysilane,? -Mercaptopropyltrimethoxysilane,? -Chloropropyltrimethoxysilane, and the like. And the content of the silane coupling agent is preferably 0.3 to 1 part by weight based on 100 parts by weight of the total composition. If it is used less than 0.3, the adhesion of glass to the glass is not good due to poor adhesion to the glass, so that the long-term performance of the module can not be guaranteed, and when it is used more than 1 part by weight, it acts as an increase factor of Y.I.

The additives may be dry-blended into an ethylene vinyl acetate copolymer resin to prepare a sheet for a solar cell encapsulant, and the additives may be introduced into an extruder or side-fed by an extruder separately from EVA.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

How to measure property

The physical properties of the EVA resin and the solar cell encapsulating material sheet were measured by the following methods and standards.

1) Light transmittance : The light transmittance in the range of 900 to 200 nm was measured using a UVvis-spectrometer. The specimens were prepared by putting the sheets produced in the extruder below between two sheets of low-iron glass for solar light and then laminating them at 150.degree.

2) Volumetric intrinsic resistance (electrical insulating property): Measured according to ASTM D257 (Voltage: 1,000 V) using an electric resistance meter. The resin composition was measured using a hot press after the production of a sheet having a thickness of 500 μm, and the sheet of the solar cell sealing material was extruded. The sample was placed on a glass plate and measured by a Damp Heat Tester after 500 hours and 1000 hours, and the change in volume resistivity was determined.

3) Measurement of YI : The manufactured solar cell sealant sheet was sandwiched between a low-iron solar cell glass and a back white back sheet for solar cell, and then laminated at 150 to prepare a sample. Using a color meter, the YI (yellow index) initial value , And the value (ΔYI) was obtained by measuring the value again after passage of 1000 hours in the thermostatic hygrostat at 85 ° C. and 85 RH.

4) PID (Potential Induced Degradation) measurement: Mini module was manufactured using 4 Si single crystals and EVA sheets manufactured, and IV curve was drawn using a solar simulator. The initial Power_max value was obtained, and the initial power_max value was measured at 85 ° C and 85 RH After holding for 96 hours under 1000V voltage, it was taken out again, and Power_max value was measured using a solar simulator to calculate the power production maintenance rate.

5) Evaluation of Na ion adsorption performance: After preparing 500 ppm solution of Na ion by using NaOH, 0.2 g of modified or unmodified silicon dioxide was added to 20 ml of the solution, and after 3 days, Na ion concentration of the solution was measured by ICP Na ion adsorption performance was directly evaluated. (Table 2)

Example 1

Silicon dioxide  Modification

The silicon dioxide was grace E300 (average particle size: 4 탆). Methacryloxypropyltrimethoxysilane was used at a weight ratio of 0.5: 1 to silicon dioxide for surface modification. The modification method was a method in which alkoxysilane was diluted with ethynol and mixed with silicon dioxide, followed by spray drying . 10 g of? -methacryloxypropyltrimethoxysilane was diluted with 100 ml of ethanol, and 20 g of silicon dioxide was added thereto, followed by stirring at room temperature for 1 hour. Thereafter, spray drying was performed under the condition of 100 degrees to remove alcohol as a solvent, and silicon dioxide to which alkoxysilane was bonded and coated was obtained. Thereafter, it was dried in a drying oven at 80 캜 for 24 hours to obtain 25 g of surface-modified silicon dioxide having a free flow characteristic.

M / B manufacture

1 kg of an ethylene vinyl acetate copolymer (VA content 28%, MI 25) and 20 g of the modified silicon dioxide prepared above were put into a Kneader, kneaded at 90 ° C and granulated to prepare a master batch containing 2wt% of modified silicon dioxide.

EVA resin polymerization

According to the method of the present invention, 28 wt% of vinyl acetate monomer was injected into a tubular reactor at 72 wt% of an ethylene monomer, Di (2-ethylhexyl) peroxy-dicarbonate, butylperoxy-3, 5, 5-trimethylhexanoate mixture (weight ratio: 20/20/30/30) at 1200 ppm using a high-pressure pump in a tubular reactor tubular reactor under the polymerization conditions of a polymerization pressure of 2650 kg / cm ² , a polymerization temperature of 240 ° C. and a polymerization time of 5 minutes to prepare an EVA resin having an MI of 25 g / 10 min. The EVA resin thus produced is granulated through an extruder.

Preparation of resin composition

The modified silicon dioxide-containing M / B was put into the EVA resin polymerization extruder so as to be uniformly dispersed in the EVA resin. The amount of modified silicon dioxide in the EVA resin composition was adjusted so that the amount of silicon dioxide was 0.1 phr.

EVA sheet manufacturing

An EVA sheet for a solar cell encapsulant was prepared using an ethylene vinyl acetate copolymer resin composition containing surface modified silicon dioxide.

0.5 part by weight of Lecerox TBEC (tert-butyl-2-ethylhexyl monoperoxycarbonate) as an acrylic resin and 0.5 part by weight of an acrylic acid copolymer of TAICROS (triallyl diisocyanate) as a crosslinking assistant was added to the ethylene vinyl acetate copolymer resin composition containing the surface- 0.2 part by weight of Chimassorb 81 (2-hydroxy-4-octyloxy-benzophenone) of Ciba, ultraviolet stabilizer Tinuvin 770 (bis-2,2,6,6- 6-tetramethyl-4-piperidinyl sebacate), and 0.3 parts by weight of OFS 6030 (methacryloxypropyltrimethoxysiloxane) of Dow Corning Corporation as a silane coupling agent were mixed. Thereafter, in a single screw extruder having a screw diameter of 40 mm and a T-die width of 400 mm, the temperature of the extruder was adjusted to 100 ° C and the rotation speed of the screw was adjusted to produce a solar EVA sheet having a thickness of 450 μm.

 The specimens were prepared according to the method described in the physical property measurement method of the EVA sheet, and the physical properties were measured according to each item. The measurement results are summarized in Table 1 below.

Example 2

Except that the weight ratio of alkoxysilane to silicon dioxide was changed to 1: 1 in the modification of silicon dioxide in Example 1 and that the content of modified silicon dioxide in the resin composition for solar cell encapsulant was adjusted to 0.2 phr Was prepared in the same manner as in Example 1.

Example 3

Except that the weight ratio of alkoxysilane and silicon dioxide was changed to 2: 1 in the modification of silicon dioxide in Example 1 and the content of modified silicon dioxide in the resin composition for solar cell encapsulation was adjusted to 0.2 phr Was prepared in the same manner as in Example 1.

Comparative Example 1

A sheet for solar cell encapsulant was manufactured and evaluated in the same manner as in Example 1 by using the resin prepared in Example 1 without adding the modified silicon dioxide M / B to the resin at all.

Comparative Example 2

The evaluation was made and evaluated in the same manner as in Example 2, except that the silicon dioxide not modified in Example 2 was used.

Comparative Example 3

The evaluation was made in the same manner as in Example 2 except that the silicon dioxide not modified in Example 2 was used and that the content of the silane coupling agent was changed from 0.3 phr to 1.0 phr in the production of the sheet for solar cell encapsulant.

Comparative Example 4

The procedure of Example 1 was repeated except that fumed silica having an average particle size of 0.03 mu m (30 nm) of silicon dioxide was used.

Comparative Example  5

Modified silicon dioxide prepared by washing and drying three times after stirring at room temperature without using a spray drying method in the surface treatment of silicon dioxide by alkoxysilane in Example 1 was carried out in the same manner as in Example 1 Respectively.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Silicon dioxide reforming O O O Not added X X O △ Silicon dioxide average particle size (탆) 4 4 4 4 4 0.03 4 EVA resin amount (g) 100 100 100 100 100 100 100 100 Content in silicon dioxide resin composition (phr) 0.1 0.2 0.2 0.2 0.2 0.1 0.1 Alkoxysilane: silicon dioxide weight ratio 0.5: 1 1: 1 2: 1 0.5: 1 0.5: 1 The alkoxysilane (g) 0.05 0.2 0.4 0.05 0.05 The alkoxysilane (phr) 0.3 0.3 0.3 0.3 0.3 One 0.3 0.3 Total silane / silicon dioxide (wt%) 3.5 2.5 3.5 1.5 5 3.5 3.5 Resin composition volume resistivity
(Ω.cm) * 10 ^ 15 7.85E + 15 8.32E + 15 9.68E + 15 9.31E + 14 4.65E + 15 3.71E + 15 5.65E + 15 3.61E + 15 Solar sheet
Volume resistivity after crosslinking
(Ω.cm) * 10 ^ 15 8.43E + 15 8.26E + 15 8.37E + 15 2.09E + 15 5.23E + 15 4.21E + 15 4.51E + 15 3.78E + 15 Solar sheet
After crosslinking & Damp Heat after 500hr
Volume resistivity
(Ω.cm) * 10 ^ 16 6.23E + 15 6.59E + 15 7.16E + 15 3.46E + 14 7.5E + 14 5.47E + 14 1.28E + 15 9.25E + 14 Solar sheet
After crosslinking & Damp Heat after 1000hr
Volume resistivity
(? Cm) * 10 ^ 17 2.61E + 15 3.45E + 15 3.24E + 15 1.54E + 13 7.41E + 13 9.63E + 13 2.52E + 14 8.52E + 13 Light transmittance (%),
Early 90.4 89.9 89.9 89.4 86.5 87.3 87.5 87.1 Light transmittance (%)
Damp Heat after 1000hr 70.8 75.6 70.8 66.7 63.1 68.0 64.4 63.8 Output before PID Test (w) 14.5 14.4 14.4 14.5 14.4 14.5 14.5 14.5 Output after PID Test (w) 14.4 14.3 14.2 13.7 13.9 12.8 13.3 13.4 Output retention after PID test (%) 99.3 99.3 98.7 94.6 96.6 88.5 91.7 92.4 Delta Y.I (1000 hr) 1.4 1.3 1.5 1.3 1.4 2.8 1.5 1.6

Comparison of Na adsorption performance

After preparing 500 ppm solution of Na ion by using NaOH, 0.2 g of modified or unmodified silicon dioxide was added to 20 ml of the solution. After 3 days, Na ion concentration of the solution was measured by ICP to determine the modified / Na ion adsorption performance was directly evaluated.

Silicon dioxide self-adsorption performance Modification
Silicon dioxide Unmodified
Silicon dioxide Fumed silica Non-Spray drying Use Example Example 1 Example 2 Example 3 Comparative Example
Used for 2, 3 Comparative Example 4 Comparative Example 5 Average particle size
(탆) 4 4 4 4 0.03 4 Alkoxysilane: silicon dioxide weight ratio 0.5: 1 1: 1 2: 1 0.5: 1 0.5: 1 Na (ppm)
* Initial 500ppm 355 312 295 421 403 383

As shown in Table 1, when Examples 1 to 3 and Comparative Example 1 are compared, it can be seen that the volume resistivity of the resin composition and the solar cell sheet is greatly increased by the inclusion of silicon dioxide. This volume resistivity value shows that the drop in the volume resistivity is not large even after the damp heat test (FIG. 1). On the other hand, in the case of Comparative Example 1 in which silicon dioxide is not contained, the value of the volume resistivity is greatly decreased.

On the other hand, in the case of Comparative Examples 2 and 3 in which the unmodified silicon dioxide was added, the volume resistivity value of the solar cell sheet was increased as compared with Comparative Example 1 in which silicon dioxide was not added, Is very large as compared with Examples 1 to 3.

Table 2 shows the adsorption performance of the silicon dioxide itself, not the adsorption capacity of the resin.

In Comparative Example 3, the same alkoxysilane used for the modification was directly added to the production of a solar cell encapsulant sheet without using it for modification of silicon dioxide. In this case, there was no further increase in the volume resistivity value, Silane is not effectively used to increase the interfacial bond strength between silicon dioxide and EVA, but rather has a bad influence on long-term weatherability, indicating that the YI value is increased.

In Comparative Example 4, the silicon dioxide used was fumed silica with an average particle size of 0.03 탆. In this case, the volume resistivity was maintained higher than that of unmodified silicon dioxide, but the light transmittance after the initial and after 1000 hours of heat transfer was poor due to poor dispersibility in EVA, and the adsorption performance of Na was also poor .

In the case of Comparative Example 5, the spray drying was not used, and the other conditions were the same as in Example 1. In this case, since the actual bonded silane compound is less than the silicon dioxide used, the bonding with EVA is insufficient, so that the interface between silicon dioxide and EVA is desorbed during the long-term Damp Heat Test, and the light transmittance is rapidly deteriorated. The change of the volume resistivity with time also showed a decrease in the silicon dioxide level compared to the non-surface treated silicon dioxide level.

Table 2, which compares the Na adsorption performance, shows that the Na ion adsorption performance of the modified silicon dioxide is improved compared to the unmodified silicon dioxide. In particular, it can be seen that the use of spherical silicon dioxide exhibits better adsorption performance of Na ion than fumed silica. This is considered to be due to the fact that the effective surface area for adsorbing Na ions is small because the pores are not developed in the case of fumed silica.

It was possible to provide an encapsulant in which the volume resistivity was increased and the output value was remarkably reduced in the PID evaluation and the Damp Heat evaluation when the sheet for solar cell encapsulation material was produced using the resin composition completed by the present invention.

Claims (8)

An ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant comprising silicon dioxide surface-modified with an alkoxysilane compound having 3 to 20 carbon atoms
The surface-modified silicon dioxide has an average particle size of 1 to 10 mu m,
Ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant, wherein the ethylene vinyl acetate copolymer resin composition is contained in an amount of 0.05 to 2 parts by mass based on 100 parts by mass of the ethylene vinyl acetate copolymer resin composition. The method according to claim 1,
Wherein the surface-modified silicon dioxide is modified by using a weight ratio of the alkoxysilane compound and silicon dioxide of 0.1: 1 to 4: 1. The method according to claim 1,
Wherein the ethylene vinyl acetate resin has a vinyl acetate content of 23 to 29 wt% and a melt index of 5 to 30 g / 10 min (190 DEG C, 2.16 kg of ASTM D1238). Resin composition. The method according to claim 1,
The alkoxysilane compound may be at least one selected from the group consisting of vinyl trichlorosilane, vinyltris (? Methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane,? -Methacryloxypropyltrimethoxysilane,? - (Aminoethyl) gamma -aminopropyltrimethoxysilane, N-beta (aminoethyl) gamma -aminopropylmethylsilane, N- At least one member selected from the group consisting of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ- Wherein the ethylene vinyl acetate copolymer resin composition for a solar cell encapsulant is a polyvinyl alcohol copolymer. A sheet for a solar cell encapsulant, which is produced from the ethylene vinyl acetate copolymer resin composition according to any one of claims 1 to 4. 6. The method of claim 5,
Wherein the sheet for a solar cell encapsulant comprises 0.3 to 1.0 parts by weight of a crosslinking agent relative to 100 parts by weight of the ethylene vinyl acetate copolymer resin composition; 0.3 to 1.0 part by weight of a crosslinking auxiliary; 0.3 to 1.0 part by weight of a silane coupling agent; And a sheet for a solar cell encapsulation material. Mixing the alkoxysilane in the solvent and then mixing the silicon dioxide;
Spray drying the mixture to modify the silicon dioxide;
Mixing the modified silicon dioxide with an ethylene vinyl acetate copolymer to prepare a master batch; And
And injecting the master batch into an ethylene vinyl acetate resin extruder,
The silicon dioxide has an average particle size of 1-10 mu m,
Wherein the silicon dioxide is spherical silicon dioxide. ≪ RTI ID = 0.0 > 11. < / RTI > A solar cell module having the solar cell encapsulant according to claim 5.

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