JP2011216829A - Composition, sheet, and solar cell module - Google Patents

Abstract

The present invention relates to a composition, an encapsulant sheet and a solar cell, comprising an ethylene-vinyl acetate copolymer as a main component and capable of suppressing the generation of free acetic acid during molding, thermal bonding and long-term use. The purpose is to provide modules.
An ethylene-vinyl acetate copolymer includes a hydrotalcite having a hydroxyl group and a carbonate radical, a hindered amine light stabilizer, and an organic peroxide. To form a sheet. By constituting a solar cell module using this sheet as a sealing material, free acetic acid can be suppressed and a solar cell module excellent in durability can be obtained.
[Selection] Figure 1

Description

  The present invention relates to an ethylene-vinyl acetate copolymer composition for use in a solar cell module encapsulant sheet, and relates to a formulation for processing an ethylene-vinyl acetate copolymer composition that generates less free acetic acid.

  In recent years, solar cells have attracted attention as a clean power generation technology that uses sunlight. In a general solar battery module, a photoelectric conversion cell is disposed in a sealing material layer, and the outside thereof is protected by a surface protection member and a back surface protection member (see FIG. 1B).

  When manufacturing this solar cell module 100, as shown to Fig.1 (a), the surface protection member 102, the 1st sealing material sheet 1041, the photoelectric conversion cell 106, the 2nd sealing material sheet 1042, the back surface protection member The constituent members are laminated in the order of 108, and this is put into a vacuum laminator. Degassing while heating in vacuum to remove the gas between each layer, then applying a load of 1 atm in vacuum while heating, crosslinking and curing the first sealing material sheet and the second sealing material sheet Thus, the sealing material 104 is bonded and integrated to form the solar cell module 100 (FIG. 1B).

As a material for the first and second sealing material sheets, an ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”) is often used as a main resin because of excellent adhesiveness and transparency.
Such EVA is first formed into a sheet shape by extrusion molding or a calendering method and supplied to a solar cell module manufacturer. The module manufacturer sandwiches the photoelectric conversion cell with this encapsulant sheet and then applies heat and pressure to crosslink and cure the resin, thereby sealing the photoelectric conversion cell and bonding the solar cell module components. .

  Therefore, different characteristics are required in several stages, such as stability in sheet shape, adhesiveness when used as a sealing material, and durability when used as a solar cell module. Therefore, for the purpose of providing stability and durability among these properties, EVA for solar cell module sealing uses a light stabilizer, an ultraviolet absorber, etc., and a crosslinking agent for the purpose of imparting adhesiveness. In many cases, additives such as a crosslinking aid and a silane coupling agent are added at a certain ratio.

  Problems related to stability and durability include the fact that EVA tends to deacetate at high temperatures and for long-term use, so that odor is generated by free acetic acid and the wiring of modules sealed with EVA corrodes. . In particular, in use in sealing applications, since a high vinyl acetate content is used in order to enhance the adhesion at the time of sealing, the problem is great.

  On the other hand, EVA is inexpensive and has high transparency, so it is highly demanded as an agricultural film and has been improved as a PVC substitute film. However, as described above, EVA is easy to deacetate at a high temperature, and the generation of odor due to free acetic acid has been a problem. In addition, in extrusion molding at high temperatures, particularly coextrusion with a resin having a high melting point, there are problems such as the generation of odor, corrosion of the molding machine, and generation of voids in the film itself. In order to solve such a problem, a method has been proposed in which a composite metal compound having a hydroxyl group and a carbonate group and zeolite, a phenolic antioxidant, and a phosphorous light stabilizer are added to EVA (Patent Literature). 1). However, this method has a first problem of preventing deacetic acid when EVA is molded at a high temperature in order to replace PVC, and the melting point of the added phosphorous light stabilizer is high. Therefore, even if this method is applied to a sealing material, an additive such as a crosslinking agent having a low decomposition temperature cannot be used.

As a film used as an agricultural (particularly greenhouse coating) material, it is known that weather resistance is improved by blending a specific hydrotalcite compound and a hindered amine compound with respect to 100 parts by weight of a polyolefin resin. 2. An ethylene-vinyl acetate copolymer is described as an example of a polyolefin-based resin, and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 30% or less is preferable as an agricultural film in terms of transparency, weather resistance, and cost. Is described. Furthermore, it is described that a UV absorber, a phenolic antioxidant is applied, and a film is formed by a melt extrusion molding method or a calendar molding method.
However, since it is an agricultural film to the last, the heating process is performed only once at the time of film formation, and the adhesion performance is not disclosed. Since the vinyl acetate content is low and it is used for agriculture, free acetic acid is unlikely to be a problem, and corrosion problems during use are not expected. Moreover, since the plasticizer is added, it is expected that it is difficult to use it for sealing materials.

JP 2001-2854 A JP-A-64-6041

  The present invention provides a composition, a sealing material sheet, and a solar cell module that are mainly composed of an ethylene-vinyl acetate copolymer and can suppress the generation of free acetic acid during molding, thermal bonding, and long-term use. The purpose is to do.

The invention made to solve the above-mentioned problems includes that the ethylene-vinyl acetate copolymer contains hydrotalcites having a hydroxyl group and a carbonate radical, a hindered amine light stabilizer, and an organic peroxide. The composition is characterized.
More preferably, the ethylene-vinyl acetate copolymer has a vinyl acetate content of 30% by mass or more and 50% by mass or less.

Moreover, 0.1 to less than 1 part by mass of the hydrotalcite having the hydroxyl group and carbonate radical and 0.1 to less than 1 part by mass of the hindered amine light stabilizer with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. From a composition containing from 0.01 parts by weight to 0.2 parts by weight, the organic peroxide from 0.3 parts by weight to 1.5 parts by weight, and a phenolic antioxidant from 0.01 parts by weight to 1 part by weight. It becomes the sheet which becomes.
Furthermore, it is set as the solar cell module characterized by using the said sheet | seat as a sealing material.

  According to the present invention, an ethylene-vinyl acetate copolymer is provided with a hindered amine having a melting point lower than the one-hour half-life temperature of the organic peroxide in addition to the hydrotalcite having a hydroxyl group and a carbonate group and the organic peroxide. In the stage processed into a sealing material sheet and long-term use of the solar cell module, the generation of free acetic acid is suppressed, and good adhesion is achieved in the sealing of the solar cell module. Can demonstrate its sexuality.

It is a schematic diagram which shows the process of manufacturing a solar cell module.

(Composition)
(A. Ethylene-vinyl acetate copolymer)
The composition of the present invention is mainly composed of an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer is excellent in transparency and adhesiveness. In particular, when the vinyl acetate content is 30% by mass or more and 50% by mass or less, the adhesiveness is good and it is preferable as a sealing material for a solar cell module. Moreover, it is preferable that MFR (melt flow rate) is 30 g / 10min or more and 40 g / 10min or less.

(B. Hydrotalcite having a hydroxyl group and carbonate radical)
Examples of hydrotalcites having a hydroxyl group and a carbonate radical that can be used in the present invention include the following formula (1):
Mg _(1-x) Al _x (OH) ₂ (CO ₃ ) _{x / 2} · nH ₂ O (1)
(Wherein, 0 <x ≦ 0.5, n is an arbitrary integer) and the like and hydrotalcites having a hydroxyl group and a carbonate radical or related compounds thereof.

  From the viewpoint of maintaining transparency, the refractive index of the hydrotalcite having a hydroxyl group and a carbonate radical is preferably as close as possible to the refractive index of EVA, and its particle size is 5 μm or less, particularly 1 μm or less. Are preferably used. In the composition of the present invention, the hydrotalcite having the hydroxyl group and carbonate radical is contained in an amount of 0.1 part by mass or more and less than 1 part by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Is preferred.

  If the amount of hydrotalcite having a hydroxyl group and a carbonate radical is less than 0.1 parts by mass, a sufficient free acetic acid inhibitory effect cannot be obtained, and the aging deterioration of the ethylene-vinyl acetate copolymer can be suppressed. Can not. Moreover, when the addition amount is 1 part by mass or more, when the composition is finally used as a sealing material, the transparency is lowered and the photoelectric conversion efficiency is lowered. Furthermore, adhesion between the ethylene-vinyl acetate copolymer and the back surface protective member is hindered, and sufficient sealing strength cannot be obtained. A more preferable addition amount is 0.3 part by mass or more and less than 1 part by mass.

(C. Hindered amine light stabilizer)
Examples of the hindered amine light stabilizer that can be used in the present invention include TINUVIN 744, TINUVIN 770, TINUVIN 765, TINUVIN 622LD, and CHIMASSORB 944LD (all manufactured by Ciba Japan). Both are substances having a melting point of about 110 ° C. which is lower than the one-hour half-life temperature of the organic peroxide described later, and do not decompose the organic peroxide, that is, impair the adhesion at the time of sealing. In addition, the effect of suppressing free acetic acid at the time of sheet molding can be imparted to the composition. In the composition of this invention, it is preferable that 0.01 mass part or more and 1 mass part or less of a hindered amine light stabilizer are contained with respect to 100 mass parts of ethylene-vinyl acetate copolymer.

  When the added amount of the hindered amine light stabilizer is less than 0.01 parts by mass, a sufficient free acetic acid suppressing effect cannot be obtained. On the other hand, when the addition amount is larger than 1 part by mass, the adhesion between the ethylene-vinyl acetate copolymer and the back surface protective member is hindered, and sufficient sealing strength cannot be obtained. A more preferable addition amount is 0.01 parts by mass or more and 0.1 parts by mass or less.

(D. Organic peroxide)
In the composition of the present invention, an organic peroxide is added as a crosslinking agent in order to initiate a crosslinking reaction of EVA when used as a sealing material.
The organic peroxide that can be used in the present invention is preferably a substance that has a one-hour half-life temperature that does not decompose when forming a sheet of the composition and that causes a reaction when used as a sealing material. The thing whose period temperature (temperature whose half-life is 1 hour) is 120-180 degreeC can be mentioned.
When the one-hour half-life temperature is lower than 120 ° C., it becomes difficult to form EVA into a sheet without decomposing the organic peroxide. Also. When the one-hour half-life temperature is higher than 180 ° C., the heating temperature required for manufacturing the solar cell module (sealing) becomes high, and the working efficiency is lowered.

Specific examples of the organic peroxide that can be used in the present invention include 1,1-di (t-butylperoxy) cyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, and n-butyl 4. , 4-Di- (t-butylperoxy) valerate, t-butylperoxy-3,5,5-trimethylhexanoate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane , T-butylcumyl peroxide, 2,2-di- (t-butylperoxy) butane, and the like.
In the composition of this invention, it is preferable that 0.3 to 1.5 mass parts of organic peroxides are contained with respect to 100 mass parts of ethylene-vinyl acetate copolymer.

(E. Other additives)
In addition to the organic peroxide, a crosslinking aid for promoting the crosslinking reaction may be added to the composition of the present invention. Examples of the crosslinking aid include triallyl isocyanurate, diallyl phthalate, triallyl cyanurate and the like.
The addition amount of the crosslinking aid is 0.3 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

A silane coupling agent may be added to the composition of the present invention in order to improve the adhesion to the protective member. The durability as a solar cell module is improved by improving the adhesive force between the sealing material, the sound and the back surface protection member. The silane coupling agent that can be added to the composition is particularly preferably γ-methacryloxypropyltrimethoxysilane, and examples thereof include trimethoxypropylsilane, trimethoxymethylsilane, vinyltrimethoxysilane, vinyltrimethoxysilane. Also included are ethoxysilane, trichloropropylsilane, triethoxyphenylsilane and the like.
The addition amount of the silane coupling agent is, for example, 0.2 parts by mass or more and 1.3 parts by mass or less with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

An ultraviolet absorber can be added to the composition of the present invention in order to improve light resistance when used as a sealing material for a solar cell module. Examples of the ultraviolet absorber that can be added to the composition include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5- Chlorobenzotriazole, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol, 2,4-dihydroxybenzophenone, 2-hydroxy-4- and n-octyloxybenzophenone.
The addition amount of the ultraviolet absorber is, for example, 0.01 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

An antioxidant can be added to the composition of the present invention in order to improve the thermal stability during sheet processing. As the antioxidant, a phenolic antioxidant is particularly preferable, and 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [ 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tris (2,4-di-tert-butylphenyl) phosphite, 2,4-bis- (n-octylthio) -6 -(4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine and the like.
The addition amount of the antioxidant is preferably 0.01 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

(Adjustment of composition and processing into sheet)
Mixing the above ethylene-vinyl acetate copolymer, hydrotalcite having hydroxyl group and carbonate radical, hindered amine light stabilizer, organic peroxide, phenolic antioxidant and other additives, kneading machine etc. Knead to adjust the composition.
The composition thus obtained is heated and melted, and formed into a sheet by forming a film by a T-die method or a calendar method. In the film forming process, the composition (resin) in a heat-melted state is pressed against a metal or rubber roll having a concavo-convex pattern on the surface, so that the roll is provided on the surface of the resin in the form of a sheet. The concavo-convex pattern can be transferred and embossed.

(Solar cell module)
FIG.1 (b) is sectional drawing which showed the structure of the solar cell module 100 of this invention typically. The solar cell module 100 includes a surface protection member 102, a sealing material 104, a photoelectric conversion cell 106, and a back surface protection member 108. The photoelectric conversion cell 106 is provided with wiring (not shown), and both the photoelectric conversion cell 106 and the wiring are sealed with a sealing material 104.

  The solar cell module 100 is manufactured by stacking the constituent members in the order of the surface protection member 102, the first sealing material sheet 1041, the photoelectric conversion cell 106, the second sealing material sheet 1042, and the back surface protection member 108 (FIG. 1 ( a)) Put this in a vacuum laminator. After removing the gas between each layer by deaeration while heating to 150 ° C. in vacuum, the first sealing material sheet and the second sealing material are applied with a load of, for example, 1 atm in vacuum while heating as it is. The sheet is cross-linked and cured to form a sealing material 104 that is bonded and integrated (FIG. 1B). Since the solar cell module thus obtained uses a sheet using the composition of the present invention as a sealing material sheet, the adhesiveness is good, free acetic acid is not generated, and odor is not generated. Of course, the wiring does not corrode even in long-term use.

<Example 1>
The following materials were kneaded with a single screw kneader to obtain composition 1.
EVA resin (vinyl acetate content: 30% by mass, MFR: 30 g / 10 min) 100 parts by mass hindered amine light stabilizer (TINUVIN 770, melting point 85 ° C., Ciba Japan) 0.2 parts by mass organic peroxide ( Cross-linking agent)
(2,5-dimethyl-2,5-di (t-butylperoxy) hexane)
(1 hour half-life temperature 119.3 ° C.) 0.5 parts by mass crosslinking aid (triallyl isocyanurate) 0.5 parts by mass silane coupling agent (γ-methacryloxypropyltrimethoxysilane) 0.5 parts by mass UV Absorbent (2-hydroxy-4-n-octyloxybenzophenone) 0.1 parts by mass Phenol-based antioxidant (Tris (2,4-di-t-butylphenyl) phosphite) 0.1 parts by mass Hydroxyl group and carbonic acid hydrotalcite having a root _{(Mg 6 Al 2 (CO 3} ) (OH) 16 · 4H 2 O, particle size 40 nm) 0.3 parts by weight

  Composition 1 was processed into a sheet having a thickness of 400 μm by an extruder at 110 ° C. This EVA sheet was sandwiched between Teflon (registered trademark) sheets and hot-pressed at 150 ° C. for 10 minutes to crosslink and cure the EVA, thereby producing an evaluation sample 1.

<Example 2>
Composition 2 was prepared in the same manner as in Composition 1 of Example 1, except that the amount of hydrotalcite having a hydroxyl group and carbonate radical was 2 parts by mass. Using this composition 2, an evaluation sample 2 was prepared in the same manner as in Example 1.
<Example 3>
Composition 3 was prepared in the same manner as in Composition 1 of Example 1, except that the amount of hydrotalcite having a hydroxyl group and carbonate radical was 0.6 parts by mass. Using this composition 3, an evaluation sample 3 was prepared in the same manner as in Example 1.
<Example 4>
A composition 4 was prepared in the same manner as in the composition 1 of Example 1, except that the amount of hydrotalcite having a hydroxyl group and a carbonate group was 0.1 parts by mass. Using this composition 4, an evaluation sample 4 was prepared in the same manner as in Example 1.
<Example 5>
Composition 6 was prepared in the same manner as in Composition 1 of Example 1, except that the amount of hydrotalcite having a hydroxyl group and carbonate radical was 0.05 parts by mass. Using this composition 6, an evaluation sample 6 was prepared in the same manner as in Example 1.

<Example 6>
In composition 1 of Example 1, composition 6 was prepared in the same manner except that the amount of hindered amine light stabilizer (TINUVIN 770 manufactured by Ciba Japan) was 1.5 parts by mass. Using this composition 6, an evaluation sample 6 was prepared in the same manner as in Example 1.
<Example 7>
Composition 7 was prepared in the same manner as in composition 1 of Example 1, except that the amount of hindered amine light stabilizer (TINUVIN 770 manufactured by Ciba Japan) was 0.01 parts by mass. Using this composition 7, an evaluation sample 7 was prepared in the same manner as in Example 1.

<Comparative Example 1>
A composition 8 was prepared in the same manner as in the composition 1 of Example 1, except that a hindered amine light stabilizer (TINUVIN 770 manufactured by Ciba Japan) was not added. Using this composition 8, an evaluation sample 8 was prepared in the same manner as in Example 1.
<Comparative example 2>
A composition 9 was prepared in the same manner as in the composition 1 of Example 1 except that hydrotalcites having a hydroxyl group and a carbonate radical were not added. Using this composition 9, an evaluation sample 9 was prepared in the same manner as in Example 1.

<Measurement of acetic acid content>
The evaluation samples 1 to 9 obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were subjected to ion chromatography, and the acetic acid contained in the evaluation sample was quantified to obtain the acetic acid content (ppm). In the case of 70 ppm or less, it is considered that suppression of free acetic acid is sufficient, “circle”, when it is greater than 70 ppm and less than 100 ppm, “triangle”, and when it exceeds 100 ppm, acetic acid release is considered not to be suppressed. "X".

<Adhesive strength>
About compositions 1-9 obtained in Examples 1-7 and Comparative Examples 1 and 2, after processing into a sheet, it was sandwiched between a surface protection member and a back surface protection member and heated at 1 atm for 10 minutes at 150 ° C. Cure and created pseudo modules 1-9. White glass (3 mm thickness) was used as the surface protection member, and vinyl fluoride polymer (38 μm thickness) was used as the back surface protection member.
The surface protective member / sealing material sheet interface was cut with a cutter knife as a trigger for peeling, and the adhesion strength between the surface protective member / sealing material was measured by a 90-degree peel test (based on JIS K6854-1).
As the adhesive strength between the front surface and the back surface protective member / sealing material, if it is 30 N / 15 mm or more, it is considered that the adhesive strength is sufficient, “circle”, and if it is less than 30 N / 15 mm, 10 N / 15 mm “Triangle mark”, when less than 10 N / 15 mm, the adhesive strength was considered insufficient, and “X mark” was set.

<Durability>
The samples 1 to 9 for evaluation obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were subjected to a constant temperature and humidity test at 85 ° C. and 85% RH for 1000 hours. Samples 1 to 9 for evaluation after the test were subjected to ion chromatography, and acetic acid contained in the sample for evaluation was quantified to obtain an acetic acid content (ppm).
Moreover, also about the samples 1-9 for an evaluation after a constant temperature and humidity test, the adhesive strength was measured by the 90 degree | times peeling test similarly to the above.

  About compositions 1-9 prepared in Examples 1-7 and Comparative Examples 1 and 2, hydrotalcites having hydroxyl groups and carbonate radicals (referred to as hydrotalcites) and hindered amine light stabilizers (referred to as hindered amines) Table 1 shows the addition amount (parts by mass) of (based on 100 parts by mass of EVA). Table 1 shows the measurement results of the acetic acid content (ppm) and the evaluation results of the adhesive strength immediately after production and after the constant temperature and humidity test for the sample for evaluation and the pseudo module.

From the above results, in a sheet formed from a composition containing a hydrotalcite having a hydroxyl group and a carbonate radical, a hindered amine light stabilizer, and an organic peroxide on an ethylene-vinyl acetate copolymer, When used as a sealing material for battery modules, it was found that the amount of free acetic acid and adhesive strength immediately after production were good, and the generation of free acetic acid was suppressed even after the constant temperature and humidity test. Therefore, it can be seen that good power generation efficiency can be maintained without corrosion of the wiring and the like even after long-term outdoor use.
Furthermore, in Examples 1, 3, 4, and 7 in which the addition amount and the specific range of hydrotalcites having a hydroxyl group and a carbonate radical and a hindered amine light stabilizer were used, free acetic acid after production and after a constant temperature and humidity test It was found that the amount was smaller and the adhesive strength was also good.

100 solar cell module 102 surface protection member 104 sealing material 1041 first sealing material sheet 1042 second sealing material sheet 106 photoelectric conversion cell 108 back surface protection member

Claims (4)

  An ethylene-vinyl acetate copolymer comprising a hydrotalcite having a hydroxyl group and a carbonate radical, a hindered amine light stabilizer, and an organic peroxide.   The composition according to claim 1, wherein the ethylene-vinyl acetate copolymer has a vinyl acetate content of 30% by mass or more and 50% by mass or less.   0.1 parts by mass or more and less than 1 part by mass of the hydrotalcite having a hydroxyl group and a carbonate radical with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer, and 0.01 parts by mass of the hindered amine light stabilizer. 2 parts by mass or more and 0.2 parts by mass or less, 0.3 to 1.5 parts by mass of the organic peroxide, and 0.01 to 1 part by mass or less of a phenolic antioxidant. A sheet comprising the composition.   A solar cell module comprising the sheet according to claim 3 as a sealing material.

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