JP2014179634A - Resin composition for solar cell sealing material, solar cell sealing material manufactured therefrom, and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a resin composition for solar cell sealing material which contains an ethylene/α-olefin copolymer, an organic peroxide, etc., and has good crosslinking characteristic and good heat resistance; a solar cell sealing material manufactured from such a resin composition; and a solar battery module manufactured therefrom.SOLUTION: A resin composition for solar cell sealing material comprises: an ethylene/α-olefin copolymer component (A) having the characteristics (a1) and (a2) below; an organic peroxide component (B); and a hindered-amine based optical stabilizer (C). (a1)The density is 0.860-0.920 g/cm; and (a2)the total number (N) branches derived from comonomer in the ethylene/α-olefin copolymer is 54-95(/total 1000C)(where N is a number per 1000 carbon atoms of main and side chains in total as measured by NMR).

Description

  The present invention relates to a resin composition for a solar cell encapsulant, a solar cell encapsulant using the same, and a solar cell module, and more specifically, contains an ethylene / α-olefin copolymer and an organic peroxide. In addition, the present invention relates to a resin composition for a solar cell encapsulant that is excellent in crosslinking characteristics, heat resistance, and transparency, and a solar cell encapsulant and a solar cell module using the same.

As global environmental issues such as an increase in carbon dioxide are highlighted, solar power generation has come into focus again along with the effective use of hydropower, wind power, and geothermal heat.
Photovoltaic power generation generally protects solar cell elements such as silicon, gallium-arsenic, copper-indium-selenium with an upper transparent protective material and a lower substrate protective material, and the solar cell element and the protective material are sealed with resin. It uses solar cell modules that are fixed with materials and packaged, and although it is smaller in scale than hydropower and wind power, it can be distributed and placed in places where power is required. Research and development aimed at lowering the level is being promoted. In addition, the government and local governments are gradually promoting the spread of measures by substituting installation costs as a residential solar power generation system introduction promotion project. However, further cost reduction is necessary for further spread, so that not only the development of solar cell elements using new materials to replace conventional silicon and gallium arsenide, but also the manufacturing cost of solar cell modules Efforts to further reduce this are continuing.

  As a condition of the solar cell encapsulant constituting the solar cell module, in order to ensure the incident amount of sunlight so as not to decrease the power generation efficiency of the solar cell, good transparency is required. Moreover, since a solar cell module is usually installed outdoors, it is exposed to sunlight for a long period of time and the temperature rises. Therefore, in order to avoid troubles in which the resin sealing material flows and the module is deformed, it must have heat resistance. Moreover, in order to reduce the material cost of a solar cell element year by year, the thickness has been reduced, and a sealing material with further flexibility is also required.

  For example, in solar cell modules, from the viewpoint of price, workability, moisture resistance, etc., as an encapsulating material, an organic peroxide is blended with an ethylene / vinyl acetate copolymer (EVA) having a high vinyl acetate content and crosslinked. A composition having a structure is employed (see, for example, Patent Document 1). However, ethylene / vinyl acetate copolymer (EVA) resin, when used over a long period of time, has deteriorated moisture resistance due to deterioration / deterioration such as yellowing, cracking and foaming, and power generation due to corrosion of solar cells, etc. The amount was reduced. These are considered to be easily affected by sunlight and moisture because the EVA resin has an ester structure with high hydrolyzability.

  Therefore, as a sealing material for a solar cell module, a material composed of an amorphous or low crystalline α-olefin copolymer having a crystallinity of 40% or less has been proposed (see Patent Document 2). In this Patent Document 2, it is exemplified that a low crystalline ethylene / butene copolymer is mixed with an organic peroxide and a sheet is produced at a processing temperature of 100 ° C. using a profile extruder. Since processing temperature is low, there exists a problem that productivity cannot be improved.

  Moreover, as a sealing material for solar cell modules, (a) a density of less than about 0.90 g / cc, (b) a 2% secant coefficient of less than about 150 megapascals (mPa) as measured by ASTM D-882-02 (C) a melting point of less than about 95 ° C., (d) an α-olefin content of at least about 15 and less than about 50% by weight based on the weight of the polymer, (e) a Tg of less than about −35 ° C., and (f) A polymer material containing a polyolefin copolymer that satisfies one or more conditions of at least about 50 SCBDI has been proposed (see Patent Document 3).

  In the solar cell module, the solar cell encapsulant tends to become thinner as the solar cell element becomes thinner. At that time, when an impact is applied from the upper or lower protective material side of the solar cell sealing material, the wiring is likely to be disconnected. In order to improve it, it is required to increase the rigidity of the sealing material. However, in the polymer material of Patent Document 3, if the rigidity is increased, there is a problem that the crosslinking efficiency is deteriorated.

  Thus, according to the conventional technology, a resin composition for a solar cell encapsulant that is excellent in crosslinkability, heat resistance, transparency, and flexibility has not been obtained.

JP 58-023870 A JP 2006-210906 A JP 2010-504647 A

  An object of the present invention is to provide a resin composition for a solar cell encapsulant that contains an ethylene / α-olefin copolymer and an organic peroxide, and is excellent in crosslinkability, heat resistance, transparency, and flexibility. It is in.

  As a result of intensive studies to solve the above problems, the present inventors have determined that ethylene / α-olefin having characteristics such as specific density, molecular weight distribution, and number of branches due to a comonomer polymerized using a metallocene catalyst as a resin component By selecting a copolymer and adding an organic peroxide thereto, a resin composition for a solar cell encapsulant that is excellent in crosslinkability, heat resistance, transparency, and flexibility can be obtained. Obtaining knowledge that the productivity of the battery module is greatly improved, the present invention has been completed.

That is, according to 1st invention of this invention, the resin composition for solar cell sealing materials characterized by containing the following component (A), a component (B), and a component (C) is provided. .
Component (A): ethylene / α-olefin copolymer (a1) having the following characteristics (a1) to (a2): Density of 0.860 to 0.920 g / cm ³
(A2) The total number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer is 54 to 95 (pieces / total 1000C).
(However, N is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.)
Component (B): Organic peroxide Component (C): Hindered amine light stabilizer

According to a second aspect of the present invention, in the first aspect, the component (A) is an ethylene / α-olefin copolymer further having the following property (a3): A battery encapsulant composition is provided.
(A3) The ratio (Mz / Mn) of the Z average molecular weight (Mz) and the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 8.0 or less.

According to the third aspect of the present invention, in the first or second aspect, the content of the component (B) is 0.2 to 5 parts by weight with respect to 100 parts by weight of the component (A). The resin composition for solar cell sealing materials characterized by this is provided.
According to the fourth invention of the present invention, in the first invention, the content of the component (C) is 0.01 to 2.5 parts by weight with respect to 100 parts by weight of the component (A). A characteristic resin composition for a solar cell encapsulant is provided.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the component (A) is ethylene / 1-butene or an ethylene / 1-hexene copolymer. A resin composition for a solar cell encapsulant is provided.

On the other hand, according to the sixth invention of the present invention, there is provided a solar cell encapsulant comprising the resin composition for solar cell encapsulant according to any of the first to fifth inventions.
Moreover, according to the 7th invention of this invention, it is related with the 6th invention, The solar cell module using a solar cell sealing material is provided.

  The resin composition for a solar cell encapsulant of the present invention is mainly composed of an ethylene / α-olefin copolymer having specific density, molecular weight distribution, number of branches by comonomer and the like, and an organic peroxide is added thereto. Therefore, when this resin composition is made into a sheet, the ethylene / α-olefin copolymer can be cross-linked in a relatively short time, and the balance between rigidity and cross-linking efficiency is good. As a result, the module can be easily formed, and the manufacturing cost can be reduced. Moreover, the obtained solar cell module becomes excellent in transparency, flexibility, weather resistance, etc., and it can be expected to maintain stable conversion efficiency for a long period of time.

1. Resin composition for solar cell encapsulant The resin composition for solar cell encapsulant of the present invention (hereinafter also simply referred to as resin composition) comprises the following ethylene / α-olefin copolymer component (A), It contains an oxide (B) and a hindered amine light stabilizer (C).

(1) Component (A)
Component (A) used in the present invention is an ethylene / α-olefin copolymer having the following characteristics (a1) to (a2), and preferably has the characteristics (a3).
(A1) Density is 0.860-0.920 g / cm ³
(A2) The total number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer is 54 to 95 (pieces / total 1000C).
(However, N is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.)
(A3) The ratio (Mz / Mn) of the Z average molecular weight (Mz) and the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 8.0 or less.

(I) Monomer structure of component (A) The ethylene / α-olefin copolymer used in the present invention is a random copolymer of ethylene and α-olefin, the main component of which is a structural unit derived from ethylene. .
The α-olefin used as a comonomer is preferably an α-olefin having 3 to 12 carbon atoms. Specifically, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1, 4-methyl-hexene-1, 4,4-dimethylpentene- 1 etc. can be mentioned. Specific examples of such ethylene / α-olefin copolymers include ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, ethylene / 1-octene copolymers, ethylene -4-methyl-pentene-1 copolymer etc. are mentioned. Of these, ethylene / 1-butene copolymer and ethylene / 1-hexene copolymer are preferable. Moreover, 1 type, or 2 or more types of combination may be sufficient as an alpha olefin. When combining two kinds of α-olefins to form a terpolymer, ethylene / propylene / 1-hexene terpolymer, ethylene / 1-butene / 1-hexene terpolymer, ethylene / propylene -1-octene terpolymer, ethylene / 1-butene / 1-octene terpolymer, etc. are mentioned.
As a comonomer, a small amount of a diene compound such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, and 1,9-decadiene may be added to the α-olefin. When these diene compounds are blended, long-chain branching is possible, so that the crystallinity of the ethylene / α-olefin copolymer is lowered, transparency, flexibility, adhesiveness, etc. are improved, and it becomes an intermolecular crosslinking agent. So the mechanical strength increases. Moreover, since the terminal group of the long chain branch is an unsaturated group, it can easily undergo a crosslinking reaction with an organic peroxide, a copolymerization reaction with an acid anhydride group-containing compound or an epoxy group-containing compound, and a graft reaction. it can.

The ethylene / α-olefin copolymer used in the present invention has an α-olefin content of 5 to 40% by weight, preferably 10 to 35% by weight, and more preferably 15 to 30% by weight. Within this range, flexibility and heat resistance are good.
Here, the content of α-olefin is a value measured by a 13C-NMR method under the following conditions.
Device: JEOL-GSX270 manufactured by JEOL
Concentration: 300 mg / 2 mL
Solvent: Orthodichlorobenzene

(Ii) Polymerization catalyst and polymerization method of component (A) The ethylene / α-olefin copolymer used in the present invention is a Ziegler catalyst, vanadium catalyst or metallocene catalyst, preferably a vanadium catalyst or metallocene catalyst, more preferably a metallocene catalyst. Can be manufactured using. Examples of the production method include a high-pressure ion polymerization method, a gas phase method, a solution method, and a slurry method. In particular, it is preferable to use a high-pressure method such as a high-pressure ion polymerization method.
Although it does not necessarily limit as a metallocene catalyst, The catalyst which uses a metallocene compound, such as a zirconium compound coordinated with the group which has a cyclopentadienyl skeleton, etc., and a promoter as a catalyst component is mentioned. In particular, it is preferable to use a metallocene compound such as a zirconium compound in which a group having a cyclopentadienyl skeleton is coordinated. Commercially available products include Harmolex (registered trademark) series, Kernel (registered trademark) series manufactured by Japan Polyethylene, Evolue (registered trademark) series manufactured by Prime Polymer, Exelen (registered trademark) GMH series manufactured by Sumitomo Chemical, Exelen (registered trademark) FX series may be mentioned. Examples of the vanadium catalyst include a catalyst having a soluble vanadium compound and an organic aluminum halide as catalyst components.

(Iii) Characteristics of component (A) (a1) Density The ethylene / α-olefin copolymer used in the present invention has a density of 0.860 to 0.920 g / cm ³ , preferably 0.870 to 0.8. It is 915 g / cm ³ , more preferably 0.875 to 0.910 g / cm ³ . When the density of the ethylene / α-olefin copolymer is less than 0.860 g / cm ³ , the processed sheet is blocked, and when the density exceeds 0.920 g / cm ³ , the processed sheet has too high rigidity. Thus, the handling property is lacking.

  In order to adjust the density of the polymer, for example, a method of appropriately adjusting the α-olefin content, the polymerization temperature, the catalyst amount and the like is employed. The density of the ethylene / α-olefin copolymer is measured according to JIS-K6922-2: 1997 appendix (in the case of low density polyethylene) (23 ° C.).

(A2) Number of branches by comonomer in the ethylene / α-olefin copolymer (N)
In the ethylene / α-olefin copolymer used in the present invention, the number of branches (N) due to the comonomer must be 54 to 95 in total (total / 1000 C). Here, the number of branches (N) is the number per 1000 carbon atoms in total of the main chain and the side chain measured by NMR.
That is, in the present invention, the number of branches (N) is preferably 54 to 88, more preferably 55 to 85, still more preferably 56 to 83, and particularly preferably 57 to 80. The number of branches (N) due to the comonomer in the polymer is, for example, E.I. W. Hansen, R.A. Blom, and O.M. M.M. It can be calculated from the C-NMR spectrum with reference to Bade, Polymer, 36, 4295 (1997).

(A3) Ratio (Mz / Mn) of Z average molecular weight (Mz) to number average molecular weight (Mn)
The ethylene / α-olefin copolymer used in the present invention has a ratio (Mz / Mn) of Z average molecular weight (Mz) to number average molecular weight (Mn) determined by gel permeation chromatography (GPC) of 8.0. Or less, preferably 5.0 or less, more preferably 4.0 or less. Moreover, Mz / Mn is 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more. However, when Mz / Mn exceeds 8.0, transparency deteriorates. In order to adjust Mz / Mn to a predetermined range, a method of selecting an appropriate catalyst system can be used.

In addition, the measurement of Mz / Mn is performed by gel permeation chromatography (GPC), and the measurement conditions are as follows.
Apparatus: Waters GPC 150C type detector: MIRAN 1A infrared spectrophotometer (measurement wavelength: 3.42 μm)
Column: Showa Denko AD806M / S 3 (column calibration was measured by Tosoh monodisperse polystyrene (0.5 mg / ml solution of each of A500, A2500, F1, F2, F4, F10, F20, F40, and F288) The logarithmic value of the elution volume and molecular weight was approximated by a quadratic equation, and the molecular weight of the sample was converted to polyethylene using the viscosity equation of polystyrene and polyethylene, where the coefficient of the viscosity equation of polystyrene is α = 0.723, log K = -3.967, polyethylene is α = 0.733, log K = -3.407.)
Measurement temperature: 140 ° C
Concentration: 20 mg / 10 mL
Injection volume: 0.2ml
Solvent: Orthodichlorobenzene Flow rate: 1.0 ml / min

  Since the Z average molecular weight (Mz) greatly contributes to the average molecular weight of the high molecular weight component, Mz / Mn is easier to confirm the presence of the high molecular weight component than Mw / Mn. The high molecular weight component is a factor that affects the transparency, and when the high molecular weight component is large, the transparency is deteriorated. Moreover, the tendency for a crosslinking efficiency to deteriorate is seen. Therefore, a smaller Mz / Mn is preferable.

In the solar cell module, the solar cell encapsulant tends to become thinner as the solar cell element becomes thinner. In the solar cell encapsulating material having a reduced thickness, when an impact is applied from the upper or lower protective material side, the wiring is easily disconnected, so that the rigidity of the encapsulating material is required to be increased. When the rigidity is increased, the crosslinking efficiency is deteriorated. Therefore, a copolymer having a high degree of branching of the polymer chain is used to improve the fluidity of the copolymer before crosslinking and to be used as a material having excellent moldability. There is a need. In the present invention, since the number of branches (N) by the comonomer of the ethylene / α-olefin copolymer is in the above range, the crosslinkability is large and good.
When propyl, butyl, hexyl and octyl are listed as comonomer in the ethylene / α-olefin copolymer, the branches are methyl branch, ethyl branch, butyl branch and hexyl branch, respectively. Those having a total of less than 54 methyl branches, ethyl branches, butyl branches, and hexyl branches have poor crosslinking efficiency due to a small amount of propyl, butyl, and hexyl comonomers, and those having more than 95 branches in total. This is not preferable because the stickiness of the sheet increases.
If the total number of the branches is 54 to 95 (pieces / total 1000C), the amount of individual branches is not particularly limited. For example, the methyl branch is preferably 20 or more, the butyl branch is preferably 10 or more, and the ethyl branch is preferably 0.01 or more.

  The ethylene / α-olefin copolymer according to the present invention can be produced by a copolymerization reaction using a catalyst as described above, but the composition ratio of raw material monomers to be copolymerized and the type of catalyst to be used are selected. Thus, the degree of branching in the polymer chain can be easily adjusted. In order that the number of branches by the comonomer of the ethylene / α-olefin copolymer used in the present invention is 54 to 95 (pieces / total 1000 C), the comonomer is selected from propylene, 1-butene, or 1-hexene. preferable. Moreover, it is preferable to produce using a vapor phase method or a high pressure method, and it is more preferable to select a high pressure method.

(2) Component (B)
The organic peroxide of component (B) in the present invention is mainly used for crosslinking component (A).
As the organic peroxide, an organic peroxide having a decomposition temperature (temperature at which the half-life is 1 hour) is 70 to 180 ° C., particularly 90 to 160 ° C. can be used. Examples of such organic peroxides include t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxyacetate, t-butyl peroxybenzoate, dicumyl peroxide, 2 , 5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, 1 , 1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5- Diperoxybenzoate, t-butyl hydroperoxide, p-menthane hydroperoxy Id, benzoyl peroxide, p- chlorobenzoyl peroxide, t- butyl peroxy isobutyrate, hydroxyheptyl peroxide, and di cyclohexanone peroxide.

(4) Mixing ratio of component (B) The mixing ratio of component (B) is preferably 0.2 to 5 parts by weight, more preferably 0, when component (A) is 100 parts by weight. 0.5-3 parts by weight, more preferably 1-2 parts by weight. When the blending ratio of the component (B) is less than the above range, crosslinking is not performed or it takes time for crosslinking. Moreover, when larger than the said range, dispersion | distribution will become inadequate and it will be easy to become non-uniform | crosslinked.

(5) Hindered amine light stabilizer (C)
In the present invention, a hindered amine light stabilizer is blended in the resin composition. The hindered amine light stabilizer captures radical species harmful to the polymer and prevents generation of new radicals. There are many types of hindered amine light stabilizers ranging from low molecular weight compounds to high molecular weight compounds, but any conventionally known compounds can be used without particular limitation.

  Low molecular weight hindered amine light stabilizers include decanedioic acid bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and Consists of 70% by weight of a reaction product of octane (molecular weight 737) and 30% by weight of polypropylene; bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1 -Dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate (molecular weight 685); bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6 6-pentamethyl-4-piperidyl sebacate mixture (molecular weight 509); bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate ( 481); tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 791); tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 847); 2,2,6,6-tetramethyl-4-piperidyl-1,2,3,4-butane Mixture of tetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular weight 900); 1,2,2,6,6-pentamethyl-4-piperidyl-1,2,3,4-butane Examples thereof include a mixture (molecular weight 900) of tetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate.

  As the high molecular weight hindered amine light stabilizer, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2, 2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}] (molecular weight 2,000-3,100); succinic acid Polymer of dimethyl and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (molecular weight 3,100 to 4,000); N, N ′, N ″, N ″ ′-tetrakis- ( 4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10- Diamine (molecular weight 2,286) and above A mixture of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2,2 , 6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate (molecular weight 2,600-3) 400) and 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-acryloyloxy-1-ethyl -2,2,6,6-tetramethylpiperidine, 4-acryloyloxy-1-propyl-2,2,6,6-tetramethylpiperidine, 4-acryloyloxy 1-butyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6,6-pentamethyl Peridine, 4-methacryloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1-butyl-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy Examples include copolymers of cyclic aminovinyl compounds such as -2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-1-propyl-2,2,6,6-tetramethylpiperidine and ethylene. The above-mentioned hindered amine light stabilizers may be used alone or in combination of two or more.

  Among these, as the hindered amine light stabilizer, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2 , 2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}] (molecular weight 2,000-3,100); Polymer of dimethyl acid and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (molecular weight 3,100 to 4,000); N, N ′, N ″, N ″ ′-tetrakis- (4,6-Bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10 -Diamine (molecular weight 2,286) A mixture of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2 , 2,6,6-Tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate (molecular weight 2,600) ~ 3,400) It is preferable to use a copolymer of a cyclic aminovinyl compound and ethylene, because the hindered amine light stabilizer is prevented from bleeding out over time when the product is used. An agent having a melting point of 60 ° C. or higher is preferably used from the viewpoint of easy preparation of the composition.

In the present invention, the content of the hindered amine light stabilizer is 0.01 to 2.5 parts by weight, preferably 0.01 to 1 part by weight based on 100 parts by weight of the ethylene / α-olefin copolymer. 0 parts by weight, more preferably 0.01 to 0.5 parts by weight, still more preferably 0.01 to 0.2 parts by weight, and most preferably 0.03 to 0.1 parts by weight.
When the content is 0.01 parts by weight or more, a sufficient stabilizing effect is obtained, and when the content is 2.5 parts by weight or less, the resin is discolored due to excessive addition of a hindered amine light stabilizer. In the present invention, the weight ratio (B: C) of the organic peroxide (B) to the hindered amine light stabilizer (C) is 1: 0.01 to 1:10. , Preferably 1: 0.02 to 1: 6.5. Thereby, it becomes possible to remarkably suppress yellowing of the resin.

(6) Crosslinking aid Further, a crosslinking aid can be blended in the resin composition of the present invention. The crosslinking aid is effective in promoting the crosslinking reaction and increasing the degree of crosslinking of the ethylene / α-olefin copolymer. Specific examples thereof include polyaryl compounds and poly (meth) acryloxy compounds. Saturated compounds can be exemplified.
More specifically, polyallyl compounds such as triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, etc. Examples include poly (meth) acryloxy compounds and divinylbenzene. A crosslinking adjuvant can be mix | blended in the ratio of about 0-5 weight part with respect to 100 weight part of component (A).

(7) Ultraviolet absorber An ultraviolet absorber can be mix | blended with the resin composition of this invention. Examples of the ultraviolet absorber include various types such as benzophenone, benzotriazole, triazine, and salicylic acid ester.
Examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, and 2-hydroxy-4. -N-dodecyloxybenzophenone, 2-hydroxy-4-n-octadecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-5-chlorobenzophenone 2,2-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, etc. To mention Can.

The benzotriazole ultraviolet absorber is a hydroxyphenyl-substituted benzotriazole compound, for example, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-5-t-butylphenyl) Benzotriazole, 2- (2-hydroxy-3,5-dimethylphenyl) benzotriazole, 2- (2-methyl-4-hydroxyphenyl) benzotriazole, 2- (2-hydroxy-3-methyl-5-t- Butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-amylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, and the like. Can be mentioned. Examples of triazine ultraviolet absorbers include 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- ( And 4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol. Examples of salicylic acid esters include phenyl salicylate and p-octylphenyl salicylate.
These ultraviolet absorbers are blended in an amount of 0 to 2.0 parts by weight, preferably 0.05 to 2.0 parts by weight, more preferably 0.1 to 1. part by weight based on 100 parts by weight of the ethylene / α-olefin copolymer. 0 parts by weight, more preferably 0.1 to 0.5 parts by weight, and most preferably 0.2 to 0.4 parts by weight.

In the resin composition of the present invention, a silane coupling agent can be used mainly for the purpose of improving the adhesive strength between the solar cell upper protective material and the solar cell element.
Examples of the silane coupling agent in the present invention include γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyltrimethoxysilane; vinyl-tris- (β-methoxyethoxy) silane; γ-methacryloxypropyl. Β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercaptopropyltrimethoxysilane; γ-aminopropyltrimethoxysilane; N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane and the like can be mentioned. Vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane are preferable.
These silane coupling agents are used in an amount of 0 to 5 parts by weight, preferably 0.01 to 4 parts by weight, more preferably 0.01 to 2 parts by weight, based on 100 parts by weight of the ethylene / α-olefin copolymer. More preferably, it is used at 0.05 to 1 part by weight.

(8) Other additive components In the resin composition of the present invention, other additional optional components can be blended within a range that does not significantly impair the object of the present invention. As such optional components, antioxidants, crystal nucleating agents, clearing agents, lubricants, colorants, dispersants, fillers, fluorescent whitening agents, UV absorbers used in ordinary polyolefin resin materials, A light stabilizer etc. can be mentioned.

  Further, in order to impart flexibility and the like to the resin composition of the present invention, a crystalline ethylene / α-olefin copolymer polymerized by a Ziegler-based or metallocene-based catalyst within a range not impairing the object of the present invention. And / or rubber compounds such as ethylene / α-olefin elastomers such as EBR and EPR, or styrene elastomers such as SEBS and hydrogenated styrene block copolymers may be blended in an amount of 3 to 75 parts by weight. Furthermore, in order to give melt tension etc., 3-75 weight part of high pressure process low density polyethylene can also be mix | blended.

2. Solar cell encapsulant The solar cell encapsulant of the present invention (hereinafter also simply referred to as encapsulant) is a pelletized or sheeted product of the resin composition.
If this solar cell sealing material is used, a solar cell module can be manufactured by fixing a solar cell element with upper and lower protective materials. Examples of such solar cell modules include various types. For example, the upper transparent protective material / encapsulant / solar cell element / encapsulant / lower protective material sandwiched between the solar cell elements from both sides, formed on the inner peripheral surface of the lower substrate protective material A solar cell element formed on the inner peripheral surface of the upper transparent protective material, for example, a fluororesin-based transparent protective material. The thing of the structure which forms a sealing material and a lower protective material on what created the amorphous solar cell element by sputtering etc. can be mentioned.

  The solar cell element is not particularly limited, and is based on silicon such as single crystal silicon, polycrystalline silicon, amorphous silicon, III-V group or II-VI group such as gallium-arsenic, copper-indium-selenium, cadmium-tellurium. Various solar cell elements such as compound semiconductors can be used. In the present invention, those using glass as the substrate are preferred.

Examples of the upper protective material constituting the solar cell module include glass, acrylic resin, polycarbonate, polyester, and fluorine-containing resin.
The lower protective material is a single or multilayer sheet such as a metal or various thermoplastic resin films, for example, a metal such as tin, aluminum or stainless steel, an inorganic material such as glass, polyester, an inorganic vapor-deposited polyester, or fluorine. Examples of the protective material include a single layer or a multilayer such as a containing resin and polyolefin. Such an upper and / or lower protective material can be subjected to a primer treatment in order to enhance the adhesion to the sealing material. In the present invention, glass is preferred as the upper protective material.

  The solar cell encapsulant of the present invention may be used as a pellet, but is usually used after being formed into a sheet having a thickness of about 0.1 to 1 mm. If the thickness is less than 0.1 mm, the strength is small and the adhesion is insufficient. If the thickness is more than 1 mm, the transparency may be lowered, which may be a problem. A preferred thickness is 0.1 to 0.8 mm.

  The sheet-like solar cell encapsulant can be produced by a known sheet molding method using a T-die extruder, a calendar molding machine, or the like. For example, a cross-linking agent is added to an ethylene / α-olefin copolymer, and if necessary, a hindered amine light stabilizer, a cross-linking aid, a silane coupling agent, an ultraviolet absorber, an antioxidant, a light stabilizer. An additive such as an agent can be dry-blended in advance and supplied from a hopper of a T-die extruder, and extruded into a sheet at an extrusion temperature of 80 to 150 ° C. In these dry blends, some or all of the additives can be used in the form of a masterbatch. In addition, in T-die extrusion and calendering, some or all of the additive is previously melt-mixed into the amorphous α-olefin copolymer using a single screw extruder, twin screw extruder, Banbury mixer, kneader, etc. Thus obtained resin composition can also be used.

  In manufacturing the solar cell module, the sheet of the sealing material of the present invention is prepared in advance, and the above-described method is performed by pressure bonding at a temperature at which the resin composition of the sealing material melts, for example, 150 to 200 ° C. A module having a simple structure can be formed. Moreover, if the method of laminating with the solar cell element, the upper protective material or the lower protective material by extrusion coating the sealing material of the present invention is adopted, the solar cell module can be manufactured in one step without bothering to form a sheet. Is possible. Therefore, if the sealing material of this invention is used, the productivity of a module can be improved markedly.

On the other hand, when the solar cell module is manufactured, the sealing material is temporarily applied to the solar cell element or the protective material at a temperature at which the organic peroxide is not substantially decomposed and the sealing material of the present invention is melted. Adhesion is then carried out to raise the temperature, and sufficient adhesion and crosslinking of the ethylene / α-olefin copolymer can be carried out. In this case, the gel in the encapsulant layer is used in order to obtain a solar cell module with good heat resistance having a melting point (DSC method) of the encapsulant layer of 85 ° C. or higher and a storage elastic modulus of 150 ° C. of 10 ³ Pa or higher. Fraction (1 g of sample is immersed in 100 ml of xylene, heated at 110 ° C. for 24 hours, then filtered through a 20 mesh wire net and the mass fraction of unmelted portion is measured) is 50 to 98%, preferably about 70 to 95% It is better to crosslink so that

  In Patent Document 2, 100 parts by weight of an amorphous or low crystalline ethylene / butene copolymer is added to 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as an organic peroxide. A mixture of 1.5 parts by weight and 2 parts by weight of triallyl isocyanurate as a crosslinking aid was produced using a profile extruder at a processing temperature of 100 ° C. and a thickness of 0.5 mm (Example 3). ). However, when such a composition is selected, sufficient productivity cannot be obtained because the processing temperature is low.

  In the sealing operation of the solar cell element, after covering the solar cell element with the sealing material of the present invention, the solar cell element is temporarily bonded by heating to a temperature at which the organic peroxide is not decomposed for several minutes to 10 minutes, In addition, there is a method in which the organic peroxide is decomposed in the oven at a high temperature of about 150 to 200 ° C. for 5 to 30 minutes to be bonded.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation methods and resins used in the examples and comparative examples are as follows.

1. Evaluation method of resin physical properties (1) Melt flow rate (MFR): MFR of ethylene / α-olefin copolymer is measured according to JIS-K6922-2: 1997 appendix (190 ° C., 21.18 N load). did.
(2) Density: As described above, the density of the ethylene / α-olefin copolymer was measured according to JIS-K6922-2: 1997 appendix (23 ° C., in the case of low density polyethylene).
(3) Mz / Mn: Measured by GPC as described above.
(4) Melt viscosity: In accordance with JIS-K-7199-1999, using Capillograph 1-B manufactured by Toyo Seiki Seisakusho, using a capillary with set temperature: 100 ° C., D = 1 mm, L / D = 10, melt viscosity at a shear rate of _{^{2.43 × 10sec -1 (η * 1}} ), to measure the melt viscosity at a shear rate of ^{2.43 × 10 2 sec -1 (η} * 2).

(5) Number of branches: The number of branches (N) in the polymer was measured by NMR under the following conditions, and the amount of comonomer was determined by the number of main chains and side chains per 1000 carbons in total.
Apparatus: Bruker BioSpin Corporation AVANCEIII cryo-400MHz
Solvent: o-dichlorobenzene / deuterated bromobenzene = 8/2 mixed solution <sample amount>
460mg / 2.3ml
<C-NMR>
・ H decouple, NOE available ・ Number of integration: 256scan
・ Flip angle: 90 °
・ Pulse interval 20 seconds ・ AQ (acquisition time) = 5.45 s D1 (waiting time) = 14.55 s

2. Method for evaluating extruded product (sheet) (1) HAZE
It measured based on JIS-K7136-2000 using the press sheet of thickness 0.7mm. The press sheet piece was set in a glass cell containing special liquid paraffin made by Kanto Chemical Co., Ltd. and measured. The press sheet was stored in a hot press machine at 160 ° C. for 30 minutes, and prepared by crosslinking. The smaller the HAZE value, the better.

(2) Light transmittance It measured based on JIS-K7361-1-1997 using the press sheet of thickness 0.7mm. The press sheet piece was set in a glass cell containing special liquid paraffin made by Kanto Chemical Co., Ltd. and measured. The press sheet was stored in a hot press machine at 160 ° C. for 30 minutes, and prepared by crosslinking.
The light transmittance is 80% or more, preferably 85% or more, and more preferably 90% or more.

(3) Tensile modulus Measured according to ISO 1184-1983 using a press sheet having a thickness of 0.7 mm crosslinked at 160 ° C. for 30 minutes. The tensile elastic modulus was determined when the tensile rate was 1 mm / min, the test piece width was 10 mm, the distance between grips was 100 mm, and the elongation was 1%. It shows that it is excellent in the softness, so that this value is small.

(4) Heat resistance The gel fraction of a sheet crosslinked at 160 ° C and a sheet crosslinked at 150 ° C for 30 minutes was evaluated. It can be evaluated that the higher the gel fraction, the more the crosslinking proceeds and the higher the heat resistance. A gel fraction having a gel fraction of 70 wt% or more was designated as a heat resistance evaluation “◯”. As for the gel fraction, about 1 g of the sheet is cut out and weighed accurately, immersed in 100 cc of xylene, treated at 110 ° C. for 24 hours, the residue after filtration is dried and weighed, and divided by the weight before treatment. Calculate the gel fraction.

3. Used Raw Material (1) Component (A): Ethylene / α-Olefin Copolymer A copolymer of ethylene, propylene and 1-hexene polymerized in <Production Example 1>, <Production Example 2> and <Production Example 3> below. (PE-1) (PE-2) (PE-3), a commercially available ethylene / 1-octene copolymer “Dengage Engage 8400” (PE-4) was used. The physical properties are shown in Table 1.
(2) Organic peroxide: 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi, Luperox 101)
(3) Hindered amine light stabilizer: polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (manufactured by BASF, TINUVIN 622LD)
(4) UV absorber: 2-hydroxy-4-n-octoxybenzophenone (manufactured by Sun Chemical Co., Ltd., CYTEC UV531)

<Production Examples 1 and 2>
In the following Production Example 3, polymerization was carried out under the same conditions as in Production Example 3 except that the supply ratio of ethylene / propylene / 1-hexene was changed, and an ethylene / propylene / 1-hexene copolymer (PE- 1, PE-2) was obtained. The characteristics of this ethylene / propylene / 1-hexene copolymer are shown in Table 1.

<Production Example 3>
Methylaluminoxane made by Toyo Stofer is added 1000 moles to the above complex to 2.0 mmol of the complex ethylenebis (4,5,6,7-tetrahydroindenyl) zirconium dichloride and diluted to 10 liters with toluene. Thus, a catalyst solution was prepared. The catalyst solution was placed in a 1.5 liter stirred autoclave continuous reactor, and a mixture of ethylene, propylene and 1-hexene was further added to the reactor, ethylene / propylene / 1-hexene = 49/20. / 31 (wt%) was supplied, the pressure in the reactor was kept at 1000 kg / cm 2, and the reaction was carried out at 160 ° C.
Obtained after completion of the reaction, MFR is 3.7 g / 10 min, density of 0.895g ^/ cm 3, Mz ^/ Mn is 3.7 ethylene-propylene-propylene-1-hexene copolymer (PE-3) It was.
The characteristics of this ethylene / propylene / 1-hexene copolymer (PE-3) are shown in Table 1.

Example 1
As an organic peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (Arkema) is used as an organic peroxide with respect to 100 parts by weight of a copolymer of ethylene, propylene and 1-hexene (PE-1). 1.5 parts by weight of Luperox (produced by Yoshitomi Co., Ltd.) and a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol as a hindered amine light stabilizer ( 0.05 parts by weight of BASF Corporation, TINUVIN 622LD) was blended. This was sufficiently mixed and pelletized using a 40 mmφ single screw extruder under the conditions of a set temperature of 130 ° C. and an extrusion rate (17 kg / hour).
The resulting sheets, at the 160 ℃ -0kg / cm ² conditions, after 3 minutes preheat, 160 ℃ -100kg / cm (30 minutes press molding at 160 ° C.) 27 minutes pressurization at ² conditions, and then, A sheet having a thickness of 0.7 mm was produced by cooling for 10 minutes in a cooling press set to 30 ° C. under a pressure of 100 kg / cm ² . The sheet was measured for HAZE, light transmittance, tensile modulus, and heat resistance.
Separately for evaluation of heat resistance, under the condition of 150 ℃ -0kg / cm ^2, after 3 minutes preheat, 150 ℃ -100kg / cm (30 minutes press molding at 0.99 ° C.) in 27 min pressurized ^second condition and Then, a sheet having a thickness of 0.7 mm was prepared by cooling for 10 minutes on a cooling press set to 30 ° C. under a pressure of 100 kg / cm ² .
The evaluation results are shown in Table 2.

(Example 2)
In Example 1, a sheet was produced in the same manner as in Example 1 except that PE-2 was used instead of PE-1. The sheet was measured for HAZE, light transmittance, tensile modulus, and heat resistance. The evaluation results are shown in Table 2.

(Example 3)
In Example 1, a sheet was prepared in the same manner as in Example 1 except that 0.3 part by weight of 2-hydroxy-4-n-octoxybenzophenone (CYTEC UV531 manufactured by Sun Chemical Co., Ltd.) was added as an ultraviolet absorber. Produced. The sheet was evaluated for HAZE, light transmittance, tensile modulus, and heat resistance. The evaluation results are shown in Table 2.

(Comparative Example 1)
A sheet was produced in the same manner as in Example 1 except that PE-3 was used instead of the copolymer of ethylene, propylene and 1-hexene (PE-1). The sheet was evaluated for HAZE, light transmittance, tensile modulus, and heat resistance. The evaluation results are shown in Table 2.

(Comparative Example 2)
A sheet was prepared in the same manner as in Example 1 except that PE-4 (ethylene / 1-octene copolymer, Dow Engage 8400) was used instead of PE-1. The sheet was evaluated for HAZE, light transmittance, tensile modulus, and heat resistance. The evaluation results are shown in Table 2.

"Evaluation"
As a result, as is apparent from Table 2, in Examples 1 to 3, since the resin composition of the present invention was used, the sheet obtained by extrusion molding had good cross-linking properties and HAZE Small, high light transmittance, flexible and excellent heat resistance.
On the other hand, in Comparative Example 1, unlike the present invention, a resin composition containing a copolymer of propylene and 1-hexene having a total number of branches (N) of comonomer of less than 54 (total / total 1000C). As a result, the crosslinking efficiency was reduced. Moreover, the obtained sheet | seat became a thing with a small softness | flexibility and heat resistance. Since the comparative example 2 also used the resin composition containing the ethylene / 1-octene copolymer which deviates from this invention, the obtained sheet | seat resulted in inferior crosslinking efficiency and inferior heat resistance.

The resin composition for a solar cell encapsulant of the present invention is preferably used as a solar cell encapsulant because it has high crosslinking properties and is excellent in transparency, flexibility, heat resistance and the like. In particular, it is useful as a sealing material for thin film solar cells, ICs (integrated circuits), and solar cell modules.

Claims (8)

The resin composition for solar cell sealing materials characterized by containing the following component (A), a component (B), and a component (C).
Component (A): ethylene / α-olefin copolymer (a1) having the following characteristics (a1) to (a2): Density of 0.860 to 0.920 g / cm ³
(A2) The total number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer is 54 to 95 (pieces / total 1000C).
(However, N is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.)
Component (B): Organic peroxide Component (C): Hindered amine light stabilizer The resin composition for a solar cell sealing material according to claim 1, wherein the component (A) is an ethylene / α-olefin copolymer further having the following property (a3).
(A3) The ratio (Mz / Mn) of the Z average molecular weight (Mz) and the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) is 8.0 or less.   Content of a component (B) is 0.2-5 weight part with respect to 100 weight part of a component (A), The resin composition for solar cell sealing materials of Claim 1 or 2 characterized by the above-mentioned. object.   Content of a component (C) is 0.01-2.5 weight part with respect to 100 weight part of component (A), The resin composition for solar cell sealing materials of Claim 1 characterized by the above-mentioned. object.   Component (A) is ethylene / 1-butene or ethylene / 1-hexene copolymer, The resin composition for solar cell sealing materials in any one of Claims 1-4 characterized by the above-mentioned.   The component (A) is an ethylene / propylene / 1-hexene copolymer, and the resin composition for a solar cell encapsulant according to any one of claims 1 to 4.   The solar cell sealing material which consists of a resin composition for solar cell sealing materials in any one of Claims 1-6.   The solar cell module using the solar cell sealing material of Claim 7.