JP2015154004A - Resin composition for solar cell encapsulation material, solar cell encapsulation material using the same, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for a solar cell encapsulation material excellent in cross-linking properties, heat resistance properties, flexibility, and material preservability.SOLUTION: The resin composition for a solar cell encapsulation material contains components (a) to (c) below: (a) an ethylene-based copolymer containing ethylene and radical polymerizable acid anhydride as a configuration monomer; (b) a polyhydric alcohol compound having at least two hydroxyl groups in a molecule; and (c) a reaction accelerator.

Description

  The present invention relates to a resin composition for a solar cell encapsulant, a solar cell encapsulant using the resin composition, and a solar cell module. More specifically, the present invention includes ethylene and at least a radically polymerizable acid anhydride as constituent monomers. Resin composition for solar cell encapsulant having excellent crosslinking characteristics and heat resistance, obtained by blending a metal salt with a composition comprising a copolymer and a polyhydric alcohol compound having at least two hydroxyl groups in the molecule And a solar cell encapsulant and a solar cell module using the resin composition.

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.
In photovoltaic power generation, generally, a solar cell element such as silicon, gallium-arsenide, copper-indium-selenium, etc. is protected by an upper transparent protective material and a lower substrate protective material, and the solar cell element and the protective material are sealed with a resin. It is a solar cell module that is fixed with a stopper and packaged. 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 prices 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.

Moreover, since a solar cell module is normally 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) -based resins are yellowed and cracked when used over a long period of time, resulting in deterioration of moisture resistance due to deterioration and alteration such as foaming, and corrosion of solar cells. A decrease in power generation was incurred. These are considered to be because the EVA resin has an ester structure with high hydrolyzability and is easily affected by sunlight and moisture.

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.

The sealing material using polyolefin requires a crosslinked structure in order to eliminate the deviation of the solar cell element after sealing, but the method exemplified in the above example obtains a level of crosslinked structure useful as a sealing material. Therefore, organic peroxide is used. That is, after making a sheet of a polyethylene resin composition containing an organic peroxide in advance, a cross-linked structure is obtained by passing the solar cell element together with upper and lower protective materials at a temperature at which the organic peroxide is decomposed. A solar cell module having a sealing material with However, this crimping step is a rate-limiting step in the production process of the solar cell encapsulant, and the crosslinkability required as an encapsulant is obtained without using an organic peroxide to improve module productivity. A method has been proposed.
For example, a composition containing a silane-modified resin obtained by polymerizing an ethylenically unsaturated silane compound and a polyethylene for polymerization has been proposed (see Patent Document 4). This system uses a cross-linking reaction between silane and water to produce a solar cell encapsulant. However, there is a possibility that a crosslinking reaction is induced by moisture in the air during storage before processing and molding.

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

JP 58-023870 A JP 2006-210906 A JP 2010-504647 A Japanese Patent Laid-Open No. 2007-150069

  The objective of this invention is providing the resin composition for solar cell sealing materials which is excellent in crosslinkability, heat resistance, a softness | flexibility, and the preservability of material.

  As a result of intensive studies to solve the above problems, the present inventors selected a radically polymerized ethylene copolymer as a resin component, and a polyhydric alcohol compound having at least two hydroxyl groups in the molecule and a metal. By blending the salt, it is possible to obtain a resin composition for a solar cell encapsulant that is excellent in crosslinkability, heat resistance, flexibility, and material preservability. Furthermore, when this resin composition is used, production of a solar cell module As a result, 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)-(c) is provided.
Component (a): Copolymer containing ethylene and at least radically polymerizable acid anhydride as constituent monomers Component (b): Polyhydric alcohol compound having at least two hydroxyl groups in the molecule Component (c): Reaction accelerator

  According to the second invention of the present invention, in the first invention, the content of the monomer derived from the radical polymerizable acid anhydride in the ethylene copolymer is 0.03 to 10 mol%. The resin composition for solar cell sealing materials characterized by this is provided.

  According to the third invention of the present invention, in the first or second invention, the hydroxyl group in the polyhydric alcohol compound with respect to the monomer derived from the radically polymerizable acid anhydride in the ethylene-based copolymer. Provided is a resin composition for a solar cell sealing material, wherein the molar ratio of units is in the range of 0.01 to 10.

  According to the fourth invention of the present invention, in any one of the first to third inventions, 0.001 to 20 parts by weight of the reaction accelerator is contained with respect to 100 parts by weight of the ethylene copolymer. A solar cell encapsulant composition is provided.

  According to a fifth aspect of the present invention, there is provided a resin composition for a solar cell encapsulant, characterized in that, in any one of the first to fourth aspects, the reaction accelerator is a metal salt. Is done.

  According to a sixth invention of the present invention, in the fifth invention, there is provided a resin composition for a solar cell sealing material, wherein the metal salt is an organic carboxylate.

  According to a seventh invention of the present invention, in any one of the first to sixth inventions, the ethylene-based copolymer is composed of ethylene, a radical polymerizable acid anhydride and other radical polymerizable comonomers. A resin composition for a solar cell encapsulant, which is a copolymer, is provided.

  According to an eighth aspect of the present invention, in the seventh aspect, the content of the other radical polymerizable comonomer in the ethylene-based copolymer is 5.0 to 20 mol%. A resin composition for a stopper is provided.

  Moreover, according to the ninth invention of the present invention, there is provided a solar cell encapsulant obtained by melt-molding the resin composition according to any one of the first to eighth inventions and forming a crosslinked structure in the cooling process. The

  The resin composition for a solar cell encapsulant of the present invention is a polyhydric alcohol mainly comprising a copolymer containing ethylene and at least a radically polymerizable acid anhydride as constituent monomers, and having at least two hydroxyl groups in the molecule. Since the compound and the metal salt are blended, when this resin composition is made into a sheet, it does not form a crosslinked structure at the processing temperature, and can rapidly form a crosslinked structure in the cooling and solidification process after molding. In addition, the rigidity and the crosslinking efficiency are well balanced, and it is easy to form a module as a solar cell encapsulant, and the manufacturing cost can be reduced. Moreover, the obtained solar cell module becomes excellent in flexibility, weather resistance, and the like, 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”) contains the following components (a) to (c). Features.
Component (a): Copolymer containing ethylene and at least radically polymerizable acid anhydride as constituent monomers Component (b): Polyhydric alcohol compound having at least two hydroxyl groups in the molecule Component (c): Metal salt

(1) Component (a)
The component (a) used in the present invention is an ethylene copolymer having the following properties (a1) to (a2).
(A1) The content of the monomer derived from the radical polymerizable acid anhydride in the ethylene copolymer is 0.03 to 10 mol%.
(A2) The ethylene copolymer is a binary copolymer composed of ethylene, a radically polymerizable acid anhydride, or a multi-component copolymer composed of ethylene, a radically polymerizable acid anhydride and other radically polymerizable comonomers, The content of other radical polymerizable comonomer is 20 mol% or less

(I) Monomer composition of component (a) The ethylene copolymer used in the present invention is a binary copolymer composed of ethylene and a radically polymerizable acid anhydride, or ethylene, a radically polymerizable acid anhydride and others. It is a multi-component copolymer comprising a radically polymerizable comonomer.
Examples of radically polymerizable acid anhydrides constituting these ethylene copolymers include maleic anhydride, itaconic anhydride, endic acid anhydride, citraconic anhydride, 1-butene-3,4-dicarboxylic acid. Examples thereof include anhydrides, alkenyl succinic anhydride having a double bond at the terminal having at most 18 carbon atoms, and alkadienyl succinic anhydride having a double bond at the terminal having at most 18 carbon atoms. These may be used alone or in combination of two or more. Of these, maleic anhydride or itaconic anhydride is preferred.

(A1) The content of the monomer derived from the radically polymerizable acid anhydride in the ethylene copolymer as the component (a) needs to be in the range of 0.03 to 10 mol%. If the monomer derived from the acid anhydride is less than 0.03 mol%, the crosslinking density, which is the object of the present invention, becomes insufficient, such being undesirable. On the other hand, if it exceeds 10 mol%, the properties such as the flexibility and moisture absorption resistance inherent to the polyethylene resin, which are expected for an ethylene copolymer, are impaired, and further, it can be produced commercially due to an increase in cost. Since it becomes difficult, it is not preferable.
Generally, the preferable content of the monomer derived from the radically polymerizable acid anhydride in the ethylene-based copolymer is in the range of 0.3 to 5.0 mol%. However, the preferable component concentration range may vary depending on the type of the polyhydric alcohol compound used as the component (b). For example, when any of the compounds (b)-(1), (b)-(2) or (b)-(3) described later is used as the component (b), the above ethylene-based copolymer is used. The preferred component concentration derived from the radically polymerizable acid anhydride in the coalescence is in the range of 0.03 to 5.0 mol%, particularly preferably in the range of 0.15 to 3.0 mol%.

Examples of other radical polymerizable comonomer (hereinafter referred to as “third monomer”) that can be used in combination with the radical polymerizable acid anhydride include ethylene unsaturated ester compounds, ethylene unsaturated amide compounds, ethylene unsaturated monomers. Examples include saturated acid compounds, ethylenically unsaturated ether compounds, and ethylenically unsaturated hydrocarbon compounds. Here, as an ethylenically unsaturated ester compound, for example, vinyl acetate, methyl (meth) acrylate [(meth) acryl means acryl and methacryl. The same shall apply hereinafter), ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic Benzyl acid, methyl fumarate, ethyl fumarate, propyl fumarate, butyl fumarate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, methyl maleate, ethyl maleate, propyl maleate, butyl maleate Dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate and the like.
Examples of the ethylenically unsaturated amide compound include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-butyl (meth) acrylamide, N- Examples include hexyl (meth) acrylamide, N-octyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth) acrylamide. Examples of the ethylenically unsaturated acid compound include (meth) acrylic acid, maleic acid, fumaric acid and the like. Examples of the ethylenically unsaturated ether compound include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octadecyl vinyl ether, and phenyl vinyl ether. Examples of the ethylenically unsaturated hydrocarbon compound and other compounds include styrene, α-methylstyrene, norbornene, butadiene, acrylonitrile, methacrylonitrile, acrolein, crotonaldehyde, trimethoxyvinylsilane, triethoxyvinylsilane, vinyl chloride, and chloride. Examples include vinylidene.
It is preferable to use the third monomer in that the third monomer is used to reduce the crystallinity of the ethylene copolymer and to obtain a sealing material excellent in transparency.
Two or more kinds of the third monomers can be used as necessary. When the third monomer is used in combination, the component concentration of the third monomer in the ethylene copolymer of component (a) used in the present invention is preferably 20 mol% or less. When this concentration exceeds 20 mol%, the moldability is greatly lowered, and it becomes difficult to obtain a composition meeting the object of the present invention.

(Ii) Polymerization catalyst and polymerization method of component (a) The ethylene copolymer used in the present invention is produced by a polymerization method such as a bulk, solution, suspension or emulsion, but basically has a normal low density. Polyethylene manufacturing equipment and technology can be used. The most common is bulk polymerization, which is produced by radical polymerization in a temperature range of 100 to 300 ° C. under a pressure of 700 to 3000 atmospheres. The range of preferable polymerization pressure and polymerization temperature is 1000 to 2500 atm, and the average temperature in the reactor is 150 to 270 ° C. When the pressure is less than 700 atm, the molecular weight of the polymer is lowered, and the moldability and the resin physical properties of the composition are deteriorated. A pressure exceeding 3000 atm is substantially meaningless without improving the physical properties of the resin, and is not preferable because it increases the production cost. When the average polymerization temperature is less than 100 ° C., the polymerization reaction is not stable, the addition rate to the copolymer is lowered, and this is not economically preferable. Moreover, when it exceeds 300 degreeC, since the molecular weight of a copolymer falls and the danger of a runaway reaction arises, it is unpreferable.

  As the production apparatus, it is preferable to use a vessel type reactor. In particular, since radically polymerizable acid anhydrides have poor polymerization stability, the inside of the reactor needs to be highly uniform. If necessary, a plurality of reactors can be connected in series or in parallel to perform multistage polymerization. Furthermore, more precise temperature control can be performed by partitioning the inside of the reactor into a plurality of zones.

(Iii) Characteristics of component (a) The MFR of the ethylene copolymer used in the present invention (according to condition 4 in Table 1 of JIS-K7210) is preferably in the range of 0.1 to 1000 g / 10 min. Outside this range, it is difficult to obtain a composition that meets the object of the present invention.

(2) Component (b)
The polyhydric alcohol compound having at least two hydroxyl groups in the molecule of the component (b) in the present invention refers to various compounds having two or more hydroxyl groups, and is used for crosslinking the component (a).
Examples of such polyhydric alcohol compounds include ethylene glycol, glycerin, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, trimethylolmethane, trimethylol. Alcohol compounds such as methylolpropane and pentaerythritol; polyethylene glycols such as diethylene glycol, triethylene glycol, and tetraethylene glycol; polyglycerols such as diglycerin, triglycerin, and tetraglycerin; arbitol, sorbitol, xylose, arabinose, glucose, galactose, sorbose Sugars such as fructose, palatinose, maltotriose, and marezitose; dehydration condensates of these sugars; Polyoxyalkylene compounds to which propylene oxide is added; compounds in which the above various compounds are partially esterified with carboxylic acid; compounds in which the above polyoxyalkylene compound is partially esterified with carboxylic acid; Polyoxyalkylene compound obtained by adding ethylene oxide or propylene oxide to esterified compound; saponified product of ethylene-vinyl acetate copolymer, polyvinyl alcohol; polyolefin oligomer having two or more hydroxyl groups, ethylene-hydroxyethyl (meth) acrylate copolymer Examples thereof include polymers having two or more hydroxyl groups in the molecule.
The melting point of the polyhydric alcohol compound is preferably 300 ° C. or lower. These polyhydric alcohol compounds may be used in combination of two or more.

  Particularly preferred as component (b) is at least one compound selected from the following (b)-(1), (b)-(2) and (b)-(3). In addition to having an action as a so-called cross-linking agent, these compounds have an action to prevent the composition of the present invention from generating gels, blisters and the like in the molded product.

〔式中、ｍは０〜１０の整数である。〕
で示されるポリグリセリンに、エチレンオキシド又はプロピレンオキシドを付加させた構造を有するポリオキシアルキレン化合物である。
上記のポリオキシアルキレン化合物は、一般式（Ｉ）で示されるポリメチロール、又は（ＩＩ）で示されるポリグリセリンに、エチレンオキシド又はプロピレンオキシドを常法で付加反応させることによって容易に得られる。ここで、一般式（Ｉ）で示されるポリメチロールとしては、例えば、１，３−ジヒドロキシプロパン；２，２−ジメチル−１，３−ジヒドロキシプロパン；トリメチロールエタン；１，１，１−トリメチロールプロパン；１，１，１−トリメチロールヘキサン；１，１，１−トリメチロールドデカン；２−シクロヘキシル−２−メチロール−１，３−ジヒドロキシプロパン；２−（ｐ−メチルフェニル）−２−メチロール−１，３−ジヒドロキシプロパン；ペンタエリスリトールなどが挙げられる。また、一般式（ＩＩ）で示されるポリグリセリンとしては、例えば、グリセリン、ジグリセリン、ヘキサグリセリン、オクタグリセリン、デカグリセリンなどが挙げられる。これらの化合物にエチレンオキシド又はプロピレンオキシドを付加反応させて得られるポリオキシアルキレン化合物は、通常、単一の化合物として得ることは極めて困難であり、一般に複数の異なる構造の化合物の混合物として得られるが、本発明の目的には全く問題なく用いることができる。さらに、一般式（Ｉ）及び／又は（ＩＩ）で示される化合物を二種類以上用いて同時にエチレンオキシド又はプロピレンオキシドを付加反応させたポリオキシアルキレン化合物を用いても差し支えない。
一般式（Ｉ）又は（ＩＩ）で示される化合物へのエチレンオキシド又はプロピレンオキシドの付加量は、用いる上記の化合物に含まれる水酸基の数に左右されるため、一概には規定することはできないが、少なくとも上記の化合物１モルに対してエチレンオキシド又はプロピレンオキシドを２モル以上付加させることが好ましい。付加量の上限は、特にないが、一般的に付加量が一般式（Ｉ）又は（ＩＩ）で示される化合物１モルに対して５０モルを超えると、得られたポリオキシアルキレン化合物の分子量が大きくなりすぎ、組成物を調製する際の混合性が低下したり、成形後のブリードなどの問題が生ずるため好ましくない。 (I) (b)-(1)
Examples of the compound (b)-(1) include the following general formula (I)
(R ¹ ) _a C (CH ₂ OH) _b (I)
[Wherein R ¹ represents hydrogen, a linear or cyclic alkyl group having 1 to 12 carbon atoms, or an aralkyl group, a represents an integer of 0 to 2, b represents an integer of 2 to 4, and It is selected to satisfy a + b = 4. Or a polymethylol represented by the following general formula (II)

[In formula, m is an integer of 0-10. ]
Is a polyoxyalkylene compound having a structure in which ethylene oxide or propylene oxide is added to the polyglycerol represented by the formula (1).
The above polyoxyalkylene compound can be easily obtained by subjecting polymethylol represented by the general formula (I) or polyglycerin represented by (II) to an addition reaction of ethylene oxide or propylene oxide by a conventional method. Here, examples of the polymethylol represented by the general formula (I) include 1,3-dihydroxypropane; 2,2-dimethyl-1,3-dihydroxypropane; trimethylolethane; 1,1,1-trimethylol. 1,1,1-trimethylolhexane; 1,1,1-trimethyloldodecane; 2-cyclohexyl-2-methylol-1,3-dihydroxypropane; 2- (p-methylphenyl) -2-methylol- 1,3-dihydroxypropane; pentaerythritol and the like. Examples of the polyglycerin represented by the general formula (II) include glycerin, diglycerin, hexaglycerin, octaglycerin, decaglycerin and the like. Polyoxyalkylene compounds obtained by addition reaction of these compounds with ethylene oxide or propylene oxide are usually very difficult to obtain as a single compound and are generally obtained as a mixture of compounds having a plurality of different structures. The present invention can be used without any problem. Furthermore, a polyoxyalkylene compound obtained by addition reaction of ethylene oxide or propylene oxide using two or more compounds represented by the general formula (I) and / or (II) may be used.
The amount of addition of ethylene oxide or propylene oxide to the compound represented by the general formula (I) or (II) depends on the number of hydroxyl groups contained in the above-mentioned compound to be used. It is preferable to add 2 mol or more of ethylene oxide or propylene oxide to at least 1 mol of the above compound. The upper limit of the addition amount is not particularly limited. Generally, when the addition amount exceeds 50 mol with respect to 1 mol of the compound represented by the general formula (I) or (II), the molecular weight of the obtained polyoxyalkylene compound is decreased. This is not preferable because it becomes too large, resulting in poor mixing during preparation of the composition and problems such as bleeding after molding.

〔式中、ｎは０〜２０の整数である。〕
で示されるポリグリセリンとを脱水縮合させた構造を有し、分子内に２個以上の水酸基を有するポリグリセリンエステル化合物である。
上記の（ｂ）−（２）化合物は、一般式（ＩＩＩ）で示される有機カルボン酸又はその等価体（例えば、アルカリ金属塩，酸ハロゲン化物など）と一般式（ＩＶ）で示されるポリグリセリンとを、一般に知られている方法で脱水縮合させることによって容易に製造することができる。ここで、一般式（ＩＩＩ）の有機カルボン酸としては、例えば、酢酸、プロピオン酸、酪酸、イソ酪酸、吉草酸、ヘキサン酸、カプリル酸、カプリン酸、ステアリン酸、オレイン酸、ラウリン酸、フェニル酢酸、フェニルプロピオン酸、フェニル酪酸などが挙げられる。（ｂ）−（２）として使用されるポリグリセリンエステル化合物は、分子内に２個以上の水酸基を有することが必要である。したがって、一般式（ＩＶ）のポリグリセリンをエステル化する際の有機カルボン酸の使用量は、ポリグリセリンに含まれる水酸基の個数を考慮して決定する必要がある。
（ｂ）−（２）のポリグリセリンエステルとしては、例えば、グリセリンモノステアレート、グリセリンモノオレエート、グリセリンモノラウレート、グリセリンモノカプリレート、グリセリンモノヘキサノエート、グリセリンモノフェネチルエステル、グリセリンモノプロピオネート、ジグリセリンモノステアレート、ジグリセリンジステアレート、ジグリセリンモノオレエート、ジグリセリンモノヘキサノエート、ジグリセリンジオクタノエート、テトラグリセリンモノステアレート、テトラグリセリントリステアレート、テトラグリセリンテトラステアレート、テトラグリセリントリヘキサノエート、テトラグリセリンモノフェネチルエステル、ヘキサグリセリンモノステアレート、ヘキサグリセリンジステアレート、ヘキサグリセリンペンタステアレート、ヘキサグリセリントリオレエート、ヘキサグリセリンモノラウレート、ヘキサグリセリンペンタラウレート、デカグリセリンモノステアレート、デカグリセリンオクタステアレート、デカグリセリンペンタオレエート、デカグリセリンジラウレート、ペンタデカグリセリンジステアレート、ペンタデカグリセリンデカオレート、オクタデカグリセリンテトラステアレートなどが挙げられる。また、これらのポリグリセリンエステルを二種以上併用することもできる。 (Ii) (b)-(2)
Examples of the compound (b)-(2) include the following general formula (III)
R ² —COOH (III)
[Wherein R ² represents a chain alkyl group having 2 to 25 carbon atoms, a cyclic alkyl group, an aralkyl group or an alkenyl group. ]
An organic carboxylic acid compound represented by the following general formula (IV)

[In formula, n is an integer of 0-20. ]
It is a polyglycerin ester compound having a structure obtained by dehydration condensation with polyglycerin represented by the formula and having two or more hydroxyl groups in the molecule.
The compound (b)-(2) is composed of an organic carboxylic acid represented by the general formula (III) or an equivalent thereof (for example, alkali metal salt, acid halide, etc.) and a polyglycerin represented by the general formula (IV). Can be easily produced by dehydration condensation by a generally known method. Here, as the organic carboxylic acid of the general formula (III), for example, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, caprylic acid, capric acid, stearic acid, oleic acid, lauric acid, phenylacetic acid , Phenylpropionic acid, phenylbutyric acid and the like. The polyglycerin ester compound used as (b)-(2) needs to have two or more hydroxyl groups in the molecule. Therefore, the amount of the organic carboxylic acid used when esterifying the polyglycerol of the general formula (IV) needs to be determined in consideration of the number of hydroxyl groups contained in the polyglycerol.
Examples of the polyglycerol ester (b)-(2) include glycerol monostearate, glycerol monooleate, glycerol monolaurate, glycerol monocaprylate, glycerol monohexanoate, glycerol monophenethyl ester, and glycerol monopro Pionate, diglycerol monostearate, diglycerol distearate, diglycerol monooleate, diglycerol monohexanoate, diglycerol dioctanoate, tetraglycerol monostearate, tetraglycerol tristearate, tetraglycerol tetra Stearate, tetraglycerol trihexanoate, tetraglycerol monophenethyl ester, hexaglycerol monostearate, hexaglycerol distearate, hexaglycerol Pentastearate, hexaglycerol trioleate, hexaglycerol monolaurate, hexaglycerol pentalaurate, decaglycerol monostearate, decaglycerol octastearate, decaglycerol pentaoleate, decaglycerol dilaurate, pentadecaglycerol distearate, Examples include pentadecaglycerine dekarate and octadecaglycerin tetrastearate. Two or more of these polyglycerin esters can be used in combination.

(Iii) (b)-(3)
Examples of the compound (b)-(3) include sorbitan and sorbitan derivatives having two or more hydroxyl groups in the molecule. Here, sorbitan means 1,5-sorbitan, 1,4-sorbitan, 3,6-sorbitan and mixtures thereof. The sorbitan derivatives having two or more hydroxyl groups in the molecule include various derivatives derived from the above sorbitan. Suitable sorbitan derivatives include the following sorbitan ester compounds, polyoxyalkylene sorbitan compounds and A polyoxyalkylene sorbitan ester compound can be mentioned.
First, as a sorbitan ester compound, the following general formula (V)
R ³ —COOH (V)
[Wherein R ³ represents a chain alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group, an aralkyl group or an alkenyl group. ]
And a sorbitan ester compound having a structure obtained by dehydrating and condensing sorbitan with an organic carboxylic acid compound represented by formula (2) and having two or more hydroxyl groups in the molecule. This compound is easily produced by dehydrating condensation of an organic carboxylic acid represented by the general formula (V) or an equivalent thereof (for example, alkali metal salt, halide, etc.) and sorbitan by a generally known method. can do. Specific compounds include, for example, sorbitan monocaprylate, sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan dicaprylate, sorbitan dilaurate, sorbitan distearate Etc.
Examples of the polyoxyalkylene sorbitan compound include a polyoxyalkylene sorbitan compound having a structure in which ethylene oxide or propylene oxide is added to sorbitan or the above sorbitan ester compound and having two or more hydroxyl groups in the molecule. it can. This compound can be easily obtained by subjecting sorbitan or the above sorbitan ester compound to addition reaction of ethylene oxide or propylene oxide by a conventional method. Specific examples of the compound include polyoxyethylene sorbitan (3.0 mol) adduct, polyoxypropylene sorbitan (4.0 mol) adduct, and the like.
Furthermore, the polyoxyalkylene sorbitan ester compound has a structure obtained by dehydrating and condensing the organic carboxylic acid compound represented by the general formula (V) and the polyoxyalkylene sorbitan compound. The sorbitan ester compound which has the above hydroxyl group can be mentioned. This compound can also be easily produced by dehydration condensation using an organic carboxylic acid represented by the general formula (V) or an equivalent thereof by a conventional method. Specific examples of the compound include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monomyristate, polyoxypropylene sorbitan monooleate, polyoxyethylene sorbitan dicaprylate, polyoxypropylene sorbitan distearate and the like. It is done.
In these addition reactions and condensation reactions, it is usually very difficult to obtain a single compound, and generally a mixture of compounds having a plurality of different structures can be obtained. Can do. Two or more kinds of sorbitan ester compounds, polyoxyalkylene sorbitan compounds, polyoxyalkylene sorbitan ester compounds and other sorbitan derivatives may be used in combination.

(Iv) Mixing ratio of component (b) The amount of the polyhydric alcohol compound of component (b) used is a large amount with respect to the monomer derived from the radically polymerizable acid anhydride contained in the ethylene copolymer of component (a). It is necessary for the molar ratio of the hydroxyl group units contained in the monohydric alcohol compound to be in the range of 0.01 to 10, preferably in the range of 0.05 to 5.0. When this molar ratio is less than 0.01, it is insufficient to introduce a crosslinked structure in an effective amount into the composition. On the other hand, if the molar ratio exceeds 10, not only is it meaningless in terms of effectively introducing a crosslinked structure, but also the cost is increased, which is not preferable.
Moreover, when the monomer derived from the radically polymerizable acid anhydride contained in the ethylene copolymer is in the range of 0.1 to 1% by weight, the molar ratio of the hydroxyl unit contained in the polyhydric alcohol compound Is more preferably in the range of 0.1 to 5.0.

(3) Component (c)
The reaction accelerator of component (c) in the resin composition of the present invention refers to activating a carbonyl group contained in a monomer derived from a radically polymerizable acid anhydride contained in an ethylene copolymer, and a hydroxyl group and an acid anhydride. It is a compound that promotes a reaction with a physical group.

  There are various kinds of such reaction accelerators. One example is a metal salt of an organic carboxylic acid. Examples of metal salts of organic carboxylic acids include metal salts of fatty acids having 1 to 30 carbon atoms such as acetic acid, propionic acid, butyric acid, octanoic acid, decanoic acid, lauric acid, myristic acid, valmitic acid, stearic acid, and olein. Examples include salts of acids, behenic acid and the like with metals of Group IA, IIA, IIB, and IIIB (for example, Li, Na, K, Mg, Ca, Zn, A1, etc.) of the periodic table. Specific examples include lithium acetate, sodium acetate, magnesium acetate, aluminum acetate, potassium butyrate, calcium butyrate, zinc butyrate, and sodium octoate. Calcium octoate, potassium decanoate, magnesium decanoate. Zinc decanoate, lithium laurate, sodium laurate, calcium laurate, aluminum laurate, potassium myristate, sodium myristate, aluminum myristate, sodium valmitate, zinc valmitate, magnesium valmitate. Examples include sodium stearate, potassium stearate, calcium stearate, zinc stearate, sodium oleate, and sodium behenate. Of these, lithium laurate. Sodium laurate, calcium laurate, aluminum laurate, potassium myristate, sodium myristate, aluminum myristate, sodium barmitate, zinc valmitate, magnesium palmitate, sodium stearate, potassium stearate, calcium stearate, zinc stearate, Sodium oleate and the like are preferred.

  Another example of a metal salt of an organic carboxylic acid is a polymer having a metal salt structure of a carboxylic acid. Examples of such polymers include ethylene and radical polymerizable unsaturated carboxylic acid group IA, IIA, IIB, and IIIB metal (eg, Li, Na, K, Mg, Ca, Zn, A1, etc.) salts. And those having a structure obtained by copolymerizing a metal salt of ethylene and a radically polymerizable carboxylic acid with other radically polymerizable unsaturated carboxylic acid and / or a derivative thereof.

  Further, a radically polymerizable unsaturated carboxylic acid metal salt (may be polymerized with a free unsaturated carboxylic acid and then neutralized) to a polyolefin polymer such as polyethylene, polypropylene, and free ethylene-propylene copolymer. And those having a structure in which a metal salt of a radical polymerizable carboxylic acid and another radical polymerizable unsaturated carboxylic acid and / or a derivative thereof are simultaneously co-grafted to a polyolefin polymer. It is done. The radical polymerizable unsaturated carboxylic acid and derivatives thereof used here include (meth) acrylic acid, maleic acid, fumaric acid, monomethyl maleate, monomethyl fumarate, monoethyl maleate, monoethyl fumarate, monobutyl maleate, fumarate Examples include monobutyl acid, methyl (meth) acrylate, dimethyl maleate, dimethyl fumarate, diethyl maleate, diethyl fumarate, dibutyl maleate, and dibutyl fumarate.

  Other examples of the reaction accelerator used in the resin composition of the present invention include tertiary amine compounds. Specific examples of the tertiary amine compound used here include trimethylamine, triethylamine, triisopropylamine, trihexylamine, trioctylamine, trioctadecylamine, dimethylethylamine, methyldioctylamine, dimethyloctylamine, diethylcyclohexylamine, N, N-diethyl-4-methylcyclohexylamine, diethylcyclododecylamine, N, N-diethyl-1-adamantanamine, 1-methylpyrrolidine, 1-ethylpyrrolidine, l-ethylpiperidine, quinuclidine, triphenylamine, N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl-m-phenethiazine, 4-t-butyl-N, N-dimethylaniline and the like can be mentioned.

  Other examples of reaction accelerators can further include quaternary ammonium salts. Examples of the quaternary ammonium salt used herein include tetramethylammonium tetrafluoroborate, tetramethylammonium hexafluorophosphate, tetramethylammonium promide, tetraethylammonium promide, tetraethylammonium promide, and methyltri n-butylammonium chloride. Tetrabutylammonium promide, tetrahexylammonium promide, tetraheptylammonium promide, phenyltrimethylammonium promide, benzyltriethylammonium chloride and the like.

  Further, Group IIA, IIB, and IIIB metal hydroxides or Group IIA and IIB metal halides can be used as reaction accelerators. Here, examples of the metal hydroxides of the IlA group, IIB group, and IIIB group include calcium hydroxide, magnesium hydroxide, aluminum hydroxide, and the like. Examples thereof include calcium chloride, calcium bromide, and magnesium chloride.

  Furthermore, an oxo acid and a metal salt of Group IA, Group IIA, Group IIB, or Group IIIB can be used as a reaction accelerator. Specific examples include sodium nitrate, calcium nitrate, zinc nitrate, magnesium nitrate, aluminum nitrate, sodium phosphate, calcium phosphate, sodium carbonate, calcium carbonate, magnesium carbonate, sodium sulfate, zinc sulfate, magnesium sulfate, aluminum sulfate, chloric acid. Examples thereof include sodium, potassium chlorate, and sodium iodate.

In addition, LiBF ₄ , NaBF ₄ , KBF ₄ , NaPF ₆ , KPF ₆ , NaPCl ₆ , KPCl ₆ , NaFeCl ₄ , NaSnCl ₄ , NaSbF ₆ , NaAsF ₆ , NaAsCl ₆ , and alkali metal such as KAsCl ₆ Can be used as an accelerator.

  Of the reaction accelerators exemplified above, a metal salt of a polymer containing a carboxyl group and a metal salt of an organic carboxylic acid are preferably used. In addition, two or more kinds of the above various reaction accelerators can be used in combination as necessary.

  The amount of the reaction accelerator used must be in the range of 0.001 to 20 parts by weight with respect to 100 parts by weight of the ethylene copolymer of component (a), and 0.01 to 15 parts by weight. It is preferable to be in the range. When this amount is less than 0.001 part by weight, the reaction becomes too slow to make it difficult to effectively introduce a crosslinked structure into the composition, and when it exceeds 20 parts by weight, the reaction rate is improved. Not only is it meaningless, it is also economically undesirable.

(4) Hindered amine light stabilizer In this invention, it is preferable to mix | blend a hindered amine light stabilizer with a 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, 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 octane. Of 70% by weight of a reaction product (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] butylmalonate (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 (min Amount 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-butanetetra Mixture of carboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular weight 900); 1,2,2,6,6-pentamethyl-4-piperidyl-1,2,3,4-butanetetra Examples thereof include a mixture of carboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular weight 900).

  As a 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); dimethyl succinate 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 the above 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-pentamethylpiperidine, 4-methacryloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1-butyl-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2, Examples include copolymers of ethylene with cyclic aminovinyl compounds such as 2,6,6-tetramethylpiperidine and 4-crotonoyloxy-1-propyl-2,2,6,6-tetramethylpiperidine. The hindered amine light stabilizers may be used alone or in a 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); 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 A mixture of a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2, Polycondensate of 2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine (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. It is preferable to use one having a melting point of 60 ° C. or higher from the viewpoint of ease of production 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 1.0 parts by weight, with respect to 100 parts by weight of the ethylene copolymer. More preferably, it is 0.01-0.5 weight part, More preferably, it is 0.01-0.2 weight part, Most preferably, it is good to set it as 0.03-0.1 weight part.
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, resin discoloration due to excessive addition of a hindered amine light stabilizer is suppressed. be able to.

(5) 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 1.0 parts by weight, based on 100 parts by weight of the ethylene copolymer. More preferably, it is 0.1 to 0.5 part by weight, and most preferably 0.2 to 0.4 part 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 5.0 parts by weight, preferably 0.01 to 5.0 parts by weight, more preferably 0.01 to 2. parts by weight based on 100 parts by weight of the ethylene copolymer. It is used at 0 part by weight, more preferably 0.05 to 1.0 part by weight.

(6) 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.

  The resin composition of the present invention contains the component (a), the component (b), and the component (c) as main components, and various polyolefin resins can be blended depending on applications and purposes. Examples of such polyolefin resin include homopolymers such as polyethylene, polypropylene, polyisoprene, polybutene, poly-3-methylbutene-1, poly-4-methylpentene-1, polybutadiene, and polystyrene. In addition, copolymers of these comonomers constituting these homopolymers, such as ethylene-propylene copolymer; straight-chains containing butene-1,4-methylpentene-1, hexene-1, octene-1, etc. as comonomers. Mention may also be made of copolymers such as linear low-density polyethylene; propylene-ethylene block copolymers. Furthermore, the mixture of said each resin, a graft polymer, a block copolymer; Ethylene-vinyl acetate copolymer etc. can also be mentioned.

  The MFR of the polyolefin resin used in the present invention (according to condition 4 (polyethylene type) or condition 14 (polypropylene type) in Table 1 of JIS-K7210) is preferably in the range of 0.1 to 1000 g / 10 min. If this MFR is less than 0.1, it is generally difficult not only to form a composition with a resin composition, but also the moldability is lowered. On the other hand, if the MFR exceeds 1000, mixing of the resins becomes difficult and a uniform composition cannot be obtained.

The blending amount of the polyolefin resin is preferably in the range of 200 parts by weight or less with respect to 100 parts by weight of the composition mainly composed of the component (a), the component (b) and the component (c). When the blending amount of the polyolefin resin exceeds 200 parts by weight, the heat resistance and mechanical strength inherently possessed by the composition or molded article of the present invention may not be exhibited.
When producing the composition of the present invention containing a polyolefin resin, the polyolefin resin may be added simultaneously with mixing the components (a) to (c), and the components (a) to (c) may be added. It may be added again after mixing and composition.

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 acid anhydride group contained in the ethylene-based copolymer used in the resin composition of the present invention reacts with the hydroxyl group contained in the polyhydric alcohol compound to form a cross-linked structure by a reaction that forms a half ester (monoester). Is considered to be introduced into the composition. A composition comprising two components of an ethylene-based copolymer containing an acid anhydride group and a polyhydric alcohol compound alone is a so-called thermoreversible crosslinkable that dissociates the crosslinked structure at a high temperature and forms a crosslinked structure again upon cooling. Although it exhibits properties as a resin, the crosslink formation reaction rate and the crosslink dissociation reaction rate are extremely slow, and sufficient performance cannot be exhibited under general melt molding processing conditions.
However, in the present invention, by adding a metal salt to these two components, the cross-linking reaction rate and the cross-linking dissociation reaction rate are increased, and a practically usable state is obtained. This is thought to be because the metal ion of the metal salt increases the reaction rate between the acid anhydride group contained in the ethylene copolymer and the hydroxyl group contained in the polyhydric alcohol. By adding the metal salt, For the first time, a thermoreversible crosslinkable resin composition and a thermoreversible crosslinkable molded article that exhibit sufficient performance even under general thermoforming processing conditions have been provided.

  Although the resin composition of the present invention is melt-kneaded and molded, a crosslinked structure is not formed during the molding process. And after this is shape | molded in the pellet and the sheet form, in a cooling solidification process, a crosslinked structure is formed, cohesion force is raised, and heat resistance and mechanical strength are improved. In addition, once the cross-linked structure is formed, the structure is dissociated by melting to restore the moldability, and the cross-linked structure is formed again in the cooling and solidification process after the new molding, thereby producing a high-strength molded product. Arise.

  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 polyhydric alcohol and a metal salt are added to an ethylene copolymer, and if necessary, a hindered amine light stabilizer, and further addition of a silane coupling agent, an ultraviolet absorber, an antioxidant, a light stabilizer, etc. It can be obtained by dry blending the agent in advance and supplying it from a hopper of a T-die extruder and extruding it into a sheet at an extrusion temperature of 200 ° C. or higher, preferably higher than the melting point of the polyhydric alcohol of component (b). it can. 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 producing the solar cell module, the sheet of the sealing material of the present invention is prepared in advance, and is subjected to pressure bonding at a temperature at which the resin composition of the sealing material melts, for example, 150 to 220 ° C., as described above. 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 bonded to the solar cell element or the protective material at a temperature at which the sealing material of the present invention melts, and then the temperature is raised and cooled to sufficiently bond the sealing material. And an ethylene copolymer and a polyhydric alcohol can also be crosslinked.

  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 is produced using a profile extruder at a processing temperature of 100 ° C. and a sheet having a thickness of 0.5 mm. 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 sealing material of the present invention melts for about several minutes to 10 minutes, Next, there is a method of bonding by heat treatment at a high temperature of about 150 to 220 ° C. for 5 to 30 minutes in an oven.

  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): The MFR of the ethylene copolymer was measured according to JIS-K6922-2: 1997 appendix (190 ° C., 21.18 N load).
(2) Density: As described above, the density of the ethylene-based copolymer was measured according to JIS-K6922-2: 1997 appendix (in the case of 23 ° C., low density polyethylene).

2. Evaluation Method of Extruded Product (Sheet) (1) Glass Adhesive Measure the tensile strength of a 0.7mm thick press sheet prepared at 150 ° C and heat-treated at 170 ° C for 30 minutes. And evaluated as the adhesive strength between the sheet and the glass. The test was carried out at a tensile speed of 50 mm / min, a test piece width of 10 mm, and 180 ° peeling. A sample having a tensile strength of 20 N / 10 mm or more was evaluated as ○, and a sample having a tensile strength of less than 20 N / 10 mm was evaluated as ×.

(2) Weather resistance The glass adhesion measurement sample was held in an oven at 85 ° C. and 85% RH for 2000 hours and evaluated by measuring the adhesion strength of the glass. If no deterioration due to temperature and humidity is observed, it can be evaluated that the weather resistance is high. A sample having a tensile strength of 20 N / 10 mm or more was evaluated as ○, and a sample having a tensile strength of less than 20 N / 10 mm was evaluated as ×.

(3) Heat resistance A 0.7 mm thick press sheet produced at 150 ° C. was heat-treated at 170 ° C. for 30 minutes on a white plate float glass, and the sheets were bonded to each side and suspended in an oven at 130 ° C. for 24 hours. The creep test was conducted. It can be evaluated that the smaller the deviation due to the creep phenomenon, the less the deterioration of the sheet due to heat and the better the heat resistance. A sample having a deviation of 3 mm or less was marked with ◯, and a sample having a deviation larger than 3 mm was marked with ×.

(4) PID evaluation The light-receiving surface protection member, the sealing material, the solar cell element, the sealing material, and the back surface protection member were set in this order, and a solar cell module was produced using a vacuum laminator. As a light-receiving surface protection member, 3.2 mm-thick white plate float glass manufactured by Asahi Glass Fabrictech Co., Ltd., the laminate of the present invention as a sealing material, a single crystal silicon type as a solar cell element, and a product made by Toyo Aluminum Co., Ltd. as a back surface protection member A PET backsheet was used. Water was applied to the surface of the surface protection member of the produced module, and it was kept for 96 hours in a constant temperature and humidity chamber of 60 ° C. and 85% relative humidity while applying a direct current of −1000 V to the internal circuit.
In accordance with IEC61215, the IV characteristics were evaluated, and when the maximum output power Pmax of the IV characteristics after the test was less than 3% compared to the initial value, it was judged as ◯, and when the decline was 5% or more, it was judged as x.

3. Raw material used (1) Component (a): ethylene copolymer Copolymer (PE-1) of ethylene, maleic anhydride and methyl acrylate polymerized in the following <Production Example 1>, commercially available ethylene and vinyl acetate The copolymer “LV780 manufactured by Nippon Polyethylene” (PE-2) was used. The physical properties are shown in Table 1.
PE-1: Ethylene 93.2 mol%, PE-2: Ethylene 86.0 mol%
(2) Polyhydric alcohol: Trimethylolpropane (3) Metal salt: Na salt of a copolymer of ethylene and methacrylic acid (High Milan 1605, manufactured by Mitsui DuPont Polychemical Co., Ltd.)
(4) Organic peroxide: 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi, Luperox 101)
(5) Silane coupling agent: 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicone, KBM-503)

<Production example>
Ethylene and maleic anhydride having a MFR of 10 g / 10 min, a density of 0.945 g / cm ³ , and a unit derived from maleic anhydride of 2.5 wt% using a high-pressure polyethylene production facility having a tank reactor A copolymer of acid and methyl acrylate was prepared. The composition of the copolymer was determined by an infrared absorption spectrum.

Example 1
1.1 parts by weight of trimethylolpropane as a polyhydric alcohol and a copolymer of ethylene and methacrylic acid as a metal salt with respect to 100 parts by weight of a copolymer of ethylene, maleic anhydride and methyl acrylate (PE-1) 5 parts by weight of Na salt (manufactured by Mitsui DuPont Polychemical Co., Ltd., Himiran 1605) was added. This was thoroughly mixed and pelletized using a TEX35 twin screw extruder under the conditions of a set temperature of 210 ° C. and an extrusion rate (15 kg / hour).
The resulting pellet, in the conditions of 170 ℃ -0kg / cm ^2, after 3 minutes preheat, then 27 minutes under pressure at the 170 ℃ -100kg / cm ² conditions (30 minutes press molding at 170 ° C.), 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 glass adhesion, weather resistance, and heat resistance of the sheet were measured and evaluated.
Separately, for PID evaluation, a 0.7 mm thick sheet was prepared by T-die molding under the conditions of a set temperature of 220 ° C. and a take-up speed of 1.3 m / min. The evaluation results are shown in Table 2.
In addition, the molar ratio of the polyhydric alcohol in Table 2 means the molar ratio of the hydroxyl group unit in the polyhydric alcohol to the monomer derived from the radical polymerizable acid anhydride in the ethylene copolymer.

(Example 2)
In Example 1, a sheet was prepared in the same manner as in Example 1 except that trimethylolpropane was changed to 0.88 parts by weight as the polyhydric alcohol. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. 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 trimethylolpropane was used as the polyhydric alcohol in an amount of 0.66 parts by weight. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. The evaluation results are shown in Table 2.

Example 4
In Example 1, a sheet was prepared in the same manner as in Example 1 except that 0.44 parts by weight of trimethylolpropane was used as the polyhydric alcohol. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. The evaluation results are shown in Table 2.

(Example 5)
In Example 1, a sheet was prepared in the same manner as in Example 1 except that 0.44 parts by weight of trimethylolpropane and 2 parts by weight of Himiran 1605 were used as the polyhydric alcohol. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. The evaluation results are shown in Table 2.

(Comparative Example 1)
For 100 parts by weight of ethylene / maleic anhydride / methyl acrylate copolymer (PE-1), Na salt of ethylene / methacrylic acid copolymer (Mitsui / DuPont Polychemical Co., Ltd., Himiran 1605) as a metal salt. ) Was prepared in the same manner as in Example 1 except that only 5 parts by weight was blended. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. The evaluation results are shown in Table 2.

(Comparative Example 2)
For PE-1, a copolymer of ethylene and vinyl acetate (PE-2) was used. Moreover, the sheet | seat was produced similarly to Example 1 except having mix | blended only 1.1 weight part of trimethylol propane as a polyhydric alcohol as an additive. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. The evaluation results are shown in Table 2.

(Comparative Example 3)
PE-2 is used in place of PE-1, and 100 parts by weight of PE-2 is t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi, Luperox TBEC) as an organic peroxide, and silane. 3-Methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicone, KBM-503) was blended as a coupling agent. Pelletized at a set temperature of 100 ° C., and a sheet was produced in the same manner as in Example 1. The glass adhesion, weather resistance, heat resistance, and PID of the sheet were measured and evaluated. The evaluation results are shown in Table 2.

"Evaluation"
As a result, as is apparent from Table 2, in Examples 1 to 5, since the resin composition of the present invention was used, the sheet obtained by extrusion molding had good crosslinking characteristics and weather resistance. Excellent heat resistance. PID can also be suppressed by the blending amount of polyhydric alcohol and metal salt.
On the other hand, in Comparative Examples 1 and 2, since a resin composition that does not form a crosslinked structure or has a very slow crosslinking rate is used, the obtained sheet is inferior in weather resistance and heat resistance, and PID is generated. As a result. In Comparative Example 3, a resin composition containing an ethylene / vinyl acetate copolymer was used, so that a crosslinked structure was formed. However, in order to prevent cleavage of the organic peroxide, it was necessary to mold at a low temperature. The sheet resulted in PID generation.

  The resin composition for a solar cell encapsulant of the present invention is excellent in productivity because it does not form a crosslinked structure at the processing temperature and can rapidly form a crosslinked structure in the cooling and solidification process after molding. And since it is excellent in a softness | flexibility, heat resistance, etc., it is preferably utilized as a solar cell sealing material. In particular, it is useful as a sealing material for thin film solar cells, ICs (integrated circuits), and solar cell modules.

Claims (9)

The resin composition for solar cell sealing materials characterized by containing the following components (a)-(c).
(A) an ethylene copolymer containing ethylene and a radical polymerizable acid anhydride as constituent monomers; (b) a polyhydric alcohol compound having at least two hydroxyl groups in the molecule; and (c) a reaction accelerator.   2. The resin composition for a solar cell encapsulant according to claim 1, wherein the content of the monomer derived from the radical polymerizable acid anhydride in the ethylene copolymer is 0.03 to 10 mol%. object.   2. The molar ratio of hydroxyl group units in the polyhydric alcohol compound to monomers derived from radically polymerizable acid anhydrides in the ethylene-based copolymer is in the range of 0.01 to 10. Or the resin composition for solar cell sealing materials of 2.   The resin for solar cell sealing materials according to any one of claims 1 to 3, wherein 0.001 to 20 parts by weight of the reaction accelerator is contained with respect to 100 parts by weight of the ethylene copolymer. Composition.   The resin composition for a solar cell sealing material according to any one of claims 1 to 4, wherein the reaction accelerator is a metal salt.   The resin composition for a solar cell sealing material according to claim 5, wherein the metal salt is an organic carboxylate.   The solar cell encapsulant according to any one of claims 1 to 6, wherein the ethylene copolymer is a multi-component copolymer composed of ethylene, a radical polymerizable acid anhydride and other radical polymerizable comonomer. Resin composition for stopping material.   The resin composition for a solar cell sealing material according to claim 7, wherein the content of the other radical polymerizable comonomer in the ethylene-based copolymer is 5.0 to 20 mol%.   The solar cell sealing material which melt-molded the resin composition in any one of Claims 1-8, and formed the crosslinked structure in the cooling process.