JP7467654B2 - Method for producing resin composition - Google Patents

Description

The present invention relates to a resin composition, a method for producing a resin composition, a solar cell encapsulant, a method for producing a solar cell encapsulant, a solar cell module, a resin sheet for use as an interlayer for laminated glass, and laminated glass.

In recent years, solar power generation has become increasingly popular as a clean energy source. In solar power generation, solar energy is usually converted into electrical energy using semiconductors (solar cell elements) such as silicon cells. To ensure the long-term reliability of the solar cell elements, the solar cell elements are sandwiched between encapsulant to protect them and prevent the intrusion of foreign matter and moisture into the solar cell elements.

Technologies relating to solar cell encapsulant materials include, for example, those described in Patent Documents 1 to 3.

Patent Document 1 describes a resin sheet that contains at least one resin (A) selected from ethylene-vinyl acetate copolymer and ethylene-aliphatic unsaturated carboxylic acid copolymer, and a thermoplastic resin (B) other than the resin (A) and the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, wherein the resin (A) has a melt flow rate value of 0.3 g to 30 g, and the solar cell encapsulating resin sheet has an inner layer made of the resin (B) and a surface layer made of the resin (A) laminated on the inner layer.

Patent Document 2 describes a resin sealing sheet for solar cells in which the resin is softened to adhere, the resin sealing sheet containing at least one type of ionizing radiation crosslinkable resin selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, and ethylene-aliphatic unsaturated carboxylic acid ester copolymer, the ionizing radiation crosslinkable resin being irradiated with ionizing radiation to have a gel fraction of 2 to 65 mass % and a thermal shrinkage rate of 15% or less at 90°C.

Patent Document 3 describes a solar cell module in which a surface protective layer, a solar cell cell, a back protective layer, a polyvinyl acetal resin layer and a second resin layer are laminated, the content of plasticizer in the polyvinyl acetal resin layer is 20 parts by mass or less per 100 parts by mass of polyvinyl acetal, the thickness of the polyvinyl acetal resin layer is 600 μm or less, the polyvinyl acetal resin layer is arranged so as to be in contact with at least one side of the solar cell, and the second resin layer is arranged so as to be in contact with at least one of the surface protective layer and the back protective layer.

JP 2014-95083 A JP 2013-177506 A JP 2015-8285 A

A solar cell encapsulant that encapsulates a solar cell element functions as a protective material for the solar cell element, and is therefore required to have creep resistance that makes it difficult for the material to flow even when the module temperature becomes high due to sunlight.
Furthermore, in order to prevent a decrease in the conversion efficiency of the solar cell, the solar cell encapsulant is required to have high transparency (light transmittance).
Furthermore, since the solar cell encapsulant "encapsulates" the solar cell element, it is required to adhere sufficiently strongly to the solar cell element.

In recent years, the technical standards required for various properties of solar cell encapsulant have become increasingly higher.
Conventional thermoplastic solar cell encapsulants have room for improvement in terms of good creep resistance, transparency, and adhesion. In particular, when trying to improve one of these three performances, the other performances may be reduced. For example, when creep resistance is improved by designing the melting point of the thermoplastic resin to be high, transparency may be deteriorated or adhesion may be reduced. In other words, there is room for improvement in terms of improving the three performances of creep resistance, transparency, and adhesion in a balanced manner.

The present invention has been made in consideration of the above circumstances. One of the objects of the present invention is to obtain a solar cell encapsulant having excellent creep resistance, transparency, and adhesion. Another object of the present invention is to provide a resin composition capable of forming such a solar cell encapsulant.

The present inventors conducted extensive research to achieve the above object. As a result, they were able to improve the above three performances in a well-balanced manner by producing a solar cell encapsulant using a resin composition containing an ionomer of an ethylene-unsaturated carboxylic acid copolymer, at least one lubricant selected from the group consisting of fatty acids and fatty acid metal salts, an organic peroxide, and a silane coupling agent.

The present invention is as follows.

1.
A resin composition comprising (A) an ionomer of an ethylene-unsaturated carboxylic acid copolymer, (B) at least one lubricant selected from the group consisting of fatty acids and fatty acid metal salts, (C) an organic peroxide, and (D) a silane coupling agent.
2.
1. The resin composition according to 1.
The resin composition includes metal ions contained in the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer, the metal ions being two or more selected from the group consisting of lithium ions, potassium ions, sodium ions, silver ions, copper ions, calcium ions, magnesium ions, zinc ions, aluminum ions, barium ions, beryllium ions, strontium ions, tin ions, lead ions, iron ions, cobalt ions and nickel ions.
3.
1. The resin composition according to 1. or 2.,
The metal ions contained in the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer include a first metal ion and a second metal ion different from the first metal ion,
the first metal ion includes at least one metal ion selected from the group consisting of zinc ions, copper ions, iron ions, aluminum ions, silver ions, cobalt ions, and nickel ions;
The resin composition, wherein the second metal ion contains at least one metal ion selected from the group consisting of sodium ions, lithium ions, potassium ions, and magnesium ions.
4.
3. The resin composition according to 1.
A resin composition in which the ratio of the number of moles of the second metal ion multiplied by the valence to the number of moles of the first metal ion multiplied by the valence in the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer is 0.10 or more and 10.0 or less.
5.
1. The resin composition according to any one of 1. to 4.,
A resin composition, in which, in the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer, when the total of the structural units constituting the ethylene-unsaturated carboxylic acid copolymer is taken as 100 mass%, a structural unit derived from an unsaturated carboxylic acid is 5 mass% or more and 35 mass% or less.
6.
1. The resin composition according to any one of 1. to 5.,
The resin composition, wherein the degree of neutralization of the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer is 5% or more and 95% or less.
7.
1. The resin composition according to any one of 1. to 6.,
The resin composition comprises the lubricant (B) in an amount of 1 part by mass or more and 20 parts by mass or less based on 100 parts by mass of the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer.
8.
1. The resin composition according to any one of 1. to 7.,
The resin composition, wherein the lubricant (B) is a fatty acid having 12 to 36 carbon atoms or a metal salt of a fatty acid having 12 to 36 carbon atoms.
9.
1. The resin composition according to any one of claims 1 to 8,
The lubricant (B) contains a metal salt of a fatty acid having 12 to 36 carbon atoms,
A resin composition in which at least a portion of the carboxyl groups of the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer are neutralized with at least a portion of the metal constituting the metal salt of a fatty acid having 12 to 36 carbon atoms contained in the lubricant (B).
10.
1. The resin composition according to any one of claims 1 to 9,
The resin composition, wherein the silane coupling agent (D) contains a silane coupling agent having a group containing a polymerizable carbon-carbon double bond.
11.
1. The resin composition according to any one of 1. to 10.
The resin composition, wherein the organic peroxide (C) has a 10-hour half-life temperature of 100° C. or higher.
12.
1. The resin composition according to any one of 1. to 11.
A resin composition having a crossover temperature of 150° C. or higher as measured by the following method.
(Method)
A 120 mm x 75 mm x 0.4 mm film made of the resin composition is laminated between glass plates via a release film, and pressed in a vacuum laminator at 160°C, vacuum holding for 690 seconds, and 0.06 MPa (gauge pressure) for 15 minutes to obtain a laminated glass. The laminated glass obtained is then heat-treated at 165°C for 30 minutes to obtain a laminated glass body. The glass plates and release film are removed from the laminated glass body obtained to obtain a film, which is used as a sample to measure the shear modulus from -60°C to 150°C in a nitrogen atmosphere at a heating rate of 3°C/min and a frequency of 1 Hz in shear mode. The temperature at which the shear storage modulus (G') and the shear loss modulus (G") become equal is defined as the crossover temperature.
13.
1. The resin composition according to any one of 1. to 12.
A resin composition for forming a solar cell encapsulant.
14.
A method for producing the resin composition according to any one of 1. to 13.,
A step of obtaining a mixture by mixing an ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer with at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts;
After the above step, a step of mixing the mixture with an organic peroxide (C) and a silane coupling agent (D);
A method for producing a resin composition comprising the steps of:
15.
1. A solar cell encapsulant comprising a layer constituted by the resin composition according to any one of 1. to 13.
16.
14. A method for producing a solar cell encapsulant, comprising an extrusion molding step of extruding a heated and molten resin composition according to any one of 1. to 13. from a T-die of an extruder equipped with a T-die to form the resin composition into a sheet.
17.
16. A method for producing the solar cell encapsulant according to claim 1, comprising the steps of:
The method for producing a solar cell encapsulant, wherein in the extrusion molding step, the temperature of the heated molten material at an outlet of the T-die is 140° C. or lower.
18.
A solar cell element;
15. An encapsulating resin layer that encapsulates the solar cell element and is formed from the solar cell encapsulant according to 15.
A solar cell module comprising:
19.
1. The resin composition according to any one of 1. to 12.
A resin composition used to form an interlayer film for laminated glass.
20.
19. A resin sheet for an interlayer film of laminated glass, comprising a film formed from the resin composition according to 19.
21.
20. An interlayer film for laminated glass formed from the resin sheet for an interlayer film for laminated glass according to 20.
a transparent plate-like member provided on at least one surface of the laminated glass interlayer.

According to the present invention, there is provided a solar cell encapsulant having excellent creep resistance, transparency and adhesion, and a resin composition capable of forming such a solar cell encapsulant.
Incidentally, the resin composition of the present invention is preferably used for forming a solar cell encapsulant, but can also be used for other purposes, such as the production of an interlayer film for laminated glass.

FIG. 1 is a diagram (cross-sectional view) illustrating a schematic example of a structure of a solar cell module.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
In the drawings, similar components are given similar symbols and descriptions thereof will be omitted where appropriate.
In order to avoid complexity, when there are a plurality of identical components in the same drawing, only one of them may be labeled with a reference symbol, and not all of them.
The drawings are for illustrative purposes only. The shapes and dimensional ratios of the components in the drawings do not necessarily correspond to the actual products.

In this specification, the term "(meth)acrylic" refers to a concept that includes both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."
In the present specification, the upper limit or lower limit of one numerical range may be replaced with the upper limit or lower limit of another numerical range. For example, when a description is made that a certain index X is "preferably x1 or more and y1 or less, more preferably x2 or more and y2 or less," X may be x1 or more and y2 or less, or may be x2 or more and y1 or less.
In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the Examples. For a certain index X, when the specification describes it as preferably being equal to or more than x and equal to or less than y, and the value of X in the Examples is z, X may be equal to or more than x and equal to or less than z, or may be equal to or more than z and equal to or less than y.

<Resin Composition>
The resin composition of the present embodiment contains an ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer, at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts, an organic peroxide (C), and a silane coupling agent (D).

The resin composition of this embodiment contains a relatively highly reactive organic peroxide (C), and when heated to seal the solar cell elements, a crosslinking reaction occurs between the molecular chains of the ionomer (A), the lubricant (B), and the silane coupling agent (D) to form a crosslinked structure, which is thought to suppress the flow of the resin composition. This is presumably related to the good creep resistance and adhesion.

On the other hand, the resin composition of the present embodiment contains the lubricant (B), which promotes relaxation of the structure formed by the aggregation of metal ions in the ionomer (A), and therefore enables molding and processing into a sheet-shaped solar cell encapsulant at a relatively low temperature at which the organic peroxide does not decompose. This is presumably to suppress the reaction of the organic peroxide (C) to form an undesirable crosslinked structure after the resin composition is made into a sheet-shaped solar cell encapsulant and before the solar cell element is encapsulated using the solar cell encapsulant.
If the crosslinking reaction proceeds during molding, the crosslinking reaction is likely to proceed unevenly, which is likely to be disadvantageous in terms of transparency, sheet appearance, adhesiveness, and sealing of solar cell elements. However, in the present embodiment, the crosslinking reaction during molding is sufficiently suppressed, and it is presumed that the transparency, sheet appearance, adhesiveness, and sealing of solar cell elements are improved.

We will continue to explain the components, properties, and physical properties of the resin composition of this embodiment.

(Ionomer (A) of ethylene-unsaturated carboxylic acid copolymer)
The resin composition of the present embodiment contains an ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer. Hereinafter, the ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer may be simply referred to as "ionomer (A)".

Ionomer (A) is typically a resin in which at least a portion of the carboxyl groups of a polymer copolymerized with ethylene and at least one unsaturated carboxylic acid are neutralized with metal ions. Examples of ethylene-unsaturated carboxylic acid copolymers include copolymers of ethylene and unsaturated carboxylic acid, and copolymers of ethylene, unsaturated carboxylic acid, and unsaturated carboxylic acid ester.

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, 2-ethylacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, fumaric anhydride, itaconic anhydride, monomethyl maleate, monoethyl maleate, etc. Among these, acrylic acid and/or methacrylic acid are preferred from the viewpoints of productivity and hygiene of the ethylene-unsaturated carboxylic acid copolymer.
The unsaturated carboxylic acids may be used alone or in combination of two or more.
In addition, an ionomer (A) can be prepared by adding an ethylene-unsaturated carboxylic acid copolymer containing an unsaturated carboxylic acid such as acrylic acid or methacrylic acid as a constituent unit to one or more ionomers of ethylene-unsaturated carboxylic acid copolymers.

Particularly preferred ethylene-unsaturated carboxylic acid copolymers are ethylene-(meth)acrylic acid copolymers and ethylene-(meth)acrylic acid-(meth)acrylic acid ester copolymers.

In the ionomer (A), when the total of the structural units constituting the ethylene-unsaturated carboxylic acid copolymer is taken as 100% by mass, the structural units derived from ethylene are preferably 65% by mass or more and 95% by mass or less, more preferably 65% by mass or more and 90% by mass or less, and even more preferably 65% by mass or more and 85% by mass or less. When the structural units derived from ethylene are equal to or more than the above lower limit, the heat resistance, mechanical strength, water resistance, processability, etc. of the obtained solar cell encapsulant can be improved. Also, when the structural units derived from ethylene are equal to or less than the above upper limit, the transparency, flexibility, adhesion, etc. of the obtained solar cell encapsulant can be improved.

In the ionomer (A), when the total of the constituent units constituting the ethylene-unsaturated carboxylic acid copolymer is taken as 100% by mass, the constituent units derived from the unsaturated carboxylic acid are preferably 5% by mass or more and 35% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less. When the constituent units derived from the unsaturated carboxylic acid are equal to or more than the above lower limit, the transparency, flexibility, adhesiveness, etc. of the obtained solar cell encapsulant can be improved. Also, when the constituent units derived from the unsaturated carboxylic acid are equal to or less than the above upper limit, the heat resistance, mechanical strength, water resistance, processability, etc. of the obtained solar cell encapsulant can be improved.

The ionomer (A) may contain, when the total of the structural units constituting the ethylene-unsaturated carboxylic acid copolymer is taken as 100% by mass, preferably 0% by mass to 30% by mass, more preferably 0% by mass to 25% by mass of structural units derived from other copolymerizable monomers. Examples of the other copolymerizable monomers include unsaturated esters, such as vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isobutyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. If the structural units derived from other copolymerizable monomers are contained within the above range, it is preferable in terms of improving the flexibility of the resulting solar cell encapsulant.

Examples of metal ions constituting the ionomer (A) include one or more selected from the group consisting of lithium ions, potassium ions, sodium ions, silver ions, copper ions, calcium ions, magnesium ions, zinc ions, aluminum ions, barium ions, beryllium ions, strontium ions, tin ions, lead ions, iron ions, cobalt ions and nickel ions.

Preferably, the ionomer (A) contains two or more metal ions selected from the above group. Although the details are unclear, it is presumed that the inclusion of two or more metal ions in the ionomer (A) allows the crosslinking reaction to proceed moderately randomly in the system (preventing excessive crosslinking reaction from proceeding locally). This makes it possible to suppress the generation of gel, which is believed to further increase the transparency of the solar cell encapsulant.

More specifically, the ionomer (A) preferably contains the following first metal ion and a second metal ion different from the first metal ion.
First metal ion: at least one metal ion selected from the group consisting of zinc ions, copper ions, iron ions, aluminum ions, silver ions, cobalt ions, and nickel ions. Second metal ion: at least one metal ion selected from the group consisting of sodium ions, lithium ions, potassium ions, and magnesium ions. Incidentally, a particularly preferred configuration of the ionomer (A) is one that contains a zinc ion as the first metal ion and a magnesium ion as the second metal ion.

Because the ionomer (A) contains both the first metal ion and the second metal ion, unintended crosslinking reactions can be further suppressed, resulting in improved processability of the solar cell encapsulant. Furthermore, the generation of gel in the solar cell encapsulant sheet can be suppressed, resulting in even better transparency and appearance of the solar cell encapsulant.

When the ionomer (A) contains a first metal ion and a second metal ion, the ratio of the number of moles of the second metal ion multiplied by the valence to the number of moles of the first metal ion in the ionomer (A) multiplied by the valence ((number of moles of second metal ion × valence of second metal ion)/(number of moles of first metal ion × valence of first metal ion)) is preferably 0.10 or more, more preferably 0.15 or more, and even more preferably 0.20 or more, from the viewpoint of achieving a better balance between the transparency and water resistance of the obtained solar cell encapsulant.
In addition, in the resin composition (P) according to this embodiment, the ratio of the number of moles of the second metal ion multiplied by the valence to the number of moles of the first metal ion in the ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer multiplied by the valence is, from the viewpoint of improving the balance between the transparency and water resistance of the obtained solar cell encapsulant, preferably 10.0 or less, more preferably 5.0 or less, even more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less.

The ionomer (A) can be configured to include, for example, an ionomer 1 of an ethylene-unsaturated carboxylic acid copolymer and an ionomer 2 of an ethylene-unsaturated carboxylic acid copolymer different from the ionomer 1. This makes it possible to easily adjust the ratio of the first metal ion to the second metal ion in the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer by adjusting the mixing ratio of the ionomer 1 of the ethylene-unsaturated carboxylic acid copolymer and the ionomer 2 of the ethylene-unsaturated carboxylic acid copolymer.

The degree of neutralization of the ionomer (A) is not particularly limited, but from the viewpoint of improving the flexibility, adhesion, processability, etc. of the obtained solar cell encapsulant, it is preferably 95% or less, more preferably 90% or less, even more preferably 80% or less, particularly preferably 50% or less, and especially preferably 30% or less.
In addition, the degree of neutralization of the ionomer (A) is not particularly limited, but from the viewpoint of improving the transparency, mechanical strength, etc. of the obtained solar cell encapsulant, it is preferably 5% or more, more preferably 10% or more, even more preferably 15% or more, and particularly preferably 20% or more.
Here, the degree of neutralization of the ionomer (A) refers to the ratio (%) of carboxy groups neutralized with metal ions to all carboxy groups contained in the ethylene-unsaturated carboxylic acid copolymer.

The ionomer (A) may be, for example, a composition including an ionomer of an ethylene-unsaturated carboxylic acid copolymer and an ethylene-unsaturated carboxylic acid copolymer that does not contain metal ions. In this way, the degree of neutralization can be easily adjusted by adjusting the mixing ratio of the ionomer of the ethylene-unsaturated carboxylic acid copolymer and the ethylene-unsaturated carboxylic acid copolymer.

The method for producing the ethylene-unsaturated carboxylic acid copolymer constituting the ionomer (A) is not particularly limited, and the ionomer (A) can be produced by a known method. For example, the ionomer (A) can be obtained by radical copolymerization of each polymerization component under high temperature and high pressure. The ionomer (A) can also be obtained by reacting the ethylene-unsaturated carboxylic acid copolymer with a metal compound.
As the ionomer (A) of the ethylene-unsaturated carboxylic acid copolymer, commercially available products may be used.

Additionally, there is no particular limitation on the "timing" of neutralizing at least a part of the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer with a metal ion to form the ionomer (A), as long as the final resin composition contains the ionomer (A).
For example, when the final resin composition contains an ionomer (A) containing a first metal ion and a second metal ion, the resin composition may be prepared by any of the following methods (i) to (iii). In the examples shown below, the resin composition is prepared by method (ii).
(i) A resin composition is prepared by using, as a raw material, an ionomer (A) containing a first metal ion and a second metal ion as it is.
(ii) First, an ionomer containing only one of the first metal ion and the second metal ion is prepared as a raw material. Then, the ionomer is melt-mixed with, for example, a fatty acid metal salt exemplified as an example of the lubricant (B) described later, to obtain an ionomer (A) containing two kinds of metal ions. A resin composition is prepared using this ionomer (A).
(iii) First, an ethylene-unsaturated carboxylic acid copolymer that does not contain metal ions is prepared as a raw material. Then, this polymer is melt-mixed with two appropriate metal materials to obtain an ionomer (A) that contains two types of metal ions. A resin composition is prepared using this ionomer (A).

To further add, in the case of (ii) above, although the details are not clear, it is believed that since the carboxyl groups of the ionomer (A) have a lower acid dissociation constant than the carboxyl groups of the fatty acid metal salt, at least a portion of the metals constituting the fatty acid metal salt neutralize at least a portion of the carboxyl groups of the ionomer (A).

In this embodiment, the melt mass flow rate (MFR) of the ionomer (A), measured in accordance with JIS K 7210:1999 under conditions of 190°C and a load of 2160 g, is preferably 0.01 g/10 min to 100 g/10 min, more preferably 0.1 g/10 min to 80 g/10 min. If the MFR is equal to or greater than the lower limit, the processability of the solar cell encapsulant can be further improved. If the MFR is equal to or less than the upper limit, the heat resistance, mechanical strength, etc. of the obtained solar cell encapsulant can be further improved.

The content of ionomer (A) in the resin composition is preferably 50.0% by mass or more and 99.9% by mass or less, more preferably 70.0% by mass or more and 99.5% by mass or less, even more preferably 80.0% by mass or more and 99.5% by mass or less, and even more preferably 85.0% by mass or more and 99.0% by mass or less, when the entire resin composition is taken as 100% by mass. By having the content of ionomer (A) within the above range, the transparency, creep resistance, interlayer adhesion, insulation, rigidity, water resistance, and PID resistance of the obtained solar cell encapsulant can be further improved.

(Lubricant (B))
The resin composition of the present embodiment contains at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts. It is believed that the use of the lubricant (B) promotes relaxation of the structure formed by the aggregation of metal ions in the ionomer (A). Therefore, for example, when the resin composition is molded to produce a solar cell encapsulant, the molding can be performed at a relatively low temperature at which the organic peroxide (C) does not decompose.

As the fatty acid, a fatty acid having 12 to 36 carbon atoms is preferred, and a fatty acid having 16 to 30 carbon atoms is more preferred. Specific examples of fatty acids include lauric acid (12 carbon atoms), myristic acid (14 carbon atoms), palmitic acid (16 carbon atoms), stearic acid (18 carbon atoms), oleic acid (18 carbon atoms), behenic acid (22 carbon atoms), erucic acid (22 carbon atoms), montanic acid (28 carbon atoms), and melissic acid (30 carbon atoms). Only one type of fatty acid may be used, or two or more types may be used.

As the fatty acid constituting the fatty acid metal salt, a fatty acid having 12 to 36 carbon atoms is preferable, and a fatty acid having 16 to 30 carbon atoms is more preferable. In other words, the fatty acid metal salt is preferably a metal salt of a fatty acid having 12 to 36 carbon atoms. Specific examples of fatty acids constituting the fatty acid metal salt include lauric acid (12 carbon atoms), myristic acid (14 carbon atoms), palmitic acid (16 carbon atoms), stearic acid (18 carbon atoms), oleic acid (18 carbon atoms), behenic acid (22 carbon atoms), erucic acid (22 carbon atoms), montanic acid (28 carbon atoms), and melissic acid (30 carbon atoms). The fatty acid constituting the fatty acid metal salt may be only one type, or may be two or more types.

Examples of the "metal" constituting the fatty acid metal salt include alkali metals, alkaline earth metals, zinc, etc. Among these, magnesium, zinc, and calcium are preferred, and magnesium is more preferred, from the viewpoint of the relatively low melting point of the fatty acid metal salt. As the metal constituting the fatty acid metal salt, only one type may be used alone, or two or more types may be used in combination.

As the lubricant (B), a fatty acid metal salt is preferred, magnesium stearate, zinc stearate and calcium stearate are more preferred, and magnesium stearate is even more preferred.

The resin composition may contain only one type of lubricant (B), or may contain two or more types of lubricant (B).
The amount of the lubricant (B) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 4 parts by mass or more, based on 100 parts by mass of the ionomer (A). The amount of the lubricant (B) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less, based on 100 parts by mass of the ionomer (A).

Incidentally, as mentioned above, at least some of the carboxyl groups of the ionomer (A) can be neutralized with at least some of the metals constituting the fatty acid metal salt. In other words, at least some of the metal ions of the fatty acid metal salt with a high acid dissociation constant can be incorporated into the ionomer (A) with a low acid dissociation constant. The amount of the lubricant (B) above represents the total amount of the lubricant incorporated in the ionomer (A) and the amount of the lubricant that is not incorporated (free).

(Organic Peroxide (C))
The resin composition of the present embodiment contains an organic peroxide (C). Examples of the organic peroxide (C) include organic peroxides known as radical polymerization initiators.

The 10-hour half-life temperature of the organic peroxide (C) is preferably 100°C or higher, more preferably 105°C or higher, and even more preferably 110°C or higher, from the viewpoint of not causing an undesirable crosslinking reaction during sheet processing. Also, from the viewpoint of desirability of causing a crosslinking reaction during the lamination process, it is preferably 170°C or lower, more preferably 150°C or lower, and even more preferably 130°C or lower.

Examples of organic peroxides (C) include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, bis(tert-butylperoxyisopropyl)benzene, tert-butylcumyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxybenzoate, tert-butylperoxyisopropylcarbonate, and tert-butylperoxy-2-ethylhexylcarbonate.

Among these, from the viewpoints of reactivity and ease of handling, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, bis(tert-butylperoxyisopropyl)benzene, tert-butylcumyl peroxide, tert-butylperoxyisopropyl carbonate, and tert-butylperoxy-2-ethylhexyl carbonate are preferred, with 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane and tert-butylperoxyisopropyl carbonate being more preferred.

The resin composition may contain only one type of organic peroxide (C), or may contain two or more types of organic peroxide (C).
The amount of the organic peroxide (C) is preferably 0.1 parts by mass or more, more preferably 0.25 parts by mass or more, and even more preferably 0.5 parts by mass or more, based on 100 parts by mass of the ionomer (A). The amount of the organic peroxide (C) is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, based on 100 parts by mass of the ionomer (A).

From another perspective, a preferred ratio (unit: parts by mass/% by mass) of the amount of organic peroxide (C) per 100 parts by mass of ionomer (A) (unit: parts by mass) to the content (unit: % by mass) of structural units derived from unsaturated carboxylic acid in the ethylene-unsaturated carboxylic acid copolymer when the entire ethylene-unsaturated carboxylic acid copolymer is taken as 100% by mass is preferably 0.01 or more and 0.30 or less, more preferably 0.02 or more and 0.15 or less, and even more preferably 0.03 or more and 0.10 or less.

By appropriately adjusting the amount of organic peroxide (C), performance such as processability, creep resistance, transparency, and adhesion can be further improved.

(Silane Coupling Agent (D))
The resin composition of the present embodiment contains a silane coupling agent (D). Use of the silane coupling agent (D) is effective, for example, from the viewpoint of further improving the interlayer adhesion of the obtained solar cell module.

Examples of the silane coupling agent (D) include (i) a silane coupling agent having a group containing a polymerizable carbon-carbon double bond (such as a vinyl group or a (meth)acryloyl group), an amino group or an epoxy group, and (ii) a hydrolyzable group such as an alkoxy group.
Examples of silane coupling agents having a polymerizable carbon-carbon double bond include vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropylmethyldiethoxysilane, and 3-acryloxypropyltriethoxysilane.

Examples of silane coupling agents having an amino group include N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride.

Examples of silane coupling agents having epoxy groups include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, etc.

The silane coupling agent (D) preferably contains a silane coupling agent having a group containing a polymerizable carbon-carbon double bond, and more preferably contains a silane coupling agent having a (meth)acryloyl group. Particularly preferred examples include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane.

The resin composition may contain only one type of silane coupling agent (D), or may contain two or more types of silane coupling agents (D).
The amount of the silane coupling agent (D) is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.005% by mass or more and 2% by mass or less, and even more preferably 0.01% by mass or more and 1% by mass or less, based on 100 parts by mass of the ionomer (A).

(Other ingredients)
The resin composition of the present embodiment can contain components (other components) other than the above (A) to (D) within the scope of the invention.

Examples of other components include plasticizers, antioxidants, ultraviolet absorbers, wavelength conversion agents, antistatic agents, surfactants, colorants, light stabilizers, foaming agents, lubricants, crystal nucleating agents, crystallization accelerators, crystallization retarders, catalyst deactivators, heat absorbers, heat reflectors, heat dissipation agents, thermoplastic resins, thermosetting resins, inorganic fillers, organic fillers, impact resistance modifiers, slip agents, crosslinking agents, crosslinking assistants, tackifiers, processing assistants, release agents, hydrolysis inhibitors, heat stabilizers, antiblocking agents, antifogging agents, flame retardants, flame retardant assistants, light diffusing agents, antibacterial agents, antifungal agents, dispersants, and resins not falling under the category of ionomer (A).

Among the other components, a crosslinking aid is preferably used for the purposes of adjusting the curing property and improving various performances. Examples of the crosslinking aid include oximes such as p-quinone dioxime and p,p'-dibenzoylquinone dioxime; acrylates or methacrylates such as ethylene dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, cyclohexyl methacrylate, acrylic acid/zinc oxide mixture, and allyl methacrylate; vinyl monomers such as divinylbenzene, vinyl toluene, and vinyl pyridine; allyl compounds such as hexamethylene diallyl nadimide, diaryl itaconate, diallyl phthalate, diallyl isophthalate, diallyl monoglycidyl isocyanurate, triallyl cyanurate, and triallyl isocyanurate; maleimide compounds such as N,N'-m-phenylene bismaleimide and N,N'-(4,4'-methylene diphenylene) dimaleimide; and cyclic non-conjugated dienes such as vinyl norbornene, ethylidene norbornene, and dicyclopentadiene.
When a crosslinking aid is used, the amount thereof is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, based on 100 parts by mass of the ionomer (A). When a crosslinking aid is used, the amount thereof is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, based on 100 parts by mass of the ionomer (A).

When the resin composition contains other components, the resin composition may contain only one type of other component, or may contain two or more types of other components.

(Physical Properties)
For example, from the viewpoint of applicability to solar cell encapsulant, the resin composition of the present embodiment preferably satisfies the physical properties described below.

The melt mass flow rate (MFR) measured using the resin composition of this embodiment in accordance with JIS K 7210:1999 at 190°C and a load of 2160 g is preferably 20 g/10 min or less, more preferably 10 g/10 min or less, even more preferably 3 g/10 min or less, even more preferably 1 g/10 min or less, and particularly preferably 0.5 g/10 min or less. If the MFR is equal to or less than the above upper limit, the creep resistance and mechanical strength of the resulting solar cell encapsulant can be further improved.

Creep distance The creep distance measured by the method described in the examples below using the resin composition of this embodiment is preferably 5.0 mm or less, more preferably 3.0 mm or less, even more preferably 2.0 mm or less, and particularly preferably 1.5 mm or less. The lower limit of the creep distance is preferably 0 mm.

Haze The haze value measured by the method described in the Examples below using the resin composition of this embodiment is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less. The lower limit of the haze value is ideally 0%, but in reality it is, for example, 0.1%, specifically about 0.3%.

Total light transmittance The total light transmittance measured by the method described in the examples below using the resin composition of this embodiment is preferably 80% or more, more preferably 85% or more. Further preferably 87% or more, particularly preferably 90% or more. The upper limit of the total light transmittance is ideally 100%, but in reality, it is, for example, 95%, specifically about 92%.

Adhesion strength to glass plate The adhesive strength to glass plate measured by the method described in the examples below using the resin composition of this embodiment is preferably 10 N/15 mm or more, more preferably 20 N/15 mm or more, and even more preferably 30 N/15 mm or more. By increasing the adhesive strength to glass plate, the interlayer adhesion of the obtained solar cell module can be improved. Basically, the higher the adhesive strength, the better, and although the adhesive strength also depends on the rigidity of the resin, it is estimated that in reality, if the adhesive strength is 30 N/15 mm or more, the possibility of phenomena such as delamination occurring is extremely low.

Crossover temperature The crossover temperature measured by the method described in the examples below using the resin composition of this embodiment is preferably 140° C. or higher, and more preferably 150° C. or higher. It is known that there is a correlation between the crossover temperature and the creep distance, and a crossover temperature of 140° C. or higher is preferable in that the zero shear viscosity at a creep test temperature of 105° C. is sufficiently high, thereby suppressing creep.
There is no particular upper limit to the crossover temperature, but from the viewpoint of practical composition design, the upper limit is, for example, the thermal decomposition temperature of the resin composition or 240°C.

<Method of producing resin composition>
The resin composition of the present embodiment can be obtained by mixing an ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer, at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts, an organic peroxide (C), and a silane coupling agent (D). For mixing, a commonly used mixing device such as a screw extruder, a roll mixer, or a Banbury mixer can be used.
The four components (A) to (D) may be mixed simultaneously or separately, but the preferred method is to (i) first premix the ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer with at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts, and then (ii) mix the mixture obtained by this mixing with the organic peroxide (C) and the silane coupling agent (D).
By premixing the ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer with at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts, the resin composition can be given fluidity, which makes it possible to prevent the crosslinking reaction caused by the organic peroxide (C) from proceeding non-uniformly.

<Solar cell encapsulant>
The solar cell encapsulant of the present embodiment includes a layer made of the above-mentioned resin composition.
The solar cell encapsulant of this embodiment may have a single layer structure or a multilayer structure of two or more layers.
More specifically, the solar cell encapsulant of the present embodiment may be (i) a film having a single layer structure composed of a layer made of the above-mentioned resin composition, (ii) a film having a multilayer structure composed of the above-mentioned resin composition, or (iii) a film having a multilayer structure having a layer made of the above-mentioned resin composition and a layer made of a resin composition other than the above-mentioned resin composition.

When the solar cell encapsulant material of this embodiment has a multilayer structure, it is preferable that the solar cell encapsulant material has a (i) two-layer structure in which two outer layers (hereinafter also referred to as adhesive layers) are laminated, at least one of the outer layers being composed of the resin composition of this embodiment, or a (ii) three-layer structure including an intermediate layer and two outer layers formed on both sides of the intermediate layer, at least one of the outer layer and the intermediate layer being composed of the resin composition (P) according to this embodiment.
From the viewpoint of achieving both transparency and adhesiveness, the three-layer structure of (ii) above is more preferred.

In a multilayer film having multiple layers composed of the resin composition of this embodiment, the composition of each layer and the type of ionomer contained therein (for example, the copolymerization ratio of the ethylene-unsaturated carboxylic acid copolymer, the degree of neutralization, the type of metal ion, etc.) may be the same or different. In addition, layers composed of materials other than the resin composition (P) of this embodiment may or may not contain an organic peroxide.

The thickness of the solar cell encapsulant of this embodiment is, for example, 0.001 mm to 10 mm, preferably 0.01 mm to 5 mm, and more preferably 0.05 mm to 2 mm. If the thickness of the solar cell encapsulant is 0.001 mm or more, the mechanical strength of the solar cell encapsulant can be improved. Furthermore, if the thickness of the solar cell encapsulant is 10 mm or less, the transparency of the solar cell encapsulant and the processability in the lamination process can be improved.

When the solar cell encapsulant of this embodiment has a multi-layer structure, the layer formed from the resin composition of this embodiment may be an outer layer or an intermediate layer.

When the solar cell encapsulant of this embodiment includes an outer layer and an intermediate layer, the thickness of the outer layer is arbitrary, but the thickness a of the outer layer is preferably in the range of 1 μm to 500 μm, more preferably in the range of 10 μm to 500 μm, and particularly preferably in the range of 20 μm to 300 μm. When the thickness a is 1 μm or more, the adhesive strength and processability can be further improved. Furthermore, when the thickness a is 500 μm or less, the transparency is more excellent.

In addition, when the solar cell encapsulant of this embodiment includes an outer layer and an intermediate layer, the thickness of the intermediate layer in the total layer thickness may be thick in terms of transparency. Specifically, the thickness b of the intermediate layer can be freely set within a range obtained by subtracting the preferred thickness a of the outer layer from the preferred total thickness in the range of 0.1 mm to 10 mm.

Furthermore, when the solar cell encapsulant material of this embodiment includes an outer layer and an intermediate layer, the thickness ratio (a/b) of the outer layer (thickness a) to the intermediate layer (thickness b) is preferably 1/20 to 5/1, more preferably 1/15 to 3/1, and even more preferably 1/10 to 3/1. Here, when the solar cell encapsulant material of this embodiment includes two outer layers, the thickness a of the outer layer is the average value of the thicknesses of the two outer layers.
When the thickness ratio (a/b) of the outer layer to the intermediate layer is within the above range, the adhesiveness and transparency are further improved.

<Method of manufacturing solar cell encapsulant>
The method for producing the solar cell encapsulant described above is not particularly limited, and any conventionally known production method can be used, but it is preferable to produce it by the method described below.

As the manufacturing method, for example, a press molding method, an extrusion molding method, a T-die molding method, an injection molding method, a compression molding method, a cast molding method, a calendar molding method, an inflation molding method, etc. can be used. Among these, an extrusion molding method is preferable. That is, the solar cell encapsulant of the present embodiment can be obtained, for example, by a manufacturing method including an extrusion molding step in which a heated and melted product of the above-mentioned resin composition is extruded from a T-die of an extruder equipped with a T-die to be molded into a sheet shape.
The processing temperature in the extrusion molding step is not particularly limited, but from the viewpoint of suppressing the crosslinking reaction, it is preferable to adjust the processing temperature so that the temperature of the heated molten material at the outlet of the T-die is preferably 200° C. or less, more preferably 160° C. or less, even more preferably 140° C. or less, particularly preferably 130° C. or less, and especially preferably 120° C. or less. This temperature may be low as long as extrusion molding is possible, but from the viewpoint of performing smooth extrusion molding, the temperature of the heated molten material at the outlet of the T-die is, for example, 100° C. or more.

<Solar cell module>
FIG. 1 is a cross-sectional view that illustrates a schematic structure of a solar cell module (solar cell module 1) according to the present embodiment.
The solar cell module 1 includes, for example, a solar cell element 3 and an encapsulating resin layer 5 that encapsulates the solar cell element 3 and is made of the solar cell encapsulant of this embodiment. The solar cell module 1 may further include a substrate 2 onto which sunlight is incident, a protective material 4, and the like, as necessary (hereinafter, the substrate 2 onto which sunlight is incident may also be simply referred to as the substrate 2).
The solar cell module 1 can be produced, for example, by fixing a solar cell element 3 encapsulated with the solar cell encapsulant of the present embodiment onto a substrate 2 .

There are various types of solar cell module 1. For example, there are those configured such that a solar cell element is sandwiched between sealants from both sides, such as substrate/sealant/solar cell element/sealant/protective material; those configured such that a solar cell element is pre-formed on the surface of a substrate such as glass, and that the solar cell element is pre-formed on the surface of the substrate, such as substrate/solar cell element/sealant/protective material; and those configured such that a sealant and a protective material are formed on a solar cell element formed on the inner peripheral surface of a substrate, for example, an amorphous solar cell element formed on a fluororesin sheet by sputtering or the like.
When the substrate 2 onto which sunlight is incident is regarded as the upper part of the solar cell module 1, the protective material 4 is provided on the side opposite to the substrate 2 side of the solar cell module 1, i.e., on the lower part. For this reason, the protective material 4 is sometimes referred to as a lower protective material.

As the solar cell element 3, various solar cell elements can be used, including silicon-based elements such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and III-V or II-VI group compound semiconductor elements such as gallium-arsenide, copper-indium-selenium, copper-indium-gallium-selenium, and cadmium-tellurium.
In the solar cell module 1 , the multiple solar cell elements 3 are usually electrically connected in series via interconnectors 6 .

Examples of the substrate 2 constituting the solar cell module 1 include glass, acrylic resin, polycarbonate, polyester, and fluorine-containing resin.
The protective material 4 (lower protective material) is usually a single or multi-layer sheet of metal or various thermoplastic resin films, etc. Examples of the protective material 4 include single-layer or multi-layer sheets of metals such as tin, aluminum, and stainless steel, inorganic materials such as glass, polyester, inorganic material-deposited polyester, fluorine-containing resins, polyolefins, etc. The solar cell encapsulant of this embodiment exhibits good adhesion to these substrates 2 or protective materials 4.

The method for manufacturing the solar cell module 1 is not particularly limited, but may be, for example, the following method.
First, a plurality of solar cell elements 3 electrically connected using interconnectors 6 are sandwiched between solar cell encapsulant materials, and these solar cell encapsulant materials are further sandwiched between a substrate 2 and a protective material 4 to produce a laminate. Next, the laminate is heated and pressurized to bond the components together. In this manner, a solar cell module 1 is obtained.

<Resin sheet for interlayer film of laminated glass and laminated glass>
So far, the description has been mainly given of the production of a solar cell encapsulant using the resin composition of the present embodiment, and the production of a solar cell module by encapsulating solar cell elements using the solar cell encapsulant.
The resin composition of the present embodiment can be used for various applications other than sealing of solar cells. For example, the resin composition of the present embodiment can be used to produce a resin sheet for an interlayer film of laminated glass, and the resin sheet for an interlayer film of laminated glass can be used to produce laminated glass.

The resin sheet for laminated glass interlayer film may have a single layer structure or a multi-layer structure of two or more layers. Specific aspects of the multi-layer structure may be the same as those of the solar cell encapsulant described above. The thickness of the resin sheet for laminated glass interlayer film may also be approximately the same as that of the solar cell encapsulant described above. The manufacturing method of the resin sheet for laminated glass interlayer film may also be the same as that of the solar cell encapsulant described above.

By contacting a resin sheet for laminated glass interlayers with a transparent plate-like member and applying heat and pressure, laminated glass can be manufactured that includes a laminated glass interlayer and a transparent plate-like member provided on at least one side of the laminated glass interlayer. More specifically, laminated glass can be manufactured by sandwiching a resin sheet for laminated glass interlayers between two transparent plate-like members and then applying heat and pressure.

The transparent plate-like member that can be used is not particularly limited. For example, a commonly used transparent plate glass can be mentioned. Specifically, inorganic glass such as float plate glass, polished plate glass, figured plate glass, wired plate glass, lined plate glass, colored plate glass, heat absorbing plate glass, heat reflecting plate glass, and green glass can be mentioned. In addition, organic plastic plates such as polycarbonate plate, poly(meth)acrylate plate, polymethyl(meth)acrylate plate, polystyrene plate, cyclic polyolefin plate, polyethylene terephthalate plate, polyethylene naphthalate plate, and polyethylene butyrate plate can also be used.
The transparent plate-like member may be subjected to a surface treatment such as a corona treatment, a plasma treatment, or a flame treatment.

The above describes the embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. that can achieve the object of the present invention are included in the present invention.

The embodiments of the present invention will be described in detail based on examples and comparative examples. It should be noted that the present invention is not limited to the examples.

1. Measurement and Evaluation Methods First, the measurement and evaluation methods will be described.

[Dynamic viscoelasticity measurement/crossover temperature]
First, a 120 mm × 75 mm × 0.4 mm film composed of a resin composition obtained in an Example or Comparative Example described later was laminated between glass plates via a release film, and then pressed in a vacuum laminator at 160° C., held in vacuum for 690 seconds, and pressed at 0.06 MPa (gauge pressure) for 15 minutes to obtain a laminated glass.
Next, in order to complete the crosslinking reaction, the obtained laminated glass was heat-treated for 30 minutes in a circulating high-temperature dryer (product name: MOV-212F, manufactured by SANYO Electric Co., Ltd.) set at 165° C. As a result, a laminated glass body was obtained (laminated glass body: five-layer structure of glass plate-release film-membrane (crosslinked film)-release film-glass plate).
The glass plate and the release film were removed from the obtained laminated glass body to obtain a film, which was used as a sample to measure the shear modulus from -60°C to 150°C in a nitrogen atmosphere using a dynamic viscoelasticity measuring device (MCR302, manufactured by Anton Paar) equipped with parallel plates having a diameter of 8 mm, at a heating rate of 3°C/min, a frequency of 1 Hz, and in shear mode. The temperature at which the shear storage modulus (G') and the shear loss modulus (G") became equal was defined as the crossover temperature.

[Creep test]
The film made of the resin composition obtained in the examples and comparative examples shown below was cut to a size of 180 mm x 160 mm x 0.4 mm. Next, two of the obtained films were stacked, and two float glasses of 180 mm x 180 mm x 3.2 mm were sandwiched with a 2 cm shift, and the laminated glass was obtained by pressing for 5 minutes at 0.075 MPa (gauge pressure) at 150 ° C. in a vacuum laminator. Furthermore, in order to complete the crosslinking reaction, the laminated glass sample was heat-treated for 30 minutes in a circulation type high-temperature dryer (manufactured by SANYO Electric Co., Ltd., product name: MOV-212F) set at 165 ° C.
Next, one side of the obtained laminated glass was fixed while the other side was allowed to move freely. A weight of 400 g was attached to the glass that was allowed to move freely, and the glass was then placed in a circulating high-temperature dryer (manufactured by SANYO Electric Co., Ltd., product name: MOV-212F) set to 105°C.
The displacement length of the glass was measured 200 hours after it was placed in the oven. When the displacement length reached 8 cm or more, the load attached to the test specimen came into contact with the bottom surface of the oven, and therefore the measurement was not possible.

[Optical properties (haze and total light transmittance)]
The film made of the resin composition obtained in the examples and comparative examples shown below was cut to a size of 120 mm x 75 mm x 0.4 mm. The film obtained was then sandwiched between 120 mm x 75 mm x 3.2 mm white glass plates (haze 0.2% or less, total light transmittance 92% or more), and pressed at 150°C and 0.1 MPa (gauge pressure) for 5 minutes in a vacuum laminator to obtain laminated glass. In order to complete the crosslinking reaction, the laminated glass sample was heat-treated for 30 minutes in a circulating high-temperature dryer (manufactured by SANYO Electric Co., Ltd., product name: MOV-212F) set at 165°C.
The haze of the obtained laminated glass was measured in accordance with JIS K 7136: 2000. The total light transmittance of the obtained laminated glass was measured in accordance with JIS K 7361-1: 1997 using a haze meter (manufactured by Suga Test Instruments Co., Ltd., product name: haze meter HZ-V3).

[Adhesiveness]
A 120 mm x 75 mm x 0.4 mm film was obtained from the resin composition obtained in the examples and comparative examples shown below. The film obtained was then laminated on the tin surface of a 120 mm x 75 mm x 3.9 mm glass plate, and pressed for 15 minutes at 160°C, 690 seconds vacuum holding, and 0.06 MPa (gauge pressure) in a vacuum laminator. This allowed the film to adhere to the tin surface of the glass plate. To complete the crosslinking reaction, the laminated glass sample was heat-treated for 30 minutes in a circulating high-temperature dryer (manufactured by SANYO Electric Co., Ltd., product name: MOV-212F) set at 165°C.
The adhered film was cut into a strip of 15 mm width, and then the film was pulled away from the glass plate at a tensile speed of 100 mm/min and a peel angle of 180°. The maximum peel force at this time was calculated as the adhesive strength to the glass plate (N/15 mm).

2. Preparation of materials The following materials were prepared.

[Resins (ionomers and other resins)]
Resin-A: Zinc ionomer of ethylene-methacrylic acid copolymer (ethylene content: 80% by mass, methacrylic acid content: 20% by mass) (degree of neutralization: 40%, MFR (measured in accordance with JIS K 7210:1999 at 190°C and a load of 2160 g): 1.3 g/10 min)
Resin-B: Ethylene-methacrylic acid copolymer (ethylene content: 80% by mass, methacrylic acid content: 20% by mass, MFR (measured in accordance with JIS K 7210:1999 at 190°C and a load of 2160 g): 500 g/10 min)

[Lubricant]
Fatty acid metal salt: Magnesium stearate (product name: Magnesium Stearate G, manufactured by NOF Corporation)

[Organic peroxide]
Organic peroxide: (trade name: Luperox 101, manufactured by Arkema Yoshitomi Co., Ltd., 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 10-hour half-life temperature = 120°C)

[Crosslinking assistant]
Crosslinking aid: TAIC (triallyl isocyanurate, manufactured by Wako Pure Chemical Industries, Ltd.)

[Silane coupling agent]
Silane coupling agent-A: 3-methacryloxypropylmethyldiethoxysilane (product name: KBM502, manufactured by Shin-Etsu Chemical Co., Ltd.)
Silane coupling agent-B: N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane (product name: KBM602, manufactured by Shin-Etsu Chemical Co., Ltd.)

3. Production and Evaluation of Solar Cell Encapsulant First, Resin-A, Resin-B and magnesium stearate were melt-kneaded at 160°C and a discharge rate of 10 kg/hour in the proportions shown in Table 1 to obtain a kneaded product. By this kneading, at least some of the carboxy groups of Resin-A and Resin-B were neutralized by magnesium ions in the magnesium stearate.
Next, the obtained kneaded product was blended with Luperox 101, TAIC, silane coupling agent-A, and silane coupling agent-B in the mixing ratio shown in Table 1, and extrusion molded using an extruder equipped with a T-die at an extruder T-die outlet resin temperature of 120° C. and a processing speed of 1.3 to 1.9 m/min. As a result, a sheet-shaped resin molded product (solar cell encapsulant) having a thickness of 0.4 mm was obtained.

The obtained resin molding (solar cell encapsulant) was used to carry out the evaluation described above in 1.

The composition and evaluation results of each composition are shown in Table 1.
In Table 1, the units (phr) of the blending amounts of magnesium stearate, Luperox 101, TAIC, silane coupling agent-A and silane coupling agent-B mean parts by mass when the total of resin-A and resin-B is 100 parts by mass.
In Table 1, "degree of neutralization" indicates the degree of neutralization of the above-mentioned kneaded mixture of Resin A, Resin B and magnesium stearate.
In Table 1, "MFR" represents the melt mass flow rate of the resin composition measured in accordance with JIS K 7210:1999 under conditions of 190°C and a load of 2160 g.

The resin compositions of Examples 1 and 2 had an excellent balance of transparency, creep resistance, and interlayer adhesion. In contrast, the resin compositions of Comparative Examples 1 to 3 had a poor balance of transparency, creep resistance, and interlayer adhesion.

This application claims priority based on Japanese Patent Application No. 2020-160349, filed on September 25, 2020, the disclosure of which is incorporated herein in its entirety.

1 Solar cell module 2 Substrate 3 Solar cell element 4 Protective material 5 Sealing resin layer 6 Interconnector

Claims (3)

A method for producing a resin composition comprising (A) an ionomer of an ethylene-unsaturated carboxylic acid copolymer, (B) at least one lubricant selected from the group consisting of fatty acids and fatty acid metal salts, (C) an organic peroxide, and (D) a silane coupling agent,
A step of obtaining a mixture by mixing an ionomer (A) of an ethylene-unsaturated carboxylic acid copolymer with at least one lubricant (B) selected from the group consisting of fatty acids and fatty acid metal salts;
After the above step, a step of mixing the mixture with an organic peroxide (C) and a silane coupling agent (D);
A method for producing a resin composition comprising the steps of: A method for producing a solar cell encapsulant, comprising an extrusion molding step of extruding a heated and molten resin composition produced by the method for producing a resin composition according to claim 1 from a T-die of an extruder equipped with a T-die to form the resin composition into a sheet. A method for producing the solar cell encapsulant according to claim 2 , comprising the steps of:
The method for producing a solar cell encapsulant, wherein in the extrusion molding step, the temperature of the heated molten material at an outlet of the T-die is 140° C. or lower.

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