JPWO2017038374A1 - Electron beam crosslinkable ethylene resin composition, electron beam cross-linked product, method for producing electron beam cross-linked product, and laminate - Google Patents

Abstract

The electron beam crosslinkable ethylene resin composition of the present invention comprises an ethylene copolymer having a Shore A hardness of 55 or more and 95 or less as measured in accordance with ASTM D2240, and the content of the blowing agent is the above ethylene. The amount is less than 1.0 part by mass with respect to 100 parts by mass of the system copolymer.

Description

  The present invention relates to an electron beam crosslinkable ethylene resin composition, an electron beam crosslinked body, a method for producing an electron beam crosslinked body, and a laminate.

  Ethylene-based copolymers such as ethylene / α-olefin copolymers and ethylene / polar monomer copolymers are widely used as resin modifiers and the like by taking advantage of their flexibility. However, when the ethylene-based copolymer is used as a main component, the use of the resin is limited because the melting point of the resin is low. Therefore, when using an ethylene copolymer as a main component, the ethylene copolymer is used as a thermally crosslinkable resin composition containing an organic peroxide in order to impart heat resistance, foam cell stability, and the like. Used by thermal crosslinking at high temperatures.

  In general, a heat-crosslinkable resin composition is subjected to a crosslinking treatment after being molded into a desired shape such as a sheet or a foam by various molding methods such as extrusion molding, calendar molding, and injection molding. Since the said composition uses an organic peroxide as an initiator, when performing a crosslinking process, it is necessary to heat to high temperature. Therefore, for example, when cross-linking is performed by a press machine or the like, the protruding ethylene copolymer may contaminate the apparatus.

Examples of crosslinking methods that can replace thermal crosslinking include photocrosslinking using ultraviolet rays, gamma ray crosslinking using gamma rays, and electron beam crosslinking using electron beams. Photocrosslinking requires a photoinitiator and there is a concern about resin coloring. Electron beam cross-linking is mainly used for cross-linking of pipes and electric wires.
As an example of using electron beam crosslinking as a sealing material, Patent Document 1 discloses that low density polyethylene, linear low density polyethylene, and an ethylene-vinyl acetate copolymer are irradiated with an electron beam, and then a salt bath on a salt salt bath. A sealing material foamed at a temperature of 230 ° C. is described.

JP 2014-105329 A

Since the conventional foam sheet has high rigidity, when used as a sealing material or the like, a force is required for closing, and the foam sheet tends to be deformed during repeated opening and closing. Therefore, when a foam sheet is used as a sealing material, the foam sheet is required to have improved flexibility.
Even when a conventional foamed sheet is used as a cushioning material for packing, if the contents are fine or fragile, an improvement in flexibility is required on the surface of the foamed sheet to prevent damage.
In order to soften the foam sheet, a resin composition obtained by blending an ethylene-based copolymer such as an ethylene / α-olefin copolymer or an ethylene / polar monomer copolymer as a soft component to the foam sheet resin composition has been studied. ing. However, since such a resin composition contains an organic peroxide, there are restrictions on molding conditions such as molding temperature.

  In addition, in an electronic device, a resin composition containing an ethylene copolymer such as an ethylene / α-olefin copolymer or an ethylene / polar monomer copolymer for protecting a semiconductor, a solar cell element, a display, etc. A semiconductor, a solar cell element, a display, etc. are embedded by applying a pressure under atmospheric pressure to a sealing material composed of another resin composition using a thermal laminating method. However, in recent years, thinning of semiconductors, solar cell elements, displays, etc. has been promoted, and conventional thermal laminating methods tend to cause cracks and chips in semiconductors, solar cell elements, displays, etc. There is a need for a technique for embedding an entire electronic device including a battery element, a display and the like without applying stress.

  In the sealing material described in Patent Document 1, foaming is performed on the salt bath after electron beam cross-linking, so that the device tends to be contaminated. In addition, since the flexibility is insufficient, the sealing property tends to be insufficient because the sealing material is gradually compressed and deformed when repeatedly used. Furthermore, in the sealing material described in Patent Document 1, when the contents to be packed are fine, the cushioning property is insufficient and the contents tend to be damaged.

This invention is made | formed in view of the said situation, and provides the electron beam crosslinkable ethylene resin composition excellent in the balance of a crosslinking characteristic and a softness | flexibility.
Furthermore, one aspect of the present invention provides an electron beam crosslinkable ethylene resin composition capable of obtaining a molded body without being restricted by a molding temperature.

  The present inventors diligently studied in order to provide an electron beam crosslinkable ethylene resin composition having an excellent balance between crosslinking characteristics and flexibility. As a result, it has been found that by using an ethylene copolymer having a Shore A hardness in a specific range, an electron beam crosslinkable ethylene resin composition having an excellent balance between crosslinking characteristics and flexibility can be obtained. It came to.

  According to the present invention, there are provided the following electron beam crosslinkable ethylene resin composition, electron beam crosslinked body, method for producing electron beam crosslinked body, and laminate.

[1]
Including an ethylene-based copolymer having a Shore A hardness of 55 or more and 95 or less measured in accordance with ASTM D2240,
An electron beam crosslinkable ethylene resin composition in which the content of the foaming agent is less than 1.0 part by mass with respect to 100 parts by mass of the ethylene copolymer.
[2]
The electron beam crosslinkable ethylene resin composition according to the above [1], wherein the ethylene copolymer contains an ethylene / α-olefin copolymer (a) satisfying the following requirement a1).
a1) the density as measured according to ASTM D1505 is not more than 0.860 g / cm ³ or more 0.895g / cm ^{3 [3]}
The electron beam crosslinkable ethylene resin composition according to the above [1], wherein the ethylene copolymer contains an ethylene / polar monomer copolymer (b) satisfying the following requirement b1).
b1) The content of the polar monomer unit in the ethylene / polar monomer copolymer (b) is 8% by mass or more and 35% by mass or less [4].
The electron beam crosslinkable ethylene resin composition according to any one of the above [1] to [3], further comprising an organic peroxide.
[5]
The electron beam crosslinkable ethylene resin composition according to the above [4], wherein the content of the organic peroxide is less than 1.0 part by mass with respect to 100 parts by mass of the ethylene copolymer.
[6]
The electron beam crosslinkable ethylene resin composition according to any one of the above [1] to [5], wherein the gel fraction calculated by the following method is 30% or more.
(Method)
Kneading the electron beam crosslinkable ethylene-based resin composition at 100 ° C. for 5 minutes, pressing at 100 ° C. and 0 MPa for 3 minutes, pressing at 100 ° C. and 10 MPa for 2 minutes, and pressing at 10 MPa with a cooling press for 3 minutes. Thus, a sheet having a thickness of 0.5 mm is obtained. Next, the obtained sheet is irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce a crosslinked sheet. About 1 g of the obtained crosslinked sheet (weighing value is A (g)) is subjected to Soxhlet extraction with boiling toluene for 10 hours, and the obtained extract is filtered through a 30 mesh stainless steel mesh. Drying is performed under reduced pressure at 110 ° C. for 8 hours, the residual amount B (g) on the stainless mesh is calculated, and the gel fraction is calculated using the following formula.
Gel fraction (mass%) = 100 × B / A
[7]
The electron beam crosslinkable ethylene-based resin composition according to any one of [1] to [6], further including a crosslinking aid.
[8]
The electron beam crosslinking according to the above [7], wherein the crosslinking assistant contains one or more selected from divinyl aromatic compounds, cyanurate compounds, diallyl compounds, acrylate compounds, triallyl compounds, oxime compounds and maleimide compounds. Ethylene-based resin composition.
[9]
The electron beam crosslinkable ethylene resin composition according to any one of [1] to [8], wherein the ethylene copolymer further satisfies the following requirement c1).
c1) According to ASTM D1238, MFR measured under conditions of 190 ° C. and 2.16 kg load is 0.1 g / 10 min or more and 50 g / 10 min or less [10]
[1] to [9], wherein the content of the ethylene copolymer is 50% by mass or more when the entire electron beam crosslinkable ethylene resin composition is 100% by mass. An electron beam crosslinkable ethylene resin composition.
[11]
The electron beam crosslinkable ethylene resin composition according to any one of [1] to [10], wherein the total light transmittance in a HAZE meter measured by the following method is 80% or more.
(Method)
Kneading the electron beam crosslinkable ethylene-based resin composition at 100 ° C. for 5 minutes, pressing at 100 ° C. and 0 MPa for 3 minutes, pressing at 100 ° C. and 10 MPa for 2 minutes, and pressing at 10 MPa with a cooling press for 3 minutes. Thus, a sheet having a thickness of 0.5 mm is obtained. Next, the obtained sheet is sandwiched between white glass plates, pressed with a vacuum laminator at 100 ° C. under vacuum for 2 minutes, and pressed at 100 ° C. and 0.04 MPa for 3 minutes to obtain a laminate. The obtained laminate is irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce a crosslinked laminate. Next, the total light transmittance of the obtained crosslinked laminate is measured with a HAZE meter according to JIS K7361-1.
[12]
The electron beam crosslinkable ethylene resin composition according to the above [3], wherein the ethylene / polar monomer copolymer (b) comprises an ethylene / vinyl acetate copolymer.
[13]
The electron beam crosslinkable ethylene according to any one of the above [1] to [12], wherein the content of the photocrosslinking initiator is less than 0.05 parts by mass with respect to 100 parts by mass of the ethylene copolymer. -Based resin composition.
[14]
The electron beam according to [13], wherein the photocrosslinking initiator includes one or more selected from benzophenone, benzophenone derivatives, benzoin, benzoin derivatives, α-hydroxyalkylphenones, oxime esters, and anthraquinone derivatives. A crosslinkable ethylene resin composition.
[15]
The electron beam crosslinkable ethylene resin composition according to any one of [1] to [14], which is in a sheet form.
[16]
An electron beam crosslinked product obtained by electron beam crosslinking the electron beam crosslinkable ethylene resin composition according to any one of the above [1] to [15].
[17]
By irradiating the electron beam crosslinkable ethylene resin composition according to any one of [1] to [15] with an electron beam of 30 kGy to 300 kGy, the electron beam crosslinkable ethylene resin composition. The manufacturing method of the electron beam crosslinked body as described in said [16] including the process of bridge | crosslinking.
[18]
The sheet-like electron beam crosslinkable ethylene resin composition according to [15] above and a resin sheet, a metal substrate, and a translucent substrate different from the sheet-like electron beam crosslinkable ethylene resin composition are selected. The laminated body formed by laminating | stacking 1 type, or 2 or more types of sheet-like members.

  ADVANTAGE OF THE INVENTION According to this invention, the electron beam crosslinkable ethylene resin composition excellent in the balance of a crosslinking characteristic and a softness | flexibility can be provided. Furthermore, since an organic peroxide is not necessarily required in one embodiment of the present invention, a molded body can be obtained without being restricted by a molding temperature.

  Embodiments of the present invention will be described below. In addition, “A to B” in the numerical range represents A or more and B or less unless otherwise specified.

1. Electron Beam Crosslinkable Ethylene Resin Composition The electron beam crosslinkable ethylene resin composition of the present embodiment includes an ethylene copolymer having a Shore A hardness of 55 or more and 95 or less measured in accordance with ASTM D2240. From the viewpoint of improving the strength of the obtained electron beam cross-linked product, the content of the foaming agent is less than 1.0 part by mass, preferably less than 0.7 part by mass with respect to 100 parts by mass of the ethylene copolymer More preferably, it is less than 0.5 parts by mass, more preferably less than 0.3 parts by mass, and particularly preferably no foaming agent.
Examples of the foaming agent include inorganic foaming agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, and ammonium nitrite; N, N′-dinitrosopentamethylenetetramine, N, N′-dinitrosotephthalamide Azo compounds such as azodicarbonamide and azobisisobutyronitrile; hydrazide compounds such as benzenesulfonyl hydrazide and 4,4′-oxybis (benzenesulfonyl hydrazide); calcium azide and 4,4′-diphenyldi Organic foaming agents such as azide compounds such as sulfonyl azide; physical foaming agents composed of inert gases such as carbon dioxide and nitrogen, and the like.

<Ethylene copolymer>
The Shore A hardness measured according to ASTM D2240 of the ethylene copolymer used in the electron beam crosslinkable ethylene resin composition of the present embodiment is 55 to 95, preferably 60 to 95, and more. Preferably it is 63-90.
The Shore A hardness of the ethylene copolymer can be adjusted by controlling the content and density of the ethylene units in the ethylene copolymer. That is, an ethylene-based copolymer having a high ethylene unit content and a high density has a high Shore A hardness. On the other hand, an ethylene copolymer having a low ethylene unit content and a low density has a low Shore A hardness.

When the Shore A hardness is not less than the above lower limit, the crosslinkability of the electron beam crosslinkable ethylene resin composition is improved, and the creep property and heat resistance are improved.
When the Shore A hardness is less than or equal to the above upper limit, the flexibility of the electron beam crosslinkable ethylene resin composition is improved, and the sealing property when used for a sealing material or the like is improved. Moreover, the crosslinkability of the electron beam crosslinkable ethylene resin composition is improved, and the creep property and heat resistance are improved.

(Requirement c1)
According to ASTM D1238, the melt flow rate (MFR) of the ethylene copolymer measured under the conditions of 190 ° C. and 2.16 kg load is preferably 0.1 to 50 g / 10 min, more preferably It is 0.5 to 40 g / 10 minutes, more preferably 1.0 to 35 g / 10 minutes, and particularly preferably 5.0 to 25 g / 10 minutes. The MFR of the ethylene copolymer can be adjusted by adjusting the polymerization temperature during the polymerization reaction, the polymerization pressure, the molar ratio of the monomer concentration and the hydrogen concentration of the copolymerization monomer in the polymerization system, and the like.

When the MFR is not less than the above lower limit, the fluidity of the ethylene copolymer is improved, and the sheet formability becomes better.
On the other hand, when the MFR is not more than the above upper limit value, the molecular weight becomes high, so that adhesion to a roll surface such as a chill roll does not easily occur, and peeling becomes easy, so that uniform thickness sheet molding becomes easier. Furthermore, the crosslinkability of the electron beam crosslinkable ethylene resin composition is improved, the creep property is improved, and the resilience is sufficient when used as a sealing material, and the repeated sealability is improved. .

  Examples of the ethylene copolymer used in the electron beam crosslinkable ethylene resin composition of the present embodiment include ethylene and α-olefin copolymers containing ethylene and an α-olefin having 3 to 20 carbon atoms, ethylene · Olefin resins such as cyclic olefin copolymers, ethylene / α-olefin / cyclic olefin copolymers; ethylene / unsaturated carboxylic acid ester copolymers, ethylene / unsaturated carboxylic acid copolymers and salts thereof, ethylene / One or two or more selected from ethylene / polar monomer copolymers such as vinyl ester copolymers; and the like can be used.

  Among these, at least one selected from an ethylene / α-olefin copolymer and an ethylene / vinyl acetate copolymer is particularly preferably used. In the present embodiment, the above-described ethylene-based copolymer may be used alone or in combination of two or more.

  The content of the ethylene copolymer in the electron beam crosslinkable ethylene resin composition in the present embodiment is preferably 50 mass% or more when the total electron beam crosslinkable ethylene resin composition is 100 mass%. More preferably, it is 70 mass% or more, More preferably, it is 80 mass% or more, Most preferably, it is 90 mass% or more. Thereby, the electron beam crosslinkable ethylene resin composition excellent in balance of various characteristics, such as transparency, adhesiveness, heat resistance, a softness | flexibility, and a crosslinking characteristic, can be obtained.

(Ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymer used in the electron beam crosslinkable ethylene-based resin composition in the present embodiment is obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. As the α-olefin, usually, an α-olefin having 3 to 20 carbon atoms can be used alone or in combination of two or more. Among these, α-olefins having 10 or less carbon atoms are preferable, and α-olefins having 3 to 8 carbon atoms are particularly preferable. Specific examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, 4-methyl-1- Examples include pentene, 1-octene, 1-decene, 1-dodecene and the like. Among these, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene are preferable because of their availability. The ethylene / α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred from the viewpoint of flexibility.

  The ethylene / α-olefin copolymer further preferably satisfies at least one of the requirements a1) to a3), and more preferably satisfies all of the requirements a1) to a3). Moreover, when the electron beam crosslinkable ethylene resin composition of this embodiment is used as a solar cell encapsulant, it is more preferable to satisfy the following requirements a1 ′), a2) and a3 ′).

(Requirement a1)
The density of the ethylene / α-olefin copolymer measured in accordance with ASTM D1505 is preferably 0.860 to 0.895 g / cm ³ , more preferably 0.863 to 0.895 g / cm ³ . More preferably 0.865 to 0.890 g / cm ³ .
The density of the ethylene / α-olefin copolymer can be adjusted by a balance between the content ratio of ethylene units and the content ratio of α-olefin units. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased, and a high-density ethylene / α-olefin copolymer can be obtained. On the other hand, when the content ratio of the ethylene unit is lowered, the crystallinity is lowered and an ethylene / α-olefin copolymer having a low density can be obtained.

  When the density of the ethylene / α-olefin copolymer is not more than the above upper limit value, the crystallinity is lowered and the transparency can be further increased. Furthermore, the crosslinkability can be made better. Moreover, it is excellent in flexibility, and when used as a sealing material, the sealing property tends to be better.

  On the other hand, if the density of the ethylene / α-olefin copolymer is not less than the above lower limit value, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the formed sheet is less sticky, Peeling is facilitated, and a sheet composed of the electron beam crosslinkable ethylene resin composition can be obtained more easily. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since crosslinkability becomes more favorable, a heat resistant fall can be suppressed more.

(Requirement a1 ′)
When the electron beam crosslinkable ethylene-based resin composition of the present embodiment is used as a solar cell encapsulant, the density of the ethylene / α-olefin copolymer measured according to ASTM D1505 is preferably 0. .865 to 0.884 g / cm ³ , more preferably 0.866 to 0.883 g / cm ³ , still more preferably 0.866 to 0.880 g / cm ³ , and particularly preferably 0.867. ˜0.880 g / cm ³ . The density of the ethylene / α-olefin copolymer can be adjusted by a balance between the content ratio of ethylene units and the content ratio of α-olefin units. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased, and a high-density ethylene / α-olefin copolymer can be obtained. On the other hand, when the content ratio of the ethylene unit is lowered, the crystallinity is lowered and an ethylene / α-olefin copolymer having a low density can be obtained.

  When the density of the ethylene / α-olefin copolymer is not more than the above upper limit value, the crystallinity is lowered and the transparency can be further increased. Furthermore, the crosslinkability can be made better. Moreover, it is excellent in a softness | flexibility and it can suppress more that the crack of a solar cell element, the crack of a thin film electrode, etc. generate | occur | produce when carrying out temporary lamination molding before performing electron beam bridge | crosslinking of a module.

  On the other hand, if the density of the ethylene / α-olefin copolymer is not less than the above lower limit value, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the formed sheet is less sticky, Peeling is facilitated, and a sheet composed of the electron beam crosslinkable ethylene resin composition can be obtained more easily. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since crosslinkability becomes more favorable, a heat resistant fall can be suppressed more.

(Requirement a2)
When the electron beam crosslinkable ethylene-based resin composition of the present embodiment is used as a solar cell encapsulant, the Shore A hardness of the ethylene / α-olefin copolymer measured according to ASTM D2240 is preferably Is 60 to 85, more preferably 62 to 83, still more preferably 62 to 80, and particularly preferably 65 to 80. The Shore A hardness of the ethylene / α-olefin copolymer can be adjusted by controlling the ethylene unit content and density of the ethylene / α-olefin copolymer. That is, an ethylene / α-olefin copolymer having a high ethylene unit content and high density has a high Shore A hardness. On the other hand, an ethylene / α-olefin copolymer having a low ethylene unit content and a low density has a low Shore A hardness.

  When the Shore A hardness is not less than the above lower limit, the crystallization rate of the ethylene / α-olefin copolymer is increased. For this reason, it becomes difficult for the molded sheet to be sticky, it becomes easier to peel off with a cooling roll, and it becomes easier to obtain a sheet composed of an electron beam crosslinkable ethylene resin composition. Further, since stickiness generated in the sheet is suppressed, blocking can be suppressed, and the sheet feeding property tends to be better. Moreover, the crosslinkability of the electron beam crosslinkable ethylene resin composition is further improved, and the heat resistance is further improved.

  On the other hand, when the Shore A hardness is not more than the above upper limit, the crystallinity is lowered and the transparency can be increased. Furthermore, since it is highly flexible, it is possible to further suppress the occurrence of cracks in the cells that are solar cell elements, chipping of the thin-film electrodes, etc., when temporary laminate molding is performed before electron beam crosslinking of the solar cell module. .

(Requirement a3)
The content ratio of the structural unit derived from ethylene contained in the ethylene / α-olefin copolymer is preferably 78 to 93 mol%, more preferably 79 to 93 mol%, still more preferably 80 to 90 mol%. is there. The content ratio of structural units derived from an α-olefin having 3 to 20 carbon atoms (hereinafter also referred to as “α-olefin unit”) contained in the ethylene / α-olefin copolymer is preferably 7 to 22 mol%. More preferably, it is 7-21 mol%, More preferably, it is 10-20 mol%.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not less than the above lower limit, the crystallinity is lowered and the transparency can be further increased. Furthermore, the crosslinkability can be made better. Moreover, it is excellent in flexibility, and when used as a sealing material, the sealing property tends to be better.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not more than the above upper limit value, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the molded sheet becomes sticky. It is difficult, peeling with a cooling roll becomes easy, and the sheet | seat comprised by the electron beam crosslinkable ethylene resin composition can be obtained more easily. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since crosslinkability becomes more favorable, a heat resistant fall can be suppressed more.

(Requirement a3 ′)
When the electron beam crosslinkable ethylene resin composition of the present embodiment is used as a solar cell encapsulant, the content ratio of the structural unit derived from ethylene contained in the ethylene / α-olefin copolymer is preferably Is 80 to 90 mol%, more preferably 80 to 88 mol%, still more preferably 82 to 88 mol%, and particularly preferably 82 to 87 mol%. The content ratio of the structural unit derived from an α-olefin having 3 to 20 carbon atoms (hereinafter also referred to as “α-olefin unit”) contained in the ethylene / α-olefin copolymer is preferably 10 to 20 mol%. More preferably, it is 12-20 mol%, More preferably, it is 12-18 mol%, Most preferably, it is 13-18 mol%.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not less than the above lower limit, the crystallinity is lowered and the transparency can be further increased. Furthermore, the crosslinkability can be made better. Moreover, it is excellent in a softness | flexibility, and when carrying out temporary lamination shaping | molding before the electron beam bridge | crosslinking of a solar cell module, it can suppress more that the crack of a solar cell element, the crack of a thin film electrode, etc. generate | occur | produce.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not more than the above upper limit value, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the molded sheet becomes sticky. It is difficult, peeling with a cooling roll becomes easy, and the sheet | seat comprised by the electron beam crosslinkable ethylene resin composition can be obtained more easily. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since crosslinkability becomes more favorable, a heat resistant fall can be suppressed more.

(Method for producing ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymer can be produced using various metallocene compounds shown below as catalysts. As the metallocene compound, for example, the metallocene compounds described in JP-A-2006-077261, JP-A-2008-231265, JP-A-2005-314680 and the like can be used. However, a metallocene compound having a structure different from the metallocene compounds described in these patent documents may be used, or two or more metallocene compounds may be used in combination.
As a polymerization reaction using a metallocene compound, for example, the following modes can be mentioned as preferred examples.

  A conventionally known metallocene compound, (II) (II-1) an organoaluminum oxy compound, (II-2) a compound that reacts with the metallocene compound (I) to form an ion pair, and (II-3) an organoaluminum In the presence of an olefin polymerization catalyst comprising at least one compound selected from the group consisting of compounds (also referred to as a co-catalyst), one or more monomers selected from ethylene and α-olefin are supplied.

  Examples of (II-1) an organoaluminum oxy compound, (II-2) a compound that reacts with the metallocene compound (I) to form an ion pair, and (II-3) an organoaluminum compound include, for example, Metallocene compounds described in Japanese Patent No. 077261, Japanese Patent Application Laid-Open No. 2008-231265, Japanese Patent Application Laid-Open No. 2005-314680, and the like can be used. However, you may use the metallocene compound of a structure different from the metallocene compound described in these patent documents. These compounds may be put into the polymerization atmosphere individually or in advance in contact with each other. Furthermore, you may carry | support and use for the fine particle inorganic oxide support | carrier described, for example in Unexamined-Japanese-Patent No. 2005-314680 etc.

  Preferably, (II-2) the ethylene / α-olefin having excellent electrical characteristics is produced by substantially using the compound (II-2) that reacts with the metallocene compound (I) to form an ion pair. A copolymer can be obtained.

The ethylene / α-olefin copolymer can be polymerized by any of the conventionally known liquid phase polymerization methods such as a gas phase polymerization method, a slurry polymerization method, and a solution polymerization method. Preferably, it is carried out by a liquid phase polymerization method such as a solution polymerization method. When the ethylene / α-olefin copolymer is produced by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms using the metallocene compound as described above, the metallocene compound of (I) It is used in an amount of usually 10 ⁻⁹ to 10 ⁻¹ mol, preferably 10 ⁻⁸ to 10 ⁻² mol per liter of volume.

  In the compound (II-1), the molar ratio [(II-1) / M] of the compound (II-1) and all transition metal atoms (M) in the compound (I) is usually 1 to 10,000, preferably It is used in such an amount that it becomes 10-5000. In the compound (II-2), the molar ratio [(II-2) / M] of the compound (II-2) and the total transition metal (M) in the compound (I) is usually 0.5 to 50, Preferably it is used in such an amount as to be 1-20. Compound (II-3) is generally used in an amount of 0 to 5 mmol, preferably about 0 to 2 mmol, per liter of polymerization volume.

(Ethylene / polar monomer copolymer)
Examples of the ethylene / polar monomer copolymer used in the electron beam crosslinkable ethylene resin composition in the present embodiment include ethylene / (meth) ethyl acrylate copolymer and ethylene / methyl (meth) acrylate copolymer. Copolymer, ethylene / (meth) acrylic acid propyl copolymer, ethylene / (meth) butyl acrylate copolymer, ethylene / (meth) acrylic acid hexyl copolymer, ethylene / (meth) acrylic acid-2-hydroxyethyl Copolymer, ethylene / (meth) acrylic acid-2-hydroxypropyl copolymer, ethylene / (meth) acrylic acid glycidyl copolymer, ethylene / dimethyl maleate copolymer, ethylene / diethyl maleate copolymer, Ethylene / dimethyl fumarate copolymer, ethylene / diethyl fumarate copolymer, etc. Japanese carboxylic acid ester copolymer; Ethylene / unsaturated carboxylic acid such as ethylene / (meth) acrylic acid copolymer, ethylene / maleic acid copolymer, ethylene / fumaric acid copolymer, ethylene / crotonic acid copolymer Copolymers and salts thereof; ethylene / vinyl acetate copolymers, ethylene / vinyl propionate copolymers, ethylene / vinyl butyrate copolymers, ethylene / vinyl ester copolymers such as ethylene / vinyl stearate copolymers : One or two or more selected from ethylene / styrene copolymers and the like can be mentioned.

  Among these, the ethylene / polar monomer copolymer is one or two selected from an ethylene / vinyl ester copolymer and an ethylene / unsaturated carboxylic acid ester copolymer from the balance between availability and performance. It is preferable to contain a seed or more, and an ethylene / vinyl acetate copolymer is particularly preferable.

  The content of the polar monomer unit in the ethylene / polar monomer copolymer is preferably 8% by mass to 35% by mass, more preferably 10% by mass to 35% by mass, and more preferably 13% by mass to 35% by mass. is there. When the content of the polar monomer is within this range, the balance of crosslinkability, flexibility, weather resistance, and transparency is further improved.

  When the electron beam crosslinkable ethylene-based resin composition of the present embodiment is used as a solar cell encapsulant, if the content of the polar monomer is in the above range, the crosslinkability, flexibility, solar cell encapsulating sheet It is even better due to the balance of adhesion, weather resistance, transparency and mechanical properties. In addition, when the solar cell encapsulating sheet is formed, the film formability is good.

  Two or more kinds of ethylene / polar monomer copolymers having different vinyl acetate contents and MFR may be used in combination. When two or more kinds of ethylene / polar monomer copolymers are used, the total amount of these is preferably within the above range.

Since the electron beam crosslinkable ethylene resin composition of the present embodiment uses electron beam crosslinking, it does not require high temperature processing by hot pressing or vacuum lamination. Therefore, when the electron beam crosslinkable ethylene resin composition of the present embodiment is used for a buffer layer such as a sealing material or a cushion material constituted by a foamed sheet, the foamed cell of the foamed sheet does not change due to high temperature processing. Further, it is possible to make the flexible cell while holding the foam cell.
In addition, a softness | flexibility can be provided to a foamed sheet by blending the electron beam crosslinkable ethylene resin composition of this embodiment with a foamed sheet resin composition, for example, by extrusion molding.
Also, the electron beam crosslinkable ethylene resin composition of the present embodiment is extruded on a foam sheet; the foam sheet resin composition is extruded on a sheet of the electron beam crosslinkable ethylene resin composition of the present embodiment. Laminating the sheet of the electron beam crosslinkable ethylene resin composition of the present embodiment and the foam sheet using a hot press or a vacuum laminator at a low temperature such that the cells of the foam sheet do not collapse; The ethylene polymer of the present embodiment is formed by coextrusion sheet molding, extrusion lamination, pressing or laminating in the same manner as described above, etc. to form a laminate, and then irradiating with an electron beam. A laminate of the electron beam crosslinkable ethylene resin composition sheet of the embodiment and a foamed sheet can be formed, and as a result, flexibility is imparted to the foamed sheet. Can.

<Crosslinking aid>
The electron beam crosslinkable ethylene resin composition of the present embodiment preferably further includes a crosslinking aid from the viewpoint of further improving the crosslinkability.
As said crosslinking adjuvant, the 1 type (s) or 2 or more types selected from a divinyl aromatic compound, a cyanurate compound, a diallyl compound, an acrylate compound, a triallyl compound, an oxime compound, and a maleimide compound can be used, for example.

  The content of the crosslinking aid in the electron beam crosslinkable ethylene resin composition of the present embodiment is preferably 5.0 parts by mass or less with respect to 100 parts by mass of the ethylene copolymer, 3.0 The amount is more preferably no greater than part by mass, and particularly preferably no greater than 2.0 parts by mass.

  Moreover, it is preferable that content of the crosslinking adjuvant in the electron beam crosslinkable ethylene resin composition of this embodiment is 0.1 mass part or more with respect to 100 mass parts of ethylene-type copolymers, 0 More preferably 5 parts by mass or more. Thereby, it can be set as a moderate crosslinked structure. Moreover, when it uses as a solar cell sealing material, heat resistance, a mechanical physical property, and adhesiveness can be improved.

Examples of the divinyl aromatic compound include divinylbenzene and di-i-propenylbenzene.
Examples of the cyanurate compound include triallyl cyanurate and triallyl isocyanurate.
Examples of diallyl compounds include diallyl phthalate.
Examples of tolyl allyl compounds include pentaerythritol triallyl ether.

Examples of the acrylate compound include diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and tetramethylolmethane. Examples include tetra (meth) acrylate and tetramethylolmethane tetra (meth) acrylate.
Examples of the oxime compound include p-quinone dioxime, pp′-dibenzoylquinone dioxime, and the like.
Examples of the maleimide compound include m-phenylene dimaleimide.

As the crosslinking aid, a compound having at least three functional crosslinkable unsaturated bonds such as a vinyl group is preferable. Among them, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane tri (meth) acrylate, ditrimethylol. Propane tetra (meth) acrylate is preferred because it has good crosslinkability.
The electron beam crosslinkable ethylene-based resin composition of the present embodiment can be crosslinked by irradiating an electron beam after molding the resin composition into a sheet as described later. The above-described crosslinking aid is preferable because the crosslinking reaction easily proceeds even when the resin sheet is kept in a solid state.

<Silane coupling agent>
The electron beam crosslinkable ethylene resin composition of the present embodiment may further contain a silane coupling agent.
The content of the silane coupling agent in the electron beam crosslinkable ethylene resin composition of the present embodiment is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the ethylene copolymer. More preferably, it is 1-4 mass parts, and it is especially preferable that it is 0.1-3 mass parts.

Adhesiveness improves that content of a silane coupling agent is more than the said lower limit.
On the other hand, when the content of the silane coupling agent is not more than the above upper limit value, the balance between cost and performance is good, and deterioration of moisture permeability can be prevented. Moreover, when it uses as a solar cell sealing material, adhesiveness with a surface side transparent protection member, a cell, an electrode, and a back surface side protection member becomes favorable, and adhesiveness also improves. Moreover, it can suppress that a silane coupling agent itself raise | generates a condensation reaction, exists as a white stripe | line in a solar cell sealing material, and a product external appearance deteriorates.

  A conventionally well-known thing can be used for a silane coupling agent, and there is no restriction | limiting in particular. Specifically, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxysilane), γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane Etc. can be used. Preferable examples include γ-glycidoxypropylmethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, and the like, which have good adhesion.

<Organic peroxide>
The electron beam crosslinkable ethylene resin composition of the present embodiment may further contain an organic peroxide.
The content of the organic peroxide in the electron beam crosslinkable ethylene resin composition of the present embodiment is preferably less than 1.0 part by weight, more preferably 100 parts by weight of the ethylene copolymer. The amount is less than 0.8 part by mass, more preferably less than 0.5 part by mass.
Although the minimum of content of the organic peroxide in the electron beam crosslinkable ethylene resin composition of this embodiment is not specifically limited, For example, it is 0.01 mass part or more.

  The organic peroxide is used as a radical initiator in the graft modification of the silane coupling agent and the ethylene copolymer, and further as a radical initiator in the crosslinking reaction of the ethylene copolymer. It acts supplementarily during wire cross-linking. By graft-modifying the ethylene copolymer with a silane coupling agent, an electron beam crosslinkable ethylene resin composition with better adhesion to each substrate and crosslinkability can be obtained.

  The organic peroxide preferably used is not particularly limited as long as it can graft-modify a silane coupling agent on the ethylene copolymer or crosslink the ethylene copolymer. From the balance between productivity and the crosslinking rate of electron beam crosslinking, the one-minute half-life temperature of the organic peroxide is preferably 100 to 170 ° C. When the one-minute half-life temperature of the organic peroxide is equal to or higher than the above lower limit, gel is hardly generated on the sheet obtained from the electron beam crosslinkable ethylene-based resin composition during sheet molding. Moreover, since it can suppress that an unevenness | corrugation generate | occur | produces on the surface of a sheet | seat with the generate | occur | produced gel, the fall of an external appearance can be prevented.

  Known organic peroxides can be used. Preferred specific examples of the organic peroxide having a 1 minute half-life temperature in the range of 100 to 170 ° C. include dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate Dibenzoyl peroxide, t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, 1 , 1-Di (t-amylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-amylperoxy) cyclohexane, t-amylperoxyisononanoate, t-amylperoxynormal Octoate, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di ( -Butylperoxy) cyclohexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-amyl-peroxy Examples include benzoate, t-butyl peroxyacetate, t-butylperoxyisononanoate, 2,2-di (t-butylperoxy) butane, t-butylperoxybenzoate, and the like. Preferably, dilauroyl peroxide, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxybenzoate, etc. Is mentioned. The said organic peroxide may be used individually by 1 type, and may mix and use 2 or more types.

<Ultraviolet absorber, light stabilizer, heat stabilizer>
The electron beam crosslinkable ethylene resin composition of this embodiment may further contain at least one additive selected from an ultraviolet absorber, a light stabilizer, and a heat resistance stabilizer. It is preferable that the compounding quantity of these additives is 0.005-5 mass parts with respect to 100 mass parts of ethylene-type copolymers. Furthermore, it is preferable to contain at least two kinds of additives selected from the above three kinds, and it is particularly preferred that all of the above three kinds are contained. It is preferable for the amount of the additive to be in the above-mentioned range since the effect of improving weather resistance stability, heat stability, etc. can be sufficiently secured without inhibiting the crosslinking reaction of electron beam crosslinking.

Specific examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, and 2-hydroxy-4-methoxy. Benzophenone ultraviolet absorbers such as -4-carboxybenzophenone and 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2 -Hydroxy-5-methylphenyl) benzotriazole and other benzotrialisol ultraviolet absorbers; salicylic acid ester ultraviolet absorbers such as phenylsalicylate and p-octylphenylsalicylate are used.
The ultraviolet absorber may absorb light and inhibit the initiation of crosslinking by light. Therefore, it is desirable that the amount of the ultraviolet absorber described above is 0.5 parts by mass or less with respect to 100 parts by mass of the ethylene copolymer.

  Examples of the light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, 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} Hindered amine light stabilizers, hindered piperidine light stabilizers and the like are preferably used.

  Specific examples of heat-resistant stabilizers include tris (2,4-di-tert-butylphenyl) phosphite and bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester. Phosphorous acid, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, and bis (2,4-di-tert-butylphenyl) Phosphite heat stabilizers such as pentaerythritol diphosphite; lactone heat stabilizers such as the reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene; 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(methylene-2,4,6-triyl) tri-p-cresol, 1,3 , 5-Trimethyl- 2,4,6-tris (3,5-di-tert-butyl-4-hydroxyphenyl) benzylbenzene, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] Hinders such as octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] Examples include dophenol-based heat stabilizers, sulfur-based heat stabilizers, amine-based heat stabilizers, etc. In addition, these can be used singly or in combination of two or more. Stabilizers and hindered phenol heat stabilizers are preferred.

<Other additives>
The electron beam crosslinkable ethylene-based resin composition of the present embodiment can appropriately contain various components other than the components detailed above within a range not impairing the object of the present invention. Examples thereof include various polyolefins other than the ethylene copolymer, styrene, ethylene block copolymers, and propylene polymers. These may be contained in an amount of 0.0001 to 50 parts by mass, preferably 0.001 to 40 parts by mass with respect to 100 parts by mass of the ethylene copolymer. Also, various resins other than polyolefins and / or one or more additives selected from various rubbers, plasticizers, fillers, pigments, dyes, antistatic agents, antibacterial agents, antifungal agents, flame retardants, dispersants, etc. Can be contained appropriately.

<Photocrosslinking initiator>
Since the electron beam crosslinkable ethylene resin composition of the present embodiment crosslinks by electron beam irradiation, it does not need to contain a photocrosslinking initiator. Therefore, the content of the photocrosslinking initiator in the electron beam crosslinkable ethylene resin composition of the present embodiment is preferably less than 0.05 parts by mass with respect to 100 parts by mass of the ethylene copolymer, More preferably, it is less than 0.03 mass part, More preferably, it is less than 0.01 mass part. Moreover, it is particularly preferable that the electron beam crosslinkable ethylene resin composition of the present embodiment does not contain a photocrosslinking initiator.
Here, examples of the photocrosslinking initiator include one or more selected from benzophenone, benzophenone derivatives, benzoin, benzoin derivatives, α-hydroxyalkylphenones, oxime esters, anthraquinone derivatives, and the like.

<Gel fraction>
The electron beam crosslinkable ethylene resin composition of the present embodiment preferably has a gel fraction calculated by the following method of 30% or more, more preferably 50% or more, and 60% or more. Is more preferable, and 65% or more is particularly preferable. Although the upper limit of the said gel fraction of the electron beam crosslinkable ethylene resin composition of this embodiment is not specifically limited, For example, 95% or less is preferable and 90% or less is more preferable.
When the gel fraction is equal to or higher than the lower limit, the heat resistance of the crosslinked product of the electron beam crosslinkable ethylene resin composition becomes better. On the other hand, the softness | flexibility of the crosslinked material of an electron beam crosslinkable ethylene-type resin composition becomes it more favorable that a gel fraction is below the said upper limit.
(Method)
Kneading the electron beam crosslinkable ethylene-based resin composition at 100 ° C. for 5 minutes, pressing at 100 ° C. and 0 MPa for 3 minutes, pressing at 100 ° C. and 10 MPa for 2 minutes, and pressing at 10 MPa with a cooling press for 3 minutes. Thus, a sheet having a thickness of 0.5 mm is obtained. Next, the obtained sheet is irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce a crosslinked sheet. About 1 g of the obtained crosslinked sheet (weighing value is A (g)) is subjected to Soxhlet extraction with boiling toluene for 10 hours, and the obtained extract is filtered through a 30 mesh stainless steel mesh. Drying is performed under reduced pressure at 110 ° C. for 8 hours, the residual amount B (g) on the stainless mesh is calculated, and the gel fraction is calculated using the following formula.
Gel fraction (mass%) = 100 × B / A

<Total light transmittance>
The electron beam crosslinkable ethylene resin composition of the present embodiment preferably has a total light transmittance of 80% or more, more preferably 85% or more, and 90% in a HAZE meter measured by the following method. The above is particularly preferable. When the total light transmittance is at least the above lower limit, the resulting sheet has better transparency. Moreover, when the electron beam crosslinkable ethylene resin composition of this embodiment is used as a solar cell sealing material, the obtained solar cell module can obtain a much higher photovoltaic power generation amount.
(Method)
Kneading the electron beam crosslinkable ethylene-based resin composition at 100 ° C. for 5 minutes, pressing at 100 ° C. and 0 MPa for 3 minutes, pressing at 100 ° C. and 10 MPa for 2 minutes, and pressing at 10 MPa with a cooling press for 3 minutes. Thus, a sheet having a thickness of 0.5 mm is obtained. Next, the obtained sheet is sandwiched between white glass plates, pressed with a vacuum laminator at 100 ° C. under vacuum for 2 minutes, and pressed at 100 ° C. and 0.04 MPa for 3 minutes to obtain a laminate. The obtained laminate is irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce a crosslinked laminate. Next, the total light transmittance of the obtained crosslinked laminate is measured with a HAZE meter according to JIS K7361-1.

2. Sheet The electron beam crosslinkable ethylene-based resin composition of the present embodiment is also a preferred embodiment in which the overall shape is a sheet. The thickness of the layer of the sheet composed of the electron beam crosslinkable ethylene resin composition is usually 0.01 to 1.5 mm, preferably 0.05 to 1.2 mm, more preferably 0.1 to 1.0 mm. More preferably, the thickness is 0.2 to 1.0 mm, particularly preferably 0.3 to 0.9 mm, and most preferably 0.3 to 0.8 mm. When the thickness is within this range, flexibility can be expressed more effectively, and the film is more effective as a buffer layer for sealing materials, cushion materials, and the like.

There is no particular limitation on the method for forming the sheet composed of the electron beam crosslinkable ethylene resin composition of the present embodiment, but various known forming methods (cast molding, extrusion sheet molding, calendar molding, inflation molding, injection molding). , Compression molding, etc.) can be employed.
Among these, the following method is the most preferred embodiment. First, an ethylene-based copolymer, and, if necessary, a crosslinking aid, a silane coupling agent, an organic peroxide, an ultraviolet absorber, a light stabilizer, a heat stabilizer, and further necessary In response to this, other additives are blended manually, for example, in a bag such as a plastic bag, or by using a stirring mixer such as a Henschel mixer, tumbler or super mixer. Next, the obtained electron beam crosslinkable ethylene resin composition is put into, for example, a hopper of an extrusion sheet molding machine, extrusion sheet molding is performed while melt kneading, and a sheet-like electron beam crosslinkable ethylene resin composition is formed. Get things.

  As an extrusion temperature range, extrusion temperature is 80-250 degreeC, for example. When the extrusion temperature is within the above range, a better sheet can be obtained. In addition, when an organic peroxide is contained in the ethylene-based copolymer, the extrusion temperature is 80 to 130 ° C. When the extrusion temperature is within the above range, the generation of gel due to the organic peroxide can be further suppressed, and an even better sheet can be obtained.

  Moreover, the surface of the sheet | seat (or layer) comprised with the electron beam crosslinkable ethylene resin composition of this embodiment may be embossed. By decorating the surface of the sheet by embossing, blocking between the sheets or between the present sheet and other sheets can be prevented.

3. Electron beam cross-linked body The electron beam cross-linked body of the present embodiment is obtained by electron beam cross-linking the electron beam cross-linkable ethylene resin composition of the present embodiment. Moreover, the degree of crosslinking of the sheet can be adjusted by adjusting the thickness of the sheet made of the electron beam crosslinkable ethylene-based resin composition and the irradiation dose of the electron beam.
The lower limit of the electron beam irradiation dose is preferably 30 kGy or more, more preferably 40 kGy or more, and even more preferably 50 kGy or more. The upper limit of the electron beam irradiation dose is preferably 300 kGy or less, more preferably 280 kGy or less, and further preferably 250 kGy or less. In addition, the acceleration voltage of the electron beam to be irradiated is not particularly limited, and may be in a normal range, and is preferably 0.1 MeV or more and 7 MeV or less.
When the electron beam irradiation dose is at least the above lower limit, the degree of cross-linking of the electron beam cross-linked body is further improved, and the heat resistance is further improved.
When the irradiation dose of the electron beam is not more than the above upper limit value, the degree of crosslinking of the electron beam crosslinked body is further improved, and the heat resistance is further improved. Furthermore, molecular cutting of the ethylene copolymer by an electron beam is suppressed, and generation of a low molecular weight ethylene copolymer can be suppressed. Moreover, the fall of the softness | flexibility of the electron beam crosslinked body by excessive bridge | crosslinking can also be suppressed.

4). Laminate The electron beam crosslinkable ethylene resin composition of the present embodiment is a sheet, and the resin is different from the sheet electron beam crosslinkable ethylene resin composition and the sheet electron beam crosslinkable ethylene resin composition. One of preferred embodiments is to use a laminate by laminating one or two or more sheet-like members (also referred to as other layers) selected from a sheet, a metal substrate, a translucent substrate, and the like. It is. Examples of the resin sheet different from the sheet-like electron beam crosslinkable ethylene resin composition include a resin sheet made of polyethylene, polypropylene, polyethylene terephthalate (PET), or the like. Examples of the metal substrate include a silicon substrate, an aluminum substrate, a silver substrate, and a copper substrate. Examples of the translucent substrate include a quartz glass plate; a resin plate formed of acrylic resin, polycarbonate, polyester, fluorine-containing resin, or the like.
There is no particular limitation on the positional relationship between the layer formed of the electron beam crosslinkable ethylene resin composition and the other layers, and a preferable layer configuration is appropriately selected in relation to the object of the present invention. That is, the other layer may be provided between the layers composed of two or more electron beam crosslinkable ethylene resin compositions, may be provided in the outermost layer of the laminate, or other than that It may be provided at a location. Moreover, another layer may be provided only on one side of the layer comprised by the electron beam crosslinkable ethylene resin composition, and another layer may be provided on both surfaces. There is no restriction | limiting in particular in the number of layers of another layer, Arbitrary number of other layers can be provided and it is not necessary to provide another layer.

From the viewpoint of simplifying the structure and reducing costs, and from the viewpoint of effectively utilizing light by minimizing interface reflection, etc., it is constituted by the electron beam crosslinkable ethylene resin composition of this embodiment without providing other layers. What is necessary is just to produce a sheet | seat only with the made layer. However, if there are other layers necessary or useful in relation to the purpose, such other layers may be provided as appropriate.
There are no particular restrictions on the method of laminating the layer composed of the electron beam crosslinkable ethylene resin composition of the present embodiment and other layers when other layers are provided, but a cast molding machine, an extrusion sheet molding machine, A method of obtaining a laminate by coextrusion using a known melt extruder such as an inflation molding machine or an injection molding machine, or one or two selected from a pre-molded resin sheet, metal substrate, translucent substrate, etc. A method of obtaining a laminate by melting or heat laminating a layer formed of an electron beam crosslinkable ethylene-based resin composition on a layer of at least a kind of sheet-like member (also referred to as other layer) is preferable. In the case of heat lamination, pressurization can be performed as long as the shape of the other layers is not impaired.
The laminated body obtained above is irradiated with an electron beam and crosslinked to obtain a laminated body of a layer of the electron beam crosslinked body and another layer.
Further, the foamed sheet resin composition is extruded and laminated on the electron beam cross-linked sheet of the electron beam cross-linkable ethylene resin composition of the present embodiment; the electron beam of the present embodiment at a low temperature so that the cells of the foamed sheet are not crushed. The electron beam cross-linked sheet of the electron beam cross-linkable ethylene resin composition of the present embodiment is obtained by laminating the electron beam cross-linked sheet of the cross-linkable ethylene resin composition and the foamed sheet using a hot press or a vacuum laminator. And a foamed sheet can be formed. As a result, flexibility can be imparted to the foamed sheet.

5. Solar cell encapsulant The use of the electron beam crosslinkable ethylene resin composition of the present embodiment is not particularly limited, but is preferably used as a solar cell encapsulant.
Even when the electron beam crosslinkable ethylene-based resin composition of the present embodiment is used as a solar cell sealing material, it is useful to have embossing. Moreover, when using as a solar cell sealing material, in order to improve the permeation | transmission of light, it is necessary to erase | emboss. In order to erase the embossing, a vacuum laminator or a press molding machine is used. For example, a glass / solar cell encapsulant / solar cell element / solar cell encapsulant / glass structure, and a vacuum laminator is 80 to Vacuum and heat at a temperature of about 150 ° C. for 3 to 6 minutes under a vacuum pressure of 10 Torr or less; then, pressurization with atmospheric pressure is performed for about 1 to 15 minutes to erase the embossed shape and integrate the laminate. The embossing reduces the storage elastic modulus of the solar cell encapsulant (solar cell encapsulant sheet), so that the solar cell encapsulant sheet and the solar cell element are temporarily laminated with a cushion against the solar cell element and the like. Thus, damage to the solar cell element can be prevented.

6). Solar cell module A solar cell encapsulant (also referred to as a solar cell encapsulant sheet) constituted by the electron beam crosslinkable ethylene resin composition of the present embodiment seals a solar cell element in the solar cell module. Used for.
For example, a solar cell module is usually a crystal solar cell in which solar cell elements formed of single crystal silicon, polycrystalline silicon or the like are sandwiched between solar cell encapsulant sheets, and both front and back surfaces are covered with a protective sheet. Module. In particular, the configuration of a solar cell module protective sheet (transparent protective member) / light-receiving surface side sealing layer / solar cell element / back surface side sealing layer / solar cell module protective sheet (transparent protective member) This is a preferable configuration in terms of performance. Here, the solar cell sealing material of this embodiment is used to form either one or both of the light-receiving surface side sealing layer and the back surface side sealing layer, and these sealing layers are electron beam crosslinked. It can form by carrying out electron beam bridge | crosslinking of the basic ethylene resin composition.
However, the solar cell module which is one of the preferred embodiments of the present invention is not limited to the above-described configuration, and a part of each of the above layers is appropriately omitted or the above-described range within a range not impairing the object of the present invention. Other layers can be provided as appropriate. Examples of the layer other than the above include an adhesive layer, a shock absorbing layer, a coating layer, an antireflection layer, a back surface rereflection layer, and a light diffusion layer. These layers are not particularly limited, but can be provided at appropriate positions in consideration of the purpose and characteristics of each layer.

An example of the solar cell module of this embodiment is shown.
The solar cell module is a laminate in which a plurality of solar cell elements and a pair of light-receiving surface side solar cell sealing material sheets and back surface side solar cell sealing material sheets that are sealed with the solar cell elements interposed therebetween are sandwiched by transparent protective members. Prepare as a body.

(Solar cell element)
Examples of solar cell elements include silicon-based single crystal silicon, polycrystalline silicon, amorphous silicon, etc., III-V group such as gallium-arsenic, copper-indium-selenium, cadmium-tellurium, II-VI group compound semiconductors, etc. Various solar cell elements can be used.
In the solar cell module, the plurality of solar cell elements are electrically connected in series via an interconnector including a conducting wire and a solder joint.

(Transparent protective member)
Examples of the transparent protective member include a quartz glass plate; a resin plate formed of acrylic resin, polycarbonate, polyester, fluorine-containing resin, or the like.
The solar cell sealing material sheet of this embodiment shows favorable adhesiveness with respect to a transparent protective member.

(Other protective members)
Other protective members (back sheets) include single or multilayer sheets such as metals and various thermoplastic resin films. Examples thereof include metals such as tin, aluminum, and stainless steel; inorganic materials such as glass; various thermoplastic resin films formed of polyester, inorganic material-deposited polyester, fluorine-containing resin, polyolefin, and the like.
The back surface side protective member may be a single layer or a multilayer.
The solar cell sealing material sheet of this embodiment shows favorable adhesiveness with respect to other protective members.
In addition, other protection members can be used in the range which does not prevent electron beam bridge | crosslinking.

<Method for manufacturing solar cell module>
Although the manufacturing method of the solar cell module of this embodiment is not specifically limited, For example, the following method is mentioned.
First, a plurality of solar cell elements electrically connected using an interconnector are sandwiched between a pair of light receiving surface side solar cell sealing material sheets and a back surface side solar cell sealing material sheet, and further, these light receiving surface side solar cell sealing A laminated body is produced by sandwiching a material sheet and a back surface side solar cell sealing material sheet between transparent protective members. Next, the laminated body is irradiated with an electron beam, and the light receiving surface side solar cell sealing material sheet and the back surface side solar cell sealing material sheet, the light receiving surface side solar cell sealing material sheet and the transparent protective member, and the back surface side solar cell sealing. The stop sheet and the transparent protective member are bonded.
In the manufacturing method of the solar cell module of this embodiment, electron beam crosslinking of the electron beam crosslinkable ethylene resin composition which comprises a solar cell sealing material is performed by irradiating an electron beam, and a sealing layer is formed. Therefore, the heating temperature and pressure in the solar cell module manufacturing process can be set lower than the conventional thermal crosslinking by heating. Therefore, a solar cell sealing material protrudes in a solar cell module manufacturing process, and it can prevent generation | occurrence | production of the crack of a solar cell element, a thin film electrode, etc. in a solar cell module manufacturing process.

  As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and various structures other than the above are also employable.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

(1) Measuring method [Shore A hardness]
The ethylene copolymer was heated at 190 ° C., heated for 4 minutes and at 10 MPa, and then pressure-cooled at 10 MPa to room temperature for 5 minutes to obtain a 3 mm thick sheet. Using the obtained sheet, the Shore A hardness of the ethylene copolymer was measured in accordance with ASTM D2240.

[MFR]
Based on ASTM D1238, MFR of the ethylene-based copolymer was measured under the conditions of 190 ° C. and 2.16 kg load.

[Content ratio of α-olefin unit]
A solution obtained by dissolving 0.35 g of a sample in 2.0 ml of hexachlorobutadiene by heating was filtered through a glass filter (G2), 0.5 ml of deuterated benzene was added, and the mixture was charged into an NMR tube having an inner diameter of 10 mm. Using a JNM GX-400 type NMR measuring apparatus manufactured by JEOL Ltd., ¹³ C-NMR measurement was performed at 120 ° C. The number of integration was 8000 times or more. From the obtained ¹³ C-NMR spectrum, the content ratio of the α-olefin unit in the copolymer was quantified.

[Vinyl acetate content]
The vinyl acetate content was measured and calculated according to JIS K6730.

[density]
In accordance with ASTM D1505, the density of the ethylene-based copolymer was measured.

[Gel fraction]
After cutting the sheet of the electron beam crosslinkable ethylene resin composition obtained in Examples and Comparative Examples into a size of 10 cm × 10 cm, the obtained sheet is irradiated with an electron beam of 30 kGy or more and 300 kGy or less, An electron beam cross-linked sheet is prepared. About 1 g of the prepared electron beam cross-linked sheet sample is weighed (weighing value is A (g)), soxhlet extracted with boiling toluene for 10 hours, filtered through a stainless mesh with 30 mesh, and the mesh is heated at 110 ° C. for 8 hours. After drying for a period of time under reduced pressure, the residual amount B (g) on the mesh was calculated, and the gel fraction was calculated using the following formula.
Gel fraction (mass%) = 100 × B / A

[Total light transmittance]
The sheet of the electron beam crosslinkable ethylene resin composition obtained in Examples and Comparative Examples is sandwiched between white glass plates, pressed at 100 ° C. for 2 minutes under vacuum with a vacuum laminator, and pressed at 100 ° C. and 0.04 MPa for 3 minutes. The laminated body of the structure of white plate glass / sheet sample / white plate glass was obtained. The obtained laminate was irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce an electron beam crosslinked laminate. Subsequently, the total light transmittance of the said electron beam crosslinked laminated body was measured according to JISK7361-1 using the Nippon Denshoku Industries HAZE meter (brand name "NDH2000").

[Evaluation of airtightness in laminates]
The sheet | seat of the electron beam crosslinkable ethylene resin composition obtained by the Example and the comparative example and the foam sheet produced by the method similar to Example 1 of Unexamined-Japanese-Patent No. 2014-1222044 were cut out to the defined shape. Next, each sheet was stacked and charged in a vacuum laminator, placed on a hot plate adjusted to 80 ° C., and heated for 3 minutes under reduced pressure and atmospheric pressure to prepare a laminate. Subsequently, from the sheet | seat surface of the electron beam crosslinkable ethylene-type resin composition, the laminated body which irradiated the electron beam and was electron beam crosslinked was obtained.
The obtained electron beam cross-linked laminate was loaded into a cap (30PPSTD) to obtain a cap with a sealing material. The electron beam cross-linked sheet surface of the laminate was placed on the contents side. Here, the electron beam cross-linked laminate was used as a sealing material.
Water at 80 ° C. was put into a 720 ml wine bottle, a cap with a sealing material was put on the bottle mouth, and the cap was sealed with a cap sealer (Super Ermetica manufactured by OCIM) at a stoppering pressure of 20 kg. After closing, it was left at room temperature for 24 hours and opened with a force of 15 kg · cm.
Closing and opening were repeated 200 times with a force of 15 kg · cm, deformation of the electron beam cross-linked laminate was confirmed, and evaluated according to the following criteria.
○: No deformation in the electron beam cross-linked laminate ×: Deformation in the electron beam cross-linked sheet or foamed sheet By this sealing evaluation, the flexibility of the electron beam cross-linkable ethylene resin composition was evaluated.

(Synthesis Example 1)
Based on Synthesis Example 6 of WO2012 / 046456, an ethylene / α-olefin copolymer 1 was synthesized. The physical properties are shown in Table 1.

(Synthesis Example 2)
With reference to Synthesis Example 1 of WO2014 / 080856, the hydrogen supply amount was adjusted to synthesize ethylene / α-olefin copolymer 2. The physical properties are shown in Table 1.

(Synthesis Example 3)
With reference to Synthesis Example 3 of WO2012 / 046456, the 1-octene supply amount was adjusted, and an ethylene / α-olefin copolymer 3 was synthesized. The physical properties are shown in Table 1.

(Synthesis Example 4)
With reference to Synthesis Example 2 of WO2012 / 046456, the 1-butene supply amount and the hydrogen supply amount were adjusted, and an ethylene / α-olefin copolymer 4 was synthesized. The physical properties are shown in Table 1.

(Synthesis Example 5)
Based on Synthesis Example 3 of WO2012 / 046456, an ethylene / α-olefin copolymer 5 was synthesized. The physical properties are shown in Table 1.

(Synthesis Example 6)
With reference to Synthesis Example 2 of WO2012 / 046456, the 1-butene supply amount and the hydrogen supply amount were adjusted to synthesize ethylene / α-olefin copolymer 6. The physical properties are shown in Table 1.

(Synthesis Example 7)
With reference to Synthesis Example 3 of WO2012 / 046456, the amount of 1-octene supplied and the amount of hydrogen supplied were adjusted to synthesize ethylene / α-olefin copolymer 7. The physical properties are shown in Table 1.

  As the ethylene / polar monomer copolymer, ethylene / vinyl acetate copolymers 1 to 3 shown in Table 1 were used.

Example 1
1.2 parts by mass of triallyl isocyanurate as a crosslinking aid was blended with 100 parts by mass of the ethylene / α-olefin copolymer 1. No foaming agent was added.

  The above-mentioned electron beam crosslinkable ethylene resin composition was charged in a laboratory plastic mill manufactured by Toyo Seiki Co., Ltd., and kneaded for 5 minutes at 100 ° C. and a rotation speed of 30 rpm. Subsequently, the sheet was pressed at 100 ° C. and 0 MPa for 3 minutes, pressed at 100 ° C. and 10 MPa for 2 minutes, and then pressed at 10 MPa for 3 minutes with a cooling press, thereby obtaining a sheet having a thickness of 0.5 mm. The evaluation results for the obtained sheet are shown in Table 2.

(Examples 2-7, Comparative Examples 1-3, Reference Examples 1-2)
A sheet having a thickness of 0.5 mm was obtained in the same manner as in Example 1 except that the composition and irradiation dose were changed as shown in Table 2. The evaluation results for the obtained sheet are shown in Table 2. In all cases, no foaming agent was added.

(Comparative Example 4)
The sealing property of the foamed sheet produced by the same method as in Example 1 of JP 2014-122044 A was evaluated by the same method as for the laminate. As a result, the foam sheet was greatly deformed and was “x”.

As apparent from Table 2, the electron beam crosslinkable ethylene resin compositions of Examples 1 to 7 containing an ethylene copolymer having a Shore A hardness of 55 or more and 95 or less measured according to ASTM D2240 are as follows: It was excellent in the balance of various properties such as crosslinkability (gel fraction), flexibility (sealing property in the laminate), and transparency (light transmittance).
On the other hand, the electron beam crosslinkable ethylene resin compositions of Comparative Examples 1 to 3 have various properties such as crosslinkability (gel fraction), flexibility (sealing property in a laminate), and transparency (light transmittance). It was inferior in balance.

(Reference Example 3)
In the same manner as the method for producing the electron beam cross-linked laminate in the sealing evaluation, a sheet of the electron beam cross-linkable ethylene resin composition of Example 2 and the same method as Example 1 of JP 2014-122044 A An electron beam cross-linked laminate comprising the foamed sheet prepared in step 1 was prepared. Subsequently, the shape of the foam cell of the foam sheet of the obtained electron beam cross-linked laminate was confirmed. There was no change in the size of the foamed cell before and after electron beam crosslinking.

(Reference Example 4)
The electron beam cross-linked sheet of Example 2 and the foamed sheet produced by the same method as in Example 1 of Japanese Patent Application Laid-Open No. 2014-1222044 are stacked in a vacuum laminator and placed on a hot plate adjusted to 150 ° C. For 3 minutes under reduced pressure and atmospheric pressure for 5 minutes to form a laminate. The foam cell after vacuum lamination was smaller than the foam cell of the foam sheet before vacuum lamination, and hermeticity was reduced.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2015-169344 for which it applied on August 28, 2015, and takes in those the indications of all here.

Claims (18)

Including an ethylene-based copolymer having a Shore A hardness of 55 or more and 95 or less measured in accordance with ASTM D2240,
The electron beam crosslinkable ethylene resin composition whose content of a foaming agent is less than 1.0 mass part with respect to 100 mass parts of the said ethylene copolymer. The electron beam crosslinkable ethylene resin composition according to claim 1, wherein the ethylene copolymer contains an ethylene / α-olefin copolymer (a) satisfying the following requirement a1).
a1) the density as measured according to ASTM D1505 is at 0.860 g / cm ³ or more 0.895 g / cm ³ or less The electron beam crosslinkable ethylene resin composition according to claim 1, wherein the ethylene copolymer contains an ethylene / polar monomer copolymer (b) satisfying the following requirement b1).
b1) The content of polar monomer units in the ethylene / polar monomer copolymer (b) is 8% by mass or more and 35% by mass or less.   The electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 3, further comprising an organic peroxide.   The electron beam crosslinkable ethylene resin composition according to claim 4, wherein the content of the organic peroxide is less than 1.0 part by mass with respect to 100 parts by mass of the ethylene copolymer. 6. The electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 5, wherein a gel fraction calculated by the following method is 30% or more.
(Method)
The electron beam crosslinkable ethylene resin composition is kneaded at 100 ° C. for 5 minutes, pressed at 100 ° C. and 0 MPa for 3 minutes, pressed at 100 ° C. and 10 MPa for 2 minutes, and then pressed at 10 MPa for 3 minutes by a cooling press. Thus, a sheet having a thickness of 0.5 mm is obtained. Next, the obtained sheet is irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce a crosslinked sheet. About 1 g of the obtained crosslinked sheet (weighing value is A (g)) is subjected to Soxhlet extraction with boiling toluene for 10 hours, and the resulting extract is filtered through a 30-mesh stainless mesh, Drying is performed under reduced pressure at 110 ° C. for 8 hours, the residual amount B (g) on the stainless mesh is calculated, and the gel fraction is calculated using the following formula.
Gel fraction (mass%) = 100 × B / A   The electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 6, further comprising a crosslinking aid.   The electron beam crosslinkability according to claim 7, wherein the crosslinking aid includes one or more selected from divinyl aromatic compounds, cyanurate compounds, diallyl compounds, acrylate compounds, triallyl compounds, oxime compounds and maleimide compounds. Ethylene-based resin composition. The electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 8, wherein the ethylene copolymer further satisfies the following requirement c1).
c1) According to ASTM D1238, MFR measured under the conditions of 190 ° C. and 2.16 kg load is 0.1 g / 10 min or more and 50 g / 10 min or less.   The electron beam according to any one of claims 1 to 9, wherein the content of the ethylene copolymer is 50% by mass or more when the entire electron beam crosslinkable ethylene resin composition is 100% by mass. A crosslinkable ethylene resin composition. The electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 10, wherein the total light transmittance in a HAZE meter measured by the following method is 80% or more.
(Method)
The electron beam crosslinkable ethylene resin composition is kneaded at 100 ° C. for 5 minutes, pressed at 100 ° C. and 0 MPa for 3 minutes, pressed at 100 ° C. and 10 MPa for 2 minutes, and then pressed at 10 MPa for 3 minutes by a cooling press. Thus, a sheet having a thickness of 0.5 mm is obtained. Next, the obtained sheet is sandwiched between white glass plates, pressed with a vacuum laminator at 100 ° C. under vacuum for 2 minutes, and pressed at 100 ° C. and 0.04 MPa for 3 minutes to obtain a laminate. The obtained laminate is irradiated with an electron beam of 30 kGy or more and 300 kGy or less to produce a crosslinked laminate. Next, the total light transmittance of the obtained cross-linked laminate is measured with a HAZE meter according to JIS K7361-1.   The electron beam crosslinkable ethylene resin composition according to claim 3, wherein the ethylene / polar monomer copolymer (b) comprises an ethylene / vinyl acetate copolymer.   13. The electron beam crosslinkable ethylene resin composition according to claim 1, wherein the content of the photocrosslinking initiator is less than 0.05 parts by mass with respect to 100 parts by mass of the ethylene copolymer. object.   The electron beam crosslinking according to claim 13, wherein the photocrosslinking initiator includes one or more selected from benzophenone, benzophenone derivatives, benzoin, benzoin derivatives, α-hydroxyalkylphenones, oxime esters, and anthraquinone derivatives. Ethylene-based resin composition.   It is a sheet form, The electron beam crosslinkable ethylene-type resin composition as described in any one of Claims 1 thru | or 14.   An electron beam crosslinked product obtained by electron beam crosslinking the electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 15.   The electron beam crosslinkable ethylene resin composition according to any one of claims 1 to 15, wherein the electron beam crosslinkable ethylene resin composition is crosslinked by irradiating an electron beam of 30 kGy or more and 300 kGy or less. The manufacturing method of the electron beam crosslinked body of Claim 16 including a process.   The sheet-like electron beam crosslinkable ethylene resin composition according to claim 15 and the sheet-like electron beam crosslinkable ethylene resin composition are selected from resin sheets, metal substrates, and translucent substrates different from each other. The laminated body formed by laminating | stacking 1 type, or 2 or more types of sheet-like members.