JP2017110221A - Polyethylene resin, polyethylene resin composition, solar cell sealing material and solar cell module using the same - Google Patents

Abstract

A polyethylene resin, a polyethylene resin composition, and a solar cell encapsulant and a solar cell module using the same are provided. A polyethylene resin (A) which is an ethylene / α-olefin copolymer having the following characteristics (a1) to (a5). (A1) The content ratio of the structural unit derived from ethylene is 80 to 97 mol%, and the content ratio of the structural unit derived from α-olefin having 3 to 20 carbon atoms is 3 to 20 mol%. (A2) MFR (190 ° C., 21.18 N load) 0.1 to 100 g / 10 min (a3) Density is 0.860 to 0.920 g / cm3 (a4) Volume resistivity measured at a temperature of 23 ° C. and an applied voltage of 500 V is 1.0 × 10 16 Ω · cm or more ( a5) Boron residue concentration (M) in the resin is 0 <M <1 wtppm, and the boron residue has a thermal decomposition temperature of less than 200.degree. [Selection figure] None

Description

  The present invention relates to a polyethylene resin, a polyethylene resin composition, and a solar cell encapsulant and a solar cell module using the same, and more specifically, an insulating and cost surface comprising an ethylene / α-olefin copolymer, etc. The present invention relates to a polyethylene resin and a polyethylene resin composition excellent in cross-linking characteristics, and a solar cell sealing material and a solar cell module using the same.

  Polyethylene resins are used in electronic materials such as solar cells and cables because they have good processability, moisture resistance, flexibility, and insulation. In many cases, polyethylene resins are cross-linked to improve heat resistance and mechanical strength in these applications. The crosslinking reaction is carried out by using an electron beam irradiation or an additive having high radical reactivity, such as an organic peroxide.

  As a polyethylene resin exhibiting high insulating properties, polymerization using a catalyst that avoids a boron-containing promoter has been proposed (see Patent Document 1). With respect to the exemplified polyethylene resin, it is described that the volume resistivity, which is an index of insulation, is reduced by a boron residue derived from a boron-containing cocatalyst as compared with a sample containing an alumoxane cocatalyst alone.

  Decreasing insulation increases leakage current from the electronic material. For example, in the case of a solar cell, there is an example in which the occurrence of PID (Potential Induced Degradation) phenomenon in which the power generation capacity is reduced due to the influence of leakage current is reported. Then, a PID phenomenon can be suppressed by manufacturing a solar cell sealing material with a high volume resistivity.

  On the other hand, when a metallocene catalyst system is used, the boron-containing cocatalyst exhibits higher activity under high-temperature and high-pressure conditions than alumoxane, so that the production rate of polyethylene resin is increased (see Patent Document 2). In addition, it is known that the amount of cocatalyst required during production is smaller in the case of the boron-containing cocatalyst, and the use of the boron-containing cocatalyst is advantageous in terms of the production cost of the polyethylene resin.

  Regarding the cross-linking characteristics, the applicant has previously made various studies in order to improve the cross-linkability (heat resistance) of the ethylene / α-olefin copolymer used for the solar cell encapsulant. -It has been reported that when the number of branches contained in the olefin copolymer is large or the number of double bonds is large, good crosslinking properties can be obtained (see Patent Documents 3 and 4). However, the double bond contained in the ethylene / α-olefin copolymer includes various double bonds (vinyl, vinylidene, cis-vinylene, trans-vinylene, tri-substituted olefin). Regarding the contribution to the development of cross-linking properties due to differences, whether or not all are involved to the same extent in the development of good cross-linking properties, or the number of branches and the number of double bonds are independently determined in the olefin copolymer, There is no mention of whether or not only one of the two needs to be satisfied for the expression of characteristics.

  Thus, in the conventional technology, a polyethylene resin and a polyethylene resin composition excellent in insulation, cost, and cross-linking properties have not been obtained.

Special table 2015-508833 gazette JP 7-508545 A JP 2012-009688 A JP 2012-009691 A

  In view of the problems of the prior art, an object of the present invention is to provide a polyethylene resin, a polyethylene resin composition, and an ethylene / α-olefin copolymer, which are excellent in insulation, cost, and cross-linking properties, and the same. An object of the present invention is to provide a solar cell encapsulant and a solar cell module.

  As a result of intensive studies to solve the above problems, the present inventor, as a result, a specific MFR polymerized using a catalyst system containing a metallocene compound and a specific type and amount of a boron compound as a polyethylene resin, density, boron residue concentration, etc. By selecting an ethylene / α-olefin copolymer having the following characteristics and blending it with an organic peroxide, a polyethylene resin composition having excellent insulation, cost, and crosslinking properties can be obtained and used. Thus, the inventors have obtained knowledge that a solar cell encapsulant that has good heat resistance and suppresses leakage current from the solar cell can be obtained, and has completed the present invention.

That is, according to the first aspect of the present invention, there is provided a polyethylene resin (A) which is an ethylene / α-olefin copolymer having the following characteristics (a1) to (a5).
(A1) While the content rate of the structural unit derived from ethylene is 80-97 mol%, the content rate of the structural unit derived from a C3-C20 alpha olefin is 3-20 mol%.
(A2) MFR (190 ° C., 21.18 N load) is 0.1 to 100 g / 10 minutes (a3) Density is 0.860 to 0.920 g / cm ³
(A4) Volume resistivity measured at a temperature of 23 ° C. and an applied voltage of 500 V is 1.0 × 10 ¹⁶ Ω · cm or more (a5) The boron residue concentration (M) in the resin is 0 <M <1 wtppm The boron residue is a heat history of a boron compound having a thermal decomposition temperature of less than 200 ° C. in which a weight change occurs in an N ₂ atmosphere.

According to the second invention of the present invention, in the first invention, the polyethylene resin (A) is an ethylene / α-olefin copolymer further having the following property (a6): A polyethylene resin is provided.
(A6) The total amount of vinyl, vinylidene, cis-vinylene, trans-vinylene, and tri-substituted vinylene in the ethylene / α-olefin copolymer is 0.22 (total / total 1000 C) or more (however, vinyl, vinylidene, cis -The number of vinylene, trans-vinylene, and tri-substituted vinylene is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.

According to the third invention of the present invention, in the first or second invention, the polyethylene resin (A) is an ethylene / α-olefin copolymer further having the following property (a7): A polyethylene resin is provided.
(A7) The number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer and the total amount (V) of vinyl and vinylidene satisfy the relationship of the following formula (1).
Formula (1): N × V ≧ 10
(However, N and V are numbers per 1000 carbon atoms in total of the main chain and side chain measured by NMR.)

According to the fourth invention of the present invention, in the third invention, the polyethylene resin (A) is an ethylene / α-olefin copolymer further having the following property (a8): A polyethylene resin is provided.
(A8) The number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer satisfies the relationship of the following formula (2).
Formula (2): 54 ≦ N
(However, N is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.)

According to a fifth invention of the present invention, in any one of the first to fourth inventions, the polyethylene resin (A) further has the following property (a9): ethylene / α-olefin copolymer A polyethylene resin is provided.
(A9) Ratio (Mz / Mn) of Z average molecular weight (Mz) and number average molecular weight (Mn) obtained by gel permeation chromatography (GPC) is 8.0 or less.

  According to the sixth invention of the present invention, in any one of the first to fifth inventions, there is provided a polyethylene resin obtained by polymerizing the polyethylene resin (A) using a catalyst system containing a metallocene compound and a boron compound. Provided.

According to a seventh invention of the present invention, in any one of the first to sixth inventions, a polyethylene resin composition comprising a polyethylene resin (A) and the following component (B) is provided.
Component (B): Organic peroxide

  According to the eighth aspect of the present invention, in the seventh aspect, the content of the component (B) is 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyethylene resin (A). A polyethylene resin composition is provided.

  On the other hand, according to the ninth invention of the present invention, in the seventh or eighth invention, there is provided a solar cell encapsulant using a polyethylene resin composition.

  According to the tenth aspect of the present invention, there is provided a solar cell module using the solar cell sealing material in the ninth aspect.

  The polyethylene resin of the present invention comprises, as a main component, an ethylene / α-olefin copolymer having characteristics such as specific MFR, density, and boron residue concentration polymerized using a catalyst system containing a metallocene compound and a boron compound. Polyethylene resin composition with organic peroxide added to it can crosslink ethylene / α-olefin copolymer in a relatively short time during processing, and suppresses PID phenomenon when used for solar cell encapsulant applications can do. Moreover, the obtained solar cell module becomes excellent in heat resistance, transparency, and weather resistance, and can maintain stable conversion efficiency for a long period of time.

The present invention relates to a polyethylene resin, a polyethylene resin composition containing a specific ethylene / α-olefin copolymer and an organic peroxide as a resin component, and a solar cell sealing material and a solar cell module using the same. is there.
Hereinafter, each component used in the present invention, the obtained resin composition, a solar cell sealing material using the same, and the like will be described in detail.

1. Polyethylene resin (A)
The polyethylene resin (A) (hereinafter also simply referred to as resin) of the present invention is obtained by copolymerizing one or more of ethylene and an α-olefin, and has the following characteristics (a1) to (a5). It is an olefin copolymer.
(A1) While the content rate of the structural unit derived from ethylene is 80-97 mol%, the content rate of the structural unit derived from a C3-C20 alpha olefin is 3-20 mol%.
(A2) MFR (190 ° C., 21.18 N load) is 0.1 to 100 g / 10 minutes (a3) Density is 0.860 to 0.920 g / cm ³
(A4) The volume resistivity measured at a temperature of 23 ° C. and an applied voltage of 500 V is 1.0 × 10 ¹⁶ Ω · cm or more. (A5) The boron residue concentration (M) in the resin is 0 <M <1 wtppm, The boron residue is a heat history of a boron compound having a thermal decomposition temperature of less than 200 ° C. in which a weight change occurs in an N ₂ atmosphere. The polyethylene resin and the polyethylene resin composition of the present invention satisfy the above characteristics, Good insulation and cross-linking properties.

(I) Monomer structure of polyethylene resin The ethylene / α-olefin copolymer used in the present invention is a random copolymer of ethylene and an α-olefin mainly composed of a structural unit derived from ethylene.
The α-olefin used as a comonomer is an α-olefin having 3 to 20 carbon atoms, preferably 3 to 12 carbon atoms. Specifically, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1, 4-methyl-hexene-1, 4,4-dimethylpentene- 1 etc. can be mentioned. Specific examples of such ethylene / α-olefin copolymers include ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, ethylene / 1-octene copolymers, ethylene -4-methyl-pentene-1 copolymer etc. are mentioned. Of these, ethylene / 1-butene copolymer and ethylene / 1-hexene copolymer are preferable. Moreover, 1 type, or 2 or more types of combination may be sufficient as an alpha olefin. When combining two kinds of α-olefins to form a terpolymer, ethylene / propylene / 1-hexene terpolymer, ethylene / 1-butene / 1-hexene terpolymer, ethylene / propylene -1-octene terpolymer, ethylene / 1-butene / 1-octene terpolymer, etc. are mentioned.
As a comonomer, a small amount of a diene compound such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, and 1,9-decadiene may be added to the α-olefin. When these diene compounds are blended, long-chain branching is possible, so that the crystallinity of the ethylene / α-olefin copolymer is lowered, transparency, flexibility, adhesiveness, etc. are improved, and it becomes an intermolecular crosslinking agent. So the mechanical strength increases. Moreover, since the terminal group of the long chain branch is an unsaturated group, it can easily undergo a crosslinking reaction with an organic peroxide, a copolymerization reaction with an acid anhydride group-containing compound or an epoxy group-containing compound, and a graft reaction. it can.

(A1) Content ratio of ethylene and α-olefin-derived structural unit The polyethylene resin used in the present invention has a content ratio of α-olefin of 3 to 20 mol%. If it is this range, the softness | flexibility of a sheet | seat etc. and the heat resistance after bridge | crosslinking will become favorable. When the α-olefin content is less than 3 mol%, the flexibility of polyethylene may deteriorate. On the other hand, when it exceeds 20 mol%, the softening point of polyethylene is too low, so that blocking of the obtained sheet and the like is deteriorated and handling properties are lacking.

(Ii) Properties of polyethylene resin (a2) MFR
The polyethylene resin used in the present invention has an MFR of 0.1 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, and more preferably 2 to 40 g / 10 minutes. When the MFR of the ethylene / α-olefin copolymer is less than 0.1 g / 10 min, the molecular weight is too high and extrusion becomes difficult during kneading, whereas when the MFR exceeds 100 g / 10 min, the melt viscosity becomes too low. Thus, the handling property is lacking. The MFR of the ethylene / α-olefin copolymer is measured according to JIS-K6922-2: 1997 appendix (190 ° C., 21.18 N load).

(A3) Density The ethylene / α-olefin copolymer used in the present invention has a density of 0.860 to 0.920 g / cm 3, preferably 0.865 to 0.915 g / cm 3, and more preferably 0.870. ˜0.900 g / cm 3. If the density of the ethylene / α-olefin copolymer is less than 0.860 g / cm 3, the processed sheet will be blocked, whereas if the density exceeds 0.920 g / cm 3, the processed sheet will have too high rigidity. Thus, the handling property is lacking.
In order to adjust the density of the polymer, for example, a method of appropriately adjusting the α-olefin content, the polymerization temperature, the catalyst amount and the like is employed. The density of the ethylene / α-olefin copolymer is measured according to JIS-K6922-2: 1997 appendix (in the case of low density polyethylene) (23 ° C.).

(A4) Volume resistivity The ethylene / α-olefin copolymer used in the present invention has a volume resistivity measured at a temperature of 23 ° C. and an applied voltage of 500 V of 1.0 × 10 ¹⁶ Ω · cm or more, preferably 1. 0 × 10 ¹⁷ Ω · cm. Polyethylene resin having a volume resistivity of 1.0 × 10 ¹⁶ Ω · cm or more has excellent insulation performance. For example, in solar cell encapsulant applications, PID is generated in solar cell modules using n-type cells. Can be suppressed.

(A6) Vinyl, vinylidene, cis-vinylene, trans-vinylene, tri-substituted vinylene The ethylene / α-olefin copolymer used in the present invention is vinyl, vinylidene, cis-vinylene, trans-vinylene, tri-substituted vinylene. The total amount must be in a certain range. Here, the number of vinyl, vinylidene, cis-vinylene, trans-vinylene, and tri-substituted vinylene is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.
That is, in the present invention, the total amount of vinyl, vinylidene, cis-vinylene, trans-vinylene, and tri-substituted vinylene in the ethylene / α-olefin copolymer is 0.22 (pieces / total 1000C) or more. use. The total amount is preferably 0.25 or more, more preferably 0.30 or more, further preferably 0.40 or more, and particularly preferably 0.50 or more. Examples of a method for adjusting the total number of double bonds include selection of an appropriate catalyst, polymerization temperature, and a method of appropriately adjusting the type of comonomer.
Since these groups have an unsaturated bond, the crosslinkability can be enhanced by a total of 0.22 or more in the ethylene / α-olefin copolymer.

Here, the number of unsaturated bonds can be measured by ¹ H-NMR method.
The total of vinyl, vinylidene, cis-trans-vinylene, and tri-substituted vinylene in the polymer is measured by ¹ H-NMR, and is determined by the number per 1000 carbons in total of the main chain and the side chain.
Specifically, the vinylidene number per 1000 carbon atoms was calculated from the ratio of the peak area derived from the saturated alkyl chain appearing between chemical shifts of 0.4 to 2.8 ppm and the peak area derived from vinylidene near 4.7 ppm. In addition, the intensity of each characteristic peak is used around 4.9 ppm for vinyl, around 5.2 ppm for trisubstituted vinylene, and around 5.4 ppm for cis and trans-vinylene.

(A7) Relationship between the number of branches by comonomer (N) and the number of vinyl and vinylidene (V) The ethylene / α-olefin copolymer used in the present invention is the total number of branches by comonomer (N) and vinyl and vinylidene. (V) preferably satisfies the following formula (1).
Formula (1): N × V ≧ 10
Here, the number of branches (N) and the number of vinyls and vinylidenes (V) are the number per 1000 carbon atoms in total (number / total 1000 C) of the main chain and side chain measured by NMR.

(A8) Number of branches (N)
The number of branches (N) due to the comonomer in the polymer indicates the amount of tertiary carbon contained in the polymer, and is a number per 1000 carbon atoms in total of the main chain and side chain measured by NMR, For example, E.I. W. Hansen, R.A. Blom, and O.M. M.M. It can be calculated from ¹³ C-NMR spectrum with reference to Bade, Polymer, 36, 4295 (1997).
The number of branches (N) due to the comonomer in the polymer can be adjusted by polymerization conditions such as the amount of α-olefin added during the production and the polymerization temperature. The number of branches of the polymer of the present invention is preferably 54 ≦ N. By satisfying this range, the crosslinking efficiency can be further increased.

The number of vinyl groups and vinylidene groups (V) in the ethylene / α-olefin copolymer is preferably 0.10 (pieces / total 1000 C) or more, more preferably 0.12 or more, as long as Formula 1 is satisfied. .17 or more is more preferable, and 0.2 or more is particularly preferable. The individual amounts of vinyl and vinylidene are not particularly limited, but for example, vinyl and vinylidene are each preferably 0.05 or more.
The number of vinyls and vinylidenes can be adjusted by using production conditions such as polymerization temperature or using a diene compound as a comonomer.

(A9) Ratio (Mz / Mn) of Z average molecular weight (Mz) to number average molecular weight (Mn)
When the ethylene / α-olefin copolymer used in the present invention is used for applications requiring transparency, the Z average molecular weight (Mz) and the number average molecular weight (Mn) determined by gel permeation chromatography (GPC) are used. ) (Mz / Mn) is 8.0 or less, preferably 5.0 or less, more preferably 4.0 or less. Moreover, Mz / Mn is 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more. However, when Mz / Mn exceeds 8.0, transparency deteriorates. In order to adjust Mz / Mn to a predetermined range, a method of selecting an appropriate catalyst system can be used.

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

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

(Iii) Polymerization catalyst system and polymerization method of polyethylene resin (A) The catalyst used in the production of the ethylene / α-olefin copolymer used in the present invention is not particularly limited, and a conventionally known Ziegler catalyst, vanadium. Although a catalyst, a metallocene catalyst, etc. can be used, Preferably a vanadium catalyst or a metallocene catalyst, More preferably, a metallocene catalyst is used.
Although it does not necessarily limit as a metallocene catalyst, The catalyst which uses a metallocene compound, such as a zirconium compound coordinated with the group which has a cyclopentadienyl skeleton, etc., and a promoter as a catalyst component is mentioned. In particular, it is preferable to use a metallocene compound such as a zirconium compound coordinated with a group having a cyclopentadienyl skeleton.
The production method is not particularly limited, and a high-pressure ion polymerization method, a gas phase method, a solution method, a slurry method, and the like can be used, but an ethylene / α-olefin copolymer with adjusted double bonds according to the present invention. In order to obtain the polymer, it is desirable to carry out the polymerization at a high temperature of 150 to 330 ° C., so it is preferable to use the high-pressure ion polymerization method (“Polyethylene Technology Reader”, Chapter 4; ).

(A5) Boron residue The concentration (M) of the boron residue contained in the ethylene / α-olefin copolymer used in the present invention satisfies 0 <M <1 wtppm. The concentration of the boron residue depends on the type of boron compound added as a co-catalyst in the polymerization process of the ethylene / α-olefin copolymer and the concentration used. When the boron residue concentration is below the above range, the concentration of the boron compound promoter in the polymerization process of the ethylene / α-olefin copolymer is small, and the catalytic activity is not sufficiently exhibited. On the other hand, when the boron residue concentration is above the above range, the insulating property tends to deteriorate.

A feature of the present invention is that the boron residue is a heat history of a boron compound having a thermal decomposition temperature of less than 200 ° C. at which a weight change occurs in an N ₂ atmosphere. That is, as a boron compound to be added as a co-catalyst at the time of polymerization, a boron compound having a thermal decomposition temperature of less than 200 ° C. in which a weight change occurs in an N ₂ atmosphere was selected, and a thermal history at the time of polymerization of about 180 to 230 ° C. was received. It means to contain the later heat history. Preferably, it is a heat history of a boron compound having a thermal decomposition temperature of less than 180 ° C. By using a boron compound having a thermal decomposition temperature of less than 200 ° C., the chemical structure of the original boron compound is lost due to the thermal history at the time of manufacture, so that the effect of preventing the deterioration of insulation due to boron can be obtained.

The thermal decomposition temperature of the boron compound is measured by thermogravimetric analysis (TG), and the measurement conditions are as follows. Conforms to JIS K7120.
Equipment: EXSTAR6000 / TG / DTA6200 manufactured by Seiko Instruments Inc.
Measurement temperature range: 30-400 ° C
Temperature rising rate: 10 ° C./min A sample of 10 mg was weighed and heated in the above temperature range under an N ₂ atmosphere, and the temperature at which weight loss occurred was measured from the weight change and the baseline.

Moreover, the density | concentration (M) of a boron residue can be measured on the following measurement conditions, for example.
About 10 g of polyethylene resin is collected in a Teflon (registered trademark) container, nitric acid is added, it is decomposed by a microwave decomposition apparatus, the decomposition solution is made up to a constant volume, and measured by ICP-MS.
Equipment: ETHOS One type manufactured by Milestone General, NexION300S type manufactured by Perkin Elmer

2. Polyethylene resin composition The polyethylene resin composition of the present invention (hereinafter also simply referred to as a resin composition) contains the polyethylene resin (A) and the following organic peroxide (B).

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The sheet-like solar cell encapsulant can be produced by a known sheet molding method using a T-die extruder, a calendar molding machine, or the like. For example, a cross-linking agent is added to an ethylene / α-olefin copolymer, and if necessary, a hindered amine light stabilizer, a cross-linking aid, a silane coupling agent, an ultraviolet absorber, an antioxidant, a light stabilizer. An additive such as an agent can be dry-blended in advance and supplied from a hopper of a T-die extruder, and extruded into a sheet at an extrusion temperature of 80 to 150 ° C. In these dry blends, some or all of the additives can be used in the form of a masterbatch. In addition, in T-die extrusion and calendering, some or all of the additive is previously melt-mixed into the amorphous α-olefin copolymer using a single screw extruder, twin screw extruder, Banbury mixer, kneader, etc. Thus obtained resin composition can also be used. The formed sheet is wound around a paper tube for easy storage and transportation. At this time, the sheets may adhere to each other (blocking may occur). If blocking occurs, when the sheet is fed out and used in the next step, it cannot be stably fed out, resulting in a decrease in productivity. Therefore, it is common practice to avoid blocking by roughening the sheet surface or producing an uneven structure.

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

On the other hand, when the solar cell module is manufactured, the sealing material is temporarily applied to the solar cell element or the protective material at a temperature at which the organic peroxide is not substantially decomposed and the sealing material of the present invention is melted. Adhesion is then carried out to raise the temperature, and sufficient adhesion and crosslinking of the ethylene / α-olefin copolymer can be carried out. In this case, the gel in the encapsulant layer is used in order to obtain a solar cell module with good heat resistance having a melting point (DSC method) of the encapsulant layer of 85 ° C. or higher and a storage elastic modulus of 150 ° C. of 10 ³ Pa or higher. Fraction (1 g of sample is immersed in 100 ml of xylene, heated at 110 ° C. for 24 hours, and then filtered through a 40 mesh wire net to measure the mass fraction of unmelted) is 50 to 98%, preferably about 70 to 95% It is better to crosslink so that

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

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

1. Evaluation method of resin physical properties (1) Melt flow rate (MFR)
As described above, the MFR of the ethylene / α-olefin copolymer was measured according to JIS-K6922-2: 1997 appendix (190 ° C., 21.18 N load).
(2) Density As described above, the density of the ethylene / α-olefin copolymer was measured according to JIS-K6922-2: 1997 appendix (23 ° C., in the case of low density polyethylene).
(3) Mz / Mn
As described above, it was measured by GPC.

(4) Number of branches and number of double bonds The number of branches (N) in the polymer is determined by ¹³ C-NMR, the total of vinyl, vinylidene and cis-trans-vinylene, and trisubstituted vinylene is determined by ¹ H-NMR. Measured under the following conditions, the amount of comonomer was determined by the number per 1000 carbons in total of the main chain and the side chain.
Apparatus: Bruker BioSpin Corporation AVANCE III cryo-400MHz
Solvent: o-dichlorobenzene / heavy bromobenzene = 8/2 mixed solution <sample amount>
460mg / 2.3ml
< ^13C -NMR>
・ With 1H decouple and NOE ・ Accumulation times: 256scan
・ Flip angle: 90 °
・ Pulse interval 20 seconds ・ AQ (acquisition time) = 5.45 s D1 (waiting time) = 14.55 s
<1H-NMR>
・ Accumulation count: 1400scan
・ Flip angle: 1.03 °
AQ (loading time) = 1.8 s D1 (waiting time) = 0.01 s

(5) Volume resistivity A 0.7 mm-thick press sheet was cut into a size of 10 cm × 10 cm and measured under the following conditions in accordance with IEC 60093.
Apparatus: Micro Ammeter R8340A manufactured by ADC
Measurement chamber 12704A manufactured by ADC
Temperature: 23 ° C
Applied voltage: 500V

(6) Concentration of boron residue About 10 g of polyethylene resin was collected in a Teflon (registered trademark) container, and nitric acid was added to decompose it with a microwave decomposition apparatus. The decomposition solution was fixed and measured by ICP-MS.
Equipment: ETHOS One type manufactured by Milestone General, NexION300S type manufactured by Perkin Elmer

2. Method for evaluating extruded product (1) HAZE
It measured based on JIS-K7136-2000 using the press sheet of thickness 0.7mm. A press sheet piece was set in a cell filled with liquid paraffin (manufactured by Kanto Chemical) and measured. The press sheet was stored in a hot press machine at 150 ° C. for 30 minutes, and prepared by crosslinking. The smaller the HAZE value, the better.

(2) Light transmittance was measured in accordance with JIS-K7361-1-1997 using a press sheet having a thickness of 0.7 mm. A press sheet piece was set in a cell filled with liquid paraffin (manufactured by Kanto Chemical) and measured. The press sheet was stored in a hot press machine at 150 ° C. for 30 minutes, and prepared by crosslinking. The light transmittance is 80% or more, preferably 85% or more, and more preferably 90% or more.

(3) Crosslinkability and heat resistance (gel fraction 30 minutes /%)
The resulting pellet, in the conditions of 150 ℃ -0kg / cm ^2, was preheated for 1 minute, then 150 ℃ -100kg / cm 29 min pressure in the ^second condition (press forming for 30 minutes at 0.99 ° C.), then, A crosslinked sheet having a thickness of 0.7 mm was produced by cooling for 10 minutes in a cooling press set to 30 ° C. under a pressure of 100 kg / cm ² . The gel fraction of a 0.7 mm thick sheet was evaluated. It can be evaluated that the higher the gel fraction, the more the crosslinking proceeds and the higher the heat resistance. A gel fraction having a gel fraction of 70 wt% or more was designated as a heat resistance evaluation “◯”. As for the gel fraction, about 1 g of the sheet is cut out and weighed accurately, immersed in 100 cc of xylene, treated at 110 ° C. for 24 hours, the residue after filtration is dried and weighed, and divided by the weight before treatment. Calculate the gel fraction.

(4) Mechanical strength (maximum torque)
The resulting pellet, in the conditions of 90 ℃ -0kg / cm ^2, after 3 minutes preheat, (5 minutes press molding at 90 ° C.) 2 minutes under pressure under the conditions of 90 ℃ -100kg / cm ² and, thereafter, An uncrosslinked sheet having a thickness of 1.5 mm was produced by cooling for 5 minutes on a cooling press set at 30 ° C. under a pressure of 100 kg / cm ² . Using this sheet, a torque curve was measured with a curast meter 7 (manufactured by JSR Trading). The measurement was performed at 150 ° C. for 30 minutes in accordance with JIS-K6300-2. The maximum value of the obtained torque data was evaluated.

3. Raw Material Used (1) Polyethylene Resin (A): Ethylene / α-Olefin Copolymer Ethylene / α-olefin copolymer (PE-1, PE-2) produced by the following production method was used in Examples, PE-3, PE-4 was used as a comparative example. The following commercially available ethylene / α-olefin copolymers (PE-5, PE-6) were also used as comparative examples. The physical properties are shown in Table 1.
(PE-5): Mitsui Chemicals Toughmer A-4085S
(PE-6): Exact 8230 manufactured by DEX Platamers

<Method for producing ethylene / α-olefin copolymer>
(I) Polymerization method of PE-1 and PE-2 0.3 mmol of the complex “rac-dimethylsilylenebisindenylhafnium dimethyl” prepared by the method described in JP-A-10-218921 and 0.6 mmol of “ Tris (pentafluorophenyl) borane ”(thermal decomposition temperature at which weight change occurs under N ₂ atmosphere, 166 ° C.) was dissolved in 30 L of toluene to prepare a catalyst solution.
Using a stirred autoclave type continuous reactor having an internal volume of 5.0 L, the pressure in the reactor is maintained at 80 MPa, and ethylene is 37 wt%, propylene is 27 wt%, and 1-hexene is 36 wt% at 55 kg / hr. The raw material gas was continuously supplied at a rate. Moreover, the said catalyst solution was supplied continuously and the polymerization temperature adjusted suitably within the range of 180-230 degreeC, and the ethylene-alpha-olefin copolymer of PE-1 and PE-2 was obtained.

(Ii) Polymerization method of PE-3 and PE-4 In the above (i), 0.6 mmol of N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate was added to the tris (pentafluorophenyl) borane added during the preparation of the catalyst. Polymerization was carried out in the same manner as the polymerization method of (i) above except that it was changed to (thermal decomposition temperature 263 ° C. at which weight change occurs under N ₂ atmosphere), and ethylene / α of PE-3 and PE-4 -Olefin copolymer was obtained.

(2) Organic peroxide: t-butylperoxy 2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi, Luperox TBEC)
(3) Hindered amine light stabilizer: polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (manufactured by BASF, TINUVIN 622LD)
(4) UV absorber: 2-hydroxy-4-n-octoxybenzophenone (manufactured by Sun Chemical Co., Ltd., CYTEC UV531)
(5) Silane coupling agent: γ-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM503)
(6) Antioxidant: n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate (manufactured by BASF, IRGANOX1076)

Example 1
1.0 part by weight of t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi Co., TBEC) as an organic peroxide for 100 parts by weight of polyethylene resin (PE-1), hindered amine light As a stabilizer, 0.05 part by weight of a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (BASF, TINUVIN 622LD), as an ultraviolet absorber, 0.3 part by weight of 2-hydroxy-4-n-octoxybenzophenone (CYTEC UV531 manufactured by Sun Chemical Co., Ltd.), and γ-methacryloxypropyltrimethoxysilane (KBE503 manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent 3 parts by weight, as an antioxidant, n-octadecyl-3- (3 ′, 5′-di-t-butyl -4'-hydroxyphenyl) propionate (IRGANOX1076, manufactured by BASF) was mixed with 0.025 part by weight. This was sufficiently mixed and pelletized using a 40 mmφ single screw extruder under the conditions of a set temperature of 100 ° C. and an extrusion rate (17 kg / hour).
The resulting pellet, in the conditions of 150 ℃ -0kg / cm ^2, after 3 minutes preheat, 150 ℃ -100kg / cm (30 minutes press molding at 0.99 ° C.) 27 minutes pressurization at ² conditions, and then, A crosslinked sheet having a thickness of 0.7 mm was produced by cooling for 10 minutes in a cooling press set to 30 ° C. under a pressure of 100 kg / cm ² . The sheet was measured for HAZE, light transmittance, heat resistance, and mechanical strength.

(Example 2)
In Example 1, a sheet was produced in the same manner as in Example 1 except that PE-2 was used instead of PE-1. The evaluation results are shown in Table 1.

(Comparative Example 1)
In Example 1, a sheet was produced in the same manner as in Example 1 except that PE-3 was used instead of PE-1. The evaluation results are shown in Table 1.

(Comparative Example 2)
In Example 1, a sheet was produced in the same manner as in Example 1 except that PE-4 was used instead of PE-1. The evaluation results are shown in Table 1.

(Comparative Example 3)
In Example 1, a sheet was produced in the same manner as in Example 1 except that PE-5 was used instead of PE-1. The evaluation results are shown in Table 1.

(Comparative Example 4)
In Example 1, a sheet was produced in the same manner as in Example 1 except that PE-6 was used instead of PE-1. The evaluation results are shown in Table 1.

(Evaluation)
As a result, as is apparent from Table 1, in Examples 1 and 2, since the polyethylene resin composition of the present invention was used, the sheet obtained by extrusion molding had good crosslinking characteristics and HAZE. Small, high light transmittance, excellent heat resistance, and suppresses leakage current.
On the other hand, in Comparative Examples 1 and 2, although the crosslinking characteristics, transparency, and heat resistance were good, a leakage current was generated due to the low volume resistivity of the polyethylene resin. In Comparative Examples 3 and 4, although the transparency was good, the heat resistance or mechanical strength was low, and the volume resistivity of the polyethylene resin was low, so that the weather resistance was low and leakage current was generated.

  The polyethylene resin and polyethylene resin composition of the present invention are preferably used as a solar cell encapsulating material because they have high insulation properties, good crosslinking properties, high heat resistance, and excellent transparency and mechanical strength.

Claims (10)

A polyethylene resin (A), which is an ethylene / α-olefin copolymer having the following properties (a1) to (a5):
(A1) While the content rate of the structural unit derived from ethylene is 80-97 mol%, the content rate of the structural unit derived from a C3-C20 alpha olefin is 3-20 mol%.
(A2) MFR (190 ° C., 21.18 N load) is 0.1 to 100 g / 10 minutes (a3) Density is 0.860 to 0.920 g / cm ³
(A4) Volume resistivity measured at a temperature of 23 ° C. and an applied voltage of 500 V is 1.0 × 10 ¹⁶ Ω · cm or more (a5) The boron residue concentration (M) in the resin is 0 <M <1 wtppm The boron residue is a heat history of a boron compound having a thermal decomposition temperature of less than 200 ° C. in which a weight change occurs in an N ₂ atmosphere. 2. The polyethylene resin according to claim 1, wherein the polyethylene resin (A) is an ethylene / α-olefin copolymer having the following property (a6).
(A6) The total amount of vinyl, vinylidene, cis-vinylene, trans-vinylene, trisubstituted-vinylene in the ethylene / α-olefin copolymer is 0.22 (total / total 1000 C) or more (however, vinyl, vinylidene, cis -The number of vinylene, trans-vinylene, and tri-substituted vinylene is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR. The polyethylene resin according to claim 1 or 2, wherein the polyethylene resin (A) is an ethylene / α-olefin copolymer having the following property (a7).
(A7) The number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer and the total amount (V) of vinyl and vinylidene satisfy the relationship of the following formula (1).
Formula (1): N × V ≧ 10
(However, N and V are numbers per 1000 carbon atoms in total of the main chain and side chain measured by NMR.) The polyethylene resin according to claim 3, wherein the polyethylene resin (A) is an ethylene / α-olefin copolymer further having the following property (a8).
(A8) The number of branches (N) due to the comonomer in the ethylene / α-olefin copolymer satisfies the relationship of the following formula (2).
Formula (2): 54 ≦ N
(However, N is the number per 1000 carbon atoms in total of the main chain and side chain measured by NMR.) The polyethylene resin according to any one of claims 1 to 4, wherein the polyethylene resin (A) is an ethylene / α-olefin copolymer further having the following property (a9).
(A9) Ratio (Mz / Mn) of Z average molecular weight (Mz) and number average molecular weight (Mn) obtained by gel permeation chromatography (GPC) is 8.0 or less.   The said polyethylene resin (A) is the ethylene-alpha-olefin copolymer polymerized using the catalyst system containing a metallocene compound and a boron compound, The one in any one of Claims 1-5 characterized by the above-mentioned. Polyethylene resin. The polyethylene resin composition containing the said polyethylene resin (A) in any one of Claims 1-6, and the following component (B).
Component (B): Organic peroxide   The polyethylene resin composition according to claim 7, wherein the content of the component (B) is 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyethylene resin (A).   The solar cell sealing material using the polyethylene resin composition of Claim 7 or 8.   The solar cell module using the solar cell sealing material of Claim 9.