Polymer and solar cell encapsulant using the polymer

Abstract

Provided is a polymer from which an encapsulant excellent in weather resistance and processability can be obtained when being used for an encapsulant for a solar cell. The polymer that has a main chain comprising repeating units represented by formula (1) and repeating units represented by formula (2) and satisfies requirements (a1), (a2), and (a3), ##STR00001##
(a1): the ratio of the number of the repeating units represented by formula (2) to the total number of the carbon atoms that constitute the main chain of the polymer is from 3.8% to 7.5%;
(a2): the ratio X represented by formula (3) is from 82% to 100%;
X=100A/B(3)
(a3): the polymer has a melting point of 42 C. to 90 C. as measured with a differential scanning calorimeter.

Claims

1. A polymer that has a main chain comprising repeating units represented by formula (1) and repeating units represented by formula (2) and satisfies requirements (a1), (a2), and (a3), ##STR00009## wherein R.sup.1 represents hydrogen, a methyl group, or an ethyl group, and R.sup.2 represents an acetoxy group, a methoxycarbonyl group, an ethoxycarbonyl group, or a tert-butoxycarbonyl group; (a1): the ratio of the number of the repeating units represented by formula (2) to the total number of the carbon atoms that constitute the main chain of the polymer is from 4.0% to 7.5%; (a2): the ratio X represented by formula (3) is from 82% to 100%;
X=100A/B(3) where A represents the total number of the carbon atoms of the carbonyl groups of the R.sup.2s of all the repeating units that satisfy the following requirement (a2-1) and are represented by formula (2), (a2-1): no functional group represented by the following formula (A), (B), (C), (D), (E) or (F) is bonded to any of the carbon atoms C.sup.1, C.sup.2, and C.sup.3, where C.sup.1 is a carbon atom that bonds to a repeating unit represented by formula (2), C.sup.2 is a carbon atom that bonds to C.sup.1, and C.sup.3 that bonds to C.sup.2, ##STR00010## wherein R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 each independently represent an alkyl group or hydrogen; and B is the total number of the carbon atoms of the carbonyl groups of the R.sup.2s of all the repeating units represented by formula (2); and (a3): the polymer has a melting point of 42 C. to 90 C. as measured with a differential scanning calorimeter.

2. The polymer according to claim 1, wherein the main chain further comprises repeating units represented by formula (4), ##STR00011##

3. The polymer according to claim 1, wherein the polymer has a gel fraction of 40% by mass or more where the mass of the polymer is taken as 100% by mass.

4. A solar cell encapsulant comprising the polymer according to claim 1.

5. The polymer according to claim 2, wherein the polymer has a gel fraction of 40% by mass or more where the mass of the polymer is taken as 100% by mass.

6. A solar cell encapsulant comprising the polymer according to claim 2.

7. A solar cell encapsulant comprising the polymer according to claim 3.

Description

EXAMPLES

(1) The present invention is described concretely below with reference to Examples and Comparative Examples.

(2) (Procedures of Measurement and Evaluation of Physical Properties)

(3) Physical properties in Examples and Comparative Examples were measured by the following methods.

(4) (1) the Ratio (Unit: %) of the Number of the Repeating Units Represented by Formula (2) to the Total Number of the Carbon Atoms Constituting the Polymer Main Chain

(5) A .sup.1H-NMR spectrum of a solution prepared by dissolving a polymer in ortho-dichlorobenzene was measured with a nuclear magnetic resonance apparatus. The polymers of Examples and Comparative Examples are each a polymer wherein R.sup.1 of formula (2) is hydrogen and R.sup.2 is an acetoxy group.

(6) Using the resulting .sup.1H-NMR spectrum, the ratio of the number of the repeating units represented by formula (2) to the total number of the carbon atoms constituting the polymer main chain was calculated from the following formula (6).
Y=1002/(2+)(6)

(7) In formula (6), Y is the ratio of the number of the repeating units represented by formula (2) wherein R.sup.1 is hydrogen and R.sup.2 is an acetoxy group to the total number of the carbon atoms constituting the main chain of the polymer.

(8) is the area of a peak derived from the hydrogen that is R.sup.1 in formula (2). This peak is observed near 4.9 ppm in a .sup.1H-NMR spectrum of a polymer.

(9) is the sum total of the areas of all the peaks observed near 0.7 to 2.5 ppm in a .sup.1H-NMR spectrum of a polymer. Specifically, is the sum total of the area of the peak derived from the hydrogen contained in formula (1) and the area of the peak derived from the hydrogen contained in the acetoxy group, which is R.sup.2 of formula (2).

(10) is the number of the hydrogen contained in the acetoxy group, which is R.sup.2 of formula (2). Since R.sup.2 is an acetoxy group, is 3.

(11) (2) Ratio X (Unit: %)

(12) A .sup.13C-NMR spectrum of a solution prepared by dissolving a polymer in 1,1,2,2-tetrachloroethane d2 was measured with a nuclear magnetic resonance apparatus under the following conditions.

(13) <Measurement Conditions>

(14) Instrument: AVANCE600 manufactured by Bruker

(15) Measurement probe: 10-mm cryoprobe

(16) Measurement solvent: 1,1,2,2-tetrachloroethane d2

(17) Measurement temperature: 130 C.

(18) Measurement method: proton decoupling method

(19) Pulse width: 45 degrees

(20) Pulse repetition time: 4 seconds

(21) Measurement standard: 1,1,2,2-tetrachloroethane d2 (74.2 ppm)

(22) Transients: 256

(23) Ratio X (%) was calculated from the following formula (3) using the .sup.13C-NMR spectrum produced.
X=100A/(A+B)(3)
wherein A represents the total number of the carbon atoms of the carbonyl groups of the R.sup.2s of all the repeating units that satisfy the following requirement (a2-1) and are represented by formula (2),
(a2-1): no functional group represented by the following formula (A), (B), (C), (D), (E) or (F) is bonded to any of the carbon atoms C.sup.1, C.sup.2, and C.sup.3, where C.sup.1 is a carbon atom that bonds to a repeating unit represented by formula (2), C.sup.2 is a carbon atom that bonds to C.sup.1, and C.sup.3 that bonds to C.sup.2, and B is the total number of the carbon atoms of the carbonyl groups of the R.sup.2s of all the repeating units represented by formula (2).

(24) A in formula (3) is the area of a peak observed at 170.4 ppm. B is the area of a peak observed at 170.2 ppm.

(25) (3) the Ratio (Unit: %) of the Number of the Carbon Atoms of the Repeating Units Represented by Formula (4) to the Total Number of the Carbon Atoms Constituting the Polymer Main Chain

(26) Using the .sup.13C-NMR spectrum of the polymer used for calculating X, the ratio of the number of the carbon atoms of the repeating units represented by formula (4) to the total number of the carbon atoms constituting the polymer main chain was calculated from the following formula (10).
Z=100F/{D(E1)C}(10)

(27) In formula (10), Z is the ratio of the number of the carbon atoms of the repeating units represented by formula (4) to the total number of the carbon atoms constituting the main chain of the polymer.

(28) C is the area of a peak derived from the carbon atom of the carbonyl group of R.sup.2 of formula (2) observed at between 168 ppm to about 180 ppm in a .sup.13C-NMR spectrum of the polymer.

(29) D is the sum total of the areas of all the peaks different from the peak derived from 1,1,2,2-tetrachloroethane d2 (the peak observed at 74.2 ppm) in a .sup.13C-NMR spectrum of the polymer.

(30) E is the number of the carbon atoms contained in formula (2).

(31) F is the area of a peak derived from the carbon atom of formula (4) observed at between 120 ppm to about 140 ppm in a .sup.13C-NMR spectrum of the polymer.

(32) (4) Melting Point (Unit: C.)

(33) A polymer was pressed with a pressure of 10 MPa for 5 minutes with a hot presser at 150 C., then cooled for 5 minutes with a cooling presser at 30 C., thereby being shaped into a sheet of about 100 m in thickness. Subsequently, about 10 mg of sample was cut from the sheet and sealed in an aluminum pan. Then, the aluminum pan with the sample sealed therein was (1) held at 150 C. for 5 minutes, (2) cooled from 150 C. to 0 C. at a rate of 5 C./minute, (3) held at 20 C. for 2 minutes, (4) heated from 20 C. to 150 C. at a rate of 5 C./minute by using a differential scanning calorimeter (a differential scanning calorimeter DSC-7 manufactured by PerkinElmer Inc.), and a melting curve produced during (4) was measured. From the melting curve, the temperature at the top of the melting peak greatest in peak height among the melting peaks observed between 5 C. and the melting completion temperature (that is, the temperature at which the melting curve returns to its base line on the higher temperature side) was determined and this was taken as a melting point.

(34) (5) Weight Average Molecular Weight (Mw, Unit: g/Mol), Number Average Molecular Weight (Mn, Unit: g/Mol), Molecular Weight Distribution (Mw/Mn, Unitless)

(35) The weight average molecular weight (Mw) of a polymer was determined by multiplying the polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) by the Q factor ratio of polyethylene to polystyrene (17.7/41.3). The number average molecular weight (Mn) of a polymer was determined by multiplying the polystyrene-equivalent number average molecular weight as measured by gel permeation chromatography (GPC) by the Q factor ratio of polyethylene to polystyrene (17.7/41.3). Mw/Mn is the value calculated by dividing Mw by Mn. The measurement conditions used in GPC were as follows.

(36) (1) Instrument: Waters150C, manufactured by Waters

(37) (2) Separation column: TOSOH TSKgel GMH-HT

(38) (3) Measurement temperature: 140 C.

(39) (4) Carrier: ortho-dichlorobenzene

(40) (5) Flow rate: 1.0 mL/min

(41) (6) Injection amount: 500 L

(42) (7) Sample concentration: 5 mg/5 ml-ortho-dichlorobenzene

(43) (8) Detector: differential refraction

(44) (6) Gel Fraction (Unit: % by Mass)

(45) About 1 g of crosslinked sheet was used as a sample. The sample was put in a basket made of 100-mesh wire gauze so that the sample might not leak out. The weight of the basket containing the sample was measured. The basket containing the sample was immersed in 100-ml xylene solvent and then heated for 8 hours while refluxing the xylene solvent. Subsequently, the basket containing the sample was raised from the xylene and then dried. The weight of the basket containing the dried sample was measured. From the weight measured before the heating and the weight measured after the drying was calculated the mass fraction of the components that failed to dissolve in xylene (the mass of the crosslinked sheet used was taken as 100% by mass).

(46) (7) Weathering Test 1 (Acetoxy Group Survival Ratio, Unit: %)

(47) The weather resistance of an uncrosslinked sheet was evaluated on the basis of the ratio of the number of the acetoxy groups contained in the sheet after light irradiation to the number of the acetoxy groups contained in the sheet before the light irradiation (hereinafter sometimes described as acetoxy group survival ratio). Specifically, the measurement was conducted as follows.

(48) Two uncrosslinked sheets were put into a Daipla Metal Weather (manufactured by Dipla Wintes Co., Ltd.) and then were irradiated with light with a metal halide lamp (irradiation intensity: 145 mW/cm.sup.2 at 295 nm to 430 nm, atmosphere: black panel temperature=63 C./humidity=50% RH). Light irradiation was applied for 48 hours for one sheet and light irradiation was applied for 96 hours for the other sheet.

(49) The content of acetoxy groups was calculated by the following method. An infrared absorption spectrum of an uncrosslinked sheet before light irradiation and that of the uncrosslinked sheet after the light irradiation were measured, and the absorbance of a characteristic absorption of a carbonyl group (CO) that appeared at or around 3460 cm.sup.1 was corrected with the thickness of the sheet and the content of acetoxy groups of each of the uncrosslinked sheets was determined using a calibration curve. The content of acetoxy groups of the sheet after the light irradiation determined when the content of acetoxy groups of the sheet before the light irradiation was taken as 100% was defined as an acetoxy group survival ratio. The larger the acetoxy group survival ratio, the better the weather resistance.

(50) (8) Weathering Test 2 (Survival Ratio of Strength at Break, Survival Ratio of Elongation at Break, Unit: %)

(51) The weather resistance of a crosslinked sheet was evaluated on the basis of the ratio of the strength at break of a sheet after light irradiation to the strength at break of the sheet before the light irradiation (hereinafter sometimes described as survival ratio of strength at break) and the ratio of the elongation at break of a sheet after light irradiation to the elongation at break of the sheet before the light irradiation (hereinafter sometimes described as survival ratio of elongation at break). Specifically, the measurement was conducted as follows.

(52) Two crosslinked sheets were put into a Daipla Metal Weather (manufactured by Dipla Wintes Co., Ltd.) and then were irradiated with light with a metal halide lamp (irradiation intensity: 145 mW/cm.sup.2 at 295 nm to 430 nm, atmosphere: black panel temperature=63 C./humidity=50% RH). Light irradiation was applied for 48 hours for one sheet and light irradiation was applied for 96 hours for the other sheet.

(53) A tensile test of a sheet before light irradiation and the sheet after the light irradiation was performed under the following conditions. Specimens were taken from each of the sheets using a No. 6 dumbbell-shaped form. Elongation at break and strength at break were measured by pulling the specimens at a chuck span of 65 mm and a tensile rate of 500 mm/minute according to JIS K 6251 with a tensile tester (STA-1225, manufactured by ORIENTEC Co., Ltd.) under an atmosphere of 23 C. and 50% RH. The strength at break of a sheet after light irradiation where the strength at break of the sheet before the light irradiation was taken as 100% was defined as strength at break survival ratio, and the elongation at break of a sheet after light irradiation where the elongation at break of the sheet before the light irradiation was taken as 100% was defined as elongation at break survival ratio. The larger the strength at break survival ratio or the elongation at break survival ratio, the better the weather resistance.

(54) (9) Light Transmittance of Polymer (Unit: %)

(55) A polymer was pressed with a pressure of 10 MPa for 5 minutes with a hot presser at 150 C., then cooled for 5 minutes with a cooling presser at 30 C., thereby being shaped into a sheet of about 500 m in thickness. The light transmittances within a wavelength range of 400 nm to 1200 nm were measured from a light transmission spectrum of the sheet in its thickness direction with a spectrophotometer (UV-3150, manufactured by Shimadzu Corporation), and the average thereof was calculated.

Example 1

Production of 5-acetoxy-1-cyclooctene

(56) Under an argon flow, 1,5-cyclooctadiene (1131 g, 10.455 mol, produced by Tokyo Chemical Industry Co., Ltd.) was fed into a 60-liter flask and cooled to 11 C., and then a solution of metachloroperbenzoic acid (1859 g, 65% purity, 6.97 mol) in chloroform (20 liters, produced by Wako Pure Chemical Industries, Ltd.) was dropped over about 2 hours at a temperature of 20 C. or lower. The mixture within the flask was stirred at room temperature for about 15 hours.

(57) After the completion of the reaction, the reaction liquid was filtered. The filtrate was washed with 10% aqueous NaHSO.sub.3 solution (10 liters, twice), saturated aqueous NaHCO.sub.3 solution (10 liters), and saturated aqueous NaCl solution (10 liters). The washed organic layer was concentrated under reduced pressure.

(58) The resulting crude product was purified by silica gel column chromatography (hexane/ethyl acetate=10/1, silica gel N60, produce by Kanto Chemical Co., Inc.), affording colorless, oily 1,2-epoxy-5-cyclooctene.

(59) Under an argon flow, 1,2-epoxy-5-cyclooctene (730 g, 5.87 mol) and THF (9 liters) were fed into a 20-liter flask and cooled to 5 C. Subsequently, LiAlH.sub.4 (111 g, 2.94 mol, produced by Wako Pure Chemical Industries, Ltd.) was added over about 2 hours, and then the mixture within the flask was stirred at 26 C. for 2 days.

(60) After the completion of the reaction, the flask was cooled with ice water, followed by slow addition of water (500 ml), and then the mixture within the flask was filtered. The filtrate was concentrated under reduced pressure, and then the resulting crude product was purified by silica gel chromatography (hexane/ethyl acetate=3/1, silica gel N60, produced by Kanto Chemical Co., Inc.), affording colorless, oily 5-hydroxy-1-cyclooctene.

(61) Under an argon flow, 5-hydroxy-1-cyclooctene (720 g, 5.55 mol) and pyridine (8.2 liters) were fed into a 20-liter flask and cooled to 2 C. Subsequently, acetyl chloride (988 g, 12.20 mol) was dropped over one hour, and the mixture within the flask was stirred at room temperature for one hour. After the completion of the reaction, the reaction product was diluted with diethyl ether (5 liters), water (3 liters) was added, and then the mixture within the flask was partitioned. The water layer was extracted with diethyl ether (10 liters, twice), and the entire organic layer was washed with 1N aqueous hydrochloric acid solution (5 liters), saturated aqueous NaHCO.sub.3 solution (10 liters), and saturated aqueous NaCl solution (10 liters). The washed organic layer was dehydrated (with MgSO.sub.4) and filtered, and the filtrate was concentrated under a reduced pressure. The resulting crude product was purified by silica gel column chromatography (hexane/ethyl acetate=20/1, Silica Gel N60, produced by Kanto Chemical Co., Inc.) and then distilled under reduced pressure (63 to 65 C., 0.4 kPa), affording colorless, oily 5-acetoxy-1-cyclooctene (758 g, 80%).

(62) <Production of Polymer (1)>

(63) Benzylidene-bis(tricyclohexylphosphine)dichlororuthenium (complex, 154 mg, produced by Aldrich) weighed under a nitrogen atmosphere was put into a 500 ml glass eggplant flask, which was then sealed with a three way stopcock. Nitrogen-bubbled ortho-dichlorobenzene (solvent, 64 ml), cyclooctene (monomer, 5.9 ml, produced by Tokyo Chemical Industry Co., Ltd.) and 5-acetoxy-1-cyclooctene (monomer, 5.0 ml) were dropped into the eggplant flask while rotating a stir bar within the eggplant flask. Then, the eggplant flask was put into an oil bath set at a reaction temperature (60 C.) and ring-opening metathesis polymerization was performed for 2 hours. Subsequently, the polymerization solution was dropped into methanol to perform reprecipitation, affording polymer (1). The ratio of the number of the carbon atoms in the repeating units represented by formula (4) to the total number of the carbon atoms constituting the main chain of the polymer (1) was 11.2%.

(64) The polymer (1) obtained via the reprecipitation was vacuum dried at 80 C. for 2 hours and then dissolved in ortho-dichlorobenzene (solvent, 80 ml). p-Toluenesulfonylhydrazide was dissolved in the solution and a reaction was carried out at 130 C. for 3 hours to hydrogenate the polymer (1), affording polymer (1). The results of evaluation of the resulting polymer (1) are shown in Table 1.

(65) <Production of Uncrosslinked Sheet (1)>

(66) The resulting polymer (1) was pressed with a pressure of 2 MPa for 5 minutes with a hot presser at 90 C., then cooled for 5 minutes with a cooling presser at 30 C., thereby preparing an uncrosslinked sheet (1) of about 500 m in thickness. The results of evaluation of uncrosslinked sheet (1) are shown in Table 2.

Example 2

Production of Polymer (2)

(67) Benzylidene-bis(tricyclohexylphosphine)dichlororuthenium (complex, 175 mg) weighed under a nitrogen atmosphere was put into a 500 ml glass eggplant flask, which was then sealed with a three way stopcock. Nitrogen-bubbled ortho-dichlorobenzene (solvent, 62 ml), cyclooctene (monomer, 6.1 ml) and 5-acetoxy-1-cyclooctene (monomer, 7.1 ml) were dropped into the eggplant flask while rotating a stir bar within the eggplant flask. Then, the same treatment as Example 1 was performed, affording polymer (2). The results of evaluation of the resulting polymer (2) are shown in Table 1.

(68) <Preparation of Crosslinked Sheet (2)>

(69) One hundred parts by weight of polymer (2) was impregnated with 0.4 parts by weight of tert-butylperoxy-2-ethylhexyl carbonate (PERBUTYL E, produced by NOF Corporation, one-hour half-life temperature: 121 C.; an organic peroxide as a crosslinking agent) and 0.9 parts by mass of triallyl isocyanurate (TAIC, produced by Tokyo Chemical Industry Co., Ltd.; auxiliary crosslinking agent). Three hundred parts by weight toluene was added to the polymer (2) impregnated with the organic peroxide and the auxiliary crosslinking agent, and the polymer (2) was dissolved homogeneously in the toluene at 80 C. The solution was stirred for 5 minutes, affording a mixture. Then, the mixture was vacuum dried at 40 C. for 4 hours, affording polymer composition (2). Subsequently, in order to perform a crosslinking reaction and sheet forming, the above polymer composition (2) was pressed with a pressure of 10 MPa for 5 minutes with a hot presser at 90 C., then pressed with a pressure of 10 MPa for 20 minutes with a hot presser at 150 C., and then cooled for 5 minutes with a cooling presser at 30 C., thereby preparing a crosslinked sheet (2) of about 300 m in thickness. The results of evaluation of crosslinked sheet (2) are shown in Table 3.

Example 3

Production of 5-methoxycarbonyl-1-cyclooctene

(70) A 1-liter autoclave was charged with tert-butanol (144 g, 1.94 mol), PdCl.sub.2 (2.9 g, 0.016 mol), PPh.sub.3 (21.0 g, 0.08 mol), 1,5-cyclooctadiene (336 g, 3.11 mol, Tokyo Chemical Industry Co., Ltd.), and toluene (184 ml), and CO replacement was performed three times. Then, the contents were allowed to react at 90 to 92 C. for 4 days under CO pressurization (40 MPa). During this operation, CO pressurization (adjusted to 40 MPa) was performed every 24 hours.

(71) After the completion of the reaction, the reaction liquid was filtered and the resulting filtrate was concentrated under reduced pressure, and then the residue was purified by silica gel chromatography (hexane/ethyl acetate=10/1 and then 5/1, Silica Gel N60, Kanto Chemical Co., Inc.), affording colorless oily 5-(tert-butoxy)-1-cyclooctene.

(72) 5-(tert-butoxy)-1-cyclooctene (216 g, 1.03 mol) and trifluoroacetic acid (450 ml) were charged into a 2-liter flask and then stirred at room temperature for 2 days. After the completion of the reaction, the reaction liquid was poured into a water (450 ml)-ethanol (1800 ml) mixed liquid and the resulting liquid was adjusted to pH4 with saturated sodium bicarbonate water. The resulting mixed liquid was extracted with diethyl ether (5 liters5 times) and the extract was concentrated under reduced pressure.

(73) The resulting residue was purified by silica gel chromatography (hexane/ethyl acetate=3/1, Silica Gel N60, Kanto Chemical Co., Inc.), affording white crystalline 5-methoxycarbonyl-1-cyclooctene.

(74) <Production of Polymer (7)>

(75) Benzylidene-bis(tricyclohexylphosphine)dichlororuthenium (complex, 314 mg) weighed under a nitrogen atmosphere was put into a 500 ml glass eggplant flask, which was then sealed with a three way stopcock. Nitrogen-bubbled ortho-dichlorobenzene (solvent, 120 ml), cyclooctene (monomer, 11.0 ml) and 5-methoxycarbonyl-1-cyclooctene (monomer, 12.8 ml) were dropped into the eggplant flask while rotating a stir bar within the eggplant flask. Then, the same treatment as Example 1 was performed, affording polymer (7). The results of evaluation of the resulting polymer (7) are shown in Table 4.

(76) <Preparation of Crosslinked Sheet>

(77) One hundred parts by weight of polymer (7) was impregnated with 1.0 part by weight (crosslinking condition 1) or 2.0 parts by weight (crosslinking condition 2) of tert-butylperoxy-2-ethylhexyl carbonate (PERBUTYL E, produced by NOF Corporation, one-hour half-life temperature: 121 C.; an organic peroxide as a crosslinking agent) and 0.5 parts by mass of -methacryloxypropyltrimethoxysilane (A-174, produced by Momentive Performance Materials, Inc.; silane coupling agent). The polymer (7) impregnated with the organic peroxide and the auxiliary crosslinking agent was pressed with a pressure of 10 MPa for 5 minutes with a hot presser at 90 C., then pressed with a pressure of 10 MPa for 20 minutes with a hot presser at 150 C., and then cooled for 5 minutes with a cooling presser at 30 C., thereby preparing a crosslinked sheet of about 500 m in thickness. The results of evaluation of the crosslinked sheet are shown in Table 4.

Comparative Example 1

Ethylene-Vinyl Acetate Copolymer (3)

(78) Measurement of physical properties and preparation and evaluation of an uncrosslinked sheet were carried out in the same way as Example 1 except that a commercially available ethylene-vinyl acetate copolymer (K2010, produced by Sumitomo Chemical Co., Ltd.) was used as a polymer. The results of evaluation are shown in Tables 1 and 2.

Comparative Example 2

Ethylene-Vinyl Acetate Copolymer (4)

(79) Measurement of physical properties and preparation and evaluation of a crosslinked sheet were carried out in the same way as Example 2 except that a commercially available ethylene-vinyl acetate copolymer (KA-40, produced by Sumitomo Chemical Co., Ltd.) was used as a polymer. The results of evaluation are shown in Tables 1 and 3.

Comparative Example 3

Polymer (5)

Production of Polymer (5)

(80) Benzylidene-bis(tricyclohexylphosphine)dichlororuthenium (complex, 202 mg) weighed under a nitrogen atmosphere was put into a 500 ml glass eggplant flask, which was then sealed with a three way stopcock. Nitrogen-bubbled ortho-dichlorobenzene (solvent, 61 ml), cyclooctene (monomer, 9.8 ml) and 5-acetoxy-1-cyclooctene (monomer, 4.3 ml) were dropped into the eggplant flask while rotating a stir bar within the eggplant flask. Then, the same treatment as Example 1 was performed, affording polymer (5). The results of evaluation of the resulting polymer (5) are shown in Table 1.

Comparative Example 4

Polymer (6)

Production of Polymer (6)

(81) Benzylidene-bis(tricyclohexylphosphine)dichlororuthenium (complex, 124 mg) weighed under a nitrogen atmosphere was put into a 500 ml glass eggplant flask, which was then sealed with a three way stopcock. Nitrogen-bubbled ortho-dichlorobenzene (solvent, 71 ml) and 5-acetoxy-1-cyclooctene (monomer, 11 ml) were dropped into the eggplant flask while rotating a stir bar within the eggplant flask. Then, the same treatment as Example 1 was performed, affording polymer (5). The results of evaluation of the resulting polymer (5) are shown in Table 1.

Comparative Example 5

Ethylene-Methyl Acrylate Copolymer (7)

(82) Measurement of physical properties and preparation and evaluation of an uncrosslinked sheet were carried out in the same way as Example 3 except that a commercially available ethylene-methyl acrylate copolymer pellet (CG4002, produced by Sumitomo Chemical Co., Ltd.) was used as a polymer. The results of evaluation are shown in Table 4.

(83) TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 1 2 3 4 Resin Polymer (1) Polymer (2) Ethylene- Ethylene- Polymer (5) Polymer (6) vinyl acetate vinyl acetate copolymer (3) copolymer (4) The ratio of the number of % 4.4 5.4 4.7 5.6 2.4 10.2 the repeating units represented by formula (2) to the total number of the carbon atoms constituting the polymer main chain X % 100 100 80 77 100 100 The ratio of the number of % 0 0 0 0 the repeating units represented by formula (4) to the total number of the carbon atoms constituting the polymer main chain Melting point C. 65.8 60.0 76.9 66.6 89.0 There were no peaks at 5 C. or higher. Number average molecular g/mol 40200 33800 22700 17400 40000 44800 weight (Mn) Weight average molecular g/mol 86300 59300 85300 63900 65300 70300 weight (Mw) Mw/Mn 2.2 1.8 3.7 3.7 1.6 1.6 Light transmittance % 87 89 92 92

(84) TABLE-US-00002 TABLE 2 Comparative Example 1 Example 1 Survival ratio of acetoxy group % 98.5 98.0 (After 48-hour light irradiation) Survival ratio of acetoxy group % 97.3 96.7 (After 96-hour light irradiation)

(85) TABLE-US-00003 TABLE 3 Comparative Example 2 Example 2 Survival ratio of strength at break % 33 28 (After 48-hour light irradiation) Survival ratio of strength at break % 9 8 (After 96-hour light irradiation) Survival ratio of elongation at % 85 71 break (After 48-hour light irradiation) Survival ratio of elongation at % 31 11 break (After 96-hour light irradiation) Gel fraction % by 54 58 mass

(86) TABLE-US-00004 TABLE 4 Comparative Example 3 Example 5 Resin Polymer (7) Polymer (8) The ratio of the number of % 4.8 3.9 the repeating units represented by formula (2) to the total number of the carbon atoms constituting the polymer main chain X % 100 69 The ratio of the number of mol % 0 the repeating units represented by formula (4) to the total number of the carbon atoms constituting the polymer main chain Melting point C. 49.5 67.7 Number average molecular g/mol 41100 27300 weight (Mn) Weight average molecular g/mol 79700 89900 weight (Mw) Mw/Mn 1.9 3.3 Gel fraction: Condition 1 % 81 63 Gel fraction: Condition 2 % 87 81

INDUSTRIAL APPLICABILITY

(87) The use of the polymer of the present invention makes it possible to produce a solar cell encapsulant excellent in weather resistance. The polymer of the present invention can be used suitably for the field of solar cell encapsulants.