ETHYLENE-ALPHA-OLEFIN-NONCONJUGATED POLYENE COPOLYMER RUBBER AND RUBBER COMPOSITION

Abstract

Disclosed is an ethylene-α-olefin-nonconjugated polyene copolymer rubber satisfying the following requirements (A) and (B): (A) A proportion of a cyclohexane insoluble component at 25° C. is from 0.3% to 50% by mass with respect to a mass of the ethylene-α-olefin-nonconjugated polyene copolymer rubber; and (B) A tan δ ratio calculated by the following equation:

tan δ ratio=tan δ (100° C., 5 cpm)/tan δ (100° C., 1000 cpm)

is from 3.0 to 20. The tan δ (100° C., 5 cpm) and tan δ (100° C., 1000 cpm) are a loss tangent at 100° C. and a frequency of 5 cpm and a loss tangent at 100° C. and a frequency of 1000 cpm, respectively.

Claims

1. An ethylene-α-olefin-nonconjugated polyene copolymer rubber satisfying the following requirements (A) and (B): (A) a proportion of a cyclohexane insoluble component at 25° C. is from 0.3% to 50% by mass with respect to a mass of the ethylene-α-olefin-nonconjugated polyene copolymer rubber; and (B) a tan δ ratio calculated by the following equation:
tan δ ratio=tan δ (100° C., 5 cpm)/tan δ (100° C., 1000 cpm) is from 3.0 to 20, wherein tan δ (100° C., 5 cpm) and tan δ (100° C., 1000 cpm) are a loss tangent at 100° C. and a frequency of 5 cpm and a loss tangent at 100° C. and a frequency of 1000 cpm, respectively.

2. The ethylene-α-olefin-nonconjugated polyene copolymer rubber according to claim 1, wherein a content of an ethylene unit is from 50% to 90% by mass with respect to a total amount of the ethylene unit, an α-olefin unit and a nonconjugated polyene unit.

3. A rubber composition comprising the ethylene-α-olefin-nonconjugated polyene copolymer rubber according to claim 1.

Description

EXAMPLES

[0098] Hereinafter, the present invention will be more specifically described with reference to Examples. However, the present invention is not limited to the following Examples.

[0099] 1. Synthesis of ethylene-α-olefin-nonconjugated polyene copolymer rubber

Example 1

[0100] Into a first polymerization tank which was made of stainless steel and equipped with a stirrer, hexane was supplied at a velocity of 829.0 g/(hr L), ethylene at a velocity of 39.3 g/(hr L), and propylene at a velocity of 11.7 g/(hr L) per unit time and unit volume of the polymerization tank. Into the first polymerization tank, VOCl.sub.3 was supplied at a velocity of 36.2 mg/(hr L), ethylaluminum sesquichloride (EASC) at a velocity of 144.9 mg/(hr L), and hydrogen at a velocity of 0.11 NL/(hr L). Into the first polymerization tank, 5-ethylidene-2-norbornene was further supplied at a velocity of 2.9 g/(hr L). The temperature of the first polymerization tank was kept at 50° C.

[0101] The polymerization solution withdrawn from the first polymerization tank was supplied into a second polymerization tank which was made of stainless steel and equipped with a stirrer and had the same volume as that of the first polymerization tank. Subsequently, into the second polymerization tank, hexane was supplied at a velocity of 412.5 g/(hr L), ethylene at a velocity of 19.7 g/(hr L), and propylene at a velocity of 5.8 g/(hr L) per unit time and unit volume of the polymerization tank. Into the second polymerization tank, VOCl.sub.3 was supplied at a velocity of 19.4 mg/(hr L) and ethylaluminum sesquichloride (EASC) at a velocity of 38.8 mg/(hr L). Into the second polymerization tank, 5-ethylidene-2-norbornene was further supplied at a velocity of 1.5 g/(hr L). The temperature of the second polymerization tank was kept at 51° C. In the second polymerization tank, ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber was produced at 81 g/(hr L) per unit time and unit volume of the polymerization tank. The copolymer rubber recovered from the polymerization solution was dried to obtain a solid copolymer rubber.

Comparative Examples 1 to 3

[0102] Ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber or ethylene-propylene-dicyclopentadiene-5-ethylidene-2-norbornene copolymer rubber was synthesized in the same manner as in Example 1 except that the kinds and amounts of the respective components supplied were changed as described in Table 1. In Comparative Example 1, ethanol was supplied into the first polymerization tank and the second polymerization tank. In Comparative Example 3, dicyclopentadiene was further supplied into the first polymerization tank and the second polymerization tank.

TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 1 Ex. 2 Ex. 3 First polymerization tank Hexane g/hr .Math. L 829.0 242.4 228.0 727.9 Propylene g/hr .Math. L 11.7 11.6 10.5 7.4 Ethylene g/hr .Math. L 39.3 17.4 18.4 33.8 VOCl.sub.3 mg/hr .Math. L 36.2 26.9 37.4 27.2 EASC mg/hr .Math. L 144.9 153.1 186.8 108.9 Ethanol mg/hr .Math. L 0 12.9 0 0 Hydrogen NL/hr .Math. L 0.11 0.068 0.033 0.24 Dicyclopentadiene mg/hr .Math. L 0 0 0 0.44 5-Ethylidene- g/hr .Math. L 2.9 1.4 1.6 2.5 2-norbornene Polymerization ° C. 50 44 48 50 temperature Second polymerization tank Hexane g/hr .Math. L 412.5 106.1 98.8 361.4 Propylene g/hr .Math. L 5.8 5.8 5.2 3.7 Ethylene g/hr .Math. L 19.7 8.7 9.2 16.9 VOCl.sub.3 mg/hr .Math. L 19.4 15.5 28.8 13.4 EASC g/hr .Math. L 38.8 88.4 115.2 26.8 Ethanol mg/hr .Math. L 0 7.4 0 0 Hydrogen NL/hr .Math. L 0 0 0 0 Dicyclopentadiene mg/hr .Math. L 0 0 0 0.22 5-Ethylidene- g/hr .Math. L 1.5 0.68 0.78 1.3 2-norbornene Polymerization ° C. 51 47 50 51 temperature Produced amount g/hr .Math. L 81 45 45 66

2. Evaluation

(1) Intrinsic Viscosity [η]

[0103] The reduced viscosity (viscosity number) of a copolymer solution of which the concentration was known was measured in tetralin at 135° C. by using an Ubbelohde viscometer. The intrinsic viscosity of the copolymer rubber was determined from the measurement results according to the calculation method described in “Koubunshi Youeki, Koubunshi Zikkengaku 11 (Polymer Solutions and Polymer Experiments 11)” (1982, published by Kyoritsu Shuppan Co., Ltd.), page 491.

[0104] (2) Content of Ethylene Unit and Content of Propylene Unit

[0105] The ethylene-α-olefin-nonconjugated polyene copolymer rubber was molded to produce a film having a thickness of about 0.1 mm by using a hot press machine. The infrared absorption spectrum of the film was measured by using an infrared spectrophotometer (IR-810 manufactured by JASCO Corporation). The content of ethylene unit and the content of propylene unit with respect to the total amount of the ethylene unit, the propylene unit and the nonconjugated polyene unit were determined from the infrared absorption spectrum obtained according to the method described in the reference literatures (“Characterization of polyethylene by infrared absorption spectrum by Takayama”, Usami et al. or Die Makromolekulare Chemie, 177, 461 (1976) by Mc Rae, M. A., Maddam S, W. F. et al.).

[0106] (3) Iodine Value

[0107] Three types of ethylene-propylene-5-ethylidene-2-norbornene copolymer rubbers having different iodine known values in accordance with “JIS K0070-1992 6. Iodine Value” were each molded by a hot press machine to produce films having a thickness of about 0.2 mm The infrared absorption spectrum of each film was measured by an infrared spectrophotometer (IR-700 manufactured by JASCO Corporation). Transmittances of a peak derived from 5-ethylidene-2-norbornene (absorption peak at 1686 cm.sup.−1) and a base peak (absorption peak at 1664 to 1674 cm.sup.−1) for each film were obtained from the obtained infrared absorption spectrum, and the IR index was calculated by the following formula (I). A is the transmittance of the base peak, B is the transmittance of the peak derived from 5-ethylidene-2-norbornene, and D (mm) is the thickness of the film.

IR index=Log(A/B)/D   formula (I)

[0108] A calibration curve of iodine values represented by the following formula (II) was obtained from the IR index and the above-described known iodine values. α and β in the formula (II) are each a constant.

Iodine value=α×IR index+β  formula (II)

[0109] The IR indexes of the films obtained by molding the ethylene-propylene-5-ethylidene-2-norbornene copolymer rubbers were measured, and, from the obtained value and the calibration curve, the iodine values of the ethylene-propylene-5-ethylidene-2-norbornene copolymer rubbers were determined.

[0110] (4) Mooney Viscosity

[0111] The Mooney viscosities at 125° C. (ML.sub.1+4 125° C(copolymer rubber)) of the copolymer rubbers were measured according to JIS K6300-1994.

[0112] (5) Proportion of Cyclohexane Insoluble Component

[0113] A portion having a thickness of 1 mm was cut off from the side face of the solid copolymer rubber by using scissors. The small pieces cut were further cut to obtain a substantially cubic sample of 1 mm square. The mass (A) of about 0.5 g of the sample obtained was precisely weighed by using an electronic balance. Subsequently, the sample was placed in an Erlenmeyer flask with a stopper having a volume of 500 mL. Thereinto, 250 mL of cyclohexane was weighed by using a measuring cylinder and poured to immerse the sample in the cyclohexane. In the cyclohexane, 6-bis(tert-butyl)-4-methylphenol (Sumilizer BHT) having a concentration of 0.1% by mass had been dissolved in advance. The Erlenmeyer flask was left to stand in a constant temperature water bath at 25° C. for 24 hours. The Erlenmeyer flask taken out from the constant temperature water bath was stoppered and then shaken for 1 hour by using a shaker The shaking speed was set to 120 rpm.

[0114] The mass (B) of a 120-mesh wire gauze was precisely weighed by using an electronic balance. The solution in the flask was filtered through this wire gauze. At the time of filtration, the residue in the Erlenmeyer flask was washed toward the wire gauze with about 20 mL of new cyclohexane. The wire gauze after filtration was dried on a hot plate at from 60° C. to 90° C. for 3 hours together with the filtered solid components on the wire gauze. The wire gauze after drying was cooled to room temperature in a desiccator over about 30 minutes. The mass (C) of the wire gauze after cooling was precisely weighed by using an electronic balance.

[0115] The proportion (% by mass) of the cyclohexane insoluble component was calculated by substituting the mass A of the sample before being immersed in cyclohexane, the mass B (tare) of the wire gauze, and the mass C of the wire gauze after filtration and drying into the following equation.

Proportion of Cyclohexane Insoluble Component={(C−B)/A}×100

[0116] (6) Tan δ Ratio

[0117] The viscoelasticity of the copolymer rubber was measured by using a viscoelasticity measuring apparatus (RUBBER PROCESS ANALYZER RPA 2000P manufactured by ALPHA TECHNOLOGIES) under the following conditions.

[0118] Temperature: 100° C.

[0119] Strain: 13.95%

[0120] Frequency: 5 cpm or 1000 cpm

[0121] From the measurement results, tan δ (100° C., 5 cpm) which was the loss coefficient at a frequency of 5 cpm and tan δ (100° C., 1000 cpm) which was the loss coefficient at a frequency of 1000 cpm were determined. The tan δ ratio was calculated by substituting these values into the following equation.

Tan δ ratio=tan δ (100° C., 5 cpm)/tan δ (100° C., 1000 cpm)

[0122] (7) Glass Transition Temperature (Tg)

[0123] The differential scanning calorie (DSC) of the copolymer rubber was measured at a rate of temperature increase of 5° C./min. The temperature at the midpoint of the glass transition portion in the DSC thermogram obtained was taken as the glass transition temperature.

[0124] (8) Molecular Weight Distribution (Mw/Mn)

[0125] The values of weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer rubber in terms of standard polystyrene were measured by gel permeation chromatography (GPC) under the following conditions. The molecular weight distribution (Mw/Mn) was calculated from the Mw and Mn obtained. [0126] GPC apparatus: HLC-8121 GPC/HT (trade name) manufactured by Tosoh Corporation [0127] Column: TSKgel GMHHR-H(S) HT (trade name) manufactured by Tosoh Corporation [0128] Standard substance for molecular weight: polystyrene having molecular weight of 500 or more and 20,000,000 or less [0129] Flow rate of eluting solvent: 1.0 mL/min [0130] Concentration of sample: 1 mg/mL [0131] Measured temperature: 140° C. [0132] Eluting solvent: orthodichlorobenzene [0133] Injection volume: 500 μL [0134] Detector: differential refractometer

[0135] (9) Tensile Strength

[0136] By using a Banbury mixer (manufactured by Kobe Steel, Ltd.), 100 parts by mass of the copolymer rubber, 5 parts by mass of zinc oxide, 1 parts by mass of stearic acid (“ASAHI 60UG” manufactured by Asahi Carbon Co. Ltd.) and 80 parts by mass of paraffin-based oil (“Dianna PS4300” manufactured by Idemitsu Kosan Co.,Ltd.) were kneaded for 4 minutes at a rotor rotating speed of 80 rpm. A mixture of the resulting kneaded material, 1.5 parts by mass of sulfur, 1.25 parts by mass of Zinc di-n-butyldithiocarbamate (“Rhenogran ZDBC-80” manufactured by LANXESS), 1.25 parts by mass of tetramethylthiuram disulfide (“Rhenogran TMTD-80” manufactured by LANXESS), 1.25 parts by mass of N-cyclohexylbenzothiazolesulfenamide (“Rhenogran CBS-80” manufactured by LANXESS), and 0.71 pars by mass of dipentamethylenethiuram tetrasulfide (“Rhenogran DPPT-70” manufactured by LANXESS) was kneaded by using an 8-inch open roll (manufactured by KANSAI ROLL Co., Ltd.) to obtain a rubber composition.

[0137] The rubber composition obtained was compression-molded at a set temperature of 170° C. for 15 minutes by using a 100-ton press (trade name: PSF-B010 manufactured by KANSAI ROLL Co., Ltd.), and a dumbbell-shaped No. 3 test piece described in JIS K6251-1993 was fabricated by conducting molding and vulcanization at the same time. This test piece was subjected to a tension test in an atmosphere at 23° C. and a tension speed of 500 mm/min. As the tension test, a tension testing machine QUICK READER P-57 (manufactured by Ueshima Seisakusho Co., Ltd.) was used.

[0138] (8) Stability of Viscosity (ΔML)

[0139] By using a Banbury mixer (manufactured by Kobe Steel, Ltd.), 100 parts by mass of the copolymer rubber, 5 parts by mass of zinc oxide, 1 parts by mass of stearic acid (“ASAHI 60UG” manufactured by Asahi Carbon Co. Ltd.) and 80 parts by mass of paraffin-based oil (“Dianna PS430” manufactured by Idemitsu Kosan Co., Ltd.) were kneaded for 4 minutes at a rotor rotating speed of 80 rpm. A mixture of the resulting kneaded material, 1.5 parts by mass of sulfur, 1.25 parts by mass of Zinc di-n-butyldithiocarbamate (“Rhenogran ZDBC-80” manufactured by LANXESS), 1.25 parts by mass of tetramethylthiuram disulfide (“Rhenogran TMTD-80” manufactured by LANXESS), 1.25 parts by mass of N-cyclohexylbenzothiazolesulfenamide (“Rhenogran CBS-80” manufactured by LANXESS), and 0.71 pars by mass of dipentamethylenethiuram tetrasulfide (“Rhenogran DPPT-70” manufactured by LANXESS) was kneaded by using an 8-inch open roll (manufactured by KANSAI ROLL Co., Ltd.) to obtain a rubber composition. The Mooney viscosity of the obtained rubber composition at 100° C. (ML.sub.1+4 100° C. (rubber composition)) was measured according to JIS K6300-1994. The difference AML between ML.sub.1+4 125° C. (copolymer rubber) and ML.sub.1+4 100° C. (rubber composition) was determined. A small ΔML means high viscosity stability at the time of kneading.

TABLE-US-00002 TABLE 2 Comp. Comp. Comp. Ex 1 Ex. 1 Ex. 2 Ex. 3 Intrinsic viscosity [η] 2.3 2.2 2.3 2.1 [dl/g] Ethylene unit content 73 55 60 78 [% by mass] Propylene unit content 22 41 34 16 [% by mass] Iodine value 11 9 12 11 ML.sub.1 + 4 125° C. (copolymer) 80 83 100 72 Proportion of cyclohexane 27.5 0.1 12.3 18.9 insoluble component [% by mass] Tanδ ratio 3.2 2.5 2.9 2.5 Tg [° C.] −42 −55 −52 −36 Mw/Mn 2.6 2.5 2.7 2.5 Tensile strength 18.1 14.7 15.9 18.8 [MPa] ΔML 10 15 29 12

[0140] From the results in Table 2, it has been confirmed that the ethylene-α-olefin-nonconjugated polyene copolymer rubber in which the proportion of the cyclohexane insoluble component is from 0.3% to 50% by mass and the tan δ ratio is from 3.0 to 20 forms a molded article having a favorable mechanical strength (tensile strength) and has a stable viscosity in the process of kneading conducted to obtain a rubber composition.