Modified conjugated diene-based polymer, rubber composition, and tire

Abstract

A modified conjugated diene-based polymer, including a coupling polymer, wherein a ratio of the coupling polymer, obtained by gel permeation chromatography (GPC), is 30% by mass or more and less than 70% by mass in the entire modified conjugated diene-based polymer, and a modification ratio obtained by adsorption GPC is 30% by mass or more and less than 70% by mass in the entire modified conjugated diene-based polymer, when a peak top molecular weight, obtained by the GPC, of the coupling polymer of the modified conjugated diene-based polymer is represented by Mp.sub.1 and a peak top molecular weight of a non-coupling polymer is represented by Mp.sub.2, (Mp.sub.1/Mp.sub.2)≥3.4, and a shrinking factor (g′) is less than 0.60.

Claims

1. A modified conjugated diene-based polymer, comprising a coupling polymer, wherein: a ratio of the coupling polymer, obtained by gel permeation chromatography (GPC), is 30% by mass or more and less than 70% by mass in the entire modified conjugated diene-based polymer, and a modification ratio obtained by adsorption GPC is 30% by mass or more and less than 70% by mass in the entire modified conjugated diene-based polymer, the modified conjugated diene-based polymer has two molecular weight peaks in the GPC, when a peak top molecular weight, obtained by the GPC, of the coupling polymer of the modified conjugated diene-based polymer is represented by Mp.sub.1 and a peak top molecular weight of a non-coupling polymer is represented by Mp.sub.2, (Mp.sub.1/Mp.sub.2)≥3.4, and a shrinking factor (g′) is less than 0.60.

2. The modified conjugated diene-based polymer according to claim 1, comprising a nitrogen atom and/or a silicon atom.

3. The modified conjugated diene-based polymer according to claim 1, wherein (Mp.sub.1/Mp.sub.2)≥3.8.

4. The modified conjugated diene-based polymer according to claim 1, wherein the shrinking factor (g′) is less than 0.50.

5. The modified conjugated diene-based polymer according to claim 2, wherein the nitrogen atom and the silicon atom are a nitrogen atom and a silicon atom derived from a coupling agent, respectively.

6. The modified conjugated diene-based polymer according to claim 1, wherein the polymer is branched, and the branching degree is 6 or more.

7. The modified conjugated diene-based polymer according to claim 1, wherein the polymer is branched, and the branching degree is 8 or more.

8. The modified conjugated diene-based polymer according to claim 1, wherein a molecular weight distribution obtained by GPC consists of two peaks.

9. A rubber composition comprising: a rubber component containing the modified conjugated diene-based polymer according to claim 1 in an amount of 10% by mass or more, and a silica-based filler in an amount of 5.0 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the rubber component.

10. A tire comprising the rubber composition according to claim 9.

11. A modified conjugated diene-based polymer, comprising a coupling polymer, wherein a ratio of the coupling polymer, obtained by gel permeation chromatography (GPC), is 30% by mass or more and less than 70% by mass in the entire modified conjugated diene-based polymer, and a modification ratio obtained by adsorption GPC is 30% by mass or more and less than 70% by mass in the entire modified conjugated diene-based polymer, when a peak top molecular weight, obtained by the GPC, of the coupling polymer of the modified conjugated diene-based polymer is represented by Mp.sub.1 and a peak top molecular weight of a non-coupling polymer is represented by Mp.sub.2, (Mp.sub.1/Mp.sub.2)≥3.4, and a shrinking factor (g′) is less than 0.50,
(Mp.sub.1/Mp.sub.2)≥3.8.

12. The modified conjugated diene-based polymer according to claim 11, wherein the polymer is branched, and the branching degree is 8 or more.

13. The modified conjugated diene-based polymer according to claim 11, wherein a molecular weight distribution obtained by GPC consists of two peaks.

14. The modified conjugated diene-based polymer according to claim 12, wherein a molecular weight distribution obtained by GPC consists of two peaks.

15. A rubber composition comprising: a rubber component containing the modified conjugated diene-based polymer according to claim 12 in an amount of 10% by mass or more, and a silica-based filler in an amount of 5.0 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the rubber component.

16. A tire comprising the rubber composition according to claim 12.

17. A rubber composition comprising: a rubber component containing the modified conjugated diene-based polymer according to claim 13 in an amount of 10% by mass or more, and a silica-based filler in an amount of 5.0 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the rubber component.

18. A tire comprising the rubber composition according to claim 13.

19. A rubber composition comprising: a rubber component containing the modified conjugated diene-based polymer according to claim 14 in an amount of 10% by mass or more, and a silica-based filler in an amount of 5.0 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the rubber component.

20. A tire comprising the rubber composition according to claim 14.

Description

EXAMPLES

(1) The present embodiment will now be described in more detail with reference to specific examples and comparative examples, and it is noted that the present embodiment is not limited to the following examples at all.

(2) Analyses of polymers of Examples 1 to 7 and Comparative Examples 1 to 7 were performed by the following methods.

(3) (1) Amount of Bound Styrene

(4) One hundred (100) mg of a sample was dissolved in chloroform to be diluted to 100 mL, and the resultant was used as a measurement sample.

(5) Based on the absorption of a phenyl group of styrene at UV 254 nm, the amount of bound styrene (% by mass) was measured (spectrophotometer “UV-2450” manufactured by Shimadzu Corporation).

(6) (2) Microstructure of Butadiene Portion (Amount of 1,2-Vinyl Bond)

(7) Fifty (50) mg of a sample was dissolved in 10 mL of carbon disulfide, and the resultant was used as a measurement sample.

(8) A solution cell was used to measure an infrared spectrum in a range of 600 to 1000 cm.sup.−1, and in accordance with a calculation formula of the Hampton method based on absorbance at a prescribed wavelength, a microstructure of a butadiene portion was obtained (Fourier transform infrared spectrophotometer “FT-IR230” manufactured by JASCO Corporation).

(9) (3) Mooney Viscosity ML.sub.1+4 (100° C.)

(10) A Mooney viscosity was measured using a Mooney viscometer (“VR1132” manufactured by Ueshima Seisakusho Co., Ltd.) in accordance with JIS K6300 (ISO289-1) and ISO289-4. A measurement temperature was set to 100° C. First, a sample was preheated for 1 minute, a rotor was rotated at 2 rpm, and a torque measured 4 minutes after was defined as a Mooney viscosity (ML.sub.1+4 (100° C.)).

(11) (4) Glass Transition Temperature (Tg)

(12) A DSC curve was recorded in accordance with ISO 22768:2006 using a differential scanning calorimeter “DSC3200S” manufactured by MAC Science Co., Ltd. under a flow of helium at 50 mL/min during temperature increase from −100° C. at a rate of 20° C./min, and a peak top (an inflection point) of the thus obtained DSC differential curve was defined as a glass transition temperature.

(13) (5) Coupling Ratio and Molecular Weight

(14) A chromatogram was measured using a GPC measurement apparatus including a series of three columns using a polystyrene-based gel as a filler, and on the basis of a calibration curve obtained using standard polystyrene, a coupling ratio, a weight average molecular weight (Mw), a number average molecular weight (Mn) and peak top molecular weights (Mp.sub.1 and Mp.sub.2) were obtained.

(15) It is noted that Mp.sub.1 corresponds to the peak top molecular weight of the coupling polymer by GPC of the modified conjugated diene-based polymer, and if the coupling polymer has a plurality of peaks, the peak top molecular weight of the highest peak is defined as Mp.sub.1.

(16) On the other hand, Mp.sub.2 corresponds to the peak top molecular weight of a non-coupling polymer of a conjugated diene-based polymer chain (i.e., the peak of the lowest molecular weight).

(17) As an eluent, tetrahydrofuran (THF) was used. As the columns, a guard column: TSKguardcolumn Super H-H manufactured by Tosoh Corporation, and columns: TSKgel SuperH5000, TSKgel SuperH6000 and TSKgel SuperH7000 manufactured by Tosoh Corporation were used. An RI detector (“HLC8020” manufactured by Tosoh Corporation) was used under conditions of an oven temperature of 40° C. and a THF flow rate of 1.0 mL/min. Ten (10) mg of a sample for the measurement was dissolved in 20 mL of THF to obtain a measurement solution, and 20 μL of the measurement solution was injected into the GPC measurement apparatus for performing the measurement.

(18) (6) Modification Ratio

(19) Measurement was performed by applying a characteristic that a modified component adsorbs to a GPC column using a silica-based gel as a filler. Specifically, a chromatogram obtained by measurement using a polystyrene-based gel column and a chromatogram obtained by measurement using a silica-based column were obtained by using a sample solution containing a sample and low molecular weight internal standard polystyrene, and based on a difference between these chromatograms, an adsorption amount in the silica column was measured to obtain a modification ratio.

(20) Preparation of Sample Solution:

(21) Ten (10) mg of a sample and 5 mg of standard polystyrene were dissolved in 20 mL of THF to obtain a sample solution.

(22) GPC Measurement Conditions Using Polystyrene-Based Column:

(23) THF was used as the eluent, and 20 μL of the sample solution was injected into the apparatus for measurement. As the columns, a guard column: TSKguardcolumn SuperH-H, and columns: TSKgel SuperH5000, TSKgel SuperH6000 and TSKgel SuperH7000 manufactured by Tosoh Corporation were used. An RI detector (HLC-8020 manufactured by Tosoh Corporation) was used under conditions of a column oven temperature of 40° C. and a THF flow rate of 1.0 mL/min to obtain a chromatogram.

(24) GPC Measurement Conditions Using Silica-Based Column:

(25) THF was used as the eluent, and 50 μL of the sample solution was injected into the apparatus for measurement. As the columns, a guard column: DIOL 4.6×12.5 mm 5 micron, and columns: Zorbax PSM-1000S, PSM-3005 and PSM-60S were used. An RI detector was used for measurement under conditions of a column oven temperature of 40° C. and a THF flow rate of 0.5 mL/min in CCP8020 series build-up GPC system: AS-8020, SD-8022, CCPS, CO-8020, RI-8021 manufactured by Tosoh Corporation to obtain a chromatogram.

(26) Calculation Method for Modification Ratio:

(27) Assuming that the whole peak area in the chromatogram obtained using the polystyrene-based column was 100, values of a peak area P1 of the sample and a peak area P2 of standard polystyrene were calculated. Besides, assuming that the whole peak area of the chromatogram obtained using the silica-based column was 100, values of a peak area P3 of the sample and a peak area P4 of standard polystyrene were calculated. By using these values, a modification ratio (%) was obtained in accordance with the following expression:
Modification Ratio (%)=[1−(P2×P3)/(P1×P4)]×100
wherein P1+P2=P3+P4=100.

(28) (7) Presence of Nitrogen Atom

(29) The measurement was performed similarly to that described in (6), and if the calculated modification ratio was 10% or more, it was determined that the sample had a nitrogen atom. Thus, it was confirmed that each of the modified conjugated diene-based polymers of Examples 1 to 7 and Comparative Examples 2 to 5 and 7 had a nitrogen atom, and that the modified conjugated diene-based polymer of Comparative Examples 1 and 6 did not have a nitrogen atom.

(30) (8) Presence of Silicon Atom

(31) Measurement was performed by using 0.5 g of a modified conjugated diene-based polymer as a sample and using an ultraviolet visible spectrophotometer (trade name “UV-1800” manufactured by Shimadzu Corporation) in accordance with JIS K 010144.3.1, and quantitative determination was performed by a molybdenum blue-spectrophotometric method. As a result, if a silicon atom was detected (low detection limit: 10 mass ppm), it was determined that the sample had a silicon atom. Thus, it was confirmed that each of the modified conjugated diene-based polymers of Examples 1 to 7 and Comparative Examples 1 to 7 had a silicon atom.

(32) (9) Shrinking Factor (g′)

(33) A GPC measurement apparatus including a series of three columns using a polystyrene-based gel as a filler (trade name “GPCmax VE-2001” manufactured by Malvern Panalytical Ltd.) was used and three detectors sequentially connected, including a light scattering detector, an RI detector and a viscosity detector (trade name “TDA305” manufactured by Malvern Panalytical Ltd.), were used to obtain the absolute molecular weight with a modified conjugated diene-based polymer as a sample from the measurement results of the light scattering detector and the RI detector based on standard polystyrene, and obtain the intrinsic viscosity from the measurement results of the RI detector and the viscosity detector. A linear polymer was assumed to have an intrinsic viscosity according to intrinsic viscosity [η]=−3.883 M.sup.0.771, and the shrinking factor (g′) as a corresponding ratio of the intrinsic viscosity to each molecular weight was calculated. In the expression, M represents the absolute molecular weight.

(34) The peak height was gradually lowered from the peak top molecular weight of the peak derived from the coupling polymer, according to an increase in the molecular weight, and the average of the shrinking factors (g′) corresponding to the molecular weights until the height reached less than 10% of the height of the peak top molecular weight was used as the shrinking factor (g′) of the modified conjugated diene-based polymer.

(35) THF including 5 mmol/L of triethylamine was used as the eluent. As the columns, a column of trade name “TSKgel G4000HXL”, “TSKgel G5000HXL”, and “TSKgel G6000HXL” manufactured by Tosoh Corporation were connected and used. Twenty (20) mg of a sample for the measurement was dissolved in 10 mL of THF to obtain a measurement solution, 100 μL of the measurement solution was injected into the GPC measurement apparatus, and measurement was performed under conditions of an oven temperature of 40° C. and a THF flow rate of 1 mL/min.

Example 1

(36) A temperature-controllable autoclave having an internal volume of 5 L (L/D: 3.4) and equipped with a stirrer and a jacket was used as a reactor, and 1995 g of normal hexane and n-butyllithium, which was used for neutralizing an impurity present in the reactor and possibly impairing a polymerization reaction, were put in the reactor, the resultant was stirred at 70° C. for 5 minutes, and then cooled to room temperature to extract a solution, and the reactor was emptied. Next, 1670 g of normal hexane, 83 g of styrene, 236 g of 1,3-butadiene, and 1.15 mmol of 2,2-bis(2-oxolanyl)propane used as a polar substance, from all of which impurities had been precedently removed, were put in the reactor, and 2.30 mmol of n-butyllithium (which is shown as “NBL” in Table 1) was added as a polymerization initiator when the temperature within the reactor was 58° C., and thus, the polymerization was started.

(37) Immediately after starting the polymerization, the temperature within the reactor increased, and reached a peak temperature, which was 78° C. When the temperature was found to lower, 0.27 mmol of tris(3-trimethoxysilylpropyl)amine (abbreviated as “a” in the table below) was added thereto as a coupling agent, and the resultant was stirred for 10 minutes. It was 2 minutes after reaching the peak temperature that the coupling agent was added.

(38) The reaction was stopped by adding 2.30 mmol of ethanol as a polymerization terminator, and thus, a modified conjugated diene-based polymer-containing polymer solution was obtained.

(39) To the thus obtained polymerization solution, 0.64 g of 2,6-di-tert-butyl-4-hydroxytoluene was added as an antioxidant, the solvent was removed by steam stripping, and a modified conjugated diene-based polymer A was obtained after vacuum drying.

(40) Analysis results of the modified conjugated diene-based polymer A are shown in Table 1.

Example 2

(41) The addition amount of the polymerization initiator was changed from 2.30 mmol to 1.55 mmol.

(42) The addition amount of the coupling agent was changed from 0.27 mmol to 0.090 mmol.

(43) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 73° C.

(44) Besides, the addition amount of the polar substance was changed to 0.886 mmol.

(45) A modified conjugated diene-based polymer B was obtained in the same manner as in Example 1 except for these.

(46) Analysis results of the modified conjugated diene-based polymer B are shown in Table 1.

Example 3

(47) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to tris(3-triethoxysilylpropyl)amine (abbreviated as “b” in the table).

(48) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 75° C.

(49) A modified conjugated diene-based polymer C was obtained in the same manner as in Example 1 except for these.

(50) Analysis results of the modified conjugated diene-based polymer C are shown in Table 1.

Example 4

(51) The addition amount of the polymerization initiator was changed from 2.30 mmol to 2.12 mmol.

(52) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to tetralkis(3-trimethoxysilylpropyl)-1,3-propanediamine (abbreviated as “c” in the table), and the addition amount was changed from 0.27 mmol to 0.18 mmol.

(53) The polymerization starting temperature was 56° C., and the polymerization peak temperature was 79° C.

(54) Besides, the addition amount of the polar substance was changed to 1.12 mmol.

(55) A modified conjugated diene-based polymer D was obtained in the same manner as in Example 1 except for these.

(56) Analysis results of the modified conjugated diene-based polymer D are shown in Table 1.

Example 5

(57) The addition amount of the polymerization initiator was changed from 2.30 mmol to 1.47 mmol.

(58) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to tetralkis(3-trimethoxysilylpropyl)-1,3-propanediamine (abbreviated as “c” in the table), and the addition amount was changed from 0.27 mmol to 0.067 mmol.

(59) The polymerization starting temperature was 56° C., and the polymerization peak temperature was 78° C.

(60) Besides, the addition amount of the polar substance was changed to 0.840 mmol.

(61) A modified conjugated diene-based polymer E was obtained in the same manner as in Example 1 except for these.

(62) Analysis results of the modified conjugated diene-based polymer E are shown in Table 1.

Example 6

(63) An amount of a monomer for polymerization was adjusted as shown in Table 1 below.

(64) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 79° C.

(65) Besides, the addition amount of the polar substance was changed to 1.10 mmol.

(66) A modified conjugated diene-based polymer F was obtained in the same manner as in Example 1 except for these.

(67) Analysis results of the modified conjugated diene-based polymer F are shown in Table 1.

Example 7

(68) An amount of a monomer for polymerization was adjusted as shown in Table 1 below.

(69) The addition amount of the polymerization initiator was changed from 2.30 mmol to 2.12 mmol.

(70) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to tetralkis(3-trimethoxysilylpropyl)-1,3-propanediamine (abbreviated as “c” in the table), and the addition amount was changed from 0.27 mmol to 0.18 mmol.

(71) The polymerization starting temperature was 56° C., and the polymerization peak temperature was 77° C.

(72) Besides, the addition amount of the polar substance was changed to 1.08 mmol.

(73) A modified conjugated diene-based polymer G was obtained in the same manner as in Example 1 except for these.

(74) Analysis results of the modified conjugated diene-based polymer G are shown in Table 1.

Comparative Example 1

(75) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to 1,2-bis(trichlorosilyl)ethane (abbreviated as “d” in the table).

(76) The polymerization starting temperature was 56° C., and the polymerization peak temperature was 76° C.

(77) A modified conjugated diene-based polymer H was obtained in the same manner as in Example 1 except for these.

(78) Analysis results of the modified conjugated diene-based polymer H are shown in Table 1.

Comparative Example 2

(79) The addition amount of the polymerization initiator was changed from 2.30 mmol to 2.64 mmol.

(80) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to bis(3-trimethoxysilylpropyl)-N-methylamine (abbreviated as “e” in the table), and the addition amount was changed from 0.27 mmol to 0.46 mmol.

(81) The polymerization starting temperature was 58° C., and the polymerization peak temperature was 74° C.

(82) Besides, the addition amount of the polar substance was changed to 1.24 mmol.

(83) A modified conjugated diene-based polymer I was obtained in the same manner as in Example 1 except for these.

(84) Analysis results of the modified conjugated diene-based polymer I are shown in Table 1.

Comparative Example 3

(85) The addition amount of the polymerization initiator was changed from 2.30 mmol to 2.35 mmol.

(86) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to bis(3-trimethoxysilylpropyl)-N-methylamine (abbreviated as “e” in the table), and the addition amount was changed from 0.27 mmol to 0.79 mmol.

(87) The polymerization starting temperature was 58° C., and the polymerization peak temperature was 75° C.

(88) Besides, the addition amount of the polar substance was changed to 1.24 mmol.

(89) A modified conjugated diene-based polymer J was obtained in the same manner as in Example 1 except for these.

(90) Analysis results of the modified conjugated diene-based polymer J are shown in Table 1.

Comparative Example 4

(91) The addition amount of the coupling agent was changed from 0.27 mmol to 0.39 mmol.

(92) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 77° C.

(93) A modified conjugated diene-based polymer K was obtained in the same manner as in Example 1 except for these.

(94) Analysis results of the modified conjugated diene-based polymer K are shown in Table 1.

Comparative Example 5

(95) The addition amount of the polymerization initiator was changed from 2.30 mmol to 1.50 mmol.

(96) The addition amount of the coupling agent was changed from 0.27 mmol to 0.073 mmol.

(97) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 74° C.

(98) Besides, the addition amount of the polar substance was changed to 0.800 mmol.

(99) A modified conjugated diene-based polymer L was obtained in the same manner as in Example 1 except for these.

(100) Analysis results of the modified conjugated diene-based polymer L are shown in Table 1.

Comparative Example 6

(101) An amount of a monomer for polymerization was adjusted as shown in Table 1 below.

(102) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to 1,2-bis(trichlorosilyl)ethane (abbreviated as “d” in the table).

(103) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 74° C.

(104) Besides, the addition amount of the polar substance was changed to 1.100 mmol.

(105) A modified conjugated diene-based polymer M was obtained in the same manner as in Example 1 except for these.

(106) Analysis results of the modified conjugated diene-based polymer M are shown in Table 1.

Comparative Example 7

(107) The coupling agent was changed from tris(3-trimethoxysilylpropyl)amine to tris(3-triethoxysilylpropyl)amine (abbreviated as “b” in the table), and the addition amount was changed from 0.27 mmol to 0.33 mmol.

(108) The polymerization starting temperature was 57° C., and the polymerization peak temperature was 75° C.

(109) A modified conjugated diene-based polymer N was obtained in the same manner as in Example 1 except for these.

(110) Analysis results of the modified conjugated diene-based polymer N are shown in Table 1.

(111) TABLE-US-00001 TABLE 1 Example Example Example Example Example Example Example 1 2 3 4 5 6 7 Modified Conjugated Diene-based Polymer (sample A B C D E F G No.) Polymerization Conditions Butadiene (g) 236 236 236 236 236 255 255 Styrene (g) 83 83 83 83 83 64 64 Normal Hexane (g) 1670 1670 1670 1670 1670 1670 1670 Polymerization Starting Temperature (° C.) 58 57 57 56 56 57 56 Polymerization Peak Temperature (° C.) 78 73 75 79 78 79 77 Polymerization Type *.sup.1 NBL NBL NBL NBL NBL NBL NBL Initiator Addition Amount (mmol) 2.30 1.55 2.30 2.12 1.47 2.30 2.12 Polar Substance.sup.2 Addition Amount (mmol) 1.15 0.886 1.15 1.12 0.840 1.10 1.08 Coupling Agent Type *.sup.3 a a b c c a c Addition Amount (mmol) 0.27 0.090 0.27 0.18 0.067 0.27 0.18 Lithium 0.70 0.35 0.70 0.68 0.37 0.70 0.68 Equivalent Ratio *.sup.4 Analysis Values Mooney Viscosity ML1 + 4 63 65 62 61 65 64 63 (100° C.) Weight Average Molecular 54.6 65.9 53.7 60.2 70.1 55.1 61.0 Weight (Mw) Number Average Molecular 34.6 33.6 33.8 36.5 34.7 35.5 37.4 Weight (Mn) Mw/Mn 1.58 1.96 1.59 1.65 2.02 1.55 1.63 Mp.sub.1/Mp.sub.2 3.67 3.68 3.60 4.45 4.48 3.71 4.50 Coupling Ratio (%) 68.5 33.7 66.3 65.8 35.0 67.1 67.4 Modification Ratio (%) 68.3 32.9 65.8 64.2 34.5 66.3 66.9 Shrinking Factor (g′) 0.53 0.52 0.55 0.40 0.41 0.51 0.40 Amount of Bound Styrene (mass %) 27 26 26 27 27 20 20 Amount of Bound 1,2-Vinyl (mol %) 54 56 56 55 55 55 54 Glass Transition Temperature (° C.) −25 −26 −25 −26 −26 −36 −35 (Tg) Com- Com- Com- Com- Com- Com- Com- parative parative parative parative parative parative parative Example Example Example Example Example Example Example 1 2 3 4 5 6 7 Modified Conjugated Diene-based Polymer (sample H I J K L M N No.) Polymerization Conditions Butadiene (g) 236 236 236 236 236 255 236 Styrene (g) 83 83 83 83 83 64 83 Normal Hexane (g) 1670 1670 1670 1670 1670 1670 1670 Polymerization Starting Temperature (° C.) 56 58 58 57 57 57 57 Polymerization Peak Temperature (° C.) 76 74 75 77 74 74 75 Polymerization Type *.sup.1 NBL NBL NBL NBL NBL NBL NBL Initiator Addition Amount (mmol) 2.30 2.64 2.35 2.30 1.50 2.30 2.30 Polar Substance.sup.2 Addition Amount (mmol) 1.15 1.24 1.24 1.15 0.800 1.100 1.15 Coupling Agent Type *.sup.3 d e e a a d b Addition Amount (mmol) 0.27 0.46 0.79 0.39 0.073 0.270 0.33 Lithium 0.70 0.70 1.3 1.30 0.29 0.70 0.85 Equivalent Ratio *.sup.4 Analysis Values Mooney Viscosity ML1 + 4 64 62 65 64 60 63 59 (100° C.) Weight Average Molecular 55.1 50.5 39.6 49.9 67.2 54.7 51.3 Weight (Mw) Number Average Molecular 35.3 33 31.5 38.4 33.3 36.0 31.7 Weight (Mn) Mw/Mn 1.56 1.53 1.26 1.30 2.02 1.52 1.62 Mp.sub.1/Mp.sub.2 3.68 2.98 2.60 3.22 3.69 3.67 3.42 Coupling Ratio (%) 65.1 67.7 71.8 84.8 28.3 68.0 68.5 Modification Ratio (%) — 67.2 71.2 83.8 27.9 — 68.1 Shrinking Factor (g′) 0.53 0.72 0.72 0.63 0.53 0.52 0.64 Amount of Bound Styrene (mass %) 27 26 27 27 26 21 26 Amount of Bound 1,2-Vinyl (mol %) 55 56 56 55 55 53 56 Glass Transition Temperature (° C.) −26 −25 −25 −26 −26 −35 −25 (Tg)

(112) Signs used in Table 1 have the following meanings:

(113) *1

(114) NBL: normal butyllithium

(115) *2

(116) 2,2-bis(2-oxolanyl)propane used

(117) *3

(118) a: tris(3-trimethoxysilylpropyl)amine: (hexafunctional)

(119) b: tris(3-triethoxysilylpropyl)amine (hexafunctional)

(120) c: tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine: (octafunctional)

(121) d: 1,2-bis(trichlorosilyl)ethane: (hexafunctional)

(122) e: bis(3-trimethoxysilylpropyl)-N-methylamine: (tetrafunctional)

(123) *4

(124) Assuming that a trialkoxysilyl group is di-functional, a dialkoxysilyl group is mono-functional, a monoalkoxysilyl group is zero-functional, a halogenated silyl group has functional groups in the same number as that of halogens, and an aza-silyl group is mono-functional, the number of functional groups of the coupling agent was calculated, and a value obtained by dividing the number of functional groups by a mole number of the polymerization initiator was shown as a lithium equivalent ratio.

(125) The sign “-” in the Modification Ratio in Table 1 means no detection of any modification ratio.

[Examples 8 to 14] [Comparative Examples 8 to 14]

(126) The modified conjugated diene-based polymers obtained in Examples 1 to 7 and Comparative Examples 1 to 7 (samples A to N) were used as starting material rubbers, and rubber compositions respectively containing the starting material rubbers were obtained in accordance with the following compositions:

(127) Modified conjugated diene-based polymer (any of the samples A to N): 100 parts by mass (oil removed)

(128) Silica (“Ultrasil 7000 GR” manufactured by Evonik Degussa Gmbh, nitrogen adsorption specific surface area: 170 m.sup.2/g): 75.0 parts by mass

(129) Carbon black (“SEAST KH (N339)” manufactured by Tokai Carbon Co., Ltd.): 5.0 parts by mass

(130) Silane coupling agent (“Si75” manufactured by Evonik Degussa Gmbh, bis(triethoxysilylpropyl)disulfide): 6.0 parts by mass

(131) S-RAE oil (“Process NC140” manufactured by JX Nippon Mining & Metals Corporation): 30.0 parts by mass

(132) Zinc oxide: 2.5 parts by mass

(133) Stearic acid: 2.0 part by mass

(134) Antioxidant (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine): 2.0 parts by mass

(135) Sulfur: 1.7 parts by mass

(136) Vulcanization accelerator 1 (N-cyclohexyl-2-benzothiazyl sulfinamide): 1.7 parts by mass

(137) Vulcanization accelerator 2 (diphenylguanidine): 2.0 parts by mass

(138) Total: 227.9 parts by mass

(139) The above-described materials were kneaded as follows to obtain a rubber composition.

(140) A sealed mixer (internal volume: 0.3 L) equipped with a temperature controller was used, and as a first stage of kneading, the starting material rubber (any of the samples A to M), the fillers (the silica and the carbon black), the silane coupling agent, the process oil, the zinc oxide and the stearic acid were kneaded under conditions of a filling rate of 65% and a rotator rotational speed of 30 to 50 rpm. Here, the temperature of the sealed mixer was controlled to obtain each rubber composition (compound) at a discharging temperature of 155 to 160° C.

(141) Next, as a second stage of the kneading, the antioxidant was added thereto, after cooling the compound obtained in the first stage of the kneading to room temperature, and the resultant was kneaded again to improve the dispersibility of the silica. Also in this case, the discharging temperature for the compound was adjusted to 155 to 160° C. by the temperature control of the mixer.

(142) After cooling the compound obtained in the second stage of the kneading to room temperature, as a third stage of the kneading, sulfur and vulcanization accelerators 1 and 2 were added to and mixed with the resultant compound by an open roll set to 70° C.

(143) Thereafter, the resultant was molded and vulcanized at 160° C. for 20 minutes by a vulcanizing press. The rubber composition before the vulcanization and the rubber composition after the vulcanization were evaluated.

(144) Specifically, these compositions were evaluated as follows. The results are shown in Table 2.

(145) (Evaluation 1) Mooney Viscosity of Compound

(146) A compound after the second stage of the kneading and before a third stage of the kneading, obtained above, was used as a sample, and the Mooney viscosity was measured using a Mooney viscometer in accordance with JIS K6300-1 after preheating the sample at 130° C. for 1 minute, and after rotating a rotor for 4 minutes at 2 rpm.

(147) A smaller value indicates better processability.

(148) (Evaluation 2) Viscoelasticity Parameter

(149) A viscoelasticity testing machine “ARES” manufactured by Rheometric Scientific, Inc. was used to measure a viscoelasticity parameter in a torsion mode.

(150) Each measurement value was shown as an index obtained assuming that a result obtained with respect to the rubber composition of Comparative Example 7 was 100.

(151) A tan δ measured at 50° C. at a frequency of 10 Hz and strain of 3% was used as an index of the low hysteresis loss property. A lower index indicates better low hysteresis loss property.

(152) (Evaluation 3) Change Over Time (Increase in Mooney Viscosity after 1 Month)

(153) The modified conjugated diene-based polymer was stored at normal temperature and normal pressure for 1 month, the Mooney viscosity thereof after the storage was measured, and the difference from the Mooney viscosity measured immediately after polymerization was calculated.

(154) A smaller value indicates less change over time and better quality stability.

(155) TABLE-US-00002 TABLE 2 Com- Com- Com- Com- Com- Com- Com- parative parative parative parative parative parative parative Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- ample ample ample ample ample ample ample ample ample ample ample ample ample ample 8 9 10 11 12 13 14 8 9 10 11 12 13 14 Modified Conjugated Diene- A B C D E F G H I J K L M N based Polymer (Sample No.) Mooney Viscosity of Modified 63 65 62 61 65 64 63 64 62 65 64 60 63 59 Conjugated Diene-based Polymer (100° C.) Mooney Viscosity of 55 53 56 49 47 54 50 65 60 59 58 55 66 52 Compound (130° C.) Increase in Mooney Viscosity 3 1 2 1 0 2 2 0 5 11 7 0 0 12 after 1 Month Physical 50° C. Index 85 96 84 78 92 73 66 100 88 99 83 99 92 83 Properties tanδ of (Strain Vulcanizate 3%)

(156) As shown in Table 2, it was confirmed that the rubber compositions (the modified conjugated diene-based polymer compositions) of Examples 8 to 14 have lower Mooney viscosities of the compounds obtained for obtaining vulcanizates, have better processability, and are better in the low hysteresis loss property obtained when in the form of a vulcanizate as compared with the rubber composition of Comparative Example 8 although the Mooney viscosities before obtaining the compounds were equivalent. Besides, it was confirmed that the rubber compositions of Examples 8 to 14 have lower Mooney viscosities of the compounds obtained for obtaining vulcanizates, have better processability, are also less in increase in the Mooney viscosity after the storage for 1 month, and have better quality stability as compared with the rubber compositions of Comparative Examples 9, 10 and 14 although the Mooney viscosities before obtaining the compounds were equivalent.

(157) It was confirmed that the rubber composition of Example 9 is better in the low hysteresis loss property obtained when in the form of a vulcanizate as compared with the rubber composition of Comparative Example 12.

(158) It was confirmed that the rubber compositions of Examples 8, 9 and 10 have lower Mooney viscosities of the compounds obtained for obtaining vulcanizates, have better processability, and are better in the low hysteresis loss property obtained when in the form of a vulcanizate as compared with the rubber composition of Comparative Example 8 although the Mooney viscosities before obtaining the compounds were equivalent. It was further confirmed that the rubber compositions of Examples 8, 9 and 10 are less in increase in the Mooney viscosity after 1 month of polymerization and have better quality stability as compared therewith.

(159) As shown in Table 2, it was confirmed that the rubber compositions of Examples 13 and 14 have lower Mooney viscosities of the compounds obtained for obtaining vulcanizates, have better processability, and are better in the low hysteresis loss property obtained when in the form of a vulcanizate as compared with the rubber composition of Comparative Example 13 although the Mooney viscosities before obtaining the compounds were equivalent.

(160) This application is based upon the prior Japanese patent application (Japanese Patent Application No. 2016-161429), filed to the Japanese Patent Office on Aug. 19, 2016, the entire contents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

(161) A modified conjugated diene-based polymer according to the present invention is excellent in the low hysteresis loss property when in the form of a vulcanized rubber, and is also excellent in the processability when used for obtaining a composition through mixing with another component or obtaining a vulcanized rubber, and hence can be suitably used as a material of various members such as tire treads, shoes and industrial products.