ORGANOSILICON COMPOUND GRAFT COPOLYMER AND RUBBER COMPOSITION FOR TIRE INCLUDING THE COPOLYMER

Abstract

An object of the present invention is to provide a modifier suitable for obtaining a lubricating oil, a coating material, an adhesive, and the like with better smoothness and few bumps and to provide a rubber composition for a tire, which is suitable for preparing a tire with both excellent braking performance and excellent fuel efficiency. The present invention relates to an organosilicon compound graft copolymer (X) including a main chain derived from an ethylene/a-olefin copolymer (A) and a graft part derived from an organosilicon compound (B) having one or more unsaturated groups; and a rubber composition for a tire, including 1 to 30 parts by mass of the organosilicon compound graft copolymer (X) based on 100 parts by mass of a diene rubber including an aromatic vinyl-conjugated diene copolymerized rubber.

Claims

1. An organosilicon compound graft copolymer (X), comprising a main chain derived from an ethylene/α-olefin copolymer (A) and a graft part derived from an organosilicon compound (B) having one or more unsaturated groups.

2. The organosilicon compound graft copolymer (X) according to claim 1, wherein the main chain derived from an ethylene/α-olefin copolymer (A) is an ethylene/α-olefin copolymer (A) having a weight-average molecular weight (Mw) of 2,000 to 14,000, a number-average molecular weight (Mn) of 1,600 to 7,000 and a molecular weight distribution (Mw/Mn) of 1.4 to 2.1.

3. The organosilicon compound graft copolymer (X) according to claim 1, wherein the main chain derived from an ethylene/α-olefin copolymer (A) is an ethylene/α-olefin copolymer (A) comprising 41 to 48% by mass of a component derived from ethylene (the total amount of the component derived from ethylene and a component derived from α-olefin is 100% by mass).

4. The organosilicon compound graft copolymer (X) according to claim 1, wherein the mass of the graft part derived from an organosilicon compound (B) is 1% or more and less than 100% (the total amount of the main chain and the graft part is 100% by mass).

5. The organosilicon compound graft copolymer (X) according to claim 1, wherein the organosilicon compound (B) is vinyltrimethoxysilane.

6. The organosilicon compound graft copolymer (X) according to claim 1, having a weight-average molecular weight (Mw) of 1,800 to 13,000, a number-average molecular weight (Mn) of 1,500 to 6,500, and a molecular weight distribution (Mw/Mn) of 1.4 to 2.1.

7. The organosilicon compound graft copolymer (X) according to claim 1, further having a content of 0 to 0.3% by mass of a polymer component having a peak of molecular weight M determined by GPC in the range of 5≤Log M≤6.

8. A rubber composition for a tire, comprising 1 to 30 parts by mass of the organosilicon compound graft copolymer (X) according to claim 1 based on 100 parts by mass of a diene rubber comprising an aromatic vinyl-conjugated diene copolymerized rubber.

9. The rubber composition for a tire according to claim 8, further comprising 5 to 150 parts by mass of an inorganic filler.

10. The rubber composition for a tire according to claim 9, wherein the inorganic filler is silica.

11. The rubber composition for a tire according to claim 8, wherein the diene rubber comprises SBR as the aromatic vinyl-conjugated diene copolymerized rubber and the diene rubber is a mixture of the SBR and BR comprising the SBR and the BR at a ratio of SBR/BR=100/0 to 1/99 (mass ratio).

Description

EXAMPLES

[0100] Hereinafter the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0101] The ethylene/α-olefin copolymer (A), the organosilicon compound graft copolymer (X), the diene rubber, and other components used in Examples and Comparative Examples are shown below.

[0102] [Ethylene/propylene copolymer (A-1)]

[0103] An ethylene/propylene copolymer (A-1) having a Mw of 12,500, Mn of 6,600, and Mw/Mn of 1.9 with an ethylene content of 44.8% by mass was used as the ethylene/α-olefin copolymer (A) (described as “(A)” in Table 1).

[0104] «Organosilicon compound graft copolymer (X)»

[0105] An organosilicon compound graft copolymer (X-1) (may be abbreviated as (X-1) below) prepared by the following method was used as the organosilicon compound graft copolymer (X) (described as “(X)” in Table 1).

[0106] [Production of organosilicon compound graft copolymer (X-1)]

[0107] 181 g of the above ethylene/propylene copolymer (A-1) and 25.5 g of vinyltrimethoxysilane (VTMOS), which is an organosilicon compound (B) having one or more unsaturated groups , were put in a 1 L glass reaction vessel. The air of the vessel was replaced with nitrogen and then the vessel was sealed. The temperature was increased to 160° C. with stirring by a double anchor blade at 200 rpm. 50 mL of a solution prepared by dissolving 1.02 g of dicumyl peroxide (made by NOF Corporation, product name: PERCUMYL D) in toluene was added dropwise thereto with stirring at 400 rpm over 60 minutes. After the completion of the dropwise addition, stirring was continued for 90 minutes. Then the rotation number of stirring was reduced to 300 rpm and the solution was cooled to 50° C. The pressure of the vessel was released and the vessel was opened. The reaction solution was taken out and toluene, the solvent, and VTMOS were vacuum distilled using an evaporator. Subsequently, the resultant was vacuum dried at 90° C. to give an organosilicon compound graft copolymer (X-1).

[0108] The amount of graft of VTMOS in the organosilicon compound graft copolymer (X-1) was 11.1% by mass.

[0109] The resulting organosilicon compound graft copolymer (X-1) has a weight-average molecular weight (Mw) of 11,600, a number-average molecular weight (Mn) of 6,100 and a molecular weight distribution (Mw/Mn) of 1.9.

[0110] [Ethylene/α-olefin copolymer (A-2)]

[0111] An ethylene/propylene copolymer (A-2) having a Mw of 2,700, a Mn of 1,800, and a Mw/Mn of 1.5 with an ethylene content of 42.9% by mass was used as the ethylene/α-olefin copolymer (A).

[0112] «Organosilicon compound graft copolymer (X-2)»

[0113] An organosilicon compound graft copolymer (X-2) prepared by the following method was used as the organosilicon compound graft copolymer (X).

[0114] [Production of organosilicon compound graft copolymer (X-2)]

[0115] 177 g of the above ethylene/propylene copolymer (A-2) and 25.5 g of vinyltrimethoxysilane (VTMOS), which is an organosilicon compound (B) having one or more unsaturated groups, were put in a 1 L glass reaction vessel. The air of the vessel was replaced with nitrogen and then the vessel was sealed. The temperature was increased to 160° C. with stirring by a double anchor blade at 200 rpm. 50 mL of a solution prepared by dissolving 1.02 g of dicumyl peroxide (made by NOF Corporation, product name: PERCUMYL D) in toluene was added dropwise thereto with stirring at 400 rpm over 60 minutes. After the completion of the dropwise addition, stirring was continued for 90 minutes. Then the rotation number of stirring was reduced to 300 rpm and the solution was cooled to 50° C. The pressure of the vessel was released and the vessel was opened. The reaction solution was taken out and toluene, the solvent, and VTMOS were vacuum distilled using an evaporator. Subsequently, the resultant was vacuum dried at 90° C. to give an organosilicon compound graft copolymer (X-2).

[0116] The amount of graft of VTMOS in the organosilicon compound graft copolymer (X-2) was 11.9% by mass.

[0117] The resulting organosilicon compound graft copolymer (X-2) has a weight-average molecular weight (Mw) of 2,600, a number-average molecular weight (Mn) of 1,650, and a molecular weight distribution (Mw/Mn) of 1.6.

[0118] [Ethylene/α-olefin copolymer (A-3)]

[0119] An ethylene/propylene copolymer (A-3) having a Mw of 4,800, a Mn of 2,800, and a Mw/Mn of 1.7 with an ethylene content of 41.3% by mass was used as the ethylene/α-olefin copolymer (A).

[0120] «Organosilicon compound graft copolymer (X-3)»

[0121] An organosilicon compound graft copolymer (X-3) prepared by the following method was used as the organosilicon compound graft copolymer (X).

[0122] [Production of organosilicon compound graft copolymer (X-3)]

[0123] 177 g of the above ethylene/propylene copolymer (A-3) and 25.5 g of vinyltrimethoxysilane (VTMOS), which is an organosilicon compound (B) having one or more unsaturated groups, were put in a 1 L glass reaction vessel. The air of the vessel was replaced with nitrogen and then the vessel was sealed. The temperature was increased to 160° C. with stirring by a double anchor blade at 200 rpm. 50 mL of a solution prepared by dissolving 1.02 g of dicumyl peroxide (made by NOF Corporation, product name: PERCUMYL D) in toluene was added dropwise thereto with stirring at 400 rpm over 60 minutes. After the completion of the dropwise addition, stirring was continued for 90 minutes. Then the rotation number of stirring was reduced to 300 rpm and the solution was cooled to 50° C. The pressure of the vessel was released and the vessel was opened. The reaction solution was taken out and toluene, the solvent, and VTMOS were vacuum distilled using an evaporator. Subsequently, the resultant was vacuum dried at 90° C. to give an organosilicon compound graft copolymer (X-3).

[0124] The amount of graft of VTMOS in the organosilicon compound graft copolymer (X-3) was 12.1% by mass.

[0125] The resulting organosilicon compound graft copolymer (X-3) has a weight-average molecular weight (Mw) of 4,600, a number-average molecular weight (Mn) of 2,750, and a molecular weight distribution (Mw/Mn) of 1.7.

[0126] «Organosilicon compound graft copolymer (X-4)»

[0127] An organosilicon compound graft copolymer (X-4) prepared by the following method was used as the organosilicon compound graft copolymer (X).

[0128] [Production of organosilicon compound graft copolymer (X-4)]

[0129] 181 g of the above ethylene/propylene copolymer (A-1) and 25.5 g of vinyltrimethoxysilane (VTMOS), which is an organosilicon compound (B) having one or more unsaturated groups, were put in a 1 L glass reaction vessel. The air of the vessel was replaced with nitrogen and then the vessel was sealed. The temperature was increased to 160° C. with stirring by a double anchor blade at 200 rpm. 50 mL of a solution prepared by dissolving 10.01 g of dicumyl peroxide (made by NOF Corporation, product name: PERCUMYL D) in toluene was added dropwise thereto with stirring at 400 rpm over 60 minutes. After the completion of the dropwise addition, stirring was continued for 90 minutes. Then the rotation number of stirring was reduced to 300 rpm and the solution was cooled to 50° C. The pressure of the vessel was released and the vessel was opened. The reaction solution was taken out and toluene, the solvent, and VTMOS were vacuum distilled using an evaporator. Subsequently, the resultant was vacuum dried at 90° C. to give an organosilicon compound graft copolymer (X-4).

[0130] The amount of graft of VTMOS in the organosilicon compound graft copolymer (X-4) was 10.9% by mass.

[0131] The resulting organosilicon compound graft copolymer (X-4) was found to be bimodal in the measurement of the molecular weight by GPC. The organosilicon compound graft copolymer (X-4) has a weight-average molecular weight (Mw) of 20 14,600, a number-average molecular weight (Mn) of 6,300, and a molecular weight distribution (Mw/Mn) of 2.3 at the first peak. The organosilicon compound graft copolymer (X-4) has a weight-average molecular weight (Mw) of 458,100, a number-average molecular weight (Mn) of 412,700, and a molecular weight distribution (Mw/Mn) of 1.1 at the second peak.

[0132] Properties of the resulting organosilicon compound graft copolymer (X) were observed by the following methods.

[0133] [Observation of surface]

[0134] 0.327 g and 0.109 g each of the organosilicon compound graft copolymer (X-1) was applied to two 26 mm long×26 mm wide glass plates (at a film thickness of 0.6 mm and 0.2 mm, respectively, and a density of 0.838 g/cm.sup.3). The presence of bump was visually observed.

[0135] [Measurement of polymer component of organosilicon compound graft copolymer (X)]

[0136] The amount of the polymer component in the organosilicon compound graft copolymer (X) was measured by the method described above.

[0137] [Examples 1 to 4]

[0138] The surface of the organosilicon compound graft copolymers (X-1), (X-2), (X-3), and (X-4) produced by the above method was observed by the above method. As a result, no bump was found in any of the compounds. Meanwhile, for (X-1), (X-2), and (X-3), the number of cells mixed in the coating film (0.6 mm thick) was each 0, 10, and 90, which are less than 100 (excellent coating properties). By contrast, for (X-4), the number of cells mixed in the coating film (0.6 mm thick) was 150, which is 100 or more and less than 250 (moderate coating properties).

[0139] The evaluation criteria for coating properties are as follows in Table 1.

[0140] Good: the number of cells mixed in coating film (0.6 mm thick) is 0 to less than 100.

[0141] Moderate: the number of cells mixed in coating film (0.6 mm thick) is 100 to less than 250.

[0142] Poor: the number of cells mixed in coating film (0.6 mm thick) is 250 or more.

[0143] The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 (A) A-1 A-2 A-3 A-1 Mw 12,500 2,700 4,800 12,500 Mn 6,600 1,800 2,800 6,600 Mw/Mn 1.9 1.5 1.7 1.9 Radical initiator Part(s) by 0.56 0.58 0.56 5.50 based on (A) mass (X) X-1 X-2 X-3 X-4 Mw 11,600 2,600 4,600 14,600 Mn 6,100 1,650 2,750 6,300 Mw/Mn 1.9 1.6 1.7 2.3 Polymer Mw 458,100 component in Mn 412,700 (X) Mw/Mn 1.1 Amount of polymer 0 0 0 1 component in (X) (% by mass) Presence of bump in coating None None None None film Coating properties Good Good Good Moderate

[0144] «Diene rubber»

[0145] (1) Diene rubber-1: styrene/butadiene rubber (SBR), Nipol (registered trademark) NS116 (made by ZEON CORPORATION) [styrene content=21%, Mooney viscosity=45, specific 5 gravity 0.93]

[0146] (2) Diene rubber-2: butadiene rubber (BR) Nipol (registered trademark) 1220 (made by ZEON CORPORATION) [Mooney viscosity=44, specific gravity=0.90]

[0147] «Compounding agent»

[0148] (1) Zinc white, JIS#2

[0149] (2) Aroma process oil: Diana Process (registered trademark) AH-16 (made by Idemitsu Kosan Co., Ltd.)

[0150] (3) Wet silica: Nipsil (trademark) VN3 (made by Tosoh Silica Corporation)

[0151] (4) Carbon black: Asahi #80 (Asahi Carbon Co., Ltd.)

[0152] (5) Silane coupling agent: Silanogran (trademark) Si69 (made by Techno Preknead HIDA)

[0153] (6) Vulcanization accelerator (CBS): Sancelar (trademark) CM (Sanshin Chemical Industry Co., Ltd.)

[0154] (7) Vulcanization accelerator (DPG): Sancelar (trademark) D-G (Sanshin Chemical Industry Co., Ltd.)

[0155] Properties of the rubber compositions and the like prepared in Examples and Comparative Examples were measured by the following methods.

[0156] (1) Compression set (CS)

[0157] A cross-linked body with a diameter of 29 mm and a height (thickness) of 12.5 mm was used as a specimen according to JIS K 6262. The specimen was compressed by 25% relative to the height of the specimen before applying load (12.5 mm). The specimen was set in a gear oven at 70° C. together with the spacer and heat-treated for 22 hours. The specimen was taken out and left at room temperature for 30 minutes. Then the height of the specimen was measured and the compression set (%) was calculated by the following equation.

[0158] For the compression set (0° C.), the specimen was set in a thermostatic bath at 0° C. and treated for 22 hours. Then the specimen was taken out from the thermostatic bath and left for 30 minutes. After that, the height of the specimen was measured and the compression set (%) was calculated by the following equation.

[0159] Compression set (%)={(t0-t1)/(t0-t2)}×100 [0160] t0: Height of specimen before a test [0161] t1: Height of specimen after being treated under the above conditions and being left at room temperature for 30 minutes [0162] t2: Height of specimen attached to the mold for measurement

[0163] (2) Dynamic viscoelasticity test

[0164] The temperature dependency of loss tangent, tan 5 (an index of vibration damping), of a 1 mm thick vulcanized rubber sheet was measured by using a viscoelastometer (Model RDS-2) made by Rheometric Scientific under conditions of a measurement temperature of 70 to 100° C., a frequency of 10 Hz, a distortion factor of 1.0% and a temperature increase rate of 4° C./ minute. tan 5 (damping rate) at 0° C. of the rubber composition was defined as an indicator of the braking performance of the tire. A larger tan S at 0° C. indicates a better braking performance. Furthermore, tan S (damping rate) at 60° C. of the rubber composition was defined as an indicator of the fuel efficiency of the car. A smaller tan S at 60° C. indicates a higher fuel efficiency.

[0165] [Example 5]

[0166] Diene rubber-1, diene rubber-2, the graft copolymer (X-1), silica, and a silane coupling agent were mixed in the amount shown in Table 2 using a 1.7 1 closed Banbury mixer for 2 minutes. Then, carbon black, aroma oil, zinc white, and stearic acid were added thereto and the mixture was mixed for 2 minutes to prepare a master batch. This master batch, a vulcanization accelerator, and sulfur were mixed by an 8 inch open roll whose temperature of the front roll and the rear roll was 50° C. to prepare a rubber composition, and the rubber composition was pressed and vulcanized in a mold of 10×10×0.1 cm at 170° C. for 10 minutes to prepare a vulcanized rubber composition for a tire. The resulting rubber composition for a tire was tested for dynamic viscoelasticity. Furthermore, the rubber composition for a tire was cross-linked under conditions of 170° C. and 15 minutes to give a vulcanized rubber composition with a thickness of 12.5 mm and a diameter of 29 mm. The compression set was measured using the resulting rubber composition. The properties of the resulting vulcanized rubber for a tire were measured by the method described above. The results of the evaluation are shown in Table 2.

[0167] [Example 6]

[0168] A vulcanized rubber composition for a tire was prepared in the same manner as in Example 5 except for changing the formulation to that shown in Table 2 instead of preparing the rubber composition for a tire used in Example 5. The properties of the resulting vulcanized rubber for a tire were measured by the method described above. The results of the evaluation are shown in Table 2.

[0169] [Example 7]

[0170] A vulcanized rubber composition for a tire was prepared in the same manner as in Example 5 except for changing the formulation to that shown in Table 2 instead of preparing the rubber composition for a tire used in Example 5. The properties of the resulting vulcanized rubber for a tire were measured by the method described above. The results of the evaluation are shown in Table 2.

[0171] [Comparative Example 1]

[0172] A vulcanized rubber composition was prepared in the same manner as in Example 1 except for not using the graft copolymer (X-1) used in Example 1. The properties of the resulting vulcanized rubber were measured by the method described above. The results of the evaluation are shown in Table 2.

TABLE-US-00002 TABLE 2 Ex. 5 Ex. 6 Ex. 7 Comp. Ex. 1 <Formulation> Diene rubber-1: 75 75 75 75 Nipol NS116R Diene rubber-2: 25 25 25 25 Nipol 1220 Nipsil VN3 36 36 36 36 Si-69 4 4 4 4 Asahi #80 40 40 40 40 Zinc white# 1 3 3 3 3 Stearic acid 2 2 2 2 AH-16 45 37.5 25 50 Graft copolymer (X-1) 5 12.5 25 — <Properties> Compression set 14 13 12 14 CS@0° C. × 22 h (%) <Tensile viscoelasticity> tanδ @0° C. 0.33 0.32 0.33 0.34 tanδ @60° C. 0.15 0.15 0.14 0.17