JP5347353B2 - Method for producing silica-containing diene rubber composition - Google Patents

Description

  The present invention relates to a method for producing a silica-containing diene rubber composition. More specifically, the present invention relates to a process for producing a silica-containing diene rubber composition having good processability, low rolling resistance and exothermicity when vulcanized, and excellent wear resistance.

  In order to improve various characteristics of a pneumatic tire molded from a diene rubber in a silica-containing diene rubber composition, a method using a terminal-modified polymer has been proposed. It cannot be avoided that the modification step becomes complicated, and a solvent may be required in some cases.

A diene rubber preferably containing 50% by weight or more of SBR, a modifier having a functional group that reacts with a vinyl group in the SBR and an amino group or an amide group, such as cysteamine HSCH ₂ CH ₂ NH ₂ .HCl A compound having a mercapto group and an amino group, or a compound having a disulfide bond and an amino group such as cystamine H ₂ NCH ₂ CH ₂ SSCH ₂ CH ₂ NH ₂ and a radical generator are mixed to prepare a pre-mixture. By adding a filler such as silica, silica-carbon black (which is also a radical generator) to the obtained pre-mixture and mixing, it is possible to achieve both rolling resistance and wet grip without increasing the number of modified polymer species. It is possible to form the tire tread portion of the illustrated pneumatic tire.
Japanese Patent Laid-Open No. 2008-19401

  In this pre-mixing process, SBR is modified by reacting SBR with a diene rubber containing SBR, a modifier and an organic peroxide, an azo initiator, or a radical generator that uses carbon black. Under stirring conditions such as 140 ° C. or higher, more preferably 160 to 200 ° C. (180 ° C. in the examples), the mercapto group or disulfide bond moiety reacts with the vinyl group in the SBR. An amino group is introduced into the main chain, that is, the main chain of the polymer molecule can be modified by premixing with respect to SBR in which the main chain is unmodified.

  An object of the present invention is to provide a method for producing a silica-containing diene rubber composition having good processability, low rolling resistance and heat generation when vulcanized, and excellent wear resistance. There is.

The object of the present invention is to provide 0.01 to 5 parts by weight of dithiosalicylic acid, L-cystine, 3,3′-dithiodipropionic acid or dithiodithiol to 100 parts by weight of diene rubber containing 50% by weight or more of natural rubber. This is achieved by premixing a disulfide compound, which is aniline, at a temperature of 20 to 135 ° C., and then mixing 20 to 120 parts by weight of silica to produce a silica-blended diene rubber composition.

The silica-containing diene rubber composition produced by the method of the present invention has good processability indicated by Mooney viscosity ML _{1 + 4} (100 ° C.), and rolling resistance and heat build-up indicated by tan δ (60 ° C.). Therefore, it can be suitably used as a material for forming a tire tread portion of a pneumatic tire.

  As the diene rubber, those containing 50% by weight or more of natural rubber are used, and the natural rubber is used alone. When the content ratio of the natural rubber is less than 50% by weight, not only the ratio derived from non-petroleum resources but also the physical properties are decreased. As the synthetic rubber used with natural rubber, styrene butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), etc. are used. SBR is preferably used. As SBR, either emulsion polymerization SBR (E-SBR) or solution polymerization SBR (S-SBR) can be used.

The diene rubber containing 50% by weight or more of natural rubber has 0.01 to 5 parts by weight, preferably 0.02 to 2 parts by weight, more preferably 0.03 to 1 part by weight of a polyfunctional group-containing disulfide compound per 100 parts by weight thereof. Is added and premixed at a temperature of 40-100 ° C. The preliminary mixing is performed for about 0.5 to 5 minutes using a Banbury mixer, kneader, roll or the like.

  If the addition ratio of the polyfunctional group-containing disulfide compound is less than this, the improvement of various properties desired in the present invention as described above cannot be achieved, whereas if it is used at a higher addition ratio, the final rubber Breaking physical properties are lowered. Further, if the premixing at 20 to 135 ° C. is not performed, the improvement of various properties desired in the present invention as described above is not achieved, and if the premixing temperature is higher than 135 ° C., the rubber The molecular weight is greatly reduced, and the physical properties of rubber are reduced.

L-シスチン
HOOCCH(NH₂)CH₂SSCH₂CH(NH₂)COOH
3,3′-ジチオジプロピオン酸(略号：DPS)
HOOCCH₂CH₂SSCH₂CH₂COOH
8,8′-ジチオジオクタン酸
HOOC(CH₂)₇SS(CH₂)₇COOH
ジチオジグリコール酸(ジチオ二酢酸)
HOOCCH₂SSCH₂COOH
ジチオサリチル酸(略号：DTS)

ただし、ジアミノ基含有ジスルフィド化合物であるジチオジアニリン等については、天然ゴム100重量％よりなるジエン系ゴムに適用される。 As the polyfunctional group-containing disulfide compound, the following compounds are used.
Dithiodianiline (abbreviation: DTDA)

L-cystine
HOOCCH (NH ₂ ) CH ₂ SSCH ₂ CH (NH ₂ ) COOH
3,3'-dithiodipropionic acid (abbreviation: DPS)
HOOCCH ₂ CH ₂ SSCH ₂ CH ₂ COOH
8,8'-dithiodioctanoic acid
HOOC (CH ₂ ) ₇ SS (CH ₂ ) ₇ COOH
Dithiodiglycolic acid (dithiodiacetic acid)
HOOCCH ₂ SSCH ₂ COOH
Dithiosalicylic acid (abbreviation: DTS)

However, dithiodianiline, which is a diamino group-containing disulfide compound, is applied to a diene rubber composed of 100% by weight of natural rubber.

The diene rubber premixed with these disulfide compounds is blended with 20 to 120 parts by weight, preferably 30 to 100 parts by weight of silica per 100 parts by weight of the diene rubber. There are two types of silica, wet and dry, depending on the synthesis method, and wet silica is preferably used for tire applications from the viewpoint of performance and cost. By using silica as a filler in the tread formulation of passenger car pneumatic tires, it is possible to achieve both high rolling resistance and high tire performance on wet surfaces without sacrificing wear resistance. The silica having the above blending ratio is mixed, but in the present invention in which a specific modifier is blended with a diene rubber and premixed, improvement in wear resistance is also achieved.

  Silica used as a filler has poor affinity with rubber polymers, and in rubber, silica has the ability to generate hydrogen bonds through silanol groups and lower the dispersibility of silica in rubber. In order to improve the properties required for the above and the dispersibility with the diene rubber, the silane coupling agent is used in a proportion of 2 to 18% by weight, preferably 5 to 10% by weight, based on the silica weight. If the proportion of silane coupling agent used is less than this, the properties required of silica and dispersibility with diene rubber will not be fully exhibited, while if it is used in a proportion higher than this, workability will deteriorate. Will come to do.

The silane coupling agent has a general formula
(R ′) _3-n (OR) _n SiR ″ SxR ″ Si (OR) _n (R ′) _3-n
R: an alkyl group having 1 to 3 carbon atoms
R ′: an alkyl group having 1 to 3 carbon atoms
R ″: an alkylene group having 1 to 5 carbon atoms
X: 2-4
n: 1 to 3
A polysulfide silane coupling agent having an alkoxysilyl group that reacts with a silanol group on the silica surface and a sulfur chain that reacts with a polymer is used. Specifically, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) ) Disulfide and the like are preferably used.

After premixing a specific disulfide compound at a temperature of 20 to 135 ° C. with a silica-containing diene rubber composition containing the above components as essential components, that is, a diene rubber containing 50% by weight or more of natural rubber, silica is added. In the mixed composition, a compounding agent generally used as a compounding agent for rubber, for example, a reinforcing agent or filler represented by carbon black, a vulcanizing agent such as sulfur depending on the type of diene rubber Further, vulcanization accelerators such as thiazole, sulfenamide, guanidine, and thiuram, processing aids such as stearic acid, paraffin wax, and aroma oil, anti-aging agents, and plasticizers are appropriately blended and used.

  Preparation of the composition is carried out by mixing other compounding agents excluding vulcanizing system components for about 1 to 10 minutes using a closed Banbury mixer, etc. The mixture is discharged out of the mixer and allowed to cool to room temperature, and then the vulcanized components are blended using an open roll and mixed to produce a desired silica-blended diene rubber composition. .

  The silica-containing diene rubber composition produced in this manner is extruded into a tread shape of a pneumatic tire, and is bonded to the casing portion by a normal method on a tire molding machine to form an unvulcanized tire. This can be pressurized and heated in a vulcanizer to obtain a pneumatic tire having a tread portion and the like formed from this composition.

  Next, the present invention will be described with reference to examples.

Comparative example 1 (standard example)
Natural rubber (RSS # 3) 100 parts by weight Carbon black (Cabot Japan product show black N339) 5 〃
Silica (Rhodia product ZEOSIL 1165MP) 50 〃
Silane coupling agent (Eponic Degussa Japan product Si69) 4 〃
Stearic acid (NOF product beads stearic acid) 2 〃
Zinc Hana (Zinc Oxide Industrial Products, 3 types of zinc oxide) 3 〃
Anti-aging agent (Santoflex 6PPD, product of Flexis) 1 〃
Anti-aging agent (Ouchi Emerging Chemical Industry Product Nocrack 224) 1 〃
Sulfur (Hosoi Chemical Products Oil Treatment Sulfur) 1.5 〃
Vulcanization accelerator (Ouchi Emerging Chemical Industry Noxeller NS) 1.5 〃
Among the above components, components other than sulfur and vulcanization accelerator are mixed for 5 minutes using a closed Banbury mixer, and these mixtures are discharged to the outside of the mixer and cooled to room temperature, and then opened. Using a roll, sulfur and a vulcanization accelerator were blended and mixed.

The rubber composition thus obtained was vulcanized at 160 ° C. for 15 minutes to obtain a predetermined vulcanized rubber test piece, and the following items were measured for the rubber composition and the vulcanized rubber test piece. .
Mooney viscosity ML _{1 + 4} (100 ° C): JIS K6300 compliant Lubke JIS hardness: JIS K6253 compliant, measured at 0 ° C, 20 ° C and 60 ° C Tensile test: JIS K6251 vulcanized rubber Using JIS No. 3 dumbbell from the test piece, thickness
2mm-thick rubber sheet is punched out and 100% modular under 500mm / min tensile speed condition.
Lath (M100), 300% modulus (M300), tensile strength (TB) and elongation at break (EB)
Viscoelasticity test (rolling resistance / heat generation): Using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho
Strain 10 ± 2%, frequency 20Hz, ambient temperature 60 ℃
Measure tanδ under conditions
The smaller this value, the lower the rolling resistance and heat generation.
Abrasion test: In accordance with JIS K6264, using a Lambourn abrasion tester, load 15N, slip
Measured at a rate of 50%
It is indicated by an index with the wear amount of the standard example as 100.
Good wear

Examples 1-7
In Comparative Example 1, first, natural rubber and various disulfide compounds were premixed for 1 minute at 80 ° C. using a Banbury mixer, and then the components other than sulfur and the vulcanization accelerator were mixed, and then sulfur. And vulcanization accelerators were mixed using open rolls.
DTS: Kanto Chemicals Special Grade
Dithiosalicylic acid
L-cystine: Kanto Chemicals special grade
HOOCCH (NH ₂ ) CH ₂ SSCH ₂ (NH ₂ ) COOH
DPS: Kanto Chemical Products Special Grade
3,3'-dithiodipropionic acid HOOCCH ₂ CH ₂ SSCH ₂ CH ₂ COOH
DTDA: Kanto Chemicals Special Grade
Dithiodianiline

The measurement results in the above Examples 1 to 7 and Comparative Example 1 are shown in the following Tables 1 and 2 together with the type and amount (parts by weight) of the disulfide compound used.
Table 1 (with silica 50phr)
Ratio-1 Real-1 Real-2 Real-3
[Disulfide compound]
DTS 0.06
L-cystine 0.05
DPS 0.04

Premixing temperature (° C) −80 80 80
〔Measurement item〕
ML _{1 + 4} (100 ° C) 82.6 80.9 81.5 81.6
Lyubke JIS hardness
0 ° C 68 68 68 67
20 ° C 67 67 68 67
60 ° C 65 65 65 64
Tensile test
M100 (MPa) 3.4 3.1 3.0 3.0
M300 (MPa) 13.4 12.4 12.2 12.2
TB (MPa) 31.4 30.7 29.8 30.2
EB (%) 590 590 580 590
Viscoelasticity test
tanδ (60 ° C) 0.1100 0.1002 0.0993 0.1027
Abrasion test
Index 100 118 111 105
Table 2 (with silica 50phr)
Real-4 Real-5 Real-6 Real-7
[Disulfide compound]
DTS 0.80
L-cystine 0.80
DPS 0.80
DTDA 0.10

Premixing temperature (℃) 80 80 80 80
〔Measurement item〕
ML _{1 + 4} (100 ° C) 67.8 66.8 64.9 79.4
Lyubke JIS hardness
0 ° C 67 67 66 67
20 ° C 66 66 65 66
60 ° C 64 64 63 64
Tensile test
M100 (MPa) 3.2 3.1 3.1 3.4
M300 (MPa) 12.5 12.1 12.0 13.3
TB (MPa) 30.3 30.7 30.7 30.9
EB (%) 580 590 590 570
Viscoelasticity test
tanδ (60 ° C) 0.0821 0.0915 0.1004 0.1033
Abrasion test
Index 107 110 107 108

Comparative Example 2 and Example 8
In Comparative Example 1 and Example 1, the silica content was changed to 38 parts by weight, and the silane coupling agent content was changed to 6 parts by weight. Furthermore, in Example 8 in which the premixing temperature was changed to 70 ° C., the disulfide compound was used in a predetermined blending amount.

The measurement results in the above Example 8 and Comparative Example 2 are shown in the following Table 3 together with the type and blending amount (parts by weight) of the disulfide compound used.
Table 3 (with silica 38phr)
Ratio-2 Real-8
[Disulfide compound]
L-cystine 0.05

Premixing temperature (℃) −70
〔Measurement item〕
ML _{1 + 4} (100 ℃) 62.0 56.6
Lyubke JIS hardness
0 ° C 67 67
20 ° C 66 67
60 ° C 64 64
Tensile test
M100 (MPa) 3.6 3.6
M300 (MPa) 15.5 15.3
TB (MPa) 30.0 30.3
EB (%) 500 500
Viscoelasticity test
tanδ (60 ° C) 0.0549 0.0535
Abrasion test
Index 92 94

Comparative Example 3 and Example 9
In Comparative Example 1 and Example 1, the silica content was changed to 80 parts by weight, and the silane coupling agent content was changed to 8 parts by weight. Furthermore, in Example 9 , a disulfide compound was used in a predetermined blending amount.

The measurement results in Example 9 and Comparative Example 3 are shown in the following Table 4 together with the type and amount (parts by weight) of the disulfide compound used.
Table 4 (with silica 80phr)
Ratio-3 Real-9
[Disulfide compound]
DTS 0.80

Premixing temperature (℃) −80
〔Measurement item〕
ML _{1 + 4} (100 ℃) 95.3 91.6
Lyubke JIS hardness
0 ° C 73 72
20 ° C 72 70
60 ℃ 70 69
Tensile test
M100 (MPa) 4.5 4.4
M300 (MPa) 14.9 14.6
TB (MPa) 35.3 34.2
EB (%) 490 480
Viscoelasticity test
tanδ (60 ° C) 0.1689 0.1638
Abrasion test
Index 119 127

Comparative Example 4 and Example 10
In Comparative Example 1 and Example 1, 20 parts by weight of 100 parts by weight of natural rubber were replaced with SBR (Nippon Zeon product Nipol 1502). Furthermore, in Example 10 in which the premixing temperature was changed to 100 ° C., 0.80 part by weight of DTS was used as the disulfide compound.

The measurement results in Example 10 and Comparative Example 4 are shown in the following Table 5 together with the type and blending amount (parts by weight) of the disulfide compound .
Table 5 (NR 80 parts, SBR 20 parts blend)
Ratio-4 Real-10
[Disulfide compound]
DTS 0.80
Premixing temperature (℃) −100
〔Measurement item〕
ML _{1 + 4} (100 ℃) 74.3 71.8
Lyubke JIS hardness
0 ° C 68 67
20 ° C 68 67
60 ° C 65 64
Tensile test
M100 (MPa) 3.0 3.0
M300 (MPa) 12.2 12.1
TB (MPa) 29.8 29.4
EB (%) 580 570
Viscoelasticity test
tanδ (60 ° C) 0.1227 0.1201
Abrasion test Index 98 102

Comparative Example 5 and Example 11
In Comparative Example 1 and Example 1, 40 parts by weight of 100 parts by weight of natural rubber were replaced with SBR (Nipol 1502). Furthermore, in Example 11 in which the premixing temperature was changed to 100 ° C., 0.80 part by weight of DTS was used as the disulfide compound.

The measurement results in Example 11 and Comparative Example 5 are shown in the following Table 6 together with the type and blending amount (parts by weight) of the disulfide compound .
Table 6 (NR 60 parts, SBR 40 parts blend)
Ratio-5 Real-11
[Disulfide compound]
DTS 0.80
Premixing temperature (℃) −100
〔Measurement item〕
ML _{1 + 4} (100 ° C) 69.8 67.5
Lyubke JIS hardness
0 ° C 67 67
20 ° C 66 66
60 ° C 63 64
Tensile test
M100 (MPa) 2.8 2.6
M300 (MPa) 11.5 11.3
TB (MPa) 26.8 26.4
EB (%) 560 550
Viscoelasticity test
tanδ (60 ° C) 0.1328 0.1317
Abrasion test Index 93 97

Comparative Example 6
In Example 1 , the disulfide compound DTS was not premixed with natural rubber and was mixed together during mixing of the components except for sulfur and vulcanization accelerator.

The measurement results in Comparative Example 6 above are shown in the following Table 7 together with the type and blending amount (parts by weight) of the disulfide compound .
Table 7 (Presence / absence of premix)
Real-1 ratio-6
[Disulfide compound]
DTS 0.10 0.10

Premixing temperature (° C) 80 −
〔Measurement item〕
ML _{1 + 4} (100 ℃) 80.9 82.9
Lyubke JIS hardness
0 ° C 68 68
20 ° C 67 67
60 ° C 65 65
Tensile test
M100 (MPa) 3.1 3.4
M300 (MPa) 12.4 13.4
TB (MPa) 30.7 31.3
EB (%) 590 580
Viscoelasticity test
tanδ (60 ° C) 0.1002 0.1103
Abrasion test
Index 118 100

Claims (3)

Dithiosalicylic acid 0.01 to 5 parts by weight of natural rubber against the diene rubber 100 parts by weight containing at least 50 wt.%, L-cystine, a disulfide compound which is 3,3'-dithiodipropionic acid or dithio dianiline 40 A method for producing a silica-containing diene rubber composition, characterized by mixing 20 to 120 parts by weight of silica after premixing at a temperature of -100 ° C. The method for producing a silica-containing diene rubber composition according to claim 1, wherein a disulfide compound having a diamino group is premixed with a diene rubber comprising 100% by weight of natural rubber. Preliminary mixing and silica mixing are performed in a closed Banbury mixer, and the resulting vulcanized system component is compounded with the silica-containing diene rubber composition according to claim 1 using an open roll. For producing a diene rubber composition containing a functional silica.