JP2011173986A - Rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which is used for tires, comprises a carboxyl group-modified solution-polymerized SBR and silica, and is further improved in the points of abrasion weight loss, wet performance, exothermic properties, heat-resistant sagging properties, vulcanization speed and the like. <P>SOLUTION: The rubber composition for tires is characterized by comprising 100 pts.wt. of a dienic rubber containing 50 to 100 wt.% of a carboxyl group-modified solution-polymerized SBR, 5 to 15 pts.wt. of a rubber gel having hydroxyl groups and/or carboxyl groups on the surfaces of the particles and having particle cores exhibiting a Tg of -50 to -100°C, and 10 to 150 pts.wt. of silica having a BET specific surface area of 100 to 300 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition for tires. More specifically, the present invention relates to a rubber composition for tires that is suitably used as a molding material for tire treads.

  With regard to a cap compound containing a large amount of silica, it is a problem to improve the physical properties of the vulcanized rubber, particularly the wet performance and the rolling resistance, by avoiding the high cohesiveness of the silica itself. Further, from the viewpoint of recent environmental measures and safety enhancement, further improvement of physical properties is expected.

  In Patent Document 1, an aromatic vinyl monomer and a diolefin are solution-polymerized, a carboxyl group or a salt thereof is introduced into the solution-polymerized rubber, a solution-polymerized rubber present in a solvent is mixed with a filler, A method for producing a rubber compound by removing the solution is described. And it is stated that the anionically polymerized solution rubber containing a double bond, such as solution polybutadiene and solution SBR, is advantageous in the production of treads because it exhibits a low rotational resistance compared to the corresponding emulsion polymerized rubber.

For example, carboxyl group-containing mercaptans are introduced into solution polymerized rubber.
HS-R′-COOX
-R ': optionally substituted with up to 3 carboxyl groups, or N, O,
Good linear be separated by the S atom, alkyl of C ₁ -C ₃₆ branched or cyclic
Len group
X: H atom, a metal atom or an alkyl group of C ₁ -C _36, cycloalkyl group or
Or ammonium groups substituted by aryl groups, such as thioglycolic acid, 2- or 3-mercaptopropionic acid, 4-mercaptobutyric acid, mercaptoundecanoic acid, 2-mercaptosuccinic acid or their alkali metal salts, alkaline earth metals It is said to be carried out by reacting at 40 to 150 ° C. in the presence of a salt, an ammonium group, a hydrocarbon solvent and a radical initiator.

  However, a vulcanized molded product of a rubber composition obtained by blending silica with such carboxyl group-modified solution polymerized SBR has a weight loss indicated by lambone wear, wet performance indicated by tan δ (0 ° C.), tan δ (60 ℃) exothermic property, hardness (60 ℃) / hardness (0 ℃) function ∆H heat resistance (hardness temperature dependence) and T95 vulcanization rate Is required.

JP 2000-256513 A JP 2001-31798 A JP 2009-51941 A JP 2009-102481 A

  An object of the present invention is to provide a tire rubber composition containing carboxyl group-modified solution-polymerized SBR and silica, which is further improved in terms of weight loss, wet performance, heat generation, heat resistance, heat resistance, vulcanization speed, and the like. It is to provide.

The object of the present invention is to provide 100 parts by weight of a diene rubber containing 50 to 100% by weight of a carboxyl group-modified solution polymerized SBR, having a hydroxyl group and / or a carboxyl group on the particle surface, and a particle core having a particle core of -50 to -100. This is achieved by a tire rubber composition comprising 5 to 15 parts by weight of a rubber gel exhibiting a Tg of ° C. and 10 to 150 parts by weight of silica having a BET specific surface area of 100 to 300 m ² / g.

  The rubber gel for tires containing the carboxyl group-modified solution-polymerized SBR and silica according to the present invention, further having a hydroxyl group and / or a carboxyl group on the particle surface, and a particle core having a Tg of -50 to -100 ° C The weight loss indicated by lambone wear, the wet performance indicated by tan δ (0 ° C), the exothermic property indicated by tan δ (60 ° C), the function ΔH of hardness (60 ° C) / hardness (0 ° C) Further improvement is achieved in terms of the heat resistance drooping property (temperature dependence of hardness) indicated by ## EQU3 ## and the vulcanization rate indicated by T95. The rubber composition for tires of the present invention having such characteristics is suitably used as a molding material for tire treads.

  As described above, the carboxyl group-modified solution polymerization SBR can be obtained by reacting a solution polymerization SBR [S-SBR] with a carboxyl group-containing mercaptan. Preferably, the content of styrene bound 5 to 30% by weight of styrene copolymerized with 0.2 to 2.5% by weight of a carboxyl group bound to S-SBR or a salt thereof and 95 to 70% by weight of butadiene, and 1,2-bound butadiene (Vinyl content) is included in the range of 5 to 55% by weight.

  Actually, the carboxyl group-modified S-SBR is not necessarily oil-extended, but when oil-extended, it is oil-extended with mineral oil, aroma oil (T-DAE) or the like. The oil spreading ratio is about 10-50 phr. In addition, the advantage that processability is improved by using the oil-extended carboxyl group-modified S-SBR can be seen.

  The carboxyl group-modified S-SBR is used in such a ratio that it accounts for 50 to 100% by weight in the diene rubber. That is, it can be used alone (100% by weight), but it can also be blended with other diene rubbers such as natural rubber, butadiene rubber, isoprene rubber, SBR other than carboxyl group-modified S-SBR, etc. When the ratio of carboxyl group-modified S-SBR is less than 50% by weight in the diene rubber, the wet grip performance is deteriorated, so the lower limit of the blend ratio is 50% by weight.

The tire rubber composition of the present invention, BET specific surface area (ASTM D1993-03 compliant) is 100 to 300 m ² / g, the silica preferably 100 to 250 m ² / g, preferably wet method in terms of cost and performance Silica is used in combination. As described above, the rubber compound may be formed by mixing silica in the solution in which the carboxyl group-modified S-SBR is formed. Of course, silica may be blended together with other blending components.

Silica having a BET specific surface area of 100 to 300 m ² / g is used by blending in an amount of 10 to 150 parts by weight, preferably 30 to 100 parts by weight, per 100 parts by weight of diene rubber. The BET specific surface area is limited to such a range from the viewpoint of performance and workability, and if the blending ratio is less than this, the balance of tanδ at 0 ° C and 60 ° C will be deteriorated. On the other hand, if it is used in a proportion higher than this, the deterioration of workability due to the increase in viscosity becomes large.

  In the present invention, in addition to carboxyl group-modified S-SBR and silica, a rubber gel is blended and used as an essential component. The rubber gel has a hydroxyl group and / or carboxyl group, preferably a carboxyl group on the particle surface, and the particle core exhibits a glass transition temperature (Tg) of -50 to -100 ° C.

Such rubber gel is described in Patent Documents 2 to 4 and the like, and is a crosslinked rubber based on natural rubber, butadiene rubber, SBR, chloroprene rubber, NBR, etc., and the introduction of a hydroxyl group is, for example, 2-hydroxyethyl It is carried out by graft copolymerizing methacrylate or the like. The particle size is about 5 to 1000 nm, preferably about 20 to 600 nm.

Actually, a commercially available product such as a rubber gel “Nanoprene” manufactured by LANXESS is used, and the basic features thereof include the following items.
(Particle surface)
1. The particle surface is highly hydroxylated.
2. Hydroxyl groups react with silica and silane.
(Particle core)
1. The particle core is highly cross-linked so that the particle morphology is not destroyed by high shear.
2. Due to the high degree of crosslinking, compounding additives such as oil, sulfur and accelerators are not absorbed.
3. Depending on the chemical composition and crosslink density, the particle core exhibits a specific Tg that affects the temperature depending on the damping properties of the vulcanizate (rolling resistance, wet traction friction).

  Such rubber gel is used in a ratio of 5 to 15 parts by weight, preferably 5 to 10 parts by weight, per 100 parts by weight of the diene rubber. If it is used at a ratio below this, the properties intended by the present invention will not be improved. On the other hand, if it is used at a ratio higher than this, the weight loss will increase, and the wet performance will decrease.

  In the tire rubber composition containing the above components as essential components, a silane coupling agent is preferably used in combination because silica is used.

  In other words, the properties required of silica and dispersibility with diene rubber (silica has poor affinity with rubber polymers, and silica in rubber generates hydrogen bonds through silanol groups, and silica is dispersed in rubber. Silane coupling agent is added in an amount of about 0.5 to 15 parts by weight per 100 parts by weight of silica. Examples of the silane coupling agent include polysulfide silane coupling agents having an alkoxysilyl group that reacts with a silanol group on a silica surface and a sulfur chain that reacts with a polymer, such as bis (3-triethoxysilylpropyl) tetrasulfide, bis (2 -Triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide and the like are preferably used.

  Further, carbon black is also used in combination with silica, and furnace black such as SAF, ISAF, HAF, FEF, GPF, and SRF is generally used as the carbon black. These carbon blacks, which are effective components for forming a tread portion of a pneumatic tire, particularly a cap tread portion, are generally used at a ratio of 30 to 120 parts by weight per 100 parts by weight of diene rubber.

  In the rubber composition containing the above components as essential components, sulfur and thiazole (MBT, MBTS, ZnMBT, etc.), sulfenamide (CBS, DCBS, BBS, etc.), guanidine ( DPG, DOTG, OTBG, etc.), thiuram (TMTD, TMTM, TBzTD, TETD, TBTD, etc.), dithiocarbamate (ZTC, NaBDC, etc.), xanthate (ZnBX, etc.), etc. One or more types are blended and used. Furthermore, other compounding agents generally used as rubber compounding agents, such as reinforcing agents or fillers such as talc, clay, graphite, calcium silicate, processing aids such as stearic acid, zinc oxide, softeners, A plasticizer, an antiaging agent, and the like are appropriately blended and used as necessary.

  Preparation of the composition is carried out by kneading by a general method using a kneader such as a kneader, a Banbury mixer or a mixer and an open roll, and the obtained composition is molded into a predetermined shape, The rubber is vulcanized at a vulcanization temperature corresponding to the type of diene rubber, vulcanizing agent and vulcanization accelerator used and the blending ratio thereof to form a tread portion of a pneumatic tire.

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

Reference example
After adding 288 g of 3-mercaptopropionic acid and 23 g of dilauroyl peroxide in an 80 ° C solution in which 45 kg of S-SBR (LANXESS product rubber beech VSL 5025-0) was dissolved in 275 kg of cyclohexane, this temperature was maintained. The mixture was stirred for 2 hours. To this was added 230 g of stabilizer (LANXESS product Vulkanox 4020) and Mobil product Mobil Sol K 17.12 kg, after which the solvent was removed by steam distillation. After drying at 70 ° C. under reduced pressure, mineral oil (H & R Vivatec 500) was added at a rate of 37.5 phr to obtain oil-extended carboxyl group-modified S-SBR.

Standard example 1
S-SBR (LANXESS product VSL 5025-2) (S-SBR (A)) 70 parts by weight Butadiene rubber (Nippon Zeon product Nipol BR1220) (BR) 30 部
N339 Carbon Black (Cabot Japan Product Show Black) 20 〃
Silica (Zeosil 165GR, Rhodia product; BET specific surface area 165m ² / g) 60 〃
Silane coupling agent (Eponic Degussa Japan product Si69) 5.1 〃
Zinc oxide (Zondox Chemical Products Zinc Oxide 3 types) 3 〃
Stearic acid (NOF product beads stearic acid YR) 2 〃
Aroma-based oil (Showa Shell Product Extract No. 4 S) 15 〃
Sulfur (Hosoi Chemical Products Oil Processing Sulfur) 1.5 〃
Vulcanization accelerator (Sanshin Chemical Products Sunseller CM-G) 1.7 〃
Among the above components, each component excluding sulfur and vulcanization accelerator was kneaded with a closed kneader, and then sulfur and vulcanization accelerator were added and kneaded with an open roll.

The kneaded product was subjected to press vulcanization at 160 ° C. for 20 minutes, and the following items were measured for the unvulcanized product and the obtained vulcanized product. The measured values are indicated by an index with the standard example 1 being 100, and the larger the index value, the better the index value for Lambourne wear, tanδ (0 ° C), and the smaller the index value for tanδ (60 ° C), ΔHS, and T95. Moderately good.
Lambourne wear: Measure wear loss under conditions of 20 ° C temperature and 50% slip rate using Lambourne wear tester
tanδ (0 ° C) or (60 ° C): Measured under conditions of initial strain 10%, dynamic strain 2%, temperature 0 ° C or 60 ° C using a Toyo Seiki viscoelastic spectrometer
tanδ (0 ° C) is an indicator of wet performance, and tanδ (60 ° C) is an indicator of heat generation, in other words, fuel efficiency. ΔHS: 100- [Hardness (60 ° C) / Hardness (0 ° C)] × The value ΔHS obtained by 100 is an index of heat sag resistance (temperature dependence of hardness).
T95: Measures the time to reach 95% of maximum torque measured by rheometer, which is an index of vulcanization speed

Comparative Example 1
In Standard Example 1, an additional 10 parts by weight of OH-modified rubber gel (LANXESS product Nanoprene BM75 OH; Tg-77 ° C.) [modified rubber gel A] was used.

Comparative Example 2
In Standard Example 1, the same amount (70 parts by weight as a non-oil extended product) of oil-extended carvone S-SBR [modified S-SBR] obtained in Reference Example was used instead of S-SBR (A).

Comparative Example 3
In Comparative Example 2, 10 parts by weight of S-SBR (Asahi Kasei Toughden 1000; Tg-70 ° C.) [S-SBR (B)] was additionally used.

Comparative Example 4
In Comparative Example 2, an additional 10 parts by weight of OH-modified rubber gel (LANXESS product Nanoprene BM15 OH; Tg-15 ° C.) [modified rubber gel B] was used.

Example 1
In Comparative Example 2, an additional 5 parts by weight of OH-modified rubber gel (Nanoprene BM75 OH) [modified rubber gel A] was used.

Example 2
In Comparative Example 2, 10 parts by weight of OH-modified rubber gel (Nanoprene BM75 OH) [modified rubber gel A] was additionally used.

Example 3
In Comparative Example 2, an additional 15 parts by weight of OH-modified rubber gel (Nanoprene BM75 OH) [modified rubber gel A] was used.

Comparative Example 5
In Comparative Example 2, an additional 30 parts by weight of OH-modified rubber gel (Nanoprene BM75 OH) [modified rubber gel A] was used.

Example 4
In Example 2, the amount of oil-extended carboxylic acid-modified S-SBR [modified S-SBR] was changed to 50 parts by weight, and 20 parts by weight of S-SBR (VSL 5025-2) [S-SBR (A)] was further added. Used in addition.

Comparative Example 6
In Example 2, the amount of oil-extended carboxylic acid-modified S-SBR [modified S-SBR] was changed to 30 parts by weight, and 40 parts by weight of S-SBR (VSL 5025-2) [S-SBR (A)] was further added. Used in addition.

Standard example 2
In Standard Example 1, the amount of S-SBR (VSL 5025-2) [S-SBR (A)] was changed to 100 parts by weight, and no butadiene rubber was used.

Example 5
In Example 2, the amount of oil-extended carboxylic acid-modified S-SBR (VSL 5025-2) [modified S-SBR] was changed to 100 parts by weight, and butadiene rubber was not used.

The measurement results obtained in the above standard examples, examples, and comparative examples are shown in the following table together with the blending amounts (unit: parts by weight) of each component excluding N339 carbon black to vulcanization accelerator. In addition, the index of Example 5 shows a numerical value when the standard example 2 is index 100.
table
Standard 1 ratio-1 ratio-2 ratio-3 ratio-4 actual-1 actual-2 actual-3 ratio-5 actual-4 ratio-6 standard-2 actual-5
[Composition ingredients]
S-SBR (A) 70 70 − − − − − − − 20 40 100 −
Modified S-SBR − − 70 70 70 70 70 70 70 50 30 − 100
BR 30 30 30 30 30 30 30 30 30 30 30 − −
S-SBR (B) − − − 10 − − − − − − − − − −
Modified rubber gel A − 10 − − − 5 10 15 30 10 10 − 10
Modified rubber gel B----10--------
〔Measurement result〕
Lambourne wear 100 120 109 94 105 133 136 132 90 126 120 100 115
tanδ (0 ° C) 100 93 104 87 110 106 105 104 85 104 93 100 105
tanδ (60 ° C) 100 81 87 84 67 65 57 61 84 75 78 100 62
ΔHS 100 76 114 91 189 92 70 67 69 67 70 100 77
T95 100 95 102 96 121 99 97 92 88 96 98 100 98

Based on the above results, wet performance, low heat build-up, heat sag resistance and friction resistance are improved while improving productivity by blending specific amounts of specific SBR-containing diene rubber, specific rubber gel and specific silica. Can be made compatible with higher order.

Claims (3)

Rubber gel 5 having a hydroxyl group and / or carboxyl group on the particle surface and a particle core having a Tg of -50 to -100 ° C. in 100 parts by weight of a diene rubber containing 50 to 100% by weight of carboxyl group-modified solution polymerized SBR A rubber composition for tires comprising ˜15 parts by weight and 10 to 150 parts by weight of silica having a BET specific surface area of 100 to 300 m ² / g.   The tire rubber composition according to claim 1, which is used as a molding material for a tire tread.   A pneumatic tire obtained by molding and vulcanizing the tire rubber composition according to claim 2 to form a tread portion.