JP2009242576A - Diene-based rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diene-based rubber composition giving a molded article having a high elastic modulus and excellent in heat aging resistance, chipping resistance and cutting resistance, while suppressing an increase of heating value. <P>SOLUTION: The diene-based rubber composition is obtained by blending (a) 100 pts.wt. of diene-based rubber, (b) 3-8 pts.wt. of zinc monomethacrylate, (c) ≥30 pts.wt. of a carbon black, (d) 2-30 pts.wt. of silica, and (e) 0.5-5 pts.wt. of at least one selected from modified gum rosin, p-octylphenol resin, 1,3-pentadiene resin and dicyclopentadiene resin, wherein the carbon black and silica are blended in a total amount of 40-60 pts.wt. The diene-based rubber composition is effectively used as a forming material of at least one of a cap tread and a base tread of a tire. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diene rubber composition. More specifically, the present invention relates to a diene rubber composition capable of forming a pneumatic tire tread portion excellent in chip resistance and cut resistance.

  For non-paved roads, such as truck bus radial tires (TBR) for running on rough roads where rocks are exposed, the tread and sidewalls are often cut and rubber strips are generated by driving and braking the vehicle. Phenomenon such as chipping such as a large number of chipping is likely to occur. Therefore, for the tread portion of TBR, a rubber composition that provides a molded article having excellent chip-cut resistance is required.

  Generally, in order to improve the cut resistance of the rubber composition by improving the strength and elongation of the tread portion, a method of highly filling carbon black is conceivable, but this improves the cut resistance. However, there is a problem that the chipping resistance and heat generation required together with the cut resistance when traveling on a rough road are remarkably inferior.

In response to such demands, a rubber composition has been proposed that can improve the cut resistance and chip resistance of a molded product by blending a specific hydrocarbon resin in the rubber composition. However, it does not sufficiently improve the chip cut resistance while suppressing an increase in the amount of heat generation.
JP 62-184039 A

  An object of the present invention is to provide a diene rubber composition capable of providing a molded article having excellent high elastic modulus, heat aging resistance, and chip / cut resistance while suppressing an increase in calorific value.

  The purpose of the present invention is (a) 100 parts by weight of diene rubber, (b) 3-8 parts by weight of zinc monomethacrylate, (c) 30 parts by weight or more of carbon black, (d) 2-30 parts of silica. Part and 0.5 to 5 parts by weight of (e) modified gum rosin, paraoctylphenol resin, 1,3-pentadiene resin and dicyclopentadiene resin, and the total amount of carbon black and silica is 40 to 60 This is achieved by the diene rubber composition in parts by weight.

  The molded article obtained from the diene rubber composition according to the present invention has excellent effects such as an increase in the amount of heat generation and a high elastic modulus, heat aging resistance and chip / cut resistance.

  The diene rubber composition of the present invention having such characteristics can be effectively used for forming at least one of a cap tread and a base tread of a pneumatic tire, particularly a truck bus radial tire.

  As the diene rubber of component (a), natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), nitrile rubber (NBR), styrene butadiene rubber ( SBR) or the like is used alone or as a blend rubber, preferably NR, IR or a blend rubber thereof. As SBR, either emulsion polymerization SBR (E-SBR) or solution polymerization SBR (S-SBR) can be used.

Component (b), zinc monomethacrylate, is thought to be coordinated with methacrylic acid with respect to zinc and is distinguished from zinc dimethacrylate represented by [CH (CH ₃ ) = CHCOO] ₂ Zn. Is done. Actually, Sartomer's product SR709 etc. marketed as zinc monomethacrylate can be used as it is. Further, as an example of synthesis of zinc monomethacrylate, it was obtained by reacting methacrylic acid and zinc oxide with an excess of base, for example, 60 wt% zinc monomethacrylate and 30 wt% zinc dimethacrylate, 10 wt% % Of mixed zinc oxide.
Japanese National Patent Publication No. 11-512776

  Zinc monomethacrylate is used in a ratio of 3 to 8 parts by weight per 100 parts by weight of the diene rubber. If the blending ratio of zinc monomethacrylate is less than this, the elastic modulus will decrease and the calorific value will also increase. On the other hand, if it is used at a ratio higher than this, the elongation at break will deteriorate, which is preferable. Absent. Here, zinc monomethacrylate can be used alone as a zinc compound without being used in combination with zinc oxide, and can be used in combination with zinc oxide or the like if the total amount of the zinc compound is within 8 parts by weight. .

Here, although not intended to improve the chip-cut resistance, as a method of reducing rolling resistance without significantly reducing the wear resistance of the tire, (A) 100 parts by weight of a rubber component (B) 1 to 3 parts by weight or 0.5 to 4 parts by weight of Mg salt, Zn salt or Al salt of methacrylic acid, (C) N, N′-bis (2-methyl-2-nitropropyl)- A rubber composition has been proposed in which 1,3-hexanediamine, 1-3 parts by weight, 0.1-1.4 parts by weight, or 0.3-0.7 parts by weight, and (D) silica and / or carbon black are blended.
JP 2003-213045 A JP 2003-292683 A JP 2003-286367 A

  In the inventions of Patent Documents 3 to 5 which are preferably used for forming a tire tread, not only the component (C) diamine compound is an essential component, but also the Mg salt or Zn salt used as the component (B). Sanshin Chemical Industries Sunester SK-13 or SK-30, which is a commercial product, is used, and these are dimethacrylic acid Mg salt or Zn salt from the description of Sunester HP.

Further, for Zn salt of methacrylic acid (A) 100 parts by weight of natural rubber, (B) 35-50 parts by weight of carbon black, (C) 3-15 parts by weight of silica, (D) 0.1-3.0 parts by weight of glycol And (E) a proposal for a rubber composition containing 0.05 to 0.8 parts by weight of zinc monomethacrylate or zinc dimethacrylate was also found, and this rubber composition was stated to be excellent as a rubber coating for tire steel rubber. However, there is no description of the component (E), zinc monomethacrylate or zinc dimethacrylate, and the trade name is not described.
JP-A-5-51491

The carbon black of component (c), the nitrogen adsorption specific surface area N ₂ SA (JIS K6217-2 compliant) 90m ² / g or more, 30 preferably of 100~160m ² / g is, the diene rubber 100 parts by weight per It is used in such a proportion that it is not less than part by weight, preferably 35 to 55 parts by weight, and the total blending amount with silica described later is 40 to 60 parts by weight, preferably 45 to 55 parts by weight.

As carbon black having such nitrogen adsorption specific surface area N ₂ SA, carbon black of grade such as ISAF and SAF is used, and carbon black having nitrogen adsorption specific surface area below this, for example, FEF, GPF, HAF carbon black is used. In such a case, the wear resistance is insufficient. Further, the blending ratio is also related to the total blending amount with silica, but if it is less than 30 parts by weight per 100 parts by weight of the diene rubber, the reinforcing effect of carbon black is not exhibited, and high rigidity cannot be satisfied. Further, if the total blending amount with silica is larger than this, the exothermic property will be deteriorated. On the other hand, if it is smaller than this, the rigidity required for the tire cannot be satisfied.

As the silica of component (d), a CTAB (cetyltrimethylammonium bromide) specific surface area (measured in accordance with JIS K6217-3) of 95 to 175 m ² / g, preferably 110 to 160 m ² / g is used. These include the pyrolysis method of halogenated silicic acid or organosilicon compounds and the dry method of silica and sodium silicate pyrolysis method, which is produced by heating and reducing silica sand and air-oxidizing the evaporated SiO. Wet process silica to be produced, etc., and wet process silica is preferably used in terms of cost and performance. Actually, a commercial product marketed for the rubber industry can be used as it is. The blending ratio is 2 to 30 parts by weight, preferably 4 to 20 parts by weight per 100 parts by weight of the diene rubber, and is used so that the total blending amount with the carbon black becomes the above ratio. Rolling resistance is improved by the blending of silica, but if it is used in a larger blending ratio, the processability deteriorates.

  Thus, the properties required of silica and dispersibility with diene rubbers (silica has poor affinity with rubber polymers, and silica in rubber forms hydrogen bonds through silanol groups, and silica is incorporated into rubber. In order to further improve (having the property of reducing dispersibility), the silane coupling agent can be used in a proportion of 2 to 15% by weight, preferably 5 to 10% by weight, based on the silica weight. Examples of the silane coupling agent include polysulfide silane coupling agents having an alkoxysilyl group that reacts with a silanol group on the 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. 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. On the other hand, if it is used in a proportion higher than this, processability will deteriorate. To come.

  As the resin of component (e), at least one resin of modified gum rosin, paraoctylphenol resin, 1,3-pentadiene resin and dicyclopentadiene resin is 0.5 to 5 parts by weight, preferably 0.8 parts per 100 parts by weight of diene rubber. Used in a proportion of ~ 4.5 parts by weight. By blending these resins, it is possible to improve the elastic modulus and suppress an increase in the calorific value. If the resin is used at a ratio other than this, the elastic modulus cannot be improved.

  Gum rosin is a mixture of several resin acids obtained by cutting and purifying raw pine oil that exudes from the pine trunk and then removing the turpentine oil by steam distillation. Has a carboxyl group and a double bond. In the present invention, a modified gum rosin such as a gum rosin-modified maleic resin, for example, a commercially available Harima Chemicals product Halitac AQ-90A or the like is used.

  The paraoctylphenol resin is a resin using isobutylene as a raw material, and for example, Hitachi Chemical Industrial product Hitanol 1502Z which is a commercial product is used.

1,3 The pentadiene resin, for example, C ₅ high purity extracted from fractions 1,3 petroleum resin prepared main ingredient, such as commercially available products include Zeon products Quinton A100, Mataji As the cyclopentadiene resin, for example, a petroleum resin produced from high-purity dicyclopentadiene extracted from a C ₅ fraction as a main raw material, for example, a commercial product, Nippon Zeon product Quinton 1100, etc. is used.

  In the diene rubber composition containing the above components as essential components, a compounding agent generally used as a compounding agent for rubber, for example, a vulcanizing agent such as sulfur depending on the type of diene rubber, thiazole , Accelerators such as sulfenamide, guanidine and thiuram, reinforcing agents or fillers such as talc, clay, graphite and calcium silicate, processing aids such as stearic acid, paraffin wax and aroma oil, aging An inhibitor, a plasticizer, and the like are appropriately blended and used as necessary.

で表わされる環状ポリスルフィド化合物(ここで、Rは置換もしくは非置換のC₂〜C₁₀のアルキレン基、置換もしくは非置換のC₂〜C₁₈のオキシアルキレン基を含むアルキレン基であり、xは2〜6の整数であり、nは1〜15の整数である)が、ジエン系ゴム組成物100重量部当り0.5〜8重量部、好ましくは0.7〜7重量部の割合で用いられる。このような環状ポリスルフィド化合物は、一般式X-R-X′(ここで、XおよびX′はハロゲン原子であり、Rは置換もしくは非置換のC2〜C10のアルキレン基又は置換もしくは非置換のC2〜C18のオキシアルキレン基を含むアルキレン基を示す)で表わされるジハロゲン化合物と、一般式M₂S_x(ここで、Mはアルカリ金属であり、xは2〜6の整数である)で表わされるアルカリ金属の多硫化物とを、親水性及び親油性溶媒の非相溶混合溶媒中で2相系で反応させることにより製造することができる。この環状ポリスルフィド化合物を用いると、耐熱性および加硫後にゴムが軟化する加硫戻りをさらに改善することができるため、使用末期まで高い耐チップ・カット性を維持することができる。
特開２００２−２９３７８３号公報 Here, as a vulcanizing agent, preferably the following general formula instead of or together with sulfur

In represented by cyclic polysulfide compound (where, R is an alkylene group containing an alkylene, a substituted or oxyalkylene group unsubstituted C ₂ -C ₁₈ of C ₂ -C ₁₀ substituted or unsubstituted, x is 2 Is an integer of ˜6 and n is an integer of 1 to 15), but is used in a ratio of 0.5 to 8 parts by weight, preferably 0.7 to 7 parts by weight per 100 parts by weight of the diene rubber composition. Such a cyclic polysulfide compound has the general formula XRX ′ (where X and X ′ are halogen atoms, R is a substituted or unsubstituted C2-C10 alkylene group or a substituted or unsubstituted C2-C18 oxy group). A dihalogen compound represented by general formula M ₂ S _x (where M is an alkali metal, and x is an integer of 2 to 6). It can be produced by reacting a sulfide with a two-phase system in an incompatible mixed solvent of a hydrophilic and lipophilic solvent. When this cyclic polysulfide compound is used, heat resistance and reversion to vulcanization in which the rubber is softened after vulcanization can be further improved, so that high chip-cut resistance can be maintained until the end of use.
JP 2002-293783 A

  The composition was prepared by kneading by a general method using a kneader such as a kneader, a Banbury mixer, and an open roll, and the obtained composition was a diene rubber, a vulcanizing agent, Vulcanization is performed at a vulcanization temperature corresponding to the type of vulcanization accelerator and the blending ratio thereof, and for example, at least one of the cap tread 4 and the base tread 5 of the truck bus radial tire shown in FIG.

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

Example 1
Natural rubber (STR20) 100 parts by weight Carbon black (Cabot Japan product show black N110; 40 〃
(Nitrogen adsorption specific surface area N ₂ SA 144m ² / g)
Silica (Nippon Silica Kogyo product nip seal AQ; CTAB specific surface area 157 m ² / g) 10 〃
Zinc monomethacrylate (Sartomer product SR709) 5 〃
Stearic acid (Chiba fatty acid product industrial stearic acid) 1 〃
Modified gum rosin (Harima Chemical Industries Haritac AQ-90A) 2 〃
Anti-aging agent (Sumitomo Chemical Antigen RD-G) 2
Sulfur (Tsurumi Chemical Co., Ltd., Jinhua Ink Fine Powdered Sulfur) 2 〃
Vulcanization accelerator (Ouchi Emerging Chemical Industry Noxeller NS-F) 1.5 〃
Among the above components, the components other than the vulcanization accelerator and sulfur were kneaded for 5 minutes with a 1.5 L closed mixer and released when the temperature reached 160 ° C. to obtain a master batch. A vulcanization accelerator and sulfur were added to this master batch and kneaded with an open roll to obtain a diene rubber composition.

Example 2
In Example 1, the amount of zinc monomethacrylate was changed to 8 parts by weight.

Example 3
In Example 1, the amount of zinc monomethacrylate was changed to 3 parts by weight, and further 1 part by weight of zinc oxide (3 types of Zinc Chemical Products Zinc Oxide) was used.

Example 4
In Example 1, 4 parts by weight of the cyclic polysulfide compound represented by the above formula [I] (R: (CH ₂ ) ₆ , x: average of 5, n: 1 to 4) was used instead of sulfur. This cyclic polysulfide compound is prepared by adding 80 g of water, 48 g (0.15 mol) of sulfur and 1.16 g (0.0045 mol) of tetrabutylammonium bromide as a catalyst to 89.76 g (0.15 mol) of 30% sodium polysulfide (Na ₂ S ₄ ) aqueous solution. After reacting at 80 ° C. for 2 hours, 100 g of toluene was added, and 23.3 g (0.15 mol) of 1,6-dichlorohexane was added dropwise at 90 ° C. for 1 hour, and further reacted for 4 hours. After completion of the reaction, the organic layer was decomposed. By concentrating at 90 ° C. under reduced pressure, 35.2 g (yield 95%) was synthesized.

Example 5
In Example 4, instead of the modified gum rosin, the same amount of paraoctylphenol resin (Hitanol Chemical Product Hitanol 1502Z) was used.

Example 6
In Example 4, the same amount of 1,3-pentadiene resin (Nippon Zeon product Quinton A100) was used instead of the modified gum rosin.

Example 7
In Example 4, the same amount of dicyclopentadiene resin (Nippon Zeon product Quinton 1100) was used instead of the modified gum rosin.

Example 8
In Example 1, the amount of sulfur was changed to 1 part by weight, and the cyclic polysulfide compound represented by the formula [I] (R: (CH ₂ ) ₆ , x: average of 5, n: 1 to 4 mixture) 2 parts by weight were used.

Example 9
In Example 8, the amount of zinc monomethacrylate was changed to 3 parts by weight, and 1 part by weight of zinc oxide was used.

Example 10
In Example 1, the amount of natural rubber was changed to 50 parts by weight, and 50 parts by weight of synthetic polyisoprene rubber (Nippon Zeon product Nipol IR2200) was used.

Comparative Example 1
In Example 1, 3 parts by weight of zinc oxide was used instead of zinc monomethacrylate.

Comparative Example 2
In Example 1, the amount of carbon black was changed to 45 parts by weight, and 3 parts by weight of zinc oxide was used instead of zinc monomethacrylate.

Comparative Example 3
In Example 1, 3 parts by weight of zinc oxide was used instead of zinc monomethacrylate, and the amount of modified gum rosin was changed to 0.1 parts by weight.

Comparative Example 4
In Example 1, 3 parts by weight of zinc oxide was used instead of zinc monomethacrylate, and the amount of modified gum rosin was changed to 10 parts by weight.

Comparative Example 5
In Example 1, the amount of zinc monomethacrylate was changed to 1 part by weight.

Comparative Example 6
In Example 1, 3 parts by weight of zinc oxide was used instead of zinc monomethacrylate, and the cyclic polysulfide compound (R: (CH ₂ ) ₆ , x: average 5, n: 1 0.1 part by weight of a mixture of ˜4) was used.

Comparative Example 7
In Example 1, 3 parts by weight of zinc oxide was used instead of zinc monomethacrylate, and the cyclic polysulfide compound represented by the above formula [I] (R: (CH ₂ ) ₆ , x: average of 5, n instead of sulfur : 1 to 4 mixture) was used in an amount of 10 parts by weight.

Comparative Example 8
In Example 1, the amount of zinc monomethacrylate was changed to 15 parts by weight, and instead of sulfur, a cyclic polysulfide compound (R: (CH ₂ ) ₆ , x: average of 5, n: 4 parts by weight of a mixture of 1-4) was used.

About the vulcanized rubber sheet obtained by vulcanizing the diene rubber composition obtained in each of the above Examples and Comparative Examples at 150 ° C. for 30 minutes to obtain a vulcanized rubber sheet (15 × 15 × 0.2 cm) The dynamic viscoelasticity and elongation at break were measured. Also, a tire of size 11R22.5 using the diene rubber composition obtained in each example and comparative example as a cap tread was prepared, and chipping / cutting (chip / cut) properties were obtained using the obtained tire. Was evaluated.
Dynamic viscoelasticity: Compliant with JIS K6394; First using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho
Storage elasticity at 20 ° C under conditions of 10% initial strain, ± 2% amplitude, and 20Hz frequency
Rate (E ′) and loss tangent (tan δ) are measured, and the value obtained in the standard example is 100
Indicated by the index
(The greater E ', the greater the elasticity, and the greater tan δ, the less the heat generation.
(Indicates that
Elongation at break: JIS K6251 compliant; 2 mm sheet punched out with No. 3 dumbbell at room temperature or 100
After storage in a sealed container at ℃ for 2 days, elongation at break with a pulling speed of 500mm / min
, And the index obtained by taking the value obtained in the standard example as 100
(The larger the value, the better the elongation at break)
Tip / cut evaluation: In about six months after mounting the above tire on a car with a loading weight of 50 tons,
After traveling a total of approximately 60,000 km on paved and unpaved roads, wear
The appearance of the cap tread, which was the end of the term, is 5 levels according to the following criteria:
Evaluated on the floor.
5: Many chip / cut scratches occurred, and the scratches reached the belt.
Has reached
4: Many chip / cut wounds occur, but the scratches are
Not reached
3: Chip / cut flaw has occurred
2: Some chip / cut scratches have occurred
1: There is almost no chip / cut wound.

The results obtained are shown in the following table.
table
Dynamic viscoelastic fracture extension /
Example E ′ tan δ Cut evaluation after heat aging before heat aging Example 1 108 102 102 103 2
〃 2 115 104 100 102 2
３ 3 109 101 103 105 2
４ 4 109 100 104 112 1
〃 5 106 102 103 110 1
６ 6 110 103 100 108 1
〃 7 108 105 106 114 1
〃 8 108 100 103 110 1
〃 9 106 101 101 114 1
〃 10 108 102 105 104 2
Comparative Example 1 100 100 100 100 5
〃 2 105 90 95 94 5
３ 3 99 111 106 106 5
〃 4 97 76 108 109 5
〃 5 96 98 106 104 4
〃 6 101 102 100 100 5
〃 7 106 94 86 94 4
８ 8 120 107 81 88 5

From the above results, the following can be said.
(1) In each example, high elasticity, elongation at break, heat aging resistance, and chip / cut resistance are improved in a well-balanced manner while suppressing an increase in heat generation.
(2) Compared with Comparative Example 1, which is a standard example, when the amount of carbon black is increased, the storage elastic modulus increases, but the calorific value increases and the elongation at break including after heat aging deteriorates (Comparison Example 2).
(3) Although the calorific value is suppressed when the amount of the resin is reduced compared with the standard example, the storage elastic modulus is not improved (Comparative Example 3).
(4) When the amount of the resin is increased as compared with the standard example, the elongation at break including after heat aging is improved, but the storage elastic modulus is lowered and the calorific value is increased (Comparative Example 4).
(5) Compared to the standard example, when 1 part by weight of zinc monomethacrylate was used instead of zinc oxide, the elongation at break including after heat aging was improved, but the storage modulus was not improved, In addition, the calorific value increases (Comparative Example 5).
(6) When 0.1 part by weight of the cyclic polysulfide compound is further used as compared with the standard example, the storage elastic modulus is slightly improved, but the chip-cut resistance is not changed (Comparative Example 6).
(7) When 10 parts by weight of the cyclic polysulfide compound is used instead of sulfur as compared with the standard example, the storage elastic modulus is improved, but the calorific value increases, and the elongation at break including after heat aging deteriorates. (Comparative Example 7)
(8) Compared to the standard example, when the cyclic polysulfide compound is used instead of sulfur and zinc monomethacrylate is used in a specified amount in place of zinc oxide, the storage elastic modulus and low heat build-up are improved. The elongation at break including after heat aging deteriorates (Comparative Example 8).

It is principal part sectional drawing of a truck bus radial tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Cap tread 5 Base tread 6 Belt 7 Carcass

Claims (7)

  (a) 100 parts by weight of diene rubber, (b) 3-8 parts by weight of zinc monomethacrylate, (c) 30 parts by weight or more of carbon black, (d) 2-30 parts by weight of silica, and (e) modification A diene rubber comprising 0.5 to 5 parts by weight of at least one of gum rosin, paraoctylphenol resin, 1,3-pentadiene resin and dicyclopentadiene resin, and a total compounding amount of carbon black and silica of 40 to 60 parts by weight. Composition.   The diene rubber composition according to claim 1, wherein the diene rubber as component (a) is natural rubber and / or isoprene rubber.   The diene rubber composition according to claim 1 or 2, wherein zinc oxide ZnO is used together with zinc monomethacrylate as component (b) so that the total amount with zinc monomethacrylate is 8 parts by weight or less. General formula as vulcanizing agent

In represented by cyclic polysulfide compound (wherein, R is an alkylene group containing an alkylene group, a substituted or oxyalkylene group unsubstituted C ₂ -C ₁₈ of C ₂ -C ₁₀ substituted or unsubstituted, x is 2 The diene rubber composition according to claim 1, 2 or 3, wherein 0.5 to 8 parts by weight is compounded with an integer of ~ 6 and n is an integer of 1 to 15.   The diene rubber composition according to claim 1, 2, 3, or 4, which is used as a forming material of at least one of a tire tread and a base tread.   A pneumatic tire in which at least one of a cap tread and a base tread of the tire is formed from the diene rubber composition according to claim 5.   The pneumatic tire according to claim 6, which is used as a truck bus radial tire.

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