JP2009242579A - Diene-based rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diene-based rubber composition which is suitably used as a vulcanization molding material and so on for forming a lower hard bead filler having an improved balance of high rigidity, heat aging resistance, and an elasticity modulus while suppressing increase in the heat release value, and having improved durability. <P>SOLUTION: The diene-based rubber composition is obtained by compounding: (b) zinc monomethacrylate of 8-14 pts.wt.; (c) carbon black of 60-80 pts.wt.; and (d) at least one of a para-octylphenol resin, a modified gum rodin, a 1,3-pentadiene resin, and a dicyclopentadiene resin of 0.5-8 pts.wt., based on 100 pts.wt (a) the diene-based rubber. <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 suitably used as a vulcanization molding material for forming a lower hard bead filler.

Conventionally, for the purpose of improving the handling stability of pneumatic tires such as heavy-duty tires, bead fillers arranged on the outer periphery side of the bead core are lower bead fillers made of high-hardness rubber having a JIS-A hardness of 85 to 95 and JIS- It has been proposed to have a two-layer structure with an upper bead filler made of low-hardness rubber with A hardness of 70 to 80, and to set the cross-sectional height of the whole bead filler, the cross-sectional height of the lower bead filler, etc. to a specific range .
JP-A-6-262913 JP-A-5-131815

  This lower hard bead filler needs to be highly rigid (high hardness) in order to suppress the movement of the bead part and carcass turn-up edge and prevent edge separation, weight reduction of the tire, improvement of steering stability, etc. Therefore, a high elastic modulus is required. Here, it is generally considered to increase the amount of reinforcing filler such as carbon black in order to achieve high rigidity. However, increasing the amount of reinforcing filler leads to an increase in calorific value, which in turn reduces the durability. For this reason, the lower hard bead filler is required to satisfy both high rigidity and suppression of increase in calorific value.

On the other hand, for the purpose of a high-hardness rubber composition having a high dynamic elastic modulus after vulcanization and excellent fracture properties, the present applicant has previously described carbon black having a specific particle size with respect to 100 parts by weight of a diene rubber. From 70 to 90 parts by weight, from 5 to 20 parts by weight of a novolac-type modified phenolic resin, from 1 to 10 parts by weight of a single or partial condensate of hexa (or penta) methoxyhexamethylolmelamine, and from 20 to 35 parts by weight of a polymerized cardanol having a specific viscosity A rubber composition is proposed. Although such a rubber composition can achieve a desired purpose, there is a demand for improvement in terms of increasing the hardness and suppressing the calorific value in order to further improve durability.
Japanese Patent Laid-Open No. 5-98081

  The object of the present invention is suitably used as a vulcanization molding material for forming a lower hard bead filler which improves the high rigidity, heat aging resistance and elastic modulus in a balanced manner while suppressing an increase in calorific value, and thus has improved durability. It is to provide a diene rubber composition to be used.

  The object of the present invention is (a) 100 parts by weight of diene rubber, (b) 8-14 parts by weight of zinc monomethacrylate, (c) 60-80 parts by weight of carbon black and (d) paraoctylphenol resin. And a diene rubber composition comprising 0.5 to 8 parts by weight of at least one of a modified gum rosin, 1,3-pentadiene resin and dicyclopentadiene resin.

  The diene rubber composition according to the present invention improves the high rigidity, heat aging resistance and elastic modulus in a balanced manner while suppressing an increase in the calorific value of the molded product, and improves the durability. It can be suitably used as a molding material for forming the bead filler.

  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, and preferably NR, BR, SBR or a blend rubber thereof is used. 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 proportion of 8 to 14 parts by weight, preferably 10 to 14 parts by weight, per 100 parts by weight of diene rubber. When the proportion of zinc monomethacrylate is less than this, the heat aging resistance deteriorates and the calorific value also increases. On the other hand, when it is used at a higher ratio, the heat aging resistance deteriorates. Therefore, it is not preferable. 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 14 parts by weight. .

  As the carbon black of component (c), carbon black of grades such as SAF, ISAF, and HAF, preferably HAF carbon black is 60 to 80 parts by weight, preferably 65 to 75 parts by weight per 100 parts by weight of diene rubber. Used in proportions. If carbon black is used in a smaller proportion, the reinforcing effect of carbon black will not be exhibited, so high rigidity cannot be satisfied, and durability will deteriorate, whereas if it is used in a proportion higher than this, The calorific value increases and the durability deteriorates.

  As the resin of component (d), at least one of paraoctylphenol resin, modified gum rosin, 1,3-pentadiene resin and dicyclopentadiene resin is 0.5 to 8 parts by weight, preferably 1 to 6 parts per 100 parts by weight of diene rubber. Used in parts by weight. By blending these resins, it is possible to suppress an increase in the amount of heat generation and improve durability. If the resin is used at a ratio below this, the durability will be deteriorated, which is not preferable.

  The paraoctylphenol resin is a resin using isobutylene as a raw material, and for example, commercially available product Hitachi Chemical Industrial Co., Ltd. Hitanol 1502Z is used.

  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 commercial product Harima Chemical Industry Co., Ltd. Haritac AQ-90A 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.

  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, The lower hard bead filler 1 shown in FIG. 1 is formed by vulcanization at a vulcanization temperature corresponding to the type of vulcanization accelerator and its blending ratio.

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

Standard example (Comparative example 1)
Natural rubber (STR20) 70 parts by weight Styrene butadiene copolymer rubber (Nippon Zeon product Nipol 1502) 30 部
HAF carbon black (Tokai carbon product seast V) 80 〃
Zinc oxide (Zondox chemical products, 3 types of zinc oxide) 6 〃
Stearic acid (stearic acid for industrial use in Chiba fatty acid products) 2 〃
Paraoctylphenol resin (Hitanol Chemical Product Hitanol 1502Z) 2 〃
Aromatic oil (Idemitsu Kosan product Diana Process Oil AH-20) 3 〃
Anti-aging agent (Sumitomo Chemical Antigen RD-G) 2
Insoluble sulfur (Flexsys product Christex HS OT 20) 4 〃
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 2 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.

Comparative Example 2
In Comparative Example 1, the amount of carbon black was changed to 85 parts by weight.

Comparative Example 3
In Comparative Example 1, the amount of zinc oxide was changed to 8 parts by weight.

Comparative Example 4
In Comparative Example 1, the amount of paraoctylphenol resin was changed to 8 parts by weight.

Comparative Example 5
In Comparative Example 1, 6 parts by weight of zinc monomethacrylate (Sartomer product SR709) was used instead of zinc oxide.

Example 1
Natural rubber (STR20) 70 parts by weight Styrene butadiene copolymer rubber (Nipol 1502) 30 部
HAF carbon black (Seast V) 70 〃
Zinc monomethacrylate (SR709) 12 〃
Stearic acid (industrial stearic acid) 2 〃
Paraoctylphenol resin (Hitanol 1502Z) 6 〃
Aromatic oil (Diana Process Oil AH-20) 3 〃
Anti-aging agent (Antigen RD-G) 2 〃
Insoluble sulfur (Christex HS OT 20) 4 〃
Vulcanization accelerator (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 2 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 same amount of modified gum rosin (Harima Chemical Industries Co., Ltd. Haritac AQ-90A) was used in place of paraoctylphenol resin.

Example 3
In Example 1, the same amount of 1,3-pentadiene resin (Nippon Zeon product Quinton A100) was used instead of paraoctylphenol resin.

Example 4
In Example 1, the same amount of dicyclopentadiene resin (Nippon Zeon product Quinton 1100) was used instead of paraoctylphenol resin.

Example 5
In Example 1, the amount of carbon black was changed to 60 parts by weight, the amount of zinc monomethacrylate was changed to 14 parts by weight, and the amount of paraoctylphenol resin was changed to 2 parts by weight.

Comparative Example 6
In Example 1, the amount of paraoctylphenol was changed to 10 parts by weight.

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 following items were measured.
Hardness: JIS K6253 compliant; standard example based on values measured using a Type A durometer
The value obtained in (Comparative Example 1) is shown as an index with 100 as the value.
(This value indicates that the higher the value, the higher the hardness.)
Breaking strength: Conforms to JIS K6251; Measures strength at break (TB) at 20 ° C, and shows an index with the value obtained in the standard example as 100
(The larger the value, the greater the breaking strength.)
Heat aging resistance: Conforms to JIS K6251; Measures strength at break (TB) after 96 hours at 80 ° C,
Calculate the rate of change from the breaking strength at room temperature, and calculate the value obtained in the standard example.
The reciprocal of 100 is shown as an exponent
(The larger the value, the smaller the amount of change)
Exothermic: JIS K6394 compliant; using Toyo Seiki Seisakusho Viscoelastic Spectrometer
Measure tanδ at 20 ° C under the conditions of distortion 10%, amplitude ± 2%, frequency 20Hz.
Shown as an index with the value obtained in the standard example as 100
(The larger the value, the lower the amount of heat generated.)
Elastic modulus: JIS K6394 compliant; using Toyo Seiki Seisakusho viscoelasticity spectrometer, initial
Measure the elastic modulus at 20 ° C under the conditions of strain 10%, amplitude ± 2%, frequency 20Hz.
Indicated by an index with the value obtained in the standard example as 100
(The larger the value, the higher the elastic modulus)

The results obtained are shown in the following table.
table
Example Hardness breaking strength Heat aging exothermic elastic modulus
Comparative Example 1 100 100 100 100 100
〃 2 103 94 96 94 107
〃 3 101 100 98 105 103
４ 4 99 91 112 92 91
〃 5 105 102 82 95 112
Example 1 104 101 104 108 142
〃 2 102 103 101 108 140
３ 3 102 102 100 108 141
４ 4 103 104 103 107 144
〃 5 100 110 105 106 127
Comparative Example 6 102 96 112 100 134

From the above results, the following can be said.
(1) Compared with the standard example (Comparative Example 1), increasing the amount of carbon black increases the hardness but increases the calorific value (Comparative Example 2).
(2) Heat aging resistance deteriorates when the amount of zinc oxide is increased as compared with the standard example (Comparative Example 3).
(3) All physical properties decrease when the amount of resin is increased as compared with the standard example (Comparative Example 4).
(4) Compared to the standard example, even when zinc monomethacrylate is used instead of zinc oxide, the hardness and elastic modulus are good if the amount is less than the specified amount of the present invention, but the heat aging resistance is low. It deteriorates and the calorific value increases (Comparative Example 5).
(5) Compared to the standard example, even if the specified amount of zinc monomethacrylate is used instead of zinc oxide, if the resin is used more than the specified amount, the breaking strength decreases and the calorific value increases (comparison) Example 6).
(6) In each of Examples 1 to 4, hardness, heat aging resistance, and elastic modulus are improved in a well-balanced manner while suppressing an increase in calorific value.
(7) In Example 5, the amount of carbon black was the lower limit of the specified amount, and the amount of zinc monomethacrylate was the upper limit of the specified amount. While the hardness was not different from the standard example, the heat aging resistance was improved. Achieves low exothermicity and high elastic modulus.

It is principal part sectional drawing of a pneumatic tire.

Explanation of symbols

1 Lower hard bead filler 2 Bead insulation rubber 3 Upper soft bead filler 4 Bead core 5 Carcass 6 Chafer 7 Rim cushion

Claims (3)

  (a) 100 parts by weight of diene rubber, (b) 8-14 parts by weight of zinc monomethacrylate, (c) 60-80 parts by weight of carbon black, and (d) paraoctylphenol resin, modified gum rosin, 1,3 -A diene rubber composition comprising 0.5 to 8 parts by weight of at least one of pentadiene resin and dicyclopentadiene resin.   The diene rubber composition according to claim 1, which is used as a vulcanization molding material for a lower hard bead filler of a pneumatic tire.   A pneumatic tire having a lower hard bead filler vulcanized from the diene rubber composition according to claim 2.

Images