JP2016084404A - Rubber composition and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit generation of cracks by ultraviolet by enable blooming wax before transition of a tackifier to a rubber surface even when a large amount of the tackifier is blended.SOLUTION: There is provided a rubber composition by blending a diene rubber, a tackifier consisting of a resin having melt viscosity at 200°C of 120 mPa s to 350 mPa s and wax, where the wax contains 20.0 to 40.0 mass% of a linear saturated hydrocarbon having 25 to 30 carbon atoms, 8.0 to 18.0 mass% of linear saturated hydrocarbon having 35 to 40 carbon atoms and 1.0 to 6.0 mass% of linear saturated hydrocarbon having 45 or more carbon atoms and the blended amount of the tackifier is larger than that of the wax.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  Conventionally, for example, a rubber composition constituting a sidewall portion of a pneumatic tire has been blended with wax in order to improve ozone resistance. The wax blooms on the rubber surface after vulcanization and forms a wax film on the rubber surface, thereby blocking ozone and protecting the rubber.

  On the other hand, in the rubber composition, a resin as a tackifier may be blended for the purpose of improving the adhesion to the roll in the kneading step. It is also known that such a tackifier has an effect of increasing the storage elastic modulus of a rubber composition that contributes to an improvement in exercise performance as a tire (for example, see Patent Document 1 below).

  Rubber compositions in which these waxes and tackifiers are blended are known and variously proposed (see, for example, Patent Documents 2 to 4 below).

JP 2006-282830 A JP 2010-053249 A JP 2013-028884 A JP 2000-086824 A

  By the way, when a large amount of the resin as the tackifier is added for improving roll adhesion, the tackifier moves to the rubber surface before the wax and cures, and the cured resin film breaks. It was found that cracks propagated to the rubber surface and generated on the rubber surface. It was also found that the tackifier that migrated to the rubber surface inhibits wax bloom and promotes the generation of cracks due to ultraviolet rays.

  The present invention was made to solve such a new problem, and even when a large amount of a tackifier is blended, the wax can be bloomed before the tackifier moves to the rubber surface. An object of the present invention is to provide a rubber composition capable of suppressing the occurrence of cracks due to ultraviolet rays.

  The rubber composition according to the present invention is obtained by blending a diene rubber with a tackifier made of a resin having a melt viscosity at 200 ° C. of 120 mPa · s to 350 mPa · s, and a wax, C25-25 straight chain saturated hydrocarbons 20.0-40.0% by weight, C35-40 straight chain saturated hydrocarbons 8.0-18.0% by weight, 45 or more carbon atoms The linear saturated hydrocarbon of 1.0-6.0 mass% is contained, and the compounding quantity of the said tackifier is more than the compounding quantity of the said wax.

  The pneumatic tire according to a preferred embodiment of the present invention uses the rubber composition for at least a part thereof.

  According to the present invention, by using a tackifier composed of a resin having the specific melt viscosity and a wax having the specific carbon number distribution, even when the tackifier is blended in a larger amount than the wax, The wax can be bloomed before the tackifier migrates to the rubber surface. Therefore, generation of cracks due to ultraviolet rays can be suppressed.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition according to this embodiment is obtained by blending a tackifier and a wax with a diene rubber.

  The diene rubber as the rubber component is not particularly limited. Examples of usable diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, and styrene-butadiene. -Isoprene rubber, nitrile rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like can be mentioned, and these can be used alone or in combination of two or more. More preferably, it is NR, SBR, BR, or a blend rubber of two or more thereof.

  In this embodiment, as the tackifier, a resin having a melt viscosity at 200 ° C. of 120 mPa · s or more and 350 mPa · s or less is used. If the melt viscosity of the resin that is a tackifier is too small, it may move to the rubber surface before the wax, and cracks may occur in the resin film cured on the rubber surface. Moreover, when the melt viscosity of the resin is too large, the processability of the rubber composition may be deteriorated. The melt viscosity of the resin is more preferably 130 to 300 mPa · s.

  Examples of resins used as tackifiers include petroleum resins, phenolic resins, coumarone resins, terpene resins, rosin resins, and aromatic vinyl polymers (obtained by polymerizing α-methylstyrene and / or styrene. Resin) and the like. These may be used alone or in combination of two or more.

  Examples of petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. The aliphatic petroleum resin is a resin obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions corresponding to 4 to 5 carbon atoms (C5 fraction) (C5 petroleum resins). It may also be hydrogenated. An aromatic petroleum resin is a resin obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fraction) having 8 to 10 carbon atoms (C9 petroleum). It may also be referred to as a resin) and may be hydrogenated. The aliphatic / aromatic copolymer petroleum resin is a resin obtained by copolymerizing the C5 fraction and the C9 fraction (also referred to as C5 / C9 petroleum resin), and is hydrogenated. There may be.

  Examples of phenolic resins include phenol formaldehyde resins, alkylphenol formaldehyde resins, alkylphenol acetylene resins, and oil-modified phenol formaldehyde resins. Examples of the coumarone resin include coumarone resin and coumarone-indene resin. Examples of the terpene resin include polyterpene and terpene-phenol resin. Examples of the rosin resin include a natural resin rosin and a rosin-modified resin obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification or the like. Examples of the aromatic vinyl polymer include a homopolymer of α-methylstyrene, a homopolymer of styrene, and a copolymer of α-methylstyrene and styrene.

  Among these, it is preferable to use at least one petroleum resin selected from the group consisting of aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins.

In the present embodiment, a wax having the following carbon number distribution is used. That is, the content of linear saturated hydrocarbon having 25 to 30 carbon atoms in 100% by mass of wax is X (mass%), and the content of linear saturated hydrocarbon having 35 to 40 carbon atoms is Y ( Mass%), and when the content of the linear saturated hydrocarbon having 45 or more carbon atoms is Z (mass%),
20.0 ≦ X ≦ 40.0, 8.0 ≦ Y ≦ 18.0, and 1.0 ≦ Z ≦ 6.0
Use a wax that satisfies the following conditions.

  When X is less than 20.0% by mass, the tackifier tends to migrate to the rubber surface before the wax in a low temperature range. When Y is less than 8.0% by mass, the tackifier tends to migrate to the rubber surface before the wax at room temperature. When Z is less than 1.0% by mass, the tackifier tends to migrate to the rubber surface before the wax in a high temperature range. When the tackifier first moves to the rubber surface, the cured resin film causes cracking, and it becomes difficult to suppress the occurrence of cracks due to ultraviolet rays. If X exceeds 40.0% by mass, the appearance may be impaired due to excessive blooming of wax in a low temperature range. If Y exceeds 18.0% by mass, the appearance may be impaired due to excessive blooming of the wax at room temperature. When Z exceeds 6.0% by mass, the appearance may be impaired due to excessive blooming of the wax in a high temperature range.

The carbon number distribution of the wax is more preferably
24.0 ≦ X ≦ 35.0, 9.0 ≦ Y ≦ 17.0, and 2.0 ≦ Z ≦ 6.0
Is to satisfy. In addition, the upper limit of the carbon number of the straight chain saturated hydrocarbon having 45 or more carbon atoms defined by the content rate Z is not particularly limited, but usually the carbon number is 80 or less. Further, the content of the linear saturated hydrocarbon in 100% by mass of the wax is not particularly limited, but is preferably 70% by mass or more, and more preferably 80% by mass or more.

  The method for preparing petroleum wax (paraffin wax) having the carbon number distribution as described above is not particularly limited. For example, known methods such as vacuum distillation, solvent deoiling, sweating, and press deoiling are combined. Thus, a fraction obtained by concentrating the respective components can be obtained, and the fraction can be prepared by mixing so as to achieve the blending ratio.

  The carbon number distribution of the wax can be measured by a known method using gas chromatography. Specifically, a capillary GC is used as a measuring apparatus, and a polyimide coated capillary column is used to measure from 180 ° C. to 390 ° C. with a carrier gas: helium, a flow rate: 4 mL / min, and a heating rate: 15 ° C./min. A method is mentioned.

  In the rubber composition according to this embodiment, the compounding amount of the tackifier is larger than the compounding amount of the wax. This is because when the amount of the tackifier is large, the tackifier easily moves to the rubber surface before the wax, and the above-described problem occurs.

  The blending amount of the tackifier is preferably more than 5 parts by mass and 20 parts by mass or less, more preferably 7 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the diene rubber. When the compounding amount of the tackifier is more than 5 parts by mass, the effect of improving the roll adhesion can be enhanced. Moreover, when the compounding amount of the tackifier is 20 parts by mass or less, it is possible to prevent the processability from being excessively adhered to the roll.

  The blending amount of the wax is preferably 1.5 parts by mass or more and 5 parts by mass or less, and more preferably 1.5 parts by mass or more and 4.0 parts by mass or less with respect to 100 parts by mass of the diene rubber. Ozone resistance can be maintained when the blending amount of the wax is 1.5 parts by mass or more. Moreover, when the compounding quantity of a wax is 5 mass parts or less, the excessive bloom to the rubber | gum surface can be suppressed and an external appearance deterioration can be prevented.

  Carbon rubber and / or silica can be blended as a filler in the rubber composition according to this embodiment. The carbon black is not particularly limited, and is used as a rubber reinforcing agent. SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series) (both ASTM grades) ) And other grades of furnace carbon black can be used. The silica is not particularly limited, but wet silica (hydrous silicic acid) is preferable. Although the compounding quantity of a filler is not specifically limited, It is preferable that it is 10-150 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 20-120 mass parts, More preferably, it is 30-100. Part by mass. As one embodiment, the compounding amount of carbon black may be 10 to 120 parts by mass or 20 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. Moreover, 10-120 mass parts may be sufficient with respect to 100 mass parts of diene rubbers, and 20-100 mass parts may be sufficient as the compounding quantity of a silica.

  When silica is blended as a filler, a silane coupling agent such as sulfide silane or mercaptosilane may be blended in order to improve the dispersibility of silica. Although the compounding quantity of a silane coupling agent is not specifically limited, It is preferable that it is 2-20 mass% with respect to a silica compounding quantity.

  In the rubber composition according to the present embodiment, in addition to the above-described components, oil, zinc white, stearic acid, anti-aging agent, vulcanizing agent, vulcanization accelerator, and the like, which are generally used in rubber compositions. Additives can be blended. Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount is 100 parts by mass of diene rubber. It is preferable that it is 0.1-10 mass parts with respect to it, More preferably, it is 0.5-5 mass parts.

  The rubber composition according to the embodiment can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, in the first mixing stage, to the diene rubber, together with the tackifier and the wax, other additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed, and then the resulting mixture is finally mixed. A rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in stages.

  The rubber composition thus obtained can be used for various rubber members for tires, vibration-proof rubbers, conveyor belts and the like. Preferably, it is used for tires, and can be applied to various parts of tires such as tread rubber, sidewall rubber, rim strip rubber of various sizes such as passenger cars, heavy loads of trucks and buses, and pneumatic tires of sizes. . The rubber composition is formed into a predetermined shape by, for example, extrusion processing according to a conventional method, and after making a green tire by combining with other parts, for example, by vulcanization molding at 140 to 180 ° C., a pneumatic tire Can be manufactured. Among these, it is preferable to use for rubber | gum for tire outer layers, for example, it is especially preferable to use as a compound for treads, a compound for side walls, and a compound for rim strips.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, according to the blending (parts by mass) shown in Table 1 below, first, in the first mixing stage, other blending agents excluding sulfur and vulcanization accelerator are added and kneaded (discharge) Then, in the final mixing stage, sulfur and a vulcanization accelerator were added and kneaded (discharge temperature = 90 ° C.) to prepare a rubber composition. The details of each component in Table 1 are as follows.

・ SBR1: "VSL5025-0HM" manufactured by LANXESS
・ SBR2: "SBR1502" manufactured by JSR Corporation
Carbon black: N339, “Seast KH” manufactured by Tokai Carbon Co., Ltd.
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
Silane coupling agent: “Si75” manufactured by Evonik Degussa
Paraffin oil: “Process NC140” manufactured by JX Nippon Oil & Energy
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.

Resin A: aliphatic / aromatic copolymer petroleum resin, “Quinton G100B” manufactured by Nippon Zeon Co., Ltd., melt viscosity = 130 mPa · s
Resin B: aliphatic / aromatic copolymer petroleum resin, “Quinton D200” manufactured by Nippon Zeon Co., Ltd., melt viscosity = 180 mPa · s
Resin C: aliphatic petroleum resin, “Quinton C210” manufactured by Nippon Zeon Co., Ltd., melt viscosity = 300 mPa · s
Resin D: Aliphatic petroleum resin, “Quinton B170” manufactured by Zeon Corporation, melt viscosity = 50 mPa · s
Resin E: aliphatic / aromatic copolymer petroleum resin, “Quinton G115” manufactured by Nippon Zeon Co., Ltd., melt viscosity = 380 mPa · s

Wax A: Paraffin wax prepared with X = 35.0 mass%, Y = 9.8 mass%, and Z = 2.6 mass%. Linear saturated hydrocarbon content = 73 mass%, iso component content = 27 mass%
Wax B: Paraffin wax prepared with X = 32.6% by mass, Y = 14.3% by mass, and Z = 2.6% by mass. Linear saturated hydrocarbon content = 80 mass%, iso component content = 20 mass%
Wax C: Paraffin wax prepared with X = 24.6% by mass, Y = 16.2% by mass, and Z = 5.1% by mass. Linear saturated hydrocarbon content = 71% by mass, iso component content = 29% by mass
Wax D: Paraffin wax prepared with X = 41.4 mass%, Y = 0.9 mass%, and Z = 3.2 mass%. Linear saturated hydrocarbon content = 62% by mass, iso component content = 38% by mass
Wax E: Paraffin wax prepared with X = 11.8% by mass, Y = 16.1% by mass, and Z = 7.3% by mass. Linear saturated hydrocarbon content = 61 mass%, iso component content = 39 mass%
Wax F: Paraffin wax prepared with X = 26.9% by mass, Y = 20.2% by mass, and Z = 2.1% by mass. Linear saturated hydrocarbon content = 80 mass%, iso component content = 20 mass%
Wax G: Paraffin wax prepared with X = 29.1% by mass, Y = 18.9% by mass, and Z = 0.9% by mass. Linear saturated hydrocarbon content = 71% by mass, iso component content = 29% by mass

  The melt viscosity of the resins A to E used as the tackifier is the kinematic viscosity (unit: mPa · s) at 200 ° C. 27 and a value measured with a Thermocell Brookfield viscometer.

  Each rubber composition was evaluated for processability (Mooney viscosity) and roll adhesion in an unvulcanized state, and vulcanized at 150 ° C. for 30 minutes to produce a test piece. ), Appearance and ozone resistance (low temperature, normal temperature, high temperature) were evaluated. Each evaluation method is as follows.

  ・ Processability (Mooney viscosity): In accordance with JIS K6300, using a rotorless Mooney measuring machine manufactured by Toyo Seiki Co., Ltd., preheated the unvulcanized rubber at 100 ° C for 1 minute, and then measured the torque value after 4 minutes. Measured in units and expressed as an index with the value of Example 1 being 100. A larger index indicates a higher Mooney viscosity and inferior processability.

  -Roll adhesion: After mixing the rubber composition, the rubber sheet was roll-kneaded, and the adhesion with the roll at that time was subjected to sensory evaluation. Evaluation is performed in 5 stages of 1 to 5 points, 3 points are standard, 1 point or 2 points means insufficient adhesion, 4 points or 5 points means excessive adhesion.

  ・ Crack property (outdoor exposure test): In accordance with JIS K6266: 2007, exposed to the outdoors for 2 months, the surface of the vulcanized rubber piece is visually observed, “O” indicates that there is no crack, and “O” indicates that there is a crack. Is indicated by “×”.

Appearance (low temperature, normal temperature, high temperature): Vulcanized rubber pieces were placed in an oven adjusted to 10 ° C., 25 ° C., and 50 ° C., respectively, and left for 3 weeks. Thereafter, the surface of the vulcanized rubber piece was visually observed to evaluate the appearance according to the following criteria.
○: The surface is black. Or hardly notice discoloration.
Δ: Slightly white or brown.
X: Discolored to white or brown.

  -Ozone resistance: In accordance with JIS K6259, for each condition of temperature 10 ° C, 25 ° C, 50 ° C, after standing at 25% elongation and ozone concentration 50 pphm for 24 hours, the occurrence of cracks was visually observed, Those with no cracks are indicated by “◯”, and those with cracks are indicated by “×”.

  The results are as shown in Table 2. In Comparative Example 1, although the appearance and ozone resistance were excellent, the compounding amount of the resin was small and the roll adhesion was poor. In Comparative Examples 2-5, roll adhesion could be improved by blending a large amount of resin, but because the carbon number distribution of the wax was outside the predetermined range, the outdoor exposure test due to the resin precipitating first. Generation of cracks was observed, and depending on temperature conditions, appearance deteriorated due to excessive blooming of wax, and conversely, ozone resistance decreased due to insufficient bloom. In Comparative Example 6, since the melt viscosity of the resin was small, cracks were observed due to the cured resin that migrated to the rubber surface before the wax. In Comparative Example 7, since the melt viscosity of the resin was large, the Mooney viscosity index in an unvulcanized state exceeded 110, and the workability deteriorated. On the other hand, in Examples 1 to 5 in which a resin having a specific melt viscosity and a wax having a specific carbon number distribution are used in combination with a large amount of resin, the wax is bloomed before the resin moves to the rubber surface. It was possible to suppress the occurrence of cracks due to ultraviolet rays while improving roll adhesion and without impairing workability, and it was excellent in appearance and ozone resistance.

Claims (3)

A diene rubber is blended with a tackifier made of a resin having a melt viscosity at 200 ° C. of 120 mPa · s to 350 mPa · s, and a wax,
The wax has a linear saturated hydrocarbon of 25 to 30 carbon atoms in an amount of 20.0 to 40.0 mass%, a linear saturated hydrocarbon of 35 to 40 carbon atoms in an amount of 8.0 to 18.0 mass%, Containing 1.0 to 6.0% by mass of a straight-chain saturated hydrocarbon having 45 or more carbon atoms,
The rubber composition, wherein the compounding amount of the tackifier is larger than the compounding amount of the wax. The blending amount of the tackifier is more than 5 parts by weight and 20 parts by weight or less with respect to 100 parts by weight of the diene rubber, and the blending amount of the wax is 1.5 parts by weight or more and 5 parts by weight or less. The rubber composition according to 1.   A pneumatic tire using the rubber composition according to claim 1.