JP6789782B2 - Rubber composition and pneumatic tire - Google Patents

Description

The present invention relates to rubber compositions and pneumatic tires.

It is known that a rubber composition for a tire containing a diene rubber and a filler such as silica or carbon black contains a hydrocarbon resin (Patent Documents 1 and 2).

In particular, in Patent Document 2, by using an alicyclic hydrocarbon resin containing a specific amount of unsaturated groups as the above-mentioned hydrocarbon resin, the alicyclic hydrocarbon resin is the main chain of rubber when vulcanized. It is described that the cut resistance and bending resistance of pneumatic tires can be improved because the strength of rubber molecules can be improved by cross-linking with.

On the other hand, among the rubber compositions for tires containing the above-mentioned diene-based rubber and filler, those containing highly polar rubber are known (Patent Documents 3 to 5). In particular, Patent Document 3 describes that the wet grip performance, fuel efficiency performance, and wear resistance of pneumatic tires can be improved by using acrylonitrile-butadiene rubber containing a specific amount of acrylonitrile as a highly polar rubber. There is.

Japanese Patent Publication No. 2011-526310 Japanese Unexamined Patent Publication No. 2000-344947 Japanese Unexamined Patent Publication No. 2011-57922 Japanese Unexamined Patent Publication No. 6-9926 Japanese Unexamined Patent Publication No. 11-286575

On the other hand, in the market, there is a demand for pneumatic tires using a rubber composition having more excellent tear resistance (cut resistance), which can be obtained from a rubber composition as in the above patent document. Vulcanized rubber such as pneumatic tires did not satisfy the characteristics. In particular, in the rubber composition as in Patent Document 2 described above, the dispersion of silica is not sufficient, and further, the increase in the crosslink density causes silica to be trapped in the crosslinked network chain, resulting in insufficient dispersion of the vulcanized rubber. It is thought that

The present invention has been made in view of the above circumstances, and provides a rubber composition capable of obtaining a vulcanized rubber having excellent tear resistance (cut resistance).

The present invention is a rubber composition containing a diene rubber, silica, and a hydrocarbon resin, wherein the diene rubber contains an acrylonitrile-butadiene rubber and other diene rubbers other than the acrylonitrile-butadiene rubber. The acrylonitrile-butadiene rubber has an acrylonitrile content of 25% by weight or more, the hydrocarbon resin is an unsaturated group-containing hydrocarbon resin, and has a softening point of 80 to 120 ° C., and the acrylonitrile-butadiene rubber has a softening point of 80 to 120 ° C. The present invention relates to a rubber composition, wherein the amount of rubber is 1 to 25 parts by weight with respect to 100 parts by weight of the other diene rubber.

The present invention also relates to a pneumatic tire made of the rubber composition.

The rubber composition of the present invention uses acrylonitrile-butadiene rubber (hereinafter, also referred to as NBR) containing a specific amount of acrylonitrile and other diene-based rubbers other than the NBR as raw materials for the rubber, and contains silica and an unsaturated group. It contains a hydrocarbon resin. Since the NBR has a higher polarity than the other diene-based rubbers, the polarity of the entire rubber component contained in the rubber composition can be lowered. Therefore, it is presumed that the dispersibility of silica in the rubber matrix can be improved because the polarity difference between the polarity of the entire rubber component and the silica in the rubber composition can be reduced. As a result, even when the unsaturated groups of the above hydrocarbon resin and the components of the diene rubber are crosslinked by vulcanization, the silica has high dispersibility (the value of the pain effect of the crosslinked rubber is small). The vulcanized rubber obtained from the rubber composition has excellent tear resistance (cut resistance).

Further, by using an unsaturated group-containing hydrocarbon resin having a softening point of about 80 to 120 ° C. and using a specific amount of the above NBR, the crosslink density of the vulcanized rubber is not excessively increased (rubber strength is sufficient). Since it is expected to have an effect (having an appropriate cross-linking density that can be exhibited in the above), the improvement range of tear resistance (cut resistance) expected from the simple combination of the above patent documents is obtained from the rubber composition. However, a vulcanized rubber having greatly improved tear resistance can be obtained.

<Rubber composition>
The rubber composition of the present invention contains a diene-based rubber, silica, and a hydrocarbon resin. In addition, the rubber composition can contain various compounding agents in an appropriate combination.

<Diene rubber>
The diene-based rubber of the present invention contains an acrylonitrile-butadiene rubber (NBR) and other diene-based rubbers other than the acrylonitrile-butadiene rubber (NBR).

The acrylonitrile-butadiene rubber (NBR) has an acrylonitrile content (bonded acrylonitrile amount) of 25% by weight or more. From the viewpoint of imparting high tear resistance to the vulcanized rubber, the NBR preferably has an acrylonitrile content of 30% by weight or more, preferably 50% by weight or less, and preferably 40% by weight or less. Is more preferable. The content of acrylonitrile described above is calculated by measuring the amount of nitrogen generated in accordance with the mill oven method described in JIS K6364.

Other diene rubbers other than the acrylonitrile-butadiene rubber (NBR) include, for example, natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and butyl rubber (IIR). , Synthetic diene rubber such as chloroprene rubber (CR). Other diene-based rubbers may be used alone or in combination of two or more.

From the viewpoint of imparting tear resistance to the vulcanized rubber, the other diene-based rubber is preferably used in combination with natural rubber (NR) and synthetic diene-based rubber, and SBR and BR are preferably used as the synthetic rubber. .. The weight ratio of the natural rubber to the synthetic diene rubber (natural rubber / synthetic diene rubber) is preferably 20/80 to 70/30, and more preferably 30/60 to 60/40.

<Silica>
The silica of the present invention is not limited as long as it can be used as a reinforcing filler, but wet silica (hydrous silicic acid) is preferable. Colloidal properties of the silica is also not particularly limited, preferably has a nitrogen adsorption specific surface area (BET) is 150 to 250 ² / g by BET method, and more preferred is a 180~230m ² / g .. The BET of silica is measured according to the BET method described in ISO 5794. Silica may be used alone or in combination of two or more.

<Hydrocarbon resin>
The hydrocarbon resin of the present invention is an unsaturated group-containing hydrocarbon resin and has a softening point of 80 to 120 ° C. The softening point is preferably 85 ° C. or higher, and preferably 115 ° C. or lower, from the viewpoint of imparting high tear resistance to the vulcanized rubber. The softening point is measured according to the ring-and-ball formula described in JIS K2207.

The hydrocarbon resin is not particularly limited as long as it has an unsaturated carbon bond (for example, an ethylene hydrocarbon, a conjugated double bond, etc.) that can be crosslinked by vulcanization, but for example, petroleum. Examples thereof include based hydrocarbon resins, terpene resins, styrene resins, and rosin resins. The hydrocarbon resin may be used alone or in combination of two or more.

Examples of the petroleum-based hydrocarbon resin include C5-based aliphatic hydrocarbon resins, C9-based aromatic hydrocarbon resins, and C5 / C9-based aliphatic / aromatic copolymer-based hydrocarbon resins. .. The aliphatic hydrocarbon resin is a resin obtained by cation polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions (C5 fractions) equivalent to 4 to 5 carbon atoms, and is partially water. It may be attached. Aromatic hydrocarbon resins are resins obtained by cationically polymerizing monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fractions) equivalent to 8 to 10 carbon atoms. It may be hydrocarbonized. The aliphatic / aromatic copolymer-based hydrocarbon resin is a resin obtained by copolymerizing the above C5 fraction and C9 fraction by cationic polymerization, and may be partially hydrolyzed.

Examples of the terpene resin include terpene resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer, and modification of these terpene resins (phenol modification, aromatic modification, hydrocarbon modification, etc.). ) Modified terpene-based resin (for example, terpene phenol-based resin, styrene-modified terpene-based resin, aromatic-modified terpene-based resin, etc.) and the like.

Examples of the styrene-based resin include styrene-based thermoplastic elastomers such as a copolymer composed of a polystyrene block and an elastomer block having a polyolefin structure, and examples thereof include styrene-butadiene-styrene block copolymer (SBS) and styrene-isoprene-styrene. Block copolymers (SIS), styrene-ethylene / butylene-styrene block copolymers (SEBS), styrene-ethylene / propylene-styrene block copolymers (SEPS), etc., and some of these partially hydrogenated.

Examples of the rosin-based resin include raw material rosins such as gum rosin, wood rosin, and tall oil rosin, non-uniformized raw material rosins, rosins such as polymerized rosins, esterified products of rosins (rosin ester resin), and phenol-modified rosins. Examples include unsaturated acid (maleic acid and the like) modified rosins, and formylated rosins obtained by reducing rosins.

Hereinafter, the blending amount of each component of the rubber composition of the present invention will be described.

The amount of the acrylonitrile-butadiene rubber (NBR) is 1 to 25 parts by weight with respect to 100 parts by weight of the other diene-based rubber. From the viewpoint of imparting high tear resistance to the vulcanized rubber, the NBR is preferably 3 parts by weight or more and 18 parts by weight or less with respect to 100 parts by weight of the other diene rubber. It is more preferably 13 parts by weight or less, and even more preferably 8 parts by weight or less.

The silica is preferably 10 to 120 parts by weight, more preferably 50 to 100 parts by weight, based on 100 parts by weight of the other diene rubber.

The hydrocarbon resin is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the other diene rubber. From the viewpoint of imparting high tear resistance to the vulcanized rubber, the hydrocarbon resin is preferably 3 parts by weight or more, preferably 8 parts by weight or more, based on 100 parts by weight of the other diene rubber. Is more preferable, and it is preferably 18 parts by weight or less, and more preferably 13 parts by weight or less.

<Various compounding agents>
In the rubber composition, various compounding agents can be further used. Possible compounding agents include, for example, sulfur-based vulcanizing agents, vulcanization accelerators, antiaging agents, carbon black, silane coupling agents, zinc oxide, methylene acceptors and methylene donors, stearic acid, vulcanization promoting. Examples include auxiliaries, vulcanization retardants, organic peroxides, softeners such as waxes and oils, and compounding agents commonly used in the rubber industry such as processing auxiliaries.

The sulfur as the sulfur-based vulcanizing agent may be ordinary sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The sulfur-based vulcanizing agent may be used alone or in combination of two or more.

The sulfur content is preferably 0.3 to 6.5 parts by weight with respect to 100 parts by weight of the other diene rubber. If the sulfur content is less than 0.3 parts by weight, the crosslink density of the vulcanized rubber is insufficient and the rubber strength etc. is lowered, and if it exceeds 6.5 parts by weight, both heat resistance and durability are particularly high. Getting worse. In order to ensure good rubber strength of the vulcanized rubber and further improve heat resistance and durability, the sulfur content is 1.0 to 5.5 weight by weight with respect to 100 parts by weight of the other diene rubber. It is more preferable that it is a part.

The vulcanization accelerator may be an ordinary vulcanization accelerator for rubber, for example, a sulfenamide-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a thiazole-based vulcanization accelerator, or a thiourea-based vulcanization. Examples thereof include an accelerator, a guanidine-based vulcanization accelerator, and a dithiocarbamate-based vulcanization accelerator. The vulcanization accelerator may be used alone or in combination of two or more.

The content of the vulcanization accelerator is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the other diene rubber.

The anti-aging agent may be an ordinary anti-aging agent for rubber, for example, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, and the like. Examples thereof include polyphenol-based anti-aging agents, dithiocarbamate-based anti-aging agents, and thiourea-based anti-aging agents. The anti-aging agent may be used alone or in combination of two or more.

The content of the antiaging agent is preferably 1 to 5 parts by weight with respect to 100 parts by weight of the other diene rubber.

The carbon black is not particularly limited, and for example, in addition to carbon black used in the ordinary rubber industry such as SAF, ISAF, HAF, FEF, and GPF, conductive carbon black such as acetylene black and Ketjen black can be used. Can be used. The carbon black may be a granulated carbon black or an ungranulated carbon black that has been granulated in consideration of its handleability in the ordinary rubber industry. Carbon black may be used alone or in combination of two or more.

The content of the carbon black is preferably 1 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the other diene rubber.

The silane coupling agent may be any ordinary silane coupling agent for rubber, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-). Sulfides such as triethoxysilylethyl) tetrasulfide, bis (4-triequethylsilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide; 3-mercaptopropyl Mercaptosilanes such as trimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane; 3-octanoylthio-1-propyltriethoxysilane, 3 -Protected mercaptosilanes such as propionylthiopropyltrimethoxysilane and the like. The silane coupling agent may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 2% by weight or more, more preferably 4% by weight or more, and 20% by weight, from the viewpoint of fully exerting the effect of addition thereof. It is preferably% or less, and more preferably 15% by weight or less.

<Manufacturing method of rubber composition>
The method for producing the rubber composition of the present invention will be specifically described below.

In the method for producing the rubber composition, the rubber composition is produced by dry-mixing the diene-based rubber, the silica, and the hydrocarbon resin. Further, in the dry mixing, the various compounding agents can be blended as needed.

In the dry mixing, the blending method of each raw material (each component) is not particularly limited, but for example, components other than the vulcanization-based components such as a sulfur-based vulcanizing agent and a vulcanization accelerator are added in an arbitrary order and kneaded. A method of adding and kneading at the same time, a method of adding all the components at the same time and kneading, and the like.

Examples of the dry mixing method include a method of kneading using a kneader used in a normal rubber industry such as a Banbury mixer, a kneader, and a roll. The number of kneading may be one or more. The kneading time varies depending on the size of the kneading machine used, but is usually about 2 to 5 minutes. Further, when the rubber composition does not contain the vulcanization-based component, the discharge temperature of the kneader is preferably 120 to 170 ° C, more preferably 120 to 150 ° C. When the rubber composition contains the vulcanization-based component, the discharge temperature of the kneader is preferably 80 to 110 ° C, more preferably 80 to 100 ° C.

The vulcanized rubber obtained from the rubber composition of the present invention has good tear resistance and is therefore suitable for pneumatic tire applications.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Ingredients used)
a) Acrylonitrile-butadiene rubber (NBR):
NBR (AN content 35% by weight): "JSR N230S" (manufactured by JSR Corporation)
NBR (AN content 40% by weight): "Nipol DN4050" (manufactured by Zeon Corporation)
NBR (AN content 19.5% by weight): "JSR N250S" (manufactured by JSR Corporation)
b) Hydrocarbon resin:
Hydrocarbon resin (softening point 95 ° C): "Petro Tac 90" (manufactured by Tosoh Corporation)
Hydrocarbon resin (softening point 115 ° C): "PX1150" (manufactured by Yasuhara Chemical Co., Ltd.)
Hydrocarbon resin (softening point 140 ± 5 ° C): "Arcon P140" (manufactured by Arakawa Chemical Industries, Ltd.)
c) Styrene-butadiene rubber (SBR): "VSL5025-0HM" (manufactured by LANXESS)
d) Natural rubber (NR): "RSS # 3"
e) Silica: "Nip Seal AQ" (manufactured by Tosoh Silica)
f) Carbon black (CB): "Diablack N341" (manufactured by Mitsubishi Chemical Corporation)
g) Silane coupling agent: "Si69" (manufactured by Evonik Degussa)
h) Zinc Oxide: "Zinc Oxide No. 1" (manufactured by Mitsui Mining & Smelting Co., Ltd.)
i) Anti-aging agent: "Antigen 6C" (manufactured by Sumitomo Chemical Co., Ltd.)
j) Stearic acid: "Lunac S-20" (manufactured by Kao Corporation)
k) Wax: "OZOACE0355" (manufactured by Nippon Seiro Co., Ltd.)
l) Sulfur: "Fine powder sulfur with 5% oil" (manufactured by Tsurumi Chemical Industry Co., Ltd.)
m) Vulcanization accelerator: "Sulfur CZ" (manufactured by Sumitomo Chemical Co., Ltd.)

<Manufacturing of rubber composition>
A rubber composition is produced by dry-mixing each of the raw materials (components excluding sulfur and vulcanization accelerator) shown in Table 1 using a Banbury mixer (kneading time: 3 minutes, discharge temperature: 150 ° C.). did. Next, the sulfur and vulcanization accelerator shown in Table 1 were added to the obtained rubber composition, and dry mixing was performed using a Banbury mixer (kneading time: 1 minute, discharge temperature: 90 ° C.). A vulcanized rubber composition was produced. The blending ratio in Table 1 is shown in parts by weight (phr) when the rubber component of the diene-based rubber other than acrylonitrile-butadiene rubber (NBR) is 100 parts by weight.

<Examples 2 to 9, Comparative Examples 1 to 4>
An unvulcanized rubber composition was produced by the same method as in Example 1 except that the types of each raw material and the blending amount thereof were changed as shown in Table 1.

A vulcanized rubber was produced by vulcanizing the unvulcanized rubber compositions obtained in the above Examples and Comparative Examples at 150 ° C. for 30 minutes. The following evaluation was performed on the obtained vulcanized rubber. The evaluation results are shown in Table 1.

<Evaluation of tear resistance>
The tear resistance was evaluated by punching out the vulcanized rubber obtained above in a crescent shape specified by JIS K6252, and a sample having a notch of 0.50 ± 0.08 mm in the center of the recess was obtained. The tear strength was measured at a tensile speed of 500 mm / min with a tensile tester manufactured by Shimadzu Corporation. Examples 1 to 9 and Comparative Examples 2 to 4 are displayed as an index with the value of Comparative Example 1 as 100. The larger the index, the better the tear resistance (cut resistance).

<Evaluation of pain effect>
Using a viscoelastic tester manufactured by Toyo Seiki Co., Ltd., the obtained test piece of vulcanized rubber is stored at a temperature of 60 ° C., a frequency of 10 Hz, and a static strain of 10% when the dynamic strain is 0.1 and 10%. The elastic moduli (E'(0.1) and E'(10)) were measured, and the pain effect (δE'= E'(0.1) -E'(10)) was calculated. Examples 1 to 9 and Comparative Examples 2 to 4 are displayed as an index with the value of Comparative Example 1 as 100. The smaller the index, the smaller the pane effect and the better the dispersibility of the filler.

Claims (3)

A rubber composition containing a diene-based rubber, silica, and a hydrocarbon resin.
The diene-based rubber contains an acrylonitrile-butadiene rubber and other diene-based rubbers other than the acrylonitrile-butadiene rubber.
The acrylonitrile-butadiene rubber has an acrylonitrile content of 25% by weight or more.
The hydrocarbon resin is an unsaturated group-containing hydrocarbon resin and has a softening point of 80 to 120 ° C.
The amount of the hydrocarbon resin is 1 to 20 parts by weight with respect to 100 parts by weight of the other diene rubber.
A rubber composition, wherein the acrylonitrile-butadiene rubber is 1 to 25 parts by weight with respect to 100 parts by weight of the other diene-based rubber. The rubber composition according to claim 1 , wherein the silica is 10 to 120 parts by weight with respect to 100 parts by weight of the other diene rubber. A pneumatic tire using the rubber composition according to claim 1 or 2 .