JP7753767B2 - Aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin and rubber composition - Google Patents

Description

The present invention relates to aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resins and rubber compositions using the same. In particular, the present invention relates to novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resins and rubber compositions using the same that, when used in the tread portion of a tire, improve the fracture resistance, an indicator of tire durability, while also achieving both wet grip and rolling resistance.

In recent years, demands for tire performance have increased as automobiles have become more powerful and functional. For example, there is a demand for tires with improved wet grip and rolling resistance, which are mutually exclusive. Furthermore, electric vehicles and plug-in hybrid vehicles equipped with drive batteries have increased vehicle weight, which places greater loads on tires, resulting in a demand for tires with improved durability. Conventional techniques for improving wet grip and rolling resistance include blending silica into rubber, and using terminally modified rubber, which has functional groups at the terminals that have a high affinity for or can chemically bond with silica, to improve rolling resistance and abrasion resistance.

With the aim of improving the mechanical properties of tires and imparting good adhesion to unvulcanized rubber compositions, it has been proposed to blend aliphatic/aromatic copolymer resins (see, for example, Patent Document 1) or aliphatic/alicyclic copolymer resins (see, for example, Patent Document 2) into rubber.

In addition, with the aim of achieving high control performance on both dry and wet road surfaces, it has been proposed to blend thermoplastic resins such as C5 resin, C5/C9 resin, and C9 resin into a rubber component containing 70% or more by mass of natural rubber (see, for example, Patent Document 3).

Furthermore, it has been proposed to blend an aliphatic-aromatic-dicyclopentadiene copolymer petroleum resin with diene rubber in order to improve the wet grip, rolling resistance, and abrasion resistance of tires and to enable improved processability (see, for example, Patent Document 4).

Patent No. 5309529 Patent No. 5375101 Patent No. 6346325 Japanese Patent Application Laid-Open No. 2020-203962

However, the methods proposed in Patent Documents 1 and 2 propose blending natural rubber as the main rubber and carbon black as the filler, and do not consider achieving both wet grip and rolling resistance. The methods proposed in Patent Documents 3 and 4 do not consider the effect of fracture resistance. Therefore, there is a need for a new aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin and a rubber composition using the same that solves these issues, improves fracture resistance, and enables both wet grip and rolling resistance to be achieved.

The present invention aims to solve the problems of the prior art by providing a new petroleum resin and a rubber composition using the same that improves the fracture resistance of rubber compositions and enables tires to achieve both wet grip and rolling resistance.

As a result of intensive research aimed at solving the above-mentioned problems, the inventors discovered that an aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin that satisfies specific properties, and a rubber composition using the same, are rubber compositions that exhibit excellent fracture resistance, wet grip properties, and rolling resistance, leading to the completion of the present invention.

That is, the present invention relates to an aliphatic hydrocarbon-aromatic compound-dicyclopentadienes copolymer petroleum resin, which is a copolymer of unsaturated aliphatic hydrocarbons, which are thermal cracking fractions of petroleum, unsaturated aromatic compounds, and dicyclopentadienes, and which satisfies the following properties (1) to (3):
(1) A softening point according to JIS K-2531 (1960) (ring and ball method) of 80 to 130°C.
(2) The weight average molecular weight (hereinafter sometimes referred to as Mw) is 1500 to 2500, the Z average molecular weight (hereinafter sometimes referred to as Mz) is 2500 to 6000, and the ratio of Mz to Mw (hereinafter sometimes referred to as Mz/Mw) is 1.5 to 2.5, as measured by gel permeation chromatography (hereinafter sometimes referred to as GPC) in accordance with JIS K-0124 (1994) using standard polystyrene as the standard substance.
(3) In a proton NMR spectrum measured in deuterated chloroform at room temperature, (I) the area ratio of the peak located at 0.2 to 4.0 ppm due to aliphatic hydrogen is 69 to 74%, (II) the area ratio of the peak located at 4.4 to 5.4 ppm due to acyclic double bond hydrogen is 2.0 to 4.0%, (III) the area ratio of the peak located at 5.4 to 6.3 ppm due to dicyclopentadiene double bond hydrogen is 1.3 to 2.5%, and (IV) the area ratio of the peak located at 6.3 to 7.6 ppm due to aromatic hydrogen is 20 to 27%.

The present invention is described in detail below.

The aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention is obtained by polymerizing a thermal cracking fraction obtained by the separation and refinement of petroleum products. For example, it is a petroleum resin obtained by copolymerizing an aliphatic hydrocarbon fraction, such as a C5 fraction (e.g., a fraction with a boiling point range of 20 to 110°C), an aromatic compound fraction, such as a C9 fraction (e.g., a fraction with a boiling point range of 140 to 280°C), and, in some cases, a dicyclopentadiene fraction. It satisfies the properties (1) to (3) above. The petroleum products used in this process include not only petroleum-derived products such as naphtha, but also plant-derived oils such as bioethanol and bionaphtha, and oils derived from chemically recycled plastics such as polyolefins, polyvinyl chloride, acrylics, and polystyrene.

The aliphatic hydrocarbon components constituting the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention include components belonging to a fraction known as a C5 fraction, which is an aliphatic hydrocarbon fraction. Examples include fractions with a boiling point range of 20 to 110°C, more specifically linear unsaturated aliphatic hydrocarbons such as isoprene and piperylene; cyclic unsaturated aliphatic hydrocarbons such as cyclopentadiene and methylcyclopentadiene; and mixtures thereof. Furthermore, since cyclopentadienes have the ability to dimerize and become dicyclopentadienes during storage, C5 fractions containing cyclopentadienes may also contain their dimers, dicyclopentadienes.

The aromatic compound components constituting the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention include fractions known as C9 fractions, which are aromatic compound fractions, such as fractions with a boiling point range of 140 to 280°C, more specifically unsaturated aromatic compounds having 8 carbon atoms such as styrene; unsaturated aromatic compounds such as α-methylstyrene, vinyltoluene, indene, 1-methylindene, 2-methylindene, and 3-methylindene; and mixtures thereof.

The dicyclopentadiene component constituting the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention may be any dicyclopentadiene, such as dicyclopentadiene, methyldicyclopentadiene, dimethyldicyclopentadiene, and mixtures thereof. The dicyclopentadienes may also be those contained in the C9 component.

The novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention (1) has a softening point, as measured by JIS K-2531 (1960) (ring and ball method), of 80 to 130°C, preferably 85 to 125°C. If the softening point is less than 80°C, the wet grip performance will be poor when the composition is blended with rubber to form a tire. If the softening point exceeds 130°C, the rubber composition will have poor rolling resistance when formed into a tire.

The novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention has an Mw of 1500 to 2500, an Mz of 2500 to 6000, and an Mz/Mw ratio of 1.5 to 2.5, as measured by GPC in accordance with JIS K-0124 (1994) using standard polystyrene as the standard substance. If the Mw is less than 1500 or the Mz is less than 2500, the wet grip performance of the resulting tire will be poor when blended with rubber. If the Mw is more than 2500 or the Mz is more than 6000, the rolling resistance of the resulting tire will be poor. Furthermore, if the Mz/Mw is less than 1.5, the fracture resistance of the resulting tire will be poor. If the Mz/Mw is more than 2.5, the rubber composition will have poor compatibility, resulting in poor rolling resistance.

The novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention is a petroleum resin that satisfies the following criteria: (I) an aliphatic hydrogen area ratio of 69 to 74%, (II) an acyclic double bond hydrogen area ratio of 2.0 to 4.0%, (III) a dicyclopentadiene double bond hydrogen area ratio of 1.3 to 2.5%, and (IV) an aromatic hydrogen area ratio of 20 to 27%, and each hydrogen area ratio can be measured under the following conditions (A) to (D) as a percentage of the peak area of the spectrum measured and observed by proton NMR using deuterated chloroform as a solvent.
(a) Determined from the area ratio of hydrogen derived from aliphatic components observed between 0.2 and 4.0 ppm.
(a) Determined from the area ratio of hydrogen derived from the double bond of the non-cyclic component observed at 4.4 to 5.4 ppm.
(c) Determined from the area ratio of hydrogen derived from the double bonds of dicyclopentadiene components observed at 5.4 to 6.3 ppm.
(d) Determined from the area ratio of hydrogen derived from aromatic components observed at 6.3 to 7.6 ppm.

The novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention satisfies all of the properties (I) to (IV), and therefore has excellent compatibility with rubber, particularly diene rubber, making it possible to produce tires with excellent performance when made into tires.

Furthermore, the novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention exhibits an excellent balance of fracture resistance and flexibility, particularly when blended with rubber. (4) 30 parts by weight of the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin, 1.5 parts by weight of sulfur, and 2.5 parts by weight of a sulfenamide vulcanization accelerator are blended with 100 parts by weight of styrene-butadiene rubber, and the resulting vulcanized rubber is subjected to a tensile test in accordance with JIS K-6251. It is preferable that the resulting breaking strength (MPa) and breaking elongation (%) satisfy the relationship: breaking strength (MPa) × breaking elongation (%) > 500.

There are no particular limitations on the method for producing the novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention, and any production method may be used. For example, the resin can be produced by using as a feedstock a mixture containing an aliphatic hydrocarbon fraction (C5 fraction) with a boiling point range of 20 to 110°C obtained by thermal cracking of petroleum, an aromatic compound fraction (C9 fraction) with a boiling point range of 140 to 280°C, and, in some cases, a dicyclopentadiene fraction, and adding a catalyst to this mixture, heating, and polymerizing. There are no particular limitations on the catalyst used in the polymerization, and examples include aluminum trichloride, aluminum tribromide, boron trifluoride, and complexes thereof. The solvent used during polymerization can be saturated hydrocarbons from the C5 fraction and C9 fraction.

There are no particular restrictions on the polymerization temperature during production, but a temperature of 20 to 80°C is preferred, with 30 to 60°C being particularly preferred, as this results in high polymerization activity and excellent productivity. The amount of catalyst and polymerization time can be selected appropriately depending on the temperature and the water concentration in the feedstock oil. Typically, for example, 0.1 to 2.0% by weight of catalyst relative to the feedstock oil and a polymerization time of 0.1 to 10 hours are preferred. There are no particular restrictions on the reaction pressure, either, with atmospheric pressure to 1 MPa being preferred. There are also no particular restrictions on the atmosphere, with a nitrogen atmosphere being preferred.

The novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention, when blended with rubber, particularly diene rubber, results in a rubber composition that exhibits excellent fracture resistance, wet grip properties, and rolling resistance. Examples of diene rubbers include natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber. These may be used alone or in combination. There are no particular restrictions on the method for producing the diene rubber, and it may be an anionic polymer or an emulsion polymer. The molecular terminals of the diene rubber may be modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized. Due to their excellent compatibility with the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin, it is particularly preferable to use at least one of natural rubber, polybutadiene rubber, and polyisoprene rubber in combination with styrene-butadiene copolymer rubber. Furthermore, since the rubber composition will result in a tire rubber composition and tire with excellent wet grip properties, fuel economy, and fracture resistance, it is preferable that the rubber composition contain 1 to 50 parts by weight of the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin per 100 parts by weight of diene rubber.

The rubber composition can also be compounded with silica to improve wet grip and rolling resistance. There are no particular restrictions on the type of silica used, and those used in commercially available rubber compositions can be used. Among these, wet silica (hydrated silica), dry silica (anhydrous silica), colloidal silica, etc. are particularly preferred, with wet silica being particularly preferred. The amount of silica used is preferably in the range of 20 to 200 parts by weight per 100 parts by weight of diene rubber, and more preferably 30 to 150 parts by weight, to result in a rubber composition with excellent wet grip, rolling resistance, and processability.

When using silica, it is preferable to use a silane coupling agent in combination. By using a silane coupling agent in combination, the bond between the diene rubber and the silica is strengthened via the silane coupling agent, improving wet grip, rolling resistance, and fracture resistance. Examples of silane coupling agents include sulfide-based, mercapto-based, vinyl-based, amino-based, epoxy-based, glycidyl-based, nitro-based, and chloro-based silane coupling agents. These silane coupling agents can be used alone or in combination of two or more types.

In addition to the silica, the rubber composition can also contain other reinforcing fillers, such as carbon black. Examples of carbon black that can be used include grades such as SAF, ISAF, HAF, FEF, and SRF. There are no particular restrictions on the amount of carbon black, but it is preferably 1 to 100 parts by weight per 100 parts by weight of diene rubber.

The rubber composition may further contain compounding agents typically used in resin compositions and rubber compositions. For example, compounding agents such as crosslinking agents such as sulfur, vulcanization accelerators, stearic acid, zinc oxide, plasticizers, oils, waxes, and antioxidants may be added. Commercially available compounds can be used as these compounding agents.

The rubber composition may be of any composition, form, or shape as long as it contains rubber, and may be a crosslinked product (vulcanizate) that contains a crosslinking agent, vulcanization accelerator, vulcanization accelerator aid, etc., and when used as a tire tread in particular, it is possible to provide a tire with excellent wet grip, rolling resistance, and durability.

The novel aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention, when blended with rubber components in particular, improves fracture resistance and makes it possible to provide a rubber composition that combines wet grip and rolling resistance for tires.

The present invention will be explained below using examples, but the present invention is not limited to these examples. The analytical methods for the raw material oils used in the examples and comparative examples and the resulting petroleum resins are as follows:

1. Raw material <raw oil>
The compositions of the C5 fraction ((A), (B)) having a boiling point range of 20 to 110°C, which is an aliphatic hydrocarbon fraction obtained by cracking and refining naphtha, the C9 fraction ((A), (B)) having a boiling point range of 140 to 280°C, which is an aromatic compound fraction, and the dicyclopentadiene fraction are shown in Tables 1 to 3. In Tables 1 to 3, DCPD is an abbreviation for dicyclopentadiene, and CPD is an abbreviation for cyclopentadiene.

<Catalyst for petroleum resin production>
Boron trifluoride phenol: 30% by weight of boron trifluoride (manufactured by Stella Chemifa Co., Ltd.).
Boron trifluoride butanol: 30% by weight of boron trifluoride (manufactured by Stella Chemifa Co., Ltd.).

<Rubber>
Styrene-butadiene rubber: SL563 (trade name) manufactured by JSR Corporation.
Isoprene rubber: IR2200 (product name) manufactured by JSR Corporation.

<Combined ingredients>
Silica: Nipsil AQ (trade name) manufactured by Tosoh Silica.
Silane coupling agent: CABRUS2 (trade name) manufactured by Osaka Soda.
Carbon black: Asahi #70 (trade name) manufactured by Asahi Carbon.
Oil: Diana Process Oil AH-16 (trade name) manufactured by Idemitsu Kosan.
Stearic acid: Reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.
Zinc oxide: Manufactured by Inoue Lime Industry.
Anti-aging agent: Nocrac 6C (trade name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Wax: Sunnock (product name) manufactured by Ouchi Shinko Chemical Industry.
Sulfur: Sulfax 5 (trade name) manufactured by Tsurumi Chemical Industry Co., Ltd.
Vulcanization accelerator 1: Noccela CZ (trade name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noccela D (trade name) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

2. Analysis method <Raw oil component analysis>
The analysis was carried out using gas chromatography in accordance with JIS K-0114 (2000).

<Proton NMR Measurement>
Proton NMR spectra were measured in deuterated chloroform using a nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd., trade name GSX400, frequency 400 MHz).

<Measurement of Mn, weight average molecular weight (Mw), and Mz>
Using polystyrene as a standard substance, measurements were made by GPC in accordance with JIS K-0124 (1994).

<Softening Point Measurement>
Measurement was carried out according to JIS K-2531 (1960) (ring and ball method).

<Wet grip>
Using a viscoelasticity measuring device (manufactured by Rheometrics), tan δ was measured at a temperature of 0°C, a strain of 5%, and a frequency of 50 Hz, and the value at 0°C was used as an index of wet grip performance. A larger tan δ value was determined to be more excellent in wet grip performance.

<Rolling resistance>
Using a viscoelasticity measuring device (manufactured by Rheometrics), tan δ was measured at a temperature of 60°C, a strain of 5%, and a frequency of 50 Hz, and the value at 60°C was used as an index of rolling resistance. A smaller tan δ value was determined to indicate better rolling resistance.

<Destruction resistance characteristics>
The breaking strength and breaking elongation were measured using a tensile tester (manufactured by Shimadzu Corporation) in accordance with the test method of JIS K-6251. Those satisfying the relationship of breaking strength (MPa) × breaking elongation (%) > 500 were judged to have excellent fracture resistance.

Example 1
A 2-liter glass autoclave was charged with 200 g of C5(A) fraction (see Table 1 for composition) obtained by cracking naphtha as feedstock oil and 300 g of C9 fraction (A) (see Table 2 for composition) (C5 fraction (A)/C9 fraction (A) = 40/60 (wt %)). Next, the mixture was heated to 40°C under a nitrogen atmosphere, and then 0.4 g of premixed boron trifluoride phenol was added to the feedstock oil, followed by polymerization at 40°C for 2 hours. After completion of the polymerization reaction, an aqueous caustic soda solution was added for neutralization, and the unreacted oil in the oil layer was distilled to recover an aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin (hereinafter sometimes referred to as petroleum resin A).

The polymerization conditions and results are shown in Table 4, and the physical properties of the resulting petroleum resin A (molecular weight, softening point, and NMR analysis values) are shown in Table 5.

100 parts by weight of styrene-butadiene copolymer rubber (SBR) (manufactured by JSR Corporation) and 30 parts by weight of petroleum resin A were added to a Laboplastomill (600 cc capacity), and the mixture was removed after a total mixing time of 5 minutes. The ram pressure and rotation speed were adjusted so that the compound temperature at the time of removal was 120-130°C. After cooling the resulting compound to room temperature, 1.5 parts by weight of sulfur (product name: Sulfax 5, manufactured by Tsurumi Chemical Industry Co., Ltd.), 1.2 parts by weight of vulcanization accelerator 1 (product name: Noccela CZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and 1.8 parts by weight of vulcanization accelerator 2 (product name: Noccela D, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added and kneaded for 1 minute. The mixture was then sheeted using a roll to obtain an unvulcanized rubber composition. This was then vulcanized using a heated press at a temperature of 150°C for 30 minutes to obtain a vulcanized rubber.

The resulting vulcanized rubber was subjected to tensile testing to determine its breaking strength and breaking elongation. The resulting petroleum resin A was capable of providing vulcanized rubber with excellent fracture resistance, with a breaking strength x breaking elongation = 864. The results are shown in Table 6.

Examples 2 to 4
Aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymerized petroleum resins (petroleum resins B to D) were obtained in the same manner as in Example 1, except that the blends and amounts of the raw material oils and the types and amounts of the polymerization catalysts were changed as shown in Table 4.

The physical properties (molecular weight, softening point, NMR analysis values) of the resulting petroleum resins B to D are shown in Table 5, and the evaluation results when vulcanized rubber was produced in the same manner as in Example 1 are shown in Table 6. It was possible to provide vulcanized rubber with excellent fracture resistance.

Comparative Examples 1 to 4
Petroleum resins (petroleum resins E to H) were obtained in the same manner as in Example 1, except that the blend and amount of the raw material oil and the type and amount of the polymerization catalyst were as shown in Table 4.

The physical properties (molecular weight, softening point, NMR analysis values) of the obtained petroleum resins E to H are shown in Table 5, and the evaluation results when vulcanized rubber was produced in the same manner as in Example 1 are shown in Table 6. None of the obtained petroleum resins E to H were able to provide vulcanized rubber with excellent fracture resistance properties.

Reference Example A vulcanized rubber was prepared in the same manner as in Example 1, except that no petroleum resin was added, and the evaluation results are shown in Table 6. The vulcanized rubber obtained was inferior in fracture resistance.

Example 5
In a Labo Plastomill (volume 600 cc), 70 parts by weight of styrene-butadiene copolymer rubber (SBR) (manufactured by JSR Corporation, (trade name) SL563) and 30 parts by weight of isoprene rubber (IR) (manufactured by JSR Corporation, (trade name) IR2200) were masticated for 30 seconds, and then 60 parts by weight of silica (manufactured by Tosoh Silica, (trade name) Nipsil AQ), 4.8 parts by weight of a silane coupling agent (manufactured by Osaka Soda, (trade name) CABRUS2), and 1.0 parts by weight of carbon black (manufactured by Asahi Carbon, (trade name) Asahi To the mixture were added 15 parts by weight of ethanol (#70), 10 parts by weight of oil (Idemitsu Kosan (trade name) Diana Process Oil AH-16), 2 parts by weight of stearic acid (Fujifilm Wako Pure Chemical Industries (reagent)), 3 parts by weight of zinc oxide (Inoue Lime Industry), 1 part by weight of antioxidant (Ouchi Shinko Chemical Industry (trade name) Nocrac 6C), 2 parts by weight of wax (Ouchi Shinko Chemical Industry (trade name) Sunnock), and 15 parts by weight of the petroleum resin A obtained in Example 1, and the compound was taken out after a total mixing time of 5 minutes. The ram pressure and rotation speed were adjusted so that the compound temperature at the time of takeout was 140 to 150°C, and a rubber composition was obtained.

Furthermore, 1.5 parts by weight of sulfur (product name: Sulfax 5, manufactured by Tsurumi Chemical Industry Co., Ltd.), 1.2 parts by weight of vulcanization accelerator 1 (product name: Noccela CZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), and 1.8 parts by weight of vulcanization accelerator 2 (product name: Noccela D, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were added and kneaded for 1 minute. After that, the mixture was sheeted using an 8-inch roll to obtain an unvulcanized rubber composition. This was then vulcanized using a heated press at a vulcanization temperature of 150°C for 30 minutes to obtain a vulcanized rubber composition.

The measurement results for the wet grip properties and rolling resistance of the obtained vulcanized rubber composition are shown in Table 7.

Examples 6 to 8
Rubber compositions were prepared and evaluated in the same manner as in Example 5, except that petroleum resin B, C, and D were used instead of petroleum resin A. The results are shown in Table 7.

Example 9
A rubber composition was prepared in the same manner as in Example 5, except that 30 parts by weight of petroleum resin A was used instead of 15 parts by weight, and the rubber composition was evaluated. The results are shown in Table 7.

Comparative Example 1
A rubber composition was obtained in the same manner as in Example 5, except that petroleum resin A was not used. The obtained rubber composition had poor wet grip properties. The evaluation results are shown in Table 7.

Comparative Examples 6 to 9
Rubber compositions were prepared and evaluated in the same manner as in Example 1, except that petroleum resins E, F, G, and H were used instead of petroleum resin A. It was difficult for the resulting rubber compositions to achieve both wet grip properties and low rolling resistance. The results are shown in Table 7.

The aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin of the present invention makes it possible to provide a rubber composition that has excellent fracture resistance, wet grip properties, and rolling resistance. This rubber composition can be used as tire tread rubber, and its industrial value is extremely high.

Claims (8)

An aliphatic hydrocarbon-aromatic compound-dicyclopentadienes copolymer petroleum resin is a copolymer of unsaturated aliphatic hydrocarbons, which are thermal cracking fractions of petroleum, unsaturated aromatic compounds, and dicyclopentadienes, and is characterized by satisfying the following properties (1) to (3):
(1) A softening point according to JIS K-2531 (1960) (ring and ball method) of 80 to 130°C.
(2) A weight-average molecular weight (Mw) of 1,500 to 2,500, a Z-average molecular weight (Mz) of 2,500 to 6,000, and a ratio of the Z-average molecular weight to the weight-average molecular weight (Mz/Mw) of 1.5 to 2.5, as measured by gel permeation chromatography in accordance with JIS K-0124 (1994) using standard polystyrene as the standard substance.
(3) In a proton NMR spectrum measured in deuterated chloroform at room temperature, (I) the area ratio of the peak located at 0.2 to 4.0 ppm due to aliphatic hydrogen is 69 to 74%, (II) the area ratio of the peak located at 4.4 to 5.4 ppm due to acyclic double bond hydrogen is 2.0 to 4.0%, (III) the area ratio of the peak located at 5.4 to 6.3 ppm due to dicyclopentadiene double bond hydrogen is 1.3 to 2.5%, and (IV) the area ratio of the peak located at 6.3 to 7.6 ppm due to aromatic hydrogen is 20 to 27%. The aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin according to claim 1, further satisfying the following characteristic (4):
(4) When a vulcanized rubber obtained by compounding 100 parts by weight of styrene-butadiene rubber with 30 parts by weight of aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin, 1.5 parts by weight of sulfur, and 2.5 parts by weight of a sulfenamide vulcanization accelerator and press-vulcanizing the rubber at 150°C for 30 minutes is subjected to a tensile test in accordance with JIS K-6251, the breaking strength (MPa) x breaking elongation (%) > 500 is satisfied. The aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin according to claim 1 or 2, characterized in that the thermal cracking fraction of petroleum is a thermal cracking oil containing plant-derived oil and/or chemically recycled oil. A rubber composition characterized by containing at least the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin described in any one of claims 1 to 3 in combination with a diene rubber. The rubber composition described in claim 4, characterized in that it contains 1 to 50 parts by weight of the aliphatic hydrocarbon-aromatic compound-dicyclopentadiene copolymer petroleum resin per 100 parts by weight of diene rubber. The rubber composition according to claim 4 or 5, characterized in that the diene rubber contains 10% by weight or more of styrene-butadiene rubber. The rubber composition according to any one of claims 4 to 6, further comprising 20 to 200 parts by weight of silica per 100 parts by weight of diene rubber. A tire comprising the rubber composition according to any one of claims 4 to 7.