AU2018203160B2

AU2018203160B2 - Rubber composition for conveyor belt, and conveyor belt

Info

Publication number: AU2018203160B2
Application number: AU2018203160A
Authority: AU
Inventors: Deqing Zou
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2017-05-10
Filing date: 2018-05-07
Publication date: 2019-07-25
Anticipated expiration: 2038-05-07
Also published as: JP2018188584A; AU2018203160A1; CN108864505A; JP6952234B2; CN108864505B

Abstract

Abstract Resolution Means: A rubber composition for a conveyor belt, the rubber composition including a rubber component containing greater than 50 mass% and 100 mass% or less of a butadiene rubber and a carbon black, a content of the carbon black being from 60 to 100 parts by mass per 100 parts by mass of the rubber component, and a content of a bound rubber at 250C being from 45 to 70 mass%; and a conveyor belt including an upper surface cover rubber layer formed from the rubber composition for a conveyor belt, a reinforcing layer, and a lower surface cover rubber layer. Selected Drawing: FIG. 1

Description

RUBBER COMPOSITION FOR CONVEYOR BELT, AND CONVEYOR BELT

Technical Field [0001]

The present invention relates to a rubber composition for a conveyor belt and a conveyor belt.

Background Art [0002]

In recent years, a conveyor belt having a long life has been in demand from the perspective of environmental consideration. To address such a problem, rubber compositions aimed at wear resistance enhancement in belt conveyors have been proposed in the related art. For example, Patent Document 1 describes a rubber composition for a belt of belt conveyor, the rubber composition containing, as a rubber component, a polybutadiene rubber synthesized with a neodymium-based catalyst.

Citation List

Patent Literature [0003]

Patent Document 1: JP 2003-105136 A

Summary of Invention

Technical Problem [0004]

Under such circumstances, the inventors of the present invention prepared and evaluated the rubber composition according to Patent Document 1, and found that there are some cases where such a rubber composition may have poor wear resistance.

Thus, an object of the present invention is to provide a rubber composition for a conveyor belt and a conveyor belt, which have excellent wear resistance.

2018203160 07 May 2018

Solution to Problem [0005]

As a result of diligent research to solve the above problems, the inventors of the present invention found that a rubber composition containing a rubber component containing a predetermined amount of butadiene rubber and a carbon black, wherein the amounts of the carbon black and a bound rubber are in a predetermined range provides a predetermined effect, and thus achieved the present invention.

The present invention is based on the findings described above and, specifically, solves the problems described above by the following features.

[0006]

1. A rubber composition for a conveyor belt including :

a rubber component containing greater than 50 mass% and 100 mass% or less of a butadiene rubber; and a carbon black; a content of the carbon black being from 60 to 100 parts by mass per 100 parts by mass of the rubber component; and a content of a bound rubber at 25°C being from 45 to 70 mass%.

. The rubber composition for a conveyor belt according to 1 above, where a nitrogen adsorption 25 specific surface area of the carbon black is from 115 to 160 m²/g, and a dibutyl phthalate oil absorption is from 115 to 140 mL/100 g.

3. The rubber composition for a conveyor belt according to 1 or 2 above, where a weight average molecular weight of the butadiene rubber is from 500000 to 1000000.

. The rubber composition for a conveyor belt according to any one of 1 to 3 above, where a ratio of weight average molecular weight of the butadiene rubber to long-chain branching index of the butadiene rubber (weight average molecular weight/long-chain branching index) is from 5.5 * 10⁴ to 16.6 * 10⁴.

2018203160 07 May 2018

5. A conveyor belt including: an upper surface cover rubber layer formed from the rubber composition for a conveyor belt described in any one of 1 to 4 above; a reinforcing layer; and a lower surface cover 5 rubber layer.

Advantageous Effects of Invention [0007]

The rubber composition for a conveyor belt and a conveyor belt according to an embodiment of the present invention have excellent wear resistance.

Brief Description of Drawing [0008]

FIG. 1 is a cross-sectional perspective view schematically illustrating a part of a preferred embodiment of the conveyor belt according to an embodiment of the present invention.

Description of Embodiments [0009]

Embodiments of the present invention are described in detail below.

Note that in the present specification, numerical ranges indicated using (from)... to... include the former number as the lower limit value and the later number as the upper limit value.

In the specification, for each component, a single substance corresponding to the component may be used, or two or more types of substances may be used in combination unless noted otherwise. When the component contains the content of the two or more types of substances, component means the total content of the substances .

Rubber composition rubber for a conveyor belt composition for a conveyor belt according to an embodiment of the present invention

2018203160 07 May 2018 (the composition of an embodiment of the present invention) includes: a rubber component containing greater than 50 mass% and 100 mass% or less of a butadiene rubber; and a carbon black; a content of the carbon black

100 parts by content of a

Each of being from 60 to 100 parts by mass per mass of the rubber component; and a bound rubber at 25°C being from 45 to 70 the components included in the composition according to an invention will be described embodiment of the present in detail below.

Rubber component

The composition of an embodiment of the present invention contains a rubber component containing a butadiene rubber .

Butadiene rubber

Butadiene rubber (BR) is a homopolymer of butadiene .

[0014]

Weight average molecular weight of butadiene rubber The weight average molecular weight of butadiene rubber is preferably from 500000 to 1000000, more preferably from 500000 to 800000, even more preferably from 500000 to 700000, from the perspective of achieving superior wear resistance, adjusting the amount of bound rubber within an appropriate range, and achieving an excellent balance between the amount of bound rubber and wear resistance.

In an embodiment of the present invention, the weight average molecular weight of butadiene rubber is a value obtained by gel permeation chromatography (GPC) measured based on calibration with polystyrene standard using cyclohexane as a solvent.

[0015]

Long-chain branching index of butadiene rubber

2018203160 07 May 2018

The long-chain branching index (LCB Index) of butadiene rubber is preferably from 0.1 to 12.0, and more preferably 11.0 or less from the perspective of superior wear resistance.

In an embodiment of the present invention, the long-chain branching index of butadiene rubber is measured using an RPA 2000 tester (available from Alpha Technologies) at 100°C according to a large amplitude oscillatory shear (LAOS) method.

As the long-chain branching index is closer to zero, the degree of branching of butadiene rubber is low .

For the details of the long-chain branching index (LCB Index), for example, FT-Rheology, a Tool to

Quantify Long Chain Branching (LCB) in Natural Rubber and its Effect on Mastication, Mixing Behaviour and Final Properties. (Henri G. Burhin, Alpha Technologies, UK 15 Rue du Culot B-1435 Hevillers, Belgium) can be used as a reference.

[0016]

Weight average molecular weight/long-chain branching index

The ratio of weight average molecular weight of butadiene rubber to long-chain branching index of butadiene rubber (weight average molecular weight/long-chain branching index) is preferably from 5.5 x 10⁴ to 16.6 x 10⁴, more preferably from 5.8 χ 10⁴to 16.6 χ 10⁴, and even more preferably from 7.0 χ 10⁴to 14.2 χ 10⁴, from the perspective of achieving superior wear resistance, ability to adjust the amount of bound rubber within an appropriate range, and achieving an excellent balance between the amount of bound rubber and wear resistance.

[0017]

Microstructure of butadiene rubber

The 1,4-cis structure of butadiene rubber is preferably 97% or greater, and more preferably 98% or

2018203160 07 May 2018 greater from the perspective of superior wear resistance .

The 1,4-trans structure of butadiene rubber is preferably 1.5% or less, and more preferably 1.0% or less from the perspective of superior wear resistance. The 1,2-vinyl structure of butadiene rubber is preferably 1.5% or less, and more preferably 1.0% or less from the perspective of superior wear resistance.

In an embodiment of the present invention, the microstructure of butadiene rubber is analyzed by infrared absorption spectrometry. A peak at 740 cm^-1 is an absorption band corresponding to the 1,4-cis structure, a peak at 967 cm^-1 is an absorption band corresponding to the 1,4-trans structure, and a peak at 910 cm^-1 is an absorption band corresponding to the 1,2-vinyl structure. The microstructure was determined from absorption intensity ratios.

[0018]

Method of producing butadiene rubber

Examples of the method of producing butadiene rubber include a method of synthesizing butadiene rubber by polymerizing butadiene using a catalyst such as a cobalt-based catalyst and/or neodymium-based catalyst. The cobalt-based catalyst and neodymium25 based catalyst are not particularly limited. The cobalt-based catalyst may be a compound containing cobalt. The neodymium-based catalyst may be a compound containing neodymium (Nd). In particular, a neodymiumbased catalyst is preferred.

[0019]

Butadiene rubber content

In an embodiment of the present invention, the content of butadiene rubber is greater than 50 mass% and 100 mass% or less relative to the total amount of the rubber component. The expression greater than 50 mass% means that the content exceeds 50 mass%.

The content of butadiene rubber is preferably from 60 to 90 mass%, more preferably from 70 to 90

2018203160 07 May 2018 mass%, and even more preferably from 75 to 90 mass% relative to the total amount of the rubber component from the perspective of achieving superior wear resistance, ability to adjust the amount of bound rubber within an appropriate range, and achieving an excellent balance between the amount of bound rubber and wear resistance.

[0020]

Rubber other than butadiene rubber

In an embodiment of the present invention, the rubber component may further contain another rubber besides the butadiene rubber.

Examples of the other rubber other than butadiene rubber include diene rubbers (excluding butadiene rubber).

The diene rubbers are not particularly limited, and examples thereof include natural rubber (NR), isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber (e.g. styrene-butadiene rubber (SBR) ) , 20 nitrile-butadiene rubber (NBR, acrylonitrile-butadiene rubber), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). Of these, natural rubber and styrene-butadiene rubber are preferable .

[0021]

Carbon black

The composition according to an embodiment of the present invention contains a carbon black.

[0022]

Nitrogen adsorption specific surface area of carbon black

The nitrogen adsorption specific surface area (N²SA) of carbon black is preferably from 115 to 160 m²/g, more preferably from 125 to 160 m²/g, and even more 35 preferably from 125 to 150 m²/g, from the perspective of achieving superior wear resistance, ability to adjust the amount of bound rubber within an

2018203160 07 May 2018 appropriate range, and achieving an excellent balance between the amount of bound rubber and wear resistance.

Note that the nitrogen adsorption specific surface area of carbon black is a value obtained by measuring the amount of nitrogen adsorbed to the surface of carbon black in accordance with JIS K62172:2001 (Part 2: Determination of specific surface area - Nitrogen adsorption methods - Single-point procedures ) .

[0023]

Dibutyl phthalate oil absorption of carbon black

The dibutyl phthalate oil absorption of carbon black (DBP oil absorption) is preferably from 115 to 140 mL/100 g, more preferably from 115 to 135 mL/100 g, and even more preferably from 115 to 130 mL/100 g from the perspective of achieving superior wear resistance.

The dibutyl phthalate oil absorption of carbon black is measured in accordance with JIS K 6217-4:2008 (Carbon black for rubber industry Fundamental characteristics, Part 4: Determination of oil absorption number (OAN) and oil absorption number of compressed sample (COAN)).

[0024]

Examples of the carbon black include Super Abrasion Furnace (SAF) carbon black, Intermediate Super Abrasion Furnace (ISAF) carbon black, and High Abrasion Furnace (HAF)-HS (high-structured) carbon black .

In particular, the carbon black is preferably SAF from the perspective of achieving superior wear resistance, ability to adjust the amount of bound rubber within an appropriate range, and achieving an excellent balance between the amount of bound rubber and wear resistance.

[0025]

Carbon black content

2018203160 07 May 2018

In an embodiment of the present invention, the content of carbon black is from 60 to 100 parts by mass per 100 parts by mass of the rubber component.

The content of carbon black is preferably from 60 to 90 parts by mass, more preferably from 60 to 80 parts by mass, and even more preferably from 60 to 75 parts by mass per 100 parts by mass of the rubber component, from the perspective of achieving superior wear resistance, ability to adjust the amount of bound rubber within an appropriate range, and achieving an excellent balance between the amount of bound rubber and wear resistance.

[0026]

Additives

The composition according to an embodiment of the present invention may further contain additives other than the components described above within a scope that does not inhibit the effect or purpose of the present invention. Examples of the additives include white fillers, anti-aging agents such as 6C, zinc oxide, stearic acid, processing aids, paraffin wax, aroma oils, liquid polymers, terpene-based resins, thermosetting resins, vulcanizing agents such as sulfur, vulcanization aids, vulcanization accelerators, and vulcanization retarders.

The content of the additives may be selected as desired.

[0027]

Method of producing composition of present invention

The method of producing the composition according to an embodiment of the present invention is not particularly limited. For example, the composition of an embodiment of the present invention can be produced by mixing the components described above (excluding a vulcanizing agent such as sulfur and a vulcanization accelerator) in a Banbury mixer or the like to obtain a mixture, and then adding the vulcanizing agent such as sulfur and the vulcanization accelerator to the

2018203160 07 May 2018 mixture and kneading the mixture in a roll kneader or the like.

[0028]

Bound rubber content

In the composition according to an embodiment of the present invention, the content of bound rubber at 25°C is from 4 5 to 7 0 mass%.

The content of bound rubber is preferably from 45 to 65 mass%, and more preferably from 46 to 58 mass% from the perspective of superior wear resistance.

The method of measuring the content of bound rubber will be described later.

[0029]

Method of vulcanizing and/or crosslinking composition of present invention

Conditions for vulcanization and/or crosslinking of the composition according to an embodiment of the present invention are not particularly limited. For example, the composition according to an embodiment of 20 the present invention can be vulcanized and/or crosslinked by applying heat and pressure at 140 to 160°C.

[0030]

A conveyor belt can be formed from the composition according to an embodiment of the present invention .

[0031]

Conveyor belt

The conveyor belt according to an embodiment of the present invention includes an upper surface cover rubber layer formed from the rubber composition for a conveyor belt according to an embodiment of the present invention, a reinforcing layer, and a lower surface cover rubber layer.

[0032]

The rubber composition constituting the upper surface cover rubber layer is not particularly limited as long as it is the rubber composition for a conveyor

2018203160 07 May 2018 belt according to an embodiment of the present invention .

The upper surface cover rubber layer may be composed of a single layer or a plurality of layers.

The same applies to the reinforcing layer and the lower surface cover rubber layer.

[0033]

The conveyor belt according to an embodiment of the present invention will be described below with reference to an attached drawing. However, the present invention is not limited by the attached drawings.

In FIG. 1, the conveyor belt 1 has an upper surface cover rubber layer 2, a reinforcing layer 3, and a lower surface cover rubber layer 4, which are layered in this order. The surface of the upper surface cover rubber layer 2 may serve as a conveying face for transporting articles 5. The upper surface cover rubber layer 2 is formed from the composition according to an embodiment of the present invention. [0034]

Note that, when the upper surface cover rubber layer 2 has two or more layers as illustrated in FIG. 1, at least one layer or all the layers of the two or more layers may be formed from the composition according to an embodiment of the present invention.

In addition, at least the outermost layer is preferably formed from the composition according to an embodiment of the present invention.

In FIG. 1, the upper surface cover rubber layer 2 has an outer layer 11 and an inner layer 12. The outer layer 11 and/or the inner layer 12 may be formed from the composition according to an embodiment of the present invention, and at least the outer layer 11 is

2018203160 07 May 2018 preferably formed from the composition according to an embodiment of the present invention.

In a case where the outer layer 11 is formed from the composition according to an embodiment of the present invention, the inner layer 12 may be a layer for adhering the reinforcing layer 3 and the outer layer 11.

[0035]

The rubber composition used in the lower surface cover rubber layer is not particularly limited.

Examples of the rubber composition include the composition according to an embodiment of the present invention .

In FIG. 1, the lower surface cover rubber layer 4 has an outer layer 16 and an inner layer 15. The outer layer 16 and the inner layer 15 may be formed from the same or different rubber composition (s) .

[0036]

The reinforcing layer is not particularly limited, 20 and materials typically used in conveyor belts can be suitably selected and used.

The reinforcing layer may include, for example, a core body and an adhesive rubber.

Examples of the material for the core body include fibers such as polyester fibers, polyamide fibers, aramid fibers; and metals such as steel. The fibers described above can be used as fabric. The fabric refers to plain-weave fabric.

The adhesive rubber is not particularly limited.

Examples thereof include known adhesive rubber.

Furthermore, the shape of the reinforcing layer is not particularly limited and, for example, may has a sheet shape illustrated in FIG. 1. The reinforcing layer may be one in which reinforcing wires (e.g., steel cords) are embedded side-by-side in the reinforcing layer.

2018203160 07 May 2018

Examples of the sheet-shaped reinforcing layer include a single layer of fabric, and a multilayer including a plurality of fabrics.

[0037]

The thickness of the upper surface cover rubber layer is preferably from 3 to 25 mm.

The thickness of the lower surface cover rubber layer is preferably from 3 to 20 mm, and more preferably from 5 to 15 mm.

Note that, when the upper surface layer includes two or more layers, the thickness of the upper thickness cover rubber thickness surface cover rubber layer of these layers. This also of the lower surface cover is the total applies to the rubber layer .

The method for producing the conveyor belt of present invention is not particularly limited. Examples thereof the include known methods .

Examples [0039]

The present invention is described below in detail using examples but the present invention is not limited to the examples .

[0040]

Production of composition

The components listed in Table 1 below were used in compositions (part by mass) listed in Table 1 and mixed by an agitator to produce a composition.

Specifically, components listed in Table 1 below excluding sulfur and a vulcanization accelerator were mixed in a Banbury mixer at 140°C. Then, the sulfur and the vulcanization accelerator were added to the obtained mixture and mixed at 30°C using a roll 35 kneader to produce a composition.

[0041]

Measurement of bound rubber content

2018203160 07 May 2018

The composition produced as described above (before vulcanization) was cut into an approximately 1 mm square to prepare a cut sample, and 0.2 g of the cut sample was precisely weighed. A 100-mesh metal wire basket which is used as a container for the cut sample was also precisely weighed.

Then, the cut sample was placed in the metal wire basket and the metal wire basket was placed in a glass bottle containing 200 mL of toluene. The metal wire basket containing the cut sample was immersed in the toluene and left to stand at 25°C for 72 hours. In an embodiment of the present invention, 25°C in the amount of bound rubber at 25°C refers to a temperature condition when a metal wire basket containing a cut sample is immersed in toluene and left to stand for 72 hours.

After letting the cut sample stand for 72 hours, the metal wire basket was taken out from the toluene, dried by a dryer for 24 hours, and the mass of the dried metal wire basket was measured.

The mass of remaining undissolved sample after the test was determined by subtracting the mass of metal wire basket precisely weighed in advance from the measured mass.

The mass of the remaining undissolved sample after the test was defined as A, the mass of the initial cut sample was defined as B (0.2 g), the blended parts of component insoluble in toluene (carbon black) in the composition produced as described above (before cutting) was defined as C, the blended parts of entire composition was defined as D, and the blended parts of rubber component was defined as E. The bound rubber content was calculated from the following equation.

The bound rubber content (mass%) = [A - (B x C/D)]/(B x E/D) x 100 [0042]

Evaluation

2018203160 07 May 2018

The following evaluations were performed using the composition produced as described below. The results are reported in Table 1.

(Wear resistance: Lambourn abrasion) [0043]

Production of vulcanized rubber sample for evaluation

The composition produced as described above was placed in a mold, vulcanized by heating at 148°C for 30 minutes to produce a disc-shaped vulcanized rubber 10 sample having a diameter of 49 mm and a thickness of 5 mm.

[0044]

Lambourn abrasion test

Using the vulcanized rubber sample above,

Lambourn abrasion test was performed at 25°C using a

Lambourn abrasion test machine in accordance with JIS

K 6264-2:2005. The wear volume of the vulcanized rubber sample (Lambourn abrasion loss) was measured. [0045]

Evaluation criteria

The wear volumes as measured above were expressed as index values with the result of Comparative Example 1 being assigned the index value of 100.

Larger index values indicate superior wear resistance.

[0046] [Table 1]

Table 1	Comparative Examples	Examples
1	2	3	1	2	3	4	5	6	7	8	9	10
NR	40	40	20	40	40	20	20	20	20	20	10	20	30
BRI	60	60	80	60	60	80
BR2							80	80		80	90		70
BR3 (Nipol 12 2 0)									80
BR4												80
CB1		40			60	60	60	80	80	70	80	80	80

2018203160 07 May 2018

CB2	40			60
CB3: ISAF			50
Anti-aging agent 6C	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5	2.5
Zinc oxide	3	3	3	3	3	3	3	3	3	3	3	3	3
Stearic acid	2	2	2	2	2	2	2	2	2	2	2	2	2
Paraffin wax	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5
Aroma oil	5	5	5	5	5	5	5	5	5	5	5	5	5
Vulcanization
accelerator	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4	1 . 4
NS
Sulfur	1.2	1.2	1 . 2	1 . 2	1.2	1 . 2	1.2	1 . 2	1.2	1 . 2	1.2	1.2	1.2
Bound rubber content (%)	39	43	38	52	61	52	46	62	59	54	58	53	67
Wear resistance Lambourn abrasion	100	93	99	91	85	71	77	83	86	82	76	91	90

[0047]

Details of the components described in Table 1 are as follows.

NR: Natural rubber (RSS #3) [0048]

BRI: Butadiene rubber; weight average molecular weight (Mw) of 770000; long-chain branching index (LCB) of 8.5; Mw/LCB = 9.1 χ 10⁴ (Buna CB21; available from Lanxess Co., Ltd.; butadiene rubber obtained by polymerizing butadiene in the presence of a neodymiumbased catalyst; microstructure: 1,4-cis structure 97.9%, 1,4-trans structure 1.9%, 1,2-vinyl structure

0.2%) [0049]

BR2: Butadiene rubber; weight average molecular weight (Mw) of 560000; long-chain branching index (LCB) of 7.3; Mw/LCB = 7.7 χ 10⁴ (Ubepol BR-360L; available from Ube Industries, Ltd.; butadiene rubber

2018203160 07 May 2018 obtained by polymerizing butadiene in the presence of a cobalt-based catalyst; microstructure: 1,4-cis structure 97.8%, 1,4-trans structure 0.9%, 1,2-vinyl structure 1.3%) [0050]

BR3: Butadiene rubber; weight average molecular weight (Mw) of 500000; long-chain branching index (LCB) of 9.5; Mw/LCB = 5.3 χ 10⁴ (trade name, Nipol 1220, available from Zeon Corporation);

microstructure: 1,4-cis structure 98%, 1,4-trans structure 1.0%, 1,2-vinyl structure 1.0% [0051]

BR4: Butadiene rubber; weight average molecular weight (Mw) of 380000; long-chain branching index (LCB) of 12.3; Mw/LCB = 3.1 χ 10⁴ (trade name, UBEPOL BR130B, available from Ube Industries, Ltd.); microstructure: 1,4-cis structure 96.0%, 1,4-trans structure 1.3%, 1,2-vinyl structure 2.7% [0052]

CB1: Carbon black; nitrogen adsorption specific surface area of 144 m²/g; dibutyl phthalate oil absorption of 115 mL/100 g (Show Black N110, SAF-grade, available from Cabot Japan K.K.) [0053]

CB2: Carbon black; nitrogen adsorption specific surface area of 123 m²/g; dibutyl phthalate oil absorption of 123 mL/100 g (Show Black N234, ISAF-HS grade, available from Cabot Japan K.K.) [0054]

CB3: Carbon black; nitrogen adsorption specific surface area of 111 m²/g; dibutyl phthalate oil absorption of 115 mL/100 g (Show Black N220, ISAF-LS grade, available from Cabot Japan K.K.) [0055]

Anti-aging agent 6C: NOCRAC 6C (available from

Ouchi Shinko Chemical Industrial Co., Ltd.)

Zinc oxide: Zinc Oxide III (available from Seido

Chemical Industry Co., Ltd.)

2018203160 07 May 2018

Stearic acid: Stearic acid YR (available from NOF Corporation)

Paraffin wax: OZOACE-0015 (available from Nippon Seiro Co ., Ltd.)

Aroma oil: A-OMIX (available from Sankyo Yuka

Kogyo K.K.)

Accelerator NS: NOCCELER NS-P (available from

Ouchi Shinko Chemical Industrial Co., Ltd.)

Sulfur: Sulfur powder (available from Hosoi

Chemical Industry Co., Ltd.) [0056]

As is clear from the results reported in Table 1, the rubber compositions of Comparative Examples 1 to 3, which contained a smaller amount of carbon black than 15 a predetermined range and a smaller amount of bound rubber than a predetermined range, exhibited poor wear resistance .

[0057]

In contrast, the composition of an embodiment of the present invention exhibited excellent wear resistance .

In a comparison of Examples 1 and 2, the rubber composition of Example 2, which had a greater nitrogen adsorption specific surface area of carbon black, exhibited superior wear resistance compared to Example .

In a comparison of Examples 3 and 4, the rubber composition of Example 3, which had higher Mw/LCB, exhibited superior wear resistance compared to Example 30 4. In Examples 5, 6, and 9, rubber compositions which had higher Mw/LCB exhibited superior wear resistance. [0058]

In a comparison between Examples 2 and 3, the rubber composition of Example 3, which contained a greater amount of butadiene rubber, exhibited superior wear resistance compared to Example 2. Among Examples 8, 5, and 10, rubber compositions which contained a

2018203160 07 May 2018 greater amount of butadiene rubber exhibited superior wear resistance.

In a comparison among Examples 4, 7, and 5, rubber compositions which contained a smaller amount of carbon black exhibited superior wear resistance.

Among Examples 1 to 10, the rubber compositions of Examples 3, 4, 7, and 8, which contained from 46 to mass% of bound rubber, exhibited superior wear resistance. Thus, the rubber compositions of Examples 10 3, 4, 7, and 8 exhibit an excellent balance between the amount of bound rubber and wear resistance.

Reference Signs List [0059]

1 Conveyor belt

Upper surface cover rubber layer

Reinforcing layer

Lower surface cover rubber layer

Conveying face for transporting articles

11, 16 Outer layer

Claims

[Claim 1]

A rubber composition for a conveyor belt compri s ing:

a rubber component containing greater than 50 mass% and 100 mass% or less of a butadiene rubber; and a carbon black;

a content of the carbon black being from 60 to 100 parts by mass per 100 parts by mass of the rubber component; and a content of a bound rubber at 25°C being from 45 to 70 mass%.
[Claim 2]

The rubber composition for a conveyor belt according to claim 1, wherein a nitrogen adsorption specific surface area of the carbon black is from 115 to 160 m²/g, and a dibutyl phthalate oil absorption is from 115 to 140 mL/100 g.
[Claim 3]

The rubber composition for a conveyor belt according to claim 1 or 2, wherein a weight average molecular weight of the butadiene rubber is from 500000 to 1000000.
[Claim 4]

The rubber composition for a conveyor belt according to any one of claims 1 to 3, wherein a ratio of weight average molecular weight of the butadiene rubber to long-chain branching index of the butadiene rubber (weight average molecular weight/long-chain branching index) is from 5.5 χ 10⁴ to 16.6 χ 10⁴ [Claim 5]

A conveyor belt comprising:

2018203160 07 May 2018 an upper surface cover rubber layer formed from the rubber composition for a conveyor belt described in any one of claims 1 to 4;

a reinforcing layer; and a lower surface cover rubber layer.