AU2015344658B2

AU2015344658B2 - Rubber composition for conveyor belts, and conveyor belt using same

Info

Publication number: AU2015344658B2
Application number: AU2015344658A
Authority: AU
Inventors: Hidehiro SASAKUMA; Takahiro Suzuki; Deqing Zou
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2014-11-05
Filing date: 2015-08-28
Publication date: 2018-11-08
Anticipated expiration: 2035-08-28
Also published as: WO2016072134A1; AU2015344658A1; JP2016089046A; JP6467873B2; CN107075178A

Abstract

The purpose of the present invention is to provide: a rubber composition for conveyor belts, which has excellent wear resistance and excellent cutting resistance; and a conveyor belt which uses this rubber composition for conveyor belts. The present invention provides: a rubber composition for conveyor belts, which contains 45-70 parts by mass of a carbon black that has a nitrogen adsorption specific surface area of 115-160 m

Description

Technical Field [ 0001]

The present invention relates to a rubber composition for conveyor belts, and conveyor belt using such a rubber composition.

Background Art [ 0002]

In recent years, conveyor belts are required to have long life due to concerns for the environment. In response to such a problem, rubber compositions that aim at enhancing long wear resistant life of belt conveyors have been proposed. For example, Patent Document 1 describes a rubber composition for belts of belt conveyors, the rubber component containing a polybutadiene rubber synthesized by a neodymium-based catalyst as a rubber component (Claim 1). Furthermore, in examples of Patent Document 1, a rubber composition in which a carbon black, sulfur, and the like are blended to a rubber component containing a polybutadiene rubber and the like has been described.

Citation List Patent Literature [ 0003]

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-105136A [ 0004]

Cover rubbers of conveyor belts (in particular, topsurface-cover rubbers; hereinafter the same) are easily worn by friction between the cover rubbers and materials to be transported which are loaded thereon, and are required to have wear resistance. At the same time, since the conveyor belt may transport materials having a sharp

2015344658 24 Jul2018 portion, the cover rubber is required to be scratch resistant (has high cut resistance). The inventors of the present invention think that making these performances excellent leads to longer life of a cover belt.

In such circumstances, when the inventors prepared the rubber composition based on Patent Document 1, it was found that such a rubber composition may not satisfy wear resistance and cut resistance that have been required recently.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims .

Throughout this specification the word comprise, or variations such as comprises or comprising, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary [ 0005]

As a result of diligent research, the inventors of the present invention found that predetermined effects can be obtained when the Mooney viscosity at 100°C and the weight average molecular weight of a polybutadiene rubber are within particular ranges, the nitrogen adsorption specific surface area and the dibutyl phthalate oil absorption of a carbon black are within particular ranges, and the content of sulfur is within a particular range.

[ 0006]

1. A rubber composition for conveyor belts, the rubber composition containing:

2015344658 24 Sep 2018

100 parts by mass of a rubber component containing from 40 to 80 mass% of a polybutadiene rubber that has a Mooney viscosity at 100°C of 50 to 100 and a weight average molecular weight of 5.5 χ 10⁵ to 10.0 χ 10⁵, from 45 to 70 parts by mass of a carbon black having a nitrogen adsorption specific surface area of 120 to 155 m²/g and a dibutyl phthalate oil absorption of 115 to 140 mL/100 g, and

0.3 parts by mass or greater but less than 2.0 parts by mass of sulfur.

2. The rubber composition for conveyor belts according to 1 above, where the weight average molecular weight is 5.5 χ 10⁵ to 9.0 χ 10⁵.

3. The rubber composition for conveyor belts according to 1 or 2 above, where the polybutadiene rubber is synthesized using a neodymium-based catalyst.

4. A conveyor belt comprising the rubber composition for conveyor belts described in any one of 1 to 3 above.

5. The conveyor belt according to 4 above, where the rubber composition for conveyor belts is used in a topsurface-cover rubber.

[ 0007]

According to the present disclosure, a rubber composition for conveyor belts, which has excellent wear resistance and excellent cut resistance; and a conveyor belt which includes this rubber composition for conveyor belts can be provided.

Brief Description of Drawing [ 0008]

FIG. 1 is a cross-sectional view schematically illustrating an embodiment of the conveyor belt of the present invention.

Description of Embodiments [ 0009]

2015344658 24 Jul2018

An embodiment of the present invention is 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.

Furthermore, in the present specification, when a component contains two or more types of substances, the content of the component indicates the total content of the two or more types of substances.

[ 0010]

Rubber composition

The rubber composition for conveyor belts (the composition of an embodiment of the present invention) is a rubber composition for conveyor belts, the rubber composition containing:

100 parts by mass of a rubber component containing from 40 to 80 mass% of a polybutadiene rubber that has a Mooney viscosity at 100°C of 50 to 100 and a weight average molecular weight of 5.1 χ 10⁵ to 10.0 χ 10⁵, from 45 to 70 parts by mass of a carbon black having a nitrogen adsorption specific surface area of 120 to 155 m²/g and a dibutyl phthalate oil absorption of 115 to 140 mL/100 g, and

0.3 parts by mass or greater but less than 2.0 parts by mass of sulfur.

[ 0011]

The composition is thought to achieve desired effects as a result of having such a configuration. Although the reason for this is unknown, the reason is presumed to be as follows.

According to the present disclosure, the weight average molecular weight of the polybutadiene rubber is relatively large, and it is conceived that dispersibility of the carbon black is low in such a polybutadiene rubber. The inventors of the present invention presume that, due to a large nitrogen adsorption specific surface area and a large dibutyl phthalate oil absorption, i.e.

2015344658 24 Jul2018 the high-structured carbon black (having a well-developed aggregate structure) and an extremely small particle size of base particles constituting the carbon black, the dispersibility of the carbon black in high molecular weight polybutadiene rubber and processability of the rubber composition are enhanced, thereby achieving predetermined effects.

Furthermore, the inventors of the present invention presume that, since the content of the sulfur is within a predetermined range, the degree of vulcanization of the polybutadiene rubber becomes appropriate, thereby achieving the predetermined effects.

[ 0012]

Each component contained in the composition will be described in detail hereinafter.

Rubber component

The composition contains a rubber component, and the rubber component contains a predetermined polybutadiene rubber .

[ 0013]

Polybutadiene rubber

The polybutadiene rubber used in the composition has a Mooney viscosity at 100°C (ML₁₊₄, at 100°C) of 50 to 100 and a weight average molecular weight of 5.1 χ 10⁵ to 10.0 χ 10⁵.

The Mooney viscosity (ML₁₊₄, at 100°C) of the polybutadiene rubber described above is preferably from 50 to 90, and more preferably from 50 to 80.

According to the present disclosure, the Mooney viscosity of the polybutadiene rubber was measured in a condition at 100°C in accordance with a method stipulated in JIS K 6300-1:2001.

[ 0014]

The weight average molecular weight of the polybutadiene rubber is preferably from 5.5 χ 10⁵ to 9.0 χ 10⁵, and more preferably from 5.5 χ 10⁵ to 8.0 χ 10⁵.

According to the present disclosure, the weight average molecular weight of the polybutadiene rubber is a

2015344658 24 Jul2018 measurement value obtained by gel permeation chromatography (GPC) measured based on calibration with polystyrene standard using cyclohexane as a solvent.

[ 0015]

Examples of the method of producing the polybutadiene rubber include a method in which the butadiene is polymerized using a catalyst, such as a cobalt-based catalyst and/or a neodymium-based catalyst. The cobalt-based catalyst and the neodymium-based catalyst are not particularly limited. The cobalt-based catalyst may be a compound having cobalt. The neodymiumbased catalyst may be a compound having neodymium (Nd).

In particular, a neodymium-based catalyst is preferred.

One type of the polybutadiene rubber can be used alone or a combination of two or more types of the polybutadiene rubbers can be used.

[ 0016]

Rubber except polybutadiene rubber

According to the present disclosure, the rubber that can be contained in the rubber component, besides the polybutadiene rubber, is not particularly limited.

Examples thereof include diene rubbers. Specific examples thereof include natural rubber (NR), isoprene rubber (IR), polybutadiene rubber (BR) except those described above, aromatic vinyl-conjugated diene copolymer rubber (e.g. styrene butadiene rubber (SBR)), nitrile-butadiene rubber (NBR, acrylonitrile butadiene rubber), butyl rubber (HR), halogenated butyl rubber (e.g. Br-IIR, ClIIR), and chloroprene rubber (CR). Among these, natural rubber and styrene-butadiene rubber are preferred.

As the rubber that can be contained in the rubber component, besides the polybutadiene rubber, one type or a combination of two or more types of these can be used.

[ 0017]

According to the present disclosure, the proportion of the polybutadiene rubber in the rubber component is from 20 to 80 mass%. The proportion of the polybutadiene rubber is preferably from 30 to 70 mass%, and more

2015344658 24 Jul2018 preferably from 40 to 60 mass%. The rest of the proportion may be rubber that can be contained in the rubber component, besides the polybutadiene rubber.

[ 0018]

Carbon black

The carbon black contained in the composition has a nitrogen adsorption specific surface area of 115 to 160 m²/g and a dibutyl phthalate oil absorption of 115 to 140 mL/10 0 g.

The nitrogen adsorption specific surface area (N₂SA) of the carbon black is preferably from 120 to 155 m²/g, more preferably from 120 to 145 m²/g, and even more preferably from 120 to 140 m²/g.

According to the present disclosure, the nitrogen adsorption specific surface area of carbon black was measured in accordance with JIS K 6217-2:2001.

[ 0019]

The dibutyl phthalate oil absorption (DBP oil absorption) of the carbon black is preferably from 115 to 130 mL/100 g, more preferably from 116 to 130 mL/100 g, and even more preferably from 120 to 130 mL/100 g.

According to the present disclosure, the dibutyl phthalate oil absorption was measured in accordance with JIS K 6217-4:2008.

[ 0020]

Specific examples of the carbon black include SAF and ISAF-HS.

The carbon black may be used alone or a combination of two or more types of carbon blacks may be used.

[ 0021]

The content of the carbon black is from 45 to 70 parts by mass, preferably from 45 to 65 parts by mass, and more preferably from 45 to 55 parts by mass, per 100 parts by mass of the rubber component.

[ 0022]

Sulfur

2015344658 24 Jul2018

The sulfur contained in the composition is not particularly limited. Examples thereof include conventionally known sulfurs.

The content of the sulfur is from 0.3 parts by mass or greater but less than 2.0 parts by mass, preferably from 0.8 to 1.5 parts by mass, and more preferably from 1.0 to 1.5 parts by mass, per 100 parts by mass of the rubber component.

[ 0023]

Additives

The composition may further contain additives besides the components described above within a scope that does not inhibit the effect or purpose of the present disclosure. Examples of the additive include carbon black other than the predetermined carbon black, anti-aging agents such as an anti-aging agent 6C, zinc oxide, stearic acid, processing aids, paraffin waxes, aroma oils, liquid polymers, terpene-based resins, thermosetting resins, vulcanization agents other than sulfur, vulcanization aids, vulcanization accelerators, and vulcanization retarders.

[ 0024]

The production of the composition is not particularly limited. For example, the production can be performed by kneading the components described above (except the vulcanizing agent such as sulfur and the vulcanization accelerator) in a Banbury mixer or the like, adding the vulcanizing agent such as sulfur and the vulcanization accelerator to the obtained mixture, and then kneading by a roll kneader or the like.

Furthermore, the conditions of vulcanization are not particularly limited. For example, the vulcanization can be performed by applying heat and pressure in a condition at 140 to 160°C.

[ 0025]

The composition can be used as a rubber composition to produce conveyor belts.

[ 0026]

2015344658 24 Jul2018

Conveyor belt

The conveyor belt is a conveyor belt that uses the rubber composition for conveyor belts of the present disclosure. The conveyor belt is not particularly limited as long as the composition disclosed herein is used.

[ 0027]

Examples of the form of the conveyor belt include a conveyor belt provided with a top-surface-cover rubber layer, a bottom-surface-cover rubber layer, and a reinforcing layer, and having the reinforcing layer in between the top-surface-cover rubber layer and the bottom-surface-cover rubber layer.

The composition may be used in any of the topsurface-cover rubber layer, the bottom-surface-cover rubber layer, or the reinforcing layer. Among these, the composition is preferably used in the top-surface-cover rubber layer.

[ 0028]

The conveyor belt will be described below using an attached drawing. However, the present invention is not limited to the attached drawing.

In FIG. 1, the conveyor belt 1 has a top-surfacecover rubber layer 2, a reinforcing layer 3, and a bottom-surface-cover rubber layer 4, which are laminated in this order. The surface of the top-surface-cover rubber layer 2 serves as a conveying face for transporting articles 5. The top-surface-cover rubber layer 2 is preferably formed by using the composition disclosed herein.

[ 0029]

When the top-surface-cover rubber layer 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 by using the composition of the present disclosure. Furthermore, at least the outermost layer is preferably

2015344658 24 Jul2018 formed by using the composition of the present disclosure .

In FIG. 1, the top-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 by using the composition of the present disclosure, and at least the outer layer 11 is preferably formed by using the composition of the present disclosure.

When the outer layer 11 is formed by using the composition of the present disclosure, the inner layer 12 may be a layer for adhering the reinforcing layer 3 and the outer layer 11.

[ 0030]

The rubber composition used in the bottom-surfacecover rubber layer is not particularly limited.

The bottom-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 by using the same or different rubber composition (s) .

[ 0031]

The reinforcing layer is not particularly limited, and substances typically used in conveyor belts can be suitably selected and used. Furthermore, the shape of the reinforcing layer is not particularly limited and, for example, may be a sheet form illustrated in FIG. 1. Furthermore, the reinforcing layer may be in a form where reinforcing wires are embedded in parallel in the reinforcing layer (not illustrated).

[ 0032]

The thickness of the top-surface-cover rubber layer is preferably from 3 to 25 mm. The thickness of the bottom-surface-cover rubber layer is preferably from 3 to 20 mm, and more preferably from 5 to 15 mm. Note that, if the top-surface-cover rubber layer is composed of two or more layers, the thickness of the top-surface-cover rubber layer can be the total thickness of these layers. This also applies to the thickness of the bottom-surfacecover rubber layer.

2015344658 24 Jul2018 [ 0033]

The production of the conveyor belt is not particularly limited. Examples thereof include conventionally known methods.

The conveyor belt can be used to, for example, transport limestone.

Examples [ 0034]

An embodiment of the present invention is described below in detail using examples but the present invention is not limited to such examples.

Production of composition

A composition was produced using the component shown in Table II below in the composition (part by mass) shown in Tables 1-1 and 1-2 below. Specifically, the composition was produced by mixing the components shown in Tables 1-1 and 1-2 below except the sulfur and the vulcanization accelerator in a Banbury mixer for 5 minutes, and then mixing the sulfur and the vulcanization accelerator to the obtained mixture using a roll.

[ 0035]

Production of vulcanized rubber sheet for evaluation

The composition (unvulcanized) produced as described above was formed into a sheet shape and heated and vulcanized at 148°C for 30 minutes (40 minutes for test piece for cut resistance) to produce a vulcanized rubber sheet.

[ 0036]

Evaluation

The following evaluations were performed using the vulcanized rubber sheet produced as described above. The results are shown in Tables 1-1 and 1-2.

• Wear resistance (DIN abrasion test)

According to the method described in DIN 53516, the

DIN abrasion test was performed in a condition at room temperature using a DIN abrasion tester to measure wear volume (DIN abrasion) of the vulcanized rubber sheet.

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The proportion (vol%) of the wear volume measured as described above relative to the volume of the vulcanized rubber sheet used in the DIN abrasion test was shown as the result of the abrasion resistance.

The proportion of 25 vol% or less indicates excellent wear resistance.

[ 0037] • Cut resistance

A blade (blade length: 100 mm; edge angle at 2 mm from the blade edge: 20°; weight: 8 kg) was naturally dropped onto the vulcanized rubber sheet produced as described above (length 100 mm χ width 20 mm χ height 40 mm) from 25 cm above the vulcanized rubber sheet at room temperature, and the depth (mm) of cracks caused on the vulcanized rubber sheet was measured.

The depth of 10 mm or less indicates excellent cut resistance .

[ 0038] [ Table 1]

e 1-1	Comparative Example 1	Comparative Example 2	Comparative Example 3	Comparative Example 4	Comparative Example 5	Comparative Example 6	Comparative Example 7
orient	Formulation (part by mass)
NR	40	40	40	40	40	40	40
Coir Ltive BR 1	60	60	60
BR 1
BR 2						60	60
Comparative BR 2				60	60
Carbon black 1	40	50	50		50		50
Carbon black 2
Comparative carbon black				50		50
Vulcanization accelerator NS	1.4	1.4	1.4	1.4	1.4	1.4	1.4
Sulfur	1.2	1.2	2.3	2.0	1.2	1.2	2.0

2015344658 24 Jul2018

ince (%)	26.1	22.9	34.7	41.3	20.9	36.6	32.7
ustance	13.6	13.8	18.4	16.0	14.3	13.8	12.4

[ 0039] [ Table 2]

Table 1-2	Example 1	Example 2	Example 3
Component	Formulation (part by mass)
NR	40	40	40
Comparative BR 1
BR 1	60
BR 2		60	60
Comparative BR 2
Carbon black 1	50	50
Carbon black 2			50
Comparative carbon black
Vulcanization accelerator NS	1.4	1.4	1.4
Sulfur	1.2	1.2	1.2
Wear resistance (%)	23.4	22.9	15.6
Cut resistance (mm)	9.0	7.8	8.3

[ 0040]

Details of the components described in Tables 1-1 and 1-2 are as follows. [ Table 3]

Table IT
Component	Trade name/Manufacturer	Physical properties of polybutadiene rubber
NR	Natural rubber RSS#3	Mw (X10⁵)	MLl+4@100°C
Comparative BR 1	Nipol BR1220, manufactured by Zeon Corporation	4.9	44
BR 1	UBE BR-360L, manufactured by Ube Industries, Ltd.; cobalt-based catalyst was used	5.6	54
BR 2	CB21, manufactured by Buna; neodymium-based catalyst was used	7.7	73

2015344658 24 Jul2018_

comparative BR 2	CB25, manufactured by Buna \| 5.9 \|	47
arbon black 1	SAF carbon black, manufactured by Cabot Japan K.K., Sho N₂SA: 144 m²/g; DBP oil absorption: 116 mL/100 g	Black S118;
arbon black 2	ISAF-HS carbon black, manufactured by Cabot Japan K.K., N234; N₂SA: 123 m²/g; DBP oil absorption: 121 mL/100 g	Sho Black
comparative	ISAF carbon black, manufactured by Cabot Japan K.K., Sho	Black N220;
arbon black	N₂SA: 111 m²/g; DBP oil absorption: 115 mL/100 g
ulcanization	NOCCELER NS (manufactured by Ouchi Shinko Chemical Industrial Co.,
ccelerator NS	Ltd. )
ulfur	Sulfur

[ 0041]

As is clear from the results shown in Table 1-1, Comparative Example 1, which contained the polybutadiene rubber having the Mooney viscosity and the weight average molecular weight that were outside the predetermined ranges and which had the amount of the carbon black that was less than the predetermined amount, exhibited poor wear resistance and cut resistance.

Comparative Example 2, in which the content of the carbon black was increased compared to Comparative Example 1, exhibited low cut resistance.

Comparative Examples 3 and 7, in which the content of the sulfur was greater than the predetermined ranges, exhibited low wear resistance and cut resistance.

Comparative Example 4, which contained the polybutadiene rubber having the Mooney viscosity that was outside the predetermined range, the carbon black having the nitrogen adsorption specific surface area that was outside the predetermined range, and the content of the sulfur that was greater than the predetermined range, exhibited low wear resistance and cut resistance.

Comparative Example 5, which contained the polybutadiene rubber having the Mooney viscosity that was outside the predetermined range, exhibited low cut resistance .

2015344658 24 Jul2018

Comparative Example 6, which contained the carbon black having the nitrogen adsorption specific surface area that was outside the predetermined range, exhibited low wear resistance and cut resistance.

[ 0042]

On the other hand, Examples 1 to 3 exhibited excellent wear resistance and cut resistance.

Furthermore, when Examples 1 and 2 are compared, Example 2 achieved even better predetermined effects than that of Example 1. From these, it was found that the case where the weight average molecular weight of the polybutadiene rubber was from 6.0 χ 10⁵ to 10.0 χ 10⁵, the case where the Mooney viscosity was from 55 to 100, or the case where the polybutadiene rubber was produced using a neodymium-based catalyst, excellent wear resistance and cut resistance were achieved.

Furthermore, when Examples 2 and 3 are compared, Example 3 achieved even better wear resistance than that of Example 2. From these, it was found that the case where the nitrogen adsorption specific surface area of the carbon black was from 120 to 140 m²/g and/or the case where the dibutyl phthalate oil absorption was from 120 to 130 mL/100 g, excellent wear resistance was achieved.

Reference Signs List [ 0043]

Conveyor belt

Top-surface-cover rubber layer

Reinforcing layer

Bottom-surface-cover rubber layer

Conveying face for transporting articles

11, 16 Outer layer

12, 15 Inner layer

2015344658 24 Sep 2018

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:1 .

A rubber composition for conveyor belts, the rubber composition comprising:

100 parts by mass of a rubber component containing from 40 to 80 mass% of a polybutadiene rubber that has a Mooney viscosity at 100°C of 50 to 100 and a weight average molecular weight of 5.5 χ 10⁵ to 10.0 χ 10⁵;

from 45 to 70 parts by mass of a carbon black having a nitrogen adsorption specific surface area of 120 to 155 m²/g and a dibutyl phthalate oil absorption of 115 to 140 mL/100 g; and

0.3 parts by mass or greater but less than 2.0 parts by mass of sulfur.
2 .

The rubber composition for conveyor belts according to claim 1, wherein the weight average molecular weight is 5.5 χ 10⁵ to 9.0 χ 10⁵.
3.

The rubber composition for conveyor belts according to claim 1 or 2, wherein the polybutadiene rubber is synthesized using a neodymium-based catalyst.
4 .

A conveyor belt comprising the rubber composition for conveyor belts described in any one of claims 1 to 3.
5.

The conveyor belt according to claim 4, wherein the rubber composition for conveyor belts is used in a topsurface-cover rubber.

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