JP2009298542A - Rubber composition for conveyor belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conveyor belt, particularly an inner circumferential cover rubber thereof, which is excellent in both low loss property and tear resistance while having high wear resistance to be effectively usable for a belt conveyor, particularly as an inner circumferential cover belt of the belt conveyor. <P>SOLUTION: A rubber composition for the belt conveyor contains (A) a butadiene polymer in an amount of 50-85 mass%, which includes a molecular weight distribution (Mw/Mn) of 1.6 to 3.5 and, as measured by Fourier transform infrared spectrometry, a cis-1, 4-bond content not less than 98% and a vinyl-bond content not more than 0.3% in 1, 3-butadiene monomer units and (B) diene rubber in an amount of 50-15 mass%. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention uses a rubber composition for a conveyor belt (in particular, a rubber composition for an inner circumference (back face) cover rubber of the conveyor belt), an inner circumference (back face) cover rubber of the conveyor belt, and the inner circumference (back face) cover rubber. The present invention relates to a conveyor belt and a belt conveyor equipped with the conveyor belt.

BACKGROUND ART A belt conveyor is frequently used as a means for transporting articles, and a belt (conveyor belt) to be mounted on the belt conveyor usually has a core body (reinforcing material) therein, and an upper side of the core body (on the conveyor belt). The surface that becomes the outer periphery when used.) [Hereinafter referred to as the outer peripheral cover rubber. ] Of the cover rubber and the inner periphery (back surface when used for a conveyor belt, lower side) [Hereinafter, it may be referred to as an inner peripheral cover rubber. ] Is covered with cover rubber. The required physical properties of the outer peripheral cover rubber and the inner peripheral cover rubber located on the back surface thereof are different, and the inner peripheral cover rubber not only wear resistance, but also reduces energy loss due to contact between the conveyor belt and a large number of rollers. That is, it is necessary to reduce the power consumption by reducing the loss, and it is also necessary to have high tear resistance in order to prevent tearing of the conveyor belt due to foreign matter being caught.
Conventionally, as rubber compositions for conveyor belts, rubber compositions containing butadiene rubber (BR) or styrene butadiene rubber (SBR) in various combinations with natural rubber (NR) are known (Patent Documents 1 to 5). reference).

JP-A-11-139523 JP 2001-26670 A JP 2003-48609 A JP 2003-105136 A JP 2004-346220 A

However, when SBR is contained as in the rubber compositions described in Patent Documents 1 and 5, the tear resistance tends to be good, but the energy loss in the conveyor belt is large and the demand for energy saving can be met. There was no problem. On the other hand, when BR is contained as in the rubber compositions described in Patent Documents 1 to 5, the loss of energy can be reduced (lower loss), but the tear resistance tends to be lower. There is a problem that the amount of blending is limited and the loss cannot be sufficiently reduced. Thus, the conventional technique cannot achieve both low loss and tear resistance.
Conventionally, the tear resistance target level has been set to 10 N / mm or more, but the current situation is that the market is not satisfied with a tear force of about 10 N / mm. Currently, the tear force is 15 N / mm or more. There is a need for materials that are In addition, as an index of the degree of energy loss due to contact between the conveyor belt and the roller, there is tan δ / E ′ ^0.32 [tan δ is a loss tangent, E ′ is a dynamic elastic modulus (N / mm)]. When tan δ / E ′ ^{0.32 at} −5 ° C. is 0.11 or less, the energy loss is considered to be small (excellent in low loss property), which is the target value. It is desired to develop a rubber material that satisfies the market demand for tear resistance and low loss and also has wear resistance.

  As a result of intensive research on the rubber composition for conveyor belts, particularly the rubber composition for inner peripheral cover rubber, the present inventors have focused on the above problems, and as a result, (A) the molecular weight distribution is 1.6 to 3.5. And a butadiene-based polymer having a cis-1,4 bond content of 98% or more and a vinyl bond content of 0.3% or less in the 1,3-butadiene monomer unit as measured by Fourier transform infrared spectroscopy. [Hereinafter referred to as Super Hi-cis BR. And (B) a rubber composition containing a diene rubber in a certain composition has high wear resistance, and is excellent in both low loss and tear resistance, and for belt conveyors, particularly belt conveyors. The present invention has been completed by finding that it can be effectively used as an inner cover belt.

That is, the present invention
[1] (A) The molecular weight distribution (Mw / Mn) is 1.6 to 3.5, and cis-1 in the 1,3-butadiene monomer unit is measured by Fourier transform infrared spectroscopy. The rubber composition for conveyor belts containing 50 to 85% by mass of a butadiene polymer having a 4-bond content of 98% or more and a vinyl bond content of 0.3% or less and (B) 50 to 15% by mass of a diene rubber. object,
[2] The cis-1,4 bond content and the vinyl bond content in the 1,3-butadiene monomer unit are represented by the following formula:
Vinyl bond content (%) ≦ 0.25 × (“cis-1,4 bond content (%)”-97)
The rubber composition for conveyor belts according to [1], which satisfies the relationship:
[3] The rubber composition for conveyor belts according to the above [1] or [2], wherein the molecular weight distribution (Mw / Mn) is 1.6 to 2.7.
[4] The above [1], wherein the butadiene-based polymer is composed of 80 to 100% by mass of 1,3-butadiene monomer and 20 to 0% by mass of other monomer copolymerizable with 1,3-butadiene. ] The rubber composition for conveyor belts in any one of [3],
[5] The rubber composition for conveyor belts according to the above [4], wherein the butadiene-based polymer consists only of 1,3-butadiene monomer,
[6] The rubber composition for conveyor belts according to any one of [1] to [5], wherein the number average molecular weight (Mn) is 100,000 to 500,000.
[7] The rubber composition for conveyor belts according to [6], wherein the number average molecular weight (Mn) is 150,000 to 300,000,
[8] The rubber composition for conveyor belts according to any one of the above [1] to [7], wherein the diene rubber is natural rubber and / or isoprene rubber,
[9] The rubber composition for conveyor belts according to any one of [1] to [8], further including a low-loss agent,
[10] The rubber composition for conveyor belts according to any one of the above [1] to [9], further containing silica,
[11] The rubber composition for a conveyor belt according to any one of the above [1] to [10], which is for an inner peripheral cover rubber of the conveyor belt.
[12] An inner peripheral cover rubber for a conveyor belt obtained from the rubber composition for conveyor belts according to any one of [1] to [11],
[13] A conveyor belt using the inner cover rubber according to [12],
[14] A belt conveyor equipped with the conveyor belt according to [13],
Is to provide.

  According to the present invention, by including ultra-high cis BR in the rubber composition, a conveyor belt excellent in wear resistance, low loss and tear resistance (tearing force: 15 N / mm or more), in particular, a conveyor belt. A circumferential cover rubber can be provided. Further, by adding a low-loss agent to the rubber composition, the low-loss property can be further increased, and by containing silica, the tear resistance can be further increased.

  The rubber composition for conveyor belts of the present invention has (A) a molecular weight distribution of 1.6 to 3.5, and a 1,3-butadiene unit as measured by Fourier transform infrared spectroscopy (FT-IR). Butadiene polymer (ultra high cis BR) having a cis-1,4 bond content of 98% or more and a vinyl bond content of 0.3% or less in the monomer unit, and (B) a diene rubber 50 Contains -15% by weight.

First, the super high cis BR of component (A) will be described.
The ultra high cis BR is preferably composed of 80 to 100% by mass of 1,3-butadiene monomer and 20 to 0% by mass of other monomer copolymerizable with 1,3-butadiene. More preferably, the monomer consists of 100% by mass.
Examples of other monomers copolymerizable with 1,3-butadiene include, for example, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1, C5-C8 conjugated diene monomers such as 3-hexadiene; aromatic vinyl monomers such as styrene, p-methylstyrene, α-methylstyrene and vinylnaphthalene.

  The molecular weight distribution (Mw / Mn) of the ultra high cis BR is 1.6 to 3.5, preferably 1.6 to 2.7, more preferably 1.9 to 2.7, more preferably 2 More preferably, it is 2 to 2.4. In the present specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values in terms of polystyrene measured by gel permeation chromatography (GPC). If the molecular weight distribution of the butadiene-based polymer is less than 1.6, bagging (a phenomenon in which the rubber band that has passed through the roll gap) will occur when the rubber composition is kneaded with a roll machine, resulting in poor kneading workability. However, the physical properties of the inner peripheral cover rubber of the conveyor belt (hereinafter sometimes simply referred to as inner peripheral cover rubber) cannot be sufficiently improved. On the other hand, if it exceeds 3.5, the physical properties of the inner peripheral cover rubber will deteriorate due to hysteresis loss or the like.

  Although there is no restriction | limiting in particular in a number average molecular weight (Mn), It is preferable that it is 100,000-500,000, and it is more preferable that it is 150,000-300,000. Within such a range, the elastic modulus of the inner peripheral cover rubber is stable, hysteresis loss is not increased, and wear resistance is not reduced. Further, it is preferable when the rubber composition for the inner peripheral cover rubber is kneaded. Workability is not lowered, and the physical properties of the inner peripheral cover rubber can be sufficiently improved, which is preferable.

As described above, the ultra high cis BR has a cis-1,4 bond content in the 1,3-butadiene monomer unit of 98% or more and a vinyl bond content in the measurement by Fourier transform infrared spectroscopy (FT-IR). Is a butadiene-based polymer in which the cis-1,4 bond content in the 1,3-butadiene monomer unit is 98.2% or more and the vinyl bond content is 0.2% or less. Preferably, the cis-1,4 bond content is 98.35% or more and the vinyl bond content is 0.15% or less. When measured by FT-IR, if the cis-1,4 bond content is less than 98% or the vinyl bond content exceeds 0.3%, the stretched crystallinity is insufficient and the inner cover rubber The effect of improving the wear resistance, tear resistance and wear resistance is poor. In addition, the measurement method of the microstructure by FT-IR should just follow a well-known method, for example, can refer to Unexamined-Japanese-Patent No. 2005-15590.
The ultra high cis BR has a cis-1,4 bond content and a vinyl bond content in a 1,3-butadiene monomer unit represented by the following formula:
Vinyl bond content (%) ≦ 0.25 × (“cis-1,4 bond content (%)”-97)
It is preferable to satisfy. If this relationship is satisfied, the elongation crystallinity of the ultra high cis BR is further improved, so that the wear resistance, cut resistance and bending fatigue resistance of the inner peripheral cover rubber are further improved.

  The ultra high cis BR has a high cis-1,4 bond content and a low vinyl bond content in the 1,3-butadiene monomer unit as compared with the conventional butadiene polymer. For example, “BR01” (trade name, manufactured by JSR Corporation) marketed as “Hicis BR”, which has a relatively high cis-1,4 bond content, has a cis-1,4 bond content as measured by FT-IR. Is 96.29% and the vinyl bond content is 2.20%. In addition, “BR150L” (trade name, manufactured by Ube Industries, Ltd.), which is also commercially available as High cis BR, has a cis-1,4 bond content of 97.18% and a vinyl bond content as measured by FT-IR. Is 1.63%. Although the cis-1,4 bond content of ultra-high cis BR is a difference of several percent, and the vinyl bond content is also a difference of several percent, the present invention has a large difference in the stretch crystallinity of rubber, It has been found that it greatly affects the performance of the conveyor belt, particularly the inner peripheral cover rubber, and is very useful as an alternative to the conventional BR and Hi-Sis BR.

  A known method can be used as a method for producing such an ultra high cis BR (see Japanese Patent Application Laid-Open No. 2005-15590). For example, (1) a compound containing a rare earth element having an atomic number of 57 to 71 in the periodic table or a reaction product of the compound with a Lewis base, (2) an organoaluminum compound and (3) a Lewis acid, a metal halide and Lewis In the presence of at least one halogen compound selected from the group consisting of a complex compound with a base and an organic compound containing an active halogen, and (4) a catalyst consisting of an aluminoxane as necessary, 1,3-butadiene and Accordingly, it is obtained by polymerizing the other monomer copolymerizable with the 1,3-butadiene at 25 ° C. or lower.

Next, the diene rubber of component (B) will be described.
As the diene rubber of component (B), natural rubber (NR), isoprene rubber (IR), (high cis) butadiene rubber [(high cis) BR], styrene butadiene rubber (SBR), ethylene-propylene rubber (EPR), Examples thereof include ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber, chloroprene rubber, or a mixture thereof. (High cis) BR is a butadiene rubber having a cis-1,4 bond content of less than 90% in a 1,3-butadiene monomer unit or a cis-1,4 bond content of 90% as measured by FT-IR. This is a high-cis butadiene rubber of less than 98%. From the viewpoint of balance of physical properties of the inner cover rubber, the component (B) is preferably natural rubber (NR), isoprene rubber (IR), or a mixture thereof, and more preferably NR.
The component (B) is contained such that the component (A): component (B) = 50 to 85:50 to 15 (mass ratio). From the viewpoint of wear resistance, the component (A): component ( B) = 60 to 80:40 to 20 (mass ratio) is more preferable. When the component (B) exceeds the upper limit (the component (A) is less than the lower limit), the effect of improving the wear resistance and low loss of the inner peripheral cover rubber is reduced, while the component (B) is reduced. If it is less than the lower limit (component (A) exceeds the upper limit), the tear resistance tends to be reduced, and the life of the inner peripheral cover rubber is reduced.

  Other additives may be added to the rubber composition for the inner peripheral cover rubber of the present invention as long as the object of the present invention is not impaired. Such additives are not particularly limited as long as they are usually contained in the conveyor belt cover rubber. For example, carbon black, oil, fatty acid such as stearic acid, low loss agent, zinc oxide, anti-aging, etc. Agents, waxes, silica, silica coupling agents, sulfur, vulcanization accelerators, vulcanization retarders (scorch inhibitors), peptizers, ozone cracking inhibitors, antioxidants, clays, calcium carbonate and the like. A commercial item can be used for these. The amount of the additive added can be appropriately selected by those skilled in the art as long as the object of the present invention is not impaired.

Examples of carbon black include standard varieties such as SAF, ISAF, HAF, FEF, GPF, SRF (furnace for rubber) and MT carbon black (pyrolytic carbon). When using carbon black, it is preferable that the usage-amount is 20-90 mass parts with respect to a total of 100 mass parts of a component (A) and (B), and it is more preferably 30-70 mass parts. preferable.
Examples of the oil include spindle oil, paraffinic, naphthenic, and aromatic process oils. When using oil, it is preferable that the usage-amount is 1-10 mass parts with respect to a total of 100 mass parts of a component (A) and (B).

When using a fatty acid, the usage-amount is preferable 0.1-10 mass parts with respect to a total of 100 mass parts of a component (A) and (B), and 0.5-5 mass parts is more preferable.
The loss reducing agent is not particularly limited as long as it reduces energy loss in the conveyor belt. For example, 3-hydroxy-N ′-(1,3-dimethylbutylidene) -2-naphthoic acid hydrazide (BMH) ) (Made by Otsuka Chemical Co., Ltd.). When the low-loss agent is used, the amount used is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass in total of the components (A) and (B). .
When using zinc oxide, the usage-amount is preferable 0.5-10 mass parts with respect to a total of 100 mass parts of a component (A) and (B), and 1-5 mass parts is more preferable.
As the anti-aging agent, a known anti-aging agent can be selected and used. For example, N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (“NOCRACK (registered trademark) 6C, manufactured by Ouchi Shinsei Chemical Co., Ltd.”) or N-phenyl-N′-isopropyl -P-phenylenediamine ("NOCRACK (registered trademark) 3C, manufactured by Ouchi Shinsei Chemical Co., Ltd."), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), and the like.
As the silica, a commercial product of nip seal AQ (trade name, manufactured by Tosoh Silica Co., Ltd.) can be used. When using silica, the usage-amount is preferable 1-20 mass parts with respect to a total of 100 mass parts of a component (A) and (B), and 5-15 mass parts is more preferable.

When using sulfur, the usage-amount is 0.5-10 mass parts as a sulfur content with respect to a total of 100 mass parts of a component (A) and (B), and 0.5-3 mass parts is more preferable. .
The vulcanization accelerator is not particularly limited. For example, M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), CZ (N-cyclohexyl-2-benzothiazylsulfenamide), etc. And guanidine vulcanization accelerators such as DPG (diphenylguanidine). Examples of commercially available products include “Noxeller (registered trademark) NS-F” (trade name, manufactured by Ouchi Shinsei Chemical Co., Ltd.). When a vulcanization accelerator is used, the amount used is preferably 0.1 to 5 parts by mass, more preferably 0.1 to 2 parts by mass with respect to 100 parts by mass in total of components (A) and (B). It is.

Thus, the rubber composition for the inner peripheral cover rubber of the present invention can be obtained by kneading the components (A) and (B) and necessary additives as appropriate. The kneading method may be in accordance with a method commonly practiced by those skilled in the art. For example, all components other than sulfur and a vulcanization accelerator are kneaded using a Banbury mixer, Brabender, kneader, high shear mixer, etc. After that, sulfur and a vulcanization accelerator may be added (B kneading) and kneaded with a kneading roll machine or the like. The resulting rubber composition for the inner peripheral cover rubber has tan δ / E ′ ^0.32 of 0.11 or less, and the tearing force measured using a trouser-shaped test piece in accordance with JIS K6252 is 15 N / mm or more. Suitable for use. An inner peripheral cover rubber can be obtained by molding the composition for a conveyor belt with a heating mold.
The inner peripheral cover rubber forms a single conveyor belt sandwiching the core (reinforcing material) together with the outer peripheral (upper surface) cover rubber, and is attached to the belt conveyor.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. Each analysis was performed as follows.

[Analysis method of microstructure by FT-IR]
Using the carbon disulfide of the same cell as a blank, the FT-IR transmittance spectrum of a carbon disulfide solution of a butadiene polymer prepared to a concentration of 5 mg / mL was measured, and the peak value near 1130 cm ⁻¹ of the spectrum was measured. a, when a valley peak value b in the vicinity of 967 cm ^-1, a valley peak value c near 911 cm ^-1, a valley peak value around 736cm ^-1 d, the following matrix equation

Using the values of e, f, and g derived from
(Cis-1,4 bond content) = e / (e + f + g) × 100 (%)
(Trans-1,4 bond content) = f / (e + f + g) × 100 (%)
(Vinyl bond content) = g / (e + f + g) × 100 (%)
To determine the cis-1,4 bond content and vinyl bond content in the 1,3-butadiene monomer unit. In the above spectrum, the peak value a near 1130 cm ⁻¹ is the baseline, the valley peak value b near 967 cm ⁻¹ is the trans-1,4 bond, and the valley peak value c near 911 cm ⁻¹ is the vinyl bond. , A valley peak value d in the vicinity of 736 cm ⁻¹ indicates a cis-1,4 bond.

[Measurement of number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)]
It was measured by GPC [manufactured by Tosoh Corporation, HLC-8020] using a refractometer as a detector, and was shown in terms of polystyrene using monodisperse polystyrene as a standard. The column is GMHXL (manufactured by Tosoh Corporation) and the eluent is tetrahydrofuran.

<Production Example 1> Production of Super High-cis BR -Catalyst Preparation-
In a glass bottle with a rubber stopper with an internal volume of 100 mL that has been dried and purged with nitrogen, 7.11 g of a cyclohexane solution of butadiene (butadiene concentration: 15.2% by mass) and a cyclohexane solution of neodymium neodecanoate (neodymium concentration: 0.1) are sequentially added. 56M) 0.59 mL, PMAO (trade name, polymethylaluminoxane, manufactured by Tosoh Finechem Co., Ltd.) in toluene solution (aluminum concentration: 3.23 M) 10.32 mL, hexane solution of diisobutylaluminum hydride [manufactured by Kanto Chemical Co., Inc.] (0.90 mol / L) 7.77 mL was added, and after aging for 2 minutes at room temperature, 1.45 mL of a hexane solution (0.95 mol / L) of diethylaluminum chloride [manufactured by Kanto Chemical Co., Ltd.] was added, and at room temperature Aged for 15 minutes with occasional stirring. The neodymium concentration in the catalyst solution thus obtained was 0.011 mol / L.
-Manufacture of ultra high cis BR-
A glass bottle with a rubber stopper with an internal volume of 1 L that has been dried and substituted with nitrogen is charged with a dry-purified cyclohexane solution of 1,3-butadiene and a dry cyclohexane, respectively, and 400 g of butadiene in a cyclohexane solution (butadiene concentration: 5.0 mass%) Was sufficiently cooled in a 10 ° C. water bath. Next, 1.56 mL (0.017 mmol in terms of neodymium) of the catalyst solution prepared as described above was added, and polymerization was performed in a 10 ° C. water bath for 3.5 hours. Subsequently, 2 mL of an isopropanol solution (concentration: 5% by mass) of 2,2′-methylene-bis (4-ethyl-6-t-butylphenol) was added as an antiaging agent to stop the reaction. , 2'-methylene-bis (4-ethyl-6-t-butylphenol), re-precipitated in an isopropanol solution, and then dried by a conventional method to obtain an ultra high cis BR (number average) in a yield of about 100%. A molecular weight of 205,000 and a molecular weight distribution of 2.3) were obtained. When the microstructure was analyzed by FT-IR, the cis-1,4 bond content in the 1,3-butadiene monomer unit was 98.43%, and the vinyl bond content was 0.13%. In addition, it was 0.25 × (“cis-1,4 bond content” −97) = 0.48.

<Examples 1-7 and Comparative Examples 1-7>
In the formulation shown in Table 1 and Table 2 (unit: phr), each component excluding sulfur and vulcanization accelerator is kneaded (A kneading) with a Banbury mixer, and then sulfur and vulcanization accelerator are added and kneaded. (B kneading) to obtain a rubber composition for a conveyor belt, and molding the rubber composition at a mold temperature of 160 ° C. gave an inner peripheral cover rubber used for the conveyor belt.
The wear resistance, low loss resistance and tear resistance of the obtained inner peripheral cover rubber were measured as follows, and the results are shown in Tables 1 and 2.

[Abrasion resistance]
In accordance with JIS K6264-2, the amount of wear was measured at room temperature using a DIN abrasion tester. It shows that it is excellent in abrasion resistance, so that a value is small.
[Low loss]
A sheet having a length of 40 mm, a width of 5 mm, and a thickness of 2 mm was prepared from the rubber composition for a conveyor belt. Using such a sheet, a dynamic viscoelasticity measurement was performed with a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho) under measurement conditions of a distance between chucks of 10 mm, a dynamic strain of 2%, and a frequency of 10 Hz. Loss tangent (tan δ) at 20 ° C. and 20 ° C. was measured. When the dynamic elastic modulus was E ′ (N / mm), tan δ / E ′ ^0.32 was obtained to obtain a low loss index. It shows that it is excellent in low-loss property, so that a value is small.
[Tear resistance]
In accordance with JIS K6252, the tearing force (N / mm) was measured using a trouser-shaped test piece. It shows that it is excellent in tearing resistance, so that a value is large.

^{* 1} : Super high cis butadiene rubber produced in Production Example 1
^{* 2} : BR01 (trade name), high-cis butadiene rubber, manufactured by JSR Corporation
^{* 3} : Natural rubber, grade; RSS-3
^{* 4} : IR2200 (trade name), isoprene rubber, manufactured by JSR Corporation
^{* 5} : Seast 6P (trade name), ISAF Carbon, Tokai Carbon Co., Ltd.
^{* 6} : “Lunac (registered trademark) RA” (trade name), manufactured by Kao Corporation
^{* 7} : Zinc flower No. 3, manufactured by Hakusui Chemical Co., Ltd.
^{* 8} : “NOCRACK (registered trademark) 6C” (trade name), manufactured by Ouchi Shinsei Chemical Co., Ltd.
^{* 9} : BMH (trade name), manufactured by Otsuka Chemical Co., Ltd.
^{* 10} : Nip seal AQ (trade name), manufactured by Tosoh Silica Corporation
^{* 11} : Sulfax Z (trade name), manufactured by Tsurumi Chemical Co., Ltd.
^{* 12} : “Noxeller (registered trademark) NS-F” (trade name), manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

As shown in Table 1, when the rubber component is NR or IR and super high cis BR, when the super high cis BR is 50 to 80% by mass in the rubber component (Examples 1 to 7), the tearing force is 15 N / mm. Thus, the tear resistance is excellent and the low loss property at −30 to 20 ° C. is excellent. In particular, tan δ / E ′ ^{0.32 at} −30 ° C. is 0.18 or less, at −5 ° C. is 0.11 or less, and at 20 ° C. It turns out that it is 0.08 or less. Furthermore, the amount of wear is small and it can be said that the wear resistance is good. On the other hand, as shown in Table 2, when the rubber component is only ultra high cis BR (Comparative Example 1) or consists of NR and ultra high cis BR, and the ultra high cis BR is 90% by mass (Comparative Example 4), Although it is excellent in low loss and wear resistance, the tearing force is less than 15 N / mm, which does not meet the current market demand in terms of tear resistance. Further, when the rubber component is composed of NR and ultra high cis BR and the ultra high cis BR is 20% by mass or 40% by mass in the rubber component (Comparative Examples 2 and 3), although the tear resistance is excellent, low loss and Abrasion resistance was greatly reduced. In particular, tan δ / E ′ ^{0.32 at} −5 ° C. exceeds 0.11, energy loss increases, and the demand for conveyor belts is low. In Examples 1, 3 and 4, when the conventional high cis BR was used instead of the ultra high cis BR (Comparative Examples 5 to 7), both the tear resistance and the wear resistance were greatly reduced, and the low loss property was slightly Declined.
Further, as in Example 6, the rubber composition contained a low-loss agent, and the low-loss property could be improved without substantially reducing the tear resistance and wear resistance. Further, as in Example 7, by adding silica to the rubber composition, it was possible to improve the tear resistance without substantially reducing the low loss property and the wear resistance.

  The rubber composition of the present invention is excellent in both low loss and tear resistance while having high wear resistance, and thus can be used for a long time while suppressing power consumption. It can be used as an inner circumference (back side) cover rubber of the conveyor belt.

Claims (14)

  (A) The molecular weight distribution (Mw / Mn) is 1.6 to 3.5, and the cis-1,4 bond in the 1,3-butadiene monomer unit is measured by Fourier transform infrared spectroscopy. A rubber composition for a conveyor belt, comprising 50 to 85% by mass of a butadiene polymer having a content of 98% or more and a vinyl bond content of 0.3% or less and (B) 50 to 15% by mass of a diene rubber. The cis-1,4 bond content and vinyl bond content in the 1,3-butadiene monomer unit are represented by the following formula:
Vinyl bond content (%) ≦ 0.25 × (“cis-1,4 bond content (%)”-97)
The rubber composition for conveyor belts of Claim 1 which satisfy | fills these relationships.   The rubber composition for conveyor belts of Claim 1 or 2 whose molecular weight distribution (Mw / Mn) is 1.6-2.7.   The butadiene-based polymer is composed of 80 to 100% by mass of 1,3-butadiene monomer and 20 to 0% by mass of another monomer copolymerizable with 1,3-butadiene. The rubber composition for conveyor belts in any one.   The rubber composition for a conveyor belt according to claim 4, wherein the butadiene-based polymer is composed only of 1,3-butadiene monomer.   The rubber composition for conveyor belts in any one of Claims 1-5 whose number average molecular weights (Mn) are 100,000-500,000.   The rubber composition for conveyor belts of Claim 6 whose number average molecular weights (Mn) are 150,000-300,000.   The rubber composition for conveyor belts according to any one of claims 1 to 7, wherein the diene rubber is natural rubber and / or isoprene rubber.   Furthermore, the rubber composition for conveyor belts in any one of Claims 1-8 containing a low loss agent.   Furthermore, the rubber composition for conveyor belts in any one of Claims 1-9 containing a silica.   The rubber composition for conveyor belts in any one of Claims 1-10 which is an object for inner peripheral cover rubber | gum of a conveyor belt.   The inner peripheral cover rubber of a conveyor belt obtained from the rubber composition for conveyor belts in any one of Claims 1-11.   A conveyor belt using the inner peripheral cover rubber according to claim 12.   A belt conveyor equipped with the conveyor belt according to claim 13.