JP2020055939A - Rubber composition for conveyor belt and conveyor belt - Google Patents

Abstract

To provide a rubber composition for conveyor belt capable of providing a conveyor belt excellent in energy-saving effect and further excellent in durability, and further a conveyor belt obtained from the rubber composition for conveyor belt.SOLUTION: There is provided a rubber composition for conveyor belt containing a rubber component and a filler, in which the rubber component contains terminal modified polybutadiene, the filler contains carbon black A and carbon black B satisfying following requirements (1) or (2), the terminal modified polybutadiene has one or more kind of functional group selected from a specific amino group and a specific cyclic amino group at a terminal. Requirement (1):NSAof the carbon black A is 36 m/g to 140 m/g, and NSAof the carbon black B is 10 m/g to 35 m/g. Requirement (2):NSAof the carbon black A is 100 m/g to 140 m/g, and NSAof the carbon black B is 10 m/g to 50 m/g.SELECTED DRAWING: None

Description

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

BACKGROUND ART A belt conveyor is used as a means for transporting various loads such as materials and foods. In recent years, large-sized ones have been used in order to increase the transportation volume and the transportation efficiency, and those having a total length of several kilometers have appeared. For this reason, higher durability is required and reduction in power consumption is required.
A belt (conveyor belt) to be mounted on the belt conveyor usually has a core body as a reinforcing material inside, and a cover rubber (a surface which becomes an outer periphery when used for the conveyor belt) of the core body. Hereinafter, it is referred to as an “outer peripheral cover rubber” and an inner periphery (a back surface when used for a conveyor belt. The lower side) is sandwiched between cover rubbers (hereinafter, referred to as “inner peripheral cover rubber”). The required physical properties are different between the outer peripheral cover rubber and the inner peripheral cover rubber located on the rear surface thereof. The inner peripheral rubber reduces not only the tear resistance but also the energy loss due to the 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.

Patent Document 1 discloses a rubber composition for a conveyor belt that achieves both energy saving and durability as (A) 100 parts by mass of a diene polymer and (B) a nitrogen adsorption specific surface area of 60 to 100 m ² / g. And carbon black (b-1) having a dibutyl phthalate oil absorption of less than 110 ml / 100 g and carbon black (b-2) having a nitrogen adsorption specific surface area of less than 60 m ² / g and a dibutyl phthalate oil absorption of 110 ml / 100 g or more. A rubber composition for conveyor belts containing 25 to 55 parts by mass of black is disclosed.
Patent Literature 2 discloses a rubber composition having excellent power saving properties and flex fatigue resistance, comprising a diene rubber containing natural rubber and butadiene rubber, carbon black 1 and carbon black 2, and The amount of the rubber is 40 to 90% by mass in the diene rubber, the amount of the butadiene rubber is 60 to 10% by mass in the diene rubber, and the nitrogen adsorption specific surface area of the carbon black 1 is 60 to 90%. 100m was ² / g, the dibutyl phthalate absorption of the carbon black 1 or less 120 cm ^3/100 g, the nitrogen adsorption specific surface area of the carbon black 2 was the 20 to 40 m ² / g, dibutyl of the carbon black 2 and a phthalate oil absorption of 70~95cm ³ / 100g or less, the total of the carbon black 1 and the carbon black 2 Amount, with respect to the diene rubber 100 parts by weight, 25 to 50 parts by mass, the rubber composition is disclosed.

JP 2013-12018 A WO 2005/182499

  SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for a conveyor belt, from which a conveyor belt having excellent energy saving properties and excellent durability can be obtained. The present invention further provides a conveyor belt obtained from the rubber composition for a conveyor belt.

  The present inventors have conducted extensive studies and found that a rubber composition containing a rubber component and a filler, containing a specific terminal-modified polybutadiene as a rubber component, and containing at least two specific carbon blacks as a filler. It has been found that the above problems can be solved.

That is, the present invention relates to the following <1> to <7>.
<1> A rubber composition for a conveyor belt containing a rubber component and a filler, wherein the rubber component contains a terminal-modified polybutadiene and the filler satisfies the following requirement (1) or (2): And carbon black B, wherein the terminal-modified polybutadiene has at least one functional group selected from the group consisting of an amino group represented by the following formula (I) and a cyclic amino group represented by the following formula (II) A rubber composition for a conveyor belt, having at the end.
Requirement (1): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 36 m ² / g or more and 140 m ² / g or less, and the carbon black B has a nitrogen adsorption specific surface area (N ₂ SA _B ) of 10 m ^2. / G or more and 35 m ² / g or less Requirement (2): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 100 m ² / g or more and 140 m ² / g or less, and the nitrogen adsorption ratio of carbon black B The surface area (N ₂ SA _B ) is 10 m ² / g or more and 50 m ² / g or less.

(In the formula (I), R ¹ each independently represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group or an aralkyl group, and in the formula (II), R ² has a 3 to 16 methylene group. An alkylene group, a substituted alkylene group, an oxyalkylene group or an N-alkylamino-alkylene group is shown.)

<2> The rubber component further contains at least one selected from natural rubber and synthetic isoprene rubber, and the mass ratio of the total amount of the natural rubber and the synthetic isoprene rubber to the terminal-modified polybutadiene is 70:30 to 10:90. The rubber composition for a conveyor belt according to <1>.
<3> The rubber composition for a conveyor belt according to <1> or <2>, wherein the mass ratio of the content of carbon black A to the content of carbon black B is 1: 7 to 7: 1.
<4> The rubber for a conveyor belt according to any one of <1> to <3>, wherein the mass ratio of the content of carbon black A to the content of carbon black B is 1: 1 to 5: 1. Composition.
<5> The nitrogen adsorption specific surface area (N ₂ SA _A ) of carbon black _A and the nitrogen adsorption specific surface area (N ₂ SA _B ) of carbon black B satisfy the following formula (A): The rubber composition for a conveyor belt according to any one of the above.
_{N 2 SA A -N 2 SA B} > 10m 2 / g (A)
<6> The terminal-modified polybutadiene according to any one of <1> to <5>, wherein the terminal-modified polybutadiene has at least one tin-carbon bond derived from a coupling agent represented by the following formula (V). Rubber composition for conveyor belt.

(In the formula (V), R ³ is each independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl having 7 to 20 carbon atoms. X represents independently chlorine or bromine, b represents 0 to 3, c represents 1 to 4, and b + c = 4.

  <7> A conveyor belt using the rubber composition according to any one of <1> to <6>.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for conveyor belts which is excellent in energy-saving property and can obtain the conveyor belt excellent also in durability can be provided. Further, according to the present invention, it is possible to provide a conveyor belt obtained from the rubber composition for a conveyor belt.

Hereinafter, the present invention will be described in detail based on its embodiments. In the following description, “A to B” indicating a numerical range indicates a numerical range including A and B, which are end points, and is “A or more and B or less” (when A <B) or “A Hereinafter, B or more "(when A> B).
Further, parts by mass and% by mass are synonymous with parts by weight and% by weight, respectively.

[Rubber composition for conveyor belt]
The rubber composition for a conveyor belt of the present invention (hereinafter, also simply referred to as “rubber composition”) contains a rubber component and a filler, the rubber component contains a terminal-modified polybutadiene, and the filler has the following requirements. It contains carbon black A and carbon black B satisfying (1) or (2), and the terminal-modified polybutadiene has an amino group represented by the following formula (I) and a cyclic amino group represented by the following formula (II) At least one functional group selected from the group consisting of:
Requirement (1): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 36 m ² / g or more and 140 m ² / g or less, and the carbon black B has a nitrogen adsorption specific surface area (N ₂ SA _B ) of 10 m ^2. / G or more and 35 m ² / g or less Requirement (2): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 100 m ² / g or more and 140 m ² / g or less, and the nitrogen adsorption ratio of carbon black B The surface area (N ₂ SA _B ) is 10 m ² / g or more and 50 m ² / g or less.

(In the formula (I), R ¹ each independently represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group or an aralkyl group, and in the formula (II), R ² has a 3 to 16 methylene group. An alkylene group, a substituted alkylene group, an oxyalkylene group or an N-alkylamino-alkylene group is shown.)

  Conventionally, as rubber compositions for conveyor belts that achieve both energy saving and durability, Patent Literatures 1 and 2 disclose rubber compositions using a rubber composition containing two specific types of carbon black. As a result of intensive studies, the present inventors have found that a rubber composition for a conveyor belt containing a terminal-modified polybutadiene having a specific functional group at the terminal as a rubber component, and further containing at least two types of carbon black satisfying specific requirements. It has been found that the use of a belt makes it possible to obtain a conveyor belt which is excellent in energy saving properties and further excellent in durability, and has completed the present invention.

The detailed mechanism by which the above effects can be obtained is unknown, but is presumed as follows. The rubber composition of the present invention contains a terminal-modified polybutadiene having a specific functional group at a terminal as a rubber component, thereby interacting with carbon black to improve the dispersibility of carbon black, and as a result, the durability is improved. It is considered that a conveyor belt having improved and energy saving properties was obtained. Furthermore, by using a carbon black having a specific nitrogen adsorption specific surface area (N ₂ SA) in combination, the carbon black is dispersed in the rubber composition so as to be more highly packed, and furthermore, durability and energy saving are further improved. It is estimated that the property has improved.
Hereinafter, the rubber composition of the present invention will be described in more detail.

<Rubber component>
The rubber composition of the present invention contains a rubber component, and as the rubber component, at least one selected from the group consisting of an amino group represented by the above formula (I) and a cyclic amino group represented by the above formula (II). It contains end-modified polybutadiene having various functional groups at its ends.
(Terminal-modified polybutadiene)
The terminal-modified polybutadiene has at its terminal at least one type of functional group selected from the group consisting of an amino group represented by the following formula (I) and a cyclic amino group represented by the following formula (II).

(In the formula (I), R ¹ each independently represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group or an aralkyl group, and in the formula (II), R ² has a 3 to 16 methylene group. An alkylene group, a substituted alkylene group, an oxyalkylene group or an N-alkylamino-alkylene group is shown.)

In the formula (I), R ¹ each independently represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group or an aralkyl group, and examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group and an isopropyl group. Groups, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group and the like.
Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.
Examples of the aralkyl group include a benzyl group and a 3-phenyl-1-propyl group.
Among these, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an octyl group, a cyclohexyl group, and a 3-phenyl-1-propyl group are preferably exemplified.
Two R ¹ in the formula (I) may be the same or different.

In the cyclic amino group represented by the formula (II), R ^{2 in} the formula is a divalent alkylene group having 3 to 16 methylene groups, a substituted alkylene group, an oxyalkylene group, or an N-alkylamino-alkylene. There is no particular limitation as long as it is a group.
Here, the substituted alkylenes include mono- to octa-substituted alkylenes. Preferred substituents are linear or branched alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups, bicycloalkyl groups, aryl groups, and aralkyl groups.
Preferred R ^2, a trimethylene group, Te Bok Ramechiren group, hexamethylene group, oxy Siji ethylene group, N- alkyl aza diethylene group, dodecamethylene group, and the like hexamethylene decamethylene and the like.

  Also, there are many useful examples of cyclic amines containing alkyl, cycloalkyl, aryl and aralkyl substituents, including but not limited to 2- (2-ethylhexyl) pyrrolidine, 3- (2- Propyl) pyrrolidine, 3,5-bis (2-ethylhexyl) piperidine, 4-phenylpiperidine, 7-decyl-1-azacyclotridecane, 3,3-dimethyl-1-azacyclotetradecane, 4-dodecyl-1- Azacyclooctane, 4- (2-phenylbutyl) -1-azacyclooctane, 3-ethyl-5-cyclohexyl-1-azacycloheptane, 4-hexyl-1-azacycloheptane, 9-isoamyl-1-aza Cycloheptadecane, 2-methyl-1-azacycloheptadec-9-ene, 3-isobutyl-1-azashi Rhododecane, 2-methyl-7-t-butyl-1-azacyclododecane, 5-nonyl-1-azacyclododecane; 8- (4′-methylphenyl) -5-pentyl-3-azabicyclo [5.4. 0] undecane, 1-butyl-6-azabicyclo [3.2.1] octane, 8-ethyl-3-azabicyclo [3.2.1] octane, 1-propyl-3-azabicyclo [3.2.2] Nonane, 3- (t-butyl) -7-azabicyclo [4.3.0] nonane, 1,5,5-trimethyl-3-azabicyclo [4.4.0] decane and the like can be mentioned. Therefore, the cyclic amino group represented by the formula (II) is a group obtained by removing the hydrogen group from the NH group constituting the ring of the above cyclic amines.

  In the present invention, the terminal-modified polybutadiene is preferably blended in an amount of 10% by mass or more of the whole rubber component. By blending the terminal-modified polybutadiene in an amount of 10% by mass or more, excellent low heat build-up can be obtained. The content of the terminal-modified polybutadiene is more preferably 20 to 80% by mass, even more preferably 30 to 65% by mass of the whole rubber component. By blending the terminal-modified polybutadiene within the above range, the durability of the rubber composition can be maintained, and excellent low heat build-up can be obtained.

  As a method for introducing at least one functional group selected from the group consisting of a disubstituted amino group represented by the formula (I) and a cyclic amino group represented by the formula (II) into polybutadiene, for example, A method of bonding to an organic group having a bonded 2-hydroxy-1,3-propylene group via at least one nitrogen atom in a cyclic amino group (described in detail in JP-A-2001-131227), and the like However, a method in which a lithioamine or a mixture of a lithioamine and an organic alkali metal is used as a polymerization initiator to modify the polymerization initiation terminal with a cyclic amino group or the like is preferably used.

That is, a solution of 1,3-butadiene is formed in a hydrocarbon solvent, and lithioamine represented by the following formula (III) or a mixture of the lithioamine and an organic alkali metal compound is used as a polymerization initiator. By polymerizing the above 1,3-butadiene, a terminal-modified polybutadiene can be obtained.
(AM) Li (Q) y (III)
In the formula (III), y is 0 or about 0.5 to 3, Q is a solubilizing component selected from the group consisting of hydrocarbons, ethers, amines or mixtures thereof, and AM is It is represented by (I) or formula (II).

(In the formulas (I) and (II), R ¹ and R ² are as described above.)

The lithioamine is represented by the formula (III).
Q is a solubilizing component and may be a hydrocarbon, ether, amine, or a mixture thereof. The presence of this Q makes the initiator soluble in the hydrocarbon solvent.
Q also includes dienyl or vinyl aromatic polymers or copolymers having a degree of polymerization of from 3 to about 300 polymerized units. The polymers include polybutadiene, polystyrene, polyisoprene, and copolymers thereof. Other examples of Q include polar ligands, such as tetrahydrofuran (THF) and tetramethylethylenediamine (TMEDA).
AM represents an amino functional group, for example, by incorporation at the polymer start site or at the head to synthesize a polybutadiene terminated with the functional group.

When the solubilizing component Q is an ether or an amino compound, a solution of the functionalizing agent AM-H is prepared in the presence of Q in an anhydrous aprotic solvent such as cyclohexane, and then the solution is added to the solution. The initiator can be generated by adding an organolithium compound in the same or similar solvent.
The organolithium compound is represented by the following formula (IV).
R-Li (IV)
In the formula (IV), R is a short group having not more than 25 units obtained from alkyl, cycloalkyl, alkenyl, aryl, aralkyl, diolefin and vinylaryl monomers having 1 to 20 carbon atoms. It is selected from the group consisting of low molecular weight polymers of chain length.

For example, typical alkyl groups include an n-butyl group, a sec-butyl group, a methyl group, an ethyl group, and an isopropyl group. Examples of the cycloalkyl include a cyclohexyl group and a menthyl group, and examples of the alkenyl group include an allyl group and a vinyl group.
Further, aryl and aralkyl groups include phenyl group, benzyl group, oligo (styryl) group and the like, and short-chain long polymers are formed by initiating oligomerization of a suitable monomer with organolithium. Oligo (butadienyl) s, oligo (isoprenyl) s, oligo (styryl) s, and the like. Further, an in situ method (a method described in JP-A-6-199921) is also suitably used.
As the organic lithium compound, n-butyllithium is preferable.
Instead of adding the above lithioamine, a substituted amine or cyclic amine represented by AM-H and an organic lithium compound may be added.

The organic alkali metal compound optionally used as the initiator is preferably represented by R ⁴ M, R ⁵ OM, R ⁶ C (O) OM, R ⁷ R ⁸ NM, and R ⁹ SO ₃ M. Wherein each of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ is an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group, It is selected from the group consisting of an alkenyl group, an aryl group, and phenyl. This metal component M is selected from the group consisting of Na, K, Rb and Cs. Preferably, M is Na or K.

  Further, the initiator may suitably contain the organic alkali metal compound in a mixing ratio of 0.5 to 0.02 equivalent per equivalent of lithium in the lithioamine initiator.

Furthermore, chelating agents can be used with the initiator as an aid to prevent the polymerization from becoming non-uniform. Useful chelating agents include, for example, tetramethylethylenediamine (TMEDA), oxolanyl cyclic acetals, and cyclic oligomeric oxolanyl alkanes. Particularly preferred are cyclic oligomeric oxolanyl alkanes, and specific examples include 2,2-bis (tetrahydrofuryl) propane.
As the polymerization solvent, for example, various hexanes, heptanes, octanes, and mixtures thereof are used.

  In order to give the conveyor belt even better low heat build-up, the terminal-modified polybutadiene is selected from the group consisting of the amino group represented by the formula (I) and the cyclic amino group represented by the formula (II). It preferably has at least one selected functional group at the terminal and has at least one tin-carbon bond derived from a coupling agent represented by the following formula (V).

(In the formula (V), R ³ is each independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl having 7 to 20 carbon atoms. X represents independently chlorine or bromine, b represents 0 to 3, c represents 1 to 4, and b + c = 4.

In the formula (V), R ³ is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl having 7 to 20 carbon atoms. For example, R ³ includes a methyl group, an ethyl group, an n-butyl group, a neophyl group, a cyclohexyl group, an n-octyl group, a 2-ethylhexyl group, and the like.
X is chlorine or bromine, b is 0-3, c is 1-4, where b + c = 4.
Preferred coupling agents include tin tetrachloride (SnCl ₄ ), (R ³ ) SnCl ₃ , (R ³ ) ₂ SnCl ₂ , (R ³ ) ₃ SnCl and the like, with tin tetrachloride (SnCl ₄ ) being particularly preferred. preferable.

  Further, other modifiers may be used for the terminal-modified polybutadiene. Preferred modifiers include carbodiimides, N-methylpyrrolidinone, cyclic amides, cyclic ureas, isocyanates, Schiff bases, 4,4'-bis (diethylamino) benzophenone, and the like.

One suitable end-modified polybutadiene used in the rubber composition of the present invention is a polymer containing at least one functional group AM, wherein AM is obtained from the reaction product of an amine and an organolithium compound. Be guided. Further, a preferred modified diene-based polymer is a polymer that exhibits polyfunctionality because the polymer also has a tin-carbon bond, and the tin-carbon bond includes, for example, a terminator, a coupling agent, and a linking agent. The agent can be derived from a denaturing agent.
After adding these modifiers to the reaction vessel, the vessel can be agitated for about 1 to about 1000 minutes to introduce a tin-carbon bond into the polymer. As a result, a terminal-modified polybutadiene having higher affinity for carbon black as a reinforcing filler, improved dispersibility of carbon black, and excellent low heat buildup can be obtained.

[Other rubber components]
The rubber composition for a conveyor belt of the present invention may contain other rubber components in addition to the terminal-modified polybutadiene. As the other rubber component, a diene polymer is preferable. Examples of the diene polymer include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), and ethylene. -Propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber, chloroprene rubber, and the like. These may be used alone or in combination of two or more.

In the present invention, it is preferable to include at least one selected from natural rubber and synthetic isoprene rubber as another rubber component from the viewpoint of achieving both energy saving and durability.
That is, in the present invention, it is preferable that the rubber component further contains at least one selected from natural rubber and synthetic isoprene rubber in addition to the above-mentioned terminal-modified polybutadiene.
The mass ratio of the total amount of the natural rubber and the synthetic isoprene rubber to the terminal-modified polybutadiene (the total amount of the natural rubber and the synthetic isoprene rubber: the terminal-modified polybutadiene (mass ratio)) is preferably 95: 5 or less, more preferably 90:10, and still more. It is preferably at most 80:20, more preferably at most 70:30, even more preferably at least 60:40, preferably at least 5:95, more preferably at least 10:90, even more preferably at least 15:85, more preferably It is more preferably at least 20:80, even more preferably at least 30:70, even more preferably at least 40:60.

  In the present invention, the total amount of the terminal-modified polybutadiene and the natural rubber and the synthetic isoprene rubber based on the entire rubber component is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more, It may be 100% by mass.

<Filler>
The rubber composition of the present invention contains a filler, and the filler contains carbon black A and carbon black B satisfying the following requirement (1) or (2).
Requirement (1): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 36 m ² / g or more and 140 m ² / g or less, and the carbon black B has a nitrogen adsorption specific surface area (N ₂ SA _B ) of 10 m ^2. / G or more and 35 m ² / g or less Requirement (2): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 100 m ² / g or more and 140 m ² / g or less, and the nitrogen adsorption ratio of carbon black B Surface area (N ₂ SA _B ) is 10 m ² / g or more and 50 m ² / g or less By using a combination of carbon black A and carbon black B as described above, the filling property of carbon black in the rubber composition , The reinforcing effect is improved, and a conveyor belt having more excellent durability can be obtained.
The carbon black A and the carbon black B satisfying the requirements (1) and (2) are not particularly limited as long as they contain the carbon black A and the carbon black B. The total content of the carbon black A and the carbon black B in the carbon black is as follows: It is preferably at least 60% by mass, more preferably at least 80% by mass, still more preferably at least 90% by mass, and even more preferably, only carbon black A and carbon black B are contained as carbon black.
Further, as the carbon black A, two or more types of carbon black satisfying the requirements may be contained. Similarly, as the carbon black B, two or more types of carbon black B satisfying the requirements may be contained.
Hereinafter, each requirement will be described in detail.

[Requirements (1)]
In the requirement (1), the nitrogen adsorption specific surface area (N ₂ SA _A ) of the carbon black A is from 36 m ² / g to 140 m ² / g, and the nitrogen adsorption specific surface area (N ₂ SA _B ) of the carbon black B is 10 m. ^{It is 2} / g or more and 35 m ² / g or less.
In the requirement (1), the nitrogen adsorption specific surface area (N ₂ SA _A ) of the carbon black A is 36 m ² / g or more, preferably 37 m ² / g or more from the viewpoint of obtaining a conveyor belt having excellent durability and low heat generation. , more preferably ^38m 2 / g or more, more preferably ^39m 2 / g or more, and, 140 m ² / g or less, preferably 120 m ² / g or less, more preferably ^{80 m} 2 / g or less, more preferably 60m ² / g or less, more preferably 50 m ² / g or less.
In the requirement (1), the DBP oil absorption of the carbon black A is preferably 20 ml / 100 g or more, more preferably 50 g / 100 g or more, and still more preferably 70 ml / g from the viewpoint of obtaining a conveyor belt having excellent durability and low heat build-up. It is 100 g or more, more preferably 100 ml / 100 g or more, and preferably 140 ml / 100 g or less, more preferably 135 ml / 100 g or less, still more preferably 130 ml / 100 g or less, and even more preferably 125 ml / 100 g or less.
In the requirement (1), the carbon black A is preferably exemplified by FEF grade and ISAF grade carbon black, and more preferably FEF grade carbon black.
In addition, the nitrogen adsorption specific surface area of carbon black is measured based on JISK6217-2: 2017. The DBP oil absorption of carbon black is measured according to JIS K 6217-4: 2017.

In the requirement (1), the nitrogen adsorption specific surface area (N ₂ SA _B ) of the carbon black B is 10 m ² / g or more, preferably 14 m ² / g or more from the viewpoint of obtaining a conveyor belt excellent in durability and low heat generation. , More preferably at least 18 m ² / g, even more preferably at least 20 m ² / g, and at most 35 m ² / g, preferably at most 34 m ² / g, more preferably at most 33 m ² / g, still more preferably at most 32 m ² / g or less.
In requirement (1), the DBP oil absorption of carbon black B is preferably 20 ml / 100 g or more, more preferably 40 g / 100 g or more, and still more preferably 60 ml / g, from the viewpoint of obtaining a conveyor belt having excellent durability and low heat build-up. It is 100 g or more, and preferably 125 ml / 100 g or less, more preferably 115 ml / 100 g or less, still more preferably 80 ml / 100 g or less, and even more preferably 72 g / 100 g or less.
In the requirement (1), the carbon black B is preferably exemplified by SRF grade carbon black.

[Requirements (2)]
In the requirement (2), the nitrogen adsorption specific surface area (N ₂ SA _A ) of the carbon black A is 100 m ² / g or more and 140 m ² / g or less, and the nitrogen adsorption specific surface area (N ₂ SA _B ) of the carbon black B is 10 m. ² / g or more and 50 m ² / g or less.
In the requirement (2), the nitrogen adsorption specific surface area (N ₂ SA _A ) of the carbon black A is 100 m ² / g or more, preferably 103 m ² / g or more from the viewpoint of obtaining a conveyor belt having excellent durability and low heat generation. , More preferably at least 105 m ² / g, even more preferably at least 110 m ² / g, and at most 140 m ² / g, preferably at most 135 m ² / g, more preferably at most 130 m ² / g, even more preferably at least 125 m ² / g. ² / g or less, more preferably 120 m ² / g or less.
In the requirement (2), the DBP oil absorption of the carbon black A is preferably 20 ml / 100 g or more, more preferably 50 g / 100 g or more, and still more preferably 80 ml / g from the viewpoint of obtaining a conveyor belt having excellent durability and low heat build-up. It is 100 g or more, and preferably 125 ml / 100 g or less, more preferably 120 ml / 100 g or less, and still more preferably 115 ml / 100 g or less.
In the requirement (2), the carbon black A is preferably exemplified by ISAF grade carbon black.

In the requirement (2), the nitrogen adsorption specific surface area (N ₂ SA _B ) of the carbon black B is 10 m ² / g or more, preferably 20 m ² / g or more from the viewpoint of obtaining a conveyor belt having excellent durability and low heat generation. And more preferably 30 m ² / g or more, further preferably 35 m ² / g or more, and 50 m ² / g or less, preferably 47 m ² / g or less, more preferably 45 m ² / g or less.
In requirement (2), the DBP oil absorption of carbon black B is preferably 20 ml / 100 g or more, more preferably 60 g / 100 g or more, and still more preferably 100 ml / g, from the viewpoint of obtaining a conveyor belt having excellent durability and low heat build-up. It is 100 g or more, and preferably 125 ml / 100 g or less, more preferably 123 ml / 100 g or less.
In the requirement (2), the carbon black B is preferably exemplified by FEF grade and SRF grade carbon black, and more preferably FEF grade.

  In the requirement (1) and the requirement (2), the mass ratio of the content of carbon black A to the content of carbon black B in the rubber composition (carbon black A: carbon black B) improves the filling ratio of carbon black. From the viewpoint of obtaining a conveyor belt having excellent durability and low heat build-up, the ratio is preferably 1: 7 or more, more preferably 1: 3 or more, still more preferably 1: 1 or more, and preferably 7: 1 or less. , More preferably 6: 1 or less, still more preferably 5: 1 or less.

In the requirements (1) and (2), the nitrogen adsorption specific surface area (N ₂ SA _A ) of the carbon black _A and the nitrogen adsorption specific surface area (N ₂ SA _B ) of the carbon black B satisfy the following formula (A). Is preferred.
_{N 2 SA A -N 2 SA B} > 10m 2 / g (A)
By using carbon black A and carbon black B satisfying the above formula (A), the filling rate of carbon black is further improved, and as a result, a conveyor belt having excellent durability and low heat generation can be obtained.
N ₂ SA _A -N ₂ SA _B is more preferably at least 10 m ² / g, further preferably at least 15 m ² / g, and still more preferably at least 20 m ² / g. The upper limit is not particularly limited, but is preferably 100 m ² / g or less, more preferably 90 m ² / g or less, and still more preferably 80 m ² / g or less from the same viewpoint.

  The carbon black may be produced by any method such as a furnace method, a channel method, an acetylene method, and a thermal method, and is particularly preferably produced by a furnace method. Specific examples of carbon black include standard varieties SAF, ISAF, HAF, FEF, GPF, SRF (above, furnace for rubber), MT carbon black (pyrolytic carbon) and the like. , SRF and FEF are preferred. From these, carbon black that meets the above-mentioned rules may be appropriately selected and used.

  In the rubber composition of the present invention, the content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of obtaining a conveyor belt having excellent durability and low heat buildup. Or more, more preferably 25 or more parts, even more preferably 30 or more parts, even more preferably 35 or more parts, and from the same viewpoint, preferably 70 parts or less, more preferably 60 parts or less. , More preferably 55 parts by mass or less, even more preferably 50 parts by mass or less.

<Other ingredients>
Other additives may be further added to the rubber composition of the present invention as long as the effects of the present invention are not significantly impaired. The additive is not particularly limited as long as it is usually contained in the cover rubber of the conveyor belt. Examples of the additive include fatty acids such as stearic acid, zinc oxide (zinc white), an antioxidant, sulfur, a vulcanization accelerator, a vulcanization retarder (an anti-scorch agent), oil, resin, wax, silica, Examples include silica coupling agents, peptizers, antiozonants, antioxidants, clays, calcium carbonate, and the like. These can use a commercial item.

When a fatty acid is used, its amount is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.
When zinc oxide is used, the amount is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.
As the antioxidant, a known antioxidant can be selected and used. For example, N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6C), N-phenyl-N′-isopropyl-p-phenylenediamine (3C), 2,2,4-trimethyl -1,2-dihydroquinoline polymer (RD) and the like. The antioxidants may be used alone or in combination of two or more. When an antioxidant is used, the amount thereof is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and further preferably 1 to 5 parts by mass, based on 100 parts by mass of the rubber component. preferable.

When sulfur is used, the amount thereof is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and still more preferably 1.5 parts by mass or more, based on 100 parts by mass of the rubber component. And it is preferably at most 10 parts by mass, more preferably at most 4 parts by mass, even more preferably at most 1.5 parts by mass.
The vulcanization accelerator is not particularly limited, but, for example, 2-mercaptobenzothiazole (M), dibenzothiazyl disulfide (DM), N-cyclohexyl-2-benzothiazylsulfenamide (CZ) And guanidines such as diphenylguanidine (DPG) and sulfenamides such as N-tert-butyl-2-benzothiazolylsulfenamide (NS-F). Can be. The vulcanization accelerators may be used alone or in combination of two or more. When a vulcanization accelerator is used, its amount is preferably from 0.1 to 5 parts by mass, more preferably from 0.1 to 2 parts by mass, per 100 parts by mass of the rubber component.
Those skilled in the art can appropriately select the amount of other additives to be added within a range that does not impair the purpose of the present invention.

  The rubber composition of the present invention is obtained by kneading the rubber component and the filler, and the necessary additives as appropriate. The kneading method may be in accordance with a method usually performed by those skilled in the art. For example, all components other than sulfur and the vulcanization accelerator are kneaded at 80 to 200 ° C. (preferably 100 to 180 ° C.) using a mixer such as a Banbury mixer, Brabender, kneader, or high shear mixer (A kneading). ), And then adding sulfur and a vulcanization accelerator (B kneading) and kneading at 80 to 200 ° C (preferably 100 to 180 ° C) with a kneading roll machine or the like. A method of kneading at 80 to 200 ° C (preferably 100 to 180 ° C) may be mentioned.

The conveyor belt (outer peripheral cover rubber or inner peripheral cover rubber) of the present invention can be obtained by molding the rubber composition thus obtained with a heating mold. Usually, the outer peripheral cover rubber and the inner peripheral cover rubber form a single conveyor belt with a core body as a reinforcing material interposed therebetween, and are mounted on a belt conveyor.
INDUSTRIAL APPLICABILITY The rubber composition for a conveyor belt of the present invention has both energy saving (low heat generation) and durability, and is therefore useful as a conveyor belt, particularly as an inner peripheral cover rubber.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified, “%” and “parts” all indicate “% by mass” and “parts by mass”. In addition, the description of the amount of addition in the table is "parts by mass" in all cases.
Using the rubber compositions for conveyor belts obtained in each of the examples in Table 1, durability (wear resistance and tear resistance) and heat generation were evaluated according to the methods described below.

[Preparation of rubber composition for conveyor belt]
A rubber composition for a conveyor belt having the formulation shown in Table 1 was prepared. The rubber for conveyor belts produced by vulcanizing the rubber composition at 160 ° C. for 15 minutes was evaluated for abrasion resistance, tear resistance and weight reduction according to the following methods.
The components used are as follows.

<Production of terminal modified polybutadiene>
283 g of cyclohexane, 50 g of 1,3-butadiene, 0.0057 mmol of 2,2-ditetrahydrofurylpropane, and 0.513 mmol of hexamethyleneimine were each placed in a dried, nitrogen-substituted pressure-resistant glass vessel having an internal volume of about 900 ml, and dissolved in cyclohexane. After adding 0.57 mmol of n-butyllithium (BuLi), polymerization was carried out in a 50 ° C warm water bath equipped with a stirrer for 4.5 hours. The polymerization addition rate was almost 100%. To this polymerization system, 0.100 mmol of tin tetrachloride was added as a cyclohexane solution, followed by stirring at 50 ° C. for 30 minutes. Thereafter, the reaction was further stopped by adding 0.5 ml of a 5% solution of 2,6-di-t-butylparacresol (BHT) in isopropanol, and further dried according to a conventional method to obtain a terminal-modified polybutadiene (terminal-modified BR). I got
The amount of vinyl bond (1,2-bond) in the obtained terminal-modified BR was determined from the integration ratio in the ¹ H-NMR [manufactured by JEOL Ltd., Alpha 400 MHz NMR apparatus, in CDCl ₃ ] spectrum, and the butadiene unit was determined. Was 14%. The coupling efficiency of the obtained terminally modified BR was calculated using the area ratio of the peak on the high molecular weight side in the data obtained by gel permeation chromatography (GPC), and the coupling efficiency was 65%. there were. The glass transition temperature was -95C.

<Measurement of nitrogen adsorption specific surface area and DBP oil absorption of carbon black>
The nitrogen adsorption specific surface area of the carbon black used was measured according to JIS K 6217-2: 2017. The DBP oil absorption of carbon black was measured according to JIS K 6217-4: 2017.

<Carbon black>
CB-1 (carbon black-1, HAF): # 70, Asahi Carbon Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 71 m ² / g, DBP oil absorption = 103 ml / 100 g
CB-2 (carbon black-2, FEF): Seast SO, Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 42 m ² / g, DBP oil absorption = 120 ml / 100 g
CB-3 (carbon black-3, SRF): # 50, Asahi Carbon Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 21 m ² / g, DBP oil absorption = 68 ml / 100 g
CB-4 (carbon black-4, ISAF): Seast 6, Tokai Carbon Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 119 m ² / g, DBP oil absorption = 114 ml / 100 g

<Rubber component>
Terminal-modified BR: terminal-modified polybutadiene obtained by the above-described production methodNR: TSR20
・ BR: Diene NF35R, Asahi Kasei Corporation

<Other ingredients>
-Anti-aging agent: ANTIGENE 6C (N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine), Sumitomo Chemical Co., Ltd.-Vulcanization accelerator: Noxeller NS-F (N-tert-butyl) -2-benzothiazolylsulfenamide), Ouchi Shinko Chemical Co., Ltd., Aroma oil: Diana Process Oil AH-58, Idemitsu Kosan Co., Ltd.

[Evaluation method]
(1) Abrasion resistance The abrasion resistance was evaluated by measuring the defect volume in a DIN abrasion test. The result is represented by an index when Comparative Example 2 is set to 100, and the larger the value, the better the wear resistance. Table 2 shows the evaluation results.

(2) Tear resistance The abrasion resistance was evaluated by measuring the tear force by a trouser type test. The result is represented by an index when Comparative Example 2 is set to 100, and the larger the value, the higher the tear resistance and the better the result. Table 2 shows the evaluation results.

(3) Light weight (lower cover rubber thinner (lower cover thinner))
The reduction in weight was evaluated by calculating the degree of thinning of the lower cover rubber of the conveyor belt. The results are expressed as a relative value (%) when Comparative Example 2 is set to 0. The larger the numerical value, the thinner the film is, and the better the result. Table 2 shows the evaluation results.
More specifically, when a low numerical value is Z in the above-described evaluation of the wear resistance and the crack resistance, (Z-100) was used as an index of thinning. That is, (Z-100) was used as an index of how much the thickness can be reduced in order to obtain the same abrasion resistance and crack resistance as in Comparative Example 2.

(4) Heat generation at low temperature The heat generation at low temperature was evaluated by performing a viscoelasticity test (test conditions: 10 Hz, 2%) of the lower cover rubber of the conveyor belt at -20 ° C and 20 ° C. The results are expressed as an index when the viscoelasticity of Comparative Example 2 is set to 100. The smaller the numerical value, the lower the heat build-up, energy saving is achieved, and the result is good. Table 2 shows the evaluation results.
The exothermicity at −20 ° C. is preferably 110 or less, more preferably 105 or less, and further preferably 100 or less. The exothermicity at 20 ° C. is preferably 100 or less, more preferably 98 or less, further preferably 95 or less, and more preferably 90 or less.

  Since the rubber composition of the present invention is excellent in energy saving properties and further excellent in durability, it is suitable as a conveyor belt, particularly as an inner peripheral cover rubber of the conveyor belt.

Claims (7)

A rubber composition for a conveyor belt containing a rubber component and a filler,
The rubber component contains a terminal-modified polybutadiene,
The filler contains carbon black A and carbon black B satisfying the following requirements (1) or (2),
Requirement (1): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 36 m ² / g or more and 140 m ² / g or less, and the carbon black B has a nitrogen adsorption specific surface area (N ₂ SA _B ) of 10 m ^2. / G or more and 35 m ² / g or less Requirement (2): The carbon black A has a nitrogen adsorption specific surface area (N ₂ SA _A ) of 100 m ² / g or more and 140 m ² / g or less, and the nitrogen adsorption ratio of carbon black B The terminal-modified polybutadiene having a surface area (N ₂ SA _B ) of 10 m ² / g or more and 50 m ² / g or less is obtained from an amino group represented by the following formula (I) and a cyclic amino group represented by the following formula (II) A rubber composition for a conveyor belt having at its terminal at least one functional group selected from the group consisting of:

(In the formula (I), R ¹ each independently represents an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group or an aralkyl group, and in the formula (II), R ² has a 3 to 16 methylene group. An alkylene group, a substituted alkylene group, an oxyalkylene group or an N-alkylamino-alkylene group is shown.)   The rubber component further comprises at least one selected from a natural rubber and a synthetic isoprene rubber, and a mass ratio of the total amount of the natural rubber and the synthetic isoprene rubber to the terminal-modified polybutadiene is 70:30 to 10:90. Item 4. The rubber composition for a conveyor belt according to Item 1.   The rubber composition for a conveyor belt according to claim 1 or 2, wherein the mass ratio of the content of carbon black A to the content of carbon black B is 1: 7 to 7: 1.   The rubber composition for a conveyor belt according to any one of claims 1 to 3, wherein a mass ratio of the content of carbon black A to the content of carbon black B is 1: 1 to 5: 1. The nitrogen adsorption specific surface area (N ₂ SA _A ) of carbon black _A and the nitrogen adsorption specific surface area (N ₂ SA _B ) of carbon black B satisfy the following formula (A). The rubber composition for a conveyor belt according to the above.
_{N 2 SA A -N 2 SA B} > 10m 2 / g (A) The rubber composition for a conveyor belt according to any one of claims 1 to 5, wherein the terminal-modified polybutadiene has at least one tin-carbon bond derived from a coupling agent represented by the following formula (V). Stuff.

(In the formula (V), R ³ is each independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl having 7 to 20 carbon atoms. X represents independently chlorine or bromine, b represents 0 to 3, c represents 1 to 4, and b + c = 4.   A conveyor belt using the rubber composition according to any one of claims 1 to 6.