JPWO2017141909A1 - Rubber composition for conveyor belt and conveyor belt - Google Patents

Abstract

The present invention provides a rubber composition for a conveyor belt capable of producing a conveyor belt having a cover rubber layer excellent in wear resistance, and a conveyor belt using the same. The rubber composition for conveyor belts of the present invention contains a rubber component containing 45 to 100% by mass of butadiene rubber, ultrahigh molecular weight polyethylene, and carbon black, and the content of the ultrahigh molecular weight polyethylene is the above rubber. 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the component, and the content of the carbon black is 25 to 45 parts by mass with respect to 100 parts by mass of the rubber component. The specific surface area is 85 to 160 m ² / g, and the dibutyl phthalate oil absorption is 105 to 140 ml / 100 g.

Description

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

  A rubber belt used as a conveyor belt is a core (hereinafter referred to as “reinforcing layer”) made of canvas or steel cord, and the upper and lower surfaces of the core are covered with an upper cover rubber layer and a lower cover rubber layer, respectively. It is a laminated structure. This rubber belt is processed into a loop-shaped conveyor belt with both ends joined to each other, and circulates and drives a conveyance path formed by a large number of rollers and pulleys. A belt conveyor that continuously conveys bulk materials such as grains; bulk items such as boxes, bags, and pallets; etc.) along the conveyance path.

  The belt conveyor drives the conveyor belt by rotating the pulley. It is known that the power consumption at this time generally increases when the conveying path is long and the belt conveyor becomes a long machine length. This is thought to be because the number of rollers that support the conveyor belt increases as the machine length increases, so that the power loss (energy loss) caused by the contact between the lower belt rubber layer of the conveyor belt and the roller increases. .

  In contrast, Patent Document 1 contains “natural rubber (NR) and butadiene rubber (BR), and the mass ratio (NR / BR) of the natural rubber (NR) and the butadiene rubber (BR) is 90. The rubber component which is / 10-55 / 45, ultra high molecular weight polyethylene, and carbon black are contained, and the content of the ultra high molecular weight polyethylene is 5 to 22 parts by mass with respect to 100 parts by mass of the rubber component. Yes, the carbon black content is 5 to 55 parts by mass with respect to 100 parts by mass of the rubber component, and the fatty acid amide content is less than 5 parts by mass with respect to 100 parts by mass of the rubber component. "Conveyor belt rubber composition" and "Conveyor belt using at least the lower cover rubber" as a composition thereof are described ([Claim 1] [Claim 4]).

JP 2012-57001 A

Here, it is known that the cover rubber layer of the conveyor belt is gradually broken in a minute region due to friction repeatedly generated between the conveyor belt and the object to be conveyed. This phenomenon is referred to as wear, and the strength against wear of the cover rubber layer (wear resistance) is directly related to the useful life of the conveyor belt itself, so that the cover rubber layer is required to have excellent wear resistance.
And when this inventor examined the conveyor belt which used the rubber composition of patent document 1 for the cover rubber layer, it discovered that the abrasion resistance of the cover rubber layer was not enough.

  Then, this invention makes it a subject to provide the rubber composition for conveyor belts which can produce the conveyor belt which has the cover rubber layer excellent in abrasion resistance, and a conveyor belt using the same.

As a result of intensive studies to solve the above-mentioned problems, the present inventor made the rubber component containing a predetermined amount of butadiene rubber contain ultrahigh molecular weight polyethylene and carbon black having predetermined characteristics, thereby providing wear resistance. It has been found that a rubber composition for a conveyor belt capable of producing a conveyor belt having a cover rubber layer having excellent properties and a conveyor belt using the same can be obtained.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) containing a rubber component containing 45 to 100% by mass of butadiene rubber, ultrahigh molecular weight polyethylene, and carbon black;
The ultra high molecular weight polyethylene content is 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the rubber component,
The carbon black content is 25 to 45 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for a conveyor belt, wherein the carbon black has a nitrogen adsorption specific surface area of 85 to 160 m ² / g and a dibutyl phthalate oil absorption of 105 to 140 ml / 100 g.
(2) The rubber composition for conveyor belts according to (1), wherein the butadiene rubber has a weight average molecular weight of 500,000 to 1,000,000.
(3) The ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index (LCB value) of the butadiene rubber (weight average molecular weight / long chain branching index) is 5.5 × 10 ^{4 to} 16.6 × 10 ⁴ . The rubber composition for conveyor belts according to (1) or (2).
(4) The rubber composition for conveyor belts according to any one of (1) to (3), wherein the ultra high molecular weight polyethylene has a viscosity average molecular weight of 500,000 to 4,000,000.
(5) It has an upper surface cover rubber layer, a reinforcing layer, and a lower surface cover rubber layer. Conveyor belt.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for conveyor belts which can produce the conveyor belt which has the cover rubber layer excellent in abrasion resistance, and a conveyor belt using the same can be provided.

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

  Hereinafter, the present invention will be described in detail.

  The rubber composition for conveyor belts according to the present invention is characterized in that a rubber component containing a predetermined amount of butadiene rubber contains ultrahigh molecular weight polyethylene and carbon black having predetermined characteristics. In order to improve the wear resistance of the cover belt layer of the conveyor belt, the present inventor is required to use a rubber composition for a conveyor belt after vulcanization (hereinafter simply referred to as “rubber composition after vulcanization”). In addition to the results of the conventional wear resistance test, the stress (hereinafter referred to as “M50”) and loss tangent (tan δ) when the specimen is stretched 50% in the tensile test are controlled. This is the first thing that can be achieved through the formulation design after knowing that is important.

  The wear of the cover rubber layer of the conveyor belt is, for example, an upper surface cover rubber layer, which is a destruction phenomenon of the rubber composition after vulcanization in a minute region caused by friction between the object to be conveyed and the cover rubber layer. The amount of wear increases as the frictional force between the individuals that rub against each other increases, and the frictional force varies depending on various factors such as load, sliding speed, surface roughness, and ambient temperature. This indicates that when the environment in which the conveyor belt is used is different, the main factor that causes wear, that is, the factor that affects the frictional force is different. Therefore, as in the past, a conveyor belt having a cover rubber layer with excellent wear resistance can be produced even if a compounding design is performed by paying attention only to the numerical value of the abrasion resistance test result of the vulcanized rubber composition. It was difficult to obtain a rubber composition for a conveyor belt and a conveyor belt using the same.

However, as a result of diligent study by the present inventor, in addition to the results of the abrasion resistance test for the rubber composition after vulcanization, the compounding design is performed by paying attention to the M50 and loss tangent of the rubber composition after vulcanization. It has been found that a rubber composition for a conveyor belt capable of producing a conveyor belt having a cover rubber layer excellent in wear resistance, and a conveyor belt using the same can be obtained.
That is, the inventor of the present invention expresses the basic principle of solid friction in which the friction force F generated between individuals is represented by the sum of the adhesion term F _s , hysteresis term F _e , and digging friction term F _p (F = F _s + F _e + F _p ). Is applied to the analysis of conveyor belt wear, and it is found that it can improve the wear resistance by controlling the pico wear, M50 and loss tangent of the rubber composition after vulcanization. The invention has been completed.

The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Rubber composition for conveyor belts]
A rubber composition for a conveyor belt according to an embodiment of the present invention (hereinafter referred to as “the rubber composition of the present invention”) includes a rubber component containing 45 to 100 mass% of butadiene rubber, ultrahigh molecular weight polyethylene, carbon And the content of the ultra high molecular weight polyethylene is 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the carbon black is 100 parts by mass of the rubber component. The rubber composition for conveyor belts, wherein the carbon black has a nitrogen adsorption specific surface area of 85 to 160 m ² / g and a dibutyl phthalate oil absorption of 105 to 140 ml / 100 g. is there.
Below, each component contained in the rubber composition of this invention is demonstrated.

[Rubber component]
The rubber component contained in the rubber composition of the present invention contains 45 to 100% by mass of butadiene rubber (BR). When the content of butadiene rubber is less than the lower limit, M50 decreases, loss tangent and pico wear increase, and wear resistance is poor.
Further, the content of butadiene rubber (BR) in the rubber component is preferably 55 to 100% by mass, more preferably 75 to 95% by mass, and further preferably 85 to 90% by mass. . If the content of butadiene rubber (BR) is equal to or greater than the lower limit, the vulcanizate of the rubber composition of the present invention is more excellent in wear resistance when used for a cover rubber layer of a heavy load and low speed operation conveyor belt. Have sex. Moreover, if content of butadiene rubber (BR) is below an upper limit, a rubber composition will have the outstanding workability.

The rubber component may contain rubber other than butadiene rubber (BR). Examples of rubber other than butadiene rubber (BR) include natural rubber (NR), isoprene rubber, styrene-butadiene rubber, and ethylene-propylene-diene rubber. Of these, natural rubber (NR) is preferred because of its excellent compatibility with butadiene rubber (BR).
When natural rubber (NR) is contained in the rubber component, the content mass ratio (NR / BR) of the content of natural rubber (NR) to the content of butadiene rubber (BR) in the rubber component is 10 / 90-55 / 45 is preferable, 20 / 85-45 / 55 is more preferable, and 25 / 75-45 / 55 is still more preferable. When NR / BR is within this range, the loss tangent of the rubber composition after vulcanization becomes smaller, and when the vulcanized product of the rubber composition of the present invention is used for the cover rubber layer of a conveyor belt operating at high speed. , Have better wear resistance.

<Butadiene rubber (BR)>
The weight average molecular weight of butadiene rubber (BR) in the rubber component is preferably 500,000 to 1,000,000, and more preferably 700,000 to 1,000,000. When the weight average molecular weight is from 500,000 to 1,000,000, the M50 in the rubber composition after vulcanization is larger and the loss tangent tends to be smaller. When used for the cover rubber layer of a high-speed conveyor belt, it has better wear resistance.
In addition, a weight average molecular weight is a weight average molecular weight (polystyrene conversion) measured by gel permeation chromatography (Gel permeation chromatography (GPC)), and it is preferable to use tetrahydrofuran (THF) as a solvent for the measurement.

40-90 are preferable and, as for the Mooney viscosity in the unvulcanized state of the said butadiene rubber (BR), 50-80 are more preferable. When the Mooney viscosity of butadiene rubber (BR) is within this range, the processability of the rubber composition is more excellent.
The Mooney viscosity is a Mooney viscosity (ML1 + 4) at 100 ° C. measured using a Mooney viscometer in accordance with JIS K6300.

The ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index (LCB value) of the butadiene rubber (BR) (weight average molecular weight / long chain branching index) is 5.5 × 10 ^{4 to} 16.6 × 10 ^4. Is preferably 5.8 × 10 ^{4 to} 15.3 × 10 ⁴ , more preferably 7.5 × 10 ^{4 to} 14.2 × 10 ⁴ , and 8.2 ×. it is particularly preferably 10 ⁴ ~14.2 × 10 ^4. When the ratio of the weight average molecular weight to the long chain branching index (LCB value) is 5.5 × 10 ^{4 to} 16.6 × 10 ⁴ , the M50 in the rubber composition after vulcanization is larger, and the loss tangent is more When the vulcanizate of the rubber composition of the present invention is used for a cover rubber layer of a conveyor belt with a small load and / or a high speed operation, the wear resistance is more excellent.
In this specification, the long chain branching index (LCB value: Long Chain Branch) is a value measured by a LAOS (Large Amplitude Oscillation Shear) measurement method using an RPA2000 type tester (manufactured by Alpha Technologies). . The long chain branching index indicates that the polymer obtained has a higher degree of linearity and a lower degree of branching as the obtained numerical value approaches zero. Therefore, the ratio of the weight average molecular weight to the long chain branching index (LCB value) is considered to have a positive correlation with the number of molecular chain terminals per unit amount of the butadiene rubber, and this value is within the above range. Thus, it is presumed that the effect of reducing the loss tangent in particular is obtained. For details of the long chain branching index (LCB value), see “FT-Rheology, a Tool to Quantify Long Chain Branching (LCB) in Natural Rubber and its Effect on Mastication, Mixing Behavior and Final Properties.” (Henri G. Burhin, Alpha Technologies, UK 15 Rue du Culot B-1435 Hevillers, Belgium).

When the rubber composition contains two or more butadiene rubbers, the ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index (LCB value) (weight average molecular weight / long chain branching index) is Can be calculated.
Formula: M / L = Σ {(M _i / L _i ) × a _i }
In the above formula, M / L represents the ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index (LCB value), and M _i , L _i , and a _i are each the weight average molecular weight of each butadiene rubber. Represents the mass fraction of each butadiene rubber relative to the total butadiene rubber contained in the rubber composition, and Σ represents the sum.

  The butadiene rubber (BR) can be synthesized by a known method, and can be produced, for example, by polymerizing butadiene in an inert organic solvent in the presence of a catalyst containing a transition metal compound. Examples of the catalyst include cobalt, vanadium, lithium, nickel, and neodymium. Of these, cobalt and neodymium are preferable, and neodymium is more preferable. Butadiene rubber obtained by polymerizing butadiene in the presence of a neodymium-based catalyst is easy to be linear with few branches in the microstructure, and as described above, the loss tangent of the rubber composition after vulcanization is smaller. Prone.

[Ultra high molecular weight polyethylene]
The rubber composition of the present invention contains ultra high molecular weight polyethylene (U-PE). Thereby, M50 can be enlarged, maintaining the loss tangent of the rubber composition after vulcanization. Ultra-high molecular weight polyethylene has poor compatibility with the butadiene rubber in the rubber component, and blending this has little effect on the loss tangent of the rubber component itself, while U-PE is dispersed in the rubber component. Therefore, it is estimated that it contributed to the improvement of M50.

  Content of the said ultra high molecular weight polyethylene (U-PE) is 1.0-15.0 mass parts with respect to 100 mass parts of said rubber components. When the content of ultrahigh molecular weight polyethylene (U-PE) is smaller than the lower limit value, the M50 of the rubber composition after vulcanization is small and the wear resistance is inferior. On the other hand, if it is larger than the upper limit value, loss tangent and pico wear increase, and as a result, the wear resistance of the rubber composition after vulcanization is inferior. Especially, 1.0-12.0 mass parts is more preferable, and 1.0-10.0 mass parts is more preferable at the point which the rubber composition after vulcanization has the outstanding bending resistance.

The molecular weight of the ultra high molecular weight polyethylene (U-PE) is preferably a viscosity average molecular weight of 500,000 to 4,000,000, more preferably 1,000,000 to 3,000,000. When the molecular weight is within this range, M50 is further improved and the processability is hardly impaired.
The viscosity average molecular weight of ultra high molecular weight polyethylene (U-PE) is a molecular weight measured by an intrinsic viscosity method (ASTM D4020-11 X5. NOMINAL VISCOSITY AVERAGE MOLECULAR WEIGHT OF ULTRA-HIGH MOLECULAR-WEIGHT POLYETLEENE).

Moreover, it is preferable that the average particle diameter of the said ultra high molecular weight polyethylene (U-PE) is 1-300 micrometers, and it is more preferable that it is 10-50 micrometers. If the average particle size is within this range, the dispersibility in the rubber tends to be good.
The ultra high molecular weight polyethylene (U-PE) is available as, for example, Mipelon XM220 (manufactured by Mitsui Chemicals), Hi-Zex Million 340M (manufactured by Mitsui Chemicals), or the like.

〔Carbon black〕
The rubber composition of the present invention contains carbon black (CB). Content of the said carbon black (CB) is 25-45 mass parts with respect to 100 mass parts of said rubber components, and 30-40 mass parts is preferable. When the content of carbon black (CB) is less than the lower limit, the M50 of the rubber composition after vulcanization is small and pico wear is also increased, resulting in poor wear resistance of the rubber composition after vulcanization. . On the other hand, if it is larger than the upper limit value, the loss tangent increases, resulting in poor wear resistance after vulcanization.

The carbon black contained in the rubber composition of the present invention has a nitrogen adsorption specific surface area of 85 to 160 m ² / g and a dibutyl phthalate oil absorption of 105 to 140 ml / 100 g. When carbon black (CB) having the above characteristics is not contained, M50 of the rubber composition after vulcanization is small and pico abrasion is increased, resulting in poor wear resistance of the rubber composition after vulcanization.
Examples of such carbon black include SAF, ISAF-HS, ISAF-LS, and HAF-HS grades, and the rubber composition after vulcanization has a larger M50 and a smaller loss tangent. HAF-HS, ISAF-HS, and ISAF-LS grades are more preferred in that the rubber composition after vulcanization is more excellent in wear resistance.
Commercially available carbon black is available as Show Black N110, N234, N220, N339 (all manufactured by Cabot Japan).
Further, the nitrogen adsorption ratio of carbon black (CB) in that the M50 of the rubber composition after vulcanization is larger and the loss tangent is smaller, and as a result the wear resistance of the rubber composition after vulcanization is more excellent. More preferably, the surface area is 85 to 125 m ² / g and the dibutyl phthalate oil absorption is 110 to 125 ml / 100 g.
The nitrogen adsorption specific surface area is a value measured in accordance with ASTM D4820-93, and is an index representing the small particle diameter of carbon black particles. The dibutyl phthalate oil absorption is in accordance with ASTM D2414-93. It is an index that represents the degree of connection of carbon black particles, the so-called structure size (complexity of shape).

[Others]
The rubber composition of the present invention may contain a crosslinking agent or a vulcanization retarder such as a vulcanizing agent, a vulcanization aid, and a vulcanization accelerator in addition to the above-described components. Various compounding agents may be contained as long as the purpose is not impaired.

Examples of the vulcanizing agent include sulfur-based, organic peroxide-based, metal oxide-based, phenol resins, quinone dioxime vulcanizing agents, and the like.
Examples of the sulfur vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide and the like.

Examples of vulcanization accelerators include aldehyde / ammonia, guanidine, thiourea, thiazole, sulfenamide, thiuram, and dithiocarbamate vulcanization accelerators.
Specific examples of sulfenamide vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide (CZ), Nt-butyl-2-benzothiazolylsulfenamide (NS ) And the like.

  As the vulcanization aid, general rubber aids can be used together, and examples thereof include zinc white, stearic acid, oleic acid, and Zn salts thereof.

  The total content in the case of containing such a vulcanizing agent, a vulcanization accelerator and a vulcanizing aid is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component, More preferably, it is 0.5-5 mass parts. When the content range is within this range, the effect of the present invention is superior.

Examples of compounding agents include reinforcing agents (fillers) other than the above-described carbon black, anti-aging agents, antioxidants, pigments (dyes), plasticizers, thixotropic agents, ultraviolet absorbers, flame retardants, solvents, Surfactants (including leveling agents), dispersants, dehydrating agents, rust preventives, adhesion-imparting agents, antistatic agents, processing aids and the like can be mentioned.
As these compounding agents, those generally used for rubber compositions can be used. Their blending amounts are not particularly limited and can be arbitrarily selected.

[Production method]
The rubber composition of the present invention is prepared by adding the above-mentioned rubber component, ultrahigh molecular weight polyethylene, carbon black, and other various compounding agents, kneading with a Banbury mixer or the like, and then using a mixing roll machine or the like with a vulcanizing agent or a vulcanizing agent. It can be carried out by kneading a vulcanization aid and a vulcanization accelerator.
Further, vulcanization can be carried out under the usual conditions. Specifically, for example, it is carried out by heating at a temperature of about 148 ° C. for 30 minutes.

[Conveyor belt using rubber composition for conveyor belt]
〔Constitution〕
A conveyor belt according to an embodiment of the present invention (hereinafter referred to as “conveyor belt of the present invention”) includes an upper surface cover rubber layer, a reinforcing layer, and a lower surface cover rubber layer. It is a conveyor belt using the rubber composition of the present invention.
Below, the conveyor belt of this invention is demonstrated using FIG. 1, However, The structure of the conveyor belt of this invention is not limited to this. For example, you may use the rubber composition of this invention for an upper surface cover rubber layer and a lower surface cover rubber layer.

FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of a conveyor belt according to the present invention. The conveyor belt 10 is a laminated structure in which a reinforcing layer 1 and upper and lower surfaces thereof are covered with an upper cover rubber layer 2 and a lower cover rubber layer 3.
The top cover rubber layer 2 has an outer layer 2a and an inner layer 2b in order from the conveying surface 4 side. Similarly, the lower surface cover rubber layer 3 also has an outer layer 3a and an inner layer 3b in order from a surface in contact with a drive pulley or roller of a belt conveyor (not shown). These outer layers (2a, 3a) and inner layers (2b, 3b) may be formed using the same rubber composition, or may be formed using different rubber compositions. The outer layers (2a, 3a) and the inner layers (2b, 3b) may have a multilayer structure.

  The conveyor belt 10 is a conveyor belt using the rubber composition of the present invention for at least the upper cover rubber layer 2. Therefore, at least one layer selected from the group consisting of the outer layer 2a and the inner layer 2b may be formed using the rubber composition of the present invention. The rubber composition of the present invention is preferable as a rubber composition used for the outer layer 2a that is in direct contact with the object to be conveyed. On the other hand, the inner layer 2b is preferably formed using another rubber composition because manufacturing costs and adhesiveness with the reinforcing layer 1 are important. For the above reasons, the upper cover rubber layer 2 is composed of a plurality of layers. It is preferable that it is comprised.

  Similarly, the lower cover rubber layer 3 of the conveyor belt 10 is preferably composed of a plurality of layers. At this time, the rubber composition of the present invention may be used for either or both of the outer layer 3a and the inner layer 3b, or a rubber composition different from the rubber composition of the present invention may be used for the outer layer 3a and the inner layer 3b. good.

The core of the reinforcing layer 1 is not particularly limited and can be appropriately selected from those used for ordinary conveyor belts. For example, a rubber paste is applied to a material composed of cotton cloth and chemical fiber or synthetic fiber, and infiltrated. And those obtained by folding a material treated with RFL (Resorcin Formalin Latex), canvas, special woven nylon canvas, steel cord, and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.
Moreover, the shape of the reinforcement layer 1 is not specifically limited, A sheet form may be sufficient and a wire-shaped reinforcement wire may be embedded in parallel.

  The manufacturing method of the conveyor belt 10 is not specifically limited, The method etc. which are normally used are employable. Specifically, first, the rubber composition of the present invention or other rubber composition is kneaded using a roll, a kneader, a Banbury mixer or the like, and then the top cover rubber layer 2 is used using a calender roll or the like. And the bottom cover rubber layer 3 is formed into a sheet shape, and then the obtained layers are laminated in a predetermined order so as to sandwich the reinforcing layer 1 and pressed at a temperature of 130 to 170 ° C. for 5 to 30 minutes. Is done.

  The conveyor belt 10 of the present invention is excellent in wear resistance because the upper cover rubber layer 2, preferably the outer layer 2a thereof, is formed using the rubber composition of the present invention.

  Hereinafter, the present invention will be described in more detail based on examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples.

[Preparation of rubber composition and rubber composition after vulcanization]
Each component shown in Table 1 was blended in the blending amount (parts by mass) shown in the same table, and these were uniformly kneaded using a Banbury mixer. The rubber compositions of the examples and comparative examples shown in Table 1 A product was prepared. The obtained rubber composition was vulcanized at 148 ° C. for 30 minutes to prepare a vulcanized rubber composition.

[Physical properties after vulcanization]
<M50>
Using a test piece punched out from each prepared vulcanized rubber composition into a No. 3 dumbbell shape, a tensile test was conducted at a tensile speed of 500 mm / min according to JIS K6251-2004, and M50 (MPa) was brought to room temperature. Measured. The obtained results are shown in Table 1 as an index with Comparative Example 1 as 100. The larger this value, the better the abrasion resistance when used for the cover rubber layer of a conveyor belt with a small load.
<Loss tangent (tan δ)>
The loss tangent (tan δ) was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho using a test piece cut into a strip shape (length 20 mm × width 5 mm × thickness 2 mm) from each vulcanized rubber composition prepared. did. The measurement was performed by extending 10% at a measurement temperature of 20 ° C. and applying vibration with an amplitude of ± 2% at a frequency of 10 Hz. The obtained results are shown in Table 1 as an index with Comparative Example 1 as 100. The smaller this value, the better the wear resistance when used for the cover rubber layer of a conveyor belt operating at high speed.
<Pico wear>
According to JIS K6264, the rubber composition after vulcanization was subjected to FERRY MACHINE CO. It measured using the Pico abrasion tester by a company. The measurement conditions were a load 44N, a turntable rotation speed of 60 ± 2 times per minute, and a total turntable rotation speed of 80 times (20 forward rotations and 20 reverse rotations were alternately performed twice each). The obtained results are shown in Table 1 as an index with Comparative Example 1 as 100. The smaller this index is, the better the wear resistance is when it is used for the cover rubber layer of a conveyor belt with a heavy load and low speed operation.

As each composition component shown in Table 1, the following components were used.
・ NR: Natural rubber (RSS # 3)
BR1: Butadiene rubber (Nipol BR1220, weight average molecular weight 460,000, manufactured by Nippon Zeon, long chain branching index 9.5, Mooney viscosity 44, butadiene rubber obtained by polymerizing butadiene in the presence of a cobalt-based catalyst)
BR2: Butadiene rubber (Ubepol BR-360L, weight average molecular weight 560,000, manufactured by Ube Industries, long chain branching index 7.3, Mooney viscosity 54, butadiene obtained by polymerizing butadiene in the presence of a cobalt-based catalyst Rubber)
BR3: Butadiene rubber (Buna CB21, weight average molecular weight 770,000, manufactured by LANXESS, long chain branching index 8.5, Mooney viscosity 73, butadiene rubber obtained by polymerizing butadiene in the presence of a neodymium catalyst)
CB1: carbon black (show black N110, nitrogen adsorption specific surface area 144 m ² / g, dibutyl phthalate oil absorption 115 ml / 100 g, SAF grade, manufactured by Cabot Japan)
CB2: carbon black (show black N234, nitrogen adsorption specific surface area 123 m ² / g, dibutyl phthalate oil absorption 123 ml / 100 g, ISAF-HS grade, manufactured by Cabot Japan)
CB3: carbon black (show black N326, nitrogen adsorption specific surface area 81 m ² / g, dibutyl phthalate oil absorption 75 ml / 100 g, HAF-LS grade, manufactured by Cabot Japan)
CB4: carbon black (show black N220, nitrogen adsorption specific surface area 111 m ² / g, dibutyl phthalate oil absorption 115 ml / 100 g, ISAF-LS grade, manufactured by Cabot Japan)
CB5: carbon black (show black N339, nitrogen adsorption specific surface area 88 m ² / g, dibutyl phthalate oil absorption 121 ml / 100 g, HAF-HS grade, manufactured by Cabot Japan)
U-PE: Ultra high molecular weight polyethylene (Miperon XM220, viscosity average molecular weight 2.2 million, average particle size 20 μm, manufactured by Mitsui Chemicals)
Anti-aging agent 6C: Antigen 6C (Sumitomo Chemical Co., Ltd.)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Stearic acid YR (manufactured by NOF Corporation)
Paraffin wax: OZOACE-0015 (manufactured by Nippon Seiwa Co., Ltd.)
Aroma oil: A-OMIX (Sankyo Oil Chemical Co., Ltd.)
・ Vulcanization accelerator NS: Noxeller NS-P (Ouchi Shinsei Chemical Co., Ltd.)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)

From the results shown in Table 1, Example 1 is superior to Comparative Example 1 in that M50 of the rubber composition after vulcanization is large, loss tangent (tan δ) and pico wear are small, and wear resistance is excellent. all right. In Comparative Example 1 and Comparative Examples 2 to 5, the desired effect was not obtained.
Comparing Example 1, Example 2 and Example 3, Example 2 and Example 3 containing BR having a weight average molecular weight of 500,000 to 1,000,000 are more excellent in M50 and loss tangent after vulcanization. It has been found that when used in a cover rubber layer of a conveyor belt that is lightly loaded and / or operated at high speed, it has better wear resistance. Among them, Example 3 in which the ratio (weight average molecular weight / long chain branching index) of the weight average molecular weight and long chain branching index (LCB value) of the butadiene rubber contained is 9.0 × 10 ⁴ is 7.6 × 10 6. ^As compared with Example 2 which is ⁴ , it was found that M50 and loss tangent after vulcanization were further improved.
Further, when Examples 6, 10, and 11 are compared with Example 1, carbon black (CB) has a nitrogen adsorption specific surface area of 85 to 125 m ² / g and a dibutyl phthalate oil absorption of 110 to 125 ml / g. It was found that when it was 100 g, the M50 of the rubber composition after vulcanization was larger and the loss tangent was smaller, and as a result, the rubber composition after vulcanization was more excellent in wear resistance.

DESCRIPTION OF SYMBOLS 10 Conveyor belt 1 Reinforcement layer 2 Upper surface cover rubber layer 3 Lower surface cover rubber layer 2a, 3a Outer layer 2b, 3b Inner layer 4 Conveying surface

Claims (5)

Containing a rubber component containing 45 to 100% by mass of butadiene rubber, ultrahigh molecular weight polyethylene, and carbon black;
The ultra high molecular weight polyethylene content is 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the rubber component,
The content of the carbon black is 25 to 45 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for a conveyor belt, wherein the carbon black has a nitrogen adsorption specific surface area of 85 to 160 m ² / g and a dibutyl phthalate oil absorption of 105 to 140 ml / 100 g.   The rubber composition for conveyor belts according to claim 1, wherein the butadiene rubber has a weight average molecular weight of 500,000 to 1,000,000. The rubber composition for a conveyor belt according to claim 1 or 2, wherein a ratio of a weight average molecular weight of the butadiene rubber to a long-chain branching index of the butadiene rubber is 5.5 x 10 ^{4 to} 16.6 x 10 ⁴ . .   The rubber composition for conveyor belts of any one of Claims 1-3 whose viscosity average molecular weights of the said ultra high molecular weight polyethylene are 500,000-4 million. An upper cover rubber layer, a reinforcing layer, and a lower cover rubber layer;
The conveyor belt using the rubber composition for conveyor belts of any one of Claims 1-4 for the said upper surface cover rubber layer at least.