JP6904328B2 - Rubber composition for conveyor belts and conveyor belts - Google Patents

Description

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

The rubber belt used as a conveyor belt has a core made of canvas, steel cord, etc. (hereinafter referred to as "reinforcing layer"), and the upper and lower surfaces of the core are covered with an upper surface cover rubber layer and a lower surface cover rubber layer, respectively. It is a laminated structure. This rubber belt is processed into a loop-shaped conveyor belt by joining both ends to each other, and by circulating driving a transport path formed by a large number of rollers and pulleys, the transported object (for example, ore, earth and sand, and sediment) It constitutes a belt conveyor that continuously conveys loose objects such as grains; bags such as boxes, bags, and pallets; etc.) along the above-mentioned transport path.

The belt conveyor drives the conveyor belt by rotating the pulley. It is known that the power consumption at this time is generally longer when the transport path is long and increases when the belt conveyor has a long machine length. It is thought that this is because the number of rollers that support the conveyor belt increases as the length of the machine increases, and the power loss (energy loss) caused by the contact between the rubber layer on the underside cover of the conveyor belt and the rollers increases. ..

On the other hand, Patent Document 1 states that "natural rubber (NR) and butadiene rubber (BR) are contained, and the mass ratio (NR / BR) of the natural rubber (NR) to the butadiene rubber (BR) is 90. It contains a rubber component of / 10 to 55/45, ultra-high molecular weight polyethylene, and carbon black, 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. The content of the carbon black is 5 to 55 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the fatty acid amide is less than 5 parts by mass with respect to 100 parts by mass of the rubber component. "Rubber composition for conveyor belt" and "conveyor belt using at least the composition for the bottom cover rubber" are described ([Claim 1] [Claim 4]).

Japanese Unexamined Patent Publication No. 2012-57001

Here, it is known that the cover rubber layer of the conveyor belt is gradually broken in a minute region due to repeated friction with the object to be conveyed. This phenomenon is called wear, and the resistance to wear (wear resistance) of the cover rubber layer is directly linked to the service life of the conveyor belt itself, so that the cover rubber layer is required to have excellent wear resistance.
Then, when the present inventor examined a conveyor belt using the rubber composition described in Patent Document 1 for the cover rubber layer, it was found that the wear resistance of the cover rubber layer was not sufficient.

Therefore, an object of the present invention is to provide a rubber composition for a conveyor belt capable of producing a conveyor belt having a cover rubber layer having excellent wear resistance, and a conveyor belt using the same.

As a result of diligent studies to solve the above problems, the present inventor has made the rubber component containing a predetermined amount of butadiene rubber contain ultra-high molecular weight polyethylene and carbon black having a predetermined property to resist abrasion. 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, it was found that the above problem can be solved by the following configuration.

(1) A rubber component containing 45 to 100% by mass of butadiene rubber, ultra-high molecular weight polyethylene, and carbon black are contained.
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.
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 dibutylphthalate oil absorption amount of 105 to 140 ml / 100 g.
(2) The rubber composition for a conveyor belt 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 a conveyor belt according to (1) or (2).
(4) The rubber composition for a conveyor belt 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 million.
(5) The rubber composition for a conveyor belt according to any one of (1) to (4) is used for at least the upper surface cover rubber layer having the upper surface cover rubber layer, the reinforcing layer, and the lower surface cover rubber layer. The conveyor belt that was there.

According to the present invention, it is possible to provide a rubber composition for a conveyor belt capable of producing a conveyor belt having a cover rubber layer having excellent wear resistance, and a conveyor belt using the same.

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.

One of the features of the rubber composition for a conveyor belt of the present invention is that a rubber component containing a predetermined amount of butadiene rubber contains ultra-high molecular weight polyethylene and carbon black having predetermined characteristics. This is because, in order for the present inventor to improve the wear resistance of the cover rubber layer of the conveyor belt, the rubber composition for the conveyor belt after vulcanization (hereinafter, simply referred to as "rubber composition after vulcanization") In addition to the results of the wear resistance test that has been carried out in the past, the stress when the test piece is stretched by 50% in the tensile test (hereinafter referred to as "M50") and the loss tangent (tan δ) should be controlled. This was only possible by designing the formulation after knowing that is important.

The wear of the cover rubber layer of the conveyor belt is, for example, in the case of the upper surface cover rubber layer, a destruction phenomenon of the rubber composition after vulcanization in a minute region caused by friction between the transported object and the cover rubber layer. The amount of wear increases as the frictional force between the rubbing individuals increases, and the frictional force changes depending on various factors such as load, sliding speed, surface roughness, and atmospheric temperature. This indicates that different environments in which the conveyor belt is used have different main factors that cause wear, that is, factors that affect the frictional force. Therefore, a conveyor belt having a cover rubber layer having excellent wear resistance can be produced even if the compounding design is performed by paying attention only to the numerical values of the wear resistance test results of the rubber composition after vulcanization as in the conventional case. It has been difficult to obtain a rubber composition for a conveyor belt that can be used and a conveyor belt using the same.

However, as a result of diligent studies by the present inventor, in addition to the results of the abrasion resistance test on the vulcanized rubber composition, the compounding design was performed by paying attention to the M50 of the vulcanized rubber composition and the loss direct contact. , 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 wear resistance, and a conveyor belt using the rubber composition can be obtained.
That is, the present inventor expresses the frictional force F generated between individuals by _{the sum of the adhesion term F s} , the hysteresis term F _e , and the digging friction term F _p (F = F _s + F _e + F _p ), which is the basic principle of solid friction. By applying the above to the abrasion analysis of the conveyor belt, it was found that the pico wear, M50 and loss tangent of the rubber composition after vulcanization can be controlled to improve the abrasion resistance, and the formulation design was carried out. It is the perfection of the invention.

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

[Rubber composition for conveyor belt]
The rubber composition for a conveyor belt according to the embodiment of the present invention (hereinafter, referred to as "the rubber composition of the present invention") is a rubber component containing 45 to 100% by mass of butadiene rubber, ultra-high molecular weight polyethylene, and carbon. The content of the ultra-high molecular weight polyethylene containing black 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. A rubber composition for a conveyor belt, which is 25 to 45 parts by mass, has a nitrogen adsorption ratio surface area of 85 to 160 m ² / g, and has a dibutylphthalate oil absorption amount of 105 to 140 ml / 100 g. is there.
Hereinafter, each component contained in the rubber composition of the present invention will be described.

[Rubber component]
The rubber component contained in the rubber composition of the present invention contains 45 to 100% by mass of butadiene rubber (BR). If the content of the butadiene rubber is less than the lower limit, the M50 becomes small, the loss tangent and the pico wear become large, and the wear resistance is inferior.
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 even more preferably 85 to 90% by mass. .. When the content of butadiene rubber (BR) is equal to or higher than the lower limit, better wear resistance is obtained 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 a high load and at a low speed. Has sex. Further, when the content of butadiene rubber (BR) is not more than the upper limit value, the rubber composition has excellent processability.

The rubber component may contain a rubber other than butadiene rubber (BR). Examples of rubbers 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 preferable because it has 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 with natural rubber (NR) to the content of butadiene rubber (BR) in the rubber component is 10 /. 90 to 55/45 is preferable, 20/85 to 45/55 is more preferable, and 25/75 to 45/55 is even more preferable. When NR / BR is in 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 high-speed operation conveyor belt. , Has better wear resistance.

<butadiene rubber (BR)>
The weight average molecular weight of the butadiene rubber (BR) in the rubber component is preferably 500,000 to 1,000,000, more preferably 700,000 to 1,000,000. When the weight average molecular weight is 500,000 to 1,000,000, the M50 in the vulcanized rubber composition is larger, the loss tangent is likely to be smaller, and the vulcanized product of the rubber composition of the present invention is subjected to a small load and / or It has better wear resistance when used as a cover rubber layer for high-speed conveyor belts.
The weight average molecular weight is a weight average molecular weight (polystyrene equivalent) measured by gel permeation chromatography (GPC), and tetrahydrofuran (THF) is preferably used as a solvent for the measurement.

The Mooney viscosity of the butadiene rubber (BR) in the unvulcanized state is preferably 40 to 90, more preferably 50 to 80. When the Mooney viscosity of the butadiene rubber (BR) is in this range, the processability of the rubber composition is more excellent.
The Mooney viscosity is the 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, more preferably from ^{5.8 × 10 4 ~15.3 × 10 4} , more preferably from ^{7.5 × 10 4 ~14.2 × 10 4} , 8.2 × It is particularly preferably 10 ^{4 to} 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 vulcanized rubber composition is larger and the loss tangent is larger. It tends to be small and has better wear resistance when the vulcanized product of the rubber composition of the present invention is used for the cover rubber layer of a conveyor belt with a small load and / or high speed operation.
In the present specification, the long chain branching index (LCB value: Long Chain Branch) is a value measured by a LAOS (Large Amplitude Oscillation Shear) measuring method using an RPA2000 type testing machine (manufactured by Alpha Technologies). .. The long-chain bifurcation index indicates that the closer the obtained value is to zero, the higher the linearity of the polymer and the lower the degree of bifurcation. 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. Therefore, it is presumed that the effect of reducing the loss tangent was obtained. For details on 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) etc. can be referred to.

When the rubber composition contains two or more types of butadiene rubber, 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 as follows. Can be calculated by.
Formula: M / L = Σ {(M _i / Li _i ) × a _i }
In the above formula, M / L is for the long chain branching index (LCB value) represents the ratio of the weight average molecular weight of butadiene rubber, M _{i, L i,} and each is a _i, a weight average molecular weight of each butadiene rubber , LCB value, and the mass ratio of each butadiene rubber to the total butadiene rubber contained in the rubber composition, and Σ represents the total.

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-based, vanadium-based, lithium-based, nickel-based, and neodymium-based catalysts. Of these, cobalt-based and neodymium-based are preferable, and neodymium-based is more preferable. Butadiene rubber obtained by polymerizing butadiene in the presence of a neodymium-based catalyst has few branches and tends to be linear in its 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). As a result, M50 can be increased while maintaining the loss tangent of the rubber composition after vulcanization. Ultra-high molecular weight polyethylene has poor compatibility with butadiene rubber in the above rubber component, and by blending this, U-PE is dispersed in the rubber component while having little effect on the loss tangent of the rubber component itself. It is presumed that this contributed to the improvement of M50.

The content of the ultra-high molecular weight polyethylene (U-PE) is 1.0 to 15.0 parts by mass with respect to 100 parts by mass of the rubber component. When the content of ultra-high molecular weight polyethylene (U-PE) is smaller than the lower limit, the M50 of the vulcanized rubber composition is small and the wear resistance is inferior. On the other hand, if it is larger than the upper limit, the loss tangent and the pico wear become large, and as a result, the wear resistance of the rubber composition after vulcanization is deteriorated. Among them, 1.0 to 12.0 parts by mass is more preferable, and 1.0 to 10.0 parts by mass is more preferable, in that the rubber composition after vulcanization has excellent bending resistance.

As the molecular weight of the ultra-high molecular weight polyethylene (U-PE), the viscosity average molecular weight is preferably 500,000 to 4 million, more preferably 1 million to 3 million. When the molecular weight is in this range, M50 is further improved and the workability is not easily impaired.
The viscosity average molecular weight of ultra-high molecular weight polyethylene (U-PE) is measured by the intrinsic viscosity method (ASTM D4020-11 X5. NOMINAL VISCOSITY AVERAGE MOLECULAR WEIGHT OF ULTRA-HIGH MOLECULAR-WEIGHT POLYETHYLE).

The average particle size of the ultra-high molecular weight polyethylene (U-PE) is preferably 1 to 300 μm, more preferably 10 to 50 μm. When the average particle size is in this range, the dispersibility in the rubber tends to be good.
The ultra-high molecular weight polyethylene (U-PE) is available as, for example, Miperon XM220 (manufactured by Mitsui Chemicals, Inc.), Hi-Zex Million 340M (manufactured by Mitsui Chemicals, Inc.) and the like.

〔Carbon black〕
The rubber composition of the present invention contains carbon black (CB). The content of the carbon black (CB) is 25 to 45 parts by mass, preferably 30 to 40 parts by mass, with respect to 100 parts by mass of the rubber component. If the content of carbon black (CB) is less than the lower limit, the M50 of the vulcanized rubber composition is small and the pico wear is also large, resulting in inferior wear resistance of the vulcanized rubber composition. .. On the other hand, if it is larger than the upper limit, the loss tangent becomes large, and as a result, the wear resistance after vulcanization is inferior.

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, the M50 of the vulcanized rubber composition is small, the pico wear is large, and as a result, the wear resistance of the vulcanized rubber composition is inferior.
Examples of such carbon black include SAF, ISAF-HS, ISAF-LS, and HAF-HS grades, in which the rubber composition after vulcanization has a larger M50 and a smaller loss tangent, resulting in a smaller loss tangent. HAF-HS, ISAF-HS, and ISAF-LS grades are more preferred in that the rubber composition after vulcanization has better wear resistance.
As commercially available carbon black products, they are available as Show Black N110, N234, N220, and N339 (all manufactured by Cabot Japan).
In addition, the carbon black (CB) nitrogen adsorption ratio is such that the M50 of the vulcanized rubber composition is larger, the loss tangent is smaller, and as a result, the wear resistance of the vulcanized rubber composition is better. More preferably, the surface area is 85 to 125 m ² / g and the dibutylphthalate oil absorption is 110 to 125 ml / 100 g.
The nitrogen adsorption specific surface area is a value measured according to ASTM D4820-93, which is an index indicating the small particle size of carbon black particles, and the amount of dibutylphthalate oil absorbed is based on ASTM D2414-93. It is an index showing the degree of connection of carbon black particles, the so-called structure size (complexity of shape).

[Other]
In addition to the above-mentioned components, the rubber composition of the present invention may contain a cross-linking agent such as a vulcanizing agent, a vulcanization aid, a vulcanization accelerator, or a vulcanization retarder, and further, the present invention Various compounding agents may be contained as long as the purpose is not impaired.

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

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

As the vulcanization aid, a general rubber aid can be used in combination, and examples thereof include zinc oxide, stearic acid, oleic acid, and Zn salts thereof.

When such a vulcanizing agent, a vulcanization accelerator and a vulcanization aid are contained, the total content 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 to 5 parts by mass. When the content range is in this range, the effect of the present invention is more excellent.

Examples of the compounding agent include a reinforcing agent (filler) other than the above-mentioned carbon black, an antioxidant, an antioxidant, a pigment (dye), a plasticizer, a rocking modifier, an ultraviolet absorber, a flame retardant, and a solvent. Examples include surfactants (including leveling agents), dispersants, dehydrating agents, rust preventives, adhesion-imparting agents, antistatic agents, processing aids and the like.
As these compounding agents, general ones for rubber compositions can be used. The blending amount thereof is not particularly limited and can be arbitrarily selected.

[Manufacturing method]
In the rubber composition of the present invention, the above-mentioned rubber component, ultra-high molecular weight polyethylene, carbon black, and various other compounding agents contained therein are added, kneaded with a Bambari mixer or the like, and then vulcanized and added with a mixing roll machine or the like. It can be carried out by kneading a vulcanization aid and a vulcanization accelerator.
In addition, vulcanization can be carried out under the conditions normally used. Specifically, for example, it is carried out by heating under the conditions of a temperature of about 148 ° C. for 30 minutes.

[Conveyor belt using rubber composition for conveyor belt]
〔Constitution〕
The conveyor belt according to the embodiment of the present invention (hereinafter, referred to as “conveyor belt of the present invention”) has an upper surface cover rubber layer, a reinforcing layer, and a lower surface cover rubber layer, and at least the upper surface cover rubber layer It is a conveyor belt using the rubber composition of the present invention.
Hereinafter, the conveyor belt of the present invention will be described with reference to FIG. 1, but the structure of the conveyor belt of the present invention is not limited thereto. For example, the rubber composition of the present invention may be used for the upper surface cover rubber layer and the lower surface cover rubber layer.

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

The conveyor belt 10 is a conveyor belt using at least the rubber composition of the present invention for the upper surface 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 by using the rubber composition of the present invention. The rubber composition of the present invention is preferable as the rubber composition used for the outer layer 2a that comes into direct contact with the object to be transported. On the other hand, the inner layer 2b is preferably formed by using another rubber composition because the manufacturing cost and the adhesiveness with the reinforcing layer 1 are emphasized. For the above reasons, the upper surface cover rubber layer 2 is a plurality of layers. It is preferably composed of.

Similarly, the lower surface 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 body of the reinforcing layer 1 is not particularly limited, and those used for ordinary conveyor belts can be appropriately selected and used. For example, rubber glue is applied and infiltrated into a material composed of cotton cloth and chemical fibers or synthetic fibers. Examples include those made, those treated with RFL (Resorcin Formalin Latex) and folded, canvas, specially woven nylon canvas, and steel cord. These may be used individually by 1 type, and may be used in combination of 2 or more type.
Further, the shape of the reinforcing layer 1 is not particularly limited, and may be a sheet shape or a wire-shaped reinforcing wire may be embedded in parallel.

The method for manufacturing the conveyor belt 10 is not particularly limited, and a commonly used method or the like can be adopted. Specifically, first, the rubber composition of the present invention or another rubber composition is kneaded using a roll, a kneader, a Bambari mixer or the like, and then the upper surface cover rubber layer 2 is kneaded using a calendar roll or the like. And the bottom cover rubber layer 3 is formed into a sheet, 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. It is done by.

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

The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the examples shown below.

[Preparation of rubber composition and rubber composition after vulcanization]
Each component shown in Table 1 is blended in the blending amount (part by mass) shown in the same table, and these are uniformly kneaded using a Bambari mixer to uniformly knead the rubber compositions of the respective Examples and Comparative Examples shown in Table 1. The thing was prepared. The obtained rubber composition was vulcanized at 148 ° C. for 30 minutes to prepare a vulcanized rubber composition.

[Physical characteristics after vulcanization]
<M50>
Using a test piece punched into a No. 3 dumbbell shape from each of the prepared rubber compositions after vulcanization, a tensile test was performed at a tensile speed of 500 mm / min according to JIS K6251-2004, and M50 (MPa) was brought to room temperature. Was measured. The obtained results are shown in Table 1 as an index with Comparative Example 1 as 100. The larger this value is, the more excellent the wear resistance is when used for the cover rubber layer of a conveyor belt with a small load.
<Loss tangent (tan δ)>
Using a test piece cut out from each prepared rubber composition after vulcanization into a strip shape (length 20 mm x width 5 mm x thickness 2 mm), measure the loss tangent (tan δ) using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho. did. The measurement was carried out under a measurement temperature of 20 ° C. by stretching by 10% and applying vibration having 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 is, the more excellent the wear resistance is when used for the cover rubber layer of a conveyor belt operating at high speed.
<Pico wear>
Pico wear of the rubber composition after vulcanization according to JIS K6264, FERRY MACHINE CO. It was measured using a pico wear tester manufactured by the company. The measurement conditions were a load of 44 N, 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 more excellent the wear resistance is when used for the cover rubber layer of a conveyor belt that operates at a large load and at a low speed.

As each composition component shown in Table 1 above, those shown below were used.
・ NR: Natural rubber (RSS # 3)
BR1: Butadiene rubber (Nipol BR1220, weight average molecular weight 460,000, manufactured by Zeon Corporation, 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, Ltd., 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, Dibutylphthalate 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, Dibutylphthalate 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, Inc.)
・ Anti-aging agent 6C: Antigen 6C (manufactured by Sumitomo Chemical Co., Ltd.)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
-Stearic acid: YR stearic acid (manufactured by NOF CORPORATION)
-Paraffin wax: OZOACE-0015 (manufactured by Nippon Seiro Co., Ltd.)
・ Aroma oil: A-OMIX (manufactured by Sankyo Yuka Kogyo Co., Ltd.)
-Vulcanization accelerator NS: Noxeller NS-P (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
・ Sulfur: Fine sulfur powder containing Jinhua stamp oil (manufactured by Tsurumi Chemical Industry Co., Ltd.)

From the results shown in Table 1, it can be seen that Example 1 has a larger M50 of the vulcanized rubber composition, less loss tangent (tan δ) and pico wear, and is excellent in wear resistance as compared with Comparative Example 1. all right. The desired effect was not obtained in Comparative Example 1 and Comparative Examples 2 to 5.
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 have better M50 and loss tangent after vulcanization. , It was found to have better wear resistance when used in the cover rubber layer of conveyor belts with small loads and / or high speed operation. The ratio embodiment (weight average molecular weight / the long chain branching index) is 9.0 × 10 ⁴ Examples of weight average molecular weight and long chain branching index of butadiene rubber (LCB value) 3 containing among others is, 7.6 × 10 ⁴ a is compared to example 2, is M50 and loss tangent after vulcanization was found that further excellent.
Comparing Examples 6, 10 and 11 with Example 1, the nitrogen adsorption specific surface area of carbon black (CB) was 85 to 125 m ² / g, and the oil absorption of dibutylphthalate was 110 to 125 ml / g. It was found that when the amount was 100 g, the M50 of the vulcanized rubber composition was larger and the loss tangent was smaller, and as a result, the wear resistance of the vulcanized rubber composition was more excellent.

10 Conveyor belt 1 Reinforcing layer 2 Top cover rubber layer 3 Bottom cover rubber layer 2a, 3a Outer layer 2b, 3b Inner layer 4 Conveyor surface

Claims (5)

It contains a rubber component containing 75 to 100% by mass of unmodified butadiene rubber, ultra-high molecular weight polyethylene, and carbon black.
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.
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 dibutylphthalate oil absorption amount of 105 to 140 ml / 100 g. The rubber composition for a conveyor belt 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 the ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index of the butadiene rubber is 5.5 × 10 ^{4 to} 16.6 × 10 ^4. .. The rubber composition for a conveyor belt according to any one of claims 1 to 3, wherein the ultra-high molecular weight polyethylene has a viscosity average molecular weight of 500,000 to 4,000,000. It has an upper surface cover rubber layer, a reinforcing layer, and a lower surface cover rubber layer.
A conveyor belt using at least the rubber composition for a conveyor belt according to any one of claims 1 to 4 on the upper surface cover rubber layer.

Images