JP2011016876A - Rubber composition for conveyor belt and conveyor belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a conveyor belt that maintains basic physical properties such as hardness, breaking strength, and elongation at break, and sufficiently reduces power consumption, and to provide a conveyor belt.SOLUTION: The rubber composition for conveyor belts comprises a rubber component and glass balloon. The glass balloon has an average particle diameter of 20-100 μm and an average film thickness of 0.9-1.5 μm. The content of the glass balloon is 2-15 pts.mass based on 100 pts.mass of the rubber component.

Description

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

Conveyor belts are often used for transporting materials, etc., but they are required to be larger and stronger due to increased transport volume and improved transport efficiency. Has also appeared.
For this reason, equipment costs and power consumption are increasing, and there is a need for a belt conveyor system with low cost and low power consumption. In particular, by improving the rubber characteristics of the belt, the belt conveyor can be reduced in cost and power consumption. Electricity is being considered.

For example, in Patent Document 1, “loss of physical property of rubber on the inner surface of a belt that is in contact with the pulley of the conveyor belt in a conveyor belt that is used in a conveyance system for an article that is wound between a driving pulley and an idle pulley and travels. A conveyor belt characterized in that the factor (tan δ) and the dynamic elastic modulus (E ′) are 0.04 ≦ tan δ ≦ 0.12 and E ′ ≧ 20 kgf / cm ² , respectively. A conveyor belt used in a system for conveying articles that are wound around an idler pulley, and the inner surface rubber of the conveyor belt is a polymer comprising 40 to 100 parts by weight of natural rubber and 60 to 0 parts by weight of BR rubber. The conveyor belt characterized by blending 20 to 55 parts by weight of carbon black ”.

Further, according to the present applicant, “a rubber composition for a conveyor belt containing 30 to 65 parts by mass of carbon black having colloidal characteristics shown below with respect to 100 parts by mass of a rubber component.
1) Nitrogen adsorption specific surface area (N ₂ SA) is 80 (m ² / g) or less 2) Iodine adsorption amount (IA) is 70 (mg / g) or less 3) Dibutyl phthalate (DBP) oil absorption is 100 (cm ³⁾ / 100 g) or more ”or“ a rubber composition for conveyor belts having a frequency coefficient of 10 Hz, a dynamic strain of 2%, and a loss coefficient tan δ at 20 ° C. of more than 0.120 and not more than 0.200 ”(Patent Documents). 2).

  Further, the present applicant has stated that “(A) natural rubber (NR) and butadiene rubber containing crystalline syndiotactic-1,2-polybutadiene resin (SPB-BR)”, NR, SPB-BR, The rubber composition for conveyor belts containing 100 parts by mass of a rubber component having a mass ratio (NR / SPB-BR) of 80/20 to 20/80 and (B) 20 to 65 parts by mass of carbon black. Has been proposed (see Patent Document 3).

Furthermore, by the present applicant, “containing a rubber component made of natural rubber (NR) and polybutadiene rubber (BR), carbon black, silica, a silane coupling agent, and diethylene glycol,
The ratio of natural rubber to polybutadiene rubber (NR / BR) in the rubber component is 80/20 to 25/75,
The carbon black content is 15 to 35 parts by mass with respect to 100 parts by mass of the rubber component,
The silica content is 5 to 25 parts by mass with respect to 100 parts by mass of the rubber component,
The content of the silane coupling agent is 0.5 to 3 parts by mass with respect to 100 parts by mass of the rubber component,
The rubber composition for conveyor belts whose content of the said diethylene glycol is 0.5-4.5 mass parts with respect to 100 mass parts of said rubber components. Is proposed (see Patent Document 4).

JP-A-11-139523 Japanese Patent Laid-Open No. 2004-18752 JP 2004-346220 A JP 2008-38133 A

However, the conveyor belt described in Patent Document 1 is intended to reduce power consumption by reducing the tan δ value. However, if the tan δ value is too small, the breaking strength (T _B ) and the breaking elongation (E _B ) Also decreases and the fatigue resistance is inferior, so that the surface destruction of the cover rubber and the like proceeds during the running of the conveyor belt, causing the surface failure of the conveyor belt, and the operation is not stable.

Moreover, since the energy loss index | exponent becomes high, the conveyor belt using the rubber composition for conveyor belts of patent documents 2 and 3 has a difference in a belt operation line (for example, especially a gradient of a line, a curve, etc.), In some cases, power consumption is not sufficiently reduced. Further, since the tan δ value is reduced, the breaking strength (T _B ) and the breaking elongation (E _B ) may be reduced as in the conveyor belt described in Patent Document 1.

  Moreover, the conveyor belt using the rubber composition for conveyor belts described in Patent Document 4 has a small loss coefficient tan δ and energy loss index (ΔH), and can sufficiently reduce power consumption, but it is hard and has a sharp point. It was found that the surface of the conveyor belt, such as the cover rubber, could be destroyed depending on the impact when the object is loaded.

  Accordingly, an object of the present invention is to provide a rubber composition for a conveyor belt and a conveyor belt that can maintain basic physical properties such as hardness, breaking strength, and elongation at break and can sufficiently reduce power consumption.

As a result of intensive studies to solve the above problems, the present inventor has found that a conveyor belt forming a back surface using a rubber composition containing a specific amount of a specific glass balloon has basics such as hardness, breaking strength, and breaking elongation. The inventors have found that the physical properties can be maintained and the power consumption can be sufficiently reduced, and the present invention has been completed.
That is, the present invention provides the following (1) to (5).

(1) contains a rubber component and a glass balloon,
The glass balloon has an average particle size of 20 to 100 μm,
The glass balloon has an average film thickness of 0.9 to 1.5 μm,
The rubber composition for conveyor belts whose content of the said glass balloon is 2-15 mass parts with respect to 100 mass parts of said rubber components.

  (2) The rubber composition for a conveyor belt according to (1), wherein 90% by mass or more of the rubber component is a diene rubber.

(3) Natural rubber (NR) and butadiene rubber (BR) are used in combination as the diene rubber,
The rubber composition for conveyor belts according to (2) above, wherein the quantity ratio (NR / BR) of the natural rubber and the butadiene rubber is 25/75 to 90/10.

(4) Furthermore, carbon black is contained,
The carbon black has a nitrogen adsorption specific surface area of 20 to 60 m ² / g,
Dibutyl phthalate absorption of the carbon black is a 30~140cm ³ / 100g,
The rubber composition for conveyor belts according to any one of (1) to (3), wherein the content of the carbon black is 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

(5) A conveyor belt comprising an upper cover rubber layer, a reinforcing layer and a lower cover rubber layer,
A conveyor belt, wherein at least the back surface of the bottom cover rubber layer is formed of the rubber composition for conveyor belts according to any one of (1) to (4).

  As will be described below, the present invention is useful because it can provide a conveyor belt that can maintain basic physical properties such as hardness, breaking strength, elongation at break and the like and can sufficiently reduce power consumption. is there.

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

The present invention is described in detail below.
The rubber composition for a conveyor belt of the present invention contains a rubber component and a glass balloon, the glass balloon has an average particle size of 20 to 100 μm, and the glass balloon has an average film thickness of 0.9 to 1.5 μm. And a rubber composition in which the content of the glass balloon is 2 to 15 parts by mass with respect to 100 parts by mass of the rubber component.
Next, each component of the rubber composition for conveyor belts of this invention is explained in full detail.

<Rubber component>
The rubber component contained in the rubber composition for conveyor belts of the present invention is not particularly limited. In addition to diene rubbers such as natural rubber (NR) and isoprene rubber (IR), acrylic rubber (ACM), fluoro rubber (FKM) Non-diene rubbers such as these can also be used.

In the present invention, 90% by mass or more of the rubber component is preferably a diene rubber, and more preferably 100% by mass is a diene rubber.
When the content ratio of the diene rubber is in the above range, the rupture strength after vulcanization of the resulting rubber composition for a conveyor belt of the present invention is further improved, and the basic physical properties as a conveyor belt can be maintained well. it can.

(Diene rubber)
Specific examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber. (CR), butyl rubber (IIR), ethylene-propylene-diene rubber (EPDM) and the like may be mentioned, and these may be used alone or in combination of two or more.

In the present invention, it is preferable to use natural rubber in a proportion of 25% by mass or more of the diene rubber, more preferable to use natural rubber in a proportion of 25 to 90% by mass, and a combination of natural rubber and butadiene rubber. More preferably.
Further, the amount ratio (NR / BR) when natural rubber and butadiene rubber are used in combination is preferably 25/75 to 90/10, more preferably 50/50 to 90/10, and 70 / More preferably, it is 30-85 / 15.
When the content ratio of natural rubber and butadiene rubber is in the above range, the resulting rubber composition for conveyor belts of the present invention has further improved rupture strength after vulcanization, and the basic physical properties as a conveyor belt are better maintained. can do. Moreover, since the energy loss index | exponent ((DELTA) H) mentioned later after vulcanization of the rubber composition for conveyor belts of this invention obtained also becomes a more favorable range, reduction of power consumption can fully be aimed at.

  In the present invention, the butadiene rubber preferably has a weight average molecular weight of 400,000 or more, more preferably 450,000 or more. When the weight average molecular weight is within this range, the breaking strength after vulcanization of the resulting rubber composition for conveyor belts of the present invention is further improved, and the wear resistance is also improved.

Furthermore, in the present invention, the butadiene rubber is preferably a terminal-modified butadiene rubber.
The terminal-modified butadiene rubber is not particularly limited as long as it is a butadiene rubber having a terminal modified. Moreover, as a terminal modification | denaturation method of a butadiene rubber, the method of modify | modifying the terminal (active terminal) of BR using a modifier can be used, for example.
Specific examples of such modifiers include, for example, tin halides such as tin tetrachloride and tin tetrabromide; halogenated organotin compounds such as tributyltin chloride; silicon compounds such as silicon tetrachloride and chlorotriethylsilane. An isocyanate group-containing compound such as phenyl isocyanate; an amide compound such as N-methylpyrrolidone (NMP); a lactam compound; a urea compound; an isocyanuric acid derivative; Of these, N-methylpyrrolidone is preferred.

  By using such a terminal-modified butadiene rubber, the loss coefficient tan δ and energy loss index (ΔH) described later after vulcanization of the rubber composition for a conveyor belt of the present invention obtained are both in a better range. Thus, the power consumption can be more sufficiently reduced. This is thought to be because the modified end portion is bonded to the filler, and energy loss at the polymer end is reduced.

A commercially available product can be used as the terminal-modified butadiene rubber having a weight average molecular weight of 400,000 or more.
Specific examples include Nipol BR1250H (weight average molecular weight: 570,000, NMP modified) manufactured by Nippon Zeon.

<Glass balloon>
The glass balloon contained in the rubber composition for a conveyor belt of the present invention is not particularly limited as long as the glass hollow body has an average particle diameter of 20 to 100 μm and an average film thickness of 0.9 to 1.5 μm. Various conventionally known glass balloons can be used.
Here, the average particle diameter is a value measured by a laser diffraction particle size meter, and the average film thickness is an average value of values measured using an electron microscope.

In this invention, it is preferable that the average particle diameter of the said glass balloon is 30-90 micrometers, and it is preferable that the average film thickness of the said glass balloon is 1.0-1.4 micrometers.
When the average particle diameter and / or average film thickness of the glass balloon is in the above-mentioned range, the strength of the glass balloon itself is high, and the breaking strength after vulcanization of the rubber composition for the conveyor belt of the present invention obtained is further improved. The basic physical properties of the conveyor belt can be maintained better. Moreover, since the energy loss index | exponent ((DELTA) H) mentioned later after vulcanization of the rubber composition for conveyor belts of this invention obtained also becomes a more favorable range, reduction of power consumption can fully be aimed at.

For the same reason, the 90% by volume residual pressure of the glass balloon is preferably 20 to 150 MPa, and more preferably 35 to 130 MPa.
Here, the 90 volume% residual pressure is a value measured by a nitrogen method. Specifically, for a sample in which a glass balloon and talc are mixed, a value obtained by measuring the pressure when the volume is reduced by 10% using the change in specific gravity when pressurized with dry nitrogen gas. is there.

A commercial item can be used as such a glass balloon.
Specifically, for example, Glass Bubbles K-46 (average particle diameter: 75 μm, average film thickness: 1.13 μm, 90% by volume residual pressure: 38 MPa, manufactured by Sumitomo 3M), Glass Bubbles VS-5500 (average) Particle size: 70 μm, average film thickness: 1.31 μm, 90 volume% residual pressure: 42 MPa, manufactured by Sumitomo 3M), Glass Bubbles S60HS (average particle diameter: 45 μm, average film thickness: 1.31 μm, 90 volume% remaining) Pressure: 124 MPa, manufactured by Sumitomo 3M Limited).

In this invention, content of the said glass balloon is 2-15 mass parts with respect to 100 mass parts of said rubber components, and it is preferable that it is 5-10 mass parts.
By containing the glass balloon in the above range, the resulting rubber composition for conveyor belts of the present invention has a 25% elongation while maintaining a low loss coefficient tan δ described below without adversely affecting the physical properties after vulcanization. The tensile stress (M ₂₅ ) at the time can be increased. As a result, since the energy loss index (ΔH) is in a favorable range, the power consumption can be sufficiently reduced.
As shown also in Comparative Examples 4 to 6 described later, when a glass balloon larger than a specific average particle diameter is used, although the tensile stress (M ₂₅ ) can be increased, the specific gravity and loss factor tan δ are also large. As a result, it can be seen that this is a very excellent effect considering that power consumption cannot be reduced.

<Carbon black>
The rubber composition for conveyor belts of the present invention is one of the preferred embodiments that contain carbon black in addition to the above-described components.
Specific examples of the carbon black include, for example, HAF (High Absorption Furnace), SAF (Super Abrasion Furnace), ISAF (Intermediate Super Abrasion Furnace), FEF (Fast Extrusion Gurning, FEF (Fast Extrusion Gurning). (Semi-Reinforming Furnace), FT (Fine Thermal), MT (Medium Thermal) and the like.

In the present invention, is preferably a nitrogen adsorption specific surface area of the carbon black is 20~60m ² / g, a dibutyl phthalate oil absorption is preferably 30~140cm ³ / 100g.
Here, the nitrogen adsorption specific surface area is a surrogate property of the surface area that carbon black can be used for adsorption with rubber molecules, and the nitrogen adsorption amount on the surface of carbon black is determined according to JIS K6217-2: 2001 “Part 2: Specific surface area”. It is the value measured according to “How to find out—Nitrogen adsorption method—Single point method”.
Dibutyl phthalate oil absorption is a substitute characteristic of a structure in which carbon black can incorporate rubber molecules, and was measured with an abstract meter according to JIS K6217-4: 2001 “Part 4: How to determine DBP absorption”. Value.

A commercial item can be used as such carbon black.
Specifically, for example, SRF-HS (nitrogen adsorption specific surface area: 32m ² / g, a dibutyl phthalate oil absorption: 140cm ^3/100 g, manufactured by Tokai Carbon Co.), SRF-HS (nitrogen adsorption specific surface area: 29m ² / g dibutyl phthalate absorption: 152cm ^3/100 g, manufactured by Tokai carbon Co., Ltd.), FEF-HS (nitrogen adsorption specific surface area: 42m ² / g, a dibutyl phthalate oil absorption: 160cm ^3/100 g, manufactured by Tokai carbon Co., Ltd.) .

In the present invention, when the carbon black is contained as desired, the content is preferably 1 to 50 parts by mass, more preferably 10 to 35 parts by mass with respect to 100 parts by mass of the rubber component. The amount is preferably 10 to 25 parts by mass.
By containing the carbon black in the above-described range, not only coloring but also basic physical properties (particularly elongation) such as hardness after vulcanization, breaking strength, elongation at break of the rubber composition for the conveyor belt of the present invention obtained. In addition, since the loss coefficient tan δ and the energy loss index (ΔH), which will be described later, are both in a better range, the power consumption can be more sufficiently reduced.

<Sulfur vulcanizing agent>
The rubber composition for a conveyor belt according to the present invention is a sulfur-based vulcanizing agent that causes a chemical bond (crosslinking) via sulfur between the rubber of the rubber component and the rubber as a crosslinking agent in addition to the above-described components. It is one of the preferable embodiments to contain.
Specific examples of the sulfur-based vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide, and the like. 1 type may be used independently and 2 or more types may be used together.

In the present invention, the content when the sulfur-based vulcanizing agent is optionally contained is preferably 3 to 4 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is part.
When the content of the sulfur-based vulcanizing agent is in the above-mentioned range, the loss coefficient tan δ and energy loss index (ΔH) described later after vulcanization of the rubber composition for a conveyor belt of the present invention obtained are both better. Therefore, the power consumption can be more sufficiently reduced.

<Silane coupling agent>
The rubber composition for conveyor belts of the present invention is one of the preferred embodiments that contains a silane coupling agent in addition to the components described above.
The silane coupling agent is preferably a polysulfide silane coupling agent used for rubber applications.
Specific examples of the polysulfide-based silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide.
Among these, bis (3-triethoxysilylpropyl) tetrasulfide is preferable because the breaking strength after vulcanization of the resulting rubber composition for conveyor belts of the present invention is further improved.

A commercial item can be used as such a silane coupling agent.
Specifically, bis (3-triethoxysilylpropyl) tetrasulfide (Si69, manufactured by Degussa), bis (3-triethoxysilylpropyl) disulfide (Si75, manufactured by Degussa) and the like are exemplified.

In this invention, it is preferable that content in the case of containing the said silane coupling agent depending on necessity with respect to 100 mass parts of said rubber components is 0.1-10 mass parts.
When the content of the silane coupling agent is within the above range, the breaking strength after vulcanization of the rubber composition for a conveyor belt of the present invention to be obtained is further improved. This is considered to be because the chemical bond between the silane coupling agent and the silica increases.

<Diethylene glycol>
The rubber composition for conveyor belts of the present invention is one of the preferred embodiments that contains diethylene glycol in addition to the above-described components.
The diethylene glycol is a compound represented by a chemical formula of (CH ₂ OHCH ₂ ) ₂ O.
As the diethylene glycol, a commercial product manufactured by Nippon Shokubai Co., Ltd. can be used.

In the present invention, when the diethylene glycol is optionally contained, the content is preferably 0.5 to 4.5 parts by mass with respect to 100 parts by mass of the rubber component, and 0.5 to 2 parts by mass. It is more preferable that it is 0.6 to 1.8 parts by mass.
When the content of diethylene glycol is in the above-mentioned range, the loss coefficient tan δ and energy loss index (ΔH) described later of the resulting rubber composition for conveyor belts of the present invention are both in a better range, thereby reducing power consumption. Can be achieved more fully. This is considered to be because the interaction between molecules between silica and the rubber component can be reduced.

  The rubber composition for conveyor belts of the present invention contains a crosslinking agent such as a vulcanizing agent other than the above sulfur-based vulcanizing agent, a vulcanization aid, and a vulcanization accelerator and a vulcanization retarder in addition to the above-described components. In addition, various compounding agents may be contained as long as the object of the present invention is not impaired.

Examples of the vulcanizing agent other than the sulfur-based vulcanizing agent include vulcanizing agents such as organic peroxides, metal oxides, phenol resins, and quinone dioximes.
Specific examples of the organic peroxide vulcanizing agent include benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-di- (T-Butylperoxy) hexane, 2,5-dimethylhexane-2,5-di (peroxylbenzoate) and the like.
Other examples include magnesium oxide, risurge, p-quinonedioxime, p-dibenzoylquinonedioxime, poly-p-dinitrosobenzene, methylenedianiline, and the like.

Examples of the vulcanization accelerator include aldehyde / ammonia, guanidine, thiourea, thiazole, sulfenamide, thiuram, and dithiocarbamate vulcanization accelerators.
Specific examples of the aldehyde / ammonia vulcanization accelerator include hexamethylenetetramine (H).
Specific examples of the guanidine vulcanization accelerator include diphenyl guanidine.
Specific examples of the thiourea vulcanization accelerator include ethylene thiourea and the like.
Specific examples of the thiazole-based vulcanization accelerator include dibenzothiazyl disulfide (DM), 2-mercaptobenzothiazole, and a Zn salt thereof.
Specific examples of sulfenamide vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide (CZ), Nt-butyl-2-benzothiazolylsulfenamide (NS ) And the like.
Specific examples of the thiuram vulcanization accelerator include tetramethylthiuram disulfide (TMTD), dipentamethylene thiuram tetrasulfide, and the like.
Specific examples of the dithiocarbamate vulcanization accelerator include Na-dimethyldithiocarbamate, Zn-dimethyldithiocarbamate, Te-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, and pipecoline. Examples include pipecolyl dithiocarbamate.

  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 15 parts by mass with respect to 100 parts by mass of the rubber component, More preferably, it is 0.5-12.5 mass parts. When the content range is within this range, the resulting rubber composition for conveyor belts of the present invention has better rupture strength after vulcanization, and the loss coefficient tan δ and energy loss index (ΔH) described later are also better. Become.

Specific examples of the compounding agent include, for example, fillers other than the above-described carbon black, anti-aging agents, antioxidants, pigments (dyes), plasticizers, thixotropic agents, ultraviolet absorbers, flame retardants, and solvents. , Surfactants (including leveling agents), dispersants, dehydrating agents, rust inhibitors, adhesion-imparting agents, antistatic agents, processing aids, and the like.
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.

The rubber composition for conveyor belts of the present invention contains a specific amount of the above-mentioned rubber component and glass balloon, and contains the above-mentioned various compounding agents (including carbon black, sulfur-based vulcanizing agent, etc., the same applies hereinafter). By doing so, the tensile stress (M ₂₅ ) at 25% elongation can be increased while the loss coefficient tan δ is kept low, and the energy loss index (ΔH) can be in a favorable range.
Specifically, the loss factor tan δ measured by extending 10% at a measurement temperature of 20 ° C. and applying a vibration with an amplitude of ± 2% at a frequency of 10 Hz is maintained as low as about 0.056 to 0.062. The tensile stress (M ₂₅ ) at 25% elongation can be improved to about 0.80 to 1.25 MPa, and the energy loss index (ΔH) represented by the following formula [1] can be set to about 0.076 or less.
ΔH = (SpGr × tan δ) / M ₂₅ [1]
Here, SpGr is a specific gravity (g / cm ³ ) at 20 ° C., tan δ is a loss measured by extending 10% at a measurement temperature of 20 ° C., and giving a vibration of amplitude ± 2% at a frequency of 10 Hz. The coefficient, M _25, is the tensile stress (MPa) at 25% elongation.

(Loss factor tan δ)
The loss coefficient tan δ is expressed by the ratio of the storage elastic modulus E ′ and the loss elastic modulus E ″ representing the dynamic properties of the rubber composition, tan δ = E ″ / E ′, and the smaller the value, the more the deformation of the rubber composition. This means that the amount of energy dissipated as heat during the period (energy loss amount) is small, and can be used as a measure of energy loss.
On the other hand, if the tan δ value is small, it is considered that power consumption can be reduced. However, as described above, if the tan δ value is too small, the breaking strength (T _B ) and the breaking elongation (E _B ) also decrease. The operation of the conveyor belt is not stable.
In the present invention, a specific amount of the above-described rubber component and glass balloon are contained, and the above-described various compounding agents are optionally contained, whereby a tensile stress (M _{25 is} maintained while maintaining tan δ as low as about 0.056 to 0.062. ) Can be increased to about 0.80 to 1.25 MPa.

(Energy loss index (ΔH))
The energy loss index (ΔH) is expressed by the above formula [1].
The above formula [1] is a formula that serves as a measure of the efficiency of reducing friction with the road surface that has been used in the field of conventional tires, but is also considered to be effective in reducing power consumption of the rubber composition for conveyor belts.
SpGr in the above formula [1] indicates the specific gravity (g / cm ³ ) at 20 ° C. If this value is small, the total mass can be reduced, so that a low power consumption effect equivalent to that of a small load can be obtained.
Further, tan δ in the above formula [1] affects energy loss due to deformation of the rubber composition when the roller is moved over. When this value is small, a low power consumption effect is obtained.
In addition, M ₂₅ in the above formula [1] indicates a tensile stress (MPa) at 25% elongation, but can be considered as a substitute characteristic of hardness as belt rigidity. Affect. When this value is large, the deflection becomes small and a low power consumption effect is obtained. In the present invention, M ₂₅ is a test piece punched out into a No. 3 dumbbell from a vulcanized product obtained by vulcanizing the rubber composition for conveyor belts of the present invention at 148 ° C. for 30 minutes. According to JIS K6251-2004, a tensile test was conducted at a tensile speed of 500 mm / min, and a tensile stress (M ₂₅ ) [MPa] at 25% elongation was measured at room temperature.
Therefore, the technical significance of the above formula [1] is that by dividing the product of SpGr and tan δ by M ₂₅ , based on these physical properties, the energy loss when the rubber composition gets over the roller is comprehensively considered. It can be judged that the rubber composition for the conveyor belt is an indicator as to whether or not the conveyor belt is suitable for a conveyor belt that reduces power consumption.
In the present invention, the rubber component and glass balloon described above are contained in specific amounts, and the various compounding agents described above are optionally contained, so that the tensile stress (M ₂₅ ) at 25% elongation can be maintained while maintaining the loss factor tan δ low. As a result, the energy loss index (about 0.076 or less) that can sufficiently reduce power consumption can be obtained.

The rubber composition for conveyor belts of the present invention can be produced by adding the above-described rubber component and glass balloon and various compounding agents contained as desired, kneading with a Banbury mixer or the like, and then kneading or vulcanizing with a kneading roll machine or the like. 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 under conditions of a temperature of about 140 to 150 ° C. and 0.5 hours.

The conveyor belt of the present invention is a conveyor belt comprising an upper surface cover rubber layer, a reinforcing layer, and a lower surface cover rubber layer, and at least the back surface of the lower surface cover rubber layer is made of the above-described rubber composition for conveyor belts of the present invention. It is a conveyor belt to be formed.
Hereinafter, the conveyor belt according to the present invention will be described with reference to FIG. 1. The structure of the conveyor belt according to the present invention may employ the above-described rubber composition for a conveyor belt according to the present invention on the back surface of the bottom cover rubber layer. The present invention is not particularly limited to this.

FIG. 1 is a cross-sectional view schematically showing an example of a preferred embodiment of the conveyor belt of the present invention. In FIG. 1, 1 is a conveyor belt, 2 is an upper cover rubber layer, 3 is a reinforcing layer, 4 is a lower cover rubber layer, 5 is a transporting surface for transported goods, 11 and 16 are outer layers, and 12 and 15 are inner layers.
As shown in FIG. 1, the conveyor belt 1 has a reinforcing layer 3 as a central layer, and an upper surface cover rubber layer 2 and a lower surface cover rubber layer 4 are provided on both sides thereof, and the upper surface cover rubber layer 2 includes an outer layer 11 and an inner layer. The bottom cover rubber layer 4 is composed of two layers of an outer layer 16 and an inner layer 15. Here, the outer layer and the inner layer (the outer layer 11 and the inner layer 12, the outer layer 16 and the inner layer 15) of the upper surface cover rubber layer 2 and the lower surface cover rubber layer 4 may be formed using different rubber compositions.

In FIG. 1, the upper cover rubber layer 2 is composed of two layers, an outer layer 11 and an inner layer 12, but in the conveyor belt of the present invention, the number of layers constituting the upper cover rubber layer 2 is limited to two. It may be 1 or 3 or more. In the case of 3 or more, these layers may be formed using different rubber compositions. The same applies to the bottom cover rubber layer 4.
The outer layer 11 constituting the transported material conveying surface 5 of the upper cover rubber layer 2 is preferably formed from a rubber composition having excellent heat resistance, wear resistance, oil resistance, and the like. Since the inner layer 12 contributes to the adhesion between the reinforcing layer 3 and the outer layer 11, the upper cover rubber layer 2 is preferably composed of two layers, an outer layer and an inner layer.
The outer layer 16 constituting the back surface of the lower cover rubber layer 4 is formed of the above-described rubber composition for conveyor belts of the present invention, and the inner layer 15 of the lower cover rubber layer 4 is manufactured in terms of manufacturing cost and adhesiveness to the reinforcing layer 3. Therefore, the cover rubber layer 4 is preferably composed of two layers.

The core of the reinforcing layer 3 is not particularly limited, and those used for ordinary conveyor belts can be appropriately selected and used. Specific examples thereof include those made of cotton cloth and chemical fibers or synthetic fibers and rubber paste. Coated and infiltrated; RFL-treated cotton cloth and chemical fiber or synthetic fiber folded; special woven nylon canvas, steel cord, etc., may be used alone or in combination of two kinds You may use the above thing laminated | stacked.
Moreover, the shape of the reinforcement layer 3 is not specifically limited, As shown in FIG. 1, a sheet form may be sufficient and a wire-shaped reinforcement line may be embedded in parallel.

  The rubber composition forming the inner layer 12 of the upper surface cover rubber layer 2 and the inner layer 15 of the lower surface cover rubber 4 is not particularly limited, and a rubber composition used for a normal conveyor belt can be appropriately selected and used. Or two or more of them may be used in combination.

  The rubber composition for forming the outer layer 11 of the upper cover rubber layer 2 is not particularly limited, and a rubber composition used for a normal conveyor belt is made of basic characteristics required for the outer layer (for example, heat resistance, wear resistance, The oil resistance can be appropriately selected according to the oil resistance.

  In the conveyor belt of the present invention, since at least the back surface of the lower cover rubber layer is formed of the rubber composition for conveyor belt of the present invention, the basic physical properties such as hardness, breaking strength, elongation at break are maintained, and power consumption is reduced. Can be sufficiently achieved.

In the conveyor belt of this invention, it is preferable that the thickness of a lower surface cover rubber layer is 5-20 mm, and it is more preferable that it is 6-15 mm. Here, the thickness of the lower surface cover rubber layer refers to the total thickness of these layers when the lower surface cover rubber layer is composed of an inner layer and an outer layer.
When the thickness of the lower surface cover rubber layer is within this range, even when a high-temperature transported material is used for transport, it is possible to prevent belt warping (capping) caused by rubber deterioration or the like.

Examples The rubber composition for conveyor belts of the present invention will be described in more detail below, but the present invention is not limited to these.
(Examples 1-8, Comparative Examples 1-7)
Each rubber composition for conveyor belts was prepared with the composition component (part by mass) shown in Table 1 below with respect to 100 parts by mass of the rubber component. About each obtained rubber composition, the various physical properties after vulcanization were measured and evaluated by the method shown below. The results are shown in Table 1 below.

<Physical properties after vulcanization>
(1) Hardness The obtained unvulcanized rubber composition was vulcanized for 30 minutes using a press molding machine at 148 ° C. under a surface pressure of 3.0 MPa to prepare a vulcanized sheet having a thickness of 2 mm. A JIS No. 3 dumbbell-shaped test piece was punched from this sheet.
About this test piece, Shore A hardness was measured according to the "type A durometer hardness test" of JISK6253: 2006.
If Shore A hardness is 50 or more, it can be evaluated as having a suitable hardness as a conveyor belt.

(2) Tensile stress, breaking strength and breaking elongation Each obtained rubber composition was vulcanized at 148 ° C. for 30 minutes to prepare a vulcanized rubber composition.
Using test pieces punched out from each of the prepared vulcanized rubber compositions into a No. 3 dumbbell shape, a tensile test was conducted at a tensile speed of 500 mm / min in accordance with JIS K6251-2004, and a tensile stress at 25% elongation (M ₂₅ ) [MPa], breaking strength (T _B ) [MPa] and breaking elongation (E _B ) [%] were measured at room temperature.
If the breaking strength is 15 MPa or more, it can be evaluated as having a high breaking strength.
If the elongation at break is 400% or more, it can be evaluated as having a high elongation at break.

(3) Loss coefficient tan δ
A loss factor 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. 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.

(4) Energy loss index (ΔH)
The specific gravity at 20 ° C. of each vulcanized rubber composition thus prepared was measured according to “Method for measuring density and specific gravity of chemical products” described in JIS K0061: 2001.
Subsequently, the energy loss index (ΔH) of each prepared vulcanized rubber composition was determined from the above formula [1] using the specific gravity and the values of M ₂₅ and loss coefficient tan δ measured above.

The following components were used as the composition components such as the rubber component shown in Table 1 above.
・ Natural rubber (NR): RSS # 3
BR: Nipol BR1250H (weight average molecular weight: 570,000, terminal NMP modified, manufactured by Nippon Zeon)
Carbon black: FEF (nitrogen adsorption specific surface area: 35m ² / g, a dibutyl phthalate oil absorption: 101cm ³ / 100g, manufactured by Tokai Carbon Co., Ltd.)
Silica: hydrous fine silicic acid (specific surface area by nitrogen adsorption: 215m ² / g, a dibutyl phthalate oil absorption: 280 cm ^3/100 g, Nipsil AQ, manufactured by Nippon Silica Industrial Co., Ltd.)

Resin balloon: Matsumoto Microsphere (average particle size: 10-30 μm, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.)
Ceramic balloon: E-SPHERES SL75 (average particle size: 45 μm, manufactured by Taiheiyo Cement)
Glass balloon 1: Glass bubbles K-20 (average particle size: 110 μm, average film thickness: 0.89 μm, 90% by volume residual pressure: 3.4 MPa, manufactured by Sumitomo 3M)
Glass balloon 2: Glass bubbles K-46 (average particle size: 75 μm, average film thickness: 1.13 μm, 90 volume% residual pressure: 38 MPa, manufactured by Sumitomo 3M)
Glass balloon 3: Glass bubbles VS-5500 (average particle size: 70 μm, average film thickness: 1.31 μm, 90 volume% residual pressure: 42 MPa, manufactured by Sumitomo 3M)
Glass balloon 4: Glass bubbles S60HS (average particle diameter: 45 μm, average film thickness: 1.31 μm, 90% by volume residual pressure: 124 MPa, manufactured by Sumitomo 3M)

・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industries)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
Anti-aging agent: NOCRACK 6C (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
Diethylene glycol: manufactured by Nippon Shokubai Co., Ltd. Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide (Si69, manufactured by Degussa)
Aroma oil: A-OMIX (Sankyo Oil Chemical Co., Ltd.)
・ Vulcanizing agent: Sulfur (oil-treated sulfur, manufactured by Hosoi Chemical Co., Ltd.)
・ Vulcanization accelerator: N-tert-butyl-2-benzothiazolylsulfenamide (Noxeller NS, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

From the results shown in Table 1, although the rubber compositions of Comparative Examples 2 and 3 prepared using a resin balloon or a ceramic balloon are improved in tensile stress (M ₂₅ ) as compared with the rubber composition of Comparative Example 1. As a result, tan δ increased, and as a result, the energy loss index (ΔH) also increased, and it was found that the rubber composition cannot reduce power consumption.
In addition, the rubber compositions of Comparative Examples 4 to 6 prepared using the glass balloon 1 whose average particle diameter or the like is not within the predetermined range are improved in tensile stress (M ₂₅ ) as compared with the rubber composition of Comparative Example 1. As a result, the specific gravity and tan δ increased, and as a result, the energy loss index (ΔH) became equal to or higher, and it was found that the rubber composition cannot sufficiently reduce power consumption.
Furthermore, the rubber composition of Comparative Example 7 prepared by containing a specific amount or more of the glass balloon 2 having an average particle diameter or the like in a predetermined range can reduce power consumption compared to the rubber composition of Comparative Example 1. Although it became a rubber composition, it was found that the fracture strength was poor and the basic physical properties as a conveyor belt could not be maintained.

On the other hand, the rubber compositions of Examples 1 to 8 prepared by containing a specific amount of glass balloons 2 to 4 having an average particle diameter or the like in a predetermined range are compared with the rubber composition of Comparative Example 1 in the loss coefficient tan δ. As a result, the tensile stress (M ₂₅ ) was increased while maintaining low, and as a result, the energy loss index (ΔH) was also decreased, and it was found that the rubber composition can sufficiently reduce power consumption.

1: Conveyor belt 2: Upper cover rubber layer 3: Reinforcement layer 4: Lower cover rubber layer 5: Transported material transport surface 11, 16: Outer layer 12, 15: Inner layer

Claims (5)

Contains a rubber component and a glass balloon,
The glass balloon has an average particle size of 20 to 100 μm,
The glass balloon has an average film thickness of 0.9 to 1.5 μm,
The rubber composition for conveyor belts whose content of the said glass balloon is 2-15 mass parts with respect to 100 mass parts of said rubber components.   The rubber composition for a conveyor belt according to claim 1, wherein 90% by mass or more of the rubber component is a diene rubber. Natural rubber (NR) and butadiene rubber (BR) are used in combination as the diene rubber,
The rubber composition for a conveyor belt according to claim 2, wherein a quantitative ratio (NR / BR) of the natural rubber and the butadiene rubber is 25/75 to 90/10. In addition, containing carbon black,
The carbon black has a nitrogen adsorption specific surface area of 20 to 60 m ² / g,
Dibutyl phthalate absorption of the carbon black is a 30~140cm ³ / 100g,
The rubber composition for a conveyor belt according to any one of claims 1 to 3, wherein a content of the carbon black is 1 to 50 parts by mass with respect to 100 parts by mass of the rubber component. A conveyor belt comprising an upper cover rubber layer, a reinforcing layer and a lower cover rubber layer,
The conveyor belt in which at least the back surface of the said lower surface cover rubber layer is formed with the rubber composition for conveyor belts in any one of Claims 1-4.

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