JP7365107B2 - Rubber composition for cover rubber layer and conveyor belt - Google Patents

Description

The present invention relates to a rubber composition used for forming a cover rubber layer constituting the conveyance surface of a conveyor belt, and a conveyor belt provided with a cover rubber layer formed from this rubber composition.

Belt conveyors have conventionally been widely used as conveyance devices for articles, etc., and various types of conveyor belts, which are the main component of the belt conveyor, are known.
Conveyor belts in which the main body is made of a rubber composition are widely used. For example, a conveyor belt of the type in which a core layer comprising canvas or steel cords is sandwiched between two cover rubber layers is widely used. things are widely used.
In addition to conveyor belts that are made up of only a belt body made by processing a long belt into an endless belt, there are also conveyor belts that have a horizontal bar extending in the width direction of the belt body, and conveyor belts that have a horizontal bar extending in the width direction of the belt body, and belts that have a horizontal bar extending in the width direction of the belt body. Conventionally, those having an ear crosspiece extending along the line are widely known.

Such a belt conveyor is normally used to load an object with the conveying surface of the conveyor belt facing upward, and to transport the object to an unloading location by rotating the conveyor belt in this state.
Belt conveyors are usually configured to turn the conveyor belt at the unloading location, and this turn changes the conveying surface of the conveyor belt from upward to downward, causing the objects loaded on the conveying surface to drop. It is configured to allow
After that, the conveyor belt is returned to the loading area with the conveyance surface facing downward, and is turned again so that the conveyance surface is facing upward, and the conveyed object is loaded thereon.

By the way, when the conveyed object conveyed by the belt conveyor is relatively fine granular, there is a possibility that the conveyed object may be scattered during the conveyance due to vibrations, surrounding air currents, etc.
As a conveyor belt used for conveying such relatively fine granular objects, a conveyor belt called a pipe conveyor or the like is conventionally known (see Patent Document 1 below).
Furthermore, if the conveyed object is in the form of relatively fine particles, the conveyed object may adhere to the conveying surface and fall on the way back to the loading area without falling at the unloading area.
For this reason, in the above-mentioned pipe conveyor, although it is not necessary to make the conveyor belt into a cylindrical shape after unloading, the conveyor belt is also made into a cylindrical shape when returning to the loading area to prevent deposits from falling. It is sometimes used in a rounded form.

Japanese Patent Application Publication No. 2001-310809

For the reasons described above, it is desired that the cover rubber layer of the conveyor belt has an effect of suppressing adhesion to conveyed objects.
Such requirements are not only required for pipe conveyors that convey relatively fine particles, but are also generally required for various types of conveyor belts.
However, sufficient studies have not been conducted to satisfy this type of demand, and a conveyor belt that sufficiently suppresses the adhesion of conveyed objects has not been provided.
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to satisfy the above-mentioned problems, and to provide a conveyor belt with suppressed adhesion to conveyed objects.

In order to solve the above-mentioned problems, the present inventor conducted intensive studies and found that the above-mentioned needs could be met by incorporating surfactants and lubricants into the rubber composition used for forming the cover rubber layer that constitutes the conveying surface of the conveyor belt. The present invention has been completed based on the discovery that the following can be satisfied.

That is, the rubber composition for a cover rubber layer of the present invention is used to form a cover rubber layer constituting the conveyance surface of a conveyor belt, and contains an adhesion suppressant that suppresses the adhesion of conveyed objects to the conveyance surface together with rubber. The adhesion inhibitor contains at least one selected from the group consisting of , surfactants, and lubricants.

Further, in order to solve the above problems, the present invention provides a conveyor belt including a cover rubber layer constituting a conveying surface, wherein the cover rubber layer is formed of the above-mentioned rubber composition for cover rubber layer. We provide conveyor belts.

According to the present invention, a rubber composition can be provided that is effective in forming a cover rubber in which adhesion of conveyed materials is suppressed.

FIG. 1 is a schematic cross-sectional view showing the structure of a conveyor belt according to the present embodiment.

Preferred embodiments of the present invention will be described below.
Here, the present invention will be explained by taking as an example a conveyor belt which has only a belt body formed by processing a flat long belt into an endless shape and is not provided with a horizontal crosspiece or an ear crosspiece.
FIG. 1 is a diagram showing a conveyor belt according to the present embodiment, and is a diagram schematically showing a cross section of a belt main body taken along an imaginary plane perpendicular to its longitudinal direction.

As shown in this figure, the conveyor belt according to this embodiment includes a belt body having a three-layer laminated structure in the thickness direction.
Specifically, the belt main body 1 of this embodiment has a core layer 20 interposed between two cover rubber layers 10.
In other words, the belt main body 1 of this embodiment has the cover rubber layer 10 laminated on both the front and back surfaces of the core layer 20.
The belt main body 1 of the conveyor belt in this embodiment includes a first cover rubber layer 10a that constitutes an outer circumferential surface (hereinafter also referred to as a "conveying surface" or "surface") on which conveyed objects are placed, and an inner circumferential surface. The core layer 20 between the two cover rubber layers and the second cover rubber layer 10b constituting the "surface opposite to the conveyance surface" or "back surface" is made of canvas.
In this embodiment, the canvas and the cover rubber layer are bonded to each other by adhesive rubber (not shown).

The first cover rubber layer 10a and the second cover rubber layer 10b of the conveyor belt in this embodiment are formed of a rubber elastic body that is excellent in preventing adhesion of conveyed objects.
The rubber elastic body in this embodiment is made of a crosslinked rubber composition.
A rubber composition for a cover rubber layer (hereinafter also simply referred to as "rubber composition") that forms the cover rubber layer contains rubber and an adhesion inhibitor.
The adhesion inhibitor is for suppressing the adhesion of conveyed objects to the conveyance surface.
In addition, whether or not it can be used as an adhesion suppressant by exhibiting the effect of suppressing the adhesion of conveyed objects to the conveyance surface will be determined in detail in the example below as "method for 'verification of adhesion suppression effect'". This can be verified using the method shown in the following.
That is, "verification of the adhesion suppressing effect" is carried out using rubber compositions that have the same formulation content in addition to the presence or absence of the adhesion inhibitor, and the adhesion suppressor is added to a predetermined amount or more (for example, 10 parts by mass or more per 100 parts by mass of rubber). If there is a significant difference between the verification results obtained when the adhesion inhibitor is blended at a ratio of 1 and the verification results obtained when the adhesion inhibitor is not included, it can be determined that the adhesion inhibitor functions effectively.

The rubber composition of this embodiment contains one or more compounds selected from the group consisting of surfactants and lubricants as the adhesion inhibitor.
The rubber composition of this embodiment further contains a filler, a crosslinking agent, an additive, and the like.

The rubber composition of this embodiment contains a diene rubber and a thermoplastic elastomer as the rubber.
Examples of the diene rubber contained in the rubber composition of this embodiment include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and chloroprene rubber.
Among these, it is preferable that the rubber composition of this embodiment contains natural rubber and butadiene rubber.
The rubber composition of the present embodiment may contain only one selected from a plurality of commercially available natural rubbers, or may contain a blend of a plurality of natural rubbers.
The same applies to butadiene rubber, and it is possible to select only one type from among multiple types of butadiene rubber on the market and include it in the rubber composition, or to blend multiple types and include it in the rubber composition. good.

The mass proportion of natural rubber in all the rubbers contained in the rubber composition is preferably 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 50% by mass or more.
The mass proportion of natural rubber in all the rubbers contained in the rubber composition is preferably 95% by mass or less, more preferably 85% by mass or less, and particularly preferably 75% by mass or less.

The mass ratio of butadiene rubber to all the rubbers contained in the rubber composition is preferably 20% by mass or more, more preferably 25% by mass or more, and particularly preferably 30% by mass or more.
The mass ratio of butadiene rubber to all the rubbers contained in the rubber composition is preferably 55% by mass or less, more preferably 50% by mass or less, and particularly preferably 45% by mass or less.

When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of rubber other than these is preferably less than 15 parts by mass, and preferably less than 12.5 parts by mass. It is more preferable that the amount is present, and particularly preferably less than 10 parts by mass.
When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of rubber other than these preferably exceeds 0 parts by mass, and more preferably exceeds 1 part by mass. Preferably, more than 2 parts by mass is particularly preferred.

Rubbers other than natural rubber and butadiene rubber that are suitable for inclusion in the rubber composition include the thermoplastic elastomers described above.
The thermoplastic elastomer can be, for example, a polyolefin thermoplastic elastomer (TPO), a styrene thermoplastic elastomer (TPS), a polyurethane thermoplastic elastomer (TPU), or a polyamide thermoplastic elastomer (TPA).

The thermoplastic elastomer is preferably a block copolymer having a plurality of low polar blocks, for example.
Monomers serving as the constituent units of the low polar block include α-olefins having 2 or more carbon atoms.
The monomers include, for example, ethylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-decene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1- Examples include octene.
It is preferable that one low polarity block among the plurality of low polarity blocks constituting the thermoplastic elastomer is composed of ethylene, and the other low polarity block among the plurality of low polarity blocks is α- Preferably, it is composed of an olefin.
The thermoplastic elastomer is preferably an ethylene/α-olefin block copolymer.
The α-olefin constituting the thermoplastic elastomer is preferably 1-octene.
That is, the thermoplastic elastomer is preferably an ethylene/1-octene block copolymer.

When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the first thermoplastic elastomer is preferably 0.5 parts by mass or more, and 1 part by mass. It is more preferably at least 1 part by mass, particularly preferably at least 2 parts by mass.
When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the first thermoplastic elastomer is preferably 6 parts by mass or less, and 5 parts by mass or less. It is more preferable that

The thermoplastic elastomer contained in the rubber composition may include a repeating unit having a polar group in order to improve the affinity between the surfactant and the lubricant and the diene rubber.
The thermoplastic elastomer may be, for example, a block copolymer having a high polar block such as a polyacrylic acid ester block and a low polar block having a lower polarity than the high polar block.
Monomers serving as the constituent units of the low polar block include α-olefins having 2 or more carbon atoms.
The monomers include, for example, ethylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-decene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1- Examples include octene.
Examples of monomers serving as constituent units of the highly polar block include unsaturated acids such as acrylic acid and methacrylic acid; Acrylic esters formed from methacrylic acid such as methyl methacrylate and ethyl methacrylate and alkyl alcohols having 1 to 10 carbon atoms; Vinyl cyanide such as acrylonitrile and methacrylonitrile; Vinyl acetate and propionic acid Vinyl esters such as vinyl; acrylic esters formed from acrylic acid and long-chain glycols with a molecular weight of 80 to 6,000, such as polyethylene glycol acrylate and polytetramethylene glycol acrylate; polyethylene glycol methacrylate, polytetramethylene glycol methacrylate Methacrylic acid esters formed from methacrylic acid such as methacrylic acid and long chain glycol with a molecular weight of 80 to 6000; unsaturated epoxy compounds such as glycidyl methacrylate; 3-hydroxy-1-propene, 4-hydroxy-1-butene, cis- Compounds with hydroxyl groups such as 1,4-dihydroxy-2-butene, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2-hydroxyethyl crotonate; maleic acid, fumaric acid, Examples include maleic anhydride and maleimide.

When the thermoplastic elastomer contains a low polar block and a high polar block, the thermoplastic elastomer has a mass proportion of the low polar block of 55 mass % or more and 95 mass % or less (a high polar block of 5 mass % or more and 45 mass %). % or less).
The rubber composition of this embodiment does not need to contain only one type of thermoplastic elastomer, and may contain multiple types of thermoplastic elastomers.

Examples of the surfactant contained in the rubber composition as the adhesion inhibitor include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

Examples of the anionic surfactant include sodium fatty acid, potassium fatty acid, sodium alkylbenzene sulfonate, sodium alkyl sulfate, sodium alkyl sulfonate, sodium alkyl ether sulfate, monoalkyl phosphate, and polyoxyethylene alkyl ether phosphate. Examples include sodium acid ester, sodium fatty acid ester sulfonate, sodium fatty acid ester sulfate, sodium fatty acid alkylose amide sulfate, and sodium fatty acid amide sulfonate.

Examples of the cationic surfactant include alkylmethylammonium chloride, alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, alkyldimethylbenzylammonium chloride, and alkylpyridinium chloride.

Examples of the nonionic surfactants include sucrose fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene lanolin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycol monofatty acid ester, isopropanolamide, alkylamine oxide, and polyoxyethylene glycol monofatty acid ester. Examples include oxyethylene amine, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, and the like.

Examples of the zwitterionic surfactants include carboxybetaine, alkylbetaine, sulfobetaine, and phosphobetaine.

When a surfactant is contained in the rubber composition of the present embodiment, it is not necessary to contain only one type of surfactant, and multiple types of surfactants may be contained.

Examples of the lubricant contained in the rubber composition as the adhesion inhibitor include fatty acid salts and fatty acid amides.

Examples of the fatty acid salts include metal salts of saturated fatty acids such as lauric acid, palmitic acid, stearic acid, and behemic acid; and unsaturated fatty acids such as erucic acid, oleic acid, brassic acid, and elaidic acid. Examples include magnesium salts, calcium salts, sodium salts, potassium salts, and the like.
Examples of the fatty acid amide include lauric acid amide, palmitic acid amide, stearic acid amide, behemic acid amide, erucic acid amide, oleic acid amide, brassic acid amide, elaidic acid amide, methylene bisstearic acid amide, methylene bis oleic acid amide. Examples include amide, ethylene bisstearamide, ethylene bisoleic acid amide, and the like.

When the rubber composition of this embodiment contains a lubricant, it is not necessary to contain only one type of lubricant, and multiple types of lubricants may be contained.

Fatty acid amide is suitable as the lubricant.
The number of carbon atoms in the fatty acid amide is preferably 10 to 25, more preferably 12 to 22.
The melting point of the fatty acid amide is preferably 40°C or higher and 110°C or lower, more preferably 60°C or higher and 95°C or lower.

The melting point of fatty acid amide can be measured by the so-called transparency method using a capillary tube.
Specifically, the melting point of fatty acid amide is determined according to the test method based on "7.5.2 Visual method" of JIS K6220-1:2015 "Rubber compounding agents - Organic chemicals - Test methods - Part 1: General". can be measured.

The fatty acid amide used as the lubricant has an unsaturated bond, so it can form a chemical bond with the diene rubber when crosslinking the rubber composition, and it can be lost from the cover rubber layer due to bleed-out. It can be suppressed from being put away.
The fatty acid amide preferably has an iodine value of 70 or more.
The iodine value of the fatty acid amide is more preferably 72 or more.
The iodine value of the fatty acid amide is preferably 90 or less, more preferably 85 or less, particularly preferably 80 or less.
The fatty acid amide used as a lubricant in this embodiment is preferably erucic acid amide.

The iodine value of fatty acid amide shall be measured based on the method described in JIS K0070:1992 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value, and unsaponifiable substances of chemical products." Can be done.

When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the lubricant is preferably 0.5 parts by mass or more, and preferably 1 part by mass or more. is more preferable, and particularly preferably 2 parts by mass or more.
When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the lubricant is preferably 10 parts by mass or less, more preferably 8 parts by mass or less. The amount is preferably 5 parts by mass or less, particularly preferably 5 parts by mass or less.

It is preferable that the rubber of the rubber composition in this embodiment further contains oil and fat as the adhesion inhibitor.

Examples of fats and oils include fatty acids and fatty acid esters in which a carboxyl group is bonded to the end of a hydrocarbon chain (a chain of hydrogen-bonded carbons) having about 6 to 18 carbon atoms.
Examples of the oils and fats include vegetable oils such as soybean oil, rapeseed oil, palm oil, and coconut oil; animal oils such as beef tallow, lard, and liver oil; and mineral oils such as paraffinic mineral oil.

When the rubber composition of the present embodiment contains an oil or fat, it is not necessary to contain only one type of oil or fat, and a plurality of types of oil or fat may be contained.

The surfactant, the lubricant, and the oil and fat bleed out onto the surface of the cover rubber to suppress adhesion of conveyed objects.
The thermoplastic elastomer exhibits a function of slowing down this bleed-out.
Among these, the thermoplastic elastomer is effective in releasing the lubricant in a sustained manner.
Therefore, it is preferable that the rubber composition of the present embodiment contains the lubricant as the adhesion inhibitor, and that the rubber further contains a thermoplastic elastomer together with the diene rubber.

If the lubricant or the oil or fat has an unsaturated bond, there is a risk that after it bleeds out onto the conveying surface, the molecular weight will be increased by ultraviolet rays or the like, producing a sticky compound.
Therefore, it is preferable that the lubricant and the oil/fat have a small number of unsaturated bonds, or have a certain level of unsaturated bonds or more, so that when exposed to sunlight, etc., the lubricant and the oil/fat quickly form a film and dry out.
Therefore, the lubricant and the oil have an iodine value of 100 or less as determined by JIS K0070-1992 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value, and unsaponifiables of chemical products" The iodine value is preferably either 90 or less or 150 or more.

In this embodiment, it is preferable that the rubber composition contains a plurality of adhesion inhibitors.
It is preferable that the rubber composition of this embodiment contains the surfactant as the adhesion inhibitor and further contains oil and fat as the adhesion inhibitor.
The rubber composition of this embodiment preferably contains both the surfactant and the lubricant as the adhesion inhibitor.

These adhesion inhibitors are preferably contained in the rubber composition in a predetermined ratio with respect to the diene rubber.
The total content of the adhesion inhibitor is preferably 1 part by mass or more and 35 parts by mass or less, more preferably 5 parts by mass or more and 20 parts by mass or less, and 8 parts by mass based on 100 parts by mass of the diene rubber. More preferably, the amount is 17 parts by mass or less.

The rubber composition of the present embodiment preferably further contains a compatibilizer in order to suppress excessive bleed-out of the adhesion inhibitor to the surface of the cover rubber.
The compatibilizer is preferably a thermoplastic resin, and preferably a block copolymer comprising a low polarity block and a high polarity block.
The low polar block in the block copolymer used as the compatibilizer is preferably composed of ethylene.
Preferably, the highly polar block of the block copolymer is composed of acrylic acid.
That is, the rubber composition of the present embodiment preferably contains an ethylene-ethyl acrylate block copolymer (EEA) as the compatibilizer.

It is preferable that the rubber composition of this embodiment further contains a compatibilizer other than the ethylene/ethyl acrylate block copolymer.
That is, the rubber composition of the present embodiment contains a first compatibilizer that is an ethylene/ethyl acrylate block copolymer, and a second compatibilizer different from the first compatibilizer. is preferred.

The second compatibilizer is preferably a graft copolymer obtained by grafting another block copolymer onto the same or different ethylene/ethyl acrylate block copolymer as the first compatibilizer. .
That is, the second compatibilizer is preferably a graft copolymer in which the main chain is composed of an ethylene/ethyl acrylate block copolymer and has a side chain composed of the other block copolymer.
The block copolymer constituting the side chain of the graft copolymer is preferably a terpolymer of n-butyl acrylate/2-hydroxypropyl acrylate/styrene.

When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the first compatibilizer is preferably 0.5 parts by mass or more, and 1 part by mass. It is more preferably at least 1 part by mass, particularly preferably at least 2 parts by mass.
When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the first compatibilizer is preferably 10 parts by mass or less, and 8 parts by mass or less. It is more preferable that

When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the second compatibilizer is preferably 0.5 parts by mass or more, and 1 part by mass. It is more preferably at least 1 part by mass, particularly preferably at least 2 parts by mass.
When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the content of the second compatibilizer is preferably 6 parts by mass or less, and 5 parts by mass or less. It is more preferable that

When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the total content of all compatibilizers is preferably 1 part by mass or more, and preferably 2 parts by mass or more. It is more preferable that the amount is at least 4 parts by mass, and particularly preferably 4 parts by mass or more.
When the total amount of natural rubber and butadiene rubber contained in the rubber composition is 100 parts by mass, the total content of all compatibilizers is preferably 16 parts by mass or less, and 15 parts by mass or less. It is more preferable that the amount is 14 parts by mass or less, and particularly preferably 14 parts by mass or less.

The rubber composition of this embodiment further contains a filler, a crosslinking agent, and an additive as described above.
Examples of the filler include carbon black, silica, calcium carbonate, talc, clay, aluminum hydroxide, and magnesium hydroxide.
The rubber composition of this embodiment does not need to contain only one type of filler, and may contain multiple types of fillers.

Among those exemplified above, carbon black is preferably included in the rubber composition because it has a particularly excellent reinforcing effect on rubber.
The rubber composition of the present embodiment preferably contains 20 parts by mass or more and 100 parts by mass or less of carbon black, and contains 30 parts by mass or more and 90 parts by mass or less of carbon black, based on 100 parts by mass of the diene rubber. It is more preferable that you do so.

Examples of the crosslinking agent to be included in the rubber composition include sulfur and organic peroxides.
As the crosslinking agent contained in the rubber composition of this embodiment, sulfur is preferable.
Further, the rubber composition may further contain a vulcanization accelerator such as N-cyclohexyl-2-benzothiazolylsulfenamide, a vulcanization accelerator such as zinc oxide, and the like.

Examples of the additives include functional agents such as amine-ketone compounds, aromatic secondary amine compounds, benzimidazole compounds, anti-aging agents such as special wax; flame retardants; weathering agents; etc. .
Further, examples of the additives include processability improvers such as process oil, mastication accelerator, and scorch inhibitor.

In addition, in the conveyor belt, a common rubber composition may be used to form the first cover rubber layer 10a and the second cover rubber layer 10b, or they may be formed from different rubber compositions. You may also do so.
Further, the first cover rubber layer 10a and the second cover rubber layer 10b may have different or common thicknesses.
In particular, in the conveyor belt, it is preferable that the first cover rubber layer is thicker than the second cover rubber layer.
For example, the thickness of the first cover rubber layer 10a constituting the conveyance surface is preferably 1.1 times or more the thickness of the second cover rubber layer 10b constituting the opposite surface to the conveyance surface; It is more preferably .5 times or more, and particularly preferably 2 times or more.
The thickness of the first cover rubber layer 10a is usually 5 mm or more and 15 mm or less, and the thickness of the second cover rubber layer 10b is usually 1 mm or more and less than 5 mm.

The canvas for forming the core layer 20 is not particularly limited, and any canvas used in general conveyor belts can be used in this embodiment as well.
Furthermore, the core layer 20 may be formed using steel cord or the like instead of canvas.

Further, the adhesive rubber used in general conveyor belts can be used in this embodiment as well, without any particular limitation.

The method of manufacturing the conveyor belt of this embodiment is not particularly limited, and can be manufactured in the same manner as a general conveyor belt.
The conveyor belt is manufactured by kneading a rubber composition for the cover rubber layer using, for example, a Banbury mixer, a kneader mixer, an open roll, etc., and then forming the rubber composition into a sheet using a calender or the like to form the cover rubber layer. It can be manufactured by preparing an unvulcanized sheet for use and vulcanizing and integrating the unvulcanized sheet with a canvas on which adhesive rubber is supported on the surface.

In addition, in this embodiment, the rubber composition for cover rubber layer does not need to be used only for the cover rubber layer, and may be used for forming adhesive rubber, ear rubber, etc.
Further, in this embodiment, an embodiment in which cover rubber layers are provided on both sides of the core layer is exemplified, but the cover rubber layer formed from the rubber composition for cover rubber layers of this embodiment has at least a core layer. It suffices if it is provided on one side (transportation side) of the body layer.
In this embodiment, the conveyor belt is exemplified as having only a flat belt-shaped belt body, but the belt body itself is given a three-dimensional shape by being produced using a hot press with an uneven press surface. Conveyor belts of a type in which a horizontal crosspiece or an ear crosspiece are attached as separate parts to a flat belt-like belt body are also within the scope of the conveyor belt of the present invention.
In a conveyor belt having horizontal bars and edge bars, it is also possible to use a rubber composition for conveyor belts to form the horizontal bars and edge bars.

The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

(Materials used)
Table 1 below shows the abbreviations of the compounding agents used for adding the adhesion inhibitor and their specific contents.

上記のような原料を表３に示す配合割合で含有するゴム組成物を用いて加硫ゴムシートを作製し、該加硫ゴムシートによって各評価を実施した。
Further, Table 2 below shows abbreviations of anti-aging agents and their specific contents.

A vulcanized rubber sheet was prepared using a rubber composition containing the above raw materials in the proportions shown in Table 3, and various evaluations were performed using the vulcanized rubber sheet.

Note that "oil sulfur" was specifically used as the sulfur in the above formulation.
Further, N-cyclohexyl-2-benzothiazolylsulfenamide was used as a vulcanization accelerator.

(Evaluation 1: Verification of adhesion suppression effect)
Rubber sheets for evaluation (crosslinked rubber sheets) were prepared with the formulations shown in Table 3 for each example, and the adhesion of the transported objects was evaluated according to the following steps 1) to 5).

1) Put fine granular coal adjusted to a predetermined moisture content into a plastic container.
2) Place a test piece cut into a predetermined shape from a rubber sheet into the same plastic container.
3) Set the plastic container on a rotary stirring device and stir the contents (coal, test piece).
4) Take out the test piece and collect the coal attached to the surface of one side.
5) Measure the mass of the collected coal.

In addition, an adhesion test using fine granular iron ore (iron ore adjusted to a particle size of 2 mm or less by classification) was conducted in the same manner as in steps 1) to 5) above.
Furthermore, an adhesion test using Masago soil was conducted in the same manner as in steps 1) to 5) above.
The results are also shown in Table 3.

From the above results, it can be seen that according to the present invention, an excellent adhesion suppressing effect can be exerted on a conveyor belt.

1: Belt body (conveyor belt), 10: Cover rubber layer (10a: first cover rubber layer, 10b: second cover rubber layer), 20: core layer

Claims (4)

Used to form the cover rubber layer that makes up the conveying surface of a conveyor belt.
Containing an adhesion inhibitor together with rubber that suppresses adhesion of conveyed objects to the conveyance surface,
The adhesion inhibitor includes a surfactant and an oil or fat ,
A rubber composition for a cover rubber layer containing a thermoplastic elastomer as well as a diene rubber as the rubber. Used to form the cover rubber layer that makes up the conveying surface of a conveyor belt.
Containing an adhesion inhibitor together with rubber that suppresses adhesion of conveyed objects to the conveyance surface,
The adhesion inhibitor includes both a surfactant and a lubricant,
A rubber composition for a cover rubber layer containing a thermoplastic elastomer as well as a diene rubber as the rubber. A conveyor belt comprising a cover rubber layer constituting a conveyance surface, the conveyor belt comprising:
A conveyor belt, wherein the cover rubber layer is formed of the rubber composition for a cover rubber layer according to claim 1 or 2 . a first cover rubber layer constituting the conveyance surface;
a second cover rubber layer forming a surface opposite to the conveying surface;
The conveyor belt according to claim 3 , wherein the first cover rubber layer is thicker than the second cover rubber layer.

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