JPWO2015083746A1 - Conveyor belt - Google Patents

Abstract

An object of the present invention is to provide a conveyor belt that has good characteristics and does not require much labor for manufacturing. In the present invention, the rubber composition of the crosslinked rubber in contact with the steel cord in the belt body is 1 part by mass or more and 10 parts by mass or less of the modified resorcin / formaldehyde condensate with respect to 100 parts by mass of the base rubber, and the modified etherified methylol melamine resin. 0.5 to 7 parts by mass, diethylene glycol 1 to 5 parts by mass, and silica 5 to 45 parts by mass.

Description

  The present invention relates to a conveyor belt, and more particularly to a conveyor belt having a belt body formed of a crosslinked rubber.

BACKGROUND ART Conventionally, a belt conveyor has been widely used as a conveying device for articles and the like, and various forms of conveyor belts are known as the main constituent members of the belt conveyor.
As the conveyor belt, in addition to a belt main body obtained by processing a long belt-like belt into an endless shape, a belt provided with a horizontal rail extending in the width direction of the belt main body or a side edge of the belt main body A thing having an ear cross provided along is widely known conventionally.
As the conveyor belt, one in which the belt main body is formed of a crosslinked rubber is widely used. For example, a core body such as a steel cord is sandwiched between cover rubbers constituting the front and back of the belt main body, A material in which a core is embedded in a crosslinked rubber is widely used.

The steel cord is embedded in, for example, an adhesive rubber provided between front and back cover rubbers.
It is known that the strength of the belt body and the service life of the belt body greatly depend on the bonding state between the steel cord and the crosslinked rubber forming the belt body such as cover rubber and adhesive rubber.

For these reasons, it has been conventionally demanded that the conveyor belt exhibits excellent adhesion between the steel cord and the crosslinked rubber and stabilizes this excellent adhesion over a long period of time.
As a method for improving the adhesion between the steel cord and the crosslinked rubber, an organic acid cobalt salt is blended in a rubber composition that forms a crosslinked rubber in contact with the steel cord as shown in Patent Document 1 below. The method is known.

Japanese Laid-Open Patent Publication No. 11-021389

By the way, steel cords are not used for forming conveyor belts as soon as they are manufactured. Usually, steel cords are stored at a cord manufacturer or a belt manufacturer for a certain period of time, so that the surface of the steel cord is greatly oxidized. May have.
And the steel cord which surface-oxidized greatly has a possibility that the adhesiveness with a crosslinked rubber may be reduced significantly compared with what is surface-oxidized only slightly.
For this reason, in producing a conveyor belt having excellent properties such as strength, for example, it is oxidized from the surface of the steel cord immediately before manufacturing the conveyor belt by chemical treatment such as pickling or mechanical treatment such as polishing. It is conceivable to remove substances and hydroxides.
However, in such a case, there is a risk that a great deal of labor may be generated in the manufacture of the conveyor belt due to the processing as described above.
That is, the conventional conveyor belt has a problem that it is difficult to easily manufacture a belt having good characteristics.

  This invention makes it a subject to satisfy the above problems, and makes it a subject to provide the conveyor belt which has a favorable characteristic and does not require great effort for manufacture.

  In order to solve the above problems, the present invention includes a belt body formed of a crosslinked rubber, the belt body includes a steel cord as a core, and the steel cord is embedded in the crosslinked rubber. The cross-linked rubber forming a portion in contact with the core is composed of a rubber composition containing a base rubber and an organic acid cobalt salt, and a part or all of the base rubber is a natural rubber or styrene-butadiene copolymer. The rubber composition further includes a modified resorcin / formaldehyde condensate, a modified etherified methylol melamine resin, diethylene glycol, and silica, and the modified resorcin / formaldehyde with respect to 100 parts by mass of the base rubber. 1 to 10 parts by mass of the condensate and 0 to the modified etherified methylol melamine resin 5 parts by mass or more 7 parts by weight, the diethylene glycol and 1 part by mass or more 5 parts by weight, to provide a conveyor belt which is characterized by containing the silica at a ratio of less than 45 parts by 5 parts by mass or more.

In the present invention, the cross-linked rubber in contact with the steel cord is formed of a specific rubber composition, so that the cross-linked rubber and the steel cord have good adhesion, and the adhesion is affected by the surface condition of the steel cord. It becomes difficult.
That is, according to the present invention, it is possible to obtain a conveyor belt having good characteristics without performing the treatment for removing the oxide film on the steel cord, which has good characteristics and takes a great deal of time for manufacturing. A conveyor belt that is not required can be provided.

The schematic perspective view which showed the belt conveyor of one aspect. The schematic sectional drawing which showed the structure of the conveyor belt of this embodiment.

The preferred embodiments of the present invention will be described below.
Here, the present invention will be described by taking as an example a conveyor belt which has only a belt main body formed by processing a flat belt-like belt into an endless shape and which is not provided with a cross rail, an ear cross or the like.
FIG. 1 is a schematic perspective view showing a belt conveyor in a state in which the conveyor belt of this embodiment is used.
FIG. 2 is a diagram showing the conveyor belt of the present embodiment, and is a diagram schematically showing a cross section of the belt main body cut by a virtual plane perpendicular to the longitudinal direction (the arrow line II in FIG. 1). Sectional view).

As also shown in this figure, the conveyor belt according to the present embodiment is, for example, endless and used for the belt conveyor 1.
The conveyor belt according to the present embodiment includes a belt body 10 having a three-layer laminated structure in the thickness direction.
And the belt main body 10 of the conveyor belt in this embodiment includes an upper cover rubber layer 11 constituting an outer peripheral surface (front side) on which a conveyed product is placed, and a lower cover rubber constituting an inner peripheral surface (back side). Two cover rubber layers 11 and 12 with the layer 12 and an adhesive rubber layer 13 for adhering both cover rubber layers between them are provided.
In the adhesive rubber layer 13, a core body 14 for embedding a tensile strength to the belt body 10 is embedded.
The core wire 14 is embedded in the adhesive rubber layer 13 so that the longitudinal direction thereof is the longitudinal direction of the belt.
The adhesive rubber layer 13 is not formed over the entire width of the belt body 10 but is formed at the center in the width direction excluding both ends of the belt body 10 as shown in the figure.
And in this embodiment, the ear rubber part 15 is formed in the part in which this adhesive rubber layer 13 is not formed with the rubber composition common to the cover rubber layers 11 and 12.

A steel cord is employed as the core body 14 in the present embodiment.
The steel cord in the present embodiment may be a single wire or a stranded wire composed of a plurality of strands.
The steel cord is preferably galvanized and more preferably hot dip galvanized.
Such a steel cord has a zinc coating by plating on its surface, so that good adhesiveness can be exhibited between the steel cord and the crosslinked rubber constituting the adhesive rubber layer 13.

It is important that the adhesive rubber layer 13 formed of the cross-linked rubber in which the steel cord is embedded is formed of a specific rubber composition of the cross-linked rubber (hereinafter also referred to as “adhesive rubber”). The adhesive rubber layer 13 is made of a specific rubber composition in order to exert good adhesiveness with the adhesive rubber not only on the steel cord having a slight surface oxidation but also on the steel cord having a large surface oxidation. It is important that it be formed.
That is, the rubber composition includes a base rubber containing at least one of natural rubber and styrene-butadiene copolymer rubber, an organic acid cobalt salt, a modified resorcin / formaldehyde condensate, a modified etherified methylol melamine resin, diethylene glycol, In addition, it is important that silica is contained in a predetermined ratio in order to exert good adhesion between the adhesive rubber and the steel cord.

In addition, the ratio of each component may be adjusted so that the rubber composition may have a hardness (instantaneous value) of less than 90 at the normal temperature (23 ° C.) of the adhesive rubber measured by JIS K6253 type A durometer. preferable.
It is preferable that the adhesive rubber has the hardness as described above. Even when the belt body is subjected to bending fatigue, the adhesive rubber is less likely to be cracked, and the useful life of the conveyor belt is shortened. This is because it can be prevented.

Part or all of the base rubber is natural rubber or styrene-butadiene copolymer rubber.
That is, the base rubber may be one kind of natural rubber (NR) or one kind of styrene-butadiene copolymer rubber (SBR), or a blend of two or more kinds of natural rubber or two or more kinds. A blend of styrene-butadiene copolymer rubber may also be used.
The base rubber may be a blend of one or more types of natural rubber and one or more types of styrene-butadiene copolymer rubber.
The base rubber is preferably composed of only natural rubber or styrene-butadiene copolymer rubber. If necessary, polyisoprene rubber (IR), polybutadiene rubber (BR), acrylonitrile butadiene rubber (NBR), Other rubbers such as ethylene-α / olefin copolymer rubber (EPDM), chloroprene rubber (CR), butyl rubber (IIR) may be blended.
However, the total content of rubber other than natural rubber (NR) and styrene-butadiene copolymer rubber (SBR) in the base rubber is preferably 30% by mass or less, and more preferably 10% by mass or less. preferable.
That is, the ratio of the total of natural rubber (NR) and styrene-butadiene copolymer rubber (SBR) to the base rubber is preferably 70% by mass or more, and more preferably 90% by mass or more.

  The natural rubber and the styrene-butadiene copolymer rubber are blended and used, so that excellent adhesiveness with a steel cord or the like is maintained even when heat aging occurs in the adhesive rubber. The natural rubber and the styrene-butadiene copolymer rubber are blended so that the mass ratio (NR: SBR) is 50:50 to 20:80. It is preferable to make it exhibit, and it is particularly preferable to blend so that the mass ratio is 45:60 to 25:75.

Examples of the organic acid cobalt salt constituting the rubber composition together with such a base rubber include, for example, cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oilate and the like. The organic acid cobalt salt may be a complex salt in which a part of the organic acid is replaced with boric acid or the like.
Among these, it is preferable to contain cobalt naphthenate in the rubber composition.
The organic acid cobalt salt can be usually contained in the rubber composition so that the mass ratio with respect to 100 parts by mass of the base rubber is 2 parts by mass or more and 6 parts by mass or less.
The content of the organic acid cobalt salt in the rubber composition is preferably 3 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber.

The modified resorcin / formaldehyde condensate is usually obtained by reacting resorcin, alkylphenol, and formaldehyde. In the present embodiment, for example, as the modified resorcin / formaldehyde condensate, alkylphenol and formaldehyde are used. After forming a resole-type condensate by the above, a product obtained by reacting the condensate with resorcin can be employed.
Examples of the alkylphenol as a constituent unit of the modified resorcin / formaldehyde condensate include, for example, o-cresol, o-ethylphenol, o-n-propylphenol, o-iso-propylphenol, m-cresol, m-ethylphenol, mn-propylphenol, m-iso-propylphenol, p-cresol, p-ethylphenol, pn-propylphenol, p-iso-propylphenol, pn-butylphenol, pt-butylphenol, p -T-octylphenol, p-sec-octylphenol, p-nonylphenol and the like.

The modified resorcin / formaldehyde condensate is effective in improving the adhesiveness between the adhesive rubber and the steel cord, and need not be one kind like the base rubber. A plurality of types of objects may be mixed.
The modified resorcin / formaldehyde condensate can be contained in the rubber composition so that the total content thereof is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the base rubber.
The content of the modified resorcin / formaldehyde condensate in the rubber composition is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber.

  The modified etherified methylol melamine resin in the present embodiment is a condensate of melamine, formaldehyde and methanol, and specific examples include hexakis (methoxymethyl) melamine and pentakis (methoxymethyl) methylol melamine.

The modified etherified methylolmelamine resin is usually contained in the rubber composition so that the total content thereof is 0.5 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the base rubber. Can do.
The content of the modified etherified methylolmelamine resin in the rubber composition is preferably 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the base rubber.

The diethylene glycol is an effective component for improving the adhesion between the adhesive rubber and the steel cord.
The diethylene glycol has a function of shortening the heating time when the rubber composition is cross-linked, and is an effective component for making the belt body easy to manufacture.
The diethylene glycol in the present embodiment can usually be contained in the rubber composition so that the content thereof is 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base rubber.
The content of the diethylene glycol in the rubber composition is preferably 2 parts by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the base rubber.

The silica is an effective component for improving the adhesion between the adhesive rubber and the steel cord together with the modified resorcin / formaldehyde condensate, the modified etherified methylol melamine resin and the like.
As the silica in the present embodiment, those obtained by a dry method such as a combustion method or an arc method, or those obtained by a wet method such as a precipitation method or a gel method can be adopted, and in particular, obtained by a precipitation method. It is preferable to employ silica.
The particle state of silica obtained by the sedimentation method is usually aggregated particles in which a plurality of primary particles are aggregated.
The silica in the present embodiment is preferably aggregated particles having an average particle diameter of 5 μm or more and 50 μm or less, and the primary particles constituting the aggregated particles are preferably 5 nm or more and 50 nm or less.

The silica does not need to be one kind like the other components, and a plurality of kinds may be mixed in the rubber composition.
That is, in this embodiment, both the silica by the dry method and the silica by the wet method may be contained in the rubber composition.
In the present embodiment, a plurality of types of silica having different surface treatments such as a silica silane coupling agent-treated product and a fatty acid metal salt-treated product may be contained in the rubber composition. You may make it make a rubber composition contain the untreated goods which are not surface-treated.
In addition, the said silica can be normally contained in the said rubber composition so that the total content may be 5 to 45 mass parts with respect to 100 mass parts of said base rubbers.
The content of the silica in the rubber composition is preferably 7 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the base rubber, and 8 parts by mass or more and 20 parts by mass with respect to 100 parts by mass of the base rubber. It is more preferable that the amount is not more than parts.

In the present embodiment, the rubber composition for forming an adhesive layer may further contain various additives widely used as rubber chemicals.
Examples of the additive include a crosslinking agent for crosslinking the base rubber such as sulfur; a vulcanization accelerator such as a sulfenamide compound and a thiazole compound; and stearic acid for enhancing the activity of the vulcanization accelerator. Zinc oxide, carbon black, etc. are mentioned in addition to these.
Examples of the additive include softeners, anti-aging agents, processability improvers, flame retardants, antibacterial agents, rust inhibitors, and pigments.

In addition, when using sulfur as said crosslinking agent, it is preferable that content in the said rubber composition shall be 0.5 to 5 mass parts with respect to 100 mass parts of said base rubbers.
Further, when the rubber composition contains the vulcanization accelerator, it is preferable to employ a sulfenamide compound as the vulcanization accelerator.
The content of the vulcanization accelerator in the rubber composition is preferably 0.1 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the base rubber.
When the stearic acid is contained in the rubber composition, the content of the stearic acid in the rubber composition is preferably 0.1 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the base rubber. .
When the rubber composition contains the zinc oxide, the content of the zinc oxide in the rubber composition is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the base rubber.
Moreover, when making the rubber composition contain the carbon black, the content of the carbon black in the rubber composition is preferably 30 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the base rubber.

The adhesive rubber layer 13 in the belt body of the conveyor belt of this embodiment is formed of a rubber composition containing the above components.
On the other hand, the rubber composition forming the upper cover rubber layer 11 and the lower cover rubber layer 12 can be the same as that of a conventional belt body having the same laminated structure as the conveyor belt of this embodiment. .
The rubber composition for forming the cover rubber layers 11 and 12 is appropriately changed, for example, with the base rubber and other components in common with the rubber composition exemplified for the adhesive rubber layer 13 in the amount of each component. It is good also as what was prepared so that a desired characteristic may be exhibited.

About the method of forming a belt body using these rubber composition and steel cord, the same method as the conventional method of manufacturing a conveyor belt can be adopted.
That is, the belt body in the present embodiment can be manufactured by sequentially performing the following steps (a) to (c), for example.
(A) A rubber composition for a cover rubber or a kneaded material for adhesive rubber using a Banbury mixer, a kneader mixer, a roll or the like is molded into a belt shape using a calendar or the like and is unvulcanized for a cover rubber A sheeting process for producing a sheet and an unvulcanized sheet for adhesive rubber.
(B) A structure in which steel cords serving as cores are arranged at predetermined intervals are sandwiched between two unvulcanized sheets for adhesive rubber, and further sandwiched between two unvulcanized sheets for cover rubber A laminating process for forming a sandwich-like laminated body.
(C) A crosslinking step in which the laminated body is heated while being pressed in the thickness direction using a hot press or the like to unify the unvulcanized sheets by crosslinking and to bond the adhesive rubber and the core wire with an excellent adhesive force.

  The cover rubber layers 11 and 12 and the ear rubber portion 15 are not particularly limited in the content of the mixture, but a base rubber of the same system as the rubber composition used for forming the adhesive rubber layer is used. Preferably it is formed.

In this embodiment, a conveyor belt having only a flat belt-like belt body is illustrated, but a three-dimensional shape is imparted to the belt body itself by being produced using a hot press having unevenness on the press surface. Conveyor belts of the type of the present invention are also intended as conveyor belts of the present invention, and conveyor belts of a type in which a horizontal beam and an ear beam are attached as separate parts to a flat belt-like belt body.
Moreover, in this embodiment, although what has an adhesive rubber layer and an ear rubber part is illustrated, the adhesive rubber layer is provided over the whole belt width and the ear rubber part is not provided, or an adhesive rubber layer Is not included, and the aspect in which the core is directly sandwiched between the upper and lower cover rubber layers is also within the range intended as the conveyor belt of the present invention.
Needless to say, the conveyor belt of the present invention can be modified from the above-described examples with various modifications.

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

(Materials used)
Table 1 below shows the abbreviations and specific contents of the raw materials used in the evaluation.

  An evaluation sample was prepared using a rubber composition containing the raw materials as described above in the blending ratios shown in Table 2, and each evaluation was performed.

(Evaluation)
(Adhesive strength evaluation)
Samples were prepared according to each formulation, and the adhesive strength was evaluated.
The test method of the adhesive strength was carried out according to “9.10 Steel cord pull-out test” of JIS K6369 “Steel cord conveyor rubber belt”.
In the test, “pull-out test piece (a)” defined in the same standard was used.
For the evaluation of the adhesive strength, a steel cord (φ5.0) that was allowed to stand for 24 hours in an environment of 35 ° C. and 90% RH and sufficiently oxidized was used.

Here, the evaluation result of the adhesive strength was determined according to the following criteria.

B: It is a level that cannot be said to be particularly superior to a conventional conveyor belt in which a special treatment for removing the surface oxide film is not applied to the steel cord.
A: A level at which performance equal to or higher than that of a conveyor belt using a steel cord subjected to a treatment for removing the surface oxide film is exhibited.

(Repeated stretch durability)
A “pulling test piece (a)” defined in “9.10 Steel cord pull-out test” of JIS K6369 “Steel cord conveyor rubber belt” was produced.
The operation of extending and retracting the pull-out test piece was repeated, and the number of times of expansion and contraction until the steel cord at the center in the width direction of the test piece was broken between the rubber and the rubber was measured.
The expansion and contraction was carried out in such a manner that after a pulling test piece was pulled in the longitudinal direction and a stress of 3.5 kN was applied, the stress was immediately released to return to the original state (stress 0 kN).
The results were determined according to the following criteria.
(Criteria)
B: When the steel cord breaks with rubber less than 1000 times.
A: When the steel cord breaks with rubber in 1000 times or more and less than 1500 times.
AA: When the steel cord does not break between the rubber and the rubber even after being expanded and contracted 1500 times.

(Rubber hardness)
In addition, about rubber hardness, the hardness (instantaneous value) in normal temperature (23 degreeC) was measured with the type A durometer prescribed | regulated to JISK6253.

(Comprehensive evaluation)
The above evaluation results and comprehensive evaluation are shown in Table 2.
In this comprehensive evaluation, the following criteria were used in consideration of the adhesiveness (adhesive strength, repeated stretching durability) of the steel cord.

B: Either or both of adhesive strength and repeated stretch durability are “B” determinations.
A: Both the adhesive strength and the repeated stretching durability are the results of “A” judgment or more.

  From the results shown in this table, it can be seen that according to the present invention, it is possible to obtain a conveyor belt that has good characteristics and does not require much labor for manufacturing.

  10: belt body (conveyor belt), 11: upper cover rubber layer, 12: lower cover rubber layer, 13: adhesive rubber layer, 14: core (steel cord)

Claims (1)

It has a belt body made of crosslinked rubber,
The belt body includes a steel cord as a core, and the steel cord is embedded in the crosslinked rubber.
The cross-linked rubber forming a portion in contact with the core is composed of a rubber composition containing a base rubber and an organic acid cobalt salt, and a part or all of the base rubber is a natural rubber or styrene-butadiene copolymer. Polymer rubber,
The rubber composition further contains a modified resorcin / formaldehyde condensate, a modified etherified methylol melamine resin, diethylene glycol, and silica, and 1 part by mass of the modified resorcin / formaldehyde condensate with respect to 100 parts by mass of the base rubber. 10 parts by mass or less, 0.5 to 7 parts by mass of the modified etherified methylol melamine resin, 1 to 5 parts by mass of diethylene glycol, and 5 to 45 parts by mass of silica. Conveyor belt characterized by containing in.

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