JP2021059627A - Rubber composition for steel cord adhesion and conveyor belt - Google Patents

Abstract

To provide a rubber composition for steel cord adhesion excellent in water-resistant adhesiveness and processing stability, and a conveyor belt.SOLUTION: The rubber composition for steel cord adhesion contains a rubber component containing at least a diene rubber, an organic acid cobalt salt, sulfur, and a vulcanization retarder and does not substantially contain a vulcanization accelerator. The organic acid cobalt salt is cobalt borate neodecanoate. The vulcanization retarder is N-cyclohexylthiophthalimide. A conveyor belt 1 is formed of a cover rubber layer 6, galvanized steel cords 2, and a coat rubber layer 4 comprising the rubber composition for adhesion.SELECTED DRAWING: Figure 1

Description

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

Conventionally, various rubber compositions have been proposed for the purpose of improving the adhesive performance to the steel cord.
For example, in Patent Document 1, with respect to 100 parts by weight of sulfur vulcanizable rubber, 3 to 15 parts by weight of rosin or a rosin derivative and 0.2 to 1.0 parts by weight of an organocobalt salt as cobalt amount. , A method for adhering a rubber composition containing 3 to 50 parts by weight of an organic chlorine compound to a zinc-plated steel cord, a method for adhering a zinc-plated steel cord to rubber, and the like are described.

Japanese Unexamined Patent Publication No. 11-21389

Under such circumstances, the present inventor prepared a rubber composition with reference to Patent Document 1 and evaluated it as a rubber composition for adhering a steel cord. As a result, the rubber and the steel cord obtained from such a rubber composition were found. It was clarified that there is room for improvement in the water resistance and processing stability (rubber burning during processing) between the two.
Therefore, an object of the present invention is to provide a rubber composition for bonding a steel cord, which is excellent in water resistance and processing stability. In the present invention, the water-resistant adhesiveness includes the moisture-resistant adhesiveness.
Another object of the present invention is to provide a conveyor belt having excellent water resistance and processing stability.

As a result of diligent research to solve the above problems, the present inventor contains a rubber component containing at least a diene-based rubber, an organic acid cobalt salt, sulfur, and a vulcanization retarder, and substantially realizes a vulcanization accelerator. It has been found that a rubber composition for adhering a steel cord, which is not contained in a specific manner, can improve the water resistance and processing stability between the rubber obtained from the rubber composition and the steel cord.
The present invention is based on the above findings and the like, and specifically solves the above problems by the following configurations.

式中、Ｒ¹は炭化水素基を表し、Ｒ²は水素原子、炭化水素基又はアルコキシ基を表わす。
［４］ 上記加硫遅延剤が、Ｎ−シクロヘキシルチオフタルイミドである、［１］〜［３］のいずれかに記載のスチールコード接着用ゴム組成物。
［５］ 亜鉛メッキスチールコードを接着させるために使用される、［１］〜［４］のいずれかに記載のスチールコード接着用ゴム組成物。
［６］ ［１］〜［５］のいずれかに記載のスチールコード接着用ゴム組成物を用いて形成されたコンベヤベルト。 [1] A rubber component containing at least a diene-based rubber and
Organic acid cobalt salt and
With sulfur
Contains a vulcanization retarder and
A rubber composition for bonding steel cords that contains substantially no vulcanization accelerator.
[2] The rubber composition for adhering a steel cord according to [1], wherein the organic acid cobalt salt is cobalt neodecanoate borate.
[3] The rubber composition for bonding a steel cord according to [1] or [2], wherein the vulcanization retarder is a compound represented by the following formula (1).

In the formula, R ¹ represents a hydrocarbon group and R ² represents a hydrogen atom, a hydrocarbon group or an alkoxy group.
[4] The rubber composition for bonding a steel cord according to any one of [1] to [3], wherein the vulcanization retarder is N-cyclohexylthiophthalimide.
[5] The rubber composition for adhering a steel cord according to any one of [1] to [4], which is used for adhering a galvanized steel cord.
[6] A conveyor belt formed by using the rubber composition for adhering a steel cord according to any one of [1] to [5].

The rubber composition for bonding steel cords of the present invention is excellent in water resistance and processing stability.
Further, the conveyor belt of the present invention is excellent in water resistance and processing stability.

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

The present invention will be described in detail below.
The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
In the present specification, unless otherwise specified, each component may use a substance corresponding to the component individually or in combination of two or more kinds. When a component contains two or more substances, the content of the component means the total content of the two or more substances.
In the present specification, unless otherwise specified, each component is not particularly limited in its production method. For example, a conventionally known method can be mentioned.
In the present specification, one or both of water resistance and processing stability may be more excellent, and the effect of the present invention may be more excellent.

[Rubber composition for bonding steel cord]
The rubber composition for adhering steel cords of the present invention (composition of the present invention) is
With rubber components containing at least diene rubber,
Organic acid cobalt salt and
With sulfur
Contains a vulcanization retarder and
A rubber composition for adhering steel cords that does not substantially contain a vulcanization accelerator.

Since the composition of the present invention has the above-mentioned structure, it is considered that a desired effect can be obtained. The reason is not clear, but it is presumed to be as follows.
Generally, in a rubber composition containing a diene rubber, sulfur and a vulcanization accelerator, a vulcanization retarder is used for the purpose of suppressing scorch (early vulcanization) by the vulcanization accelerator.
On the other hand, the present inventor is studying that a vulcanization accelerator is substantially not contained in order to improve the water resistance adhesion between the rubber composition and the steel cord.
Among them, the present inventor presents that when the rubber composition contains a diene rubber, an organic acid cobalt salt and sulfur and substantially does not contain a vulcanization accelerator, the organic acid cobalt salt is a diene rubber due to sulfur. It was found that vulcanization can be promoted as a vulcanization accelerator in the vulcanization of. When cobalt organic acid or the like promotes vulcanization, rubber burning during processing is promoted, so that the processing stability of the rubber composition is lowered.
Therefore, in the composition of the present invention, the organic acid cobalt salt or the cobalt reacts with the vulcanization retarder before the organic acid cobalt salt (or the cobalt contained in the organic acid cobalt salt) reacts with sulfur. The present inventor presumes that this suppresses rubber burning during processing and is excellent in processing stability.
Further, as described above, by reacting the organic acid cobalt salt or the cobalt with a vulcanization retarder before reacting with sulfur, the consumption of sulfur by vulcanization in the rubber composition is suppressed, and the rubber composition is suppressed. The present inventor speculates that the amount of sulfur that can contribute to the adhesion between the object and the steel cord increases, and as a result, the composition of the present invention has excellent water adhesion resistance.
Hereinafter, each component contained in the composition of the present invention will be described in detail.

<Rubber component>
The composition of the present invention contains a rubber component containing at least a diene-based rubber.

<Diene rubber>
The diene-based rubber contained in the composition of the present invention is not particularly limited as long as it is a polymer obtained by polymerizing a diene-based monomer.
Examples of the diene rubber include natural rubber, isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber (for example, styrene-butadiene copolymer rubber), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), and halogen. Examples thereof include butylated rubber and chloroprene rubber (CR).

As the diene rubber, natural rubber, isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber (for example, styrene butadiene copolymer rubber) are excellent from the viewpoint of being excellent in the effect of the present invention and excellent in durability. ) Is preferable, and a combination of natural rubber and aromatic vinyl-conjugated diene copolymer rubber (among others, styrene-butadiene copolymer rubber) or isoprene rubber (IR) is more preferable.

-Natural rubber The above natural rubber (NR) is not particularly limited. For example, conventionally known ones can be mentioned.

-Isoprene rubber The isoprene rubber is not particularly limited as long as it is a homopolymer of isoprene. For example, conventionally known ones can be mentioned.

-Styrene-butadiene copolymer rubber The above-mentioned styrene-butadiene copolymer rubber is not particularly limited as long as it is a copolymer of styrene and butadiene.

(Amount of bonded styrene of styrene-butadiene copolymer rubber)
The amount of bonded styrene of the styrene-butadiene copolymer rubber is superior to the total amount of the styrene-butadiene copolymer rubber from the viewpoint that the glass transition temperature of the styrene-butadiene copolymer rubber described later is lowered due to the effect of the present invention. It is preferably 5 to 40% by mass, more preferably 10 to 30% by mass.

(Amount of vinyl in styrene-butadiene copolymer rubber)
The amount of vinyl (1,2-vinyl bond amount) due to butadiene of the styrene-butadiene copolymer rubber is excellent due to the effect of the present invention, and the glass transition temperature of the styrene-butadiene copolymer rubber described later is lowered. It is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, based on the total amount of butadiene repeating units contained in the styrene-butadiene copolymer rubber.
In the present invention, the amount of bonded styrene and the amount of vinyl contained in the styrene-butadiene copolymer rubber can be measured by ^{1 H-NMR.}

(Weight average molecular weight of styrene-butadiene copolymer rubber)
The weight average molecular weight of the styrene-butadiene copolymer rubber is not particularly limited. For example, it can be 200,000 to 3 million.
In the present invention, the weight average molecular weight of the styrene-butadiene copolymer rubber is a standard polystyrene-equivalent value based on a value measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

(S-SBR)
The production method of the styrene-butadiene copolymer rubber is not particularly limited. For example, styrene-butadiene copolymer rubber (S-SBR) by solution polymerization and styrene-butadiene copolymer rubber (E-SBR) by emulsion polymerization can be mentioned. Among them, the styrene-butadiene copolymer rubber preferably contains S-SBR from the viewpoint of being superior to the effect of the present invention.

The S-SBR is not particularly limited as long as it is an SBR produced by copolymerizing styrene and butadiene in the presence of a catalyst in an organic solvent. The solution polymerization is not particularly limited. As the S-SBR and the solution polymerization, for example, conventionally known ones can be mentioned.

All or part of the above rubber components may be diene-based rubber. One of the preferred embodiments is that all of the above rubber components are diene-based rubbers.
The content of the diene-based rubber is preferably 70 to 100 parts by mass with respect to 100 parts by mass of the rubber component.
When the rubber component contains the natural rubber and the styrene-butadiene copolymer rubber, the content of the natural rubber is 20 to 20 to 100 parts by mass of the rubber component from the viewpoint of being more excellent in the effect of the present invention. 80 parts by mass is preferable, 30 to 70 parts by mass is more preferable, and 40 to 60 parts by mass is further preferable.
The content of the styrene-butadiene copolymer rubber can be an amount obtained by subtracting the content of the natural rubber from 100 parts by mass of the rubber component.

When the rubber component contains a rubber other than the diene rubber, examples of the rubber other than the diene rubber include non-diene rubbers such as ethylene propylene rubber (EPM) and ethylene propylene diene rubber (EPDM). ..

The diene rubber does not contain liquid polyisoprene, which may have a modifying group as compound A, which will be described later.
The weight average molecular weight of the diene rubber may be 100,000 or more.
In the present invention, the weight average molecular weight of the diene-based rubber can be a standard polystyrene-equivalent value based on a value measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

<Organic acid cobalt salt>
The organic acid cobalt salt contained in the composition of the present invention is not particularly limited as long as it is a salt formed of an organic acid and cobalt.

(Organic acid)
Examples of the organic acid constituting the above-mentioned organic acid cobalt salt include compounds having a carboxy group. The carboxy group can be attached to an organic group. The organic group is not particularly limited. For example, a hydrocarbon group can be mentioned. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a combination thereof.
Examples of the aliphatic hydrocarbon group include linear, branched, cyclic, and combinations thereof. Aliphatic hydrocarbon groups may have unsaturated bonds.

(Carboxy ion)
When the organic acid forming the organic acid cobalt salt is a compound having a carboxy group, the carboxy ion (−COO ⁻ ) contained in the organic acid cobalt salt can be derived from the carboxy group of the organic acid.

(Cobalt ion)
In the above organic acid cobalt salt, the counterion of the anion (due to the acid) such as the above carboxy ion is the cobalt ion (for example, Co ²⁺ , Co ³⁺ ) contained in the organic acid cobalt salt.

Examples of the organic acid cobalt salt include boron-free organic acid cobalt such as cobalt naphthenate, cobalt stearate, cobalt octylate, and cobalt neodecanoate;
Examples thereof include cobalt-containing organic acid cobalt such as a cobalt boron complex such as cobalt borate neodecanoate represented by the following formula (1).

The organic acid cobalt salt is preferably cobalt naphthenate, cobalt neodecanoate, and cobalt borate neodecanoate, and more preferably cobalt naphthenate and cobalt borate neodecanoate, from the viewpoint of being superior in the effects of the present invention and being excellent in durability. , Cobalt neodecanoate is more preferred.

(Cobalt content in organic acid cobalt salt)
The content of cobalt in the organic acid cobalt salt is preferably 0.22 to 1.20 parts by mass and 0.25 to 0.80 parts by mass with respect to 100 parts by mass of the rubber component. Is more preferable, and 0.30 to 0.70 parts by mass is further preferable.

<Sulfur>
The composition of the present invention contains sulfur. The sulfur is not particularly limited. For example, elemental sulfur can be mentioned.

(Sulfur content)
The sulfur content is preferably 2.1 to 8.0 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of being excellent in the effect of the present invention and excellent in durability, 3.5. ~ 5.0 parts by mass is more preferable.

<Vulcanization retarder>
The vulcanization retarder contained in the composition of the present invention is not particularly limited.
Examples of the vulcanization retarder include phthalic anhydride, benzoic acid, salicylic acid, N-nitrosodiphenylamine, N, N ′, N ″ -tris (isopropylthio) -N, N ′, N ″ -triphenylphos. Examples thereof include holictriamide, a compound represented by the following formula (1), and N- (trichloromethylthio) benzenesulfonamide.

式中、Ｒ¹は炭化水素基を表し、Ｒ²は水素原子、炭化水素基又はアルコキシ基を表わす。

In the formula, R ¹ represents a hydrocarbon group and R ² represents a hydrogen atom, a hydrocarbon group or an alkoxy group.

・ R ¹
Specifically, the hydrocarbon group as R ¹ is, for example, a linear hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group such as a cyclohexyl group, or an aromatic hydrocarbon group such as a phenyl group. Can be mentioned.
R ¹ is preferably an alicyclic hydrocarbon group, more preferably a cyclohexyl group, from the viewpoint of being more excellent in the effects of the present invention.

・ R ²
Specific examples of the hydrocarbon group as R ² include a linear hydrocarbon group having 1 to 4 carbon atoms and a branched hydrocarbon group having 3 to 4 carbon atoms.
Specific examples of the alkoxy group as R ² include an alkoxy group having a linear alkyl group having 1 to 4 carbon atoms and an alkoxy group having a branched alkyl group having 3 to 4 carbon atoms.
R ² is preferably a hydrogen atom from the viewpoint of being superior to the effect of the present invention.
The compound represented by the above formula (1) ^{has one R 2} in the formula (1), but when R ² is a hydrogen atom, it is contained in the naphthalimide skeleton represented by the formula (1). Four hydrogen atoms are bonded to the benzene ring.
^{Further, the bond position of R 2 in} the benzene ring represented by the formula (1) is not particularly limited.

Examples of the compound represented by the above formula (1) include N-cyclohexylthiophthalimide.

The vulcanization retarder is preferably a compound represented by the formula (1), and more preferably N-cyclohexylthiophthalimide (following structure) from the viewpoint of being more excellent in the effect of the present invention.

(Content of vulcanization retarder)
The content of the vulcanization retarder is preferably 0.1 to 2.0 parts by mass, preferably 0.1 to 0.5 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of being more excellent in the effect of the present invention. Parts are more preferable, and 0.2 to 0.5 parts by mass are further preferable.

(Mass ratio of cobalt / vulcanization retarder in organic acid cobalt salt)
The mass ratio of the cobalt content in the organic acid cobalt salt to the content of the vulcanization retarder (cobalt in the organic acid cobalt salt / vulcanization retarder) is 1 from the viewpoint of being more excellent in the effect of the present invention. It is preferably .25 to 8.00, more preferably 0.6 to 7.00.

<Vulcanization accelerator>
The composition of the present invention is substantially free of vulcanization accelerators.
In the present invention, "substantially free of vulcanization accelerator" means that the content of the vulcanization accelerator is 0.0 to 0.5 parts by mass with respect to 100 parts by mass of the rubber component. ..

The vulcanization accelerator is not particularly limited as long as it is a vulcanization accelerator that can be used in a rubber composition capable of vulcanization with sulfur.

<Compound A>
The composition of the present invention preferably further contains at least one compound A selected from the group consisting of liquid polyisoprene, rosins, phenolic resins and chlorinated paraffins which may have a modifying group.
The composition of the present invention is more excellent in the effect of the present invention by further containing the compound A.

(Liquid polyisoprene that may have a modifying group)
The liquid polyisoprene as compound A, which may have a modifying group, is a polymer having a repeating unit of isoprene, which may have a modifying group and is liquid under room temperature (23 ° C.) conditions.
The skeleton of the liquid polyisoprene which may have a modifying group may be either a homopolymer or a copolymer.
Examples of the skeleton of the liquid polyisoprene which may have a modifying group include copolymers of isoprene; copolymers such as styrene-isoprene copolymer and butadiene-isoprene copolymer.
When the liquid polyisoprene has a modifying group, for example, the skeleton may be modified by the modifying group. Further, examples of the liquid polyisoprene having a modifying group include a copolymer obtained by copolymerizing a monomer containing at least an isoprene and a monomer into which the modifying group can be introduced.

The liquid polyisoprene preferably has a modifying group from the viewpoint of being superior in the effect of the present invention and excellent in durability.
Examples of the modifying group include a carboxy group, a hydroxy group, and an acid anhydride.
Of these, a carboxy group and an acid anhydride are preferable from the viewpoint of being superior in the effects of the present invention and excellent in durability.
The modifying group can be attached to the backbone directly or via an organic group. The organic group is not particularly limited.

The weight average molecular weight of the liquid polyisoprene can be less than 100,000, and is preferably 20,000 to 70,000 from the viewpoint of being excellent in the effect of the present invention and excellent in durability. More preferably, it is between 0,000 and 50,000.
In the present invention, the weight average molecular weight of the liquid polyisoprene is a standard polystyrene-equivalent value based on a value measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

The content of the liquid polyisoprene is preferably 3 to 10 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of being excellent in the effect of the present invention and excellent in durability.

(Phenol resin)
As the phenol resin, one that can be blended in a rubber composition can be generally used. The phenol resin can include a resin obtained by reacting phenols with an aldehyde and a modified product thereof. Examples of phenols include phenol, cresol, xylenol, resorcin, and the like. Further, as the aldehyde, for example, formaldehyde, acetaldehyde, furfural and the like can be exemplified.
The composition of the present invention preferably does not contain a curing agent for a phenol resin.

The content of the phenol resin is preferably 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of being excellent in the effect of the present invention and excellent in durability.

(Rosins)
The composition of the present invention can further contain rosins.
Examples of rosins include rosins and rosin derivatives.

-Rosin Rosin is generally a natural resin obtained by distilling pine fat.
When rosin is exemplified from the viewpoint of manufacturing as described above, examples of rosin include gum rosin, wood rosin, and tall rosin.
The rosin is preferably gum rosin (among gum rosin, wood rosin and tall rosin) from the viewpoint of being superior to the effect of the present invention.

Rosin also generally contains a resin acid.
Examples of the resin acid include abietic acid, neo-abietic acid, palastolic acid, pimalic acid, isopimalic acid, and dehydroabietic acid.
The various resin acids are common in that they have a carboxy group as a functional group.

The rosin may include at least one selected from the group consisting of abietic acid, neo-abietic acid, palastolic acid, pimalic acid, isopimalic acid and dehydroabietic acid. Further, the rosin may be a mixture containing at least two kinds selected from the above group.
In addition, the ratio of the composition of the resin acid generally differs depending on the type of rosin such as gum rosin.

-Rosin derivative Examples of the rosin derivative (modified rosin) include compounds obtained by acid-modifying, disproportionating (double bond), hydrogenating, dimerizing, or esterifying the above resin acid.

The rosins preferably contain rosins from the viewpoint of being more excellent in the effects of the present invention.

The content of the rosins is preferably 3 to 10 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of being excellent in the effect of the present invention and excellent in durability.

-Chlorinated paraffin The above-mentioned chlorinated paraffin is not particularly limited as long as it is a paraffin containing chlorine. For example, a chain saturated hydrocarbon compound having 26 carbon atoms on average, in which all or part of hydrogen atoms in the compound are replaced with chlorine atoms, can be mentioned.
The amount of chlorine contained in the chlorinated paraffin is preferably 40 to 80% by mass with respect to the total amount of chlorinated paraffin.

The content of the chlorinated paraffin is preferably 3 to 8 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of being excellent in the effect of the present invention and excellent in durability.

From the viewpoint that the above-mentioned compound A is superior in the effect of the present invention and excellent in durability,
It preferably contains at least a liquid polyisoprene that may have a modifying group.
Liquid polyisoprene, which may have a modifying group,
More preferably, it contains at least one compound B selected from the group consisting of rosins, phenolic resins and chlorinated paraffins.
Liquid polyisoprene, which may have a modifying group,
With rosins,
Phenol resin and
It is more preferable to include chlorinated paraffin.

(Carbon black)
The composition of the present invention can further contain carbon black.
The carbon black is not particularly limited.
Among them, the above-mentioned carbon black is preferably HAF grade carbon black or ISAF grade carbon black, and more preferably HAF grade carbon black, from the viewpoint of being more excellent in the effect of the present invention.

(Nitrogen adsorption specific surface area of carbon black)
Nitrogen adsorption specific surface area of the carbon black (N ₂ SA) of from the viewpoint of obtaining superior effects of the present invention, preferably ^{60~120m 2 / g, 65~95m 2 /} g is more preferable.
The nitrogen adsorption specific surface area of carbon black can be measured by measuring the amount of nitrogen adsorbed on the surface of carbon black according to JIS K 6217-2: 2017 "Part 2: How to obtain the specific surface area-Nitrogen adsorption method-Single point method".

(Carbon black content)
The content of the carbon black is preferably 35 to 75 parts by mass, more preferably 40 to 70 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of being more excellent in the effect of the present invention.

(Anti-aging agent)
The composition of the present invention can further contain an anti-aging agent.
The anti-aging agent is not particularly limited. For example, conventionally known anti-aging agents can be mentioned.

The content of the anti-aging agent is preferably 1.0 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of being more excellent in the effect of the present invention.
The upper limit of the content of the anti-aging agent can be 5.0 parts by mass or less with respect to 100 parts by mass of the rubber component.

(Zinc oxide)
The composition of the present invention can further contain zinc oxide. The zinc oxide is not particularly limited.

(Zinc oxide content)
The content of zinc oxide is preferably 5.0 parts by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of being more excellent in the effect of the present invention.
The upper limit of the zinc oxide content can be 20 parts by mass or less with respect to 100 parts by mass of the rubber component.

The composition of the present invention, if necessary, in addition to the above-mentioned essential components, as long as it does not impair the object of the present invention, further, for example, a metal salt other than an organic acid cobalt salt, a filler other than stearic acid, and a filler other than carbon black. , Oil and other additives can be contained.

The composition of the present invention can be produced by mixing the above-mentioned essential components, the above-mentioned carbon black and the like which can be used if necessary, using a roll mill, a Banbury mixer or the like.

The compositions of the present invention can be used, for example, to bond steel cords (specifically, for example, galvanized steel cords).
A composite having a vulcanized rubber and a steel cord can be obtained by using the composition of the present invention together with a steel cord (for example, a galvanized steel cord) and vulcanizing, for example. In the above composite, the vulcanized rubber and the steel cord can be adhered to each other.

Examples of the steel cord include a steel cord; a steel cord plated with zinc.
The steel cord is preferably galvanized from the viewpoint of being excellent in the effect of the present invention and excellent in rust prevention.
For example, the wire diameter or the cord diameter of the steel cord (including the galvanized steel cord; the same applies hereinafter) can be appropriately selected. The surface of the steel cord may be untreated.

The temperature at which the composition of the present invention is vulcanized can be, for example, about 140 to 160 ° C.

The composition of the present invention can be suitably used, for example, in the production of a conveyor belt. When the composition of the present invention is used for producing a conveyor belt, the composition of the present invention forms, for example, a coated rubber layer (for example, cushion rubber and / or tie rubber) for coating a steel cord as a member constituting the conveyor belt. Is preferable. The one coated rubber layer that coats the steel cord may have the functions of both cushion rubber and tie rubber.

Examples of the cushion rubber include, when the conveyor belt has a cover rubber layer, rubber adjacent to the cover rubber layer.
Examples of the tie rubber include rubber that can connect a conveyor belt, for example, at an end. Conveyor belts can be lengthened and / or endless by connecting with tie rubber.

[Conveyor belt]
Next, the conveyor belt of the present invention will be described below.
The conveyor belt of the present invention is a conveyor belt formed by using the rubber composition for adhering a steel cord of the present invention.

The conveyor belt of the present invention preferably has a steel cord. The steel cord is preferably galvanized from the viewpoint of being more excellent in the effects of the present invention.

The rubber composition for adhering steel cords used for the conveyor belt of the present invention is not particularly limited as long as it is the composition of the present invention.
From the viewpoint that the composition of the present invention is more excellent in the effect of the present invention, it is preferable to form a coated rubber layer (for example, cushion rubber and / or tie rubber) coated with a steel cord.
The conveyor belt of the present invention is further mentioned as one of preferred embodiments having a cover rubber layer. The rubber composition capable of forming the cover rubber layer is not particularly limited.

When the coated rubber layer formed by the composition of the present invention is tie rubber, the cover rubber layer may or may not be adjacent to the coated rubber layer.

The conveyor belt of the present invention will be described below with reference to the accompanying drawings. The conveyor belt of the present invention is not limited to the accompanying drawings.
FIG. 1 is a cross-sectional perspective view schematically showing an example of the conveyor belt of the present invention.
In FIG. 1, the conveyor belt 1 has cover rubber layers 6 on both surfaces, and has a steel cord 2 and a coated rubber layer 4 between the cover rubber layers 6. The coated rubber layer 4 coats the steel cord 2. The coated rubber layer 4 is preferably formed of the rubber composition for adhering steel cords of the present invention.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

<Manufacturing of composition>
Each component in Table 1 below was used in the composition (parts by mass) shown in the same table.
First, the components shown in Table 1 below, excluding sulfur, vulcanization accelerator and vulcanization retarder, are mixed with a Banbury mixer, and then sulfur and vulcanization retarder are added to the obtained mixture. If necessary, vulcanization accelerators were added in the amounts shown in Table 1 and these were mixed using a roll to prepare each composition.

<< Evaluation >>
The following evaluations were carried out using each composition produced as described above. The results are shown in Table 1.

<Water resistance>
Water resistance and adhesiveness were evaluated with rubber.
-Evaluation method Each composition produced as described above is applied to a zinc-plated steel cord having a diameter of 4.1 mm, which has been stored in a desiccator and treated to be dust-proof and moisture-proof, to a thickness of 15 mm. A composite with a steel cord (the steel cord is embedded in the composition) is prepared, and the above composite is pressure vulcanized for 20 minutes under the conditions of 153 ° C. and a surface pressure of 2.0 MPa using a press molding machine. A test piece (rubber / galvanized steel cord composite) was prepared. In the above test piece, the boundary between the rubber and the steel cord where the steel cord protrudes from the rubber surface was sealed with beeswax, and left in a constant temperature and humidity chamber at a temperature of 50 ° C. and a relative humidity of 95% for 3 weeks. Then, a pull-out test was carried out in which the steel cord was pulled out from each test piece under the condition of room temperature (23 ° C.). The above pull-out test was performed in accordance with DIN 22131.
After the pull-out test, the state of the pulled-out steel cord was confirmed, and the ratio of the rubber covering area remaining on the surface of the pulled-out steel cord to the surface area of the initial steel cord (rubber covering ratio,%) was calculated. The rubber coverage calculated as described above is shown in Table 1 as having rubber.

-Evaluation Criteria In the present invention, when the rubber coverage (rubber coverage) exceeds 85%, it is evaluated as having excellent water resistance and adhesiveness.
When the amount with rubber was 85% or less, it was evaluated that the water resistance and adhesiveness were inferior.
It was evaluated that the larger the rubber attachment was, the better the water resistance and adhesiveness were.

<Processing stability>
Processing stability was evaluated by Mooney Scoach.
Using each composition produced as described above, the scorch time was measured under the condition of a test temperature of 125 ° C. using an L-shaped rotor according to JIS K6300-1: 2013.

-Evaluation Criteria In the present invention, when the scorch time exceeds 15 minutes, it is evaluated that the processing stability of the rubber composition is excellent.
When the scorch time was 15 minutes or less, it was evaluated that the processing stability of the rubber composition was inferior.
It was evaluated that the larger the scorch time was, the better the processing stability of the rubber composition was.

The details of each component shown in Table 1 are as follows.
(Diene rubber)
-Diene rubber 1 (NR): Natural rubber. TSR20
-Diene rubber 2 (SBR): Solution-polymerized styrene-butadiene copolymer rubber. Product name Tough Den 2000R (manufactured by Asahi Kasei Corporation). Glass transition temperature -70 ° C. Weight average molecular weight 320,000, bound styrene amount 27% by mass, vinyl amount 9% by mass

上記式中、ｎは３であり、ｍ＋ｎは上記重量平均分子量に対応する値とできる。 (Compound A)
-Liquid polyisoprene (LIR-403): LIR-403 manufactured by Kuraray. Weight average molecular weight 34000. Polyisoprene having an acid anhydride group (structure below). Liquid under room temperature (23 ° C) conditions.

In the above formula, n is 3, and m + n can be a value corresponding to the above weight average molecular weight.

-Phenol resin: Sumilite resin PR-175, Sumitomo Durez Co., Ltd. It is a mixture of cresol resin, phenol, cresol, and formaldehyde.
-Rosin (Gum rosin): Made by China Rosin WW, Arai Chemical Industry Co., Ltd.
-Chlorinated paraffin: Chlorinated paraffin (chlorine content 70% by mass). Empara 70S, manufactured by Ajinomoto Fine Techno.

(Cobalt organic acid salt)
-Cobalt organic acid salt 1 (cobalt borate neodecanoate): Cobalt borate neodecanoate represented by the following formula (1). DICATE NBC-II manufactured by DIC CORPORATION (cobalt content 22.2% by mass in cobalt borate neodecanoate)

-HAF grade carbon black: Cabot Japan Co., Ltd. Shiyo Black N330T (nitrogen adsorption specific surface area 74 m ² / g)

-Anti-aging agent (OD-3): p, p'-dioctyldiphenylamine represented by the following formula. Non-flex OD-3, manufactured by Seiko Kagaku Co., Ltd.

・ Zinc oxide: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. ・ Stearic acid: YR stearate (manufactured by NOF Corporation)

(Vulcanization accelerator)
-Vulcanization accelerator (DM): Thiazole-based vulcanization accelerator. Dibenzothiadyl disulfide (structure below). Sun Cellar DM-PO, (manufactured by Sanshin Chemical Industry Co., Ltd.)

・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Industry Co., Ltd.)

(Vulcanization retarder)
-Vulcanization retarder: SHANDONG YANGGU HUATAI CHEMICAL Co., manufactured by LTD, trade name CTP. N-cyclohexyl-thiophthalimide (structure below) (in the above formula (1), R ¹ : cyclohexyl group, R ² : hydrogen atom compound).

As is clear from the results shown in Table 1, Comparative Example 1 containing a vulcanization accelerator and not containing a vulcanization retarder was inferior in water adhesion resistance and processing stability.
Comparative Example 2 in which a vulcanization retarder was added to Comparative Example 1 was inferior in water adhesion resistance and processing stability.
Comparative Example 3 containing no vulcanization retarder was inferior in water resistance and processing stability.

On the other hand, the composition of the present invention was excellent in water resistance and processing stability.

1 Conveyor belt 2 Steel cord 4 Coated rubber layer 6 Cover rubber layer

Claims (6)

With rubber components containing at least diene rubber,
Organic acid cobalt salt and
With sulfur
Contains a vulcanization retarder and
A rubber composition for bonding steel cords that contains substantially no vulcanization accelerator. The rubber composition for adhering a steel cord according to claim 1, wherein the organic acid cobalt salt is cobalt borate neodecanoate. The rubber composition for bonding a steel cord according to claim 1 or 2, wherein the vulcanization retarder is a compound represented by the following formula (1).

In the formula, R ¹ represents a hydrocarbon group and R ² represents a hydrogen atom, a hydrocarbon group or an alkoxy group. The rubber composition for bonding a steel cord according to any one of claims 1 to 3, wherein the vulcanization retarder is N-cyclohexylthiophthalimide. The rubber composition for adhering a steel cord according to any one of claims 1 to 4, which is used for adhering a galvanized steel cord. A conveyor belt formed by using the rubber composition for adhering a steel cord according to any one of claims 1 to 5.

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