JP7356008B2 - Rubber composition for adhering steel cords and conveyor belts - Google Patents

Description

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

Conventionally, various rubber compositions have been proposed for the purpose of improving adhesive performance to steel cords.
For example, in Patent Document 1, for 100 parts by weight of raw rubber, (1) 0.8 to 2 parts by weight of a thiazole vulcanization accelerator, (2) 1 to 15 parts by weight of metacresol resin, (3) Co element A rubber composition containing 0.05 to 0.6 parts by weight of an organic acid cobalt salt and (4) 3 to 10 parts by weight of sulfur and having good adhesion to metal materials upon vulcanization is described. There is.

Further, Patent Document 2 discloses that 0.2 to 1.0 parts by weight of an organic acid cobalt salt is added as a cobalt amount to 100 parts by weight of sulfur-vulcanizable rubber, and a dithiophosphorus represented by the following formula [1] is added. A rubber composition is described that improves adhesion to steel cord and contains 0.5 to 3.0 parts by weight of a metal salt of an acid.
Here, R ¹ to R ⁴ may be the same or different and represent an alkyl group, and M is a metal.

Japanese Unexamined Patent Publication No. 57-92035 Japanese Patent Application Publication No. 08-259740

Under these circumstances, the present inventor prepared a rubber composition with reference to Patent Documents 1 and 2 and evaluated it as a rubber composition for bonding steel cords, and found that the rubber obtained from such a rubber composition and steel It became clear that there is room for improvement in the water-resistant adhesion between the cord and the cord.
Therefore, an object of the present invention is to provide a rubber composition for adhering steel cords, which has excellent water-resistant adhesive properties. Note that in the present invention, water-resistant adhesiveness includes moisture-resistant adhesiveness.
Another object of the present invention is to provide a conveyor belt with excellent water-resistant adhesive properties.

As a result of intensive research to solve the above problems, the present inventor found that the composition includes a rubber component containing at least a diene rubber, an organic acid cobalt salt, sulfur, and a vulcanization accelerator that does not contain a nitrogen atom. Between the rubber obtained from the rubber composition and the steel cord, by containing at least one member selected from the group consisting of liquid polyisoprene, rosin, phenolic resin, and chlorinated paraffin, which may have a modifying group. It has been found that the water-resistant adhesion of
The present invention is based on the above-mentioned findings, and specifically aims to solve the above-mentioned problems with the following configuration.

[1] A rubber component containing at least a diene rubber;
an organic acid cobalt salt;
sulfur and
A vulcanization accelerator that does not contain nitrogen atoms,
A rubber composition for bonding steel cords, comprising at least one compound A selected from the group consisting of liquid polyisoprene, which may have a modified group, rosins, phenolic resins, and chlorinated paraffins.
[2] The rubber composition for adhering steel cords according to [1], wherein the vulcanization accelerator has a phosphorus atom.
[3] The rubber composition for adhering steel cords according to [1] or [2], wherein the vulcanization accelerator is a dithiophosphate metal salt.
[4] The steel cord according to any one of [1] to [3], wherein the content of the vulcanization accelerator is 0.1 to 2.0 parts by mass based on 100 parts by mass of the rubber component. Adhesive rubber composition.
[5] The rubber composition for adhering steel cords according to any one of [1] to [4], wherein the organic acid cobalt salt is cobalt neodecanoate borate.
[6] The content of cobalt in the organic acid cobalt salt is 0.25 to 0.80 parts by mass based on 100 parts by mass of the rubber component, according to any one of [1] to [5]. Rubber composition for adhesion of steel cords.
[7] The above compound A is
Liquid polyisoprene which may have the above-mentioned modifying group;
The rubber composition for adhering steel cords according to any one of [1] to [6], comprising at least one compound B selected from the group consisting of the rosin, the phenol resin, and the chlorinated paraffin.
[8] The above compound A is
Liquid polyisoprene which may have the above-mentioned modifying group;
The above rosin and
The above phenolic resin,
The rubber composition for adhering steel cords according to any one of [1] to [7], which contains the above-mentioned chlorinated paraffin.
[9] The rubber composition for adhering steel cords according to any one of [1] to [8], wherein the liquid polyisoprene has a modified group.
[10] The rubber composition for adhering steel cords according to any one of [1] to [9], which is used for adhering galvanized steel cords.
[11] A conveyor belt formed using the rubber composition for adhering steel cords according to any one of [1] to [10].

The rubber composition for adhering steel cords of the present invention has excellent water-resistant adhesion.
Furthermore, the conveyor belt of the present invention has excellent water-resistant adhesive properties.

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 explained in detail below.
In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as the lower limit and upper limit.
In this specification, unless otherwise specified, each component can be used alone or in combination of two or more of the substances corresponding to the component. When a component contains two or more types of substances, the content of the component means the total content of the two or more types of substances.
In this specification, unless otherwise specified, there is no particular restriction on the manufacturing method of each component. For example, conventionally known methods may be used.
In this specification, the effect of the present invention is sometimes referred to as being superior in water-resistant adhesion.

[Rubber composition for adhering steel cords]
The rubber composition for adhering steel cords of the present invention (composition of the present invention) is
Rubber and components containing at least diene rubber;
an organic acid cobalt salt;
sulfur and
A vulcanization accelerator that does not contain nitrogen atoms,
This is a rubber composition for bonding steel cords, containing at least one member selected from the group consisting of liquid polyisoprene which may have a modified group, rosins, phenolic resins, and chlorinated paraffins.

Since the composition of the present invention has such a configuration, it is considered that the desired effect can be obtained. Although the reason is not clear, it is assumed to be as follows.
First, sulfur as a vulcanizing agent in the composition of the invention can react with a vulcanization accelerator. When the composition of the present invention containing the above-mentioned reactant is placed adjacent to the steel cord, the above-mentioned reactant migrates to the interface between the composition of the present invention and the steel cord over time, and the sulfur in the above-mentioned reactant is transferred to the steel cord. It is believed that the composition of the present invention has excellent water-resistant adhesion properties by forming, for example, covalent bonds or hydrogen bonds with the surface of the cord.
Furthermore, since the composition of the present invention contains a vulcanization accelerator that does not contain nitrogen atoms, the composition of the present invention is degraded by amines that may be generated from the vulcanization accelerator that contains nitrogen atoms. The inventor assumes that there is nothing to do. The present inventor believes that the absence of such deterioration due to amines can be proven by durability. Since the composition of the present invention does not deteriorate due to the amines described above, it is considered that the composition can maintain the above-mentioned excellent water-resistant adhesion properties over a long period of time.
Furthermore, the composition of the present invention contains at least one compound A selected from the group consisting of liquid polyisoprene that may have a modifying group, rosins, phenolic resins, and chlorinated paraffins, and the compound A is The present inventors have discovered that the above-mentioned reactant contributes to water-resistant adhesion without inhibiting the above-mentioned migration and the like.
As described above, the composition of the present invention has excellent water-resistant adhesion by containing sulfur, a predetermined vulcanization accelerator, and the above-mentioned compound A, and can maintain the above-mentioned excellent water-resistant adhesion over a long period of time. It seems possible.
Each component contained in the composition of the present invention will be described in detail below.

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

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

The above-mentioned diene-based rubbers include natural rubber, isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber (for example, styrene-butadiene copolymer rubber) from the viewpoint of being superior to the effects of the present invention and having excellent durability. ) is preferred, and a combination of natural rubber and aromatic vinyl-conjugated diene copolymer rubber (especially styrene-butadiene copolymer rubber) or isoprene rubber (IR) is more preferred.

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

- Isoprene rubber The above-mentioned isoprene rubber is not particularly limited as long as it is an isoprene homopolymer. 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 bound styrene in styrene-butadiene copolymer rubber)
The amount of bound styrene in the styrene-butadiene copolymer rubber is determined based on the total amount of the styrene-butadiene copolymer rubber, from the viewpoint that the effect of the present invention is superior and the glass transition temperature of the styrene-butadiene copolymer rubber described later is lowered. The amount is preferably 5 to 40% by weight, more preferably 10 to 30% by weight.

(Vinyl content of styrene-butadiene copolymer rubber)
From the viewpoint that the vinyl content (1,2-vinyl bond amount) due to butadiene in the styrene-butadiene copolymer rubber is superior due to the effect of the present invention, and the glass transition temperature of the styrene-butadiene copolymer rubber described below 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 bound 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 3,000,000.
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 method for producing the styrene-butadiene copolymer rubber is not particularly limited. Examples include styrene-butadiene copolymer rubber (S-SBR) produced by solution polymerization and styrene-butadiene copolymer rubber (E-SBR) produced by emulsion polymerization. Among these, it is preferable that the styrene-butadiene copolymer rubber contains S-SBR from the viewpoint of providing better effects of the present invention.

S-SBR is not particularly limited as long as it is SBR produced by copolymerizing styrene and butadiene in an organic solvent in the presence of a catalyst. Further, the solution polymerization described above is not particularly limited. Examples of S-SBR and solution polymerization include conventionally known methods.

In the present invention, the rubber component includes at least the diene rubber, and the content of the diene rubber is preferably 70 to 100 parts by mass based on 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 parts by mass based on 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention. 80 parts by weight is preferable, and 30 to 70 parts by weight is more preferable. More preferably 40 to 60 parts by mass.
The content of the styrene-butadiene copolymer rubber can be the amount obtained by subtracting the content of the natural rubber from 100 parts by mass of the rubber component.

In addition, when the rubber component includes the natural rubber and the styrene-butadiene copolymer rubber, the content of the natural rubber is determined based on 100 parts by mass of the diene rubber, from the viewpoint of improving the effect of the present invention. , preferably 20 to 80 parts by weight, more preferably 30 to 70 parts by weight. More preferably 40 to 60 parts by mass.
The content of the styrene-butadiene copolymer rubber can be the amount obtained by subtracting the content of the natural rubber from 100 parts by mass of the diene rubber.
The same applies when the rubber component further includes a rubber other than diene rubber, which will be described later.

When the rubber component further contains a rubber other than diene rubber, examples of the rubber include non-diene rubbers such as ethylene propylene rubber (EPM) and ethylene propylene diene rubber (EPDM).
When the rubber component further contains a rubber other than diene rubber, the content of the rubber is preferably 30 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the rubber component.
When the rubber component further contains a rubber other than diene rubber, the content of the diene rubber is preferably 70 parts by mass or more and less than 100 parts by mass, and 95 parts by mass or more, based on 100 parts by mass of the rubber component. More preferred.

Note that 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 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 from an organic acid and cobalt.

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

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

(cobalt ion)
In the above-mentioned organic acid cobalt salt, the counter ion of the anion (based on the acid), such as the above-mentioned carboxy ion, is a cobalt ion (eg, Co ²⁺ , Co ³⁺ ) that the organic acid cobalt salt has.

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

The above-mentioned organic acid cobalt salt is preferably cobalt naphthenate, cobalt neodecanoate, or cobalt neodecanoate borate, and more preferably cobalt naphthenate or cobalt neodecanoate borate, from the viewpoint of superior effects of the present invention and excellent durability. , cobalt neodecanoate borate is more preferred.

The content of cobalt in the organic acid cobalt salt is preferably 0.22 to 1.20 parts by mass, and preferably 0.25 to 0.80 parts by mass, based on 100 parts by mass of the rubber component. is more preferable, and even more preferably 0.30 to 0.70 parts by mass.

<Sulfur>
The composition of the invention contains sulfur. The above sulfur is not particularly limited. An example is simple sulfur.

(Sulfur content)
The content of sulfur is preferably 2.1 to 5.5 parts by mass, and 3.5 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoint of achieving better effects of the present invention and excellent durability. ~5.0 parts by mass is more preferred.

<Vulcanization accelerator that does not contain nitrogen atoms>
The composition of the present invention contains a vulcanization accelerator that does not contain nitrogen atoms.
The composition of the present invention has excellent water-resistant adhesion and durability because it contains a vulcanization accelerator that does not contain nitrogen atoms.

The above-mentioned vulcanization accelerator preferably has a phosphorus atom from the viewpoint of being more excellent in the effects of the present invention and having excellent durability.
In addition to the phosphorus atom, the vulcanization accelerator may further contain, for example, a carbon atom, a hydrogen atom, an oxygen atom, a sulfur atom, or a metal atom such as zinc or copper.

The vulcanization accelerator is preferably a metal salt of dithiophosphate, more preferably a zinc salt of dithiophosphate or a copper salt of dithiophosphate, from the viewpoint of superior effects of the present invention and excellent durability, and zinc salt of dithiophosphate is more preferred. More preferred.
The above-mentioned vulcanization accelerator is preferably a metal salt of dialkyldithiophosphate, more preferably a zinc salt of dialkyldithiophosphate or a copper salt of dialkyldithiophosphate, from the viewpoint of superior effects of the present invention and excellent durability. More preferred are acid zinc salts.

Examples of the alkyl group contained in the dialkyldithiophosphate metal salt (or dialkyldithiophosphate zinc salt or dialkyldithiophosphate copper salt) include alkyl groups having 1 to 5 carbon atoms. Specific examples include methyl group, ethyl group, propyl group (n-propyl group, i-propyl group), butyl group (n-butyl group, i-butyl group, t-butyl group), and pentyl group. . Among them, a butyl group is preferred.

Examples of dialkyldithiophosphate metal salts include compounds represented by the following formula [1].

In formula [1], R ¹ to R ⁴ each independently represent an alkyl group and may be the same or different, and M is a metal.
The alkyl groups as R ¹ to R ⁴ are the same as above.
M is preferably Cu or Zn, and more preferably Zn, from the viewpoint of superior effects of the present invention and excellent durability.

The above-mentioned vulcanization accelerator is preferably dibutyldithiophosphate zinc salt from the viewpoints of superior effects of the present invention and excellent durability.

The content of the vulcanization accelerator is preferably 0.1 to 2.0 parts by mass based on 100 parts by mass of the rubber component, from the viewpoint of superior effects of the present invention and excellent durability. More preferably 0.3 to 1.0 parts by mass, and even more preferably 0.3 to 0.8 parts by mass.
In addition, in the present invention, when the vulcanization accelerator is used as a mixture of the vulcanization accelerator and other substances, the net content of the vulcanization accelerator in the mixture is the same as that of the vulcanization accelerator. shall mean the content.

<Compound A>
The composition of the present invention contains at least one compound A selected from the group consisting of liquid polyisoprene that may have a modifying group, rosins, phenolic resins, and chlorinated paraffins.
By containing Compound A, the composition of the present invention has excellent water-resistant adhesion.

(Liquid polyisoprene that may have a modified group)
The liquid polyisoprene which may have a modifying group as the compound A is a polymer having repeating units 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 liquid polyisoprene which may have a modifying group include isoprene homopolymers; copolymers such as styrene-isoprene copolymers and butadiene-isoprene copolymers.
When the liquid polyisoprene has a modifying group, for example, the skeleton may be modified with the modifying group. Examples of the liquid polyisoprene having a modifying group include a copolymer obtained by copolymerizing a monomer containing at least isoprene and a monomer capable of introducing the above-mentioned modifying group.

The above-mentioned liquid polyisoprene preferably has a modified group from the viewpoint of being superior to the effects of the present invention and having excellent durability.
Examples of the above-mentioned modifying group include a carboxy group, a hydroxy group, and an acid anhydride group.
Among these, a carboxy group and an acid anhydride group are preferred from the viewpoints of superior effects of the present invention and excellent durability.
The modifying group can be bonded to the skeleton directly or via an organic group. The above organic group is not particularly limited.

The weight average molecular weight of the liquid polyisoprene can be less than 100,000, and from the viewpoint of better effects of the present invention and excellent durability, it is preferably 20,000 to 70,000, and 30,000 to 70,000. 0.0000 to 50.000 is more preferable.
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 based on 100 parts by mass of the rubber component from the viewpoint of superior effects of the present invention and excellent durability.

(phenolic resin)
As the phenol resin, those that can be generally blended into rubber compositions can be used. The above-mentioned phenolic resins can include resins obtained by reacting phenols with aldehydes and modified products thereof. Examples of phenols include phenol, cresol, xylenol, and resorcinol. Examples of the aldehyde include formaldehyde, acetaldehyde, and furfural.
In addition, it is mentioned as one of the preferable aspects that the composition of this invention does not contain the hardening|curing agent of phenol resin.

The content of the phenolic resin is preferably 2 to 8 parts by mass based on 100 parts by mass of the rubber component from the viewpoint of superior effects of the present invention and excellent durability.

<Rosin>
The composition of the present invention contains rosin.
Examples of rosins include rosin and rosin derivatives.

・Rosin Rosin is a natural resin that is generally obtained by distilling pine resin.
Examples of rosin from the production standpoint include gum rosin, wood rosin, and tall rosin.
The above-mentioned rosin is preferably gum rosin (among gum rosin, wood rosin, and tall rosin) from the viewpoint of superior effects of the present invention.

Rosin also generally contains resin acids.
Examples of the resin acid include abietic acid, neoabietic acid, parastric acid, pimaric acid, isopimaric acid, and dehydroabietic acid.
The various resin acids mentioned above have in common that they have a carboxy group as a functional group.

The rosin may contain at least one selected from the group consisting of abietic acid, neoabietic acid, parastric acid, pimaric acid, isopimaric acid, and dehydroabietic acid. Further, the rosin may be a mixture containing at least two or more selected from the above group.
Note that the composition ratio of the resin acid generally differs depending on the type of rosin such as the gum rosin.

- Rosin derivative Examples of the rosin derivative (modified product of rosin) include compounds obtained by acid modification, disproportionation (of double bonds), hydrogenation, dimerization, or esterification of the above resin acids.

It is preferable that the above-mentioned rosin contains rosin from the viewpoint that the effect of the present invention is more excellent.

- Softening point of rosins The softening point of the above-mentioned rosins is preferably 40 to 130°C, more preferably 50 to 100°C, from the viewpoint of superior effects of the present invention.
The softening point of rosins can be measured according to JIS K5902-1969.

- Acid value of rosin The acid value of the rosin can be 50 mgKOH/g or more.
The acid value of the above-mentioned rosins is preferably 50 to 200 mgKOH/g, more preferably 80 to 180 mgKOH/g, from the viewpoint of achieving better effects of the present invention.
The acid value of rosins can be measured according to JIS K2501:2003.

- Molecular weight of rosins The molecular weight of the above-mentioned rosins is preferably 200 to 1000, more preferably 250 to 400, from the viewpoint of providing better effects of the present invention.
The molecular weight of rosins can be measured by gel permeation chromatography (GPC).
Note that since rosins are generally mixtures, the molecular weight of the rosins may be an average value.

The content of the rosin is preferably 3 to 10 parts by mass based on 100 parts by mass of the rubber component from the viewpoint of superior effects of the present invention and excellent durability.

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

The content of the chlorinated paraffin is preferably 3 to 8 parts by mass based on 100 parts by mass of the rubber component from the viewpoint of superior effects of the present invention and excellent durability.

From the viewpoint that the above compound A is superior to the effects of the present invention and has excellent durability,
Preferably, it contains at least 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;
Rosin and
phenolic resin,
It is more preferable to include chlorinated paraffin.

(Carbon black)
The composition of the present invention can further contain carbon black.
The above carbon black is not particularly limited.
Among these, the above-mentioned carbon black is preferably HAF class carbon black or ISAF class carbon black, and more preferably HAF class carbon black, from the viewpoint of superior effects of the present invention.

(Nitrogen adsorption specific surface area of carbon black)
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably from 60 to 120 m ² /g, more preferably from 65 to 95 m ² /g, from the viewpoint of achieving better effects of the present invention.
The nitrogen adsorption specific surface area of carbon black can be determined by measuring the amount of nitrogen adsorbed onto the carbon black surface in accordance with JIS K 6217-2:2017 "Part 2: Determination of 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 achieving better effects of the present invention.

(Anti-aging agent)
The composition of the invention may further contain an anti-aging agent.
The anti-aging agent is not particularly limited. Examples include conventionally known anti-aging agents.
The anti-aging agent may contain, for example, a nitrogen atom.

The content of the anti-aging agent is preferably 1.0 parts by mass or more based on 100 parts by mass of the rubber component, from the viewpoint of improving 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 based on 100 parts by mass of the rubber component.

(zinc oxide)
The compositions of the invention may further contain zinc oxide. The above zinc oxide is not particularly limited.

(Content of zinc oxide)
The content of the zinc oxide is preferably 5.0 parts by mass or more based on 100 parts by mass of the rubber component, from the viewpoint of improving the effects of the present invention.
The upper limit of the content of the zinc oxide can be 20 parts by mass or less based on 100 parts by mass of the rubber component.

The composition of the present invention may optionally contain additives such as metal salts other than organic acid cobalt salts, stearic acid, and oil, in addition to the above-mentioned essential components, to the extent that the object of the present invention is not impaired. Can be included.

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

The compositions of the invention can be used, for example, to bond steel cords, in particular galvanized steel cords, for example.
By using the composition of the invention in conjunction with steel cord (for example galvanized steel cord), for example by vulcanization, a composite comprising vulcanized rubber and steel cord can be obtained. In the above composite, the vulcanized rubber and the steel cord can be bonded together.

Examples of the above-mentioned steel cord include steel cord; galvanized steel cord.
The above-mentioned steel cord is preferably galvanized from the viewpoint of being superior to the effects of the present invention and having excellent rust prevention properties.
For example, the wire diameter or the cord diameter of the steel cord (including galvanized steel cord; the same applies hereinafter) can be selected as appropriate. 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 manufacture of conveyor belts. When the composition of the present invention is used to manufacture a conveyor belt, the composition of the present invention can be used to form a coating rubber layer (for example, cushion rubber and/or tie rubber) for coating steel cords as a member constituting the conveyor belt. is preferred. One coating 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, a rubber adjacent to the cover rubber layer.
Tie rubbers include, for example, rubbers with which conveyor belts can be connected, for example at the ends. The conveyor belt can be made long and/or endless by connecting with tie rubber.

[Conveyor belt]
Next, the conveyor belt of the present invention will be explained below.
The conveyor belt of the present invention is a conveyor belt formed using the rubber composition for bonding steel cords of the present invention.

A preferred embodiment of the conveyor belt of the present invention includes steel cords. The above-mentioned steel cord is preferably a steel cord plated with zinc from the viewpoint that the effects of the present invention are more excellent.

The rubber composition for adhering steel cords used in the conveyor belt of the present invention is not particularly limited as long as it is the rubber composition for adhering steel cords of the present invention.
The composition of the present invention preferably forms a coating rubber layer (for example, cushion rubber and/or tie rubber) that coats the steel cord from the viewpoint of achieving better effects of the present invention.
One preferred embodiment of the conveyor belt of the present invention further includes a cover rubber layer. The rubber composition that can form the cover rubber layer is not particularly limited.

In addition, when the coat rubber layer formed from the composition of the present invention is a tie rubber, the cover rubber layer may or may not be adjacent to the coat rubber layer.

The conveyor belt of the present invention will be described below with reference to the accompanying drawings. The conveyor belt of the invention is not limited to the attached drawings.
FIG. 1 is a cross-sectional perspective view schematically showing an example of the conveyor belt of the present invention.
In FIG. 1, a conveyor belt 1 has a cover rubber layer 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 coat rubber layer 4 is preferably formed of the steel cord adhesive rubber composition of the present invention.

EXAMPLES The present invention will be specifically described below with reference to Examples. However, the present invention is not limited to these.

<Manufacture 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 and vulcanization accelerator, are mixed in a Banbury mixer, and then sulfur and vulcanization accelerator are added to the resulting mixture in the amounts shown in Table 1. In addition, these were mixed using a roll to produce each composition.

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

<Water resistant adhesion>
Water-resistant adhesion was evaluated using rubber.
・Evaluation method Each composition produced as described above was applied to a thickness of 15 mm on a 4.1 mm diameter galvanized steel cord that had been stored in a desiccator and subjected to dust-proof and moisture-proof treatment. A composite with a steel cord (the steel cord is embedded in the composition) is made, and the composite is pressure vulcanized for 20 minutes at 153 ° C. and a surface pressure of 2.0 MPa using a press molding machine. A test specimen (rubber/galvanized steel cord composite) was prepared. In the above test specimen, the boundary between the rubber and the steel cord where the steel cord protruded from the rubber surface was sealed with beeswax, and the specimen was left in a constant temperature and humidity chamber at a temperature of 50° C. and a relative humidity of 95% for three weeks. Thereafter, a pull-out test was conducted in which the steel cord was pulled out from each test piece under room temperature (23°C) conditions. The above-mentioned pull-out test was carried out in accordance with DIN22131.
After the pulling test, the condition of the pulled steel cord was confirmed, and the ratio of the rubber coverage area remaining on the surface of the steel cord after pulling to the initial surface area of the steel cord (rubber coverage ratio, %) was calculated. The rubber coverage calculated as described above is shown in Table 1 with rubber included.

-Evaluation Criteria In the present invention, when the rubber coverage (rubber coverage) was 80% or more, it was evaluated as having excellent water-resistant adhesion.
When the rubber adhesion was less than 80%, it was evaluated that the water-resistant adhesiveness was poor.
It was evaluated that the higher the rubber attachment was than 80%, the more excellent the water resistant adhesiveness was.

<Durability>
Durability was evaluated by elongation at break (EB) retention.
- Evaluation method Each of the above compositions was pressure-vulcanized for 20 minutes at 153° C. and a surface pressure of 2.0 MPa using a press molding machine to obtain an initial vulcanized rubber.
Separately, each of the above compositions (unvulcanized rubber compositions produced as described above) was placed at 153° C. for 80 minutes to obtain time-vulcanized rubber.
JIS No. 3 dumbbell-shaped initial test pieces (thickness: 2 mm) were punched out from each of the initial vulcanized rubbers obtained as described above. Similarly, aged test pieces were obtained from each aged vulcanized rubber.
In accordance with JIS K6251:2017, a tensile test was conducted on the initial test piece and aged test piece obtained as above at room temperature (23°C) and a tensile speed of 500 mm/min, and the elongation at break (EB) was measured. did.
The elongation at break values of the obtained initial test piece and aged test piece were applied to the following formula to calculate the retention rate of elongation at break.
Elongation at break (EB) retention rate (%) = (Elongation at break of aged test piece) / (Elongation at break of initial test piece) x 100

-Evaluation Criteria In the present invention, it was evaluated that the larger the above-mentioned elongation retention at break, the more excellent the durability.

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: Tuffden 2000R (manufactured by Asahi Kasei Corporation). Glass transition temperature -70°C. Weight average molecular weight 320,000, bound styrene content 27% by mass, vinyl content 9% by mass
- Diene rubber 3 (IR): polyisoprene rubber. Weight average molecular weight: 1.84 million. Product name: NIPOL IR2200, manufactured by Zeon Corporation

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 Co., Ltd. Weight average molecular weight 34,000. Polyisoprene with acid anhydride groups (structure below). Liquid at room temperature (23°C).

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): China Rosin WW, manufactured by Arai Chemical Industry Co., Ltd. Softening point: 65°C, acid value: 162mgKOH/g, molecular weight: 289
- Chlorinated paraffin: Chlorinated paraffin (chlorine content 70% by mass). Empara 70S, manufactured by Ajinomoto Fine Techno.

(Organic acid cobalt salt)
- Organic acid cobalt salt 1 (cobalt naphthenate 10%): cobalt naphthenate. Cobalt content in cobalt naphthenate is 10% by mass. Product name: "Cobalt naphthenate 10%", manufactured by DIC CORPORATION. Organic acid cobalt salt 2 (cobalt neodecanoate borate): Cobalt neodecanoate borate represented by the following formula (1). DICNATE NBC-II manufactured by DIC CORPORATION (cobalt content in cobalt neodecanoate borate: 22.2% by mass)

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

- Anti-aging agent (OD-3): p,p'-dioctyl diphenylamine represented by the following formula. Nonflex OD-3, manufactured by Seiko Kagaku Co., Ltd.

・Zinc oxide: 3 types of zinc oxide manufactured by Seido Kagaku Kogyo Co., Ltd. ・Stearic acid: Stearic acid YR (manufactured by NOF Corporation)

(vulcanization accelerator)
- Comparative vulcanization accelerator (DM): Thiazole vulcanization accelerator. Di-2-benzothiazyl disulfide (structure below). Suncella DM-PO (manufactured by Sanshin Kagaku Kogyo Co., Ltd.), a comparative vulcanization accelerator, is a vulcanization accelerator containing a nitrogen atom.

- Vulcanization accelerator (Rhenogran TP-50): Zinc salt of dibutyldithiophosphoric acid (structure below). 50/50 (mass ratio) EPDM masterbatch
In the above formula, R represents a butyl group.

・Sulfur: Kinka-in oil-filled fine powder sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.)

As is clear from the results shown in Table 1, Comparative Examples 1 and 3, which did not contain the predetermined vulcanization accelerator but instead contained a vulcanization accelerator containing a nitrogen atom, had poor water-resistant adhesion.
Comparative Example 2, which did not contain Compound A, had poor water-resistant adhesion.

In contrast, the composition of the present invention had excellent water-resistant adhesion.
Furthermore, the composition of the present invention also had excellent durability. Therefore, it is thought that the composition of the present invention can maintain excellent water-resistant adhesion over a long period of time.

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

Claims (8)

a rubber component containing at least a diene rubber;
cobalt neodecanoate borate ;
sulfur and
A vulcanization accelerator that does not contain nitrogen atoms,
Contains at least one compound A selected from the group consisting of liquid polyisoprene, rosins, phenolic resins, and chlorinated paraffins that may have modified groups,
A rubber composition for adhering steel cords , wherein the vulcanization accelerator is a metal salt of dithiophosphate . The rubber composition for bonding steel cords according to claim 1 , wherein the content of the vulcanization accelerator is 0.1 to 2.0 parts by mass based on 100 parts by mass of the rubber component. The rubber composition for bonding steel cords according to claim 1 or 2 , wherein the content of cobalt in the cobalt neodecanoate borate is 0.25 to 0.80 parts by mass based on 100 parts by mass of the rubber component. thing. The compound A is
Liquid polyisoprene which may have the modified group;
The rubber composition for bonding steel cords according to any one of claims 1 to 3 , comprising at least one compound B selected from the group consisting of the rosin, the phenol resin, and the chlorinated paraffin. The compound A is
Liquid polyisoprene which may have the modified group;
The rosin and
The phenolic resin;
The rubber composition for adhering steel cords according to any one of claims 1 to 4 , which contains the chlorinated paraffin. The rubber composition for bonding steel cords according to any one of claims 1 to 5 , wherein the liquid polyisoprene has a modified group. The rubber composition for adhering steel cords according to any one of claims 1 to 6 , which is used for adhering galvanized steel cords. A conveyor belt formed using the rubber composition for bonding steel cords according to any one of claims 1 to 7 .