JP7287232B2 - Steel cord adhesive rubber composition and conveyor belt - Google Patents

Description

TECHNICAL FIELD 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 adhesiveness to steel cords.
For example, in Patent Document 1, 3 to 15 parts by weight of rosin or a rosin derivative and 0.2 to 1.0 parts by weight of organic cobalt salt in terms of cobalt content are used for 100 parts by weight of sulfur-vulcanizable rubber. , and a method of adhering a galvanized steel cord to a rubber composition containing 3 to 50 parts by weight of an organic chlorine compound and a galvanized steel cord.

JP-A-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 steel cords. It has become clear that there is room for improvement in the water-resistant adhesion between rubber and steel cord, not only when the vulcanization is proper, but also when the vulcanization is overvulcanized.
Accordingly, an object of the present invention is to provide a rubber composition for adhering steel cords, which is excellent in water-resistant adhesion even when overvulcanized. Incidentally, in the present invention, water-resistant adhesiveness includes moisture-resistant adhesiveness. Further, in the present invention, even when the vulcanization of the rubber composition is overvulcanization, the term "excellent in water-resistant adhesion" may simply mean that the rubber composition has excellent water-resistant adhesion.
Another object of the present invention is to provide a conveyor belt having excellent water-resistant adhesiveness.

As a result of intensive research to solve the above problems, the inventors of the present invention have found that a , the content of the rosin is 1.0 to 12.0 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the diethylene glycol is 0.1 part by mass with respect to 100 parts by mass of the rubber component. 3 to 2.5 parts by mass of the rubber composition for adhering steel cords, the water-resistant adhesion between the rubber obtained from the rubber composition and the steel cord is improved, and the vulcanization of the rubber composition is overvulcanization. We have found that whether or not (properly vulcanized or overvulcanized) can be improved.
The present invention is based on the above knowledge and the like, and specifically solves the above problems with the following configuration.

[1] a rubber component containing at least a diene rubber;
rosins and
diethylene glycol; and
a vulcanization accelerator;
an organic acid cobalt salt;
containing sulfur and
The content of the rosin is 1.0 to 12.0 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for adhering steel cords, wherein the diethylene glycol content is 0.3 to 2.5 parts by mass with respect to 100 parts by mass of the rubber component.
[2] The rubber composition for adhering steel cords according to [1], wherein the organic acid cobalt salt contains cobalt neodecanoate borate.
[3] For adhering steel cords according to [1] or [2], wherein the softening point of the rosin is 40 to 130° C., or the acid value of the rosin is 50 to 200 mgKOH/g. rubber composition.
[4] The rubber composition for bonding steel cords according to any one of [1] to [3], wherein the vulcanization accelerator contains a benzothiazole-based vulcanization accelerator.
[5] The rubber for bonding steel cords according to any one of [1] to [4], wherein the content of the vulcanization accelerator is 2.0 parts by mass or less with respect to 100 parts by mass of the rubber component. Composition.
[6] The rubber composition for adhering steel cords according to any one of [1] to [5], which is used for adhering galvanized steel cords.
[7] A conveyor belt formed using the steel cord bonding rubber composition according to any one of [1] to [6].

The rubber composition for adhering steel cords of the present invention is excellent in water-resistant adhesion.
Moreover, the conveyor belt of the present invention is excellent in water-resistant adhesiveness.

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.
In this specification, the numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.
In this specification, unless otherwise specified, each component can be used singly or in combination of two or more substances corresponding to the component. When the 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, each component is not particularly limited in its production method unless otherwise specified. For example, a conventionally known method can be used.
In this specification, the effect of the present invention is said to be superior when the water-resistant adhesion is superior (even when the vulcanization of the rubber composition is overvulcanization).

[Rubber composition for adhering steel cord]
The steel cord bonding rubber composition of the present invention (the composition of the present invention) is
a rubber component containing at least a diene rubber;
rosins and
diethylene glycol; and
a vulcanization accelerator;
an organic acid cobalt salt;
containing sulfur and
The content of the rosin is 1.0 to 12.0 parts by mass with respect to 100 parts by mass of the rubber component,
The content of the diethylene glycol is 0.3 to 2.5 parts by mass with respect to 100 parts by mass of the rubber component.

Since the composition of the present invention has the composition as described above, it is believed that the desired effect can be obtained. Although the reason is not clear, it is presumed to be approximately as follows.
It is believed that the composition of the present invention is excellent in water-resistant adhesiveness due to the inclusion of rosins and diethylene glycol (DEG).
The rosins have the function of reducing (removing) metal oxides (such as zinc oxide) on the surface of the steel cord, and are believed to contribute to the reaction between the composition of the present invention and the surface of the steel cord.
By using DEG in combination with rosins having such functions, DEG improves the reaction stability of rosin acid during the production or vulcanization of the composition of the present invention. The inventors speculate that the efficiency of the reaction between the inventive composition and the surface of the steel cord may be improved.
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 a diene monomer.
Examples of diene rubber include natural rubber, isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber (eg, styrene-butadiene copolymer rubber), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), halogen butyl 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) can be used from the viewpoint of being excellent in the effect of the present invention and having excellent durability. ), more preferably a combination of natural rubber and aromatic vinyl-conjugated diene copolymer rubber (especially styrene-butadiene copolymer rubber), natural rubber, or isoprene rubber (IR).

- Natural rubber The natural rubber (NR) is not particularly limited. For example, a conventionally well-known thing is mentioned.

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

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

(Bound styrene content of styrene-butadiene copolymer rubber)
The amount of bound styrene in the styrene-butadiene copolymer rubber is superior to the effect of the present invention, and the glass transition temperature of the styrene-butadiene copolymer rubber described later is lowered. is preferably 5 to 40% by mass, more preferably 10 to 30% by mass.

(Vinyl content of styrene-butadiene copolymer rubber)
From the viewpoint that the vinyl content (1,2-vinyl bond content) of the styrene-butadiene copolymer rubber due to butadiene 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 in the styrene-butadiene copolymer rubber.
In the present invention, the bound styrene content and the vinyl content of 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 conversion value based on a measurement 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. Examples thereof include styrene-butadiene copolymer rubber (S-SBR) obtained by solution polymerization and styrene-butadiene copolymer rubber (E-SBR) obtained by emulsion polymerization. Among them, the styrene-butadiene copolymer rubber preferably contains S-SBR from the viewpoint of being superior in the effects of the present invention.

S-SBR is not particularly limited as long as it is produced by copolymerizing styrene and butadiene in an organic solvent in the presence of a catalyst. Examples of S-SBR include those conventionally known.
Moreover, the solution polymerization is not particularly limited. For example, a conventionally well-known thing is mentioned.

All or part of the rubber component may be a diene rubber. One preferred embodiment is that all of the rubber components are diene-based rubbers.
The content of the diene 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 parts per 100 parts by mass of the rubber component, from the viewpoint that the effect of the present invention is superior. 80 parts by mass is preferable, and 30 to 70 parts by mass is more 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 rubber other than diene rubber, examples of rubber other than diene rubber include non-diene rubber such as ethylene propylene rubber (EPM) and ethylene propylene diene rubber (EPDM). .

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

・Rosin Rosin is generally a natural resin obtained by distilling pine resin.
Examples of rosin from the viewpoint of production as described above 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 superior effects of the present invention.

Rosins also generally contain resin acids.
Resin acids include, for example, abietic acid, neoabietic acid, parastric acid, pimaric acid, isopimaric acid, and dehydroabietic acid.
The above various resin acids are common in that they have a carboxyl group as a functional group.

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. Also, the rosin may be a mixture containing at least two selected from the above group.
In general, the composition ratio of the resin acid differs depending on the type of rosin such as gum rosin.

Rosin Derivatives Rosin derivatives (modified rosin) include, for example, compounds obtained by acid-modifying, disproportionating (double bond), hydrogenating, dimerizing, or esterifying the above resin acids.

The above rosins preferably contain rosin from the viewpoint that the effect of the present invention is superior.

- Softening point of rosins The softening point of the 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 Rosins The acid value of the rosins is preferably 50 to 200 mgKOH/g, more preferably 80 to 180 mgKOH/g, from the standpoint of superior 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 rosins is preferably 200 to 1,000, more preferably 250 to 400, from the viewpoint of superior effects of the present invention.
The molecular weight of rosins can be measured by gel permeation chromatography (GPC).
Since rosins are generally mixtures, the molecular weight of the rosins may be an average value.

<Content of rosins>
In the present invention, the content of the rosin is 1.0 to 12.0 parts by mass with respect to 100 parts by mass of the rubber component.
The content of the rosin is preferably 4 to 9 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of achieving superior effects of the present invention.

<Diethylene glycol>
The compositions of the invention contain diethylene glycol.
ADVANTAGE OF THE INVENTION This invention is excellent in water-resistant adhesiveness by using rosin acid and diethylene glycol together.
Diethylene glycol (HO--CH ₂ CH ₂ --O--CH ₂ CH ₂ --OH) contained in the composition of the present invention is not particularly limited. The diethylene glycol may be, for example, a simple substance of diethylene glycol, or a mixture of diethylene glycol and silica (a blend in which both are mixed in advance).

<Diethylene glycol content>
In the present invention, the content of diethylene glycol is 0.3 to 2.5 parts by mass with respect to 100 parts by mass of the rubber component.
When the content of diethylene glycol is within the above range, excellent water-resistant adhesiveness is obtained. If the content of diethylene glycol exceeds 2.5 parts by mass with respect to 100 parts by mass of the rubber component, the water-resistant adhesiveness is lowered.

The content of the diethylene glycol is preferably 0.4 to 2.0 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, and 0.5 More than 1.5 parts by mass or less is more preferable.

<Vulcanization accelerator>
The composition of the present invention contains a vulcanization accelerator.

The vulcanization accelerator contained in the composition of the present invention is not particularly limited as long as it is a vulcanization accelerator that can be used in rubber compositions that can be vulcanized with sulfur.
Examples of the vulcanization accelerator include aldehyde-ammonia, aldehyde-amine, thiourea, guanidine, thiazole, sulfenamide, thiuram, dithiocarbamate, xanthate, and mixtures thereof. is mentioned.
In addition, when a vulcanization accelerator generally classified as a non-thiazole vulcanization accelerator has a thiazole skeleton, the vulcanization accelerator as described above is referred to herein as a thiazole vulcanization accelerator. shall be classified as

The vulcanization accelerator preferably contains a thiazole-based vulcanization accelerator, more preferably a benzothiazole-based vulcanization accelerator, from the viewpoint of achieving more excellent water-resistant adhesion.
The thiazole-based vulcanization accelerator is not particularly limited as long as it is a vulcanization accelerator having a thiazole skeleton. Examples of thiazole-based vulcanization accelerators include benzothiazole-based vulcanization accelerators having a benzothiazole skeleton.

Vulcanization accelerator having benzothiazolylsulfide group Examples of the benzothiazole-based vulcanization accelerator include vulcanization accelerators having a benzothiazolylsulfide group.

The benzothiazolyl sulfide group can be represented, for example, by the following structure. In the structures below, a hydrogen atom in the benzothiazolyl ring may be substituted with a substituent. Substituents are not particularly limited.

In the benzothiazolyl sulfide group represented by the above structure, the sulfur atom that does not form a ring structure is, for example, -SH (mercapto group); (poly) sulfide bond, sulfenamide bond (e.g. -S- NH—, —SN<) (eg divalent or trivalent linking groups); salts can be formed with metals such as zinc or alkali metals such as sodium.

When the benzothiazolylsulfide group has the linking group, the group that further bonds to the linking group is not particularly limited. Examples include hydrocarbon groups that may have heteroatoms such as oxygen, nitrogen and sulfur. Examples of the hydrocarbon group include aliphatic hydrocarbon groups (including linear, branched, and cyclic), aromatic hydrocarbon groups, heterocyclic rings, and combinations thereof.

When the sulfur atom not forming a ring structure in the benzothiazolyl sulfide group forms a sulfenamide bond (a benzothiazole-based vulcanization accelerator having a sulfenamide bond), for example, N-cyclohexyl- 2-benzothiazolesulfenamide, N-tert-butyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, N,N-diisopropyl-2-benzothiazylsulfenamide and amides, N,N-dicyclohexyl-2-benzothiazylsulfenamide.

The vulcanization accelerator (or benzothiazole-based vulcanization accelerator) is a benzothiazole having a mercapto group or a polysulfide bond, or a mercaptobenzothiazole that forms a salt with a metal or an alkali metal, from the viewpoint of superior water-resistant adhesion. is preferably included.

Examples of the benzothiazole having a mercapto group include 2-mercaptobenzothiazole (structure below).

Benzothiazoles having a polysulfide bond include, for example, benzothiazoles having a disulfide bond such as di-2-benzothiazolyl disulfide (structure below).

Mercaptobenzothiazoles that form salts with metals or alkali metals include, for example, zinc salts of 2-mercaptobenzothiazole (structure below),

Examples include the sodium salt of 2-mercaptobenzothiazole (structure below).

The vulcanization accelerator (or benzothiazole-based vulcanization accelerator) is 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole from the viewpoint of being more excellent in water-resistant adhesion. is preferred, and di-2-benzothiazolyl disulfide is more preferred.

(Content of vulcanization accelerator)
The content of the vulcanization accelerator is preferably 2.0 parts by mass or less, more preferably 0.1 to 0.8 parts by mass, with respect to 100 parts by mass of the rubber component, from the viewpoint of superior water-resistant adhesion. .

<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 by 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 carboxy group can be attached to an organic group. The organic group is not particularly limited. Examples include hydrocarbon groups. Examples of the hydrocarbon groups include aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and combinations thereof.
Linear, branched, cyclic, and combinations thereof may be mentioned for the above-mentioned aliphatic hydrocarbon group. 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 organic acid cobalt salt may have a carboxy ion (—COO ⁻ ) derived from the carboxy group of the organic acid.

(cobalt ion)
In the organic acid cobalt salt, the counterion of the (acidic) anion such as the carboxy ion is a cobalt ion (eg, Co ²⁺ , Co ³⁺ ) possessed by the organic acid cobalt salt.

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

The 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 being superior in the effect of the present invention and having excellent durability. , cobalt neodecanoate borate.

The content of cobalt in the organic acid cobalt salt is preferably 0.22 to 1.20 parts by mass, more preferably 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 even more preferable.

Cobalt salt of organic acid/diethylene glycol The mass ratio of the cobalt salt of organic acid to the content of diethylene glycol (cobalt salt of organic acid/diethylene glycol) is 0.4-12. It is preferably 0, more preferably 1.0 to 5.0.

<Sulfur>
The compositions of the invention contain sulfur. The sulfur is not particularly limited. For example, elemental sulfur may be mentioned.

(sulfur content)
The content of sulfur is preferably 2.1 to 6.0 parts by mass with respect to 100 parts by mass of the rubber component, and 3.5 parts by mass, from the viewpoint of superior effects of the present invention and excellent durability. It is more preferably up to 5.0 parts by mass, and more preferably more than 4.0 parts by mass and 5.0 parts by mass or less.

(Phenolic resin)
The compositions of the present invention may further contain phenolic resins.
The composition of the present invention preferably further contains a phenolic resin from the viewpoint of being more excellent in water-resistant adhesiveness.

As the phenolic resin, those that can generally be blended into the rubber composition can be used. The phenolic resin may include resins obtained by reaction of phenols and aldehydes and modified products thereof. Examples of phenols include phenol, cresol, xylenol, resorcinol, and the like. Examples of aldehydes include formaldehyde, acetaldehyde, furfural, and the like.
The composition of the present invention preferably does not contain a phenolic resin curing agent.

The content of the phenol resin is preferably 2 to 8 parts by mass, more preferably 3 to 7 parts by mass, with respect to 100 parts by mass of the rubber component, from the viewpoint of excellent durability due to the effects of the present invention. more preferred.

(chlorinated paraffin)
The compositions of the invention may additionally contain chlorinated paraffins.
The composition of the present invention preferably further contains chlorinated paraffin from the viewpoint of being more excellent in water-resistant adhesiveness.

The chlorinated paraffin is not particularly limited as long as it is a paraffin containing chlorine. Examples thereof include chain saturated hydrocarbon compounds having an average of 26 carbon atoms, in which all or part of the hydrogen atoms in the compounds are substituted with chlorine atoms.
The amount of chlorine contained in the chlorinated paraffin is preferably, for example, 40 to 80% by mass with respect to the total amount of chlorinated paraffin.

When the composition of the present invention further contains chlorinated paraffin, the content of chlorinated paraffin is 3 per 100 parts by mass of the rubber component, from the viewpoint of superior durability due to the effects of the present invention. It is preferably 8 parts by mass.

(Carbon black)
The composition of the invention may further contain carbon black.
It is preferable that the composition of the present invention further contains carbon black from the viewpoint of being more excellent in water-resistant adhesiveness.

The carbon black is not particularly limited.
Among them, the above carbon black is preferably HAF grade carbon black or ISAF grade carbon black, and more preferably HAF grade carbon black, from the viewpoint that the effect of the present invention is superior.

(Nitrogen adsorption specific surface area of carbon black)
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 60 to 120 m ² /g, more preferably 65 to 95 m ² /g, from the standpoint of superior effects of the present invention.
The nitrogen adsorption specific surface area of carbon black can be measured by measuring the amount of nitrogen adsorbed on the carbon black surface according to 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, with respect to 100 parts by mass of the rubber component, from the viewpoint of achieving superior effects of the present invention.

(Antiaging agent)
The composition of the present invention can further contain anti-aging agents.
There are no particular restrictions on the anti-aging agent. Examples thereof include conventionally known anti-aging agents.

The content of the anti-aging agent is preferably 1.0 parts by mass or more with respect to 100 parts by mass of the rubber component, from the viewpoint of achieving superior effects 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 compositions of the invention may further contain zinc oxide. The zinc oxide is not particularly limited.

(Zinc oxide content)
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 zinc oxide content is preferably 5.0 parts by mass or more, more preferably 5 to 15 parts by mass, with respect to 100 parts by mass of the rubber component, from the viewpoint of achieving superior effects of the present invention.

The composition of the present invention can contain additives such as stearic acid, fillers other than carbon black, oils, etc., in addition to the above-mentioned essential components, if necessary, as long as the objects of the present invention are not impaired. .

The composition of the present invention is not particularly limited in its production method. For example, it can be produced by mixing the above-mentioned essential components, optionally used stearic acid, carbon black, etc., using a roll mill, Banbury mixer, rolls, or the like.

The compositions of the invention can be used, for example, to bond steel cords, in particular, for example galvanized steel cords.
Composites comprising vulcanized rubber and steel cords can be obtained by using the compositions of the present invention together with steel cords (eg galvanized steel cords) and vulcanizing them, for example. The vulcanized rubber and the steel cord can be bonded together in the composite.

Examples of the steel cords include steel cords; galvanized steel cords.
The above steel cord is preferably galvanized from the viewpoint of being excellent in the effect of the present invention and having excellent rust resistance.
For example, the wire diameter or cord diameter of the steel cord (including galvanized steel cord; the same shall apply hereinafter) can be appropriately selected. The steel cord may have an untreated surface.

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

The composition of the present invention can be suitably used, for example, in the production 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 (e.g., cushion rubber and/or tie rubber) for coating steel cords as a member constituting the conveyor belt. is preferred. A single coat rubber layer that coats the steel cord may have the functions of both the cushion rubber and the tie rubber.

For example, when the conveyor belt has a cover rubber layer, the cushion rubber includes rubber adjacent to the cover rubber layer.
Tie rubbers include, for example, rubbers with which conveyor belts can be connected, for example at their ends. Conveyor belts can be made long and/or endless by means of tie rubber connections.

[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 adhering steel cords of the present invention.

A preferred embodiment of the conveyor belt of the present invention includes steel cords. From the viewpoint that the steel cord is superior in the effect of the present invention, it is preferable to use a steel cord plated with zinc.

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 composition of the present invention.
The composition of the present invention preferably forms a coating rubber layer (for example, cushion rubber and/or tie rubber) for coating steel cords from the viewpoint of being superior in the effects of the present invention.
One of preferred aspects of the conveyor belt of the present invention is that it further has a cover rubber layer. The rubber composition that can form the cover rubber layer is not particularly limited.

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

Conveyor belts of the present invention will be described below with reference to the accompanying drawings. The conveyor belt of the invention is not restricted 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, a conveyor belt 1 has cover rubber layers 6 on both surfaces, and steel cords 2 and a coat rubber layer 4 between the cover rubber layers 6 . The coated rubber layer 4 coats the steel cord 2. - 特許庁The coat rubber layer 4 is preferably made of the steel cord bonding 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.

<Production of composition>
Each component shown in Table 1 below was used in the composition (parts by mass) shown in the same table.
First, among the components shown in Table 1 below, the components excluding sulfur and the vulcanization accelerator are mixed in a Banbury mixer to obtain a mixture. Each composition was prepared by adding the amount indicated and mixing them on a roll.

In the column of organic acid cobalt salt 1 in Table 1, the upper value is the net amount of the organic acid cobalt salt, and the lower value is the cobalt content in the organic acid cobalt salt.

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

<Water resistant adhesion>
Water-resistant adhesion was evaluated with rubber.
<Preparation of test body>
・When vulcanized under normal vulcanization conditions Each composition produced as above is applied to a thickness of 15 mm on a galvanized steel cord with a diameter of 4.1 mm that has been stored in a desiccator and subjected to dust and moisture proof treatment. to form a composite of each composition and steel cord (the steel cord is embedded in the composition), and the composite is formed using a press molding machine at 153 ° C. and a surface pressure of 2.0 MPa. A test piece (rubber/galvanized steel cord composite) was prepared under normal vulcanization conditions by pressure vulcanization for a vulcanization time of 20 minutes under normal vulcanization conditions.

- When vulcanized under overvulcanization conditions A test sample was prepared in the same manner as the test sample under the above normal vulcanization conditions, except that the vulcanization time was changed from 20 minutes to 80 minutes, and the overvulcanization conditions A lower specimen was obtained.

・Evaluation method In the test specimen under the above normal vulcanization conditions, the boundary between the rubber and the steel cord where the steel cord protrudes from the rubber surface is sealed with beeswax, and the temperature is constant at 50 ° C and the relative humidity is 95%. It was left in a constant humidity bath for 3 weeks.
In the test piece under the above overvulcanization conditions, the boundary between the rubber and the steel cord where the steel cord protrudes from the rubber surface is sealed with beeswax, and a constant temperature and humidity chamber at a temperature of 50 ° C and a relative humidity of 95%. It was left inside for 5 weeks.
After being placed in the constant temperature and humidity chamber for the above period, a pull-out test was performed by pulling out the steel cord from each specimen under room temperature (23° C.) conditions. The pull-out test was performed in accordance with DIN22131.
After the pull-out test, the state of the pulled-out steel cord was checked, and the ratio of the rubber-covered area remaining on the surface of the steel cord after the pull-out to the surface area of the initial steel cord (rubber coverage, %) was calculated. The rubber coverage calculated as described above is shown in Table 1 as "with rubber".

・Evaluation criteria In the present invention, the rubber attachment (rubber coverage) of the specimen under the normal vulcanization conditions is 70% or more, and the rubber attachment of the specimen under the overvulcanization conditions is 50%. When it exceeded, regardless of the vulcanization conditions (not only when vulcanization was proper but also when overvulcanization was performed), the water-resistant adhesion was evaluated as being excellent.
If the rubber adhesion of the specimen under the normal vulcanization conditions is less than 70%, or if the rubber adhesion of the specimen under the overvulcanization conditions is 50% or less, the waterproof adhesion is evaluated as inferior. bottom.
When the water-resistant adhesion is excellent as described above (when the rubber adhesion of the specimen under normal vulcanization conditions is 70% or more, and when the rubber adhesion of the specimen under overvulcanization conditions exceeds 50%), Water-resistant adhesion was evaluated to be more excellent as the rubber adhesion of the specimen under the normal vulcanization conditions was greater than 70% or the rubber adhesion of the specimen under the overvulcanization conditions was greater than 50%.

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. Trade name Tufden 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

(Rosins)
- Rosins 1 (rosin): Gum rosin. Chinese rosin WW, manufactured by Arai Chemical Industry Co., Ltd. Softening point: 65°C, acid value: 162 mgKOH/g, molecular weight: 289

(diethylene glycol)
Diethylene glycol: As diethylene glycol, trade name DST Powder 1.6 (a blend of diethylene glycol:silica=60:40 (mass ratio), manufactured by Nippon Pigment Co., Ltd.) was used. The amount shown in the diethylene glycol column of Table 1 is the amount of diethylene glycol contained in the DST powder used.

(Organic acid cobalt salt)
• Organic acid cobalt salt 1 (cobalt neodecanoate borate): cobalt neodecanoate borate represented by the following formula (1). DICNATE NBC-II manufactured by DIC CORPORATION (cobalt content in cobalt borate neodecanoate is 22.2% by mass).

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

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

・Phenolic resin: Sumilite Resin PR-175, Sumitomo Durez Co., Ltd.

- Chlorinated paraffin: chlorinated paraffin (70% by mass of chlorine content). Empara 70S, manufactured by Ajinomoto Fine Techno Co., Ltd.

・Zinc oxide: 3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.

- Stearic acid: YR stearate (manufactured by NOF Corporation).

(Vulcanization accelerator)
- Vulcanization accelerator 1 (DM): a benzothiazole-based vulcanization accelerator. Di-2-benzothiazyl disulfide (structure below). Sancellar DM-PO, (manufactured by Sanshin Chemical Industry Co., Ltd.)

(sulfur)
・Sulfur: Fine powdered sulfur with Kinkain oil (manufactured by Tsurumi Kagaku Kogyo Co., Ltd.)

As is clear from the results shown in Table 1, Comparative Examples 1 and 2 containing no diethylene glycol were inferior in water-resistant adhesiveness.
Comparative Example 2 containing no rosins was inferior in water-resistant adhesiveness.
Comparative Example 3, in which the content of rosins was outside the predetermined range, was inferior in water-resistant adhesiveness.
Comparative Example 4, in which the content of diethylene glycol was outside the predetermined range, was inferior in water-resistant adhesiveness.

In contrast, the composition of the present invention was excellent in water-resistant adhesiveness.

1 Conveyor Belt 2 Steel Cord 4 Coat Rubber Layer 6 Cover Rubber Layer

Claims (7)

a rubber component containing at least a diene rubber;
rosins and
diethylene glycol; and
a vulcanization accelerator;
an organic acid cobalt salt;
containing sulfur and
The content of the rosin is 1.0 to 12.0 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for adhering steel cords, wherein the diethylene glycol content is 0.3 to 2.5 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition for adhering steel cords according to claim 1, wherein the organic acid cobalt salt contains cobalt neodecanoate borate. The softening point of the rosin is 40 to 130 ° C., or
3. The rubber composition for adhering steel cords according to claim 1, wherein said rosin has an acid value of 50 to 200 mgKOH/g. The rubber composition for adhering steel cords according to any one of claims 1 to 3, wherein the vulcanization accelerator contains a benzothiazole-based vulcanization accelerator. The rubber composition for adhering steel cords according to any one of claims 1 to 4, wherein the content of said vulcanization accelerator is 2.0 parts by mass or less with respect to 100 parts by mass of said rubber component. The rubber composition for adhering steel cords according to any one of claims 1 to 5, which is used for adhering galvanized steel cords. A conveyor belt formed using the steel cord bonding rubber composition according to any one of claims 1 to 6.

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