RU2578145C1 - Rubber composition and conveyor belt - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: rubber composition contains the rubber component which contains butadiene rubber, chloroprene rubber and natural rubber; an organic cobalt salt; colophony or a colophony derivative; and an organochlorine compound. The content of butadiene rubber ranges from 5 pts.wt to 20 pts.wt per 100 pts.wt of the rubber component. The content of chloroprene rubber ranges from 20 pts.wt to 65 pts.wt per 100 pts.wt of the rubber component. The content of the organic cobalt salt ranges from 0.2 pts.wt to 1.0 pts.wt per 100 pts.wt of the rubber component with respect to the content of the organic cobalt salt per weight of cobalt. The content of colophony or colophony derivative ranges from 2 pts.wt to 9 pts.wt per 100 pts.wt of the rubber component. The content of organochlorine compound ranges from 5 pts.wt to 35 pts.wt per 100 pts.wt of the rubber component.

EFFECT: invention provides excellent adhesion with respect to zinc-plated steel-wire cords, improved fire resistance and frost resistance.

3 cl, 1 dwg, 1 tbl

Description

FIELD OF THE INVENTION

The present invention provides a rubber composition and a conveyor belt having fire resistance and frost resistance.

BACKGROUND

Traditionally, a rubber composition comprising an organic cobalt salt and rosin has been used to attach a galvanized steel cord to a rubber composition (for example, see Patent Document 1). In addition, the idea of introducing a flame-retardant substance, such as a halogen compound, or establishing the content of chloroprene rubber (CR), which is fire-resistant rubber, at the level of 100 parts by weight is also known. without the use of halogenated rubber in order to give fire resistance to the binder rubber (for example, see patent document 2).

Patent Document 1 describes a rubber composition having excellent adhesion to plated metallic materials. The rubber composition described in Patent Document 1 is a composition containing, in predetermined amounts, rosin or a derivative of rosin, a cobalt salt of an organic acid and an organochlorine compound per 100 wt. including vulcanizable sulfur rubber.

Patent Document 2 describes a chloroprene-based rubber binder composition having excellent fire resistance and heat resistance. The rubber binder composition described in Patent Document 2 is made by mixing in predetermined amounts an organic acid cobalt salt, zinc oxide, sulfur and 2-mercaptoimidazoline per 100 wt. including chloroprene rubber.

BACKGROUND OF THE INVENTION

PATENT DOCUMENT

Patent Document 1: Japanese Unexamined Patent Application Publication No. H11-21389A.

Patent Document 2: Japanese Unexamined Patent Application Publication No. H8-59896A.

SUMMARY OF THE INVENTION

The problem solved by the invention

Although for the rubber composition described in Patent Document 1 and whose fire resistance is achieved without using halogenated rubber, adhesion is retained, insufficient attention is paid to its frost resistance and fire resistance. In addition, in the case of a rubber binder composition, which is described in patent document 2 and contains 100 wt. including chloroprene rubber, adhesion is ensured, but frost resistance is not taken into account, and there is a problem that this composition may not be suitable for use in cold regions. Thus, these compositions are not suitable for use in cold regions or in an operating environment in which fire resistance is required, and there is the possibility of their further improvement.

Accordingly, there is a need for a rubber composition for bonding metals that has excellent adhesion to galvanized steel cords and also has high fire resistance and excellent frost resistance.

In light of the problems described above, it is an object of the present invention to provide a rubber composition having excellent adhesion to galvanized steel cords, improved fire and frost resistance, and a conveyor belt.

Means of solving the problem

The present invention is described in the following paragraphs (1) to (3).

(1) A rubber composition comprising a rubber component comprising butadiene rubber, chloroprene rubber and natural rubber; organic cobalt salt; rosin or a derivative of rosin; and organochlorine compound; moreover

the content of butadiene rubber is from 5 parts by weight up to 20 parts by weight per 100 parts by weight rubber component;

the content of chloroprene rubber is from 20 wt.h. up to 65 parts by weight per 100 parts by weight rubber component;

the content of organic cobalt salt is from 0.2 wt.h. up to 1.0 mass.h. per 100 parts by weight the rubber component when recalculating the mass of the organic cobalt salt to the mass of cobalt;

the content of rosin or derived rosin is from 2 wt.h. up to 9 parts by weight per 100 parts by weight rubber component; and

the content of organochlorine compounds is from 5 wt.h. up to 35 parts by weight per 100 parts by weight rubber component.

(2) The rubber composition according to paragraph (1), in which the numerical value of A determined by the formula (1) below is not more than 83 parts by weight. per 100 parts by weight rubber component.

[Formula 1]

A = chloroprene rubber (CR) × 0.8 + organochlorine compound × 1.5 + rosin × 2.5 (1)

(3) A conveyor belt comprising a composite material obtained by vulcanizing a product containing the rubber composition according to (1) or (2), and a galvanized steel cord.

EFFECT OF THE INVENTION

The present invention provides excellent adhesion to galvanized steel cords and makes it possible to improve fire resistance and frost resistance.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective cross-sectional view of a conveyor belt according to an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Further, the present invention is explained in detail. However, the present invention is not limited to the embodiments of the invention (hereinafter referred to as “the embodiments”), which are described below. In addition, the constituent components that are described in the embodiments include constituent components that one skilled in the art can readily understand, and constituent components that are substantially identical or, in other words, equivalent in properties. In addition, the constituent components that are described in the embodiments may be combined as much as desired.

Rubber composition

The rubber composition according to this embodiment (hereinafter referred to as the "composition according to this embodiment") comprises a rubber component comprising butadiene rubber (BR), chloroprene rubber (CR), and natural rubber (NR); organic cobalt salt; rosin or a derivative of rosin; and organochlorine compound.

Rubber component

Vulcanizable gray rubber is used as the rubber component contained in the composition according to this embodiment. Vulcanizable sulfur rubber is rubber that can be vulcanized using sulfur, for example natural rubber, synthetic rubber, or a mixture thereof, and examples include diene rubbers, etc. Specific examples of diene rubbers include natural rubbers, isoprene rubbers (IR), a variety of butadiene rubbers (BR), 1,2-butadiene rubbers, a variety of styrene-butadiene copolymer rubbers (SBR), acrylonitrile-butadiene copolymer rubbers (NBR), butyl rubbers (IIR) and ethylene-propylene-diene rubbers (EPDM). One type of these rubber components can be used individually, or two or more types can be used in combination.

Of these rubbers, butadiene rubbers, chloroprene rubbers and natural rubbers are used, since they have excellent adhesion, fire resistance and frost resistance.

The weight average molecular weight (Mw) of butadiene rubber is preferably at least 400,000 and more preferably at least 450,000. When the weight average molecular weight is in this range, the tensile strength and elongation at break of the rubber composition after vulcanization are further increased. The weight average molecular weight is the weight average molecular weight (with respect to polystyrene) as measured by gel permeation chromatography (GPC), and tetrahydrofuran (THF) is preferably used as a measurement solvent. A commercially available product may be used as butadiene rubber, and specific examples include Nipol BR1220 and Nipol BR1250H (manufactured by Zeon Corporation)

Examples of chloroprene rubbers include type G modified gray rubbers, type W non-modified gray rubbers and high crystalline types of rubbers, and a variety of known chloroprene rubbers can be used. A commercially available product can be used as chloroprene rubber, and specific examples include GRT neoprene and WRT neoprene (manufactured by Showa Denko Du Pont) and Denka chloroprene PM-40 and S-41 (manufactured by Denki Kagaku Kogyo K.K.).

Natural rubber is a polymer having a structure comprised of head-to-tail molecules of cis-1,4-polyisoprene, and the commonly used natural rubber can be used. A commercially available product can be used as natural rubber, and specific examples include TSR-20 and RSS # 3.

The content of butadiene rubber in the rubber component is from 5 parts by weight up to 20 parts by weight and preferably from 5 parts by weight up to 15 parts by weight per 100 parts by weight the rubber component according to this embodiment. In addition, the content of chloroprene rubber in the rubber component is from 20 wt.h. up to 65 parts by weight and preferably from 25 parts by weight up to 60 parts by weight per 100 parts by weight the rubber component according to this embodiment. In addition, the content of natural rubber in the rubber component is the residual amount determined by subtracting the total content of butadiene rubber and chloroprene rubber from 100 parts by weight the rubber component according to this embodiment, that is, from 15 parts by weight up to 75 parts by weight and preferably from 25 parts by weight up to 70 parts by weight

When the content of butadiene rubber, chloroprene rubber and natural rubber are within each of the ranges described above, it becomes possible to improve fire resistance and frost resistance while maintaining the adhesive ability of the composition according to this embodiment. In addition, after vulcanization of the composition according to this embodiment, tensile strength and elongation at break, which are physical properties, become favorable.

Organic cobalt salt

The organic cobalt salt that is contained in the composition according to this embodiment is not limited in a specific way, provided that it is a conventionally known substance that is commonly used as a liquid phase oxidation catalyst. An organic cobalt salt can be obtained by performing a precipitation method in an exchange reaction by adding a solution of cobalt acetate to an aqueous solution containing an alkali metal salt and the corresponding organic acid, a method of heating and melting the organic acid and cobalt (II) oxide, a method of adding an aqueous solution of cobalt sulfate, or cobalt nitrate in a solution of an organic acid in benzene, etc. Specific examples of organic cobalt salts include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt orthoborate, cobalt octylate, cobalt versatate, cobalt palmitate, cobalt and rosin salt, cobalt propionate and cobalt complexes. Of these, cobalt naphthenate, cobalt neodecanoate, cobalt and boron complexes, etc., are preferred for use, since they further increase the adhesive ability. A commercially available product can be used as the organic cobalt salt, and a specific example is 10% cobalt naphthenate (manufactured by DIC Corporation) or a similar product.

The content of organic salt of cobalt is from 0.2 wt.h. up to 1.0 mass.h. and preferably from 0.3 parts by weight up to 0.7 parts by weight per 100 parts by weight rubber component when recalculating the mass of organic cobalt salt to the mass of cobalt. When the organic cobalt salt content is within the range described above, the adhesive ability with respect to galvanized steel cords (with rubber) becomes favorable. In addition, when the content of the organic cobalt salt is less than 0.2 parts by mass, the adhesion with respect to galvanized steel cords and the peeling resistance in the wet state are reduced, and when the content exceeds 1.0 parts by mass, the resistance to aging of the rubber composition, which is not preferred. In particular, the content of the organic cobalt salt is preferably 0.2 mass parts. up to 1.0 mass.h. from the point of view of simultaneously achieving adhesion, wet peeling and other properties of rubber.

Rosin

The rosin that is contained in the composition according to this embodiment is a type of natural rosin, the so-called pine rosin. In addition, examples of rosin derivatives include resin rosins extracted from pine wood with a solvent, or similar materials, wood rosins, tall oil rosins, polymers of these rosins, disproportionate rosins, maleated rosins, aldehyde-modified rosins, hydrogenated rosins and related products thereof. As a rosin or a derivative of rosin, a known product that is commonly used as a tackifier can be used. A commercially available product can be used as a rosin or a rosin derivative, and specific examples are gum rosin or wood rosin (manufactured by Arakawa Chemical Industries, Ltd.), tall oil rosin (manufactured by Harima Chemicals Group, Inc.), and hydrogenated rosin (manufactured by Hercules Co., Ltd.).

The content of rosin or a derivative of rosin is from 2 wt.h. up to 9 parts by weight and preferably from 3 parts by weight up to 7 parts by weight per 100 parts by weight rubber component. When the content of rosin or a derivative of rosin is within the range described above, the adhesion to galvanized steel cords (with rubber) is suitable, the suitability for rolling is also suitable, and frost resistance is improved. When the content of rosin or a derivative of rosin is less than 2 parts by mass, the wet peeling resistance between the rubber composition and the galvanized steel cord becomes insufficient, and when the content exceeds 9 parts by mass, the stickiness of the rubber composition is increased and its suitability for rolling. In particular, the content of rosin or a derivative of rosin is preferably from 2 parts by weight up to 9 parts by weight from the point of view of simultaneously providing resistance to peeling in the wet state and practical suitability for processing.

The composition according to this embodiment contains rosin or a derivative of rosin, and thus has excellent adhesion to galvanized steel cords and resistance to wet peeling. In addition, rosin or a derivative of rosin is typically used as a tackifier, and when the composition according to this embodiment contains rosin or a derivative of rosin, its tackiness is improved and its adhesion to the roller is enhanced. When the stickiness with respect to the roller becomes excessively high, the suitability for rolling decreases. Suitability for rolling means stickiness and suitability for processing the material of the unvulcanized rubber composition and is a characteristic of the fact that the substance can be easily molded into a sheet during processing (in particular, in the factory rolling process).

Organochlorine compound

An organochlorine compound, commonly used as a chlorine-containing flame retardant, can be used as the organochlorine compound contained in the composition according to this embodiment. As the organochlorine compound, it is preferable to use, for example, an unbranched chain organochlorine compound. Specific examples of straight-chain organochlorine compounds are chlorinated paraffin and chlorinated polyethylene. Commercially available products can be used as these compounds. For example, there are commercially available chlorinated paraffins with a chlorine content of 40% to 80%, and any of these products can be used. Examples of commercially available products are Toyoparax (chlorine content 70 wt.%, Manufacturer Tosoh Corporation) and Enpara 70S (chlorine content 70 wt.%, Manufacturer Dover Chemical Company).

The content of organochlorine compounds is from 5 wt.h. up to 35 parts by weight and preferably from 5 parts by weight up to 30 parts by weight per 100 parts by weight rubber component. When the content of the organochlorine compound is within the range described above, the fire resistance of the composition according to this embodiment is improved. In addition, when the content of the organochlorine compound is less than 5 parts by mass, the adhesion becomes unstable, and when the content exceeds 35 parts by mass, the stickiness of the composition according to this embodiment becomes excessively high, which makes processing difficult. In particular, the content of the organochlorine compound is preferably from 5 parts by weight. up to 35 parts by weight from the point of view of simultaneously providing adhesion and processing suitability.

By virtue of the content of the organochlorine compound, the adhesive ability (in particular, the initial adhesiveness of the composition according to this embodiment is suitable). In addition, the organochlorine compound gives fire resistance, thus, due to the content of the organochlorine compound within the range described above, the composition according to this embodiment the implementation simultaneously demonstrates excellent fire resistance and excellent frost resistance. oh cord conveyor belt, made with the use of the composition according to the present embodiment, as described below, sufficiently provides fire resistance required for a steel cord comprising a conveyor belt used in mines or similar conditions, and it can also be used in cold regions.

As described above, the composition according to this embodiment contains, in predetermined amounts, butadiene rubber, chloroprene rubber and natural rubber, and also contains, in predetermined amounts, an organic cobalt salt, rosin or rosin derivative and an organochlorine compound as required components per 100 parts by weight . rubber component, which gives excellent adhesion to galvanized steel cords and makes it possible to improve fire resistance and frost resistance.

In addition, it turns out to be preferable if the composition according to this embodiment contains six essential components, which are described above, and the numerical value A determined by the following formula (1) is not more than 83 parts by weight. per 100 parts by weight rubber component.

[Formula 2]

A = chloroprene rubber (CR) × 0.8 + organochlorine compound × 1.5 + rosin × 2.5 (1)

For the three components, including chloroprene rubber, an organochlorine compound and rosin, the numerical value determined by the above formula (1) is not more than 83 parts by weight, preferably from 50 parts by weight up to 83 parts by weight and more preferably from 60 parts by weight up to 83 parts by weight By establishing the quantities of the three components, including chloroprene rubber, organochlorine compound and rosin, in predetermined proportions, satisfying the condition that the numerical value determined by the above formula (1) is not more than 83 parts by weight, the composition according to this the embodiment exhibits excellent adhesion with respect to galvanized steel cords, makes it possible to improve fire resistance and frost resistance, and also increases the suitability for rolling.

In addition to the required components described above, the composition according to this embodiment may also contain a phenol-aldehyde polymer containing carboxyl groups, liquid isoprene rubber (made by introducing a carboxyl group into the isoprene polymer rubber during solution polymerization) and other substances within the ranges, which do not interfere with the objectives of the present invention. In addition, the composition may also contain various other additives as necessary. Examples of additives are composition-promoting substances or other substances that are commonly used, including fillers such as carbon black; vulcanization promoting additives, such as zinc oxide and stearic acid; vulcanization accelerators, such as dibenzothiazyl disulfide; anti-aging agents, such as amine-based, phenol-based or wax-based; sulfur; as well as plasticizers, such as plasticizers based on vegetable oil or plasticizers based on mineral oil. The composition may contain two or more types of these additives. Additives and other substances can be mixed and converted into a composition in the usual way, and then used in the process of vulcanization or crosslinking. The relative content of these additives in the composition may be any conventional standard number, provided that this does not impede the performance of the tasks of this embodiment.

An example of a method for manufacturing a composition according to this embodiment is a method comprising adding from 5 parts by weight up to 20 parts by weight butadiene rubber, from 20 parts by weight up to 65 parts by weight chloroprene rubber and a predetermined amount of natural rubber as a residual rubber component per 100 parts by weight rubber component, which is described above, the introduction of the composition from 0.2 wt.h. up to 1.0 mass.h. organic cobalt salt per 100 parts by weight the rubber component when converting the mass of organic cobalt salt to the mass of cobalt, from 2 wt.h. up to 9 parts by weight rosin or a derivative of rosin per 100 parts by weight rubber component, as well as from 5 parts by weight up to 35 parts by weight organochlorine compounds per 100 parts by weight rubber component, the proper selection and introduction in specified amounts of fillers, vulcanization accelerators, anti-aging substances and plasticizers, which are described above, as necessary, and mixing the mixture for a predetermined period of time at a given temperature using a roller mill, a Banbury mixer or a similar device for producing a rubber composition.

The rubber composition obtained as described above can be attached to a galvanized steel cord and cured with sulfur for a predetermined period of time at a predetermined temperature so that a composite rubber material and a galvanized steel cord are obtained.

The product obtained by plating the untreated surface of a steel cord, for example, can be used as a steel cord for attaching to the rubber composition as described above. As a coating method, electrodeposition, immersion in a hot melt, etc. can be used. The galvanized product is preferably used as a steel cord for the manufacture of conveyor belts, etc. in terms of preventing corrosion and durability. The diameter of the thread, the diameter of the cord and other parameters of the galvanized steel cord can be appropriately selected in accordance with the application when the galvanized steel cord is attached to the rubber composition according to this embodiment for the manufacture of a composite material.

As an example of a method of attaching a composition according to this embodiment to a galvanized steel cord, the rubber composition can be fastened to a galvanized steel cord with a predetermined thickness, and curing under pressure can be carried out for 30 minutes at 150 ° C to make a composite material from the rubber composition and galvanized steel cord. Since the composition according to this embodiment exerts excellent adhesion to galvanized steel cords, it can be used in products in which galvanized steel cords are used as reinforcing material. In addition, the composition can be used not only for steel cords, but also for other galvanized metal materials.

The composition according to this embodiment is suitably used in the manufacture of a steel cord-containing conveyor belt because it has the excellent characteristics described above, and it can also be properly used to make hoses, tracks, marine hoses, tires, etc.

Assembly line

Next, a case will be described in which the composition according to this embodiment is used in a conveyor belt. FIG. 1 is a perspective cross-sectional view of a conveyor belt according to this embodiment (hereinafter referred to as “conveyor belt according to this embodiment”). As illustrated in FIG. 1, the conveyor belt 10 has outer rubber layers 11a and 11b, a cover rubber layer 12 and a galvanized steel cord 13. The conveyor belt 10 is a conveyor belt 10 in which a galvanized steel cord 13, on which the rubber cover layer 12 is applied, is present, for example , as the core between the outer rubber layers 11a and 11b, for example in the conveyor belt 10, the rubber cover layer 12 contains a composite material obtained by vulcanizing a product containing the aforementioned rubber composition and zinc ovanny steel cord 13. A method for producing a composite material by curing product having rubber composition according to the present embodiment and the galvanized steel cord 13 is as described above.

The surface layer of the conveyor belt 10 is made up of two layers representing the outer rubber layers 11a and 11b, and the cover rubber layer 12, containing the galvanized steel cord 13 as the core, is between two layers representing the outer rubber layers 11a and 11b. The rubber cover layer 12 is made by molding the rubber composition according to this embodiment and turning it into a sheet using a roller or the like, introducing a galvanized steel cord 13 as a core and curing the product. The surfaces of the rubber composition and the galvanized steel cord 13 are then firmly bonded to form a rubber cover layer 12. The rubber cover layer 12 serves as a bonding layer for the galvanized steel cord 13 and the rubber cover 11, and also as a cushioning material for the galvanized steel cord 13. Rubber composition containing a component that is characterized by excellent fire resistance, heat resistance, frost resistance, oil resistance, wear resistance or resistance to atmospheric effects lenium is preferably used to cover the rubber layer 11 in accordance with the use of conveyor belt 10.

Since the conveyor belt 10 according to this embodiment takes the configuration described above, it has excellent adhesion to the galvanized steel cord 13, and its fire resistance and frost resistance can be improved so that the conveyor belt 10 has excellent durability and long-term reliability. In addition, since the conveyor belt 10 according to this embodiment has frost and fire resistance, it can be used even in cold regions with an ambient temperature of about -30 ° C, and mine fires can also be prevented.

A method of manufacturing a conveyor belt 10 according to this embodiment is not limited in a particular way and can be carried out in a commonly used method or in a similar way. A specific example of a method that can be appropriately carried out is a method comprising mixing the raw materials using a roller, mixer, Banbury mixer or similar device, molding the product and turning it into a sheet for each of the outer rubber layers 11a and 11b using a roller or a similar device, the subsequent lamination of each of the resulting layers in a predetermined order, so that a covering rubber layer (reinforcing layer) 12 is obtained, ka mentioned above, and the final pressure is applied for 10 to 60 minutes at a temperature of from 140 to 170 ° C.

The rubber composition and conveyor belt of the present invention have been described above in detail, but the above examples do not limit the present invention, and various types of modifications and enhancements can be used within the scope of the present invention without deviating from its idea.

EXAMPLES

Next, the composition according to this embodiment will be described in detail using working examples. However, the composition according to this embodiment is not limited to these working examples.

The manufacture of rubber compositions (working examples 1-6 and comparative examples 1-8)

The components shown in table 1 were combined with each other in the compositional ratios (parts by weight), which are presented in the table, and mixed until smooth using a Banbury mixer to make rubber compositions in working examples 1-6 and comparative examples 1 -8. The compositional ratios of all components in the respective working examples and comparative examples are presented in table 1.

Evaluation of adhesiveness, wet peeling resistance, fire resistance, frost resistance and suitability for rolling was carried out using the methods presented below for each of the rubber compositions obtained in each of the working examples and comparative examples. The results are presented in table 1.

Adhesive ability

Each rubber composition in each working example and comparative example was applied with a thickness of 15 mm on a galvanized steel cord 4.1 mm in diameter, which was held in a desiccator and subjected to dust and moisture treatment, so as to make a composite material from each rubber composition and steel cord, and this composite material was subjected to pressure and vulcanization for 30 minutes at 150 ° C to produce a test sample (containing rubber / galvanized steel cord composite material). Steel cord was drawn from each test sample obtained, and adhesiveness was evaluated by determining the degree of rubber coating (%). Extraction studies were carried out in accordance with DIN22131. The degree of rubber coating was calculated as the ratio (%) of the rubber-covered area remaining on the surface of the steel cord after stretching and the total surface area of the steel cord. The results were determined to be favorable when the degree of rubber coating was 70% or more. The evaluation results are presented below in table 1. A higher degree of rubber coating shows an improvement in adhesiveness.

Wet peeling resistance

The parts where the steel cord protrudes from the rubber surface of each of the same test samples as the samples made for the above adhesion tests were sealed with beeswax and kept for three weeks in a thermostatic bath at a temperature of 50 ° C and a relative humidity of 95%. The steel cord was then pulled from each test sample obtained, and the wet peeling resistance was evaluated by determining the degree of rubber coating (%). Extraction studies were carried out in accordance with DIN22131. The results were determined to be favorable when the degree of rubber coating was 50% or more. The evaluation results are presented below in table 1. A higher degree of rubber coating indicates an improvement in wet peeling resistance.

Fire resistance

Each rubber composition obtained in each working example and comparative example described above was cured for 30 minutes at 150 ° C. and a surface pressure of 3.0 MPa using a compression molding apparatus to produce a cured sheet having a thickness of 2 mm . A test sample (150 mm × 60 mm) was cut from this sheet, and the oxygen index was measured in accordance with JIS K6269-1998. The results were determined to be favorable when the oxygen index was 32 or more. The evaluation results are presented below in table 1. A higher measured oxygen index shows increased fire resistance.

Frost resistance

The test sample was made from vulcanized rubber for each rubber composition, as provided for in the “Low temperature brittleness test” of JIS K6261-2006 “Vulcanized or Thermoplastic Rubber — Determination of Properties at Low Temperature”. Under the influence of shock bending on the test samples under specified conditions, the temperature was measured at which 50% of the total number of test samples was destroyed (brittle temperature). The results were determined to be favorable when the brittle temperature was −35 ° C. or less. The evaluation results are presented below in table 1. The lower measured temperature of brittleness shows increased frost resistance.

Suitability for rolling

Each rubber composition obtained in each working example and comparative example described above was passed between rollers heated to 40 ° C. into a gap of 2.0 mm, and suitability for rolling was evaluated by visually observing peeling from the rollers. Suitability for rolling was evaluated based on the following evaluation criteria. The evaluation results are presented below in table 1.

Criteria for evaluation

: There is no adhesion of the rubber composition to the surface of the roller.

○: A slight adhesion of the rubber composition to the surface of the roller is observed, but sheet removal is possible.

Δ: Significant adhesion of the rubber composition to the surface of the roller is observed, but sheet removal is possible.

×: Adhesion of the rubber composition to the surface of the roller is observed, and sheet removal is difficult.

Table 1 Working example 1 Working example 2 Working example 3 Working example 4 Working example 5 Working example 6 Comparative Example 1 Reference Example 2 Reference Example 3 Reference Example 4 Reference Example 5 Reference Example 6 Reference Example 7 Reference Example 8 Nr 70.0 40,0 40,0 55.0 25.0 55.0 50,0 90.0 45.0 63.0 - 60.0 70.0 25.0 SBR - - - - - - 50,0 - - - 40,0 - - - CR1 - - 45.0 - - - - 10.0 55.0 27.0 45.0 - - - CR2 25.0 45.0 - 30,0 60.0 30,0 - - - - - 33.0 25.0 50,0 BR 5,0 15.0 15.0 15.0 15.0 15.0 - - - 10.0 15.0 7.0 5,0 15.0 Organochlorine compound 27.0 12.0 12.0 24.0 5,0 24.0 20,0 27.0 27.0 27.0 12.0 38,0 27.0 2.0 Wearproof soot 40,0 35.0 35.0 35.0 35.0 35.0 50,0 50,0 50,0 50,0 35.0 40.0 40.0 35.0 Rosin 5.0 3.0 3.0 3.0 3.0 3.0 - - - - 3.0 5.0 10.0 3.5 Organic cobalt salt (in terms of metal) 0.4 0.4 0.4 0.4 0.4 0.8 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Zinc oxide 4.0 4.3 4.3 4.0 4.6 4.0 6.5 6.5 6.5 6.5 4.3 4.0 4.0 4.3 Sulfur 3.0 3,5 3,5 3,5 3,5 3,5 3,5 3.0 3.0 3.0 3,5 3.0 3.0 3,5 The value calculated by the formula 1 73.0 61.5 61.5 67.5 63.0 67.5 30,0 48.5 84.5 62.1 61.5 95.9 85.5 63.0 Adhesive ability (degree of rubber coating (%)) 80 95 95 90 85 one hundred 90 fifteen 5 10 90 75 one hundred one hundred Wet peeling resistance (degree of rubber coating (%) after three weeks of moisture protection) 60 95 95 80 80 80 thirty 0 0 0 0 75 one hundred 80 Fire resistance (oxygen index)) 32 35 35 33 39 33 28 28 33 33 35 38 32 thirty Frost resistance (brittle temperature (° C)) -36.2 -39 -41.4 -39.8 -37.0 -43.3 -45.8 -33.4 -23.8 -35.8 -41.8 -31.4 -34.6 -37.9 Suitability for rolling ○ ○ ○ ○ ○ ○  ○  ○ ○   ○

Table 1 presents the following components.

- NR: Natural Rubber, TSR-20

- SBR: styrene-butadiene rubber, trade name NIPOL 1502, manufacturer Zeon Corporation

- CR1: chloroprene rubber, sulfur-modified chloroprene rubber, trade name Denka Chloroprene PM-40, manufacturer Denki Kagaku Kogyo K.K.

- CR2: chloroprene rubber, unmodified sulfur chloroprene rubber, trade name Denka Chloroprene S-41, manufacturer Denki Kagaku Kogyo K.K.

- BR: butadiene rubber, trade name Nipol BR1220, manufacturer Zeon Corporation

- Organochlorine compound: chlorinated paraffin, chlorine content 70%, trade name Enpara 70S, manufacturer Dover Chemical Company

- Wear-resistant furnace carbon black: carbon black, trade name Niteron # 200, manufactured by Tokai Carbon Co., Ltd.

- Rosin: resin rosin, manufacturer Arakawa Chemical Industries, Ltd.

- Organic cobalt salt: cobalt naphthenate, cobalt content 10%, manufacturer DIC Corporation

- Zinc oxide: vulcanization accelerating additive, trade name Zinc Oxide III, manufacturer Seido Chemical Industry Co., Ltd.

- Sulfur: vulcanizing agent, sulfur for processing petroleum products, manufacturer Hosoi Chemical Industry Co., Ltd.

- The value calculated by formula 1: the numerical value determined by the following formula [A = chloroprene rubber (CR) × 0.8 + organochlorine compound × 1.5 + rosin × 2.5] per 100 parts by weight rubber component

The results presented in table 1, confirmed that all the samples in working examples 1-6 showed excellent adhesive ability, resistance to peeling in the wet state, fire resistance, frost resistance and suitability for rolling.

On the other hand, in comparative example 1, it was confirmed that the fire resistance was unsatisfactory since chloroprene rubber was not contained in the composition and the wet peeling resistance was unsatisfactory because rosin was not contained in the composition. In addition, in comparative example 2, it was confirmed that the frost resistance was unsatisfactory because the composition did not contain butadiene rubber, the fire resistance was unsatisfactory because the chloroprene rubber content was insufficient, and the adhesive ability and resistance to peeling in the wet state were unsatisfactory, since the composition was not contained rosin. In addition, in comparative example 3, it was confirmed that the frost resistance was unsatisfactory because the composition did not contain butadiene rubber, the adhesive ability and the resistance to peeling in the wet state were unsatisfactory because the composition did not contain rosin, and the suitability for rolling was unsatisfactory, since the value calculated by formula 1 exceeded 83. In addition, in comparative example 4, it was confirmed that the adhesive ability and resistance to peeling in wet conditions were unsatisfactory because rosin was not contained in the composition. In addition, in comparative example 5, it was confirmed that the peeling resistance in the wet state was unsatisfactory because the composition did not contain natural rubber. In addition, in comparative example 6, it was confirmed that the frost resistance was unsatisfactory because the organochlorine compound content was excessive and the suitability for rolling was unsatisfactory since the value calculated by formula 1 exceeded 83. In addition, in comparative example 7 it was confirmed that frost resistance was unsatisfactory because the rosin content was excessive, and the suitability for rolling was unsatisfactory, since the value calculated by formula 1 was averaged 83. In addition, in comparative example 8, it was confirmed that the fire resistance was unsatisfactory since the content of the organochlorine compound was insufficient.

Accordingly, a rubber composition containing predetermined amounts of butadiene rubber, chloroprene rubber, and natural rubber as a residual rubber component, as well as predetermined amounts of an organic salt of cobalt, rosin or a derivative of rosin and an organochlorine compound per 100 parts by weight the rubber component gives excellent adhesion to galvanized steel cords and makes it possible to improve fire resistance and frost resistance (see working examples 1-6).

In addition, due to the content of the six mandatory components described above and the inclusion of the three components described above, so that the numerical value determined by the following formula [A = chloroprene rubber × 0.8 + organochlorine compound × 1.5 + rosin × 2.5 (1)], is not more than 83 parts by weight per 100 parts by weight rubber component, it becomes possible to further improve the suitability for rolling (see working examples 1-6).

Accordingly, it was determined that the composition according to this embodiment can be appropriately used in the manufacture or modification of a steel cord-containing conveyor belt based on the fact that the composition exhibits excellent adhesion to galvanized steel cords and makes it possible to improve fire resistance and frost resistance Compared to traditionally used rubber compositions.

CONVENTIONS

10 - conveyor belt

11, 11a, 11b - External rubber layers

12 - Cover rubber layer

13 - Steel cord (galvanized steel cord)

Claims (3)

1. A rubber composition comprising:
a rubber component comprising butadiene rubber, chloroprene rubber, and natural rubber;
organic cobalt salt;
rosin or a derivative of rosin; and
organochlorine compound;
moreover:
the content of butadiene rubber is from 5 mass. hours to 20 mass. hours per 100 mass. including rubber component;
the content of chloroprene rubber is from 20 mass. hours to 65 mass. hours per 100 mass. including rubber component;
the content of organic salt of cobalt is from 0.2 mass. hours to 1.0 mass. hours per 100 mass. including the rubber component when recalculating the mass of the organic cobalt salt to the mass of cobalt;
the content of rosin or derived rosin is from 2 mass. hours to 9 mass. hours per 100 mass. including rubber component; and
the content of organochlorine compounds is from 5 wt. hours to 35 mass. hours per 100 mass. including rubber component. 2. The rubber composition according to p. 1, in which the numerical value of A, determined by the following formula (1), is not more than 83 mass. hours per 100 mass. including rubber component:
[Formula 1]
A = chloroprene rubber (CR) × 0.8 + organochlorine compound × 1.5 + rosin × 2.5 (1). 3. A conveyor belt comprising a composite material obtained by vulcanizing a product containing the rubber composition according to claim 1 or 2, and a galvanized steel cord.

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