Rubber composition for conveyor belt, and conveyor belt

Abstract

The purpose of the present invention is to provide: a rubber composition which has excellent flame retardancy, ozone resistance, blooming resistance and power saving properties after being made into vulcanized rubber; and a conveyor belt. The present invention is a rubber composition for conveyor belts, which contains a rubber component that contains natural rubber and butadiene rubber and has a mass ratio of the natural rubber content to the butadiene rubber content of 30 / 70 to 80 / 20, a flame retardant that contains a bromine-based flame retardant and antimony trioxide, a hydrocarbon-based wax (W), and a filler, the present invention relates to a rubber composition comprising a rubber component, a bromine-based flame retardant, an anti-aging agent containing an amine-based anti-aging agent, a vulcanization accelerator, and sulfur, in which the content of a hydrocarbon-based wax (W) is 2.5 parts by mass or less and the mass ratio of the content of the bromine-based flame retardant to the content of the hydrocarbon-based wax (W) is 8.0 or more per 100 parts by mass of the rubber component, the hydrocarbon-based wax W contains a hydrocarbon-based wax (w1) having a melting point of 65 DEG C or more, and the content of the bromine-based flame retardant and the content of the hydrocarbon-based wax (W) is 2.0 parts by mass or more per 100 parts by mass of the rubber component. The content of the amine-based anti-aging agent is 3.0 parts by mass or more.

Description

Technical Field

[0001] The present invention relates to a rubber composition for a conveyor belt and a conveyor belt. Background Art

[0002] Conventionally, it has been known that a rubber composition containing a butadiene rubber or the like can be used for a conveyor belt (for example, Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2017 / 141909 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Vulcanized rubber obtained from a rubber composition containing a butadiene rubber (BR) and wax or the like is liable to cause bloom of wax or the like. When the covering rubber layer of a conveyor belt is formed of the above rubber composition, if wax or the like blooms excessively on the surface of the covering rubber layer, the bloomed wax or the like adheres to the roller, and further, lime powder adheres to the roller, which may cause deterioration of the running resistance of the roller of the conveyor belt, that is, deterioration of the running performance of the conveyor belt.

[0008] In addition, in recent years, in mining plants and ironworks using conveyor belts, due to the decrease in the operating rate caused by fire failures and safety measures, the demand for flame-retardant conveyor belts has been increasing. So far, the conveyor belts have been made flame-retardant by adding a flame retardant, but there is a demand for developing a flame-retardant conveyor belt with additional values such as improved weather resistance (ozone resistance), abrasion resistance, and belt running performance.

[0009] Regarding the flame-retardant treatment of rubber, it has been known to add a flame retardant to a rubber composition as described above, but by adding a flame retardant to a rubber composition, the physical properties of the obtained vulcanized rubber (for example, belt running performance (power saving property) etc.) sometimes deteriorate.

[0010] Among them, the present inventors evaluated a rubber composition containing a butadiene rubber (BR), a flame retardant, wax or the like, and as a result, found that the ozone resistance of the vulcanized rubber obtained from such a rubber composition sometimes deteriorates.

[0011] Therefore, an object of the present invention is to provide a rubber composition having excellent flame retardancy, ozone resistance, bloom resistance, and power saving property after being made into vulcanized rubber.

[0012] In addition, an object of the present invention is to provide a conveyor belt.

[0013] Means for Solving the Problems

[0014] The inventor of the present invention has conducted in-depth research to solve the above problems, and as a result, it has been found that by making the rubber composition contain:

[0015] a rubber component containing natural rubber and butadiene rubber, the mass ratio of the content of the natural rubber to the content of the butadiene rubber being within a specified range,

[0016] a flame retardant containing a brominated flame retardant and antimony trioxide,

[0017] a hydrocarbon wax (W),

[0018] a filler,

[0019] an antioxidant containing an amine-based antioxidant,

[0020] a vulcanization accelerator, and

[0021] sulfur,

[0022] the content of the hydrocarbon wax (W), the mass ratio of the content of the brominated flame retardant to the content of the hydrocarbon wax (W), and the content of the amine-based antioxidant are respectively within specific numerical ranges, and the hydrocarbon wax (W) contains a hydrocarbon wax (w1) having a melting point of 65 °C or higher. Thus, flame retardancy can be imparted to the obtained vulcanized rubber, the power saving property of the above vulcanized rubber is excellent, and a balance between improvement of ozone resistance and bloom resistance (inhibiting excessive blooming of antioxidants, etc.) is achieved, and ozone resistance and bloom resistance can be improved simultaneously, thereby completing the present invention.

[0023] Based on the above insights and the like, the present invention specifically solves the above problems through the following solutions.

[0024] [1]. A rubber composition, which contains:

[0025] a rubber component containing natural rubber and butadiene rubber, the mass ratio of the content of the natural rubber to the content of the butadiene rubber, that is, natural rubber / butadiene rubber, being 30 / 70 to 80 / 20,

[0026] a flame retardant containing a brominated flame retardant and antimony trioxide,

[0027] a hydrocarbon wax (W),

[0028] a filler,

[0029] an antioxidant containing an amine-based antioxidant,

[0030] a vulcanization accelerator, and

[0031] sulfur,

[0032] relative to 100 parts by mass of the rubber component, the content of the hydrocarbon wax (W) is 2.5 parts by mass or less,

[0033] The mass ratio of the content of the bromine-based flame retardant to the content of the hydrocarbon wax (W), i.e., bromine-based flame retardant / hydrocarbon wax (W), is 8.0 or more.

[0034] The hydrocarbon wax (W) contains a hydrocarbon wax (w1) having a melting point of 65°C or higher.

[0035] The content of the amine-based anti-aging agent is 3.0 parts by mass or more relative to 100 parts by mass of the rubber component.

[0036] [2]. The rubber composition for a conveyor belt as described in [1], wherein the mass ratio of the content of the natural rubber to the content of the butadiene rubber is 40 / 60 to 70 / 30.

[0037] [3]. The rubber composition for a conveyor belt as described in [1] or [2], wherein the mass ratio of the content of the bromine-based flame retardant to the content of the hydrocarbon wax (W) is 10 or more and 20 or less.

[0038] [4]. The rubber composition for a conveyor belt as described in any one of [1] to [3], wherein the hydrocarbon wax (w1) contains n-paraffin, and the number of carbon atoms at the peak of the carbon atom number distribution of the n-paraffin is in the range of 30 to 40.

[0039] [5]. The rubber composition for a conveyor belt as described in any one of [1] to [4], wherein the hydrocarbon wax (w1) contains n-paraffin, and the content of the n-paraffin is 80% by mass or more in the hydrocarbon wax (w1).

[0040] [6]. The rubber composition for a conveyor belt as described in any one of [1] to [5], wherein the amine-based anti-aging agent contains a p-phenylenediamine-based compound.

[0041] [7]. The rubber composition for a conveyor belt as described in any one of [1] to [6], wherein the bromine-based flame retardant contains a compound represented by the following formula (1).

[0042]

[0043] In formula (1), R represents an aliphatic hydrocarbon group which may contain an unsaturated group.

[0044] [8]. The rubber composition for a conveyor belt as described in any one of [1] to [7], wherein the hydrocarbon wax (W) further contains a hydrocarbon wax (w2) having a melting point lower than 65°C.

[0045] [9]. The rubber composition for a conveyor belt as described in [8], wherein the hydrocarbon wax (w2) contains n-paraffin, and the number of carbon atoms at the peak of the carbon atom number distribution of the n-paraffin is in the range of 25 to 35.

[0046]

[10] . The rubber composition for a conveyor belt as described in [8] or [9], wherein the hydrocarbon wax (w2) contains normal paraffin, and the content of the normal paraffin is 80% by mass or more in the hydrocarbon wax (w2).

[0047]

[11] . A conveyor belt is formed by using the rubber composition for a conveyor belt according to any one of [1] to

[10] .

[0048]

[12] . The conveyor belt as described in

[11] has a covering rubber formed by using the rubber composition.

[0049] Advantages of the Invention

[0050] According to the present invention, it is possible to provide a rubber composition excellent in flame retardancy, ozone resistance, anti-blooming property, and power saving property after being made into vulcanized rubber, and a conveyor belt formed by using the above rubber composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a sectional view of an embodiment of the conveyor belt of the present invention.

[0052] Figure 2 It is a sectional view of another embodiment of the conveyor belt of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] The present invention will be described in detail below.

[0054] In addition, in this specification, the numerical range represented by "~" means the range including the numerical values described before and after "~".

[0055] In this article, unless otherwise specified, there are no particular limitations on the preparation methods of the respective components. For example, conventionally known methods can be cited.

[0056] In this specification, unless otherwise specified, as the respective components, two or more substances corresponding to the component can be used alone or in combination. When the component contains two or more substances, the content of the component means the total content of the two or more substances.

[0057] 〔Rubber Composition〕

[0058] The rubber composition for a conveyor belt of the present invention (the rubber composition of the present invention) contains:

[0059] A rubber component containing natural rubber and butadiene rubber, and the mass ratio of the content of the natural rubber to the content of the butadiene rubber, that is, natural rubber / butadiene rubber, is 30 / 70 to 80 / 20.

[0060] A flame retardant containing a bromine-based flame retardant and antimony trioxide.

[0061] Hydrocarbon wax (W),

[0062] Filler,

[0063] Antioxidant containing amine - based antioxidant,

[0064] Vulcanization accelerator, and

[0065] Sulfur,

[0066] With respect to 100 parts by mass of the rubber component, the content of the hydrocarbon wax (W) is 2.5 parts by mass or less.

[0067] The mass ratio of the content of the bromine - based flame retardant to the content of the hydrocarbon wax (W), that is, bromine - based flame retardant / hydrocarbon wax (W) is 8.0 or more.

[0068] The hydrocarbon wax W contains a hydrocarbon wax (w1) having a melting point of 65°C or higher.

[0069] With respect to 100 parts by mass of the rubber component, the content of the amine - based antioxidant is 3.0 parts by mass or more.

[0070] It can be considered that the rubber composition of the present invention has such a structure, and thus the desired effects can be obtained. The reason is not clear, but it is presumably as follows.

[0071] Generally, bromine - based flame retardants and antimony trioxide, which are flame retardants, are not contained in the polymer cross - linking of vulcanized rubber after the vulcanization of the rubber composition. Therefore, similar to the case of adding a filler having no reinforcing effect, the physical properties (such as ozone resistance, electrical power saving property, etc.) of the vulcanized rubber containing the above - mentioned flame retardants deteriorate. The reason for the deterioration of the above physical properties is not clear, but it can be considered that there is a possibility of decomposition during the processing of the flame retardant and excessive blooming of waxes, etc.

[0072] It is speculated that the deterioration of ozone resistance is due to the physical hindrance caused by the presence of the flame retardant as a filler, resulting in a decrease in physical properties, and the consumption of the antioxidant due to the decomposition of the flame retardant during processing or over time. Regarding the above problems, in the present invention, it has been found that by making the antioxidant containing the amine - based antioxidant be a specified amount or more, the ozone resistance of the vulcanized rubber containing the flame retardant can be improved.

[0073] In addition, regarding the excessive blooming of waxes, etc., it can be considered that in the present invention, by adding the flame retardant as a filler, the blooming of the hydrocarbon wax (W) is suppressed (physical hindrance), and the bloom resistance is improved.

[0074] Moreover, antioxidants are generally transferred to the surface of vulcanized rubber through the blooming effect of wax and exist on the above-mentioned surface (i.e., blooming state). The antioxidants on the surface of vulcanized rubber can prevent the vulcanized rubber in contact with external air from deteriorating. Therefore, the formation of the wax film on the surface of vulcanized rubber and the transferred antioxidants are necessary conditions for obtaining ozone resistance, and an appropriate amount of wax is required.

[0075] On the other hand, if an excessive amount of wax is added to the rubber composition to improve ozone resistance, excessive blooming will occur on the surface of vulcanized rubber, and the conveyed matter will adhere to the above-mentioned blooming, resulting in deterioration of physical running performance (decrease in power saving performance).

[0076] In this way, it is very difficult to coexist ozone resistance and blooming resistance at a high level and improve power saving performance.

[0077] Regarding the above problems, in the present invention, it has been found that by containing a hydrocarbon wax (W) containing a hydrocarbon wax (w1) in an amount below a specified amount, ozone resistance and blooming resistance can coexist at a high level and power saving performance can be improved. The present inventors speculate that the reason is that due to poor dispersion of flame retardants, fillers, etc. in the rubber composition, the hydrocarbon wax (W) containing the hydrocarbon wax (w1) may act like a processing agent and improve the processability (dispersion of flame retardants, fillers, etc.) of the rubber composition.

[0078] Hereinafter, each component contained in the rubber composition of the present invention will be described in detail.

[0079] [Rubber component]

[0080] The rubber composition of the present invention contains a rubber component, and the above rubber component contains natural rubber and butadiene rubber.

[0081] By containing natural rubber and butadiene rubber as rubber components in the rubber composition of the present invention, the vulcanized rubber obtained has excellent ozone resistance, blooming resistance, and abrasion resistance.

[0082] [Natural rubber]

[0083] In the rubber composition of the present invention, there is no particular limitation on the natural rubber (NR) contained as a rubber component. For example, conventionally known natural rubbers can be cited.

[0084] [Butadiene rubber]

[0085] In the rubber composition of the present invention, there is no particular limitation on the butadiene rubber (BR) contained as a rubber component. For example, conventionally known butadiene rubbers can be cited.

[0086] Regarding BR, as one of the preferred forms, polybutadiene that is solid at 23°C can be cited, for example. In addition, BR can be unmodified BR or modified BR.

[0087] From the viewpoints of more excellent power saving property and excellent abrasion resistance, the weight-average molecular weight of BR is preferably 200,000 or more, more preferably 300,000 to 1,000,000.

[0088] In this specification, the weight-average molecular weight (Mw) of BR can be the standard polystyrene conversion value obtained by gel permeation chromatography (GPC) under the following conditions.

[0089] · Solvent: Tetrahydrofuran

[0090] · Detector: RI detector

[0091] [Mass ratio of the content of natural rubber to the content of butadiene rubber]

[0092] In the rubber composition of the present invention, the mass ratio of the content of natural rubber to the content of butadiene rubber (natural rubber / butadiene rubber) is 30 / 70 to 80 / 20.

[0093] Since the above mass ratio of the rubber composition of the present invention is within the above range, it has excellent ozone resistance, blooming resistance, and power saving property.

[0094] From the viewpoints of more excellent ozone resistance and blooming resistance, the mass ratio of the content of natural rubber to the content of butadiene rubber is preferably 40 / 60 to 70 / 30, more preferably 50 / 50 to 70 / 30.

[0095] (Total content of natural rubber and butadiene rubber)

[0096] From the viewpoint of more excellent ozone resistance, the total content of natural rubber and butadiene rubber is preferably 80 to 100% by mass in the total amount of the rubber components, more preferably 100% by mass.

[0097] (Other rubbers)

[0098] When the total content of natural rubber and butadiene rubber is less than 100% by mass in the total amount of the rubber components, the rubber components may further contain rubbers other than natural rubber and butadiene rubber (other rubbers).

[0099] (Content of rubber components)

[0100] The content of the rubber components (total amount) may be 50 to 90% by mass in the total amount of the rubber composition. From the viewpoints of more excellent ozone resistance and blooming resistance, the content of the rubber components (total amount) is preferably 50 to 80% by mass in the total amount of the rubber composition.

[0101] [Flame retardant]

[0102] The rubber composition of the present invention contains a flame retardant, and the above-mentioned flame retardant contains a brominated flame retardant and antimony trioxide.

[0103] By containing a flame retardant, the rubber composition of the present invention provides vulcanized rubber with excellent flame retardancy and anti-bleeding properties.

[0104] [Brominated flame retardant]

[0105] The brominated flame retardant is a flame retardant containing bromine. In the present invention, the brominated flame retardant can also function as a filler.

[0106] From the viewpoint of more excellent flame retardancy, the brominated flame retardant preferably contains a brominated flame retardant having a melting point of 300 °C or higher.

[0107] From the viewpoints of more excellent flame retardancy and anti-bleeding properties, the brominated flame retardant preferably contains a compound having bromine and an aromatic hydrocarbon skeleton.

[0108] As the above-mentioned aromatic hydrocarbon skeleton, for example, a benzene skeleton and a biphenyl skeleton can be mentioned. Bromine and the aromatic hydrocarbon skeleton can be directly bonded. The brominated flame retardant having bromine and an aromatic hydrocarbon skeleton may also have an aliphatic hydrocarbon group (saturated aliphatic hydrocarbon group or unsaturated aliphatic hydrocarbon group) that may contain an unsaturated group.

[0109] From the viewpoints of more excellent flame retardancy and anti-bleeding properties, the brominated flame retardant preferably contains a compound represented by the following formula (1), and more preferably contains bis(pentabromophenyl)ethane.

[0110]

[0111] In formula (1), R represents an aliphatic hydrocarbon group that may contain an unsaturated group.

[0112] In formula (1), as the aliphatic hydrocarbon group that may contain an unsaturated group represented by R (hereinafter referred to as "R"), a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group can be mentioned. Regarding the above R, as a preferred form, a saturated aliphatic hydrocarbon group can be mentioned.

[0113] The above R can be any of linear, branched, cyclic, or a combination thereof, but as a preferred form, a linear form can be mentioned.

[0114] There is no particular limitation on the number of carbon atoms of the above R. For example, it can be 1 to 10. The number of carbon atoms is preferably 2 to 8.

[0115] As the above-mentioned saturated aliphatic hydrocarbon group, for example, methylene, ethylene, 1,3-propylene, 1,2-propylene, butylene, pentylene, hexylene, heptylene, octylene can be mentioned.

[0116] Examples of the unsaturated group that R can have include, for example, vinyl, vinylene, ethynyl, and ethynylene.

[0117] When R is an unsaturated aliphatic hydrocarbon group, examples of the unsaturated aliphatic hydrocarbon group include, for example, the above-mentioned unsaturated groups or combinations of saturated aliphatic hydrocarbon groups and unsaturated groups.

[0118] Examples of the compound represented by formula (1) include, for example, bis(pentabromophenyl)ethane.

[0119] [Antimony trioxide]

[0120] In the present invention, there is no particular limitation on the antimony trioxide (Sb2O3) contained as a flame retardant.

[0121] Antimony trioxide can function as a flame retardant aid for the above-mentioned brominated flame retardant. In the present invention, antimony trioxide is treated as a flame retardant. In the present invention, antimony trioxide can also function as a filler.

[0122] (Content of brominated flame retardant)

[0123] From the viewpoint of more excellent flame retardancy, the content of the brominated flame retardant is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass, relative to 100 parts by mass of the above rubber component.

[0124] (Content of antimony trioxide)

[0125] From the viewpoint of more excellent flame retardancy, the content of antimony trioxide is preferably 3 to 12 parts by mass, more preferably 4 to 9 parts by mass, relative to 100 parts by mass of the above rubber component.

[0126] (Total content of brominated flame retardant and antimony trioxide in the total flame retardant)

[0127] From the viewpoint of more excellent flame retardancy, the total content of the brominated flame retardant and antimony trioxide is preferably 80 to 100% by mass, more preferably 100% by mass, in the total flame retardant.

[0128] (Total content of brominated flame retardant and antimony trioxide relative to 100 parts by mass of the rubber component)

[0129] From the viewpoint of more excellent flame retardancy, the total content of the brominated flame retardant and antimony trioxide is preferably 15 to 50 parts by mass, more preferably 20 to 40 parts by mass, and further preferably 25 to 35 parts by mass, relative to 100 parts by mass of the above rubber component.

[0130] (Other flame retardants)

[0131] The flame retardant may also contain flame retardants other than brominated flame retardants and antimony trioxide (other flame retardants). As the other flame retardants, there is no particular limitation as long as they are compounds capable of imparting flame retardancy (however, brominated flame retardants and antimony trioxide are excluded).

[0132] In addition, as one of the preferred forms, the rubber composition of the present invention can be exemplified as not containing chlorinated paraffin.

[0133] 〔Hydrocarbon wax (W)〕

[0134] The hydrocarbon wax (W) contained in the rubber composition of the present invention contains aliphatic hydrocarbon compounds as the main component.

[0135] The hydrocarbon wax (W) is solid at normal temperature (for example, 23 °C).

[0136] The hydrocarbon wax (W) can be any one of a linear aliphatic hydrocarbon compound (n-paraffin), a branched aliphatic hydrocarbon compound (for example, isoparaffin), or a cycloaliphatic aliphatic hydrocarbon compound, or a mixture thereof (for example, what is commonly called paraffin wax, and the above-mentioned paraffin wax usually contains n-paraffin and isoparaffin).

[0137] The aliphatic hydrocarbon compounds contained in the hydrocarbon wax (W) are preferably composed only of carbon and hydrogen.

[0138] As the hydrocarbon wax (W), for example, waxes commonly called paraffin wax, microcrystalline wax, and solid wax can be exemplified.

[0139] In addition, the description of "the hydrocarbon wax (W) contains aliphatic hydrocarbon compounds as the main component... waxes called... solid wax can be exemplified." also applies to the hydrocarbon waxes (w1) and (w2) described later.

[0140] 〔Hydrocarbon wax (w1)〕

[0141] In the present invention, the hydrocarbon wax (W) contains a hydrocarbon wax (w1) having a melting point of 65 °C or higher.

[0142] 〔Melting point of hydrocarbon wax (w1)〕

[0143] In the present invention, the melting point of the hydrocarbon wax (w1) is 65 °C or higher.

[0144] Since the melting point of the hydrocarbon wax (w1) is 65 °C or higher, the ozone resistance of the vulcanized rubber obtained from the rubber composition of the present invention is excellent. In addition, when the use environment temperature of the obtained vulcanized rubber is in a high temperature region (for example, 20 °C or higher), it is easy to form a wax coating film formed by the exudation of the hydrocarbon wax (W) in the vulcanized rubber. In addition, the above-mentioned wax coating film can be formed for a long time.

[0145] The melting point of the hydrocarbon wax (w1) can be 100 °C or lower.

[0146] From the viewpoint of more excellent effects of the present invention, the melting point of the hydrocarbon wax (w1) is preferably 65 to 90 °C.

[0147] In the present invention, the melting point of the hydrocarbon wax (W) can be measured in accordance with JIS K 2235:2022 (Petroleum wax).

[0148] (Normal paraffin)

[0149] From the viewpoints of more excellent effects of the present invention, the wax film formed by the exudation of the hydrocarbon wax (W) in the vulcanized rubber is likely to become uniform, and the flexibility, adhesion to rubber, and stability are excellent, the hydrocarbon wax (w1) preferably contains normal paraffin.

[0150] (Carbon number distribution of normal paraffin)

[0151] When the hydrocarbon wax (w1) contains normal paraffin, as the carbon number distribution of the normal paraffin contained in the hydrocarbon wax (w1), for example, the carbon number is 15 to 50 can be cited. That is, as the normal paraffin contained in the hydrocarbon wax (w1), for example, a mixture of linear saturated aliphatic hydrocarbon compounds having 15 to 50 carbon atoms can be cited.

[0152] Regarding the normal paraffin contained in the hydrocarbon wax (w1), from the viewpoints of more excellent effects of the present invention, the wax film is easily formed in the high temperature region, and the wax film can be formed for a long time, in the carbon number distribution of the normal paraffin contained in the hydrocarbon wax (w1), the carbon number at the peak of the carbon number distribution is preferably in the range of 30 to 40, more preferably in the range of 32 to 35.

[0153] (Content of normal paraffin)

[0154] When the hydrocarbon wax (w1) contains normal paraffin, from the viewpoints of more excellent effects of the present invention, the wax film formed by the exudation of the hydrocarbon wax (W) in the vulcanized rubber is likely to become uniform, and the flexibility, adhesion to rubber, and stability are excellent, the content of the normal paraffin is preferably 80% by mass or more in the hydrocarbon wax (w1), more preferably 85 to 95% by mass.

[0155] (Method for measuring the carbon number of the component contained in the hydrocarbon wax (W) and the content of the component)

[0156] In the present invention, the analysis of the carbon number distribution and the content of the component (for example, normal paraffin) of the hydrocarbon wax (W) is carried out under the following conditions.

[0157] Analytical device: Gas chromatograph <GC-17A>, manufactured by Shimadzu Corporation

[0158] Chromatographic column: Ultra ALLOY UA1(MS / HT) 15 m × 0.25 mm × 0.25 μm

[0159] Inlet temperature, detector temperature: 420 °C

[0160] Detector: FID

[0161] Dilution solvent: Cyclohexane

[0162] Temperature rising condition: 10 °C / min

[0163] (Hydrocarbon wax (w2))

[0164] From the viewpoint that the effects of the present invention (especially power saving property) are more excellent and the service ambient temperature of the obtained vulcanized rubber can be extended to, for example, -30 to +60 °C, the hydrocarbon wax (W) preferably further contains a hydrocarbon wax (w2) having a melting point lower than 65 °C.

[0165] (Melting point of hydrocarbon wax (w2))

[0166] From the viewpoint that the effects of the present invention are more excellent and the service ambient temperature of the obtained vulcanized rubber can be extended, the melting point of the hydrocarbon wax (w2) is preferably 30 °C or higher and lower than 65 °C.

[0167] The measuring method of the melting point of the hydrocarbon wax (w2) can be the same as described above.

[0168] (Normal paraffin)

[0169] From the viewpoint that the effects of the present invention are more excellent, the wax coating film formed by exudation of the hydrocarbon wax (W) in the vulcanized rubber is likely to become uniform not only in the high temperature region but also under the conditions in the low temperature region (for example, lower than 20 °C), and the flexibility, adhesion to rubber, and stability are excellent, the hydrocarbon wax (w2) preferably contains normal paraffin.

[0170] (Carbon atom number distribution of normal paraffin)

[0171] When the hydrocarbon wax (w2) contains normal paraffin, as the carbon atom number distribution of the normal paraffin contained in the hydrocarbon wax (w2), for example, carbon atom numbers 15 to 45 can be cited. That is, as the normal paraffin contained in the hydrocarbon wax (w2), for example, a mixture of linear saturated aliphatic hydrocarbon compounds having carbon atom numbers 15 to 45 can be cited.

[0172] Regarding the normal paraffin contained in the hydrocarbon wax (w2), from the perspective that the effects of the present invention are more excellent, and it is easy to form the above-mentioned wax coating film not only under high-temperature conditions but also under low-temperature conditions (e.g., below 20°C), and the above-mentioned wax coating film can be formed for a long time. In the carbon atom number distribution of the normal paraffin contained in the hydrocarbon wax (w2), the carbon atom number at the peak of the above-mentioned carbon atom number distribution is preferably in the range of 25 to 35, more preferably in the range of 27 to 30.

[0173] (Content of normal paraffin)

[0174] When the hydrocarbon wax (w2) contains normal paraffin, from the perspective that the effects of the present invention are more excellent, the wax coating film formed by the exudation of the hydrocarbon wax (W) in the vulcanized rubber is easily made uniform even under low-temperature conditions, and has excellent flexibility, adhesion to rubber, and stability. The content of the above-mentioned normal paraffin is preferably 80% by mass or more in the hydrocarbon wax (w2), more preferably 80 to 90%.

[0175] [Content of hydrocarbon wax (W)]

[0176] In the rubber composition of the present invention, the content of the hydrocarbon wax (W) is 2.5 parts by mass or less relative to 100 parts by mass of the rubber component.

[0177] By making the content of the hydrocarbon wax (W) the above amount, the blooming resistance of the vulcanized rubber obtained from the rubber composition of the present invention is excellent.

[0178] From the perspective that the effects of the present invention (especially blooming resistance) are more excellent, the content of the hydrocarbon wax (W) is more preferably 1.0 to 2.0 parts by mass relative to 100 parts by mass of the rubber component.

[0179] In addition, the content of the hydrocarbon wax (w1) can be used as at least a part or all of the content of the hydrocarbon wax (W).

[0180] (Mass ratio of hydrocarbon wax (w1) to hydrocarbon wax (w2))

[0181] When the hydrocarbon wax (W) further contains the hydrocarbon wax (w2), from the perspective that the effects of the present invention (especially ozone resistance, blooming resistance, and power saving) are more excellent, the content of the hydrocarbon wax (w1) is preferably 50 to 90% by mass in the total amount of the hydrocarbon wax (W), more preferably 55 to 70%.

[0182] When the hydrocarbon wax (W) further contains the hydrocarbon wax (w2), the content of the hydrocarbon wax (w2) can be the remainder after removing the above content of the hydrocarbon wax (w1) from the total amount of the hydrocarbon wax (W).

[0183] [Mass ratio of the content of the bromine-based flame retardant to the content of the hydrocarbon wax (W)]

[0184] In the rubber composition of the present invention, the mass ratio (brominated flame retardant / hydrocarbon wax (W)) of the content of the brominated flame retardant to the content of the hydrocarbon wax (W) is 8.0 or more.

[0185] With the above mass ratio being the above amount, the vulcanized rubber obtained from the rubber composition of the present invention has excellent ozone resistance, power saving property, and bloom resistance. In addition, in the case of the above mass ratio, even when the amount of the brominated flame retardant changes, the hydrocarbon wax (W) can compensate for the disadvantages of adding the brominated flame retardant.

[0186] From the viewpoint of more excellent bloom resistance of the obtained vulcanized rubber, the above mass ratio (brominated flame retardant / hydrocarbon wax (W)) is preferably 10 or more and 20 or less.

[0187] 〔Filler〕

[0188] The rubber composition of the present invention contains a filler. However, the brominated flame retardant and antimony trioxide as the above flame retardant are removed from the above filler.

[0189] By containing a filler in the rubber composition of the present invention, the obtained vulcanized rubber has excellent ozone resistance, bloom resistance, flame retardancy, and power saving property.

[0190] Examples of the filler include white fillers such as carbon black and silica.

[0191] From the viewpoints of further improving the power saving property and mechanical strength of the obtained vulcanized rubber, the filler preferably contains carbon black and / or silica.

[0192] (Carbon black)

[0193] When the rubber composition of the present invention contains carbon black (CB) as a filler, the carbon black preferably contains carbon black having a nitrogen adsorption specific surface area of 20 to 100 m 2 / g and / or carbon black having a dibutyl phthalate oil absorption of 70 to 120 cm 3 / 100 g, and preferably contains carbon black having a nitrogen adsorption specific surface area of 20 to 100 m 2 / g and a dibutyl phthalate oil absorption of 70 to 120 cm 3 / 100 g.

[0194] (Nitrogen adsorption specific surface area of CB)

[0195] From the viewpoint of more excellent power saving property of the obtained vulcanized rubber, the N2SA of CB is preferably 20 to 100 m 2 / g, and more preferably 30 to 70 m 2 / g.

[0196] The nitrogen adsorption specific surface area (N2SA) of carbon black can be measured in accordance with JIS K6217-2:2017.

[0197] (Oil absorption of DBP of CB)

[0198] From the viewpoint of more excellent power saving property of the obtained vulcanized rubber, the DBP of CB is preferably 70 to 120 cm 3 / 100 g, more preferably 70 to 90 cm 3 / 100 g.

[0199] The oil absorption of dibutyl phthalate (DBP) of carbon black can be measured in accordance with JIS K6217-4:2017.

[0200] (Silica)

[0201] When the rubber composition of the present invention contains silica as a filler, there is no particular limitation on the silica. For example, conventionally known silica can be mentioned. Specifically, for example, wet silica, dry silica, and pyrogenic silica can be mentioned.

[0202] (Content of filler)

[0203] From the viewpoints of more excellent power saving property and excellent mechanical strength of the obtained vulcanized rubber, the content of the filler is preferably 20 to 50 parts by mass, more preferably 20 to 40 parts by mass, based on 100 parts by mass of the above rubber component.

[0204] 〔Antioxidant〕

[0205] The rubber composition of the present invention contains an antioxidant, and the antioxidant contains an amine-based antioxidant.

[0206] By containing an amine-based antioxidant, the ozone resistance of the vulcanized rubber obtained from the rubber composition of the present invention is excellent.

[0207] 〔Amine-based antioxidant〕

[0208] The amine-based antioxidant contained as an antioxidant in the rubber composition of the present invention is an antioxidant having an amino group (-NH2) or an imino group (-NH-).

[0209] As the amine-based antioxidant, for example, diamine-based compounds such as p-phenylenediamine-based compounds; monoamine compounds such as p,p'-dioctyldiphenylamine can be mentioned.

[0210] (P-phenylenediamine-based compound)

[0211] From the viewpoint of more excellent ozone resistance of the obtained vulcanized rubber, the amine-based antioxidant preferably contains a diamine-based compound, and more preferably contains a p-phenylenediamine-based compound.

[0212] The p-phenylenediamine-based compound is a compound having a p-phenylenediamine skeleton. The two nitrogen atoms in the p-phenylenediamine skeleton can each independently form an amino group or an imino group, and at least one of the above nitrogen atoms is preferably an imino group, and more preferably both are imino groups.

[0213] Examples of the p-phenylenediamine-based compound include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-dinaphthyl-p-phenylenediamine (DNPD), and N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD).

[0214] From the viewpoint of more excellent ozone resistance of the obtained vulcanized rubber, the p-phenylenediamine-based compound preferably contains N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

[0215] [Content of amine-based antioxidant]

[0216] In the rubber composition of the present invention, the content of the amine-based antioxidant is 3.0 parts by mass or more relative to 100 parts by mass of the rubber component.

[0217] By the content of the amine-based antioxidant being the above amount, the ozone resistance of the vulcanized rubber obtained from the rubber composition of the present invention is excellent.

[0218] From the viewpoints of more excellent ozone resistance and non-blooming property, the content of the amine-based antioxidant is preferably 3.0 to 5.0 parts by mass, and more preferably 3.0 to 4.0 parts by mass relative to 100 parts by mass of the rubber component.

[0219] [Vulcanization accelerator]

[0220] The rubber composition of the present invention contains a vulcanization accelerator.

[0221] The vulcanization accelerator may be any one used for rubber vulcanization and is not particularly limited. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazyl sulfenamide (CZ) and N-tert-butyl-2-benzothiazyl sulfenamide (NS); thiuram-based vulcanization accelerators such as tetra(2-ethylhexyl)thiuram disulfide (TOT-N); and guanidine-based vulcanization accelerators such as diphenylguanidine (DPG).

[0222] From the viewpoints of more excellent flame retardancy and power saving property, the vulcanization accelerator preferably contains a sulfenamide-based vulcanization accelerator.

[0223] From the viewpoint of more excellent flame retardancy and power saving property, the content of the vulcanization accelerator is preferably 0.5 to 8.0 parts by mass with respect to 100 parts by mass of the above rubber component.

[0224] [Sulfur]

[0225] The rubber composition of the present invention contains sulfur.

[0226] Sulfur is not particularly limited as long as it is used for rubber vulcanization. For example, sulfur known in the past can be cited.

[0227] From the viewpoints of more excellent flame retardancy, power saving property, and excellent rubber physical properties, the content of sulfur is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the above rubber component.

[0228] (Additive)

[0229] In addition to the above components, the rubber composition of the present invention may further contain additives. Examples of the additives include zinc oxide, stearic acid, and vulcanization retarders.

[0230] (Manufacturing method)

[0231] There is no particular limitation on the manufacturing method of the rubber composition of the present invention. For example, a method of mixing the above essential components and additives that can also be used as needed with a Banbury mixer or the like can be cited.

[0232] (Vulcanization)

[0233] The vulcanization of the rubber composition of the present invention can be carried out under ordinary conditions. The vulcanization temperature can be, for example, 120 to 180 °C. Pressurization can also be carried out during vulcanization.

[0234] (Use)

[0235] Examples of the use of the rubber composition of the present invention include conveyor belts.

[0236] [Conveyor belt]

[0237] The conveyor belt of the present invention is a conveyor belt formed using the rubber composition of the present invention.

[0238] There is no particular limitation on the rubber composition used for the conveyor belt of the present invention as long as it is the rubber composition of the present invention.

[0239] The conveyor belt of the present invention has no particular limitation other than being formed using the rubber composition of the present invention.

[0240] The conveyor belt of the present invention is formed using the above rubber composition of the present invention, and thus has excellent flame retardancy, ozone resistance, anti-spraying property, and power saving property.

[0241] There is no particular limitation on which constituent member of the conveyor belt of the present invention the rubber composition of the present invention is applied to. All or part of the rubber constituting the conveyor belt of the present invention can be formed from the rubber composition of the present invention.

[0242] Since the vulcanized rubber obtained from the rubber composition of the present invention is excellent in ozone resistance, blooming resistance, flame retardancy, and power saving property, as one of the preferred forms, the conveyor belt of the present invention can be exemplified as having a covering rubber formed using the rubber composition of the present invention.

[0243] Hereinafter, embodiments of the conveyor belt of the present invention will be described with reference to the drawings. In addition, the present invention is not limited by the drawings.

[0244] Figure 1 It is a cross-sectional view of an embodiment of the conveyor belt of the present invention. Figure 1 An embodiment of the conveyor belt of the present invention shown here (hereinafter, also referred to as the first embodiment of the conveyor belt of the present invention) is a conveyor belt 4 in which a core material layer is formed by covering a cloth layer 1 with a coating rubber (adhesive rubber) 2, and the periphery thereof is covered with a covering rubber 3. It is preferable that the covering rubber 3 is formed using the rubber composition of the present invention.

[0245] In Figure 1 the conveyor belt 4 has the cloth layer 1 as a core material, and the number of laminated sheets of the cloth layer 1, the thickness of the covering rubber 3, the belt width, etc. can be appropriately determined according to the use purpose.

[0246] As the cloth layer, for example, a canvas composed of a woven fabric of synthetic fibers such as nylon, vinylon, and polyester can be exemplified.

[0247] The thicknesses T1 and T2 of the covering rubber 3 are usually about 1.5 to 20 mm respectively.

[0248] In addition, as the coating rubber 2, a coating rubber used for a known conveyor belt can be used. As the above coating rubber, for example, a rubber composition containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), ethylene-propylene rubber (EPT), ethylene-propylene-diene rubber (EPDM), etc. as rubber components can be used.

[0249] Next, Figure 2 will be used to describe the second embodiment of the conveyor belt of the present invention.

[0250] Figure 2 It is a cross-sectional view of another embodiment of the conveyor belt of the present invention.

[0251] As shown in Figure 2As shown in the figure, the second embodiment of the conveyor belt of the present invention is a core material layer formed by covering a steel cord 5 with a buffer rubber (adhesive rubber) 6, and a conveyor belt 8 covering the periphery thereof with a covering rubber 7. The covering rubber 7 is preferably formed using the rubber composition of the present invention.

[0252] For the conveyor belt 8, for example, a core material can be formed by arranging about 50 to 230 steel cords 5 with a diameter of about 2.0 to 9.5 mm formed by twisting multiple wires with a diameter of about 0.2 to 0.4 mm side by side. Generally, the total thickness T of the conveyor belt 8 can be about 10 to 50 mm.

[0253] In addition, as the buffer rubber 6, for example, an adhesive rubber that can bond to the galvanized steel cord used in a known steel conveyor belt can be used. Specifically, as the buffer rubber, for example, a rubber composition containing natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), etc. as rubber components can be used.

[0254] The conveyor belt of the present invention can be manufactured, for example, according to a conventional method, by interposing a cloth layer, a steel cord, or a core material layer that becomes a core material between unvulcanized rubber sheets formed from the rubber composition of the present invention, and heating, pressurizing, and vulcanizing. The vulcanization conditions can be, for example, about 10 to 90 minutes under conditions of about 120 to 180 °C and about 0.1 to 4.9 MPa.

[0255] The conveyor belt of the present invention can be used, for example, under temperature conditions of -30 to +60 °C.

[0256] Examples

[0257] Examples are shown below to specifically illustrate the present invention. However, the present invention is not limited thereto.

[0258] <Manufacture of Rubber Composition>

[0259] Each component in Table 1 below was used in the composition (parts by mass) shown in the table, and they were mixed with a Banbury mixer to manufacture each rubber composition (unvulcanized).

[0260] (Production of Vulcanized Rubber Sheet)

[0261] Each rubber composition (unvulcanized) manufactured as described above was vulcanized for 30 minutes under a surface pressure of 3.0 MPa using a stamping molding machine at 148 °C to produce a vulcanized rubber sheet with a length of 150 mm, a width of 150 mm, and a thickness of 2 mm.

[0262] <Evaluation>

[0263] The following evaluations were performed using each of the vulcanized rubber sheets produced as described above. The results are shown in Table 1.

[0264] Ozone resistance

[0265] According to JIS K6259-1:2015, each vulcanized rubber sheet prepared as described above was placed in an ozone chamber (40 °C, 50 pphm), and an ozone resistance test (acceleration test) was carried out for 96 hours, 168 hours, 336 hours, and 504 hours while being stretched by 20%. After the above ozone resistance test, the surface of the vulcanized rubber sheet was visually observed.

[0266] When there are no cracks in the vulcanized rubber sheet after the ozone resistance test at each time, it is recorded as "N.C.".

[0267] ·Evaluation criteria for ozone resistance

[0268] In the present invention, when there are no cracks in the vulcanized rubber sheet after the ozone resistance test for 504 hours, the ozone resistance of the obtained vulcanized rubber is evaluated as very excellent.

[0269] Although cracks occurred in the vulcanized rubber sheet after the ozone resistance test for 504 hours, but there are no cracks in the vulcanized rubber sheet after the ozone resistance test for 336 hours, the ozone resistance of the obtained vulcanized rubber is evaluated as slightly excellent.

[0270] In the present invention, when there are no cracks in the vulcanized rubber sheet at least after the ozone resistance test for 336 hours, the ozone resistance is regarded as excellent.

[0271] On the other hand, when cracks occur in the vulcanized rubber sheet after the above ozone resistance test for 336 hours, the ozone resistance of the obtained vulcanized rubber is evaluated as poor.

[0272] In addition, when there are cracks in the vulcanized rubber sheet, based on JIS K6259-1:2015, the grade of the cracks is evaluated and displayed as a combination of letters and numbers such as the above grade "C2". In the present invention, when the elapsed time in the ozone resistance test is the same and there are cracks in the vulcanized rubber sheet after the ozone resistance test, compared with grade "A", the ozone resistance of grades "B" and "C" is poor. In addition, when the letters of the grades are the same, the larger the number after the letter, the poorer the ozone resistance is regarded as.

[0273] Blooming resistance

[0274] A blooming test was carried out by placing each vulcanized rubber sheet prepared as described above at 23 ± 2 °C for 5 weeks. After the above blooming test, the vulcanized rubber sheet was visually observed.

[0275] ·Evaluation criteria for blooming resistance

[0276] In the present invention, in the vulcanized rubber sheet after the blooming test described above, when blooming (whitening on the surface of the vulcanized rubber sheet) is not observed at all or hardly observed with the naked eye, the blooming resistance of the obtained vulcanized rubber is evaluated as being very excellent, and it is denoted as "1".

[0277] When blooming is slightly observed in the vulcanized rubber sheet after the blooming test described above, the blooming resistance of the obtained vulcanized rubber is evaluated as being slightly excellent, and it is denoted as "2".

[0278] As described above, excellent blooming resistance indicates excellent appearance of the vulcanized rubber sheet and can suppress excessive blooming.

[0279] In addition, in the case where the ozone resistance is evaluated as excellent and the blooming resistance is evaluated as excellent as described above, even if blooming is not visually observed, it can be considered that the hydrocarbon wax (W) oozes out to an invisible extent along with the anti-aging agent and forms a wax coating film on the surface of the vulcanized rubber.

[0280] On the other hand, when blooming is clearly observed in the vulcanized rubber sheet after the blooming test described above, the blooming resistance of the obtained vulcanized rubber is evaluated as poor, and it is denoted as "3".

[0281] (Power saving property: RRF)

[0282] · Fabrication of vulcanized rubber sheet

[0283] Each rubber composition manufactured as described above is heated and vulcanized at 148°C for 30 minutes to fabricate a vulcanized rubber sheet having a length of 40 mm, a width of 5 mm, and a thickness of 2 mm.

[0284] · Dynamic viscoelasticity measurement

[0285] Using the above-mentioned vulcanized rubber sheet, dynamic viscoelasticity measurement is performed under the measurement conditions of a clamp distance of 10 mm, a dynamic strain of 2%, and a frequency of 20 Hz by a viscoelastic spectrometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.). The loss tangent (tanδ) and the dynamic elastic modulus E' (N / mm) at 0°C and 20°C are measured, and the obtained loss tangent (tanδ) and dynamic elastic modulus E' are substituted into the following formula to calculate the RRF (Rolling Resistance Factor).

[0286]

[0287] In the present invention, the power saving property is evaluated by the above-mentioned RRF.

[0288] The results of the RRF are expressed as an index when the RRF of Example 4 is set as the index 100.

[0289] · Evaluation criteria for power saving property

[0290] In the present invention, when the indices of the RRF at 0°C and 20°C are both 100 or less, it is evaluated that the power saving property is excellent. The smaller the index of the above RRF, the more excellent the power saving property.

[0291] On the other hand, in the case where at least one of the indices at 0°C and 20°C exceeds 100, it is evaluated that the power saving property is poor.

[0292] (Flame retardancy)

[0293] ·Fabrication of test pieces

[0294] Using each of the rubber compositions manufactured as described above, test pieces (3 test pieces each) are fabricated in accordance with the ply conveyor rubber of Item 7.2.1 of JIS K6324:2013 "Flame-retardant conveyor belts - Classification and test methods".

[0295] ·Evaluation method

[0296] In accordance with JIS K6324:2013 "Flame-retardant conveyor belts - Classification and test methods", the duration of the flame (unit: seconds) is measured.

[0297] ·Evaluation criteria

[0298] When the flame retardancy test criteria of JIS Class 3 are satisfied [the duration of the flame is less than 60 seconds (the average value of the duration of the flame for 3 test pieces), and there is no re-ignition], it is evaluated that the flame retardancy is excellent, and it is marked as "〇".

[0299] On the other hand, when the flame retardancy test criteria of JIS Class 3 are not satisfied, it is evaluated that the flame retardancy is poor, and it is marked as "×".

[0300] Table 1

[0301]

[0302] Table 2

[0303]

[0304] Table 3

[0305]

[0306] Table 4

[0307]

[0308] The details of each component shown in Table 1 are as follows.

[0309] (Rubber component)

[0310] ·NR: Natural rubber. RSS#3

[0311] ·BR: Butadiene rubber. Trade name: Nipol BR1220 (weight-average molecular weight: 460,000, manufactured by Zeon Corporation, Japan)

[0312] ·SBR: Styrene-butadiene rubber. Trade name: Nipol 1502, manufactured by Zeon Corporation, Japan

[0313] (Flame retardant)

[0314] · Brominated flame retardant: Bis(pentabromophenyl)ethane. Trade name: “SAYTEX8010” (manufactured by ALBEMARLE CORPORATION). It has a melting point of over 300 °C.

[0315] · Chlorinated paraffin (for comparison): Empal 70S (trade name) manufactured by Dover Chemical Corporation. Chlorine content: 68 - 72 mass%

[0316] · Antimony trioxide: PATOX-M (trade name) manufactured by Nippon Concentrates Co., Ltd.

[0317] (Hydrocarbon wax (W))

[0318] · Hydrocarbon wax (w1): Paraffin wax. Trade name: OZOACE-0015 (Nippon Seiro Co., Ltd.). It contains at least a mixture of n-paraffin and isoparaffin. The number of carbon atoms at the peak of the carbon atom number distribution of the above n-paraffin is in the range of 32 - 35. The content of the above n-paraffin is 89 mass% of the total amount of the above solid paraffin. Melting point: 68 °C

[0319] · Hydrocarbon wax (w2): Paraffin wax. Trade name: OZOACE-0037 (Nippon Seiro Co., Ltd.). It contains at least a mixture of n-paraffin and isoparaffin. The number of carbon atoms at the peak of the carbon atom number distribution of the above n-paraffin is in the range of 27 - 30. The content of the above n-paraffin is 81 mass% of the total amount of the above solid paraffin. Melting point: 61 °C

[0320] (Antioxidant)

[0321] · Amine antioxidant (Antioxidant 6C): N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. Trade name: Ozonone 6C (manufactured by Seiko Chemical Co., Ltd.)

[0322] (Filler)

[0323] · GPF grade CB: GPF grade carbon black. Trade name: Nitron #GN, manufactured by Shin Nippon Carbon Co., Ltd.

[0324] · Silicon dioxide: Trade name: “Nipsil AQ” (manufactured by Tosoh Silica Corporation)

[0325] (Additive)

[0326] · Zinc Oxide: Trade Name: "Zinc Oxide 3 Types" (manufactured by Sho-Dowa Kogyo Co., Ltd.)

[0327] · Stearic Acid: Trade Name: "Stearic Acid 50S" (manufactured by Chiba Fatty Acid Co., Ltd.)

[0328] (Vulcanization Accelerator)

[0329] · Vulcanization Accelerator NS: N-tert-butyl-2-benzothiazole sulfenamide (Trade Name: Nocceler NS, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0330] (Sulfur)

[0331] · Insoluble Sulfur: Manufactured by Shikoku Chemicals Corporation (Trade Name) Micron OT-20

[0332] From the results shown in Table 1, it can be seen that Comparative Examples 1 to 3, which do not contain a flame retardant and the content of the amine-based anti-aging agent does not meet the specified amount, have poor flame retardancy. In Comparative Example 1, the resistance to blooming is also poor.

[0333] In Comparative Example 4, which does not contain butadiene rubber but contains SBR and the content of the amine-based anti-aging agent does not meet the specified amount, the ozone resistance and power saving performance are poor. From this, it can be seen that depending on the type of rubber component, even if hydrocarbon wax (W) is contained, the ozone resistance and the like are not good.

[0334] In Comparative Example 5, which does not contain a bromine-based flame retardant but contains chlorinated paraffin, the resistance to blooming and power saving performance are poor.

[0335] In Comparative Example 6, where the content of the amine-based anti-aging agent does not meet the specified amount, the ozone resistance is poor.

[0336] In Comparative Example 7, where the content of hydrocarbon wax (W) and the mass ratio of bromine-based flame retardant / hydrocarbon wax (W) do not meet the specified values, the resistance to blooming is poor.

[0337] In Comparative Examples 8 and 9, where the mass ratio of natural rubber / butadiene rubber is outside the specified range, at least one of the ozone resistance, resistance to blooming, and power saving performance is poor.

[0338] In Comparative Example 10, which does not contain hydrocarbon wax (W) and the content of the amine-based anti-aging agent does not meet the specified amount, the ozone resistance and power saving performance are poor.

[0339] In Comparative Examples 11 to 13, where the content of the amine-based anti-aging agent does not meet the specified amount, the ozone resistance is poor. In addition, Comparative Example 13 also does not contain hydrocarbon wax (w1).

[0340] In Comparative Example 14, where the mass ratio of bromine-based flame retardant / hydrocarbon wax (W) does not meet the specified value, the resistance to blooming is poor.

[0341] In Comparative Example 15 where the content of hydrocarbon wax (W) does not meet the specified value, the frost resistance is poor.

[0342] In Comparative Example 16 where the contents of hydrocarbon wax (W) and amine-based anti-aging agent do not meet the specified amounts, the ozone resistance and frost resistance are poor.

[0343] In Comparative Examples 17 and 18 which do not contain hydrocarbon wax (w1) but contain hydrocarbon wax (w2), the ozone resistance is poor.

[0344] In contrast, the rubber composition of the present invention, after being made into vulcanized rubber, has excellent flame retardancy, ozone resistance, and frost resistance.

[0345] Explanation of reference numerals

[0346] 1: Fabric layer

[0347] 2: Coating rubber

[0348] 3, 7: Cover rubber

[0349] 4, 8: Conveyor belt

[0350] 5: Steel cord

[0351] 6: Buffer rubber

Claims

1. A rubber composition for a conveyor belt, which contains: A rubber component containing natural rubber and butadiene rubber, and the mass ratio of the content of the natural rubber to the content of the butadiene rubber, that is, natural rubber / butadiene rubber, is 30 / 70 to 80 / 20. A flame retardant containing a brominated flame retardant and antimony trioxide. Hydrocarbon wax W. A filler. An antioxidant containing an amine-based antioxidant. A vulcanization accelerator, and Sulfur. With respect to 100 parts by mass of the rubber component, the content of the hydrocarbon wax W is 2.5 parts by mass or less. The mass ratio of the content of the brominated flame retardant to the content of the hydrocarbon wax W, that is, brominated flame retardant / hydrocarbon wax W, is 8.0 or more. The hydrocarbon wax W contains a hydrocarbon wax w1 having a melting point of 65°C or higher. With respect to 100 parts by mass of the rubber component, the content of the amine-based antioxidant is 3.0 parts by mass or more.

2. The rubber composition for a conveyor belt according to claim 1, wherein the mass ratio of the content of the natural rubber to the content of the butadiene rubber is 40 / 60 to 70 / 30.

3. The rubber composition for a conveyor belt according to claim 1 or 2, wherein the mass ratio of the content of the brominated flame retardant to the content of the hydrocarbon wax W is 10 or more and 20 or less.

4. The rubber composition for a conveyor belt according to any one of claims 1 to 3, wherein the hydrocarbon wax w1 contains normal paraffin, and the number of carbon atoms at the peak of the carbon atom number distribution of the normal paraffin is in the range of 30 to 40.

5. The rubber composition for a conveyor belt according to any one of claims 1 to 4, wherein the hydrocarbon wax w1 contains normal paraffin, and the content of the normal paraffin is 80% by mass or more in the hydrocarbon wax w1.

6. The rubber composition for a conveyor belt according to claim 1, wherein the amine-based antioxidant contains a p-phenylenediamine-based compound.

7. The rubber composition for a conveyor belt according to any one of claims 1 to 6, wherein the brominated flame retardant contains a compound represented by the following formula (1). In formula (1), R represents an aliphatic hydrocarbon group which may contain an unsaturated bond.

8. The rubber composition for a conveyor belt according to any one of claims 1 to 7, wherein the hydrocarbon wax W further contains a hydrocarbon wax w2 having a melting point lower than 65°C.

9. The rubber composition for a conveyor belt according to claim 8, wherein the hydrocarbon wax w2 contains normal paraffin, and the number of carbon atoms at the peak of the carbon atom number distribution of the normal paraffin is in the range of 25 to 35.

10. The rubber composition for a conveyor belt according to claim 8 or 9, wherein the hydrocarbon wax w2 contains normal paraffin, and the content of the normal paraffin is 80% by mass or more in the hydrocarbon wax w2.

11. A conveyor belt formed by using the rubber composition for a conveyor belt according to any one of claims 1 to 10.

12. The conveyor belt according to claim 11, which has a covering rubber formed by using the rubber composition.

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