JP2018188584A - Rubber composition for conveyor belt, and conveyor belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for conveyor belt and a conveyor belt, which are excellent in abrasion resistance.SOLUTION: There are provided a rubber composition for conveyor belt which contains a rubber component containing more 50 mass% and 100 mass% or less of a butadiene rubber and carbon black, where a content of the carbon black is 60-100 pts.mass based on 100 pts.mass of the rubber component, and a bound rubber amount at 25°C is 45-70 mass%; and a conveyor belt which is formed of the rubber composition for conveyor belt and has an upper surface cover rubber layer, a reinforcement layer and a lower cover rubber layer.SELECTED DRAWING: Figure 1

Description

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

  In recent years, conveyor belts are required to have a long service life from the viewpoint of environmental considerations. In order to solve such a problem, a rubber composition for improving the wear-resistant life of a belt conveyor has been proposed. For example, Patent Document 1 describes a rubber composition for a belt of a belt conveyor, which contains a polybutadiene rubber synthesized with a neodymium catalyst as a rubber component.

JP 2003-105136 A

Under such circumstances, the present inventor prepared a rubber composition with reference to Patent Document 1 and evaluated it, and found that the abrasion resistance of such a rubber composition may be poor.
Then, an object of this invention is to provide the rubber composition for conveyor belts which is excellent in abrasion resistance, and a conveyor belt.

As a result of earnest research to solve the above problems, the inventor contains a rubber component containing butadiene rubber in a predetermined amount and carbon black, and the content of carbon black and the amount of bound rubber are in a predetermined range. Thus, the inventors have found that a desired effect can be obtained, and have reached the present invention.
The present invention is based on the above knowledge and the like, and specifically, solves the above problems by the following configuration.

1. A rubber component containing more than 50% by mass and 100% by mass or less of butadiene rubber;
Containing carbon black,
The content of the carbon black is 60 to 100 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for a conveyor belt, wherein the amount of bound rubber at 25 ° C is 45 to 70 mass%.
2. The carbon black has a nitrogen adsorption specific surface area of 115 to 160 m ² / g,
2. The rubber composition for conveyor belts according to 1 above, wherein the carbon black has a dibutyl phthalate oil absorption of 115 to 140 ml / 100 g.
3. The rubber composition for conveyor belts according to 1 or 2 above, wherein the butadiene rubber has a weight average molecular weight of 500,000 to 1,000,000.
4). The ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index of the butadiene rubber (weight average molecular weight / long chain branching index) is 5.5 × 10 ^{4 to} 16.6 × 10 ^4. The rubber composition for conveyor belts according to any one of the above.
5. An upper cover rubber layer formed of the rubber composition for a conveyor belt according to any one of the above 1 to 4,
A reinforcing layer;
A conveyor belt having a bottom cover rubber layer.

  The rubber composition for conveyor belts of the present invention and the conveyor belt of the present invention are excellent in wear resistance.

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

The present invention will be described in detail below.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In this specification, unless otherwise specified, each component can be used alone or in combination of two or more of the substances corresponding to the component. When a component contains two or more types of substances, the content of the component means the total content of the two or more types of substances.

[Rubber composition for conveyor belts]
The rubber composition for conveyor belts of the present invention (the composition of the present invention)
A rubber component containing more than 50% by mass and 100% by mass or less of butadiene rubber;
Containing carbon black,
The carbon black content is 60 to 100 parts by mass with respect to 100 parts by mass of the rubber component,
It is a rubber composition for conveyor belts whose bound rubber amount at 25 ° C. is 45 to 70% by mass.

  Hereinafter, each component contained in the composition of this invention is explained in full detail.

<< Rubber component >>
The composition of the present invention contains a rubber component, and the rubber component contains butadiene rubber.

<Butadiene rubber>
Butadiene rubber (BR) is a homopolymer of butadiene.

(Weight average molecular weight of butadiene rubber)
The weight average molecular weight of the butadiene rubber is preferably from 500,000 to 1,000,000, more preferably from 500,000 to 800,000, and even more preferably from 500,000 to 700,000, from the viewpoint of being superior in wear resistance.
In the present invention, the weight average molecular weight of the butadiene rubber is a standard polystyrene equivalent value based on a value measured by gel permeation chromatography (GPC) using cyclohexane as a solvent.

(Long-chain branching index of butadiene rubber)
The long chain branching index (LCB Index) of the butadiene rubber is preferably 0.1 to 12.0, and more preferably 11.0 or less, from the viewpoint of superior wear resistance.
In the present invention, the long-chain branching index of butadiene rubber is measured by a LAOS (Large Amplitude Oscillator Shear) measurement method using a RPA2000 type tester (manufactured by Alpha Technologies) at 100 ° C. did.
The closer the long chain branching index is to zero, the lower the degree of branching of the butadiene rubber.
For details of the long chain branching index (LCB Index), see, for example, “FT-Rheology, a Tool to Quantitative Long Chain Branching (LCB) in Natural Rubber and It's Effect on Mastic. Burchin, Alpha Technologies, UK 15 Rue du Clot B-1435 Hevillers, Belgium) and the like.

<Weight average molecular weight / Long chain branching index>
The ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index of the butadiene rubber (weight average molecular weight / long chain branching index) is 5.5 × 10 ^{4 to} 16.6 × 10 ⁴ from the viewpoint of being superior in wear resistance. Is preferably 5.8 × 10 ^{4 to} 16.6 × 10 ⁴ , and more preferably 7.0 × 10 ^{4 to} 14.2 × 10 ⁴ .

(Microstructure of butadiene rubber)
The 1,4-cis structure of butadiene rubber is preferably 97% or more, more preferably 98% or more, from the viewpoint that it is more excellent in wear resistance.
The 1,4-trans structure of butadiene rubber is preferably 1.5% or less, and more preferably 1.0% or less, from the viewpoint of superior wear resistance.
The 1,2-vinyl structure of the butadiene rubber is preferably 1.5% or less, and more preferably 1.0% or less, from the viewpoint of superior wear resistance.
In the present invention, the microstructure of the butadiene rubber was analyzed by infrared absorption spectrum analysis. 740 cm ^-1 1,4-cis structure, 967 cm ^-1 1,4-trans structure, 910 cm ^-1 is the absorption band of the 1,2-vinyl structure, was calculated microstructure from each absorption intensity ratio.

(Production method of butadiene rubber)
Examples of the method for producing butadiene rubber include a method of synthesizing butadiene by polymerizing it using a catalyst such as a cobalt catalyst and / or a neodymium catalyst. The cobalt-based catalyst and neodymium-based catalyst are not particularly limited. The cobalt-based catalyst can be a compound having cobalt. The neodymium catalyst can be a compound having neodymium (Nd). Of these, neodymium catalysts are preferable.

<Butadiene rubber content>
In the present invention, the content of butadiene rubber is more than 50% by mass and 100% by mass or less based on the total amount of rubber components. “Over 50% by mass” means exceeding 50% by mass.
The content of the butadiene rubber is preferably 60 to 90% by mass, more preferably 70 to 90% by mass, and further preferably 75 to 90% by mass with respect to the total amount of the rubber component, from the viewpoint of being superior in wear resistance.

(Rubbers other than butadiene rubber)
In the present invention, the rubber component can further contain rubber other than butadiene rubber.
Examples of rubber other than butadiene rubber include diene rubber (excluding butadiene rubber).
Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), aromatic vinyl-conjugated diene copolymer rubber (for example, styrene butadiene rubber (SBR)), nitrile butadiene rubber (NBR, acrylonitrile butadiene rubber). ), Butyl rubber (IIR), halogenated butyl rubber (for example, Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Of these, natural rubber and styrene butadiene rubber are preferable.

<< carbon black >>
The composition of the present invention contains carbon black.

(Nitrogen adsorption specific surface area of carbon black)
The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably from 115 to 160 m ² / g, more preferably from 125 to 160 m ² / g, and more preferably from 125 to 150 m ² / g, from the viewpoint of superior wear resistance. preferable.
The nitrogen adsorption specific surface area of carbon black is a value obtained by measuring the nitrogen adsorption amount on the carbon black surface in accordance with JIS K6217-2: 2001 “Part 2: Determination of specific surface area—nitrogen adsorption method—single point method”. .

(Carbon black dibutyl phthalate oil absorption)
The dibutyl phthalate oil absorption amount (DBP oil absorption amount) of carbon black is preferably 115 to 140 ml / 100 g, more preferably 115 to 135 ml / 100 g, and still more preferably 115 to 130 ml / 100 g from the viewpoint of superior wear resistance.
The oil absorption of dibutyl phthalate of carbon black was measured according to JIS K 6217-4: 2008 “Carbon black for rubber—Basic characteristics—Part 4: Determination of oil absorption”.

As carbon black, for example,
SAF (Super Ablation Furnace) carbon black,
ISAF (Intermediate Super Absorption Furnace) carbon black,
HAF (High Ablation Furnace) -HS (High Structure) carbon black may be mentioned.
Among them, SAF is preferable from the viewpoint that the carbon black is more excellent in wear resistance.

<Carbon black content>
In this invention, content of carbon black is 60-100 mass parts with respect to 100 mass parts of rubber components.
The content of carbon black is preferably 60 to 90 parts by weight, more preferably 60 to 80 parts by weight, and more preferably 60 to 75 parts by weight with respect to 100 parts by weight of the rubber component, from the viewpoint of being superior in wear resistance. .

(Additive)
The composition of this invention can contain an additive further in the range which does not impair the effect and objective of this invention other than each component mentioned above. Examples of additives include white fillers, anti-aging agents such as anti-aging agent 6C, zinc oxide, stearic acid, processing aids, paraffin wax, aroma oil, liquid polymers, terpene resins, thermosetting resins, Examples thereof include vulcanizing agents such as sulfur, vulcanizing aids, vulcanization accelerators, and vulcanization retarders.
The content of the additive can be appropriately selected.

(Method for producing the composition of the present invention)
The composition of the present invention is not particularly limited with respect to its production method. For example, the above-mentioned components (excluding vulcanizing agents such as sulfur and vulcanization accelerators) are mixed with a Banbury mixer or the like to obtain a mixture, and then the vulcanizing agent such as sulfur is added to the obtained mixture. The composition of the present invention can be produced by adding a vulcanization accelerator and kneading these with a kneading roll machine or the like.

<Bound rubber amount>
The bound rubber amount at 25 ° C. of the composition of the present invention is 45 to 70% by mass.
The bound rubber amount is preferably 45 to 65% by mass, and more preferably 46 to 58% by mass from the viewpoint that it is more excellent in wear resistance.
A method for measuring the bound rubber amount will be described later.

(Vulcanization or crosslinking of the composition of the present invention)
The conditions for vulcanization or crosslinking of the composition of the present invention are not particularly limited. As said vulcanization | cure or bridge | crosslinking, the composition of this invention can be vulcanized | cured or bridge | crosslinked by heating and pressurizing on the conditions of 140-160 degreeC, for example.

  The composition of the present invention can be used to form a conveyor belt.

[Conveyor belt]
The conveyor belt of the present invention is
An upper cover rubber layer formed of the rubber composition for a conveyor belt of the present invention;
A reinforcing layer;
A conveyor belt having a bottom cover rubber layer.

The rubber composition for forming the upper cover rubber layer is not particularly limited as long as it is a rubber composition for conveyor belts of the present invention.
The top cover rubber layer can be a single layer or a plurality of layers. The same applies to the reinforcing layer and the bottom cover rubber layer.

Hereinafter, a conveyor belt according to the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the attached drawings.
FIG. 1 is a cross-sectional perspective view schematically showing a part of an example of a preferred embodiment of the conveyor belt of the present invention.
In FIG. 1, the conveyor belt 1 has the upper surface cover rubber layer 2, the reinforcement layer 3, and the lower surface cover rubber layer 4, and is laminated | stacked in this order. The surface of the upper cover rubber layer 2 can serve as a transported material transport surface 5. The top cover rubber layer 2 is formed using the composition of the present invention.

As shown in FIG. 1, when the top cover rubber layer has two or more layers, at least one or all of the two or more layers can be formed using the composition of the present invention. . Moreover, it is preferable to form at least the outermost layer using the composition of the present invention.
In FIG. 1, the upper cover rubber layer 2 has an outer layer 11 and an inner layer 12. The outer layer 11 and / or the inner layer 12 can be formed using the composition of the present invention, and at least the outer layer 11 is preferably formed using the composition of the present invention.
When the outer layer 11 is formed using the composition of the present invention, the inner layer 12 can be a layer for bonding the reinforcing layer 3 and the outer layer 11 together.

The rubber composition used for the bottom cover rubber layer is not particularly limited. Examples of the rubber composition include the composition of the present invention.
In FIG. 1, the lower cover rubber layer 4 has an outer layer 16 and an inner layer 15. The outer layer 16 and the inner layer 15 may be formed using the same or different rubber composition.

A reinforcement layer is not specifically limited, What is used for a normal conveyor belt can be selected suitably, and can be used.
The reinforcing layer can include, for example, a core body and an adhesive rubber.
Examples of the material of the core include fibers such as polyester fibers, polyamide fibers, and aramid fibers; and metals such as steel. The fiber can be used as a canvas. Canvas means a plain weave cloth.
The adhesive rubber is not particularly limited. For example, a conventionally well-known thing is mentioned.
The shape of the reinforcing layer is not particularly limited, and may be, for example, a sheet shape as shown in FIG. Moreover, you may embed a wire-like reinforcement wire (for example, steel cord) in parallel in a reinforcement layer.
Examples of the sheet-like reinforcing layer include a single layer of canvas; a laminate of a plurality of layers of canvas.

The thickness of the upper cover rubber layer is preferably 3 to 25 mm.
3-20 mm is preferable and, as for the thickness of a lower surface cover rubber layer, 5-15 mm is more preferable.
When the upper cover rubber layer is composed of two or more layers, the thickness of the upper cover rubber layer can be the sum of the thicknesses of these layers. The same applies to the thickness of the bottom cover rubber layer.

  The conveyor belt of the present invention is not particularly limited with respect to its manufacturing method. For example, a conventionally well-known thing is mentioned.

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

<Production of composition>
Each component of the following Table 1 was used in the composition (parts by mass) shown in the same table, and these were mixed with a stirrer to produce a composition. Specifically, first of all the components shown in Table 1 below, except for sulfur and vulcanization accelerator, were mixed with a Banbury mixer at 140 ° C., and then sulfur and vulcanization acceleration were added to the resulting mixture. An agent was added, and these were mixed using a kneading roll machine at 30 ° C. to produce a composition.

<Measurement of bound rubber amount>
0.2 g of a cut sample obtained by cutting the composition produced as described above (before vulcanization) into a square of about 1 mm was weighed. Further, a 100-mesh wire mesh basket for accommodating the cut sample was precisely weighed.
Next, the cut sample is accommodated in a wire mesh cage, and the wire mesh cage is placed in a glass bottle containing 200 ml of toluene, and the mesh mesh cage containing the cut sample is immersed in toluene, and is allowed to stand at 25 ° C. for 72 hours. I put it. In the present invention, “25 ° C.” of “the amount of bound rubber at 25 ° C.” means a temperature condition when a wire mesh container containing a cut sample is immersed in toluene and allowed to stand for 72 hours.
After leaving still for 72 hours, the wire mesh basket was taken out from toluene and dried with a dryer for 24 hours, and the mass of the wire mesh basket after drying was measured.
From the obtained mass, the mass of the wire mesh cage that was precisely weighed in advance was subtracted, and the mass of the undissolved sample after the test was determined.
The undissolved sample mass after the above test is A, the initial cut sample mass is B (0.2 g), and the toluene-insoluble component (carbon) in the composition manufactured before (cut) The amount of bound rubber was calculated based on the following equation, where C was the compounding part of black, D was the total compounding part of the composition, and E was the compounding part of the rubber component.
Bound rubber amount (% by mass) = [A− (B × C / D)] / (B × E / D) × 100

<Evaluation>
The following evaluation was performed using the composition manufactured as described above. The results are shown in Table 1.
(Abrasion resistance: Lambone wear)

-Preparation of vulcanized rubber sample for evaluation The composition produced as described above is placed in a mold and vulcanized by heating at 148 ° C for 30 minutes to form a disc-shaped vulcanized rubber having a diameter of 49 mm and a thickness of 5 mm. A sample was made.

・ Lambourn abrasion test Using the above vulcanized rubber sample, according to JIS K 6262-2: 2005, a lambourn abrasion test was performed at 25 ° C. using a lambourn abrasion tester. The volume (lambane wear amount) was measured.

Evaluation Criteria The wear volume measured as described above was displayed as an index with the result of Comparative Example 1 being 100.
The smaller the index, the better the wear resistance.

Details of each component shown in Table 1 are as follows.
・ NR: Natural rubber (RSS # 3)

BR1: butadiene rubber, weight average molecular weight (Mw) 770,000, long chain branching index (LCB) 8.5, Mw / LCB = 9.1 × 10 ⁴ (Buna CB21, manufactured by LANXESS, in the presence of a neodymium catalyst) Butadiene rubber obtained by polymerizing butadiene with a micro structure: 1,4-cis structure 97.9%, 1,4-trans structure 1.9%, 1,2-vinyl structure 0.2%)

BR2: butadiene rubber, weight average molecular weight (Mw) 560,000, long chain branching index (LCB) 7.3, Mw / LCB = 7.7 × 10 ⁴ (Ubepol BR-360L, manufactured by Ube Industries, Ltd., cobalt catalyst) A butadiene rubber obtained by polymerizing butadiene in the presence of water: Microstructure: 97.8% 1,4-cis structure, 0.9% 1,4-trans structure, 1.3% 1,2-vinyl structure )

BR3: butadiene rubber, weight average molecular weight (Mw) 500,000, long chain branching index (LCB) 9.5, Mw / LCB = 5.3 × 10 ⁴ (trade name Nipol 1220, manufactured by Nippon Zeon Co., Ltd.) Microstructure: 1 , 4-cis structure 98%, 1,4-trans structure 1.0%, 1,2-vinyl structure 1.0%)

BR4: butadiene rubber, weight average molecular weight (Mw) 380,000, long chain branching index (LCB) 12.3, Mw / LCB = 3.1 × 10 ⁴ (trade name UBEPOL BR130B, manufactured by Ube Industries) Microstructure: 1,4-cis structure 96.0%, 1,4-trans structure 1.3%, 1,2-vinyl structure 2.7%)

CB1: carbon black, nitrogen adsorption specific surface area 144 m ² / g, dibutyl phthalate oil absorption 115 ml / 100 g (show black N110, SAF grade, manufactured by Cabot Japan)

CB2: carbon black, nitrogen adsorption specific surface area 123 m ² / g, dibutyl phthalate oil absorption 123 ml / 100 g (trade name Show Black N234, ISAF-HS grade, manufactured by Cabot Japan)

CB3: carbon black, nitrogen adsorption specific surface area 111 m ² / g, dibutyl phthalate oil absorption 115 ml / 100 g (trade name Show Black N220, ISAF-LS grade, manufactured by Cabot Japan)

Anti-aging agent 6C: NOCRACK 6C (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Stearic acid YR (manufactured by NOF Corporation)
Paraffin wax: OZOACE-0015 (manufactured by Nippon Seiwa Co., Ltd.)
Aroma oil: A-OMIX (Sankyo Oil Chemical Co., Ltd.)
・ Vulcanization accelerator NS: Noxeller NS-P (Ouchi Shinsei Chemical Co., Ltd.)
・ Sulfur: Fine sulfur (Hosoi Chemical Co., Ltd.)

  As is apparent from the results shown in Table 1, Comparative Examples 1 to 3 in which the carbon black content is less than the predetermined range and the bound rubber amount is smaller than the predetermined range have poor wear resistance.

In contrast, the composition of the present invention was excellent in wear resistance.
When Examples 1 and 2 were compared, Example 2 with higher nitrogen adsorption specific surface area of carbon black was superior to Example 1 in wear resistance.
Comparing Examples 3 and 4, Example 3 with higher Mw / LCB was superior to Example 4 in wear resistance. In Examples 5, 6, and 9, the higher the Mw / LCB, the better the wear resistance.

Comparing Examples 2 and 3, Example 3 having a higher content of butadiene rubber was more excellent in wear resistance than Example 2. In Examples 8, 5, and 10, the higher the butadiene rubber content, the better the wear resistance.
When Examples 4, 7, and 5 were compared, the lower the carbon black content, the better the abrasion resistance.

1: Conveyor belt 2: Upper cover rubber layer 3: Reinforcement layer 4: Lower cover rubber layer 5: Transported material transport surface 11, 16: Outer layer 12, 15: Inner layer

Claims (5)

A rubber component containing more than 50% by mass and 100% by mass or less of butadiene rubber;
Containing carbon black,
The carbon black content is 60 to 100 parts by mass with respect to 100 parts by mass of the rubber component,
A rubber composition for a conveyor belt, wherein the amount of bound rubber at 25 ° C is 45 to 70 mass%. The carbon black has a nitrogen adsorption specific surface area of 115 to 160 m ² / g,
The rubber composition for conveyor belts of Claim 1 whose dibutyl phthalate oil absorption of the said carbon black is 115-140 ml / 100g.   The rubber composition for conveyor belts according to claim 1 or 2, wherein the butadiene rubber has a weight average molecular weight of 500,000 to 1,000,000. The ratio of the weight average molecular weight of the butadiene rubber to the long chain branching index of the butadiene rubber (weight average molecular weight / long chain branching index) is 5.5 × 10 ^{4 to} 16.6 × 10 ⁴ . 4. The rubber composition for conveyor belts according to any one of 3 above. An upper cover rubber layer formed of the rubber composition for a conveyor belt according to any one of claims 1 to 4,
A reinforcing layer;
A conveyor belt having a bottom cover rubber layer.