JP2017066176A - Rubber composition for belt and rubber belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for belt excellent in processability and abrasion resistance and a rubber belt.SOLUTION: There is provided a rubber composition for belt containing polybutadiene (I) manufactured by polymerizing butadiene in a presence of a cobalt-based catalyst and satisfying following (1) to (5) requirements. (1) Mooney viscosity is 43 to 70. (2) a ratio of 5 wt.% toluene solution viscosity (Tcp) and Mooney viscosity (ML) (Tcp/ML) is 0.9 to 1.7. (3) stress relaxation time by 80% attenuation of a value of torque when the torque at Mooney viscosity measurement completion is 100% is 10.0 to 40.0 sec. (4) molecular weight distribution (Mw/Mn) is 2.50 to 4.00. (5) percentage of a cis-1,4 structure unit in a micro structure analysis is 94.0 to 98.0 mol%.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for a belt using polybutadiene having improved processability and wear resistance as a base rubber for a rubbery portion, and a rubber belt obtained using the rubber composition for a belt.

  Polybutadiene generally has higher wear resistance than other rubbers but is inferior in workability. However, wear resistance and workability are in a trade-off relationship, and attempts to improve one cause the performance of the other to deteriorate, so various improvements have been made so far.

  For example, by specifying the ratio (Tcp / ML) of 5% toluene solution viscosity (Tcp) and Mooney viscosity (ML) of polybutadiene synthesized using a cobalt catalyst, both wear resistance and workability can be achieved. A polybutadiene composition has been reported (Patent Document 1). Furthermore, in addition to defining the ratio (Tcp / ML) of 5% toluene solution viscosity (Tcp) and Mooney viscosity (ML) of polybutadiene synthesized using a cobalt catalyst, the Mooney viscosity rate dependence index (n value) Attempts have been made to achieve both wear resistance and workability by specifying (Patent Documents 2 and 3).

  In general, industrial rubber belts are broadly divided into a conductive belt for transmitting power and a conveyor belt for conveying objects. Examples of rubber materials include natural rubber, polybutadiene rubber, styrene / butadiene rubber, ethylene / propylene / diene rubber, Chloroprene rubber, chlorosulfonated polyethylene rubber, nitrile rubber, hydrogenated nitrile rubber and the like are used. It is desirable that the rubber composition used for the rubber belt further has a high tensile strength, is flexible and elastic with an appropriate hardness, has a high flexibility, and has a high impact resistance.

  In the following Patent Document 4, the present applicant uses a rubber composition for a belt using a vulcanizable rubber and syndiotactic-1,2-polybutadiene (SPB) having a reduced viscosity of 0.1 to 4, as a rubber component, And in Patent Document 5 listed below, a rubber composition for a belt using a specific syndiotactic-1,2-polybutadiene crystal fiber, vinyl cis-polybutadiene rubber, and a diene rubber other than the above as a rubber component was proposed. .

JP 2004-339467 A JP 2004-211048 A International Publication No. 2007/081018 JP 2003-105139 A International Publication No. 2008-105415

  In the above Patent Documents 1 to 5, polybutadiene having improved wear resistance, workability and the like has been proposed. However, in the present invention, polybutadiene having further improved wear resistance, workability and the like is used as a base of the rubbery portion. It aims at providing the rubber composition for belts used for material rubber, and a rubber belt.

  In view of the above prior art, the applicant further uses wear resistance and workability by using polybutadiene which is manufactured using a cobalt-based catalyst and satisfies the requirements (A) to (E) described later. The present inventors have found that a rubber composition for belts having improved properties can be obtained, and have completed the present invention. That is, the gist of the present invention is the invention described in the following (1) to (7).

(1) A rubber composition for belts comprising polybutadiene (I) produced by polymerizing butadiene in the presence of a cobalt-based catalyst and satisfying the requirements described in (A) to (E) below.
(A) Mooney viscosity (ML _{1 + 4,100 ° C.} ) is 43 to 70
(B) Ratio (Tcp / ML _{1 + 4,100 ° C.} ) of 5 wt% toluene solution viscosity (Tcp) to Mooney viscosity (ML _{1 + 4,100 ° C.} ) is 0.9 to 1.7.
(C) ML _{1 + 4, 100 ° C.} When the torque at the end of measurement is 100%, the stress relaxation time (T ₈₀ ) until the value attenuates by 80% is 10.0 to 40.0 seconds (D) Molecular weight distribution (Weight average molecular weight (Mw) / number average molecular weight (Mn)) is 2.50 to 4.00.
(E) The ratio of cis-1,4 structural units in the microstructure analysis is 94.0-98.0 mol%.
(2) The rubber composition for belts according to (1), wherein the polybutadiene (I) further satisfies the requirements described in (F) to (H) below.
(F) The weight average molecular weight (Mw) is 40.0 × 10 ^{4 to} 75.0 × 10 ^4.
(G) 5 wt% toluene solution viscosity (Tcp) is 42 to 160 cps
(H) Number average molecular weight (Mn) is 12.5 × 10 ^{4 to} 30.0 × 10 ⁴

(3) The belt according to (1) or (2), wherein the polybutadiene (I), a diene rubber (J) other than the polybutadiene (I), and a rubber reinforcing agent (L) are contained. Rubber composition.
(4) From 5 to 90% by weight of the polybutadiene (I) and 95 to 10% by weight of diene rubber (J) other than the polybutadiene (I) (here, the total of the weight% is 100% by weight). The rubber reinforcing agent (L) is contained in a proportion of 20 to 70 parts by weight with respect to 100 parts by weight of the resulting rubber component (K), for the belt according to the above (1) or (3) Rubber composition.
(5) The rubber composition for belts according to (3) or (4), wherein the rubber component (J) is natural rubber and / or polyisoprene.
(6) The rubber composition for belts according to any one of (3) to (5) above, wherein the rubber reinforcing agent (L) is carbon black and / or silica.
(7) A rubber belt, wherein the rubber composition for a belt according to any one of (1) to (6) is used as a rubber base material.

  The rubber composition for belts of the present invention is excellent in wear resistance and processability. The rubber belt obtained from the rubber composition for belts of the present invention has the same effect.

The belt rubber composition and rubber belt of the present invention will be described below.
[1] Rubber composition for belt The polybutadiene (I) used as the base rubber of the rubber composition for belts of the present invention, the method for producing polybutadiene (I), and the rubber composition for belts will be described.

(1) Polybutadiene (I)
The polybutadiene (I) used in the rubber composition for belts of the present invention (hereinafter sometimes referred to as the composition of the present invention) has the following characteristics.
(A) Mooney viscosity (ML _{1 + 4,100 ° C.} ) measured at 100 ° _C. is 43-70. The Mooney viscosity (ML _{1 + 4,100 ° C.} ) is preferably 48 to 70, and more preferably 50 to 65. By setting ML _{1 + 4,100 ° C.} to 43 or higher, the wear resistance is improved, and by setting it to 70 or lower, workability is improved. The Mooney viscosity in the present invention is an industrial viscosity index measured using a Mooney viscometer which is a kind of rotational plasticity meter, and [ML _{1 + 4, 100 ° C.} ] is used as a unit symbol in the present invention. In this case, M is Mooney viscosity, L is a large rotor (L-type), 1 + 4 is a preheating time of 1 minute, and a rotor rotation time is 4 minutes, and measured at a temperature of 100 ° C. Means. The Mooney viscosity (ML _{1 + 4, 100 ° C.} ) is a value measured by the method described in Examples described later.

(B) The ratio (Tcp / ML _{1 + 4,100 ° C.} ) of the 5 wt% toluene solution viscosity (Tcp) to the Mooney viscosity (ML _{1 + 4,100 ° C.} ) is 0.9 to 1.7. Tcp / ML _{1 + 4, 100 ° C} is preferably 1.4 to 1.7. Tcp / ML _{1 + 4,100 ° C.} is an index of the degree of branching of polybutadiene. If Tcp / ML _{1 + 4,100 ° C.} is less than 0.9, the degree of branching may be too high and wear resistance may decrease. is there. On the other hand, if Tcp / ML _{1 + 4, 100 ° C.} exceeds 1.7, the degree of branching is too low and cold flow is likely to occur, which may reduce the storage stability of the product. Incidentally, the 5 wt% toluene solution viscosity (Tcp) and (Tcp / ML _{1 + 4, 100 ° C.} ) are values measured by the method described in Examples described later.

(C) Mooney viscosity (ML _{1 + 4, 100 ° C.} ) When the torque at the end of measurement is 100%, the stress relaxation time (T ₈₀ ) until the value is attenuated by 80% is 10.0 to 40.0 seconds. It is. T ₈₀ is preferably 11.0 to 26.0 seconds, and more preferably 12.0 to 20.0 seconds. When T ₈₀ is less than 10.0 seconds, holding power of less shear stress entanglement rubber molecules is insufficient, it may become difficult to obtain dispersion state of good filler. On the other hand, if T ₈₀ is greater than 40.0 seconds, the residual stress during molding is increased, workability inferior dimensional stability may be lowered. In addition, stress relaxation time ( _T80 ) is a value measured by the method described in the Example mentioned later. The transition of the stress relaxation of rubber is determined by the combination of the elastic component and the viscous component. A slow stress relaxation indicates that there are many elastic components, and a fast stress relaxation indicates that there are many viscous components.

  (D) The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) is 2.50 to 4.00. The Mw / Mn is preferably 2.60 to 3.60, and more preferably 2.70 to 3.20. If the Mw / Mn is less than 2.50, workability may be reduced. On the other hand, if Mw / Mn exceeds 4.00, the wear resistance may be reduced. In addition, a number average molecular weight (Mn), a weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) are the values measured by the method described in the Example mentioned later.

Polybutadiene has a so-called microstructure that includes a bond portion formed by polymerization at the 1,4-position (1,4-structure) and a bond portion formed by polymerization at the 1,2-position (1,2-structure). Coexist in the molecular chain. The 1,4-structure is further divided into two types, a cis structure and a trans structure. On the other hand, the 1,2-structure is a structure having a vinyl group as a side chain. Used in the composition of the present invention.
For the polybutadiene (I) used in the composition of the present invention, the proportion of cis-1,4 structural units in (E) microstructure analysis is 94.0-98.0 mol%, and 95.0-97. It is preferably 6 mol%. By setting the ratio of cis-1,4 structural units in the microstructure analysis to 98.0 mol% or less, it has a sufficient branched polymer chain, and the required stress relaxation time is easily obtained. On the other hand, when the ratio of the cis-1,4 structural unit in the microstructure analysis is less than 94.0, the wear resistance tends to decrease. In addition, the ratio of cis-1,4 structural units, etc. in the microstructure analysis is a value measured by the method described in the examples described later.

Furthermore, in the polybutadiene (I) used in the rubber composition for belts of the present invention, (F) the weight average molecular weight (Mw) is preferably 40.0 × 10 ^{4 to} 75.0 × 10 ⁴ , 46. It is more preferably 0 × 10 ^{4 to} 65.0 × 10 ⁴ , and further preferably 52.0 × 10 ^{4 to} 62.0 × 10 ⁴ . By setting Mw to 40.0 × 10 ⁴ or more, the wear resistance is further improved. On the other hand, workability improves more by making Mw into 75.0 * 10 < ⁴ > or less.

  In the polybutadiene (I) used in the composition of the present invention, (G) toluene solution viscosity (Tcp) is preferably 42 to 160, more preferably 55 to 135, and 68 to 120. Is more preferable. By setting Tcp to 42 or more, the wear resistance is further improved. On the other hand, by making Tcp 160 or less, workability is further improved.

In the polybutadiene (I) used in the composition of the present invention, the (H) number average molecular weight (Mn) is preferably 12.5 × 10 ^{4 to} 30.0 × 10 ⁴ , and 16.0 × More preferably, it is 10 ^{4 to} 23.0 × 10 ⁴ , and further preferably 17.0 × 10 ^{4 to} 20.3 × 10 ⁴ . By setting Mn to 12.5 × 10 ⁴ or more, the wear resistance is further improved. On the other hand, workability improves more by making Mn into 30.0 * 10 < ⁴ > or less.

  In the polybutadiene (I) used in the composition of the present invention, the proportion of vinyl structural units in the microstructure analysis is preferably 2 mol% or less, and more preferably 1.8 mol% or less. When the proportion of the vinyl structural unit in the microstructure analysis is 2 mol% or less, the molecular mobility becomes good, and the tan δ of the dynamic viscoelastic property after vulcanization becomes good. The proportion of vinyl structural units in the microstructural analysis is preferably as small as possible, but may be 1.0 mol% or more, for example.

  In the polybutadiene (I) used in the composition of the present invention, the proportion of trans-1,4 structural units in the microstructure analysis is preferably 2.0 mol% or less, and 1.6 mol% or less. Is more preferable, and it is still more preferable that it is 1.3 mol% or less. By setting the ratio of the trans-1,4 structural unit in the microstructure analysis to 2.0 mol% or less, the wear resistance is further improved. In addition, it is preferable that the ratio of the trans-1 and 4 structural units in the microstructural analysis is as small as possible.

  The polybutadiene (I) used in the composition of the present invention may be modified with disulfur dichloride, monosulfur monochloride, other sulfur compounds, organic peroxides, t-butyl chloride, etc. It does not have to be.

(2) Production method of polybutadiene (I) Polybutadiene (I) used in the composition of the present invention is produced by polymerizing butadiene in the presence of a cobalt-based catalyst. Examples of the cobalt-based catalyst include a catalyst system composed of a cobalt catalyst, an organoaluminum compound, and water. Cobalt catalysts include cobalt chloride, cobalt bromide, cobalt nitrate, cobalt octylate (ethylhexanoate), cobalt naphthenate, cobalt acetate, cobalt malonate, etc .; cobalt bisacetylacetonate, cobalt trisacetylacetonate , Ethyl acetoacetate cobalt, organic base complexes such as pyridine complexes and picoline complexes of cobalt salts, and ethyl alcohol complexes. Of these, octylic acid (ethylhexanoic acid) cobalt is preferable. Regarding the usage-amount of a cobalt-type catalyst, it can adjust suitably so that it may be set as the polybutadiene which has desired Mooney viscosity.

  Examples of organoaluminum compounds include trialkylaluminum; halogen-containing organoaluminum compounds such as dialkylaluminum chloride, dialkylaluminum bromide, alkylaluminum sesquichloride, alkylaluminum sesquibromide, alkylaluminum dichloride, alkylaluminum dibromide; dialkylaluminum hydride, alkylaluminum Examples thereof include organic aluminum hydride compounds such as sesquihydrite. An organoaluminum compound can be used individually by 1 type, and can also be used together 2 or more types.

  Specific examples of the trialkylaluminum include trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, and tridecylaluminum.

  Examples of the dialkylaluminum chloride include dimethylaluminum chloride and diethylaluminum chloride. Examples of the dialkylaluminum bromide include dimethylaluminum bromide and diethylaluminum bromide. Examples of the alkylaluminum sesquichloride include methylaluminum sesquichloride and ethylaluminum sesquichloride. Examples of the alkylaluminum sesquibromide include methylaluminum sesquibromide and ethylaluminum sesquibromide. Examples of the alkylaluminum dichloride include methylaluminum dichloride and ethylaluminum dichloride. Examples of the alkylaluminum dibromide include methylaluminum dibromide and ethylaluminum dibromide.

  Examples of the dialkylaluminum hydride include diethylaluminum hydride and diisobutylaluminum hydride. Examples of the alkylaluminum sesquihydride include ethylaluminum sesquihydride and isobutylaluminum sesquihydride.

Regarding the mixing ratio of the organoaluminum compound and water, since the polybutadiene having the desired T ₈₀ can be easily obtained, it is preferable that an aluminum / water (molar ratio) is 1.5 to 3, 1.7 to 2 .5 is more preferable.

  Furthermore, in order to obtain polybutadiene having a desired Mooney viscosity, non-conjugated dienes such as cyclooctadiene, allene, and methylallene (1,2-butadiene); α-olefins such as ethylene, propylene, and 1-butene; A molecular weight regulator can also be used. A molecular weight regulator can be used individually by 1 type, and can also use 2 or more types together.

  There is no particular limitation on the polymerization method of butadiene, and bulk polymerization (bulk polymerization) in which a monomer is polymerized while using a conjugated diene compound monomer such as 1,3-butadiene as a polymerization solvent, or polymerization is performed in a state where the monomer is dissolved in the solvent. Solution polymerization or the like can be applied. Solvents used in the solution polymerization include aromatic hydrocarbons such as toluene, benzene and xylene; saturated aliphatic hydrocarbons such as n-hexane, butane, heptane and pentane; alicyclic hydrocarbons such as cyclopentane and cyclohexane; Examples include olefinic hydrocarbons such as cis-2-butene and trans-2-butene; petroleum solvents such as mineral spirits, solvent naphtha, and kerosene; halogenated hydrocarbons such as methylene chloride. Among these, toluene, cyclohexane, or a mixed solvent of cis-2-butene and trans-2-butene is preferably used.

The polymerization temperature is preferably in the range of −30 to 150 ° C., more preferably in the range of 30 to 100 ° C., and further preferably 70 to 80 ° C. from the viewpoint of easily obtaining polybutadiene having a desired stress relaxation time (T ₈₀ ). The polymerization time is preferably in the range of 1 minute to 12 hours, and more preferably in the range of 5 minutes to 5 hours.

  After the polymerization reaction reaches a predetermined polymerization rate, an anti-aging agent can be added as necessary. Anti-aging agents include phenol-based anti-aging agents such as 2,6-di-t-butyl-p-cresol (BHT), phosphorus-based anti-aging agents such as trinonylphenyl phosphite (TNP), and 4,6 -Sulfur-based anti-aging agents such as -bis (octylthiomethyl) -o-cresol and dilauryl-3,3'-thiodipropionate (TPL). One type of anti-aging agent can be used alone, or two or more types can be used in combination. The addition amount of the antioxidant is preferably 0.001 to 5 parts by weight with respect to 100 parts by weight of polybutadiene (I).

  After performing the polymerization for a predetermined time, the inside of the polymerization tank is released as necessary, and further post-treatment such as washing and drying steps is performed to produce polybutadiene having desired characteristics.

(3) Rubber composition for belts As described above, the rubber composition for belts of the present invention is produced by polymerizing butadiene in the presence of a cobalt catalyst, and meets the requirements described in (A) to (E) above. A composition comprising satisfactory polybutadiene (I). Further, in the rubber composition for a belt of the present invention, in order to improve energy loss, the polybutadiene (I) includes a diene rubber component (J) other than the polybutadiene (I) and a rubber reinforcing material (L). It is preferable to contain. In this case, with respect to 100 parts by weight of the rubber component (K) comprising 5 to 90% by weight of the polybutadiene (I) and 95 to 10% by weight of the diene rubber component (J) other than the polybutadiene (I), rubber reinforcement More preferably, the material (L) is contained in a proportion of 20 to 70 parts by weight.

(3-1) Diene rubber component (J)
When the rubber composition for a belt of the present invention contains a diene rubber component (J) other than the polybutadiene (I), specific examples of the diene rubber component (J) include natural rubber, polyisoprene rubber, High cis polybutadiene rubber, low cis polybutadiene rubber (BR), emulsion polymerization or solution polymerization styrene / butadiene rubber (SBR), ethylene / propylene / diene rubber (EPDM), nitrile rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR) ) And the like. In addition, derivatives of these rubbers such as polybutadiene rubber modified with tin compounds and the above-mentioned rubbers modified with epoxy, silane, and maleic acid can be used. These rubbers can be used alone or in combination of two or more. May be. In the present invention, the diene rubber component (J) is not limited to the above rubber component. Among these diene rubber components (J), one or more selected from natural rubber and polyisoprene rubber are preferable.

(3-2) Rubber component (K)
When the diene rubber component (J) is contained in the rubber composition for belts of the present invention, the polybutadiene (I) is 5 to 95% by weight and the diene rubber component (J) 95 other than the polybutadiene (I) is 95. It is more preferable to use a rubber component (K) consisting of from 10 to 10% by weight, and the lower limit of the blending range of the polybutadiene (I) in the rubber component (K) is more preferably 20% by weight, most preferably 40%. preferable. On the other hand, the upper limit of the blending range of polybutadiene (I) is more preferably 90% by weight, and most preferably 80% by weight.

(3-3) Rubber reinforcement (L)
The rubber composition for a belt of the present invention can contain a rubber reinforcing material (L) in order to improve the low energy loss in addition to the improvement of wear resistance and workability. Specific examples of the rubber reinforcing material (L) include carbon black, silica, various white carbons, activated calcium carbonate, and ultrafine magnesium silicate. Among these rubber reinforcing materials (L), one or more selected from carbon black and silica are preferable, and particularly preferable is a particle diameter of 90 nm or less and dibutyl phthalate (DBP) oil absorption. The carbon black is 70 ml / 100 g or more, and examples thereof include FEF, FF, GPF, SAF, ISAF, SRF, and HAF. The blending ratio of the rubber reinforcing material (L) is preferably 20 to 70 parts by weight, and more preferably 30 to 60 parts by weight with respect to 100 parts by weight of the rubber component (K). Moreover, it is preferable that the compounding quantity of the silica in a rubber reinforcing agent is 70 mass% or less, It is more preferable that it is 5-65, It is especially preferable that it is 10-63. If the amount of silica is increased, energy loss can be reduced. However, if the amount of silica exceeds 70% by mass, durability such as resistance to flex crack growth is inferior.

(3-4) Other additives In the rubber composition for a belt of the present invention, a silane coupling agent, a vulcanizing agent, a vulcanization accelerator, a filler, as necessary, in addition to the rubber reinforcing material (L). In addition, components usually used in the rubber industry such as process oil, zinc white, and stearic acid may be kneaded. Examples of the vulcanizing agent include known vulcanizing agents such as sulfur, organic peroxides, resin vulcanizing agents, and metal oxides such as magnesium oxide. Examples of the vulcanizing accelerator include known vulcanizing agents. Auxiliaries such as aldehydes, ammonia, amines, guanidines, thioureas, thiazoles, thiurams, dithiocarbamates, xanthates and the like can be mentioned.

  Examples of the filler include inorganic fillers such as clay, Lissajous, and diatomaceous earth; and organic fillers such as recycled rubber and powder rubber. As the process oil, any of an aromatic process oil, a naphthenic process oil, and a paraffin process oil may be used. Further, low molecular weight liquid polybutadiene or tackifier may be used.

(3-5) Method of kneading belt rubber composition The belt rubber composition of the present invention is not particularly limited in the blending order of the above components, and all the components may be blended and kneaded at once. Kneading can also be performed by blending each component in two or three stages. In kneading, a Banbury, an open roll, a kneader, a biaxial kneader, or the like can be used. In forming the belt, a known molding machine such as an extrusion molding machine or a press machine can be used.

[2] Rubber belt The rubber belt of the present invention is characterized by using the rubber composition for a belt as a rubber base material. Since the rubber composition for belts of the present invention is polybutadiene (I) having improved wear resistance and processability, the rubber belt of the present invention using the rubber composition for belts as a rubber base material is wear resistant. Excellent in workability and workability. When the rubber composition for a belt of the present invention contains a rubber reinforcing material (K) in order to improve low energy loss, the belt rubber composition was used as a rubber base material. The rubber belt of the present invention is excellent in wear resistance and workability, and can further improve low energy loss and the like. A method for producing a rubber belt using the rubber composition for a belt of the present invention is not particularly limited. For example, a rubber belt is produced by placing the rubber composition for a belt in a mold and press vulcanizing. be able to.

  EXAMPLES Examples according to the present invention will be specifically described below, but the present invention is not limited to these examples. In Examples 1 to 11 and Comparative Examples 1 to 7, the physical properties of polybutadiene used in the rubber composition for belts, and the workability and wear resistance of the compositions obtained by adding the compound to the polybutadiene. Etc. were evaluated. In Example 12 and Comparative Examples 8 to 11, the physical properties of the polybutadiene used in the rubber composition for belts and the rubber composition for belts obtained by blending a co-crosslinking agent with the polybutadiene were processed. , Hardness, and low energy loss (tan δ) were evaluated.

First, evaluation methods in this example and comparative examples are described.
(1) Mooney viscosity (ML _{1 + 4,100 ° C.} )
The Mooney viscosity (ML1 + 4, 100 ° C.) of the polybutadiene and the blend is preheated at 100 ° C. for 1 minute using a Mooney viscometer (manufactured by Shimadzu Corporation, model: SMV-300RT) in accordance with JIS K6300. The value was measured for 4 minutes. The smaller the Mooney viscosity of the blend, the lower the viscosity and the better the processability.
(2) Toluene solution viscosity (Tcp)
The 5 wt% toluene solution viscosity (Tcp) of polybutadiene was obtained by dissolving 2.28 g of polymer in 50 ml of toluene, 400 was measured at 25 ° C. As a standard solution, a viscometer calibration standard solution (JIS Z8809) was used.
(3) Stress relaxation time (T ₈₀ )
The stress relaxation time (T ₈₀ ) of polybutadiene was calculated by stress relaxation measurement according to ASTM D1646-7. Specifically, under the measurement conditions of ML _{1 + 4 and} 100 ° C. measured at 100 ° C. measured according to JIS K6300, the torque when the rotor stopped after 4 minutes of measurement (0 seconds) was taken as 100%, and the value was 80% time to relaxation (i.e. until attenuated to 20%) (in seconds) was measured as a stress relaxation time T _80.

(4) Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn)
The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of polybutadiene adopt GPC method (product name: HLC-8220, manufactured by Tosoh Corporation), and converted to standard polystyrene. Calculated by Tetrahydrofuran was used as the solvent, two columns (trade name: Shodex (registered trademark) KF-805L) manufactured by Showa Denko KK were connected in series, and a suggested refractometer (RI) was used as the detector.
(5) Microstructure analysis The ratio of the cis-1,4 structural unit, the trans-1,4 structural unit, and the vinyl structural unit in the microstructural analysis of polybutadiene was calculated by infrared absorption spectrum analysis. Specifically, a peak derived from the microstructure position (cis (cis): 740 cm ^-1, vinyl (vinyl): 910 cm ^-1, trans (trans): 967cm ^-1) from the absorption intensity ratio of polybutadiene microstructure The percentage of units was calculated.

(6) Hardness The hardness of the rubber composition for belts was measured by a durometer type (type D) according to the measurement method defined in JIS K6253.
(7) 100% tensile stress, tensile strength, tensile elongation 100% tensile stress was measured according to JIS K6251.
For the tensile strength, the tensile strength at break was measured according to JIS K6251.
The tensile elongation was determined by measuring the tensile elongation at break according to JIS K6251.
(8) Lambourne wear Lambourne wear was measured at a slip rate of 20% in accordance with the measurement method defined in JIS K6264, and indicated as an index with Comparative Example 1 being 100. The larger the index, the better the lamborn wear.
(9) Exothermicity The exothermicity was indexed with Comparative Example 1 as 100 by measuring the calorific value increased at 100 ° C. for 25 minutes with a flexometer according to JIS K6265. The larger the index, the better the heat buildup.

[Example 1]
In a 1.5 liter (L) stainless steel reactor equipped with a stirrer, the content was replaced with nitrogen gas. 1.0 L (butadiene (BD): 34.2 wt%, cyclohexane (CH): 31.2 wt) %, The rest being 2-butenes). Further, water (H ₂ O) 1.52 mmol, diethylaluminum chloride (DEAC) 2.08 mmol, triethylaluminum (TEA) 0.52 mmol, (total aluminum / water = 1.71 (mixing molar ratio)), cobalt octoate (Co _cat ) 20.94 μmol and cyclooctadiene (COD) 6.05 mmol were added, and the mixture was stirred at 72 ° C. for 20 minutes to carry out 1,4-cis polymerization. Thereafter, ethanol containing 4,6-bis (octylthiomethyl) -o-cresol was added to stop the polymerization, and unreacted butadiene and 2-butenes were removed by evaporation to obtain polybutadiene. Table 1 shows the physical properties of the obtained polybutadiene.

  Next, a rubber composition containing styrene butadiene rubber (SBR) was produced using the obtained polybutadiene. Specifically, first, Labo Plast Mill (manufactured by Toyo Seiki Seisakusyo Co., Ltd.), in which 30 parts by weight of polybutadiene and 70 parts by weight of styrene butadiene rubber (SBR) were set at a temperature of 90 ° C. and a rotation speed of 68 rpm. Name: BR-250 type) and mixed for 30 seconds. Then, 32.5 parts by weight of silica (Evonik Degussa, trade name: Ultrasil 7000GR), which is half the prescribed amount, and 5.2 parts by weight of a silane coupling agent (Evonik Degussa, trade name: si75). ). Subsequently, the remaining 32.5 parts by weight of silica, 25 parts by weight of oil (manufactured by H & R, trade name: VivaTec400), and 3 parts by weight of ZnO (manufactured by Sakai Chemical Industry Co., Ltd., trade name: Sazex 1) 1 part by weight of stearic acid (manufactured by Adeka Co., Ltd., trade name: Adeka Fatty Acid SA-300) and 1 part by weight of AO (antioxidant, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: NOCRACK 6C) And kneaded for a total of 6 minutes.

  Next, the obtained kneaded product was cooled and allowed to cool with a 6-inch roll, and then re-milled. Further, 1.7 parts by weight of the first vulcanization accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller CZ (CBS)) and 2 parts by weight of the second vulcanization are added to the kneaded product. Accelerator (trade name: Noxeller D (DPG), manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) and 1.4 parts by weight of vulcanizing agent (powder sulfur) are mixed by a 6 inch roll, thereby blending Was made. The physical properties (Mooney viscosity) of the blend are shown in Table 1.

  And the rubber composition was produced by putting the obtained compound into a metal mold | die and carrying out press vulcanization | cure. The vulcanization time was twice as long as the vulcanization characteristic t90 at 160 ° C. obtained with a viscoelasticity measuring apparatus (trade name: RPA 2000, manufactured by Alpha Technologies). Table 1 shows the physical properties (Lambourn wear coefficient) of the rubber composition obtained.

[Examples 2 to 6]
The same procedure as in Example 1 was performed except that the raw material mixing ratio and the polymerization temperature were changed as shown in Table 2. The results are shown in Table 1. In Examples 4 and 5, triethylaluminum (TEA) was not used.

[Comparative Example 1]
The same operation as in Example 1 was performed except that a commercially available polybutadiene (manufactured by Ube Industries, Ltd., trade name: BR150L) was used. The results are shown in Table 1.

[Comparative Example 2]
It implemented similarly to Example 1 except having used commercially available polybutadiene (Ube Industries, Ltd. make, brand name: BR150B). The results are shown in Table 1.

[Comparative Example 3]
The same procedure as in Example 1 was performed except that trial polybutadiene was used. The results are shown in Table 1.

[Comparative Example 4]
It implemented like Example 1 except having used commercially available polybutadiene (Ube Industries, Ltd. make, brand name: BR710). The results are shown in Table 1.

[Example 7]
A rubber composition containing natural rubber was prepared using the polybutadiene obtained in Example 1. Specifically, first, 50 parts by weight of polybutadiene and 50 parts by weight of natural rubber (RSS # 1; ML _{1 + 4} , adjusted to _{100 ° C.} = 70) were set at a temperature of 90 ° C. and a rotation speed of 68 rpm. Mixing was performed for 60 seconds using a mill (trade name: BR-250, manufactured by Toyo Seiki Seisakusho Co., Ltd.). Thereafter, 50 parts by weight of carbon black (ISAF), 3 parts by weight of oil (manufactured by H & R, trade name: VivaTec400), and 3 parts by weight of ZnO (manufactured by Sakai Chemical Industry Co., Ltd., trade name: Sazex1) And 2 parts by weight of stearic acid (manufactured by Adeka Co., Ltd., trade name: Adeka Fatty Acid SA-300) and 2 parts by weight of antioxidant (manufactured by Sumitomo Chemical Co., Ltd., trade name: Antigen 6C) And kneaded for a total of 4 minutes.

  Next, 1 part by weight of a vulcanization accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller NS) and 1.5 parts by weight of a vulcanizing agent (powdered sulfur) are added to the kneaded product obtained. Were mixed with a 6 inch roll to make a formulation. Table 3 shows the physical properties (Mooney viscosity) of the blend.

  The obtained composition was placed in a mold and press vulcanized to produce a rubber composition. The vulcanization time was twice as long as the vulcanization characteristic t90 at 150 ° C. determined by a viscoelasticity measuring apparatus (trade name: RPA 2000, manufactured by Alpha Technologies). Table 3 shows the physical properties (Lambourn wear coefficient) of the rubber composition obtained.

[Examples 8 to 11]
The same operation as in Example 7 was carried out except that the polybutadiene obtained in Examples 3 and 4 to 6 was used. The results are shown in Table 3.

[Comparative Examples 5 to 7]
The same operation as in Example 7 was carried out except that the polybutadienes used in Comparative Examples 1, 2, and 4 were used. The results are shown in Table 3.

[Summary of evaluation]
From the results of Examples 1 to 11 and Comparative Examples 1 to 7, by using polybutadiene that is synthesized using a cobalt-based catalyst and satisfies the requirements (A) to (E), for the rubber composition for a belt. It was confirmed that the wear resistance and workability can be improved to a higher degree.

[Example 12]
Polybutadiene was prepared by polymerizing butadiene in the presence of a cobalt-based catalyst, and the polybutadiene was evaluated. Next, a rubber composition for a belt was prepared by blending natural rubber, carbon black and the like with the obtained polybutadiene and kneading and the like, and the rubber composition for the belt was evaluated.
(1) Preparation and evaluation of polybutadiene In a 1.5 L stainless steel reaction vessel with a stirrer, the content was replaced with nitrogen gas, 1.0 L of a polymerization solution (butadiene (BD): 35.0 wt%, cyclohexane (CH): 28.0 wt%, the rest being 2-butenes). Furthermore, 1.05 mmol of water (H ₂ O), 1.90 mmol of diethylaluminum chloride (DEAC) (aluminum / water = 1.81 (mixing molar ratio)), 20.95 μmol of cobalt octoate (Cocat), and cyclooctadiene (COD) 8.06 mmol was added, and it stirred at 72 degreeC for 20 minute (s), and 1, 4-cis polymerization was performed. Thereafter, ethanol containing 4,6-bis (octylthiomethyl) -o-cresol was added to stop the polymerization, and unreacted butadiene and 2-butenes were removed by evaporation to obtain polybutadiene. The physical properties are shown in Table 4.

(2) Production and evaluation of rubber composition for belt and sample for evaluation Laboplast in which 70 parts by weight of polybutadiene obtained and 30 parts by weight of natural rubber (RSS # 1) were set at a temperature of 90 ° C. and a rotation speed of 68 rpm. It was mixed for 1 minute using a mill (trade name: BR-250 type, manufactured by Toyo Seiki Seisakusho Co., Ltd.). Thereafter, 50 parts by weight of carbon black (ISAF), 3 parts by weight of oil (manufactured by H & R, trade name: VivaTec 400), 3 parts by weight of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., trade name: Sazex 1), 1 part by weight of stearic acid (manufactured by Shin Nippon Rika Co., Ltd., trade name: stearic acid 50S) and 1 part by weight of antioxidant (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: NOCRACK 6C) And kneaded for a total of 4 minutes. The obtained kneaded product was mixed with a 6-inch roll by 1 part by weight of a vulcanization accelerator (manufactured by Sanshin Chemical Industry Co., Ltd., trade name: Sunseller NS-G) and 1.5 parts by weight of a vulcanizing agent (powder sulfur). And a rubber composition for belts was prepared. Next, the obtained rubber composition for a belt was put into a mold and press vulcanized to prepare a sample for evaluation. The vulcanization time was twice as long as the vulcanization characteristic t90 at 150 ° C. obtained with a viscoelasticity measuring apparatus (trade name: RPA 2000, manufactured by Alpha Technologies). Table 4 shows the evaluation results of the obtained evaluation samples.

[Comparative Example 8]
A composition and a sample for evaluation were prepared and evaluated in the same manner as in Example 12 except that a commercially available polybutadiene (manufactured by Ube Industries, Ltd., trade name: BR710) was used. The evaluation results are shown in Table 4.

[Comparative Example 9]
A composition and an evaluation sample were prepared and evaluated in the same manner as in Example 12 except that a commercially available polybutadiene (trade name: BR150L, manufactured by Ube Industries, Ltd.) was used. The evaluation results are shown in Table 4.

[Comparative Example 10]
A composition and a sample for evaluation were prepared and evaluated in the same manner as in Example 12 except that a commercially available polybutadiene (manufactured by Ube Industries, Ltd., trade name: BR360L) was used. The evaluation results are shown in Table 4.

[Comparative Example 11]
A composition was prepared and evaluated in the same manner as in Example 12 except that Ube Industries, Ltd., a prototype UBEPOL Z704 was used. The evaluation results are shown in Table 4.

[Summary]
As described above, the rubber composition for belts produced in Example 12 has good processability while keeping the Mooney viscosity low while maintaining the wear resistance as compared with the compositions produced in Comparative Examples 8-11. It was confirmed that the rubber composition showed excellent exothermic properties.

  The rubber composition for belts of the present invention can improve workability while maintaining wear resistance by using polybutadiene having predetermined characteristics, and further, other polyene rubber and rubber reinforcing material to the polybutadiene. By containing the rubber belt, it is possible to provide a rubber belt that achieves both workability and heat generation.

Claims (7)

A rubber composition for belts comprising polybutadiene (I) produced by polymerizing butadiene in the presence of a cobalt-based catalyst and satisfying the requirements described in (A) to (E) below.
(A) Mooney viscosity (ML _{1 + 4,100 ° C.} ) is 43 to 70
(B) Ratio (Tcp / ML _{1 + 4,100 ° C.} ) of 5 wt% toluene solution viscosity (Tcp) to Mooney viscosity (ML _{1 + 4,100 ° C.} ) is 0.9 to 1.7.
(C) ML _{1 + 4, 100 ° C.} When the torque at the end of measurement is 100%, the stress relaxation time (T ₈₀ ) until the value attenuates by 80% is 10.0 to 40.0 seconds (D) Molecular weight distribution (Weight average molecular weight (Mw) / number average molecular weight (Mn)) is 2.50 to 4.00.
(E) The ratio of cis-1,4 structural units in the microstructure analysis is 94.0-98.0 mol%. The rubber composition for a belt according to claim 1, wherein the polybutadiene (I) further satisfies the requirements described in the following (F) to (H).
(F) The weight average molecular weight (Mw) is 40.0 × 10 ^{4 to} 75.0 × 10 ^4.
(G) 5 wt% toluene solution viscosity (Tcp) is 42 to 160 cps
(H) Number average molecular weight (Mn) is 12.5 × 10 ^{4 to} 30.0 × 10 ⁴   The rubber composition for a belt according to claim 1 or 2, comprising the polybutadiene (I), a diene rubber (J) other than the polybutadiene (I), and a rubber reinforcing agent (L).   Rubber reinforcing agent (L) with respect to 100 parts by weight of rubber component (K) comprising 5 to 90% by weight of polybutadiene (I) and 95 to 10% by weight of diene rubber (J) other than polybutadiene (I) Is contained in a proportion of 20 to 70 parts by weight, The rubber composition for belts according to claim 1 or 3.   The rubber composition for a belt according to claim 3 or 4, wherein the rubber component (J) is natural rubber and / or polyisoprene.   The rubber composition for a belt according to any one of claims 3 to 5, wherein the rubber reinforcing agent (L) is carbon black and / or silica. A rubber belt comprising the rubber composition for a belt according to any one of claims 1 to 6 as a rubber base material.