JP2010265341A - Vulcanized rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vulcanized rubber composition enhancing heat aging-resistance while increasing tensile break strength and elongation at an initial stage of vulcanization when it is vulcanization-adhered to a metal member. <P>SOLUTION: The vulcanized rubber composition is obtained by vulcanizing a rubber composition in which 2-20 pts.wt. of zinc sulfide is formulated relative to 100 pts.wt. of a diene based rubber, and contains 0.2 wt.% of free sulfur. The half value width of a diffraction peak of the zinc sulfide in which 2θ measured by X-ray diffraction appears in a range of 28.5°±0.2° is 0.5° or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vulcanized rubber composition, and more specifically, a vulcanization that improves heat aging resistance while increasing tensile fracture strength and elongation at the initial stage of vulcanization when vulcanized and bonded to a metal member. The present invention relates to a rubber composition.

  A carcass layer, a belt layer, a bead core and the like of a pneumatic tire are configured by a reinforcing rubber layer in which a steel cord is covered with a covering rubber. These reinforced rubber layers perform vulcanization of the coating rubber and adhesion between the coating rubber and the steel cord at the same time as vulcanization molding. Since the vulcanization of the coated rubber and the adhesion between the steel cords act in a competitive reaction, it is necessary to vulcanize so that both are compatible.

  On the other hand, these reinforced rubber layers are required to have excellent toughness, and the coated rubber is also required to have high tensile breaking strength and elongation. However, even if excellent tensile breaking strength and elongation were obtained at the initial stage of vulcanization, there was a problem that the tensile breaking strength and breaking elongation were reduced due to thermal aging. In order to suppress heat aging, it is conceivable to add an anti-aging agent, but as the amount of the anti-aging agent increases, the adhesiveness with the steel cord deteriorates, so the anti-aging agent suppresses heat aging. There was a limit.

  In order to improve the heat aging resistance of rubber, Patent Document 1 proposes to use a rubber composition in which zinc sulfide and zinc oxide are blended with diene rubber. However, even though this rubber composition can improve the heat aging resistance, it is not necessarily a sufficient measure for increasing the initial physical properties of the tensile strength and elongation at break of the vulcanized rubber composition.

JP 2003-246885 A

  An object of the present invention is to provide a vulcanized rubber composition in which, when vulcanized and bonded to a metal member, the heat aging resistance is improved while increasing the tensile breaking strength and elongation at the initial stage of vulcanization. .

  The vulcanized rubber composition of the present invention that achieves the above object is a vulcanized rubber composition obtained by vulcanizing a rubber composition containing 2 to 20 parts by weight of zinc sulfide with respect to 100 parts by weight of a diene rubber. The vulcanized rubber composition contains free sulfur in an amount of 0.2% by weight or more, and the zinc sulfide is a half of the diffraction peak in which 2θ measured by X-ray diffraction appears in the range of 28.5 ° ± 0.2 °. The value width is 0.5 ° or less.

  The rubber composition may further contain a hydrate of an inorganic compound. Further, 5 to 15 parts by weight of zinc oxide and 2 to 10 parts by weight of sulfur may be blended with 100 parts by weight of the diene rubber.

  This vulcanized rubber composition is suitable for constituting a rubber member vulcanized and bonded to a metal member. In particular, it may be used for a rubber covered with a steel cord of a pneumatic tire.

  The vulcanized rubber composition of the present invention has a 2θ measured by X-ray diffraction of zinc sulfide by vulcanizing a rubber composition containing 2 to 20 parts by weight of zinc sulfide to 100 parts by weight of diene rubber. Since the half-value width of the diffraction peak appearing in the range of 28.5 ° ± 0.2 ° is 0.5 ° or less, the vulcanized rubber composition is oxidized by trapping oxygen by this zinc sulfide. Can be suppressed and heat aging resistance can be improved. Moreover, since the vulcanized rubber composition contains 0.2% by weight or more of free sulfur, the tensile rupture strength and elongation can be secured at a high level without the vulcanized rubber composition being overvulcanized. .

  In the present invention, the rubber component is a diene rubber. The diene rubber is not particularly limited, and examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and butyl rubber. These diene rubbers can be used alone or as any blend.

  The vulcanized rubber composition of the present invention can be obtained by vulcanizing a rubber composition in which zinc sulfide, zinc oxide, sulfur and, if necessary, a hydrate of an inorganic compound are blended with the above-described diene rubber. As zinc sulfide, α-type crystals or a mixture of α-type crystals and β-type crystals can be used. A mixture of α-type crystal and β-type crystal is preferable.

  In the vulcanized rubber composition of the present invention, since zinc sulfide traps oxygen in the diene rubber, the oxidative deterioration is suppressed by suppressing the rubber component from binding to oxygen. Improved heat aging resistance. The zinc sulfide in the vulcanized rubber composition has a half-value width of a diffraction peak appearing in a range of 2θ of 28.5 ° ± 0.2 ° measured by X-ray diffraction of 0.5 ° or less, preferably 0.1 It needs to be between 0 ° and 0.3 °. Zinc sulfide in which the half-value width of the diffraction peak appearing in the range of 2θ of X-ray diffraction in the range of 28.5 ° ± 0.2 ° is larger than 0.5 ° is obtained by overvulcanizing an unvulcanized rubber composition containing zinc oxide. Produced when vulcanized up to. The vulcanized rubber composition in the overvulcanized state is unable to achieve the intended purpose because the tensile strength at break and the initial physical properties of elongation are lowered. Therefore, the vulcanized rubber composition shall not contain zinc sulfide having a half-value width of diffraction peaks appearing in the range where 2θ of X-ray diffraction is 28.5 ° ± 0.2 ° is larger than 0.5 °. In the present invention, X-ray diffraction of zinc sulfide is performed using an X-ray diffractometer manufactured by Panalical, using X-ray source: CuKα ray, tube voltage: 45 kV, tube current: 40 mA, diverging slit: 0.5 It was assumed that copper was measured as a target metal under measurement conditions consisting of °, anti-scattering slit: 0.5 °, and step width: 0.03 °.

  The vulcanized rubber composition of the present invention contains 0.2% by weight or more of free sulfur, preferably 0.2 to 1.0% by weight. When the content of free sulfur is less than 0.2% by weight, it means that the vulcanized rubber composition is in the overvulcanized state, and the initial physical properties of tensile strength at break and elongation at break cannot be increased. In the present invention, the content of free sulfur in the vulcanized rubber composition is a value determined by a measuring method based on JIS K6234.

  The action of sulfur sulfide to trap oxygen can be increased by blending the vulcanized rubber composition of the present invention with a hydrate of an inorganic compound. That is, the presence of water molecules released from the hydrate of the inorganic compound in the vulcanized rubber composition increases the action of sulfur sulfide to trap oxygen. The blending amount of the inorganic compound hydrate is not particularly limited, and is preferably 0.2 to 5.0 parts by weight, more preferably 0.2 to 3.0 parts by weight based on 100 parts by weight of the diene rubber. It is better to use parts by weight. If the blending amount of the inorganic compound hydrate is less than 0.2 parts by weight, the effect of increasing sulfur sulfide trapping of oxygen cannot be sufficiently obtained. Moreover, when the compounding quantity of the hydrate of an inorganic compound exceeds 5.0 weight part, adhesiveness with metal members, such as a steel cord, will worsen.

  The hydrate of the inorganic compound is not particularly limited. For example, calcium sulfate dihydrate, magnesium sulfate heptahydrate, magnesium phosphate octahydrate, iron sulfate monohydrate To pentahydrate, magnesium carbonate hydroxide hydrate, and the like. Of these, calcium sulfate dihydrate is preferable.

  The vulcanized rubber composition part vulcanizes by adding sulfur to the rubber composition and vulcanizes the unvulcanized rubber and simultaneously bonds the unvulcanized rubber and the metal member. The amount of sulfur is preferably 2 to 10 parts by weight, more preferably 4 to 8 parts by weight, based on 100 parts by weight of the diene rubber. When the amount of sulfur is less than 2 parts by weight, the adhesion between the metal member and the rubber is deteriorated, and the tensile strength at break of the vulcanized rubber is lowered. Moreover, when the compounding quantity of sulfur exceeds 10 weight part, the adhesiveness of a metal member and rubber will worsen.

  In addition, the rubber composition is blended with zinc oxide and vulcanized, thereby vulcanizing the unvulcanized rubber and promoting the adhesion between the unvulcanized rubber and the metal member. The blending amount of zinc oxide is preferably 5 to 15 parts by weight, more preferably 5 to 10 parts by weight with respect to 100 parts by weight of the diene rubber. If the amount of sulfur in zinc oxide is less than 5 parts by weight, the desired effect cannot be obtained. On the other hand, if the amount of sulfur exceeds 10 parts by weight, the tensile strength at break decreases.

  Commonly used compounding agents such as carbon black, inorganic fillers and additives can be added to the vulcanized rubber composition of the present invention. As the inorganic filler, for example, silica, clay, calcium carbonate, talc, mica, aluminum hydroxide, magnesium carbonate and the like can be blended as necessary. As additives, various additives generally used in vulcanized rubber compositions such as vulcanization or crosslinking agents, vulcanization accelerators, processing aids, anti-aging agents, and plasticizers can be blended. The amount of these compounding agents can be a conventional general compounding amount as long as the object of the present invention is not violated.

  A vulcanized rubber composition is prepared by mixing an unvulcanized rubber composition by mixing each of the above components using a known rubber kneading machine, such as a Banbury mixer, a kneader, or a roll. It can be produced by vulcanizing the rubber composition so as not to be over-vulcanized.

  The vulcanized rubber composition of the present invention is suitable for constituting a rubber member vulcanized and bonded to a metal member. In particular, it may be used for a rubber covered with a steel cord of a pneumatic tire. These rubber members and coated rubbers have high initial tensile strength and elongation properties, and are excellent in heat aging resistance, and therefore can suppress a decrease in tensile strength and elongation due to thermal deterioration. Are better.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Seven kinds of rubber compositions (Examples 1 to 4 and Comparative Examples 1 to 3) having the composition shown in Table 1 were weighed with the composition ingredients except sulfur and a vulcanization accelerator, respectively, and a 1.7 L Banbury mixer. The mixture was kneaded for 5 minutes, and the master batch was discharged at a temperature of 150 ° C. and cooled at room temperature. This master batch was subjected to an 8-inch open roll, and sulfur and a vulcanization accelerator were added and mixed for 4 minutes to prepare an unvulcanized rubber composition.

  Of the seven types of unvulcanized rubber compositions obtained, the vulcanization conditions for the unvulcanized rubber compositions of Examples 1 to 4 and Comparative Example 1 were set to 150 ° C. for 30 minutes, and the vulcanization conditions of Comparative Example 2 were set. The vulcanization conditions of Comparative Example 3 were set at 170 ° C. for 20 minutes and 170 ° C. for 30 minutes, respectively, and vulcanized in a predetermined mold to prepare a test piece made of a vulcanized rubber composition.

  Using the test pieces of the obtained seven types of rubber compositions (Examples 1 to 4, Comparative Examples 1 to 3), the X-ray diffraction peak of zinc sulfide in the vulcanized rubber composition was measured by the method described below. The full width at half maximum, the content of free sulfur, the oxygen bond amount of the rubber component, the tensile breaking strength, the tensile breaking elongation, and each characteristic after the heat aging test were measured.

FWHM of X-ray diffraction peak Using a test piece of vulcanized rubber composition, X-ray source: CuKα ray, tube voltage: 45 kV, tube current: 40 mA, divergence X-ray diffraction was performed using copper as the target metal under the measurement conditions of slit: 0.5 °, anti-scattering slit: 0.5 °, and step width: 0.03 °. The full width at half maximum of the diffraction peak at which 2θ measured by X-ray diffraction of this zinc sulfide appears in the range of 28.5 ° ± 0.2 ° was measured, and the obtained results are shown in Table 1.

Content of free sulfur Using a test piece of a vulcanized rubber composition, the content [% by weight] of free sulfur in the vulcanized rubber composition was measured according to JIS K6234. The obtained results are shown in Table 1.

Oxygen bond amount of rubber component Oxygen bond amount [wt%] bound to the rubber component in the vulcanized rubber composition using a test piece of vulcanized rubber composition and using an organic element analyzer manufactured by Thermo Electron Was measured. The obtained results are shown in Table 1.

Tensile strength at break and elongation at break The tensile strength at break [MPa] and the elongation at break [%] at 23 ° C. were measured in accordance with JIS K6251 using test pieces of vulcanized rubber composition. The obtained results are shown in Table 1.

Heat aging test and physical property evaluation A heat aging test was conducted by heating a test piece of a vulcanized rubber composition at 80 ° C for 96 hours. Using the test piece after the heat aging test, the oxygen bond amount, tensile breaking strength, and breaking elongation of the rubber component were measured by the methods described above. The obtained results are shown in Table 1, respectively.

In addition, the kind of raw material used in Table 1 is shown below.
NR: natural rubber, RSS # 3
Carbon black: Toast Carbon Co., Ltd. Seest 300
Zinc oxide: Toho Zinc Co., Ltd.
Stearic acid: NOF Beads Stearic Acid YR
Anti-aging agent: SANTOFLEX 6PPD manufactured by FLEXSYS
Cobalt salt: Rhodia Manobond C225 (Co content 22.5%)
Sulfur: Christex HS OT 20 manufactured by FLEXSYS
Vulcanization accelerator: Noxeller DZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
Zinc sulfide: Zinc sulfide manufactured by Kanto Chemical Co., Inc., a diffraction peak in which 2θ measured by X-ray diffraction in a mixture of α-type crystal and β-type crystal, and vulcanized rubber composition was in the range of 28.5 ° ± 0.2 ° The half-value width of was 0.2 °.
Calcium sulfate dihydrate: Calcium sulfate dihydrate manufactured by Kanto Chemical Co., Inc.

Claims (5)

  A vulcanized rubber composition obtained by vulcanizing a rubber composition containing 2 to 20 parts by weight of zinc sulfide with respect to 100 parts by weight of a diene rubber, and 0.2% by weight of free sulfur in the vulcanized rubber composition In addition to the above, a vulcanized rubber composition in which the half width of the diffraction peak in which the zinc sulfide is 28.5 measured by X-ray diffraction in the range of 28.5 ° ± 0.2 ° is 0.5 ° or less.   The vulcanized rubber composition according to claim 1, wherein the rubber composition is blended with a hydrate of an inorganic compound.   The vulcanized rubber composition according to claim 1 or 2, wherein the rubber composition contains 5 to 15 parts by weight of zinc oxide and 2 to 10 parts by weight of sulfur with respect to 100 parts by weight of the diene rubber.   The vulcanized rubber composition according to claim 1, 2 or 3, which is used for a rubber member vulcanized and bonded to a metal member.   A pneumatic tire having a reinforced rubber layer in which a steel cord is coated with the vulcanized rubber composition according to claim 1.