JP4518195B2 - Manufacturing method of natural rubber masterbatch - Google Patents

Description

  The present invention relates to a method for producing a natural rubber masterbatch, and more specifically, in a method for producing a natural rubber masterbatch by drying a mixture of a natural rubber latex and a silica slurry, the hysteresis loss of the natural rubber masterbatch is reduced. The present invention relates to a method for producing a natural rubber masterbatch.

  In recent years, rubber compositions that constitute pneumatic tires are required to improve fuel efficiency performance by reducing hysteresis loss. In order to improve such required performance, the rubber masterbatch blended in the rubber composition is also required to have a performance for reducing hysteresis loss.

As a countermeasure, Patent Document 1 proposes a method for producing a natural rubber masterbatch by mixing natural rubber latex and silica, heat-treating them, and then removing water. However, even the natural rubber masterbatch obtained by this production method has been insufficient in the effect of reducing the hysteresis loss and improving the fuel efficiency.
JP 2005-179436 A

  An object of the present invention is to reduce the viscosity of a natural rubber masterbatch and reduce the hysteresis loss in a method for producing a natural rubber masterbatch by drying a mixture of a natural rubber latex and a silica slurry. It is in providing the manufacturing method of.

The method for producing a natural rubber masterbatch of the present invention that achieves the above object is the production of a natural rubber masterbatch in which a natural rubber latex is mixed with a silica slurry in which silica is dispersed in water, and the resulting mixture is dried. in the method, previously the natural rubber latex, a heat treatment at 60 ° C. or higher 90 ° C. temperature below at least one treatment selected micro NamiTeru morphism process or these five minutes so as not to exceed 80 ° C. 5 seconds This is characterized by denaturing the protein in the natural rubber latex and mixing the treated latex with the silica slurry.

  The silica is preferably wet silica, dry silica or colloidal silica. The natural rubber latex may be at least one selected from field latex and concentrated latex.

  The mixed liquid containing the natural rubber latex and the silica slurry may be dried by spraying the mixed liquid into a shock wave atmosphere by pulse combustion. Or it is good to dry the said liquid mixture by solidifying the natural rubber in a liquid mixture and solid-solid-separating a solid component.

  The natural rubber masterbatch obtained by such a method for producing a natural rubber masterbatch can be blended in the rubber composition.

Method for producing a natural rubber master batch of the present invention, prior to mixing the natural rubber latex and silica slurry, heat treatment at the natural rubber latex 60 ° C. or higher 90 ° C. temperature below so as not to exceed 80 ° C. 5 by performing at least one treatment selected micro NamiTeru morphism process or these five minutes seconds. Thus denature proteins in advance the natural rubber latex, the protein in the natural rubber latex through the mixing operation and drying operation Thus, a natural rubber masterbatch with improved silica dispersibility and reduced hysteresis loss can be produced.

  The natural rubber latex used in the present invention is at least one selected from a field latex collected from a rubber tree and filtered, and a concentrated latex obtained by treating the field latex. That is, either field latex or concentrated natural rubber latex may be used, or both may be blended. A concentrated natural rubber latex is preferably used.

Method for producing a natural rubber master batch of the present invention is performed as a pretreatment for mixing and drying the natural rubber latex and silica slurry, heating the natural rubber latex, at least one processing selected micro NamiTeru morphism treatment or al . By performing preheated to natural rubber latex and / or micro NamiTeru morphism processing, thereby increasing the efficiency of modifying proteins by a simple process. In this way, by modifying the protein in the natural rubber latex in advance to reduce the influence of the protein as much as possible during the production of the natural rubber masterbatch, the treated latex and the silica slurry are uniformly mixed and dispersed. The silica is uniformly dispersed in the dried natural rubber masterbatch, and hysteresis loss can be reduced.

In contrast, a mixture obtained by mixing the natural rubber latex and silica slurry, heating, in case of performing a treatment selected either et morphism micro NamiTeru will become difficult to uniformly disperse the natural rubber and silica Natural rubber master batches with low hysteresis loss cannot be produced.

  In the production method of the present invention, the treatment conditions for denaturing the protein by heating the natural rubber latex are preferably mixed and stirred at a temperature of 60 to 90 ° C. for 0.1 to 2.0 hours. When the heating temperature is less than 60 ° C., the protein cannot be sufficiently denatured. If the mixing temperature exceeds 90 ° C., the natural rubber latex may be thermally deteriorated or gelled. When the mixing time is less than 0.1 hour, protein denaturation becomes insufficient. Further, even when the mixing time exceeds 2.0 hours, protein denaturation reaches its peak and productivity decreases.

  In the production method of the present invention, the treatment conditions for denaturing proteins by irradiating the natural rubber latex with microwaves are preferably irradiated with microwaves for 5 seconds to 5 minutes so as not to exceed 80 ° C. In particular, the microwaves may be irradiated for 5 minutes so as not to exceed 80 ° C. If the microwave irradiation time is less than 10 seconds, protein denaturation is insufficient. Moreover, when the time for irradiating microwaves exceeds 10 minutes, productivity deteriorates. In addition, when irradiating microwaves, it is preferable that the processing temperature does not exceed 80 ° C. because the temperature is likely to rise rapidly.

  In the production method of the present invention, a mixed solution is prepared in which a treated latex obtained by modifying a protein in natural rubber latex in advance by the above-described treatment is mixed with a silica slurry. The silica slurry is a suspension in which water is used as a dispersion medium and silica particles are uniformly dispersed. Hysteresis loss can be reduced by blending silica into the natural rubber masterbatch. Moreover, it does not restrict | limit especially as a kind of silica, For example, wet silica, dry silica, or colloidal silica can be illustrated.

  The weight fraction of silica in the silica slurry is preferably 15 to 40% by weight. When the weight fraction of silica in the slurry is less than 15% by weight, the labor for removing moisture from the mixed solution of the silica slurry and the treated latex becomes great. On the other hand, when the weight fraction of silica in the slurry exceeds 40% by weight, the viscosity becomes very high when mixed with the treated latex, and it becomes difficult to adjust the temperature due to insufficient moisture during drying.

  In the production method of the present invention, the method of mixing the treated latex and the silica slurry is not particularly limited as long as the rubber particles in the treated latex and the silica in the silica slurry are uniformly mixed and dispersed. Good.

  In the production method of the present invention, a natural rubber masterbatch is produced by drying a mixed solution containing a natural rubber latex obtained by modifying the protein obtained as described above and a silica slurry. As a drying method used in the present invention, a method of solid-liquid separation and drying a solid component obtained by coagulating natural rubber in a mixed solution or a method of drying a mixed solution by a pulse combustion shock wave drying method is preferable.

  Examples of the method for solid-liquid separation of the solidified solid component include filtration and centrifugation. Examples of the method for drying the obtained solid component include a hot air drying method, a vacuum drying method, a drying method while applying shear, a natural drying method, a freeze coagulation method, and an alcohol coagulation method.

  The pulse combustion shock wave drying method is a drying method in which a mixed liquid containing natural rubber latex and silica slurry is injected into an atmosphere of shock wave by pulse combustion, without applying excessive heat to the rubber particles in the mixed liquid. Since it is dried at a low temperature, the natural rubber can be prevented from thermal degradation and gelation. For this reason, the natural rubber masterbatch which reduced the viscosity and maintained the uniform mixing state of rubber particles and silica can be manufactured.

  The pulse combustion shock wave drying can be performed using a commercially available pulse combustion shock wave drying device (for example, High Palcon manufactured by Partec Co., Ltd.). The drying conditions are such that the frequency of pulse combustion is preferably 50 to 1200 Hz, more preferably 250 to 1000 Hz, and the temperature of the drying chamber for injecting a mixture of natural rubber latex and silica slurry is preferably 40 to 100 ° C., more preferably It is good to make it 50-70 degreeC. By making the conditions of pulse combustion shock wave drying within the above-mentioned range, it is possible to prevent the natural rubber from being thermally deteriorated and gelled, and to dry in a uniform mixed state of the rubber particles and silica in the natural rubber masterbatch. it can.

  In the method for producing a natural rubber masterbatch of the present invention, a concentrated latex is used as a natural rubber latex, a treatment for denaturing proteins in the concentrated latex is performed, and the mixed liquid of the concentrated latex and the silica slurry is used as the pulse combustion shock wave described above. It is particularly preferable to dry by a drying method. By producing in this way, the dispersibility of the silica of the natural rubber masterbatch can be further improved.

  The natural rubber masterbatch obtained by the production method of the present invention can reduce hysteresis loss. The rubber composition containing such a natural rubber masterbatch has excellent characteristics with a small hysteresis loss. In addition to the natural rubber masterbatch, compounding agents such as fillers and additives usually used in tire rubber compositions can be added to the rubber composition. Examples of the filler include silica and other inorganic fillers. Examples of the other inorganic fillers include carbon black, clay, calcium carbonate, talc, mica, aluminum hydroxide, and magnesium carbonate. Examples of additives include vulcanization or modification agents, vulcanization accelerators, zinc white, stearic acid, anti-aging agents, plasticizers, softeners, lubricants, colorants, tackifiers, coupling agents, and the like. be able to. The blending amounts of these fillers and additives can be conventional conventional blending amounts as long as the object of the present invention is not violated.

  The rubber composition obtained by the above is suitable for constituting at least one member of a pneumatic tire. Examples of the constituent member of the pneumatic tire include a tread portion, a sidewall portion, a bead portion, and covering rubber of various reinforcing cords. The rubber member molded by using the rubber composition containing the natural rubber masterbatch of the present invention effectively extracts the characteristics of the natural rubber, uniformly disperses the silica, and has a small hysteresis loss. Can be improved.

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

Manufacture of a natural rubber masterbatch A mixed liquid prepared by mixing natural rubber latex (NR latex, Comparative Example 1) or treated latex (Examples 1 and 2 ) and silica slurry with the composition shown in Table 1 is prepared. Four kinds of natural rubber master batches (Examples 1 and 2 and Comparative Examples 1 and 2) were produced by drying.

Comparative Example 1
Concentrated natural rubber latex (solid component 60 wt%) is used as natural rubber latex, and natural rubber latex and silica slurry are blended so that silica is 60 parts by weight with respect to 100 parts by weight of solid component in natural rubber latex. The mixture was obtained by mixing and homogenizing at room temperature. Next, using the pulse combustion shock wave drying apparatus (participator for high palcon small lab manufactured by Partec Co., Ltd.), the obtained mixed solution is 2 L / hour in the shock wave atmosphere (frequency 1000 Hz, temperature 60 ° C.) by pulse combustion. The natural rubber masterbatch of Comparative Example 1 was produced by spraying at a flow rate of and drying.

Comparative Example 2
The natural rubber masterbatch of Comparative Example 2 was prepared in the same manner as in Comparative Example 1 except that the mixture prepared in Comparative Example 1 was further heated and stirred at a temperature of 80 ° C. for 2 hours. Manufactured.

Example 1
The natural rubber masterbatch of Example 1 modified the protein in the natural rubber latex by heating and stirring the same natural rubber latex as in Comparative Example 1 at 80 ° C. for 1 hour instead of the natural rubber latex in Comparative Example 1. A natural rubber masterbatch was produced in the same manner as in Comparative Example 1 except that the treated latex was used.

Example 2
The natural rubber masterbatch of Example 2 is obtained by subjecting the same natural rubber latex as that of Comparative Example 1 to microwave irradiation treatment for 10 seconds so as not to exceed 80 ° C. instead of the natural rubber latex of Comparative Example 1. A natural rubber masterbatch was produced in the same manner as in Comparative Example 1 except that a treated latex obtained by modifying the protein in the latex was used.

Evaluation of Natural Rubber Masterbatch Four kinds of rubber compositions (Examples 3 and 4 and Comparative Examples) containing the natural rubber masterbatch (referred to as “NR masterbatch” in Table 2) obtained with the formulation shown in Table 2. 3,4) was prepared. In the preparation method, the ingredients other than the vulcanization accelerator and sulfur were weighed, kneaded with a 0.6 L Banbury mixer for 4 minutes, discharged at 130 to 140 ° C. and cooled to room temperature. A vulcanization accelerator and sulfur were added to the kneaded product and mixed using an electric heating roll to produce four types of rubber compositions.
Four types of rubber compositions obtained (Examples 3 and 4 and Comparative Examples 3 and 4) were each vulcanized in a predetermined mold at 160 ° C. for 10 minutes to prepare test pieces, which are shown below. Tan δ was measured by the method.

tan δ
Tan δ of the obtained test piece was measured at a temperature of 60 ° C. under conditions of an elongation deformation strain rate of 10% ± 2% and a frequency of 20 Hz using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. Are shown in Table 2. A smaller tan δ (60 ° C.) at a temperature of 60 ° C. means smaller hysteresis loss and better fuel efficiency.

In addition, the kind of raw material used in Table 1 is shown below.
NR Latex: Concentrated natural rubber latex manufactured by FELTX (treated with a centrifuge so that the amount of solid components is 60% by weight)
Water: Ion exchange water Silica: Aerosil R202 manufactured by Nippon Aerosil Co., Ltd.

In addition, the kind of raw material used in Table 2 is shown below.
Anti-aging agent: NOCRACK MBZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Zinc stearate for industrial use Hua: Zinc oxide type 3 silane coupling agent manufactured by Shodo Chemical Industry Co., Ltd .: Si69 manufactured by Degussa
Carbon black: Dia Black A manufactured by Mitsubishi Chemical Corporation
Aroma oil: Desolex 3 vulcanization accelerator manufactured by Showa Shell Sekiyu KK: Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Insoluble sulfur (20% oil treatment)

Claims (6)

In a method for producing a natural rubber masterbatch, in which a natural rubber latex is mixed with a silica slurry in which silica is dispersed in water, and the resulting mixture is dried . heat treatment at a temperature to denature the proteins of the natural rubber latex by performing at least one treatment selected micro NamiTeru morphism process or these 5 minutes 5 seconds so as not to exceed 80 ° C., the treated latex And a method for producing a natural rubber masterbatch in which the silica slurry is mixed. The method for producing a natural rubber masterbatch according to claim 1 , wherein the silica is wet silica, dry silica, or colloidal silica. The method for producing a natural rubber masterbatch according to claim 1 or 2 , wherein the natural rubber latex is at least one selected from a field latex and a concentrated latex. The method for producing a natural rubber masterbatch according to claim 1, 2 or 3 , wherein the liquid mixture is dried by spraying the liquid mixture into a shock wave atmosphere by pulse combustion. The method for producing a natural rubber masterbatch according to claim 1, 2 or 3 , wherein the liquid mixture is dried by solidifying the natural rubber in the liquid mixture and separating the solid components into solid and liquid. The rubber composition containing the natural rubber masterbatch obtained by the manufacturing method in any one of Claims 1-5 .