JP5394993B2 - COMPOSITE MANUFACTURING METHOD, RUBBER COMPOSITION, AND PNEUMATIC TIRE - Google Patents

Description

The present invention relates to a method for producing a composite, a rubber composition containing the composite, and a pneumatic tire using the rubber composition.

Conventionally, the rolling resistance of tires has been reduced to suppress heat generation and reduce the fuel consumption of vehicles. In recent years, there has been a great demand for low fuel consumption, and there is a great demand for low fuel consumption for treads having a high occupation ratio in tires, and for other members such as sidewalls. In recent years, a reduction in fuel consumption is required not only for passenger car tires but also for heavy duty tires for trucks and buses, and at the same time, it is important to improve wear resistance.

Known methods for satisfying the low heat build-up of the rubber composition include a method using a low reinforcing filler, a method for reducing the content of the reinforcing filler, and the like. However, such low fuel consumption has the problem that the rubber composition's reinforcing properties are reduced, resulting in a decrease in wear resistance and breaking performance. Low fuel consumption (low rolling resistance) and wear resistance and breaking performance are also problems. It is difficult to achieve both.

In addition, when natural rubber is used as a rubber component, Mooney viscosity is higher than other synthetic rubbers and the processability is poor, so usually after adding mastication agent and masticating, and reducing Mooney viscosity used. Therefore, productivity is reduced when natural rubber is used. Moreover, since the molecular chain of natural rubber is cleaved by mastication, there is a problem that the characteristics (excellent wear resistance performance, low fuel consumption performance, rubber strength, etc.) of the inherent high molecular weight polymer are lost.

Patent Document 1 discloses a method for producing a composite by mixing rubber latex with fine particle silica produced from water glass in a liquid state. However, only a production method in which silica is dispersed in rubber using a substantially natural rubber latex is disclosed here. In addition, there is room for improvement in terms of improving fuel economy, wear resistance, and fracture performance in a well-balanced manner while having excellent processability.

JP 2009-51955 A

An object of the present invention is to solve the above-mentioned problems and to provide a method for producing a composite that can improve the fuel economy, wear resistance, and fracture performance in a well-balanced manner while having excellent workability. Moreover, it aims at providing the rubber composition containing the composite_body | complex obtained by this manufacturing method, and a pneumatic tire using the same.

The present invention includes a step (I) of preparing a compounded latex by mixing a saponified natural rubber latex and a carbon black dispersion, a step (II) of coagulating the compounded latex obtained in the step (I), and The present invention relates to a method for producing a composite comprising the step (III) of washing the coagulated product obtained in the step (II) and adjusting the phosphorus content in the rubber to 200 ppm or less.

The saponified natural rubber latex is preferably obtained by saponifying natural rubber latex with an alkali in the presence of a surfactant.

The present invention relates to a composite obtained by the above production method.
The present invention relates to a rubber composition containing a composite obtained by the above production method.
The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, after coagulating a compounded latex prepared by mixing a saponified natural rubber latex and a carbon black dispersion, the resulting coagulated product has a phosphorus content of 200 ppm or less. Since it is a manufacturing method which wash | cleans until it becomes, when the composite body prepared by this manufacturing method is used for the rubber composition for tires, low-fuel-consumption property, abrasion resistance, and destruction performance can be improved with good balance. Therefore, a pneumatic tire excellent in these performances can be provided by using the rubber composition for a tire member such as a tread.

In addition, since the obtained composite is excellent in processability, good processability can be obtained without performing a kneading step in advance in the production of a rubber composition using the composite. Therefore, the molecular chain of natural rubber can be prevented from being broken by mastication, and the characteristics of the inherent high molecular weight polymer can be maintained, so that more excellent fuel economy, wear resistance, and breaking performance can be obtained.

<Method for producing composite>
The method for producing a composite of the present invention includes a step (I) of preparing a blended latex by mixing a saponified natural rubber latex and a carbon black dispersion, and a step of coagulating the blended latex obtained in the step (I). This is a production method including (II) and the step (III) of washing the coagulated product obtained in the step (II) and adjusting the phosphorus content in the rubber to 200 ppm or less. That is, first, a natural rubber latex subjected to a saponification treatment and a dispersion in which carbon black is dispersed in water are prepared, and then the latex and the dispersion are mixed in a liquid state to form a compounded latex (mixed solution). ) And coagulated, the resulting coagulated product is washed to reduce the amount of phosphorus in natural rubber, thereby producing a composite containing modified natural rubber (HPNR) with a phosphorus content of 200 ppm or less Has been. For this reason, a composite in which carbon black is uniformly dispersed in modified natural rubber (HPNR) can be produced.

(Process (I))
The saponified natural rubber latex used in step (I) can be prepared by saponifying natural rubber latex with an alkali. The saponification treatment can be performed by adding an alkali and, if necessary, a surfactant to natural rubber latex and allowing to stand at a predetermined temperature for a predetermined time. In addition, you may perform stirring etc. as needed. When the saponification treatment is performed, the phosphorus compound separated by saponification in the step (III) described later is washed and removed, so that the phosphorus content in the natural rubber contained in the prepared composite can be suppressed. Moreover, since the protein in the natural rubber is decomposed by the saponification treatment, the nitrogen content of the natural rubber can be suppressed. In the present invention, alkali can be added to natural rubber latex for saponification, but by adding it to natural rubber latex, there is an effect that saponification can be efficiently performed.

Natural rubber latex is collected as sap of heavy trees and contains rubber, water, proteins, lipids, inorganic salts, etc., and the gel content in rubber is thought to be based on the complex presence of various impurities. . In the present invention, raw latex produced by tapping heavy trees or purified latex concentrated by centrifugation can be used. Furthermore, high ammonia latex to which ammonia is added by a conventional method may be used to prevent the progress of decay due to bacteria present in the raw rubber latex and to avoid coagulation of the latex.

Examples of the alkali used for the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, and an amine compound. From the viewpoint of the effect of the saponification treatment and the influence on the stability of the natural rubber latex, it is particularly hydroxylated. Sodium or potassium hydroxide is preferably used.

The amount of alkali added is not particularly limited, but the lower limit is preferably 0.1 parts by mass or more and more preferably 0.3 parts by mass or more with respect to 100 parts by mass of the solid content of the natural rubber latex. The upper limit of the addition amount is preferably 12 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less. If the amount of alkali added is less than 0.1 parts by mass, saponification may take time. Conversely, if the amount of alkali added exceeds 12 parts by mass, the natural rubber latex may be destabilized.

As the surfactant, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant and the like can be used. Examples of the anionic surfactant include carboxylic acid-based, sulfonic acid-based, sulfate ester-based and phosphate ester-based anionic surfactants. Examples of nonionic surfactants include nonionic surfactants such as polyoxyalkylene ethers, polyoxyalkylene esters, polyhydric alcohol fatty acid esters, sugar fatty acid esters, and alkyl polyglycosides. Examples of amphoteric surfactants include amphoteric surfactants such as amino acid type, betaine type, and amine oxide type. Among these, an anionic surfactant is preferable, and a sulfonic acid anionic surfactant is more preferable.

The addition amount of the surfactant is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 1.1 parts by mass or more with respect to 100 parts by mass of the solid content of the natural rubber latex. preferable. The upper limit of the addition amount is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, and further preferably 3.5 parts by mass or less. If it is less than 0.01 parts by mass, the natural rubber latex may become unstable during the saponification treatment. On the other hand, if it exceeds 6.0 parts by mass, the natural rubber latex may become too stable and it may become difficult to coagulate.

The temperature of the saponification treatment can be appropriately set within a range where the saponification reaction with alkali can proceed at a sufficient reaction rate and within a range where the natural rubber latex does not undergo alteration such as coagulation, but is usually 20 to 70 ° C. Preferably, 30-70 degreeC is more preferable. Further, the treatment time is 3 to 48 hours in consideration of both sufficient treatment and productivity improvement, depending on the treatment temperature when the treatment is performed with natural rubber latex standing. Is preferable, and 3 to 24 hours is more preferable.

In step (I), a carbon black dispersion is used. That is, not a dry carbon black powder but a dispersion (slurry) in which carbon black is dispersed in water is used. By using the above dispersion liquid, a rubber reinforcing effect can be obtained, and excellent wear resistance and fracture performance can be obtained.

The carbon black dispersion can be produced by a known method, and is not particularly limited. For example, the carbon black dispersion can be prepared using a high-pressure homogenizer, an ultrasonic homogenizer, a colloid mill, or the like. Specifically, the dispersion can be prepared by adding water to a colloid mill, adding carbon black while stirring, and then circulating with a surfactant using a homogenizer. The amount of carbon black added to the dispersion is not particularly limited, but is preferably 0.5 to 30% by weight, more preferably 2 to 2%, from the viewpoint of uniform dispersibility in the dispersion (100% by weight). 10 mass% is preferable.

Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, more preferably 50 m ² / g or more, and still more preferably 70 m ² / g or more, from the viewpoint that sufficient reinforcement can be obtained. Also, _N 2 SA of carbon black is from the viewpoint of excellent low heat build-up (fuel economy), preferably from 200 meters ² / g or less, more preferably ^{150m 2 / g, 125m 2 /} g or less is more preferable. In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

The dibutyl phthalate oil absorption (DBP) of carbon black is preferably 50 ml / 100 g or more, more preferably 80 ml / 100 g or more, and still more preferably 90 ml / 100 g or more, from the viewpoint that sufficient reinforcing properties can be obtained. Further, the DBP of carbon black is preferably 200 ml / 100 g or less, more preferably 150 ml / 100 g or less, and still more preferably 125 ml / 100 g or less, from the viewpoint of low elongation at break (Eb). In addition, DBP of carbon black is calculated | required by the measuring method of JISK6217-4.

From the viewpoint of dispersibility, it is preferable to add a surfactant to the carbon black dispersion as described in the method for producing the dispersion. Examples of the surfactant that can be added include those described in the above saponification treatment. In addition, in the preparation of the dispersion, the amount of the surfactant added is not particularly limited, but is preferably 0.01 to 0.2 mass from the viewpoint of uniform dispersibility of the carbon black in the dispersion (100 mass%). %, And more preferably 0.03 to 0.1% by mass.

In step (I), the saponified natural rubber latex and the carbon black dispersion are mixed by a known method, and then the mixed latex is mixed sufficiently by stirring until the mixed latex becomes a uniform solution. Can be prepared.
The saponified natural rubber latex preferably has a rubber solid content of 10 to 70% by mass.

Moreover, in the said mixing process, it is preferable to mix a carbon black dispersion liquid so that carbon black may be 5-150 mass parts with respect to 100 mass parts (solid content) of modified natural rubber in the composite obtained. If the amount is less than 5 parts by mass, the amount of carbon black may be reduced when used as a master batch. When it exceeds 150 parts by mass, it is difficult to obtain uniform dispersion of carbon black in the compounded latex, and the uniform dispersion of carbon black in the rubber composition tends to be lowered. More preferably, it is 10-120 mass parts, More preferably, it is 30-90 mass parts.

(Process (II))
In step (II), the blended latex obtained in step (I) is coagulated (aggregated). The coagulation of the compounded latex includes acid coagulation, salt coagulation, methanol coagulation and the like, but acid coagulation, salt coagulation, or a combination thereof is preferable in order to coagulate the rubber latex and carbon black by uniform dispersion. Examples of the acid for coagulation include sulfuric acid, hydrochloric acid, formic acid, acetic acid and the like. Examples of the salt include 1 to 3 metal salts (calcium salts such as sodium chloride, magnesium chloride, calcium nitrate, and calcium chloride).

Especially, coagulation | solidification of mixing | blending latex adjusts the pH of mixing | blending latex to 5-9 (preferably 6-8, more preferably 6.5-7.5) by addition of an acid or a salt, and solidifies solid content. It is preferable to be implemented.

(Step (III))
In step (III), the coagulated product (aggregate containing agglomerated rubber and carbon black) obtained in step (II) is washed, and the phosphorus content in the rubber (natural rubber) is adjusted (reduced) to 200 ppm or less. . By performing the washing treatment after the saponification treatment, the amount of phosphorus in the natural rubber in the coagulated product can be reduced to 200 ppm or less. Examples of the washing method in the step (III) include a method of diluting a rubber component with water and then centrifuging, or a method of standing still to float the rubber and discharging only the aqueous phase. When centrifuging, it may be first diluted with water so that the rubber content of the natural rubber latex is 5 to 40% by mass, preferably 10 to 30% by mass, and then centrifuged at 5000 to 10000 rpm for 1 to 60 minutes. The washing may be repeated until the desired phosphorus content is reached. Also, when the rubber is floated by standing, the addition of water and stirring may be repeated until the desired phosphorus content is obtained.

After washing, it is usually dried by a known method (such as an oven). When the rubber is kneaded with a biaxial roll or Banbury after drying, a composite containing modified natural rubber (HPNR) having a phosphorus content of 200 ppm or less and carbon black is obtained. In the above composite, carbon black is uniformly dispersed in a rubber matrix and can be used as a master batch. In addition, the said composite_body | complex may contain another component in the range which does not inhibit the effect of this invention.

The modified natural rubber contained in the composite has a phosphorus content of 200 ppm or less. If it exceeds 200 ppm, the Mooney viscosity will increase during storage and the processability will deteriorate, and excellent fuel efficiency will not be obtained, and there will be a tendency that the performance and wear resistance and fracture performance cannot be improved in a well-balanced manner. The phosphorus content is preferably 150 ppm or less, more preferably 100 ppm or less. Here, the phosphorus content can be measured by a conventional method such as ICP emission analysis. Phosphorus is derived from phospholipids (phosphorus compounds).

The nitrogen content of the modified natural rubber contained in the composite is preferably 0.3% by mass or less, more preferably 0.15% by mass or less. If it exceeds 0.3% by mass, the Mooney viscosity will increase during storage, resulting in poor processability, and excellent fuel efficiency will not be obtained, and there is a tendency that the performance and wear resistance and fracture performance cannot be improved in a balanced manner. There is. Nitrogen is derived from proteins. The nitrogen content can be measured by a conventional method such as Kjeldahl method.

The modified natural rubber contained in the composite preferably has a gel content of 20% by mass or less, more preferably 10% by mass or less, measured as a toluene insoluble component in the solid content. If it exceeds 20% by mass, the Mooney viscosity tends to increase and the processability tends to deteriorate. The gel content means a value measured as an insoluble content with respect to toluene which is a nonpolar solvent, and may be simply referred to as “gel content” or “gel content” below. The measuring method of the content rate of a gel part is as follows. First, a natural rubber sample is soaked in dehydrated toluene, light-shielded in the dark and left for 1 week, and then the toluene solution is centrifuged at 1.3 × 10 ⁵ rpm for 30 minutes to obtain an insoluble gel content and a toluene soluble content. Isolate. Methanol is added to the insoluble gel and solidified, and then dried, and the gel content is determined from the ratio between the mass of the gel and the original mass of the sample.

<Rubber composition>
The rubber composition of this invention contains the composite_body | complex obtained by the said manufacturing method. Since a composite in which carbon black is uniformly dispersed in HPNR is used, similarly, a rubber composition in which carbon black is uniformly dispersed can be obtained. For this reason, low fuel consumption, wear resistance, and fracture performance can be improved in a balanced manner.

The rubber composition of the present invention may contain a rubber component other than the modified natural rubber. Examples of other rubber components include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), Examples include chloroprene rubber (CR) and acrylonitrile butadiene rubber (NBR).

About the rubber component (modified natural rubber and other rubber components in the composite) contained in the rubber composition, the content of the modified natural rubber (solid content) contained in the composite in 100% by mass of the rubber component The amount is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. If it is less than 60% by mass, sufficient fuel efficiency and wear resistance may not be obtained.

In the rubber composition, the carbon black content (the total content of carbon black blended in the composite and other carbon black used) is preferably 5 parts by mass with respect to 100 parts by mass of the rubber component. As mentioned above, More preferably, it is 10 mass parts or more, More preferably, it is 30 mass parts or more. If it is less than 5 parts by mass, sufficient reinforcement may not be obtained. The carbon black content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 90 parts by mass or less. If it exceeds 150 parts by mass, sufficient fuel efficiency and wear resistance may not be obtained.

In addition to the above materials, the rubber composition of the present invention includes silica, silane coupling agents, zinc oxide, stearic acid, anti-aging agents, sulfur, vulcanization accelerators and the like that are commonly used in the tire industry. These various materials may be appropriately blended.

As a method for producing the rubber composition of the present invention, known methods can be used. For example, the above components are kneaded using a rubber kneader such as an open roll, a Banbury mixer, a closed kneader, and then added. It can be manufactured by a method of sulfurating. When producing a rubber composition containing natural rubber, a natural rubber mastication step is usually performed before the kneading step of each component such as a rubber component and a filler. In the present invention, since the above composite is used, the kneading step can be carried out satisfactorily without performing the kneading step, and a desired rubber composition can be produced (particularly, NR ( If it does not contain unmodified)).

The rubber composition can be applied to each member of a tire, and among them, it can be suitably used for a tread and a sidewall.

<Pneumatic tire>
The rubber composition of the present invention is suitably applied to a pneumatic tire. In this case, since a composite in which carbon black is uniformly dispersed in HPNR is used, low heat build-up, wear resistance, and fracture performance can be improved in a balanced manner.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, a rubber composition containing various additives as necessary is extruded in accordance with the shape of each member of the tire at an unvulcanized stage and molded by a normal method on a tire molding machine. After forming an unvulcanized tire by heating, the tire can be manufactured by heating and pressing in a vulcanizer.

Moreover, the pneumatic tire of the present invention can be suitably used for passenger cars, trucks and buses, and low-pollution vehicles (eco-cars) compatible with global environmental conservation.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.
The various chemicals used in the examples are described below.
Natural rubber latex: Field latex obtained from Taitex Co., Ltd. Surfactant (1): Emar E-70C (polyoxyethylene lauryl ether sodium sulfate) manufactured by Kao Corporation
Surfactant (2): Demol N (sodium salt of β-naphthalenesulfonic acid formalin condensate) manufactured by Kao Corporation
NaOH: NaOH manufactured by Wako Pure Chemical Industries, Ltd.
Natural rubber: TSR
Carbon black (1): N220 manufactured by Cabot Japan Co., Ltd. (N ₂ SA: 120 m ² / g, DBP: 114 ml / 100 g)
Carbon Black (2): Dia Black H (N330, N ₂ SA: 79 m ² / g, DBP: 100 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Anti-aging agent manufactured by NOF Corporation: Nocrack 6C (N- (1,3- Dimethylbutyl) -N′-phenyl-p-phenylenediamine)
Sulfur: Powder sulfur vulcanization accelerator NS manufactured by Tsurumi Chemical Co., Ltd. NS: Noxeller NS (N-tetra-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

(Preparation of saponified natural rubber latex with alkali)
After adjusting the solid content concentration (DRC) of natural rubber latex to 30% (w / v), 10 g of Emar E-70C and 20 g of NaOH are added to 1000 g of natural rubber latex, and saponification reaction is performed at room temperature for 48 hours. Natural rubber latex was obtained.

(Production of saponified natural rubber (solid rubber))
After adding water to the saponified natural rubber latex obtained above to adjust the solid content concentration (DRC) to 15% (w / v), formic acid is added while slowly stirring to adjust the pH to 4.0-4. .5 and agglomerated. The agglomerated rubber was pulverized, washed repeatedly with 1000 ml of water, and then dried at 110 ° C. for 2 hours to obtain a solid rubber (saponified natural rubber).

(Preparation of carbon black dispersion (1))
A colloid mill with a rotor diameter of 30 mm was charged with 1425 g of deionized water and 75 g of carbon black (1) (N220), and stirred for 10 minutes at a rotor-stator interval of 1 mm and a rotation speed of 2000 rpm. Next, demole N (anionic surfactant) was added to a concentration of 0.05% by mass, and the mixture was circulated three times using a pressure type homogenizer to prepare dispersion (1).

(Preparation of carbon black dispersion (2))
A colloid mill with a rotor diameter of 30 mm was charged with 1425 g of deionized water and 75 g of carbon black (2) (N330), and stirred for 10 minutes at a rotor-stator interval of 1 mm and a rotation speed of 2000 rpm. Next, demole N (anionic surfactant) was added to a concentration of 0.05% by mass, and the mixture was circulated three times using a pressure homogenizer to prepare dispersion (2).

(Preparation of compounded latex, coagulation, preparation of composite)
Saponified natural rubber latex or natural rubber latex was mixed with the carbon black dispersions (1) to (2) in the compounding amounts as shown in Table 1 to prepare compounded latex. After sufficiently stirring until the blended latex became uniform, the blended latex was adjusted to pH 7 with sulfuric acid and coagulated. The obtained coagulated product (solid material) was filtered to collect a rubber component, and repeatedly washed with 1000 ml of water, and then dried at 110 ° C. for 2 hours to obtain composites (A) to (H).

The modified natural rubber included in the composites (A) to (D), the natural rubber included in (E) to (H), the saponified natural rubber (solid rubber), and the TSR are subjected to nitrogen by the following method. Content, phosphorus content, and gel content were measured.
The results are shown in Table 2.

(Measurement of nitrogen content)
The nitrogen content was measured using CHN CORDER MT-5 (manufactured by Yanaco Analytical Industries). For the measurement, first, a calibration curve for determining the nitrogen content was prepared using antipyrine as a standard substance. Next, about 10 mg of each composite, saponified natural rubber or TSR sample was weighed, and an average value was obtained from the measurement results of three times to obtain the nitrogen content of the sample.

(Measurement of phosphorus content)
The phosphorus content was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation).

(Measurement of gel content)
A raw rubber sample 70.00 mg cut to 1 mm × 1 mm was weighed, 35 mL of toluene was added thereto, and the mixture was allowed to stand in a cool dark place for 1 week. Subsequently, centrifugation was performed to precipitate a gel component insoluble in toluene, the soluble component of the supernatant was removed, and only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (%) was determined by the following formula.
Gel content (mass%) = [mass mg after drying / mg of initial sample] × 100

As shown in Table 2, the HPNR forming the composites (A) to (D) has a reduced phosphorus content, nitrogen content, and gel content compared to the composites (E) to (H). It was.

(Production of rubber test piece)
In accordance with the formulation shown in Table 3, 1.7 L Banbury was used to knead chemicals other than sulfur and a vulcanization accelerator. Next, using a roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized product.
In Comparative Examples 5 to 6 using TSR, 0.4 part by mass of a peptizer was added to 100 parts by mass of the rubber component of TSR, and mastication was performed in advance using a 1.7 L Banbury mixer. It was. On the other hand, natural rubber was not masticated in the examples and other comparative examples.
Each obtained unvulcanized rubber composition and vulcanized product were evaluated as follows, and the results are shown in Table 3.

(Measurement of Mooney viscosity)
About the obtained unvulcanized rubber composition, it measured at 130 degreeC according to the measuring method of the Mooney viscosity based on JISK6300. The Mooney viscosity (ML _{1 + 4} ) of Comparative Example 5 was set to 100, and indexed by the following formula (Mooney viscosity index). The larger the index, the lower the Mooney viscosity and the better the processability.
(Mooney viscosity index) = (ML _{1 + 4} of Comparative Example 5) / (ML _{1 + 4 of} each formulation) × 100

(Rolling resistance)
Loss tangent (tan δ) of each compound (vulcanized product) using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of a temperature of 50 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. Was measured, and the loss coefficient tan δ of Comparative Example 5 was taken as 100 and expressed as an index according to the following formula (rolling resistance index). The larger the index, the better the rolling resistance characteristics.
(Rolling resistance index) = (tan δ of Comparative Example 5) / (tan δ of each formulation) × 100

(Abrasion test)
Using a Lambourn abrasion tester, the Lambourn abrasion amount was measured under the conditions of a temperature of 20 ° C., a slip ratio of 20% and a test time of 2 minutes. Further, the volume loss amount was calculated from the measured lamborn wear amount, and the volume loss amount of each compound (vulcanized product) was displayed as an index according to the following calculation formula with the lamborn wear index of Comparative Example 5 being 100. In addition, it shows that it is excellent in abrasion resistance, so that a Lambourn abrasion index is large.
(Lambourn wear index) = (volume loss amount of Comparative Example 5) / (volume loss amount of each formulation) × 100

(Rubber strength)
A vulcanized product was used to prepare a No. 3 dumbbell-shaped rubber test piece, which was subjected to a tensile test according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. The time elongation (EB) was measured, and the product (TB × EB) was calculated. The rubber strength (TB × EB) of each compounding (vulcanized product) was indicated by an index by the following calculation formula with TB × EB of Comparative Example 5 being 100. In addition, it shows that it is excellent in fracture performance, so that a rubber | gum strength index is large.
(Rubber strength index) = (TB of each formulation × EB) / (TB of comparative example 5 × EB) × 100

From the results in Table 3, the rubber composition using the composite containing the modified natural rubber and carbon black having a low phosphorus content in Examples 1 to 4 is usually obtained by using the rubber and carbon black that have broken TSR. Compared to the rubber compositions of Comparative Examples 5 to 6 produced in the kneading step, the processability was excellent and the fuel efficiency was excellent, although not cheated.

In the examples, since the composite was produced by the above-described production method, the dispersibility of the carbon black was greatly improved, and the wear resistance and fracture performance were significantly improved. Moreover, compared with the rubber composition of the comparative examples 7-8 produced by the normal kneading | mixing process using saponified natural rubber and carbon black, abrasion resistance performance and fracture performance were improving significantly. Furthermore, all the performances were excellent even when compared with the rubber compositions of Comparative Examples 1 to 4 using a composite obtained from a compounded latex obtained by mixing a normal natural rubber latex and a carbon black dispersion.

Claims (7)

A step (I) of preparing a compounded latex by mixing a saponified natural rubber latex and a carbon black dispersion, a step (II) of coagulating the compounded latex obtained in the step (I), and the step (II) The manufacturing method of the composite_body | complex including process (III) which wash | cleans the solidified material obtained by 1 and adjusts phosphorus content in rubber | gum to 200 ppm or less. The method for producing a composite according to claim 1, wherein the saponified natural rubber latex is obtained by saponifying natural rubber latex with an alkali in the presence of a surfactant. The composite_body | complex obtained by the manufacturing method of Claim 1 or 2. A rubber composition comprising a composite obtained by the production method according to claim 1. A pneumatic tire produced using the rubber composition according to claim 4. A step (I) of preparing a compounded latex by mixing a saponified natural rubber latex and a carbon black dispersion, a step (II) of coagulating the compounded latex obtained in the step (I), and the step (II) A method for producing a rubber composition comprising the step (III) of washing the coagulated product obtained in step 1 and adjusting the phosphorus content in the rubber to 200 ppm or less. A step (I) of preparing a compounded latex by mixing a saponified natural rubber latex and a carbon black dispersion, a step (II) of coagulating the compounded latex obtained in the step (I), and the step (II) The manufacturing method of a pneumatic tire including the process (III) which wash | cleans the solidified material obtained by this, and adjusts phosphorus content in rubber | gum to 200 ppm or less.