JP5164384B2 - Processed powder rubber, rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a processed powder rubber, a rubber composition containing the processed powder rubber, and a pneumatic tire using the rubber composition. Particularly, the scattering property is low, the handling is good, and the processability of the rubber composition is impaired. The present invention relates to a processed powder rubber that maintains high fracture characteristics and can improve the recycling of rubber products such as used tires.

  Waste tires have a higher recovery rate than ordinary plastic products, and are reused as fuel, especially in cement factories. However, in recent years, with increasing environmental problems, there has been a demand for an improvement in the so-called material recycling rate in which tire rubber pieces or rubber powders are used as they are. However, when powder rubber itself is simply blended with new rubber, an increase in the viscosity of the blend cannot be avoided. In particular, when the blending amount of the powder rubber is increased, since the processability of the blend is markedly deteriorated, the blending amount must be limited to a very small amount.

  On the other hand, heat desulfurization treatment of powdered rubber by an oil pan method is known as a technique for avoiding deterioration of workability. However, in this method, since it is usual to heat-desulfurize the powdered rubber after roll pulverization as it is, a decrease in physical properties is inevitable. Accordingly, it is extremely difficult to achieve both workability and physical properties (destructive properties) for powder rubber or recycled rubber that is currently on the market.

  In JP 2001-89601 A and JP 2001-89603 A, a rubber composition containing recycled rubber pulverized by a specific twin-screw extruder or a composition containing roll pulverized recycled rubber has sheet processability and breaking characteristics. However, in any case, in order to ensure sufficient workability, it is essential to make the crushed rubber into a vulcanized master batch.

JP 2001-89601 A JP 2001-89603 A

  However, when the pulverized rubber is used as a vulcanized master batch, it is generally necessary to add the vulcanized master batch in the step of kneading with the vulcanizing agent, and there are restrictions on the upper limit of the kneading step and the kneading temperature. Here, if the kneading temperature in the process of kneading with the vulcanizing agent is increased more than necessary, problems such as scorch and burns occur during kneading. On the other hand, when considering the dispersibility of the reclaimed rubber in the new rubber, it is desirable to blend the reclaimed rubber in the step of kneading the polymer or filler that is generally at a higher kneading temperature than the step of kneading with the vulcanizing agent, It is difficult to implement it with a vulcanized masterbatch.

  In addition, in Japanese Patent Application No. 2005-176386, the present applicant has proposed a method for producing a fine rubber powder. By using this method, a fine rubber having sufficient characteristics can be obtained. Because of the diameter, the rubber powder rises during weighing and kneading, which is not preferable in terms of the working environment. In general, the raw material of fine powder such as carbon black is granulated to improve the working environment.

  Furthermore, conventional powdered rubber is powdery and has a low density, so it takes a lot of time to put it into the tank of the factory, and it may be clogged with piping when it is put into the tank. Can be. Furthermore, since the conventional rubber powder is powdery, it takes time to weigh, and after weighing, when it is put into the kneader, it is sucked up by the dust absorber and blended with a mass different from the measured value. Since the mass is not constant, the physical properties of the compounded rubber also vary.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and in the process of kneading the polymer and filler, it can be blended without problems, handling is improved compared to conventional powdered rubber, The object is to provide a new material derived from recycled rubber that can improve the working environment and can improve the recycling of rubber products such as used tires. Another object of the present invention is to provide a rubber composition containing such a new rubber-based material and having improved processability while maintaining high fracture characteristics, and a pneumatic tire using the rubber composition. There is.

  As a result of intensive studies to achieve the above object, the present inventor, as a result of processing fine powder of powdered rubber obtained by pulverizing waste rubber by a conventional method, by adding oil and combining it with good handling It has been found that the use of rubber can improve the working environment, and the rubber composition containing such processed powdered rubber has improved processability and has high fracture characteristics and wear resistance. The invention has been completed.

That is, the processed powder rubber of the present invention is obtained by adding oil to fine powder rubber ,
The powdered rubber contains 50% by mass or more of a rubber that has passed through a 100 mesh sieve by subjecting it to a fine particle size treatment .

  In the processed powder rubber of the present invention, the oil is preferably a process oil, and the process oil is selected from the group consisting of a process oil for naphthenic rubber, a process oil for paraffinic rubber, and a process oil for aromatic rubber. It is preferable that it is at least one kind. The amount of oil added is preferably in the range of 5 to 50% by mass.

Oite the machining dust rubber of the present invention, the powder rubber raw material preferably contains fine diameter handle 200 mesh sieve 50 mass% or more of those passing through the by subjecting, at least 75 wt% It is more preferable to contain.

Further, the rubber composition of the present invention is characterized in that the processed powder rubber is blended in an amount of 20 parts by mass or less with respect to 100 parts by mass of the new rubber, and the pneumatic tire of the present invention comprises such a rubber composition. It is used.

  According to the present invention, processed powder that has low scattering properties, good handling, can maintain high fracture characteristics without impairing the processability of the rubber composition, and can improve the recycling of rubber products such as used tires. Rubber can be provided. Moreover, according to this invention, the pneumatic tire using the rubber composition containing this processed rubber | gum rubber and this rubber composition can be provided. In addition, the processed powder rubber of the present invention can be blended without any problem even in the step of kneading the polymer or filler. Moreover, according to the processed rubber powder of the present invention, productivity can be improved because it is possible to prevent clogging with piping or the like when being charged into the tank while shortening the time for charging into the tank of the factory. Furthermore, according to the processed powder rubber of the present invention, it is possible to blend with a mass close to the measured value while shortening the measurement time, and the mass becomes constant, so that the physical properties of the rubber composition to be manufactured Can be suppressed.

  The present invention is described in detail below. The processed powder rubber of the present invention is characterized by adding oil to fine powder rubber. The rubber type of the waste rubber used as a raw material for the powder rubber used in the present invention is not particularly limited as long as it contains at least one selected from natural rubber and synthetic rubber. The synthetic rubber is preferably a diene rubber such as cis-1,4-polyisoprene, styrene-butadiene copolymer, low cis-1,4-polybutadiene, high cis-1,4-polybutadiene, or ethylene-propylene. -Diene copolymer, chloroprene rubber, halogenated butyl rubber, acrylonitrile-butadiene rubber and the like.

  Normally, waste rubber (vulcanized rubber), which is the raw material for powder rubber, includes silane coupling agents, sulfur, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids that are commonly used in the rubber industry, Antioxidants, antiozonants, antioxidants, process oils, zinc white (ZnO), stearic acid, peroxides, and the like are blended.

  In the present invention, not only powdered rubber obtained by pulverizing waste tires and tubes made of such vulcanized rubber by conventional methods, but also unvulcanized scrap generated during tire production, spew generated during tire vulcanization. It is also possible to use rubber powder obtained by pulverizing a piece or the like.

The powder rubber used as a raw material for the processed powder rubber of the present invention is subjected to a fine particle size treatment . Here, the method for reducing the particle size of the powdered rubber is not particularly limited, and examples thereof include freeze pulverization and millstone pulverization. As a particularly preferable method for reducing the particle size, disclosed in Japanese Patent Application No. 2005-176408 is (i) a coarse pulverization step in which a pulverized rubber raw material is processed into coarse pulverized rubber by coarse pulverization means, and (ii) the coarse pulverization step. A fine pulverization step in which the pulverized rubber is processed into fine pulverized rubber by means of fine pulverization equipped with a fine pulverization roll; and (iii) impact is applied to the rubber particles contained in the finely pulverized rubber and connected to each other by a separator. And a separation process method including a separation step of applying force and forcibly separating to a finely pulverized rubber.

Flour rubber subjected to the fine-diameter treatment preferably contains those passing through the sieve of 100 mesh contains more than 50 wt%, 200 that passed through the sieve of mesh 50 wt%, 200 mesh It is more preferable to contain 75% by mass or more of what has passed through the sieve.

  If 50% by mass or more of powder rubber that has passed through a 100-mesh sieve is present, there is little possibility of becoming a fracture nucleus, and the effect of suppressing the reduction in fracture strength is great. In addition, when 50% by mass or more of the rubber powder that has passed through a 200-mesh sieve is contained, the possibility of becoming a fracture nucleus is extremely reduced, which is extremely effective for suppressing a decrease in fracture strength. Further, when 75% by mass or more of the rubber powder that has passed through a 200 mesh sieve is contained, there is almost no effect on the breaking strength of the rubber composition as compared to a rubber composition to which no processed rubber powder is added. .

  As the powder rubber becomes finer in this way, the influence on the physical properties of the rubber becomes smaller, but there is a concern that the working environment will deteriorate due to the influence of dust. Therefore, in the present invention, oil can be added to the powdered rubber whose particle size has been reduced, and scattering of the fine powdered rubber can be suppressed by the oil. Moreover, by adding oil to the fine rubber powder, handling is improved, dust can be suppressed, and the working environment can be improved.

  Here, the amount of oil added to the rubber powder is preferably in the range of 5 to 50% by mass. If the amount of oil added is less than 5% by mass, the effect of suppressing dust is small. On the other hand, if the amount of oil added exceeds 50% by mass, it is not preferable from the viewpoint of improving the material recycling rate of waste tires.

  As the oil, a process oil is preferable, and as the process oil, a process oil for naphthenic rubber, a process oil for paraffinic rubber, and a process oil for aromatic rubber are preferable. These oils may be used alone or in combination of two or more.

Further, the rubber composition of the present invention is to provide new rubber 100 parts by weight, by blending the machining dust rubber above 20 parts by mass or less. Since the rubber composition of the present invention contains the above-described processed powder rubber derived from rubber products such as used tires, the material recycling rate can be improved. In addition, when the processed powder rubber is used in a rubber composition, the working environment can be improved as compared with the case where a conventional powder rubber is used, and the breaking strength and wear resistance of the rubber composition can also be improved. . Furthermore, when the above processed powder rubber is used in the rubber composition, the processing powder rubber can be charged into the tank of the factory in a short time, and the processed powder rubber is not clogged by piping or the like when it is charged into the tank. The productivity of the composition can be improved. Furthermore, when the processed powder rubber is used in the rubber composition, the processing powder rubber can be measured in a short time, and the processed powder rubber can be blended with the rubber composition in a mass close to the measured value. Since it becomes fixed, the variation in the physical property of the rubber composition manufactured can be suppressed. In addition, when the compounding amount of the processed powder rubber exceeds 20 parts by mass with respect to 100 parts by mass of the new rubber, the fracture characteristics of the rubber composition may not be sufficiently ensured. Further, the lower limit of the amount of the processed powder rubber is not particularly limited, but from the viewpoint of improving the material recycling rate of the waste tire, it is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the new rubber. .

  The new rubber used in the rubber composition of the present invention is not particularly limited. For example, in addition to natural rubber (NR), polybutadiene rubber (BR), polyisoprene rubber (IR), styrene / butadiene copolymer rubber (SBR). ) And the like. These new rubbers may be used alone or as a mixture of plural kinds.

  In the rubber composition of the present invention, in addition to the above-mentioned processed powder rubber and new rubber, it is usual in the rubber industry such as fillers, anti-aging agents, vulcanizing agents, vulcanization accelerators, zinc oxide, stearic acid, and softening agents. The compounding agent used can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition of the present invention is produced by blending a processed rubber with a new rubber and various compounding agents appropriately selected as necessary, kneading, heating, extruding, and the like. be able to.

  The pneumatic tire of the present invention is characterized by applying the above-described rubber composition to any member. When the rubber composition containing the processed powder rubber is used for a tire, the breaking strength and wear resistance of the tire are improved as compared with the case where the rubber composition containing the conventional powder rubber is used for the tire. Can do. In addition, since the processed powder rubber compounding rubber composition mentioned above has sufficient fracture characteristics, it can be used for various members of a tire including a tread. Moreover, as gas with which the pneumatic tire of this invention is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

<Manufacture of processed powder rubber>
The powder rubber was subjected to a fine particle size treatment by the production method described in JP-A No. 2006-176560. Next, 90 g of the fine particle size-treated powder rubber and 10 g of Diana process oil [manufactured by Idemitsu Kosan Co., Ltd.] were placed in a mortar and mixed for 10 minutes to obtain a 10% oil-added fine particle size powder rubber (processed powder rubber). Each other mass was changed to a predetermined addition percentage.

<Preparation of rubber composition>
By blending the compounding agent and powdered rubber or processed powdered rubber with the blending ratio shown in Table 1 below for 100 parts by mass of the new styrene butadiene rubber (SBR, new rubber), and kneading them using a 90cc plast mill Each rubber composition was obtained. The kneading was performed in two steps as follows. That is, first, in the first step, the powder rubber is kneaded with a synthetic rubber, carbon black, aroma oil (softener), stearic acid and an anti-aging agent at a maximum temperature of 160 ° C., and then in the second step. The rubber composition obtained in the first step, zinc white, vulcanization accelerator A, vulcanization accelerator B, vulcanization accelerator C and powdered sulfur were kneaded at a maximum temperature of 105 ° C. In addition, about the comparative example 1, it knead | mixed by the same method except not adding powder rubber and processed powder rubber.

<Evaluation of rubber composition>
For the rubber composition, processability and fracture characteristics were measured by the following methods. In addition, evaluation was displayed by an index with the value of Comparative Example 1 (using only new rubber not using powdered rubber or processed rubber) as 100 for each characteristic. The results are shown in Table 2 or Table 3.

(1) Workability (Mooney viscosity)
The Mooney viscosity (ML1 + 4) was measured according to JIS K6300-1: 2001, and the value of Comparative Example 1 was set to 100 and displayed as an index. ML1 + 4 was measured at a preheating time of 1 minute, a rotor operating time of 4 minutes, and a temperature of 130 ° C. Basically, it can be said that the smaller the index value, the better the workability, but if this value is too low, the rubber composition may be easily adhered. Therefore, in order not to impair the workability, it is desirable that the index value be in the range of 90 to 105. If it is this range, it is a level which does not cause problems, such as an ear piece. On the other hand, when the index value exceeds 110, the processability is greatly deteriorated, and problems such as deterioration of rubber skin and ear cutting become prominent.

(2) Fracture characteristics The obtained rubber composition was pressure vulcanized at 160 ° C. for 13 minutes to obtain a vulcanized rubber sample, and the fracture strength (Tb) of the sample was measured according to JIS K6251: 2004. The value of Comparative Example 1 was taken as 100 and displayed as an index. The larger the index value, the better the fracture characteristics, and it is desirable that it is 90 or more.

<(Processing) Evaluation of powdered rubber>
Moreover, the scattering amount was measured with the following method with respect to the powder rubber or processed powder rubber used for said rubber composition. The results are shown in Table 2 or Table 3.

(3) Scattering amount Using a powder tester PT-N manufactured by Hosokawa Micron Co., Ltd., the scattering property was determined using the dispersion degree measuring method of the same device. Specifically, 10 g of the sample was weighed, the sample was dropped from a height of about 60 cm, and the rate of scattering and disappearing from the mass remaining on the underlying tray without scattering was calculated. The same operation was performed 3 times, and the average value was defined as the scattering amount (%). The smaller the scattering amount, the harder it is to fly, and in view of workability, it is preferably 20 or less.

* 1 SBR # 1500 [manufactured by JSR Corporation]
* 2 Seast KH [Tokai Carbon Co., Ltd.]
* 3 Nocrack 6C [Ouchi Shinsei Chemical Co., Ltd.]
* 4 Noxeller DM-P [Ouchi Shinsei Chemical Co., Ltd.]
* 5 Noxeller NS-P [Ouchi Shinsei Chemical Co., Ltd.]
* 6 Noxeller D [Ouchi Shinsei Chemical Co., Ltd.]

  From Table 2 and Table 3, it can be seen that the processed powder rubber used in the rubber compositions of Examples 1-2 and 4-9 has a small amount of scattering. In addition, since the processed powder rubber used for the rubber composition of Example 3 had an oil ratio of less than 5% by mass, the effect of reducing the amount of scattering was small. Therefore, it can be seen that the amount of oil added to the rubber powder is preferably 5% by mass or more.

  In addition, the rubber compositions of Examples 4 to 9 have a Mooney viscosity (workability) index value in the range of 90 to 105 and a fracture property index value of 90 or more, and are excellent in both processability and fracture property. I understand that. On the other hand, the rubber composition of Comparative Example 7 had poor processability because the amount of the processed powder rubber exceeded 20 parts by mass with respect to 100 parts by mass of the rubber component. In the rubber compositions of Example 1 and Example 2, fracture nuclei were generated because the proportion of the blended processed rubber powder that passed through a 100 or 200 mesh sieve was less than 50% by mass. The destructive properties were degraded. Therefore, it can be seen that the proportion of the raw rubber powder that has passed through the 100 or 200 mesh sieve is preferably 50% by mass or more.

<(Evaluation of tires>
Furthermore, the wear resistance of the tire produced using the rubber composition was evaluated by the following method. The results are shown in Table 4.

(4) Actual wear resistance of tires Each rubber composition is applied as a tread rubber to produce pneumatic tires (PSR) for passenger cars of tire size 195 / 65R15, and tires are mounted on 2000cc domestic cars. Measure the remaining groove depth after traveling 3-50000km, the following formula:
(Remaining groove depth of tire of Comparative Example 1) / (Remaining groove depth of test tire) × 100
The actual wear resistance was evaluated. The results were expressed as an index with the value of Comparative Example 1 being 100. The larger the value, the better the result.

  From Table 4, it can be confirmed that the tire using the rubber composition containing the processed powder rubber according to the present invention for the tread rubber maintains a sufficient wear resistance.

Claims (8)

Oil is added to fine powder rubber ,
Processed rubber , characterized in that the powdered rubber contains 50% by mass or more of what passed through a 100-mesh sieve by subjecting it to a particle size reduction treatment .   The processed powder rubber according to claim 1, wherein the oil is a process oil.   The processing powder according to claim 2, wherein the process oil is at least one selected from the group consisting of a process oil for naphthenic rubber, a process oil for paraffinic rubber, and a process oil for aromatic rubber. Rubber. 2. The processed powder rubber according to claim 1 , wherein the powder rubber contains 50% by mass or more of what has passed through a 200-mesh sieve by subjecting to a fine particle size treatment. 5. The processed powder rubber according to claim 4 , wherein the powder rubber contains 75% by mass or more of what passed through a 200-mesh sieve by subjecting to a fine particle size treatment.   The processed powder rubber according to claim 1, wherein the amount of the oil added is 5 to 50 mass%. A rubber composition comprising 20 parts by mass or less of the processed powder rubber according to any one of claims 1 to 6 with respect to 100 parts by mass of new rubber. A pneumatic tire using the rubber composition according to claim 7 .