JP4467424B2 - Microbial treated rubber powder and rubber composition containing the rubber powder - Google Patents

Description

  The present invention is a rubber powder containing a polyisoprene-based rubber, which is a rubber powder treated with a microorganism by BS-HA1 strain (FERM P-19378) which is an actinomycete belonging to the genus Nocardia, and the rubber powder is blended The present invention relates to a rubber composition.

  Waste tires have a higher recovery rate than ordinary plastic products, and are reused as fuel, especially in cement factories. However, with the recent increase in environmental problems, there is a demand for an improvement in the so-called material recycling rate in which rubber pieces or rubber powders that have been cut or destroyed from waste tires are reused. In addition to the method of mechanically pulverizing waste tires at room temperature such as a roll pulverization method, there are a freezing pulverization method of pulverizing after freezing with liquid nitrogen or the like, and a water hammer pulverization method using ultra-high pressure water, Attempts have been made to produce fine particles at low cost.

  On the other hand, in order to knead powder rubber into unvulcanized rubber and use it as a vulcanized rubber product, vulcanization adhesion between powder rubber and new unvulcanized rubber is important. Recycled rubber that has been mixed, heated, desulfurized, and made into a sheet with a roll has also been used for a long time. Various desulfurization methods for the surface of the powder rubber have been proposed. For example, there is a method in which a large shear force is applied to the powder rubber by a twin screw extruder or the like to pulverize and desulfurize. However, these methods are disadvantageous in that the energy cost is high because the processing temperature is high and the processing is performed with a high shearing force.

  Therefore, treatment with microorganisms can be considered as an energy-saving method. Since microbial treatment is a low-temperature treatment, it can be said to be the treatment method with the least energy consumption. Regarding microbial treatment, Japanese Patent Application Laid-Open No. 9-194624 and Japanese Patent Application Laid-Open No. 11-60793 report methods for efficiently decomposing hard rubber using bacteria of the genus Nocardia. It is intended to completely disassemble the pieces, and nothing is said about how to make powder rubber that is effective for material recycling.

JP-A-9-194624 Japanese Patent Laid-Open No. 11-60793

  Accordingly, it is an object of the present invention to provide a powdered rubber that can be used as a raw material for recycled rubber effective for material recycling and that exhibits suitable characteristics when blended in a rubber composition by microbial treatment.

  Therefore, as a result of intensive investigations by the present inventors to solve the above-described problems, the surface of the pulverized rubber having a specific size pulverized by the conventional method is further subjected to microbial treatment with the BS-HA1 strain. It was confirmed that rubber powder with physical properties could be obtained.

The present invention comprises the following (1) to (8).
(1) Rubber powder obtained by microbial treatment using BS-HA1 strain (FERM P-19378), which is a actinomycete belonging to the genus Nocardia, containing polyisoprene rubber.
(2) The rubber powder according to (1), wherein the rubber powder has a polyisoprene rubber content of 10% by weight or more.
(3) The rubber powder according to (1), wherein the polyisoprene rubber is cis polyisoprene rubber.
(4) The rubber powder according to (1), wherein the rubber powder contains carbon black.
(5) The rubber powder according to (1), wherein the rubber powder has an average particle size of 500 microns or less and 10 microns or more.
(6) A rubber composition comprising the rubber powder according to any one of (1) to (5).
(7) The rubber composition according to (6), wherein the blended number of the rubber powder is 0.01 to 100 phr.
(8) A tire produced using the rubber composition according to (6) or (7).

  According to the present invention, rubber powder having good physical properties can be obtained by subjecting the surface of the crushed rubber to microbial treatment with the BS-HA1 strain. The rubber powder of the present invention and the rubber composition containing it are effective for material recycling.

Embodiments of the invention will be specifically described below.
The present invention is a rubber powder obtained by microbial treatment using BS-HA1 strain (FERM P-19378) which is an actinomycete belonging to the genus Nocardia. A rubber composition can also be obtained by blending the rubber powder of the present invention. Nocardia genus actinomycetes are known to degrade natural rubber and other polyisoprene-based rubbers, but normal Nocardia genus bacteria cannot decompose hard rubber compounded with carbon black. is there. In the present invention, as a result of intensive screening of natural rubber-degrading bacteria from many soils, the inventor has found BS-HA1 strain capable of degrading rubber powder made of carbon-containing rubber used in rubber products such as tires.

  The BS-HA1 strain was deposited on June 5, 2003 as FERM P-19378 strain at the National Institute of Advanced Industrial Science and Technology. In the present invention, the BS-HA1 strain grows while assimilating the powdered rubber in a liquid medium of an inorganic salt. It is considered that BS-HA1 strain acts on the powder rubber surface in the process of assimilating the powder rubber, thereby modifying the powder rubber surface and facilitating vulcanization adhesion with unvulcanized rubber. Examples of the inorganic salt include nitrogen, phosphorus, potassium, calcium, and magnesium.

The strain was fixed based on a comparison of 16S rRNA genes that have become the mainstream. Details of the method will be described below. The strain was inoculated into YM agar medium (Becton Dickinson NJ, USA) and cultured at 30 ° C. for 5 days. Thereafter, genomic DNA was extracted from the cells by PrepMan Methods (Applied Bjosystems, CA, USA). The extracted genomic DNA was used as a template to amplify a 5 bp side region of 500 bp in the 16S ribosomal RNA gene (16S rDNA) by PCR. Thereafter, the amplified base sequence was sequenced to obtain a 16S rDNA partial base sequence of the specimen. From the obtained 16S rDNA base sequence, homology scrutiny of species considered to be closely related to the specimen was performed, and the following 10 top strains were determined.
Homology strain 97.8% Nocardia transvalensis
96.8% Nocardia nova
96.6% Nucardia brasiliensis
96.6% Nocardia asteroides
96.4% Nocardia farcinia
95.8% Nocardia pseudobrasiliensis
95.6% Nocardia otidiscaviaum
95.6% Rhodococcus Globerulus
95.4% Nocardia brevicatena
95.4% Tsukamurella wratislaviensis
From this result, the BS-HAI strain was obtained from Nocardia sp. And identified as a strain belonging to

  If the vulcanized rubber which is the raw material of the powder rubber in the present invention is an isoprene-based rubber, a silane coupling agent, sulfur, vulcanizing agent, vulcanization accelerator, vulcanization accelerating agent usually used in the rubber industry , Antioxidant, ozone degradation inhibitor, anti-aging agent, process oil, zinc white (ZnO), stearic acid, peroxide, and the like may be blended. However, when a compounding agent that inhibits the growth of the BS-HA1 strain is blended in the rubber compounding agent, it is necessary to solvent-extract the powdered rubber and remove it. The powder rubber used in the present invention is not limited to powder rubber obtained by pulverizing waste tires and tubes, but also pulverized unvulcanized scraps generated during tire production, spew pieces generated during tire vulcanization, etc. Powdered rubber may be used.

  Examples of the polyisoprene rubber to which the present invention is applied include rubbers or elastomers whose main chain is cis polyisoprene and trans polyisoprene. In the present invention, rubber which is cis polyisoprene is most preferable, but the present invention can also be applied to rubber or elastomer having a copolymer of isoprene and another monomer as a main chain. Specific examples of cis polyisoprene include, but are not limited to, natural rubber and synthetic cis polyisoprene such as Natsyn, and trans polyisoprene includes natural rubber such as gutta percha.

  If the content of the polyisoprene rubber in the rubber elastomer constituting the rubber powder is 10% by weight or more, the present method can be applied. The polyisoprene in the rubber elastomer is preferably 50% by weight or more, more preferably 80% by weight or more, but is not limited to this range. The rubber powder targeted in the present invention can contain carbon black. The carbon black content is 30 to 70 phr if it is a powder rubber collected from a normal waste tire, but is not limited to that range, and even if the carbon black content is 30 phr or less and 70 phr or more, The inventive method is adaptable.

  The rubber particles obtained according to the present invention preferably have an average particle size of 500 microns or less and 10 microns or more, more preferably an average particle size of 200 to 50 microns, but not limited to that range. Absent. In the case of 500 microns or more, the surface area is small, and even if microbial treatment is performed, there is no effect. On the other hand, it is difficult to produce a product of 10 microns or less.

  In the present invention, when powdered rubber subjected to microbial treatment is blended with unvulcanized rubber, physical properties of vulcanized rubber such as breaking strength and elastic modulus are improved as compared with blended powdered rubber not subjected to microbial treatment.

  Furthermore, the rubber composition which mix | blended the microbially processed rubber powder obtained by this invention can be prepared. The blending number of the microbially treated rubber powder is not limited to the range, but is 0.01 to 100 phr, and the effect of the microbial treatment hardly appears at 0.01 phr or less or 100 phr or more. More preferably, the blending number of the rubber powder is 1 to 30 phr. The rubber composition containing the powdered rubber obtained by the microbial treatment according to the present invention can be used as a tire member, and is mainly preferably applied to side and tread members.

  Silane coupling agents, sulfur, vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, antioxidants, antiozonants, antiaging agents, process oils, zinc oxide (ZnO), commonly used in the rubber industry ), Stearic acid, peroxide and the like can be blended to prepare a rubber composition. It is known in the art to blend these additives, and those skilled in the art can blend them appropriately to obtain the desired rubber composition. EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

  A natural rubber powder rubber (average particle size 100 μm) extracted with acetone was added at 10 g / L to a medium having the composition shown in Table 1 prepared in a glass container with a silicone stopper, and sterilized at 90 ° C. in an autoclave. To this was added BS-HA1 strain that had been pre-cultured using glove rubber as the sole carbon source, and after 20 days of rotation with a magnetic stirrer at 30 ° C, autoclaving was performed at 121 ° C. And filtered. The powder rubber on the filter paper was washed several times with acetone, then with pure water, and after confirming that it was sufficiently dried, a powder rubber sample to be blended was used.

(Evaluation of recycled rubber)
A rubber component was prepared by using powdered rubber treated with microorganisms in the above Examples and further mixing a new rubber. A rubber compounding agent was added to the obtained rubber component, and the rubber compounding shown in Table 2 was kneaded using a 60 ml plastmill to obtain a rubber composition.

  In Table 2, Comparative Example 1 is a rubber composition containing powdered rubber not treated with microorganisms, and Comparative Example 2 is a rubber composition containing no powdered rubber.

  The composition was subjected to a ring tensile test to evaluate the properties of the recycled rubber. In the evaluation, both the strain and the stress were expressed as an index with the elongation at break and the break strength of Comparative Example 2 being 1 (FIG. 1). The larger the index, the better the characteristics. In FIG. 1, an Example is shown by a solid line, Comparative Example 1 is shown by a two-dot chain line, and Comparative Example 2 is shown by a dotted line.

  When the untreated powdered rubber of Comparative Example 1 was blended with Comparative Example 2 in which no powdered rubber was added, the elastic modulus decreased. On the other hand, it was confirmed that the use of powdered rubber inoculated with BS-HA1 strain and treated with microorganisms this time improved the elastic modulus and obtained SS characteristics similar to those of Comparative Example 2 in which powdered rubber was not added.

  According to the present invention, rubber powder having good physical properties can be obtained by subjecting the surface of the crushed rubber to microbial treatment with the BS-HA1 strain. The rubber powder of the present invention and the rubber composition containing the rubber powder have low energy costs and are effective for material recycling. In addition, since the present invention uses a method by microbial treatment, it also has the advantage that the energy cost required to obtain rubber powder is low.

FIG. 1 is a graph showing the results of evaluating recycled rubber by a ring tensile test.

Claims (8)

  A rubber powder obtained by microbial treatment using BS-HA1 strain (FERM P-19378), which is a actinomycete belonging to the genus Nocardia, containing a polyisoprene rubber.   The rubber powder according to claim 1, wherein the rubber powder has a polyisoprene rubber content of 10% by weight or more.   The rubber powder according to claim 1, wherein the polyisoprene rubber is cis polyisoprene rubber.   The rubber powder according to claim 1, wherein the rubber powder contains carbon black.   The rubber powder according to claim 1, wherein the rubber powder has an average particle size of 500 microns or less and 10 microns or more.   A rubber composition comprising the rubber powder according to any one of claims 1 to 5.   The rubber composition according to claim 6, wherein the rubber powder has a compounding part number of 0.01 to 100 phr.   A tire produced using the rubber composition according to claim 6.

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