TW201938652A - Method for producing carbon-nanotube-rich rubber granules - Google Patents

Abstract

Provided is a method for producing CNT-rich rubber granules which does not require complicated processes such as introducing functional groups, and in which CNTs are coated with various types of rubber latex as binders, and the rubber is made to penetrate into the interiors of the CNTs, thereby forming CNT-rich granules and greatly reducing dispersiveness. The method for producing carbon-nanotube-rich rubber granules comprises: (1) a water mixing step for introducing carbon nanotubes and an amount of water equivalent to 0.1-8 weight%, inclusive, of the concentration of the carbon nanotubes into a container, and stirring to create a dispersion; (2) a rubber mixing step for adding an amount of rubber latex such that the added amount of carbon nanotubes is equivalent to 100-5,000 parts by weight, inclusive, per 100 parts by weight of the rubber component (solids) of the rubber latex, and mixing; (3) a granulation step for subsequently stirring the obtained mixture while adding a non-water-soluble solvent dropwise and while causing the carbon nanotubes to migrate from the aqueous phase to the rubber phase to produce granules (rubber granules); (4) a separation step for subsequently separating the aqueous phase and the granules; and (5) a drying step for drying the separated granules.

Description

Manufacturing method of rubber granules with highly blended carbon nanotubes

The invention relates to a method for manufacturing rubber granules with a high degree of mixing of carbon nanotubes.

In recent years, carbon nanotubes (hereinafter referred to as CNTs) have attracted much attention as fantasy new-generation materials. They have been used not only as antistatic agents or conductivity-imparting materials, but also for use in tires, capacitors, and Li batteries. Development of applications for conductive additives and fiber-reinforced plastics.

CNT has a diameter of several nm to about 500 nm, a length of about 10 μm to 1,000 μm, a large aspect ratio, and is a carbon crystal with a tubular structure. There are various types, such as single-walled CNTs having a single-layer structure, and two-layer double-walled CNTs belonging to the category of multi-walled CNTs having a multilayer structure. In addition, there are several types including closed ends, single-end closed types, open ends, and spiral-type structures and armchair types.

CNTs are manufactured by arc discharge method, catalyst vapor phase manufacturing method, laser ablation method or other methods, each of which has advantages and disadvantages.

In general, it is known that by blending CNTs into various substrates such as synthetic resins or rubbers, it is possible to impart conductivity or high elasticity, high strength, thermal conductivity, and the like to the substrate.

However, when using CNTs, there are the following issues: concerns about its safety, CNTs are tubular and entangled one after another, making it difficult to make them scattered and scattered, and lacking dispersibility; and they are easy to scatter and lack handling. Therefore, it has been highly anticipated as a "dream material" but it has been slow to progress in practical applications.

Regarding the safety of CNT, according to the opinions published by IARC (International Cancer Research Agency) in 2014, it is believed that most of CNTs belong to the "Group 3" (cannot be classified as carcinogenic), but are currently used in general They are strongly recognized as "however CNT is a dangerous material." It is said that one of the reasons is that CNTs have the same fibrous structure as asbestos; their body density is 1 to 5g / 100cc, which is extremely low, they can be involved in a large amount of air, have extremely high dispersibility, and have a great risk of being inhaled by the human body.

Generally speaking, environmental risk refers to the possibility that chemical substances and other substances will adversely affect human health or the growth and growth of plants and animals through the environment; conceptually, it is expressed as "risk = harmfulness (toxicity) × "Exposure (intake)" means that the material is obviously toxic. If there is no amount of exposure, the material can also be called roughly safe.

As a substance that reduces the amount of exposure, it is preferably a dispersing step that does not pulverize and scatter during packaging, transportation, inventory, or actual use, and when mixing or molding a masterbatch or composite of synthetic resin. It shows easily dispersed spherical granules. In addition, if it is a granulated material that will not be pulverized, it is a matter of course that the bulk density is also high. In the mixing step of, for example, synthetic resin, it can prevent bridges from occurring in the storage tank or automatic metering during supply. , And has the advantages of reachable transportation or reduction of inventory costs.

As the carbon-based powder having spherical particles in the final form of the product, there is carbon black (hereinafter referred to as CB) manufactured and sold at 12 million tons per year worldwide. The bulk density of CB is not as large and extremely low as that of CNT. Therefore, disk-type granulation method, drum-type granulation method, screw extrusion-type granulation method, stirring-type granulation method, etc. are generally used with water as an adhesive. Granulation methods such as compression molding granulation. CB's primary particles are spherical and form a structure formed by fused particles. The surface of the particles has functional groups such as oxygen or hydrogen. It also has affinity with water that functions as an adhesive, making it easier to granulate. In contrast, CNT has a relatively complete crystal structure and few surface functional groups. Even in powder aggregates, more air is involved than CB. Therefore, it has poor affinity with water and is not easy to granulate.
To solve this problem, a high-speed airflow flushing method as shown in Patent Documents 1 and 2 is proposed. Patent Document 3 proposes a method for producing granules of CNTs in which rubbers such as rubber latex are used as adhesives in addition to solid rubber.
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-239531
[Patent Document 2] Japanese Patent Laid-Open No. 2006-143532
[Patent Document 3] Japanese Patent No. 5767466

[Problems to be Solved by the Invention]

However, the above-mentioned conventional techniques have the following problems:
(1) The technology disclosed in Patent Document 1 or Patent Document 2 is a device for pulverizing powders in a high-speed airflow and then compositing the powders. The original purpose of this device is to make different types of powder particles adhere to the surface of the powder mother particles by impact in a high-speed airflow. It is not only difficult to granulate only one kind of CNT, even if it can be performed, its granulation The particle size of the material is also extremely small at 200 μm or less, and it is estimated that granulation at the millimeter level is difficult to achieve.
Therefore, there are problems in terms of safety, environmental pollution, and handling properties associated with scattering.

(2) Furthermore, even if the general granules without using an adhesive as disclosed in Patent Document 1 or Patent Document 2 are used, the scattering properties during transportation, filling, etc. can be significantly reduced compared with those using powder. Environmental pollution, and it can improve the blending, mixing, and kneading properties of synthetic resins, rubbers, and media. However, to meet the increasingly stringent "preventive measures for preventing exposure to nanomaterials," etc., it is not enough to take a single approach to scattering. In addition, there is a problem that initial blendability or dispersibility when blended in a synthetic resin or the like is still insufficient.

(3) The technology disclosed in Patent Document 3 provides a method for manufacturing CNT granules, which has the following characteristics: by coating the inner or outer surface of CNT with solid rubber or rubber latex, the handling property of CNT is improved, It has excellent effects on improving the dispersibility of the matrix resin, improving the quantitative supply property during kneading, and greatly improving the safety of the human body caused by the drastic reduction of scattering. In particular, the technique of using rubber latex for a coating material according to claim 4 is preferable because a step of dissolving the rubber with a solvent in advance is required when solid rubber is not required.
However, the above technology is through the following steps: (1) the step of dispersing rubber latex in water to make a rubber dispersion; (2) the step of suspending CNTs in water; (3) adding (1) rubber to this suspension A step of dispersing the liquid to form a feather-like block; (4) a step of dehydrating the feather-like block; (5) a step of dehydrating the feather-like block by using a wet granulation mechanism to obtain granules of 0.2 to 2 mm; 6) A method for manufacturing the desired granular product can be obtained by drying the granular material. Not only are the steps extremely large, but the dehydration step and wet granulation step require large-scale equipment. Furthermore, it is extremely troublesome to switch from the previous step to the dehydration step and the wet granulation step, and the operation requires a long time and has a problem of lack of productivity.

Next, the dehydration step and the wet granulation step will be described in more detail. There are many types of dehydrators, and there are many ways or improved models; currently the main dehydrators commonly used are belt presses, filter presses, centrifugal dewatering machines, rotary presses, vacuum dewatering machines, screw presses, multiple rounds Tray dehydrator, etc. However, these models are mostly non-suitable for dehydration of dispersion liquids dispersed to the μm level because of the large opening diameter of the filter section (the mechanism cannot be reduced) and the need to use coagulants in combination. A filter press that is more commonly used for fine particle dispersions is a filter press, but it is not easy to operate continuously, and clogging of the filter cloth often occurs, which requires manual cleaning by human hands, rather than a high-efficiency dehydrator. Furthermore, considering the single batch processing time for cleaning the filter cloth, although it varies with the processing volume, it still takes several hours to tens of hours.

In addition, as the wet granulation method, a) disk granulation method, b) drum granulation method, c) screw extrusion granulation method, d) stirring granulation method, etc. are representative; as for a) and b) Due to the low density of the particles and the softness of the granulated product, a granulated product that is easily scattered toward the environment will be formed. c) Although a granulated product having a high hardness and a sharp particle size distribution can be obtained, the particle shape is cylindrical, and it is not suitable when a spherical product is targeted. d) The agitation granulation method can obtain an approximately spherical shape, but it is a granulated material with a large particle size distribution. (For reference, the "Fertilizer Processing" wet granulation-stirring granulation method issued by BSI Institute of Biological Sciences also details the comparison of various wet granulation methods).

The present invention is intended to solve the above-mentioned conventional problems. That is, the present invention is to provide a complicated operation that does not require the introduction of a functional group, to cover (coat) CNTs with various rubber latexes as adhesives, and to allow the CNTs to be highly dispersed by allowing the rubber to penetrate into the CNTs. The compounding amount is granulated, and the method for producing a highly granular CNT-doped rubber granule with significantly reduced scattering properties is aimed at.

In addition, the present invention aims to provide a workability such as remarkably improved workability and handleability, wettability with polymer matrix, dispersibility, electrical conductivity, and mechanical properties, and does not require large-scale equipment, can shorten manufacturing steps, and can The purpose of the method is to produce a highly granular CNT-doped rubber granule with a sharp particle size distribution of the granulated material at a low cost.

[Means for solving problems]

In order to solve the above problems, the method for producing a highly granular CNT-containing rubber pellet of the present invention has the following configuration.
The manufacturing method of the highly granular CNT-doped rubber granules according to the first embodiment of the present invention is a manufacturing method of the highly granular CNT-doped rubber granules, which comprises:
(1) Put a nano carbon tube and water in an amount corresponding to the concentration of the aforementioned nano carbon tube in an amount of 0.1 to 8% by weight into a container, and stir to form a water mixing step of a dispersion liquid;
(2) a rubber mixing step of adding and mixing a rubber latex to the dispersion; the amount of the rubber latex is equivalent to 100 parts by weight of the rubber component (solid content) of the above-mentioned nano carbon tube relative to the rubber component (solid content) of the rubber latex; 100 ~ 5000 parts by weight;
(3) a granulation step of producing granulated materials (rubber granules) while dripping a water-insoluble solvent while stirring the obtained mixed solution, while transferring the nano carbon tube from an aqueous phase to a rubber phase;
(4) Secondly, a separation step for separating the aforementioned aqueous phase from the aforementioned granulated material; and
(5) A drying step of drying the separated granules.

The manufacturing method of the highly granular CNT-doped rubber granules according to the second embodiment of the present invention is a manufacturing method of the highly granular CNT-doped rubber granules, which comprises:
(1) Put water into the container in an amount corresponding to the concentration of the carbon nanotubes of 0.1 to 8% by weight, and the amount of the carbon nanotubes added to the rubber component (solid content) of the rubber latex (100 weight). A step of making a rubber latex in an amount of 100 to 5000 parts by weight and stirring to prepare a dispersion liquid;
(2) a step of adding a nano carbon tube to the aforementioned dispersion and mixing and dispersing;
(3) a granulation step of producing granulated materials (rubber granules) while dripping a water-insoluble solvent while stirring the obtained mixed solution, while transferring the nano carbon tube from an aqueous phase to a rubber phase;
(4) a separation step for separating the aforementioned aqueous phase from the aforementioned granulated matter; and
(5) A drying step of drying the separated granules.

The third embodiment of the present invention is a method for manufacturing highly granular CNT-doped rubber granules.
(1) Put 100% by weight of rubber latex in terms of the rubber component (solid content) of rubber latex, and put carbon nanotubes in an amount equivalent to 100 to 5000 parts by weight, and make the concentration of the aforementioned nanocarbon tubes 0.1. A mixing and dispersing step of mixing and dispersing water in an amount of ˜8% by weight;
(2) Secondly, a granulation step of manufacturing granules (rubber granules) while dripping a water-insoluble solvent to transfer a carbon nanotube from an aqueous phase to a rubber phase;
(3) secondly, a separation step for separating the aforementioned aqueous phase from the aforementioned granulated material; and
(4) A drying step of drying the separated granules.

According to any of the structures of the first to third embodiments of the present invention, the following effects can be obtained:
(1) Because the surface of CNTs that are highly doped with CNTs (hereinafter referred to as rubber granules) is coated with rubber, the rubber also penetrates and covers the inside of the CNT aggregate, thereby greatly reducing the CNTs. The degree of scattering can significantly improve handling, which can significantly reduce security risks.

(2) Because the outer surface of the CNTs that are rubber particles are covered by rubber, and the rubber particles having a large bulk density are formed without strong aggregation between the CNTs and CNTs, and the dispersion is dispersed in the dispersion medium. In the case of a polymer matrix such as resin or rubber (hereinafter referred to as a matrix resin or a matrix rubber), it can be infiltrated as a matrix resin or a matrix rubber (good wettability), thereby exhibiting excellent dispersibility.

(3) When blended with a matrix resin or a matrix rubber, since it has high dispersibility and high wettability, it can impart excellent physical properties, such as imparting high electrical conductivity or improving mechanical physical properties, and it has excellent processability.

(4) Different from the method of manufacturing rubber granules with high CNT content, which is different from claim 4 of Patent Document 3 using rubber latex, the present invention does not require a dehydration step or a wet granulation step that requires a long time to be processed. It can significantly reduce equipment investment by reducing production man-hours or manufacturing equipment. In addition, labor can be saved and the cost of the product can be reduced.

(5) The quality of the obtained rubber granules is not only sharper than the rubber granules obtained by the manufacturing method of claim 4 in Patent Document 3, but also has a sharp particle size distribution and excellent fluidity. Fewer particles can also reduce the scattering of particles, and is a granular material with less risk to the safety of the environment.

(6) Manufacturing equipment can be significantly streamlined, utility costs are reduced, and energy saving is excellent.

The structure of the present invention will be described in more detail.
In the mixing and dispersing step, about 100 parts by weight of CNTs corresponding to 100 to 5,000 parts by weight of CNTs contained in the container is added with about 100 times the weight of water of the CNTs and mixed and dispersed. In this mixing and dispersing step, the rubber latex is first poured into water and stirred to dilute the rubber latex, and the CNT is poured into the CNT. After the CNTs are fused in the water, the stirrer is changed to a disperser to disperse the entire liquid. After adding CNTs in water or water, stirring, and then adding rubber latex and stirring, the method is changed to a disperser to disperse the entire liquid.

Here, as the rubber latex, for example, polybutadiene latex 0700 (registered trademark of JSR Corporation), styrene butadiene copolymer latex SBR2108 (registered trademark of JSR Corporation), or natural rubber latex is mainly used. MBR latex (methyl methacrylate-butadiene polymer), VP latex (2-vinylpyridine-styrene-butadiene copolymer), NBR latex (acrylonitrile-butadiene copolymer) Material), CR latex (chloroprene), etc. As a dispersion liquid for diluting and dispersing rubber latex, water is mostly used, but an organic solvent may be used.

The amount of CNT added is 100 to 5000 parts by weight, and preferably 200 to 4000 parts by weight, based on 100 parts by weight of the rubber latex. CNTs are used after being mixed with about 100 times water.

With the amount of CNT blended in highly granular CNT-containing rubber granules, it is gradually less than 200 parts by weight relative to 100 parts by weight of rubber latex. When used as a masterbatch for matrix rubber or matrix resin, a greater amount is required. Rubber granules. From this, it can be seen that the influence of the rubber in the rubber pellets on the base rubber or the base resin becomes large, and it is difficult to obtain physical properties in design. Moreover, there is a tendency to lack handling. When the amount of the CNT blended is less than 100 parts by weight, the influence of the rubber becomes large, and the tendency to deteriorate the handleability becomes more obvious and unfavorable.

In addition, as the amount of CNTs blended in the rubber granules exceeds 4000 parts by weight, when mixed with other base rubbers or matrix resins, the rubber granules will be pulverized, resulting in small particle sizes in the rubber granules. Particles or CNTs are more likely to scatter, and tend to be less environmentally friendly or safer. When the CNT blending amount exceeds 5000 parts by weight, CNTs and the like are likely to be scattered significantly and are not good.

The CNT concentration in the dispersion is preferably 0.1 to 8% by weight, and more preferably 0.5 to 5% by weight. As it is less than 0.5% by weight, the productivity tends to deteriorate; if it is 0.1% by weight or less, this tendency is more significant and unfavorable. When it is more than 5% by weight, the viscosity of the water-CNT mixed solution will increase, the CNTs cannot be sufficiently dispersed, and large CNT agglomerates can be easily formed, and the rubber coating cannot be sufficiently performed. The tendency of the physical properties of the granular material to deteriorate is more significant and unfavorable if it is 10% by weight or more.

For adjusting the dispersion method of the CNT dispersion liquid, a ball mill, a sand mill ("Nanomizer" manufactured by Shinmaru Enterprises Corporation, etc.), a wet jet mill, a mill, a bead mill, a CoBall Mill, a homomixer, a homogenizer, Ultrasonic disperser, ultrasonic homogenizer, dissolver, disperser, etc. The use of media such as glass beads or zirconia beads is not good in terms of preventing complicated steps and mixing of impurities; the dispersers that can be preferably used are homogenizers, homogenizers, ultrasonic dispersers, ultrasonic homogenizers, Dissolver and so on.

The dispersing time depends on the type of disperser used. For convenience, it is preferred to take a dispersion solution of CNT and water onto a glass plate with a dropper and spread it with a doctor blade until there is no undispersed block.
The use of a dispersant in combination is not good in terms of mixing impurities; if it is a CNT that is extremely difficult to disperse, such as a single-walled nanometer tube, it is advisable to use a dispersant.

Next, the granulation step of granulating while transferring the CNT from the aqueous phase to the rubber phase while dropping a water-insoluble solvent will be described in detail.

The disperser used when dispersing the CNT and the rubber latex was changed to a stirrer as described below and stirred. As the mixer, for example, SUPERMAG MIXER, PORTABLE MIXER, MULTIMIXER (all of which are the trade names of Satake Chemical Machinery Co., Ltd.), energy-saving mixers from AS ONE, and air mixers can be used.

The stirring intensity is preferably such that a vortex can be formed on the liquid surface, and the non-aqueous solvent is continuously dripped from the stirring liquid in this state. Since the CNTs coated with rubber according to the aforementioned dispersion step are lipophilic, they are continuously granulated while transferring from the aqueous phase to the solvent phase to form rubber granules.

In the stirring step, the size of the granules can be gradually increased while stirring, and the size of the granules can be obtained. Therefore, the rubber granules can be grown to a size that is advantageous for the treatment of CNTs, and the scattering properties during use can be improved, and handling properties such as handling properties and workability can be improved. In addition, the dispersibility during kneading in a base rubber or a base resin can be improved, and water and rubber particles can be easily separated in the separation and drying steps in the subsequent steps.

Examples of the water-insoluble solvent include toluene, xylene, hexane, tetrahydrofuran, benzene, cyclohexane, carbon tetrachloride, and the like.

Secondly, in the separation step of separating the aqueous phase from the rubber granules, since the granules are grown in the previous step to particles that are advantageous for the treatment of CNTs, a sieve can also be used in the separation operation.

In the drying step of drying the obtained rubber pellets, a method such as steam drying or vacuum drying is used. The drying temperature at this time is preferably 200 ° C or lower in the case of a steam dryer, or 150 ° C or lower in the case of vacuum drying. This is because, above these temperatures, the tendency of the rubber coated (coated) with CNTs to deteriorate is seen.

The highly granular CNT-containing rubber particles obtained in the present invention can be mixed with rubbers used as fillers, rubbers of the same type or different types of base rubbers, and even various base resins.

Furthermore, when the rubber granules are mixed with different kinds of base rubbers or matrix resins, the higher the mixing ratio of the rubber granules with respect to the different kinds of base rubbers or matrix resins, the mechanical properties such as impact strength will change. difference. Therefore, the smaller the mixing ratio of the rubber granules with respect to the base rubber or the matrix resin is, the better, since the present invention is a highly granular CNT-doped rubber granules, only a small amount of rubber granules can be added as much as possible CNT blending amount.

The kneaded rubber granules that are highly CNT blended with the matrix rubber or matrix resin are obtained by mixing the two at a desired ratio, and heating the mixture to 130 to 270 ° C in a state where the mixture is softened or melted. This is performed using a mixing roll, an extruder, a Henschel mixer, or the like.

By using the rubber granules, CNTs do not scatter at the job site, which is excellent in safety, and can disperse a desired amount of CNTs in a matrix resin or a matrix rubber in a short mixing time, thereby achieving excellent productivity.

As the matrix resin, polyvinyl chloride, polyethylene, polypropylene, polystyrene, acrylonitrile styrene resin, nylon 6, nylon 66, vinyl acetate resin, acrylonitrile butadiene resin, etc. are used. In particular, acrylonitrile styrene butadiene resin or thermoplastic resins such as nylon 6, nylon 66 can be suitably used.

As the base rubber, natural rubber, polybutadiene, styrene butadiene copolymer, butadiene acrylonitrile copolymer, polyisoprene, fluorine rubber, silicone rubber, and urethane rubber are suitably used. , Butyl rubber, ethylene · propylene rubber, chloroprene rubber, acrylic rubber, polyvulcanized rubber, ethylene · vinyl acetate rubber, polyepichlorohydrin rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, etc.

The invention of claim 4 is a method for producing a rubber granule highly blended with CNTs as claimed in any one of claims 1 to 3, which is a fiber having the aforementioned CNTs having a fiber diameter of 1 to 200 nm and a fiber length of 1 to 500 μm. Make up.

With this configuration, in addition to the effects obtained by the invention according to any one of claims 1 to 3, the following effects can be obtained.

(1) The coating of the rubber with respect to the CNTs can be performed uniformly. As a result, the bulk density can be increased by granulation, and the scattering properties can be significantly improved.

(2) It can significantly improve the dispersibility of the matrix rubber or matrix resin.

In addition, when the fiber diameter of CNT is greater than 200 nm or the fiber length is less than 1 μm, although granulation can be performed, it is difficult to impart conductivity to CNT or improve mechanical properties. When it is made into rubber granules, it can penetrate through the base rubber or matrix. Resin kneading, etc., does not improve physical properties. When the fiber diameter of the CNTs is less than 1 nm, the dispersibility to water becomes extremely poor, and the CNT blocks in an aggregated state are covered with rubber, so it is difficult to obtain various physical properties required by the present invention.

In addition, when the fiber is longer than 500 μm, the viscosity during water dispersion becomes high, so the CNT concentration during water dispersion cannot be increased, and there is a tendency that the productivity is not good. In addition, the fibers are easily broken during the dispersion of the water, and the broken fibers may form a coccus-like agglomerate, which is not preferable.

[Effect of the invention]

According to the method for producing a highly granular CNT-containing rubber pellet of the present invention, the following advantageous effects can be obtained.

(1) The CNTs in the suspension are hardly lost, and rubber granules coated with CNTs that are highly blended with CNTs are produced at a high yield, and are used in coated rubbers, compared with conventional CNT rubbers such as wet master batch A small amount of the composition is sufficient. Therefore, it is possible to provide a method for producing a highly granular CNT-containing rubber granule having a wide range of applications and excellent productivity.
In addition, the influence of the coated rubber on the matrix resin or the matrix rubber is discussed. The maximum CNT blending amount of the wet masterbatch method is 30% or less; and the CNT blending amount of the present invention is 98-50%. Reduce the effect of coated rubber on the matrix resin or matrix rubber.

(2) Since water can be used for the dilution or dispersion of the rubber latex, it is possible to provide a highly CNT-containing rubber granule which is highly advantageous in terms of manufacturing cost, environment, and equipment cost. Method for manufacturing granular materials.

(3) Because it is a rubber granule that does not use a wet granulation step and uses a water-insoluble solvent as an adhesive, the particles of the rubber granule are approximately spherical, and the particle size distribution is also sharp.

According to the method for producing a highly granular CNT-containing rubber granule according to the present invention, the following highly granular CNT-containing rubber granule having excellent physical properties can be obtained at a high yield.

(1) Not only granulate CNTs in powder form to improve safety, but also to form CNTs (micro-encapsulated) rubber particles around the CNT particles with a small amount of rubber to form CNTs. The degree of scattering itself becomes extremely low, which significantly improves handling. As a result, the working environment at the processing site can be significantly improved. Furthermore, it is possible to provide a rubber pellet which can ensure a significant quantitative accuracy in a step requiring a quantitative supply.

(2) Since the scattering property during processing can be almost zero, it is possible to greatly eliminate the general user's perception that CNT is a dangerous material. That is, the safety risk represented by "risk = harmfulness (toxicity) x exposure amount (intake amount)" can be said to be a non-safe and safe CNT because there is almost no exposure amount.

(3) Since the wettability with the polymer matrix can be greatly improved, the wetting to the matrix is better and it disperses as if dissolved therein, so the dispersing time can be shortened, and fracture can also be suppressed. In addition, it can provide excellent physical properties such as more stable and higher electrical conductivity than granulated or non-granulated products of uncoated (coated) rubber, which can be highly incorporated into the polymer matrix and Industrial use of highly valuable CNT-containing rubber pellets.

Here, as to why the dispersion time of the rubber granules of the present invention can be shortened, and why the dispersibility can be improved, it is judged that when the rubber granules highly blended with CNTs contact the base resin or the base rubber, the compounder melts. In the heating part, the CNT-coated rubber part will be melted first and continuously entangled in the CNT at the same time. In other words, the rubber portion coated on the surface of the CNT that has been melted before can be said to exhibit an effect as an adhesive or dispersant to the matrix resin or the matrix rubber.

(4) During granulation, the rubber latex diluted with water can also be uniformly covered inside the CNT dispersion block with the help of a water-insoluble solvent, thereby stabilizing the physical properties. Therefore, it is possible to provide a highly granular CNT-containing rubber pellet having excellent scattering properties, dispersibility, handling properties, and quantitative supply properties.

[Form of Implementing Invention]

Hereinafter, the present invention will be specifically described based on examples. Furthermore, the present invention is not limited by these examples.

As the CNT, a multi-walled CNT product name K-Nanos-100P manufactured by Kumho Corporation was used. The physical properties of this CNT are shown in Table 1.

(Example 1)
A 10L stainless steel round container was equipped with a homogenizer with a maximum number of rotations of 10,000 and a PORTABLE MIXER with paddles, and 4455 g of water was charged with an emulsion polymerized styrene butadiene rubber latex (trade name JSR1502 manufactured by JSR Corporation. Bonded benzene Ethylene 23.5%) 21.3 g, 45 g of CNTs were added in small amounts one by one while stirring at about 600 rpm. After the entire amount was added, the mixer was switched to a homogenizer and dispersed at about 6000 rpm for 30 minutes.
A number of this dispersion was dropped onto a glass plate with a dropper and spread with a spatula. The results of visually and fingering the undispersed blocks were observed without any coarse undispersed blocks.
Here, the concentration of CNT with respect to water is about 1 wt%, and the ratio of rubber to CNT is about 10 wt%.

Next, the homogenizer was switched to PORTABLE MIXER, and while stirring at 700 rpm, 400 g of toluene as a water-insoluble solvent was dropped using an automatic dropping device for 20 minutes to obtain a rubber pellet having a diameter of about 1 mm.

After separating the obtained rubber granules from water with a 60 mesh sieve, the rubber granules were naturally dried in a ventilated room at normal temperature for about 20 hours. Next, a vacuum dryer was used to heat and dry at 70 to 80 ° C until the solvent and residual water in the rubber pellets had a weight loss of less than 0.5% at 150 ° C for 1 hour, thereby obtaining a highly CNT-containing rubber. Granules (separation and drying steps).

(Example 2)
Except that the addition amount of the aforementioned rubber latex was 10.1 g (5 wt% with respect to CNT), the same method as in the example was adopted.

(Example 3)
The same method as in Example 1 was adopted except that the addition amount of the rubber latex was 5.9 g (3 wt% relative to CNT).

(Example 4)
In addition to using 9.1 g of "low-odor latex" (non-volatile content 55%, viscosity 100-200 mpa.S) (10 wt% relative to CNT) instead of the emulsified polymerized styrene butadiene rubber latex used in Example 1 Except for the above, the same method as in Example 1 was adopted; wherein the low-odor latex was prepared by grafting copolymerization of methyl methacrylate with natural rubber latex made by MUSASHINO CHEMICAL Company to reduce the ammonia in the MG series. Smelly.

(Comparative example 1)
The emulsion polymerized styrene butadiene rubber latex used in Example 1 was diluted with water to prepare a rubber latex dispersion with a rubber content of 3% by weight.

Next, a uniform suspension having a CNT concentration of 1% by weight was prepared using the CNTs and water of Example 1 under the same conditions and methods as in Example 1. While stirring this suspension, 167 g of the above rubber latex dispersion liquid (10% relative to CNT) was added. By continuously stirring the entirety, a feathery mass formed by combining CNTs with rubber is generated.

Thereafter, the feather-shaped block was dehydrated by a centrifugal dehydrator so that the water content thereof became 80% by weight or less.
Next, the feather-shaped block was granulated by a granulator, and then dried at 90 ° C. for 5 hours using a hot air dryer to prepare a rubber pellet.

(Comparative example 2)
Except that the emulsified polymerized styrene butadiene rubber latex of Comparative Example 1 was changed to the natural rubber latex used in Example 4, the CNT highly blended granules were prepared under the same formulation or kneading conditions as those of Comparative Example 1. .

(Test example)
(1) Measurement of the amount of inhalable dust The amount of inhalable dust refers to the inhalable dust reaching the alveoli, and generally indicates the dust below 10 μm. For the measurement system, "Shikada Science and Technology Co., Ltd.'s SKY-2 dust accumulation device" was used.

CNTs were introduced into the airflow flowing at a speed of 10 L / min in the apparatus shown in FIG. 1 from below. The amount of CNTs to be charged was changed to a minimum of 50 mg, and the range in which the amount of dust converged between 0 and 10 mg was changed in five steps. For example, in the case of k-Nanos 100P, the amount of dust when the input amount is changed by 50 mg, 100 mg, 150 mg, 200 mg, and 300 mg is measured. The pulverized particles are classified by a multi-layer type separating device, and only the particles below 10 μm are adsorbed on the filter paper located at the subsequent stage. The amount of scattering is determined as the amount of inhaled dust by measuring the weight adsorbed on the filter paper; the comparison amount of dust among all the samples is determined by the amount of dust when the input amount is 268 mg. A total of 6 measurement samples were K-Nanos100p manufactured by Kumho and Examples 1 to 4 and Comparative Examples 1 and 2 which were processed. The measurement results are shown in Table 2.

(2) Fluidity of rubber granules After a glass funnel with the inner diameter of 5 mm in the thinnest part was set on a 100 cc beaker, 10 g of CNT was poured into the funnel, and the time until all of the funnel flowed out of the beaker was measured.
The test results are shown in Table 3.

(3) The particle size distribution of the rubber granules is based on the measurement method in JIS K 6219-4 ("Characteristics of Carbon Black Granulated Particles for Rubber-Part 4 Distribution of Granulated Particles"). 8 and 6 are used as sieve systems. , 12, 16, 30, 60, and 100.
The test results are shown in Table 1.

(Exquisite results)
From Table 2, it was found that the amount of re-dust was significantly reduced compared to K-Nanos-100p, which was used as a raw material in any of the granulated products of Examples 1 to 4 and Comparative Examples 1 to 2. Comparing Examples 1 and 2 with Comparative Examples 1 and 2 loaded with 10% by weight and 5% by weight of rubber latex, it is determined that the granulated product of the example is less than 1/5 to 1 / of the amount of re-emission dust compared to the comparative example. 9. In addition, if the examples are examined with each other, the smaller the loading amount of rubber, the higher the amount of re-dust, and the tendency of SBR latex products to have a lower amount of re-dust than that of NR latex products.

According to Table 3, if the particle size distributions of Examples 1 and 2 and Comparative Examples 1 and 2 in which 10% of rubber is loaded with respect to CNT are compared, the rubber particles in the examples are mainly those having a particle size of 1000 to 1400 μm. There are few particles below 100 μm. On the other hand, the rubber particles of the comparative example are more than 500-250 μm of the small particles of the example, and there are also more of 100 μm to 100 μm that are easy to scatter. In addition, if 4 pieces of Examples are observed in detail, it can be seen that the smaller the amount of rubber loaded, the smaller the particle size of the granulated product tends to be. In addition, it was found that there was almost no difference between SBR latex and NR latex.

In addition, the difference in this particle size distribution is also related to the fluidity of the rubber granules. The time it takes for 10 g of the sample to fall in the funnel with a diameter of 5 mm indicates that the example is 5 to 6 seconds. In contrast, the comparative example requires about 10 to 12 seconds, which is about twice the time.

The worse the fluidity, the less “mass flow” can be obtained, and “funnel flow” (only the phenomenon that the powder directly above the discharge port is discharged first) or “bridge” (the powders are at The discharge port of the hopper forms an arch bridge structure and is blocked); the mass flow is discharged from the hopper, etc., and the powder surface sinks almost horizontally like a liquid and is discharged completely.

Based on the results of the examples described above, the safety risk represented by harmfulness (toxicity) × exposure (intake) can be greatly reduced, and it is possible to reduce the cognition among operators who are deeply implanted in handling CNTs. "However, CNT is a dangerous material."

[Industrial availability]

In the present invention, CNTs are coated with various rubber latexes as adhesives, and by allowing rubber to penetrate into the CNTs, the CNTs are granulated with a high blending amount, which can greatly reduce scattering properties, thereby greatly reducing safety. risks of. In addition, it can be used for mass production at low cost, and can significantly improve workability such as processability and handling when blended with matrix resin or matrix rubber, wettability with polymer matrix, dispersibility, electrical conductivity, and mechanical properties. And, it does not require large equipment, can shorten the manufacturing steps, and the particle size distribution of the rubber granules is sharp. The usefulness of the highly granular CNT-blended rubber granules is extremely high. The manufacturing method of the highly granular CNT-blended rubber granules .

FIG. 1 is an explanatory diagram of the dust re-dusting device.

Claims (4)

A method for manufacturing rubber granules with highly blended carbon nanotubes, comprising: (1) Put a nano carbon tube and water in an amount corresponding to the concentration of the aforementioned nano carbon tube in an amount of 0.1 to 8% by weight into a container, and stir to form a water mixing step of a dispersion liquid; (2) a rubber mixing step of adding and mixing a rubber latex to the dispersion; the amount of the rubber latex is equivalent to 100 parts by weight of the rubber component (solid content) of the above-mentioned nano carbon tube relative to the rubber component (solid content) of the rubber latex; 100 ~ 5000 parts by weight; (3) a granulation step of producing granulated materials (rubber granules) while dripping a water-insoluble solvent while stirring the obtained mixed solution, while transferring the nano carbon tube from an aqueous phase to a rubber phase; (4) Secondly, a separation step for separating the aforementioned aqueous phase from the aforementioned granulated material; and (5) A drying step of drying the separated granules. A method for manufacturing rubber granules with highly blended carbon nanotubes, comprising: (1) Put water into the container in an amount corresponding to the concentration of the carbon nanotube of 0.1 to 8% by weight, and the rubber component (solid content) corresponding to the amount of the carbon nanotube added to the rubber latex (100%) A step of making a rubber latex in an amount of 100 to 5000 parts by weight and stirring to prepare a dispersion liquid; (2) a step of adding a nano carbon tube to the aforementioned dispersion and mixing and dispersing; (3) a granulation step of producing granulated materials (rubber granules) while dripping a water-insoluble solvent while stirring the obtained mixed solution, while transferring the nano carbon tube from an aqueous phase to a rubber phase; (4) a separation step for separating the aforementioned aqueous phase from the aforementioned granulated matter; and (5) A drying step of drying the separated granules. A method for manufacturing rubber granules with highly blended carbon nanotubes, comprising: (1) Put 100% by weight of rubber latex in terms of the rubber content (solid content) of rubber latex, and put carbon nanotubes in an amount equivalent to 100 to 5000 parts by weight and the concentration of 0.1 to 8 equivalent to the aforementioned carbon nanotubes. A mixing and dispersing step of mixing and dispersing water in an amount of% by weight; (2) Secondly, a granulation step of manufacturing granules (rubber granules) while dripping a water-insoluble solvent to transfer a carbon nanotube from an aqueous phase to a rubber phase; (3) secondly, a separation step for separating the aforementioned aqueous phase from the aforementioned granulated material; and (4) A drying step of drying the separated granules. The method for producing a rubber granule with a highly mixed carbon nanotube according to any one of claims 1 to 3, wherein the fiber diameter of the carbon nanotube is 1 to 200 nm and the fiber length is 1 to 500 μm.