JP2019052275A - Carbon nanotube/carbon black/rubber composite and production method of the same - Google Patents

Abstract

To provide a CNT/carbon black/rubber hybrid composite in which carbon nano-tubes (CNTs) and carbon black are disposed in potential-energetically stable coordination positions and are highly uniformly dispersed.SOLUTION: In a CNT/carbon black/rubber composite, the second creep, which is measured in the dynamic creep and in which transition to stable coordination positions of the CNT/carbon black in the rubber occurs, is 25% or less of the total creep amount. In a production method of the CNT/carbon black/rubber composite, a mixed liquid of a CNT aqueous dispersion prepared by dispersing CNTs in water and a carbon black aqueous dispersion prepared by dispersing carbon black in water is ejected from a high pressure nozzle by using a water jet type wet fine comminution apparatus and is subjected to shear collision mixing and dispersing so as to obtain a mixed dispersion, and the mixed dispersion is subjected to co-coagulation with a rubber latex.SELECTED DRAWING: Figure 5

Description

  In the present invention, carbon nanotubes (hereinafter sometimes referred to as “CNT”) and carbon black (hereinafter sometimes referred to as “CB”) are arranged in a stable configuration in terms of potential energy in rubber. The present invention relates to a uniformly dispersed carbon nanotube / carbon black / rubber hybrid composite and a method for producing the same.

  CNTs are expected to improve mechanical strength, impart electrical conductivity, and the like by blending with CNTs and rubber. However, since CNTs have strong cohesiveness and are entangled with each other, it is very difficult to uniformly disperse them in resin or rubber. Therefore, various dispersion improvement methods have been proposed.

For example, Patent Document 1 discloses a method of kneading by applying high shear force with an open roll having a roll interval of 0.5 mm or less, and Patent Document 2 kneading by applying a high shear force by dividing the roll gap into two stages. Each method has been proposed. Patent Document 3 describes a method of kneading by adjusting the shear rate at the initial stage of kneading to 10 to 1000 cm ⁻¹ .
However, in these methods, there is a concern that the molecular chain of the rubber is cut and deteriorated, and there is a concern that the CNT is broken due to a large shearing force. These kneading methods are called DRY-mix methods, and when the present inventors re-examined the examples described in Patent Documents 1 and 2 that the CNT dispersion is most advanced, As will be described later, the amount of the second creep was 28.1 to 28.3% of the total creep amount (Comparative Example 6), which was not far from 25% or less of the present invention.

  As a method that does not apply a high shearing force, a so-called wet-type wet masterbatch method has been proposed in which CNTs are mixed into a water slurry and mixed with rubber latex to solidify. For example, Patent Document 4 describes a technique in which a water slurry of carbon black and carbon fiber is mixed with rubber latex and solidified. In Patent Document 4, CNTs are dispersed in water using a colloid mill or a homogenizer. However, when the inventor re-executed the embodiment of Patent Document 4, the water jet type wet refiner as in the present invention is used. Therefore, the obtained composite has a second creep amount of 29.1 to 29.2% of the total creep amount as shown in Comparative Example 1 described later. It was not stable.

  Patent Document 5 describes a method in which nano-carbon of 5 phr (parts by weight per 100 parts by weight of rubber) or less is mixed with natural rubber latex by a wet method. This method uses carbon black only with CNTs. This is a method different from the present invention in which the interaction between CNT and carbon black is essential (Comparative Example 2 described later).

  In Patent Document 6, a conductive material is unevenly distributed in two or more kinds of rubber blend sea-island structure seas (continuous phase), most of which are DRY-mix methods. Although there is a description of the method, as in Patent Document 5, this is a method different from the present invention, which is a CNT-only system and requires interaction with carbon black (Comparative Example 2 described later).

  In Patent Document 7, 100 parts by weight of rubber is dissolved in a solvent, and stirred with a large amount of water slurry of 100 to 1500 parts by weight of CNT with respect to 100 parts by weight of rubber, CNT is transferred to a rubber phase, and CNT is coated with rubber. Yes. Patent Document 7 also describes that 100 to 1500 parts by weight of 100 parts by weight of rubber latex is brought into contact with a large amount of CNT water slurry. However, this system is also a method different from the present invention in which the interaction with carbon black is essential only with CNT (Comparative Example 2 described later).

  Patent Document 8 discloses a rubber / former in which a rubber latex containing an alkylbenzene sulfonate as an emulsifier is mixed with a CNT dispersion obtained by dispersing CNT in an aqueous solution containing a cationic polymer / nonionic surfactant / anionic surfactant. CNT composites are described. This method also does not perform powerful shear collision mixing and dispersion by a water jet type wet micronizer as in the present invention (Comparative Example 1 described later), and is a CNT-only system. This is a technique different from that of the present invention in which the action is essential (Comparative Example 2 described later).

  Patent Document 9 proposes a method using conductive carbon black instead of CNT as a filler. Generally, conductive carbon black has poor dispersibility in rubber, so that it has fracture characteristics and flex crack resistance. There is a problem that decreases.

  Any of these documents is merely an example of a wet method and does not suggest a method for producing the CNT / carbon black / rubber hybrid composite of the present invention.

JP 2005-97525 A JP 2008-024800 A JP 2009-46547 A JP 2006-193620 A Special table 2015-532660 gazette JP2013-204209A JP2012-126653A JP 2016-37531 A Japanese Patent Laid-Open No. 2015-34280

  As described above, although various proposals have been made for a method for producing a CNT / carbon black / rubber composite, all of the conventional methods are so-called a mixture of rubber, CNT, and carbon black. It cannot be said that carbon black is well co-dispersed.

  An object of the present invention is to provide a CNT / carbon black / rubber hybrid composite in which CNT and carbon black are arranged in a stable configuration in terms of potential energy and are uniformly dispersed in rubber.

As a result of repeated studies on a method for producing a CNT / carbon black / rubber composite in order to solve the above-mentioned problems, the present inventors have found that a CNT / carbon black / rubber composite produced by a specific method is CNT in rubber. And carbon black are arranged in a stable configuration in terms of potential energy, and are a highly uniformly dispersed CNT / carbon black / rubber hybrid composite, so that the CNT / carbon black measured by dynamic creep measurement It has been found that the second creep that transfers to a stable coordination position with low potential energy in rubber is 25% or less of the total creep amount.
That is, when co-coagulating an aqueous dispersion of CNT and carbon black with rubber latex, a CNT aqueous dispersion in which CNT is super-dispersed in water with a homogenizer or the like, and carbon black in which carbon black is super-dispersed in water with a homogenizer or the like The water dispersion is sprayed from a high-pressure nozzle with a water jet type wet micronizer and is strongly sheared and mixed, so that the carbon black and CNT are strongly entangled and interacted without self-aggregation of the CNT. It was found that a CNT / carbon black / rubber hybrid composite that was well dispersed in rubber with carbon black entering the CNT fiber gaps and coordinated stably in terms of potential energy was obtained.

  The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] A carbon nanotube / carbon black / rubber composite in which the second creep measured by the following dynamic creep measurement method is 25% or less of the total creep amount.
<Dynamic creep measurement method>
To 160 parts by weight of the carbon nanotube / carbon black / rubber composite, 1.0 part by weight of stearic acid, 3.0 parts by weight of zinc oxide, 1.75 parts by weight of sulfur and 1.40 parts by weight of vulcanization accelerator were added and kneaded. The obtained unvulcanized product was vulcanized under the condition of 160 ° C. to obtain a cylindrical vulcanized sample having a diameter of 10 cm and a height of 20 cm. The dynamic creep is measured at 839 Hz and a shear stress of 0.55 to 0.70 MPa.

[2] The carbon nanotube / carbon black / rubber composite according to [1], which contains 22% by weight or more of bound rubber.

[3] The carbon nanotube / carbon black / rubber composite according to [1] or [2], wherein the carbon nanotube and carbon black dispersion degree according to ASTM D2663 is 97% or more.

[4] The carbon nanotube / carbon black / rubber composite according to any one of [1] to [3], which has a volume resistivity value of 10 ⁵ Ω · cm or less.

[5] A method for producing a carbon nanotube / carbon black / rubber composite by co-coagulation of a rubber latex and an aqueous dispersion of carbon nanotubes and carbon black, wherein the carbon nanotubes are dispersed in water to form carbon nanotubes. A step of preparing an aqueous dispersion, a step of preparing a carbon black aqueous dispersion by dispersing carbon black in water, and using a water jet type wet micronizer, the carbon nanotube aqueous dispersion and the carbon black water A step of obtaining a mixed water dispersion of carbon nanotubes and carbon black by spraying the mixed liquid of the dispersion from a high-pressure nozzle and dispersing and dispersing the mixture, and a step of co-coagulating the mixed water dispersion with the rubber latex. Carbon nanotube / carbon black / rubber composite Method of manufacturing the body.

[6] The carbon nanotube / carbon black / rubber composite manufacturing method according to [5], wherein the carbon nanotube has a fiber diameter of 8 nm to 15 nm and an aspect ratio of 100 or more.

[7] The carbon nanotube according to [5] or [6], wherein the carbon black is a non-oxidized carbon black having a nitrogen adsorption specific surface area of 30 to 120 m ² / g and / or a DBP oil absorption of 50 to 140 ml / 100 g. A method for producing a carbon black / rubber composite.

  According to the present invention, it is possible to provide a CNT / carbon black / rubber hybrid composite in which CNT and carbon black are arranged in a stable configuration in terms of potential energy in rubber and are highly uniformly dispersed.

It is a schematic diagram which shows the principle of the dynamic creep measuring method. It is a graph which shows the dynamic creep curve of carbon black mixing | blending SBR vulcanizate. It is an image figure of a stable coordination structure. It is an image figure which shows the transition to the stable coordination structure of CNT / carbon black / rubber composite of this invention, and a conventional product. It is a graph which shows the measurement result of the dynamic creep of Example 1 and Comparative Example 3. It is a graph which shows the measurement result of the dynamic creep of Example 2 and Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described in detail.

[Method for producing CNT / carbon black / rubber composite]
First, a method for producing the CNT / carbon black / rubber composite of the present invention will be described.

In the method for producing a CNT / carbon black / rubber composite of the present invention, in producing a CNT / carbon black / rubber composite by co-coagulating a rubber latex and an aqueous dispersion of CNT and carbon black,
A step of ultra-dispersing CNT in water with a homogenizer or the like to prepare a carbon nanotube aqueous dispersion (hereinafter sometimes referred to as “CNT water slurry”);
A step of preparing a carbon black aqueous dispersion (hereinafter sometimes referred to as “carbon black water slurry”) by superdispersing carbon black in water with a homogenizer or the like;
Mixing and dispersing CNT and carbon black by mixing the obtained CNT water slurry and carbon black water slurry, and spraying this mixture from a high-pressure nozzle using a water jet type wet micronizer and shearing and mixing and dispersing. A step of obtaining a liquid (hereinafter sometimes referred to as “mixed water slurry”);
A CNT / carbon black / rubber composite is manufactured through a step of co-coagulating the obtained mixed water slurry with rubber latex.

  In accordance with the present invention, a mixture of CNT water slurry and carbon black water slurry is ejected from a high-pressure nozzle of a water jet type wet micronizer, and CNT and carbon black obtained by mixing and dispersing by powerful shear collision. By co-coagulating the mixed water slurry with rubber latex, the CNT and carbon black are strongly entangled, and the carbon black enters the gap between the CNT fibers without self-aggregation of the CNT. It is possible to obtain a CNT / carbon black / rubber hybrid composite that is uniformly dispersed in the rubber by interaction and is stably coordinated in terms of potential energy.

<Carbon nanotube (CNT)>
The CNT used in the present invention is not particularly limited, and examples thereof include single wall (single layer) CNT and multi wall (multilayer) CNT. The CNT used in the present invention has a small fiber diameter, preferably a fiber. Those having a diameter of 8 nm to 15 nm and an aspect ratio of 100 or more, for example, 100 to 3,500 are preferable. The aspect ratio here is the ratio of the length of the CNT to the diameter.
The fiber diameter and aspect ratio of CNT are the average values measured by an electron microscope, but catalog values can be adopted for commercial products.

  CNT may use only 1 type and may use it in combination of multiple types.

<CNT water slurry>
The method for producing the CNT water slurry is not particularly limited. For example, water is added to CNT to prepare a slurry, and a dispersant is added to the water slurry, followed by stirring and dispersing with a homogenizer, a bead mill, or the like. A slurry is preferred.

  The dispersant is not particularly limited, and lignin sulfonate, naphthalene sulfonate, alkylphenols, quaternary ammonium salts, glycidyl ethers, ether alcohols, amino acids, proteins, and the like can be used. Among these dispersants, a CNT water slurry can be prepared using one or more suitable dispersants.

  The CNT concentration of the CNT water slurry is preferably 1.0% by weight or less, particularly 0.8% by weight or less, while 0.20% by weight or more, particularly 0.28% by weight or more. When the CNT concentration of the CNT water slurry is less than or equal to the above upper limit, the CNT dispersibility of the CNT water slurry is easily improved, and when the CNT concentration is greater than or equal to the above lower limit, productivity can be increased.

  Further, the dispersant is preferably added in a proportion by weight of water of 0.2% by weight or more, particularly 0.5% by weight or more, while 2.0% by weight or less, particularly 1.5% by weight or less. When the amount of the dispersant used is within the above range, the dispersion effect by the dispersant can be sufficiently obtained.

  There is no particular limitation on the dispersion treatment time by a homogenizer or the like for preparing the CNT water slurry, and it is sufficient that a CNT water slurry in which CNTs are sufficiently loosened and dispersed can be obtained, but it is usually about 20 to 50 minutes.

<Carbon black>
As the carbon black, non-oxidized carbon black that is not oxidized and has a nitrogen adsorption specific surface area of 30 to 120 m ² / g and / or DBP oil absorption of 50 to 140 ml / 100 g is used. Since it is high, it is preferable from the viewpoint that the reinforcing property of rubber can be enhanced. Oxidized carbon black is not preferable because of its poor rubber reinforcement. Further, carbon black having both a nitrogen adsorption specific surface area and a DBP oil absorption amount outside the above ranges is not preferable because the reinforcing property of the rubber is poor. Here, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is measured according to JIS K6217. The DBP oil absorption of carbon black is measured according to JIS K6221A.

<Carbon black water slurry>
The method for producing the carbon black water slurry is not particularly limited, and the dispersant described in the CNT water slurry may be used, but in the case of carbon black, it is prepared by vigorous stirring with a homogenizer or the like without using the dispersant. It is also possible.

  The carbon black concentration of the carbon black water slurry is preferably 8.0% by weight or less, particularly 7.0% by weight or less, while being 3.0% by weight or more, particularly 4.0% by weight or more. When the carbon black concentration of the carbon black water slurry is not more than the above upper limit, the carbon black water slurry has a good dispersibility of the carbon black. On the other hand, when the carbon black concentration is not less than the above lower limit, the productivity is increased. be able to.

  There is no particular limitation on the dispersion treatment time by a homogenizer or the like for preparing a carbon black water slurry, and it is sufficient that a water slurry in which carbon black is sufficiently uniformly dispersed can be obtained, but it is usually about 20 to 50 minutes.

<Preparation of mixed water slurry of CNT and carbon black>
In the present invention, it is important to enhance the interaction between CNT and carbon black when co-coagulating a rubber slurry and a water slurry of CNT and carbon black. For this purpose, in the present invention, CNT and carbon black are separately dispersed in water using a homogenizer or the like, and then mixed together, and the mixture is vigorously sheared and collided with a water jet wet micronizer. That is, the CNT water slurry and the carbon black water slurry are stirred and mixed by a homogenizer or the like for about 20 to 50 minutes, and this mixed solution is sprayed from a high-pressure nozzle of a water jet type wet micronizer to be subjected to shear collision mixing and dispersion.
Here, the shear collision mixing dispersion means that a high shearing force is applied from a high pressure nozzle to apply a large shear force to collide CNT and carbon black in the injection liquid, and these are highly dispersed and mixed. Sure.

  As a water jet type wet micronizer, Sugino Machine Optimizer HJP-25005 can be used, but the water jet type wet micronizer to be used is not particularly limited.

Moreover, it is preferable that the nozzle diameter (injection port diameter) of the high pressure nozzle used for injection of a liquid mixture is about 0.1 to 0.15 mm. If the nozzle diameter of the high pressure nozzle is smaller than the lower limit, the injection efficiency is poor, and if it is larger than the upper limit, it may be difficult to apply a sufficiently large shearing force.
The pressure applied during injection is preferably 200 MPa or more, for example, about 200 to 245 MPa, and the injection speed is preferably 500 m / sec or more, for example, about 500 to 700 m / sec. If the pressure applied during injection and the injection speed are too small, sufficient shearing force cannot be applied. However, there is an upper limit to the pressure and jetting speed due to the specifications of the water jet type wet micronizer, and it is usually below the upper limit.
In addition, you may repeat the shear collision mixing dispersion | distribution by a water jet type wet refinement | miniaturization apparatus in multiple times.

  Thus, by co-solidifying the mixed water slurry obtained by the shear collision mixing and dispersion using the water jet type wet micronizer with the rubber latex, the CNT and the carbon black are strongly entangled, and the CNT is self-propagating. It is possible to obtain a CNT / carbon black / rubber composite in which carbon black and CNT are uniformly dispersed in rubber by interaction without coagulation and coordinated in a stable arrangement in terms of potential energy.

  In addition, the mixing ratio of the mixed liquid of the CNT water slurry and the carbon black water slurry used for the water jet type wet micronizer is based on the rubber solid content in the CNT / carbon black / rubber composite produced in the co-coagulation step described later The mixing ratio of each water slurry is appropriately adjusted according to the CNT concentration and the carbon black concentration of each water slurry so that the CNT content and the carbon black content fall within the preferable ranges described later.

<Rubber latex>
The rubber latex used in the present invention is not particularly limited as long as it can be made into a latex. For example, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), isoprene rubber (IR), butadiene rubber ( BR) etc. 1 type or 2 types or more are mentioned.
In particular, styrene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR) are preferable, and SBR is particularly preferable.

The molecular weight (weight average molecular weight (Mw)) of the rubber component is not particularly limited, but is 1 × 10 ⁴ to 1 × 10 ⁷ , particularly 1 × 10 ⁵ to 1 × 10 ⁶ , particularly 4 × 10 ^{5 to} 7 × 10. ⁶ is preferable.

The rubber latex is prepared, for example, in the presence of an emulsifier, with the reaction solution obtained by synthesizing the synthetic rubber by an emulsion polymerization method as it is, or by appropriately diluting or adding an emulsifier. Alternatively, a latex may be prepared by phase inversion of a reaction solution obtained by synthesizing a synthetic rubber by a solution polymerization method into an aqueous system in the presence of an emulsifier.
Examples of the emulsifier include long-chain linear alkylbenzene sulfonate having about 10 to 18 carbon atoms. Of these, sodium salts, particularly sodium dodecylbenzenesulfonate, are preferred. The rubber component concentration in the rubber latex is usually about 18 to 25% by weight.

<Co-coagulation process>
In the present invention, the rubber latex is co-coagulated with the mixed water slurry obtained by the shear collision mixing and dispersion using the water jet type wet micronizer described above.

  Specifically, by mixing rubber latex and mixed water slurry, adding a coagulant and co-coagulating it at a predetermined pH, carbon black and CNT can be well rubberized without self-aggregation of CNT. A CNT / carbon black / rubber composite that is uniformly dispersed therein and stably coordinated is obtained.

  The mixing ratio of the rubber latex and the mixed water slurry at this time is such that the CNT content is 1 to 40 parts by weight, particularly 2 to 30 parts by weight, based on 100 parts by weight of the rubber solid content of the obtained CNT / carbon black / rubber composite. It is preferable that the carbon black content is 30 to 100 parts by weight, particularly 35 to 80 parts by weight. Further, the total content of CNT and carbon black in the obtained CNT / carbon black / rubber composite is 20 to 100 parts by weight, particularly 30 to 80 parts by weight with respect to 100 parts by weight of the rubber solid content. It is preferable to prepare such that the weight ratio of CNT: carbon black = 1: 7-30. If the content of CNT and carbon black is less than the above lower limit, it is not possible to sufficiently obtain an effect of improving mechanical strength and conductivity by dispersing them in the rubber, and conversely, the content is higher than the upper limit. And processability of the obtained CNT / carbon black / rubber composite is lowered. In addition, from the viewpoint of dispersion interaction between CNT and carbon black, the content ratio of CNT and carbon black is generally preferably more carbon black than CNT, and the weight ratio of CNT and carbon black is It is preferable to be within the range.

  Further, the total concentration of CNT and carbon black with respect to the water in the mixed liquid of the rubber latex and the mixed water slurry (including water in the rubber latex but not in the coagulant aqueous solution described later) is 1 It is preferably from 0.0 to 6.0% by weight, particularly from 1.2 to 5.0% by weight, from the viewpoint of co-coagulation stability and productivity.

  As the coagulant, it is preferable to use an inorganic acid and a polyamine and not use a salt. By using an inorganic acid and polyamine without using a salt as a coagulant, the coagulation rate can be adjusted to an appropriate range, and CNT / carbon black / carbon black / carbon black / carbon black / carbon black / carbon / A rubber composite can be obtained.

  As the inorganic acid as the coagulant, one or more of sulfuric acid, formic acid, hydrochloric acid and the like can be used, but sulfuric acid is preferably used from the viewpoint of controlling the coagulation pH.

As _{the, H 2 NC 2 H 4 (} NHC 2 H 4) n NH 2 (n is an integer of five or more) is preferable to use those represented by polyamines, _{particularly, H 2 NC 2 H 4 (} NHC It is preferable to use a mixture of a polyamine of ₂ H ₄ ) _n NH ₂ (n is an integer of 5 or more) and pentaethylenehexamine (straight chain).

  The inorganic acid as the coagulant is used in the range of 0.9 to 2.2% by weight, particularly 1.0 to 2.0% by weight, based on the rubber solid content in the mixture of the rubber latex and the mixed water slurry. Preferably, the polyamine is used in the range of 0.3 to 0.9% by weight, particularly 0.4 to 0.7% by weight, based on the rubber solid content in the mixed solution, and the total of the inorganic acid and the polyamine is used. Thus, it is preferable to use 1.2 to 3.1% by weight based on the rubber solid content.

_{Polyamine, H 2 NC 2 H 4 (} NHC 2 H 4) n NH 2 if (n is integer of 5 or more) using a mixture of the pentaethylenehexamine (linear), _H 2 _NC 2 _H in the mixture ₄ (NHC ₂ H ₄ ) _n NH ₂ (n is an integer of 5 or more) / pentaethylenehexamine (straight chain) has a weight ratio of 1.05 / 0.45 to 2.45 / 1.05. preferable.

  By setting the addition amount of the coagulant in the above range, the rubber component is coagulated at an appropriate rate, CNT and carbon black are uniformly dispersed in the rubber, and there are many CNT, carbon black and rubber contacts, so-called Alloying makes it possible to obtain a CNT / carbon black / rubber composite having strong compatibility and adhesion between CNT and carbon black and rubber.

  The above-mentioned coagulant is usually added to the mixed solution of the mixed water slurry and the rubber latex as an aqueous solution of about 0.7 to 2.5% by weight.

  In addition, it is preferable that pH in the liquid mixture in a coagulation process is 2.8-4.8. Moreover, you may add an emulsifier, an extension oil component, etc. to the liquid mixture of this coagulation process as needed. Moreover, you may add electroconductive components other than CNT and carbon black, the additive at the time of the rubber vulcanization mentioned later, etc.

<Separation of CNT / carbon black / rubber composite>
After the above co-coagulation step, the formed solid coagulated crumb is separated, washed with water, dehydrated, and dried at about 80 to 110 ° C. to obtain the CNT / carbon black / rubber composite of the present invention. .

[CNT / carbon black / rubber composite]
Next, various physical properties of the CNT / carbon black / rubber composite of the present invention will be described.
The CNT / carbon black / rubber composite of the present invention is not limited to the above-described method for producing the CNT / carbon black / rubber composite of the present invention as long as it can obtain a material satisfying the following suitable physical properties. It may be manufactured by any method.

<Dynamic creep characteristics>
In the CNT / carbon black / rubber composite of the present invention, in the dynamic creep measured by the following method, the second creep that transitions to a stable coordination position having a low potential energy in the rubber of CNT / carbon black, It is characterized by being 25% or less of the total creep amount.
<Dynamic creep measurement method>
To 160 parts by weight of the carbon nanotube / carbon black / rubber composite, 1.0 part by weight of stearic acid, 3.0 parts by weight of zinc oxide, 1.75 parts by weight of sulfur and 1.40 parts by weight of vulcanization accelerator were added and kneaded. The obtained unvulcanized product was vulcanized under the condition of 160 ° C. to obtain a cylindrical vulcanized sample having a diameter of 10 cm and a height of 20 cm. The dynamic creep is measured at 839 Hz and a shear stress of 0.55 to 0.70 MPa.

  Dynamic creep refers to plastic deformation when subjected to dynamic repeated shear stress. For example, as shown in FIG. 1, the dynamic creep is measured by continuously rotating the cylindrical vulcanized sample 1 while applying a constant load of shearing force and measuring the dynamic strain.

  The carbon black composite rubber vulcanizate is a particle-dispersed heterogeneous system and at the same time forms a heterogeneous structure in which rubber molecular chain aggregate phases with different thermodynamic states are dispersed (K. Fujimoto, T. Nishi, Nihon Gomu Kyoukaishi 43,465 (1970)). When such a system is subjected to mechanical stimulation, it has been reported that the system sequentially transitions to a thermodynamically stable state (K. Fujimoto. Nihon Gomu Kyoukaishi, 49, 867 (1976)). In the transition phenomenon to the stable structure in this rubber heterogeneous system, the dynamic creep curve when the system is repeatedly subjected to stress τ in the room temperature range is shown in FIG. It has been found that it is divided into two creeps (K. Fujimoto, T. Hatakeyama, Nihon Gomu Kyoukaishi, 62, 448 (1989)). In the initial stage, the weak physical bond mainly due to the interaction between the rubber molecular chains is sequentially broken (first creep), and then the carbon black particles and CNT are transferred to a stable coordination position with low potential energy (second creep). That is, in FIG. 2, the first creep is a creep resulting from the sequential breakage of the weak physical bond mainly due to the interaction between the rubber molecular chains in the initial stage. In the second creep, the carbon black particles and the CNT have potential energy. Creep caused by transition to a low and stable coordination position.

  The dynamic creep measurement method and measurement results in the present invention will be described in more detail in the Examples section below, but the CNT / carbon black / rubber composite of the present invention contains CNT / carbon black in rubber. The second creep strain that transfers to a stable coordination position with low potential energy is 25% or less of the total creep amount. This value is preferably as small as possible. In the present invention, this value is preferably 24% or less, but since it is a rubber elastic body, its lower limit is usually 17%.

  Among the conventional methods described above, even in the two-stage mixing method (kneading the roll gap in two stages) of Patent Document 1 and Patent Document 2 where the CNT dispersion is best in dry kneading (dry method) kneaded with a roll or the like, As shown in Comparative Example 6 below, the second creep is 28% or more, which is inferior in terms of stable coordination as compared with the CNT / carbon black / rubber composite of the present invention. That is, the second creep is small relative to the total creep amount. The CNT / carbon black / rubber composite of the present invention has a large amount of CNT / carbon black that was originally stably coordinated in terms of energy. It shows that a structure is formed.

  Fig. 3 is a simple image of this. When the sand 3 is put in the cup 2 and tapped up and down as shown in FIG. 3A, the sand surface slightly sinks as shown in FIG. This tapping is a mechanical stimulus in the later stage of the dynamic creep test, and the amount of sand that has sinked corresponds to the second creep strain. That is, as shown in FIG. 4, since the CNT / carbon black in the CNT / carbon black / rubber composite (FIG. 4 (c)) of the present invention is originally arranged more uniformly microscopically, It can be seen that the second creep strain is smaller than that of 4 (a)).

<Bound rubber amount>
The CNT / carbon black / rubber composite of the present invention preferably has a bound rubber content as much as 22% by weight or more.
The bound rubber here refers to the rubber that remains unextracted while bound to the CNT / carbon black when the unvulcanized CNT / carbon black / rubber composite is extracted with a solvent (for example, toluene). A large amount of rubber means that there are many contact points between CNT / carbon black and rubber, and so-called rubber is strongly reinforced with CNT / carbon black.
The larger the bound rubber amount, the better. However, the upper limit is usually 28% by weight.
In addition, the bound rubber amount is specifically measured by the method described in the section of the examples described later.

<CNT / carbon black dispersion degree>
The CNT / carbon black / rubber composite of the present invention has a CNT / carbon black dispersity measured according to ASTM D2663, preferably 97% or more, more preferably 98% or more. It is excellent. The degree of dispersion of CNT / carbon black is preferably as large as possible, and the upper limit is usually 100%.
Specifically, the degree of dispersion of CNT / carbon black is measured by the method described in the Examples section below.

<Volume specific resistance value>
The volume resistivity value of the CNT / carbon black / rubber composite of the present invention is preferably 10 ⁵ Ω · cm or less, more preferably 10 ³ Ω · cm or less. The smaller the volume resistivity value, the better the conductive performance as a CNT / carbon black / rubber composite.
In addition, the volume specific resistance value of the CNT / rubber composite is specifically measured by the method described in the Examples section below.

[Molding and vulcanization of CNT / carbon black / rubber composite]
Addition of additives such as crosslinking agents, crosslinking accelerators, heat stabilizers, anti-aging agents, fillers, plasticizers, colorants, etc. to the CNT / carbon black / rubber composite of the present invention at a predetermined ratio Then, the kneaded product is molded and vulcanized under the rubber vulcanization conditions to obtain products made of various CNT / carbon black / rubber composites.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

CNT and carbon black, other raw materials, and chemicals used in the following examples and comparative examples are as follows.
CNT-1: K-Nanos100T manufactured by Kumu Hopetro Chemical Co., Ltd.
Diameter: 10nm
Length: 26μm
Aspect ratio (length / diameter): 2,600
CNT-2: NC7000 manufactured by Nanocyl
Diameter: 9.5nm
Length: 1.5μm
Aspect ratio (length / diameter): 158
Carbon black: Dia Black I (N220) manufactured by Mitsubishi Chemical Corporation
Nitrogen adsorption specific surface area 114 m ² / g, DBP oil absorption 114 ml / 100 g
Non-oxidizing carbon black

SBR: SBR1502 latex manufactured by Mitsubishi Chemical Corporation and its solidified rubber (SBR1502)
Mooney viscosity: ML _{1 + 4} (100 ° C.) 52
Chloroprene rubber: Denka chloroprene rubber M40
Extension oil: NS oil (TDAE) manufactured by JX Holdings
Emulsifier: Etol 7D manufactured by Harima Chemicals
Stearic acid: manufactured by Nippon Oil & Fats, Inc. Zinc stearate oxide: manufactured by Sakai Chemical Co., Ltd. Zinc oxide type 2 vulcanization accelerator: Sanshin Chemical NS-G

[Evaluation of CNT / carbon black / rubber composite]
The evaluation method of the characteristics of the CNT / carbon black / rubber composites obtained in the following examples and comparative examples is as follows.

<Dynamic creep>
Dynamic creep uses a rotary shear test device (K. Fujimoto, T. Hatakeyama, Nihon Gomu Kyoukaishi, 62,448 (1989)), and a cylindrical vulcanized sample (diameter 10 cm, height 20 cm) that rotates at a constant speed. The rubber composite vulcanizate) was continuously rotated while applying a constant load with a hydraulic cylinder, and its dynamic strain was measured. The frequency was 0.839 Hz, the shear stress τ was tested in two stages of 0.55 MPa and 0.70 MPa, and the creep strain normalized by the instantaneous dynamic strain, that is, the stress dependency of the dynamic creep strain was measured. The normalization was calculated based on a strain with a load time t = 0.1 sec (= instantaneous strain). The sample temperature was measured through a slip ring using a thermocouple attached to the center of the sample, and simultaneously controlled by forced air cooling so that the temperature at the center was in the range of 23 to 27 ° C.

<Bound rubber amount>
About 0.5 g of the CNT / carbon black / rubber composite was cut into 1 mm square, precisely weighed, wrapped in a 325 mesh wire net, and immersed in 60 cc of toluene. After immersing at 25 ° C. for 24 hours, the 325 mesh was taken out and the toluene was discarded. Furthermore, after adding 60 cc of new toluene and immersing for 24 hours, the toluene was similarly discarded, air-dried, dried with a drier, and then calculated as the weight percentage of rubber not eluted in toluene. The measurement was performed at n = 2 and the average value was taken.

<Dispersion degree of CNT / carbon black>
Based on ASTM D2663 (METHOD B), CNT and carbon black dispersities were calculated. That is, the area percentage of undispersed agglomerates of 5 μm or more was measured, and the percentage of CNT and carbon black dispersed to 5 μm or less from the total area of CNT and carbon black in the composite was obtained as CNT / carbon black dispersion (The value obtained by subtracting the area percentage of undispersed agglomerates of 5 μm or more from 100% is CNT / carbon black dispersion degree%). For example, when there is no undispersed lump of 5 μm or more, the CNT / carbon black dispersion degree is 100%, and when the CNT / carbon black amount 10% exists as an undispersed lump, the CNT / carbon black dispersion degree is 90%. The greater the undispersed mass, the smaller the CNT / carbon black dispersion value.

<Volume specific resistance value>
In accordance with JISK7194, when the resistance of the test piece exceeds 10 ⁶ Ω, Hirestar UP (MCP-HT450) (manufactured by Mitsubishi Chemical Corporation) is used, and when it is 10 ⁶ Ω or less, Lorester GP (MCP-T600) ) (Manufactured by Mitsubishi Chemical Co., Ltd.) in an atmosphere of 25 ° C. and humidity of 60%, and calculated according to the following formula.
Volume resistivity (Ω · cm) = Test piece resistance × RCF × T (cm)
RCF: Resistivity correction coefficient T: Test piece thickness (cm)

[Manufacture of CNT / carbon black / rubber wet masterbatch]
A CNT / carbon black / rubber wet masterbatch was produced according to the weight parts in Table 1. Production Example 4 is a production example in which CNT and carbon black were dispersed with a homogenizer, and then was not subjected to shear collision mixing without using a wet micronizer, and Production Example 5 was a production of only CNT / rubber without using carbon black. It is an example.

[Production Example 1]
<Preparation of CNT water slurry>
Add 1715 g of water to 35 g of CNT-1 to make a 2 wt% water slurry, and add 0.2% by weight of lignin sulfonic acid soda and naphthalene sulfonic acid sodium as dispersants to water each, and use a homogenizer for 30 minutes. Stir.

<Preparation of carbon black water slurry>
7560 g of water was added to 315 g of carbon black to form a 4 wt% water slurry, which was stirred for 30 minutes with a homogenizer to prepare a carbon black water slurry.

<Preparation of CNT / carbon black mixed water slurry>
The CNT water slurry and the carbon black water slurry prepared above were mixed, stirred for 5 minutes with a homogenizer, and then pressurized to 200 MPa with a water jet type wet micronizer (Altitizer HJP-25005 manufactured by Sugino Machine). It was jetted at a speed of 500 m / sec with a nozzle having a diameter of 14 mm, and was subjected to strong shear collision mixing. In this way, a CNT / carbon black mixed water slurry was obtained in which CNT and carbon black were strongly entangled and carbon black entered the gap between the CNT fibers.

<Preparation of CNT / carbon black / SBR composite>
To 2,226 g of SBR1502 rubber latex having a rubber solid content of 21.7% by weight (700 g of SBR rubber), 20107 g of diluted water was added, and the CNT / carbon black mixed water slurry prepared above was added with stirring (35 g of CNT, carbon Black amount 315 g). On the other hand, 70 g of safety aroma oil “NS oil” which is an extension oil was added by emulsification with “etol 7D” added with caustic soda as an emulsifier. While stirring these, sulfuric acid and polyamine were added dropwise without adding salts, and coagulation was performed at pH 3.6. The resulting solidified crumb is washed with water, squeezed with a dehydrator and dried with a dryer at 90 ° C, and the carbon black and CNT are well dispersed in the rubber without any self-aggregation of the CNTs. CNT / carbon black / SBR composite was obtained.

[Example 1]
The CNT / carbon black / SBR composite prepared in Production Example 1 was kneaded at 160 ° C. for 3 minutes using a Banbury mixer with the formulation shown in Table 2 to obtain a kneaded product. . Subsequently, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 60 ° C. using a biaxial open roll to obtain an unvulcanized rubber.
This unvulcanized rubber was vulcanized at 160 ° C. to produce a vulcanized sample.

<CNT / carbon black dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 23.4% by weight. The dispersion of CNT / carbon black in the rubber was 99.1% by cross-sectional observation with an optical microscope vulcanized and pressed into a thin film, and CNT and carbon black were well dispersed in SBR. The volume resistivity value was 5.42 × 10 ⁰ Ω · cm.

The dynamic creep measurement results of the vulcanized sample obtained in Example 1 are shown in FIG.
The second creep amount transferred to a stable coordination position in the rubber of the CNT / carbon black of Example 1 measured by dynamic creep was 23.7% of the total creep amount at a shear force τ = 0.55 MPa. When the shearing force was 0.70 MPa, the creep amount was 22.0%. It can be seen that the amount of second creep was small and CNT / carbon black was originally stably coordinated in the rubber.
Incidentally, the second creep amount of Comparative Example 3 (DRY-Mix) described later is 30.0% of the total creep amount when the shearing force τ = 0.55 MPa, and 31.7% of the total creep amount when the shearing force is 0.70 MPa. There was a large amount of second creep transferred to a stable configuration. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

[Production Example 2]
<Preparation of CNT water slurry>
Add 3430 g of water to 70 g of CNT-1 to make a 2% by weight water slurry, and add 0.2% by weight of lignin sulfonic acid soda and naphthalene sulfonic acid sodium as dispersants to water each, and use a homogenizer for 30 minutes. Stir.

<Preparation of carbon black water slurry>
6720 g of water was added to 280 g of carbon black to form a 4 wt% water slurry, which was stirred for 30 minutes with a homogenizer to prepare a carbon black water slurry.

<Preparation of CNT / carbon black mixed water slurry>
The CNT water slurry and the carbon black water slurry prepared above were mixed, stirred for 5 minutes with a homogenizer, and then pressurized to 200 MPa with a water jet type wet micronizer (Altitizer HJP-25005 manufactured by Sugino Machine). It was jetted at a speed of 500 m / sec with a nozzle having a diameter of 14 mm, and was subjected to strong shear collision mixing. In this way, a CNT / carbon black mixed water slurry was obtained in which CNT and carbon black were strongly entangled and carbon black entered the gap between the CNT fibers.

<Preparation of CNT / carbon black / SBR composite>
To 2,226 g of SBR1502 rubber latex having a rubber solid content of 21.7% by weight (700 g of SBR rubber), 20107 g of diluted water was added, and the CNT / carbon black mixed water slurry prepared above was added with stirring (CNT amount of 70 g, carbon Black amount 280 g). On the other hand, 70 g of safety aroma oil “NS oil” which is an extension oil was added by emulsification with “etol 7D” added with caustic soda as an emulsifier. While stirring these, sulfuric acid and polyamine were added dropwise without adding salts, and coagulation was performed at pH 3.7. The resulting solidified crumb is washed with water, squeezed with a dehydrator and dried with a dryer at 90 ° C, and the carbon black and CNT are well dispersed in the rubber without any self-aggregation of the CNTs. CNT / carbon black / SBR composite was obtained.

[Example 2]
Using the CNT / carbon black / SBR composite prepared in Production Example 2, an unvulcanized rubber was obtained in the same manner as in Example 1 except that the formulation of Table 2 was used, and a vulcanized sample was produced in the same manner.

<CNT / carbon black dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 25.2% by weight. The dispersion of CNT / carbon black in the rubber was 98.5% by cross-section observation with an optical microscope vulcanized and pressed into a thin film, and CNT and carbon black were well dispersed in SBR. The volume resistivity value was 1.02 × 10 ⁰ Ω · cm.

The dynamic creep measurement results of the vulcanized sample obtained in Example 2 are shown in FIG.
The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Example 2 measured by dynamic creep was 22.7% of the total creep amount at a shear force τ = 0.55 MPa, At a shearing force of 0.70 MPa, the creep amount was 20.1%. It can be seen that the amount of second creep was small and CNT / carbon black was originally stably coordinated in the rubber.
Incidentally, the second creep amount in Comparative Example 1 (without water jet type wet micronizer treatment) to be described later is 31.0% of the total creep amount when the shearing force τ = 0.55 MPa, and the total creep amount when the shearing force is 0.70 MPa. The second creep amount transferred to the stable coordination was large. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

[Production Example 3]
<Preparation of CNT water slurry>
Add 3430 g of water to 70 g of CNT-2 to make a 2% by weight water slurry, and add 0.2% by weight of lignin sulfonic acid soda and naphthalene sulfonic acid sodium as dispersants to water each, and use a homogenizer for 30 minutes. Stir.

<Preparation of carbon black water slurry>
6720 g of water was added to 280 g of carbon black to form a 4 wt% water slurry, which was stirred for 30 minutes with a homogenizer to prepare a carbon black water slurry.

<Preparation of CNT / carbon black mixed water slurry>
The CNT water slurry and the carbon black water slurry prepared above were mixed, stirred for 5 minutes with a homogenizer, and then pressurized to 200 MPa with a water jet type wet micronizer (Altitizer HJP-25005 manufactured by Sugino Machine). It was jetted at a speed of 500 m / sec with a nozzle having a diameter of 14 mm, and was subjected to strong shear collision mixing. In this way, a CNT / carbon black mixed water slurry was obtained in which CNT and carbon black were strongly entangled and carbon black entered the gap between the CNT fibers.

<Preparation of CNT / carbon black / SBR composite>
To 2,226 g of SBR1502 rubber latex having a rubber solid content of 21.7% by weight (700 g of SBR rubber), 20107 g of diluted water was added, and the CNT / carbon black mixed water slurry prepared above was added with stirring (CNT amount of 70 g, carbon Black amount 280 g). On the other hand, 70 g of safety aroma oil “NS oil” which is an extension oil was added by emulsification with “etol 7D” added with caustic soda as an emulsifier. While stirring these, sulfuric acid and polyamine were added dropwise without adding salts, and coagulation was performed at pH 3.6. The resulting solidified crumb is washed with water, squeezed with a dehydrator and dried with a dryer at 90 ° C, and the carbon black and CNT are well dispersed in the rubber without any self-aggregation of the CNTs. CNT / carbon black / SBR composite was obtained.

[Example 3]
An unvulcanized rubber was obtained in the same manner as in Example 1 except that the CNT / carbon black / SBR composite prepared in Production Example 3 was used and the formulation of Table 2 was used, and a vulcanized sample was produced in the same manner.

<CNT / carbon black dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 22.7% by weight. The dispersion of CNT / carbon black in the rubber was 99.0% by cross-sectional observation with an optical microscope vulcanized and pressed into a thin film, and CNT and carbon black were well dispersed in SBR. The volume resistivity value was 8.42 × 10 ⁰ Ω · cm.

  As a result of the dynamic creep measurement of the vulcanized sample obtained in Example 3, the second creep amount transferred to a stable coordination position in the CNT / carbon black rubber was the total creep amount when the shear force τ = 0.55 MPa. When the shear force was 0.70 MPa, the total creep amount was 21.0%.

[Production Example 4]
<Preparation of CNT water slurry>
Add 3430 g of water to 70 g of CNT-1 to make a 2% by weight water slurry, and add 0.2% by weight of lignin sulfonic acid soda and naphthalene sulfonic acid sodium as dispersants to water each, and use a homogenizer for 30 minutes. Stir.

<Preparation of carbon black water slurry>
6720 g of water was added to 280 g of carbon black to form a 4 wt% water slurry, which was stirred for 30 minutes with a homogenizer to prepare a carbon black water slurry.

<Preparation of CNT / carbon black mixed water slurry>
The CNT water slurry prepared above and the carbon black water slurry were mixed and stirred for 30 minutes with a homogenizer to obtain a CNT / carbon black mixed water slurry. In addition, the collision stirring mixing by the water jet type wet micronizer was not performed.

<Preparation of CNT / carbon black / SBR composite>
To 2,226 g of SBR1502 rubber latex having a rubber solid content of 21.7% by weight (700 g of SBR rubber), 20107 g of diluted water was added, and the CNT / carbon black mixed water slurry prepared above was added with stirring (CNT amount of 70 g, carbon Black amount 280 g). On the other hand, 70 g of safety aroma oil “NS oil” which is an extension oil was added by emulsification with “etol 7D” added with caustic soda as an emulsifier. While stirring these, sulfuric acid and polyamine were added dropwise without adding salts, and coagulation was performed at pH 3.6. The produced solid crumb was washed with water, water was squeezed with a dehydrator and dried with a dryer at 90 ° C. to obtain a CNT / carbon black / SBR composite.

[Comparative Example 1]
Using the CNT / carbon black / SBR composite prepared in Production Example 4, an unvulcanized rubber was obtained in the same manner as in Example 1 except that the formulation shown in Table 2 was used, and a vulcanized sample was produced in the same manner.

<CNT / carbon black dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 16.4% by weight. The dispersion of CNT / carbon black in the rubber was 92.3% by cross-sectional observation with an optical microscope vulcanized and pressed into a thin film, and some poorly dispersed lumps in which CNT self-aggregated in the rubber were found. The volume resistivity value was 2.23 × 10 ¹ Ω · cm.

The dynamic creep measurement result of the vulcanized sample obtained in Comparative Example 1 is shown in FIG.
The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Comparative Example 1 (without treatment with a water jet type wet micronizer) is 31 of the total creep amount when the shear force τ = 0.55 MPa. At 0.0% and a shearing force of 0.70 MPa, the total creep amount was 29.2%, and the second creep amount transferred to the stable configuration was large. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

[Production Example 5]
<Preparation of CNT water slurry>
Add 3430 g of water to 70 g of CNT-1 to make a 2% by weight water slurry, and add 0.2% by weight of lignin sulfonic acid soda and naphthalene sulfonic acid sodium as dispersants to water each, and use a homogenizer for 30 minutes. Stir. Thereafter, carbon black slurry is not added, and only CNT slurry is 500 m / sec by a water jet type wet micronizer (Sugino Machine Ultiizer HJP-25005) with a 0.14 mm diameter nozzle pressurized to 200 MPa. The CNT water slurry was obtained by injecting at a speed of 5 ° C.

<Preparation of CNT / SBR composite>
To 2226 g of SBR1502 rubber latex having a rubber solid content of 21.7% by weight (SBR rubber amount 700 g), 20107 g of diluted water was added, and the CNT water slurry prepared above was added with stirring (CNT amount 70 g). While stirring, without adding salts, sulfuric acid and polyamine were added dropwise to achieve coagulation at pH 3.4. The produced solid crumb was washed with water, water was squeezed with a dehydrator, and dried with a dryer at 90 ° C. to obtain a CNT / SBR composite.

[Comparative Example 2]
An unvulcanized rubber was obtained in the same manner as in Example 1 except that the CNT / SBR composite prepared in Production Example 5 was used and the formulation of Table 2 was used, and a vulcanized sample was produced in the same manner.

<CNT dispersion state / electric resistance measurement evaluation>
The resulting CNT / SBR composite was vulcanized and pressed into a thin film, and the dispersity of CNT in the rubber was 92.1% by cross-sectional observation with an optical microscope. It was. The volume resistivity value was 1.31 × 10 ¹ Ω · cm.

  The second creep amount transferred to a stable coordination position in the rubber of the CNT of Comparative Example 2 measured by dynamic creep was 28.5% of the total creep amount when the shear force τ = 0.55 MPa, and the shear force was 0. At .70 MPa, it was 29.7% of the total creep amount, and the second creep amount transferred to the stable configuration was large. This means that there are many CNTs that were not originally stably coordinated in the rubber. This is probably because carbon black does not exist and the interaction between CNT and carbon black does not work, and CNT partially self-aggregates.

[Comparative Example 3]
Without using a wet masterbatch, dry blending of SBR1502, CNT-1, carbon black, developing oil, and rubber chemicals was performed with a Banbury mixer according to the formulation shown in Table 2. First, materials other than sulfur and vulcanization accelerator are kneaded at 160 ° C. for 3 minutes, then sulfur and vulcanization accelerator are added to the obtained kneaded material, and kneaded at 60 ° C. for 5 minutes using a biaxial open roll. And unvulcanized rubber. Next, this vulcanized rubber was vulcanized in the same manner as in Example 1 to produce a vulcanized sample.

<CNT dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 16.3% by weight. The dispersion of CNT / carbon black in the rubber was 89.1% by cross-sectional observation with an optical microscope that was vulcanized and pressed into a thin film. The volume resistivity value was 6.69 × 10 ¹ Ω · cm.

  The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Comparative Example 3 measured by dynamic creep was 30.0% of the total creep amount when the shear force τ = 0.55 MPa. When the shearing force was 0.70 MPa, it was 31.7% of the total creep amount, and the second creep amount transferred to the stable coordination was large. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

[Comparative Example 4]
Without using a wet masterbatch, dry blending of SBR1502, CNT-1, carbon black, developing oil, and rubber chemicals was performed with a Banbury mixer according to the formulation shown in Table 2. First, materials other than sulfur and vulcanization accelerator are kneaded at 160 ° C for 3 minutes, then sulfur and vulcanization accelerator are added to the obtained kneaded material, and kneaded at 60 ° C for 5 minutes using a biaxial open roll. An unvulcanized rubber was obtained. Next, this vulcanized rubber was vulcanized in the same manner as in Example 1 to produce a vulcanized sample.

<CNT dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 18.3% by weight. Further, the dispersion degree of CNT / carbon black in the rubber was 86.7% by cross-sectional observation with an optical microscope vulcanized and pressed into a thin film, and in some cases, poorly dispersed lumps in which CNT self-aggregated in the rubber were found. The volume resistivity value was 9.42 × 10 ⁰ Ω · cm.

  The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Comparative Example 4 measured by dynamic creep was 31.6% of the total creep amount when the shear force τ = 0.55 MPa. When the shearing force was 0.70 MPa, it was 31.9% of the total creep amount, and the second creep amount transferred to the stable coordination was large. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

[Comparative Example 5]
Without using a wet masterbatch, dry blending of SBR1502, CNT-2, carbon black, developing oil and rubber chemicals was carried out with a Banbury mixer according to the formulation shown in Table 2. First, materials other than sulfur and vulcanization accelerator are kneaded at 160 ° C for 3 minutes, then sulfur and vulcanization accelerator are added to the obtained kneaded material, and kneaded at 60 ° C for 5 minutes using a biaxial open roll. An unvulcanized rubber was obtained. Next, this vulcanized rubber was vulcanized in the same manner as in Example 1 to produce a vulcanized sample.

<CNT dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 15.8% by weight. Further, the dispersion degree of CNT / carbon black in the rubber was 91.2% by cross-sectional observation with an optical microscope vulcanized and pressed into a thin film, and in some cases, a poor dispersion lump in which CNT self-aggregated in the rubber was found. The volume resistivity value was 3.31 × 10 ¹ Ω · cm.

  The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Comparative Example 5 measured by dynamic creep was 29.5% of the total creep amount when the shear force τ = 0.55 MPa. When the shear force was 0.70 MPa, it was 30.2% of the total creep amount, and the second creep amount transferred to the stable coordination was large. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

[Comparative Example 6]
In the dry mix kneaded with a roll or the like without using a wet masterbatch, the two-stage mixing method of Patent Document 1 and Patent Document 2 in which the CNT dispersion is the best, SBR1502, CNT-1 Carbon black, developing oil, and rubber chemicals were dry kneaded. With reference to Patent Document 1 and Patent Document 2, materials other than sulfur and a vulcanization accelerator are first kneaded at a biaxial open roll temperature of 10 to 20 ° C. and a roll gap of 1.5 mm, and then taken out from the roll, and then the roll gap is further removed. Was narrowed to 0.3 mm and roll kneading was performed. Further, thinning was performed 10 times. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes using a biaxial open roll to obtain an unvulcanized rubber. Next, this vulcanized rubber was vulcanized in the same manner as in Example 1 to produce a vulcanized sample.

<CNT dispersion state / electric resistance measurement evaluation>
The amount of bound rubber of the obtained CNT / carbon black / SBR composite was 20.1% by weight. The dispersion of CNT / carbon black in the rubber was relatively good, 94.1%, as observed by a cross section with an optical microscope vulcanized and pressed into a thin film. However, a small amount of CNT undispersed mass was found in the rubber, and the CNT dispersion state was inferior to that of the example. Further, the volume resistivity value was 1.53 × 10 ¹ Ω · cm.

  The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Comparative Example 6 measured by dynamic creep was 28.1% of the total creep amount when the shear force τ = 0.55 MPa. When the shearing force was 0.70 MPa, it was 28.3% of the total creep amount, and the second creep amount transferred to the stable coordination was larger than that of the example of the present invention. This is because the second creep is 28% or more even in the two-stage mixing method of Patent Document 1 and Patent Document 2, which is considered to have the best CNT dispersion in a dry mix kneaded with a roll or the like, and is more stable than the product of the present invention. Indicates not.

[Example 4]
The CNT / carbon black / SBR composite prepared in Production Example 2 and chloroprene rubber (CR) were kneaded at 160 ° C. for 3 minutes using a Banbury mixer with the formulation shown in Table 2. A kneaded product was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded at 60 ° C. for 5 minutes using a biaxial open roll to obtain an unvulcanized rubber. Next, this vulcanized rubber was vulcanized in the same manner as in Example 1 to produce a vulcanized sample.

<CNT / carbon black dispersion state / electric resistance measurement evaluation>
The resulting CNT / carbon black / SBR / CR composite was vulcanized and pressed into a thin film, and the dispersion of CNT / carbon black in the rubber was 98.2% by cross-sectional observation with an optical microscope. Carbon black was well dispersed. Moreover, the volume resistivity value was 2.43 × 10 ² Ω · cm.

  The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Example 4 measured by dynamic creep was 18.7% of the total creep amount at a shear force τ = 0.55 MPa, The shear force of 0.70 MPa was 19.6% of the total creep amount, and it was found that there were many CNT / carbon blacks that were originally stably coordinated.

[Comparative Example 7]
Without using the wet masterbatch, SBR1502, chloroprene rubber (CR), CNT-1, carbon black, developing oil and rubber chemicals were dry kneaded with a Banbury mixer according to the formulation shown in Table 2. First, materials other than sulfur and vulcanization accelerator are kneaded at 160 ° C for 3 minutes, then sulfur and vulcanization accelerator are added to the obtained kneaded material, and kneaded at 60 ° C for 5 minutes using a biaxial open roll. An unvulcanized rubber was obtained. Next, this vulcanized rubber was vulcanized in the same manner as in Example 1 to produce a vulcanized sample.

<CNT dispersion state / electric resistance measurement evaluation>
The resulting CNT / carbon black / SBR / CR composite was vulcanized and pressed into a thin film, and the dispersion of CNT / carbon black in the rubber was 89.5% by cross-sectional observation with an optical microscope. Agglomerated defective dispersion masses were observed. Moreover, the volume resistivity value was 8.87 × 10 ³ Ω · cm.

  The second creep amount transferred to a stable coordination position in the CNT / carbon black rubber of Comparative Example 7 measured by dynamic creep was 27.2% of the total creep amount when the shear force τ = 0.55 MPa. When the shear force was 0.70 MPa, the total creep amount was 28.0%, and the second creep amount transferred to the stable coordination position was larger than that in Example 4. This means that there are many CNT / carbon blacks that were not originally stably coordinated in the rubber.

From Tables 1 and 2, the following can be understood.
That is, in Examples 1 to 4 according to the present invention, when co-solidifying CNT and carbon black with rubber latex, a mixed liquid of CNT water slurry and carbon black water slurry is strengthened by a high pressure nozzle with a water jet type wet micronizer. CNT and carbon black are strongly entangled with each other by collision and dispersion, and carbon black and CNT are dispersed well in the rubber by interaction without self-aggregation of CNT, and the potential energy is stably coordinated. It can be seen that a CNT / carbon black / rubber hybrid composite was obtained. The CNT / carbon black / rubber hybrid composite thus obtained has a good CNT / carbon black dispersion (dispersity of 97% or more in accordance with ASTM D2663) and a large amount of bound rubber (22% by weight or more). The second creep in which the CNT / carbon black measured by dynamic creep moves to a stable coordination position in rubber is less than 25% of the total creep amount, and is originally positioned in a stable potential energy coordination. I understand that it was.

On the other hand, in Comparative Example 1 in which the CNT slurry and the carbon black slurry were not strongly collided, mixed and dispersed by the water jet wet micronizer, the second creep amount transferred to a stable configuration was large, and CNT and carbon It can be seen that the black was not stably coordinated in the rubber. In Comparative Example 2 in which no carbon black was added, the interaction between CNT and carbon black did not work, and the CNT self-aggregated, resulting in unstable coordination in the rubber (second creep amount large).
In Comparative Examples 3 to 7 which are dry kneading (dry method), CNT and carbon black were kneaded into SBR to produce a CNT / carbon black / rubber composite, but the CNT / carbon black dispersion was low, There are also few bound rubbers. Moreover, there are many 2nd creeps, electroconductivity is also inferior compared with the example of this invention, and the CNT / carbon black / rubber composite excellent in the dispersibility like this invention cannot be obtained. The second creep is 28% or more even in the roll two-stage mixing method (kneading the roll gap in two stages) described in Patent Document 1 and Patent Document 2 in which the CNT dispersion is the best in dry kneading, which is more stable than the present invention. A moderate CNT / carbon black / rubber composite was not obtained.
Further, according to the present invention, as in Example 4, it is possible to achieve a stable coordination even by using a blend with another polymer (for example, chloroprene rubber: CR), which is a useful material for various industrial articles and parts. I understand that there is.

1 Vulcanized sample 2 Cup 3 Sand

Claims (7)

A carbon nanotube / carbon black / rubber composite in which the second creep measured by the following dynamic creep measurement method is 25% or less of the total creep amount.
<Dynamic creep measurement method>
To 160 parts by weight of the carbon nanotube / carbon black / rubber composite, 1.0 part by weight of stearic acid, 3.0 parts by weight of zinc oxide, 1.75 parts by weight of sulfur and 1.40 parts by weight of vulcanization accelerator were added and kneaded. The obtained unvulcanized product was vulcanized under the condition of 160 ° C. to obtain a cylindrical vulcanized sample having a diameter of 10 cm and a height of 20 cm. The dynamic creep is measured at 839 Hz and a shear stress of 0.55 to 0.70 MPa.   The carbon nanotube / carbon black / rubber composite according to claim 1, comprising 22% by weight or more of bound rubber.   The carbon nanotube / carbon black / rubber composite according to claim 1 or 2, wherein the carbon nanotube and carbon black dispersion degree according to ASTM D2663 is 97% or more. The carbon nanotube / carbon black / rubber composite according to any one of claims 1 to 3, wherein the volume resistivity value is 10 ⁵ Ω · cm or less. A method of producing a carbon nanotube / carbon black / rubber composite by co-coagulating rubber latex and an aqueous dispersion of carbon nanotubes and carbon black,
Preparing a carbon nanotube aqueous dispersion by dispersing carbon nanotubes in water;
A step of preparing a carbon black water dispersion by dispersing carbon black in water;
Dispersion of carbon nanotubes and carbon black mixed water by spraying a mixed liquid of the carbon nanotube aqueous dispersion and the carbon black aqueous dispersion from a high pressure nozzle and carrying out shear collision mixing dispersion using a water jet type wet micronizer Obtaining a liquid;
A method for producing a carbon nanotube / carbon black / rubber composite comprising the step of co-coagulating the mixed water dispersion with rubber latex.   The method for producing a carbon nanotube / carbon black / rubber composite according to claim 5, wherein the carbon nanotube has a fiber diameter of 8 nm to 15 nm and an aspect ratio of 100 or more. The carbon nanotube / carbon black / rubber composite according to claim 5 or 6, wherein the carbon black is a non-oxidized carbon black having a nitrogen adsorption specific surface area of 30 to 120 m ² / g and / or a DBP oil absorption of 50 to 140 ml / 100 g. Body manufacturing method.

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