JP6933146B2 - Method for manufacturing carbon nanotube / rubber composite - Google Patents

Description

The present invention relates to a method for producing a carbon nanotube / rubber composite in which carbon nanotubes (hereinafter, sometimes referred to as “CNT”) are uniformly dispersed in rubber.

CNT is expected to improve mechanical strength and impart conductivity by blending with resin or 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.

Patent Document 1 describes a diallylamine-based cationic polymer mixture comprising 70 to 90% by weight of a diallylamine-based cationic polymer having a molecular weight of 10,000 to 50,000 and 10 to 30% by weight of a diallylamine-based cationic polymer having a molecular weight of 100,000 to 300,000. , A CNT dispersant comprising an aqueous solution containing an anionic surfactant and a nonionic surfactant is disclosed.

Patent Document 2 describes a carbon nanotube dispersion liquid in which carbon nanotubes are dispersed in a dispersion medium consisting of an aqueous solution containing a diallylamine-based cationic polymer having a molecular weight of 100,000 to 300,000, a nonionic surfactant, and an anionic surfactant. , And a rubber / carbon nanotube composite comprising a rubber latex are disclosed.

However, in the methods disclosed in Patent Documents 1 and 2, there is a problem that solidification is not completed because the nonionic surfactant stabilizes the rubber latex.
Further, Patent Documents 1 and 2 do not describe or suggest the use of diallylamine-based cationic polymers having a weight average molecular weight of 550,000 to 900,000.

Japanese Unexamined Patent Publication No. 2010-241668 Japanese Unexamined Patent Publication No. 2016-37531

An object of the present invention is to simply complete the coagulation of rubber latex and CNT without using a nonionic surfactant that inhibits coagulation and without using a coagulant such as acid, and without self-aggregation of CNTs. It is an object of the present invention to provide a method for producing a CNT / rubber composite uniformly dispersed in rubber.

As a result of repeated studies on a method for producing a CNT / rubber composite in order to solve the above problems, the present inventor has obtained a high molecular weight diallylamine-based cationic polymer having a molecular weight of 550,000 to 900,000 without using a nonionic surfactant. , A low molecular weight diallylamine-based cationic polymer having a molecular weight of 10,000 to 40,000 is used in a predetermined compounding weight ratio, and CNT is dispersed therein to obtain a suspension in which CNT is well dispersed. It has been found that by stirring and mixing with rubber latex, rubber and CNT are completely solidified without adding a coagulant such as acid or amine, and a CNT / rubber composite having uniform CNT dispersion can be obtained.
That is, when a diallylamine-based cationic polymer having a specific molecular weight is mixed at a specific ratio and CNTs are dispersed to co-coagulate the CNT suspension and the rubber latex, the CNTs do not self-aggregate and are uniformly contained in the rubber. The rubber latex is moderately charge-unstable because it is dispersed in the rubber and no nonionic surfactant is added, and the coagulation of the CNT / rubber composite is simply completed without adding a coagulant. As a result, a CNT / rubber composite in which CNTs are uniformly dispersed in rubber is obtained.
At this time, after dispersing the CNT suspension with a homogenizer, a water jet type wet miniaturizer is used, for example, at a pressure of 200 MPa or more and a nozzle having a diameter of 0.1 to 0.15 mm at a speed of 500 m / sec or more. It may be sprayed. In this case, the dispersion of CNTs in the rubber becomes even better.

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

[1] In the absence of a nonionic surfactant, a diallylamine-based cationic polymer having a weight average molecular weight of 550,000 to 900,000 (hereinafter referred to as "high molecular weight diallylamine-based cationic polymer") and a weight average molecular weight of 10,000 to 10,000. A step of preparing a carbon nanotube suspension by mixing 40,000 diallylamine-based cationic polymers (hereinafter referred to as "low molecular weight diallylamine-based cationic polymer") and carbon nanotubes in the presence of an aqueous solvent. It has a step of mixing the carbon nanotube suspension and the rubber latex, and the compounding weight ratio of the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer is high molecular weight diallylamine-based cationic polymer: low molecular weight diallylamine-based. A method for producing a carbon nanotube / rubber composite, wherein the cationic polymer is 100: 10 to 100:30.

[2] In the absence of a nonionic surfactant, an aqueous solution of a diallylamine-based cationic polymer having a weight average molecular weight of 550,000 to 900,000 (hereinafter referred to as "high molecular weight diallylamine-based cationic polymer") and carbon nanotubes are mixed. Then, a step of preparing a carbon nanotube suspension by mixing a diallylamine-based cationic polymer having a weight average molecular weight of 10,000 to 40,000 (hereinafter, referred to as “low molecular weight diallylamine-based cationic polymer”) and the obtained carbon. It has a step of mixing an nanotube suspension and a rubber latex, and the compounding weight ratio of the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer is high molecular weight diallylamine-based cationic polymer: low molecular weight diallylamine-based cationic polymer. = 100: 10 to 100:30, a method for producing a carbon nanotube / rubber composite.

[3] The carbon nanotube / rubber composite according to [1] or [2], wherein the carbon nanotube suspension is prepared through a dispersion step using a homogenizer and then an injection step using a water jet type wet miniaturization apparatus. How to make a body.

[4] The method for producing a carbon nanotube / rubber composite according to any one of [1] to [3], which comprises producing a carbon nanotube / rubber composite having a carbon nanotube dispersibility of 98% or more according to ASTM D2663.

[5] volume resistivity to produce a carbon nanotube / rubber composite is less than ^{10 2 Ω · cm, [1} ] ~ [4] the method of manufacturing the carbon nanotube / rubber composite according to any one of.

[6] The method for producing a carbon nanotube / rubber composite according to any one of [1] 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 method for producing a carbon nanotube / rubber composite according to any one of [1] to [6], wherein the diallylamine-based cationic polymer is polydiallyldimethylammonium chloride.

According to the present invention, it is possible to produce a CNT / rubber composite in which CNT is uniformly dispersed in rubber without using a nonionic surfactant or a coagulant.

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

[Manufacturing method of CNT / rubber composite]
In the method for producing a CNT / rubber composite of the present invention, a nonionic surfactant is used when the aqueous dispersion of CNT (hereinafter, may be referred to as “CNT water slurry”) is co-coagulated with the rubber latex. Instead, a high molecular weight diallylamine-based cationic polymer having a weight average molecular weight of 550,000 to 900,000 and a low molecular weight diallylamine-based cationic polymer having a weight average molecular weight of 10,000 to 40,000 are mixed at a weight ratio of 100: 10 to 100:30. CNTs are dispersed in the rubber, and this CNT water slurry is added to the rubber latex and stirred to completely solidify the rubber together with the CNTs without using a coagulant such as acid, and the CNTs are uniformly dispersed in the rubber CNT / rubber composite. Get the body. In the present invention, coagulation is simply completed because no nonionic surfactant is used.

<Carbon nanotube (CNT)>
The CNTs used in the present invention are not particularly limited, and examples thereof include single-wall (single-walled) CNTs and multi-walled (multi-walled) CNTs. 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 average values of values measured by an electron microscope, but catalog values can be adopted for commercially available products.

Only one type of CNT may be used, or a plurality of types may be used in combination.

<Diallylamine-based cationic polymer>
Examples of the diallylamine-based cationic polymer used in the present invention include polymers of secondary amine salts such as diallylamine hydrochloride and sulfate, and quaternary ammonium salt polymers such as diallyldialkylammonium chloride and diallyldialkylammonium bromide. Of these, a polymer of a quaternary ammonium salt is preferable, and polydiallyldimethylammonium chloride (hereinafter, may be abbreviated as "PDADMAC") is particularly preferable.

In the present invention, among the above-mentioned diallylamine-based cationic polymers, a high-molecular-weight diallylamine-based cationic polymer having a weight average molecular weight of 550,000 to 900,000, preferably 600,000 to 800,000, and a weight average molecular weight of 10,000 to 40,000 are preferable. Is characterized by being used in combination with a low molecular weight diallylamine-based cationic polymer of 10,000 to 30,000. Here, it is considered that the high molecular weight diallylamine-based cationic polymer contributes to the suppression of self-reaggregation of CNTs, and the low molecular weight diallylamine-based cationic polymer contributes to the improvement of dispersion (dispersion) of CNTs. A CNT water slurry having excellent CNT dispersibility can be obtained by the synergistic effect of the combined use of the low molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer.

In the present invention, the weight average molecular weight of the diallylamine-based cationic polymer is a value obtained by gel filtration chromatography (manufactured by Tosoh Corporation, standard polystyrene).

In the present invention, the above-mentioned high-molecular-weight diallylamine-based cationic polymer and low-molecular-weight diallylamine-based cationic polymer are used as high-molecular-weight diallylamine-based cationic polymer: low-molecular-weight diallylamine-based cationic polymer = 100: 10 to 100:30, preferably 100:12. It is used in the range of ~ 100: 20. That is, the low molecular weight diallylamine-based cationic polymer is used in the range of 10 to 30 parts by weight, preferably 12 to 20 parts by weight, based on 100 parts by weight of the high molecular weight diallylamine-based cationic polymer. If it is out of this range, the effect of the present invention cannot be sufficiently obtained by using the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer in combination.

Further, it is preferable to use the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer so that the total of these is 5 to 20 parts by weight, particularly 8 to 15 parts by weight with respect to 100 parts by weight of the CNT. When the total amount of the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer used is less than the above lower limit, the effect of improving dispersibility by using these diallylamine-based cationic polymers can be sufficiently obtained. However, if the above upper limit is exceeded, the manufacturing cost will increase and the conductivity may deteriorate.

The high molecular weight diallylamine-based cationic polymer can usually be used as an aqueous solution of about 0.1 to 0.5% by weight, and the low molecular weight diallylamine-based cationic polymer can usually be used as an aqueous solution of about 0.05 to 0.2% by weight. Can be used.

<Preparation of CNT water slurry>
In the present invention, the above high molecular weight polydiallyl dimethylammonium chloride, low molecular weight polydiallyl dimethylammonium chloride, and CNT are mixed in the presence of an aqueous solvent to prepare a CNT water slurry without using a nonionic surfactant. Prepare.

In the step of preparing the CNT water slurry, an aqueous solution of a high molecular weight diallylamine cationic polymer and CNT are mixed without using a nonionic surfactant, dispersed with a homogenizer or the like, and then the low molecular weight diallylamine cationic polymer is prepared. It is preferable to add an aqueous solution of the above water solution and further disperse it with a homogenizer or the like, and spray the obtained mixed liquid from a high-pressure nozzle of a water jet type wet micronizing device to prepare a CNT water slurry by shearing collision mixing and dispersion.

In this way, by first mixing the CNT and the high molecular weight diallylamine-based cationic polymer and then mixing the low molecular weight diallylamine-based cationic polymer, the CNT is opened with a high shearing force of the high molecular weight diallylamine-based cationic polymer. Is promoted and self-reaggregation of CNT is suppressed, and the dispersion effect is higher than the method of mixing the low molecular weight diallylamine-based cationic polymer first and then mixing the high molecular weight diallylamine-based cationic polymer, or the method of mixing these at the same time. Can be obtained.

In addition, by injecting from a high-pressure nozzle at high speed and high pressure using a water jet type wet miniaturization device, a large shearing force can be applied to cause the CNTs in the injection liquid to collide with each other, and these can be highly dispersed and mixed. can.

As the water jet type wet miniaturizing device, Sugino Machine's Ultimizer HJP-25005 can be used, but the water jet type wet miniaturizing device to be used is not particularly limited.

The amount of the aqueous solvent when preparing the CNT water slurry includes the amount of water in the aqueous solution of the high molecular weight diallylamine-based cationic polymer and the aqueous solution of the low molecular weight diallylamine-based cationic polymer, and the CNT concentration in the prepared CNT water slurry is 0. The amount is preferably 5 to 2.0% by weight, particularly preferably about 0.7 to 1.7% by weight. When the CNT concentration of the CNT water slurry is not more than the above upper limit, it is easy to improve the CNT dispersibility of the CNT water slurry, and at the same time, the coagulation rate with the rubber becomes appropriate, while the CNT concentration is not more than the above lower limit. And you don't have to lose productivity.

The dispersion treatment time with a homogenizer or the like for preparing the CNT water slurry is not particularly limited, and it is sufficient if the CNT water slurry in which the CNTs are sufficiently uniformly dispersed can be obtained. However, usually, the high molecular weight diallylamine-based cationic polymer and the CNTs are used. It takes about 5 to 15 minutes to disperse with and then about 15 to 25 minutes after adding the low molecular weight diallylamine-based cationic polymer.

Further, the nozzle diameter (injection diameter) of the high-pressure nozzle of the water jet type wet miniaturization device used for injecting the mixed liquid is preferably about 0.1 to 0.15 mm. If the nozzle diameter of the high-pressure nozzle is smaller than the above lower limit, the injection efficiency is poor, and if it is larger than the above upper limit, it may be difficult to apply a sufficiently large shearing force.
Further, the pressing force at the time of 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 pressing force at the time of injection or the injection speed is too small, it may not be possible to apply a sufficient shearing force. However, the pressing force and the injection speed have an upper limit due to the specifications of the water jet type wet miniaturization device, and are usually not more than the above upper limit.
The shear collision mixing and dispersion by the water jet type wet miniaturization device may be repeated a plurality of times.

In this way, the CNT water slurry obtained by shear collision mixing and dispersion using a water jet type wet micronization device is mixed with the rubber latex and co-solidified, so that the CNTs do not self-aggregate independently and the CNTs are good. It is possible to obtain a CNT / rubber composite that is uniformly dispersed in rubber and coordinated in a stable arrangement in terms of potential energy.

<Rubber latex>
The rubber type of the rubber latex used in the present invention is not particularly limited as long as it can be latexd, and for example, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), isoprene rubber (IR), and butadiene rubber ( One type or two or more types such as BR) can be mentioned.
Styrene-butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) are particularly preferable, and SBR is particularly preferable.

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

The rubber latex is prepared, for example, in the presence of an emulsifier, by using the reaction solution obtained by synthesizing synthetic rubber by an emulsion polymerization method as it is, or by appropriately diluting or adding an emulsifier. Further, the reaction solution obtained by synthesizing the synthetic rubber by the solution polymerization method may be phase-inverted to an aqueous system in the presence of an emulsifier to prepare a latex.
The concentration of the rubber component in the rubber latex is usually about 18 to 25% by weight.

<Mixing / solidification process>
In the present invention, the above-mentioned rubber latex and the above-mentioned CNT water slurry are mixed and co-coagulated.

In the present invention, CNTs are well dispersed by dispersing CNTs by using the above-mentioned high molecular weight diallylamine-based cationic polymer and low-molecular-weight diallylamine-based cationic polymer in a predetermined ratio without using a nonionic surfactant. A water slurry is obtained, and by stirring and mixing the CNT water slurry and the rubber latex, the rubber and the CNT are completely solidified without adding a coagulant such as an acid or an amine, and the uniform dispersibility of the CNT is excellent. A CNT / rubber composite can be obtained. That is, when CNTs are dispersed by using polydiallyldimethylammonium chloride having a specific molecular weight in a specific ratio, the obtained CNT water slurry and rubber latex are co-coagulated, and the CNTs are uniform without self-aggregation. Since the rubber latex is dispersed in the rubber and no nonionic surfactant is added, the rubber latex becomes moderately charge-unstable, and the coagulation of the CNT / rubber composite is simply completed without adding a coagulant. In this way, a CNT / rubber composite in which the CNTs are uniformly dispersed in the rubber can be obtained.

At this time, the mixing ratio of the rubber latex and the CNT water slurry is such that the content of CNT with respect to 100 parts by weight of the rubber solid content of the obtained CNT / rubber composite is 2 to 30 parts by weight, particularly 3 to 25 parts by weight. It is preferable to do so. If the CNT content is less than the above lower limit, the effect of improving the mechanical strength and the effect of imparting conductivity by dispersing them in the rubber cannot be sufficiently obtained, and conversely, if it is more than the above upper limit, it is obtained. The workability of the CNT rubber composite is reduced.

The concentration of CNT with respect to water (including water in the rubber latex) in the mixed solution of the rubber latex and the CNT water slurry is 0.5 to 2.0% by weight, particularly 0.7 to 1.7% by weight. Is preferable from the viewpoint of coagulation stability and productivity.

An emulsifier, a spreading oil component, or the like may be added to the mixed solution in the coagulation step, if necessary. Further, a conductive component other than CNT, an additive for rubber vulcanization described later, or the like may be added.

<Separation of CNT / rubber composite>
After the above mixing / solidifying step, the produced massive solidified crumb is separated by mesh filtration or the like, dehydrated, and dried at about 80 to 110 ° C. to obtain a CNT / rubber composite.

[CNT / rubber composite]
Next, various characteristics of the CNT / rubber composite produced by the method for producing the CNT / rubber composite of the present invention (hereinafter, may be referred to as “CNT / rubber composite of the present invention”) will be described.

<CNT dispersion degree>
The CNT / rubber composite of the present invention is one in which CNTs are uniformly dispersed, with a CNT dispersion degree of preferably 98% or more measured in accordance with ASTM D2663. The larger the dispersion of CNTs, the more preferable, and the upper limit thereof is usually 100%.
Specifically, the dispersion degree of CNT is measured by the method described in the section of Examples described later.

<Volume resistivity value>
Volume resistivity of the CNT / rubber composite of the present invention is preferably 10 ² Ω · cm or less, more preferably less 10 ¹ Ω · cm. The smaller the volume resistivity value, the better the conductive performance as a CNT / rubber composite.
The volume resistivity value of the CNT / rubber composite is specifically measured by the method described in the section of Examples described later.

[Forming / vulcanization of CNT / rubber composite]
Add additives such as vulcanization agent, vulcanization accelerator, other heat stabilizer, antiaging agent, filler, plasticizer, colorant, etc. to the CNT / rubber composite of the present invention in a predetermined ratio and knead. Then, by molding and vulcanizing the kneaded product under the vulcanization conditions of rubber, a product made of various CNT / rubber composites can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

The CNTs, other raw materials, and chemicals used in the following examples and comparative examples are as follows.

<CNT>
K-Nanos100T manufactured by Kumho Petrochemical Co., Ltd.
Diameter: 10 nm
Length: 26 μm,
Aspect ratio (length / diameter): 2,600

<Diallylamine-based cationic polymer; polydiallyldimethylammonium chloride>
PDADMAC (molecular weight 700,000): Unisense FPA1002L manufactured by Senka Co., Ltd. (weight average molecular weight 700,000)
PDADMAC (molecular weight 20,000): Unisense FPA100L manufactured by Senka Co., Ltd. (weight average molecular weight 20,000)
PDADMAC (molecular weight 130,000): Unisense FPA1000L manufactured by Senka Co., Ltd. (weight average molecular weight 130,000)
PDADMAC (molecular weight 200,000): Unisense FPA1001L manufactured by Senka Co., Ltd. (weight average molecular weight 200,000)

<Anionic surfactant>
Sodium Lauryl Sulfate: Kao Corporation Emar 2F-30

<Nonion-based surfactant>
Polyoxyethylene oleyl ether: Emargen 404 manufactured by Kao Corporation
Polyoxyethylene sorbitan monostearate: manufactured by NOF CORPORATION ST-221

<Rubber latex>
SBR: SBR1502 Latex manufactured by Mitsubishi Chemical Corporation and its coagulated rubber (SBR1502)
Mooney Viscosity: ML _{1 + 4} (100 ° C) 52

<Others>
Stearic acid: Made by Nippon Oil & Fats Zinc oxide: Made by Sakai Chemicals Zinc oxide 2 types Vulcanization accelerator: Sanshin Chemicals Sunseller NS-G

[Confirmation of solidification status of CNT / rubber wet masterbatch]
In order to produce the CNT / rubber composite, a solidification step of the CNT water slurry and the rubber latex is required. That is, it is necessary to "complete" the solidification during the production of the wet masterbatch of CNT / rubber. In the present invention, a diallylamine-based cationic polymer having a specific molecular weight is mixed at a specific ratio without using a nonionic surfactant, CNT is dispersed therein, and this CNT water slurry is added to rubber latex and stirred. It is characterized in that rubber and CNT are completely solidified without adding a coagulant such as acid or amine, and a CNT / rubber composite in which CNT is uniformly dispersed in rubber can be obtained. As described above, since the nonionic surfactant is not used for the preparation of the CNT water slurry in the present invention, the coagulation can be simply completed without using the coagulant in the subsequent mixing step with the rubber latex.
The coagulation state in the following Examples and Comparative Examples was determined as follows.
1. 1. Coagulation is complete: The coagulation liquid (water separated from the coagulation crumb) becomes transparent. Not completed: The coagulant does not become transparent and becomes cloudy (uncoagulated rubber latex remains)
3. 3. No solidification: A state in which solidification does not proceed and the rubber latex remains as it is.

[Evaluation of CNT / rubber composite]
The method for evaluating the characteristics of the CNT / rubber composites obtained in the following Examples and Comparative Examples is as follows.

<CNT dispersion degree>
The CNT dispersion in rubber was calculated according to ASTM D2663 (METHOD B). That is, the area percentage of undispersed agglomerates of 5 μm or more is measured, and the percentage of CNTs dispersed in 5 μm or less is calculated from the total area of CNTs in the complex, which is the CNT dispersion degree% (CNTs of 5 μm or more). The value obtained by subtracting the area percentage of the undispersed agglomerates from 100% is the CNT dispersion degree%). For example, when there is no CNT undispersed mass of 5 μm or more, the CNT dispersion degree is 100%, and when the CNT amount of 10% exists as an undispersed mass, the CNT dispersion degree is 90%. The larger the number of undispersed CNTs, the smaller the value of CNT dispersion.

<Volume resistivity value>
Conforms to the JISK7194, if the resistance of the specimen is more than 10 ⁶ Ω, high Leicester UP (MCP-HT450) in the case of (Mitsubishi Chemical Co., Ltd.), also 10 ⁶ Ω or less Loresta GP (MCP-T600 ) (Made by Mitsubishi Chemical Corporation) in an atmosphere of 25 ° C. and 60% humidity, and calculated according to the following formula.
Volume resistivity (Ω · cm) = Test piece resistance x RCF x t (cm)
RCF: resistivity correction coefficient t: thickness of test piece (cm)

[Example I-1]
<Preparation of CNT water slurry>
40 g of CNT was added to 1333 g of a 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 10 minutes. To this, 660 g of a 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution was added, and the mixture was further stirred with a homogenizer at 15,000 rpm for 20 minutes.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 1333 g of a 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution, and 660 g of a 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution) were added while stirring with a stirring blade. Stirring was carried out for 40 minutes without adding any coagulants such as acids and polyamines, salts, nonionic surfactants and the like. As for the state of solidification, the solidification started to proceed after 20 to 30 minutes of stirring, and the solidification was completed after 40 minutes. This is because the rubber latex is moderately charge-unstable and coagulation proceeds smoothly because no nonionic surfactant is added, and the coagulation liquid (water separated from the coagulation crumb) becomes transparent and solidification is complete. Indicates that it has been completed. The produced solidified crumb was squeezed with water by a dehydrator and dried in a dryer at 90 ° C. In this way, a CNT / SBR rubber composite in which the CNTs were well dispersed in the rubber was obtained without the CNTs self-aggregating independently.

[Example I-2]
<Preparation of CNT water slurry>
40 g of CNT was added to 1333 g of a 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 10 minutes. To this, 660 g of a 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution was added, and the mixture was further stirred with a homogenizer at 15,000 rpm for 20 minutes. The CNT water slurry prepared in this way is injected at a speed of 500 m / sec with a 0.14 mm diameter nozzle pressurized to 200 MPa with a water jet type wet micronizing device (Sugino Machine's Ultiizer HJP-25005). Strong shear collision mixing was used to prepare a CNT water slurry with better CNT dispersion.

<Preparation of CNT / SBR rubber composite>
A CNT / rubber composite was prepared in the same manner as in Example I-1 except that the CNT water slurry obtained above was used.
Similar to Example I-1, solidification was successfully completed.

[Example I-3]
The CNT water slurry was prepared in the same manner as in Example 1 except that the CNT was 30 g, the 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution was 1000 g, and the 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution was 440 g. Preparation and preparation of CNT / rubber composite were carried out.
Similar to Example I-1, solidification was successfully completed.

[Comparative Example I-1]
<Preparation of CNT water slurry>
40 g of CNT was added to 1333 g of a 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 30 minutes to prepare a CNT water slurry.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution 1333 g) was added while stirring with a stirring blade. Further, 660 g of a 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution was added while stirring with a stirring blade, and stirring was performed for 60 minutes without adding any coagulants such as acids and polyamines, salts, nonionic surfactants and the like. rice field. As for the state of coagulation, coagulation was not completed even after 60 minutes of stirring, and although a small amount of coagulation crumb was produced, the coagulation liquid (water separated from the coagulation crumb) did not become transparent and remained cloudy. This indicates that unsolidified rubber latex remained and solidification was not completed. In addition, it can be seen that a part of the CNTs self-aggregates and is not embraced by the rubber, and only the CNTs are in the shape of "lumps".

[Comparative Example I-2]
<Preparation of CNT water slurry>
40 g of CNT was added to 1553 g of a 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 30 minutes to prepare a CNT water slurry.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.3 wt% PDADMAC (molecular weight 700,000) aqueous solution (1553 g) was added while stirring with a stirring blade. Stirring was carried out for 60 minutes without adding any coagulants such as acids and polyamines, salts, nonionic surfactants and the like. As for the state of coagulation, coagulation was not completed even after 60 minutes of stirring, and although a small amount of coagulation crumb was produced, the coagulation liquid (water separated from the coagulation crumb) did not become transparent and remained cloudy. This indicates that unsolidified rubber latex remained and solidification was not completed. In addition, it can be seen that a part of the CNTs self-aggregates and is not embraced by the rubber, and only the CNTs are in the shape of "lumps".

[Comparative Example I-3]
<Preparation of CNT water slurry>
40 g of CNT was added to 4660 g of a 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 30 minutes to prepare a CNT water slurry.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.1 wt% PDADMAC (molecular weight 20,000) aqueous solution (4660 g) was added while stirring with a stirring blade. Stirring was carried out for 60 minutes without adding any coagulants such as acids and polyamines, salts, nonionic surfactants and the like. As for the state of coagulation, coagulation was not completed even after 60 minutes of stirring, and although a small amount of coagulation crumb was produced, the coagulation liquid (water separated from the coagulation crumb) did not become transparent and remained cloudy. This indicates that unsolidified rubber latex remained and solidification was not completed. In addition, it can be seen that a part of the CNTs self-aggregates and is not embraced by the rubber, and only the CNTs are in the shape of "lumps".

[Comparative Example I-4]
<Preparation of CNT water slurry>
40 g of CNT was added to 1553 g of a 0.3 wt% PDADMAC (molecular weight 130,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 30 minutes to prepare a CNT water slurry.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.3 wt% PDADMAC (molecular weight 130,000) aqueous solution (1553 g) was added while stirring with a stirring blade. Stirring was carried out for 60 minutes without adding any coagulants such as acids and polyamines, salts, nonionic surfactants and the like. As for the state of coagulation, coagulation was not completed even after 60 minutes of stirring, and although a small amount of coagulation crumb was produced, the coagulation liquid (water separated from the coagulation crumb) did not become transparent and remained cloudy. This indicates that unsolidified rubber latex remained and solidification was not completed. In addition, it can be seen that a part of the CNTs self-aggregates and is not embraced by the rubber, and only the CNTs are in the shape of "lumps".

[Comparative Example I-5]
<Preparation of CNT water slurry>
40 g of CNT was added to 1553 g of a 0.3 wt% PDADMAC (molecular weight 200,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 30 minutes to prepare a CNT water slurry.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.3 wt% PDADMAC (molecular weight 200,000) aqueous solution (1553 g) was added while stirring with a stirring blade. Stirring was carried out for 60 minutes without adding any coagulants such as acids and polyamines, salts, nonionic surfactants and the like. As for the state of coagulation, coagulation was not completed even after 60 minutes of stirring, and although a small amount of coagulation crumb was produced, the coagulation liquid (water separated from the coagulation crumb) did not become transparent and remained cloudy. This indicates that unsolidified rubber latex remained and solidification was not completed. In addition, it can be seen that a part of the CNTs self-aggregates and is not embraced by the rubber, and only the CNTs are in the shape of "lumps".

[Comparative Example I-6]
<Preparation of CNT water slurry>
40 g of CNT was added to 1553 g of a 0.3 wt% PDADMAC (molecular weight 200,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 10 minutes. To this, 4.4 g of a 10 wt% sodium lauryl sulfate aqueous solution (anionic surfactant) and 186 g of 1 wt% polyoxyethylene sorbitan monostearate (nonionic surfactant) were added, and the mixture was further stirred with a homogenizer at 15000 rpm for 20 minutes. bottom.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Corporation, Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.3 wt% PDADMAC (molecular weight 200,000) aqueous solution 1553 g, 10 wt% sodium lauryl sulfate aqueous solution (anionic surfactant) 4.4 g, 1 wt% polyoxyethylene sorbitan monostearate (nonionic surfactant) ) 186 g) was added while stirring with a stirring blade. If coagulants such as acids and polyamines and salts were not added, coagulation did not occur at all even after 60 minutes, so sulfuric acid and polyamine were added and stirring was attempted for another 60 minutes, but coagulation did not proceed at all and a cloudy rubber latex was formed. It was in a state where it remained as it was. It is considered that this is because the nonionic surfactant stabilized the rubber latex and inhibited the coagulation reaction.

[Comparative Example I-7]
<Preparation of CNT water slurry>
40 g of CNT was added to 46000 g of a 0.1 wt% PDADMAC (molecular weight 30,000) aqueous solution, and the mixture was stirred with a honogenizer at 15,000 rpm for 10 minutes. To this, add 6666 g of a 0.3 wt% PDADMAC (molecular weight 200,000) aqueous solution, 120 g of a 10 wt% sodium lauryl sulfate aqueous solution (anionic surfactant), and 4000 g of a 1 wt% polyoxyethylene oleyl ether (nonionic surfactant). Further, the mixture was further stirred with a homogenizer at 15,000 rpm for 20 minutes.

<Preparation of CNT / SBR rubber composite>
SBR1502 rubber latex with a rubber solid content of 22.5% by weight (manufactured by Mitsubishi Chemical Co., Ltd., Mooney viscosity: ML _{1 + 4} (100 ° C) 52) 889 g (SBR rubber amount 200 g), and the CNT water slurry (CNT amount) prepared above. 40 g, 0.1 wt% PDADMAC (molecular weight 30,000) aqueous solution 46000 g, 0.3 wt% PDADMAC (molecular weight 200,000) aqueous solution 6666 g, 10 wt% sodium lauryl sulfate aqueous solution (anionic surfactant) 120 g, 1 wt% poly Oxyethylene oleyl ether (nonionic surfactant) 4000 g) was added while stirring with a stirring blade. If coagulants such as acids and polyamines and salts were not added, coagulation did not occur at all even after 60 minutes, so sulfuric acid and polyamine were added and stirring was attempted for another 60 minutes, but coagulation did not proceed at all and a cloudy rubber latex was formed. It was in a state where it remained as it was. It is considered that this is because the nonionic surfactant stabilized the rubber latex and inhibited the coagulation reaction.

[Example II-1]
<Manufacturing of unvulcanized CNT / SBR rubber composition>
The CNT / SBR rubber composite prepared in Example I-1 was kneaded with a Banbury mixer according to the formulation shown in Table 3 at 160 ° C. for 3 minutes to obtain a kneaded formulation. rice field. Next, sulfur and a vulcanization accelerator were added to the obtained kneading mixture, and the mixture was kneaded at 60 ° C. for 5 minutes using a twin-screw open roll to obtain an unvulcanized CNT / SBR rubber composition.

<Evaluation of CNT dispersion / volume resistivity>
The CNT dispersion in the CNT / SBR rubber composite by cross-sectional observation with an optical microscope obtained by vulcanizing and pressing the obtained unvulcanized CNT / SBR rubber composition into a thin film under the condition of 160 ° C. was 99.1%, and SBR. The CNTs were well dispersed in it. The volume resistivity value was 1.99 × 10 ^-1 Ω · cm.

[Example II-2]
<Manufacturing of unvulcanized CNT / SBR rubber composition>
The CNT / SBR rubber composite prepared in Example I-2 was used in the formulation shown in Table 3 to obtain an unvulcanized CNT / SBR rubber composition in the same manner as in Example II-1.

<Evaluation of CNT dispersion / volume resistivity>
The CNT dispersion in the CNT / SBR rubber composite by cross-sectional observation with an optical microscope obtained by vulcanizing and pressing the obtained unvulcanized CNT / SBR rubber composition into a thin film under the condition of 160 ° C. was 99.7%, and SBR. The CNTs were well dispersed in it. The volume resistivity value was 1.23 × 10 ^-1 Ω · cm.

[Example II-3]
<Manufacturing of unvulcanized CNT / SBR rubber composition>
The CNT / SBR rubber composite prepared in Example I-3 was used in the formulation shown in Table 3 to obtain an unvulcanized CNT / SBR rubber composition in the same manner as in Example II-1.

<Evaluation of CNT dispersion / volume resistivity>
The CNT dispersion in the CNT / SBR rubber composite by cross-sectional observation with an optical microscope obtained by vulcanizing and pressing the obtained unvulcanized CNT / SBR rubber composition into a thin film under the condition of 160 ° C. was 99.0%, and SBR. The CNTs were well dispersed in it. The volume resistivity value was 4.92 × 10 ^-1 Ω · cm.

[Example II-4]
<Manufacturing of unvulcanized CNT / SBR rubber composition>
SBR1502 was added to the CNT / SBR rubber composite prepared in Example I-1, and dilution was performed so that the amount of CNT was 5 parts by weight with respect to 100 parts by weight of SBR. Specifically, materials other than sulfur and the vulcanization accelerator were kneaded at 160 ° C. for 3 minutes using a Banbury mixer in the formulation of Table 3 to obtain a kneaded formulation. Next, sulfur and a vulcanization accelerator were added to the obtained kneading mixture, and the mixture was kneaded at 60 ° C. for 5 minutes using a twin-screw open roll to obtain an unvulcanized CNT / SBR rubber composition.

<Evaluation of volume resistivity>
The obtained unvulcanized CNT / SBR rubber composition was vulcanized under the condition of 160 ° C., and the measured volume resistivity value was 1.39 × 10 ² Ω · cm.

[Example II-5]
<Manufacturing of unvulcanized CNT / SBR rubber composition>
As the CNT / SBR rubber composite, the CNT / SBR rubber composite prepared in Example I-2 was used, and an unvulcanized CNT / SBR rubber composition was obtained in the same manner as in Example II-4.

<Evaluation of volume resistivity>
The obtained CNT / SBR rubber composition was vulcanized under the condition of 160 ° C., and the measured volume resistivity value was 5.12 × 10 ¹ Ω · cm.

The results of Examples I-1 to I-3 are shown in Table 1, the results of Comparative Examples I-1 to I-7 are shown in Table 2, and the results of Examples II-1 to II-5 are shown in Table 2. It is shown in Table 3.

From Tables 1 to 3, the following can be seen.
That is, in Examples I-1 to I-3 according to the present invention, a high molecular weight diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 700,000 (550,000 to 900,000) and a low molecular weight of 20,000 (10,000 to 40,000) are used. CNTs are well dispersed by mixing a molecular weight diallylamine-based cationic polymer (PDADMAC) at a ratio of 100:16 (100: 10 to 100:30) and dispersing CNTs therein without adding a nonionic surfactant. CNT water slurry can be obtained, and by adding this CNT water slurry to SBR rubber latex and stirring, the coagulation of rubber and CNT is completed without adding a coagulant such as acid or amine, and the coagulated crumb produced is completed. The condition was also good. The CNT / rubber composite thus obtained has very good CNT dispersion as in Examples II-1 to II-3 (dispersity according to ASTM D2663 is 98% or more) and is excellent in electrical conductivity (volume). It can be seen that it is a CNT / rubber composite (with extremely low resistivity).

On the other hand, as in Comparative Example I-1, a diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 700,000 and a low-molecular-weight diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 20,000 are not mixed in combination, and have a high molecular weight of 700,000. In a system in which CNT is dispersed only in a diallylamine-based cationic polymer (PDADMAC) and a low molecular weight diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 20,000 is added and stirred at the time of solidification, uncoagulated rubber latex remains and solidification is completed. I didn't. This is because high / low molecular weight interactions occur unless CNTs are dispersed in the presence of high molecular weight components and low molecular weight components of diallylamine-based cationic polymer (PDADMAC) as in the present invention (Examples I-1 to I-3). It is probable that this was because the CNT dispersion did not work well and the CNTs self-reaggregated and the coagulation was not completed.

Further, Comparative Example I-2 using only a high molecular weight diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 700,000, Comparative Example I-3 using only a low molecular weight diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 20,000, and a molecular weight of 13. In Comparative Example I-4 using only the diallylamine-based cationic polymer (PDADMAC) of 10,000, and Comparative Example I-5 using only the diallylamine-based cationic polymer (PDADMAC) having a molecular weight of 200,000, the coagulated liquid remained cloudy and became transparent. It can be seen that the solidification of the CNT and the rubber is not completed without (that is, the unsolidified rubber latex remains). In addition, it can be seen that a part of the CNTs self-aggregates, and only the CNTs are in the shape of "lumps" without being embraced by the rubber. It is considered that this is because CNTs acting as a coagulation aid (promoting the coagulation reaction) hindered the completion of coagulation of the entire system by partially self-reaggregating. Although the reason is not clear, in Examples I-1 to I-3 according to the present invention, the self-aggregation of CNTs is suppressed by the interaction between the high molecular weight component and the low molecular weight component of the diallylamine-based cationic polymer (PDADMAC). Although the dispersion is enhanced, it is presumed that the synergistic effect was not exhibited in Comparative Examples I-1 to I-5.

Comparative Example I-6 is a retest of Example 1 of Patent Document 2, and Comparative Example I-7 is a retest of the system of Example 1 of Patent Document 1. In each system, CNT is dispersed in an aqueous solution containing a cationic polymer / nonionic surfactant / anionic activator, added to the rubber latex, and stirred, but in reality, the presence or absence of a coagulant such as acid or polyamine is present. Regardless of this, solidification did not proceed at all and the cloudy rubber latex remained as it was. It is considered that this is because the nonionic surfactant stabilizes the rubber latex and inhibits the coagulation reaction.

In the present invention, in particular, a CNT prepared by combining a diallylamine-based cationic polymer (PDADMAC) having a specific molecular weight by performing shear collision mixed dispersion using a water jet type wet miniaturization apparatus as in Example I-2. The slurry can be highly dispersed, and the CNT dispersion in the rubber can be further improved.

Claims (7)

In the absence of a nonionic surfactant, a diallylamine-based cationic polymer having a weight average molecular weight of 550,000 to 900,000 (hereinafter referred to as "high molecular weight diallylamine-based cationic polymer") and a weight average molecular weight of 10,000 to 40,000. A step of preparing a carbon nanotube suspension by mixing a diallylamine-based cationic polymer (hereinafter referred to as "low molecular weight diallylamine-based cationic polymer") and carbon nanotubes in the presence of an aqueous solvent.
It has a step of mixing the obtained carbon nanotube suspension and rubber latex.
A carbon nanotube / rubber composite in which the compounding weight ratio of the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer is high molecular weight diallylamine-based cationic polymer: low molecular weight diallylamine-based cationic polymer = 100: 10 to 100:30. Manufacturing method. In the absence of a nonionic surfactant, an aqueous solution of a diallylamine-based cationic polymer having a weight average molecular weight of 550,000 to 900,000 (hereinafter referred to as "high molecular weight diallylamine-based cationic polymer") and carbon nanotubes are mixed, and then carbon nanotubes are mixed. A step of preparing a carbon nanotube suspension by mixing a diallylamine-based cationic polymer having a weight average molecular weight of 10,000 to 40,000 (hereinafter, referred to as "low molecular weight diallylamine-based cationic polymer").
It has a step of mixing the obtained carbon nanotube suspension and rubber latex.
A carbon nanotube / rubber composite in which the compounding weight ratio of the high molecular weight diallylamine-based cationic polymer and the low molecular weight diallylamine-based cationic polymer is high molecular weight diallylamine-based cationic polymer: low molecular weight diallylamine-based cationic polymer = 100: 10 to 100:30. Manufacturing method. The method for producing a carbon nanotube / rubber composite according to claim 1 or 2, wherein the carbon nanotube suspension is prepared through a dispersion step using a homogenizer and then an injection step using a water jet type wet miniaturization apparatus. The method for producing a carbon nanotube / rubber composite according to any one of claims 1 to 3, wherein the carbon nanotube / rubber composite having a carbon nanotube dispersibility of 98% or more according to ASTM D2663 is produced. Volume resistivity to produce a carbon nanotube / rubber composite is less than 10 ² Ω · cm, the method of manufacturing the carbon nanotube / rubber composite according to claim 1. The method for producing a carbon nanotube / rubber composite according to any one of claims 1 to 5, wherein the carbon nanotube has a fiber diameter of 8 nm to 15 nm and an aspect ratio of 100 or more. The method for producing a carbon nanotube / rubber composite according to any one of claims 1 to 6, wherein the diallylamine-based cationic polymer is polydiallyldimethylammonium chloride.