JP2010248383A - Composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel carbon nanotube composite material wherein resistance value shows low dependence to voltage. <P>SOLUTION: The composite material comprises a carbon nanotube and a polymer, provided that the carbon nanotube has a diameter of 11-90 nm. Under low-temperature low-humidity conditions, the composite material shows a property expressed by formula (1):-0.4≤log<SB>10</SB>R<SB>100</SB>-log<SB>10</SB>R<SB>1000</SB>≤0.4 (wherein R<SB>100</SB>is a volume resistivity value (Ωcm) when voltage of 100 V is applied; and R<SB>1000</SB>is a volume resistivity value (Ωcm) when voltage of 1,000 V is applied). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a composite material containing carbon nanotubes, and more particularly to a composite material having a low resistance value with respect to voltage.

  In general, an inorganic filler is added to a polymer compound such as plastic or rubber. Among them, carbon-based fillers have been widely used from the viewpoint of strength and conductivity. For the carbon filler, carbon black has been used for a long time, and recently, it has been well studied to use carbon fibers and particularly nanocarbons such as carbon nanotubes (CNT). Recently, among them, CNT is often used because it can impart high strength and high conductivity to the product (for example, Patent Document 1). Patent Document 1 discloses a technique capable of adjusting a stable resistance value from a normal temperature and normal humidity to a high temperature and high humidity in a polyimide resin composition. However, moldings obtained from these resin compositions are films and belts, and are solid.

Japanese Patent Laid-Open No. 2003-246927

  An object of the present invention is to provide a novel carbon nanotube composite material having a low resistance dependency on voltage.

  In particular, when a conductive resin is foamed, the amount of conductive filler added is limited from the viewpoint of foam physical properties such as foam foam retention, foam formation, and flexibility / hardness strain characteristics. That is, conventionally, when the amount of conductive filler such as ketjen black is increased, for example, in urethane foam, the limit is about 8% for polyol, and if the concentration is higher than that, the liquid viscosity becomes too high. As a result, there is a manufacturing restriction that the pump cannot be delivered and the urethane foam cannot be manufactured. (It is about 3.4% with respect to the resin molded product at this time.) In addition, it becomes difficult to hold the foam in the foam, poor molding of the foam, or the flexibility is lowered and the hardness is increased. Or distortion gets worse. For this reason, the amount of the conductive filler added to the resin in the foam is relatively small as compared with the solid resin molded product. Note that the urethane resin is towable, flexible, and tough. Due to the characteristics of urethane resin, polyurethane foam is widely used for OA parts and the like. Accordingly, it is an object of the present invention to provide a novel carbon nanotube composite material that has high conductivity (low resistance) and low resistance value dependency on voltage in the field of conductive resin foams.

The present invention (1) is a composite material comprising a carbon nanotube and a polymer.
The carbon nanotube has a diameter of 11 to 90 nm,
It is a composite material characterized by having the characteristic of the following formula (1) under a low temperature and low humidity environment.
−0.4 ≦ log ₁₀ R ₁₀₀ −log ₁₀ R ₁₀₀₀ ≦ 0.4 (1)
{Here, R ₁₀₀ is a volume resistance value (Ω · cm) at an applied voltage of 100 V, and R ₁₀₀₀ is a volume resistance (Ω · cm) at an applied voltage of 1000 V. }

  This invention (2) is a composite material of the said invention (1) whose content of the said carbon nanotube is 1-4 mass% on the basis of the total mass of a composite material.

  The present invention (3) is the composite material of the invention (1) or (2), wherein the polymer is a urethane resin.

  This invention (4) is a composite material of the said invention (3) whose said urethane type resin is a polyurethane foam.

  The invention (5) is the composite material according to the invention (3) or (4), wherein the urethane resin is produced through a step of mixing a carbon nanotube polyol dispersion and a polyisocyanate.

This invention (6) is a composite material of the said invention (5) in which the said carbon nanotube polyol dispersion liquid contains the nanocarbon dispersing agent containing at least 1 type of the compound represented by following formula 1.
R-X- (Y) _n (Formula 1)
{Wherein R is a hydrocarbon group having 13 to 21 carbon atoms, X represents an oxygen atom, a nitrogen atom, CO, COO, CON, or a direct bond, and Y are different or the same. A polyalkylene oxide group [C ₂ H ₃ (C _a H _{2a + 1} ) · O] _b —H (wherein a is an integer of 0 to 2 and b is 1 to 100), n is , X is 1 when oxygen atom, CO, COO, direct bond, and 2 when X is nitrogen atom, CON. }

  This invention (7) is the composite material of the said invention (6) in which the said dispersing agent contains polyoxyalkylene alkylamines.

The present invention (8) is the composite material of the invention (7), wherein the polyoxyalkylene alkylamine is a compound of the following formula 2.
RN (AO) ₂ (Formula 2)
{Wherein R is an alkyl group having 13 to 21 carbon atoms (wherein one or more hydrogen atoms of the alkyl group may be substituted with a hydrocarbon group, and further between adjacent nitrogen atoms) And AO represents a polyalkylene oxide group [C ₂ H ₃ (C _a H _{2a + 1} ) · O] _b —H that is different or identical to each other (here, A represents an integer of 0 to 2, and b is 1 to 100). }

  The present invention (9) is the composite material according to any one of the inventions (5) to (8), wherein the carbon nanotube polyol dispersion is produced by a method in which carbon nanotubes are directly dispersed in a polyol. .

  According to the present invention (1), there is an effect that it is possible to obtain a composite material having a low resistance dependency on voltage.

  According to the present invention (2), it is possible to obtain a composite material having a low dependency of the resistance value on the voltage.

  According to the present invention (3) to (7), although it is a foam-like composite material, CNT can be dispersed at a high concentration, so that it has high conductivity, and furthermore, the composite has low dependency of the resistance value on voltage. There is an effect that a material can be obtained.

  According to the present invention (8) and (9), it is easy to hold foam foam, and there is an effect that it is difficult to cause defective molding of the foam.

The composite material according to the present invention includes carbon nanotubes and a polymer. The carbon nanotube has a diameter of 11 to 90 nm. Carbon nanotubes having this diameter exhibit a particularly low voltage-dependent electrical resistance value. In addition, the composite material of the present invention has the following formula (1) under a low temperature and low humidity (LL) environment.
−0.4 ≦ log ₁₀ R ₁₀₀ −log ₁₀ R ₁₀₀₀ ≦ 0.4 (1)
{Here, R ₁₀₀ is a volume resistance value (Ω · cm) at an applied voltage of 100 V, and R ₁₀₀₀ is a volume resistance (Ω · cm) at an applied voltage of 1000 V. } R ₁₀₀ and R ₁₀₀₀ are measured by the method described in the examples.
In the low temperature and low humidity (LL) environment, the upper limit value of the formula (1) is preferably 0.3, and more preferably 0.2. In addition, the lower limit of the formula (1) is preferably −0.3, and more preferably −0.2 under a low temperature and low humidity (LL) environment.

  Further, the upper limit value of the formula (1) under a normal temperature and normal humidity (NN) environment is preferably 0.3 or less, more preferably 0.2 or less, and More preferably, it is 1 or less. Further, the lower limit of the formula (1) under a normal temperature and normal humidity (NN) environment is preferably −0.3 or more, more preferably −0.2 or more, More preferably, it is −0.1 or more.

  Furthermore, the upper limit value of the formula (1) under a high temperature and high humidity (HH) environment is preferably 0.2 or less, more preferably 0.15 or less, and More preferably, it is 1 or less. Further, the lower limit of the formula (1) under a high temperature and high humidity (HH) environment is preferably −0.2 or more, more preferably −0.15 or more, More preferably, it is −0.1 or more.

Carbon nanotube The carbon nanotube according to the present best mode may be a single wall carbon nanotube (SWCNT) or a multi-wall carbon nanotube (MWCNT). The diameter of a carbon nanotube needs to be 11-90 nm, 12-90 nm is more suitable, 13-50 nm is still more suitable, and 13-18 nm is especially suitable. Thus, by setting the diameter in the range of 11 to 90 nm, the electric resistance characteristics with low voltage dependency are obtained. In addition, let the average diameter of the said tube be the value measured about 100 or more structures which exist in a predetermined range using TEM (transmission electron microscope).

  In addition, 0.1-100 micrometers is suitable for the average length of a carbon nanotube, 0.1-50 micrometers is more suitable, and 0.1-20 micrometers is still more suitable. In addition, the average length of the said tube is measured about 100 or more structures which exist in a predetermined range using SEM (scanning electron microscope), and is taken as the average value. In addition, 0.5-8 mass% is suitable for content of a carbon nanotube with respect to the whole composite material, 1-6 mass% is more suitable, and 1-4 mass% is still more suitable.

  Also, the carbon nanotube synthesis method is not particularly limited, and any synthesis method such as an electric discharge method (C. Journet et al., Nature 388, 756 (1997) and DS Bethune et al., Nature 363, 605 (1993) )), Laser deposition (RESmally et al., Science 273, 483 (1996)), gas phase synthesis (R. Andrews et al., Chem. Phys. Lett., 303,468, 1999), thermochemical vapor phase Vapor deposition (WZLi et al., Science, 274, 1701 (1996), Shinohara et al., Jpn. J. Appl. Phys. 37, 1257 (1998)), plasma enhanced chemical vapor deposition (ZFRen et al. , Science. 282, 1105 (1998)) or the like. In addition, about the crude product in which the metal catalyst was used in the synthesis | combination, it is suitable to process with an acid and to remove a metal catalyst. Regarding acid treatment, for example, as disclosed in JP-A-2001-26410, a nitric acid solution or a hydrochloric acid solution is used as an aqueous acid solution. For example, a nitric acid solution is diluted 50 times with water, and a hydrochloric acid solution is also 50 times. A method using a solution diluted in water can be mentioned. And after acid-treating in this way, it wash | cleans and filters and it is set as carbon nanotube aqueous solution.

The polymer used in the composite material according to the best mode of the present invention is not particularly limited, and examples thereof include resins such as thermoplastic resins, thermosetting resins, photocurable resins, rubber-based elastomers, thermoplastic elastomers, and the like. An elastomer is mentioned. Specific examples of the resin include olefin resin, acrylic resin, polyester resin, urethane resin, nylon resin, epoxy resin, vinylidene chloride resin, fluorine resin, silicone resin, polycarbonate resin, polyphenylene sulfide. Resin, polyimide resin, epoxy resin, vinyl resin and the like. Specific examples of elastomers include natural rubber (NR), epoxidized natural rubber (ENR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPR, EPDM). ), Butyl rubber (IIR), chlorobutyl rubber (CIIR), acrylic rubber (ACM), silicone rubber (Q), fluorine rubber (FKM), butadiene rubber (BR), epoxidized butadiene rubber (EBR), epichlorohydrin rubber (CO, CEO), urethane rubber (U), rubber elastomers such as polysulfide rubber (T), olefin (TPO), polyvinyl chloride (TPVC), polyester (TPEE), polyurethane (TPU), polyamide (TPEA), styrene (SBS), etc. It includes thermoplastic elastomers. These polymers may be used alone or in combination of two or more. Furthermore, the polymer is more preferably a foam (foam) from the viewpoint of restraining production conditions, foam-forming properties, and physical properties. Among these, polyurethane foam is particularly preferable. Hereinafter, the polyurethane foam will be described in detail.

Polyurethane Foam The polyurethane foam according to the present best mode is a resin obtained by a reaction between the polyol according to the present best mode and a polyisocyanate. Here, in the best mode, it is preferable to disperse the carbon nanotubes in the polyol before the reaction. If necessary, a crosslinking agent, a foaming agent, a catalyst, an antioxidant, a foam stabilizer, a pigment, a light stabilizer, an ultraviolet absorber, a release agent, and other inorganic / organic fillers may be contained. Further, as a conductive auxiliary material, a conductive filler other than carbon nanotubes, for example, carbon fiber, carbon black (furnace black, ketjen black, acetylene black) and the like may be used together as necessary. Hereinafter, each raw material will be described in detail.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
In the method for producing a polyurethane foam (hereinafter also simply referred to as foam or foam) in the present embodiment, first, a raw material for polyurethane foam containing a polyol, a polyisocyanate, a catalyst, a foam stabilizer and a conductive component by a mechanical floss method. A raw material dispersion in which the inert gas is finely dispersed is obtained by blowing and mixing the inert gas.
Subsequently, the target polyurethane foam is manufactured by heating the raw material dispersion and reacting and curing each component in the raw material dispersion.

(Raw material of polyurethane foam)
The raw material of the polyurethane foam contains a polyol, a polyisocyanate, a catalyst, a foam stabilizer, and a conductive component. As the polyol, polyether polyol or polyester polyol is used. As the polyether polyol, a polymer obtained by addition polymerization of propylene oxide to a polyhydric alcohol, a polymer obtained by addition polymerization of ethylene oxide, a polymer obtained by addition polymerization of propylene oxide and ethylene oxide, or a modified product thereof is used. It is done. Examples of the modified product include those obtained by adding acrylonitrile or styrene to the polyether polyol, or those obtained by adding both acrylonitrile and styrene. Here, the polyhydric alcohol is a compound having a plurality of hydroxyl groups in one molecule, and examples thereof include glycerin and dipropylene glycol.

  Since these polyether polyols have a primary hydroxyl group at the terminal, the reactivity with polyisocyanate is high. The mass average molecular weight of the polyether polyol is preferably 2000 to 6000. When the mass average molecular weight is less than 2000, the stability of the resulting polyurethane foam is lowered, and when it exceeds 6000, the reactivity is lowered, and the polyurethane foam tends to be difficult to mold. Show. A polymer polyol obtained by graft polymerization of a vinyl monomer to a polyether polyol can also be used. The graft portion of the polymer polyol reinforces the polyurethane foam, and the polyether polyol having a mass average molecular weight of 2000 to 6000 increases the soft segment of the polyurethane foam and improves the physical properties such as flexibility and elongation of the polyurethane foam. Have.

  Polyester polyols include condensed polyester polyols obtained by reacting polycarboxylic acids such as adipic acid and phthalic acid with polyols such as ethylene glycol, propylene glycol and glycerin, as well as lactone polyester polyols and polycarbonate polyester polyols. Is used. The above polyol component can change the functional group number and hydroxyl value of a hydroxyl group by adjusting the kind of raw material component, molecular weight, polymerization degree, condensation degree, and the like. The raw material of the polyurethane foam may contain a crosslinking agent as a trifunctional or higher functional polyol for the hydroxyl group in order to increase the crosslinking density of the polyurethane foam and improve the physical properties such as hardness. Examples of such a crosslinking agent include glycerin, trimethylolpropane, pentaerythritol and the like.

  The polyisocyanate to be reacted with the polyol is a compound having a plurality of isocyanate groups, specifically, tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), Aromatic polyisocyanates such as triphenylmethane triisocyanate, xylylene diisocyanate (XDI), alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), or Free isocyanate prepolymers by reaction of these with polyols, modified polyisocyanates such as carbodiimide-modified polyisocyanates, and mixtures thereof Polyisocyanate, or the like is used. Of these, tolylene diisocyanate and derivatives thereof, 4,4-diphenylmethane diisocyanate and derivatives thereof are preferable, and these can also be used as a mixture.

  The isocyanate index (isocyanate index) of the polyisocyanate may be 100 or less or more than 100, but it is preferably changed in the range of 90 to 130 in order to make the polyurethane foam flexible. When the isocyanate index is less than 90, the polyurethane foam becomes soft, and when it is used as a conductive foam, for example, as a roller for OA equipment, the function tends to deteriorate and the distortion characteristics tend to deteriorate. On the other hand, when the isocyanate index exceeds 130, the polyurethane foam has a high crosslinking density and tends to be hard, and there is a risk that the roller for OA equipment damages the counterpart member or is too hard to match the function. Here, the isocyanate index represents the equivalent ratio of the isocyanate group of the polyisocyanate to the active hydrogen group such as the hydroxyl group of the polyol in percentage.

  Next, the catalyst is for accelerating each reaction such as a urethanization reaction (resinization reaction) between a polyol and a polyisocyanate and a curing reaction (crosslinking reaction) between the product and the polyisocyanate. Specific examples of such catalysts include tertiary amines such as triethylenediamine (TEDA), dimethylethanolamine, N, N ′, N′-trimethylaminoethylpiperazine, tin octylate (tin octoate), iron acetylacetonate, and the like. These organic metal compounds, acetates, alkali metal alcoholates and the like are used. As other catalysts, morpholine catalysts such as N-methylmorpholine and N-ethylmorpholine can also be used in order to improve the curability on the foam surface. The content of the catalyst is about 1 to 8 parts by mass per 100 parts by mass of the polyol.

Subsequently, the foam stabilizer smoothly foams the foam material, and is used for foam retention and stability, and any of those usually blended in the polyurethane foam material can be used.
Specific examples of the foam stabilizer include nonionic surfactants such as dimethylpolysiloxane, organosiloxane-polyoxyalkylene copolymer, and silicone-grease copolymer, or mixtures thereof, sodium dodecylbenzenesulfonate, lauryl Examples thereof include anionic surfactants such as sodium sulfate, and phenolic compounds.

  The content of the foam stabilizer is set in the range of 1 to 5 parts by mass per 100 parts by mass of polyol in order to suppress the migration to the foam surface. When the content of the foam stabilizer is less than 1 part by mass, the foam raw material cannot be smoothly foamed, the foam retainability / stability is lost, and a good foam cannot be obtained. . On the other hand, when the amount is more than 5 parts by mass, the foam regulating action is sufficiently exhibited, but when the foam stabilizer is transferred to the foam surface and the foam is used as a roller for electronic equipment, the photosensitive member. It is inappropriate because it contaminates the mating member.

For the conductive component, a conductive material is mixed with a polyurethane foam raw material dispersion obtained by a mechanical floss method described later, and, for example, the above-mentioned CNT is essential, and a carbon material such as acetylene black or carbon black. It is possible to use a small amount together. In addition, a cell opener such as polyalkylene oxide polyol, a flame retardant such as a condensed phosphate ester, an antioxidant, a plasticizer, an ultraviolet absorber, a colorant, and the like can be blended with the raw material of the polyurethane foam. Furthermore, since the affinity with the polyol which is a urethane raw material will become favorable when the thing of the compound represented by following formula 1 is used for the dispersion liquid of CNT, a viscosity can be reduced and a high concentration CNT dispersion liquid is used. It is preferable at the point which obtains and the electroconductivity of the polyurethane foam obtained by it becomes high.
R-X- (Y) _n (Formula 1)
{Wherein R is a hydrocarbon group having 13 to 21 carbon atoms, X represents an oxygen atom, a nitrogen atom, CO, COO, CON, or a direct bond, and Y are different or the same. A polyalkylene oxide group [C ₂ H ₃ (C _a H _{2a + 1} ) · O] _b —H (wherein a is an integer of 0 to 2 and b is 1 to 100), n is , X is 1 when oxygen atom, CO, COO, direct bond, and 2 when X is nitrogen atom, CON. }

  Here, as for the total carbon number m of R, 13-21 are suitable, 14-20 are more suitable, and 15-19 are still more suitable. When m is lower than this range, it means that the affinity for nanocarbon is lowered, which causes poor dispersion. On the other hand, if it is higher than this range, the affinity with the dispersion medium may be lowered, or the viscosity of the dispersion itself may be increased. Moreover, 4-40 are suitable for the repeating unit number b of alkylene oxide, 5-30 are more suitable, and 6-25 are still more suitable. When b is lower than this range, it means that the affinity with the dispersion medium is lowered, which causes poor dispersion. On the other hand, if it is higher than this range, foaming of the dispersion is likely to occur or the viscosity of the dispersion itself may be high, which is not preferable.

Here, R is not particularly limited as long as the total number of carbon atoms m is a hydrocarbon group (hydrocarbon residue) having a range of 13 to 21, but for example, one or two or more hydrogen atoms are other alkyl or aryl. And an alkyl or aryl group (hydrocarbon residue) which may be substituted with a group, and the total carbon number m of R is 13 to 21.
More specifically, a linear, branched, or cyclic hydrocarbon group (an alkyl group, an alkenyl group, a cycloalkyl group, a phenyl group, or the like) that may include a double / triple bond may be mentioned.
Examples of the linear alkyl group include tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, and heneicosyl group. Examples of the linear alkenyl group include a palmitoyl group, an oleyl group, a linole group, and a linolenic group. Examples of the cycloalkyl group include octylcyclopentyl group, nonylcyclopentyl group, decylcyclopentyl group, nonylcyclopentyl group, decylcyclopentyl group, undecylcyclopentyl group, dodecylcyclopentyl group, tridecylcyclopentyl group, tetradecylcyclopentyl group, pentadecylcyclopentyl group, Examples include hexadecylcyclopentyl group, heptylcyclohexyl group, octylcyclohexyl group, nonylcyclohexyl group, decylcyclohexyl group, undecylcyclohexyl group, dodecylcyclohexyl group, tridecylcyclohexyl group, tetradecylcyclohexyl group, and pentadecylcyclohexyl group. Other aryl groups include heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, tridecylphenyl, tetradecylphenyl, pentadecylphenyl, propylnaphthyl Butyl naphthyl group, pentyl naphthyl group, hexyl naphthyl group, heptyl naphthyl group, octyl naphthyl group, nonyl naphthyl group, decyl naphthyl group, and undecyl naphthyl group.

Here, as a suitable example of the dispersing agent to be used, polyoxyalkylene alkylamines may be mentioned. More specifically, the compound of following formula 2 is mentioned.
RN (AO) ₂ (Formula 2)
{Wherein R is an alkyl group having 13 to 21 carbon atoms (wherein one or more hydrogen atoms of the alkyl group may be substituted with a hydrocarbon group, and further between adjacent nitrogen atoms) And AO represents a polyalkylene oxide group [C ₂ H ₃ (C _a H _{2a + 1} ) · O] _b —H that is different or identical to each other (here, A represents an integer of 0 to 2, and b is 1 to 100). }

  When such a dispersant is used, the carbon nanotubes exhibit good dispersibility with respect to the polyol, and the viscosity of the dispersion liquid is lowered. Furthermore, since it has two hydroxyl groups and has ethylene oxide in the molecular chain, it has good affinity with the main polyol, which is a urethane raw material, and the viscosity of the polyol component can be reduced, and high-concentration CNTs can be obtained. It is preferable from the viewpoint of obtaining a dispersion, and adapts to the reaction during the production of polyurethane and exhibits good foamability. For this reason, the polyurethane foam obtained thereby forms a resin skeleton in which CNTs are finely dispersed in polyurethane, and as a result, the following conductivity is increased (resistance value variation due to voltage change is small) ) Is preferable.

  A high concentration of fillers such as carbon black and CNT was studied without using a dispersant, and a high concentration slurry of 5.3% of urethane resin was created, but the viscosity became too high and the pump Delivery is impossible and urethane foam cannot be manufactured. As described above, since urethane foam is produced mainly by the reaction between polyol and isocyanate, both main raw materials are in liquid form, and are delivered and measured from the raw material tank to the mixing head by a pump. It is. Accordingly, if the amount of filler such as carbon black or CNT is increased, the liquid viscosity becomes high, and a load is applied to the pump and piping, and delivery may not be possible. Such a problem can be solved by using the suitable dispersant described above. In addition, if blended at a concentration slightly lower than such a critical high concentration, it is possible to obtain a polyurethane foam dispersed at a relatively high concentration in which conductive fillers such as carbon black and CNT are dispersed. It is possible.

  However, in the case of a method for producing a flexible slab polyurethane foam, a raw material such as a polyol in which the conductive filler is dispersed and an isocyanate raw material are mixed and discharged from a mixing head as a liquid reaction mixture. And then, since the compound having active hydrogen such as polyol and water reacts with isocyanate to generate carbon dioxide gas, the polymerization reaction such as urethane bond and urea bond reacts sequentially and competitively. The polyurethane foams, and the liquid level of the urethane raw material rises while thickening due to polymerization. A soft slab polyurethane foam is produced from such a liquid (non-foamed) material by the above-mentioned reaction, and therefore undergoes a very large volume change. Therefore, a soft material in which a conductive filler is dispersed at a relatively high concentration. Even if a slab urethane foam can be formed without restriction of pump delivery, it is brittle, has low strength, and has poor physical properties. Therefore, also from this viewpoint, the filling amount of the conductive filler or the like is restricted to be low.

  On the other hand, it is possible to obtain a flexible polyurethane foam in which a conductive filler having the same high concentration is dispersed by the mechanical floss method. This is because, in the mechanical froth method, a conductive filler or the like is dispersed in a raw material such as polyol, and a gas such as air is pre-stirred to prepare a mixture of polyol or the like in which the gas is dispersed in advance. Then, it is made to react by stirring and mixing with isocyanate. At this time, the foaming reaction may be performed using water, but in any case, since the gas is dispersed in the reaction mixture immediately after the reaction with the isocyanate, the volume fluctuations before and after the foaming reaction There are relatively few. Therefore, the flexible polyurethane foam obtained by the manufacturing method by the mechanical floss method can disperse the conductive filler or the like at a higher concentration than the composition for the soft slab. Therefore, the resistance value can be further reduced.

(Mechanical floss method)
In the mechanical floss method, an inert gas is blown into the raw material of the polyurethane foam, stirred and mixed without using a foaming agent for producing a normal soft slab-based polyurethane foam. This is a method of forming fine cells (bubbles). In this mechanical froth method, the inert gas expands due to a temperature rise, and there is no generation of carbon dioxide gas due to the reaction between polyisocyanate and water, such as chemical foaming. And the target polyurethane foam can be manufactured by making this raw material component react and harden | cure. According to this mechanical floss method, the cells in the polyurethane foam can be made fine, and at the same time, the cells can be formed uniformly.

  As the inert gas, nitrogen gas, helium gas, or the like is used. The amount of inert gas used is preferably in the range of 5 to 500 ml with respect to 100 ml of the raw material dispersion. When the amount of the inert gas used is less than 5 ml, the foam cells based on the inert gas are not sufficiently formed, and it is difficult to reduce the density of the foam. On the other hand, when the amount exceeds 500 ml, roughening of the foam cell based on the inert gas is unavoidable, which is not preferable.

  Depending on the amount of CNT blended, it is preferable to stir the raw material dispersion at a rotational speed of 500 to 2000 revolutions / minute and sufficiently stir. When this rotational speed is less than 500 revolutions / minute, the back pressure becomes high, resulting in poor stirring and unevenness of cells, which is not preferable. On the other hand, when it exceeds 2000 rpm, it is not preferable because it requires a large stirring device such as a motor and a high stirring ability.

(Polyurethane foam)
As described above, a polyurethane foam is produced by reacting and curing the polyurethane foam raw material dispersion by mechanical flossing. The resulting polyurethane foam is, for example, a soft polyurethane foam. Here, the soft polyurethane foam is a polyurethane foam having an open-cell structure, flexibility and resilience.

  In the urethanization reaction, a prepolymer method can be employed in addition to a method of directly reacting raw material components of the polyurethane foam. That is, the prepolymer method is a method in which a part of a polyol and a polyisocyanate is reacted in advance to obtain a prepolymer having an isocyanate group or a hydroxyl group at the terminal, and the remaining polyol or polyisocyanate is reacted therewith.

  The reaction when the polyurethane foam is formed is complicated, but basically the following reaction is mainly used. That is, a urethanation reaction (addition polymerization reaction, resinification reaction) between a polyol and a polyisocyanate and a curing (crosslinking) reaction (allophanate reaction, burette reaction, etc.) between the reaction product and the polyisocyanate. Further, when water is used as the foaming agent, water reacts with isocyanate to generate carbon dioxide gas (foaming reaction). The polyurethane foam thus obtained has a structure in which a skeleton extends in a three-dimensional network, and a large number of fine cells are uniformly formed therebetween. In addition, the polyurethane foam can exhibit a certain strength and required elasticity based on the properties of polyurethane composed of hard segments and soft segments.

  The polyurethane foam thus obtained is suitably used as a toner supply roller, a transfer roller, a cleaning roller and the like in the image forming apparatus. Polyurethane foam can adjust the cell diameter by changing the content of foam stabilizer and the content of air. Therefore, when polyurethane foam is used as a toner supply roller, it can hold and transport toner. The transferability of the transfer roller can be improved, and the scraping property of the cleaning roller can be improved. When used as these OA rolls, the present invention is particularly beneficial because it has characteristics that are not easily affected by voltage fluctuations.

  Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Examples 1-2 and Comparative Examples 1-3)
The raw materials of the polyurethane foam in each Example and Comparative Example were prepared with the compositions shown in Table 1. The content of each component in Table 1 represents parts by mass. The contents of each component are shown below.

Polyether polyol: Propylene glycol-based diol, weight average molecular weight 3000, hydroxyl value 38 mgKOH / g, manufactured by Mitsui Takeda Chemical Co., Ltd., trade name “ACTCOL ED-37B”
Polymer polyol: Polyether polyol obtained by addition polymerization of propylene oxide to glycerin and graft polymerization of a mixture of styrene and acrylonitrile, mass average molecular weight 3700, hydroxyl value 31 mgKOH / g, hydroxyl group functional group number 3, Mitsui Takeda Chemical Co., Ltd. Product name POP-24 / 30
Cross-linking agent (TMP): Trimethylolpropane foam stabilizer: Silicone (linear dimethylpolysiloxane), manufactured by GE Silicones, trade name “Niax Silicone L5614”
Conductive member 1 (CNT): manufactured by Bayer MaterialScience, multi-wall carbon nanotube C150P (tube diameter 13 to 16 nm, length 1 to 10 μm),
Mitsui & Co., multi-wall carbon nanotube MWNT-7 (tube diameter 40-90 nm, length 4 μm or more),
Multi-wall carbon nanotube NC7000 (tube diameter: 8-10 nm, length: about 1.5 μm), manufactured by Nanosil
Conductive member 2 (carbon black): Ketjen Black, manufactured by Lion Corporation, trade name “Ketjen Black EC300J”
Polyisocyanate: Carbodiimide-modified MDI, isocyanate group content 30.88%, manufactured by Nippon Polyurethane Industry Co., Ltd., trade name Millionate MTL-S

(Preliminary dispersion of CNT)
Naimine S220, manufactured by Bayer MaterialScience Co., as a dispersant, 180 g of multi-wall carbon nanotube C150P (tube diameter (diameter, fiber diameter) 13 to 16 nm, length 1 to 10 μm) 180 g (6 wt% with respect to the total polyol dispersion) In addition to polyether polyol (propylene glycol-based diol, mass average molecular weight 3000, hydroxyl value 38 mgKOH / g, manufactured by Mitsui Takeda Chemical Co., Ltd., trade name “ACTCOL ED-37B”) The mixture was treated with a bead mill for 3 hours to obtain a carbon nanotube dispersion liquid, and the viscosity of the dispersion liquid was 13000 cP. Of 15 to the total polyol dispersion Dispersion and amount% also can be created.

  In addition, instead of Naimine S220 as a dispersant, 3% by weight (CNT is also 3% by weight) and 6% by weight (CNT is also 6% by weight) are blended with respect to the total polyol dispersion, The mixing / dispersing process was performed in the same manner as described above. However, the viscosity of these dispersions was 300,000 cP or more, exceeding the measurement limit of the rotary type B viscosity type. Furthermore, the above-mentioned mixing / dispersing treatment was carried out with 3% by weight of CNT without using any dispersant, but again, the viscosity of these dispersions was 300,000 cP or more, and the rotary B-type viscosity type The measurement limit was exceeded. (The same was true when CNT was changed to Mitsui's.)

(Mixing by mechanical floss method)
While stirring the raw material at a speed of 1000 rpm, nitrogen gas as an inert gas is blown in the range of 5 to 500 ml per 100 ml of the raw material, and the nitrogen gas is finely dispersed in the raw material to produce a foam-like dispersion A liquid was obtained. The amount of nitrogen gas blown was set to a target value of the apparent density of the foam in each example.

(Heating cure)
Thereafter, the obtained polyurethane foam was heated for 2 minutes by passing through a 10 m heating zone heated to 110 ° C. as curing heating. Further, as post-heating, the polyurethane foam was placed in a heating furnace and subjected to heat treatment at 110 ° C. for 4 hours. In this way, a desired flexible polyurethane foam was produced.

  Here, in Examples 1 and 2 and Comparative Examples 1 to 3, molding was performed at 140 ° C. for 30 minutes using a conventional mold to obtain a polyurethane foam. In Comparative Example 1, Ketjen Black is used as the conductive material, and in Comparative Examples 2 and 3, CNT having a tube diameter of 8 to 10 nm is used as the conductive material.

The apparent density, average cell diameter, compression residual strain, hardness, and resistance value shown below were measured for each of the flexible polyurethane foams obtained as described above.
Apparent density (kg / m ³ ): Measured according to JIS K7222: 1999.
Compression residual strain (%): Measured according to JISK6400-4: 2004.
Hardness (N): Measured according to JISK6400-2: 2004.

Regarding the electrical resistance measurement method, the sample was placed for 24 hours under the following environmental conditions, and then measured as follows.
1. A roller is set on the measuring jig, and a load of 500 g is applied to both ends of the roller.
2. The voltage is changed to 100 and 1000 V, and the respective resistance values are measured.
3. After measuring up to 1000V, change the circumferential direction of the roller (by 90 °).
4). 2. ~ 3. The resistance value in four directions is measured repeatedly.
The average value of each voltage of 100 and 1000 V in the four directions is set as the resistance value of each voltage of the roller.
The HH environment is room temperature: 28 ° C., humidity: 85%, the NN environment is room temperature: 22 ° C., humidity: 55%, and the LL environment is room temperature: 10 ° C., humidity: 15%.
Resistance meter: ADVANTEST R8340A ULTRA HIGH RESISTANCE METER

  The ketjen black composition of Comparative Example 1 has a problem that the resistance value depends on the voltage in the LL environment / NN environment and the voltage fluctuates. (In HH environment, the effect is small due to fluctuations.) Even if Ketjen Black is mixed in a large amount to greatly reduce the resistance value, if it is dispersed in polyol, the concentration becomes high and the viscosity is very high. However, it is unsuitable for the production of polyurethane foam.

Instead of ketjen black, CNTs having a tube diameter of 8 to 10 nm were used (Comparative Examples 2 and 3). Due to the effect of the specific dispersant, a dispersion having a relatively low viscosity could be obtained, and a polyurethane foam could be obtained. In particular, it was possible to obtain a foam having a high resistance (5.3%) having a low resistance value. However, in a low-concentration (3.3%) product, the voltage dependence of the resistance value is large, and no problems are seen.
On the other hand, when CNTs having a tube diameter of 13 to 16 nm (Example 1) and 40 to 90 nm (Example 2) are used, the CNT concentration is 3.3% based on the polyurethane foam resin due to the low-viscosity CNT dispersion. Example 1 and Example 2) and a polyurethane foam having high conductivity (5.3%) could be obtained. In the low-concentration (3.3%) product, Example 1 and Example 2 show excellent electrical resistance values with very little voltage dependency not only in the NN environment but also in the LL environment.

Claims (9)

In a composite material comprising carbon nanotubes and a polymer,
The carbon nanotube has a diameter of 11 to 90 nm,
A composite material having the following formula (1) under a low temperature and low humidity environment.
−0.4 ≦ log ₁₀ R ₁₀₀ −log ₁₀ R ₁₀₀₀ ≦ 0.4 (1)
{Here, R ₁₀₀ is a volume resistance value (Ω · cm) at an applied voltage of 100 V, and R ₁₀₀₀ is a volume resistance (Ω · cm) at an applied voltage of 1000 V. }   The composite material according to claim 1, wherein a content of the carbon nanotube is 1 to 4% by mass based on a total mass of the composite material.   The composite material according to claim 1, wherein the polymer is a urethane-based resin.   The composite material according to claim 3, wherein the urethane resin is a polyurethane foam.   The composite material according to claim 3 or 4, wherein the urethane resin is produced through a step of mixing a carbon nanotube polyol dispersion and a polyisocyanate. The composite material according to claim 5, wherein the carbon nanotube polyol dispersion contains a nanocarbon dispersant containing at least one compound represented by the following formula 1.
R-X- (Y) _n (Formula 1)
{Wherein R is a hydrocarbon group having 13 to 21 carbon atoms, X represents an oxygen atom, a nitrogen atom, CO, COO, CON, or a direct bond, and Y are different or the same. A polyalkylene oxide group [C ₂ H ₃ (C _a H _{2a + 1} ) · O] _b —H (wherein a is an integer of 0 to 2 and b is 1 to 100), n is , X is 1 when oxygen atom, CO, COO, direct bond, and 2 when X is nitrogen atom, CON. }   The composite material according to claim 6, wherein the dispersant contains polyoxyalkylene alkylamines. The composite material according to claim 7, wherein the polyoxyalkylene alkylamine is a compound of the following formula 2.
RN (AO) ₂ (Formula 2)
{Wherein R is an alkyl group having 13 to 21 carbon atoms (wherein one or more hydrogen atoms of the alkyl group may be substituted with a hydrocarbon group, and further between adjacent nitrogen atoms) And AO represents a polyalkylene oxide group [C ₂ H ₃ (C _a H _{2a + 1} ) · O] _b —H that is different or identical to each other (here, A represents an integer of 0 to 2, and b is 1 to 100). }   The composite material according to any one of claims 5 to 8, wherein the carbon nanotube polyol dispersion is produced by a method in which carbon nanotubes are directly dispersed in a polyol.