JP2007269947A - Surface-modified carbon black and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-modified carbon black excellent in dispersing property to a reactive silicone polymer, especially silicone rubber, imparting high heat conductivity while suppressing electric conductivity and to provide a method for producing the same. <P>SOLUTION: The invention relates to the carbon black characterized by having a triisocyanate compound which has three isocyanate groups bonding to all three terminal, and one isocyanate group is bonding to a functional group on the surface of the carbon black particle and the other two isocyanate groups are bonding with a diol-modified reactive polymer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

   The present invention is excellent in dispersibility in surface-modified carbon black, more specifically in a silicone polymer. In particular, the surface modification can be suitably used as a filler for imparting high thermal conductivity while suppressing conductivity in silicone rubber. The present invention relates to a quality carbon black and a production method thereof.

 In recent years, electric vehicles have been actively researched and developed for the purpose of reducing harmful substances contained in exhaust gas and reducing fuel consumption. Hybrid vehicles that combine high-power secondary batteries and gasoline engines are also becoming popular.

  In electric vehicles and hybrid vehicles, development of highly efficient motors is indispensable, and high-performance insulating members are required as members of these motors. An insulating member of an automobile motor, particularly a coil binding member, is required to have excellent heat resistance, high temperature oil resistance, and the like. Silicone rubber is an example of an elastomer that satisfies such a requirement.

  In silicone rubber for insulating members, high thermal conductivity is required in order to improve heat dissipation in addition to the above performance. Conventionally, in order to improve the thermal conductivity of silicone rubber, a method using fine powders such as aluminum oxide, aluminum hydroxide, and magnesium oxide as a filler has been proposed (see Patent Document 1), which is 200 ° C. or higher. When used under high temperature conditions, there is a drawback that silicone rubber deteriorates due to the influence of impurities and pH.

  On the other hand, carbon black has been widely used as a filler for imparting heat resistance, wear resistance, and reinforcement to rubbers and elastomers (see, for example, Patent Document 2), and carbon black improves thermal conductivity. However, since carbon black is a conductive material, there is a problem in terms of insulation when used as a filler for an insulating member.

As a means for imparting high electrical resistance to carbon black, a technique for applying a specific oxidation treatment to the surface (see Patent Document 3), a technique for coating with a multifunctional epoxy resin, etc. (see Patent Document 4), and the like have been proposed. However, the volume resistivity of carbon black that can be achieved by these methods is about 5 to 50 Ωcm.
JP-A-55-3766 Japanese Patent No. 2874622 Japanese Patent Laid-Open No. 11-181324 Japanese Patent Laid-Open No. 9-25571

  The present invention has been made as a result of many tests and examinations on the surface modification of carbon black in order to eliminate the above-mentioned conventional problems of carbon black particularly when used as a filler for an insulating material. In particular, the object is to provide a surface-modified carbon black capable of imparting high thermal conductivity to silicone rubber while suppressing conductivity, and a method for producing the same.

  In order to achieve the above object, the surface-modified carbon black according to claim 1 is characterized in that one isocyanate group of a triisocyanate compound having isocyanate groups at all three ends is bonded to a functional group on the surface of carbon black particles. It is characterized in that the other two isocyanate groups of the compound are bound to a diol-modified reactive polymer.

  The method for producing a surface-modified carbon black according to claim 2 comprises dissolving a triisocyanate compound having isocyanate groups at all three ends and a diol-modified reactive polymer in a non-reactive solvent, and adding carbon black to the solvent. To combine the functional group on the surface of the carbon black particle and one isocyanate group of the triisocyanate compound, and the reactive group of the diol-modified reactive polymer and the other two isocyanate groups of the triisocyanate compound. It is characterized by making it.

The method for producing surface-modified carbon black according to claim 3 is the method according to claim 2, wherein the functional group on the surface of the carbon black particles is a hydroxyl group, a carboxyl group, or a hydroxyl group and a carboxyl group, and the functional group is a hydroxyl group. When the amount is 0.14 μeq / m ² or more, when the functional group is a carboxyl group, the amount of the functional group is 0.14 μeq / m ² or more, and when the functional group is a hydroxyl group and a carboxyl group, the sum of both functional groups is 0. It is 14 μeq / m ² or more.

  According to the present invention, surface modification that can be suitably used as a filler that is excellent in dispersibility in reactive polymers, particularly silicone polymers such as silicone rubber, and can impart high thermal conductivity while suppressing conductivity in silicone rubber. Quality carbon black and a method for producing the same are provided.

  The surface modified carbon black according to the present invention has a surface modified by reacting the particle surface with an insulating diol-modified reactive polymer, preferably with a dimethylpolysiloxane skeleton as the main structure, such as silicone rubber. In addition to having a high specific volume resistance, it has excellent dispersibility in silicone rubber. Therefore, it exhibits good dispersibility as a filler for silicone rubber, and it is possible to improve thermal conductivity as long as the insulating property of the silicone rubber is not impaired. The surface-modified carbon black according to the present invention is also expected to have many uses in the application fields of inks, electrostatic charge developing toners, paints, and other silicone polymers due to the improved dispersibility in silicone polymers.

  The type of carbon black applied in the present invention is not particularly limited, and any of carbon black generated by the furnace method, thermal black generated by the thermal method, and channel black generated by the channel method can be used. Since carbon black having a primary particle size of less than 0.01 μm has a high cohesive force acting between the particles, it tends to agglomerate. Therefore, the primary particle size measured by electron microscope observation is 0.01 μm or more. It is preferable to use carbon black.

  In the surface-modified carbon black of the present invention, the functional group on the surface of the carbon black particle and one (first terminal) isocyanate group of a triisocyanate compound having isocyanate groups at all three terminals are bonded, and further, the triisocyanate compound The other two (second and third terminal) isocyanate groups have a structure in which a reactive group such as a hydroxyl group of a diol-modified reactive polymer is bonded.

  As the carbon black to which the reactive polymer is bonded, any carbon black having a reactive functional group on its surface can be used without particular limitation. Examples of the reactive functional group include a hydroxyl group, a carboxyl group, a quinone group, an amino group, a sulfone group, and an epoxy group. In particular, carbon black having acidic functional groups such as hydroxyl groups and carboxyl groups, and amino groups on the particle surface is preferred.

Some of the functional groups on the surface of the carbon black particles are present from the generation process stage, and can be generated and controlled by chemically modifying the carbon black. The method for chemically modifying the functional group is as follows.
Hydroxyl group, carboxyl group, and quinone group generation: gas-phase oxidation treatment methods such as exposing carbon black to a gas atmosphere such as ozone, oxygen, NOx, SOx, treating carbon black with low-temperature oxygen plasma, and carbon black Method of oxidizing in aqueous solution of ozone water, hydrogen peroxide solution, peroxodiacid or its salt, method of oxidizing carbon black in aqueous solution of hypohalite, dichromate, permanganate, carbon black A liquid phase oxidation method such as a method in which oxidizer is oxidized in an aqueous oxidizing agent solution such as nitric acid.

Amino group generation: A method in which carbon black is oxidized in a nitric acid / sulfuric acid mixed system to generate a nitro group, and the nitro group is reduced with a reducing agent such as formaldehyde.
Sulfon group generation: A method of sulfonating carbon black with concentrated sulfuric acid.
Generation of epoxy group: A method of reacting a hydroxyl group and a carboxyl group of carbon black with a halide having an epoxy group.

  In addition, it is preferable to use carbon black having a pH of 5 or less for the degree of chemical modification. Commercially available acidic carbon black or channel black having a pH of 5 or less can be applied as it is without performing the above oxidation treatment. .

The functional group of the carbon black particle surface, easy to obtain a hydroxyl group or a carboxyl group, although and efficiently functioning, as the amount of these functional groups, when the functional group is a hydroxyl group 0.14μeq / m ² As described above, when the functional group is a carboxyl group, it is preferably 0.14 μeq / m ² or more, and when the functional group is a hydroxyl group and a carboxyl group, the sum of both functional groups is preferably 0.14 μeq / m ² or more. If the functional group amount is less than 0.14 μeq / m ² , it is difficult to uniformly react the triisocyanate compound having isocyanate groups at all three ends on the surface of the carbon black particles. For example, the second and third end isocyanate groups and one end Even when the hydroxyl group of the diol-modified polymer is bonded to the diol-modified polymer, more components are precipitated, and it is difficult to impart sufficient electric resistance to the surface-modified carbon black.

 By reacting the functional group on the surface of the carbon black particles with a triisocyanate compound having isocyanate groups at all three ends, the isocyanate compound is additionally bonded to the surface of the carbon black particles by a chemical bond. An example of this reaction is shown in Chemical Formula 1. Chemical formula 1 is a reaction example in which a hydroxyl group as a functional group on the surface of carbon black particles and a hexane isocyanate compound having an isocyanurate structure as a triisocyanate compound having isocyanate groups at all three ends are urethane-bonded.

  Triisocyanate compounds having isocyanate groups at all three ends include those having an isocyanurate structure, for example, D-127N, D-170N, D-170HN, D-172N, D-177N manufactured by Mitsui Takeda Chemical Co., Ltd. Etc.

 In the carbon black of the present invention, the unreacted second and third isocyanate groups of the triisocyanate compound having isocyanate groups at all three ends bonded to the functional groups on the surface of the carbon black particles are bonded to the diol-modified reactive polymer. The reactive group contained in the reactive polymer can be used without particular limitation as long as it is chemically bonded to an isocyanate group, such as a hydroxyl group, an amino group, a mercapto group. And carboxyl group.

  Among these, in the case of a highly reactive substance such as an amino group, the triisocyanate compound having an isocyanate group at all three ends becomes an intermediate and the reactive polymers are easily bonded to each other, and the surface modification of carbon black is performed. In this case, after binding the triisocyanate compound, it is necessary to wash away the triisocyanate compound released in the solvent using a centrifuge, and bind the reactive polymer again. It is.

  In the case where the unreacted second and third isocyanate groups of the triisocyanate compound having isocyanate groups at all three ends bonded to the functional groups on the surface of the carbon black particles are bonded to the diol-modified reactive polymer to modify the surface. A reaction example is shown in Chemical Formula 2. Chemical formula 2 has a structure in which a reactive silicone polymer having a diol group as a reactive group is bonded via a urethane bond to carbon black in which a triisocyanate compound having an isocyanate group is bonded to all three ends shown in chemical formula 1. The chemical reaction which surface-modified carbon black produces | generates is shown.

  That is, the production of the surface-modified carbon black by the chemical formula 2 is performed by dissolving a triisocyanate compound having isocyanate groups at all three ends and a diol-modified reactive silicone polymer having a reactive group only at one end in a solvent. Carbon black is added and mixed to urethane bond an isocyanate group to the surface of the carbon black particle, and an unreacted second and third isocyanate group is urethane bonded to the hydroxyl group of the one-end diol-modified reactive polymer. In practice, the triisocyanate compound functions as an intermediate for binding carbon black and reactive polymer.

  The reactive polymer is not particularly limited as long as it has insulating properties, but a reactive silicone polymer is particularly preferably used. Of the reactive polymers, reactive polymers having reactive groups at both ends are poor in reactivity with the carbon black surface reactive groups, and therefore, reactive polymers having reactive groups only at one end are preferred. In order to obtain excellent dispersibility in silicone silicone rubber, a reactive silicone polymer having a dimethylpolysiloxane skeleton similar to that of silicone rubber is suitable.

  As the reactive polymer, those having a molecular weight of 500 to 30,000 are preferable. A polymer having a molecular weight of less than 500 has a small steric hindrance and hardly contributes to the suppression of aggregation of the carbon black particles. When the molecular weight exceeds 30000, the graft rate tends to decrease due to the steric hindrance of the polymer chain.

  Hereinafter, the method for producing the surface-modified carbon black according to the present invention will be described. A triisocyanate compound having an isocyanate group at all three ends and a diol-modified reactive polymer are dissolved in a solvent, and the carbon black is added to the solvent and stirred. After stirring and defoaming with a defoamer and mixing, the mixture is kneaded using a three-roll mill or the like to obtain a kneaded product, and reactive functional groups such as a hydroxyl group and a first terminal isocyanate group on the carbon black particle surface. Then, an unreacted second and third terminal isocyanate groups and a reactive group of a reactive polymer modified with a one-end diol, such as a hydroxyl group, are urethane-bonded. At this time, when a small amount of a dehydrating condensing agent such as dibutyltin dilaurate is added, the urethane reaction easily proceeds.

  As a solvent to be used, a solvent that sufficiently dissolves a triisocyanate compound having isocyanate groups at all three ends and a reactive polymer modified with a one-end diol is preferable. For example, a ketone, an acetic ester solvent, silicone oil, or the like is used. Can do. On the other hand, it is better not to use water or an alcohol-based solvent because the isocyanate is deactivated.

  Examples of the dehydrating condensing agent include dibutyltin dilaurate, concentrated sulfuric acid, N, N′-dicyclohexylcarbodiimide, N, N′-diisopropylcarbodiimide, N-ethyl-N ′-(3 dimethylamipropyl) carbodiimide, 1- Hydroxybenzotriazole, diethyl phosphorocyanide, 1-ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinone, isobutyl chloroformate, trityl chloride, pivaloyloxymethyl chloride, dibutyltin laurate, hafnium chloride, etc. Is mentioned. A similar catalytic effect can be obtained even with a compound having an —N═N— bond or an anhydride.

  The kneaded product is diluted by adding a solvent, and then dispersed using an ultrasonic homogenizer, a high-pressure homogenizer, a process homogenizer, a ball mill, a bead mill, etc. The isocyanate group at the first terminal of the triisocyanate compound having isocyanate groups at all three terminals and the functional groups on the surface, the unreacted second and third terminal isocyanate groups, and the reactive group of the one-end diol-modified reactive polymer such as hydroxyl group Are firmly bonded with urethane bonds.

  The dispersion after the heat treatment is subjected to a centrifugal separation treatment to remove the unreacted isocyanate compound and the like, and purification is performed to obtain surface-modified carbon black. The refined carbon black is dried and ground.

  FIG. 1 is a flowchart showing an example of a process for obtaining a dispersion of reactive polymer-bonded surface-modified carbon black using oxidized carbon black oxidized by chemical modification.

 Hereinafter, examples of the present invention will be described and the effects thereof will be demonstrated. In addition, this Example shows one embodiment of the present invention, and the present invention is not limited to this.

Example 1
Carbon black TB # 75550F manufactured by Tokai Carbon Co., Ltd. was vapor-phase oxidized with ozone to obtain oxidized carbon black powder having acidic functional groups on the particle surfaces.

  180 g of silicone oil KF96L-1cs made by Shin-Etsu Chemical Co., Ltd. was added to 125 g of the oxidized carbon black obtained to make it wet, and then 23.625 g of D-177N made by Mitsui Takeda Chemical Co., Ltd. 81.25 g of modified silicone polymer FM-DA211 (molecular weight 5000) was added and mixed, stirred for 2 minutes and defoamed for 2 minutes using Shintaro Awatori Rentaro Co., Ltd., and pre-kneaded.

  This pre-kneaded product was further kneaded for 15 minutes with a three roll, then a silicone oil solution in which 3.54 g of dibutyltin dilaurate was dissolved at a concentration of 15 wt% was added, and kneaded with a three roll for 15 minutes. A kneaded product was obtained.

  Silicone oil was added to the obtained kneaded material to make a 30% by weight dispersion, which was treated with an ultrasonic homogenizer for 10 minutes to perform mechanical dispersion.

   The dispersion is heat-treated in a 1-liter separable flask at 70 ° C. with sufficient stirring for 6 hours. After the heat treatment, washing by centrifugal separation and drying are performed to obtain a dry body of surface-modified carbon black. The dried product was pulverized to obtain 120 g of pulverized carbon black.

  With respect to the obtained surface-modified carbon black, the compression electric resistance by 5.0 MPa pressurization was measured and found to be 650 Ωcm. On the other hand, when the compression electrical resistance of untreated carbon black TB # 75550F by 5.0 MPa pressurization was measured, it was 0.6 Ωcm.

It is a flowchart which shows the process until it obtains the dispersion of reactive polymer coupling | bonding surface-modified carbon black using oxidation carbon black.

Claims (3)

One isocyanate group of a triisocyanate compound having isocyanate groups at all three ends is bonded to a functional group on the surface of the carbon black particle, and the other two isocyanate groups of the triisocyanate compound are bonded to a diol-modified reactive polymer. Surface-modified carbon black characterized by A triisocyanate compound having an isocyanate group at all three ends and a reactive polymer modified with a diol are dissolved in a non-reactive solvent, carbon black is added to the solvent and mixed, and the functional group on the surface of the carbon black particles and the above trimethyl compound are mixed. A method for producing a surface-modified carbon black characterized by bonding one isocyanate group of an isocyanate compound and bonding a reactive group of a diol-modified reactive polymer and the other two isocyanate groups of a triisocyanate compound . In the functional group of the carbon black particle surface hydroxyl group or a carboxyl group or a hydroxyl group and a carboxyl group, if the functional group is a hydroxyl group content functional groups 0.14μeq / m ² or more, when the functional group is a carboxyl group functionality 3. The surface modification according to claim 2, wherein the amount of the group is 0.14 μeq / m ² or more, and when the functional group is a hydroxyl group and a carboxyl group, the sum of both functional groups is 0.14 μeq / m ² or more. Of producing high quality carbon black.

Images