JP2012236902A - Spherical carbon material-containing resin material and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin material excellent in electric conductivity in a smaller amount of a carbon material added.SOLUTION: A carbon material-containing resin material is formed by mixing the carbon material with a base resin. A spherical carbon material formed of spherical particles each having an average particle diameter of 1 μm or lower is used as the carbon material. The carbon material accounts for 20 mass% or lower of the base resin.

Description

  The present invention relates to a spherical carbon material-containing resin material and a method for producing the same.

Resin materials (resin-molded products) that are electrodeposited on the surface, such as automotive bumpers and fenders, as well as automotive interior components, electrical components, other electrical and electronic components, and OA components are conductive. It is required to have Therefore, the conductivity imparting material is mixed in these resin materials. For example, Patent Document 1 relates to a polyamide resin composition, and by adding 1 to 15% by weight of carbon black (Ketjen Black) as a conductivity-imparting material, the volume resistivity is less than 1 × 10 ¹⁰ Ω · cm. The surface resistivity is described as less than 1 × 10 ¹² Ω · cm.

JP 2007-70457 A

  As described above, when a carbon material such as carbon black is added to the resin material, conductivity can be obtained. However, if the amount added is increased, the conductivity increases, but the mechanical properties such as impact resistance decrease. .

  Therefore, the present invention provides a resin material that can achieve expected conductivity even with a small carbon material addition amount, and a method for producing the resin material.

  In order to solve the above-described problems, the present invention uses a carbon material made of spherical particles having an average particle diameter of 1 μm or less as the conductivity imparting material.

  Specifically, the spherical carbon material-containing resin material presented here is formed by mixing a carbon material with a base resin, and the carbon material is composed of spherical particles having an average particle diameter of 1 μm or less, and the carbon material for the base resin. The content of the material is 20% by mass or less (the amount of the carbon material with respect to 100 parts by mass of the base resin is 20 parts by mass or less), and the volume resistivity is 2.6 MΩ · cm or less.

  That is, resin materials such as PP (polypropylene), PE (polyethylene), PA (polyamide) such as nylon, and epoxy resin have a structure in which innumerable thread-like polymers 1 are entangled as schematically shown in FIG. . For this reason, even if the conventional carbon black 2 is added to the resin material as a conductivity-imparting material, its particle size is large (for example, 5000 nm or more) and is indefinite, so that its dispersibility is low and expected conductivity. In order to obtain the properties, it is necessary to increase the amount of addition.

  On the other hand, in the case of the present invention, the carbon material is composed of spherical particles having an average particle diameter of 1 μm or less. Therefore, as schematically shown in FIG. The particles 3 enter and the dispersibility thereof becomes high. As a result, even if the content of the carbon material is 20% by mass or less, or even 10% by mass or less, a reliable electron transfer path is constructed over the entire resin material, and good conductivity is obtained. . The content of the carbon material is preferably 2% by mass or more. The average particle size of the carbon material is preferably 500 nm or less.

  The “average particle diameter” is a number average particle diameter obtained by selecting 100 particles by SEM (scanning electron microscope) observation and measuring the diameters to calculate an average value. This also applies to the average particle size described below.

  Such a spherical carbon material-containing resin material can be obtained by the method described below. A step of preparing a carbon material comprising spherical particles having an average particle diameter of 1 μm or less, a step of obtaining a molding material obtained by mixing the carbon material in a proportion of 20% by mass or less with respect to the base resin, And a step of molding a resin material from a molding material.

  In the step of obtaining the molding material, it is preferable to mix the carbon material in the presence of a dispersant with respect to the base resin in order to improve the dispersibility of the carbon material. In particular, when the content of the carbon material is 10% by mass or less, it is preferable to add a dispersant. In this case, the additive rate of the dispersant with respect to the base resin is, for example, 0.5% by mass to 3% by mass. Hereinafter, or 1/10 to 1/4 (mass ratio) of the carbon material content. As such a dispersant, a nonionic dispersant made of a compound containing at least one hydrophobic group and one hydrophilic group is preferable. In this case, the hydrophobic group may be a hydrocarbon (which may contain fluorine and / or silicon) or a long polypropylene oxide chain. The hydrophilic group may have a polar group such as a hydroxyl group, an ester group, a phosphate ester group, an ether group, an ether ester group, an amide group, an amino group, an amine oxide group, an imide group, or a sulfoxide group. The properties of the nonionic dispersant are not particularly limited, such as powder, paste, and oil.

  Examples of such a nonionic dispersant include 1) an imide type nonionic dispersant, 2) a polyalkylene glycol type nonionic dispersant, and 3) a polyhydric alcohol type nonionic dispersant.

  1) Examples of the imide type nonionic dispersant include polyvinylpyrrolidone, lauric acid diethanolamide, mono (diethylamino) alkyl ether, and the like.

  2) Nonionic dispersants having a polyethylene glycol chain or a polypropylene glycol chain include polyoxyethylene cetyl ether, polyoxyethylene octyldodecyl ether, polyoxyethylene alkylene allyl ether, polyoxyethylene distyrenated phenyl ether, polyoxy Examples include ethylene monoglycerin ester, polyoxyethylene hexaglycerin ester, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, and polyoxyethylene rosin ester.

  3) As polyhydric alcohol type nonionic dispersant, stearic acid monoglyceride, oleic acid diglyceride, palmitic acid diglyceride, sorbitan monolaurate, sorbitan monopalmitate, mono-distearic acid diglycerin, trimyristic acid pentaglycerin, Examples thereof include condensed ricinoleic acid tetraglycerin, condensed ricinoleic acid hexaglycerin, and condensed ricinoleic acid pentaglycerin.

  According to the present invention, since the carbon material mixed with the base resin is composed of spherical particles having an average particle diameter of 1 μm or less, the resin material is used even when the carbon material content in the resin material is 20% by mass or less. A reliable electron transfer path is constructed as a whole, and good conductivity can be obtained without impairing the mechanical properties of the resin material.

It is a schematic diagram which shows the dispersion state of the carbon material in the conventional resin material. It is a schematic diagram which shows the dispersion state of the carbon material in the resin material which concerns on this invention. It is a scanning electron micrograph of the spherical phenol resin which concerns on this invention. It is a scanning electron micrograph of the spherical carbon material which concerns on this invention. It is a graph which shows the relationship between the molar ratio of an acid catalyst, and the average particle diameter of spherical phenol resin and a spherical carbon material. 4 is a scanning electron micrograph of a resin material according to Example 2. It is a scanning electron micrograph of the resin material which did not add a dispersing agent. It is a graph which shows the relationship between the carbon material content rate and resistance value of an Example and a comparative example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its use.

<Method for producing spherical carbon material-containing resin material>
-Preparation of spherical phenol resin-
CTAB (cetyltrimethylammonium bromide) as a surfactant and hexamethylenetetramine as a curing agent were mixed in water, and phenol, formaldehyde, and hydrochloric acid as an acid catalyst were added thereto and mixed. The mixed solution was stirred for 24 hours while being heated to a temperature of 95 ° C. (polymerization reaction). Thereafter, the reaction solution was centrifuged, and the resulting product was washed with water and methanol to obtain a spherical phenol resin which is a precursor of spherical carbon particles. The spherical phenol resin was cured by heating in an argon gas atmosphere and maintaining the temperature at 270 ° C. for 2 hours.

  The surfactant is not limited to CTAB, and other cationic surfactants or anionic surfactants can be used. As the acid catalyst, other hydrogen halides, nitric acid, or sulfuric acid can also be used. The addition ratio of the acid catalyst to the phenol is preferably 0.01 or more and 0.15 or less in terms of molar ratio.

  In this case, surfactant micelles are formed in the aqueous phase, phenol is introduced into the micelles, and the condensation polymerization reaction proceeds in the presence of an acid catalyst. Spherical phenol resin particles are obtained by the progress of the polymerization reaction in the micelle. In addition, the surfactant can be dispersed by the acid catalyst, and as a result, the micelle size is reduced, so that the resulting spherical phenol resin particles have a reduced particle size.

  That is, by adjusting the addition amount of the acid catalyst, spherical phenol resin particles having an average particle size of 300 nm or more and 1000 nm or less can be obtained. Table 1 shows the influence of the addition amount of the acid catalyst (hydrochloric acid) on the particle diameter of the obtained spherical phenol resin. The raw material addition ratio is as shown in Table 1. The larger the amount of hydrochloric acid added, the smaller the particle size of the resulting spherical phenol resin.

  FIG. 3 is an SEM image of the spherical phenol resin according to Sample 2 in Table 1. It turns out that the spherical phenol resin particle obtained by the said preparation method has high sphericity. The average particle diameter was 0.82 μm.

-Preparation of fine spherical carbon materials (spherical carbon particles)-
The above-described cured spherical phenol resin was heated under an argon gas atmosphere and maintained at a temperature of 800 ° C. for 1 hour. This is a carbonization treatment of a spherical phenol resin. Next, the carbonized product was heated in a nitrogen gas atmosphere containing saturated water vapor and held at a temperature of 900 ° C. for 55 minutes. This is a steam activation treatment.

  FIG. 4 is an SEM image of a fine spherical carbon material obtained by subjecting the spherical phenol resin of Sample 2 to the carbonization treatment and the steam activation treatment. Even after the carbonization and steam activation of the spherical phenol resin particles, the spherical shape of the particles is maintained. That is, the individual carbon particles have a spherical shape separated and independent from each other. The average particle diameter after carbonization and steam activation is 0.33 μm (330 nm). It can be seen that the spherical phenol resin particles become spherical carbon particles having a small particle diameter by carbonization and steam activation.

  FIG. 5 shows the average particle diameter of the spherical phenol resin particles of Samples 1 to 5 and the spherical carbon particles obtained by carbonizing and steam-activating them. Spherical carbon particles having an average particle size of 100 nm to 400 nm are obtained from spherical phenol resin particles having an average particle size of 320 nm to 930 nm.

-Preparation of resin material molding material-
The fine spherical carbon material is mixed with a base resin. When a thermoplastic resin such as PP or PA is employed as the base resin, a resin kneading extruder can be used. That is, the base resin pellets and the fine spherical carbon material are introduced into this extruder, and a dispersant is introduced as necessary, and the base resin is melted and mixed with the fine spherical carbon material. As such an extruder, a co-rotating twin screw extruder (for example, BT-30-S2-36-L manufactured by Plastics Engineering Laboratory) can be preferably used. In this case, the barrel temperature is set to 190 to 280 ° C. so that the base resin is melted and has a viscosity. The screw rotation speed may be about 150 rpm.

  When a thermosetting resin such as an epoxy resin or a phenol resin is employed as the base resin, a resin material molding material is obtained by mixing a carbon material with the liquid or semi-liquid resin having an uncured viscosity. At that time, a dispersant is used as necessary.

-Molding of resin material-
A resin material (molded product) having a predetermined shape is obtained from the resin material molding material. For the molding, an appropriate molding method according to the product such as compression molding, injection molding, or extrusion molding can be employed.

<Examples and Comparative Examples>
-Examples 1-3
A spherical carbon material-containing resin material having an epoxy resin as a base resin was produced. That is, an uncured liquid epoxy resin (prepolymer) before addition of the curing agent and the above-mentioned microspherical carbon material (average particle diameter 330 nm) as a conductivity imparting material are dispersed using a vacuum mixer. Mixed in the presence. The rotation speed of the vacuum mixer is 2000 rpm, and the mixing time is 10 minutes. As the dispersant, polyvinyl pyrrolidone (average molecular weight 10,000) manufactured by Tokyo Chemical Industry was used. Then, a liquid epoxy resin in which the spherical carbon material is dispersed and a curing agent (modified aliphatic amine (trade name; HARDENER HY 956) manufactured by Nagase Sangyo Co., Ltd.) are mixed, and the obtained molding material is used as a mold. Poured and left overnight to obtain a cylindrical sample (radius 5 mm, length (thickness) 3 mm) according to the example.

  Example 1 has a fine spherical carbon material content of 5% by mass and a dispersant addition rate of 1% by mass, and Example 2 has a fine spherical carbon material content of 10% by mass and a dispersant addition rate of 1% by mass. In Example 3, the content of the microspherical carbon material is 20% by mass, and the dispersant addition rate is 0% by mass.

  FIG. 6 is an SEM image of the resin material according to Example 2. FIG. 7 is an SEM image of the resin material to which no dispersant was added in Example 2. In the case of Example 2, the fine spherical carbon particles 3 are highly dispersed and the base resin (epoxy resin) is not exposed, but in the case where the dispersant was not added (FIG. 7), the fine spherical carbon particles 3 is agglomerated and the base resin 4 is partially exposed.

-Comparative Examples 1-3
Samples of Comparative Example 1 containing no conductivity-imparting material and a dispersant, Comparative Example 2 and Comparative Example 3 using ketjen black as the conductivity-imparting material were prepared in the same manner as in the above Examples. Comparative Example 2 has a ketjen black content of 10% by mass and a dispersant addition rate of 1% by mass, and Comparative Example 3 has a ketjen black content of 20% by mass and a dispersant addition rate of 0% by mass. The same dispersant as that used in the example was used.

-Measurement of volume resistivity-
Silver paste was applied to both surfaces of each sample of the examples and comparative examples, and the resistance value was measured with a high-voltage tester to determine the volume resistivity. The results are shown in Table 2 and FIG. In Examples 1 to 3, although the volume resistivity is 2.6 MΩ · cm or less (2.0 MΩ · cm or less) and the carbon material content is 20% by mass or less, the resin material is made of a microspherical carbon material. It can be seen that a reliable electron transfer path is constructed throughout and good conductivity is obtained.

1 Polymer 2 Carbon Black 3 Microspherical Carbon Particles 4 Base Resin

Claims (4)

A carbon material mixed with a base resin,
The carbon material is composed of spherical particles having an average particle size of 1 μm or less,
The content of the carbon material relative to the base resin is 20% by mass or less,
A spherical carbon material-containing resin material having a volume resistivity of 2.6 MΩ · cm or less. In claim 1,
A spherical carbon material-containing resin material, wherein the content is 10% by mass or less. Preparing a carbon material comprising spherical particles having an average particle diameter of 1 μm or less;
A step of obtaining a molding material obtained by mixing the carbon material at a ratio of 20% by mass or less with respect to the base resin;
And a step of molding a resin material from the molding material. In claim 3,
In the step of obtaining the molding material, the carbon material is mixed into the base resin in the presence of a dispersant.