JP5201823B2 - Conductive polyamide resin composition and method for producing the same - Google Patents

Description

  The present invention relates to a conductive polyamide resin composition and a method for producing the same.

  Conductive resin compositions are widely used for automobile applications and electronic / electrical component applications. This is because it is lighter than metal and has excellent formability. However, such a resin composition has a drawback in that the inherent moldability and mechanical properties of the resin are sacrificed because the conductive material, that is, the conductive material, is mixed with the originally non-conductive resin.

  In view of this, improvements have been made in that the conductive material is subjected to a surface treatment for increasing the affinity with the resin, or the kneading conditions during the production of the resin composition are strengthened. For example, surface treatment of graphite as a conductive material with a lubricating oil as described in Patent Document 1, or surface treatment of carbon fiber as a conductive material with an electrolyte compound as described in Patent Document 2 Furthermore, as described in Patent Document 3, a method is proposed in which carbon particles as a conductive material are heat-treated at 25 ° C. to 600 ° C. in an atmosphere containing air or ozone to oxidize the surface.

In particular, Patent Document 3 oxidizes the surface of carbon particles by immersing the carbon particles in an oxidizing agent such as nitric acid or potassium permanganate. These treated carbon particles are melt-kneaded with a polymer to produce a conductive resin composition. However, in the resin composition produced in this way, the carbon particles as the conductive material are surface-treated, and thus there is a risk of increasing the electrical resistance at the interface between the conductive material and the resin. Furthermore, if the kneading conditions are strengthened, there is an effect of cutting the contact between the carbon particles exhibiting electrical conductivity, so that it is very difficult to control the electrical resistance value as the resin composition. In particular, the use of film and yarn is limited because it is difficult to control variation in resistance value within a lot.
JP 63-23993 A JP 2002-212876 A JP 2003-86405 A

  The present invention has been made in view of the above circumstances, and its purpose is to provide a conductive polyamide resin composition having improved mechanical properties and conductivity while maintaining the moldability and chemical resistance of the polyamide resin. And providing a manufacturing method thereof.

The present inventors have found that the following resin composition can improve the mechanical properties and conductivity while maintaining the moldability and chemical resistance of the polyamide resin, and have completed the present invention. did.
That is, the gist of the present invention is as follows.

(1) Carbon particles having a mass reduction rate of 1 to 20% by mass when wet-treated with 100 parts by mass of a polyamide resin and an acid solvent and heated from 25 ° C. to 600 ° C. in an inert gas atmosphere. a resin composition containing 5 to 40 parts by weight, the polyamide resin is a polyamide 6 or polyamide 66, conductive polyamide resin composition, wherein the carbon particles are natural black lead.

(2) Carbon particles having a mass reduction rate of 1 to 20% by mass when wet treated with 100 parts by mass of a polyamide monomer and an acid solvent and heated from 25 ° C. to 600 ° C. in an inert gas atmosphere. A method for producing a resin composition in which 5 to 40 parts by mass of the polyamide monomer is polymerized, and ε-caprolactam is used as the polyamide monomer or a mixture of hexamethylenediamine and adipic acid the use, as the carbon particles, method for producing a conductive polyamide resin composition which comprises using a natural black lead.

  According to the present invention, by using specific carbon particles subjected to a special treatment, the conductive polyamide having improved mechanical properties and conductivity while maintaining the moldability and chemical resistance of the polyamide resin. A resin composition can be obtained. Therefore, the conductive polyamide resin composition of the present invention combines the electrical conductivity and mechanical properties with the moldability and chemical resistance inherent in the polyamide resin. -It can be used in a wide range of fields such as the electric field or the field of static electricity prevention and automobile exterior materials.

  The conductive polyamide resin composition of the present invention has a mass reduction rate of 1 to 20 when it is wet-treated with 100 parts by mass of a polyamide resin and an acid solvent and heated from 25 ° C. to 600 ° C. in an inert gas atmosphere. It contains 0.5 to 40 parts by mass of carbon particles that are mass%.

  The production method of the conductive polyamide resin composition of the present invention is a mass reduction rate when the wet treatment is performed with 100 parts by mass of a polyamide monomer and an acid solvent and the temperature is raised from 25 ° C. to 600 ° C. in an inert gas atmosphere. The polyamide monomer is polymerized in a state where 0.5 to 40 parts by mass of carbon particles of 1 to 20% by mass coexist.

  Any monomer may be used as long as it forms a polyamide resin by polycondensation to produce an amide bond. In general, (i) a case where an amide bond is present in one kind of cyclic monomer and the ring is opened with an initiator such as water to form a polyamide polymer; and (ii) a monomer having two amide groups in the molecule; Similarly, there are cases where a substantially equimolar amount of a monomer having two carboxyl groups in the molecule is blended to produce an amide bond at a high temperature to form a polyamide polymer.

  For example, in the case of polyamide 6, ring-opening polymerization is performed by raising the temperature of a mixture of ε-caprolactam, which is a cyclic monomer, and a small amount of water to about 240 ° C. Thereby, polyamide 6 is obtained. In this case, the polymerization degree and polymerization rate can be controlled by adding a small amount of acid. Other than this, polyamide 12 can be obtained from ω-laurolactam or 12-aminododecanoic acid, which can also be used in the present invention.

  In the case of polyamide 66, hexamethylenediamine and adipic acid are mixed in an equimolar amount, and the temperature is raised to 280 ° C. to polycondensate to obtain polyamide 66. Polyamide 46, polyamide 612, and aromatic polyamide with aromatics introduced into the components by changing the monomers can also be used in the present invention.

Carbon particles used in the present invention must be a natural graphite, it is preferable laminate of graphene sheets in the material is obtained by somewhat developed. According to the present invention, the point is that acid ions are inserted between the layers of the graphene sheet laminate. As such carbon particles, specifically, natural scaly graphite or bulk graphite, expanded graphite, kish graphite is exemplified. A mixture of these can also be used.

  As a method of inserting acid ions between the layers of carbon particles, 97% sulfuric acid, 94% nitric acid or a mixture thereof, and carbon particles are mixed and stirred at room temperature, and this cleaning liquid becomes neutral using pure water as a cleaning liquid. And then vacuum-dried at about 100 ° C. for 24 hours or longer. In this case, the acid used is not particularly limited as long as it has an oxidizing power for carbon particles. Inorganic acids such as sulfuric acid, nitric acid, potassium permanganate, phosphoric acid, hydrochloric acid, acetic acid, and organic acids can be used separately. Or it can be used as a mixture.

This method is different from the surface oxidation treatment described in Patent Document 3 described above. In Patent Document 3, hydroxyl groups and carboxyl groups are introduced on the surface of carbon particles using a low concentration acid such as 0.3% potassium permanganate. In the present invention, the 97% sulfuric acid and 94% described above are used. By using a high concentration acid such as a mixture with nitric acid, acid ions are inserted between layers of carbon particles such as graphite.

  In addition to this, an electrolytic method can be used as a method for inserting an acid ion. In this method, the target carbon particles are attached to one electrode, and electricity is passed in an acid solvent, whereby acid ions are inserted between the layers of the carbon particles.

  That is, the present invention introduces a functional group such as a hydroxyl group or a carboxyl group to the surface of the carbon particles by bringing it into contact with air at a high temperature as shown in Patent Document 1 or Patent Document 3 described above, Moreover, it differs from the method of attaching a silane coupling agent to the surface of carbon particles in order to improve the compatibility with the resin.

  Furthermore, in those described in Patent Documents 1 to 3, graphite having specific physical properties or acid-treated graphite and a thermoplastic resin are melted and kneaded. Is different in that the monomer is polymerized in the state of coexistence. In the present invention, carbon particles that have been wet-treated with an acid solvent between the layers are used. Therefore, the dispersibility of the carbon particles in the resin is good, and the effect of improving the conductivity of the resin composition obtained is higher than in the case of melt kneading.

  In the present invention, carbon particles in which acid ions are inserted between layers of the graphene sheet are used. By using such carbon particles, for example, when the polyamide resin is polyamide 6, the carbon particles are present in the graphene sheet. Since the acid ion serves as a polymerization initiator for ε-caprolactam and ε-caprolactam is polymerized between the graphene sheets, the graphene sheets are cleaved, and the dispersibility of the carbon particles in the polyamide 6 is improved. At this time, as the insertion amount of acid ions increases, the dispersibility of the carbon particles further progresses, so that the conductivity of the obtained resin composition improves. On the other hand, when the amount of insertion decreases, the effect of improving the conductivity of the resulting resin composition decreases.

  The amount of acid ions inserted between the layers of the graphene sheet of carbon particles can be determined by measuring the mass reduction rate when the temperature is raised from 25 ° C. to 600 ° C. under an inert gas flow such as nitrogen. . The carbon particles having a mass reduction rate of 1 to 20% by mass can be used in the present invention. When the mass reduction rate is less than 1% by mass, the insertion amount of acid ions is insufficient, and the effect of improving conductivity and the effect of improving mechanical properties such as bending elastic modulus cannot be expected. Carbon particles having a mass reduction rate exceeding 20% by mass cannot be obtained by the above method.

  The content rate of the carbon particles in the resin composition is 0.5 to 40 parts by mass with respect to 100 parts by mass of the polyamide resin. When the carbon particle content is less than 0.5 parts by mass, no improvement in conductivity can be expected. On the contrary, when the content of the carbon particles exceeds 40 parts by mass, the polymerization of the monomer is inhibited, so that a polymer cannot be obtained.

In the present invention, there is no limitation on the average particle size of the carbon particles, it is possible to use those of a few hundred micrometers, such as natural flake graphite, for example.

The present invention will be described in detail below based on examples.
The wet treatment of the carbon particles with the acid solvent was performed according to the contents shown in Table 1. The details are as follows. In addition, about the following carbon particles of C-1 to C-3 , the inert gas used when measuring the mass reduction rate when the temperature was raised from 25 ° C. to 600 ° C. in an inert gas atmosphere was nitrogen. Met.

  C-1: 50 g of natural scaly graphite (manufactured by Nippon Graphite Co., Ltd., average particle size: 380 μm) was put into a mixed solvent of 2000 ml of 90% sulfuric acid and 1000 ml of 80% nitric acid, and mixed and stirred at room temperature for 20 minutes. Thereafter, a large amount of pure water was introduced into the interior as a cleaning liquid, and cleaning work was performed. This washing operation was repeated until the pH of the washing solution reached 6-7. Next, hot air drying at 80 ° C. × 24 h was performed, and then vacuum drying at 80 ° C. × 48 h was performed. As a result, carbon particles C-1 were obtained. The carbon particles C-1 had a mass reduction rate of 3.0% by mass when heated from 25 ° C. to 600 ° C. in an inert gas atmosphere.

  C-2: The acid solvent was changed to a mixed solvent of 2000 ml of 97% sulfuric acid and 1000 ml of 94% nitric acid. Other than that was carried out similarly to C-1, and produced the carbon particle C-2. The mass reduction rate of the obtained carbon particles C-2 was 15.0% by mass.

C-3 : The acid solvent was changed to a mixed solvent of 2000 ml of 10% sulfuric acid and 1000 ml of 25% nitric acid. Other than that produced carbon particle C-3 like C-1. The mass reduction rate of the obtained carbon particles C-3 was 0.5 mass%.

The above-mentioned carbon particles C-1 to C-3 are shown together in Table 1.

Evaluation of moldability in the following examples and comparative examples was performed as follows. That is, in Examples 1 to 3 and Comparative Examples 1, 4, and 5, using an EC100 type molding machine manufactured by Toshiba Machine Co., Ltd., a molding temperature of 260 ° C., a mold temperature of 80 ° C., injection and pressure holding time of 10 seconds, cooling Ten ASTM bending test pieces were molded under the condition of a time of 15 seconds. At that time, the case where all 10 pieces were normally released from the mold was evaluated as good moldability (◯). When the number of molds that were normally released from the mold was 9 or less, the moldability was evaluated as poor (x).

In Example 4 and Comparative Example 2, the molding temperature was changed to 220 ° C and the mold temperature was changed to 70 ° C. Other molding conditions were evaluated as described above.
In Example 5 and Comparative Example 3, the molding temperature was changed to 240 ° C and the mold temperature was changed to 100 ° C. Other molding conditions were evaluated as described above.

Measurement of the amount of carbon particles in the resin compositions in the following Examples and Comparative Examples was performed by refluxing the resin compositions in 6N hydrochloric acid to remove the polymer.
Example 1
100 parts by mass of ε-caprolactam (hereinafter abbreviated as “ε-CL”), 5 parts by mass of C-1, and 10 parts by mass of pure water were prepared, and these were put into an autoclave. The temperature was raised to 260 ° C. and held at this temperature for 2 hours to polymerize ε-CL. And after paying out the contents in the form of pellets, it was immersed in hot water at 100 ° C. to remove unreacted monomers and dried to obtain a resin composition. Table 2 shows the results of measuring the flexural modulus and volume resistivity of the obtained resin composition and the results of evaluating the moldability.

The flexural modulus was measured based on ASTM D638, and the volume resistivity was measured based on ASTM D257.
Example 2
100 parts by mass of ε-CL, 30 parts by mass of C-1 and 10 parts by mass of pure water were prepared, and these were put into an autoclave to prepare a resin composition in the same manner as in Example 1 to obtain a flexural modulus. The volume resistivity was measured and the moldability was evaluated. The results are shown in Table 2.
Example 3
100 parts by mass of ε-CL, 10 parts by mass of C-2, and 10 parts by mass of pure water were prepared, and these were put into an autoclave to prepare a resin composition in the same manner as in Example 1 to obtain a flexural modulus. The volume resistivity was measured and the moldability was evaluated. The results are shown in Table 2.
Example 4
100 parts by mass of 12-aminododecanoic acid, 10 parts by mass of C-2, and 10 parts by mass of pure water were prepared, and these were put into an autoclave. Moreover, the hot water immersion after discharge | payout was not performed compared with Example 1. FIG. Other than that, a resin composition was prepared in the same manner as in Example 1, and the flexural modulus and volume resistivity were measured and the moldability was evaluated. The results are shown in Table 2.
Example 5
44 parts by mass of hexamethylenediamine, 56 parts by mass of adipic acid, 10 parts by mass of C-2, and 10 parts by mass of pure water were prepared, and these were put into an autoclave. Moreover, the hot water immersion after discharge | payout was not performed compared with Example 1. FIG. Other than that, a resin composition was prepared in the same manner as in Example 1, and the flexural modulus and volume resistivity were measured and the moldability was evaluated. The results are shown in Table 2.

Comparative Examples 1-3
Each of the monomers shown in Table 3 was charged into an autoclave, carbon particles were not added, and the other monomers were polymerized in the same manner as in Example 1 to produce resin compositions of Comparative Examples 1 to 3. did. However, in Comparative Example 2 and Comparative Example 3, hot water immersion after dispensing was not performed. The resin compositions of Comparative Examples 1 to 3 thus prepared were measured for flexural modulus and volume resistivity and evaluated for moldability. The results are shown in Table 3.
Comparative Example 4
100 parts by mass of ε-CL, 10 parts by mass of C-3, and 10 parts by mass of pure water were prepared, and these were put into an autoclave to prepare a resin composition in the same manner as in Example 1 to obtain a flexural modulus. The volume resistivity was measured and the moldability was evaluated. The results are shown in Table 3.
Comparative Example 5
100 parts by mass of ε-CL, 50 parts by mass of C-2 and 10 parts by mass of pure water were prepared, and these were put into an autoclave, and an attempt was made to produce a resin composition in the same manner as in Example 1. However, since there were too many compounding quantities of C-2, (epsilon) -CL did not fully polymerize but it did not become a polymer.

The resin compositions of Examples 1 to 5 were wet-treated with an acid solvent with respect to 100 parts by mass of the polyamide resin, and had a mass reduction rate of 1 to 1 when the temperature was raised from 25 ° C. to 600 ° C. in an inert gas atmosphere. Since it contained 0.5 to 40 parts by mass of carbon particles of 20% by mass, the required flexural modulus was exhibited and the volume resistivity was reduced to a satisfactory level. The moldability was also good. That is, it has required mechanical properties, conductivity, and moldability.

On the other hand, since the resin compositions of Comparative Examples 1 to 3 did not contain carbon particles, the flexural modulus and moldability were satisfactory, but the conductivity was poor.
The resin composition of Comparative Example 4 uses carbon particles having a mass reduction rate of less than a required level when heated from 25 ° C. to 600 ° C. in an inert gas atmosphere, that is, graphene of carbon particles Since the insertion of acid ions between the layers of the sheet was insufficient, even when the amount of carbon particles to be blended was the same as in Example 3, the volume resistivity was greatly increased and the flexural modulus was decreased. The moldability was poor.

Claims (2)

Carbon particles having a mass reduction rate of 1 to 20% by mass when the wet process is performed with 100 parts by mass of a polyamide resin and an acid solvent and the temperature is increased from 25 ° C. to 600 ° C. in an inert gas atmosphere. a resin composition containing a mass portion, wherein the polyamide resin is a polyamide 6 or polyamide 66, conductive polyamide resin composition, wherein the carbon particles are natural black lead. Carbon particles having a mass reduction rate of 1 to 20% by mass when the wet process is performed with 100 parts by mass of a polyamide monomer and an acid solvent and the temperature is increased from 25 ° C. to 600 ° C. in an inert gas atmosphere. It is a method for producing a resin composition in which the polyamide monomer is polymerized in a state where a mass part coexists, and as the polyamide monomer, ε-caprolactam is used, or a mixture of hexamethylenediamine and adipic acid is used, production method of Examples carbon particles, conductive polyamide resin composition which comprises using a natural black lead.