JP4889814B1 - Method for producing carbon aggregate forming raw material and method for producing electromagnetic induction cooking device - Google Patents

Abstract

Disclosed is a carbon aggregate forming raw material that exhibits excellent fluidity in a mold after being discharged from a gate and that has higher strength and heat conduction, and a method for producing an electromagnetic induction cooking device.
The method for producing a carbon aggregate forming raw material according to the present invention comprises a graphite group having a needle shape obtained by rolling a surface of a graphite column block in a state where a graphite column block is rotated. A coating film of an uncured phenolic resin is coated on the surface by polymerizing in the presence of a surfactant together with a compound containing a group.
[Selection] Figure 2

Description

  The present invention relates to a method for producing a carbon aggregate forming raw material using a composite in which the surface of graphite powder having an acicular shape is coated with a phenol resin. Moreover, it is related with the manufacturing method of an electromagnetic induction heating cooking appliance.

  Stoves and rice cookers that are cooking utensils applying electromagnetic induction heating use electromagnetic induction heating in which iron or stainless steel, which is a magnetic metal, generates heat due to eddy current generated by an induction heating coil that is a high-frequency magnetic field generator. Thus, it has a feature that rapid and uniform heating can be obtained.

  In the cooker, a clad material laminated with aluminum or copper was used as a pan-shaped molded product. However, the clad material is difficult to be shaped into a pan or a pot, and the surface is heat resistant resin such as fluororesin. There were also problems such as peeling of each laminated interface on the painted surface.

  For this reason, it has been proposed to use a carbon condensate having moderate conductivity, dielectric properties and excellent thermal conductivity as a material for an electromagnetic induction heating cooker that replaces conventional iron and stainless steel. (For example, refer to Patent Document 1).

  Further, a cut product of a compressed body pressed into a rod-pillar shape has been introduced (see, for example, Patent Document 2).

  According to the above-described method of manufacturing a cooking utensil, a carbon pillar such as coke is molded into a rod-column shape by a mixture mainly composed of a binder that is a high carbon content such as phenol or pitch, and this is formed in an oxygen-free atmosphere. After obtaining a graphitized carbon aggregate obtained by heating at 1000 to 3000 ° C., it is cut into an arbitrary shape.

  However, the means for obtaining an arbitrary shape by cutting a carbon sintered body has a problem that the material in the hollow portion of the container that occupies most of the cutting is discarded, and the number of processing steps is large.

  In addition, it is difficult to detect defects existing in the carbon compression body in advance, and the characteristics such as design and strength are adversely affected by the exposure of the defects by cutting.

  As a means for solving these problems, the molded product obtained after molding by injecting a mixture of graphite particles and a binder material such as a phenol resin raw material liquid or tar pitch into a mold and pressurizing it, is used. Means for obtaining a carbon aggregate formed into a pan shape by firing is disclosed (for example, see Patent Document 3).

  According to the above-mentioned Patent Document 3, in order to obtain a high flow state in the mold, a raw material in which graphite particles and a binder are mixed needs to contain a large amount of a phenol resin or the like that melts under injection temperature conditions as a binder. . On the other hand, as a cooking utensil capable of electromagnetic induction heating, it is necessary to have a high mixing ratio of graphite particles in order to obtain a carbon aggregate molded product having excellent strength, electrical conduction and thermal conduction. However, a raw material with a low phenolic resin content and a high mixing ratio of graphite grains improves the viscosity and lowers the fluidity, and the surface of the graphite grains does not wet sufficiently so that they aggregate and flow. To lose.

  In addition, as described above, the phenol resin as a binder is reduced and a large amount of graphite particles are mixed, so that a defect portion where the binder is not applied is generated on the surface of the graphite particles, and the strength of the aggregate is reduced. However, with the decrease in fluidity, there is a problem that many pores remain without being densely packed and the thermal conductivity is lowered.

  In response to the above problems, a molding material in which the surface of graphite powder is completely covered with a resin has been introduced (for example, see Patent Document 4).

  According to Patent Document 4, a compound of a phenolic compound and an aldehyde compound is polymerized while being mixed with graphite particles in the presence of a catalyst. A film is formed. On the other hand, since it is possible to obtain a molding material with a thin coating on the sharp convex portions existing on the surface of the graphite grains, it is difficult to obtain the effect of suppressing the aggregation of the graphite grains, and the fluidity during molding is low. Due to the low density, there is a problem that since the dense filling cannot be performed, many pores remain and the original strength and thermal conductivity cannot be obtained.

  In response to the above problem, graphite particles are stirred and dispersed in water in the presence of a surfactant in a reaction stage where both compounds containing a phenol group and an aldehyde group are polymerized to obtain an uncured phenol resin. Thus, there has been proposed a granular composite forming raw material in which the surface of graphite particles is completely covered with a coating film of an uncured portion and spheroidized with the polymerization of a phenol resin. The molding raw material is shaped by curing in pressure heating molding, and the obtained molded product is carbonized with a phenol resin by baking treatment in an oxygen-free high-temperature atmosphere, so that a coagulated body in which the above-described problems are solved can be obtained ( For example, see Patent Document 5).

  However, in the case of composites using granular graphite, as the heat transfer element that forms the continuity in the plane direction, there are many carbon parts carbonized by the phenol resin that forms heat transfer resistance at the contact parts between the graphite particles. There is a problem that the decrease in thermal conductivity becomes large.

  On the other hand, since the heat transfer distance in graphite with high thermal conductivity is increased and the graphites have multiple contacts to promote heat transfer, high heat conduction is achieved by using needle-shaped graphite grains. Rate is obtained.

  For example, as a conductive resin composition, at least a discontinuous fibrous substance or acicular graphite is selected from among styrene resin, polycarbonate, polyphenylene ether, polyamide, polyester, polyphenylene sulfide, polyolefin resin, liquid crystal resin, and phenol resin. A mixture of at least one selected from (see, for example, Patent Document 6) has been introduced.

  However, acicular graphite is acicular obtained in a firing process in which raw coke obtained by carbonizing a relatively high boiling coal tar distillate at a predetermined temperature and pressure is crushed and heated at a temperature of 1300 to 1500 ° C. In order to obtain coke and convert it into acicular graphite, a green electrode formed by extruding a mixture of coal tar and binder pitch at 90 to 120 ° C. was baked and carbonized at a temperature of 800 to 900 ° C. It is necessary to later graphitize by heating to a temperature of 2700 to 3300 ° C. (see, for example, Patent Document 7).

JP-A-9-75211 JP 9-70352 A JP 2007-04257 A JP 2003-48934 A JP 2010-059372 A JP 2002-231051 A Special table 2009-542842

  That is, it is indispensable to leave acicular coke in an oxygen-free high-temperature atmosphere and graphitize it, and it cannot be easily used because it requires enormous facilities and processes. In addition, since acicular graphite obtained based on the above-mentioned means contains a lot of fine particles, the molding material mixed with the phenol resin has high viscosity and poor fluidity. It was impossible to apply to a molded product having a thin wall and a long flow distance.

  The present invention has been made to solve the above-described problems, and exhibits a high fluidity in a mold after discharging from a gate, and has a higher strength and heat conduction. The manufacturing method of this and the manufacturing method of an electromagnetic induction heating cooking appliance are provided.

  The method for producing a carbon aggregate forming raw material according to the present invention is a compound containing a phenol group and an aldehyde group formed from needle-like graphite grains obtained by rolling a surface of a graphite column block in a state where the graphite column block is rotated. At the same time, the surface is coated with a coating film of an uncured phenolic resin by polymerization in the presence of a surfactant.

  The method for producing a carbon aggregate forming raw material according to the present invention is a compound containing a phenol group and an aldehyde group formed from needle-like graphite grains obtained by rolling a surface of a graphite column block in a state where the graphite column block is rotated. At the same time, since the coating film of the uncured phenolic resin is coated on the surface by polymerization in the presence of the surfactant, excellent fluidity in the mold after discharging from the gate is exhibited. Moreover, even if the chance of contact between the graphite grains is increased, since no defect is included, a carbon aggregate molded article having higher strength and heat conduction can be obtained.

In the figure shown for comparison, resin adhesion of a mixture obtained by pressure-kneading a carbon powder and a phenol resin uncured material obtained by crushing a lump only by kneading with a general molding raw material with an extruder or the like Conceptual diagram. The figure which shows Embodiment 1 and is the conceptual diagram of the shaping | molding raw material which complexed the phenol resin uncured material on the surface. In the figure which shows Embodiment 1, about the carbon aggregate molded product of the rice cooker inner pot, the bottom face which arranged the gate which inject | poured the carbon aggregate formation raw material at the time of shaping | molding, The figure which shows the measurement result of the thermal conductivity which shows the increase effect of the contact strength of density, the bending strength which shows the joining state of a graphite grain, and the acicular graphite grain as an alternative characteristic of porosity.

Embodiment 1 FIG.
<Overview>
In the present embodiment, heat conduction in the surface direction is improved by discharging into the mold using a composite in which the surface of the graphite particles forming a needle-like shape is coated with phenolic resin as a raw material for carbon aggregate molded product The present invention relates to a method for producing a raw material for a carbon aggregate molded article and a method for producing an electromagnetic induction heating cooking utensil.

  A composite using acicular graphite particles is held by a phenolic resin by obtaining an orientation that promotes orientation in the surface direction when flowing in a mold cavity forming a thin molded product wall. To form a molded product. This is fired in an oxygen-free high-temperature atmosphere at 1000 ° C., and the phenol resin is carbonized to form graphite and aggregates.

  In the case of a composite using granular graphite, since the carbonized part of the phenol resin that forms the heat transfer resistance is interposed in the contact part between the graphite particles forming the heat transfer element continuity in the plane direction, the thermal conductivity of Decrease increases.

  On the other hand, when acicular graphite is used, heat transfer in graphite with high thermal conductivity becomes overwhelmingly long, and graphite has multiple contacts to promote heat transfer. Conductivity is obtained.

<Means>
Graphite cylinders obtained by burning a mixture of petroleum coke and a mixture of tar and pitch melt into a mold, which is cooled and solidified while being compressed in a mold, and calcined at 3000 ° C. in an oxygen-free state. A needle-shaped graphite pulverized product is obtained by rolling the surface with a flat surface (span only) with the block rotated. The obtained acicular graphite pulverized product preferably has a diameter of about 1 to 100 μm and a length of 10 to 1000 μm.

  Next, the graphite pulverized product is mixed in a water containing a surfactant and dispersed in an emulsified state to advance a polymerization reaction between the compound containing a phenol group and the compound containing an aldehyde group, thereby forming a graphite surface. Thus, a graphite composite coated with an uncured phenolic resin having a softening state without melting at the mold temperature is obtained.

  As a result, the resulting graphite composite fuses uncured phenolic resin as a binder at the part where the particles are in contact with each other during heating and pressurization such as injection molding and compression molding. When the resin is simply mixed, the uncoated defect portions are not formed by contact of the uncovered portions of the binder.

<Effect (Inventive step)>
By using a molding material obtained by compositing needle-like graphite grains with phenol resin in a cooking utensil such as a charcoal kettle, a condensate free from defects was obtained by increasing the chance of contact between the graphite grains. In addition, since the uncured phenolic resin that does not melt at the time of molding is coated, in the flow stage of the molding material, the coating film of the uncured phenolic resin is held without being peeled off by contact between the molding materials, Compared with a compound product in which a phenol resin and graphite are simply mixed, the aggregate does not have a defect portion in which the entire surface of the graphite is coated with the phenol resin and the particles are not joined to each other. Obtained.

  Furthermore, the use of needle-like graphite grains increases the contact area of the particles, facilitating heat transfer, and the defects on the particle surface that become the starting point of the fracture are dispersed, resulting in destruction due to impact stress. It has the feature of being difficult.

  Regarding a means for obtaining a pot-shaped molded product by transfer molding, a method for manufacturing an electromagnetic induction heating cooker obtained by filling a pot-shaped mold with a mixture of carbon powder and a binder as a raw material will be described in detail below. To do.

  First, means for producing acicular graphite grains will be described. A columnar graphite product is obtained by firing a cylindrical molded product obtained by cooling and solidifying a mixture of petroleum coke and a mixture of tar and pitch melt in a mold at a temperature of 3000 ° C. in an oxygen-free atmosphere. Obtained. The obtained cylindrical block is rotated, and the smooth surface obtained by removing the outermost surface is scraped with a flat surface (only palm) to obtain acicular graphite grains.

  The obtained graphite particles are on a sieve having an opening of 180 μm using a horizontal vibration sieve and the passing material of the sieve having an opening of 420 μm is collected. The passing material is slightly mixed with a long axis of 500 μm or more. It is important to adjust the depth at which the flat shaft is applied so that the diameter of the short axis is 30 μm or less at the stage of rolling with a flat plate (only palm). As a result, the excessively long acicular graphite obtained is easily broken at the time of molding to an appropriate length, but this is acceptable because it does not significantly affect the molding state and various physical properties.

  Next, a method for producing a carbon aggregate forming raw material will be described. The obtained acicular graphite particles were stirred so as to be uniformly dispersed in water, and then a quaternary ammonium salt type cationic surfactant was added and mixed uniformly. Thereafter, a phenol compound and an aldehyde compound were further added so that 25 wt% of the phenol resin adhered. At this time, the surfactant has protective colloid properties and exhibits a polymer electrolyte behavior, and forms an ion complex with the anionic water-soluble resin.

  If the graphite particles used here have a diameter of 30 μm or less, phenolic compounds and aldehyde compounds are formed inside the protective colloid centered on the graphite particles formed by the surfactant dispersed in the solution, that is, on the surface of the graphite particles. The phenol resin obtained by reacting with the above has a spherical behavior so as to cover the acute angle portion of the fractured end piece, and is formed into a granular form in which the uncured phenol resin is complexed.

  As the quaternary ammonium salt type cationic surfactant that forms the protective colloid described above, alkyltrimethyl type and alkyldimethylbenzyl type cationic surfactants are preferable, and the alkyl moiety is highly pure lauryl, palmityl, stearyl, behenyl, etc. Those having a C number of about 10 to 20 are effective.

  The reaction of the phenol resin was determined by the water temperature and the mixing time, and was adjusted so that it would be softened without melting at 160 ° C., which is the mold temperature at the time of molding. Moreover, it is necessary to adjust the resin adhesion efficiency to the graphite grains to an appropriate stirring speed, and when the flow speed accompanying stirring is too slow, the particles aggregate to form particles in which graphite and phenol resin are combined. It will be. On the other hand, if it is too fast, the resin adhering to the surface of the graphite grains peels off and the curing proceeds independently, and the amount of adhesion on the surface of the graphite grains decreases as a spherical resin is formed.

  After the phenolic resin reaches a semi-cured state and forms a complexed state coated on the surface of the desired graphite grains, it is recovered by filtering, and further dried by low-temperature hot air, thereby forming a carbon aggregate forming raw material. Got.

  FIG. 1 is a diagram for comparison, and is a mixture obtained by pressure-kneading a carbon powder and a phenol resin uncured product obtained by crushing a lump by only kneading with a general molding raw material with an extruder or the like. It is a conceptual diagram of resin adhesion. FIG. 2 is a diagram showing the first embodiment, and is a conceptual diagram of a molding raw material in which an uncured phenol resin is complexed on the surface.

  As shown in FIG. 2, the carbon aggregate forming raw material obtained by the above-mentioned means is composed of carbon particles obtained by crushing a lump only by kneading with the general forming raw material shown in FIG. Compared with the resin adhesion of the mixture obtained by pressure kneading with an extruder or the like, it precipitates on the surface of the carbon particle 1 so as to cover the sharp end face of the carbon particle during the phenol resin polymerization process. However, the uncured phenol resin 2 forms a coating film and forms a smooth surface.

  For this reason, the carbon aggregate molding raw material according to the present embodiment retains the resin without melting in the mold when pressurized under heating at a molding temperature of about 160 ° C. and discharged into the mold. However, it is easy to move to a suitable position by filling the gap, that is, it has a feature of excellent fluidity.

  Next, a method for forming a rice cooker inner pot of an electromagnetic induction heating cooker will be described. The mold was heated to 160 ° C. as the curing temperature, and was discharged into the mold using a transfer molding machine in which an arbitrary amount of molding raw material was injected from the bottom center part in a pressurized state. At this time, the time during which the apparent viscosity at the time of flow during which the phenol resin is cured is promoted to promote the diffusion of gas such as water vapor as a by-product at the initial stage of the reaction, and the reaction proceeds, is 20 to 20 in this embodiment. After holding for 60 seconds in an unfilled state in which the powder of carbon aggregate forming raw material maintains a state of having sufficient pores, high pressure to obtain a molded product having a dense molded product internal structure, In the form, it was taken out from the mold after a holding time of 6 minutes for complete curing in a state pressurized at 15 MPa.

  The carbon aggregate forming raw material according to the present embodiment obtained by the above-described means is softened at 160 ° C., but does not melt. Therefore, when injected into the mold, it can act as a fluid by pressurizing to easily fill the voids in the mold, and the graphite particle surface is coated in the process of flowing in the overheated mold. The phenol resin flows out, and the graphite having sharp end pieces is not exposed excessively, so that the fluidity is excellent.

  Separately from this, using graphite particles pulverized and classified to 250 μm or less, massive phenol is polymerized in an emulsified state that is stirred and dispersed in water containing a surfactant, as in the present embodiment. Then, using the carbon aggregate molding raw material with a resin adhesion amount of 25 wt% coated on the surface of the graphite grains, the contact pressure and the high pressure are applied in a 160 ° C. mold similar to the inner pot molded product of the present embodiment. A molded product molded by curing the phenol resin under the pressure of was obtained (Comparative Example 1).

  On the other hand, acicular graphite particles having a large particle diameter on a sieve having an opening of 500 μm equipped in a horizontal vibrating sieve machine and having passed through a sieve having an opening of 600 μm contain phenol groups in water containing a surfactant as in the above-described means. A graphite composite obtained by proceeding a polymerization reaction in an emulsified state formed by mixing a compound and a compound containing an aldehyde group and coating the uncured phenolic resin on the graphite surface is used as a comparative example, and the inner pot molded product of the present embodiment A phenol resin was cured under the same molding conditions as above to obtain a molded product (Comparative Example 2).

  The obtained molded product was allowed to stand in an oxygen-free high temperature atmosphere at 1100 ° C., and the graphite particles formed by carbonization of the phenol resin were condensed to obtain a carbon aggregate molded product. At this time, in order to prevent local bulging due to the fact that the cracked gas generated along with the carbonization of the phenol resin does not diffuse from the molded product and stays inside to generate a fault crack, the temperature is increased stepwise. It is important.

  That is, the temperature is gradually increased or maintained in the vicinity of 350 ° C., 500 ° C., and 800 ° C. where the decomposition of the phenol resin becomes active and causes a rapid weight loss. Specifically, the temperature was raised to 300 ° C. at 0.5 ° C./min, then reached 350 ° C. with a gentle temperature rise of 1 ° C./hr, and held for 5 hours. Further, the temperature was maintained at 5 ° C./hr up to 450 ° C. and 1 ° C./hr up to 500 ° C., and held for 5 hours. Further, after reaching 5 ° C./hr up to 750 ° C. and 2 ° C./hr up to 800 ° C., it was held for 3 hours, and then it reached 1100 ° C. at 0.5 ° C./min and held for 2 hours. .

  Moreover, about cooling, it cooled to room temperature vicinity at 0.5 degree-C / min.

  The outer surface of the rice cooker inner pot, which is a molded product of the carbon aggregate, is heat-resistant silicone resin for the purpose of preventing dirt and wear during handling, and the inner surface is fluororesin for the purpose of preventing adhesion of cooking utensils. It is used as an inner pot of a rice cooker with the coating of.

  FIG. 3 is a diagram showing the first embodiment, and for the carbon aggregate molded product of the rice cooker inner pot, the bottom of the gate into which the carbon aggregate molding raw material is charged at the time of molding and the upper part of the side surface near the end point in the flow process are shown. It is a figure which shows the measurement result of the thermal conductivity which shows the increase effect of the contact strength of density, the bending strength which shows the joining state of a graphite grain, and the acicular graphite grain as an alternative characteristic of a porosity about each site | part.

  Next, about the carbon aggregate molded product of the rice cooker inner pot obtained by the above means, about the bottom surface where the gate into which the carbon aggregate molding raw material was injected at the time of molding was arranged, and each part on the side surface near the end point in the flow process As an alternative characteristic of porosity, the density, the bending strength indicating the joining state of the graphite grains, and the thermal conductivity showing the effect of increasing the chance of contact between the acicular graphite grains were measured.

  FIG. 3 shows a comparison between the present embodiment using acicular graphite particles and Comparative Examples 1 and 2 using granular graphite particles obtained by crushing a lump.

  The molded product according to the present embodiment has very little difference in characteristics at the upper and lower positions (bottom surface, upper side surface) associated with flow, and is excellent in fluidity as compared with Comparative Example 1 using granular graphite particles. On the other hand, the thermal conductivity based on the improvement of the bending strength correlated with the joining of the graphite grains and the increased contact between the graphite grains is superior to that of the comparative example 1, and the cooking that can ensure the durability and temperature uniformity effective for cooking. It was suggested that the instrument was easy to obtain.

  Moreover, it has confirmed that it was excellent in bending strength compared with the comparative example 2 using the 500-600 micrometers graphite particle | grains which the sieve equipped in the horizontal vibration sieve machine hold | maintained. Molding materials using large-sized needle-like graphite grains have a greater chance of orientation without crossing when the graphite grains are in contact with each other. In Example 2, the application effect of the acicular particles was not obtained, and the bending strength was lowered.

  In addition, the carbon aggregate molded article according to the present embodiment had no appearance of deformation or cracking that impeded practical use, and exhibited a good appearance.

  As shown in the above results, the carbon aggregate forming raw material according to the present embodiment maintains high fluidity, and with the use of acicular graphite grains, the obtained molded product is essential for practical use. It was confirmed that the strength and thermal conductivity, which are important characteristics, are excellent.

  1 carbon powder, 2 uncured phenol resin.

Claims (8)

  By polymerizing graphite particles in the form of needles obtained by rolling the surface of the graphite block in a state of rotating a graphite block in the presence of a surfactant together with a compound containing a phenol group and an aldehyde group, A method for producing a carbon aggregate forming raw material, wherein a coating film of an uncured phenolic resin is coated on a surface.   The method for producing a carbon aggregate forming raw material according to claim 1, wherein the surfactant forms a cationic solution that exhibits a polymer electrolyte behavior and forms an ion complex with a phenol resin in a polymerization process.   The surfactant is a quaternary ammonium salt type having an alkyltrimethyl group or an alkyldimethylbenzyl group, and the alkyl group includes at least one of a lauryl group, a palmityl group, a stearyl group, and a behenyl group. The method for producing a carbon aggregate forming raw material according to claim 1.   The method for producing a carbon aggregate forming raw material according to claim 1, wherein the graphite particles are passed through a sieve having an opening of 100 to 500 μm. While mixing acicular graphite grains obtained in刮physician cylindrical block surface flat chisel while rotating the graphite in water containing an interfacial active agent, containing the compound and an aldehyde group containing phenolic groups by adding the non-reduction compound, a step Ru obtain a carbon aggregate molding material holding the phenolic resin uncured material that does not melt at the curing temperature by the polymerization reaction in the graphite grains of the surface, the carbon aggregates molding electromagnetic induction cooking, characterized in that the heating and pressurized is injected into a mold and cured molded product obtained by Rukoto the material, and a step of baking treatment at a high temperature under an oxygen-free atmosphere Instrument manufacturing method.   6. The method of manufacturing an electromagnetic induction heating cooking appliance according to claim 5, wherein the graphite particles are passed through a sieve having an opening of 100 to 500 [mu] m.   6. The method for producing an electromagnetic induction cooking device according to claim 5, wherein the surfactant forms a cationic solution that exhibits a polymer electrolyte behavior and forms an ion complex with a phenol resin in a polymerization process.   6. The method for producing an electromagnetic induction cooking device according to claim 5, wherein the surfactant is a quaternary ammonium salt type having an alkyltrimethyl group or an alkyldimethylbenzyl group.

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