KR101820370B1 - Manufacturing method of graphite oxide for heater - Google Patents

Manufacturing method of graphite oxide for heater Download PDF

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Publication number
KR101820370B1
KR101820370B1 KR1020150050957A KR20150050957A KR101820370B1 KR 101820370 B1 KR101820370 B1 KR 101820370B1 KR 1020150050957 A KR1020150050957 A KR 1020150050957A KR 20150050957 A KR20150050957 A KR 20150050957A KR 101820370 B1 KR101820370 B1 KR 101820370B1
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South Korea
Prior art keywords
graphite
powder
reactor
mixture
tank
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KR1020150050957A
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Korean (ko)
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KR20160121232A (en
Inventor
유시흥
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김현주
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C01B32/23—Oxidation
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
    • H05B3/145—Carbon only, e.g. carbon black, graphite

Abstract

The method for producing graphite oxide for a heating element according to an embodiment of the present invention includes the steps of preparing high purity graphite powder by calcining and pulverizing a normal graphite mineral; Adding sulfuric acid, nitric acid, and potassium nitrate powder to the reactor to produce mixed acid, and adding the high purity graphite powder to the reactor and mixing; A step of aging the mixture stirred in the reactor; a step of heating and reacting the aged mixture and then adding distilled water to cool the aged mixture; Filtering and dewatering the cooled mixture to produce an oxidized graphite paste; And neutralizing the prepared graphite oxide powder to a pH of 7 to 8.

Description

Technical Field [0001] The present invention relates to a method of manufacturing graphite oxide for a heating element,

The present invention relates to a method for producing graphite oxide for use in a heating element, and more particularly, to a graphite oxide graphite for a surface heating element capable of minimizing fine sparks that may occur between carbon coated on a heating element and a metal electrode supplying power. And a manufacturing method thereof.

The planar heating element is not a linear heating element using a normal nichrome wire but a heating element that generates heat on the surface. Unlike the conventional linear heating element, the heating element generates a uniform heat on the whole surface,

In general, the surface heating element is preferably formed by uniformly spraying or printing copper, aluminum, iron, nickel, graphite powder or the like having high thermal conductivity on a resin in a film form or the like or by using conductive carbon, graphite, carbon black, Is coated on the polymer resin.

In particular, carbon has strong heat and durability, good thermal conductivity, low thermal expansion coefficient and light weight. In addition, graphite is much easier to manufacture and cheaper than etching a metal heating element. Carbon materials are widely used because they have excellent electrical / physical properties such as high electrical conductivity, thermal conductivity, heat resistance, corrosion resistance, abrasion resistance and lubricity.

According to Korea Patent Publication No. 10-2010-0105817 (Sep. 30, 2010) and Korean Patent Laid-Open No. 10-2005-0081314 (Aug. 19, 2005), it has been reported that a polymer heat- However, in order for the polymer heat-generating sheet in which the carbon black powder is dispersed to exhibit excellent heat-generating properties, continuous contact between the carbon black powders in the polymer heat-generating sheet is required to ensure high electrical conductivity.

In addition, since the surface heating element including carbon may cause fine sparks between the heating element coated with the heat generating carbon and the metal electrode supplying power, it is not stable. In addition, the durability may be problematic due to the chemical reaction between the carbon and the metal electrode and the peeling phenomenon between the carbon and the adhesive binder caused by the wavelength of the AC power source.

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as adhering to the prior art already known to those skilled in the art.

Patent Document 1: Korean Patent Laid-Open No. 10-2010-0105817 (September 30, 2010) Patent Document 2: Korean Patent Publication No. 10-2005-0081314 (August 18, 2005)

SUMMARY OF THE INVENTION The present invention has been conceived to solve such problems, and it is an object of the present invention to provide a method for improving the stability of graphite by using a mixed acid to increase the oxidation rate of graphite oxide, And a method for producing graphite oxide for a heating element.

According to an aspect of the present invention, there is provided a method for preparing graphite oxide for a heating element, the method comprising: preparing a high purity graphite powder by calcining and pulverizing a normal graphite mineral; Adding sulfuric acid, nitric acid, and potassium nitrate powder to the reactor to produce mixed acid, and adding the high purity graphite powder to the reactor and mixing; A step of aging the mixture stirred in the reactor; a step of heating and reacting the aged mixture and then adding distilled water to cool the aged mixture; Filtering and dewatering the cooled mixture to produce an oxidized graphite paste; And neutralizing the prepared graphite oxide powder to a pH of 7 to 8.

The high purity graphite powder may be prepared by calcining at a temperature of 2600 to 3000 ° C. and then pulverizing the powder to a size of 0.5 to 2 μm.

In the mixing step, 5 to 6 kg of 98% sulfuric acid, 2 to 3 kg of 68% nitric acid and 0.5 to 1.5 kg of potassium nitrate powder are added to the reactor and stirred. 0.5 to 1.5 kg of the high purity graphite powder may be added to the mixed acid solution in small portions and stirred.

The aging process may be maintained for 10-14 hours.

The heating and cooling may be performed by heating at 75 to 90 ° C for 2 to 4 hours, followed by cooling.

In the neutralization step, the pH may be adjusted by adding distilled water and adding ammonia.

The method for producing graphite oxide for a heating element according to the present invention has the following effects.

When applied to a surface heating element, it improves the filling rate, does not cause fine sparking, has excellent electric conductivity, and does not need an adhesive / filler / dispersant separately. Especially, it emits far infrared rays and negative ions, and it has high dispersion and heat efficiency, so it can reduce power consumption and can be used stably at high temperature.

Also, it is possible to secure oxidation efficiency of graphite at the same level as that in the case of using high purity nitric acid by using low purity nitric acid, and there is an advantage that the graphite oxide can be produced more safely.

1 is a flow chart showing a method for producing graphite oxide for a heating element according to an embodiment of the present invention.
2 and 3 are schematic views of an apparatus for producing graphite according to an embodiment of the present invention.
4 is a schematic view of an apparatus for producing graphite oxide for a heating element according to an embodiment of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, a method for producing graphite oxide for a heating element according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a flow chart showing a method for producing graphite oxide for a heating element according to an embodiment of the present invention. 1, a method for producing graphite oxide for a heating element according to an embodiment of the present invention comprises the steps of (S10) preparing a high purity graphite powder by calcining and pulverizing a normal graphite mineral, Mixing the potassium nitrate powder to prepare a mixed acid, adding the high purity graphite powder to the reactor (S20), aging the mixture in the reactor (S30), heating the aged mixture (S50) of dehydrating the cooled mixture to prepare an oxidized graphite paste (S50), and neutralizing the prepared graphite oxide with a pH of 7 to 8 .

Each step is divided into more detail.

1. Preparation process of high purity graphite powder (S10)

High purity graphite powder is prepared by high temperature firing. 2600 ~ 3000? As the high temperature is continuously heated for a certain period of time, the impurities in the graphite mineral are calcined, so pure graphite having a purity of 99.98% or more can be obtained. At this time, the firing temperature is a temperature for volatilizing the impurities contained in the graphite water.

The graphite thus obtained is pulverized through a conventional pulverizer, and the pulverized fine particles are selected through a sorter to separate small and small particles to obtain small particles, and the large particles are pulverized again to continue the process of obtaining small particles. By doing so, it is possible to produce graphite powder particles having a diameter of 0.5 to 2 μm.

2. Mixing process of mixed acid and graphite powder (S20)

In the reactor, 5 to 6 kg of 98% sulfuric acid, 2 to 3 kg of 68% nitric acid, and 0.5 to 1.5 kg of potassium nitrate powder are added and stirred. 0.5 to 1.5 kg of the pulverized graphite is added in small portions to the mixed acid solution and stirred. (When the suction injecting NO 2 gas to the jet nozzle to the generated NO 2 degasser using a high-pressure pump may be NO 2 gas is absorbed into the NaOH mixture to remove the NO 2 gas, and removed by the carbon filter, as needed .)

98% sulfuric acid requires more than 90% of high purity nitric acid for the oxidation of graphite, but since it uses 68% of nitric acid, it does not sufficiently oxidize under 5 kg of sulfuric acid, Range.

When a certain amount of graphite is oxidized by using 68% of nitric acid, 98% sulfuric acid is oxidized. When the graphite is less than 2 kg, oxidation is not sufficiently performed.

The potassium nitrate powder is added in order to increase the purity of nitric acid. Oxidation is not sufficiently carried out at a weight of 0.5 kg or less, and the oxidization improving effect at 1.5 kg or more is insignificant.

At this time, high purity nitric acid of 75% or more is suitable for graphite oxidation. It is difficult and dangerous to handle high purity nitric acid, while 68% nitric acid is easy to purchase and convenient to handle. However, when 68% of nitric acid is added, The dispersion rate is low and the quality is deteriorated. In order to overcome this problem, 0.5 to 1.5 kg of potassium nitrate powder can be added to 75 ~ 80% nitric acid to obtain oxidation efficiency.

3. Aging step (S30)

The agitated mixture in the reactor is aged for 10 to 14 hours.

4. Heating and cooling step (S40)

After reaction with 75 to heat 90 ℃ 2 ~ 4 time after the hydrolyzing contents heater is off NO 2 gas generated in the reactor will continue to input and filtered in the filtering device, into the distilled water 8L per 1L and, NO 2 gas is generated When not in use, 12 L of distilled water is added, reacted for 3 hours, and then the contents are cooled for about 30 minutes.

5. Cleaning step (S50)

(1) The lower part of the reactor is opened, the contents are taken out by a 0.8 mu m paper filter box, and the dehydration step is carried out by a vacuum motor.

(2) After dewatering, 20 L of distilled water is put into the paper filter and dehydrated by a vacuum motor.

6. Neutralization step (S60)

Add 20 L distilled water and stir for 30 minutes while adjusting the pH to 7 ~ 8 with ammonia. The average solid content of the graphite thus produced is 20 to 30% of the graphite oxide paste. The average particle size of the oxidized graphite obtained is 200 to 300 nm, the specific surface area is 1800 m 2 / g, the oxygen application rate is about 12%, and the dispersion ratio is 100%. The thus-produced graphite oxide can be dispersed in distilled water. Normally, distilled water is mixed and used up to 10% solids.

Hereinafter, a method for producing graphite oxide for a heating element according to the present invention will be described in detail with reference to graphite powder production equipment and graphite oxide production equipment. The apparatus used here is only intended to explain the manufacturing method in more detail, and the invention is not limited by the apparatus.

Fig. 2 and Fig. 3 are diagrams schematically showing an apparatus for high-temperature firing graphite. A floor 40 provided with a refractory brick, four walls 20 provided with a refractory brick so as to form a work space in the upper part of the floor 40, A cover box 30 installed in the inner work space to produce pure graphite, and a cover box 30 installed in the inner work space to cover the upper and lower portions of the wall 20, And the other end of the wall 20 and the electrode bar 80 provided at both ends of the container box 30 are connected to one side and the container box 30, .

In the preparation of graphite powder of high purity, three container boxes 30 are prepared from graphite mineral 500 to 1000 탆 particles of graphite material 700 mm length 350 mm height 350 mm, and the same graphite mineral diameter 500 to 1000 탆 Fill the particles and keep them tight.

The refractory bricks are stacked and the graphite prepared in a box with a bottom thickness of 300 mm is put into a container box. After closing the cover, electricity of 100 kW or more is connected to both sides of the graphite electrode rod (nitrogen is injected if necessary) When the temperature is higher than 3000 ℃, the airtightness of surrounding graphite mineral is maintained and oxygen is not supplied. Therefore, the vacuum is maintained and oxidation is prevented. When the high temperature is continuously heated at 2800-3000 ° C or above for a predetermined time, impurities in the graphite mineral are sintered Pure graphite having a purity of 99.98% or more can be obtained.

4 is a schematic view of an apparatus for producing graphite oxide. As shown in Fig. 4, the raw materials are fed into the reactor A, the aging machine B, the aeration tank C, the heater D, the cooler E, the vacuum dehydrator G, the neutralization tank F, G) are sequentially circulated by a pump to produce graphite oxide,

A distillation water supply tank 101, a sulfuric acid supply tank 102, a nitric acid supply tank 103, a potassium nitrate supply tank 103, and a nitrate supply tank 103, which are installed in the upper part of the reactor (A) (104), and graphite supply tank (105).

A reactor temperature adjusting jacket 110 installed outside the reactor A, a stirring motor installed at an outer side of the reactor A, an agitator connected to the stirring motor and installed in the reactor A, A is connected to a plurality of agitators B and an aeration tank C by a discharge pipe at one side of the lower part of the tank.

A nitrogen dioxide exhaust pipe 150 connected to one side of the reactor A to exhaust the nitrogen dioxide gas generated in the reactor A, a jet nozzle 151 installed at an end of the nitrogen dioxide exhaust pipe 150, A nitrogen oxide absorption tank 170 connected with a jet nozzle 151 at an end of the nitrogen oxide absorption tank 170, a high pressure pump 155 installed at one side of the nitrogen oxide absorption tank 170, A connected caustic soda tank 160, and a carbon filter 180 connected to the nitrogen oxide absorption tank 170.

The aging machine (B) is composed of 12 agitators, and is connected to the exhaust pipe of the reactor (A). The agitator is provided with an agitating motor installed on the outside of the agitator, an agitator connected to the agitator and passing through the agitator, The nitrogen dioxide absorbing tank (not shown) is connected to the aeration tank C through which oxygen is supplied from the nitrogen oxide absorption tank 310, 170, and an exhaust pipe at the bottom.

 Three heating devices D are installed and connected to the aging device B and the aeration tank C by piping in the upper part. The heating device D is installed outside and is heated by the boiler 410 to heat the heater D, A jacket 450, an exhaust pipe installed at the lower part, a stirring motor provided at the upper side of the outside, and an agitator connected to the stirring motor and installed inside the heater through the heater.

 The cooler E includes a cooling jacket 550 connected to an externally installed cooling pump 510 to be connected to the three heaters D via a pipe to cool the introduced mixture, And a stirrer connected to the stirring motor through the cooler and disposed inside the stirrer. The vacuum dehydrator G is connected to the heater D and the cooler E by a pipe An inlet pipe connected to the neutralization tank F at one side of the upper portion, a screen and paper filter 850 installed at an intermediate side, a colloidal graphite outlet 800 installed at one side of the screen and the paper filter 850, A discharge pipe connected to the neutralization tank F installed on the other side of the screen and the paper filter 850 and a waste water collecting tank 710 installed below the screen and paper filter 850, 710) And a vacuum tank 720 connected to the vacuum pump 740 to maintain the vacuum.

The neutralization tank F is connected to a discharge pipe of the vacuum dehydrator G and includes an agitation motor installed on the upper side of the agitator, an agitator connected to the agitation motor to penetrate the neutralization tank, A caustic soda feed pipe connected to the caustic soda feed tank 160 and a caustic soda feed pipe provided by the automatic feeder by an ammonia feed tank 190 provided under the feed soda feed pipe for feeding ammonia, And a drain pipe connected to the neutralization tank F at the lower part of the structure.

The graphite prepared in the graphite preparing step S10 is put into the graphite supply tank 105 and then connected to the sulfuric acid supply tank 102, the nitric acid supply tank 103, the potassium nitrate supply tank 104 and the graphite supply tank 105 The temperature of the reactor is adjusted by the reactor temperature adjusting jacket 110 provided outside the reactor A and the temperature of the reactor is adjusted at the outer side of the reactor A, The stirring motor and each raw material supplied by the stirrer provided in the reactor (A), which are connected to the stirring motor, are mixed. At this time, the distilled water supply tank 101 is mixed with the raw materials without supplying distilled water.

The mixture is conveyed to the twelve aging machine (B) and the aeration tank (C) by the discharge pipe connected to the lower side of the reactor (A).

The nitrogen dioxide gas generated in the mixing process in the reactor A is introduced into the nitrogen nozzle 150 through the nitrogen dioxide exhaust pipe 150 by the operation of the high pressure pump 155 and the caustic soda connected to the jet nozzle 51 installed at the end of the nitrogen dioxide exhaust pipe 150 Absorbed in the nitrogen dioxide absorbing tank 170 and, if necessary, treated with the carbon filter 180 connected to the nitrogen dioxide absorbing tank 170.

Each of the twelve aging units B is connected to an aeration tank C, which is connected to the agitation motor and flows in the mixture, and is supplied with oxygen from the compressor 310, The inside of the aging machine (B) is aerated with oxygen. At this time, the nitrogen dioxide produced in the aging process of each aging unit (B) is transferred through the discharge pipe to the nitrogen dioxide absorption tank 170 in which the caustic soda described above is embedded, and if necessary, the nitrogen dioxide absorption tank 170 And a carbon filter 180 connected to the carbon filter 180.

Thereafter, the aged mixture is transferred to three heaters (D) through an exhaust pipe connected to the lower part of the aging machine (B), and then heated by a boiler (410) 450 to heat the heater D and stir the mixture inside the heater D by the stirring motor provided at the upper side of the heater D and the stirring motor.

The mixture is transferred from the heater to the cooler and then cooled by a cooling jacket 550 connected to an external cooling pump 510. The cooling jacket 550 is connected to a stirring motor provided at the upper side of the mixing chamber, And stirred with an agitator installed therein.

And is connected to a vacuum pump 740 at one side of a waste water collecting tank 710 provided under the screen and paper filter 850 and is connected to a vacuum tank 720 to maintain the inside of the vacuum dehydrator in a vacuum state. The filtrate is firstly filtered by a screen and paper filter 850 provided at the intermediate side, and the filtrate is discharged through the lower wastewater collection tank 710.

Distilled water was further introduced into the vacuum dehydrator G and stirred for 30 minutes to be connected to the vacuum pump 740 at one side of the waste water collecting tank 710 provided under the screen and paper filter 850, The inside of the vacuum dehydrator G is kept in a vacuum state by the filter 720 and the secondary screen is filtered with the screen and paper filter 850 installed at the intermediate side and the filtrate is discharged through the lower wastewater collection tank 710.

After the secondary filtered graphite mixture is transferred to the neutralization tank F, ammonia and distilled water are automatically supplied to the ammonia supply pipe supplied by the automatic feeder and the distilled water supply pipe 195 by the ammonia supply tank 190 The agitating motor provided at the outer side of the supply port and the stirring motor are connected to the agitating machine and agitated sufficiently by an agitator provided therein to adjust the pH to 7 to 8 to prepare graphite oxide.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You will understand.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

10: cover 20: wall 30: container box 40: bottom
50: through hole 70: support base 80: electrode rod 101: distilled water supply tank
102: sulfuric acid supply tank 103: nitric acid supply tank 104: potassium nitrate supply tank
105: Graphite feed tank 110: Reactor temperature control jacket 150: Nitrogen dioxide exhaust pipe
155: high pressure pump 151: jet nozzle 160: caustic soda feed tank
170: caustic soda nitrogen dioxide absorption tank 180: carbon filtration tank
190: ammonia supply tank 195: distilled water supply pipe
250: Reactor temperature control jacket 310: Compressor 410: Hot water boiler
450: heating jacket 510: cooling pump 550: cooling jacket 710: wastewater collection tank
720: Vacuum tank 740: Vacuum pump 800: Colloidal graphite outlet
850: Screen and paper filters
A: Reactor B: Aging machine C: Aeration tank D: Heater E: Cooler
F: neutralization tank G: vacuum dehydrator

Claims (6)

Calcining a normal graphite mineral at a temperature of 2600 to 3000 占 폚 and pulverizing the powder to a diameter of 0.5 to 2 占 퐉 to prepare a high purity graphite powder;
5 to 6 kg of 8 mass% sulfuric acid, 2 to 3 kg of 68 mass% of nitric acid and 0.5 to 1.5 kg of potassium nitrate powder were added to the reactor and stirred to prepare mixed acid, and 0.5 to 1.5 kg of the high purity graphite powder was added to the reactor Mixing process;
Aging the mixture in the reactor for 10 to 14 hours:
The aged mixture is heated at 75 to 90 ° C. and allowed to react for 2 to 4 hours. Then, distilled water is added to cool the mixture
Filtering and dewatering the cooled mixture to produce an oxidized graphite paste; And
Adding the distilled water to the graphite oxide powder and neutralizing the graphite paste to pH 7 to 8 by adding ammonia,
The neutralized graphite oxide paste has an average solids content of 20 to 30% by weight, an average particle size of 200 to 300 nm, a specific surface area of 1800 m 2 / g, an oxygen coverage of 12% and a dispersion ratio of 100% Wherein the graphite powder is a graphite powder. delete delete delete delete delete
KR1020150050957A 2015-04-10 2015-04-10 Manufacturing method of graphite oxide for heater KR101820370B1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102108679B1 (en) 2019-04-02 2020-05-08 주식회사 동우브이엔씨 Far infrared heat mats and manufacturing method thereof

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100808631B1 (en) 2006-04-21 2008-02-29 유석용 Heating element material and construction with carbon
KR100890561B1 (en) * 2008-06-24 2009-03-25 유석용 Oxidation colloid nano graphite manufacturing method

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100534295B1 (en) 2004-02-13 2005-12-08 이춘구 Method of preparation for a heating element with carbon coating fiber
KR101020377B1 (en) 2009-03-22 2011-03-08 박상구 Conductive elastomer composition and method of producing same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100808631B1 (en) 2006-04-21 2008-02-29 유석용 Heating element material and construction with carbon
KR100890561B1 (en) * 2008-06-24 2009-03-25 유석용 Oxidation colloid nano graphite manufacturing method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102108679B1 (en) 2019-04-02 2020-05-08 주식회사 동우브이엔씨 Far infrared heat mats and manufacturing method thereof

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