CN105016332A - Preparation technology of expandable graphite - Google Patents
Preparation technology of expandable graphite Download PDFInfo
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- CN105016332A CN105016332A CN201510489775.4A CN201510489775A CN105016332A CN 105016332 A CN105016332 A CN 105016332A CN 201510489775 A CN201510489775 A CN 201510489775A CN 105016332 A CN105016332 A CN 105016332A
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Abstract
The invention discloses a preparation technology of expandable graphite. Reasonable expandable graphite production raw materials are selected; the content of sulphur in the raw materials is reduced through early-stage thermal treatment; the expanded graphite is prepared through expansion, wherein the expandable graphite production raw materials are selected, sulphur is removed through thermal treatment, cleaning is performed through deionized water, expansion treatment is performed, suction filtration is performed, cleaning is performed through deionized water and drying is performed. The expandable graphite production raw materials are large scale natural graphite, or pyrolytic graphite or polycrystal graphite. Oxalic acid is adopted as an inserting agent during expansion treatment, 98% concentrated sulfuric acid, 25% hydrogen peroxide and potassium dichromate are added, good ventilation is kept in the expansion process, the temperature is 800-900 DEG C, and time is 45-50 s. Drying temperature is 60-70 DEG C. The expandable graphite prepared through the technology is resistant to high temperature, acid and alkali and has the tensile performance, the compression resistance and other mechanical property, the content of sulphur is effectively reduced in the preparation process, and pollution to the environment is smaller.
Description
Technical field
The present invention relates to a kind of preparation technology of expansible black lead.
Background technology
Expanded graphite take natural flake graphite as raw material, the method of physics or chemistry is utilized to make some atom or atomic group insert graphite layers, a kind of compound between graphite layers obtained, i.e. expansible black lead, expansible black lead expands after TRANSIENT HIGH TEMPERATURE process, and a kind of of formation has the material enriching pore texture, low bulk density, high chemical stability.1840, first by Schafhaeutl, sulfuric acid and nitric acid are mixed to join in crystalline flake graphite, find that through heating graphite produces the phenomenon of volumetric expansion, but the application of expanded graphite then just start after a century.TiO2 is a kind of solid particulate oxidation thing, under UV-irradiation, some organic compound can be degraded, so it is a kind of Photodegradation catalyst.TiO2 as a kind of green environment Treatment process, because of its have that efficiency is high, energy consumption is low, easy and simple to handle, reaction conditions is gentle, applied widely, the outstanding advantages such as secondary pollution can be reduced and become study hotspot both domestic and external.
Expanded graphite not only remains many advantages of natural graphite, such as erosion resistance, thermotolerance, radiation resistance, electrical and thermal conductivity, self lubricity and pressuretightness etc.; Also possesses the superperformance not available for natural graphite, such as light soft, compressible, pliability, rebound resilience are excellent, its main manifestations is as follows: erosion resistance: except minority strong oxidizer certain concentration medium, in very wide temperature, pressure, time range, chemical reaction is there is not with medium, all applicable to most of mineral acid, alkali, salt., especially not because of pressure and temperature alternation or shaken, and there is seal failure in high temperature resistant and low temperature: in the environment of non-oxide medium or rare gas element, when using within the scope of-200 DEG C ~ 2500 DEG C, high temperature does not soften, and low temperature does not become fragile.So thermal stability, anti-oxidant in have more superiority than the material such as asbestos, rubber.
Self lubricity: easy along the raw Relative sliding of graphite carbon layer plane direction generation under external force.Compressibility: through calendering energy manufactured Board, through mechanical workouts such as horizontal pressure, roll extrusion, various sealing article can be produced.Pressuretightness: open-textured expanded graphite, through extruding, after graphite worm bonds mutually, has excellent impermeable character to gas and liquid medium.
Flexibility: because self there is many special modular constructions, as long as just can reach good with less fastening force
Autohension, is formed and effectively seals.
, under the long-term irradiation of beta, gamma and neutron, there is not considerable change in radiation resistance: at α.
Anti-oxidant: to compare with other conventional sealing material, the oxidizing temperature of expanded graphite is higher, and the oxidation rate of goods is also very little.
Low density: volume density is 0.002 ~ 0.005gcm-3, and extrudate density is 1.0 ~ 1.6gcm-3.
Anisotropy: have excellent anisotropy, large 28 times of the thermal conductivity ratio thickness direction in plane layer direction in heat transfer and conduction, large 500 times of electric conductivity, large 30 ~ 80 times of coefficient of thermal expansion.
1.1.2 the application of expanded graphite
1.1.2.1 sealing material
Expanded graphite through deep processing is a kind of very excellent sealing material, is called soft graphite after its pressure rolling.Compared with the conventional sealing material such as asbestos, rubber, Mierocrystalline cellulose, soft graphite available temperature range is wider, and thermal expansivity is little, and high temperature does not soften, and low temperature does not become fragile, and has the good reputation of " sealing king ".Many producers of current China are in production and manufacture this product.The flexible graphite sealing material of high-quality can be high temperature resistant and anticorrosive, may be used for the high temperature fluid sealing of chemical industry, oil, electric power, metallurgy, automobile and other industries.Soft graphite is formed by the expanded graphite compacting after high temperature puffing, remains in a small amount of intercalator in soft graphite and become the quality and performance of branch to product to have a huge impact.Initial inventor does intercalator and oxygenant with the vitriol oil, main effect is the sealing material doing metal parts, but be through long-term use and find that the metal of a small amount of sulphur residual in expanded graphite to contact exists the serious corrosion imagination afterwards, for the domestic trial having some scholars to improve of this point, obtain expandable sulfur-free graphite as used acetic acid or other acid anhydrides as intercalator intercalation.
At high temperature the character of undergoes rapid expansion and nontoxic characteristic can be applied to flame retardant area to utilize expansible black lead.Expanded graphite itself is under general condition difficult to burning on the one hand; Expansible black lead absorbs amount of heat in expansion process on the other hand, can play the effect of cooling, and burning things which may cause a fire disaster can be separated with combustiblematerials after instantaneous expansion by expansible black lead.Meanwhile, the research taking expansible black lead as the composite flame-proof material of matrix is also more active, Jiang Shu is by the fire-retardant superior performance of EG/PP matrix material of expanded graphite and polypropylene compression moulding, overcome polyacrylic oxygen index low, easy burning, and rate of combustion is fast, thermal value is high, and with molten drop phenomenon, hold the shortcoming of fire hazardous etc.Yan Aihua etc. have carried out the poly research of expansible black lead/ammonium polyphosphate synergetic flame-retardant, and result shows that expanded graphite/ammonium polyphosphate has played cooperative flame retardant effect, defines form compact and stable foamed char.
Expanded graphite pore texture enriches, and specific surface area is large, can organic pollutant in adsorbed water body.People utilize these characteristics of expanded graphite, and begin one's study its application in environment protection.Shen Wanci [3] etc. study discovery: expanded graphite is still made up of graphite microcrystal organizationally, and absorption has ambitendency, and to adsorb non-polar molecule, but also can adsorb polar molecule in certain environment.
It is allowance for expansion that Toyoda Masahiro etc. reports one of important factor affecting expanded graphite absorption property.Cao Hong etc. have studied the impact for expanded graphite adsorptive capacity of temperature and viscosity.Zheng Yong-Ping etc. have studied the morphology change in expanded graphite worm adsorption and desorption process, and he thinks that expanded graphite particles is inner different from the kind of adsorbing oil product between particle.During the regenerative adsorption problem of Inagaki Michio after studying expanded graphite absorption oil product, think and use suction method to be adsorbed on the heavy oil sucking-off of expanded graphite inside, and the expanded graphite after suction filtration still can be used for Sorption of Heavy Oil, but adsorptive capacity obviously declines.Lee increases and new etc. thinks that expanded graphite is structurally a kind of nanocomposite, has two-dimensional physical and chemical property.The people such as Sun Lixue have studied the absorption of modified expanded graphite PARA FORMALDEHYDE PRILLS(91,95) gas, and expanded graphite increases substantially through the adsorptive power of modified PARA FORMALDEHYDE PRILLS(91,95) gas, and this result of study is that expanded graphite is expanded new application and provided foundation.Wangkai have studied the character of expanded graphite-calcium chloride mixed adsorbent, makes the thermal conductivity of mixed adsorbent expand 23 times, shortens absorption refrigeration cycling time, in two heat pipe type absorbing refrigeration system, obtains applied research.In addition, expanded graphite also can be used for the oil removing of trade effluent milk sap and removes oil-soluble material, as agricultural chemicals etc., and has good adsorption effect to the harmful liquid, gas, dyestuff etc. of other organic or inorganics many.Expanded graphite is made up of pure carbon substantially, nontoxic and have unreactiveness, so can not cause secondary pollution to environment.These application can play an important role in environmental pollution improvement predictive of expanded graphite.
Do expansible black lead prepared by intercalator by sulfuric acid, to sulfuric acid, there is load effect, therefore can use it for the reaction of prototropy.Pang Xiuyan etc. take expansible black lead as catalyzer, have synthesized biofuel by transesterification reaction.
The research that expanded graphite prepares polymer base conductive composite material aspect [25-27] as conductive filler material becomes focus in recent years.Be that nano graphite sheet is dispersed in the matrix of polymkeric substance by expanded graphite, polymer-based nano conducing composite material can be obtained.Graphite is in the base in nano-dispersed shape, therefore the mechanical property of matrix reduces little, and graphite is sheet simultaneously, is therefore easy to form conductive network in the base, can reach good conductivity with little graphite, this adopts other conductive filler material to accomplish.
Expanded graphite is made hospital gauze, its adsorptive capacity be the 4-5 of common gauze doubly, can adsorb thoroughly and organize ejecta, there is sterilization, anti-oedema, the excellent properties of protecting from infection.Therefore expanded graphite will have at medical field and apply more widely.
Expanded graphite also has a wide range of applications in other field.In military field, utilize expanded graphite to the absorption characteristic of infrared waves, can be made into infrared shielding material.The intercalation compound of expanded graphite can do electromagnetic shielding material.
Expansible black lead is understood expanded fast and is disperseed in the blast process of pyrotechnic composition, can play the effect of interference.Expanded graphite has promoter action to Aspergillus Niger Growth, and the growth-promoting effect of large size expanded graphite to aspergillus niger is better than than small size expanded graphite.In addition, expanded graphite or a kind of potential hydrogen storage material.
The preparation method of current domestic expanded graphite mainly contains chemical oxidization method, electrochemical oxidation process.
Chemical oxidization method is joined by raw graphite in the mixed solution of oxygenant and intercalator composition, stirring reaction at a certain temperature, then through washing, drying can obtain compound between graphite layers, namely expansible black lead, at high temperature instantaneous expansion can obtain expanded graphite.The method requires that the oxidation capacity of oxygenant is strong, and major ingredient content is high, is generally: potassium permanganate, nitric acid, hydrogen peroxide, ammonium peroxydisulfate, potassium bichromate, Potcrate, perchloric acid etc.Intercalator generally uses the vitriol oil, also occur now many with organic acid or acid anhydrides [36-38] for intercalator prepares the method for sulphur-free expanded graphite.
The advantage of chemical oxidization method is that preparation technology is simple, and production cost is lower, is suitable for a large amount of production.But also there are some shortcomings in the method, as: reaction is comparatively violent, and a large amount of reaction heat of generation not easily discharge rapidly and cause expansible black lead to produce primary expansion; In reaction, nitric acid can occur to decompose and generate harmful NO2 gas; Washing step can produce a large amount of acid waste water, thus causes the pollution to water body environment.
Electrochemical oxidation process raw graphite and supporting electrode thereof is inserted in the electrolytic solution that forms with sulfuric acid or sulfuric acid and other auxiliary agent, passes into galvanic current, under the effect of extra electric field, enter graphite layers, then can obtain expansible black lead through washing and drying.Expanding method is identical with chemical method.
The advantage of electrochemical oxidation process is: level of automation is high, and adjustable current intensity and electrolysis time control the degree of intercalation; Electrolytic solution recoverable, thus the usage quantity reducing sulfuric acid; The consumption of oxygenant comparatively chemical method greatly reduces, and can reduce the pollution of water washing process to water body like this.Equally, also there is shortcoming in the method: intercalation is not easily even, and cause insufficient oxidation and over oxidation to exist, namely product performance are stable not simultaneously; Reaction process will consume a large amount of electric energy.
Summary of the invention
The object of the invention is to the preparation technology proposing a kind of expansible black lead.
For reaching this object, the present invention by the following technical solutions:
A kind of preparation technology of expansible black lead, select rational expanded graphite raw materials for production, the content of sulphur in raw material is reduced through initial stage thermal treatment, prepare expanded graphite by expanded, comprising: the raw materials for production selecting expanded graphite------------dry in puffing to adopt washed with de-ionized water in thermal treatment sulphur removal by suction filtration---washed with de-ionized water---.The raw materials for production of expanded graphite are large scale natural graphite, pyrolytic graphite or glomerocryst graphite.Puffing adopts oxalic acid as intercalating agent, and add 98% vitriol oil, 25% hydrogen peroxide and potassium bichromate, keep good ventilation in puffing process, temperature is 800---900 degree, the time is 45---50s.Bake out temperature is 60---70 degree.
Embodiment
Embodiment 1
A kind of preparation technology of expansible black lead, select rational expanded graphite raw materials for production, the content of sulphur in raw material is reduced through initial stage thermal treatment, prepare expanded graphite by expanded, comprising: the raw materials for production selecting expanded graphite------------dry in puffing to adopt washed with de-ionized water in thermal treatment sulphur removal by suction filtration---washed with de-ionized water---.The raw materials for production of expanded graphite are large scale natural graphite.Puffing adopts oxalic acid as intercalating agent, and adds 98% vitriol oil, 25% hydrogen peroxide and potassium bichromate, and keep good ventilation in puffing process, temperature is 900 degree, and the time is 50s.Bake out temperature is 70 degree.
Embodiment 2
A kind of preparation technology of expansible black lead, select rational expanded graphite raw materials for production, the content of sulphur in raw material is reduced through initial stage thermal treatment, prepare expanded graphite by expanded, comprising: the raw materials for production selecting expanded graphite------------dry in puffing to adopt washed with de-ionized water in thermal treatment sulphur removal by suction filtration---washed with de-ionized water---.The raw materials for production of expanded graphite are pyrolytic graphite.Heat treated temperature is 300 degree, and puffing adopts acetic acid and acetic anhydride as intercalating agent, and adds 98% vitriol oil, 20% hydrogen peroxide and diacetyl oxide, and keep good ventilation in puffing process, temperature is 800 degree, and the time is 45s.Bake out temperature is 70 degree.
Claims (4)
1. the preparation technology of an expansible black lead, it is characterized in that selecting rational expanded graphite raw materials for production, the content of sulphur in raw material is reduced through initial stage thermal treatment, prepare expanded graphite by expanded, comprising: the raw materials for production selecting expanded graphite------------dry in puffing to adopt washed with de-ionized water in thermal treatment sulphur removal by suction filtration---washed with de-ionized water---.
2. method according to claim 1, is characterized in that, the raw materials for production of described expanded graphite are large scale natural graphite, pyrolytic graphite or glomerocryst graphite.
3. method according to claim 1, is characterized in that, described puffing adopts oxalic acid as intercalating agent, and add 98% vitriol oil, 25% hydrogen peroxide and potassium bichromate, keep good ventilation in puffing process, temperature is 800---900 degree, the time is 45---and 50s.
4. method according to claim 1, is characterized in that, described bake out temperature is 60---70 degree.
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106315577A (en) * | 2016-08-31 | 2017-01-11 | 陈连捷 | Method for removing sulfuric acid from expandable graphite |
| CN106422528A (en) * | 2016-09-20 | 2017-02-22 | 芜湖成德龙过滤设备有限公司 | Expanded graphite filter material and preparation method thereof |
| CN106564893A (en) * | 2016-11-10 | 2017-04-19 | 电子科技大学 | Hundred micron-order graphene oxide and preparation method thereof |
| CN106621574A (en) * | 2016-09-20 | 2017-05-10 | 芜湖成德龙过滤设备有限公司 | Expanded graphite filter material and preparation method thereof |
| CN107934954A (en) * | 2017-11-23 | 2018-04-20 | 孙川平 | A kind of pure graphite Far infrared thermal radiation heating film and preparation method thereof |
| CN108465772A (en) * | 2018-06-22 | 2018-08-31 | 佛山市高明利钢精密铸造有限公司 | A kind of preparation method of the special molding sand of large-size stainless steel product monoblock cast |
| CN108705026A (en) * | 2018-06-22 | 2018-10-26 | 佛山市高明利钢精密铸造有限公司 | A kind of complex-shaped stainless steelwork casts the preparation method of special molding sand |
| CN111250648A (en) * | 2020-03-27 | 2020-06-09 | 霍山县东胜铸造材料有限公司 | Preparation process of casting riser smooth coating |
| CN114212784A (en) * | 2021-11-26 | 2022-03-22 | 唐山金湾特碳石墨有限公司 | Preparation method of graphite for friction material |
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| CN101100298A (en) * | 2007-08-07 | 2008-01-09 | 哈尔滨工程大学 | Method for preparing expanded graphite |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106315577A (en) * | 2016-08-31 | 2017-01-11 | 陈连捷 | Method for removing sulfuric acid from expandable graphite |
| CN106422528A (en) * | 2016-09-20 | 2017-02-22 | 芜湖成德龙过滤设备有限公司 | Expanded graphite filter material and preparation method thereof |
| CN106621574A (en) * | 2016-09-20 | 2017-05-10 | 芜湖成德龙过滤设备有限公司 | Expanded graphite filter material and preparation method thereof |
| CN106621574B (en) * | 2016-09-20 | 2019-06-21 | 芜湖成德龙过滤设备有限公司 | Expanded graphite filtering material and preparation method thereof |
| CN106564893A (en) * | 2016-11-10 | 2017-04-19 | 电子科技大学 | Hundred micron-order graphene oxide and preparation method thereof |
| CN107934954A (en) * | 2017-11-23 | 2018-04-20 | 孙川平 | A kind of pure graphite Far infrared thermal radiation heating film and preparation method thereof |
| CN108465772A (en) * | 2018-06-22 | 2018-08-31 | 佛山市高明利钢精密铸造有限公司 | A kind of preparation method of the special molding sand of large-size stainless steel product monoblock cast |
| CN108705026A (en) * | 2018-06-22 | 2018-10-26 | 佛山市高明利钢精密铸造有限公司 | A kind of complex-shaped stainless steelwork casts the preparation method of special molding sand |
| CN108465772B (en) * | 2018-06-22 | 2020-02-07 | 佛山市高明利钢精密铸造有限公司 | Preparation method of molding sand special for integral casting of large stainless steel parts |
| CN111250648A (en) * | 2020-03-27 | 2020-06-09 | 霍山县东胜铸造材料有限公司 | Preparation process of casting riser smooth coating |
| CN114212784A (en) * | 2021-11-26 | 2022-03-22 | 唐山金湾特碳石墨有限公司 | Preparation method of graphite for friction material |
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Application publication date: 20151104 |