CS231762B1 - Manufacturing process of carbon foam material - Google Patents

Description

^; The present invention provides a process for the production of a carbon foam material which can be used as a heat insulating material in an inert environment or under vacuum up to 3000 ° C, as a catalyst carrier, electrode, and the like.

Carbon foam material whose bulk density is of the order of magnitude lower than the density of carbon has not yet been found in practice. Carbon materials known as "low bulk density" are known in the literature, but the ratio of bulk density to carbon density is only five times lower and the production process is unknown.

^The thermal insulating material in vacuum or an inert atmosphere up to 3000 ° C uses carbon felt or carbon wool, which is made of fibers that are either visicose or polyaminonitrile, which are first partially oxidized, then carbonized ^! and further processed into the final product in conventional ways. The disadvantage of these materials is their demanding production technology.

For less demanding applications it is possible to use carbon crumb or carbon black as an insulating material up to 3000 ° C. Their production is simple, but the disadvantage is limited technical use and considerable pollution of the working environment.

A common feature of the carbon-based heat insulating materials is their low specific weight, which is as follows:

Carbon black 0,29 g / om ³

Carbon crumb 0,40 g / cm ³

Carbon felt 0.09 g / cm ³

The foamed phenol-formaldehyde material is prepared according to the Czechoslovak patent No. 128,582.

A mixture of 100 parts by weight of phenol-formaldehyde resin containing 13% methyl groups, 0.3 parts by weight of a surfactant prepared by the addition of 17 moles of ethylene oxide per mole of ricinoleic acid glyceride, 4.4 parts by weight of a mixture of aliphatic hydrocarbons distilling between 30 and 100 degrees Celsius. and 6.4 parts by weight of the reaction catalyst prepared from phenol and sulfuric acid, so that the excess free sulfuric acid is at most 15%, is stirred while gradually adding the individual components to a temperature of 39 ° C. The mixture is then poured into a wooden mold heated to 65 ° C where it is allowed to foam and cure. After 24 hours the cooled block is removed from the mold and after a further 24 hours it is cut to the desired dimensions, for example 50 x 120 x 170 mm, which are placed in an iron container. 20 mm wide gaps are left between the blocks, which are filled with graphite or powdered coke with a grain size below 2 mm and baked to 1000 ° C with this curve.

Within Temperature rise: from 20 to 100 ° C max 50 ° C per hour from 101 to 150 [deg.] C max 5 ° C per hour from 151 to 300 [deg.] C max 5 ° C per hour from 301 to 500 ° C max 8 ° C from 501 to 1000 ° C max 20 ° C So made carbon foam-

Rial has the following characteristics:

These drawbacks are reduced by the use of the carbon foam material produced according to the present invention, which is based on: The firing of a surfactant-activated foamed phenol-formaldehyde resin in a carbon powder with a grain size of max.

In this way, the following material properties are achieved:

Specific gravity 0.07 to 0.03 g / cm ³

Compressive strength 6 to 2 MPa

Měrný elektr.

resistance 500 to 700 microohm.m.

Pore size 0.05 to 0.5 mm

Thermal conductivity less than 0.2 W / m K. Popo-1 max. 3.0%.

Specific weight Compressive strength Specific electr. resistance

Pore size Ash

Thermal conductivity

0.056 g / cm ³ 2 MPa

700 mikroohm. m. 0.05 to 0.3 mm.

2,7 i%

0.11 W / m K

There is no significant volume change when fired at 2500 ° C or higher. The carbon foam shall be wrapped in a carbon muffle or in a carbon tray, covered with a coke filling of a grain size of up to 2 mm and baked in an aggressive oven at 2500 ° C with the following firing curve:

These properties outperform the hitherto known thermal insulation materials operating up to 3000 ° C. Another advantage of the present invention is the surface area, chemical purity and its high resistance to aggressive non-oxidizing agents.

Example of carbon foam production:

Within:

up to 1000 ° C from 1001 to 1500 ^l0 C from 1500 to 2500 ^! ° C

Temperature rise:

max 500 ° C per hour max 300 ° C per hour max 500 ° C per hour

The electrographitated carbon foam material has the following characteristics:

231782

Specific weight 0.058 g / cm ³ Compressive strength Impala Měrný elektr. resistance 400 microohm. m. Pore size 0.05 to 0.3 mm ash 0.3% Carbon foam material relative to

its low sorbent properties of X-ray radiation can be used as a heat insulating material in an ionizing radiation environment, due to its electrical resistance it can be used for the production of electric heating elements, possibly as an electrode material in electrochemical cells and the like.

Claims (4)

A method of producing carbon foam material by firing a surfactant-activated phenol-formaldehyde ' s resin, characterized in that the resin is fired in a carbon powder with a grain size of max. 2 mm to a temperature of 20 ° C to 100 ° C max. 50 ° C per hour, from 101 to 150 ° C max. 3 ° C per hour, from 151 to 300 ^and C max. 4 ° C per hour, BETWEEN 300 to 500 ° C max. 8 ° C per hour, from 500 to 1000 ° C max. 20 ° C per hour, when firing to a higher temperature the carbon foam is recovered by increasing the temperature: Oid 20 to 1000 ° C max. 500 ° C per hour, from 1001 to 1500 ° C max. 300 ° C per hour, from 1501 to 2500 ° C max. 500 ° C per hour.