Plastic and nonmetallic article shaping or treating: processes – Carbonizing to form article
Patent
1988-02-04
1990-04-17
Thurlow, Jeffrey
Plastic and nonmetallic article shaping or treating: processes
Carbonizing to form article
264126, 264140, 26433112, 26433122, 264DIG59, 423449, 524386, 524594, B29C 4300, B29C 6720, C01B 3102
Patent
active
049178350
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the production of shaped porous resin and carbon articles with improved strength.
Porous phenolic resin articles may be used for example as filters or membrane supports.
Porous carbon articles can be used for:
GB 1 130 829 discloses the production of carbon articles with a predetermined shape by moulding. Ground coke is mixed with a carbonizable aromatic binder e.g. pitch. The mixture is then formed into the desired shape, the binder is carbonized, and the resulting product further heated. However the pitch used as binder in the above process will tend to fill up the spaces between the coke particles so making the product difficult to carbonize. In addition the internal porosity of the coke particles may become partly filled up by the pitch, leading to low porosity products.
It is well known that activated carbon can be produced in the form of pellets by carbonizing pellets of organic material e.g. wood chips. However the mechanical strength of such pellets is relatively low, even after carbonization at high temperature.
WO 81/03167 discloses the production of a porous carbon by depositing particles of carbonizable polymer in such a way that the particles produce a regularly packed deposit. This is partially degraded to make it form stable, and then heated to carbonized it.
U.S. Pat. No. 4 263 268 shows the preparation of porous carbon from a phenolic resin which is deposited within the pores of an inorganic material. The resin is polymerised within the pores, the inorganic material is removed, and the resin pyrolyzed to form carbon. The resulting carbon is very porous but has a very poor mechanical strength. The fragility of the product is specifically mentioned in the specification.
GB 1 330 296 discloses the formation of carbonized materials from powdered phenolic resins. However the resins are specifically stated to be thermoplastic resins. We have attempted to repeat the process of GB 1 330 296. We have not found it possible to make strong porous articles or articles with shape stability.
We have now found a method of producing porous shaped article having improved strength, with continuous open pore structure.
According to one aspect of the present invention the process for the production of a shaped porous phenolic resin article comprises:
(a) partially curing a phenolic resin mixture to a solid,
(b) comminuting the partially cured resin,
(c) forming the resulting comminuted resin into a pre-determined shape,
(d) sintering the comminuted resin so as to produce a form-stable sintered product, give a degree of cure sufficient to give a sinterable product.
According to another aspect of the present invention the process for the production of a shaped porous carbon article comprises:
(a) partially curing a phenolic resin mixture to a solid,
(b) comminuting the partially cured resin,
(c) forming the resulting comminuted resin into a pre-determined shape,
(d) sintering the compound resin so as to produce a form-stable sintered product, and
(e) carbonizing the shaped article. give a degree of cure sufficient to give a sinterable product.
By "sintering" we mean a step which causes the individual particles of phenolic resin to adhere together without the need for a separately introduced binder, while retaining their individual identity to a substantial extent on heating to carbonization temperatures. Thus the particles must not melt after forming so as to produce a molten mass of resin as this would eliminate the internal open porosity of the article. The open porosity (as opposed to the closed cells found in certain types of polymer foams) is believed to be important in enabling formed articles to retain their shape on carbonization.
Phenolic resins are well known materials. They are made by the reaction of a phenol and an aldehyde e.g. formaldehyde. The condensation is initially carried out to produce a partially condensed product. The condensation may be carried out so as to produce a resin which is fully curable on further heating. Alternatively the condensation may be ca
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Lear Anthony M.
Satchell Paul W.
Tennison Stephen R.
Tentoni Leo B.
The British Petroleum Company p.l.c.
Thurlow Jeffrey
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