Cork insulation; a complete illustrated textbook on cork insulation ...

236 CORK INSULATION
fying agent, one that is non-adhesive, capable of colloidal dis-
persion and of inferior adsorptive power in the presence of the
basic asphalt colloids. In a word, the colloids of the emulsi-
fying agent must be such as to be held to the surface of the
dispersed asphalt colloids in sufficient quantity and with sufficient
bond to prevent the colloidal particles of asphalt from
sticking together as they touch each other during propulsion
about through the aqueous alkaline solution by the forces
that make colloidal suspension possible.
U. S. Letters Patent No. 1,582,467, for example, sets forth
as one of its claims the follow^ing:
A process for producing an aqueous bituminous emulsion
which consists in melting solid bitumen of the type artificially
prepared from petroleum, adding thereto with agitation
a proportion less than 10% of an emulsifying agent
comprising a substance of the starch-dextrin type, and then
separately adding a dilute aqueous solution of alkali, and
maintaining the heating and agitation of the mixture until
emulsification has been efifected.
U. S. Letters Patent No. 1,567,061 sets forth certain claims
relating to the admixture of a flocculating agent* to an asphalt
emulsion to increase the degree of protection to the suspended
asphalt colloids by causing the colloids of the emulsifying
agent to more tenaciously cling to the suspended colloidal
asphalt, as follows
:
A process of forming a non-adhesive emulsion, consisting
in emulsifying an adhesive bituminous substance with colloidal
clay in an aqueous vehicle, adding aluminum sulphate
to the emulsion to cause the emulsifying particles to more
tenaciously gather about the bituminous substance.
The colloidal dispersion of asphalt in water is usually
accomplished by heating the asphalt to about 225° F. and
adding it to a hot aqueous alkaline solution under vigorous
and intimate agitation ; and there have been a number of
patents issued covering mechanical equipment for many ways
of accomplishing such dispersion. It would therefore appear
that the equipment used and the care exercised in the manufacturing
process may have considerable to do with the worth
of the finished product. For instance, if the asphalt were not
actually broken up into microscopic particles sufficiently small
to place them in the colloidal realm, then the tendency of that
*Aromoni3 salts arp frequently used in emulsions as flocculating agents.