Bituminous foam

Details Bituminous foam Bituminous foam

2002-06-03

2004-03-30

Foelak, Morton (Department: 1711)

Compositions: coating or plastic

Coating or plastic compositions

Pore forming

C106S277000, C106S278000, C427S373000, C427S427000, C521S029000, C521S083000

Reexamination Certificate

active

06712895

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a method of producing a bituminous foam. An apparatus for carrying out the method and a method using the foam are also described.
This invention relates to a method of producing a bituminous foam. An apparatus for carrying out the method and a method using the foam are also described.
Foamed bitumen binders have been known for many years. For example, up to and during the late 1940's and 1950's, when steam road sprayers and steam rollers were commonly used in road preparation, foaming of a coal tar binder was an established practice for use in grouting techniques and for stabilisation of road bases. In the process, superheated steam was used to raise the temperature of tar to about 120° C. prior to injection of low pressure steam (wet steam) immediately prior to discharge through a hand lance or spray bar jets. This provided a crude (but nonetheless effective) means of creating foam thereby to increase the volume of the tar (binder) and assist dispersion of the tar into a road under construction immediately after contact of the tar with the road, roller tines and harrows were used to effect in situ mixing.
U.K. Patent No. GB 1 325 916 (Mobil) describes a method and apparatus for producing foamed materials, especially foamed bituminous materials. The method essentially comprises providing bitumen at an elevated temperature and then mixing the hot bitumen with a liquid, for example water, which is insoluble in the bitumen. The liquid evaporates on discharge of the mixture to ambient conditions and thereby causes expansion of the bitumen which, accordingly, foams. Thus, in essence, the method comprises a two-stage process. Disadvantageously, the two stage process necessitates very careful control of the flow rates of the bitumen and water and, accordingly, relatively complicated apparatus. Furthermore, the second stage of the process is potentially hazardous due to the violent reaction between hot bitumen and water.
It is an object of the present invention to address the above described problems.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a method of producing a bituminous foam, the method comprising raising the temperature of an emulsion which includes bitumen and a liquid which is substantially insoluble in said bitumen (hereinafter “said insoluble liquid”); and discharging said emulsion from a first environment wherein the pressure is P
1
to a second environment wherein the pressure is P
2
and P
1
>P
2
, whereby said emulsion foams after discharge into said second environment.
Said insoluble liquid may be such as to produce a relatively high ratio of vapour per wt % thereof included in said emulsion. To this end, said insoluble liquid preferably has a low molecular weight which is suitably less than 100, preferably less than 80, more preferably less than 65. Said insoluble liquid may comprise a mixture of components. Said insoluble liquid may be water or a lower alcohol, especially a C
1-3
alcohol, or a mixture comprising any of the aforesaid. Preferably, said insoluble liquid comprises a major amount of water.
In the context of this specification, a “major amount” may mean at least 60 wt %, suitably at least 75 wt %, preferably at least 90 wt %, more preferably at least 95 wt %, especially at least 99 wt % of the referenced component is present in a referenced formulation.
Preferably, said insoluble liquid consists essentially of water.
In the method, the temperature of said emulsion is suitably raised, under said pressure P
1
, to a temperature at which it can vaporize sufficient of said insoluble liquid to produce the amount of vapour required for the desired expansion of the bitumen on foaming after discharge into said second environment. The emulsion may be exparded to produce a foam in said second environment, wherein the ratio of the volume of foam to the volume of said emulsion present initially is at least 5, suitably at least 10, preferably at least 15, especially at least 20.
The temperature of said emulsion at discharge is preferably greater than the boiling point of said insoluble liquid, suitably by at least 100° C., preferably at least 150° C., more preferably at least 200° C., especially at least 250° C.
The temperature of said emulsion at discharge is suitably not more than 100° C., preferably not more than 80° C., more preferably not more than 60° C., especially not more than 50° C., greater than the boiling point of said insoluble liquid.
The temperature of said emulsion at discharge may be at least 105° C., suitably at least 110° C., preferably at least 115° C., more preferably at least 120° C., especially at least 125° C.
The temperature of said emulsion at discharge may be less than 200° C., suitably less than 190° C., preferably less than 180° C., more preferably less than 170° C., especially less than 160° C.
In the method, the temperature of the emulsion may be raised through at least 20° C., suitably at least 40° C., preferably at least 60° C., more preferably at least 80° C., especially at least 100° C. The temperature may be raised through less than 200° C., suitably less than 180° C., preferably less than 160° C., especially through less than 140° C.
The temperature of said emulsion immediately prior to it being raised in the method may be at least ambient temperature.
Said emulsion preferably has a viscosity at 20° C. in the range 0.2 to 800 Poise. The viscosity at 80° C. may be in the range 0.1 to 100 Poise
A first heating means is suitably provided for raising the temperature of said emulsion. Said first heating means preferably does not cause a change in concentration of said bitumen or said insoluble liquid in said emulsion as would occur, for example, if a heated liquid was contacted with said emulsion for heating it. Said first heating means preferably comprises a heated solid body arranged to transfer heat to said emulsion by conduction. For example, said emulsion may be passed through a convoluted heating assembly, for example a heating coil, which may be heated by suitable means, for example by circulation of a heated fluid and/or by electrical heating means.
Preferably, in the method, said temperature of said emulsion is raised as described herein when said emulsion is in said first environment. Thus, said temperature is preferably raised whilst said emulsion is within an apparatus in which the pressure is P
1
.
Preferably, P
1
is at least 1.0×10
5
N/m
2
, more preferably at least 1.5×10
5
N/m
2
, especially at least 2.0×10
5
N/m
2
. P
1
may be less than 4×10
5
N/m
2
, preferably less than 3.5×10
5
N/m
2
, more preferably 3.0×10
5
N/m
2
or less.
Preferably, the pressure of said emulsion is raised to said pressure P
1
in said first environment. Prior to entry into said first environment, the emulsion may be at a pressure of less than P
1
which may be ambient pressure.
P
2
is preferably ambient pressure.
The temperature in said second environment is preferably less than the temperature in said first environment, suitably by at least 50° C., preferably at least 60° C., more preferably at least 70° C., especially at least 80° C. The temperature in said second environment is preferably ambient temperature.
The method is suitably carried out in an apparatus having a first region in which the pressure of an emulsion therein is arranged to be raised to said pressure P
1
. An inlet is suitably provided for passage of an emulsion into the first region and an outlet is suitably provided for passage of the emulsion, under pressure, out of said first region, suitably to said second environment. Said first heating means described above is suitably provided between the inlet and outlet for heating the emulsion in the first region. A first pump means is suitably provided for pumping the emulsion within the first region and, suitably, for raising the pressure thereof. The apparatus may be arranged for circulating the emulsion within the first region. First outlet valve means is suitab

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