Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE CONSOLIDATION OF GEOLOGICAL FORMATIONS
Background of the Invention
German Patent Specification 1,129,894 describes a
process for sealing or consolidating geological formations
against water or gas by means of polyurethane, wherein reaction
components, forming a cross-linked product with the group
-NH-CO-O-, namely a di- or polyisocyanate and a polyol com-
prising at least three reactive OH groups, mixed together in
a liquid vehicle, are forced under pressure into the formation
to be sealed or consolidated.
In forming the polyurethane, polyols are usually used
having an average molecular weight of 400-600 and an OH number
of 350-400. These polyols may be replaced up to about 15
or even completely by a plasticizer, in particular castor
oil. Despite many disadvantageous properties, castor oil is
used in practice as a sole or partial cross-linking agent for
isocyanates for consolidating geological formations, see
for example "Gluckauf" 104 (1968) Volume 15, pages 666-670,
German Patent Specification DOS 2,123,271,DBP 1,758,185, and
DBP 1,784,458.
One disadvantage of high castor oil contents is the
insufficient flexibility which it gives to the hardening
polyurethane, which may lead to a premature destruction of the
consolidated state of the geological formation, especially with
the high dynamic stress on coal and the surrounding rock
occurring in mechanical coal production processes in open-cast
mining. As the proportion of castor oil in the polyol com-
ponent is raised, the modulus of elasticity, the compression
strength and the bending strength of the polyurethane which :
brings about the consolidation of the geological formation are
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reduced, so that the rock pressure and the action of external
forces connected with the mechanical production process may
cause slip of the consolidated formations.
A further disadvantage is the relatively high vis-
cosity of castor oil, which is approximately 100 mPa s at
25C. With higher contents of castor oil in the polyol
component, the viscosity of the entire system is raised to
such a value that troublefree penetration into the smallest
cracks and crevices and the complete wetting of the surface
are no longer guaranteed.
The immiscibility of castor oil with water is also
a disadvantage. If damp or wet rock is to be consolidated, the
castor oil may be separated from the system by the water
absorption of the polyol compounds, which are very miscible
with water, and thus the castor oil no longer reaches the
diisocyanate for reaction. Indeed, a known method for de-
termining castor oil in polyol compounds consists of separating
the castor oil by displacement with water.
Another disadvantage is that the castor oil reduces
the binding force between the polyurethane and the rock or
coal at high castor oil contents in the polyol. Thus, the
structure of the consolidated formations is weakened.
Summary of the Invention
It has now been discovered that the aforementioned
disadvantages may be eliminated in consolidating geological
formationsby employing a process comprising applying an at least
two-component reactive polyisocyanate/polyol mixture to the
material to be consolidated wherein said reactive polyisocyanate/
polyol mixture comprises:
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(a) a polyisocyanate, and
(b) a polyol mixture comprising
(i) 5-50% by weight of a polyether polyol
having an OH number under 100 produced
by the reaction between a compound
having more than one reactive hydrogen
atom per molecule and a molar excess
of 1,2-alkylene oxide, and
(ii) 95-50% by weight of a polyol selected
from the group consisting of a poly-
hydroxyalkane having 2 to 4 hydroxy
groups with a molecular weight of
about 62 to 200 and a polyether polyol
having an OH number of about 200 to
1056 with a molecular weight of about
106 to 1,000,
and wherein said reactive polyisocyanate/polyol mixture
undergoes an isocyanate polyaddition reaction in the material
to be consolidated.
In a preferred embodiment, the geological formations
that may be consolidated by the process of the present in-
vention are geological formations encountered in coal mining.
Another embodiment of the invention pertains to a
fracturable double chamber cartridge in which one chamber
contains the polyisocyanate component noted above and the
second chamber contains the polyol mixture noted above.
The polyurethanes produced from such polyol mixtures
and which bring about the consolidation of geological forma-
tions have high flexibility with a high modulus of elasticity
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and a high bending strength, have a high binding force to
coal and surrounding rock, and resist strong dynamic stresses.
It is also easily possible to keep the composition of the
said product of reaction constant by holding the reaction
conditions constant during its production.
A further advantage of such a polyol mixture is
its good compatibility with water, so that separation of the
flexibility-conferring component on consolidation of wet or
damp formations is impossible.
The polyether preferably has an average molecular
weight of about 1500-8000 most preferably of about 2000-3500
and as stated, an OH number under 100, and preferably between
50 and 90.
Constituents with more than one reactive hydrogen
atom per molecule for producing suitable polyethers include
primarily carboxylic acids, phenols, alcohols and amines.
Examples of carboxylic acids are: phthalic acid,
adipic acid, maleic acid, succinic acid.
Examples of phenols are: hydroquinone, pyro-
catechin, 4,4'-dihydroxydiphenyl-dimethylmethane.
Examples of alcohols are: ethylene glycol, propylene
glycol, trimethylol propane, glycerin, pentaerythritol,
mannitol, glucose, fructose and sucrose.
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Examples of amines are: ammonia, mono- and di-
ethanolamine, diethylenetriamine, aniline, diaminodiphenyl-
methane, and especially ethylenediamine and triethanolamine.
Examples of 1,2-alkylene oxides are: ethylene oxide,
propylene oxide and 1,2-butylene oxide. Mixtures may be used,
or one alkylene oxide may be used in the first reaction stage
and another in the second reaction stage, in order to bring
about segmentation in the synthesis of the polyether molecule.
The production of the polyether is in accordance
with known reactions, see for example Ullmann, No. 14, pages
50-51, 3rd edition 1963 and Polyurethanes: Chemistry and
Technology, Volume 1 , pages 33-43 by Saunders and Frisch
Interscience (1962). The amount of 1,2-alkylene oxide to be
used is set by the requirement of reaching an OH number under
100.
The preferred embodiment of the process according
to the invention is the use, in the proportion of 5-50% by
weight, of those reaction products obtainable from amines and
1,2-alkylene oxides. The described advantages in comparison
with castor oil relative to the mechanical properties of the
consolidation of the geological formations and heaped rock
and earth masses are particularly evident in this case. This
result is surprising, particularly in the light of the generally
held opinion that polyols containing amine, because of their
too rapid reaction with isocyanates, would not be able to
accomplish the time consuming impregnation processes concerned
in penetrating fine crevices and fissures of the formations to
be consolidated, which represents a physical prerequisite for
the chemical consolidation itself.
Most remarkable is the fact that the described polyol
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mixtures have practically the same pot ]ife time as conventional
polyols when mixed with isocyanates, an~ may thus be used for
all presently known consolidation methods. The isocyanates
used may be any known products which comprise more than one
isocyanate group per molecule. Examples are: toluylene-
diisocyanate, prepolymers with free isocyanate groups formed
from multivalent alcohols and toluylenediisocyanate, hexa-
methylenediisocyanate and its prepolymers, diphenylmethane-
diisocyanate and mixtures of its various isomers and higher
nucleus fractions. Included are the isocyanates and isocyanate
terminated prepolymers described in Polyurethanes: Chemistry
and Technology by Saunders and Frisch, Interscien~e (1962)
which have more than one NCo group per molecule. The preferred
polyisocyanates are the well-known polyisocyanate mixtures which
are obtained by phosgenation of aniline - formaldehyde condensates.
The polyols which according to the invention are added to the
said ethers may be any polyols known in polyurethane production,
such as those described in Polyurethanes pages 32-61, above re-
ferenced. Preferred polyols are a) polyhydroxyalkanes having
from 2 to 4 hydroxy g~oups per molecule, molecular weights of
about 62 to about 200 such as e.g. ethyleneglycol,1,2_prOpane
diol, hexamethyleneglycol, trimethylolpropane, glycerol or
pentaerythrithol and/or b)~pol~ ther polyols with molecular weights
of about 106 to 1000 preferably of about 250 to 700 most ~re-
ferably of about 400 to 600 and OH-numbers of about 200 to
1056 preferably of about 250 to 800 and most preferably of
about 350 to 400. Any mixtures of components of a) and b) may
be used. The preferred polyols are the~pol~ether polyols mentioned
under b). Suchtpol~etber polyols are produced for example by
reacting trimethylolpropane with propylene oxide (hereinafter
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called polyol l) or a mixture of sucrose and 1,2-propane-
diol with propylene oxide thereinafter called polyol 6).
Further specific examples for suchtpol~ether polyols are
e-g-diethylene glycol,triethylene gly~ol, tetraethylene glycol,
di~ropylene glycol, tripropylene glycol, ethoxylation and1or
propoxylation products of low molecular weight polyhydroxy-
compounds such as e.g. those mentioned hereinbefore under a).
The proportion of the polyol component to be mixed
with the isocyanate may be varied within wide limits, but
advantageously so much isocyanate is added that 0.5-2 NCO
groups are present for each OH group. If the geological
formations or the heaped rock and earth masses to be consoli-
dated contain much moisture, it is desirable to use a large
excess of isocyanate.
Moreover it is possible to use the usual blending
agents known in polyurethane chemistry for modifying the con-
tained polyurethanes, e.g. castor oil, expanding agents such
as water and fluorinated hydrocarbons, accelerators such as
tertiary amines and metal catalysts (e.g. stannic chloride
tin-(II)-octoate or dibutyl-tin-dilaurate ) and foam regu-
lators such as organic silicon compounds. Fillers may also
be incorporated SUCh as the fly ash described in German
Auslegeschrift 1 159 865.
It is further possible to add hydrophylic substances,
such as sodium aluminosilicate of the Zeolite type, if it is
required to prevent foaming of the consolidating medium.
The advantages of the process according to the
invention will be illustrated by the following examples:
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In the specified examples, the following substances
have the meanings given:
Polyol l: a polyether polyol, produced from trimethylol
propane and propylene oxide, with an OH number
of 370, an average molecular weight of 450 and
a viscosity of 700 mPa at 25C.
oil a commercially available natural product of 1st
pressing quality, with an OH number of 148 and
a viscosity of about l000 mPa s at 25C.
10 Polvol 2: a polyether polyol, produced from trimethylol
propane and propylene oxide, with an OH number
of 56 an average molecular weight of about
3000 and a viscosity of 550 mPa s at 25C.
Po]vol 3: a polyether polyol, produced from l,2-propyle~e
glycol and propylene oxide, with an OH number
of 59, an average molecular weightof 2500 and
a viscosity of 410 mPa s at 25C.
Polyol 4: a polyether polyol, produced from ethylene
diamine and propylene oxide, with an OH number
of 61, an average molecular weight of 3500 and a
viscosity of 630 mPa s at 25C.
Polyol 5: a polyether polyol, produced from triethanol-
amine and propylene oxide until an OH number of
103 is reached, followed by reaction with ethylene
oxide until an OH number of 58 is reached, with
and average molecular weight of 3200 and a vis-
cosity of 480 mPa s at 25C.
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Polvol 6: a polyether polyol, produced from a mixture of
sucrose and l,2-propanediol in the molecular
proportion of l:5 plus propylene oxide, with an
OH number of 380, an average molecular weight
of 440 and a viscosity of 580 mPa s at 25C.
EXAMPLE 1
100 parts by volume of the polyols and polyol
mixtures given in the following Table l were mixed with an
isocyanate component with an isocyanate content of 31~ and a
viscosity of 140 mPa s at 25C, obtained by phosgenating
a formaldehyde-aniline condensation product and comprising more -
than 50~ of 4,4-diisocyanate diphenyl methane and with 5 parts
by weight of a sodium aluminosilicate of Zeolite type, and
cast in metal molds treated with a release agent. After 15
hours of hardening at room temperature, the molds were tempered
with hardening completed for 5 hours at 80C. The properties
given in columns 1-3 of Table 1 were determined for the compact
unfoamed polyurethane specimens obtained.
To estimate the binding properties with coal and
adjacent rock, clay slate and coalprismsof size 4 x 4 x 16 cm
were broken and the reaction mixture was cast into them,
keeping a constant separation gap of 2 mm. The bending strength
of the cemented prisms was then determined and used as a
measure of the binding properties. ``
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EXAMPLE 2
100 parts by volume of each of the polyol mixturesgiven in Table 2 were treated as in Example 1. The designation
of the polyols agrees with that of Example 1. The properties
given in Table 2 were measured.
TABLE 2
Polyol ~ing strength Modulus of Elas~ ing pro- MPa
MPa DIN 53 452 ticity~a DIN perties on on rock
(equivalent to 7735 coal
ASTM D 790)
100 parts by wt.l
+ 10 parts by wt.4 68 2740 1.04 2.72
100 parts by wt.l
+ 15 parts by wt.4 90 2750 1.16 2.84
100 parts by wt.l
+ 20 parts by wt.4 115 2770 1.21 3.00
100 parts by wt.l
+ 30 parts by wt.4 85 2730 1.20 ' 3.02
EXA~LE 3
100 parts by volume of each of the polyol mixtures
given in Table 3, with the same designation as Example 1, were
mixed with 1.2 parts by volume of water and 0.6 parts by
volume of a polysiloxane for foam stabilization. 100 parts by
volume of the isocyanate described in Example 1 were then
added to each and agitated for 30 seconds. Foam development
in the liquid began in each case after 4 minutes, with
solidification of the induced foam after about 15 minutes.
The properties given in Table 3 were determined for the
obtained foams.
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The polyurethane reaction system may be applied to
the material to be consolidated in a variety of ways. The
reaction system may be poured into downwards filled drill holes
which are then sealed. In such cases, it is advantageous
to employ a blowing agent such as water in the reaction system.
This process is described in greater detail in German Aus-
legeschrift No. 1,758,185 or French Patent No. 2,006,536.
Alternatively, the system can be applied by means of a
two-compartment cartridge which maintains the isocyanate
and polyol components in separate compartments. A bore hole
is drilled and one or more cartridges are inserted into the
hole. The cartridges are then fractured in such a way as to
intimately blend the two components, and the bore hole is
sealed. The reaction system in this application should con-
tain a blowing agent. This method is described in greater
detail in U. S. Patent No. 3,698,196.
In addition the reaction system may be injected
under pressure into the material to be consolidated. The
injection may be performed by machine with a working pressure
of about 60 bar as is described in Gluckauf, 108, ~uly 20,
1972, pages 615-618. As discussed therein, it is disadvan-
tageous to work at pressures greater than about 90 bar because
of the likelihood of expanding cracks and fissures already
present in the material to be consolidated. The machine
may be equipped with a two component pump which draws each of
the components separately so that they may be mixed immediately
in front of or in the hole to which the system is to be
supplied. Iron or wooden poles may be inserted into the
injection hole prior to injection of the system. This would
strengthen the consolidated mass and reduce the amount of
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system components consumed.
The injection may also be effected by placing each
of the system components under pressure in separate containers
and then supplying them from these containers to the material
to be consolidated, for instance, pipes with one way valves
may be provided from each container to a T joint at which the
components are mixed and at which additional gas may be
provided to insure a more thorough mixing of the components.
This method is described in more detail in German Offen-
legungsschrift No. 2,123,271.
Normally, in the pouring and injection embodimentsthe reactive system includes a foaming agent. However, in
certain circumstances, it may be advantageous to employ the
system without such an agent so that a solid resin is formed.
In such a case it is desirable to add a hydrophilic substance,
such as Zeolite type sodium alumino-silicate, as discussed
hereinabove. This additive will absorb water from both the
polyol component (water is quite miscible with most polyethers)
and thP environment to which the system is applied thus pre-
venting substantial foaming from occurring. The solid resinsystems offer greater strength for those special applications
wherein it is required.
A number of specific sequences for applying the
reactïonsystem of the present invention to the material to
be consolidated will occur to those skilled in the art. The
particular embodiments of the present invention are therefore
not limited to those described above but rather the scope of
the invention is defined by the claims and descriptions of
particular embodiments are merely exemplary.
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From the preceding examples and Tables, it is evident
that the binding force on coal and rock of the polyurethanes
according to the invention is considerably improved with
relation to the binding force usual with polyurethanes made
flexible with castor oil. The bending strength, deflection
and modulus of elasticity are considerably more favorable for
consolidating coal and rock.
Although the invention has been described in detail
in the foregoing for the purpose of illustration, it is to be
understood that such detail is solely for that purpose and
that variations can be made therein by those skilled in the art
without departing from the spirit and scope of the invention
except as it may be limited by the claims.
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