METHOD OF TREATING SUBTERRANEAN FORMATIONS
TECHNICAL FIELD
The present disclosure relates to a method of treating a portion of a
subterranean formation comprising the use of an aqueous fracturing fluid
containing fast dissolving and easily dispersible glyoxalated, ground guar
splits and to a process for preparing fast dissolving and easily dispersible
glyoxalated, ground guar splits.
BACKGROUND OF THE ART
Hydraulic fracturing is widely used for stimulating petroleum production
and recovery from subterranean formations.
It involves the injection of a suitable fluid down a well bore to reach a
formation; the fluid shall be injected under sufficient pressure to
extensively crack the formation and to provide passageways for the oil and
gas that is contained in the pore spaces of the formation and help them
flowing to the well bore. Suitable particulate materials (proppants) are
often injected in the formation to prevent closure of the fractures.
Usually, fracturing fluids are gelled with water soluble polymers,
especially with natural polymers or derivatized natural polymers, to most
effectively widen the fractures and inhibit fluid loss.
Water soluble polymers are manly available in powder form and must be
dissolved in the aqueous fluid to perform their viscosifying function.
Dissolution of natural polymer particles in aqueous fluids is typically
accompanied by the formation of lumps; upon contact with water, a thin,
sticky layer of gel forms on the surface of the particles preventing water
from hydrating the inner part of the particles and favoring the formation of
lumps.
As a consequence, the whole hydration step of the polymer is undesirably
prolonged, especially if the polymer shall be dissolved in large amounts
of saline aqueous fluids, which often happens in the preparation of
aqueous fracturing fluids.
Among the natural polymers that are used to thicken fracturing fluids, guar
gum flour is widely used, because it forms strong gels in combination with
crosslinkers based on titanium, zirconium and boron salts.
To provide a gelled fracturing fluid, guar gum and guar derivatives shall
be previously dissolved in the aqueous component of the fluid and then
gelled with a crosslinking composition.
Unfortunately, also the dissolution of guar gum and guar derivatives
suffers from the disadvantages described above.
Many solutions have been put into practice to avoid lumping, including
apparatus that are specifically designed to hydrate the polymers and to
continuously produce viscous treatment gel close to the oilwell site, as it is
known from US 2006107998.
Another way to rapidly hydrate the viscosifying polymers is to prepare a
concentrated slurry of the polymer in a non-aqueous carrier fluid, usually a
hydrocarbon fluid, which facilitates the polymer dispersion and slurry
mixing, but may represent a concern for the environment and an additional
cost.
It is also well known in the art (by way of example from US 5,165,479) to
treat natural gums in general with small amounts of glyoxal, borates and
the like, to inhibit hydration and minimize the formation of lumps upon
contact with water.
US 3,808,195, by way of example, describes how to treat guar gum splits
with boron salts to obtain a dispersible water soluble polygalactomannan.
Unfortunately, the reaction with borates is reversible with pH changes;
therefore, the borated product shall be pre-solubilised at acidic pH in the
fluid and, normally, the fluid shall be reverted to basic pH before
crosslinking and injection into the well bore.
Another limit of borated guar is related to the fact that boric acid
derivatives are at present classified as substances toxic for reproduction of
category CMR 2.
Therefore, it would be highly desirable to provide a guar gum which is
readily soluble at neutral or basic pH, is devoid of boric acid derivatives
and can be used as viscosifying agent for aqueous based fracturing fluids
because of its dispersibility and fast dissolving characteristics.
Although treatment with aldehydes is well known to improve
dispersibility of guar, the net result of the treatment with aldehydes
disclosed by the prior art is a guar that is dispersible but has a dissolution
time which is unsuitable for fracturing operations.
US 3,297,583, by way of example, describes a method for the rapid and
lump-free dissolution of many macromolecular substances that involves
the use of from 0.005% to 5% by weight of aldehydes.
In US 3,297,583 guar is cited among the many macromolecular substances
that can be treated and glyoxal and formaldehyde are the preferred
aldehydes, but no hint is made at fracturing fluids; according to one of the
examples, it takes half an hour to completely dissolve the glyoxal treated
guar in water at 2 wt%.
CA 2,063,365 describes a multistep process for derivatizing guar gum, in
which the alkaline derivatized guar reaction mixture is reacted with
glyoxal under acid pH conditions prior to washing, and, after washing, is
further reacted with a base. The resulting derivatized guar gum is said to
hydrate readily under both acid and alkaline pH conditions. The amount of
glyoxal used is about 0.2 to about 2% by weight based on the weight of
the starting non derivatized guar.
US 6,197,1 00 describes compositions of water soluble polymers, such as
cellulose ethers, guar, or derivatives thereof , that have been surfacetreated
with surfactants to improve the dispersibility of the polymer in
aqueous media. The treatment with surfactants may also be accomplished
on a dry, glyoxal treated polymers (obtained from an organic solvent
slurry or by spraying the polymer with an aqueous solution of glyoxal);
alternatively the surfactant and glyoxal may be applied together, dissolved
in an organic solvent (e.g. methanol or acetone).
The water soluble polymer compositions of US 6,197,100 find application
as thickeners and are tested in paper coating application, paint application
and oil field application (drilling fluids system), but not in fracturing
fluids.
A drawback of the compositions of US 6,197,100 is that the use of
surfactants may have an adverse foaming effect especially during
dissolution.
Finally, US 2003/0124195, concerns a complex method for preparing a
hydrocolloid powder compositions exhibiting good dispersibility in an
aqueous media and a controlled hydration time obtained by treating the
hydrocolloid with an aqueous solution of crosslinking agent that has been
absorbed on a highly absorptive inert support powder. Fracturing fluids
are not cited among the fields of use of the compositions of US
2003/0124195.
Although treatment with glyoxal is known to be useful for enhancing
dispersibility of guar gum, which is essential for its effective utilization,
the known glyoxalated guars hydrate slowly; the net result of glyoxal
treatment is therefore a long dissolution time which in fracturing is
particularly undesirable.
It has now been found how to obtain easily dispersible and fast dissolving
glyoxalated, ground guar splits, that can be utilized as viscosifying agent
for aqueous fracturing fluids and do not contain surfactants and are not
supported by inert water insoluble powders.
SUMMARY OF THE INVENTION
In one aspect, the disclosure relates to a method of treating a portion of a
subterranean formation comprising:
a . providing an aqueous fracturing fluid comprising dissolved therein from
0.3 to 3.0 % by weight of a viscosifying agent, wherein the viscosifying
agent is fast dissolving and easily dispersible glyoxalated, ground guar
splits containing from 0.01 to 0.05% by weight of glyoxal; b) adding a
crosslinking composition and placing the treatment fluid into a portion of
a subterranean formation.
In another aspect, the disclosure relates to a process for preparing fast
dissolving and easily dispersible glyoxalated ground guar splits
comprising the following steps: ) guar splits or ground guar splits are
soaked in 0,3 to 2 parts by weight of an aqueous solution containing 0.01
to 0.05% by weight of glyoxal based upon the guar splits, to obtain soaked
glyoxalated guar; ii) without washing the soaked glyoxalated guar,
grinding and drying it to obtain the glyoxalated ground guar splits.
In yet another aspect, the disclosure relates to a viscosifying agent for
aqueous based fracturing fluids that is obtained from the above process
and essentially consists of fast dissolving and easily dispersible
glyoxalated, ground guar splits containing from 0. to 0.05% by weight
of glyoxai that: i) provide in 3 minutes at least 70% of their maximum
0.48 wt% Fann viscosity in aqueous 2 wt% KCl at pH from 6.5 to 9 and
300 rpm; ii) provide 1 wt% aqueous solutions that show no lumps or fish
eyes after stirring at 1,200 rpm for one minute; iii) are free from
surfactants and are not supported by inert water insoluble powders.
DETAILED DESCRIPTION OF THE INVENTION
Guar is the most commonly used polygalactomannan.
Polygalactomannans are polysaccharides mainly composed of galactose
and mannose units and are usually found in the endosperm of leguminous
seeds such as guar, locust bean, honey locust, flame tree, and the like. The
polygalactomannans may be used in either their natural form or may be
substituted with one or more functional groups (e.g., carboxymethyl
group).
For the purpose of the present disclosure guar is the non-derivatized
polygalactomannan.
Guar splits are the endosperms of guar seeds; they are here meant to
include purified splits and double and triple purified splits, that are
obtainable from guar seed by mechanical separation of the endosperm
from the hull and germ of the seed.
According to the process of the present disclosure, that allows the
preparation of fast dissolving and easily dispersible glyoxalated ground
guar splits that can be used as viscosifying agents in aqueous based
fracturing fluids, guar splits can be glyoxalated as such or after being
ground.
The glyoxalated, ground guar splits containing from 0.01 to 0,05% by
weight of glyoxai which are contained in the aqueous fracturing fluid of
the method of the present disclosure are fast dissolving and easily
dispersible.
With the expression "fast dissolving" we designate products that provide
in 3 minutes at least 70% of their maximum 0.48 wt% Farm viscosity in
aqueous 2 wt% KC1 at pH from 6.5 to 9 and 300 rpm.
With the expression "easily dispersible" we designate products whose
1% by weight aqueous solutions that show no lumps or fish eyes after
stirring at 1,200 rpm for one minute after stirring at 1,200 rpm for one
minute.
In the present text, when referring to the glyoxalated, ground guar splits of
the invention, "providing no lumps" is used as a synonym of the
expression "easily dispersible".
According to a preferred embodiment of the disclosure, the glyoxalated,
ground guar splits to be used in the method of treating subterranean
formation provide their maximum 0.48 wt% Farm viscosity, which is at
least 40 mPa*s, in no more than 60 minutes in aqueous 2 wt% C1at pH
from 6.5 to 9 and 300 rpm.
The glyoxalated, ground guar splits of the disclosure preferably passes for
95% of their weight through a 200 mesh sieve (200 mesh are equivalent to
0.074 mm); beside grinding, the preparation of the glyoxalated, ground
guar splits may include a final sieving step, that may serve to shift the
average particle size of the product in this preferred range.
The amount of glyoxal which is used in the process, from 0.0 to 0.05%
by weight based on weight of guar, has proved to be one of the critical
features of the present disclosure, together with the concentration of the
aqueous glyoxal solution which is used to treat the ground guar splits or
the guar splits.
Glyoxalated, ground guar splits containing from 0.02 to 0.04% by weight
of glyoxal are most preferred; the best results in term of dispersibility and
fast hydration have been obtained by dosing about 0.03% by weight of
glyoxal in the process, based upon the weight of guar.
It is underlined that the specified amount of glyoxal contained in the
glyoxalated, ground guar splits of the present disclosure comprises both
linked and possibly unreacted glyoxal; the glyoxal content according to
the present disclosure is determinable by photometrical test after
derivatization with 3-methyl-2-benzothiazoline hydrazone hydrochloride.
In the method of treating a portion of a subterranean formation of the
disclosure, the glyoxalated, ground guar splits are obtained by a process
comprising the following steps: i) guar splits or ground guar splits are
soaked in 0.3 to 2 parts by weight of an aqueous solution containing 0.01
to 0.05% by weight of glyoxal based upon the guar splits, to obtain soaked
glyoxalated guar; ii) without washing the soaked glyoxalated guar splits,
grinding and drying them to obtain the glyoxalated ground guar splits.
Step i) of the process, in which guar splits are soaked in 0.3 to 2 parts by
weight of an aqueous solution containing glyoxal, is generally performed
temperature from 15 to 95°C for from 0.5 to 2 hours.
In spite of the low amount of glyoxal that is used in the process in respect
of guar, it has surprisingly been found that soaking the guar splits with the
above amount of glyoxal aqueous solution (i.e. with a diluted glyoxal
aqueous solution) gives a final product that has a remarkably improved
dispersibility, as compared with the product that is obtainable by operating
according to US 3,297,583, by spraying a higher amount of glyoxal
dissolved in a much more concentrated glyoxal aqueous solution.
Another advantage of the process according to the present disclosure is the
fact that it does not necessarily require the use of organic solvents, such
as acetone and methanol.
In the process of the disclosure the drying step may be accomplished at
temperature from 70 to 200°C.
According to a preferred embodiment of the disclosure, the method of
treating a portion of a subterranean formation comprises the use of
glyoxalated ground guar splits that have not been ground before being
soaked.
According to this preferred embodiment the process of the invention does
not require the use of any organic solvent; the aqueous solution in which
the guar splits are soaked does not contain organic solvents and essentially
consists of water and glyoxal (glyoxal aqueous solution).
Possibly, a weak organic acid can be present in the glyoxal aqueous
solution, although this has proven not to be strictly necessary.
In this embodiment, the preferred amount of glyoxal aqueous solution is
from 0.5 to 1.5 parts by weight based upon the weight of the guar splits;
the preferred amount of glyoxal is from 0.02 to 0.04% by weight of
glyoxal based upon the guar splits, the best result being obtained by using
0.03% by weight of glyoxal based upon the guar splits.
Alternatively, the method of treating a portion of a subterranean formation
comprises the use of guar splits that have been being ground before being
soaked.
Grinding in this case is effected to reduce the untreated splits to such a
particle size that they pass for at least 95% of their weight through a 200
mesh sieve.
According to this embodiment, in step i) the ground guar splits are
preferably soaked in from 0.3 to 0.8 parts by weight of an aqueous
solution which, more preferably, is an isopropanol aqueous solution
containing from 50 to 80% by weight of isopropanol.
The preferred amount of glyoxal to be used in step i) is the same as in the
process wherein the guar splits are treated with glyoxal before being
ground, that is from 0.02 to 0.04% by weight of glyoxal, most preferably
about 0.03% by weight, the amount of glyoxal being based upon the
ground guar splits.
The above described process provides fast dissolving and easily
dispersible glyoxalated ground guar splits that are advantageously used as
viscosifying agents in aqueous based fracturing fluids.
In the method for treating a subterranean formation according to the
disclosure, the crosslinking compositions utilizable in step b. are those
commonly used in the field.
The use of a crosslinking agent substantially increases the viscosity of the
polymer solution by forming a crosslinked polymer network in the
aqueous based fluid.
While a variety of crosslinking agents can be utilized to crosslink the
thickened aqueous fluid, preferred crosslinking agents include, but are not
limited to, boron, zirconium and titanium-based crosslinkers.
Examples of such crosslinking agents include: borate ion releasing
compounds, such as boric acid, boric oxide, pyroboric acid, metaboric
acid, borax, sodium tetraborate, pentaborate; ulexite, colemanite, and other
slow dissolving crosslinking borate minerals; transition metal ion releasing
compounds, such as titanium dioxide, zirconium oxychloride, zirconium
lactate, zirconium glycolate, zirconium lactate triethanolamine, zirconium
acetylacetonate, titanium citrate, titanium malate, titanium tartrate, and
other titanium and zirconium chelates.
If desired, mixtures of the crosslinkmg agents may be used in the
crosslinking composition.
Preferably crosslinking compositions also comprise a delaying agent.
These delaying agents delay the rate of crosslinking reaction for a
sufficient time to allow the aqueous thickened fluid to be pumped into the
subterranean zone. Glyoxal also may be introduced in the fracturing fluid
after dissolution of the glyoxalated ground guar splits to act as delaying
agent.
Most advantageously the crosslinking agents are non-borated and the
viscosifying agent is useful to provide a boron free fracturing method, that
is a method for fracturing a subterranean formation without the use of
fluids that comprise boron salts, which is particularly desirable for ecotoxicological
reasons.
The aqueous fracturing fluid, beside the viscosifying agent, the
crosslinking composition and the aqueous component, contains the
normally used additives, well laiown by those skilled in the art, such as
proppants, gel breakers, buffers.
Useful gel breakers include, but are not limited to, ammonium persulfate,
sodium persulfate, sodium bromate and sodium chlorite, enzymes.
Preferably, the gel breaker is a delayed gel breaker, such as encapsulated
ammonium persulfate. A delayed gel breaker slowly releases the oxidizer
from the polymer coating to enable a strong initial gel to carry and to
deposit the proppant in the formation.
The fluid also optionally includes one or more proppants suspended in the
fluid.
Useful proppants include, but are not limited to, gravel, sand, resin coated
sand, ceramic beads, bauxite, glass, glass beads and mixtures thereof.
The aqueous fracturing fluid also optionally includes one or more buffers.
Useful buffers include, but are not limited to, potassium carbonate, sodium
carbonate, potassium bicarbonate, sodium bicarbonate, potassium
hydroxide, sodium hydroxide, and mixtures thereof.
The buffer may be added to the fluid prior to adding the crosslinking
composition.
The aqueous fracturing fluid of the disclosure may optionally include one
or more conventional additives that do not adversely affect the
performance of the well treatment fluid. Such additives include, but are
not limited to, clay stabilizers, gel stabilizers, surfactants, bactericides and
the like.
Generally the thickened aqueous fracturing fluids of the invention have a
viscosity of above about 50 mPa*s at 0 sec 1, and, more preferably,
above about 100 mPa*s at 0 sec 1 .
The aqueous component of the fracturing fluid may be selected from fresh
water, salt water, seawater, natural or synthetic brine, mixtures of water
and water soluble organic compounds, any other aqueous liquid that does
not interact with the other components of the well treatment fluid to
adversely affect its performance, and mixtures thereof.
In the method of the disclosure, the aqueous fracturing fluid is finally
pumped or injected into the subterranean formation (e.g., from the surface
through the well bore). Preferably, the fluid is pumped or injected at a
pressure sufficient to fracture the formation (e.g., generate a plurality of
fractures), and thus to enable the particulate solid (proppant) suspended in
the well treatment fluid to be carried into the fractures by the fluid and
deposited in them.
Although the viscosifying agents of the disclosure are particularly useful
in hydraulic fracturing operations, their use is not limited thereto. The
glyoxalated ground guar splits of the invention may be used in a wide
variety of applications in the textile industry, in the paper, explosives and
pharmaceutical industry, in the cosmetic and toiletries field, in mining and
civil engineering, in the agrochemical industry, in the preparation of
paints and varnishes and in the building additives industry.
The following examples are included to demonstrate preferred
embodiments of the invention.
EXAMPLES
Example 1
8 kg of guar splits have been soaked with 1 kg of water containing 6 g of
a 40 wt% of glyoxal aqueous solution.
The guar splits have been left for 1 hour under stilling at room
temperature.
The glyoxalated guar splits (sample 1-A) have been flaked, ground, dried,
sieved at 200 mesh and then tested against the reference material (i.e.
against guar splits subjected to the same treatment but without glyoxal in
the aqueous solution, sample 1-B).
Example 2
8 kg of ground guar splits (95 wt% passing through 200 mesh) have been
soaked with an aqueous solution made from 0.8 kg of water, 2.1 kg of
isopropanol and the quantity of glyoxal reported in Table 1 by use of a 40
wt% of glyoxal aqueous solution.
The ground guar splits have been left for 45 minutes at 60°C under
stirring.
After this time the isopropanol has been distilled off from the reaction
mixture and the so obtained glyoxalated ground guar splits (samples 2-A,
2-B and 2-C) have been ground, dried, sieved at 200 mesh and then tested
against the reference material without glyoxal (i.e. against the non treated
ground guar splits, sample 2-D).
Example 3 (comparative)
Preparation of glyoxalated guar according to US 3,297,583
60 g of grounded guar splits (95 wt% passing through 200 mesh) were
sprayed in a mixing vessel with a solution consisting of 1.48 g of a 40
wt% of glyoxal aqueous solution, 2.40 g of 80% acetic acid and 2.21 g of
water. Then the moistened mixture was admixed and heated for one and a
half hours at 60°C in a drying chamber to obtain a powder that after 200
mesh sieving did not differ in appearance and grain size from the starting
grounded guar splits. The sample ( -A) has been tested against the
reference material without glyoxal (i.e. against the non treated ground guar
splits, sample 3-B)
Example 4 (comparative)
60 g of ground guar splits (95 wt% passing through 200 mesh) were
sprayed in a mixing vessel with a solution consisting of 0.048g of a 40
wt% of glyoxal aqueous solution, 2.40g of 80% acetic acid and 3.15g of
water.
Then the moistened mixture was admixed and heated for one and a half
hours at 60°C in a drying chamber to obtain a powder that after 200 mesh
sieving did not differ in appearance and grain size from the starting ground
guar splits. The sample (4-A) has been tested against the reference
material without glyoxal (i.e. against the non treated ground guar splits,
sample 3-B).
Application tests
The application tests were conducted to determine the fast dissolving and
easy dispersibility properties of the glyoxalated ground guar gum
according to the invention.
The methods used in the application test are the following:
DISPERSIBILITY TEST
In a 600 ml beaker add 396 g of tap water and 4 g of sample without
mixing. After 1 minute stir with a magnetic bar (5 cm length) at 200 rpm.
After 1 minute stop the stirring and check visually if lumps or fish eyes
(small translucent lumps) are present.
The Easy Dispersibility (as reported in Table 1) is achieved if the solution
shows no lumps or fish eyes.
FANN VISCOSITY TEST
In a Waring Blender cup add 500 ml of deionized water and 10 g of KC1.
Heat or cool the solution to 24°C.
Start the stirring at 2000 rpm and add in 5 seconds 2.40 g of sample.
Start the chronometer and run the solution for 90 seconds.
Put the solution in a FANN viscometer cup and read the viscosity at 300
rpm after 3 minutes (V3 and 5 minutes from the dissolution.
Keep the solution at 24°C and mix the solution at 600 rpm for 5 seconds
before reading the viscosity at 300 rpm at 30 minutes and 60 minutes after
the dissolution (V =Fann viscosity at 60' mPa*s in Table 1).
In Table 1, the Hydration rate at 3' (%) is calculated as (V3'/VF)*100.
The results show that the glyoxalated ground guar splits according to the
disclosure show excellent hydratability and dispersibility that render them
perfectly suitable as viscosifier for aqueous based fracturing fluids.
On the contrary, the guars of the prior art do not possess the same
characteristics.
While the compositions and methods of this invention have been described
in the terms of the preferred embodiments, it will be apparent to those of
skill in the art that variations may be applied to the process described
herein without departing from the concept and scope of the invention. All
such similar substitutes and modifications apparent to those skilled in the
art are deemed to be within the scope of the invention as it is set out in the
following claims.
Table 1
Claims
. A method of treating a portion of a subterranean formation
comprising:
a. providing an aqueous fracturing fluid comprising dissolved
therein from 0.3 to 3.0 % by weight of a viscosifying agent, wherein
the viscosifying agent is fast dissolving and easy dispersible
glyoxalated, ground guar splits containing from 0.01 to 0.05% by
weight of glyoxal; b) adding a crosslinking composition and placing
the treatment fluid into a portion of a subterranean formation.
2. A method of treating a portion of a subterranean formation
according to claim 1 in which the glyoxalated, ground guar splits
provide in 3 minutes at least 70% of their maximum 0.48 wt% Farm
viscosity in aqueous 2 wt% C1at p from 6.5 to 9 and 300 rpm
and provide 1 wt% aqueous solutions that show no lumps or fish
eyes after stirring at 1,200 rpm for one minute after stirrmg at 1,200
rpm for one minute.
3. A method of treating a portion of a subterranean formation
according to claim 2 in which the glyoxalated, ground guar splits
provide their maximum 0.48 wt% Farm viscosity, which is at least
40 mPa*s, in no more than 60 minutes in aqueous 2 wt% KC1 at pH
from 6.5 to 9 and 300 rpm.
4. A method of treating a portion of a subterranean formation
according to claim 3 in which the glyoxalated, ground guar splits
are obtained by a process comprising the following steps: i) guar
splits or ground guar splits are soaked in 0.3 to 2 parts by weight of
an aqueous solution containing 0.01 to 0.05% by weight of glyoxal
based upon the guar splits, to obtain soaked glyoxalated guar; ii)
without washing the soaked glyoxalated guar , grinding and drying
it to obtain the glyoxalated ground guar splits.
5. A method of treating a portion of a subterranean formation
according to claim 4 in which in step i) ground guar splits are used
that have not been ground before being soaked.
6. A method of treating a portion of a subterranean formation
according to claim 5 in which the guar splits are soaked in from 0.5
to 1.5 parts by weight of water containing from 0.02 to 0.04% by
weight of glyoxal based upon the guar splits.
7. A method of treating a portion of a subterranean formation
according to claim 4 in which in step i) ground guar splits are used
that have been ground before being soaked.
8. A method of treating a portion of a subterranean formation
according to claim 7 in which in step i) the ground guar splits are
soaked in from 0.3 to 0.8 parts by weight of an isopropanol/water
solution containing from 50 to 80% by weight of isopropanol and
from 0.02 to 0.04% by weight of glyoxal, the amount of glyoxal
being based upon the ground guar splits.
9. Process for preparing fast dissolvable and easy dispersible
glyoxalated ground guar splits comprising the following steps: i)
guar splits or ground guar splits are soaked in 0.3 to 2 parts by
weight of an aqueous solution containing 0.01 to 0.05% by weight
of glyoxal based upon the guar splits, to obtain soaked glyoxalated
guar; ii) without washing the soaked glyoxalated guar, grinding and
drying it to obtain the glyoxalated ground guar splits.
0.Process for preparing glyoxalated ground guar splits according to
claim 9 in which in step i) guar splits are used that have not been
being ground before being soaked.
1 .Process for preparing glyoxalated ground guar splits according to
claim 10 in which the guar splits are soaked in from 0.5 to 1.5 parts
by weight of water containing from 0.02 to 0.04% by weight of
glyoxal based upon the guar splits.
12.Process for preparing glyoxalated ground guar splits according to
claim 9 in which in step i) ground guar splits are used that have
been ground before being soaked.
13.Process for preparing glyoxalated ground guar splits according to
claim 12 in which in step i) the ground guar splits are soaked in
from 0.3 to 0.8 parts by weight of an isopropanol/water solution
containing from 50 to 80% by weight of isopropanol and from 0.02
to 0.04% by weight of glyoxal, the amount of glyoxal being based
upon the ground guar splits.
14.Glyoxalated, ground guar splits containing from 0.01 to 0.05 weight
percent of glyoxal that: i) provide in 3 minutes at least 70% of their
maximum 0.48 wt% Farm viscosity in aqueous 2 wt% KC1 at pH
from 6.5 to 9 and 300 rpm; ii) provide 1 wt% aqueous solutions at
that show no lumps or fish eyes after stirring at 1,200 rpm for one
minute; iii) are free from surfactants and are not supported by inert
water insoluble powders.
15. Glyoxalated, ground guar splits according to claim 14 that provide
their maximum 0.48 wt% Fann viscosity, which is at least 40
mPa*s, in no more than 60 minutes in aqueous 2 wt% KC1 at pH
from 6.5 to 9 and 300 rpm.