HARD WATER FOAMING AGENTS AND
METHODS FOR GYPSUM BOARD PRODUCTION
BACKGROUND OF THE INVENTION
The present invention relates to a composition and
method for improved gypsum panel foaming. More particularly, the
present invention relates to an additive and methods for using an
additive for improved gypsum panel foaming. Even more particularly,
the present invention relates to compositions and methods utilizing an
additive to reduce the impact of hard water on gypsum panel foaming.
Gypsum panels, often referred to as gypsum boards,
drywall, wallboard or plasterboard, are typically manufactured by
utilizing a faced wall board as used in dry wall construction. A pre-
generated foam is added to the panel slurry mix; the foam is
generated from a mixture of a foaming agent, air and water in a
suitable foam generating apparatus. The foamed gypsum slurry is
then deposited onto a moving paper or other substrate supported on a
long moving belt. A second substrate may be applied on top of the
slurry to constitute the second face of the gypsum board. Next,, the
sandwich passes through a forming station which determines the width
and thickness of the gypsum board. In continuous operation, the
gypsum slurry begins to set immediately after the board is formed.
Subsequently, the board is cut, dried and bundled into commercially
acceptable lengths.
Water mixed to form the foam of the foamed gypsum
slurry can vary in hardness. Hard water is typically defined as water
that has a relatively high mineral content. In contrast, soft water

contains little or no minerals. The content levels typically consist of
higher levels of calcium and magnesium metal ions in the form of
carbonates, but may include several other metals as well as
bicarbonates and sulfates. Descriptions of the hardness of water
correspond roughly with the ranges of mineral concentrations:

The use of hard water within the foam of the gypsum slurry leads to
low volumes of foam produced and board defects related to unwanted
coalescence of foam cells once the gypsum is set. In some instances,
controlled coalescence to create relatively large foam cells are desired
within the foam. In most instances, however, the use of hard water
results in unpredictable foaming which can limit line speeds and
results in foam cell voids that are much larger than desired. These
large foam voids can translate to recovery and/or quality issues,
including a reduction in the strength or integrity of the wallboard.
Short term stability of foam added to a gypsum slurry is
important in gypsum panel production. Control of this stability controls
board core bubble size and impacts gypsum panel strength. To
control foam stability, soap compositions can be selected or a foam
system blending a binary mixture of soap can be used to increase
bubble sizes and strength. It has been determined that a larger
bubble size provides greater strength to the finished gypsum panel

than smaller bubble sizes. However, excessively large bubble sizes
can be detrimental to the quality of the panel. For this reason, it is
important when developing a surfactant to take into account other
factors which may affect the bubble size in addition to existing soap
blends or a foam system to produce blends of stable and unstable
soaps to create a foam surfactant. For example, process water can
also affect foam stability and in some cases produce a board core with
excessively large foam voids, such is the case in the presence of hard
water. The present invention provides a composition and methods for
using a surfactant composition which provides increased stability and
control to the gypsum slurry over a wider range of process conditions.
The compositions in accordance with the teachings of the present
invention have potential to increase line speed and/or lower board cost
during manufacture.
Compositions contemplated for use in embodiments of
the invention maximize air entrainment and minimize usage in gypsum
panel slurries. In one embodiment, the composition is a surfactant. In
other embodiments, the composition is a blend of soaps, including
stable soaps, unstable soaps and mixtures thereof. An unstable soap
refers to a surfactant of a foaming agent which may produce copious
volumes of foam and becomes unstable upon contact with the gypsum
slurries. A stable soap refers to a soap developed to maximize air
entrainment and minimize usage in gypsum board slurries.
Compositions utilizing blends of the stable and the unstable soaps are
known, such as in U.S. Patent No. 5,643,510 issued to Sucech,
incorporated herein by reference, which blends compositions of the
stable and the unstable soaps for a desired bubble size and shape.
In some cases, other ingredients in the gypsum slurries
can cause excessively large voids. For example, the use of hard

water as process water can give rise to an excessively large foam core
bubble size and soap adjustments (even to 100% stable soap), which
are unable to reduce core bubble size to optimum levels. Thus, there
are instances in which simply using more of the stable foaming agents
(such as surfactants) will not be sufficient to adjust the bubble size. To
establish quality and control, productions lines may be resort to slower
speed, reformulation and/or higher board manufacturing costs.
BRIEF SUMMARY OF THE INVENTION
In accordance with one embodiment, a gypsum slurry is
provided. The gypsum slurry is formed from a calcined gypsum and
water. A foam is added to the gypsum slurry. The foam includes
water, dispersed air and a surfactant, where the surfactant is made of
a distribution of varying alkyl chain lengths including about 20% to
about 60% C8 chains; about 20% to about 60% C10 chains; about
14% to about 36% C12 chains and about 2% to about 20% C14
chains in the hydrophobic portion and a hydrophilic portion having
about 0.2 to 3.0 ethoxy groups.
In accordance with an embodiment of the invention, a
composition for stabilizing foam in a gypsum slurry in the presence of,
hard water is provided. The composition includes an alky! ethoxy
sulfate. The alkyl ethoxy sulfate has a hydrophilic portion including
about 0.2 to about 3.0 ethoxy groups. The alkyl ethoxy sulfate also
has a hydrophobic portion including a distribution of alkyl chain lengths
including about 20% to about 60% C8 chains, about 20% to about
60% C10 chains, about 14% to about 36% C12 chains and about 2%
to about 20% C14 chains.
In accordance with another embodiment of the invention,
a method for forming a gypsum slurry in the presence of hard water is

provided. The method includes mixing a calcined gypsum with water
to form a gypsum slurry. A foam is then added, where the foam has
stability is hard water. The foam includes water, air and a surfactant.
It is contemplated that the calcined gypsum may be mixed with hard
water or that the foam may include hard water or that both instances
will include hard water. The surfactant includes a hydrophilic portion
including about 0.2 to about 3.0 ethoxy groups. The surfactant also
includes a hydrophobic portion including a distribution of alkyl chain
lengths including about 20% to about 60% C8 chains, about 20% to
about 60% C10 chains, about 14% to about 36% C12 chains and
about 2% to about 20% C14 chains.
In accordance with still another embodiment of the
present invention, a gypsum panel formed in the presence of hard
water is provided. The gypsum panel includes a calcined gypsum and
water to be mixed with the calcined gypsum to form a gypsum slurry.
A foam is added to the gypsum slurry. The foam, which is stable in
the presence of hard water, is formed by combining water, air and a
surfactant. A hydrophilic portion of the surfactant is provided and
includes about 0.2 to about 3.0 ethoxy groups. The surfactant also
includes a hydrophobic portion that has a distribution of alkyl chain
lengths including about 20% to about 60% C8 chains, about 20% to
about 60% C10 chains, about 14% to about 36% C12 chains and
about 2% to about 20% C14 chains. A front face and a back face are
also included in the gypsum panel. The foamed gypsum slurry is
allowed to set between each of the front and back faces. Once set,
the gypsum panel can be processed for finishing.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a SITA foam tester utilized for foam
testing in accordance with an embodiment of the invention;
FIG. 2 illustrates the foam test results using the SITA
tester of FIG. 1 in accordance with an embodiment of the invention;
FIG. 3 illustrates foam generation test results for soap
blends in de-ionized water and hard water samples in accordance with
an embodiment of the invention;
FIG. 4 illustrates foam decay curves for stabilizers in de-
ionized water and hard water samples in accordance with an
embodiment of the invention;
FIG. 5 shows board core samples showing the impact of
soap stabilizers on resulting foam bubble size in accordance with an
embodiment of the invention;
FIG. 6 shows a cross-section of the control sample set
forth in Example 2 in accordance with an embodiment of the invention;
FIG. 7 shows an image analysis routine demonstrating
the voids found in the control sample in accordance with an
embodiment of the invention;
FIG. 8 shows a cross-section of Trial 1C set forth in
Example 2, in accordance with an embodiment of the invention;
FIG. 9 shows an image analysis routine demonstrating
the voids found in Trial 1C, in accordance with an embodiment of the
invention;
FIG. 10 shows a cross-section of Trial 2C set forth in
Example 2, in accordance with an embodiment of the invention;
FIG. 11 shows an image analysis routine demonstrating
the voids found in Trial 2C, in accordance with an embodiment of the
invention;

FIG. 12 shows a cross-section of Trial 3C set forth in
Example 2, in accordance with an embodiment of the invention;
FIG. 13 shows an image analysis routine demonstrating
the voids found in Trial 3C, in accordance with an embodiment of the
invention; and
FIG. 14 demonstrates a graph depicting the air void
distributions of the four samples of Example 2, showing volume
percent as a function of air void diameter (in millimeters), in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
It is thus contemplated by embodiments of the present
invention to mix an additive, such as a foaming agent or surfactant,
into a foam having excessively large voids to provide stability to the
foam by reducing the number and size of the voids to a desired
amount. It is further contemplated that the foam stability in the
presence of hard water is applicable in any number of applications,
including gypsum boards, gypsum panels, drywall, wallboard or
plasterboard for a number of different uses including drywall and
ceiling tile. It is also contemplated that the hard water may be present
in the gypsum slurry or in the foam or in both. Other applications of
the present invention include those that would be appreciated by those
of ordinary skill of art.
Liquid foams are made wherever gases and liquids are
mixed. Three elements are needed to form liquid foams, including a
liquid, which is typically soft water, distributed air or gas, which may be
added using an air/foam generator, usually from a foam generator,
and a surfactant, such as soap. A stable foam is formed as surfactant
molecules adsorption on a liquid/air interface. The packing state of the

molecules contributes to the stability of the foam. Indeed, there are
many factors that cause instability of the foam, including, but not
limited to, drainage, coarsening and film rupture. Drainage will
typically occur into the Plateau border channels until an equilibrium
state is reached. Coarsening occurs when gas diffuses through
bubbles and some bubbles grow larger while other bubbles tend to
shrink and disappear. The net result of this process is that the
average bubble size becomes larger (grows) over time. In addition,
film rupture can occur when the foam film (structure) gets too thin and
weak. The foam is thus susceptible to collapsing and thereby
vanishing with the wash.
When surfactant molecules collect at that the water/air
interface, however, the water surface tension will typically be reduced.
Pure water surface tension is typically about 72 mN/m. The ability of a
surfactant to perform as a foaming agent depends in part on its
effectiveness at reducing the surface tension of the solution. A lower
surface tension typically produces smaller and more uniform bubbles.
The surface tension measurement of mixing two soaps typically results
in that the combination of soaps will typically have a lower surface
tension than does the single soap solution. When compositions in
accordance with the present invention include blends of stable and
unstable soaps, ratios of the stable soap to the unstable soap
including 9:1, 4:1, 3:1 and 2.3:1 are contemplated for use with
embodiments of the present invention.
In certain instances, however, for example with
ammonium laureth sulfate (Steol CA-330), from Stepan Company,
there is a point where the surface tension does not significantly
change. Ammonium laureth sulfate as used herein consists of both
C12 and C14 alkyl chain lengths at the hydrophobic portion and 3

ethoxy groups at the hydrophilic portion. The ratio within the
ammonium laureth sulfate is about 80% C12 chain lengths and about
20% C14 chain lengths. The concentration of stock CA-330 soap
used herein is about 28%. Since the surface tension does not change
significantly, the ability of ammonium laureth sulfate to act as a
surfactant or foaming agent also decreases after an increase in the
amount per weight. In the example of ammonium laureth sulfate,
following an increase of about 40%, there is very little change in the
surface tension.
In one embodiment, it is desired to utilize a composition
that includes a blend of both the stable and the unstable soap.
Although a blend of soaps is described hereto, it is to be understood
that one soap may be used having a similar alkyl chain length
distribution as the blends of soaps described. Additionally and
alternatively, it is contemplated that more than two soaps may be
blended together to achieve the desired alkyl chain length distribution.
The current stable soaps used in production of gypsum board are
typically characterized by having a soap composition with a relatively
narrow alkyl chain length of about C8-C10 or C10-C12 and an ethoxy
chain length of about 0.2 to 3.5.
Examples include Hyonic. PFM from Geo Specialty
Chemicals, FA 403 from Stepan Chemicals or Thatcher TF from
Thatcher Chemical company. In the process of determining the
desired bubble size, these soaps are preferably blended with a C10-
C12 alkyl sulfate with zero ethoxy groups (the unstable soap in the
gypsum slurry). This blending operation typically produces the soap
and the resulting foam which becomes unstable in the gypsum slurries
and the foam coalesces to produce relatively larger bubbles in the
gypsum panel core and increases the panel strength.

When the gypsum slurry is made in the presence of hard
process water, the foam typically produces excessively large bubbles.
Further, the foam resists attempts to reduce the bubble size with the
addition of components that tend to make foams more stable, such as
stable surfactants in the foaming agent. Therefore, it is desired to
reduce the bubble size of foam made with hard process water while
using a blend of soaps to vary the bubble size. A balance between the
large bubble size and the smaller bubble size is desired for the
physical properties of the finished gypsum panel product.
In accordance with an embodiment of the present
invention, the addition of a C12 - C14 alkyl-ether sulfate with an
average ethoxy chain length of three has been found to stabilize foam
even in the presence of hard water. For purposes of this application
only, the phrase "stabilize the foam" refers to the reduction of
excessively large voids in the gypsum slurry as a result of the hard
water in the slurry mixture. It is also contemplated that hard water
may be utilized only in the foam water. Additionally and alternatively, it
is contemplated that hard water may present in both the slurry mixture
and the foam water in any combination as would be appreciated by
those skilled in the art. The addition of the C12 - C14 alkyl-ether
sulfate additive balances the excessively large voids. This additive
can be used in amounts of about 40% and higher based on the total
weight of the foaming agents.
In accordance with the present invention, compositions
to stabilize foam in the presence of hard water include a hydrophobic
portion and a hydrophilic portion. These compositions affect foam
generation as well as foam decay. The hydrophilic portion includes
about 0.2 to 3.5 ethoxy groups and more preferably 2.5 to 3.0 ethoxy
groups. The hydrophilic portion of the composition provides good

solubility of the composition. Compositions in accordance with the
present invention also preferably include a hydrophobic portion, which
will typically include a distribution of alkyl chain lengths. The
hydrophobic portion of the composition provides good stabilization. As
described above, a number of alkyl chain lengths are described in the
soaps and blends of soaps provide a distribution of alkyl chain lengths.
It is also contemplated that a distribution of alkyl chain lengths can be
achieved without blending soaps.
Other gypsum slurry additives, such as starches,
polycarboxylate ether dispersants or naphthelene sulfonate, also
impact the gypsum board foaming and produce larger foam core
bubbles. In some cases, the foamed core bubble size is excessively
large and the soap composition must be adjusted to reduce the bubble
size for optimum gypsum board processing and quality.
In accordance with embodiments of the present
invention, the addition of a C12-C14 alkyl-ether sulfate with an
average ethoxy chain length of three (such as Steol CA 460 soap and
CA 330 soap from Stepan Chemicals in which the alkyl chain is
approximately 80% C12) effectively stabilize foaming in hard water.
CA 460 soap as used herein consists of both C12 and C14 alkyl chain
lengths at the hydrophobic portion and 3 ethoxy groups at the
hydrophilic portion. The ratio within the CA 460 soap is about 80%
C12 chain lengths and about 20% C14 chain lengths. The
concentration of stock CA 460 soap used herein is about 60%. The
improved stability typically increases with addition levels up to about
35% of the C12-C14 alkyl-ether sulfate. Above about 40% addition of
the C12-C14 alkyl-ether sulfate, it has been observed that the stability
in the presence of hard water diminishes.

In accordance with an embodiment of the present
invention, a method is provided for forming a gypsum slurry in the
presence of hard water. The method includes mixing a calcined
gypsum with water to form a gypsum slurry. It is contemplated that in
certain embodiments of the invention, the water used to mix with the
calcined gypsum may be hard water.
Once the gypsum slurry is formed, foam is added to the
gypsum slurry. The foam added preferably is stable in the presence of
hard water. The foam itself is formed by combining water, air and a
surfactant. It is contemplated that in certain embodiments of the
invention, the water used to form the foam may be hard water. The
foam itself can be created as would conventional foam as would be
appreciated by those skilled in the art. The surfactant used, however,
will vary in accordance with the present invention. Surfactants, or alkyl
ethoxy sulfates, for use in accordance with the present invention
preferably include a hydrophilic portion and a hydrophobic portion.
While the hydrophilic portion provides good solubility, the hydrophobic
portion provides good stabilization.
Thus, utilizing a hydrophilic portion having good solubility
is preferred. For example, the use of about about 0.2 to 3.5 ethoxy
groups and more preferably 2,5 to 3.0 ethoxy groups has been shown
to provide the desired solubility. In addition, the use of a distribution of
alkyl chain lengths in the hydrophobic portion of the surfactant has
been shown to provide good stability. For example, it has been
determined that surfactants including distributions of alkyl chain
lengths of C8, C10, C12 and C14 are preferred. More particularly,
about 10% to about 80% C8 chains; about 10% to about 80% C10
chains; about 10% to about 40% C12 chains and about 2% to about
15% C14 chains. Preferably, an alkyl distribution for surfactants in

accordance with the present invention include about 20% to about
60% C8 chains; about 20% to about 60% C10 chains; about 14% to
about 36% C12 chains and about 2% to about 20% C14 chains.
It is contemplated that surfactants in accordance with the
present invention may be pre-blended and may be the result of
blending two or more previously existing soaps. It is also
contemplated that the surfactants in accordance with the present
invention may be formed without blending existing soaps, but by
manufacturing the specific soap needed. This may depend on the
application of the surfactant as would be appreciated by those skilled
in the art.
It is also contemplated that when forming the gypsum
slurry as described above, an additive may be mixed. Additives to be
used in accordance with the present invention preferably assist in
forming larger foam core bubbles. It is contemplated, however, that
any additive may be used as would be appreciated by those skilled in
the art. Preferable additives include starches, polycarboxylate ether
dispersants, naphthalene sulfonate and mixtures thereof.
Once the foam has been stabilized within the gypsum
slurry, it is contemplated that a gypsum panel may be formed by
placing a front facing paper and a back facing paper and then finished
as would be known by those of ordinary skill.
EXAMPLE 1
Tests examining foam stability were conducted with de-
ionized water and water obtained from a "hard" water source. The
hard water source in this instance was pumped from a gypsum mine

and was saturated with calcium and sulfate. An analysis of the water
is shown below in Table 1:

Testing was conducted using a SITA foam tester in
which soaps and soap blends were mixed with de-ionized water or the
hard water sample. With the SITA foam tester, as shown in FIG. 1,
the amount of foam generated with increasing agitation can be
measured. Once fully agitated, foam volume measurements continue
and foam decay is measured. Using both foam generation and decay
measurements, performance of soaps and soap blends can be
determined.
As FIG.1 demonstrates, the SITA tester 100 utilizes a
sample liquid in found in the sample liquid reserve 102. The sample
liquid enters into the double wall sampling vessel 104. which includes
a thermostat. Once inside the sampling vessel 104, the rotor 106 will
activate in order to begin foam generation. The amount of foam being
generated is measured by the sensor unit 108, which preferably
includes needle detectors. Following the generation of foam, foam
decay is measured utilizing the same sensor unit 108. A spray ring
110 automatically cleans the sampling vessel 104 utilizing a cleaning
solution/water from the cleaning solution/water vessel 112. Once
cleaned, the cleaning solution/water is collected at the bottom of the
foam tester in the collector 114.

The surface tension of soap and mixtures thereof in both
de-ionized water and the hard water sample were also measured
using a Kruss Tensiometer Model K12 Mk6. Other means for testing
the surface tension may be used as would be appreciated by those
skilled in the art. A decrease in surface tension correlates to an
improvement in foaming.
The additives were compared and analyzed for their
ability to stabilize foam in the presence of hard water. The soaps and
additives utilized included: Hyonic PFM-33 soap (Ethoxylated sulfate,
ammonium salts, alcohols), from Geo Specialty Chemicals, Inc.; Steol
CA-460 soap, 60% solids (ammonium laureth sulfate, 3 ethoxy
groups), from Stepan Company; Steol CA-330 soap, 28% solids
(ammonium laureth sulfate, 3 ethoxy groups), from Stepan Company;
and Aromox C/12-W soap (dihydroxyethyl cocamine oxide), from Akzo
Nobel.
PFM-33 soap is a stable soap for purposes of the
present application. PFM-33 soap includes C6 to C12 alkyl chain
lengths. The PFM-33 soap solution used herein is provided for in
about a 33% concentration solution. Soap blends in this example •
were prepared by adding soap stabilizers (Steol CA-460 soap; Steol
CA-330 soap and Aromox C/12-W soap) to make a resulting soap with
about 10%, 20% and 30% concentration of the stabilizer. Soap
solutions for use in the present example were prepared by blending
0.4 grams of soap with 800 grams of water (either de-ionized water or
the hard water sample), which was then added to the SITA tester.
With the SITA tester, both foam generation and foam
decay were measured. The results from the foam generation tests are
shown in FIG. 2. CA-330 soap and CA-460 soap showed significantly
increased foam generation in the hard water sample as compared to

the PFM-33 soap or other soap mixtures. CA-330 soap and CA-460
soap are similar soaps that differ primarily in the percent solid content
(concentration). Based on the higher foam generation, further testing
concentrated on soap blends with CA-330 soap and CA-460 soap.
The foam decay tests of Figure 2 utilized the following combinations:

Foam volume generated with the stabilizer additive in
hard water sample is higher than without the stabilizer additive. Foam
decay results are shown in FIG. 4, with particular emphasis in foam
breakdown within the first minute of measurement.
Surface tension measurements are shown below in
Table 3. Foam generation results for CA-460 soap and CA-330 soap
blends at about 10%, 20% and 30% concentrations in de-ionized and
hard water samples are shown in FIG. 3. As shown, surface tension is
minimized around about 20% soap stabilizer to PFM-33 soap. The
maximum soap stability corresponds with the lowest surface tension.
Based on this result, soaps containing about 20% stabilizer additive
should perform best in hard water conditions.


EXAMPLE 2
A second trial was set up for the hard water sample
using CA-330 soap with a current stable soap (FA-403 soap). The FA-
403 soap includes both C8 and C10 alkyl chain lengths for the
hydrophobic portion of the composition, having about 40% C8 chain
lengths and about 60% C10 chain lengths. CA-330 soap was utilized
since it has percent solids that are similar to other soaps typically used
in plants. A blend of CA-460 soap with soaps typically used in plants
forms a gei upon mixing the soap unless alcohoi is added to prevent
gel formation. It is to be understood that even though the present
examples are described as blends of soaps, a single soap having a
similar alkyl chain length distribution can be used. Even in instances
where sufficient alcohol was added, the potential for gel formation
exists upon contact with other soap having specific bubble sizes
during processing.

Soaps for trials were prepared one day prior to the
testing. Three 20 pound batches of soap were, for example, blended
with a CA-330 soap concentration of about 10%, 20% and 30%.
The trial was conducted on ½" SHEETROCK® brand
building panels. At the beginning, the plant was running at a 50%
blend of soaps (50% FA-403 soap and 50% Polystep B25 soap). The
Polystep B25 soap composition contains both C10 and C12 alkyl chain
lengths. More particularly, the Polystep B25 soap composition
includes about 90% C10 chain lengths and about 10% C12 chain
lengths. The Polystep B25 soap composition used herein was about a
38% concentration composition. For this trial, there were no changes
to the operating conditions or formulation. FA-403 soap in the mixture
was replaced with the test soap. The soaps tested included:

Switching of soaps for each condition had no noticeable effect on
operation. Slumps were taken to monitor the core bubble size during
the trial.
Naphthalene sulfonate (a dispersant), gypset starch and
soap blends of specified bubble size can all be used in the formulation
to increase core bubble size (even in plants where water is not an
issue). Since the trial was aimed at reducing or eliminating the impact
of hard water on foam stability, a best decrease in bubble size with the
addition of the foam stabilizer additive was desired. As the percentage

of stabilizing soap increased, the core bubble size decreased. The
bubble size in the board samples are pictured in FIG. 5. To measure
the average bubble size and size distribution, a Clemex Vision Image
Analyzer was used, as set forth in Table 5:

The cross-sections analyzed for the control sample is shown in FIG. 6.
FIG. 7 demonstrates an image analysis routine of the control sample
showing the voids "found." FIG. 8 shows the cross-section of Trial 1C,
with the image analysis routine of Trial 1C at FIG. 9. The cross
section of Trial 2C is shown at FIG. 10, while the image analysis
routine demonstrating the voids "found" is shown at FIG. 11. The
cross section of Trial 3C is shown at FIG. 12, while the image analysis
routine demonstrating the voids "found" is shown at FIG. 13. FIG. 14
is a chart showing the Air Void Volume % as a function of the air void
diameter {measured in millimeters)
While a particular embodiment of the present
compositions and methods for stabilizing foam in hard water have
been described herein, it will be appreciated by those skilled in the art
that changes and modifications may be made thereto without
departing from the invention in its broader aspects and as set forth in
the following claims.

WHAT IS CLAIMED IS:
1. A composition for stabilizing foam in a gypsum
slurry in the presence of hard water having a minimum of about 40
mg/L calcium, comprising an alkyl ethoxy sulfate including a
hydrophilic portion including about 0.2 to about 3.0 ethoxy groups and
a hydrophobic portion including a distribution of alkyl chain lengths
including about 20% to about 60% C8 chains; about 20% to about
60% C10 chains; about 14% to about 36% C12 chains and about 2%
to about 20% C14 chains.
2. The composition of claim 1 wherein said alkyl
ethoxy sulfate is a pre-blended soap.
3. The composition of claim 1 wherein said alkyl
ethoxy sulfate is a blend of more than one soap.
4. A method for forming a gypsum slurry in the
presence of hard water, the method comprising the steps of:
mixing a calcined gypsum with water to form a gypsum
slurry; and
adding a foam having stability in hard water, wherein
said foam includes water, air and a surfactant, wherein said surfactant
includes a hydrophilic portion including about 0.2 to about 3.0 ethoxy
groups and a hydrophobic portion including a distribution of alkyl chain
lengths including about 20% to about 60% C8 chains; about 20% to
about 60% C10 chains; about 14% to about 36% C12 chains and
about 2% to about 20% C14 chains.

5. The method of claim 4, wherein said surfactant is
a pre-blended soap.
6. The method of claim 4, wherein forming said
gypsum slurry further includes adding an additive; wherein said
additive assists in forming larger foam core bubbles.
7. The method of claim 6, wherein said additive
includes starches, polycarboxylate ether dispersants, naphthalene
sulfonate or mixtures thereof.
8. The method of claim 4 wherein the water added to
the calcined gypsum to form a gypsum slurry is hard water.
9. The method of claim 4 wherein the water
combined with air and the surfactant to form a foam is hard water.
10. A gypsum pane! formed in the presence of hard
water, the panel comprising:
a calcined gypsum
water to be mixed with the calcined gypsum to form a.
gypsum slurry;
a foam added to the gypsum slurry, wherein said foam is
formed by combining water, air and a surfactant, wherein said
surfactant includes a hydrophilic portion including about 0.2 to about
3.0 ethoxy groups and a hydrophobic portion including a distribution of
alkyl chain lengths including about 20% to about 60% C8 chains;
about 20% to about 60% C10 chains; about 14% to about 36% C12

chains and about 2% to about 20% C14 chains; wherein said foam is
stable in the presence of hard water; and
a front face and a back face, wherein said foamed
gypsum slurry is allowed to set between each of the front and back
faces and further wherein once set, the gypsum panel is processed for
finishing.
11. The gypsum panel of claim 10 wherein the water
added to the calcined gypsum to form a gypsum slurry is hard water.
12. The gypsum panel of claim 10 wherein the water
combined with air and the surfactant to form a foam is hard water.
13. The gypsum panel of claim 10 wherein said
surfactant is a pre-blended soap.
14. The gypsum panel of claim 10, wherein said
gypsum slurry further includes an additive; wherein said additive
assists in forming larger foam core bubbles.
15. The gypsum panel of claim 14, wherein said
additive includes starches, polycarboxylate ether dispersants,
naphthalene sulfonate or mixtures thereof.

Compositions and methods for reducing the impact of hard water on gypsum board foaming are provided The
compositions include adding a foam to water and a calcined slurry The foam includes water, dispersed air and a surfactant Surfactants
for use include a hydrophobic portion having an alkyl chain length distribution of about 20% to about 60% C8 chains, about 20% to
about 60% C10 chains, about 14% to about 36% C12 chains and about 2% to about 20% C14 chains and also having a hydrophilic
portion having about 0.2 to 3 0 ethoxy groups.