Note: Descriptions are shown in the official language in which they were submitted.
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CALCIUM ALUMINATE CEMENT AND CALCIUM SULFOALUMINATE CEMENT
CATALYSTS IN GYPSUM PANELS AND USE THEREOF
FIELD OF THE INVENTION
[0001] The present disclosure relates to compositions and methods relating
to water-
resistant gypsum products, typically water-resistant gypsum panels. More
specifically, the
present disclosure uses a novel catalyst that includes calcium aluminate
cement and/or
calcium sulfoaluminate cement.
BACKGROUND OF THE INVENTION
[0002] Many well-known useful construction products contain set
gypsum (calcium
sulfate dihydrate) as a significant, and often as the major, component. For
example, set
gypsum is the major component of paper-faced gypsum boards employed in typical
drywall construction of interior walls. It is also the major component of
gypsum/cellulose
fiber composite boards and products, as described in U.S. Pat. No. 5,320,677.
It is used
primarily as an interior wall and ceiling product. Gypsum has sound-deadening
properties.
It is relatively easily patched or replaced if it becomes damaged. There are a
variety of
decorative finishes that can be applied to the wallboard, including paint and
wallpaper.
Even with all of these advantages, it is still a relatively inexpensive
building material.
[0003] Gypsum is also known as calcium sulfate dihydrate, terra alba or
landplaster.
Synthetic gypsum, which is a byproduct of flue gas desulfurization processes
from power
plants, may also be used. Calcined gypsum is also known as stucco, Plaster of
Paris,
calcium sulfate hemihydrate, calcium sulfate half-hydrate, or calcium sulfate
semihydrate.
When it is mined, raw gypsum is generally found in the dihydrate form. In this
form, there
are approximately two water molecules of water associated with each molecule
of calcium
sulfate.
[0004] In order to produce the hemihydrate form (as in calcined
gypsum), the gypsum
can be calcined to drive off some of the water of hydration by the following
equation:
CaSar 2 H20¨>CaSO4. 1/2 H20+3/2 H20.
[0005] Typical gypsum-based construction products can be made by
mixing the
calcined gypsum with water and permitting it to set by allowing the calcium
sulfate
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hemihydrate to react with water to convert the hemihydrate into a matrix of
interlocking
calcium sulfate dihydrate crystals. As the matrix forms, the product slurry
becomes firm
and holds a desired shape. Excess water must then be removed from the product
by
drying.
[0006] Most gypsum-containing board products are prepared by forming a
mixture of
calcined gypsum (calcium sulfate hemihydrate and/or calcium sulfate anhydrite)
and
water (and other components, as appropriate), casting the mixture into a
desired shaped
mold or onto a surface, and allowing the mixture to harden to form set (i.e.,
rehydrated)
gypsum by reaction of the calcined gypsum with the water to form a matrix of
crystalline
hydrated gypsum (calcium sulfate dihydrate). This is often followed by mild
heating to
drive off the remaining free (unreacted) water to yield a dry product. It is
the desired
hydration of the calcined gypsum that enables the formation of an interlocking
matrix of
set gypsum crystals, thus imparting strength and structure to the gypsum-
containing
product.
[0007] In the absence of additives to prevent it, set gypsum could absorb
up to 50%
of its weight when immersed in water. Boards or panels that absorb water
swell, become
deformed and lose strength. This property is undesirable in products that are
likely to be
exposed to water. In areas such as bathrooms or kitchens, high temperature and
humidity
are common, and walls are likely to be splashed. In such areas, it is
preferable to use a
gypsum board that exhibits water-resistance, thus maintaining strength,
dimensional
stability, and/or health safety.
[0008] Many attempts have been made to improve the water-
resistance of gypsum
products. Various hydrocarbons, including wax, resins and asphalt have been
added to
the slurry in order to impart water resistance to the set product. The use of
siloxanes,
which form silicone resins in gypsum products, to impart water resistance is
well known.
[0009] Although the use of siloxanes in gypsum slurries is a
useful means of imparting
water-resistant to the finished product, there are drawbacks associated with
it. When
added to a slurry to form silicone resins in situ, siloxane polymerization can
be slow. The
siloxane forms a reactive silanol intermediate to yield polymethylsilicic
acid, which cross
links to form the silicone resin. The reaction proceeds slowly, often
continuing after the
gypsum is set and requiring one to two weeks to fully develop water-
resistance. Wallboard
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made using this method must be stored for a time sufficient for the water-
resistance to
develop before the board can be shipped. In some cases, the siloxane may not
polymerize within a reasonable time or it may not polymerize fully. In such
cases, the
water resistance does not develop in the gypsum board to a satisfactory level.
Additionally, failure to polymerize fully leads to using a larger dose of the
siloxane,
increasing the cost of the raw materials.
[0010] Catalysts, such as alkaline earth oxides and hydroxides,
are known to
accelerate the curing reaction of siloxane in a stucco slurry. These catalysts
are relatively
water soluble and elevate the pH of the slurry. High pH can interfere with the
rehydration
of the stucco, and can negatively react with some preferred wallboard
additives Thus,
while the siloxane polymerization is promoted, other considerations make the
use of these
catalysts undesirable.
[0011] Magnesium oxide ("MgO") is known to catalyze siloxane
reactions. However,
if catalysis is at a level sufficient to polymerize the siloxane fully,
undesirable cracking
may result. Light-burned MgO has the activity needed to polymerize siloxane
quickly, but
the activity leads to unwanted side reactions. These side reactions generate
hydrogen,
which cause expansion of the product and cracking of set gypsum. Hard-burned
or dead-
burned MgO has lower reactivity, but results in a less water-resistant
product. Thus, when
MgO is used alone, it is difficult to balance catalyst activity with the
desired extent of
siloxane polymerization.
[0012] There are also certain gypsum sources for which it is very
difficult to drive the
polymerization of siloxane. Gypsum is a complex mixture of calcium sulfate in
various
forms, salts and a variety of aluminates, silicates and aluminosilicates.
Apparently some
gypsum sources include one or more components that suppress the formation of
the
silicone resin. When used with these materials, known catalysts fall short of
the desired
level of water-resistance of less than 5% water absorbance.
[0013] More recently, other catalyst compositions have been
investigated. For
example, US Pat. No. 7,803,226 describes catalyst compositions that include
MgO and
Class C fly ash. The inclusion of Class C fly ash is described as allowing the
use of a
broader selection of MgO sources including hard-burned or light-burned MgO
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[0014] In another example, US Pat. App. Pub. No. 2018/0118940
discloses waterproof
board that is the cured product of an aqueous slurry comprising calcium
sulfate
hemihydrate, a silicone oil, and a carbonate rock mineral as a catalyst. The
carbonate
rock examples disclosed are aragonite (CaCO3), calcite (CaCO3), dolomite
(CaMg(003)2), and light burned dolomite. In addition, the slurry may further
comprise a
basic catalyst, examples of which are limestone, slaked lime, Portland cement,
MgO,
CaO, and CaMg0.
[0015] EP1112986 is another example that discloses increasing the
water resistance
of a gypsum containing material by including a polymerizable siloxane and
Portland
cement as a catalyst in a slurry.
[0016] CN110759693 discloses a water-resistant gypsum board
comprising Plaster of
Paris, modified starch, silicone oil, a silicone oil catalyst, a foaming
agent, water-resistant
mask paper, and water. A disclosed example of the silicon oil catalyst is 325-
mesh
cement, heavy calcium oxide, heavy magnesium oxide, dolomite high-temperature
calcination product, or a mixture thereof.
[0017] While the above-described catalysts may be suitable for siloxane
polymerization to impart water-resistant properties to a gypsum product, the
supply and/or
quality of many are variable. Therefore, there remains a desire for new
catalysts useful in
preparing water-resistant gypsum products.
SUMMARY
[0018] The present disclosure relates to compositions and methods
relating to water-
resistant gypsum products, typically water-resistant gypsum panels, that are
produced
using a novel catalyst that includes calcium aluminate cement and/or calcium
sulfoaluminate cement.
[0019] The present invention provides a gypsum panel having a core
comprising:
interwoven matrices of calcium sulfate dihydrate crystals and a silicone
resin,
wherein the interwoven matrices have dispersed throughout them a siloxane
polymerization catalyst comprising:
(a) 55 wt% to 100 wt% calcium aluminate cement and/or calcium aluminate cement
and
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(b) 0 wt% to 45 wt% and magnesium oxide;
wherein the weight ratio of the siloxane polymerization catalyst to the
calcium
sulfate dihydrate is 0.01-5:100, wherein the gypsum panel comprises at least
50 wt.%
calcium sulfate dihydrate, preferably at least 80 wt.% calcium sulfate
dihydrate. The
5 gypsum panel may have an absence of one or more of fly ash, Portland cement,
limestone, aragonite, calcite, dolomite, and slaked lime. Preferably the
gypsum panel has
an absence of fly ash. Preferably the gypsum panel has an absence of Portland
cement.
The gypsum panel may have an absence of magnesium oxide. The gypsum panel may
have an absence of magnesium hydroxide.
[0020] In its method respects, the present invention provides a method for
producing
the gypsum panel comprising:
making a siloxane emulsion with siloxane and water;
mixing a siloxane polymerization catalyst comprising (a) 55 wt% to 100 wt%
calcium aluminate cement and/or calcium aluminate cement and (b) 0 wt% to 45
wt% and
magnesium oxide with calcium sulfate hemihydrate to form a siloxane
polymerization
catalyst / calcium sulfate hemihydrate mixture, wherein the weight ratio of
the siloxane
polymerization catalyst to the calcium sulfate hemihydrate is 0.01-5:100;
combining the siloxane emulsion with the siloxane polymerization catalyst /
calcium sulfate hemihydrate mixture to prepare an aqueous gypsum slurry
comprising at
least 50 wt.% calcium sulfate hemihydrate on a water free (dry) basis,
preferably at least
80 wt.% calcium sulfate hemihydrate on a water free basis;
shaping the aqueous gypsum slurry and allowing the aqueous gypsum slurry to
set to form a set core of the gypsum panel; and
allowing the siloxane polymerization catalyst to polymerize the siloxane
partially or
fully. The resultant gypsum panel may have a composition according to the
foregoing
non-limiting example of a water-resistant gypsum panel. The aqueous gypsum
slurry may
have an absence of one or more of fly ash, Portland cement, limestone,
aragonite, calcite,
dolomite, and slaked lime. Preferably the aqueous gypsum slurry has an absence
of
Portland cement. The aqueous gypsum slurry may have an absence of magnesium
oxide.
The aqueous gypsum slurry may have an absence of magnesium hydroxide.
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[0021] A siloxane polymerization process comprises mixing a
siloxane with or without
catalyst in the presence of water and allowing the siloxane to cross link and
condense to
form the silicone resin. The addition of the present siloxane polymerization
catalyst makes
the siloxane polymerization take place faster.
[0022] The present invention also provides an aqueous gypsum slurry
composition
comprising:
at least 50 wt.% calcium sulfate hemihydrate on a water free basis, preferably
at
least 80 wt.% calcium sulfate hemihydrate on a water free basis;
a siloxane polymerization catalyst comprising (a) 55 wt% to 100 wt% calcium
aluminate cement and/or calcium aluminate cement and (b) 0 wt% to 45 wt% and
magnesium oxide, wherein the weight ratio of the siloxane polymerization
catalyst to the
calcium sulfate hemihydrate is 0.01-5:100; and
a siloxane emulsion with siloxane and water. The aqueous gypsum slurry may
have an absence of one or more of fly ash Portland cement, limestone,
aragonite, calcite,
dolomite, and slaked lime. Preferably the aqueous gypsum slurry has an absence
of fly
ash. Preferably the aqueous gypsum slurry has an absence of Portland cement.
The
aqueous gypsum slurry may have an absence of magnesium oxide. The aqueous
gypsum
slurry may have an absence of magnesium hydroxide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The following figures are included to illustrate certain
aspects of the present
disclosure, and should not be viewed as exclusive embodiments. The subject
matter
disclosed is capable of considerable modifications, alterations, combinations,
and
equivalents in form and function, as will occur to one having ordinary skill
in the art and
having the benefit of this disclosure.
[0024] FIG. 1 shows a perspective view of a board of the present
invention.
[0025] FIG. 2 shows a top view of a board of the present
invention.
DETAILED DESCRIPTION
[0026] The present disclosure relates to compositions and methods relating
to water-
resistant gypsum products. More specifically, the present disclosure uses a
novel catalyst
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that includes calcium aluminate cement and/or calcium sulfoaluminate cement.
The
catalyst promotes the polymerization of the siloxane to form a highly
crosslinked silicone
resin.
[0027] The gypsum products of the present disclosure may be
produced from slurries
according to Table 1. The resultant gypsum products may have a composition
according
to Table 2.
Table 1: Example Slurry Composition (parts by weight)
Component Broad Preferred
More Preferred
Range Range Range
Calcium Sulfate Hemihydrate (stucco) 100 100
100
Catalyst 0.01-5 0.1-5
0.3-3
Siloxane 0.2-2 0.2-1.5
0.2-1.2
Accelerator 0.1-5 0.5-3.5
0.5-2
Starch 0-2 0-2
0.5-1.5
Set Retarder 0-2 0-1
0-0.5
Dispersant 0.1-2 0.1-1
0.1-0.5
Filler 0-5 0-4
0-3
Other Additives (independently) 0-2 0-2
0-2
Water 50-150 75-125
80-110
Table 2: Example Set Product Composition (parts by weight)
Component Broad Preferred
More Preferred
Range Range
Range
Calcium Sulfate Dihydrate (gypsum) 100 100
100
Catalyst 0.01-5 0.1-5
0.3-3
Silicone Resin (at least partially 0.2-2 0.2-1.5
0.2-1.2
polymerized siloxane)
Accelerator 0.1-5 0.5-3.5
0.5-2
Starch 0-2 0-2
0-1
Set Retarder 0-2 0-1
0.01-0.5
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Dispersant 0.1-2 0.1-1
0.1-0.5
Filler 0-5 0-4
0-3
Other Additives (independently) 0-2 0-2
0-2
[0028] The invention provides a water-resistant gypsum panel by
including silicone
resin in the gypsum panel in an effective amount to improve the water-
resistance of the
panel compared to a gypsum panel of the same composition but not including the
silicone
resin.
[0029] Without being limited by theory, it is believed that water
resistance develops
when the siloxane cures (polymerizes) within the formed gypsum product (e.g.,
wallboard)
to make the silicone resin. The siloxane polymerization reaction proceeds
slowly on its
own, requiring that the gypsum product be stored for a time sufficient to
develop water-
resistance prior to shipping. Siloxane polymerization catalysts are known to
accelerate
the polymerization reaction, thereby reducing or eliminating the time needed
to store
gypsum product as the water-resistance develops. Preferably the invention
catalyzes
siloxane polymerization with an absence of fly ash. Preferably the invention
catalyzes
siloxane polymerization with an absence of Portland cement.
[0030] The invention may catalyze siloxane polymerization with an absence
of low-
alkali cement. The invention may catalyze siloxane polymerization with an
absence of
any cement except calcium aluminate cement and/or calcium sulfoaluminate
cement. The
invention may catalyze siloxane polymerization with an absence of magnesium
oxide
The invention may catalyze siloxane polymerization with an absence of
magnesium
hydroxide. The invention may catalyze siloxane polymerization with an absence
of
calcium silicate hydrate other than any incidentally resulting from use of
calcium
aluminate cement and/or calcium sulfoaluminate.
[0031] Gypsum Board and Method of Preparing
[0032] In a process for manufacturing gypsum-based structures, such
as gypsum
board (gypsum panels) 10 (see FIG. 1) comprising a core of set gypsum-
containing
material, a metered amount of water (called "gauging water") and any other
liquid
components are continuously fed into a slurry mixer. The mixer can be a "pin
mixer" or a
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"pinless mixer" as one skilled in the art would understand. Panel 10 also has
a gypsum
core 12, front facer sheet, 14, and back facer sheet 16 as seen in FIG. 2. The
calcined
gypsum and the other dry ingredients used to make the wallboard are usually
dry blended
and then are continuously fed to the mixer where they are mixed with the
gauging water
for a few seconds to form an aqueous slurry. Foam used to reduce the wallboard
density
may also be added to the mixer. The slurry formed in the mixer is then shaped
into the
article, such as the wall board and then the shaped article is dried.
[0033] In order to obtain the best water resistance, the process
uniformly distributes
the siloxane in the gypsum slurry. The siloxane may be mixed with water to
form a
siloxane emulsion and then the siloxane emulsion may be added into the mixer.
Because
a relatively small amount of siloxane is used, it has been found that the most
uniform
distribution of the siloxane is provided when the siloxane, in the form of an
emulsion, is
mixed with the gauging water. This uniformly distributes the siloxane
throughout the
gauging water used to form the gypsum slurry. The gauging water, premixed with
the
siloxane, is mixed with the gypsum and other dry materials in the slurry mixer
to form the
slurry. However, the siloxane can also be directly added into the mixer.
[0034] In manufacture of this gypsum board, the present invention
uses calcium
aluminate cement and/or calcium sulfoaluminate cement as the siloxane
polymerization
catalyst to polymerize the siloxanes to impart water-resistance properties to
the gypsum
panels. More specifically, the catalyst of the present invention comprises 55-
100 wt%
calcium aluminate cement, 0-45 wt% and MgO and no fly ash. Generally the board
10
(FIG) has a thickness T of 0.25 to 1 inch.
[0035] In other respects, the composition and method can be
practiced with the same
components and in the same manner as the corresponding compositions and
methods
for preparing mold resistant panels, glass-mat gypsum panels such as those
disclosed
by US 6,893,752 and US 7,892,472, both to Veeramasuneni et al, as well as US
7,803,226 to Wang et al., or water resistant panels as disclosed by US
8,070,895 to
Engbrecht et al. For instance, other aspects of preparing an aqueous siloxane
emulsion
and combining the emulsion with a cementitious slurry are as described in US
Pat.
7,803,226 to Wang et al., herein incorporated by reference_
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[0036] Briefly, a method for preparing a gypsum panel, e.g.
wallboard, may include
mixing an aqueous gypsum slurry described herein (e.g., according to Table 1).
This
includes moving the powdered stucco toward a slurry mixer. Prior to entry into
the slurry
mixer, dry additives (e.g., starches, set accelerators, and the like) are
added to the
5 powdered stucco. Some additives may be added directly to the mixer via a
separate line.
For most additives, there is no criticality regarding placing the additives in
the slurry, and
said additives may be added using whatever equipment or method is convenient.
[0037] A silicone polymerization catalyst comprising (a) calcium
aluminate cement
and/or calcium sulfoaluminate cement and (b) optionally MgO, which promotes
the
10 polymerization of the silicone to form a highly crosslinked silicone
resin is also added to
the gypsum slurry. The silicone polymerization catalyst is added typically
with the dry
ingredients fed to the slurry mixer. The silicone polymerization catalyst may
alternatively
be added directly to the mixer via a separate line.
[0038] Then, the polymerizable siloxane is added to the aqueous
gypsum slurry.
Preferably the siloxane is added in the form of an emulsion or stable
suspension. The
siloxane emulsion is preferably added to the gauging water before adding the
gauging
water to the slurry to provide sufficient time for the siloxane emulsion to
thoroughly mix
with water used to form the slurry.
[0039] Then the aqueous gypsum slurry is optionally foamed to
decrease the product
density. Foam is generated by combining foaming agent and water. The foam may
be
injected into the moving slurry after it exits from the mixer through a hose
or chute. Other
methods of injecting foam into the slurry may be used, as one skilled in the
art may
appreciate. When the foam and the slurry have been brought together, the
resulting
foamed slurry (or just the slurry if foaming is not performed) moves toward
and is poured
onto a conveyor lined with the first sheet of facing material. Another sheet
of facing
material is placed on top of the slurry, forming a sandwich with the gypsum
slurry between
the two facing materials. Thus, the method of preparing the gypsum board
comprises
contacting the gypsum slurry with the first and second facer sheets, wherein
the gypsum
slurry is disposed between the first facer sheet and the second facer sheet.
The invention
encompasses making the gypsum board with paper facer sheets on front and/or
back
faces of the board. In the alternative, the invention also encompasses making
the gypsum
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board with fibrous mat facer sheets on the front and/or back faces of the
board. Non-
limiting examples of suitable fibers include glass fibers, polyamide fibers,
polyaramid
fibers, polypropylene fibers, polyester fibers (e.g., polyethylene
terephthalate (PET)),
polyvinyl alcohol (PVOH), polyvinyl acetate (PVAc), cellulosic fibers (e.g.,
cotton, rayon,
etc.), and the like, as well as combinations thereof.
[0040] The gypsum slurry is then shaped and dried on the facing
material into a panel
under conditions that promote the polymerization of the siloxane to form the
highly
crosslinked silicone resin and allow the gypsum slurry to set, thereby forming
a core of
the wallboard; and polymerizing the siloxane. For instance, the sandwich is
fed to a
forming plate, the height of which determines the thickness of the board. Next
the
continuous sandwich is cut into appropriate lengths at the cutting knife,
usually eight feet
to twelve feet, to yield boards. Then boards are moved to a kiln for drying.
Temperatures
in the kiln typically range from 450 F to 550 F, but other temperatures may be
used
depending on manufacturing conditions as one skilled in the art would
appreciate.
[0041] The gypsum products described herein may be water-resistant gypsum-
based
wall board and ceiling board products, e.g., gypsum boards, reinforced gypsum
composite boards, or fibrous mat-faced gypsum boards.
[0042] When the slurry sets, the core may include interwoven
matrices of calcium
sulfate dihydrate crystals and a silicone resin, where the interwoven matrices
have
dispersed throughout them the catalyst comprising (a) the cement selected from
calcium
aluminate cement and/or calcium sulfoaluminate cement and (b) magnesium oxide,
preferably with an absence of fly ash.
[0043] The gypsum products described herein may have a water
absorption according
to ASTM 01396/C1396M-17 , Standard Specification for Gypsum Board, of 10 wt. %
or
less, or 5 wt. % or less. Typically glass mat gypsum panels have a water
absorption
according to ASTM C1396/C1396M-17 of wt.% is 10 wt.% or less. Typically gypsum
panels have a water absorption according to ASTM C1396/C1396M-17 of wt.% is 5
wt.
% or less.
[0044] While not wishing to be bound by theory, it is believed that water
resistance
develops when the siloxane cures within the set gypsum product. The
polymerization
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reaction proceeds slowly on its own, requiring the gypsum product to be stored
for
sufficient time to develop water resistance prior to shipping. The present
catalyst reduces
this time.
[0045] Calcium Sulfate
[0046] Although calcium sulfate, e.g., calcium sulfate
hemihydrate, is a hydraulic
component because it will react with water, it is not considered to be
hydraulic cement for
purposes of this disclosure. Calcined gypsum, also known as calcium
sulfate
hemihydrate or stucco, for use in the gypsum slurries used to make products of
the
invention typically contains beta calcium sulfate hemihydrate from natural or
synthetic
sources. The calcined gypsum may also contain minor amounts of calcium sulfate
anhydrite. The term gypsum slurry encompasses the aqueous slurries with water
and
calcined gypsum (typically calcium sulfate hemihydrate) prior to its setting
and as the
calcined gypsum sets to form set gypsum (calcium sulfate dihydrate).
[0047] The calcium sulfate hemihydrate is at least 50 wt.%, preferably at
least 80 wt.
%, of the ingredients used to make the gypsum product, e.g., gypsum board, on
a dry
(water free) basis. In many gypsum board formulations, calcium sulfate
hemihydrate is at
least 90 wt.% or at least 95 wt.% of the ingredients used to make the gypsum
product,
e.g., gypsum board, on a dry (water free) basis. Thus, the calcium sulfate
hemihydrate is
at least 50 wt.%, preferably at least 80 wt. %, of the ingredients in the
aqueous gypsum
slurry used to make the gypsum product, e.g., gypsum board, on a dry (water
free) basis.
In many gypsum board formulations, calcium sulfate hemihydrate is at least 90
wt.% or
at least 95 wt.% of the ingredients used to make the gypsum product, e.g.,
gypsum board,
on a dry (water free) basis. The method of calcination is not important, and
either alpha
or beta-calcined stucco is suitable. Typically alpha calcium sulfate
hemihydrate is
employed for its yield of set gypsum having relatively high strength. However,
beta
calcium sulfate hemihydrate or a mixture of beta calcium sulfate hemihydrate
and water-
soluble calcium sulfate anhydrite may be employed. Use of calcium sulfate
anhydrite is
also contemplated as an ingredient used to make the gypsum product. However,
calcium
sulfate anhydrite is preferably used in small amounts of less than 20 wt. % of
the
ingredients used to make the gypsum product.
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[0048] The set calcium sulfate dihydrate is at least 50 wt.%,
preferably at least 80 wt.
%, typically at least 90 wt.% or at least 95 wt.% of the gypsum board product.
[0049] Siloxane
[0050] Preferably, the siloxane is generally a fluid linear hydrogen-
modified siloxane,
but it can also be a cyclic hydrogen-modified siloxane. Such siloxanes are
capable of
forming highly crosslinked silicone resins. Such fluids are well known to
those of ordinary
skill in the art and are commercially available and are described in the
patent literature.
Typically, the linear hydrogen modified siloxanes useful in the practice of
the present
disclosure comprise those having a repeating unit of the general formula (I):
__________________________________________ Si¨O ____
(I),
wherein R represents a saturated or unsaturated mono-valent hydrocarbon
radical. In the
preferred embodiments, R represents an alkyl group and most preferably R is a
methyl
group. During polymerization, the terminal groups are removed by condensation
and
siloxane groups are linked together to form the silicone resin. Crosslinking
of the chains
also occurs. The resulting silicone resin imparts water resistance to the
gypsum matrix as
it forms.
[0051] The siloxane may be formed into an emulsion or a stable
suspension with water
as discussed above. A number of siloxane emulsions are contemplated for use in
this
slurry. The gypsum products of the present disclosure are preferably made with
a
solventless methyl hydrogen siloxane fluid.
[0052] Emulsions of siloxane in water are also available for
purchase, but the emulsion
may include emulsifying agents that tend to modify properties of the gypsum
products,
such as the paper bond in wallboard products. Emulsions or stable suspensions
prepared
without the use of emulsifiers are therefore preferred. Preferably, a
suspension is formed
in situ by mixing the siloxane fluid with water as discussed above. The
siloxane
suspension should be stable until it reaches the mixer and should remain well
dispersed
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under the conditions of the slurry and in the presence of the optional
additives. That is,
the siloxane suspension or emulsion should remain stable through the steps in
which the
slurry and gypsum products described herein are formed. Preferably, the
siloxane
suspension or emulsion remains stable for more than 40 minutes. More
preferably, the
siloxane suspension or emulsion remains stable for at least one hour. The term
"emulsion" is intended to include true emulsions and suspensions that are
stable at least
until the stucco is 50% set.
[0053] In a non-limiting example embodiment for producing gypsum
products, at least
a portion of the gauging water is continuously fed to a high shear mixer (not
the slurry
mixer) to form the siloxane emulsion. Preferably this portion of the gauging
water is
continuously fed to a high speed mixer and the two components may be mixed
from a
few seconds to a few minutes until a stable emulsion is formed. The siloxane
fluid may
be metered into the high shear mixer with the water to form the emulsion in
about 1 to 2
seconds. The proportion of water to siloxane is not critical, and a mixture of
25 parts water
to one part siloxane is known to be useful. This emulsion is stable for
several minutes
without the addition of an emulsifier, which should be long enough to mix the
slurry, form
the article, and allow it to start to set. From the high shear mixer, the
emulsion may be
added directly to the slurry mixer where the emulsion is combined with the
remainder of
the gauging water.
[0054] In an alternative method, use of a portion of the gauging water to
form the
emulsion is also contemplated. A slip stream of the gauging water may be
combined with
the siloxane in the high shear mixer. The siloxane emulsion may then
preferably be added
to the gauging water before the slurry is formed to provide sufficient time
for the siloxane
emulsion to thoroughly mix with water used to form the slurry and be uniformly
dispersed
throughout the resulting articles. This facilitates keeping the siloxane
emulsion stable
until it reaches the slurry mixer and keeping the siloxane emulsion stable
through the
steps in which the gypsum based articles are formed as well. This also
facilitates keeping
the siloxane emulsion well dispersed under the conditions of the slurry in the
presence of
the slurry additives, such as accelerators.
[0055] Siloxane polymerization catalyst
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[0056] Siloxane polymerization catalysts of the present
disclosure may comprise (a)
55 wt% to 100 wt% calcium aluminate cement and/or calcium sulfoaluminate
cement and
(b) 0 wt% to 45 wt% MgO, or (a) 65 wt% to 95 wt% calcium aluminate cement
and/or
calcium sulfoaluminate cement and (b) 5 wt% to 35 wt% MgO, or (a) 70 wt% to 90
wt%
5 calcium aluminate cement and/or calcium sulfoaluminate cement and (b) 10
wt% to 30
wt% MgO, or (a) 100 wt% calcium aluminate cement and/or calcium sulfoaluminate
cement. Thus for example, for 100 parts by weight siloxane catalyst, if the
catalyst
comprises 90 wt% calcium aluminate cement and/or calcium sulfoaluminate cement
and
10 wt% MgO, then the catalyst has (a) 90 parts by weight calcium aluminate
cement
10 and/or calcium sulfoaluminate cement and (b) 10 parts by weight MgO
[0057] Siloxane polymerization catalysts of the present
disclosure may consist
essentially of (a) 55 wt% to 100 wt% calcium aluminate cement and/or calcium
sulfoaluminate cement and (b) 0 wt% to 45 wt% MgO, or (a) 65 wt% to 95 wt%
calcium
aluminate cement and/or calcium sulfoaluminate cement and (b) 5 wt% to 35 wt%
MgO,
15 or (a) 70 wt% to 90 wt% calcium aluminate cement and/or calcium
sulfoaluminate cement
and (b) 10 wt% to 30 wt% MgO, or (a) 100 wt% calcium aluminate cement and/or
calcium
sulfoaluminate cement.
[0058] Siloxane polymerization catalysts of the present
disclosure may consist of (a)
55 wt% to 100 wt% calcium aluminate cement and/or calcium sulfoaluminate
cement and
(b) 0 wt% to 45 wt% MgO, or (a) 65 wt% to 95 wt% calcium aluminate cement
and/or
calcium sulfoaluminate cement and (b) 5 wt% to 35 wt% MgO, or (a) 70 wt% to 90
wt%
calcium aluminate cement and/or calcium sulfoaluminate cement and (b) 10 wt%
to 30
wt% MgO, or (a) 100 wt% calcium aluminate cement and/or calcium sulfoaluminate
cement.
[0059] Catalyst of the present disclosure may be free (i.e., comprise 0
wt%) of one or
more of: Portland cement, fly ash, limestone (CaCO3), aragonite (CaCO3),
calcite
(CaCO3), dolomite (CaMg(003)2), and slaked lime (Ca(OH)2). Catalyst of the
present
disclosure may be free of all of: Portland cement, fly ash, limestone (CaCO3),
aragonite
(CaCO3), calcite (CaCO3), dolomite (CaMg(003)2), and slaked lime (Ca(OH)2).
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[0060] In preferred embodiments, there is no other calcium
aluminate cement and/or
calcium sulfoaluminate cement in the methods, compositions, and products of
the
invention except that provided as the catalyst.
[0061] Per 100 parts by weight total calcium aluminate cement
and/or calcium
sulfoaluminate, the weight ratio of calcium aluminate cement to calcium
sulfoaluminate
cement may range from 0:100 to 100:0, typically 10:90 to 90:10, or typically
30:70 to
70:30. If desired, calcium aluminate cement may be used in the absence of
calcium
sulfoaluminate cement. If desired, calcium sulfoaluminate cement may be used
in the
absence of calcium aluminate cement.
[0062] Preferably the methods, compositions and products of the invention
are free of
fly ash. Typically the methods, compositions and products of the invention are
free of
Portland cement.
[0063] Calcium Aluminate Cement
[0064] Calcium aluminate cement (CAC) is a hydraulic cement. Calcium
aluminate
cement is also commonly referred to as aluminous cement or high alumina
cement.
[0065] As used herein, "calcium aluminate cement" refers to a
cement that comprises
at least 30 wt% (e.g., 30 wt% to 85 wt%) A1203. Calcium aluminate cements
preferably
have an alumina content of about 30-80 wt%. Higher purity calcium aluminate
cements
have alumina content that can range as high as about 80 wt%, but these higher
purity
calcium aluminate cements tend to be relatively more expensive. Monocalcium
aluminate
or dodecacalcium hepta-aluminate (12Ca0.7A1203, Ca12A114033 or C12A7) reacts
with
water to yield calcium aluminate hydrates.
[0066] Several calcium aluminate compounds are formed during the
manufacturing
process of calcium aluminate cements. The predominant compound formed is above-
mentioned monocalcium aluminate (CaO = A1203, also referred to as CA), in one
type of
calcium aluminate cement. In another type of calcium aluminate cement, 12Ca0 =
7A1203
also referred to as C12A7 or dodecacalcium hepta-aluminate is formed as the
primary
calcium aluminate reactive phase. The other calcium aluminate and calcium
silicate
compounds that are formed in the production of calcium aluminate cements
include CaO
= 2A1203 also referred as CA2 or calcium dialuminate, dicalcium silicate
(2CaO=Si02,
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called C2S), dicalcium alumina silicate (2Ca0 = A1203. SiO2, called C2AS).
Several other
compounds containing relatively high proportion of iron oxides are also
formed. These
include calcium ferrites such as Ca0 = Fe2O3 or CF and 2Ca0 = Fe2O3 or C2F,
and
calcium alumino-ferrites such as tetracalcium aluminoferrite (4Ca0 = A1203 =
Fe2O3 or
C4AF), 6Ca0 = A1203 = 2Fe203 or C6AF2) and 6Ca0 = 2A1203 = Fe2O3 or C6A2F).
Other
minor constituents present in the calcium aluminate cement include magnesia
(MgO),
titania (TiO2), sulfates and alkalis. The preferred calcium aluminate cements
useful of
some embodiments of the invention can have one or more of the aforementioned
phases.
Calcium aluminate cements having monocalcium aluminate (CaO = A1203 or CA)
and/or
dodecacalcium hepta-aluminate (12Ca0 = 7A1203 or C12A7) as predominant phases
are
particularly preferred of some embodiments of the present invention. Further,
the calcium
aluminate phases can be available in crystalline form and/or amorphous form.
CIMENT
FONDU (or HAC Fondu), SECARO 51, and SECARO 71 are some examples of
commercially available calcium aluminate cements that have the monocalcium
aluminate
(CA) as the primary cement phase. TERNALO EV is an example of commercially
available calcium aluminate cement that has the dodecacalcium hepta-aluminate
(12Ca0
= 7A1203 or 012A7) as the predominant cement phase.
[0067] The surface area of a typical calcium aluminate cement
that is useful in the
invention is greater than about 3,000 cm2/gram, for example about 4,000 to
6,000
cm2/gram as measured by the Blaine surface area method (ASTM C 204).
[0068] Examples of calcium aluminate cement compositions are
provided in Table 3
where other components may be present in impurity level concentrations (e.g.,
less than
0.5 wt%).
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Table 3: Example Calcium Aluminate Cement Compositions (wt%)
Calcium SiO2 A1203 Fe2O3 Ca0 MgO
T102
Aluminate
Cement
General 4 39 16 38 1
2
Purpose
Buff 5 53 2 38 0.1
2
White 3 62 0.4 34 0.1
0.4
Refractory 0.4 80 0 20 0
0.1
[0069] In the above examples, monocalcium aluminate (CaO = A1203)
makes up 46
wt% of the general purpose composition, 70 wt% of the buff composition, 70 wt%
of the
white composition, and 35 wt% of the refractory composition.
[0070] Examples of commercially available calcium aluminate
cements include, but
are not limited to, TERNALO EV (calcium aluminate cement, available from
Kerneos),
and SECARO 71 (calcium aluminate cement, available from Kerneos).
[0071] If calcium sulfoaluminate cement is employed then
compositions and methods
of the present invention may have an absence of calcium aluminate cement.
[0072] Calcium Sulfoaluminate Cement
[0073] Calcium sulfoaluminate cement (CSA) is a hydraulic cement.
As used herein,
"calcium sulfoaluminate cement" refers to cement that has a mineralogical
composition
comprising anhydrous calcium sulfoaluminate (4Ca0 = 3A1203 = CaSO4) as a major
component (e.g., at 50 wt% or more, or at 50 wt% to 80 wt%) and may comprise
minor
components of dicalcium silicate (2Ca0 = SiO2), gypsum (CaSO4
2H20), and
aluminoferrite (4Ca0 = A1203 = Fe2O3).
[0074] CSA are a different class of cements from calcium
aluminate cement or
calcium silicate based hydraulic cements, for example, Portland cement. CSA
are
hydraulic cements based on calcium sulphoaluminate, rather than calcium
aluminates
which are the basis of CAC cement or calcium silicates which are the basis of
Portland
cement. Calcium sulfoaluminate cements are made from clinkers that include
Ye'elimite
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(Ca4(A102)6SO4 or C4A3S) as a primary phase. Other major phases present in the
calcium sulfoaluminate cements may include one or more of the following:
dicalcium
silicate (C2S), tetracalcium aluminoferrite (C4AF), and calcium sulfate (CS).
The
relatively low lime requirement of calcium sulfoaluminate cements compared to
Portland
cement reduces energy consumption and emission of greenhouse gases from cement
production.
In fact, calcium sulfoaluminate cements can be manufactured at
temperatures approximately 200 C lower than Portland cement, thus further
reducing
energy and greenhouse gas emissions. The amount of Ye'elimite phase present in
the
calcium sulfoaluminate cements useful in some embodiments of this invention is
preferably about 20 to about 90 wt% and more preferably 30 to 75 wt%. When
calcium
sulfoaluminate cements are used in the present invention, they may partially
substitute
calcium aluminate cement. The amount of calcium sulfoaluminate cement
substitution in
the composition of some embodiments of the invention can be up to about 49 wt%
of the
aggregated weight of calcium aluminate cement and calcium sulfoaluminate
cement.
[0075]
Examples of calcium sulfoaluminate cement compositions are provided in
Table 4 where other components may be present in impurity level concentrations
(e.g.,
less than 0.5 wt%).
Table 4: Example Calcium Sulfoaluminate Cement Compositions (wt%)
Calcium Sulfoaluminate Cement SiO2 A1203 Fe2O3 CaO MgO
SO3
Ex. 1 8 35 2 41 0
16
In the above example, calcium sulfoaluminate (4Ca0 = 3A1203 = CaSO4) makes up
60
wt% of the cement.
[0076]
Examples of commercially available calcium sulfoaluminate cements
include,
but are not limited to, FASTROCK 500 (calcium sulfoaluminate cement, available
from
Kerneos) and RAPID SET (calcium sulfoaluminate cement, available from CTS
Cement
Manufacturing Corporation).
[0077]
If calcium aluminate cement is employed then compositions and methods
of
the present invention may have an absence of calcium sulfoaluminate cement.
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[0078] Portland Cement
[0079] As opposed to the calcium aluminate cement and the calcium
sulfoaluminate
cement, "Portland cement" is another class of hydraulic cement. As used
herein,
"Portland cement" is a calcium silicate based hydraulic cement. "Portland
cement" refers
5 to a cement that has a mineralogical composition with four chief
components: tricalcium
silicate (3Ca0 = SiO2), dicalcium silicate (2Ca0 = SiO2), tricalcium aluminate
(3Ca0 =
A1203), and tetracalcium aluminoferrite (4Ca0 = AInFe2_n03). The mineralogical
composition of Portland cement includes less than 5 wt% (e.g., 0 wt% to 5 wt%,
preferably
0 wt% to 1 wt%) monocalcium aluminate. ASTM C150/C150M-20 defines Portland
10 cement as "hydraulic cement (cement that not only hardens by reacting
with water but
also forms a water-resistant product) produced by pulverizing clinkers
consisting
essentially of hydraulic calcium silicates, usually containing one or more of
the forms of
calcium sulfate as an inter ground addition." This ASTM C150/C150M-20
specification
covers eight types of Portland cement: type I, type IA, type II, type IIA,
type III, type IIIA,
15 type IV, and type V. The cement covered by this specification shall only
contain the
following ingredients: Portland cement clinker; water or calcium sulfate, or
both;
limestone; processing additions; and air-entraining addition for air-
entraining Portland
cement. Portland cement of each of the eight types has the following chemical
compositions: aluminum oxide, ferric oxide, magnesium oxide, sulfur trioxide,
tricalcium
20 silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium
aluminofernite. As used
herein, "clinkers" are nodules (diameters, about 0.2 - about 1.0 inch [5-25
mm]) of a
sintered material that are produced when a raw mixture of predetermined
composition is
heated to high temperature. ASTM C150/C150M-20 defines the various property
and
chemical composition requirements of different Portland cement types. Examples
of
Portland cement compositions are provided in Table 5 where other components
may be
present in impurity level concentrations (e.g., less than 0.5 wt%).
Compositions and
methods of the present invention may have an absence of calcium
fluoroaluminate
cement.
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Table 5: Example Portland Cement Compositions (wt%)
Portland SiO2 A1203 Fe2O3 Ca0 MgO
SO3
Cement
Type 1 21 5 2 64 3
3
Type 11 22 5 4 64 3
2
Type III 21 5 2 65 3
3
Type IV 24 4 4 62 2
2
Type V 25 3 3 64 2
2
[0080] Fly Ash
[0081] As used herein, "fly ash" refers to a coal combustion
product that is driven out
of coal-fired boilers together with flue gases. ASTM C618-19 defines the
various property
and chemical composition requirements of different fly ash classes. For
example, Class
F fly ash requires a minimum of 70 wt% being a combination of SiO2, A1203, and
Fe2O3,
and Class C fly ash requires a minimum of 50 wt% being a combination of SiO2,
A1203,
and Fe2O3. Examples of fly ash compositions are provided in Table 6 where
other
components may be present in impurity level concentrations (e.g., less than
0.5 wt%).
Table 6: Example Fly Ash Compositions (wt%)
Fly Ash SiO2 A1203 Fe2O3 Ca0 MgO
SO3
Class F 55 26 7 9 2
1
Class C 40 17 6 24 5
3
[0082] Calcium Fluoroaluminate Cement
[0083] As opposed to the calcium aluminate cement and the calcium
sulfoaluminate
cement, "calcium fluroaluminate cement" is another class of hydraulic cement.
As used
herein, Calcium fluoroaluminate cement has the chemical formula 3Ca0.3A1203-
CaF2.
The calcium fluoroaluminate cement is often produced by first mixing lime,
bauxite and
fluorspar in such an amount that the mineral of the resulting product becomes
3Ca0.3Al2
03. CaF2 and then burning the resulting mixture at a temperature of about
1,200 -1,400
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C. Compositions and methods of the present invention may have an absence of
calcium
fluoroaluminate cement.
[0084] Magnesium Oxide
[0085] Regarding the magnesium oxide that may be included in the catalyst
compositions, there are at least three grades of magnesium oxide on the
market,
depending on the calcination temperature. "Dead-burned" magnesium oxide is
calcined
between 1500 C and 2000 C. Use of dead-burned magnesium oxide for siloxane
polymerization is described in US Pat. No. 7,892,472 to Veeramasuneni et al.,
herein
incorporated by reference. Dead-burned magnesium oxide is water-insoluble and
interacts less with other components of the slurry. Dead-burned magnesium
oxide
accelerates curing of the siloxane and, in some cases, causes the siloxane to
cure more
completely. Dead-burned magnesium oxide is commercially available with a
consistent
composition. MAGCHEMO P98-PV (available from Martin Marietta Magnesia
Specialties)
is an example of a dead burned magnesium oxide.
[0086] "Hard-burned" magnesium oxide (also known as magnesia) is
calcined at
temperatures from 1000 C to about 1500 C. It has a narrow range of reactivity,
a high
density, and is normally used in application where slow degradation or
chemical reactivity
is required, such as in animal feed and fertilizer. BAYMAGO 96 (available from
Baymag,
Inc.) and MAGCHEMO 10 (available from Martin Marietta Magnesia Specialties)
are
examples of hard-burned magnesia. A particularly preferred source of dead-
burned
magnesium oxide is BAYMAGO 96. BAYMAGO 96 has a surface area of at least 0.3
m2/g, a loss on ignition of less than 0.1% by weight.
[0087] The third grade is "light-burn" or "caustic" magnesia,
produced by calcining at
temperatures of about 700 C to about 1000 C. This type of magnesia is used in
a wide
range of applications, including plastics, rubber, paper and pulp processing,
steel boiler
additives, adhesives and acid neutralization. Examples of light burned
magnesia include
BAYMAGO 30, BAYMAGO 40, and BAYMAGO 30 (-325 Mesh) (each available from
Baymag, Inc.).
[0088] Additives
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[0089] A number of additives are useful to improve the properties
of the finished
article. Traditional amounts of additives are used. Except as noted, there are
no known
interactions of the catalyst or polysiloxane that interferes with the
additives.
[0090] Example of additives include, but are not limited to,
accelerator, set retarder,
starch, dispersant, foaming agent, filler, biocides, wax emulsions,
thickeners, fire
retardants, and the like, and any combination thereof The amounts of each to
be included
in the slurry and gypsum products described herein are provided in Tables 1
and 2,
respectively.
[0091] Set retarders and/or set accelerators may be added to
modify the rate at which
the calcined gypsum hydration reactions take place. Set retarders (up to about
2 lb./MSF
(9.8 g/m2)) or dry accelerators (up to about 35 lb./MSF (170 g/m2)) may be
added to
modify the rate at which the hydration reactions take place.
[0092] Potassium sulfate is a potential set accelerator. Calcium
sulfate accelerator is
a potential set accelerator, which may comprise 95% calcium sulfate dihydrate
co-ground
with 5% sugar and heated to 250 F (121 C) to caramelize the sugar, made
according to
U.S. Pat. No. 3,573,947. Wet ground accelerator (WGA) is a potential set
accelerator
made according to U.S. Pat. No. 6,409,825. WGA may include an organic
phosphonic
compound, a phosphate-containing compound or mixtures thereof. Heat resistant
accelerator is a potential set accelerator comprising calcium sulfate
dihydrate freshly
ground with sugar at a ratio of about 5 to 25 pounds of sugar per 100 pounds
of calcium
sulfate dihydrate, further described in U.S. Pat. No. 2,078,199. Any one or
more of these
set accelerators may typically be employed in the invention.
[0093] Examples of set retarders include, but are not limited to,
a sodium salt of
polyacrylic acid, an acrylic acid sulfonic acid copolymer, an ammonium salt of
an acrylic
acid sulfonic acid copolymer, a sodium salt of an acrylic acid sulfonic acid
copolymer, a
blend of an acrylic acid polymer with a sulfonic acid copolymer and salts
thereof, and the
like, and any combination thereof. Commercially available retarders include,
but are not
limited, to ACCUMERTm (e.g., ACCUMERTm 9000 (an acrylic acid-based polymer),
ACCUMERTm 9300 (a sodium salt of a polyacrylic acid), ACCUMERTm 9400 (a sodium
salt of polyacrylic acid) each available from Rohm & Haas).
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[0094] Starches, such as a pregelatinized starch, an acid-
modified starch and/or a
non-substituted starch, may be included in slurry and gypsum products
described herein.
The inclusion of starch(es) may increase the strength of the set and dried
gypsum cast
and may minimize or avoid the risk of paper delannination under conditions of
increased
moisture (e.g., with regard to elevated ratios of water to calcined gypsum).
One of ordinary
skill in the art will appreciate methods of pregelatinizing raw starch, such
as, for example,
cooking raw starch in water at temperatures of at least about 185 F (85 C) or
other
methods. Suitable examples of pregelatinized starch include, but are not
limited to, PCF
1000 starch (available from Bunge North America), AMERIKOR 818 (available from
Archer Daniels Midland Company), and HOM PREGEL (available from Archer Daniels
Midland Company), and the like, and any combination thereof.
[0095] Dispersants are used to improve the flowability of the
slurry and reduce the
amount of water used to make the slurry. Any known dispersant is useful,
including, but
are not limited to, polycarboxylates, sulfonated melamines, naphthalene
sulfonate, and
the like, and any combination thereof. A typical naphthalene sulfonate
dispersant is
DAXADO dispersants (available from Dow Chemical). A typical dispersant is a
linear
polycarboxylate dispersant of US Patent No. 10,442,732 to Vilinska et al.
[0096] Some embodiments may employ a foaming agent to yield voids
in the set
gypsum-containing product to provide lighter weight. In these embodiments, any
of the
conventional foaming agents known to be useful in preparing foamed set gypsum
products can be employed. Many such foaming agents are well known and readily
available commercially including the HYONIC line of soaps (available from GEO
Specialty Chemicals). A preferred method for preparing foamed gypsum products
are
disclosed in US Pat. No. 5,683,635, herein incorporated by reference.
[0097] Examples of fillers may include, but are not limited to, paper
fibers, glass fibers,
vermiculite, clay, and the like, and any combination thereof.
[0098] Biocides may be employed to reduce growth of mold, mildew,
or fungi.
Depending on the biocide selected and the intended use for the gypsum
products, the
biocide can be added to the covering, the gypsum core, or both. Examples of
biocides
include, but are not limited to, boric acid, pyrithione salts, copper salts,
and the like, and
any combination thereof. Pyrithione is known by several names, including 2-
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mercaptopyridine-N-oxide; 2-pyridinethio1-1-oxide (CAS Registry No. 1121-31-
9); 1-
hydroxypyridine-2-thione and 1 hydroxy-2(1H)-pyridinethione (CAS Registry No.
1121-
30-8). The sodium derivative (C5H4NOSNa), known as sodium pyrithione (CAS
Registry
No. 3811-73-2), is one embodiment of this salt that is particularly useful.
Pyrithione salts
5 such as sodium OMADINEO or zinc OMADINEO are commercially available from
Lonza.
[0099] Other known additives may be used as needed to modify
specific properties of
the product. For example, a trimetaphosphate compound is added to the slurry
in some
embodiments to enhance the strength of the gypsum product and to improve sag
resistance of the set gypsum. Preferably, the concentration of the
trimetaphosphate
10 compound is from about 0.07% to about 2.0% based on the weight of the
stucco in the
slurry. Gypsum compositions including trimetaphosphate compounds are disclosed
in US
Pat. Nos. 6,342,284 and 6,632,550, both herein incorporated by reference.
Examples of
trimetaphosphate salts include, but are not limited to, sodium, potassium, or
lithium salts
of trimetaphosphate. Typically the polyphosphate is sodium trimetaphosphate.
15 [0100] In another example, wax emulsions are used for water
resistance. If stiffness
is needed, boric acid is commonly added. Additionally, fire retardancy can be
improved
by the addition of vermiculite. These and other known additives are useful in
the present
slurry and gypsum products.
20 [0101] Water
[0102] Water is added to the slurry in any amount that makes a
flowable aqueous
gypsum slurry. The amount of water to be used varies greatly according to the
application
with which it is being used, the exact dispersant being used, the properties
of the stucco,
and the additives being used. The water to stucco ratio ("WSR") for gypsum
products
25 (e.g., wallboard) is typically about 0.2 to about 1.2:1 (preferably
about 0.4 to about 0.9:1)
based on the dry weight of the stucco.
[0103] All documents described herein are incorporated by
reference herein for
purposes of all jurisdictions where such practice is allowed, including any
priority
documents and/or testing procedures to the extent that they are not
inconsistent with this
text. As is apparent from the foregoing general description and the specific
embodiments,
while forms of the disclosure have been illustrated and described, various
modifications
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may be made without departing from the spirit and scope of the disclosure.
Accordingly,
it is not intended that the disclosure be limited thereby. For example, the
compositions
described herein may be free of any component, or composition not expressly
recited or
disclosed herein. Any method may lack any step not recited or disclosed
herein. Likewise,
the term "comprising" is considered synonymous with the term "including."
Whenever a
method, composition, element or group of elements is preceded with the
transitional
phrase "comprising," it is understood that we also contemplate the same
composition or
group of elements with transitional phrases "consisting essentially of,"
"consisting of,"
"selected from the group of consisting of," or "is" preceding the recitation
of the
composition, element, or elements and vice versa
[0104] Unless otherwise indicated, all numbers expressing
quantities of ingredients,
properties such as molecular weight, reaction conditions, and so forth used in
the present
specification and associated claims are to be understood as being modified in
all instances
by the term "about." Accordingly, unless indicated to the contrary, the
numerical
parameters set forth in the following specification and attached claims are
approximations
that may vary depending upon the desired properties sought to be obtained by
the
embodiments of the present invention. At the very least, and not as an attempt
to limit the
application of the doctrine of equivalents to the scope of the claim, each
numerical
parameter should at least be construed in light of the number of reported
significant digits
and by applying ordinary rounding techniques.
[0105] Whenever a numerical range with a lower limit and an upper
limit is disclosed,
any number and any included range falling within the range is specifically
disclosed. In
particular, every range of values (of the form, "from about a to about b," or,
equivalently,
"from approximately a to b," or, equivalently, "from approximately a- b")
disclosed herein
is to be understood to set forth every number and range encompassed within the
broader
range of values. Also, the terms in the claims have their plain, ordinary
meaning unless
otherwise explicitly and clearly defined by the patentee. Moreover, the
indefinite articles
"a" or "an," as used in the claims, are defined herein to mean one or more of
the element
that it introduces.
[0106] One or more illustrative embodiments are presented herein. Not all
features of
a physical implementation are described or shown in this application for the
sake of clarity.
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It is understood that in the development of a physical embodiment of the
present
disclosure, numerous implementation-specific decisions must be made to achieve
the
developer's goals, such as compliance with system-related, business- related,
government-related, and other constraints, which vary by implementation and
from time
to time. While a developer's efforts might be time-consuming, such efforts
would be,
nevertheless, a routine undertaking for one of ordinary skill in the art and
having benefit
of this disclosure.
[0107] To facilitate a better understanding of the embodiments of
the present
invention, the following examples of preferred or representative embodiments
are given.
In no way should the following examples be read to limit, or to define, the
scope of the
invention.
[0108] Clauses of the Invention
[0109] The following clauses disclose various non-limiting
aspects of the invention.
[0110] Clause 1. A gypsum panel having a core comprising: interwoven
matrices of
calcium sulfate dihydrate crystals and a silicone resin, wherein the
interwoven matrices
have dispersed throughout them a siloxane polymerization catalyst comprising:
(a) 55
wt% to 100 wt% calcium aluminate cement and/or calcium aluminate cement and
(b) 0
wt% to 45 wt% magnesium oxide; wherein the weight ratio of the siloxane
polymerization
catalyst to the calcium sulfate dihydrate is 0.01-5:100, wherein the gypsum
panel
comprises at least 50 wt.% calcium sulfate dihydrate, preferably at least 80
wt. % calcium
sulfate dihydrate, typically at least 90 wt.% calcium sulfate dihydrate or
typically at least
95 wt.% calcium sulfate dihydrate. The catalyst is the sole source of calcium
aluminate
cement, calcium sulfoaluminate cement and magnesium oxide in the panel.
[0111] Clause 2. The panel of clause 1, wherein the panel has an absence of
fly ash
and preferably also an absence of Portland cement.
[0112] Clause 3. The panel of any of clauses 1-2 comprising: 100
parts by weight
calcium sulfate dihydrate; 0.01 to 5 parts by weight siloxane polymerization
catalyst,
wherein the catalyst comprises (a) 55 wt% to 100 wt% calcium aluminate cement
and/or
calcium sulfoaluminate cement and (b) 0 wt% to 45 wt% magnesium oxide; 0.2 to
2 parts
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by weight of the silicone resin; 0.1 to 5 parts by weight gypsum setting
accelerator; and
0.1 to 2 parts by weight dispersant.
[0113] Clause 4. The panel of any of clauses 1-3, wherein the
siloxane polymerization
catalyst is present in an amount of 0.1-5 parts by weight per 100 parts by
weight calcium
sulfate dihydrate.
[0114] Clause 5. The panel of any of clauses 1-4, wherein the
siloxane polymerization
catalyst is present in an amount of 0.5-3 parts by weight per 100 parts by
weight calcium
sulfate dihydrate.
[0115] Clause 6. The panel of any of clauses 1-5, wherein the
catalyst consists of (a)
55 wt% to 100 wt% calcium aluminate cement and/or calcium sulfoaluminate
cement and
(b) 0 wt% to 45 wt% magnesium oxide.
[0116] Clause 7. The panel of any of clauses 1-6, wherein the
panel is free of one or
more of: Portland cement, limestone, aragonite, calcite, dolomite, and slaked
lime.
[0117] Clause 8. The panel of any of clauses 1-7, wherein the
catalyst consists of
calcium aluminate cement.
[0118] Clause 9. The panel of any of clauses 1-7, wherein the
catalyst consists of
calcium sulfoaluminate cement.
[0119] Clause 10. The panel of any of clauses 1-7, wherein
the catalyst consists
of calcium aluminate cement and calcium sulfoaluminate cement.
[0120] Clause 11. The panel of any of clauses 1-10, wherein
the panel absorbs
an amount equal to less than 11%, preferably less than 10% of its own weight,
in water
when immersed in water at 70 F for two hours in accordance with ASTM Standard
1396-
17 within 24 hours.
[0121] Clause 12. The panel of any of clauses 1-11, wherein
the core further
comprises an additive selected from the group consisting of: a biocide, a set
retarder, a
starch, a foaming agent, a filler, a wax emulsion, a thickener, a fire
retardant, and any
combination thereof.
[0122] Clause 13. A method for producing the gypsum panel of
any of clauses
1-12 comprising:
making a siloxane emulsion with siloxane and water;
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mixing a siloxane polymerization catalyst comprising (a) 55 wt% to 100 wt%
calcium aluminate cement and/or calcium aluminate cement and (b) 0 wt% to 45
wt%
magnesium oxide with calcium sulfate hemihydrate to form a siloxane
polymerization
catalyst / calcium sulfate hemihydrate mixture, wherein the weight ratio of
the catalyst to
the calcium sulfate hemihydrate is 0.01-5:100;
combining the siloxane emulsion with the catalyst / calcium sulfate
hemihydrate
mixture to prepare an aqueous gypsum slurry comprising at least 50 wt.%
calcium sulfate
hemihydrate on a water free basis;
shaping the aqueous gypsum slurry and allowing the aqueous gypsum slurry
to set to form a set core of the gypsum panel; and
allowing the siloxane polymerization catalyst to polymerize the siloxane
partially or fully. The catalyst is the sole source of calcium aluminate
cement, calcium
sulfoaluminate cement and magnesium oxide in the aqueous gypsum slurry. The
calcium
sulfate hemihydrate is preferably at least 80 wt. %, typically at least 90
wt.% or at least
95 wt.%, of the ingredients of the aqueous gypsum slurry on a dry (water free)
basis.
[0123] Clause 14. The method of clause 13, wherein the
aqueous gypsum slurry
has an absence of fly ash and preferably also an absence of Portland cement.
[0124] Clause 15. The method of clause 13 or 14, wherein
forming the aqueous
gypsum slurry comprises:
mixing a mixture of:
100 parts by weight calcium sulfate hemihydrate;
0.01 to 5 parts by weight of siloxane polymerization catalyst, wherein the
siloxane polymerization catalyst comprises (a) 55 wt% to 100 wt% of calcium
aluminate
cement and/or calcium sulfoaluminate cement and (b) 0 wt% to 45 wt% of
magnesium
oxide;
0.2 to 2 parts by weight of siloxane;
0.1 to 5 parts by weight gypsum setting accelerator;
0.1 to 2 parts by weight dispersant; and 50 to 150 parts by weight water;
depositing the aqueous gypsum slurry on a facing material; shaping the
aqueous gypsum slurry on the facing material into a panel;
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allowing the aqueous gypsum slurry to set, thereby forming the core of the
gypsum panel; and
allowing the polymerizing of the siloxane.
5 [0125] Clause 16. The method of any of clauses 13-15, wherein the
aqueous
siloxane emulsion comprises dispersed siloxane particles having an average
particle size
of less than about 50 microns, and does not comprise an emulsifier or
dispersant,
preferably the siloxane particles, have, an average particle size of less than
about 30
microns.
10 [0126] Clause 17. The method of any of clauses 13-16,
wherein the shaping step
comprises locating the aqueous gypsum slurry between two pieces of facing
material to
form a gypsum wallboard panel.
[0127] Clause 18. The method of any of clauses 13-17, wherein
the slurry is free
of Portland cement, fly ash, limestone, aragonite, calcite, dolomite, and
slaked lime.
15 [0128] Clause 19. The method of any of clauses 13-18,
wherein the siloxane
polymerization catalyst consists of (a) 55 wt% to 100 wt% calcium aluminate
cement
and/or calcium sulfoaluminate cement and (b) 0 wt% to 45 wt% magnesium oxide.
[0129] Clause 20. The method of any of clauses 13-18, wherein
the catalyst
consists of calcium aluminate cement or wherein the catalyst consists of
calcium
20 sulfoaluminate cement.
[0130] Clause 21. An aqueous gypsum slurry composition
comprising:
at least 50 wt.% calcium sulfate hemihydrate on a water free basis;
a siloxane polymerization catalyst comprising (a) 55 wt% to 100 wt% calcium
aluminate cement and/or calcium aluminate cement and (b) 0 wt% to 45 wt%
magnesium
25 oxide, wherein the weight ratio of the siloxane polymerization catalyst
to the calcium
sulfate hemihydrate is 0.01-5:100; and
a siloxane emulsion with siloxane and water. The catalyst is the sole source
of
calcium aluminate cement, calcium sulfoaluminate cement and magnesium oxide in
the
aqueous gypsum slurry. The calcium sulfate hemihydrate is preferably at least
80 wt. %,
30 typically at least 90 wt.% or at least 95 wt.%, of the ingredients of
the aqueous gypsum
slurry on a dry (water free) basis.
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[0131] Clause 22. The aqueous gypsum slurry composition of
clause 21
comprising:
100 parts by weight calcium sulfate hemihydrate;
0.01 to 5 parts by weight of siloxane polymerization catalyst, wherein the
siloxane polymerization catalyst comprises (a) 55 wt% to 100 wt% of calcium
aluminate
cement and/or calcium sulfoaluminate cement and (b) 0 wt% to 45 wt% magnesium
oxide;
0.2 to 2 parts by weight of siloxane;
0.1 to 5 parts by weight accelerator;
0.1 to 2 parts by weight dispersant; and
50 to 150 parts by weight water.
[0132] Clause 23. The aqueous gypsum slurry composition of
clause 21 or 22,
wherein the aqueous gypsum slurry has an absence of fly ash and preferably
also an
absence of Portland cement.
[0133] Clause 24. The aqueous gypsum slurry composition of
any of clauses 21-
23, wherein the aqueous gypsum slurry has an absence of one or more of:
Portland
cement, limestone, aragonite, calcite, dolomite, and slaked lime.
[0134] Clause 25. The aqueous gypsum slurry composition of
any of clauses 21-
23, wherein the siloxane polymerization catalyst is free of one or more of:
Portland
cement, limestone, aragonite, calcite, dolomite, and slaked lime.
[0135] Clause 26. The aqueous gypsum slurry composition of any
of clauses 21-
25, wherein the catalyst consists of (a) 55 wt% to 100 wt% calcium aluminate
cement
and/or calcium sulfoaluminate cement and (b) 0 wt% to 45 wt% magnesium oxide.
[0136] Clause 27. The aqueous gypsum slurry composition of
any of clauses 21-
25, wherein the catalyst consists of the calcium aluminate cement.
[0137] Clause 28. The aqueous gypsum slurry composition of any
of clauses 21-
25, wherein the catalyst consists of the calcium sulfoaluminate cement.
[0138] Clause 29. The aqueous gypsum slurry composition of
any of clauses 21-
25, wherein the catalyst consists of the calcium aluminate cement and the
calcium
sulfoaluminate cement.
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EXAMPLES
[0139] Wallboard samples were prepared from slurries having the
compositions
described in Tables 7 and 8 according to the following procedure. All of the
dry
components (stucco, accelerator, starch, and catalyst) were placed in a
plastic bag and
shaken to mix. A siloxane emulsion was prepared by adding 8 g of siloxane in
200 g of
water and mixing them in a high shear mixer at a rate of 7500 rpm for 2.5
minutes. The
siloxane emulsion with the rest of water and all of the liquid additives were
added into a
HOBART mixer. The slurry was prepared by soaking the dry powders in the
solution for
seconds and mixing for 10 seconds, followed by injecting the foam for 14
seconds and
10 mixing another 2 seconds. The slurry was then poured into a 1/2 inch by
13 inch by 12
inch envelope made by Manila face paper and Newsline back paper. The paper
envelope
was fixed in 1/2 inch envelope mold. After 5 minutes, the wet board were taken
out of the
mold and placed in the ambient condition for another 5 minutes. After 10
minutes, the
board was dried in 450 F oven for 17 minutes, and then transferred to 360 F
oven and
dried for 17 minutes. Finally, the board was dried at 110 F until the board
weight became
constant. The dried board was cut into 10 inch by 10 inch sample. For each of
the
samples, the board properties were a thickness of about 1/2 inch and a weight
of about
1350 pounds per 1,000 square feet (lbs/msf).
Table 7: Sample Compositions
Component Parts by Weight
Stucco 1000
Heat resistance accelerator 12
Starch 10
Catalyst 0-16 (See Table 8)
Siloxane 9
Sodium Trimetaphosphate (10% active 10
ingredient)
Set Retarder (1% active ingredient) 8
Dispersant 4
Gauge water 912
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Table 8: Catalyst Compositions (parts by weight in Table 7)
Sample Class C Fly TERNALO SECARO 71 FASTROCK
MgO
Ash EV 500
1 0 0 0 0
0
2 16 0 0 0
0
3 0 16 0 0
0
4 0 0 16 0
0
0 0 0 16 0
6 0 0 0 0
1.5
7 5 0 0 0
1.5
8 0 5 0 0
1.5
9 0 0 5 0
1.5
0 0 0 5 1.5
11 0 0 0 0
1
12 0 5 0 0
1
13 0 0 5 0
1
14 0 0 0 5
1
5 [0140] TERNALO EV (calcium aluminate cement, available from Kerneos),
SECARO
71 (calcium aluminate cement, available from Kerneos), FASTROCK 500 (calcium
sulfoaluminate cement, available from Kerneos).
[0141] The 10 inch by 10 inch sample boards were soaked in water
for two hours for
the water absorption test as specified in ASTM C1396-17. The weight gain
during the
10 soaking was used to calculate the water absorption. Table 9 reports H20%
of Mass which
is the water absorption of the sample boards. For instance, an H20% of Mass of
57.4
means that, per 100 pounds of dry board before the water absorption test, the
wet board
after the water absorption test weighed 157.4 pounds.
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Table 9: ASTM 01396-17 Test Results
Sample H20% of Mass
1 57.4
2 5.7
3 5.9
4 6.7
5.6
6 6.0
7 4.8
8 4.6
9 4.5
4.8
11 6.3
12 5.2
13 5.1
14 5.4
[0142] The board samples produced using calcium aluminate cement-
containing
catalysts are comparable in water resistance to those produced with fly ash-
containing
5 catalysts.
[0143] Therefore, the present disclosure is well adapted to
attain the ends and
advantages mentioned as well as those that are inherent therein.
[0144] The particular disclosure above is illustrative only, as
the present disclosure
may be modified and practiced in different but equivalent manners apparent to
one having
10 ordinary skill in the art and having the benefit of the teachings
herein. Furthermore, no
limitations are intended to the details of construction or design herein
shown, other than
as described in the claims below.
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