U.S. patent application number 15/158000 was filed with the patent office on 2016-09-08 for low weight and density fire-resistant gypsum panel.
This patent application is currently assigned to United States Gypsum Company. The applicant listed for this patent is United States Gypsum Company. Invention is credited to Weixin D. SONG, Srinivas VEERAMASUNENI, Qiang YU.
Application Number | 20160258157 15/158000 |
Document ID | / |
Family ID | 46001717 |
Filed Date | 2016-09-08 |
United States Patent
Application |
20160258157 |
Kind Code |
A1 |
YU; Qiang ; et al. |
September 8, 2016 |
LOW WEIGHT AND DENSITY FIRE-RESISTANT GYPSUM PANEL
Abstract
An about 5/8 inch to 3/4 inch thick low weight, low density
gypsum panel with fire resistance capabilities sufficient to
provide a Thermal Insulation Index of at least 17.0 minutes which
when subjected to U419 test procedures will not fail for at least
30 minutes and, in selected embodiments, also has outstanding water
resistance properties.
Inventors: |
YU; Qiang; (Grayslake,
IL) ; SONG; Weixin D.; (Vernon Hills, IL) ;
VEERAMASUNENI; Srinivas; (Round Lake, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United States Gypsum Company |
Chicago |
IL |
US |
|
|
Assignee: |
United States Gypsum
Company
Chicago
IL
|
Family ID: |
46001717 |
Appl. No.: |
15/158000 |
Filed: |
May 18, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14732144 |
Jun 5, 2015 |
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15158000 |
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13712732 |
Dec 12, 2012 |
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14732144 |
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13035800 |
Feb 25, 2011 |
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13712732 |
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12795125 |
Jun 7, 2010 |
8197952 |
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13035800 |
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11449177 |
Jun 7, 2006 |
7731794 |
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12795125 |
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60688839 |
Jun 9, 2005 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 2111/0062 20130101;
Y10T 428/31989 20150401; B32B 2307/72 20130101; C04B 2111/28
20130101; C04B 2103/408 20130101; C04B 28/145 20130101; C04B 28/14
20130101; Y10T 156/1052 20150115; C04B 24/20 20130101; Y10T
428/31982 20150401; C04B 2111/34 20130101; B32B 2307/536 20130101;
B32B 13/08 20130101; Y10T 428/27 20150115; C04B 24/383 20130101;
E04C 2/043 20130101; C04B 20/06 20130101; B32B 2607/00 20130101;
C04B 22/16 20130101; C04B 2201/20 20130101; Y02W 30/91 20150501;
B32B 2419/00 20130101; Y10T 428/31678 20150401; E04C 2/28 20130101;
B32B 2607/02 20130101; B32B 2307/3065 20130101; C04B 28/14
20130101; C04B 14/42 20130101; C04B 18/24 20130101; C04B 22/16
20130101; C04B 24/226 20130101; C04B 24/383 20130101; C04B 38/10
20130101; C04B 28/14 20130101; C04B 14/386 20130101; C04B 18/24
20130101; C04B 22/16 20130101; C04B 24/383 20130101; C04B 38/10
20130101; C04B 2103/408 20130101; C04B 28/14 20130101; C04B 14/386
20130101; C04B 18/24 20130101; C04B 22/16 20130101; C04B 24/38
20130101; C04B 38/10 20130101; C04B 2103/408 20130101; C04B 28/14
20130101; C04B 14/42 20130101; C04B 18/24 20130101; C04B 22/16
20130101; C04B 24/226 20130101; C04B 24/38 20130101; C04B 38/10
20130101 |
International
Class: |
E04C 2/28 20060101
E04C002/28; E04C 2/04 20060101 E04C002/04 |
Claims
1-12. (canceled)
13. A gypsum panel with a density of about 27 to about 37 pounds
per cubic foot and a Thermal Insulation Index greater than 17.0
minutes comprising: (a) about 1360-1460 lb/msf set gypsum; (b)
about 1.5-1.8% by weight pregelatinized starch; (c) about
0.10-0.15% by weight phosphate; (d) about 0.75-1.0% by weight
dispersant; (e) about 0.1-0.3% by weight mineral, glass or carbon
fiber; and (f) foam voids in an amount effective to provide the
specified panel density, wherein the percentages by weight are
based on the weight of the set gypsum and the lb/msf values are for
a nominally 5/8 inch thick panel and subject to proportional
adjustment for thicker or thinner panels.
14-28. (canceled)
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This continuation-in-part application claims the benefit of
earlier U.S. patent application Ser. No. 12/795,125, filed Jun. 7,
2010, which is a continuation of U.S. patent application Ser. No.
11/449,177, filed Jun. 7, 2006, which issued as U.S. Pat. No.
7,731,794 on Jun. 8, 2010, which claims priority to U.S.
Provisional Patent Application No. 60/688,839, filed Jun. 9, 2005,
the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The above-referenced earlier applications pertain to methods
of making gypsum slurries containing a phosphate-containing
component, pregelatinized starch and a naphthalenesulfonate
dispersant, and to products made therefrom. The earlier
applications also pertain to methods of increasing the dry strength
of low weight and density gypsum panels by introducing to the
slurry used to make the panels a phosphate-containing component,
pregelatinized starch and naphthalenesulfonate dispersant.
[0003] Conventional gypsum-containing products such as gypsum
panels have many advantages, such as low cost and easy workability,
although substantial amounts of gypsum dust can be generated when
the products are cut or drilled. Various improvements have been
achieved in the earlier applications in making gypsum-containing
products by introducing starches and other ingredients in the
slurries used to make such products. Starch can increase flexural
strength and compressive strength of gypsum-containing products
including gypsum panels.
[0004] It is generally necessary to use substantial amounts of
water in gypsum slurries containing pregelatinized starch in order
to ensure proper flowability of the slurry. Unfortunately, most of
this water must eventually be driven off by heating, which is
expensive due to the high cost of the fuels used in the heating
process. The heating step is also time-consuming. As explained in
the earlier applications, it has been found that the use of
naphthalenesulfonate dispersants can increase the fluidity of the
slurries, thus overcoming the water demand problem. In addition, it
has also been found that the naphthalenesulfonate dispersants, if
the usage level is high enough, can cross-link to the
pregelatinized starch to bind the gypsum crystals after drying,
thus increasing dry strength of the gypsum composite.
[0005] Phosphate-containing components have not in the past been
recognized to affect gypsum slurry water requirements. However, as
explained in the earlier applications, the present inventors
discovered that increasing the level of the phosphate-containing
component to hitherto unknown levels in the presence of a specific
dispersant makes it possible to achieve proper slurry flowability
with unexpectedly reduced amounts of water, even in the presence of
high starch levels. This, of course, is highly desirable because it
in turn reduces fuel usage as well as the process time associated
with subsequent water removal process steps. The present inventors
also discovered that the dry strength of gypsum panel can be
increased by using a naphthalenesulfonate dispersant in combination
with pregelatinized starch in the slurry used to make the
panels.
[0006] The inventions of the earlier applications included gypsum
panels comprising a set gypsum composition formed between two
substantially parallel cover sheets, the set gypsum composition
made using the gypsum-containing slurry of water, stucco,
pregelatinized starch, a naphthalenesulfonate dispersant and
optionally a water-soluble phosphate, preferably, sodium
trimetaphosphate. This gypsum panel has a high strength, yet much
lower weight than conventional gypsum panels. In addition, much
less dust is generated on cutting, sawing, snapping, or drilling
the panels made according to this embodiment.
[0007] Another embodiment of the invention of the earlier
applications comprised a method of making gypsum panels including
mixing a gypsum-containing slurry comprising water, stucco,
pregelatinized starch, and a naphthalenesulfonate dispersant,
wherein the pregelatinized starch is present in an amount of at
least about 0.5% by weight up to about 10% by weight based on the
weight of stucco. The resulting gypsum-containing slurry is
deposited on a first paper cover sheet, and a second paper cover
sheet is placed over the deposited slurry to form a gypsum panel.
The gypsum panel is cut after the gypsum-containing slurry has
hardened sufficiently for cutting, and the resulting gypsum panel
is dried. The gypsum-containing slurry can optionally contain a
phosphate-containing component, for example, sodium
trimetaphosphate. Other conventional ingredients will also be used
in the slurry including, as appropriate, accelerators, binders,
paper fiber, glass fiber, and other known ingredients. A soap foam
is normally added to reduce the density of the final gypsum panel
product.
[0008] The present invention generally pertains to low weight and
density gypsum panels with good thermal insulation properties, good
heat shrinkage resistance, good fire resistance, and in some
aspects of the invention, good water resistance.
[0009] Gypsum panels used in building and other construction
applications (such as gypsum wallboard or ceiling panels) typically
comprise a gypsum core with cover sheets made of paper, fiberglass
or other suitable materials. Gypsum panels typically are
manufactured by mixing "stucco" with water and other ingredients to
prepare a slurry that is used to form the cores of the panels.
[0010] As generally understood in the art, stucco comprises
predominately one or more forms of calcined gypsum, i.e. gypsum
subjected to dehydration (typically by heating) to form anhydrous
gypsum or hemihydrate gypsum (CaSO.sub.4.1/2H.sub.2O). The calcined
gypsum may comprise beta calcium sulfate hemihydrate, alpha calcium
sulfate hemihydrate, water-soluble calcium sulfate anhydrite, or
mixtures of any or all of these, from natural or synthetic sources.
When introduced into the slurry used to form the cores of the
panels, the calcined gypsum begins a hydration process which is
completed during the formation of the gypsum panels. This hydration
process, when properly completed, yields a generally continuous
crystalline matrix of set gypsum dihydrate in various crystalline
forms (i.e. forms of CaSO.sub.4.2H.sub.2O).
[0011] During the formation of the panels, the cover sheets
typically are provided as continuous webs. The gypsum slurry is
deposited as a flow or ribbon on a first of the cover sheets. The
slurry is spread across the width of the first cover sheet at a
predetermined approximate thickness to form the panel core. A
second cover sheet is then placed on top, sandwiching the gypsum
core between the cover sheets and forming a continuous panel.
[0012] The continuous panel typically is transported along a
conveyer to allow the core to continue the hydration process. When
the core is sufficiently hydrated and hardened, it is cut to one or
more desired sizes to form individual gypsum panels. The panels are
then passed through a kiln at temperatures sufficient to complete
the hydration process and dry the panels to a desired free moisture
level (typically a relatively low free moisture content).
[0013] Depending on the process employed and the expected use of
the panels and other considerations, additional slurry layers,
strips or ribbons comprising gypsum and other additives may be
applied to the first and/or second cover sheets to provide specific
properties to the finished panels, such as hardened edges or a
hardened panel face. Similarly, foam may be added to the gypsum
core slurry and/or other slurry strips or ribbons at one or more
locations in the process to provide a distribution of voids within
the gypsum core or portions of the core of the finished panels.
[0014] The resulting panels may be cut and processed for use in a
variety of applications depending on the desired panel size, cover
layer composition, core compositions, etc. Gypsum panels typically
vary in thickness from about 1/4 inch to about one inch depending
on their expected use and application. The panels may be applied to
a variety of structural elements used to form walls, ceilings and
other similar systems using one or more fastening elements, such as
screws, nails and/or adhesives.
[0015] Should the finished gypsum panels be exposed to relatively
high temperatures, such as those produced by high temperature
flames or gases, portions of the gypsum core may absorb sufficient
heat to cause the release of water from the gypsum dihydrate
crystals of the core. The absorption of heat and release of water
from the gypsum dihydrate may be sufficient to retard heat
transmission through or within the panels for a period of time. At
certain high temperature levels, the high temperature flames or
gases also may cause phase changes in the gypsum core and
rearrangement of the crystalline structures. Such temperatures
further may cause melting or other complexing of salts and
impurities in the gypsum core crystal structures. The heat absorbed
by the gypsum core as a result of such high temperature flames or
gases, in addition, can be sufficient to recalcine portions of the
core, depending on the heat source temperatures and exposure
time.
[0016] More specifically, when heated to 212.degree. F.
(100.degree. C.), the gypsum core undergoes a decomposition
reaction in which 75% of the crystalline water is driven off as
steam as the gypsum converts to hemihydrate, per Eq. 1 below:
CaSO.sub.4.2H.sub.2O.fwdarw.CaSO.sub.4.1/2H.sub.2O+11/2H.sub.2O
[1]
[0017] Further heating to 250.degree. F. (120.degree. C.) drives
off the remaining crystalline water as the hemihydrate converts to
anhydrite, which is calcium sulfate, (Eq. 2):
CaSO.sub.4.1/2H.sub.2O.fwdarw.CaSO.sub.4+1/2H.sub.2O [2]
[0018] By the time the core reaches 392.degree. F. (200.degree. C.)
all of the gypsum is converted to the anhydrite phase. These
transition temperatures are approximate and can vary with
impurities or additives in the gypsum. The heats of dehydration
required to drive reactions [1] and [2] total 390 Btu/lb (906
kJ/kg). This energy absorbed by the phase change reactions and the
heat carried away by the steam that is produced act as a
substantial heat sink and are responsible for much of gypsum's
unique quality as a fire protection material. For example, it
requires over seven times as much energy to heat gypsum from
75.degree. F. to 400.degree. F. (24 to 204.degree. C.) as it does
to heat an equal mass of concrete.
[0019] As gypsum calcines, absorbing and dissipating thermal energy
in the process, the volume of the crystal matrix shrinks. The
amount of shrinkage depends on the original composition of the
gypsum, which will include varying impurities from the mineral
deposit from which it is mined or additives from the manufacturing
process. It is commonly assumed that the majority of the shrinkage
occurs during the dehydration reactions [1] and [2] as the gypsum
converts to anhydrite.
[0020] Shrinkage of the gypsum core influences the performance of
gypsum panels in the presence of high temperate flames or gases.
The greater the shrinkage the more difficult it will be to achieve
a given level of fire resistance performance. This can be
exacerbated or diminished depending on the building assembly
itself.
[0021] Shrinkage cracks occur because the gypsum panel is
constrained from movement in the plane of the panel by its
attachment in the building assembly to framing or other support
structures. If the building assembly deflects away from the fire,
the panel on the fire side is placed into compression as it deforms
into a concave surface. Shrinkage effects are diminished as the
panel is compressed laterally and longitudinally along its length
and width. This occurs with wood stud walls where the studs char
and weaken from the fire side causing them to deflect away from the
fire under the vertical load imposed on the structure.
[0022] In contrast, if the building assembly deflects toward the
fire it will force the panel on the fire exposed side to become a
convex surface placed in tension. Sensitivity to shrinkage cracking
increases since the movement of the structure pulls on the panel.
This occurs with lightweight steel framed walls where the metal
studs heat and expand most on the fire side, as well as with
roof-ceiling and floor-ceiling assemblies where gravity loads cause
the assembly to deflect downwardly as it weakens from the fire
below. The overall impact on assembly fire resistance depends on
the relative rates of shrinkage and deflection.
[0023] Gypsum panels may experience shrinkage of the panel
dimensions in one or more directions as one result of some or all
of these high temperature heating effects, and such shrinkage may
cause failures in the structural integrity of the panels. When the
panels are attached to wall, ceiling or other framing assemblies,
the panel shrinkage may lead to the separation of the panels from
other panels mounted in the same assemblies and from their supports
and, in some instances, causing collapse of the panels or the
supports (or both). As a result, heated air at high temperatures
may pass into or through a wall or ceiling structure.
[0024] As explained above, gypsum panels resist the effects of
relatively high temperatures for a period of time, which may
inherently delay passage of high heat levels through or between the
panels and into (or through) systems using them. Gypsum panels
referred to as fire resistant or "fire rated" typically are
formulated to enhance the panels' ability to delay the passage of
heat though wall or ceiling structures and play an important role
in controlling the spread of fire within buildings. As a result,
building code authorities and other concerned public and private
entities typically set stringent standards for the fire resistance
performance of fire rated gypsum panels.
[0025] The ability of gypsum panels to resist fire and the
associated extreme heat may be evaluated by carrying out
appropriate tests. Examples of such tests that are routinely used
in the construction industry, include those published by
Underwriters Laboratories ("UL"), such as the UL U305, U419 and
U423 test procedures and protocols, as well as procedures described
in specification E119 published by the American Society for Testing
and Materials (ASTM). Such tests may comprise constructing test
assemblies using gypsum panels, normally in a single-layer
application of the panels on each face of a wall frame formed by
wood or steel studs. Depending on the test, the assembly may or may
not be subjected to load forces. The face of one side of the
assembly is exposed to increasing temperatures for a period of time
in accordance with a heating curve, such as those called for in the
UL U305, U419 and U423 test procedures and the ASTM E119
procedures.
[0026] The temperatures proximate the heated side and the
temperatures at the surface of the unheated side of the assembly
are monitored during the tests to evaluate the temperatures
experienced by the exposed gypsum panels and the heat transmitted
through the assembly to the unexposed panels. The tests are
terminated upon one or more structural failures of the panels,
and/or when the temperatures on the unexposed side of the assembly
exceed a predetermined threshold. Typically, these threshold
temperatures are based on the maximum temperature at any one of
such sensors and/or the average of the temperatures sensed by
sensors on the face of the unexposed gypsum panels.
[0027] Test procedures such as those set forth in UL U305, U419 and
U423, and ASTM E119 are directed to an assembly's resistance to the
transmission of heat through the assembly as a whole. The tests
also provide, in one aspect, a measure of the resistance of the
gypsum panels used in the assembly to shrinkage in the in the x-y
direction (width and length) as the assembly is subjected to high
temperature heating. Such tests also provide a measure of the
panels' resistance to losses in structural integrity that result in
opening gaps or spaces between panels in a wall assembly, with the
resulting passage of high temperatures into the interior cavities
of the assembly. In another aspect, the tests provide a measure of
the gypsum panels' ability to resist the transmission of heat
through the panels and the assembly. It is believed that such tests
reflect the specified system's capability for providing building
occupants and firemen/fire control systems respectively a window of
opportunity to escape or address fire conditions.
[0028] In the past, various strategies were employed to improve the
fire resistance of fire rated gypsum panels. For example, thicker,
denser panel cores have been used to increase the presence of both
water and gypsum in the panels enhancing their ability to act as a
heat sink, to reduce panel shrinkage, and to increase the
structural stability and strength of the panels. Alternatively or
in addition to increasing the density of the panel cores, various
ingredients including glass and other fibers have been incorporated
into the gypsum cores to enhance gypsum panels' fire resistance by
increasing the tensile strength of the panel cores and by
distributing shrinkage stresses throughout the core matrices.
Similarly, amounts of certain clays, such as those of less than
about one micrometer in size, and colloidal silica or alumina
additives, such as those of less than one micrometer in size, have
been used in the past to provide increased fire resistance (and
high temperature shrinkage resistance) in gypsum panel cores.
[0029] It has been an article of faith in the art, however, that
reducing the weight and/or density of the gypsum panels by reducing
the amount of gypsum in the core would adversely affect both the
structural integrity of the panels and their resistance to fire and
high heat conditions.
[0030] Another approach employed in the past to improve the fire
resistance of fire rated gypsum panels has been to add unexpanded
vermiculite (also referred to as vermiculite ore) and mineral or
glass fibers into the core of gypsum panels. In such approaches,
the vermiculite is expected to expand under heated conditions to
compensate for the shrinkage of the gypsum components of the core.
The mineral/glass fibers were believed to hold portions of dried
gypsum together. Such an approach is discussed in U.S. Pat. Nos.
2,526,066 and 2,744,022. Both references, however, rely on a high
density core to provide sufficient gypsum to act as a heat sink.
They disclose the preparation of 1/2 inch thick gypsum panels with
a weight of, 2 to 2.3 pounds per square foot (2,000 to 2,300 pounds
per thousand square feet ("lb/msf")) and densities of about 50
pounds per cubic foot ("pcf") or greater. The '022 patent, in
addition, was directed at increasing the gypsum content (and thus
density and weight) of the panels disclosed in the '066 patent and
reducing the mineral/glass fiber content of those panels to provide
a yet greater gypsum-heat sink capacity. References such as the
'022 patent further recognized that the expansive properties of
vermiculite, unless limited, would result in spalling (that is,
fragmenting, peeling or flaking) of the core and destruction of a
wall assembly made with panels containing vermiculite in a
relatively short time at high temperature conditions.
[0031] In another example, U.S. Pat. No. 3,454,456 describes the
introduction of unexpanded vermiculite into the core of fire rated
gypsum panels to resist the shrinkage of the panels. The '456
patent also relies on a relatively high gypsum content and density
to provide a desired heat sink capacity. The '456 patent discloses
panel weights for finished 1/2 inch gypsum panels with a minimum
weight of about 1925 lb/msf and a density of about 46 pa. This is a
density comparable to thicker and much heavier 5/8 inch thick
gypsum panels (about 2175 to 2300 lb/msf) presently offered
commercially for fire rated applications.
[0032] The '456 patent also discloses that using vermiculite in a
gypsum panel core to raise the panel's fire rating is subject to
significant limitations. For example, the '456 patent notes (like
the '022 patent) that the expansion of the vermiculite within the
core may cause the core to disintegrate due to spalling and other
destructive effects. The '456 patent also discloses that unexpanded
vermiculite particles may so weaken the core structure that the
core becomes Weak, limp, and crumbly. The '456 patent purports to
address such significant inherent limitations with the use of
vermiculite in gypsum panels by employing a "unique" unexpanded
vermiculite with a relatively small particle size distribution
(more than 90% of the unexpanded particles smaller than a no. 50
mesh size (approximately 0.117 inch (0.297 mm) openings), with less
than 10% slightly larger than no. 50 mesh size). This approach
purportedly inhibits the adverse effects of vermiculite expansion
on the panel, as explained at col. 2, 1. 52-72 of the '456
patent.
[0033] In another approach, U.S. Pat. No. 3,616,173 is directed to
1/2 inch thick, fire resistant gypsum panels with a gypsum core
characterized by the '173 patent as lighter weight or lower
density. The '173 patent distinguished its panels from prior art
1/2 inch panels weighing about 2,000 lb/msf or more and having core
densities in excess of about 48 pcf. Thus, '173 patent discloses
panels with a density of at or above about 35 pcf, and preferably
about 40 pcf to about 50 pcf. The '173 patent achieves its
disclosed core densities by incorporating significant amounts of
small particle size inorganic material of either clay, colloidal
silica, or colloidal alumina in its gypsum core, as well as glass
fibers in amounts required prevent the shrinkage of its gypsum
panels under high temperature conditions.
[0034] Other efforts also have been made to increase the strength
and structural integrity of gypsum panels and reduce panel weight
by various means. See, for example, U.S. Pat. Nos. 7,731,794 and
7,736,720 and US Patent Application Publications 2007/0048490 A1,
2008/0090068 A1, and 2010/0139528 A1. However, such efforts have
not been considered sufficient by themselves to make low weight
panels sufficiently resistant to fire and high heat conditions.
[0035] In many applications the provision of such low weight gypsum
panels with the ability to resist the effects of relatively high
heat or fire conditions to delay the passage of heat levels through
such panels for even an half an hour would be an important
contribution to the art. However, it has been generally believed
that appreciably reducing the density of the core in gypsum panels
will both reduce the strength properties and structural integrity
of the panels, and also will reduce their ability to delay passage
of heat through the panels for even a half hour. More particularly,
panels with expected low strength and structural integrity, and
intentionally low gypsum content are of particular concern in these
applications since they have been expected to be overly vulnerable
to shrinkage forces and other stresses caused by contact with
relatively high heat or fire conditions and ineffective in
absorbing and blocking heat associated with such conditions.
[0036] Nevertheless, it is well-recognized that reducing a gypsum
panel's weight makes it easier and more economical to transport and
easier to handle and install. Therefore, if a low weight and hence
low density gypsum panel could be prepared that performed well in
applications requiring resistance to fire and extreme heat without
relying on additives like vermiculite, clay, colloidal silica, or
colloidal alumina, it would represent an important advance in the
fire resistant gypsum panel art.
[0037] Finally, it is noted that in the absence of water resistant
additives, when immersed in water, set gypsum absorbs up to 50% of
its weight of water. And, when gypsum panels, including fire
resistant gypsum panels, absorb water, they swell, become deformed
and lose strength which may degrade their fire-resistance
properties. Low weight and density fire-resistant panels have far
more air and/or water voids than conventional heavier
fire-resistant panels. These voids would be expected to increase
the rate and extent of water-uptake, making such low weight
fire-resistant panels more water absorbent than conventional
heavier fire-resistant panels.
[0038] Many attempts have been made in the past to improve the
water resistance of gypsum panels generally. Various hydrocarbons,
including wax, resins and asphalt have been added to the slurry
used to make the panels in order to impart water resistance to the
set panels. The use of siloxanes for this purpose is also well
known.
[0039] Although the use of siloxanes in gypsum slurries is a useful
means of imparting water resistance to finished panels by forming
silicone resins in situ, siloxanes would not be expected to
sufficiently protect low weight and density panels. Thus there is a
need in the art for a method of producing low weight and density
fire-resistant gypsum panels with improved water-resistance at
reasonable cost by enhancing the water resistance normally imparted
by siloxanes.
SUMMARY OF THE INVENTION
[0040] The low weight, low density gypsum panel of this invention
is an improvement on the teaching of earlier copending U.S. patent
application Ser. No. 12/795,125, which is incorporated herein by
reference. The invention of the '125 application includes a slurry
for forming low density gypsum panels which may include stucco,
dispersant, a phosphate-containing component and pregelatinized
starch. The dispersant can be present in an amount of about
0.1%-3.0% by weight based on the weight of dry stucco. The
pregelatinized starch can be present in an amount of at least about
0.5% by weight up to about 10% by weight based on the weight of dry
stucco in the formulation. The phosphate-containing component can
be present in an amount of at least about 0.12% by weight based on
the weight of stucco. Other slurry additives can include
accelerators, binders, paper or glass fibers and other known
constituents. The invention also comprises the low weight, low
density gypsum panels made with such slurries.
[0041] In some aspects, the present invention comprises a nominal
5/8 inch thick low weight, low density gypsum panel that is far
lighter and less dense than nominal 5/8 inch thick gypsum panels
typically used for construction applications, having the ability to
delay passage of high heat levels through the panel for more than a
half hour, and methods for making such panels. In some such
aspects, the panel of the invention (core plus cover sheets) has a
density of about 27 to about 37 pounds per cubic foot ("pcf"),
preferably about 29 to about 34 pcf, and more preferably about 30
to about 32 pcf, disposed between two substantially parallel cover
sheets. In such aspects, the weight of an approximately 5/8 inch
thick panel of the invention is less than about 1900 lb/msf,
preferably less than about 1740 lb/msf and more preferably less
than about 1640 lb/msf.
[0042] In still other aspects, the formulation for the low weight
and density panels of the invention, and the methods for making
them, provide gypsum panels with the above mentioned fire
resistance properties, a density less than about less than about 37
pcf, preferably less than about 34 pcf and more preferably less
than about 32 pcf, and nail pull resistance that satisfies the
standards of ASTM C 1396/C 1396/M-09. More particularly, in
embodiments of the invention such panels have a nail-pull
resistance of at least 87 lb.
[0043] In yet other aspects of the invention, a set gypsum core
composition for a nominal 5/8 inch fire rated panel is provided
using a gypsum-containing slurry comprising at least water, stucco,
and the other components identified below. In one such embodiment,
the set gypsum core has a density of from about 25 to about 36 pcf,
and the core comprises stucco in an amount from about 1040 lbs/msf
to about 1490 lbs/msf; pregelatinized starch from about 0.3% to
about 4% by weight of the stucco; mineral, glass or carbon fiber
from about 0.1% to about 0.3% by weight of the stucco, and
phosphate from about 0.15% to about 0.5% by weight of the stucco.
(Unless otherwise stated, the percentages of the component of the
gypsum core are stated by weight based on the weight of the stucco
used to prepare the core shiny).
[0044] In other aspects, the gypsum core of the panel of the
invention has a density of from about 27 to about 33 pounds per
cubic foot, and a set gypsum core weight from about 13.15 to about
1610 pounds lb/msf. In such aspects, the gypsum core also comprises
about 0.5% to about 2.0% pregelatinized starch; about 0.1%, to
about 0.3% mineral, glass or carbon fiber; stucco, and about 0.01%
to about 0.15% phosphate.
[0045] The present invention also includes the preparation and use
of gypsum panels having a nominal % inch thickness. Such panels
will have panel constituent levels at about 120% of the values set
forth above. Also, their ability to resist fire and high heat
conditions will be at a level of at least about 120% of that of the
nominal 5/8 inch thick panels. Other aspects and variations of the
panels of the invention and core formulations are discussed herein
below.
[0046] Other conventional additives also can be employed in each of
the aspects of the core slurries and gypsum core compositions
disclosed herein, in customary amounts, to impart desirable
properties to the core and to facilitate their manufacture.
Examples of such additives are set accelerators, set retarders,
dehydration inhibitors, binders, adhesives, dispersing aids,
leveling or nonleveling agents, thickeners, bactericides,
fungicides, pH adjusters, colorants, water repellants, fillers and
mixtures thereof.
[0047] In the above mentioned aspects and other aspects of the
panels of the invention disclosed herein, and the methods of making
the same, aqueous foam is added to the core slurry in an amount
effective to provide the desired gypsum core densities, using
methods further discussed below. The addition of the foam component
to the core slurry results in a distribution of voids and void
sizes that contribute to one or more panel and/or core strength
properties. Similarly, additional slurry layers, strips or ribbons
comprising gypsum and other additives (which may have an increased
density relative to other portions of the core) may be applied to
the first or second cover sheets to provide specific properties to
the finished panel, such as hardened edges or a hardened panel
face.
[0048] Another aspect of the invention comprises a method of making
gypsum panels that are able to delay passage of heat levels through
the panels for about a half hour or more Where the set gypsum core
component is formed from a calcined gypsum-containing aqueous
slurry. In this aspect, the slurry comprises pregelatinized starch,
dispersants, phosphates, mineral/glass/carbon fibers, foam, and
other additives, stucco and water at a water/stucco weight ratio of
about 0.6 to about 1.2, preferably about 0.8 to about 1.0, and more
preferably about 0.9. The core slurry is then deposited as a
continuous ribbon on and distributed over a continuous web of a
first cover sheet. A continuous web of a second cover sheet is then
placed over the deposited slurry to form a generally continuous
gypsum panel of a desired approximate 5/8 inch (or 3/4 inch)
thickness. The generally continuous gypsum panel is cut into
individual panels of a desired length after the calcined
gypsum-containing slurry has hardened (by hydration of the calcined
gypsum to form a continuous matrix of set gypsum) sufficiently for
cutting, and the resulting gypsum panels are dried.
[0049] The need for a catalyst and a method of producing fire
resistant gypsum panels with improved water-resistance at
reasonable cost is net or exceeded by embodiments of the present
invention in which the polymerization of siloxane is accelerated
and in some cases the amount of siloxane needed to meet the
specifications of ASTM 1398 can be reduced.
[0050] More specifically, polymerization of siloxane is improved
using a slurry that includes stucco, Class C fly ash, magnesium
oxide, an emulsion of siloxane and water, and greater than 2.0% by
weight based on the weight of the stucco of pregelatinized starch.
This slurry is used in a method of making water-resistant/fire
resistant gypsum panels that includes making a slurry of an
emulsion of siloxane, pregelatinized starch and water, then
combining the slurry with a dry mixture of stucco, magnesium oxide
and Class C fly ash. The slurry is then used to manufacture the
gypsum panels as described earlier. The resulting product is useful
for making a fire-resistant water-resistant gypsum panel having a
core that includes interwoven matrices of calcium sulfate dihydrate
crystals and a silicone resin, where the interwoven matrices have
dispersed throughout them a catalyst comprising magnesium oxide and
components from a Class C fly ash.
[0051] The mixture of magnesium oxide and Class C fly ash catalyzes
the polymerization of siloxane to accelerate development of
water-resistance in product made from the slurry. Fire
resistant/water-resistant gypsum panels made in this way need not
be stored for lengthy periods of time awaiting completion of the
polymerization reactions of the siloxane.
[0052] Use of this catalyst also increases the extent of the
reaction, leading to improved water-resistance. Water absorption of
less than 5% by weight is attainable using the fly ash and magnesia
combination. Thus, in addition to causing the polymerization
reaction to accelerate, this catalyst also allows the siloxane to
polymerize more completely allowing the amount of siloxane to be
reduced in some cases. Since the siloxane is one of the more
expensive panel additives, reduction in the usage level leads to a
savings in the cost of the raw materials.
[0053] Another advantage of the present invention is the
dimensional stability of the panels. Some compounds used to
catalyze this reaction result in significant expansion as the
panels dry. As the interior of the panels expands, it causes
cracking in the exterior surface, damaging it. Use of fly ash and
magnesium oxide results in very little expansion and very little
cracking in the finished panels. It has also been unexpectedly
found that the polymerized silicone resin lessens shrinkage of the
panel under high heating conditions.
[0054] This combined fly ash and magnesia catalyst also allows for
satisfactory polymerization using a wide range of magnesium oxide
grades. While the prior art discloses only that dead-burned
magnesia is suitable to act as a catalyst for siloxane
polymerization, when combined with fly ash, even hard-burned or
light-burned magnesium oxide may be used. This feature allows
manufacturers of gypsum panels additional freedom in selection
sources of magnesium oxide to be used in the slurry.
[0055] Finally, the greater than 2.0% by weight pregelatinized
starch works in conjunction with the siloxane to achieve good water
resistance. Although it is believed that the siloxane/high
pregelatinized starch combination slows water entry through
micropores on the panel edges first by blocking water entry and
then, upon take-up of water by the starch by forming a highly
viscous starch/water combination, we do not intend to be bound by
this theory.
[0056] The above summary of the invention is not intended to limit
the scope of the invention as understood by one of ordinary skill
in the art. Other aspects and embodiments of the invention are
disclosed below and in the Figures attached hereto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] The figures listed and further discussed below, unless
otherwise expressly stated, are exemplary of and not limiting to,
the invention disclosed herein.
[0058] FIG. 1 is a plot of the maximum single sensor temperatures
and a plot of the average of the sensor temperatures on the
unexposed, unheated surface of a test assembly utilizing panels of
the invention subjected to fire testing under the conditions of
U419 as reported in Example 8 herein, as well as a plot of the ASTM
119 temperature curve used for the furnace temperatures on the
exposed, heated side of the test assembly.
[0059] FIG. 2 is an expanded plot of the data for the maximum
single sensor and average sensor temperatures shown in FIG. 1.
[0060] FIG. 3 is a plot of the maximum single sensor temperatures
and a plot of the average of the sensor temperatures on the
unexposed, unheated surface of a test assembly utilizing panels of
the invention subjected to fire testing under the conditions of
U305 as reported in Example 9 herein, as well as a plot of the ASTM
119 temperature curve used for the furnace temperatures on the
exposed, heated side of the test assembly.
[0061] FIG. 4 is an expanded plot of the data for the maximum
single sensor and average sensor temperatures shown in FIG. 3.
DETAILED DESCRIPTION
[0062] Some embodiments of the invention of the copending
applications, provide finished gypsum-containing products made from
gypsum-containing slurries containing stucco, pregelatinized
starch, and a naphthalenesulfonate dispersant. The
naphthalenesulfonate dispersant is present in an amount of about
0.1%-3.0% by weight based on the weight of dry stucco. The
pregelatinized starch is present in an amount of at least about
0.5% by weight up to about 10% by weight based on the weight of dry
stucco in the formulation. Other ingredients that may be used in
the slurry include binders, paper fiber, glass fiber, and
accelerators. A soap foam is normally added to the newly formulated
gypsum-containing slurries to reduce the density of the final
gypsum-containing product, for example, gypsum panels.
[0063] A combination of from about 0.5% by weight up to about 10%
by weight pregelatinized starch, from about 0.1% by weight up to
about 3.0% by weight naphthalenesulfonate dispersant, and a minimum
of at least about 0.12% by weight up to about 0.4% by weight of the
phosphate-containing component (all based on the weight of dry
stucco used in the gypsum slurry) unexpectedly and significantly
increases the fluidity of the gypsum slurry. This substantially
reduces the amount of water required to produce a gypsum slurry
with sufficient flowability to be used in making gypsum-containing
products such as gypsum panels. The level of trimetaphosphate salt,
which is at least about twice that of standard formulations (as
sodium trimetaphosphate), is believed to boost the dispersant
activity of the naphthalenesulfonate dispersant.
[0064] The naphthalenesulfonate dispersants used in the copending
applications include polynaphthalenesulfonic acid and its salts
(polynaphthalenesulfonates) and derivatives, which are condensation
products of naphthalenesulfonic acids and formaldehyde.
Particularly desirable polynaphthalenesulfonates include sodium and
calcium naphthalenesulfonate. The average molecular weight of the
naphthalenesulfonates can range from about 3,000 to 27,000,
although it is preferred that the molecular weight be about 8,000
to 10,000. At a given solid % aqueous solution, a higher molecular
weight dispersant has higher viscosity, and generates a higher
water demand in the formulation, than a lower molecular weight
dispersant. Useful naphthalenesulfonates include DILOFLO, available
from GEO Specialty Chemicals, Cleveland, Ohio; DAXAD, available
from Hampshire Chemical Corp., Lexington, Mass.; and LOMAR D,
available from GEO Specialty Chemicals, Lafayette, Ind. The
naphthalenesulfonates are preferably used as aqueous solutions in
the range 35-55% by weight solids content, for example. It is most
preferred to use the naphthalenesulfonates in the form of an
aqueous solution, for example, in the range of about 40-45% by
weight solids content. Alternatively, where appropriate, the
naphthalenesulfonates can be used in dry solid or powder form, such
as LOMAR D, for example.
[0065] The polynaphthalenesulfonates useful in the present
invention have the general structure (I):
##STR00001##
wherein n is >2, and wherein M is sodium, potassium, calcium,
and the like.
[0066] The naphthalenesulfonate dispersant, preferably as an about
45% by weight solution in water, may be used in a range of from
about 0.5% to about 3.0% by weight based on the weight of dry
stucco used in the gypsum composite formulation. A more preferred
range of naphthalenesulfonate dispersant is from about 0.5% to
about 2.0% by weight based on the weight of dry stucco, and a most
preferred range from about 0.7% to about 2.0% by weight based on
the weight of dry stucco. In contrast, known gypsum panels contain
this dispersant at levels of about 0.4% by weight, or less, based
on the weight of dry stucco.
[0067] Stated in an another way, the naphthalenesulfonate
dispersant, on a dry weight basis, may be used in a range from
about 0.1% to about 1.5% by weight based of the weight of dry
stucco used in the gypsum composite formulation. A more preferred
range of naphthalenesulfonate dispersant, on a dry solids basis, is
from about 0.25% to about 07% by weight based on the weight of dry
stucco, and a most preferred range (on a dry solids basis) from
about 0.3% to about 0.7% by weight based on the weight of dry
stucco.
[0068] The gypsum-containing slurry of the copending applications
can contain a phosphate-containing component, such as
trimetaphosphate salt, for example, sodium trimetaphosphate. Any
suitable water-soluble metaphosphate or polyphosphate can be used
as the phosphate-containing component in accordance with the
present invention. It is preferred that a trimetaphosphate salt be
used, including double salts, that is trimetaphosphate salts having
two cations. Particularly useful trimetaphosphate salts include
sodium trimetaphosphate, potassium trimetaphosphate, lithium
trimetaphosphate, ammonium trimetaphosphate, and the like, or
combinations thereof. A preferred trimetaphosphate salt is sodium
trimetaphosphate. It is preferred to use the trimetaphosphate salt
as an aqueous solution, for example, in the range of about 10-15%
by weight solids content. Other cyclic or acyclic polyphosphates
can also be used, as described in U.S. Pat. No. 6,409,825 to Yu et
al., herein incorporated by reference.
[0069] Sodium trimetaphosphate is a known additive in
gypsum-containing compositions, although it is generally used in a
range of from about 0.05% to about 0.08% by weight based on the
weight of dry stucco used in the gypsum slurry. In the embodiments
of the present invention, sodium trimetaphosphate (or other
water-soluble metaphosphate or polyphosphate) can be present in the
range of from about 0.12% to about 0.4% by weight based on the
weight of dry stucco used in the gypsum composite formulation. A
preferred range of sodium trimetaphosphate (or other water-soluble
metaphosphate or polyphosphate) is from about 0.12% to about 0.3%
by weight based on the weight of dry stucco used in the gypsum
composite formulation.
[0070] There are two forms of stucco, alpha and beta. These two
types of stucco are produced by different means of calcination. In
the present inventions either the beta or the alpha form of stucco
may be used.
[0071] Starches, including pregelatinized starch in particular,
must be used in gypsum-containing slurries prepared in accordance
with the copending applications. A preferred pregelatinized starch
is pregelatinized corn starch, for example pregelatinized corn
flour available from Bunge Milling, St. Louis, Mo., having the
following typical analysis: moisture 7.5%, protein 8.0%, oil 0.5%,
crude fiber 0.5%, ash 0.3%; having a green strength of 0.48 psi;
and having a loose bulk density of 35.0 lb/ft.sup.3. Pregelatinized
corn starch should be used in an amount of at least about 0.5% by
weight up to about 10% by weight, based on the weight of dry stucco
used in the gypsum-containing slurry.
[0072] The present inventors further discovered that an unexpected
increase in dry strength (particularly in gypsum panels) can be
obtained by using at least about 0.5% by weight up to about 10% by
weight pregelatinized starch (preferably pregelatinized corn
starch) in the presence of about 0.1% by weight to 3.0% by weight
naphthalenesulfonate dispersant (starch and naphthalenesulfonate
levels based on the weight of dry stucco present in the
formulation). This unexpected result can be obtained whether or not
water-soluble metaphosphate or polyphosphate is present.
[0073] In addition, it was unexpectedly been found that
pregelatinized starch can be used at levels of at least about 10
lb/MSF, or more, in the dried gypsum panels made in accordance with
the present invention, yet high strength and low weight can be
achieved. Levels as high as 35-45 lb/MSF pregelatinized starch in
the gypsum panels have been shown to be effective.
[0074] Other useful starches include acid-modified starches, such
as acid-modified corn flour, available as HI-BOND from Bunge
Milling, St. Louis, Mo. This starch has the following typical
analysis: moisture 10.0%, oil 1.4%, solubles 17.0%, alkaline
fluidity 98.0%, loose bulk density 30 lb/ft.sup.3, and a 20% slurry
producing a pH of 4.3. Another useful starch is non-pregelatinized
wheat starch, such as ECOSOL-45, available from ADM/Ogilvie,
Montreal, Quebec, Canada.
[0075] A further unexpected result may be achieved with the present
invention when the naphthalenesulfonate dispersant trimetaphosphate
salt combination is combined with pregelatinized corn starch, and
optionally, paper fiber or glass fiber. Gypsum panels made from
formulations containing these three ingredients have increased
strength and reduced weight, and are more economically desirable
due to the reduced water requirements in their manufacture.
[0076] Accelerators can be used in the gypsum-containing
compositions of the present invention, as described in U.S. Pat.
No. 6,409,825 to Yu et al., herein incorporated by reference. One
desirable heat resistant accelerator (HRA) can be made from the dry
grinding of landplaster (calcium sulfate dihydrate). Small amounts
of additives (normally about 5% by weight) such as sugar, dextrose,
boric acid, and starch can be used to make this HRA. Sugar, or
dextrose, is currently preferred. Another useful accelerator is
"climate stabilized accelerator" or "climate stable accelerator,"
(CSA) as described in U.S. Pat. No. 3,573,947, herein incorporated
by reference.
[0077] The aspects of the invention described below are not
intended to be exhaustive or to limit the invention to the specific
compositions, assemblies, methods and operations disclosed herein.
Rather, the described aspects and embodiments of the invention have
been chosen to explain the principles of the invention and its
application, operation and use in order to best enable those
skilled in the art to follow its teachings.
[0078] The present invention provides combinations of stucco and
other noted ingredients, examples of which are set forth in Table I
below. These formulations provide fire resistant, low weight and
density gypsum panels with desired fire resistance properties not
previously believed achievable by gypsum panels of such low weights
and densities. The panels of the invention also provide nail-pull
resistance suitable for a variety of construction purposes, and, in
some aspects, such properties are comparable to significantly
heavier, denser commercial fire rated panels. In yet other aspects,
when used in wall or other assemblies, such assemblies have fire
testing performance comparable to assemblies made with heavier,
denser commercial fire rated panels.
[0079] In one preferred aspect, the formulation and method of the
present invention provides 5/8 inch thick gypsum panels with a
panel density (core plus cover sheets) of about 27 to about 37 pa.
In other preferred aspects, the panel densities are from about 29
pcf to about 34 pcf or from about 30 to about 32 pcf. Such panels
of the invention provide fire resistance properties comparable to
much heavier and denser gypsum panels.
[0080] In another aspect of the present invention, a method is
provided for making fire resistant gypsum panels by preparing a
calcined gypsum containing aqueous slurry with the components
discussed herein, where the calcined gypsum (also referred to as
stucco), and water are used to create an aqueous slurry at a
preferred water/stucco weight ratio of about 0.6 to about 1.2 in
one aspect, about 0.8 to about 1.0 in another aspect, and about 0.9
in yet another aspect. The slurry is deposited as a continuous
ribbon on a continuous cover sheet web of paper, unwoven
fiberglass, or other fibrous materials or combination of fibrous
materials. A second such continuous cover sheet is then placed over
the deposited slurry ribbon to form a continuous gypsum panel of
the desired thickness and width. The continuous gypsum panel is cut
to a desired length after the calcined gypsum-containing slurry has
hardened (by hydration of the calcined gypsum to form a continuous
matrix of set gypsum) sufficiently for cutting, and the resulting
gypsum panels are dried. The dried panels, in addition, may be
subject to further cutting, shaping and trimming steps.
[0081] In other aspects of the present invention, a higher density
gypsum layer may be formed at or about the first cover sheet and/or
along the peripheral edges of the cover sheet. The higher density
layer typically provides beneficial properties to the panel
surfaces, such as increased hardness, improved nail pull strength
etc. The higher density along the peripheral edges of the cover
sheet typically provides improved edge hardness and other
beneficial properties. In other aspects, a higher density layer is
applied to either cover sheets, or the equivalent portions of the
core/cover sheet construction.
[0082] Typically, the higher density layers are applied using
conventional techniques such as by applying coatings to one or both
of the cover layers before or in close proximity of the deposition
of the core layer on the first cover sheet or the application of
the second cover sheet over the core slurry layer. Similarly, the
peripheral higher density layer may be applied as a strip or narrow
ribbon of gypsum slurry (with a density differing from that of the
core slurry) to the peripheral edges of the first cover sheet
before or in proximity to the deposition of the core slurry on the
first sheet. In some of such aspects, the higher density layers
comprise about 3% to about 4% of the board weight.
[0083] In one aspect the present invention provides a low weight
and density, fire resistant 5/8 inch thick gypsum panel suitable
for use as wallboard, ceiling board or in other construction
applications (such as exterior sheathing, roofing material, etc).
The cover sheets also may be coated with water or abuse resistant
coatings or, in some applications, gypsum, cementations materials,
acrylic materials or other coatings suitable for specific
construction needs. The panels also may be formed in a variety of
dimensions suitable for standard, non-standard, or custom
applications. Examples of such panels are nominal four feet wide
panels having a nominal length of eight feet, ten and twelve feet
typical of those used for building construction purposes.
[0084] The core density and overall density of the low weight, fire
resistant panels is a significant contributor to the overall weight
of the panels relative to conventional panels with similar with
dimensions. Thus, for 5/8 inch thick, panels, the panel weights
would be about 1380 lb/msf to about 1900 lb/msf, preferably about
1490 lb/msf to about 1740 lb/msf, and most preferably about 1540
lb/msf to about 1640 lb/msf. For 3/4 inch panel thicknesses, the
weight of the panels will be about 120% of the weights of the 5/8
inch panels.
[0085] The following table sets forth exemplary formulations for
the low weight and density, fire resistant nominal 5/8 inch gypsum
panels of the present invention.
TABLE-US-00001 TABLE I Exemplary Formulations for the Low Weight
and Density, Fire Resistant Nominal 5/8 Inch Gypsum Panels of the
Invention Core Density Of About Core Density Of About Core Density
Of About Component 25 to About 36 pcf 27 to About 33 pcf 28 to
About 30 pcf Stucco (lb/msf) about 1040 to about about 1120 to
about about 1160 to about (at least 95% 1490 1370 1245 gypsum) Set
gypsum (lb/msf) about 1220 to about about 1315 to about about 1360
to about 1750 1610 1460 Pregelatinized about 0.3 to about 4.0 about
0.5 to about 2.0 about 1.5 to about 1.8 Starch (% by weight of
stucco) Phosphate about 0.15 to about 0.5 about 0.10 to about 0.15
about 0.10 to about 0.15 (% by weight of stucco) Dispersant (% by
about 1.5 to about 0.3 about 1.2 to about 0.5 about 1.0 to about
0.75 weight of stucco) Mineral, Glass, or about 0.1 to about 0.3
about 0.1 to about 0.3 about 0.1 to about 0.3 Carbon fiber (% by
weight of stucco) Manila Paper First about 40 to about 60 about 45
to about 55 about 48 to about 53 Cover Sheets (lb/msf) Board
Density (pcf) about 27 to about 37 about 29 to about 34 about 30 to
about 32 (core and cover sheets) Board Weight about 1380 to about
about 1490 to about about 1540 to about (lb/msf) 1900 1740 1640
[0086] Other conventional additives can be employed in the practice
of the present invention in customary amounts to impart desirable
properties and to facilitate manufacturing. Example of such
additives are aqueous foams, set accelerators, set retarders,
dehydration inhibitors, binders, adhesives, dispersing aids,
leveling or nonleveling agents, thickeners, bactericides,
fungicides, pH adjusters, colorants, water repellants, fillers and
mixtures thereof.
[0087] In one aspect, utilizing one or more formulations within
those disclosed in Table L the present invention provides panels,
and methods for making same, configured as low weight and density,
nominally 5/8 inch thick for gypsum panels that will meet or exceed
a 30 minute fire rating pursuant to the fire containment and
structural integrity requirements of appropriate testing protocols.
Similar results may be achieved utilizing other formulations
consistent with the approach described herein.
[0088] The combination of low weight, fire resistance, and strength
and structural characteristics is due, it is believed, to the
unexpected results from the combination of the above components,
each of which is discussed in greater detail below.
[0089] Stucco.
[0090] In each aspect of the invention, the stucco (or calcined
gypsum) component used to form the crystalline matrix of the gypsum
panel core typically comprises beta calcium sulfate hemihydrate,
water-soluble calcium sulfate anhydrite, alpha calcium sulfate
hemihydrate, or mixtures of any or all of these, from natural or
synthetic sources. In some aspects, the stucco may include
non-gypsum minerals, such as minor amounts of clays or other
components that are associated with the gypsum source or are added
during the calicination, processing and/or delivery of the stucco
to the mixer.
[0091] By way of example, the amounts of stucco referenced in Table
I assumes that the gypsum source has at least a 95% purity.
Accordingly, the components, and their relative amounts, such as
those mentioned in Table I above, used to form the core slurry may
be varied or modified depending on the stucco source, purity and
content. For example, the composition of the gypsum core slurry may
be modified for different stucco compositions depending on the
gypsum purity, the natural or synthetic source for the gypsum, the
stucco water content, the stucco clay content, etc.
[0092] Starch.
[0093] In one important aspect of the panels of the invention, and
the methods for preparing such panels, the core slurry formulation,
such as mentioned in Table I above, includes a pregelatinized
starch. Raw starch is pregelatinized by cooking the starch in water
at temperatures of at least 185.degree. F. or by other well known
methods for causing gel formation in the starch utilized in the
panel core. The starch may be incorporated in the core slurry in a
dry form, a predispersed in liquid form or combinations of both. In
a dry form, it may be added to the core slurry mixer with other dry
ingredients or in a separate addition procedure, step or stage. In
the predispersed form, it may be added with other liquid
ingredients, such as gauging water, or in a separate addition
procedure, step or stage.
[0094] Some examples of readily available pregelatinized starches
that may be used in the practice of the present invention are (as
identified by their commercial names): PCF1000 starch, available
from Lauhoff Grain Co.; and AMERIKOR 818 and HQM PREGEL starches,
both available from Archer Daniels Midland Co. In one important
aspect, the starch component includes at least pregelatinized corn
starch, such as pregelatinized corn flour available from Bunge
Milling, St Louis, Mo. Such pregelatinized starches have the
following typical characteristics: moisture 7.5%, protein 8.0%, oil
0.5%, crude fiber 0.5%, ash 0.3%; having a green strength of 0.48
psi; and having a loose bulk density of 35.0 lb/ft.sup.3.
[0095] Fibers.
[0096] In the aspects of the invention incorporating fibers such as
mentioned in Table I above, and the methods for preparing such
panels, the fibers may include mineral fibers, glass and/or carbon
fibers, and mixtures of such fibers, as well as other comparable
fibers providing comparable benefits to the panel. In one important
aspect, glass fibers are incorporated in the gypsum core slurry and
resulting crystalline core structure. The glass fibers in such
aspects may have an average length of about 0.5 to about 0.75
inches and a diameter of about 11 to about 17 microns. In other
aspects, such glass fibers may have an average length of about 0.5
to about 0.675 inches and a diameter of about 13 to about 16
microns. In yet other aspects, E-glass fibers are utilized having a
softening point above about 800.degree. C. and one such fiber type
is Advantex.RTM. glass fibers (available from Owens Corning) having
a softening point above at least about 900.degree. C. Mineral wool
or carbon fibers such as those know to those of ordinary skill may
be used in place of or in combination with glass fibers, such as
those mentioned above.
[0097] Phosphate.
[0098] In one important aspect of the panels of the invention and
the methods for preparing such panels, a phosphate-containing
component comprising a phosphate salt or other source of phosphate
ions is added to the gypsum slurry used to produce the panel gypsum
core. The use of such phosphates contributes to providing a gypsum
core with increased strength, resistance to permanent deformation
(e.g., sag resistance), dimensional stability, and increased
strength of the panels when in a wet state, compared with set
gypsum formed from a mixture containing no phosphate. In many such
aspects, the phosphate source is added in amounts to provide
dimensional stability to the panel and panel core while the gypsum
hemihydrite in the core hydrates and forms the gypsum dihydrite
crystalline core structure (for example during the time between the
forming plate and the kiln section of the formation process).
Additionally, it is noted that to the extent that the added
phosphate acts as a retarder, an appropriate accelerator can be
added at the required level to overcome any adverse retarding
effects of the phosphate.
[0099] The phosphate-containing components useful in the present
invention are water-soluble and are in the form of an ion, a salt,
or an acid, namely, condensed phosphoric acids, each of which
comprises 2 or more phosphoric acid units; salts or ions of
condensed phosphates, each of which comprises 2 or more phosphate
units; and monobasic salts or monovalent ions of orthophosphates,
such as described, for example, in U.S. Pat. Nos. 6,342,284;
6,632,550; and 6,815,049, the disclosures of all of which are
incorporated herein by reference. Suitable examples of such classes
of phosphates will be apparent to those skilled in the art. For
example, any suitable monobasic orthophosphate-containing compound
can be utilized in the practice of the invention, including, but
not limited to, monoammonium phosphate, monosodium phosphate,
monopotassium phosphate, and combinations thereof. A preferred
monobasic phosphate salt is monopotassium phosphate.
[0100] Similarly, any suitable water-soluble polyphosphate salt can
be used in accordance with the present invention. The polyphosphate
can be cyclic or acyclic. Exemplary cyclic polyphosphates include,
for example, trimetaphosphate salts and tetrametaphosphate salts.
The trimetaphosphate salt can be selected, for example, from sodium
trimetaphosphate (also referred to herein as STMP), potassium
trimetaphosphate, lithium trimetaphosphate, ammonium
trimetaphosphate, and the like, or combinations thereof.
[0101] Also, any suitable water-soluble acyclic polyphosphate salt
can be utilized in accordance with the present invention. The
acyclic polyphosphate salt has at least two phosphate units. By way
of example, suitable acyclic polyphosphate salts in accordance with
the present invention include, but are not limited to,
pyrophosphates, tripolyphosphates, sodium hexametaphosphate having
from about 6 to about 27 repeating phosphate units, potassium
hexametaphosphate having from about 6 to about 27 repeating
phosphate units, ammonium hexametaphosphate having from about 6 to
about 27 repeating phosphate units, and combinations thereof. A
preferred acyclic polyphosphate salt pursuant to the present
invention is commercially available as CALGON.RTM. from ICL
performance Products LP, St. Louis, Mo., which is a sodium
hexametaphosphate having from about 6 to about 27 repeating
phosphate units.
[0102] Preferably, the phosphate-containing compound is selected
from the group consisting of sodium trimetaphosphate having the
molecular formula (NaPO.sub.3).sub.3, sodium hexametaphosphate
having 6-27 repeating phosphate units and having the molecular
formula Na.sub.n+2P.sub.nO.sub.3n+1 wherein n=6-27, tetrapotassium
pyrophosphate having the molecular formula K.sub.4P.sub.2O.sub.7,
trisodium dipotassium tripolyphosphate having the molecular formula
Na.sub.3K.sub.2P.sub.3O.sub.10, sodium tripolyphosphate having the
molecular formula Na.sub.5P.sub.3O.sub.10, tetrasodium
pyrophosphate having the molecular formula Na.sub.4P.sub.2O.sub.7,
aluminum trimetaphosphate having the molecular formula
Al(PO.sub.3).sub.3, sodium acid pyrophosphate having the molecular
formula Na.sub.2H.sub.2P.sub.2O.sub.7, ammonium polyphosphate
having 1000-3000 repeating phosphate units and having the molecular
formula (NH.sub.4).sub.n+2P.sub.nO.sub.3n+1 wherein n=1000-3000,
and polyphosphoric acid having 2 or more repeating phosphoric acid
units and having the molecular formula H.sub.n+2P.sub.nO.sub.3n+1
wherein n is 2 or more. Sodium trimetaphosphate is most preferred
and is commercially available from ICL performance Products LP, St.
Louis, Mo.
[0103] The phosphates usually are added in a dry form and/or an
aqueous solution liquid form, with the dry ingredients added to the
core slurry mixer, with the liquid ingredients added to the mixer,
or in other stages or procedures.
[0104] Dispersants.
[0105] In another aspect of the low weight and density, fire
resistant panels of the invention and the methods for preparing
such panels, dispersants may be included in the gypsum core slurry.
The dispersants may be added in a dry form with other dry
ingredients and/or an aqueous solution liquid form with other
liquid ingredients in the core slurry mixing operation, or in other
steps or procedures.
[0106] In one important aspect, such dispersants may include
naphthalenesulfonates, such as polynaphthalenesulfonic acid and its
salts (polynaphthalenesulfonates) and derivatives, which are
condensation products of naphthalenesulfonic acids and
formaldehyde. Such desirable polynaphthalenesulfonates include
sodium and calcium naphthalenesulfonate. The average molecular
weight of the naphthalenesulfonates can range from about 3,000 to
27,000, although it is preferred that the molecular weight be about
8,000 to 10,000. At a given solids percentage aqueous solution, a
higher molecular weight dispersant has higher viscosity, and
generates a higher water demand in the formulation, than a lower
molecular weight dispersant.
[0107] Useful naphthalenesulfonates include DILOFLO, available from
GEO Specialty Chemicals, Cleveland, Ohio; DAXAD, available from
Hampshire Chemical Corp., Lexington, Mass.; and LOMAR D, available
from GEO Specialty Chemicals, Lafayette, Ind. The
naphthalenesulfonates are preferably used as aqueous solutions in
the range 35-55% by weight solids content, for example. It is most
preferred to use the naphthalenesulfonates in the form of an
aqueous solution, for example, in the range of about 40-45% by
weight solids content. Alternatively, where appropriate, the
naphthalenesulfonates can be used in dry solid or powder form, such
as LOMAR D, for example.
[0108] Alternatively, in other aspects of the invention,
polycarboxylate dispersants useful for improving fluidity in gypsum
slurries may be used. A number of polycarboxylate dispersants,
particularly polycarboxylic ethers, are preferred types of
dispersants. One of the preferred class of dispersants used in the
slurry includes two repeating units. It is described further in
U.S. Pat. No. 7,767,019, entitled "Gypsum Products Utilizing a
Two-Repeating Unit System and Process for Making Them," which is
incorporated by reference. These dispersants are products of BASF
Construction Polymers, GmbH (Trostberg Germany) and are supplied by
BASF Construction Polymers, Inc. (Kennesaw, Ga.) (hereafter "BASF")
and are hereafter referenced as the "PCE211-Type Dispersants." A
particularly useful dispersant of the PCE211-Type Dispersants is
designated PCE211 (hereafter "211"). Other polymers in this series
useful in the present invention include PCE111. PCE211-Type
dispersants are described more fully in U.S. Ser. No. 11/827,722
(Pub. No. US 2007/0255032A1) filed Jul. 13, 2007, entitled
"Polyether-Containing Copolymer," herein incorporated by
reference.
[0109] The molecular weight of one type of such PCE211 Type
dispersants may be from about 20,000 to about 60,000 Daltons. It
has been found that the lower molecular weight dispersants cause
less retardation of set time than dispersants having a molecular
weight greater than 60,000 Daltons. Generally longer side chain
length, which results in an increase in overall molecular weight,
provides better dispensability. However, tests with gypsum indicate
that efficacy of the dispersant is reduced at molecular weights
above 50,000 Daltons.
[0110] Another class of polycarboxylate compounds that are useful
as dispersants in this invention is disclosed in U.S. Pat. No.
6,777,517, herein incorporated by reference and hereafter
referenced as the "2641-Type Dispersant." PCE211-Type and 2641-Type
dispersants are manufactured by BASF Construction Polymers, GmbH
(Trostberg, Germany) and marketed in the United States by BASF
Construction Polymers, Inc. (Kennesaw, Ga.). Preferred 2641-Type
Dispersants are sold by BASF as MELFLUX 2641F, MELFLUX 2651E and
MELFLUX 2500L dispersants.
[0111] Yet another preferred dispersant family is sold by BASF and
referenced as "1641-Type Dispersants." This dispersant is more
fully described in U.S. Pat. No. 5,798,425, herein incorporated by
reference. A one of such dispersants is a 1641-Type Dispersant is
marketed as MELFLUX 1641 F dispersant by BASF. Other dispersants
that can be used include other polycarboxylate ethers such as
COATEX Ethacryl M, available from Coatex, Inc. of Chester, S.C. and
lignosulfonates, or sulfonated lignin. Lignosulfonates are
water-soluble anionic polyelectrolyte polymers, byproducts from the
production of wood pulp using sulfite pulping. One example of a
lignin useful in the invention is Marasperse C-21 available from
Reed Lignin, Greenwich, Conn.
[0112] Retarders/Accelerator.
[0113] Set retarders (up to about 2 lb/MSF (9.8 g/m.sup.2)) or dry
accelerators (up to about 35 lb/MSF (170 g/m.sup.2)) may be added
to some aspects of the core slurry to modify the rate at which the
stucco hydration reactions take place. "CSA" is a set accelerator
including 95% calcium sulfate dihydrate co-ground with 5% sugar and
heated to 250.degree. F. (1-21.degree. C.) to caramelize the sugar.
CSA is available from USG Corporation, Southard, Okla. plant, and
is made according to U.S. Pat. No. 3,573,947, herein incorporated
by reference. Potassium sulfate is another preferred accelerator.
HRA, which is a preferred accelerator, is 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. It is further
described in U.S. Pat. No. 2,078,199, herein incorporated by
reference. Both of these are preferred accelerators.
[0114] Another accelerator, known as wet gypsum accelerator or WGA,
is also a preferred accelerator. A description of the use of and a
method for making wet gypsum accelerator are disclosed in U.S. Pat.
No. 6,409,825, herein incorporated by reference. This accelerator
includes at least one additive selected from the group consisting
of an organic phosphonic compound, a phosphate-containing compound
or mixtures thereof. This particular accelerator exhibits
substantial longevity and maintains its effectiveness over time
such that the wet gypsum accelerator can be made, stored, and even
transported over long distances prior to use. The wet gypsum
accelerator is used in amounts ranging from about 5 to about 80
pounds per thousand square feet (24.3 to 390 g/m.sup.2) of gypsum
panel.
[0115] Foam.
[0116] In another important aspect, foam may be introduced into the
core slurry in amounts that provide the above mentioned reduced
core density and panel weight. The introduction of foam in the core
slurry in the proper amounts, formulations and process will produce
a desired network and distribution of voids within the core of the
final dried panels. This void structure permits the reduction of
the gypsum and other core constituents and the core density and
weight, while maintaining desired panel structural and strength
properties. Examples of the use of foaming agents to produce
desired void structures include those discussed in U.S. Pat. No.
5,643,510, the disclosure of which is incorporated by reference
herein. The approaches for adding foam to a core slurry are known
in the art and one example of such an approach is discussed in U.S.
Pat. No. 5,683,635, the disclosure of which is incorporated by
reference herein.
[0117] Cover Sheets.
[0118] In some aspects of the invention, the first cover sheet
comprises low porosity manila paper upon which the gypsum slurry is
dispensed (which typically is exposed face of the panel when used
in a construction application). Newsline may be used as the second
cover sheet placed on the gypsum core slurry during the forming
process (which typically is the concealed back surface of the
panels when used construction applications. In other applications,
unwoven fiberglass mats, sheet materials of other fibrous or
non-fibrous materials, or combinations of paper and other fibrous
materials may be used as one or both of the cover sheets.
[0119] In aspects using paper or similar cover sheets, the first
cover sheet is a higher density and basis weight than the second
coversheet. For example, in some aspects, the first cover sheet has
a basis weight of about 40 to 60 lb/msf, and the second coversheet
has a basis weight of about 35 to 45 lb/msf. The use of such heavy
manila paper as the first cover sheet is preferred because it
improves the nail pull and flexure properties of the panels in all
applications and most particularly in ceiling applications.
[0120] The cover sheets may incorporate and may have added to their
exposed surfaces, coatings of materials providing surfaces suitable
for specific construction applications such as exterior sheathing,
roofing, tile backing, etc.
[0121] Siloxane.
[0122] Surprisingly the combination of greater than 2% by weight
based on the weight of gypsum of pregelatinaized starch and at
least about 0.4% and preferably at least about 0.7% by weight based
on the weight of the gypsum of siloxane will produce gypsum panels
with less than 5% water absorption. This is particularly surprising
since reduced weight and density panels have far more air and/or
water voids than conventional panels and these voids would be
expected to make the low weight panels far more water absorbent. It
has also been unexpectedly found that the polymerized silicone
resin lessens shrinkage of the panel under high heating
conditions.
[0123] The present invention broadly contemplates improving the
water resistance of gypsum based articles by adding a polymerizable
siloxane to the slurry used to make the gypsum based article's.
Preferably, the siloxane is added in the form of an emulsion. The
slurry is then shaped and dried under conditions which promote the
polymerization of the siloxane to form a highly cross-linked
silicone resin. A catalyst which promotes the polymerization of the
siloxane to form a highly cross-linked silicone resin is preferably
added to the gypsum slurry.
[0124] Preferably, the siloxane is generally a fluid linear
hydrogen-modified siloxane, but can also be a cyclic
hydrogen-modified siloxane. Such siloxanes are capable of forming
highly cross-linked 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
invention comprise those having a repeating unit of the general
formula:
##STR00002##
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.
Cross-linking of the chains also occurs. The resulting silicone
resin imparts water resistance to the gypsum matrix as it
forms.
[0125] Preferably, a solventless methyl hydrogen siloxane fluid
sold under the name SILRES BS 94 by Wacker-Chemie GmbH (Munich,
Germany) will be used as the siloxane. The manufacturer indicates
this product is a siloxane fluid containing no water or solvents.
It is contemplated that about 0.3 to 1.0% of the BS 94 siloxane may
be used, based on the weight of the dry ingredients. It is
preferred to use from about 0.4 to about 0.8% of the siloxane based
on the dry stucco weight.
[0126] The siloxane is formed into an emulsion or a stable
suspension with water. A number of siloxane emulsions are
contemplated for use in this slurry. Emulsions of siloxane in water
are also available for purchase, but they may include emulsifying
agents that tend to modify properties of the gypsum articles, such
as the paper bond in gypsum panel products. Emulsions or stable
suspensions prepared without the use of emulsifiers are therefore
preferred. Preferably, the suspension will be formed in situ by
mixing the siloxane fluid with water. It is essential that the
siloxane suspension be stable until used and that it remain well
dispersed under the conditions of the slurry. The siloxane
suspension or emulsion must remain well dispersed in the presence
of the optional additives, such as set accelerators, that may be
present in the slurry. The siloxane suspension or emulsion must
also remain stable through the steps in which the gypsum panels are
formed as well. Preferably, the suspension remains stable for more
than 40 minutes. More preferably, it remains stable for at least
one hour. In the discussion and claims that follow, the term
"emulsion" is intended to include true emulsions and suspensions
that are stable at least until the stucco is 50% set.
[0127] While not wishing to be bound by theory, it is believed that
water resistance develops when the siloxane cures within the formed
panels and that the at least 2.0% by weight pregelatinized starch
works in conjunction with the siloxane to slow water entry through
micropores on the panel edges first by blocking water entry and
then, upon take-up of water by the starch by forming a highly
viscous starch/water combination.
[0128] The siloxane polymerization reaction proceeds slowly on its
own, requiring that the panels be stored for a time sufficient to
develop water-resistance prior to shipping. Catalysts are known to
accelerate the polymerization reaction, reducing or eliminating the
time needed to store gypsum panels as the water-resistance
develops. Use of dead-burned magnesium oxide for siloxane
polymerization is described in co-pending U.S. Ser. No. 10/917,177,
entitled "Method of Making Water-Resistant Gypsum-Based Article",
herein incorporated by reference. Dead-burned magnesium oxide is
water-insoluble and interacts less with other components of the
slurry. It accelerates curing of the siloxane and, in some cases,
causes the siloxane to cure more completely. It is commercially
available with a consistent composition. A particularly preferred
source of dead-burned magnesium oxide is BAYMAG 96. It has a BET
surface area of at least 0.3 m.sup.2/g. The loss on ignition is
less than 0.1% by weight. The magnesium oxide is preferably used in
amounts of about 0.1 to about 0.5% based on the dry stucco
weight.
[0129] 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.degree. C. and
2000.degree. C., eliminating most, if not all, of the reactivity.
MagChem P98-PV (Martin Marietta Magnesia Specialties, Bethesda,
Md.) is an example of a "dead burned" magnesium oxide. BayMag 96
(Baymag, Inc. of Calgary, Alberta, Canada) and MagChem 10 (Martin
Marietta Magnesia Specialties, Bethesda, Md.) are examples of
"hard-burned" magnesia. "Hard-burned" magnesium oxide is calcined
at temperatures from 1000.degree. C. to about 1500.degree. 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. The third grade
is "light-burn" or "caustic" magnesia, produced by calcining at
temperatures of about 700.degree. C. to about 1000.degree. 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 BayMag 30, BayMag 40, and BayMag 30 (-325
Mesh) (BayMag, Inc. of Calgary. Alberta. Canada).
[0130] It has been discovered that preferred catalysts are made of
a mixture of magnesium oxide and Class C fly ash. When combined in
this manner, any of the grades of magnesium oxide are useful.
However, dead-burned and hard-burned magnesium oxides are preferred
due to reduced reactivity. The relatively high reactivity of
magnesium oxides, can lead to cracking reactions which can produce
hydrogen. As the hydrogen is generated, the product expands,
causing cracks where the stucco has set. Expansion also causes
breakdown of molds into which the stucco is poured, resulting in
loss of detail and deformation of the product in one or more
dimensions. Preferably, BayMag 96, MagChem P98-PV and MagChem 10
are the preferred sources of magnesium oxide. Preferably, the
magnesium oxide and fly ash are added to the stucco prior to their
addition to the gauging water. Dry components such as these are
often added to the stucco as it moves along a conveyer to the
mixer.
[0131] A preferred fly ash is a Class C fly ash. Class C hydraulic
fly ash, or its equivalent, is the most preferred fly ash
component. A typical composition of a Class C fly ash is shown in
Table 1. High lime content fly ash, greater than 20% lime by
weight, which is obtained from the processing of certain coals.
ASTM designation C-618, herein incorporated by reference, describes
the characteristics of Class C fly ash. A preferred Class C fly ash
is supplied by Bayou Ash Inc., Big Cajun, II, L A. Preferably, fly
ash is used in amounts of about 0.1% to about 5% based on the dry
stucco weight. More preferably, the fly ash is used in amounts of
about 0.2% to 1.5% based on the dry stucco weight.
[0132] Catalysis of the siloxane results in faster and more
complete polymerization and cross-linking of siloxane to form the
silicone resin. Hydration of the stucco forms an interlocking
matrix of calcium sulfate dihydrate crystals. While the gypsum
matrix is forming, the siloxane molecules are also forming a
silicone resin matrix. Since these are formed simultaneously, at
least in part, the two matrices become intertwined in each other.
Excess water and additives to the slurry, including the fly ash,
magnesium oxide and additives described below, which were dispersed
throughout the slurry, become dispersed throughout the matrices in
the interstitial spaces to achieve water resistance throughout the
panel core. The high level of pregelatinized starch works in
conjunction with the siloxane to retard water entry along the more
vulnerable edges of the panel.
EXAMPLES
[0133] The following examples further illustrate aspects of the
inventions described herein but should not be construed as in any
way limiting its scope. All values reported herein (e.g. weights,
percentages, temperatures, dimensions, times, etc.) are subject to
and include, the measurement variations and margins of error
reflected in the data as well as that which typically encountered
by one of ordinary skill in the art for the specific component,
test, property or observation to which they relate.
Example 1
Sample Gypsum Slurry Formulations
[0134] Gypsum slurry formulations are shown in Table 1 below. All
values in Table 1 are expressed as weight percent based on the
weight of dry stucco. Values in parentheses are dry weight in
pounds (lb/MSF for a nominally 1/2 inch thick panel).
TABLE-US-00002 TABLE 1 Component Formulation A Formulation B Stucco
(lb/MSF) (732) (704) sodium 0.20 (1.50) 0.30 (2.14)
trimetaphosphate Dispersant 0.18 (1.35) 0.58.sup.1 (4.05)
(naphthalenesulfonate) Pregelatinized starch 2.7 (20) 6.4 (45)
Board starch 0.41 (3.0) 0 Heat resistant (15) (15) accelerator
(HRA) Glass fiber 0.27 (2.0) 0.28 (2.0) Paper fiber 0 0.99 (7.0)
Soap* 0.03 (0.192) 0.03 (0.192) Total Water (lb.) 805 852
Water/Stucco ratio 1.10 1.21 *Used to pregenerate foam. .sup.11.28%
by weight as a 45% aqueous solution.
Example 2
Preparation of Panels
[0135] Sample gypsum panels (nominally about 1/2 inch thick) were
prepared in accordance with U.S. Pat. No. 6,342,284 to Yu et al.
and U.S. Pat. No. 6,632,550 to Yu et al., herein incorporated by
reference. This includes the separate generation of foam and
introduction of the foam into the slurry of the other ingredients
as described in Example 5 of these patents.
[0136] Test results for gypsum panels made using the Formulations A
and B of Example 1, and a control are shown in Table 2 below. As in
this example and other examples below, nail pull resistance, core
hardness, and flexural strength tests were performed according to
ASTM C-473. Additionally, it is noted that typical gypsum panel is
approximately 1/2 inch thick and has a weight of between about 1600
to 1800 pounds per 1,000 square feet of material, or lb/MSF. ("MSF"
is a standard abbreviation in the art for a thousand square feet;
it is an area measurement for boxes, corrugated media and
wallboard.)
TABLE-US-00003 TABLE 2 Control Formulation A Formulation B Lab test
result Board Board Board Board weight (lb/MSF) 1587 1066 1042 Nail
pull resistance (lb) 81.7 50.2 72.8 Core hardness (lb) 16.3 5.2
11.6 Humidified bond load (lb) 17.3 20.3 15.1 Humidified bond 0.6 5
11.1 failure (%) Flexural strength, face- 47 47.2 52.6 up (MD) (lb)
Flexural strength, face- 51.5 66.7 78.8 down (MD) (lb) Flexural
strength, face- 150 135.9 173.1 up (XMD) (lb) Flexural strength,
face- 144.4 125.5 165.4 down (XMD) (lb) MD: machine direction XMD:
across machine direction
[0137] As illustrated in Table 2, gypsum panels prepared using the
Formulation A and B slurries have significant reductions in weight
compared to the control board. With reference again to Table 1, the
comparisons of the Formulation A board to the Formulation B board
are most striking. The water/stucco (w/s) ratios are similar in
Formulation A and Formulation B. A significantly higher level of
naphthalenesulfonate dispersant is also used in Formulation B.
Also, in Formulation B substantially more pregelatinized starch was
used, about 6% by weight, a greater than 100% increase over
Formulation A accompanied by marked strength increases. Even so,
the water demand to produce the required flowability remained low
in the Formulation B slurry, the difference being about 10% in
comparison to Formulation A. The low water demand in both
Formulations is attributed to the synergistic effect of the
combination of naphthalenesulfonate dispersant and sodium
trimetaphosphate in the gypsum slurry, which increases the fluidity
of the gypsum slurry, even in the presence of a substantially
higher level of pregelatinized starch.
[0138] As illustrated in Table 2, the gypsum panels prepared using
the Formulation B slurry has substantially increased strength
compared with the panels prepared using the Formulation A slurry.
By incorporating increased amounts of pregelatinized starch in
combination with increased amounts of naphthalenesulfonate
dispersant and sodium trimetaphosphate, nail pull resistance in the
Formulation B board improved by 45% over the Formulation A board.
Substantial increases in flexural strength were also observed in
the Formulation B board as compared to the Formulation A board.
Example 3
1/2 Inch Gypsum Panel Weight Reduction Trials
[0139] Further gypsum panel examples (Boards C, D and E), including
slurry formulations and test results are shown in Table 3 below.
The slurry formulations of Table 3 include the major components of
the slurries. Values in parentheses are expressed as weight percent
based on the weight of dry stucco.
TABLE-US-00004 TABLE 3 Control Formulation Formulation Formulation
Board C Board D Board E Board Trial formulation component/parameter
Dry stucco (lb/MSF) 1300 1281 1196 1070 Accelerator (lb/MSF) 9.2
9.2 9.2 9.2 DILOFLO.sup.1 (lb/MSF) 4.1 (0.32%) 8.1 (0.63%) 8.1
(0.68%) 8.1 (0.76%) Regular starch (lb/MSF) 5.6 (0.43%) 0 0 0
Pregelatinized corn starch 0 10 (0.78%) 10 (0.84%) 10 (0.93%)
(lb/MSF) Sodium trimetaphosphate 0.7 (0.05%) 1.6 (0.12%) 1.6
(0.13%) 1.6 (0.15%) (lb/MSF) Total water/stucco ratio 0.82 0.82
0.82 0.84 (w/s) Trial formulation test results Dry board weight
1611 1570 1451 1320 (lb/MSF) Nail pull resistance (lb)
77.3.sup..dagger. 85.5 77.2 65.2 .sup..dagger.ASTM standard: 77 lb
.sup.1DILOFLO is a 45% Naphthalenesulfonate solution in water
[0140] As illustrated in Table 3, Boards C, D, and E were made from
a slurry having substantially increased amounts of starch, DILOFLO
dispersant, and sodium trimetaphosphate in comparison with the
control panels (about a two-fold increase on a percentage basis for
the starch and dispersant, and a two- to three-fold increase for
the trimetaphosphate), while maintaining the w/s ratio constant.
Nevertheless, strength as measured by nail pull resistance was not
dramatically affected and panel weight was significantly reduced.
Therefore, in this example of an embodiment of the invention, the
new formulation (such as, for example, Board D) can provide
increased starch formulated in a usable, flowable slurry, while
maintaining adequate strength.
Example 4
Wet Gypsum Cube Strength Test
[0141] The wet cube strength tests were carried out by using
Southard CKS board stucco, available from United States Gypsum
Corp., Chicago, Ill. and tap water in the laboratory to determine
their wet compressive strength. The following lab test procedure
was used.
[0142] Stucco (1000 g), CSA (2 g), and tap water (1200 cc) at about
70.degree. F. were used for each wet gypsum cube cast.
Pregelatinized corn starch (20 g, 2.0% based on stucco wt.) and CSA
(2 g, 0.2% based on stucco wt.) Were thoroughly dry mixed first in
a plastic bag with the stucco prior to mixing with a tap water
solution containing both naphthalenesulfonate dispersant and sodium
trimetaphosphate. The dispersant used was DILOFLO dispersant
(1.0-2.0%, as indicated in Table 4). Varying amounts of sodium
trimetaphosphate were used also as indicated in Table 4.
[0143] The dry ingredients and aqueous solution were initially
combined in a laboratory Warning blender, the mixture produced
allowed to soak for 10 sec, and then the mixture was mixed at low
speed for 10 sec in order to make the slurry. The slurries thus
formed were cast into three 2''.times.2''.times.2'' cube molds. The
cast cubes were then removed from the molds, weighed, and sealed
inside plastic bags to prevent moisture loss before the compressive
strength test was performed. The compressive strength of the wet
cubes was measured using an ATS machine and recorded as an average
in pounds per square inch (psi). The results obtained were as
follows:
TABLE-US-00005 TABLE 4 Sodium trimetaphosphate, DILOFLO 1 Wet cube
Test grams (wt % (wt % based weight Wet cube Sample based on dry on
dry (2'' .times. 2'' .times. 2''), compressive No. stucco) stucco)
g strength, psi 1 0 1.5 183.57 321 2 0.5 (0.05) 1.5 183.11 357 3 1
(0.1) 1.5 183.19 360 4 2 (0.2) 1.5 183.51 361 5 4 (0.4) 1.5 183.65
381 6 10 (1.0) 1.5 183.47 369 7 0 1.0 184.02 345 8 0.5 (0.05) 1.0
183.66 349 9 1 (0.1) 1.0 183.93 356 10 2 (0.2) 1.0 182.67 366 11 4
(0.4) 1.0 183.53 365 12 10 (1.0) 1.0 183.48 341 13 0 2.0 183.33 345
14 0.5 (0.05) 2.0 184.06 356 15 1 (0.1) 2.0 184.3 363 16 2 (0.2)
2.0 184.02 363 17 4 (0.4) 2.0 183.5 368 18 10 (1.0) 2.0 182.68 339
.sup.1DILOFLO is a 45% Naphthalensulfonate solution in water
[0144] As illustrated in Table 4, Samples 4-5, 10-11, and 17,
having levels of sodium trimetaphosphate in the about 0.12-0.4%
range of the present invention generally provided superior wet cube
compressive strength as compared to samples with sodium
trimetaphosphate outside this range.
Example 5
1/2 Inch Light Weight Gypsum Panel Plant Production Trials
[0145] Further trials were performed (Trial Boards 1 and 2),
including slurry formulations and test results are shown in Table 5
below. The slurry formulations of Table 5 include the major
components of the slurries. Values in parentheses are expressed as
weight percent based on the weight of dry stucco.
TABLE-US-00006 TABLE 5 Plant Plant Control Formulation Control
Formulation Board 1 Trial Board 1 Board 2 Trial Board 2 Trial
formulation component/parameter Dry stucco (lb/MSF) 1308 1160 1212
1120 DILOFLO.sup.1 (lb/MSF) 5.98 (0.457%) 7.98 (0.688%) 7.18
(0.592%) 8.99 (0.803%) Regular starch (lb/MSF) 5.0 (0.38%) 0 4.6
(0.38%) 0 Pregelatinized corn starch 2.0 (0.15%) 10 (0.86%) 2.5
(0.21%) 9.0 (0.80%) (lb/MSF) Sodium trimetaphosphate 0.7 (0.05%)
2.0 (0.17%) 0.6 (0.05%) 1.6 (0.14%) (lb/MSF) Total water/stucco
ratio 0.79 0.77 0.86 0.84 (w/s) Trial formulation test results Dry
board weight 1619 1456 1553 1443 (lb/MSF) Nail pull resistance (lb)
81.5.sup..dagger. 82.4 80.7 80.4 Flexural strength, 41.7 43.7 44.8
46.9 average (MD) (lb) Flexural strength, 134.1 135.5 146 137.2
average (XMD) (lb) Humidified bond.sup.2 load, 19.2 17.7 20.9 19.1
average (lb) Humidified bond.sup.2,3 1.6 0.1 0.5 0 failure (%)
.sup..dagger.ASTM standard: 77 lb MD: machine direction XMD: across
machine direction .sup.1DILOFLO is a 45% Naphthalensulfonate
solution in water
.sup.290.degree. F./90% Relative Humidity
[0146] .sup.3It is well understood that under these test
conditions, percentage failure rates<50% are acceptable.
[0147] As illustrated in Table 5, Trial Boards 1 and 2 were made
from a slurry having substantially increased amounts of starch,
DILOFLO dispersant, and sodium trimetaphosphate, while slightly
decreasing the w/s ratio, in comparison with the control panels.
Nevertheless, strength as measured by nail pull resistance and
flexural testing was maintained or improved, and board weight was
significantly reduced. Therefore, in this example of an embodiment
of the invention, the new formulation (such as, for example, Trial
Boards 1 and 2) can provide increased trimetaphosphate and starch
formulated in a usable, flowable slurry, while maintaining adequate
strength.
Example 6
1/2 Inch Ultra-Light Weight Gypsum Panel Plant Production
Trials
[0148] Further trials were performed (Trial Boards 3 and 4) using
Formulation B (Example 1) as in Example 2, except that the
pregelatinized corn starch was prepared with water at 10%
concentration (wet starch preparation) and a blend of HYONIC PFM
soaps (available from GEO Specialty Chemicals, Lafayette, Ind.) was
used. For example, Trial Board 3 was prepared with a blend of
HYONIC PFM 10/HYONIC PFM 33 ranging from 65-70% by weight/35-30% by
weight. For example, Trial Board 4 was prepared with a 70/30
wt./wt. blend of HYONIC PFM 10/HYONIC PFM 33. The trial results are
shown in Table 6 below.
TABLE-US-00007 TABLE 6 Trial Board 3 Trial Board 4 (Formulation B
plus (Formulation B plus HYONIC soap blend HYONIC soap blend 65/35)
70/30) Lab test result (n = 12) (n = 34)* Board weight (lb/MSF)
1106 1013 Nail pull resistance.sup.a (lb) 85.5 80.3 Core
hardness.sup.b (lb) >15 12.4 Flexural strength, 55.6 60.3.sup.1
average.sup.c (MD) (lb) Flexural strength, 140.1 142.3.sup.1
average.sup.d (XMD) (lb) *Except as marked. .sup.1n = 4 MD: machine
direction XMD: across machine direction .sup.aASTM standard: 77 lb
.sup.bASTM standard: 11 lb .sup.cASTM standard: 36 lb .sup.dASTM
standard: 107 lb
[0149] As illustrated in Table 6, strength characteristics as
measured by nail pull and core hardness were above the ASTM
standard. Flexural strength was also measured to be above the ASTM
standard. Again, in this example of an embodiment of the invention,
the new formulation (such as, for example, Trial Boards 3 and 4)
can provide increased trimetaphosphate and starch formulated in a
usable, flowable slurry, while maintaining adequate strength.
Example 7
[0150] High temperature thermal insulation testing pursuant to the
procedures discussed in ASTM Pub. WK25392 was conducted to examine
the high temperature thermal insulating characteristics of the 518
inch thick gypsum panels made in accordance with the invention.
[0151] The heat transfer conditions reflected in this test can be
described by the energy equation for one dimensional unsteady heat
conduction through the panel thickness:
.DELTA./.DELTA.x(.DELTA.T/.DELTA.x))+q=.rho.c.sub.p(.DELTA.T/.DELTA.t)
(1)
[0152] Where T is the temperature at a given time t and depth x in
the panel. The thermal conductivity (k), density (.rho.), and
specific heat (c.sub.p) are nonlinear temperature dependent
functions at elevated temperatures. The heat generation rate q
represents a variety of endothermic and exothermic reactions, e.g.,
gypsum phase changes and face paper combustion, which occur at
different temperatures and, correspondingly, at different
times.
[0153] For the purpose of evaluating the total heat conduction
through the gypsum panel and hence its thermal insulating
performance, it typically is not necessary to measure and describe
each variable separately. It is sufficient to evaluate their net
cumulative effect on heat transfer.
[0154] For this purpose, a high temperature thermal insulation test
was developed in which test specimens consisting of two 4 inch (100
mm) diameter disks are clamped together by type G bugle head
screws.
[0155] Test specimens were prepared from a gypsum panel made using
a core containing:
TABLE-US-00008 Stucco 1170 lb/msf Pregelatinized corn starch 28
lb/msf (2.3% by weight of stucco) Sodium trimetaphosphate 29 lb/msf
(2.5% by weight of stucco) (10% aqueous solution) Naphthalene
sulfonate 5 lb/msf (0.4% by weight of stucco) dispersant (45%
solids) Glass fiber 2 lb/msf (0.2% by weight of stucco) Cover paper
front 51 lb/msf (heavy manila); back 39 lb/msf (newsprint)
[0156] A thermocouple is placed at the center of the specimen
between the disks. The specimen then is mounted on edge in a rack
designed to insure uniform heating over its surface and placed in a
furnace pre-heated to 930.degree. F. (500.degree. C.).
[0157] The temperature rise at the center of the test specimen is
recorded and a thermal insulation index, TI, computed as the time,
in minutes, required for the test specimen to heat from about
105.degree. F. (40.degree. C.) to about 390.degree. F. (200.degree.
C.) is measured. The thermal insulation index of the test specimen
is calculated as:
TI=t200.degree. C.-t40.degree. C. (2)
[0158] A temperature profile developed from data collected by this
procedure often shows the transition from gypsum to hemihydrate at
about 212.degree. F. (100.degree. C.) and the conversion of
hemihydrate to the first anhydrite phase near about 285.degree. F.
(140.degree. C.). Such data also often shows that once these phase
transitions are completed, the temperature rises rapidly in a
linear fashion as no further chemical or phase change reactions of
significance typically occur below the oven temperature of about
930.degree. F. (500.degree. C.). By waiting until the specimen's
core temperature has reached about 105.degree. F. (40.degree. C.)
to begin timing, acceptable repeatability and reproducibility were
achieved.
[0159] The above thermal insulation test was performed on disks cut
from the 5/8 inch thick gypsum panel prepared in accordance with
the invention having a panel weight of 1545 lb/msf. These samples
had an average Thermal Insulation Index of 18.6 minutes. In
comparison, the average Thermal Insulation Index value for a
commercially available approximately 1500 lb/msf nominal 1/2 inch
thick commercial interior ceiling panel was 17.0 minutes. It was
unexpected that the panel of the invention (with a core density of
about 30 pcf) would have a greater Thermal Insulation Index
relative to a panel of approximately the same weight but a greater
core density (about 35 pcf).
Example 8
[0160] Samples of panels of the invention were subject to fire
testing pursuant to the procedures of UL U419 using nominal 5/8
inch thick gypsum panels in accordance with the invention having a
panel weight of about 1546 lb/msf comprising:
TABLE-US-00009 Stucco 1170 lb/msf Pregelatinized starch 28 lb/msf
(2.3% by weight based on stucco) Sodium trimetaphosphate 0.12% by
weight based on (dry basis) stucco Naphthalene sulfonate 0.14% by
weight based on dispersant (dry basis) stucco 1/2 inch chopped
e-glass fiber 0.17% by weight based on stucco Paper front 51 lb/msf
(heavy manila); back 39 lb/msf (newsprint)
[0161] The physical parameters of the 4'.times.10' gypsum panels
were as follows:
TABLE-US-00010 Average panel thickness 0.606 in. (nominally 5/8
in.) Average panel weight 61.62 lb/1545 lb/msf (4' .times. 10')
Average board density 30.64 pcf
[0162] In the U419 test, wall assemblies in a 10 foot by 10 foot
wall were constructed. The studs used were commercially available
light gauge steel studs formed from steel having a thickness from
about 0.015 inches to about 0.032 inches, and having the dimensions
of about 35/8'' or 31/2'' inches wide by about 11/4'' inches thick.
The light gauge steel studs were spaced about 24 inches apart in
the assembly per U419 specification.
[0163] The U419 test procedures are considered among the most
rigorous of the types of UL tests as the light gauge steel studs
often experience heat deformation (typically urging the exposed
panels towards the gas jet flames) due to heat transfer through the
panels and into the assembly cavity between the exposed and
unexposed panels. This deformation often causes separation of the
panel joints, or other failures, on the heated, exposed side of the
assembly allowing penetration of the gas jet flame and/or high heat
quickly into the assembly cavity and into the unexposed, unheated
side of the assembly. It is expected that the lighter the gauge of
the steel studs, the greater the likelihood of heat deformation of
the studs and assembly.
[0164] The gypsum panels were attached horizontally, i.e.
perpendicular to the vertical studs, on each side of the assembly.
Typically, two 10 foot by 4 foot panels, and one 10 foot by 2 foot
panel were used on each side of the frame. The panels were attached
to the frame with one inch type-S hi/low screws on each side of the
assembly, eight inches off center. The panels were positioned so
that the seams between the panels on each side of the frame were
aligned with each other. Then, the seams were sealed with paper
joint tape and joint compound. In the tests following the
procedures of U419, the steel used to form the light gauge studs
was either 0.015 inches or 0.018 inches thick and the assembly is
not subject to external loading.
[0165] In each of the tests, the completed panel and frame assembly
was positioned so that one side of the assembly, the exposed side,
was subjected to an array of gas jet furnace flames that heated the
exposed side of the assembly to temperatures and at a rate
specified by the ASTM standard ASTM 119. Pursuant to the U419
procedures, a set of about 14 sensors were arrayed in spaced
relation between the heated exposed side of the assembly and each
of the gas jets to monitor the temperatures used to heated the
exposed side of the assembly. Also pursuant to those procedures, a
set of sensors were arrayed in spaced relation on the opposite,
unheated, unexposed side of the assembly. Typically, 12 sensors
were applied to the, unexposed surface of the assembly in a pattern
in accordance with the UL procedures. Pursuant to those procedures,
each sensor also was covered by an insulating pad.
[0166] During the fire test procedures, the furnace temperatures
used followed the ASTM-119 heating curve starting at ambient
temperatures and increasing on the exposed side of the assembly to
over 1600.degree. F. in approximately one hour, with the most rapid
change in temperature occurring early in the test and near the
test's conclusion. The test was terminated when either there was a
catastrophic load failure on the exposed side of the assembly, the
average of the temperatures from the sensors on the unexposed side
of the assembly exceeded a preselected temperature (250.degree. F.
above ambient), or when a single sensor on the unexposed side of
the assembly exceeded a second preselected temperature (325.degree.
F. above ambient).
[0167] The data generated during the U419 test is plotted in FIGS.
1 and 2. FIG. 1 is a plot of the temperatures reported by the
single sensor that reached the maximum temperature at the test
termination and a plot of the average of the sensor temperatures
from the start of the test to the test termination. FIG. 1 also
shows a plot of the ASTM 119 temperature curve used for the furnace
temperatures on the exposed, heated side of the assembly. FIG. 2 is
an expanded plot of the data for that maximum single sensor and
average sensor temperatures shown in FIG. 1.
[0168] As indicated FIGS. 1 and 2, both maximum single sensor and
average sensor temperatures on the unexposed surface of the
assembly gradually increased during the testing relative to the
furnace temperatures, with a more rapid increase in the single
sensor temperature near the test termination. For example, at about
20 minutes elapsed time, the maximum sensor and average sensor
temperatures on the unexposed surface of the assembly were less
than about 180.degree. F. and about 175.degree. F., respectively.
At about 25 minutes, the maximum sensor and average sensor
temperatures were less than about 195.degree. F. and about
190.degree. F., respectively. At about 30 minutes, the maximum
sensor and average sensor temperatures were less than about
230.degree. F. and about 210.degree. F., respectively. The maximum
single sensor temperature did not exceed 300.degree. F., until well
after about 30 minutes elapsed time, with a temperature of less
than about 410.degree. F. at about 35 minutes. The average sensor
did not exceed 300.degree. F. until the termination of the test at
over 35 minutes, with a with a temperature of less than about
290.degree. F. at about 35 minutes.
[0169] The panels of the invention also satisfied criteria such as
that used to establish UL fire ratings, which is confirmed by the
data shown in FIGS. 1 and 2. The panels of the invention satisfied
criteria that would qualify for a "30 minute" fire rating. Among
other requirements, such criteria would require an average sensor
temperature on the unexposed surface of the assembly of no more
than the ambient temperature at the start of the test plus
250.degree. F. and a maximum individual sensor temperature of no
more than the ambient temperature at the start of the test plus
325.degree. F. (typically ambient temperatures are about 90.degree.
F. or less for such testing). The temperatures from the U419 test
under these criteria are indicated below.
TABLE-US-00011 Average Individual Unexposed Surface 319.degree. F.
394.degree. F. Limiting Temperature Criteria Ambient Temperature
69.degree. F. Unexposed Surface Not Exceeded T/C # 1 @ Temperature
Limits Reached @ 304.degree. F. 34 Min. 30 Sec.
[0170] Therefore, this test demonstrates that the panels of the
present invention have the ability to substantially delay the
passage of heat through wall or ceiling structures for over 30
minutes under the very difficult U419 protocols. Thus,
notwithstanding the panels' low core density and low panel weight
relative to the panel thickness, the panels of the invention can
play an important role in controlling the spread of fire within
buildings.
Example 9
[0171] Panels of the invention also were subjected to fire testing
following the procedures of the UL protocol U305 using the nominal
5/8 inch thick gypsum panels made in accordance with the core
formulation and paper cover sheets described in Example 8 above,
and having a panel weight of about 1580 lb/msf.
[0172] The physical parameters of the gypsum panels of the
invention used in this testing were as follows:
TABLE-US-00012 Average Panel Thickness 0.620 in. (nominally 5/8
in.) Average Panel Weight 63.10 lb/1580 lb/msf Average Density
30.57 pcf
[0173] In this example, the testing procedure of the U305 protocol
requires load bearing assemblies made from nominal 5/8 inch thick
gypsum panels and wood stud framing. Pursuant to the U305 test
procedures, the panels of the invention were applied to a framing
such as that discussed above in Example 8 made using #2 Douglas fir
2.times.4 studs (approximately 3.5 inches wide by 1.5 inches
thick), spaced about 16 inches apart, and mounted between Douglass
fir 2.times.4 base and top plates. The panels were applied
horizontally with joints aligned on opposite sides of the system
with 6d nails, and the joints were taped and sealed with joint
compound. A total load of about 17,800 pounds was applied to top of
the assembly.
[0174] The data generated during the U305 test is plotted in FIGS.
3 and 4. FIG. 3 plot of the temperatures reported by the single
sensor that reached the maximum temperature at the test termination
and a plot of the average of the sensor temperatures from the start
of the test to the test termination. FIG. 3 also shows a plot of
the ASTM 119 temperature curve used for the furnace temperatures on
the heated, exposed side of the assembly. FIG. 4 is an expanded
plot of the data for that maximum single sensor and average sensor
temperatures shown in FIG. 4. The test was terminated due to load
failure of the assembly at about 46 minutes.
[0175] As indicated FIGS. 3 and 4, both maximum single sensor and
average sensor temperatures on the unexposed surface of the
assembly gradually increased during the testing relative to the
furnace temperatures on the heated side of the assembly. For
example, at about 20 minutes elapsed time, the maximum sensor and
average sensor temperatures were less than about 175.degree. F. and
about 165.degree. F., respectively. At about 25 minutes, the
maximum sensor and average sensor temperatures were less than about
190.degree. F. and about 180.degree. F., respective. At about 30
minutes, the maximum sensor and average sensor temperatures were
less than about 205.degree. F. and about 190.degree. F.,
respective. The maximum single sensor temperature did not exceed
300.degree. F., until well after about 45 minutes elapsed time,
with a temperature of less than 225.degree. F. at about 35 minutes;
less than about 245.degree. F. at about 40 minutes; and less than
about 275.degree. F. at about 45 minutes. The average sensor
temperature did not exceed 300.degree. F. by the termination of the
test, with a temperature of less than 205.degree. F. at about 35
minutes; less than about 230.degree. F. at about 40 minutes; and
less than about 250.degree. F. at about 45 minutes.
[0176] The panels of the invention also satisfied criteria such as
that which would establish a "30 minute" fire rating, which is
confirmed by the data shown in FIGS. 3 and 4. As discussed in
Example 8, such criteria would require an average sensor
temperature on the unexposed surface of the assembly of no more
than the ambient temperature at the start of the test plus
250.degree. F. and a maximum individual sensor temperature at the
start of the test of no more than the ambient temperature plus
325.degree. F. (typically ambient temperatures are about 90.degree.
F. or less for such testing). The temperatures from the U305 test
under these criteria are indicated below, with the "not exceeded"
result indicating that the maximum temperature limits on the
unexposed side of the assembly were not reached before the test was
terminated due to load failure.
TABLE-US-00013 Average Individual Unexposed Surface 311.degree. F.
386.degree. F. Limiting Temperature Criteria Ambient Temperature
61.degree. F. Unexposed Surface Not Exceeded Not Exceeded
Temperature Limits Reached @ 259.degree. F. @ 303.degree. F.
[0177] This test further demonstrates that the panels of the
present invention have the ability to provide substantial fire
resistance and protection notwithstanding the panels' low core
density and low panel weight relative to the panel thickness, As
indicated in the above U305 tests, even while under substantial
loading, assemblies made using the panels of the invention
substantially delay the passage of heat through wall or ceiling
structures for over 30 and at least up to 45 minutes under the U305
conditions.
Example 10
[0178] In this Example, the panel of Example 8 was subjected to a
nail pull resistance testing to determine the panels' strength
properties under this commonly used criterion. The nail pull
resistance test is a measure of a combination of the strengths of a
gypsum panel's core, its cover sheets, and the bond between the
cover sheets and the gypsum. The test measures the maximum force
required to pull a nail with a head through the panel until major
cracking of the hoard occurs. In the tests of this Example, the
nail pull resistance tests were carried out in accordance with ASTM
C 473-09.
[0179] In brief summary, the tested specimen was conditioned at
about 70.degree. F. and about 50% relative humidity for 24 hours
prior to testing. A 7/64th inch drill bit was used to drill pilot
holes through the thickness of the specimens. The specimen then was
placed on a specimen-support plate with a three inch diameter hole
in the center, which was perpendicular to the travel of the test
nail. The pilot hole was aligned with the nail shank tip. Load was
applied at the strain-rate of one inch per minute until maximum
load was achieved. At 90% of the peak load after passing the peak
load, the testing was stopped and the peak load is recorded as nail
pull resistance.
[0180] The nail pull resistance results are summarized in Table 7
below.
TABLE-US-00014 TABLE 7 Nail Pull Strength Average Peak Load
Calculated Panel Board Density Sample (lb-f) Weights (lb/msf)
(lb/ft.sup.3) 1 88.2 1602 30.8 2 85.6 1586 30.5 3 90.5 1597 30.7 4
89.5 1608 30.9 5 85.7 1592 30.6 6 87.1 1591 30.6 Avg. 87.4 1596
30.7
[0181] The average nail pull resistance values for these examples
of the low weight, low density panel of the invention averaged 87.4
lb-f. This indicates that, notwithstanding the low density of the
panels of the invention, the panels of the invention can achieve
nail pull resistance values comparable to much heavier and denser
fire rated gypsum panels.
Example 11
[0182] Laboratory samples were made to evaluate the effect of
adding siloxane, and siloxane together with pregelatinized starch
in a gypsum slurry formulation and panels of the invention made
with such a slurry. The formulations used in this testing are set
out in Table 8 below.
TABLE-US-00015 TABLE 8 Test Results for Formulations of the
Invention with Siloxane and Siloxane Together with Pre-Gelled
Starch (10#/msf) Pregelatinized Siloxane Board Drying Stucco HRA
Water Corn Starch (% of STMP Dispersant Soap 350.degree. F.
116.degree. F. Siloxane (g) (g) (cc) (g) stucco) (g) (wet, g)
(drops) W/S Ratio (Min) (hr) (g) 1000 15 1600 0 0 1.5 4 5 1.6 30 48
0 1000 15 1600 0 1.0 1.5 4 5 1.6 30 48 10 1000 15 1600 20 0.0 1.5 4
5 1.6 30 48 0 1000 15 1600 20 1.0 1.5 4 5 1.6 30 48 10 1000 15 1600
40 0.0 1.5 4 5 1.6 30 48 0 1000 15 1600 40 1.0 1.5 4 5 1.6 30 48 10
Thermal Hi-Temp Insulation Water Cube Shrinkage Index MgO Flyash
Board Weight Cube Density Adsorption Strength diameter min. (g) (g)
(lb/msf) (lb/cf) (%) (psi) (%) (ave.) 0 0 1525 n/a n/a n/a 5.62
21.8 4 10 1526 28.87 22 378 3.02 21.0 0 0 1921 n/a n/a n/a 7.29
21.6 4 10 1700 31.87 3.4 459 3.13 21.9 0 0 2014 n/a n/a n/a 8.11
25.3 4 10 1799 33.91 2.1 540 3.16 23.1
[0183] A high sheer mixer running at about 7500 RPM for 2.5 minutes
was used to make the siloxane emulsion. The siloxane emulsion was
mixed with stucco and additives to make a slurry with 10 seconds
soaking plus 10 seconds mixing at high speed of a Waring blender.
To evaluate the water resistance of provided by the core slurry
formulations above, 2''.times.2''.times.2'' cubes were cast with
the slurry and dried at about 116.degree. F. overnight for a water
absorption test. The core slurry formulations also were used to
form approximately one foot by one foot panels, with a nominal 5/8
inch thickness, by laboratory casting between paper cover sheets
for high temperature shrinkage and thermal insulation tests
discussed in this example.
[0184] Using the cast cubes, the water absorption test method ASTM
C 1396 was conducted by placing dry cubes in 70.degree. F. water
for 2 hours and determining the weight gain percentage. This test
demonstrated water absorption levels of about 22% for the
formulation with only added siloxane, and a significantly improved
water absorption level about 3.4% and about 2.1% for the 1%
siloxane/2% pregelatinized starch (20 grams) and 1% siloxane/4%
pregelatinized starch (40 grams) respectively.
[0185] The high temperature shrinkage testing was carried out in
accordance with the procedures developed and reported in ASTM Pub.
WK25392 to provide a quantitative measure of the shrinkage
characteristics of gypsum panels of the present invention under
high temperature conditions. The thermal insulation testing was
carried out using the procedures discussed above in Example 7. For
the high temperature shrinkage testing and thermal insulation
testing, ten 4 inch (100 mm) diameter disks were cut from two of
the above mentioned gypsum board samples using a drill press with a
hole saw blade. Six of the disks were used for the high temperature
shrinkage testing and four were used for the thermal insulation
testing.
[0186] The high temperature shrinkage test procedure reflects the
fact that the high temperature shrinkage that gypsum panels may
experience under fire condition is influenced by factors in
addition to calcining reactions that may occur in the panel gypsum
cores under high temperature conditions. The test protocol,
accordingly, uses an unvented furnace so that there is no airflow
from outside of the furnace that might cool the test specimens. The
furnace temperature is about 1560.degree. F. (850.degree. C.) to
account for the shrinkage that may occur in the anhydrite phases of
the gypsum core structures, as well as calcining and other high
temperature effects, when exposed to the high temperatures fire
conditions.
[0187] In order to prevent thermal shock to the test specimens,
which might produce invalid test results due to spalling and
breakage, the test protocol was modified to place the test
specimens in the furnace before it was heated to about 1560.degree.
F. (850.degree. C.). The specimens were held at that temperature
for a minimum of about 20 minutes before the furnace was shut off.
The furnace door remained closed while the furnace cooled. The
specimens were not removed for measurement until after the
temperature had dropped to near room temperature.
[0188] As gypsum board is anisotropic, the amount of shrinkage will
vary slightly in the length and width directions. Therefore, two
orthogonal measurements were taken and averaged to compute the mean
diameter of the disk. In these tests, two measurements at 90
degrees to each other were taken as it has been found that this
approach provides a consistent mean diameter measurement from
specimen to specimen. Typically, if the two measurements for a disk
differed by more than 0.01 inches (0.25 mm), then the disk was
rejected and the measurements excluded from the reported results.
Shrinkage was calculated as the percent change in mean diameter
after heat exposure, and denoted "S," typically to the nearest 0.1%
for the group of six test specimens.
[0189] As can be seen from Table 7, in addition to providing
improved moisture resistance, the addition of siloxane without
added pregelatinzed starch unexpectedly improved the shrinkage
properties of the panel sample, reducing shrinkage from almost 6%
to about 3%. The addition of pregelled starch increased the
shrinkage of the samples relative to the samples without added
pregelled starch and the samples with only added siloxane. That
shrinkage increased with the increased amount of added pregelled
starch. However, the combination of added siloxane and added
pregelled starch unexpectedly, significantly improved the high
temperature shrinkage of the test samples. For example, the
addition of siloxane reduced the shrinkage of samples with 20 grams
pregelled starch from over 7% to under 3.5%. Similarly, the
addition of siloxane to the samples with 40 grams pregelled starch
reduced high temperature shrinkage from over 8% to over 3%.
Accordingly, the addition of siloxane to gypsum panels of the
invention provides further resistance to high temperature shrinkage
which should further, and unexpectedly improve the fire resistance
properties of the panels of the invention.
[0190] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. Recitation of ranges of values
herein are merely intended to serve as a shorthand method of
referring individually to each separate value falling within the
range, unless otherwise indicated herein, and each separate value
is incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0191] Preferred aspects and embodiments of this invention are
described herein, including the best mode known to the inventors
for carrying out the invention. It should be understood that the
illustrated embodiments are exemplary only, and should not be taken
as limiting the scope of the invention.
* * * * *