U.S. patent application number 11/267125 was filed with the patent office on 2007-05-10 for acoustical gypsum board for ceiling panel.
This patent application is currently assigned to USG Interiors, Inc.. Invention is credited to Mirza A. Baig.
Application Number | 20070102237 11/267125 |
Document ID | / |
Family ID | 38002609 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070102237 |
Kind Code |
A1 |
Baig; Mirza A. |
May 10, 2007 |
Acoustical gypsum board for ceiling panel
Abstract
Low density acoustical gypsum boards having a perforated cover
sheet that have good sound absorption properties and are generally
clear of falling gypsum dust. The invention optionally provides a
cover sheet having a pattern producing a textured visual effect
particularly when viewed from a distance. The acoustical gypsum
boards can be produced on modified existing gypsum board lines.
Inventors: |
Baig; Mirza A.;
(Lindenhurst, IL) |
Correspondence
Address: |
DRINKER BIDDLE & REATH LLP;ATTN: PATENT DOCKET DEPT.
191 N. WACKER DRIVE, SUITE 3700
CHICAGO
IL
60606
US
|
Assignee: |
USG Interiors, Inc.
Chicago
IL
|
Family ID: |
38002609 |
Appl. No.: |
11/267125 |
Filed: |
November 4, 2005 |
Current U.S.
Class: |
181/290 ;
181/286; 181/294 |
Current CPC
Class: |
E04B 2001/8433 20130101;
E04F 13/0867 20130101; E04F 13/148 20130101; E04B 1/8409 20130101;
E04B 2001/848 20130101; E04B 9/0464 20130101; E04B 9/045
20130101 |
Class at
Publication: |
181/290 ;
181/286; 181/294 |
International
Class: |
E04B 1/82 20060101
E04B001/82; E04B 1/84 20060101 E04B001/84 |
Claims
1. A gypsum-based acoustical board having a set gypsum core
disposed between two substantially parallel cover sheets
comprising: a set gypsum core made from a core formulation having
about 75% to about 90% by weight stucco based on the total weight
of the core formulation, about 0 to about 15% by weight perlite
based on the total weight of the core formulation, about 2% to
about 12% by weight paper fiber based on the total weight of the
core formulation, and about 0.5% to about 5% by weight starch based
on the total weight of the core formulation; and a multiplicity of
sound-absorbing perforations extending through a cover sheet and
into the set gypsum core.
2. The acoustical board of claim 1, wherein the core formulation
includes stucco in an amount from about 80% to about 85% by weight
based on the weight of the core formulation, perlite in an amount
from about 5% to about 8% by weight based on the weight of the core
formulation, paper fiber in an amount from about 6% to about 10% by
weight based on the weight of the core formulation, and starch in
an amount from about 0.5% to about 2% by weight based on the weight
of the core formulation.
3. The acoustical board of claim 1, wherein the perlite has a
density of from about 3.0 pcf to about 5.0 pcf.
4. The acoustical board of claim 1, wherein the paper fiber is
hydropulp.
5. The acoustical board of claim 1, wherein the starch is
pregelatinized corn starch.
6. The acoustical board of claim 1, including cover sheets
comprising a face paper and a back paper, the perforations
extending through the face paper and into but not through the set
gypsum core.
7. The acoustical board of claim 6, wherein the face paper has a
pattern that creates a visual appearance of a texture when viewed
from a distance.
8. The acoustical board of claim 1, wherein the perforations have a
diameter of about 0.062 inch and are present at about 1800 pins per
square foot.
9. The acoustical board of claim 1, wherein the board is about 0.54
inch thick and the perforations are from about 1/4 inch to about
1/2 inch deep.
10. The acoustical board of claim 1, wherein the board density is
from about 16 pcf to about 20 pcf.
11. The acoustical board of claim 1, wherein the board density is
from about 16 pcf to about 17 pcf.
12. The acoustical board of claim 1 having an NRC value from about
0.50 to about 0.65.
13. The acoustical board of claim 1 wherein the perlite in the core
formulation is present at a weight ratio of perlite to paper fiber
of about 1:1.1 to about 1:2.
14. The acoustical board of claim 1 wherein the perlite in the core
formulation is present at a weight ratio of perlite to paper fiber
of about 1:1.4 to about 1:1.6.
15. A gypsum-based acoustical board having a set gypsum core
disposed between a face paper and a back paper comprising: a set
gypsum core made from a core formulation having about 75% to about
90% by weight stucco based on the total weight of the core
formulation, about 0 to about 15% by weight perlite based on the
total weight of the core formulation, about 2% to about 12% by
weight paper fiber based on the total weight of the core
formulation, and about 0.5% to about 5% by weight starch based on
the total weight of the core formulation; and a multiplicity of
sound-absorbing perforations extending through the face paper and
into but not through the set gypsum core.
16. A method of making gypsum-based acoustical board, comprising
the steps of: (a) mixing a slurry of water, stucco in an amount
from about 75% to about 90% by weight based on the total solids
weight, perlite in an amount up to about 15% by weight based on the
total solids weight, paper fiber in an amount from about 2% to
about 12% by weight based on the total solids weight, and a starch
in an amount from about 0.5% to about 5% by weight based on the
total solids weight; (b) adding a soap foam having a density of
about 10 pcf to the slurry; (c) depositing the slurry on a first
cover sheet; (d) maintaining the slurry under conditions sufficient
for the stucco to form a set gypsum core; (e) placing a second
cover sheet over the set gypsum core to form an acoustical board;
(f) drying the formed board; (g) cutting the dried board; and (h)
perforating one of the cover sheets of the dried board in such a
manner that the perforations extend into but not through the set
gypsum core.
17. The method of claim 16, further comprising applying a pattern
on the second cover sheet prior to step (g).
18. A method of making gypsum-based acoustical board, comprising
the steps of: (a) mixing a slurry comprising water, stucco in an
amount from about 75% to about 90% by weight based on the total
solids weight, perlite in an amount up to about 15% by weight based
on the total solids weight, paper fiber in an amount from about 2%
to about 12% by weight based on the total solids weight, and a
starch in an amount from about 0.5% to about 5% by weight based on
the total solids weight; (b) adding a soap foam having a density of
about 10 pcf to the slurry; (c) depositing the slurry on a first
cover sheet; (d) maintaining the slurry under conditions sufficient
for the stucco to form a set gypsum core; (e) placing a second
cover sheet over the set gypsum core to form an acoustical board;
(f) drying the formed board to constant weight to produce a dried
board having a density of not more than about 20 pcf; (g) cutting
the dried board; and (h) perforating one of the cover sheets of the
dried board using pins with a pin count of about 1800 pins per
square foot and a pin diameter of about 0.062 inch, in such a
manner that the perforations extend into but not through the set
gypsum core.
19. The method of claim 18, further comprising applying a pattern
on the second cover sheet prior to step (g).
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a lightweight gypsum board
suitable for use as a soundproofing or acoustical panel. The
invention provides economical and convenient-to-use low density
acoustical gypsum boards having sound absorbing characteristics on
a par with conventional acoustic panels and a method for their
preparation.
BACKGROUND OF THE INVENTION
[0002] Acoustical panels are used to form soundproofing interior
surfaces. They typically come in the form of ceiling panels, wall
panels, and partitions (e.g., partitions between office cubicles),
and are used in commercial buildings, residential buildings, public
buildings, auditoriums, etc. The panels are generally planar and
include acoustical characteristics derived from the materials
selected for their manufacture and from their ability to accept
sound absorbing perforation without adversely affecting their
durability.
[0003] Most common acoustical panels are mineral wool-based, and
may also include fiberglass, expanded perlite, paper fiber, and
binders such as starch. Mineral wool is the most prevalent and
important ingredient in such prior acoustical panels. Mineral
wool-based acoustical panels are very porous which accounts for
their good sound absorption. Fillers, such as expanded perlite, may
be incorporated into mineral wool-based acoustic panels to reduce
the weight of the final product. In addition, mineral wool-based
acoustical panels are commonly perforated in order to further
increase their sound absorption.
[0004] Currently, acoustical panels are prepared in a manner
similar to those used in conventional papermaking processes by
water-felting dilute aqueous dispersions of mineral wool, perlite,
binder, and other ingredients as desired. In such processes, the
dispersions flow onto a moving foraminous support wire, such as
that of a Fourdrinier or Oliver mat-forming machine for dewatering,
as will be appreciated by one of ordinary skill in the art. The
dispersions are dewatered first by gravity drainage and then by
vacuum suction. The resulting dewatered but yet wet mat is dried in
a convection oven, the dried material is cut to desired dimensions,
and multiple coatings are applied to obtain the finished panel.
[0005] Acoustical panels also can be made by a wet pulp molding or
cast process such as described in U.S. Pat. No. 1,769,519. In
accordance with this process, a molding composition comprising
granulated mineral wool fibers, fillers, colorants, a binder such
as cooked starch, and water, is prepared for molding or casting the
panel. The composition is placed upon suitable trays that have been
covered with paper or a paper-backed metallic foil and then the
composition is screeded to a desired thickness with a forming
plate. A decorative surface, such as a surface with random
elongated fissures, also may be provided by a screed bar or
patterned roll. The trays filled with the mineral wool composition
are then placed in an oven to dry.
[0006] Both water felting and tray casting techniques for preparing
acoustical panels are not entirely satisfactory because of their
complexity and expense. In addition to raw material costs, these
processes require large amounts of water and energy. Furthermore,
panels prepared according to these methods may be subject to
sagging, especially if the panels are stored under conditions of
high humidity or when the panels are installed horizontally on
widely spaced supporting members. The tendency to sag is aggravated
by the presence of hygroscopic binders such as recycled paper fiber
or starch. In addition, several surface coatings are generally
required in order to achieve a proper appearance in the final
acoustical panel, due to the absorbency of the materials used.
Furthermore, where the panels are perforated care must be taken not
to cover or clog the perforated holes with the final coatings. For
example, after perforation, coatings must be applied by spraying
rather than simpler, less expensive roller-applied coating
processes to avoid clogging of the perforated holes.
[0007] Conventional gypsum wallboard, which comprises set gypsum
(calcium sulfate dihydrate), sandwiched between paper cover sheets,
is commonly used in construction applications because of its
durability, fire resistant characteristics and economy. However,
such paper covered gypsum wallboard has not in the past been
considered for use in acoustical ceiling panels for a number of
reasons. First, such gypsum wallboard does not inherently have good
sound absorption properties. Even if it is punched or perforated in
the same manner as conventional mineral wool-based acoustical
panel, little or no significant sound absorption improvement is
achieved. Furthermore, punching conventional paper covered gypsum
wallboard causes substantial amounts of gypsum dust to loosen and
fall from the perforated holes. (Conventional acoustical panels
also can exhibit some dust (powder) loss.) Also, conventional
gypsum wallboard may be heavy, ca. 40 lbs/ft.sup.3 ("pcf"), and
this weight makes conventional wallboard unsuitable in most
acoustical applications. Even the recently developed lightweight
gypsum board described in U.S. Pat. No. 5,922,447 to the present
inventor, Mirza A. Baig, typically has a density greater than or
equal to about 21 pcf, which exceeds the typical densities of
conventional mineral wool based acoustical panels of about 12-20
pcf. Therefore, the problems of lack of sound absorption, high
density, and gypsum dust loss have discouraged the use of either
conventional or lightweight face-sheeted gypsum board in acoustic
tile applications.
[0008] One type of tray cast gypsum-based acoustical panel is
discussed in U.S. patent application Publication 2004/0231916A1 to
Englert et al. This application is primarily directed to panels
that, unlike conventional wallboard preferably have no top face
paper layer. In a less preferred embodiment of Englert et al. a top
face paper is used but there is no suggestion to perforate after
drying, which is not surprising because perforating this dried
board would be expected to produce substantial dust loss.
[0009] The prior art conventional gypsum wallboard is flat and
smooth, having no significant visual surface texture. Known
acoustical panels, on the other hand, typically have a substantial
three-dimensional texture. If a way could be found to produce
acoustical gypsum boards that achieve the same visual effect (and
sound absorption properties) as are found in conventional
mineral-wool based acoustical panels without actually adding
texture and thereby damaging the outer surface of the face paper of
the boards, this would be yet another useful contribution to the
art.
[0010] Therefore, it would be advantageous if a way could be found
to make conventionally produced gypsum wallboard type products of
sufficiently low density and sufficiently good sound absorbing
properties to be useful in acoustical applications. It would be
particularly advantageous if a way could be found to make such
gypsum wallboard type products having acceptable sound absorption
properties that are not subject to the problem of falling gypsum
dust, that achieve the same visual effect as known textured
acoustical panels, and that also have resistance to sag equal to or
better than conventional mineral wool-based ceiling panels.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention comprises low density acoustical
gypsum boards, having top and bottom cover sheets, that are
relatively inexpensive to manufacture, and that can be produced
efficiently in large quantities on an existing gypsum board line.
These low density acoustical gypsum boards resist permanent
deformation, such as sag, and have sound absorption properties on a
par with conventional acoustical panels. The low density acoustical
gypsum boards are perforated and are not subject to the problem of
falling gypsum dust. Furthermore, the invention optionally provides
a top cover sheet to which a visual pattern has been applied in
order to make the surface appear to be textured, particularly when
viewed from a distance (i.e. when viewed by a person standing on
the floor of a room looking up at the ceiling). These and other
advantages of the present invention, as well as additional
inventive features, will be apparent from the description of the
invention provided herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic representation of a cut-away end view
of a low density acoustical gypsum board in accordance with the
invention including top and bottom cover sheets, a set gypsum core,
and perforations extending across the top cover sheet and into the
set gypsum core;
[0013] FIG. 2 is a plan view of a top cover sheet (face paper)
having a pattern as printed on the face paper cover sheet used in
one embodiment of the present invention; and
[0014] FIG. 3 is a plan view of the top cover sheet of the low
density acoustical gypsum board of FIG. 1 showing the printed
pattern of FIG. 2 and including small circular puncture holes
extending through the face paper and into the set gypsum core.
DETAILED DESCRIPTION OF THE INVENTION
[0015] In one embodiment of the invention, low density acoustical
gypsum boards of this invention include a set gypsum core structure
made using a core formulation including calcium sulfate hemihydrate
("stucco"), perlite, paper fiber, and starch. The set gypsum core
of the low density acoustical gypsum boards is sandwiched between
two substantially parallel top and bottom cover sheets, such as
paper cover sheets, to provide substantially flat, planar, top and
bottom surfaces. In addition, the low density acoustical gypsum
boards include perforations formed through the top (outer) surface
of the board that extend through the cover sheet and into the set
gypsum core. In a preferred embodiment, the perforations are
generally well-formed small circular holes that extend generally
perpendicularly to the top outer surface of the board through the
top cover sheet and into the set gypsum core. In another preferred
embodiment, the exposed surface of the perforated top cover sheet
is printed with a pattern. The low density acoustical gypsum boards
are manufactured generally in the same fashion as conventional
wallboard, modified as discussed below.
[0016] Preferably, the low density acoustical gypsum board of the
present invention exhibits a Noise Reduction Coefficient (NRC) of
at least about 0.5, according to ASTM C 423-02, and more
preferably, a Noise Reduction Coefficient at or near 1.0. In some
embodiments, the low density acoustical gypsum board demonstrates a
Noise Reduction Coefficient according to ASTM C 423-02 of at least
about 0.55 up to a yet more preferable NRC of at least about
0.7.
[0017] Now turning to FIG. 1, there is provided a low density
acoustical gypsum board 10 according to one embodiment of the
present invention. The acoustical gypsum board 10 includes a set
gypsum core 12 having a top surface 14 and a bottom surface 16. The
set gypsum core 12 is formed between a face cover sheet 20 and a
back cover sheet 30 with the cover sheets (20, 30) bonded to the
core. A multiplicity of perforations 40 extend through the face
cover sheet 20 and the top surface 14 into the set gypsum core
12.
[0018] FIG. 2 illustrates an exemplary pattern 50 according to one
embodiment of the present invention that is applied to the outer
surface of a face cover sheet 20a. In this example, the pattern
creates a visual appearance of texture to the human eye when viewed
from a sufficient distance or perspective, for example by a person
standing on the floor of a room looking up at the ceiling.
[0019] FIG. 3 is a plan view of the low density acoustical gypsum
board 10 of FIG. 1 covered on its top surface by the
pattern-bearing face cover sheet 20a of FIG. 2 and including a
multiplicity of perforations 40 formed through face cover sheet 20a
and into set gypsum core 12.
[0020] Set gypsum core 12 is made from an aqueous slurry of the key
core components listed below in Table 1. Other conventional
ingredients that may be added to the slurry, such as dispersants,
strength additives (e.g. metaphosphates), and accelerators, are
described generally below. TABLE-US-00001 TABLE 1 CORE FORMULATION
RANGES Amount in weight % Preferred amount in Component (wt %
solids).sup.1 weight %.sup.1 Stucco 75-90 80-85 Perlite 0-15 5-8
Paper (cellulose fiber) 2.0-12 6-10 Starch 0.5-5.0 0.5-2
Water/solids ratio 2.0-3.5 2.3-2.5 .sup.1This embodiment of the
core formulation is based on 100% solids of these four key
ingredients.
[0021] The acoustical gypsum board of the present invention has a
board density of not more than about 20 pcf. In a preferred
embodiment, the acoustical gypsum board of the present invention
has a board density of about 17 to about 19 pcf, and most
preferably the acoustical gypsum board of the present invention
will have a board density of not more than about 16 pcf.
[0022] It is preferred that perlite be used in the core
formulations (to help lower board density), although in a less
preferred embodiment, the core formulation can be free of perlite.
The presence of perlite in the core formulation, however, reduces
estimated Noise Reduction Coefficient (NRC) values of the final
acoustical gypsum boards. Paper fiber, on the other hand, can also
be used in core formulations to achieve yet lower board density
while at the same time providing increased NRC values, offsetting
the detrimental loss of noise reduction caused by the perlite.
Therefore, in preferred embodiments, as discussed below, rising
perlite levels are balanced with increased levels of paper
fiber.
[0023] In a preferred embodiment, perlite will be used in an amount
of at least about 5% by weight of the core formulation.
Additionally in this preferred embodiment, both perlite and paper
fiber must be present in the core formulation, and the weight ratio
of perlite to paper fiber will range from about 1:1.1 to about 1:2.
In a yet more preferred embodiment, the weight ratio of perlite to
paper fiber will range from about 1:1.4 to about 1:1.6.
[0024] For example, in one embodiment, the core formulation
comprises, based on the total weight of the core formulation:
TABLE-US-00002 stucco 85% by weight; perlite 5% by weight; paper
fiber 8% by weight; and starch 2% by weight.
The weight ratio of perlite to paper fiber is 1:1.6. By
incorporating a soap foam (discussed below) having a foam density
of 10 pcf (over and above the 100% solids weight % total of the
core formulation itself), this core formulation can be used to make
an acoustical gypsum board having a density as low as about 17.0
pcf. Other additives can be included over and above the 100% solids
weight % total of the core formulation itself (i.e. accelerators,
dispersants, and strength additives as discussed below).
[0025] The low density acoustical gypsum boards of the present
invention must be perforated to produce a multiplicity of
perforations that are substantially clear of gypsum dust or powder.
That such clear perforations can be achieved is quite unexpected
given that when conventional gypsum boards are perforated in the
same manner, a substantial amount of gypsum dust is released. The
perforations in boards of the present invention are illustrated,
for example, in FIGS. 1 and 3. As shown there, the acoustical
gypsum board is perforated through the face paper to produce holes
extending into the set gypsum core, but not passing through the
back paper. The orientation of the holes is, as shown, preferably
generally perpendicular to the planar surface of the first cover
sheet, or face paper. Thus, in a key aspect, the overall set gypsum
core provides sound absorption properties in the low density
acoustical gypsum boards when combined with perforations
substantially clear of gypsum dust.
[0026] The low density acoustical gypsum boards may be punched
using a perforation pin count (100% sharp pins) of about 1800 pins
per square foot, pin diameter 0.062 in. Other pin counts and pin
diameters can be used, as will be recognized by those skilled in
the art. For example, a pin count of about 1850 per square foot, of
about 1750 per square foot, or of about 1566 per square foot could
be used, and pin diameters of about 0.050 in. and about 0.045 in.
could be used. Also, any type of pin may be used, including sharp,
blunt, or combinations thereof. It will be appreciated by one
skilled in the art that pin count can be varied, and pin type,
style, and diameter can be varied, or used in various combinations,
in order to achieve the desired sound reduction properties. The
depth of the perforated holes can range from about 1/4 inch to
about 1/2 inch.
[0027] The boards can be made, and punched, according to a batch
process or in a continuous process. The punching, or perforation
step, can be applied as part of a standard commercial wallboard
production line, following the drying of the paper-covered board
product.
[0028] Cover sheets 20 and 30 may be made of paper as in
conventional gypsum wallboard, although other useful cover sheet
materials known in the art may be used. Paper cover sheets provide
strength characteristics in the acoustical gypsum board. Useful
cover sheet paper includes Manila 7-ply and News-Line 7-ply,
available from United States Gypsum Corporation, Chicago, Ill.; and
Grey-Back 3-ply and Manila Ivory 3-ply, available from Caraustar,
Newport, Ind. The paper cover sheets comprise top cover sheets, or
face paper, and bottom cover sheets, or back paper. A preferred
back cover sheet paper is News-Line. A preferred face cover sheet
paper is Manila 7-ply.
[0029] Gypsum-based products have the tendency to sag under
conditions of high humidity. The proper choice of back paper helps
reduce sag in the finished acoustical gypsum board. A preferred
back paper for this purpose in the low density acoustical gypsum
boards of the present invention is News-Line 7-ply. In addition,
strength additives such as sodium trimetaphosphate, may be added to
the core formulations to further reduce sag. Also, a
formaldehyde-based coating can be applied to the back paper of the
acoustical gypsum boards to further reduce sag.
[0030] The face paper can be used plain, or with a pattern applied
to it, as discussed above and shown in FIG. 2. Many variations of
pattern and pattern color may be used on the face paper. Tinted
papers can also be used as appropriate, and color printing or inks
can be employed to apply the pattern. The pattern as shown in FIG.
2, as well as other patterns, can be made by taking a photo of a
given design and printing the design on the face paper. Also,
printing of the face paper can be done on-line during the
production process, preferably after the face paper is dried. In
addition, after printing the pattern, a protective coating can be
applied on the outer surface of the face paper to protect the
printed pattern from abrasion and environmental conditions.
[0031] A soap foam is required in making the low density acoustical
gypsum boards of the present invention, in order to reduce the
density of the final board. The soap foam density can range from
about 5.0 pcf to about 12.0 pcf, a preferred soap foam density is
about 10 pcf, to achieve a final board density of not more than
about 20 pcf. The soap foam is used in an amount over and above the
100% solids weight % total of the core formulation itself. For
example, a soap can be used in an amount of about 2 g to about 3 g
per about 1000 g total solids (or about 0.2% to about 0.3% by
weight based on total solids) when used to make the soap foam and
added to the core formulation as in Table 1 over and above the 100%
solids weight % total of the core formulation itself. Useful soaps
for making the soap foam include FA 403-Agent X-2332 available from
Stepan Chemical Company, Northfield, Ill.
[0032] The bond between a set gypsum core and the paper cover
sheets may be adversely affected by the presence of foam in the
core formulation. Since approximately 1/3 of the gypsum boards by
volume may consist of foam, the foam can interfere with the bond
between the set gypsum core and the paper cover sheets. Thus, a
non-foamed bonding layer may be provided on the set gypsum
core-contacting surfaces of both the face paper and the back paper
prior to forming the gypsum boards. This layer formulation is
commonly the same as the core formulation, except that the foam is
omitted. In order to form this layer, foam can be mechanically
removed from the core formulation, or a different foam-free
formulation can be applied at the set gypsum/face paper
interface.
[0033] The primary component of the core formulation is calcium
sulfate hemihydrate or calcined gypsum, also referred to as stucco.
The calcined gypsum can be in the form of alpha calcium sulfate
hemihydrate, beta calcium sulfate hemihydrate, water-soluble
calcium sulfate anhydrite, or mixtures thereof. In preferred
embodiments, the calcined gypsum is in the form of beta calcium
sulfate hemihydrate. A useful calcined gypsum is CKS dry stucco,
available from United States Gypsum Corp., Chicago, Ill. The
calcined gypsum is present in an aqueous slurry of the core
formulation in an amount sufficient to allow for the formation of
an interlocking matrix of set gypsum in the final paper-covered
board. In the core formulation used to make the set gypsum core,
stucco is present in an amount ranging from about 75% to about 90%
by weight based on the total (solids) weight of the core
formulation; preferably, the stucco is present in an amount ranging
from about 80% to about 85% by weight based on the total weight of
the core formulation.
[0034] As noted earlier, it is preferred that perlite is used in
the core formulation. In the core formulation used to make the set
gypsum core, perlite can be present in an amount up to about 15% by
weight based on the total (solids) weight of the core formulation;
preferably, perlite is present in an amount ranging from about 5%
to about 8% by weight based on the total weight of the core
formulation.
[0035] In the practice of the invention, the perlite density must
be in the range of about 3 to about 8.5 pcf. The perlite can be
obtained from a number of commercial sources. In the examples
described below, Type 3-S brand perlite available from Silbrico
located in Hodgkins, Ill., was used. This perlite typically has a
density of about 3 to about 5.0 pcf.
[0036] Perlite is a form of glassy rock similar to obsidian. It
generally contains 65-75% SiO.sub.2, 10-20% Al.sub.2O.sub.3, 2-5%
H.sub.2O, and smaller amounts of soda, potash, and lime. When
perlite is heated to its softening point, it expands to form a
light fluffy material similar to pumice. In preparing the perlite
for use in the present invention it is first ground to a size finer
than minus 200 mesh. The ground perlite is then heated to a
temperature of about 1500.degree.-1800.degree. F., and preferably
about 1750.degree. F. This process is carried out in a perlite
expander by first heating the air and then introducing the finely
ground perlite into the heated air. As it is carried by the air, it
is heated and pops like popcorn to form expanded perlite. Expanded
perlite contains many fine cracks and fissures, and, when placed in
contact with water, the water penetrates the cracks and fissures
and enters into the air filled cavities of the perlite, thereby
greatly increasing the weight of the particles.
[0037] For the purposes of the present low density acoustical
panel, it is important that the perlite not be coated or treated in
any way which will make the individual perlite particles watertight
or even water resistant. If so, the water resistant coating or
treatment will result in non-uniform distribution of the perlite in
the aqueous slurry of the core formulation, and it will also be
more difficult, if not impossible, for the gypsum crystals to
penetrate and interlock with the perlite particles.
[0038] Paper fiber must be used in the core formulation. A useful
form of paper fiber is hydropulp newsprint or hydropulped waste
paper. Other cellulosic fibrous materials can be used, alone or in
combination with hydropulped paper fiber, such as wood fiber or dry
fiberized gypsum wallboard paper or Kraft paper. In the core
formulation used to make the set gypsum core, paper fiber is
present in an amount ranging from about 2% to about 12% by weight
based on the total (solids) weight of the core formulation;
preferably, paper fiber is present in an amount ranging from about
6% to about 10% by weight based on the total weight of the core
formulation.
[0039] Starch must be used in the core formulation. For example,
wheat starch can be used. In another embodiment, pearl starch can
be used, which is a known combination of starch made from corn,
potato, and/or wheat stock. The starch may be provided in raw form
or partially or fully cooked separately prior to mixing with the
core formulation. Partial cooking in the present process is
considered to occur once the starch and water slurry temperature
reaches 150.degree. F. The starch is considered to be fully cooked
once the starch slurry reaches a temperature of at least
185.degree. F. Through partial or full cooking, pearl starch is
converted from being migrating in nature to being non-migrating in
nature. When non-migrating, the starch is retained in the core
portion of the board prior to setting. The presence of the starch
in the core also aids in the binding of the face paper to the core.
Alternate sources of starch which are also contemplated are
acid-modified starches including Gypset made by Ogilive, located in
Montreal, Canada, and LC-211, a common starch made from flour,
supplied by Archer Daniels Midland of Dodge City, Kans. In the
latter two cases, the starches are of the migrating type. Another
useful starch is acid-modified corn flour, available as HI-BOND
from Bunge, 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.
[0040] Pregelatinized starch in particular, can be used in slurries
prepared in accordance with the core formulations as in Table 1. A
preferred pregelatinized starch is pregelatinized corn starch, for
example pregelatinized corn flour available from Bunge, 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.
In the core formulation used to make the set gypsum core, starch is
present in an amount ranging from about 0.5% to about 5% by weight
based on the total (solids) weight of the core formulation;
preferably, starch is present in an amount ranging from about 0.5%
to about 2% by weight based on the total weight of the core
formulation.
[0041] Accelerators can be added to the core formulations of the
present invention, for example, wet gypsum accelerator (WGA), 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 are 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. For example, an
accelerator (HRA or CSA) can be used in an amount of about 5 g/1000
g total solids (or about 0.5% by weight based on total solids) when
added to the core formulation as in Table 1 over and above the 100%
solids weight % total of the core formulation itself.
[0042] Dispersants can be added to the core formulations of the
present invention. Useful dispersants include
polynaphthalenesulfonates and BOREM, available from Boremco
Laboratories, River Falls, Mass. For example, a dispersant can be
used in an amount of about 0.9 g/1000 g total solids (or about 0.1%
by weight based on total solids) when added to the core formulation
as in Table 1 over and above the 100% solids weight % total of the
core formulation itself.
[0043] The naphthalenesulfonate dispersants that may be used in the
present invention 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 20,000, although it is preferred that the molecular weight
be about 8,000 to 10,000. A higher molecular weight dispersant has
higher viscosity, and generates a higher water demand in the
formulation. Useful naphthalenesulfonates include LOMAR D,
available from Henkel Corporation, DILOFLO, available from GEO
Specialty Chemicals, Cleveland, Ohio, and DAXAD, available from
Hampshire Chemical Corp., Lexington, Mass. It is preferred that the
naphthalenesulfonates be used in the form of an aqueous solution,
for example, in the range of about 40-45% by weight solids
content.
[0044] Useful polynaphthalenesulfonates have the general structure
(I): ##STR1## wherein n is >2, and wherein M is sodium,
potassium, calcium, and the like.
[0045] For example, a polynaphthalenesulfoante dispersant can be
used in an amount of about 0.9 g/1000 g total solids (or about 0.1%
by weight based on total solids) when added to the core formulation
as in Table 1 over and above the 100% solids weight % total of the
core formulation itself.
[0046] Strength additives can be added to the core formulations of
the present invention, for example, metaphosphates such as sodium
trimetaphosphate. Any suitable water-soluble metaphosphate or
polyphosphate can be used 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, calcium
trimetaphosphate, sodium calcium 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. For example, sodium
trimetaphosphate can be used in an amount of about 0.9 g/1000 g
total solids (or about 0.1% by weight based on total solids) when
added to the core formulation as in Table 1 over and above the 100%
solids weight % total of the core formulation itself.
[0047] As shown in the following examples, low density acoustical
gypsum panels were prepared using the core formulations of Table 1.
Except where indicated, Manila 7-ply paper, either plain or with an
applied pattern, was used as the top cover sheet or face sheet. A
non-foamed bonding layer (as described above) was applied to the
set gypsum core-contacting surfaces of both the back paper and the
face paper. The average thickness of the panels was 0.54 inch. In
addition, each acoustical gypsum board was perforated through the
face sheet. The perforation depth was 1/2 inch (except as
indicated), and the perforation pin count (100% sharp pins) was
1800 pins per square foot, pin diameter 0.062 in.
[0048] In the following examples, certain additives were included
in the core formulation as in Table 1 over and above the 100%
solids weight % total of the core formulation itself. The following
additive levels were included in all of the examples: accelerator
(HRA or CSA) at 0.5% by weight based on total solids; dispersant at
0.1% by weight based on total solids; and sodium trimetaphosphate
at 0.1% by weight based on total solids. Additionally, in each
example below (except as indicated), soap foam at a density of 10
pcf was incorporated into the core formulations.
EXAMPLE 1A
[0049] Preparation of Low density acoustical gypsum board
[0050] Sample low density acoustical gypsum boards were prepared by
a casting process in accordance with U.S. Pat. No. 5,922,447 using
the core formulations of Table 1 with a high density soap foam
(e.g. 10 pcf) incorporated into slurry of the core formulation.
EXAMPLE 1B
[0051] Preparation of Low density acoustical gypsum board by a
continuous process
[0052] Sample low density acoustical gypsum boards were prepared by
a continuous process 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
a high density foam (e.g. 10 pcf) and introduction of the foam into
the slurry of the other ingredients as described in Example 5 of
these patents.
EXAMPLE 2
[0053] Low density acoustical gypsum board--assessment of paper
fibers and high density foam
[0054] Step 1. The following core formulations were prepared as an
aqueous slurry as shown in Table 2. TABLE-US-00003 TABLE 2 Slurry
formula: Board Board Board Board Formula 1 Formula 2 Formula 3
Formula 4 (weight % (weight % (weight % (weight % Component solids)
solids) solids) solids) Stucco 85.6 85.6 85.6 85.6 Perlite 5.0 5.0
5.0 5.0 Dry paper fiber 7.4 3.7 1.9 0 Wet paper fiber 0 3.7 5.6 7.4
Total paper fiber 7.4 7.4 7.4 7.4 Starch 2.0 2.0 2.0 2.0
Water/solids ratio 2.5 2.7 2.4 2.7 Dry paper fiber: fiberized
gypsum wallboard paper Wet paper fiber: hydropulped waste paper
Additives were included in addition to the above total solids:
accelerator (HRA or CSA) at 0.5% by weight based on total solids;
dispersant at 0.1% by weight based on total solids; and sodium
trimetaphosphate at 0.1% by weight based on total solids.
[0055] Soap foam for each formulation sample was prepared as
follows. Soap (2.0 g), available as product FA 403-Agent X-2332
from Stepan Chemical Company, Northfield, Ill., was mixed with
water (148 g) in a high shear Hamilton Beach blender for 10
seconds. The resulting foam volume was 900 ml; the foam density was
10 pounds per cubic foot. This soap foam was incorporated into the
core formulations of Table 2.
[0056] Step 2. Sample boards were prepared by casting as in Example
1A using the core formulations of Table 2, and perforated, as
discussed above. The perforation depth was 1/2 inch, and the
perforation pin count (100% sharp pins) was 1800 pins per square
foot, pin diameter 0.062 in. TABLE-US-00004 TABLE 3 Properties
Board 1 Board 2 Board 3 Board 4 Thickness, inch 0.545 0.545 0.545
0.545 Density, pcf 17.5 16.7 18.0 17.5 Weight, lb/MSF 795 758 818
795 Water evaporation, 1519 1519 1475 1486 lb/MSF Estimated NRC
0.61 0.55 0.54 -- Dust, g/MSF 768 182 192 240 "MSF" is a standard
abbreviation in the art for a thousand square feet.
[0057] As shown in Table 3, the sample boards have densities lower
than 20 pcf and acceptable NRC values. Also, in Boards 2-4 dust was
significantly reduced.
EXAMPLE 3
[0058] Low density acoustical gypsum board--assessment of paper
cover sheets, paper fibers and high density foam
[0059] The following core formulation was used to make the aqueous
slurry (solids by weight %): TABLE-US-00005 stucco 86.5% perlite
5.0% paper fiber (hydropulp) 6.5% pregelatinized com starch
2.0%.
[0060] As in Example 2, a soap foam having a foam density of 10 pcf
was used. Additional additives were included in addition to the
above total solids: CSA at 0.5% by weight based on total solids;
Borem at 0.1% by weight based on total solids; and sodium
trimetaphosphate at 0.1% by weight based on total solids. The
sample boards were cast, and perforated, as in Step 2 of Example 2.
The perforation depth was 1/2 inch, and the perforation pin count
(100% sharp pins) was 1800 pins per square foot, pin diameter 0.062
in. TABLE-US-00006 TABLE 4 Components Board 5 Board 6 Board 7 Board
8 Face paper 7-ply 7-ply 3-ply 3-ply Manila Manila Manila/Ivory
Manila/Ivory Back paper 7-ply 7-ply 7-ply 7-ply News-line News-line
News-line News-line Water/solids ratio 2.3 2.4 2.3 2.4 Properties
Thickness, inch 0.555 0.555 0.555 0.555 Density, pcf 19.0 17.3 17.8
17.2 Weight, lb/MSF 879 800 823 796 Water evaporation, 1596 1526
1543 1526 lb/MSF Estimated NRC 0.45 0.55 0.44 0.46 Dust, g/MSF 173
134 160 200
[0061] As shown in Table 4, the sample boards have densities lower
than 20 pcf, and no significant difference was observed in NRC
values using 7-ply or 3-ply sheets on the top surface of the board.
However, reduction of the paper fiber level reduced NRC values.
Dust levels were acceptable in comparison to conventional
acoustical panel (300 g/MSF), as discussed above.
EXAMPLE 4
[0062] Low density acoustical gypsum board--assessment of printed
paper cover sheets and high density foam
[0063] Step 1. The following core formulations were prepared as an
aqueous slurry as shown in Table 5. TABLE-US-00007 TABLE 5 Slurry
formula: Board Formula 9 Board Formula 10 Board Formula 11 Board
Formula 12 Component (weight % solids) (weight % solids) (weight %
solids) (weight % solids) Stucco 85.0 84.2 85.0 84.0 Perlite 5.0
4.9 5.0 5.0 Paper fiber (hydropulp) 8.0 8.0 8.0 8.0 Starch 2.0 3.0
2.0 3.0 Foam.sup.1 density, pcf 10.0 10.0 10.0 10.0 Water/solids
ratio 2.4 2.4 2.4 2.4 Face paper Manila Manila Manila - printed
Manila - printed w/ pattern of FIG. 2 w/ pattern of FIG. 2
Additives were included in addition to the above total solids:
accelerator (HRA or CSA) at 0.5% by weight based on total solids;
dispersant at 0.1% by weight based on total solids; and sodium
trimetaphosphate at 0.1% by weight based on total solids.
.sup.1Soap foam prepared as in Ex. 2
[0064] Step 2. Sample boards were prepared by casting as in Step 2
of Example 2, using the core formulations of Table 5, and
perforated, as discussed above. The perforation depth was 1/2 inch,
and the perforation pin count (100% sharp pins) was 1800 pins per
square foot, pin diameter 0.062 in. TABLE-US-00008 TABLE 6
Properties Board 9 Board 10 Board 11 Board 12 Set time, min. 11.0
11.0 11.0 11.0 Thickness, inch 0.550 0.550 0.550 0.550 Density, pcf
18.1 17.4 17.8 18.2 Weight, lb/MSF 830 798 816 834 Water
evaporation, 1570 1695 1496 1568 lb/MSF Estimated NRC 0.58 0.52
0.53 0.55
[0065] As shown in Table 6, the sample boards have densities lower
than 20 pcf and acceptable NRC values. No negative impact was
observed on NRC values using either plain or printed face
paper.
EXAMPLE 5
[0066] Low density acoustical gypsum board--assessment of 3-ply and
7-ply printed paper cover sheets and high density foam
[0067] Step 1. The following core formulations were prepared as an
aqueous slurry as shown in Table 7. TABLE-US-00009 TABLE 7 Slurry
formula: Board Board Board Board Board Formula 13 Formula 14
Formula 15 Formula 16 Formula 17 Component (wt % solids) (wt %
solids) (wt % solids) (wt % solids) (wt % solids) Stucco 85.0 84.0
85.0 84.0 84.0 Perlite 5.0 5.0 5.0 5.0 5.0 Paper fiber (hydropulp)
8.0 8.0 8.0 8.0 8.0 Starch 2.0 3.0 2.0 3.0 3.0 Foam density, pcf
10.0.sup.1 10.0.sup.1 10.0.sup.1 10.0.sup.1 10.0.sup.2 Water/solids
ratio 2.4 2.4 2.4 2.4 2.4 Face paper Manila 3-ply - Manila 3-ply -
Manila 7-ply - Manila 7-ply - Manila 7-ply printed printed printed
printed w/ pattern of w/ pattern of w/ pattern of w/ pattern of
FIG. 2 and FIG. 2 and coated coated Additives were included in
addition to the above total solids: accelerator (HRA or CSA) at
0.5% by weight based on total solids; dispersant at 0.1% by weight
based on total solids; and sodium trimetaphosphate at 0.1% by
weight based on total solids. .sup.1Soap foam prepared as in Ex. 2
.sup.2Higher amount of soap foam - prepared as in Ex. 2 using 3.0 g
soap and 222 g water
[0068] Step 2. Sample boards were prepared by casting as in Step 2
of Example 2, using the core formulations of Table 7, and
perforated, as discussed above. The perforation depth was 1/2 inch,
and the perforation pin count (100% sharp pins) was 1800 pins per
square foot, pin diameter 0.062 in. TABLE-US-00010 TABLE 8
Properties Board 13 Board 14 Board 15 Board 16 Board 17 Set time,
11.0 11.0 11.0 11.0 min. Thickness, 0.555 0.555 0.555 0.555 0.555
inch Density, pcf 16.4 17.2 18.0 18.1 15.9 Weight, 759 796 833 837
735 lb/MSF Water 1354 1467 1477 1496 1388 evaporation, lb/MSF
Estimated 0.53 0.55 0.54 0.53 0.59 NRC
[0069] As shown in Table 8, the sample boards have densities lower
than 20 pcf and acceptable NRC values. For boards 13-16, no
negative impact was observed on NRC values using either 3-ply
printed paper or 7-ply printed and coated paper. For board 17, an
increased amount of high density soap foam produced lower board
density and increased the NRC value.
EXAMPLE 6
[0070] Low density acoustical gypsum board--assessment of printed
paper cover sheets, paper fibers, perlite, and high density
foam
[0071] Step 1. The following core formulations were prepared as an
aqueous slurry as shown in Table 9. TABLE-US-00011 TABLE 9 Slurry
formula: Board Formula 17 Board Formula 18 Component (weight %
solids) (weight % solids) Stucco 81.9 80.0 Perlite 7.0 7.0 Paper
fiber (hydropulp) 8.1 10.0 Starch 3.0 3.0 Foam.sup.1 density, pcf
10.0 10.0 Water/solids ratio 2.5 2.5 Face paper Manila - printed
Manila - printed w/pattern of FIG. 2 w/ pattern of FIG. 2 Additives
were included in addition to the above total solids: accelerator
(HRA or CSA) at 0.5% by weight based on total solids; dispersant at
0.1% by weight based on total solids; and sodium trimetaphosphate
at 0.1% by weight based on total solids. .sup.1Soap foam prepared
as in Ex. 2
[0072] Step 2. Sample boards were prepared by casting as in Step 2
of Example 2, using the core formulations of Table 9, and
perforated, as discussed above. The perforation depth was 1/2 inch,
and the perforation pin count (100% sharp pins) was 1800 pins per
square foot, pin diameter 0.062 in. TABLE-US-00012 TABLE 10
Properties Board 18 Board 19 Set time, min. 12.0 13.0 Thickness,
inch 0.545 0.545 Density, pcf 16.9 17.2 Weight, lb/MSF 765 782
Water evaporation, 1550 1508 lb/MSF Estimated NRC 0.61 0.53
[0073] As shown in Table 10, the sample boards have densities lower
than 20 pcf and acceptable NRC values.
EXAMPLE 7
[0074] Low density acoustical gypsum board--assessment of paper
cover sheets including a non-foamed bonding layer applied to the
set gypsum core-contacting surfaces
[0075] Two sets of three boards each were prepared using the
following core formulation to make the slurry (solids by weight %):
TABLE-US-00013 stucco 84.5% perlite 5.0% paper fiber (hydropulp)
7.5% pregelatinized corn starch 3.0%.
[0076] A soap foam having a foam density of 5.0 pcf was used.
Additional additives were included in addition to the above total
solids: CSA at 0.5% by weight based on total solids; Borem at 0.1%
by weight based on total solids; and sodium trimetaphosphate at
0.1% by weight based on total solids. The water/solids ratio was
2.4:1. The first set (Set A) of sample boards was cast, and
perforated (except at 0.375 in. depth), as in Step 2 of Example 2.
For the second set (Set B) of sample boards, prior to casting, a
non-foamed bonding layer (prepared from the same core formulation
without foam) was manually applied to the set gypsum
core-contacting surfaces of both the back paper and the face paper
using a 4.0 inch wide brush, then the second set (Set B) of sample
boards was cast, and perforated (except at 0.375 in. depth), as in
Step 2 of Example 2. The set time was approx. 11.0 min. for all
boards cast. In the following Table 11, the results are presented
as average values. TABLE-US-00014 TABLE 11 Properties Set A Set B
Thickness, inch 0.545 0.545 Density, pcf 21.7 22.0 Water
evaporation, 1787 1668 lb/MSF Estimated NRC 0.46 0.48
[0077] The boards of Set B possessed an excellent bond to the paper
cover sheets and to the set gypsum core after the board was dried.
As shown in Table 11, the bond between the set gypsum core and the
paper cover sheets was significantly improved, without adversely
affecting estimated NRC after perforation of the face paper. The
presence of the non-foamed bonding layer provided a better bond
between the paper cover sheets and the set gypsum core in the low
density acoustical gypsum boards of the present invention, with no
adverse effect on estimated NRC values after perforation of the top
surface cover sheet (face paper). The lower estimated NRC values in
both sets of boards (Sets A and B) were due to the lower
perforation depth.
EXAMPLE 8
[0078] Resistance to permanent deformation--assessment of low
density acoustical gypsum board sag resistance
[0079] The low density acoustical gypsum boards made according to
Examples 3-6 demonstrated resistance to permanent deformation such
as sag. Sag was tested in 2.times.4 foot board samples as follows.
3 inch wide.times.24 inch long strips of board were cut from the
aforementioned samples and tested under 104.degree. F./95% R.H.
conditions. The board strips were laid in a horizontal position on
two 1/4 inch wide supports, attached to a support frame, whose
length extended the full 3 inch width of the board, with one
support at each end of the board. The 3 inch wide ends in contact
with the support frame were weighted down against the supports or
clamped to the supports. The board strips remained in this position
for a specified period of time (in this example, 3 days) under
continuous surrounding conditions of 104.degree. F. and 95%
relative humidity. The extent of sag of the board (sag deflection)
was then determined by measuring the distance in inches of the
center of the top surface of the board from the imaginary
horizontal plane extending between the top edges of the ends of the
board, i.e., a plane corresponding to the surface of the board
before exposure to the test conditions. After a 3 day test period,
sag deflection for the test strips was measured in the range
0.122-0.218 inch, which is substantially superior to known
conventional ceiling panels, in which sag deflection is normally
0.3-0.5 inch under the same test conditions.
[0080] The low density acoustical gypsum boards made according to
Examples 3-6 passed the indicative flame spread test and met the
Class-A rating.
[0081] The low density acoustical gypsum boards made according to
Examples 3-6 were tested for MOR strength (psi). The average MOR
strength achieved was about 200 psi, or greater.
[0082] The low density acoustical gypsum boards made according to
Examples 3-6 were less friable than conventional acoustical panels.
Cutability, including edge detail, of these low density acoustical
gypsum boards was good using a mechanical cutting saw. Edge detail,
namely a lip, was introduced by grinding.
[0083] All references, including publications, patent applications,
and patents, cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
[0084] 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.
[0085] Preferred 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.
* * * * *