U.S. patent application number 10/701807 was filed with the patent office on 2004-05-13 for dispersant and foaming agent combination.
This patent application is currently assigned to GEO Specialty Chemicals, Inc.. Invention is credited to Elko, Dawn P., McCrary, James, Savoly, Arpad, Veal, Bennie.
Application Number | 20040092676 10/701807 |
Document ID | / |
Family ID | 31494656 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040092676 |
Kind Code |
A1 |
Savoly, Arpad ; et
al. |
May 13, 2004 |
Dispersant and foaming agent combination
Abstract
The present invention provides a dispersant and foaming agent
combination that is useful in the production of gypsum wallboard
and other aqueous cementitious products, a method of forming a
gypsum wallboard and a gypsum wallboard. The dispersant in the
combination according to the invention is a naphthalene
sulfonate-aldehyde condensate alkali salt polymer having a weight
average molecular weight of from about 17,000 to about 47,000. The
alkali is preferably an alkali metal and/or an alkaline earth
metal. The aldehyde is preferably formaldehyde. The foaming agent
used in the combination according to the invention is a soap,
preferably an alkali salt of an alkyl ether sulfate and/or an alkyl
sulfate. The combination of a high molecular weight dispersant and
a foaming agent produces a gypsum wallboard core effect that more
efficiently entrains air (i.e., creates void space), thereby
lowering overall board weight without detrimentally affecting
strength. A gypsum wallboard formed using the dispersant and
foaming agent combination according to the invention exhibits a
higher nail pull value than gypsum wallboard formed using a
conventional dispersant and a foaming agent at the same solids
loading ratio.
Inventors: |
Savoly, Arpad;
(Martinsville, NJ) ; Elko, Dawn P.; (Flemington,
NJ) ; Veal, Bennie; (Rome, GA) ; McCrary,
James; (Silver Creek, GA) |
Correspondence
Address: |
RANKIN, HILL, PORTER & CLARK, LLP
925 EUCLID AVENUE, SUITE 700
CLEVELAND
OH
44115-1405
US
|
Assignee: |
GEO Specialty Chemicals,
Inc.
Cleveland
OH
|
Family ID: |
31494656 |
Appl. No.: |
10/701807 |
Filed: |
November 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10701807 |
Nov 5, 2003 |
|
|
|
10214467 |
Aug 7, 2002 |
|
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Current U.S.
Class: |
525/535 |
Current CPC
Class: |
Y10S 516/909 20130101;
C04B 24/226 20130101; C04B 28/14 20130101; B28B 19/0092 20130101;
C04B 2103/408 20130101; C04B 28/14 20130101; E04C 2/043 20130101;
C04B 2111/0062 20130101; C04B 28/14 20130101; C04B 38/10 20130101;
C04B 38/10 20130101; C04B 40/006 20130101; C04B 40/006 20130101;
C04B 24/16 20130101; C04B 24/226 20130101; C04B 24/226 20130101;
C04B 24/085 20130101 |
Class at
Publication: |
525/535 |
International
Class: |
C08G 075/00 |
Claims
What is claimed:
1. A dispersant and foaming agent combination for use in the
production of gypsum wallboard comprising: a naphthalene
sulfonate-aldehyde condensate alkali salt polymer having a weight
average molecular weight from about 17,000 to about 47,000; and a
soap.
2. The dispersant and foaming agent combination according to claim
1 wherein the aldehyde in the naphthalene sulfonate-aldehyde
condensate alkali salt polymer is selected from the group
consisting of formaldehyde, paraformaldehyde, and
gluteraldehyde.
3. The dispersant and foaming agent combination according to claim
1 wherein the soap comprises an alkyl sulfate and/or an alkyl ether
sulfate.
4. The dispersant and foaming agent combination according to claim
1 wherein the naphthalene sulfonate-aldehyde condensate alkali salt
polymer is a sodium salt.
5. The dispersant and foaming agent combination according to claim
1 wherein the naphthalene sulfonate-aldehyde condensate alkali salt
polymer is a calcium salt.
6. A dispersant for use in the production of gypsum wallboard
comprising a naphthalene sulfonate-aldehyde condensate alkali salt
polymer having a weight average molecular weight from about 17,000
to about 47,000.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 10/214,467 filed Aug. 7, 2002 also entitled "Dispersant and
Foaming Agent Composition" which is incorporated herein by
reference.
FIELD OF INVENTION
[0002] The present invention relates to a dispersant and foaming
agent combination that is useful in the production of gypsum
wallboard and other aqueous cementitious products, a method of
forming a gypsum wallboard and a gypsum wallboard.
BACKGROUND OF THE INVENTION
[0003] Gypsum wallboard is used in the construction of residential
and commercial buildings to form interior walls and ceilings.
Because it is relatively easy to install and requires minimal
finishing, gypsum wallboard is preferred over plaster in almost all
applications.
[0004] Gypsum wallboard consists of a hardened gypsum-containing
core surfaced with paper or other fibrous material suitable to
receive a coating such as paint. It is common to manufacture gypsum
wallboard by placing an aqueous core slurry comprised predominantly
of calcined gypsum between two sheets of paper thereby forming a
sandwich structure. The aqueous gypsum core slurry is allowed to
set or harden by rehydration of the calcined gypsum, usually
followed by heat treatment in a dryer to remove excess water.
[0005] Conventionally in the manufacture of gypsum board, a
pre-generated foam is added to the board core slurry mix to
decrease the weight of the gypsum board. This foam is generated
from a mixture of a liquid foaming agent, air and water in a
suitable foam generating apparatus. The foamed gypsum slurry is
then deposited upon a moving paper substrate, which, itself, is
supported on a long moving belt. A second paper substrate is then
applied on top of the slurry to constitute the second face of the
gypsum board and the sandwich passes through a forming station,
which determines the width and thickness of the gypsum board. In
such a continuous operation the gypsum slurry begins to set
immediately after passing through the forming station. When
sufficient setting has occurred the board is cut into commercially
acceptable lengths and then passed into a board dryer. Thereafter
the board is trimmed, bundled, shipped, and stored prior to
sale.
[0006] The majority of gypsum wallboard is sold in sheets that are
four feet wide and eight feet long. The thickness of the sheets
varies from about one-quarter inch to about one inch depending upon
the particular grade and application, with a thickness of about
one-half inch being most common. A variety of sheet sizes and
thicknesses of gypsum wallboard are produced for various
applications.
[0007] Gypsum wallboard is relatively dense (approximately 43.2
lbs/ft.sup.3), which equates to an overall weight of about 1,800
pounds per thousand square feet of one-half inch wallboard. Weight,
rather than volume, determines the amount of gypsum wallboard that
can be shipped by truck, and freight charges add significantly to
the final cost of gypsum wallboard. Thus, it would be highly
desirable to be able to reduce the overall weight of gypsum
wallboard so that additional sheets could be shipped per truck. In
addition, a lighter gypsum wallboard would be easier to handle and
install at building sites.
[0008] As noted above, it is common practice to introduce air
bubbles into the aqueous gypsum core slurry to create voids in the
hardened core. The introduction of air bubbles reduces the density
of the gypsum wallboard and also reduces the amount of water
necessary to produce a workable core slurry. Air bubbles are
typically formed via the addition of foaming agents during the
formation of the slurry or by adding externally generated foam to
the slurry. The externally generated foam is normally produced by
incorporating air or other gas into an aqueous solution of a
foaming agent, which is then mixed with the slurry. Commercial
gypsum wallboard typically contains about 70% air (or void space)
by volume. About 30% of that volume results from entrained air
bubbles that are formed via the use of foaming agents.
[0009] As noted in Jobbins, U.S. Pat. No. 6,171,388, as the volume
of air bubbles in gypsum wallboard increases, the strength of the
wallboard tends to dramatically decrease, making the wallboard
commercially unacceptable. Jobbins further notes at col. 1, lines
4245, that "[experience has taught that entrainment of air alone
will not product a sufficiently improved lightweight wallboard that
has adequate strength." Generally speaking, a gypsum wallboard must
be able to pass the objective testing criteria set forth in the
ASTM C36 and C473-00 standards in order to be commercially
acceptable.
[0010] Prior art attempts to reduce the weight of gypsum wallboard
have involved dispersing lightweight particles (e.g., expanded
vermiculite, perlite, or expanded thermoplastic polymeric resins)
into the aqueous gypsum core slurry, or more recently,
incorporating a latex emulsion and an excess amount of a nonionic
surfactant or an acrylic polymer into the aqueous gypsum core
slurry. Some of these methods are effective at reducing the overall
weight of the gypsum wallboard, but are expensive and/or present
other problems. Thus, prior art efforts to create lightweight
gypsum wallboard have met with limited success.
[0011] In addition to freight costs discussed above, another
significant factor adding to the final cost of gypsum wallboard is
the energy required to remove excess water from the slurry during
curing and drying. A certain amount of water is required to hydrate
the dry calcined gypsum material, but in order to obtain a smooth,
free-flowing, low viscosity mixture that can be formed into a sheet
in a mold, it has been necessary to add two or three times as much
water to the slurry as is needed for hydration. It would be highly
desirable to reduce the amount of excess water that is necessary
during the production of gypsum wallboard.
SUMMARY OF INVENTION
[0012] The present invention provides a dispersant and foaming
agent combination that is useful in the production of gypsum
wallboard and other aqueous cementitious products, a method of
forming a gypsum wallboard and a gypsum wallboard. The dispersant
and foaming agent combination according to the invention increases
the void size of air that is entrained in the gypsum wallboard
increasing the strength of the wallboard (via nail pull), thereby
allowing one to reduce the density and overall weight of the final
product. Furthermore, the dispersant and foaming agent combination
according to the invention reduces the amount of water required to
obtain a free-flowing aqueous core slurry, which reduces the energy
costs necessary to cure and dry the gypsum wallboard thereby
decreasing production time.
[0013] The dispersant used in the combination according to the
invention is a naphthalene sulfonate-aldehyde condensate alkali
salt polymer having a weight average molecular weight of from about
17,000 to about 47,000. The alkali is preferably an alkali metal
and/or an alkaline earth metal. The aldehyde is preferably
formaldehyde. The foaming agent used in the combination according
to the invention is a soap, and preferably an alkali salt of an
alkyl ether sulfate and/or an alkyl sulfate.
[0014] Conventional dispersants used in the production of gypsum
wallboard typically have a weight average molecular weight of from
about 8,000 to about 14,000. At these molecular weights the
molecular weight differences have negligible effect on efficiency
of the dispersant, and at this molecular weight, there is virtually
no detectable interaction between the dispersant and foaming
agents. Applicants have surprisingly discovered that when a higher
molecular weight dispersant is used, the dispersing effect is
increased, and an synergistic interaction occurs between the
dispersant and the foaming agent that produces a gypsum wallboard
core effect that more efficiently entrains air (i.e., creates void
space).
[0015] The core of a gypsum wallboard formed using the dispersant
and foaming agent combination according to the invention includes
large air bubbles (i.e., large void spaces) with small air bubbles
(i.e., small void spaces) dispersed throughout. Despite the
substantial increase in the volume of air bubbles or void spaces in
the hardened core, gypsum wallboard formed using the dispersant and
foaming agent combination according to the invention exhibits a
higher nail pull value than gypsum wallboard formed using a
conventional dispersant and a foaming agent at the same solids
loading ratio.
[0016] The foregoing and other features of the invention are
hereinafter more fully described and particularly pointed out in
the claims, the following description setting forth in detail
certain illustrative embodiments of the invention, these being
indicative, however, of but a few of the various ways in which the
principles of the present invention may be employed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a graph showing slump diameter as a function of
molecular weight and dosage.
[0018] FIG. 2 is a graph showing slump diameter as a function of
dosage and molecular weight.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] The dispersant used in the combination according to the
invention comprises a naphthalene sulfonate-aldehyde condensate
salt polymer, and more preferably an alkali metal and/or an
alkaline earth metal naphthalene sulfonate-aldehyde condensate
polymer. Naphthalene sulfonate-aldehyde condensate salt polymers
are well known in the art, and are described, for example, in
Tucker, U.S. Pat. No. 2,141,569, Hattori et al., U.S. Pat. No.
3,686,133, and Pieh et al., U.S. Pat. No. 4,725,665. They are
prepared by sulfonating naphthalene and/or alkyl naphthalene (where
the alkyl group contains from about 1 to about 9 carbon atoms) with
concentrated sulfuric acid, oleum (also known as fuming sulfuric
acid), chlorosulfonic acid and/or sulfur trioxide at a mole ratio
of acid to aromatic of from about 0.5 to about 1.5, and more
preferably about 0.75 to about 1.4. Sulfonation is typically
accomplished at a temperature of from about from about 15.degree.
C. to about 190.degree. C., and more preferably from about
40.degree. C. to about 170.degree. C., and most preferably from
about 140.degree. C. to about 160.degree. C.
[0020] The naphthalenesulfonic acid thus formed is then condensed
with an aldehyde. Formaldehyde is the presently most preferred
aldehyde for use in the invention, but paraformaldehyde,
gluteraldehyde, and other conventional aldehydes can also be used.
A variety of condensation methods can be employed, including
continuous, incremental, or all-at-once addition of the aldehyde to
the aqueous aromatic mass. The degree of polymerization is such
that when using a standard GPC column, and sulfonated polystyrene
as a standard, the weight average molecular weight is from about
17,000 to about 47,000, and most preferably about 22,000.
[0021] It is critical to the practice of the invention that the
weight average molecular weight of the naphthalene
sulfonate-formaldehyde condensate salt polymer be at least about
17,000. At molecular weights below 17,000, there is very little, if
any, detectable interaction between the dispersant and the foaming
agent. It is possible to produce naphthalene sulfonate-formaldehyde
condensate salt polymers having weight average molecular weights as
high as about 60,000, but at molecular weights above 47,000, the
viscosity of the polymer becomes so high that there is a
significant risk of not being able to remove the polymer from the
reactor vessel.
[0022] After the condensation reaction, the condensate is brought
to a pH preferably between 7 and 9 using an alkali, most preferably
an aqueous solution of an alkali and/or an alkaline earth metal
base. The alkali reacts with the condensate to form a salt polymer,
most preferably an alkali metal and/or an alkaline earth metal
naphthalene sulfonate-aldehyde condensate salt polymer. Suitable
alkalis for use in the invention include, for example, the
hydroxides, oxides, and carbonates of ammonium, sodium, potassium,
and calcium.
[0023] It will be appreciated that the weight average molecular
weight of the resulting naphthalene sulfonate-aldehyde condensate
salt polymer may be adjusted by varying the mole equivalents of
aldehyde that are reacted with the sulfonated naphthalene during
the condensation reaction. A mole ratio of formaldehyde to
naphthalene sulfonate of about 1.25:1.00 will result in the
production of a naphthalene sulfonate-formaldehyde condensate salt
polymer having a weight average molecular weight of about 22,000,
which is presently most preferred. Reducing the mole ratio of
aldehyde to naphthalene sulfonate will result in a naphthalene
sulfonate-aldehyde condensate salt polymer having a lower weight
average molecular weight.
[0024] The salt polymer can be used to disperse a variety of
particles in aqueous media. In the presently most preferred
embodiment of the invention, the salt polymer is used in
combination with conventional foaming agents in the production of
gypsum wallboard to reduce the viscosity of the aqueous gypsum core
slurry. The salt polymer can also be used in the production of
other aqueous cementitious products such as Portland cement,
concrete and mortar.
[0025] The foaming agent used in the combination according to the
invention comprises a soap, most preferably an alkali salt of an
alkyl ether sulfate and/or an alkyl sulfate. Foaming agents of this
type are well known in the industry, and are disclosed in, for
example, Cukier, U.S. Pat. No. 4,156,615; Green et al., U.S. Pat.
Nos. 4,618,370, 4,6767,835, and 4,678,515; Diez et al., U.S. Pat.
No. 5,240,639; and Savoly et al., U.S. Pat. Nos. 5,158,612 and
5,714,001, all of which are hereby incorporated by reference in
their entirety. The most preferred foaming agents for use in the
invention are mixtures of alkyl sulfates and alkyl ether sulfates
in specific ratios, as disclosed in Savoly et al., U.S. Pat. Nos.
5,158,612 and 5,714,001.
[0026] There are other ways of forming foaming agents, such as
blending fatty alcohols with alkoxylated fatty alcohols, followed
by sulfation of the blend with a sulfating agent such as S03, and
then neutralization with a base, such as NH.sub.4OH. Alternatively,
about one mole of a linear and/or branched alcohol (preferably a
C.sub.8 to C.sub.10 alcohol) can be reacted with about 0.01 to just
less than 0.4 moles, and most preferably 0.05 to 0.3 moles of
ethylene oxide in the presence of a catalyst to incorporate the
oxyethylene groups. Typical examples of such catalysts include NaOH
and KOH. Once the oxyethylene groups are incorporated, the
alkoxylated fatty alcohols are then conventionally sulfated with a
sulfating agent such as SO.sub.3, and then conventionally
neutralized with a base such as NH.sub.4OH, to obtain the foaming
agent. Typical examples of cations producing a water soluble
surfactant include sodium, potassium, magnesium, ammonium, and
organic derivatives thereof, such as triethanolamine and the like.
Presently preferred cations are ammonium and organic derivatives
thereof.
[0027] As noted above, naphthalene sulfonate-aldehyde condensate
salt polymers and alkyl sulfate and/or alkyl ether sulfate foaming
agents have been present together in prior art aqueous gypsum core
slurries. However, prior art naphthalene sulfonate-aldehyde
condensate salt polymers have a weight average molecular weight
within the range of from about 8,000 to about 14,000, and most
typically of about 10,000 to 12,000. At this molecular weight,
there is no detectable interaction whatsoever between the
naphthalene sulfonate-aldehyde condensate salt polymer and the
foaming agent.
[0028] Applicants surprisingly discovered that the dispersing
effect of a higher weight average molecular weight naphthalene
sulfonate-aldehyde condensate salt polymer (e.g., 22,000) is
superior to the dispersing effect obtained through the use of a
similar polymer having a lower weight average molecular weight
(e.g., 12,000) at the same solids loading ratio. At the same solids
loading ratio, use of a higher weight average molecular weight
naphthalene sulfonate-aldehyde condensate salt polymer (e.g.,
22,000 versus 12,000) results in at least 15% reduction in the
viscosity of the aqueous gypsum core slurry as measured by
slump.
[0029] In addition to being a more efficient dispersant on a solids
weight to solids weight basis, applicants have surprisingly
discovered that a higher weight average molecular weight
naphthalene sulfonate-aldehyde condensate salt polymer
synergistically interacts with conventional foaming agents to
produce a gypsum wallboard core structure that is substantially
more efficient in entraining air bubbles or void spaces. The
hardened gypsum-containing core structure includes large bubbles
with small bubbles dispersed throughout. Contrary to conventional
wisdom, gypsum wallboards formed using the dispersant and foaming
agent combination according to the present invention have higher
nail pulls as compared to gypsum wallboards formed using
conventional dispersants and foaming agents. The higher nail pulls
allow gypsum wallboard manufacturers to lower the overall board
weight by at least 5% and still pass the objective testing criteria
set forth in ASTM C36 and C473-00 standards. This allows
manufacturers of gypsum wallboard to dry the lighter wallboard
faster, using less energy, and to ship a larger number of sheets of
gypsum wallboard per truck, which lowers the freight cost
component.
[0030] The present invention also provides a method of fabricating
a gypsum wallboard. In accordance with the method of the invention,
an aqueous slurry comprising calcined gypsum, a naphthalene
sulfonate-aldehyde condensate alkali salt polymer having a weight
average molecular weight from about 17,000 to about 47,000 and a
soap is formed. The slurry is molded into a sheet, preferably by
conventional means. The calcined gypsum in the aqueous slurry is
permitted to rehydrate. Any excess water remaining is removed from
the sheet, which hardens to form a hardened wallboard.
[0031] The invention also relates to an improved gypsum board and
particularly to a gypsum board having a decreased density, but
which has an acceptable structural strength, e.g. compressive
strength. Such strength allows the board to maintain its structural
integrity in the vicinity of fasteners, e.g. nails, screws, etc.,
that may be driven into the board. A wallboard in accordance with
the invention comprises a hardened gypsum-containing core having a
layer of paper disposed thereon. Due to the improved strength of
the gypsum-containing core, a lighter weight paper can be used.
Paper having a weight of at least about 45 pounds per thousand feet
is conventionally used in the fabrication of gypsum wallboard, but
a wallboard according to the present invention can be formed using
paper having a maximum weight of about 35 pounds per thousand
square feet, yet still exhibit a nail pull resistance of at least
about 77 pounds based upon a one-half inch board thickness as
measured in accordance with the ASTM C473-00.
[0032] A wallboard formed in accordance with the invention will
preferably have an overall weight rating of less than about 1,500
pounds per thousand square feet based upon a one-half inch board
thickness. Conventional one-half inch thick gypsum wallboard has an
overall weight rating of at least about 1,600 pounds per thousand
square feet, and more conventionally of about 1,800 pounds per
thousand square feet. Despite the lower weight, a wallboard in
accordance with the invention will have a nail pull resistance of
at least about 77 pounds based upon a one-half inch board thickness
as measured in accordance with the ASTM C473-00.
[0033] The following examples are intended only to illustrate the
invention and should not be construed as imposing limitations upon
the claims. Unless otherwise stated, all temperatures are in
degrees centigrade, all pressures are atmospheric, and all
molecular weights reported are weight average molecular
weights.
EXAMPLE 1
[0034] 1.0 mole of naphthalene was added to a reaction vessel
equipped with a condenser. The naphthalene was heated to
150.degree. C. and stirred. 1.0 mole of sulfuric acid was added
drop wise and the mixture was held at that temperature for 2 hours.
The mixture was allowed to cool to 90.degree. C. and 10 moles of
water were added and the temperature was maintained. To this
mixture, 1.25 moles of formaldehyde were added as a 37% by weight
solution in water. The mixture was heated to 105.degree. C. and
stirred until all of the free formaldehyde was consumed. The
reaction mixture was cooled to 50.degree. C. and a 50% by weight
solution of sodium hydroxide in water was added to the reaction
mixture to adjust the pH thereof to 8. The weight average molecular
weight of the resulting naphthalene sulfonate-formaldehyde
condensate alkali salt polymer was determined to be about
22,000.
[0035] This reaction process was repeated using lower molar ratios
of formaldehyde to naphthalene sulfonate to yield naphthalene
sulfonate-formaldehyde condensate alkali salt polymers having
weight average molecular weights of: 2,000; 3,000; 6,000; 9,000;
10,000; 15,000; 17,000; and 19,000.
EXAMPLE 2
[0036] 50 grams of stucco (less any solids derived from the
dispersant used) were placed into a mixing cup. 36 grams of water
(less any water derived from the dispersant used) were placed into
a second mixing cup. Various dosages of the dispersants formed in
Example 1 were added to the water in the second mixing cup to
approximate the pounds of dispersant that would be present per
thousand square feet ("MSF") of dried, finished wallboard if the
material had been used to form 1/2" gypsum wallboard. The stucco
was added into the water/dispersant mixing cup and the components
were blended by rapid hand stirring for 30 seconds. Immediately
after mixing, the slurry was poured directly onto a clean glass
surface from a height of 4 cm. A roughly uniform diameter disc was
formed in each case. The discs were allowed to set thoroughly and
when completely set (hardened/dried), were removed from the glass
surface using a metal spatula. The discs were turned over and their
diameters were measured across two set points through the center.
The mean diameter of each disc was reported as Slump Diameter (cm).
Table 1 below lists the Slump Diameter (cm) as a function of
dispersant loading and dispersant molecular weight.
1 TABLE 1 2,000 3,000 6,000 9,000 10,000 15,000 17,000 19,000
22,000 MW MW MW MW MW MW MW MW MW 1.00 9.50 9.50 9.75 10.50 10.50
10.50 10.50 10.75 11.00 LB/MSF 2.00 9.75 9.75 10.00 10.75 11.00
11.00 11.00 11.25 11.50 LB/MSF 3.00 10.00 10.00 10.25 11.25 11.50
11.50 11.50 11.50 11.75 LB/MSF 4.00 10.25 10.25 10.50 11.50 11.75
11.75 11.75 12.00 12.25 LB/MSF
[0037] The data in Table 1 is graphically depicted in FIGS. 1 and
2. FIG. 1 is a graph showing slump diameter as a function of
molecular weight and dosage. FIG. 2 is a graph showing slump
diameter as a function of dosage and molecular weight.
EXAMPLE 3
[0038] One-half inch thick gypsum wallboards were produced at a
commercial wallboard plant operating at a line speed of 410 feet
per minute. The aqueous gypsum slurries used to fabricate the
wallboards were sandwiched between sheets of paper weighing 45
pounds per MSF. The aqueous gypsum slurries consisted of mixtures
of 1,365 pounds per MSF of calcined gypsum, 10 pounds per MSF of
accelerator (ball milled gypsum crystals), 470 pounds per MSF of
gauging water, 470 pounds per MSF of raw water, 110 pounds per MSF
of foam water, 8.5 pounds per MSF of starch, 0.5 pounds per MSF of
fiberglass, 0.18 pounds per MSF of retarder
(diethylenetriaminepentaacetic acid), and the loadings in pounds
per MSF of dispersant from Example 1) and foaming agent specified
in Table 2 below. "AES" is an alkyl ether sulfate foaming agent
sold as HYONIC PFM 33, and "AES/AS" is a combination alkyl ether
sulfate/alkyl sulfate foaming agent sold as HYONIC PFM 10, both of
which are available from GEO Specialty Chemicals, Inc. of
Cleveland, Ohio. After the boards were formed and fully hardened,
they were weighed and then tested for nail pull resistance in
accordance with the ASTM C-473-00 standard. The results are
reported in Table 2 below.
2TABLE 2 Foaming Board Nail Plant Dispersant Dispersant Foaming
Agent Weight Pull Trial (MW.sub.w) Loading Agent Loading (lbs/MSF)
(lbs) 3-A 10,000 0.40 AES 0.225 1,609 75.5 3-B 10,000 0.40 AES/AS
0.225 1,634 88.0 3-C 22,000 0.40 AES 0.225 1,630 74.7 3-D 22,000
0.40 AES/AS 0.410 1,641 96.0 3-E 22,000 1.50 AES 0.410 1,667 83.5
3-F 22,000 1.50 AES/AS 0.372 1,656 99.5 3-D 22,000 2.50 AES/AS
0.372 1,563 85.3
EXAMPLE 4
[0039] One-half inch thick gypsum wallboards were produced at a
commercial wallboard plant operating at a line speed of 410 feet
per minute. The aqueous gypsum slurries used to fabricate the
wallboards had the same general composition as set forth in Example
3 above (exclusive of dispersants and foaming agents). In Plant
Trial 4-A, the aqueous gypsum slurry further comprised 4.0 pounds
per MSF of the 22,000 weight average molecular weight dispersant
formed in Example 1, but no foaming agent. In Plant Trial 4-B, the
aqueous gypsum slurry further comprised 4.0 pounds per MSF of the
22,000 weight average molecular weight dispersant formed in Example
1 and 0.26 pounds per MSF of HYONIC PFM 10 foaming agent.
Wallboards were formed by sandwiching the aqueous slurries between
sheets of paper weighing 45 pounds per thousand square feet at a
rate of 1,670 pounds of aqueous slurry per thousand square feet.
The hardened finished wallboards were then tested for nail pull
resistance. Wallboard formed in Plant Trial 4-A exhibited a mean
nail pull resistance of 85.0 pounds in accordance with the ASTM
C473-00 standard. Wallboards formed in Plant Trial 4-B exhibited a
mean nail pull resistance of 94.4 pounds in accordance with the
ASTM C473-00 standard.
[0040] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
illustrative examples shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
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