U.S. patent application number 13/899325 was filed with the patent office on 2013-09-26 for slurries and methods of making light weight gypsum board.
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 Michael R. LYNN, Weixin D. SONG, Qiang YU.
Application Number | 20130248078 13/899325 |
Document ID | / |
Family ID | 37522958 |
Filed Date | 2013-09-26 |
United States Patent
Application |
20130248078 |
Kind Code |
A1 |
YU; Qiang ; et al. |
September 26, 2013 |
SLURRIES AND METHODS OF MAKING LIGHT WEIGHT GYPSUM BOARD
Abstract
The invention generally provides gypsum-containing slurries
including stucco, naphthalenesulfonate dispersant, and
pregelatinized starch. 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
of pregelatinized starch by weight based on the weight of dry
stucco in the formulation. Other slurry additives can include
trimetaphosphate salts, accelerators, binders, paper fiber, glass
fiber, and other known ingredients. The invention also comprises
the gypsum-containing products made with such slurries, for
example, gypsum wallboard, and a method of making gypsum
wallboard.
Inventors: |
YU; Qiang; (Grayslake,
IL) ; SONG; Weixin D.; (Vernon Hills, IL) ;
LYNN; Michael R.; (Arlington Heights, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United States Gypsum Company |
Chicago |
IL |
US |
|
|
Assignee: |
United States Gypsum
Company
Chicago
IL
|
Family ID: |
37522958 |
Appl. No.: |
13/899325 |
Filed: |
May 21, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13493941 |
Jun 11, 2012 |
8470461 |
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13899325 |
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|
12795125 |
Jun 7, 2010 |
8197952 |
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13493941 |
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|
12709159 |
Feb 19, 2010 |
8257489 |
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12795125 |
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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: |
156/42 ; 106/674;
106/711; 106/779 |
Current CPC
Class: |
C04B 24/226 20130101;
C04B 11/00 20130101; C04B 2103/408 20130101; Y02W 30/91 20150501;
Y10T 428/249953 20150401; Y10T 428/31993 20150401; Y10T 428/2978
20150115; C04B 2103/0045 20130101; Y10T 442/665 20150401; C04B
2111/0062 20130101; C04B 24/383 20130101; C04B 22/16 20130101; Y10T
428/31971 20150401; C04B 28/14 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 28/14 20130101; C04B
14/42 20130101; C04B 18/24 20130101; C04B 22/16 20130101; C04B
24/383 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 28/14 20130101; C04B
14/42 20130101; C04B 18/24 20130101; C04B 22/16 20130101; C04B
24/38 20130101; C04B 2103/408 20130101 |
Class at
Publication: |
156/42 ; 106/674;
106/779; 106/711 |
International
Class: |
C04B 11/00 20060101
C04B011/00 |
Claims
1-30. (canceled)
31. A slurry comprising water, stucco, starch, and foaming agent;
the starch is in an amount from about 0.5% to about 10% by weight
based on the weight of the stucco; the foaming agent comprises a
major weight portion of unstable component and a minor weight
portion of stable component, the amount of foaming agent and the
weight ratio of said unstable component to stable component
effective to form a void distribution within a set gypsum
composition formed from said slurry; when the slurry is cast and
dried as a board comprising said set gypsum composition, the set
gypsum composition comprises a continuous crystalline matrix
substantially of calcium sulfate dihydrate, the board having a
density of about 34 pcf or less and a core hardness of at least
about 11 lb, the core hardness determined according to ASTM
standard C473.
32. The slurry of claim 31, wherein the foaming agent comprises a
blend of the unstable and stable components.
33. The slurry of claim 31, wherein the foaming agent comprises at
least about 65% by weight of unstable component.
34. The slurry of claim 31, wherein the foaming agent is in an
amount of about 0.1% or less by weight based on the weight of the
stucco.
35. The slurry of claim 31, wherein the foaming agent is in an
amount from about 0.02% to about 0.03% by weight based on the
weight of the stucco.
36. The slurry of claim 31, wherein the slurry is formed from a
water to stucco weight ratio from about 0.7 to about 1.2.
37. The slurry of claim 31, wherein when the slurry is cast and
dried as a board, the starch is effective to increase the core
hardness of the cast and dried board relative to the cast and dried
board without the starch.
38. The slurry of claim 36, wherein the starch is in an amount from
about 0.5% to about 3% by weight based on the weight of the
stucco.
39. The slurry of claim 36, wherein the starch comprises a
pregelatinized starch and is in an amount from about 0.5% to about
6% by weight based on the weight of the stucco.
40. The slurry of claim 31, wherein when the slurry is cast and
dried as a board, the board has a humidified bond load of at least
about 15 lb after being (a) conditioned for about 6 hours in an
environment sufficient to produce conditions of 90% relative
humidity and 90.degree. F. temperature, and (b) dried to constant
weight.
41. The slurry of claim 31, wherein the slurry further comprises
dispersant.
42. The slurry of claim 31, wherein the slurry further comprises
naphthalenesulfonate dispersant in an amount from about 0.2% to
about 3% by weight based on the weight of the stucco.
43. The slurry of claim 31, wherein the slurry further comprises
polyphosphate in an amount from about 0.12% to about 0.4% by weight
based on the weight of the stucco.
44. The slurry of claim 31, wherein when the slurry is cast and
dried as a board, (a) the starch is effective to increase the core
hardness of the cast and dried board relative to the cast and dried
board without the starch, and (b) the board has a humidified bond
load of at least about 15 lb after being (i) conditioned for about
6 hours in an environment sufficient to produce conditions of 90%
relative humidity and 90.degree. F. temperature, and (ii) dried to
constant weight; and at a board thickness of about 1/4 inch, the
board has a nail pull resistance of at least about 65 lb, as
determined according to ASTM standard C473.
45. The slurry of claim 36, wherein the foaming agent is in an
amount of about 0.1% or less by weight based on the weight of the
stucco; and when the slurry is cast and dried as a board that is
about 1/2 inch thick, the board has a nail pull resistance of at
least about 72 lb, as determined according to ASTM standard
C473.
46. The slurry of claim 31, wherein when the slurry is cast and
dried as a board, the board has a humidified bond load of at least
about 17 lb after being (a) conditioned for about 6 hours in an
environment sufficient to produce conditions of 90% relative
humidity and 90.degree. F. temperature, and (b) dried to constant
weight; and when the slurry is cast and dried as a board that is
about 1/2 inch thick, the board has a nail pull resistance of at
least about 77 lb, as determined according to ASTM standard
C473.
47. The slurry of claim 36, wherein when the slurry is cast and
dried as a board that is about 1/2 inch thick, the board has
flexural strength of at least about 36 lb in a machine direction
and/or about 107 lb in a cross-machine direction, as determined
according to ASTM standard C473.
48. The slurry of claim 47, wherein the slurry further comprises
dispersant in an amount from about 0.2% to about 3.0% by weight
based on the weight of the stucco, and the slurry has water to
stucco weight ratio from about 0.7 to about 1.2; and wherein, when
the slurry is cast and dried as a board the board has a humidified
bond load of at least about 17 lb after being (a) conditioned for
about 6 hours in an environment sufficient to produce conditions of
90% relative humidity and 90.degree. F. temperature, and (b) dried
to constant weight.
49. The slurry of claim 48, wherein the slurry further comprises
sodium trimetaphosphate in an amount from about 0.12% to about 0.4%
by weight based on the weight of the stucco.
50. A slurry comprising water, stucco, starch, naphthalenesulfonate
dispersant, and polyphosphate, wherein the stucco is in an amount
of at least about 700 lb/MSF; the starch is in an amount from about
0.5% to about 10% by weight based on the weight of the stucco; the
naphthalenesulfonate dispersant is in an amount from about 0.1% to
about 3.0% by weight based on the weight of the stucco; the
polyphosphate is in an amount from about 0.12% to about 0.4% by
weight based on the weight of the stucco; when the slurry is cast
and dried as a board comprising set gypsum composition, the board
has a density from about 24 pcf to about 34 pcf and a core hardness
of at least about 11 lb, as determined according to ASTM standard
C473; and the starch is effective to increase the core hardness of
the gypsum composition relative to the gypsum composition without
the starch;
51. The slurry of claim 50, wherein the stucco is in an amount from
about 700 lb/MSF to about 1300 lb/MSF.
52. The slurry of claim 50, wherein the slurry further comprises a
foaming agent having a major weight portion of unstable component
and a minor weight portion of stable component, the amount of
foaming agent and the weight ratio of said unstable component to
stable component forming a void distribution within a set gypsum
composition formed from said slurry.
53. The slurry of claim 52, wherein the foaming agent is in an
amount of about 0.1% or less by weight based on the weight of the
stucco.
54. The slurry of claim 52, wherein the foaming agent is in an
amount from about 0.02% to about 0.03% by weight based on the
weight of the stucco.
55. The slurry of claim 50, wherein the slurry further comprises
paper fiber and/or glass fiber in an amount from about 0.20% to
about 1.30% based on the weight of the dry stucco.
56. The slurry of claim 50, wherein the slurry further comprises
accelerator in an amount from about 0.2% to about 0.9% based on the
weight of the dry stucco.
57. The slurry of claim 50, wherein the slurry has a water to
stucco weight ratio from about 0.7 to about 1.2.
58. The slurry of claim 50, wherein the slurry further comprises
foaming agent and accelerator; the stucco is in an amount from
about 700 lb/MSF to about 1300 lb/MSF; the starch is in an amount
from about 0.5% to about 6% by weight based on the weight of the
stucco; the naphthalenesulfonate dispersant is in an amount from
about 0.2% to about 3.0% by weight based on the weight of the
stucco; the foaming agent has a major weight portion of unstable
component and a minor weight portion of stable component, the
amount of foaming agent and the weight ratio of said unstable
component to stable component effective to form a void distribution
within a set gypsum composition formed from said slurry, wherein
the foaming agent is in an amount of about 0.1% or less by weight
based on the weight of the stucco; when the slurry is cast and
dried as a board, the starch and the void distribution are
effective to provide a board density of about 24 lb/ft.sup.3 to
about 34 lb/ft.sup.3 and, at a board thickness of 1/2 inch, said
core hardness of at least about 11 lb, a nail pull resistance of at
least about 65 lb, and a flexural strength of at least about 36 lb
in a machine direction and/or about 107 lb in a cross-machine
direction, the nail pull resistance and the flexural strength
determined according to ASTM standard C473; and the board has a
humidified bond load of at least about 15 lb after being (a)
conditioned for about 6 hours in an environment sufficient to
produce conditions of 90% relative humidity and 90.degree. F.
temperature, and (b) dried to constant weight.
59. The slurry of claim 58, wherein the foaming agent is in an
amount from about 0.02% to about 0.03% by weight based on the
weight of the stucco.
60. The slurry of claim 58, wherein the slurry further comprises
paper fiber and/or glass fiber and the slurry has a water to stucco
weight ratio from about 0.7 to about 1.2; the starch comprises
pregelatinized starch; the phosphate comprises sodium
trimetaphosphate; the paper fiber and/or glass fiber is present in
an amount from about 0.20% to about 1.30% by weight based on the
weight of the stucco; the accelerator comprises heat resistant
accelerator and is present in an amount from about 0.2% to about
0.9% by weight based on the weight of the stucco; and when the
board is cast and dried as a board, the board has a humidified bond
load of at least about 17 lb after being (a) conditioned for about
6 hours in an environment sufficient to produce conditions of 90%
relative humidity and 90.degree. F. temperature, and (b) dried to
constant weight.
61. A method of making a light weight gypsum board, comprising: (a)
mixing at least water, stucco, starch, and foaming agent to form a
slurry, wherein the starch is in an amount from about 0.5% to about
10% by weight based on the weight of the stucco; the foaming agent
comprises a major weight portion of unstable component and a minor
weight portion of stable component, the amount of foaming agent and
the weight ratio of said unstable component to stable component
effective to form a void distribution within a set gypsum
composition formed from said slurry; (b) disposing the slurry
between a first cover sheet and a second cover sheet to form a
panel; (c) cutting the panel into a board; and (d) drying the
board; wherein, when the slurry is cast and dried as a board
comprising said set gypsum composition, the board has a density of
about 34 pcf or less and an average core hardness of at least about
11 lb as determined according to ASTM standard C473.
62. The method of claim 61, wherein the foaming agent comprises a
blend of the unstable and stable components.
63. The method of claim 61, wherein the foaming agent comprises at
least about 65% by weight of unstable component.
64. The method of claim 61, wherein the slurry has a water to
stucco weight ratio from about 0.7 to about 1.2.
65. The method of claim 61, wherein the starch is effective to
increase the core hardness of the gypsum composition relative to
the gypsum composition without the starch.
66. The method of claim 65, wherein the starch is in an amount from
about 0.5% to about 3% by weight based on the weight of the
stucco.
67. The method of claim 65, wherein the starch comprises a
pregelatinized starch and is in an amount from about 0.5% to about
6% by weight based on the weight of the stucco.
68. The method of claim 61, wherein the slurry is further formed
from dispersant.
69. The method of claim 67, wherein the slurry is further formed
from naphthalenesulfonate dispersant in an amount from about 0.2%
to about 3% by weight based on the weight of the stucco.
70. The method of claim 61, wherein the slurry is further formed
from polyphosphate in an amount from about 0.12% to about 0.4% by
weight based on the weight of the stucco.
71. The method of claim 61, wherein the board has a nail pull
resistance of at least about 72 lb, as determined according to ASTM
standard C473.
72. The method of claim 61, wherein the board has a humidified bond
load of at least about 15 lb after being (a) conditioned for about
6 hours in an environment sufficient to produce conditions of 90%
relative humidity and 90.degree. F. temperature, and (b) dried to
constant weight; and at a board thickness of about 1/2 inch, the
board has a nail pull resistance of at least about 65 lb, as
determined according to ASTM standard C473.
73. The method of claim 61, wherein the board has flexural strength
of at least about 36 lb in a machine direction and/or about 107 lb
in a cross-machine direction, as determined according to ASTM
standard C473.
74. The method of claim 61, wherein the board has a humidified bond
load of at least about 17 lb after being (a) conditioned for about
6 hours in an environment sufficient to produce conditions of 90%
relative humidity and 90.degree. F. temperature, and (b) dried to
constant weight; and at a board thickness of about 1/2 inch the
board has a nail pull resistance of at least about 77 lb, as
determined according to ASTM standard C473.
75. A method of making a light weight gypsum board, comprising: (a)
mixing at least water, stucco, starch, naphthalenesulfonate
dispersant, and polyphosphate to form a slurry, the stucco is in an
amount of at least about 700 lb/MSF; the starch is in an amount
from about 0.5% to about 10% by weight based on the weight of the
stucco; and the starch is effective to increase the core hardness
of the gypsum composition relative to the gypsum composition
without the starch; the naphthalenesulfonate dispersant is in an
amount from about 0.1% to about 3.0% by weight based on the weight
of the stucco; the polyphosphate is in an amount from about 0.12%
to about 0.4% by weight based on the weight of the stucco; (b)
disposing the slurry between a first cover sheet and a second cover
sheet to form a panel; (c) cutting the panel into a board; and (d)
drying the board; when the slurry is cast and dried as a board
comprising said set gypsum composition, the board has a density
from about 24 pcf to about 34 pcf and an average core hardness of
at least about 11 lb as determined according to ASTM standard
C473.
76. The method of claim 75, wherein the stucco is in an amount from
about 700 lb/MSF to about 1300 lb/MSF.
77. The method of claim 75, wherein the slurry comprises foaming
agent having a major weight portion of unstable component and a
minor weight portion of stable component, the amount of foaming
agent and the weight ratio of said unstable component to stable
component forming a void distribution within a set gypsum
composition formed from said slurry.
78. The method of claim 75, wherein the slurry is further formed
from paper fiber and/or glass fiber in an amount from about 0.20%
to about 1.30% based on the weight of the dry stucco.
79. The method of claim 75, wherein the slurry has a water to
stucco weight ratio from about 0.7 to about 1.2.
80. The method of claim 75, wherein the slurry is further formed
from accelerator in an amount from about 0.2% to about 0.9% based
on the weight of the dry stucco.
81. The method of claim 75, wherein the slurry is further formed
from foaming agent and accelerator; the stucco is in an amount from
about 700 lb/MSF to about 1300 lb/MSF; the starch is in an amount
from about 0.5% to about 6% by weight based on the weight of the
stucco; the naphthalenesulfonate dispersant is in an amount from
about 0.2% to about 3.0% by weight based on the weight of the
stucco; the foaming agent has a major weight portion of unstable
component and a minor weight portion of stable component, the
amount of foaming agent and the weight ratio of said unstable
component to stable component effective to form a void distribution
within a set gypsum composition formed from said slurry; the starch
and the void distribution are effective to provide a board density
of about 24 lb/ft.sup.3 to about 34 lb/ft.sup.3 and, at a board
thickness of 1/2 inch, said core hardness of at least about 11 lb,
a nail pull resistance of at least about 65 lb, and a flexural
strength of at least about 36 lb in a machine direction and/or
about 107 lb in a cross-machine direction, the nail pull resistance
and the flexural strength determined according to ASTM standard
C473; and the board has a humidified bond load of at least about 15
lb after being (a) conditioned for about 6 hours in an environment
sufficient to produce conditions of 90% relative humidity and
90.degree. F. temperature, and (b) dried to constant weight.
82. The method of claim 80, wherein the foaming agent is in an
amount from about 0.02% to about 0.03% by weight based on the
weight of the stucco.
83. The method of claim 80, wherein the slurry is further from
paper fiber and/or glass fiber; the slurry has a water to stucco
weight ratio from about 0.7 to about 1.2; the starch comprises
pregelatinized starch; the phosphate comprises sodium
trimetaphosphate; the paper fiber and/or glass fiber is present in
an amount from about 0.20% to about 1.30% by weight based on the
weight of the stucco; the accelerator comprises heat resistant
accelerator and is present in an amount from about 0.2% to about
0.9% by weight based on the weight of the stucco; and the board has
a humidified bond load of at least about 17 lb after being (a)
conditioned for about 6 hours in an environment sufficient to
produce conditions of 90% relative humidity and 90.degree. F.
temperature, and (b) dried to constant weight.
Description
[0001] This is a continuation patent application of copending U.S.
patent application Ser. Nos. 12/795,125 (filed Jun. 7, 2010) and
12/709,159 (filed Feb. 19, 2010), a continuation application and a
divisional application, respectively, of U.S. patent application
Ser. No. 11/449,177 (filed on Jun. 7, 2006), now issued as U.S.
Pat. No. 7,731,794, which in turn claims the benefit of U.S.
Provisional Patent Application No. 60/688,839 (filed on Jun. 9,
2005). All of the preceding applications are hereby incorporated by
reference in their entireties.
FIELD OF THE INVENTION
[0002] This invention pertains to a method making gypsum slurries
containing a pregelatinized starch and a naphthalenesulfonate
dispersant, and products made therefrom. It also pertains to a
method of increasing dry strength of gypsum-containing products
including wallboard by using a naphthalenesulfonate dispersant in
combination with pregelatinized starch in the slurry used to make
the products.
BACKGROUND OF THE INVENTION
[0003] Certain properties of gypsum (calcium sulfate dihydrate)
make it very popular for use in making industrial and building
products, such as gypsum wallboard. Gypsum is a plentiful and
generally inexpensive raw material which, through a process of
dehydration and rehydration, can be cast, molded or otherwise
formed into useful shapes. The base material from which gypsum
wallboard and other gypsum products are manufactured is the
hemihydrate form of calcium sulfate (CaSO.sub.4.1/2H.sub.2O),
commonly termed "stucco," which is produced by heat conversion of
the dihydrate form of calcium sulfate (CaSO.sub.4.2H.sub.2O), from
which 11/2 water molecules been removed.
[0004] Conventional gypsum-containing products such as gypsum
wallboard 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 making gypsum-containing
products using starches as ingredients in the slurries used to make
such products. Starch can increase flexural strength and
compressive strength of gypsum-containing products including gypsum
wallboard. Known gypsum wallboard contains board starch at levels
of less than about 10 lbs/MSF.
[0005] It is also 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. 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.
Trimetaphosphate salts have not in the past been recognized to
affect gypsum slurry water requirements. However, the present
inventors have discovered that increasing the level of the
trimetaphosphate salt 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. Thus the present inventors have also discovered that the dry
strength of gypsum board can be increased by using a
naphthalenesulfonate dispersant in combination with pregelatinized
starch in the slurry used to make the wallboard.
BRIEF SUMMARY OF THE INVENTION
[0006] The invention generally comprises a slurry including stucco,
naphthalenesulfonate dispersant, and pregelatinized starch. 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 slurry additives can include
accelerators, binders, paper or glass fibers and other known
constituents. The invention also comprises the gypsum-containing
products made with such slurries.
[0007] The invention also comprises a slurry including stucco,
trimetaphosphate salt, naphthalenesulfonate dispersant, and
pregelatinized starch. The sodium trimetaphosphate is present in an
amount of at least about 0.12% by weight based on the weight of
stucco. In a preferred embodiment, the trimetaphosphate salt is
present in an amount of about 0.12-0.4% by weight based on the
weight of dry stucco. 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 slurry
additives can include accelerators, binders, paper or glass fibers
and other known constituents. The invention also comprises the
gypsum-containing products made with such slurries.
[0008] A preferred gypsum-containing product is gypsum wallboard.
In this embodiment, the invention constitutes gypsum wallboard
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, and a naphthalenesulfonate dispersant. The
gypsum-containing slurry can optionally contain a trimetaphosphate
salt, for example, sodium trimetaphosphate. This gypsum wallboard
made in accordance with the invention has a high strength, yet much
lower weight than conventional boards. In addition, much less dust
is generated on cuffing, sawing, snapping, or drilling the
wallboards made according to this embodiment.
[0009] In another embodiment the invention constitutes a method of
making gypsum wallboard by 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 wallboard. The gypsum wallboard is cut after the
gypsum-containing slurry has hardened sufficiently for cutting, and
the resulting gypsum wallboard is dried. The gypsum-containing
slurry can optionally contain a trimetaphosphate salt, 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 wallboard product.
DETAILED DESCRIPTION OF THE INVENTION
[0010] According to one embodiment of the present invention, there
are provided 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 wallboard.
[0011] Optionally, the 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 trimetaphosphate salt (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 wallboard. 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.
[0012] The naphthalenesulfonate dispersants 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 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.
[0013] 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.
[0014] 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 wallboard
contains this dispersant at levels of about 0.4% by weight, or
less, based on the weight of dry stucco.
[0015] 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 0.7% 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.
[0016] The gypsum-containing slurry can optionally contain a
trimetaphosphate salt, for example, 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.
[0017] 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.
[0018] 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.
[0019] Starches, including pregelatinized starch in particular,
must be used in gypsum-containing slurries prepared in accordance
with the present invention. 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.
[0020] The present inventors have further discovered that an
unexpected increase in dry strength (particularly in wallboard) 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.
[0021] In addition, it has unexpectedly been found that
pregelatinized starch can be used at levels of at least about 10
lb/MSF, or more, in the dried gypsum wallboard 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 wallboard have been shown to be effective. As an
example, Formulation B, as shown in Tables 1 and 2 below, includes
45 lb/MSF, yet produced a board weight of 1042 lb/MSF having
excellent strength. In this example (Formulation B), a
naphthalenesulfonate dispersant as a 45% by weight solution in
water, was used at a level of 1.28% by weight.
[0022] 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.
[0023] 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 wallboard 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.
[0024] 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.
[0025] The following examples further illustrate the invention.
They should not be construed as in any way limiting the scope of
the invention.
Example 1
Sample Gypsum Slurry Formulations
[0026] 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).
TABLE-US-00001 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 Wallboards
[0027] Sample gypsum wallboards were prepared in accordance with
U.S. Pat. Nos. 6,342,284 to Yu et al. and 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.
[0028] Test results for gypsum wallboards 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 wallboard is approximately 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-00002 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 17.3 20.3 15.1 (lb) 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
[0029] As illustrated in Table 2, gypsum wallboards 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.
[0030] As illustrated in Table 2, the wallboard prepared using the
Formulation B slurry has substantially increased strength compared
with the wallboard 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 Wallboard Weight Reduction Trials
[0031] Further gypsum wallboard 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-00003 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% Naphthalensulfonate solution in water
[0032] 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 board (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 board 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
[0033] 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.
[0034] 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.
[0035] 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-00004 TABLE 4 Sodium trimetaphosphate, DILOFLO.sup.1 Wet
cube Wet cube Test grams (wt % based (wt % based on weight
compressive Sample No. on dry stucco) dry stucco) (2'' .times. 2''
.times. 2''), 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
[0036] 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 Wallboard Plant Production Trials
[0037] 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-00005 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
.sup.3It is well understood that under these test conditions,
percentage failure rates <50% are acceptable.
[0038] 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 boards.
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 Wallboard Plant Production
Trials
[0039] 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-00006 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
[0040] 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.
[0041] 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.
[0042] 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.
* * * * *