Note: Descriptions are shown in the official language in which they were submitted.
~ 3 ~
FIBROUS MAT-FACED GYPSUM BOARD
Field of the Invention-
This invention relates to improvements in exterior
~inishing systems such as, for example, exterior insulation
syste~s for buildings, and also to improvements in shaft wall
assemblies for buildings. More particularly, ~his invention
relates to an improved structural component ~or us~ as a
support sur~aca in an exterior finishin~ system, including an
exterior insulation sy~tem (sometimes referred to herein for .
convenience as ~EISystem). In addition, the present invention
encompasses improvement~ in hollow shaft wall a~semblies, ~or
example, those used in constructing elevator sha~ts and
stairwells.
~his invention will be described initially in
connection with its use in EISystems, but, as will be
explained hereinafter, its use has wider applicability.
EISystems are presently being used more and more
widely to insulate existing buildings and buildings under
construction including indus~rial, oommercial, municipal,
in~titutional, and residen~ial buildings. ~ns~allation o~ a
typical EISystem in new construction generally involves the
,
- 13~1~83~
following sequential steps: (A) constructing a frame ~or
support of the outside wall of a building; (B~ affixing to
the frame structural panels to provide a smooth continuous
surface for the support of other of the components of the
EISystem; (C) affixing to the support sur~ace panels o~
insulation; and (D) affixing to the panels of insulation a
mesh-like material which in turn is covered with an exterior
finishing material having weathering and aesthetic properties.
Such systems are designed to be not only highly insulative in
character and attractive in appearance, but also waather
resistant. EISystems can be used to advantage to conserve
energy used for heating and to conserve energy used for air-
conditioning.
EI5ystems have inherent advantages over interior
insulating systems and, in addition, they can be used to
better advantage than interior insulating sys~ems in many
applications.
For example, ~he range of temperature variation in
structural components comprising the walls of a building
insulated from the outside is less than that for such
components in a building which is insulat~d from the inside.
Accordingly, such structural components when insulated ~rom
the outside are subjected to siynificantly lower amounts of
stress caused by thermal expansion and contraction than those
insulated ~rom the insideO This is particularly advantageous
in applicationY where the structural componenks comprise
materials having markedly different co f~iciants of expansion,
as is often the case. In addition, the interior space in a
building having an EISystem tends to have a more uniform
temperature and be less drafty than that o~ a building
insulated ~rom the inside.
Certain buildings are not capable o~ being insulated
from the interior except that valuable inside space is los~ ~o
the system. The installation of an EISystem does not dlsturb
"` 130983~
the inside space of the building.
An EISystem can be used also to mo~ernize or
otherwise renovate the exterior of a ~uilding in nee~ of
renovation. Various of the EISystems which are-commercially
available give the architect a wide range of aesthetically
pleasing designs from which to choose. In addition, the oost
of installing an EISystem is relatively low when there is
taken into account both the costs of othar systems and the
improved thermal efficiencies that can be realized. The
relatively light weight of both the insulation and the
exterior finish in an EISystem i5 particularly ~dvantageous in
new construction because of reduced foundation requirements.
Th~re are, howev~r, problem~ associatad with the
design and/or installation o~ EISystems. As will be discussed
in detail below, various o~ th~ problems stem from ~he type of
material which is used as t~e supporting member for the
insulating and exterior finishing materials of the system.
The pre~ent invention involves improvements in such suppor~ing
member.
Reported DeveloPments
As mentioned a~ove, a typical EISystem includes a
supporting member to which there is affixed insulating
material, which in turn is covered with an exterior ~inishing
material. An exemplary EISystem includes a wood or m~tal
fram2 which i mechanically held in place by nails or screws
to appropriate structural members o~ the building, with panels
of the supporting member in turn mechanically affixed by natls
or screws to the frame. The supporting member, which
typically consists of a smooth continuous surface comprising
individual panels of material positioned in abutting
relationship, must be strong enough to carry tha we~ght of the
components which overlie it, including the insulatin~ and
exterior finishing materials Although low density, light
~, '
13~831
weight insulating pan~ls of expanded polystyrene are used
widely in such systems, the exterior finishing material i5
yen~rally a much denser and heavier weight material, for
ëXa~pl~ n acrylic resin/cement coating that may include
*ec~rative aggregate embedded therein.
Certain of the commercialized EISystems include the
use of panels of a Portland cement-based composition as the
structural member for the support of the overlying panels of
insulation and exterior finishing material. It is believed
that such cement-based panels are described in U.S. Patent No.
3,284,980 which discloses a building panel comprising a core
consisting of a mixture of hydraulic cement and light-weight
aggregate (for example, perlite) sandwiched between sheets of
~ibrous material (for example, woven glass fiber screen),
which are adhered to the faces of the core by separate layers
o~ bonding material containing at least 50% hydraulic cement.
Although the cores of such panels include a light-weight
aggregate, the panels are nevertheless relatively heavy. For
example, a panel 3 ' X 4 ' and 7/16 ~ in thickness
weigh~ about 40 1/2 po~nds. The handling and installation of
such panels lead to the consumption of relatively large
amounts o~ energy. This is a burden to workmen and makes
~ransportation o~ the panels relatively costly.
.
A material which is used more widely in EISystems
than the a~orementioned cement board is gypsum board, ~ha~ is,
panels co~prising a core of set gypsum (calcium sulfate
dihydrate) ~andwic~ed between paper cover sheets. The
particular typë o~ gypsum board that is recommended for use in
EISystems is known as-~gypsum sneathing~ which is gypsum board
designed for use on the exterior o~ ~uildings where it serves
as an underlying sur~ce wnich is covered wi~n~uc~ m~terials
as aluminum, wo~d si~ ;'Portlan~'ceme~t"s~c~ aA~ n the
cas~ o~!an-~ISys~em,-with insu~at'ing'an~`extërior fln"ishlng
materials. C~nv~ntion~'l gypsùm sheathing, as opposed to
conventional gypsum wàll~oard for use in th~ interior o~ a
30~8~1
building, includes a set gypsum core which contains one or
more additives which improve the water resistance of the set
core. The gypsum core o~ commercially available wallboard can
absorb as much as 40-50 wt.% water when immersed ther in at a
temperature of 70F. for about 2 hours. As the absorption of
water tends to substantially reduce the strength of the core,
materials which reduce the tendency o~ the core to absorb
water are included therein. In addition, sheathing has water-
repellant paper cover sheets which shed water. This is
temporary protection for the sheathing before it i5 installed
and before it is covered with the exterior finishing material.
Gypsum sheathing has many desirable characteristics
which make it suitable for use in an EISystem. For example,
such sheathing has relatively good fire-resistant properties,
it is relatively li~ht in weight, it has satisfactory water-
resistant properties and it can be mechanically affixed in
convenient fashion to a metal or wooden frame which underlies
the sheathing.
Notwithstanding the aforementioned, concerns have
been expressed respecting the use of such gypsum sheathiny in
EISystems. By way of background, it is noted that it is
conventional in the industry to affix panels of insulating
material to the underlying support of gypsum sheathing by the
use of an adhesive material and, in turn, to af~ix by the use
of adhesive material~ each o~ the plies which overlie the
panels of inisulation. Except for the use of mechanical
fastening meani~ in the construction of the frame of the
building and in affixing the gypsum sheathin~ to the frame,
all of the components of the EISystem are in effect glued
~et~e~ ~. .... . , ~ . ... .
.
.. ~ . . . . .... .. . . .
Tests designed to evalua~e the cohesive ~trength of
and the a~hesive stre~qths between the various components
comprisîng the EISy~tem have show~th~ itial f~ilu~e ~;
`
:
130983~
~pulling apart) of the system occurs not in any of the
adhesive layers, but in the paper cover sheet of the gypsum
sheathing. Such cover sheet consists of multi-ply paper, for
example, as many as 7 layers of paper adhered together in
a form that appears to the eye to be a monolithic sheet of
paper. Accordingly, the cohesive strength of the paper can be
characterized as the we~k portion of the system.
Another concern respecting the use of gypsum
sheathing in EISystems of the aforementioned type is tha~
water leakage through the system can lead to the deterioration
of the bond between the paper cover sheet and the gypsum core.
(Although the system is designed to be waterproof, there are
circumstances where defects in one or more plies o~ the system
and/or unusually sev~re environmental condition~ are the cause
of water seepage). It should be appreciated that
deterioration of thi bond can lead to cracking of tha
Pxterior finish, and possibly even collapse o~ portions of the
system a~ the component which is adhered to *he paper cover
sheet pulls apart.
In an effort to overcome th~ aforementioned type
problems, it has been proposed to affix the insulatlng
material to the underlying gypsum sheathing by the use of
mechanical fasteners which extend through the insulating
material, the core of the gypsum sheakhing, and into the
frame. This approach to the problem has the disadvantage that
the work time involved in installing the system is increased
significantly inasmuch as it is much mor~ time consuminq to
install fasteners than to apply an adhesive. Another
shortcoming of thq fastener approach is that the fasteners
provid~ paths for the flow o~ water which may penetrate the
~... .
system and weaken ~he bond between the paper cover shee~ and
gypsum core, as mentioned abova.
Irres~ective of how the insulating material is
affixed to the underlying gypsum sheathing, there is another
problem connected with the use of sheathiny in EISystems.
Because of it5 susceptibility to degradation by water, care
must be taken to protect the sheathing from rain and other
moisture conditions which may~b~ encountered as the sheathing
is stored at the ~ob site awaiting use and during
installation. Taking such protective precautions consumes
time, causes inconvenience, and sometimes causes delays in
installation of the system - all of which tend to increase
costs.
Although gypsum sheathing has a water-repellant
paper surface which provides some limited protection against
water degradation, this type of surface forms a relatively
poor bon* with water-based adhesives which are used to adhere
to.the.surface other components of the EISystem.
The present invention is a support member; for use
in EISystems and sha~t wall assemblies, comprised of an
improved gypsum-based structural component which is modified
in a manner suc~ that problems of the type associated with the
use of conventional gypsum sheeting are either overcome or
alleviated significantly.
5~MMARY OF THE I~VENTION
In accordance with the present invention, there i8
provided an improved structural support element comprising a
fibrous mat-faced gypsum support surface for use in an
exterior finishing system, including exterior insulating
systems, for buildings and in shaf~ wall assembliesr one
embodiment of the present invention is a gypsum board
comprising a set gypsum core sandwiched ketween two sheets of
porous glass mat of randomly dist~ibu~ g~ss~hbe~1.bonded
by an adhesive material. Each mat has~a~iinner an~ outer
surface, the inner surface of which ls adhered t~ ~he.gypsum
core by a portion of the set gypsum comprising the core. The
ou~er surface of one of the mats has portions coated with the
set gypsum o~ the core. The outer surface of the other of the
3~9831
mats is substantially free of set gypsum.
Preferably, the gypsum core has one or more
additives which improve the water resistance thereof. As will
be seen from examples repoxted below, a structural member
comprising a water-resistant gypsum core faced with glass mat,
which itself is hydrophobic, has outstanding weathering
characteristics.
An additional preferred form of the present
invention comprises a gypsum board having each of its core
faces covered with a porous glass fiber mat, with the ~at of
one of the faces being adhered to the core by ~et gypsum
penetra~ing but part-way înto the thickness of the mat and
having its outer.surface substantially free of set gypsuml As
will be described below, the glass ~iber mat surface, which is
free of set gypsum, provides an excellent substrate to which
overlying panels of insulation can be adhered.
In one embodiment of the above form of the
invention, the out~r sur~ace of the mat of the other corR face
i5 also substantially free o~ set gypsum, with set gypsum o~
the core penetrating but part-way into the thickness o~ the
mat. As will be described below, there are manufacturing
advantages which accompany the production of gypsum board o~
such embodimentO
In another embodim~nt of the aforementioned ~orm o~
the pre~en~ invention, the set gypsum of the core penetrates
substantially thr~ugh the.thickness of the mat o~ the other
c,ore fac0 o~er.s~bstanti~1.area portions thexeof in amoun.~s
which are suf~icien~t~ coa~ gla~s ~i~ers of the mat with.a
thin film of s.et-gyps.~, but~not ~ufficient t~ form a smooth,
continuou~.~oating o~ se~..gypsum. ThiS embodiment in which
signi~icant portions o~ the outer surface of the mat have set
gypsum therean provides a protective sur~acQ i~-.a .~wo,~board
package in which the~boards.are-packed to-~ether ~i~h the
.
---- 130~31
gypsum-~ree surfaces in ~ace-to-face relationship and with the
~ypsum covered faces being exposed. More particularly, this
preferred form of board comprises a set gypsum core sandwiched
between two adhering sheets o~ porous glass mat of
predetermined thickness, each of said mats ha~ing an inner and
outer surface and comprising randomly distributed glass fibers
bonded by an adhesive material, the inner surface of each of
said mats being adhered to said gypsum core, and with set
gypsum o~ the core at one sur~ace thereof penetrating
substantially through the thickness of one of said mats over
subs~antial area portions thereof and coating substantial area
portions of the outer surface thereof and with set gypsum of
the core at the other surface thereof penetrating but part~way
into the thickness of the other of said mats, the outer
surface of the other o~ said mats being substantially free of~
set gypsum.
Still another aspect o~ the present invention
comprises a process for making the aforementioned embodiments
2Q o~ gypsum board, that is, the embodiment in which bokh outer
sur~aces of the mats ars substantially free of set gypsum and
the embodiment in which the outer sur~ace of one of the mats
is substantially ~ree of set gyp~um and that of the other mat
has set gypsum thereon. The proce~s includ~s known steps used
heretofore in manufacturing in continuous fashion conventional
wallboard and known glas~-fiber mat-faced gypsum board, but
di~fers there~rom in that the viscosity of the aqueous gypsum
slurry from which the board core is made is controlled in a
manner such that the slurry penetrates into the mats to the
extent needed to~achieyç the desired result. .The basic steps
of the proc~s comp~is~
. . .
(A) forming an aqueous slurry of calcined qyp~um;
(B) continuously feeding said aqueous slurry on~o
an underlying, moving and supported porous fiber glass mat
having a predetermihed thickne~s and an outer surface;
.(Cl forming said deposited~slurry a~ it i~ carried
'
.
309~31
on said moving mat into~-a panel-like shapa; and
(D) applying to the~top surface o~ said panel like
shape of ~lurry an overIying porous f~ber glass ma~ of
predetermined thickness. ; - : ~ -
. ~
In forming gypsum boaxd in which ~oth of the outer
mat surfaces are substantially ~ypsum-free, the viscosity of
the slurry is maintained at a value such that portions of said
slurry penetrate but part-way through the thickness of each of
said underlying and overlying mats and the panel-like shape of
slurry is maintained a~ the calcined gypsum sets to form a set
gypsum core having adhered to its surfaces the und~rlying and
overlying fibQr glass mats.
: .
In ~arming the gypsum-coated/gypsum-~ree form of
glass fiber-~aced board, the viscosity of the slurry is
maintained at a valu~ such tha~ portîons of said slurry
penetrate substantially through the thickness of said
underlying m~ over substantial area portions thereof to coat
substantial area portions of the outer surface and at a valu~
such that portions o~ said slurry penetrate but part-way into
the thickness of said overlying mat.
There are numerous advantages whi~h flow from the
use of the present inven~ion. ~n EISystem which includes a
fibrou mat-faced gyp~um support surfa~e that has affixed
thereto in~ulating mat~rial hy adhesive only, that i , without
fastening means which extend through the insulating material,
has higher tensile or cohesive strength than a like sys~am
which includes convantional paper-faced ~ypsum bo~rd. Testing
of systems of ~his invention which include insulatio~ ih the
form of expanded polystyrene panels has ~hown that lnitial
failure is experienced by a pulling apart o~ th~ ex`pan~ed
polystyrene panel, thus evidencing improvement in ~réng~h
relative to conventional systems where initial faiiure is
experienced in the paper plies of the g~psum support mem~ér.
The fibrous mat-faced surface of the gypsum support member i~
30~83~
11
water resistant in contrast to conventional paper cover sheets
of gypsum board which can soak up water. This improved water
resistance gives the applicator greater flexibility in
selecting adhesives that can be used to adhare insulation
directly to the mat-faced surface of the gypsum support
element as adverse affects are not encountered by the use of
water-based adhesives. The fibrous mat-faced surface of the
gypsum support element is ~nailable~, and accordingly, it can
be secured readily to an underlying frame or other substrate
by nailing. In comparison to various of the commercially
available systems, the improved support surface of the present
invention has improved rigidity and strength uniformity in
both the length and width dimensions of the system. Unlike
conventional paper cover sheets, the fibrous mat does not
expand or contract during the manufacture of the product; this
reduces cockle and leads to uniformity of dimensions. The
preferred embodiment of the invention which includes the use
of a water-resistant core provides a substantially improved
weather-resist~nt product which better re~ists degradation
both within and outside of the system.
BRIEF D13SCRIPTION OF THE DRAWINGS
Figure 1 is a somewhat diagrammatic, fragmentary
side elevational view illustrating portions of a manufacturing
line for producing gypsum board of a type sui~able ~or use in
the manu~acture o~ gypsum board prepared for use in accordanca
with the present invention;
. .. . . . . .. . ... . ... .
Figur0 2 i~ an enlarged fragmentary sectional view,
taken as indicated toward the lè~t of ~igure 1, of an
underlying fiber glass mat used in the manufacture of the
gypsum board;
.. . .. .. . . ... . ... .
Figure 3 is a fragmentary plan view taXen as
indicat~d by the line 3-3 on Figure 2;
.. , ~,. .. . .
~.3~983~
12
Figure 4 is an enlarged sectional view taken as
indi~ated toward the right on Figure 1 and illustrating both
underlying and overlying fiber glass mats, with intervening
gypsum composition, used in the manufacture of the board;
Figure 5 is a fragmentary plan view taken as
indicated by line 5-5 on Figure 4:
Figure 6 is a fragmentary bottom view taken as
indicated by the line 6-6 on Figure 4 and illustrating the
bottom surface of the underlying mat of the board;
Figure 7 is a transverse sectional view o~ an edge
portion of the completed board, this view being taken as
indicated by the line 7-7 on Figure 4;
Figure 8 is a further enlarged fragmenta.ry sectional
view taken as indicated toward the top of Figure 4;
Figure--9 is a further enlarged fragmentary sectional
view taken as indicated toward the bottom o~ Pigure 4;
Figure 10 is a view illustrating two complete gypsum
boards fabricated according to the present invention and being
assembled for packaging, with the top fibrous mats of the two
boards presented toward each other;
Figure 11 is a view of two hoards assembled in th~
manner indicated in Figure 10 and bound together ~or purpos~s
of shipping:
Figure 12 is a somewhat dia~rammatic ve~tical
sectional view through the upper portion of an external
building wall, a~ insulated in accordanca wi~h the presen~
invention; and
.
~3~83~
13
Figure 13 is an enlarged vertical sectional view
taken substantially as indicated on Figure 12.
DETAILED DESCRIP~ION OF THE`INVENTION .-
The essential components of an EISystem comprise
insulating material which is sandwiched between an underlying
support surface and an exterior finishing material which can
be an integral part of the insulating ma~erial, ~u~ which is
usually applied to the insulating material at the site o~
installation. From one EISystem to the next, there exist
variations in structural details and components. For example,
although the exterior finishing material may be a~fixed
directly to the insulating material, various systems include a
reinforcing compo~ent sandwiched between the exterior
finishing material and the insulating material. The
reinforcing component comprises generally one or mor~ plies of
fiber glass reinforcing fabric or mesh which is adhered by
suitable mastic to the sur~ace of the insulating material. In
some systems, the support surfa~e is affixed to a wooden ~rame
attached to the exterior surface of the outside wall of a
building, whereas in other systems a metal frame is used. In
certain applications, the support sur~ace may be affixed
dixectly to the ext~rior surface of an outside wall, ~or
example, sne comprising cinder blocks or concrete bloc~s. In
new construction, the support sur~ace is typically af~ixed
directly to the frame of the building. The adhesive or mastic
for adhering together componants o~ th~ system tend~ to vary
from one system to the next, and typically comprises specially
formulated proprietary compositions. The improved support
surface of the present invention can be used satisfactorily
and to good advanta~e in EISystems which include overlying
plies o~ insulating and exterior finishing materials~ and
other optional components.
Presently, the most popularly used insulating
material in EISystems is expanded or foamed polystyrene, a
.
. . .
13~9~3~
14
material which has good moisture re~istant properties.
Although it has desirably low water vapor transmission, it is
not a vapor barrier, but instead is capable of breathing.
Rigid panels of expanded polystyrene are used most widely in
EISystems. Such panels have satisfactory compressive strength
and resilience and are presently available in thicknesses
ranging ~rom 1/2 to 6 inches, widths from 6 to 48 inches and
lengths ranging from 4 feet to 16 feet~ One commercially
available system utilizes rigid, expanded polystyrene panels
which are 2' X 4' X 1~.
other thermal insulating materials can be used in
EISystems also. Examples of such materials include extruded
polystyrene, polyurethane, isocyanurate, cement-based
insulating plaster~, and phenolic foam. Insulating materials
generally h~ve low thermal conducting and low density.
As mentioned above, various EISystems include a
reinforcing component, for example, in cloth form, sandwiched
between the insulating material and the exterior ~inishing
material. Glass cloth is most widely used at the present time
to reinforce the system, that is, to improve the impact
strength of the s~stem. The particular type or types of glass
cloth used and the number o~ plies thereof which are used
depend on the impact resistance which is desired. Examples o~
reinforcing cloth or fabric which can be used in the system
are woven glass, glass fib~r scrim and glass fiber mesh.
Installation of the reinforcing fabrir generally involves
applying a suitable adhesive to the surface of the insulating
material and then applying the fabric tAere~o. Additional
plies of fabric can be applied if desired. A cement/acrylic
resin is an example of an adhesive that can be used..
......... ... ... ..
The exterior ~inishing material can be affixed
directly to the insulating material or to an in~ermediate
surface such as, for exa~ple, the surfac~ Qf a reinfurcing
member as described ab~ve. The exte~ior inishing material
983:1
has weathering characteristics and is preferably appealing in
appearance. Presently, the most widely used exterior finish
i5 an acrylic resin-based composition which is available in a
paste-type fo~m which is spread or troweled on the underlying
substrate. One type of such composition can be described as a
ready-mixed synthetic resin plaster. Afte~ application, the
resin sets to ~orm a tough~ weather-resistant solid material
which adheres tightly to the underlying substrate. Such resin
compo~itions are available commercially in a variety of
colors. They include optionally aggregate which can vary in
size. This allows the applicator to choose a particular
composition which permits him to apply a finish that can vary
in texture from fine to coarse. Finishes which have a stuoco-
like appearance are popular. Small stones of various colors
can be embedded in the composition ~or decorative purposes.
Examples of other materials that can be used as an
exterior finish are Portland cement stucco including, for
example, sand and larger aggregats.
The exterior finish can vary in thickness over a
wide range, with a thickne s of about 1/16~ to about 1/4
being exemplary.
Turning now to a description of the improved support
member for use in exterior systems of the present invention,
it comprises a set gypsum core ~aced with a fibrous mat. The
gypsum core is basically of the type used in those gypsum
structural products which are known as gypsum wallboard, dry
wal}, gyRs,um board and gypsum sheathing. The ~GO~ o~such a
pr~duct is ~rmed by mixing water wi~h pow~red anhydrous
calcium sul~ate or calcium sulfate hemihydrata (CaSO4;1/2H20),
alsa known a~ cal~ined gypsum, and therea~ter allowing the
mixture to hydrate or set into cal~ium sulfate dihydra~e
(CaS04 2H20), a rela~ively hard material~ Tha car~ of the
support member will in general ~omprise ~t ~east ~bout 85 wt.
percen~ set gyps~m. ~: ~
.
- - :,
~3~83~
,
16
The composition from which the set gypsum core is
made can include optional constituents, including, for
example~ those included conventionally in gypsum shea~hingO
Examples of such constituents include set accelerators,
foaming agents, and dispersing agents. As will be described
in more detail below, a preferred gypsum core ~or use in the
present invention includes one or more additives which improve
the water resistant properties of the core.
The surface of the core to which the insulating
material of the system is affixed is faced wi~h a fibrous mat.
The fibrous mat should be sufficiently porous to permit water
in the aqueous gypsum slurry from which the gypsum core is
made to evaporate therethrough. As described in de~ai~ beiow,
lS the gypsum support element for use in the present inv~tion
can be made ef~iciently by forming an aqueous gypsum s~urry
which contains excess water and placing thereon the fibrous
mat. Aided by heating, excess water ~vaporates ~hrough the
porous mat as the calcined gypsum sets~
The ~ibrous mat comprises material which is capable
of forming a strong bond with the set gypsu~ compri-~ing the
core of the suppor~ sur~ace. Examples o~ such materials
include a mineral-type material such as glass ~ibers and
synthetic resin fibers. The mat can comprise con~.inuous or
discrete strands or ~ibers and be woven or nonwoven in form.
Nonwoven mats such as chopped strand mat and continuous strand
mat can bP used satis~actorily and are less costly than woven
materials. ~he strands of such mats are konded together hy
suitable adhesive. The mat can range in thickness, for
example, from ~bout~ t~ about 40~mils, ~ith a ~hickness o~
about 25 to about 35 mil-s being pr~ferred. The aforementioned
fibrous mats are known and are commercially available in many
formS. . ..
, ~ ... . ... .. . . . . .. .. . .
T~ pre~erre~ rou~ ma~ is a ~iber glass mat
30983~
60382-1268D
comprislng flber glasa filaments oriented in random pattern and
bound together with a- res~n bind~r. Plb~r glass mats of this type
. . .
are commercially available, for example, those sold under the
trademark DURA~GLASS by Manville Bullding Materials Corporation
and those sold by ELK Corpora~ion as BUR or shingle mat.
Although improvements ln an EISystem can be realized by
the use of a gypsum core which has but one of it8 surfaces faced
with flbrous ma~ as descrlbed herein, lt is preferred that both
sur~aces of the core be faced with substan~ially the ~ame f~brous
màterial. If the surfaces of the core are faced with materials
that have differqn~ coefficlent~ of expansion, the core tends to
warp. Flbrous mat-face`d gypsum board and methods for making the
same are known, for example, as described in Canadian Patent No.
993,779 and United State~ Patent No. 3,993,822.
As mentioned above, the preferred form of the fibrous
mat-faced gypsum support surface comprises a gypsum core which has
water-resistant properties. The preferred means for imparting
water-reslstant properties to the gypsum core is to lnclude in the
gypsum composltion from whlch the core ls made one or more
additiveq which lmprove the ability of the set gypsum compositlon
to resist beinq dagraded by water, for exam~le, to r~si3t dissolu-
tion. In preferred form, the water xeslstance of the core is such
that it absorbs less than 5 percent water when tested.in. ..
accordance with ASTM method C~473.
The fibrous mat for use in the present invention has
substantially better water-rasls~ant properti~s ~han ~he
conventiona.l paper facing of gypsum wallboar`d or sheathing.
17
.,. . - . , ,
~ . . .
::
~L3~9~31
60382-1268D
Nevertheless, evaluations have shown that the bond between the
fibrous mat and gypsum core can deteriorate relatively quickly
under the influence of water. For example, samples exposed to the
weather showed loosening at the glass fiber facing within
.
.: .. :.. .. . . .. -
.. , .. : ..
.. : .:
" - :;,
17a
.
~30~831
18
one to two months. In contrast, evaluations o~ water-
resistant gypsum core faced with fibrous mat in accordance
with the present invention have shown the bond between the mat
and core resists being degraded by water for indefinite
periods of time.
Examples of materials which have been reported as
being effective for improving the water-resistant propertias
of gypsum products are the following: poly(vinyl alcohol),
with or without a minor amount of poly(vinyl acetate);
metallic resinates; wax or asphalt or mixt~res thereof: a
mixture of wax and/or asphalt and also corn~lower and
potassium permanqanate; water insoluble thermoplastic organic
materials such as petroleum and natural asphalt, coal tar, and
thermoplastic synthetic resins such as poly(vinyl acetate),
poly(vinyl chloride) and a copolymer of vinyl acetate and
~inyl chloride and acrylic resins; a mixture of metal rosin
soap, a water soluble alkaline earth metal salt, and residual
fuel oil: a mixture of petroleum wax in the fonm of an
emulsion and either residual ~uel oil, pine tar or coal tar; a
mixture comprising residual fuel oil and rosin; aromatic
isocyanates and diisocyanates; organohydrogenpolysiloxanes; a
wax-asphalt emulsion with or without such materialæ as
potassium sulfate, alkali and alkaline earth aluminates, a~d
Portland cement; a wax asphalt emulsion prepared by adding to
a blend o~ molten wax and asphalt an oil-soluble, water~
dispersible emulsi~ying agent, and admixing the a~oremen~ioned
with a solution of casein which contains, as a dispersing
agent, an alkali sulfonate of a polyarylmethylene condensation
product.
A preferred material for use in impro~ing the water-
resist~nt properties of the gypsum core comprises wax-asphal~
emulsion, species o~ which are available commercially. The
3S wax portion of ~he~emuls}on is preferably a paraffin or micro
crys~alline~wax, but other WaXe5 can be used also. The asphalt
in gene~al~sh~u~d-hav~ a~soPten~ng point o~ abo~ 115~, as
'' ' : - - ~ ' '
'
3~9~31
1~
determined by the ring an~-ball method. The total amount of
wax and asphalt in the aqueous emulsion will generally
comprise about 50 to ~0 wt.% o~ the a~ueo~ls emul~ion, with the
weight ratio o~ asphalt to wax varying from about 1 to 1 to
about 10 to l. Various methods are known for preparing the
wax-asphalt emulsion, as reported in U.S. Patent No. 3,935,021
to D.R. Greve and E.D. O!Neill, assigned to the same assignee
as the present invention. Commercially availabla wax asphalt
emulsions that can be used in the composition of the present
invention are sold by United States Gypsum Co. ~W~x ~mulsion~,
Monsey Products, (No. 52 Emulsion) and Douglas Qil Co. (Docal
No. 1034). The amount of wax-a~phalt emulsion used can be
within the range of about 3 to about 10 wt.%, preferably about
5 to about 7 wt.~, pased on the.total weight of the
ingredient~ of the ccmposition fro~ which the set gypsum core
is made, said ingred~ent~ i~cluding the water of the wax~
asphalt emulsion, but not lncluding additional amounts o~
water that are added to the gyp~u~ composition for forming an
aqueous slurry thereof.
A partirularly preferred material for use in
improving the water-resistan~ prop~rties of the gypsum core
comprises a mixture o~ materials, namely, pcly(vinyl alcohol)
and wax-asphalt emulsion of the aforeme~tioned type. The use
of such additive~ to improve the water resistance oP gypsum
product~ is described in aforementioned U.S. Patent No.
3,935,021. . . . .
The source of the poly(vinyl alcohol) is preferably
. a substantially completely hydrolyzed form of poly(vin~l
ac~tate),..that is, about 97 to 100% hydrolyzed polyvinyl
acetat~.~ The poly(vinyl alcohol) should be cold-water
insoluble and soluble in water at elevated temperatures,.~or
example, at temperatures of about 140 to about 2QSF. T~ -
general, a 4 wt.% water solution of poly(~inyl alcohol) at 20C
will have a viscosity of about 25 to 70 cp as determined by
means of tha Ho~ppler- ~alling ball method. Commercially
8 3 ~
.
available poly(vinyl alcohols) for use in the composition of
the present invention are availa~le from E. I. du Pont de
Nemours and Company, sold under the trademark ~Elvanol" and
from Monsanto co., sold under the trademark "Gelvatoln~
Examples of such products are Elvanol, Grades 71-30, 72-60,
and 70-05, and Gelvatol, Grades 1-90, 3-91, 1-60, and 3-60.
Air Products Corp. also s~lls the product as WS-42.
The amounts of poly(vinyl alcohol~ and wax-asphalt
emulsion used should be at least about 0.05 wt. % and about 2
wt. % respectively. The preferred amounts of poly(vinyl
alcohol) and wax-asphalt emulsion are about 0.15 to about 0.4
wt. % and about 3.0 to about 5.0 wt. % respectively. Unless
stated otherwise, the term ~wt. %n when used herein and in the
claims means weight percent based on the total weight of the
ingredients of the composition from which the set gypsum core
is made, said ingredients including the water o~ the wax-
asphalt emulsion, but not including additional amounts of
water that are added to the gypsum composition for forming an
aqueous slurry thereof.
An attractive feature of the present invention i5
that the ~ibrous mat-faced gypsum support member can be made
utilizing existing wallboard manufacturing lines, for example,
as shown somewhat diagrammatically in Figure 1. In
~onventional fashion, dry ingredients (not shown) ~rom which
the gyp~um core is ~ormed are pre-mixed and then fed to a
mixer of the type commonly referred to as a pin mixer 2.
Water and other liquid constituents (not shown) used in making
the core are metered into the pin mixer 2 where they ~re
combined with the dry ingredients to form an aqueous gypsum
slurry. Foam is ~enera~ly-added to the slurry în the pin
mixer to control the density of the resulting corer The
slurry 4 is dispersed through one or more outlets at the
bottom of the mixer 2 onto a moving sheet of fibrous mat 6.
The shee~ o~ ~ibrous mat 6 is in~è~inite in length and is ~ed
from a roll (not s~own) of the ma~. ~
3 ~
21
As is common practice in the manufacture of conven-
tional paper-faced gypsum board, the two opposite edge
portions of the fîbrous mat 6 are progressively flexed
upwardly from the mean plane of the mat 6 and then turned
inwardly at the margins as to provide coverings for the edqes
of the resulting board 40. In Figure 1, this progressive
flexing and shapim~ of the edges o~ the mat 6 are shown for
only one side edge of the mat and the conventional guiding
devices which are ordinarily employed for this purpose are
omitted from the ~igure for the sake of clarity. Figure 7
shows an edge of the set gypsum core 42 covered by the
overlapped edge portion 6A of the mat 6. Figure 7 shows also
score marks 10 and lOA of the mat 6, the score marks
permitting the formation of good edges and flat surfaces. The
score marks 10 and lOA are mad~ by a conventional scoring
wheel 12. An advantage of using the preferred form of glass
fiber mat is that it is capable of being scored and edged like
conventional paper facing.
Another sheet o~ fibrous mat 16 is fed from a roll
(not shown) onto the top of the slurry 4, ther~by sandwiching
the slurry between the two moving fibrous mats which form the
facing~ of the set gypsum core 42 which is formed ~rom the
slurry. The mat~ 6 and 16 with the slurry 4 sandwiched there-
between enter the nip between the upper and lower forming or
shaping rolls 18 and 20, and are thereafter received on a
conveyer belt 22. Conventional edge guiding devices, such as
indicated at 24 shape and maintain the edges of the composite
until the gypsum has set sufficientl~ to reta~n i~ s~ape. In
3.0 du~c~ursa,- seguential lengths o~ the b4ar~ ar.e c~t ~nd
~urthe~ prQcessed by exposure to heat which accelerate the
drying o~. th~ board by increasing the rate of evaporation o~
excess water in the gyps~.slurry.
. . . . . ..
. . Wlth reference to Fi~e 7.,.it has been observed
.
that ths set ~ypsum o~,*he cor~ ~2 is.~ective in formin~
309~31
22
satisfactory bonds with the mats and between the edge portions
of the overlying mat 16 and the overlapped edge portion 6A.o~
the underlying mat 6, thus making it unnecessary to use a bond
improver in th~ slurry or an edge paste to form th~
aforementioned bonds.
The preferred form of mats 6 and 16, as shown in
Figures 2 and 3, comprises glass fiber filaments 30 oriented
in random pattern and bound together with a resin bind~r (not
shown).
A preferred form of glass fiber mat-faced yypsum
board 40 is shown in Figures 4 and 7. ~t comprises one in
which the set gypsum of the core 42 penetra~e~ substantially
through the thickness of the mat 6 over substantial aFea
portions thereof and in which the set gypsum or the core ~2
penetrates the mat 16 partially, with the suEfa~e being thus
substantially free of set gypsum. ~he gypsum-free surface of
mat 16, as seen in Fiqure 8, is highly textured, and provides
an excellent substrate for adhering thereto an overlying
component inasmuch as it comprises many interstices into which
an adhesive composition can flow and bond.
In shipping ~ypsum board, it is convenient to
package two boards 40 and 40A together (see Figure 10 and 11),
with the glass ~iber gypsum-free surfaces 41 and 41A in face
to face relationship, and thus protected, and with the gypsum-
coated surfaces (for example, 43A in Fiqure 11) forming ~.he
outside of the package. The set gyp~um on ~he outside
surfaces helps to keep the board from being damaged during
handling, shipping and storage, and protects the skin of those
who come in contact with`~ è board ~rom being irritated by the
glass fibers of the mat.
The phrase ~substantially penetrated hy set gypsumn,
as used herein, means that-the set gypsum of the core~ extends
fro~`th~ ma~ sur~ace which is con~i~uous to the core to the
. - . . . :
3 1
23 60382-1~68E
outer mat surface and coats glass flbers on the outer surface with
a thin film of set gypsum to the e~tent that the outline of glass
flber~ can be ~een through the thin fllm of set gypsum. The
phrase "over substantlal area portions of the outer surface", as
used hereln, means that about 30 to about 75% of the outer surface
area of the mat is substantially penetrated by set gypsum.
Preferably, about 45 to about 55% of the outer surface area of the
mat is substantlally panetrated by set gypsum. Accordlngly, the
gypsum-coated surface of thls preferred embodiment of the board
comprlses a surface that has a roughened or patterned appearance~
it does not comprlse a smooth continuous coating oE ~et ~ypsum.
Thls preferred form of board can be ~ormed with relatively small
amounts of gypsum slurry being deposlted on the underlylng support
surface, thus mlnimizing the need to clean the surface.
The need for such cleanlng can be substantlally avolded
by ad~usting the viscosity of the slurry so that it penetrates but
part-way through the underlying fibrous mat, for example, up to
about 50% of lts thlckness. Thus, this preferred form of board
has to gypsum-free fiber-faced surfaces.
The manufacture of the aforementioned preferred forms o~
board can be accomplished by controlllng the v1scosity of the
aqueous slurry of the calcined gypsum in a manner such that the
slurry penetrates the underlying and overlylng mats to the de~lred
degree. In manufacturlng each of the a~orementioned preferred
forms of board the viscosity of the slurry should be such that it
penetrates about lO to 50% of the thlckness of the overlying mat
over the entire surface thereof.
The recommended means ~or controlling the vlscosity of
~3~g~31
24 6~382--126
the slurry ls to a~d thereto a vi~coslty-control agent. Such
vlscoslty-control agents are known in the field of gypsum board
manufacture. A preferred vlscoslty-control agent is paper flber.
~xamples of other agents that can be used are celluloslc
thickeners, bentonite clays and starches.
The particular viscosity values that are used in ~he
manufacturlng operation can vary from one appllcation to the next,
dependlng on the poroslty of the mat, and the desired penetratlon
of the slurry. Accordingly, for any partlcular appllcatlon, the
vlscoslty value ls best determined empirlcally.
In using the preferred form o~ glass fiher mat, as
descri~ed above, to manufacture the aforementioned preferred ~orms
of board, developmental work has shown that satisfactory results
can be achleved utllizing a gypsum slurry having a viscosity
wlthln the range of about 5000 to 70Q0 cp. As used hereln, the
vlscoslty value refers to Brookfleld viscoslty measured ak a
temperature of 70F at 10 rpm utlllzing paddle No. 3. It should
be appreclated that the amount of vlscoslty-control agent added to
the slurry to glve the desired vlscoslty wlll vary dependlng on
the partlcular agent used and the speclfic vlsco~lty deslred.
In preferred form, the core of the ~lbrous mat-faced
gypsum board has a denslty of about 40 to about 50 lbs/cublc ft.,
most preferably about 42 to about 45 lbs/cublc ft. The manu-
facture of cores havlng densltles wlthln the preferred range can
be ef~ected by using known techniques, for example, by introducing
an approprlate amount o~ ~oam into ~he aqueous gypsum slurry ~rom
which the core i8 formed. There ar~ welght advantages tha~ can be
reallzed by the use of flbrous matfaced gypsum board ln EISystems
,
~,
~3~ 3~
24a 60382-1268E
ln that fibrous mats which are lighter in weight than conventional
paper facing are available. Eor example, the welght of a widely
used paper facing in the manufacture of conventional gypsum
sheathlng ls ln the range of about 120 lbs~1000 sq. ~t. of board,
whereas the weight of a preferred form of glass flber mat for use
ln the
. _ ~3~83 ~
present invention is about 40 lbs/1000 sq. ~t. of board.
Turning now to Figures 12 and 13, there is shown
therein an example of an exterior insulating sys~em fabrica~ed
in accordance with the present invention and comprising the
exterior portion of the building 81. The EISystem 80
comprises panels of ~ibrous mat-faced board 82 affixed by
nails 84 to wood framing 86. A foamed polystyrene panel 88,
about 1 inch thick, i5 adhered to the fibrous mat-faced board
82 by adhesive 90. A rein~orcing member comprising glass
fiber scrim 92 is sandwiched between the polystyrene panel 88
and the ~inal finishing material 94 by adhesive 96.
Various o~ the preferred forms o the gypsum board
of the present invent~on can be used also to good advantage in
place of conventional qyp~um sheathing in applications other
than EISystems. Thus, the preferred forms of board can be
used as an underlying suppor~ surfac~ which is coversd with
overlying finishing materials, for example, aluminum, wood
siding, plaster and Portland cement stucco.
EX~MPLES
The ~ormulation set forth below is an example o~ a
: 25 preferred a~ueous gypsu~ slurry which can be used in making
the core of a gypsum support member in accordance with the
: present invention.
Consti~ent~ Lb8. ~1000 sq.~t. of b~oard
calcined gypsum 1380
( aS0-1/2 H20)
wax/asphalk emulsion 130
aqueous solution o~ lO w~.%
polytvinyl alcohol) 56
paper ~iber 15
35 set accelerator 6
ammonium lauryl sulfonate (foaming agent)
calcium li~nosulfonate (dispersing agent) 2
water 260
;
~9~31
The wax/asphalt emulsion used in the above formulation
contained approximately 48 wt.% ~olids of which about 11 wt.%
was paraffin wax and-about 37 wt.% was asphalt. The set
accelerator comprised about 80 wt.% potash, about 12 wt.%
lignosulfonate and about 8 wt.% ground yypsum.
The above formulation was used to prepare gypsum
board, the surfaces of which were covered with nonwoven fiber
glass mat. The mat was composed of glass fiber filaments
oriented in a random pattern bonded together by an adhesive
referred to by the manufacturer as a ~modified urea-
formaldehyde resin~. The mat had a thickness of 33 mils, was
more porous than paper of the type used as the cover sheet of
.. . .... . .
gypsum wallbQard,,and was not significantly weakened by water,
The air permeability of the mat was 700 CFM/sq. ~t. (test
method FG 436-91~. The mat is available commercially as
DURA-GLASS 7502-~ lbs. and is an example of a preferred
fibrous mat for Use in the practice of the present invention.
Continuous length board was made from the above
gypsum slurry and gla s fiber mat on a conventional wallboard
machine. The slurry wa~ ~ed onto a moving sheet of the mat as
it was unrolled from a roll onto a moving support sur~ace.
The mat had a width of about 51 inches and was scored
continuously by con~entional scoring blades prior to the
depo~ition o~ the ~lurry thereon. Each edge of the mat was
scored with ~wo score marks, with each of the outer score~
b~ing about 1 inch from its respective edge of the mat-and:
each o~ the inner scores being about 1 1/2 inch ~rom its
re~pective edge. After the slurry Was deposited-on the mat,
the edges were folded at the score marks and overlapped on top
of the slurry. (The gypsum core formed ~rom this opëration '
had a width of 47 7/8 inches and a thicknes~ of 1j2 inch.)
Mat from another roll thereof and having a width of 47 1/2
inches was fed onto the top of the gypsum slurry and the
overlapped edge portion~ of the underlying mat. The gypsum
3~831
27
slurry penetrated the overlapped edge portions and served to
bo~d t~e edge portions of the overlying mat to the overlapped
edge portions o~ the underlying mat.
The viscosity of the gypsum slurry was about 5900 cp
at 70F. At this viscosity, the slurry penetrated
substantially throu~h some portions of the underlying mat to
form a thin film thereof on about 40 to 50% of the area o~ the
outer surface of the mat. As the gypsum in ~he film set,
substantial portions of the outer surface of the mat were
covered with a thin film of set gypsum. The surface had a
roughened appearance with outlines of the glass filaments
bei~g observable underneath the thin coatings of gypsum which
covered them. However, at the aforementioned viscosity, the
s}urry penetrated but a portion (about 5 mils) of the
thicknesq o~ tha overlying mat oYer the entire area thereof,
with no ~lurry being observed on the outer surface of the mat.
A~ the gypsum set in the intermediate portions of the mat that
were penetrated by the slurry, it formed a bond that included
a mechanical interlock with the set gypsum cors.
The continuous length board is cut into lengths of
about 8 feet. Drying o~ the gypsum board is accelerated by
heating in an oven at 350F for about 2 hours and until the
board is almo~t dry and then at 200F for about 1 hour until it
i~ dried completely. The density o~ the board is about 43 lb.
cu.ft.
Th~ gypsum-free surfaces o~ panels (2' X 2') oP
glass fibër-f~ced board as described above were adhered to
panels o~`expande~ po~'ys~ren~'utill'z`ihg ~wo different
commercially a~a~là~lé adhesive sy~tem~. In one system,
hereafter ~Sys~ëm A~, on~ of the ~aces o~ a paneI ~f expanded
polystyrenë having a thicknë~s of ~o~t I i~ch a~ 2' X ~' was
smeared with an adhesive mix~ure comprising cement~, sand, and
resin binder u~ilizing a 3/8n X 3~8~ toothed trowel. The
panel was then adhered to ~he glas~ fiber-~aced gyp~um board.
. . .~
~3~31
28
Thereafter, glass fiber reinforcing mesh was applied to the
other fa~e of the panel of expanded polystyrene and a
decorative finish was applied ~o the mesh.
In the other system, hereafter ~System B", the same
steps a described above for System A were followed except
that an acrylic adhesive was applied to the gypsu~-free
surface of the board and the polystyrene panel adhered
thereto.
Two additional systems like Systems A and B above
were assembled, except that conventional paper-faced gypsum
sheathing wa~ substituted for the glass fiber-~aced gypsum
board in each of ~ystems A and ~.
The integrity o~ each of the systems was evaluated
using 1 1/2" X 1 1/2~ cross-sectional cubes which were
extracted from the systems and which were pulled apart in a
tensile test apparatus. The results o~ the testing are set
~orth below.
Fiber Glass- Paper-
~y~ Faced Board Faced Board
A 100~ break in 66% break in the
the polystyrene paper, 33% break
panel in the polystyrene
B 100% break in 100% break in the
the polystyrene paper
panel
From t~ above re~ults, it can be ~een that the use of tha
glas~ fiber-faced gypsum support surface improved signifi-
ca~ly the strength o~ the assembly in that tensile failure
wa.~;trans.ferred ~rom the paper cover of ~he gypsu~ ~heathing
to ~h~ ~oamed polystyrene, with no failure at all experienced
in the glass ~iber mat or the gypsum core to which it wa~
adhered. Thu$~ hould b~ ap~reciated t~t, in accordance
wit~ the~present:inYention~ th~ in~ri~y sf an EI~stem ca~
, ... .. ..
13~831
29
be improved significantly becaus~ it is no longer dependent
upon the ply strength of a paper co~er sheet, but upon a
component having much higher strength. ~ ~
Glass fiber-faced gypsum boards, made as described
above, and with their edges protected, were placed outdoors
for several months and exposed to the elements. During that
period, the boards were exposed to a~out 20 inches of rain.
After this exposure, the boards were examined and ~ound to be
lo in excellent condition with no signs of deterioration~
Other outdoor tests have shown that glass fiber mat-
faced gypsum board in accardance with the presen~ invention
and having a core which includes wax-asphalt emulsion as a
water-resistant a~ditive better resists deterioration than a
like board having a core which in~ludes``sodium methyl
siliconata as the water-resistant additiY~.;
\ Gy~sum board comprising a set gypsum core faced with
20¦ a fibrous mat, as described herein, and pr~erably gypsum
i board comprising a set gypsum core sandwiched between two
sheets of porous glass mat, can be used to particular
advanta~e also a~ a component of a shaft wall assembly or
similar asse~bly in the interior of a building. In such
application, the fibrous mat-~aced board can be us~d to
particular ad~antage in place o~ conventional paper-faced
gypsum core board or shaft liner pane}s~ the core o~ which
generally include~ fire-resistant additive~. Assemblies of
this type g~nerally comprise metal framework or studs for
support o~ th~ gypsum panels which ~orm ~ha wa~ls of the
shafts of elevators~ stairwells and the lika. Example o~
such assemblies are shown in U.S. Patent Nos. 4,047,355;
4,324,0B2 and 4~364,212. Fibrous mat-~aced board~ as
described hsrein, can be used, for example, in the a~semblies
described in th~ aforementioned patents, and particularly as
the shaft liner panel. For use in such application, th core
of th~ board can include fixe resistant additives.
30 ~L3~983~
In summary, it can be said that the present
invention provides in a practical way important functional
improvements in exterior finishing systems for buildings,
including particularly exterior insulating systems, and in
shaft wall assemblies.
;, , ' .
