U.S. patent application number 13/345868 was filed with the patent office on 2013-07-11 for microfiber-containing fiber reinforced facer mats and method of making.
The applicant listed for this patent is Glenda Beth Bennett. Invention is credited to Glenda Beth Bennett.
Application Number | 20130178126 13/345868 |
Document ID | / |
Family ID | 47561303 |
Filed Date | 2013-07-11 |
United States Patent
Application |
20130178126 |
Kind Code |
A1 |
Bennett; Glenda Beth |
July 11, 2013 |
MICROFIBER-CONTAINING FIBER REINFORCED FACER MATS AND METHOD OF
MAKING
Abstract
Fiber-reinforced composite mats are described that include a
non-woven web of fibers. The web of fibers may include a first
group of fibers having an average fiber diameter from about 8 .mu.m
to about 25 .mu.m, and a second group of fibers having an average
fiber diameter from about 0.5 .mu.m to about 6.5 .mu.m. A binder
bonds together the non-woven web of fibers into the fiber
reinforced composite having an air permeability of 250 cfm/ft.sup.2
or less. Also described are gypsum boards that include one or more
facers affixed to at least one surface of the gypsum board. The
facers may be made from the above, described fiber-reinforced
composite mats.
Inventors: |
Bennett; Glenda Beth;
(Toledo, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bennett; Glenda Beth |
Toledo |
OH |
US |
|
|
Family ID: |
47561303 |
Appl. No.: |
13/345868 |
Filed: |
January 9, 2012 |
Current U.S.
Class: |
442/327 |
Current CPC
Class: |
E04C 2/043 20130101;
Y10T 442/60 20150401; D21H 13/40 20130101 |
Class at
Publication: |
442/327 |
International
Class: |
D04H 13/00 20060101
D04H013/00 |
Claims
1. A fiber-reinforced composite mat comprising: a non-woven web of
fibers, wherein the fibers comprise: a first group of fibers having
an average fiber diameter from about 8 .mu.m to about 25 .mu.m; and
a second group of fibers having an average fiber diameter from
about 0.5 .mu.m to about 6.5 .mu.m; and a binder to bond together
the non-woven web of fibers into the fiber reinforced composite,
wherein the composite has an air permeability of 250 cfm/ft.sup.2
or less.
2. The fiber-reinforced composite of claim 1, wherein the air
permeability of the composite is 250 cfm/ft.sup.2 to about 150
cfm/ft.sup.2.
3. The fiber-reinforced composite of claim 1, wherein the air
permeability of the composite is 250 cfm/ft.sup.2 to about 200
cfm/ft.sup.2.
4. The fiber-reinforced composite of claim 1, wherein the air
permeability of the composite is about 230 cfm/ft.sup.2 to about
235 cfm/ft.sup.2.
5. The fiber-reinforced composite of claim 1, wherein the first
group of fibers have an average fiber diameter of about 13
.mu.m.
6. The fiber-reinforced composite of claim 1, wherein the second
group of fibers have an average fiber diameter of about 2.5
.mu.m.
7. The fiber-reinforced composite of claim 1 wherein: the first
group of fibers comprise about 70 wt. % to about 90 wt. % of a
total weight of fibers; and the second group of fibers comprise
about 10 wt. % to about 30 wt. % of the total weight of fibers.
8. The fiber-reinforced composite of claim 7, wherein the second
group of fibers comprises about 20 wt. % of the total weight of the
fibers.
9. The fiber-reinforced composite of claim 1, wherein the thickness
of the fiber-reinforced composite comprises about 10 mils to about
30 mils.
10. The fiber-reinforced composite of claim 1, wherein the binder
comprises a styrene-acrylic copolymer.
11. The fiber-reinforced composite of claim 1, wherein the binder
comprises a water repellant additive.
12. The fiber-reinforced composite of claim 1, wherein the
composite is a facer for a building material.
13. The fiber-reinforced composite of claim 1, wherein the building
material comprises gypsum board.
14. The fiber reinforced composite of claim 1, wherein the fibers
are selected from the group consisting of glass, mineral, wool,
ceramic, carbon, metal, refractory materials, and mixtures
thereof.
15. The fiber reinforced composite of claim 1, wherein fibers are
glass fibers selected from the group consisting of E glass, C
glass, T glass, sodium borosilicate glass, and mixtures
thereof.
16. A gypsum board comprising: a fiber-reinforced composite facer
affixed to at least one surface of the gypsum board, wherein the
facer comprises: a non-woven web of fibers, wherein the fibers
comprise: a first group of fibers having an average fiber diameter
from about 8 .mu.m to about 25 .mu.m; and a second group of fibers
having an average fiber diameter from about 0.5 .mu.m to about 6.5
.mu.m; and a binder to bond together the non-woven web of fibers
into the fiber reinforced composite, wherein the fiber-reinforced
composite facer has an air permeability of 250 cfm/ft.sup.2 or
less.
17. The gypsum board of claim 16, wherein the gypsum board
comprises two or more of the fiber-reinforced composite facers.
18. A process for manufacturing a fiber-reinforced composite, the
process comprising: blending a first group of fibers having an
average fiber diameter from about 8 .mu.m to about 25 .mu.m with a
second group of fibers having an average fiber diameter from about
0.5 .mu.m to about 6.5 .mu.m to form a non-woven web of fibers;
contacting the non-woven web of fibers with a binder solution to
form a wet mat; and curing the wet mat to form a fiber-reinforced
composite mat, wherein the fiber-reinforced composite mat has an
air permeability of 250 cfm/ft.sup.2 or less.
19. The process of claim 18, wherein the process further comprises
applying an aqueous slurry to a surface of the fiber-reinforced
composite mat, wherein the slurry comprises at least one material
selected from the group consisting of calcium sulfate, calcium
sulfate hemi-hydrate, and hydraulic setting cement.
20. The process of claim 18, wherein the process further comprises:
providing a first facer comprising the fiber-reinforced composite
mat; distributing an aqueous slurry to form a layer on the first
facer, wherein the aqueous slurry comprises at least one material
selected from the group consisting of calcium sulfate, calcium
sulfate hemi-hydrate, and hydraulic setting cement; applying a
second facer onto the top of the layer formed from the aqueous
slurry to form a laminate; separating the laminate into individual
pieces; and drying the pieces, wherein the first facer provides a
first face of the dried piece with a smoothness sufficient to
permit the dried article to be directly painted.
21. The method of claim 20, where the dried piece comprises a piece
of gypsum board.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is related to co-assigned U.S. Pat.
Nos. 7,829,488 issued Nov. 9, 2010, and 7,258,759 issued Aug. 1,
2007. It is also related to co-assigned U.S. patent application
Ser. No. 12/383,027 filed Mar. 19, 2009. The entire contents of
these patent and patent application are herein incorporated by
reference for all purposes.
FIELD OF THE INVENTION
[0002] Embodiments of the invention relate to construction
materials used in building construction, including fiber-reinforced
composite faced construction board, such as gypsum board. The
fiber-reinforced composite facers on exposed surfaces of the
construction board may include a glass fiber mat made from a blend
of large and small diameter glass fibers bonded together with a
binder, such as an organic or inorganic binder.
BACKGROUND OF THE INVENTION
[0003] Wallboard formed of a gypsum core sandwiched between facing
layers is used in the construction of virtually every modern
building. In its various forms, the material is employed as a
surface for walls and ceilings and the like, both interior and
exterior. It is relatively easy and inexpensive to install, finish,
and maintain, and in suitable forms, is relatively fire
resistant.
[0004] Paper-faced wallboard (e.g., gypsum wallboard) is commonly
used for finishing interior walls and ceilings. Gypsum wallboard
and gypsum panels are traditionally manufactured by a continuous
process. In this process, a gypsum slurry is generated and
deposited on a continuously advancing, lower facing sheet, such as
kraft paper. A continuously advancing upper facing sheet is laid
over the gypsum and the edges of the upper and lower facing sheets
are pasted to each other with a suitable adhesive. The facing
sheets and gypsum slurry are passed between parallel upper and
lower forming plates or rolls in order to generate an integrated
and continuous flat strip of unset gypsum sandwiched between the
sheets. Such a flat strip of unset gypsum is known as a facing or
liner. The strip is conveyed over a series of continuous moving
belts and rollers for a period of several minutes, during which
time the core begins to hydrate. The process is conventionally
termed "setting," since the rehydrated gypsum is relatively hard.
During each transfer between belts and/or rolls, the strip is
stressed in a way that can cause the facing to delaminate from the
gypsum core if its adhesion is not sufficient.
[0005] While paper is widely used as a facing material for gypsum
board products because of its low cost, many applications demand
water resistance that paper facing cannot provide. Upon exposure to
water either directly in liquid form or indirectly through exposure
to high humidity, paper is highly prone to degradation, such as by
delamination, that substantially compromises its mechanical
strength. Gypsum products typically rely on the integrity of the
facing as a major contributor to their structural strength.
Consequently, paper-faced products are generally not suited for
exterior or other building uses in which exposure to moisture
conditions is presumed.
[0006] In addition, there is growing attention being given to the
issue of mold and mildew growth in building interiors and the
potential adverse health impact such activity might have on
building occupants. The paper facing of conventional gypsum board
contains wood pulp and other organic materials that may act in the
presence of moisture or high humidity as nutrients for such
microbial growth. A satisfactory alternative facing material less
susceptible to growth is highly sought.
[0007] A further drawback of paper-faced gypsum board is flame
resistance. In a building fire, the exposed paper facing quickly
burns away. Although the gypsum itself is not flammable, once the
facing is gone the board's mechanical strength is greatly impaired.
At some stage thereafter the board is highly likely to collapse,
permitting fire to spread to the underlying framing members and
adjacent areas of a building, with obvious and serious
consequences. A board having a facing less susceptible to burning
would at least survive longer in a fire and thus be highly
desirable in protecting both people and property.
[0008] To overcome these and other problems, alternatives to paper
facing have been proposed. For example, exterior insulation systems
have been developed that include a fibrous mat-faced gypsum board.
However, gypsum board products incorporating the fibrous mats have
proven to have certain drawbacks: Some persons are found to be
quite sensitive to the fiberglass mat, and develop skin irritations
and abrasions when exposed to the mat at various stages, including
the initial production of the mat, the manufacture of composite
gypsum board with the mat facing, and during the cutting, handling,
and fastening operations (e.g., with nails or screws) that attend
installation of the end product during building construction.
Handling of the mat, and especially cutting, is believed to release
glass fibers responsible for the irritation. The fibers may either
become airborne or be transferred by direct contact. As a result,
workers are generally forced to wear long-sleeved shirts and long
pants and to use protective equipment such as dust masks. Such
measures are especially unpleasant in the sweaty, hot and humid
conditions often encountered either in manufacturing facilities or
on a construction jobsite.
[0009] In addition, many commercial fiber-faced construction boards
have a surface roughness that makes them difficult to finish
satisfactorily by normal painting, because the texture of the mat
remains perceptible through the paint. The fibers in the mat
themselves give rise to various asperities, and to additional,
larger sized irregularities often termed in the industry with
descriptives such as "orange peel", "cockle", or similarly
evocative terms describing surface non-planarity. The perceived
smoothness of a board surface is the result of a complex interplay
between various topographic features of the board, including the
size, depth, spacing, and regularity of the features. Although some
of these attributes may be quantified somewhat using image analysis
techniques, visual comparison, especially under obliquely incident
light, is more than sufficient for comparing the relative
smoothness of different surfaces.
[0010] Moreover, making the construction board may involve the
deposition of a relatively wet slurry onto the fiber-reinforced
mat, which is generally found to result in considerable intrusion
of the slurry through the mat and onto the faced surface.
Prevention of this excess intrusion typically requires very careful
control of the slurry viscosity, which, in turn, frequently leads
to other production problems. Alternative mats, which inherently
limit intrusion, yet still have sufficient permeability to permit
water to escape during the formation and heat drying of the
construction board are thus eagerly sought as a simpler
alternative. These and other problems are address in the present
application.
BRIEF SUMMARY OF THE INVENTION
[0011] Fiber-reinforced composite mats for use in construction
board and other building materials are described, as well as
processes of making the mats, boards, and materials. The mat-faced
construction boards may have one or more of a smoother surface, a
stronger internal bond to prevent delamination of the facer when
subjected to prolonged wetness after installation, a surface
requiring less paint to produce an aesthetically acceptable
finished wall, etc., and better flame and mold resistance.
[0012] Exemplary fiber-reinforced composite mats may include a
blend of large and small fibers to give the mats lower air
permeability than conventional mats for construction board facer
applications. The fiber-reinforced composite mats may be used as
facers for construction board, such a gypsum board having a layer
of set gypsum with a first face and a second face and the
fiber-reinforced composite mat affixed as a facer to at least one
of the faces. The gypsum board may be used for a number of purposes
in building construction, such as a surface material for walls and
ceilings and as an underlayment for floors, roofs, and the like.
The present construction board may find application in both
interior and exterior environments. As a result of the selection of
fibers in the facing, the board has a smooth, uniform surface that
readily accepts paint or other surface treatments to provide a
pleasing aesthetic appearance.
[0013] The low air permeability of the mats (typically 250
cfm/ft.sup.2 at 0.5'' w.c. or less) reduces bleedthrough from
aqueous slurries of construction materials applied to the mat.
These slurries may include calcium sulfate, calcium sulfate
hemi-hydrate, and/or hydraulic setting cement that are often used
to make gypsum board, among other construction board materials. The
low air permeability of the mats permits slurry compositions with
lower viscosity to be applied without increasing the rate at which
the slurry bleeds through the mat to create a rough, uneven surface
on the exposed faces of the construction board.
[0014] Embodiments of the invention include fiber-reinforced
composite mats that include a non-woven web of fibers. The web of
fibers may include a first group of fibers having an average fiber
diameter from about 8 .mu.m to about 25 .mu.m, and a second group
of fibers having an average fiber diameter from about 0.5 .mu.m to
about 6.5 .mu.m. A binder bonds together the non-woven web of
fibers into the fiber reinforced composite having an air
permeability of 250 cfm/ft.sup.2 or less.
[0015] Embodiments of the invention further include gypsum board
having at least one fiber-reinforced composite facers affixed to at
least one surface of the gypsum board. The fiber-reinforced facer
may include a non-woven web of fibers, wherein the fibers may be a
blend of a first group of fibers having an average fiber diameter
from about 8 .mu.m to about 25 .mu.m, and a second group of fibers
having an average fiber diameter from about 0.5 .mu.m to about 6.5
.mu.m. The fiber-reinforced facers may also include a binder that
bonds together the non-woven web of fibers into the fiber
reinforced composite. The composite may have an air permeability of
250 cfm/ft.sup.2 or less.
[0016] Embodiments of the invention still further include processes
for manufacturing a fiber-reinforced composite. The processes may
include blending a first group of fibers having an average fiber
diameter from about 8 .mu.m to about 25 .mu.m with a second group
of fibers having an average fiber diameter from about 0.5 .mu.m to
about 6.5 .mu.m to form a non-woven web of fibers. The non-woven
web of fibers may be contacted with a binder solution to form a wet
mat, which may be cured to form a fiber-reinforced composite mat.
The fiber-reinforced composite mat may have an air permeability of
250 cfm/ft.sup.2 or less.
[0017] In further embodiments, an aqueous slurry may be applied to
a surface of the fiber-reinforced composite mat. The slurry may
include one or more materials such as calcium sulfate, calcium
sulfate hemi-hydrate, and hydraulic setting cement.
[0018] In still further embodiments, a first facer made of the
above-described fiber-reinforced composite mat may be provided, and
the aqueous slurry may be distributed on the first facer to form a
layer. A second facer (which may be made of the same
fiber-reinforced composite mat as the first facer or a different
material) may be applied on top of the layer to form a laminate.
The laminate may be cut into specified lengths, which may be dried
to form dried pieces that have a smoothness sufficient to be
directly painted. Exemplary dried pieces include interior gypsum
board for building construction.
[0019] Additional embodiments and features are set forth in part in
the description that follows, and in part will become apparent to
those skilled in the art upon examination of the specification or
may be learned by the practice of the invention. The features and
advantages of the invention may be realized and attained by means
of the instrumentalities, combinations, and methods described in
the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] A further understanding of the nature and advantages of the
present invention may be realized by reference to the remaining
portions of the specification and the drawings wherein like
reference numerals are used throughout the several drawings to
refer to similar components. In some instances, a sublabel is
associated with a reference numeral and follows a hyphen to denote
one of multiple similar components. When reference is made to a
reference numeral without specification to an existing sublabel, it
is intended to refer to all such multiple similar components.
[0021] FIG. 1 shows a simplified cross-sectional view of a
mat-faced construction board according to embodiments of the
invention;
[0022] FIG. 2 shows selected steps in a process for manufacturing a
fiber-reinforced composite according to embodiments of the
invention; and
[0023] FIG. 3 shows selected steps in a process for manufacturing a
faced construction board according to embodiments of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Construction boards (such as hydraulic set and cementitious
board) are described having front and back large surfaces, at least
one of which is faced with a fiber-reinforced composite mat. By
hydraulic set is meant a material capable of hardening to form a
cementitious compound in the presence of water. Typical hydraulic
set materials include gypsum, Portland cement, pozzolanic
materials, and the like.
Exemplary Fiber-Reinforced Composite Mat-Faced Construction
Board
[0025] Referring now to FIG. 1, there is shown generally at 30 a
sectional view across the width direction of one embodiment of a
fiber-reinforced composite mat-faced construction board. In the
embodiment shown, the board has a layer of set gypsum 28 which is
sandwiched between first and second fibrous mats 14, 20, and bonded
thereto. Two right-angled folds are formed in each lateral edge of
first mat 14, a first upward fold and a second inward fold. The two
folds are separated by a small distance, whereby the thickness of
board is generally determined. The second folds define
longitudinally extending strips 16 and 18 that are substantially
parallel to the main part of the mat. A second fibrous mat 20
covers the other side of the set gypsum core 28. The respective
lateral edges of second mat 20 are affixed to strips 16 and 18,
preferably with adhesive 22, 23. Ordinarily board 30 is installed
with the side bearing mat 14 facing a finished space. The board is
advantageously ready for painting, but other finishing forms such
as plaster, wallpaper or other known wall coverings may also be
applied with a minimum of surface preparation.
[0026] The mats for one or both of the large faces of the gypsum
board may include a non-woven web bonded together with a resinous
binder. The web comprises chopped continuous glass fibers, that may
be a blend of larger diameter fibers (e.g., chopped strand fibers,
staple fibers) and smaller diameter fibers (e.g., microfibers). The
larger diameter fibers may have an average fiber diameter of 7
.mu.m or more. Exemplary size ranges for the larger diameter fibers
may include about 8 .mu.m to about 25 .mu.m, about 10 .mu.m to
about 20 .mu.m, about 12 .mu.m to about 14 .mu.m, about 13 .mu.m,
etc. The smaller diameter fibers may have an average size range of
less than 7 .mu.m. Exemplary size ranges for the smaller diameter
fibers from about 0.5 .mu.m to about 6.5 .mu.m, about 2 .mu.m to
about 5 .mu.m, about 2.5 .mu.m, etc.
[0027] Embodiments include blending a larger quantity of the larger
diameter fibers with a smaller quantity of the smaller diameter
fibers to make the non-woven fiber web. For example, the larger
diameter fibers may make up more than half the total weight of the
fiber blend in the web. Exemplary quantities of the larger diameter
fibers may include about 70 wt. % to about 90 wt. % of the total
weight of the fibers (e.g., about 80 wt. %). Exemplary quantities
of the smaller diameter fibers may include about 10 wt. % to about
30 wt. % of the total weight of the fibers (e.g., about 20 wt.
%).
[0028] The fiber length of the larger diameter fibers and the
smaller diameter fibers used in the blend may be the same or
different. Exemplary fiber lengths may include about 6 mm to about
18 mm. The web of fibers may also include fibers that are broken
into two or more pieces and small glass fibers (e.g., less than 1
mm), chips, and flakes.
[0029] The web of fibers may include chopped strand fibers, staple
fibers, or both. Staple fibers are usually made by processes such
as rotary fiberization or flame attenuation of molten glass. They
typically have a wider range of lengths and fiber diameters than
chopped strand fibers.
[0030] Surfaces of the present construction boards may have an
improved "hand," i.e., an improved subjective feel, and better
accepts surface treatments because of its greater smoothness. In
contrast to conventional construction boards where even substantial
amounts of paint applied in multiple coats can still leave the
facing mat visible and aesthetically unpleasing, the present boards
may be finished to provide an aesthetic and functional surface with
less paint and the associated labor to prepare the surface and
apply the paint or other desired finish, wallpaper or other
coating, or the like.
[0031] The glass used in the fibers of the present webs may include
one or more types of glass selected from the group consisting of E,
C, and T type and sodium borosilicate glasses, and mixtures
thereof. C glass typically has a soda-lime-borosilicate composition
that provides it with enhanced chemical stability in corrosive
environments, and T glass usually has a magnesium aluminosilicate
composition and especially high tensile strength in filament form.
E glass, which is sometimes called electrical glass, generally has
a calcium aluminoborosilicate composition and a maximum alkali
content of about 2.0%. The chopped fibers of larger average
diameter can have varying lengths, but more commonly are
substantially of similar length. E glass fiber has sufficiently
high strength and other mechanical properties to produce acceptable
mats and is relatively low in cost and widely available. Exemplary
sizes of E glass fibers may include an average fiber diameter of
about 9 .mu.m to about 13 .mu.m, and a length ranging from about 6
to 12 mm.
[0032] The aforementioned glass fibers may be bound together with
an organic or inorganic binder. This may include flame and water
resistant resinous binders such as urea formaldehyde, modified urea
formaldehyde, acrylic resins, melamine resins, homopolymers or
copolymers of polyacrylic acid; crosslinking acrylic copolymers
(e.g., acrylic copolymers having a glass transition temperature
(GTT) of at least about 25.degree. C.); crosslinked vinyl chloride
acrylate copolymers (e.g., copolymers having a GTT of about
113.degree. C. or less), among other types of binders. A lower GTT
may promote better softness and smoothness of the mat surface, but
tensile strength may be improved with a higher GTT. Exemplary GTT
may range from about 15.degree. C. to 45.degree. C. Exemplary
binder systems may further include aqueous modified and plasticized
urea formaldehyde resin binders.
[0033] The binder may include an effective amount of a water
repellant to limit the intrusion of aqueous slurry during board
production. For example, vinyl acrylate latex copolymers may
further incorporate stearylated melamine for improvement in water
repellency. Exemplary concentrations of the stearylated melamine
may include about 3 wt. % to 10 wt. %, (e.g., about 6 wt. %).
Aqueous stearylated melamine emulsions are available commercially
from Omnova Solutions Inc., under the tradename SEQUAPEL.TM. 409.
The stearylated melamine is in liquid form having a solids content
of about 40 wt. percent and is mixed with a suitable copolymer
latex and water to prepare binders for the mats. This material
mixture has a pH of about 9, a viscosity of about 45 centipoises
and is anionic. In some instances, construction board faced with
fiber-reinforced composite mat that incorporates a water repellant
in the binder may also be more resistant to abrasion than similar
mats that don't use a water repellant.
[0034] Exemplary binders for the fiber-reinforced composite mats
may include an acrylate copolymer binder latex with a GTT of about
25.degree. C. These binders are commercially available from Noveon,
Inc. of Cleveland, Ohio, under the tradename Hycar.TM. 26138. As
delivered, this acrylate copolymer latex has a solids content of
about 50 weight percent solids, and in some instances may be
diluted with water to a concentration about 25 wt. percent solids
before being applied to the web of fibers. A crosslinker may be
added to the acrylate binder system, such as a melamine
formaldehyde crosslinker in a concentration of up to about 10 wt. %
(e.g., about 2 wt. % to about 5 wt. % of the binder solution
weight). In some embodiments, the webs of fibers bound with the
acrylate copolymer latex is smoother and the mat thinner for
equivalent weight and properties than with other known binders. The
binder systems do not require fluorochemical emulsions, which can
be expensive.
[0035] The amount of acrylate copolymer latex binder (and any
optional cross-linker) left in the wet mat during manufacture can
be determined by a loss on ignition (LOI) test, the result thereof
being specified as a percentage of the dry weight of the finished
mat. Exemplary amounts of binder in the final mat, based on its dry
weight, may range from about 15 wt. % to 35 wt. % (e.g., about 20
wt. % to about 30 wt. %; about 25.+-.2.5 wt. %, etc.). The upper
limit may be dictated by process constraints and cost, while the
minimum is required for adequate tensile strength.
[0036] Optionally the fiber-reinforced mats may further contain
fillers, pigments, or other inert or active ingredients either
throughout the mat or concentrated on a surface. For example, the
mat may contain effective amounts of fine particles of limestone,
glass, clay, coloring pigments, biocide, fungicide, intumescent
material, or mixtures thereof. Such additives may be added for
known structural, functional, or aesthetic qualities imparted
thereby. These qualities include coloration, modification of the
structure or texture of the surface, resistance to mold or fungus
formation, and fire resistance. Flame retardants sufficient to
provide flame resistance may be added (e.g., ASTM Standard E84,
Class 1, by the American Society for the Testing of Materials). A
biocide may added to the mat and/or aqueous slurry to resist fungal
growth, its effectiveness being measurable in accordance with ASTM
Standard D3273. The facer mat and gypsum layer may have a very low
cellulosic fiber content from which microbes could derive
nutrition. In some embodiments, any cellulosic fiber present in the
mats or gypsum is only an impurity of other ingredients.
[0037] The present construction board may be faced with a
fiber-reinforced composite mat having a basis weight ranging from
about 0.6 to 2.2 pounds per 100 square feet (e.g., ranging from
about 0.9 to 2.2 lbs./100 ft.sup.2; about 1.7.+-.0.2 lbs./100
ft.sup.2, etc.). Exemplary binder content of the dried and cured
mats may range from about 10 wt. % to about 35 wt. %, (e.g., about
15 to about 30 wt. %; about 25.+-.3 wt. %, etc., based on the
weight of the finished mat). The basis weight should be large
enough to provide the mat with sufficient tensile strength for
producing quality construction board. At the same time, the binder
content should be limited for the mat to remain sufficiently
flexible to permit it to be bent to form the corners of the board,
as shown in FIG. 1. Too thick a mat may also render the board
difficult to cut during installation. Such cuts are needed both for
overall size and to fit the board around protrusions such as
plumbing and electrical hardware.
[0038] It is conventional in the wallboard industry to characterize
mat using mechanical testing machines with samples about 7.5 cm (3
inches) wide. Tests are conducted with tension applied either in
the machine direction (i.e., along the mat's elongated dimension)
or in the cross-machine direction (i.e., along its width). Mats
having adequate strength in both the machine and cross-machine
directions are required for producing gypsum board that will
withstand the stresses invariably encountered in manufacturing,
handling, shipping, and installing the board. It is also preferred
that the combined strengths in the two directions be high for the
same reason.
[0039] The present fiber-reinforced composite mats are further
enhanced by their relatively low air permeability. During the
construction board formation process, an aqueous slurry of
cementitious material (e.g., one or more of calcium sulfate,
calcium sulfate hemihydrate, and/or hydraulic setting cement)
applied to the mats and susceptible to migrating though the mats
and onto its outer surface. In severe cases, the slurry may seep
through the mat and drip onto the underlying mat support that will
then require more frequent and involved cleaning. Decreasing the
air permeability of the mat also decreases the rate of migration of
the slurry through the mat, which in-turn reduces the instances of
slurry bleed through that can cause irregularities on the outer
surface of the facer and, in severe cases, migration of the slurry
unto the underlying processing equipment.
[0040] The air permeability of the mat may be measured by the air
flow between reservoirs separated by the mat. One such test is
called the Frazier test and is further described by ASTM Standard
Method D737, with the results ordinarily being given in units of
cubic feet per minute per square foot (cfm/ft.sup.2). The test is
carried out at a differential pressure of about 0.5 inches of
water.
[0041] The air permeability of the present fiber-reinforced
composite mats may preferably be about 250 cfm/ft.sup.2 or less.
Exemplary air permeability levels for the present mats may include
a range of about 250 cfm/ft.sup.2 to about 150 cfm/ft.sup.2; about
250 cfm/ft.sup.2 to about 200 cfm/ft.sup.2; about 240 cfm/ft.sup.2
to about 220 cfm/ft.sup.2; about 235 cfm/ft.sup.2 to about 225
cfm/ft.sup.2; and about 235 cfm/ft.sup.2 to about 230 cfm/ft.sup.2,
among other exemplary ranges. These air permeabilities produce mats
for construction board that have a reduced level of bleed through
for slurries set to conventional viscosities, which results in an
outer facer surface with reduced roughness. In addition to the
lower air permeability, the selection of the fiber blends may
produce a mat with sufficient smoothness to permit direct painting
without the application of tapes and/or surfacing materials (e.g.,
plaster) to the facer. Thus, these mats are well suited as
components of construction board such as interior gypsum board.
Exemplary Processes
[0042] FIG. 2 shows selected steps in an exemplary process 200 of
manufacturing a fiber-reinforced composite according to embodiments
of the invention. The process 200 may include the step 202 of
blending a first and second group of fibers to form a non-woven web
of fibers. The first group of fibers may have an average fiber
diameter of about 8 .mu.m to about 25 .mu.m, while the second group
of fibers may have an average fiber diameter of about 0.5 .mu.m to
about 6.5 .mu.m. An exemplary technique for the blending may
include the forming of a slurry (e.g., an aqueous slurry) with the
fibers. The fiber slurry may then be mechanically agitated to
dispense the fibers more homogeneously through the slurry.
Following the agitation, the slurry may be dispensed on a moving
screen. A vacuum may be applied to remove a substantial part of the
aqueous solution, which may be recycled into more solution for the
slurry. With a substantial portion of the aqueous solution removed,
the non-woven web of fibers is formed on the moving screen.
[0043] The non-woven web of fibers may then be contacted with a
binder solution 204 to form a wet mat. The binder solution may be
an aqueous binder solution applied to the web using, for example, a
curtain coater or a dip-and-squeeze applicator. Excess binder
solution may pass through the screen supporting the binder-coated
wet mat.
[0044] The wet mat may then be cured 206 to form the
fiber-reinforced composite mat. Exemplary curing techniques may
include heating, among other techniques. Continuing with the moving
screen technique described above, heat may be applied following the
remove of excess binder though the web of fibers to evaporate any
remaining water and cure the polymer precursors in the binder
solution into a polymerized binder that bonds together the fibers.
The heat source may be an oven though which the wet mat is conveyed
on the moving screen.
[0045] In some embodiments, the process of manufacturing the
fiber-reinforced mat may be a continuous process, with the moving
screen providing a continuous, conveyor-like loop that may be on a
slight upward incline while the fiber slurry is deposited thereon.
Subsequently, the excess slurry solution is removed and the
non-woven web of fibers is conveyed an area where binder solution
is applied. Following the spraying, curtain coating, etc., of the
binder solution, the wet mat is conveyed on the moving screen
though an oven for the drying of the mat and polymerization of the
binder. Exemplary heating conditions may include subjecting the wet
mat to temperatures of about 120.degree. C. to about 330.degree. C.
for periods of, for example, 1 to 2 minutes, less than 40 seconds,
etc. The final mat may have a thickness of, for example, about 10
mils to about 30 mils.
[0046] Referring now to FIG. 3, selected steps in a process 300 for
manufacturing a faced construction board according to embodiments
of the invention is shown. The process 300 includes the step 302 of
forming a fiber-reinforced composite mat that will act as a first
facer for the construction board. The fiber-reinforced composite
mat may be formed according to the processes described above.
[0047] The process 300 may further include the step 304 of
distributing a slurry of construction material on the first facer
to form a layer. The slurry may be an aqueous slurry that includes
one or more materials selected from the group of calcium sulfate
(CaSO.sub.4), calcium sulfate hemihydrate (CaSO.sub.4.1/2H.sub.2O),
and hydraulic setting cement. The slurry may also optionally
include reinforcing fibers, process control agents, biocides, flame
retardants, and water repellants, among other slurry additives.
[0048] The process 300 may also include the step 306 of applying a
second facer onto the top of the layer formed by the aqueous slurry
to form a laminate of the slurry material sandwiched between the
first facer and the second facer. The laminate may be separated 308
into individual pieces. Separation techniques may include cutting
the laminate into sheets having standard dimensions for
commercially sold construction board (e.g., widths of at least 2
feet, 4 feet, etc.; and lengths of at least 2 feet (e.g., about 8
ft to about 12 ft, etc.)). The individual pieces of laminate may
then be dried 310 for form the final construction board that is
faced to provide a smoothness sufficient to permit the dried
article to be directly painted.
[0049] The present construction boards exhibit a number of
desirable qualities: The fibrous mat used results in a surface that
is smoother and more amenable to painting or other surface
finishing processes, making them excellent candidates for interior
construction board. The mat is also more flexible, facilitating the
bending operations needed to fold the facer around the core during
production, as illustrated for mat 14 in FIG. 1. Moreover, board
incorporating the fibrous mat of the invention has a reduced
tendency to generate irritating dust during cutting and
handling.
Experimental
[0050] The following examples are presented to provide a more
complete understanding of the invention. The specific techniques,
conditions, materials, proportions and reported data set forth to
illustrate the principles and practice of the invention are
exemplary and should not be construed as limiting the scope of the
invention.
Preparation and Testing of a Conventional Non-Woven Glass Fiber
Mat
[0051] A non-woven glass fiber mat of types typically used as a
facer for conventional gypsum board is prepared using a wet laid
mat machine in the manner disclosed in U.S. Pat. No. 4,129,674,
which is herein incorporated in the entirety by reference for all
purposes. The mat, designated as comparative example 1, contains
chopped glass fibers and is bonded together with a polymer binder.
The specific materials used are set forth in Table I. The M137 and
K137 glass fibers are commercially available from the Johns
Manville Corporation of Denver, Colo. A conventional modified urea
formaldehyde binder is applied with a curtain coating/saturation
technique.
TABLE-US-00001 TABLE I Constituents of Conventional Non-Woven Glass
Fiber Mats Comparative Property Example 1 Fiber type K137 avg.
length (mm) 19 avg. fiber diam. (.mu.m) 13 amount (wt. %. of mat)
79 Binder type modified urea formaldehyde amount (wt. %. of mat)
21
[0052] Standard tests for characterizing the physical and
mechanical properties are carried out on the comparative example
mat, including basis weight per unit area, loss of weight on
ignition, and thickness. The test results are summarized in Table
II.
TABLE-US-00002 TABLE II Physical and Mechanical Properties of
Conventional Non-Woven Glass Fiber Mats Comparative Example 1
Physical/Mechanical Property 1 Basis weight (lbs./100 sq. ft.) 2.1
LOI (%) 21 Thickness (mils) 36.5 Machine Direction (Tensile
Strength lbs./3 in. width) 124 Cross Machine (Tensile Strength
lbs./3 in. width) 84 Tabor Stiffness 45 Frazier Permeability
(cfm/ft.sup.2) 625
[0053] Strengths are measured both along the web direction and
across the web, using a conventional mechanical testing machine to
determine the peak tensile strength of a sample about 7.5 cm wide.
The stiffness is determined using the standard Taber stiffness
test, wherein a 38 mm wide strip is deflected by applying force at
a point 50 mm from a clamping point. The torque (in g-cm) required
to achieve a 15.degree. deflection is conventionally termed the
Taber stiffness. Air permeability is measured using the Frazier
test at a differential pressure of 0.5 inches of water in
accordance with ASTM Method D737.
Preparation and Testing of Exemplary Fiber-Reinforced Composite
Mats
[0054] Fiber blends using fibers with a diameter of 8-14 .mu.m are
combined with microfibers to increase the smoothness and density of
the fiberglass facer mat produced in examples 2A-B. The present
microfibers have diameters ranging from 0.5-6.50 .mu.m, and are
produced using a flame attenuated or rotary process. The
microfibers may make up 5-30 wt. % of the total mat weight.
[0055] The fiber blends produce a dense, closed, uniform, and
smooth facer sheet which helps minimize gypsum bleed through, and
provides protection to the gypsum core. The fiberglass mats are
produced with lower air permeability and smaller pore size than the
mats made in comparative example 1. Table III below shows the
impact of different fiber combinations on the air permeability.
TABLE-US-00003 TABLE III Constituents of Exemplary Fiber-Reinforced
Composite Mats Property Example 2A Example 2B Larger avg. length
(mm) 10 10 Fibers avg. fiber diam. (.mu.m) 13 13 amount (wt. %. of
mat) 80 80 Smaller avg. length (mm) 10 10 Fibers avg. fiber diam.
(.mu.m) 2.5 2.5 amount (wt. %. of mat) 20 20 Binder Type Styrene
Acrylic Styrene Acrylic Copolymer Copolymer + Water Repellant
amount (wt. %. of mat) 21 21
[0056] The fiber-reinforced composite mats of examples 2A-B were
tested for air permeability using the Frazier test at a
differential pressure of 0.5 inches of water in accordance with
ASTM Method D737. Table IV lists the air permeability measurement
data and the rate of penetration for an aqueous gypsum slurry.
TABLE-US-00004 TABLE IV Physical Properties of Exemplary
Fiber-Reinforced Composite Mats Avg. Slurry Basis Air Pore
Penetration Weight Thickness Perm Size Time Example (lbs/100
ft.sup.2) (mm) (cfm/ft.sup.2) (.mu.m) (sec) 2A 1.7 20.3 231 13.0 87
2B 1.7 19.9 233 12.9 485
[0057] The low air permeability of examples 2A&B correlate with
longer slurry penetration times. The addition of the a water
repellant to the binder composition in example 2B was also helpful
to increase the slurry penetration time (i.e., lower the slurry
penetration rate) by making the mat more hydrophobic and hence more
difficult for an aqueous slurry to migrate through the mat.
[0058] Having described several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the invention. Additionally, a number
of well-known processes and elements have not been described in
order to avoid unnecessarily obscuring the present invention.
Accordingly, the above description should not be taken as limiting
the scope of the invention.
[0059] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
[0060] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a process" includes a plurality of such processes and reference to
"the facer" includes reference to one or more facers and
equivalents thereof known to those skilled in the art, and so
forth.
[0061] Also, the words "comprise," "comprising," "include,"
"including," and "includes" when used in this specification and in
the following claims are intended to specify the presence of stated
features, integers, components, or steps, but they do not preclude
the presence or addition of one or more other features, integers,
components, steps, acts, or groups.
* * * * *