U.S. patent application number 12/013063 was filed with the patent office on 2009-07-16 for wallboard joint system.
This patent application is currently assigned to GEORGIA-PACIFIC GYPSUM LLC. Invention is credited to Hubert C. Francis.
Application Number | 20090178357 12/013063 |
Document ID | / |
Family ID | 40848349 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090178357 |
Kind Code |
A1 |
Francis; Hubert C. |
July 16, 2009 |
WALLBOARD JOINT SYSTEM
Abstract
The present invention relates to a drywall tape or joint tape
comprising a non-woven web of fibers having a coating of a filled,
film-forming polymer on one side and being non-coated on an
opposite side for covering seams or for repairs generally in
connection with fiber mat-faced gypsum wallboard, and more
particularly pertains to a method for finishing joint seams and
making other repairs in connection with a coated fiber mat-faced
gypsum wallboard.
Inventors: |
Francis; Hubert C.;
(Lithonia, GA) |
Correspondence
Address: |
PATENT GROUP GA030-43;Georgia-Pacific LLC
133 PEACHTREE STREET, N.E.
ATLANTA
GA
30303-1847
US
|
Assignee: |
GEORGIA-PACIFIC GYPSUM LLC
Atlanta
GA
|
Family ID: |
40848349 |
Appl. No.: |
12/013063 |
Filed: |
January 11, 2008 |
Current U.S.
Class: |
52/417 ;
52/309.1; 52/745.19 |
Current CPC
Class: |
E04F 13/042 20130101;
E04C 2/043 20130101 |
Class at
Publication: |
52/417 ;
52/309.1; 52/745.19 |
International
Class: |
E04B 2/02 20060101
E04B002/02 |
Claims
1. A drywall joint comprising a seam region formed by two adjacent
coated fiber mat-faced gypsum wallboards; a drywall tape covering
said seam region, said drywall tape comprising a non-woven web of
fibers having a coating of a filled, film-forming polymer thereon,
said non-woven web of fibers forming an integral bond with joint
compound in the seam region characterized by said fibers being
embedded in dried joint compound.
2. The drywall joint of claim 1 wherein said film-forming polymer
is selected from the group consisting of at least one polymer
derived from monomers of alkyl halides of from 2-12 C atoms, alkene
halides of from 2-12 C atoms, alkyl acrylamides of from 2-12 C
atoms, alkene acrylamides of from 2-12 C atoms, alkyl acrylates of
from 2-12 C atoms, and alkene acrylates of from 2-12 C atoms.
3. The drywall joint of claim 2 wherein said film-forming polymer
is selected from the group consisting of at least one polymer
derived from at least one monomer selected from styrene,
dimethylstyrene, vinyltoluene, chloroprene, butadiene, ethylene,
acrylamide, acrylonitrile, acrolein, methylacrylate, ethylacrylate,
acrylic acid, methacrylic acid, methyl methacrylate, n-butyl
acrylate, vinylidene chloride, vinyl ester, vinyl chloride, vinyl
acetate, acrylated urethane, hydroxyethyl acrylate,
dimethylaminoethyleneacrylate, and vinyl acrylate.
4. The drywall joint of claim 1 wherein said film-forming polymer
is selected from the group consisting of styrene-butadiene-rubber,
styrene-butadiene-styrene, ethylene-vinyl-chloride,
poly-vinylidene-chloride, modified poly-vinyl-chloride,
poly-vinyl-alcohol, ethylene-vinyl-actate, poly-vinyl-acetate,
polymers and copolymers of acrylic acid, polymers and copolymers of
methacrylic acid, polymers and copolymers of acrylic acid esters,
polymers and copolymers of methacrylic acid esters, polymers and
copolymers of acrylonitrile, acetate acrylic acid polymers,
styrene/acrylate polymers and combinations thereof.
5. The drywall joint of claim 1, further comprising a feathering
portion of said joint compound at edges of drywall tape.
6. A finished drywall seam region or repair region, comprising an
unfinished seam region or repair region formed a coated, fiber
mat-faced gypsum wallboard; a drywall tape comprising a non-woven
web of fibers having a coating of a filled, film-forming polymer on
one side and being non-coated on an opposite side, wherein fibers
on the non-coated opposite side are embedded in dried joint
compound forming an integral bond between the drywall tape and
joint compound in said seam region or repair region.
7. The finished drywall seam region or repair region of claim 6
wherein said film-forming polymer is selected from the group
consisting of at least one polymer derived from monomers of alkyl
halides of from 2-12 C atoms, alkene halides of from 2-12 C atoms,
alkyl acrylamides of from 2-12 C atoms, alkene acrylamides of from
2-12 C atoms, alkyl acrylates of from 2-12 C atoms, and alkene
acrylates of from 2-12 C atoms.
8. The finished drywall seam region or repair region of claim 7
wherein said film-forming polymer is selected from the group
consisting of at least one polymer derived from at least one
monomer selected from styrene, dimethylstyrene, vinyltoluene,
chloroprene, butadiene, ethylene, acrylamide, acrylonitrile,
acrolein, methylacrylate, ethylacrylate, acrylic acid, methacrylic
acid, methyl methacrylate, n-butyl acrylate, vinylidene chloride,
vinyl ester, vinyl chloride, vinyl acetate, acrylated urethane,
hydroxyethyl acrylate, dimethylaminoethyleneacrylate, and vinyl
acrylate.
9. The finished drywall seam region or repair region of claim 6
wherein said film-forming polymer is selected from the group
consisting of styrene-butadiene-rubber, styrene-butadiene-styrene,
ethylene-vinyl-chloride, poly-vinylidene-chloride, modified
poly-vinyl-chloride, poly-vinyl-alcohol, ethylene-vinyl-actate,
poly-vinyl-acetate, polymers and copolymers of acrylic acid,
polymers and copolymers of methacrylic acid, polymers and
copolymers of acrylic acid esters, polymers and copolymers of
methacrylic acid esters, polymers and copolymers of acrylonitrile,
acetate acrylic acid polymers, styrene/acrylate polymers and
combinations thereof.
10. The finished drywall seam region or repair region of claim 6
further comprising a feathering portion of said joint compound at
edges of the drywall tape.
11. A method of making a drywall joint in a seam region formed by
two adjacent coated fiber mat-faced gypsum wallboards comprising
applying a water-containing drying type joint compound or a
setting-type joint compound to the seam region, applying a drywall
tape comprising a non-woven web of fibers having a coating of a
filled, film-forming polymer on one side and being non-coated on an
opposite side onto the joint compound to embed fibers on the
non-coated opposite side in joint compound to form an integral bond
between the drywall tape and dried joint compound in said seam
region.
12. The method of claim 11, further comprising: applying a
feathering portion of said joint compound at edges of the drywall
tape.
13. The method of claim 11 wherein said film-forming polymer is
selected from the group consisting of at least one polymer derived
from monomers of alkyl halides of from 2-12 C atoms, alkene halides
of from 2-12 C atoms, alkyl acrylamides of from 2-12 C atoms,
alkene acrylamides of from 2-12 C atoms, alkyl acrylates of from
2-12 C atoms, and alkene acrylates of from 2-12 C atoms.
14. The method of claim 13 wherein said film-forming polymer is
selected from the group consisting of at least one polymer derived
from at least one monomer selected from styrene, dimethylstyrene,
vinyltoluene, chloroprene, butadiene, ethylene, acrylamide,
acrylonitrile, acrolein, methylacrylate, ethylacrylate, acrylic
acid, methacrylic acid, methyl methacrylate, n-butyl acrylate,
vinylidene chloride, vinyl ester, vinyl chloride, vinyl acetate,
acrylated urethane, hydroxyethyl acrylate,
dimethylaminoethyleneacrylate, and vinyl acrylate.
15. The method of claim 11 wherein said film-forming polymer is
selected from the group consisting of styrene-butadiene-rubber,
styrene-butadiene-styrene, ethylene-vinyl-chloride,
poly-vinylidene-chloride, modified poly-vinyl-chloride,
poly-vinyl-alcohol, ethylene-vinyl-actate, poly-vinyl-acetate,
polymers and copolymers of acrylic acid, polymers and copolymers of
methacrylic acid, polymers and copolymers of acrylic acid esters,
polymers and copolymers of methacrylic acid esters, polymers and
copolymers of acrylonitrile, acetate acrylic acid polymers,
styrene/acrylate polymers and combinations thereof.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a drywall tape or joint
tape for covering seams or for repairs generally in connection with
fiberglass faced gypsum wallboard constructions, and more
particularly pertains to a method for finishing joint seams and
making other repairs in connection with a coated fiberglass faced
gypsum wallboard.
BACKGROUND OF THE INVENTION
[0002] Recently, a gypsum wallboard product has become commercially
available that has the conventional multi-ply paper facer replaced
with a coated, non-woven mat of glass fibers. Aspects of this
wallboard construction are described in U.S. Patent Publications
2005/0266225 and 2006/0240236, the disclosures of which are
incorporated herein by reference.
[0003] This new wallboard product is installed and finished in a
very similar fashion to conventional paper-faced wallboard or
drywall by affixing the boards to studs or joints and filling and
coating the joints with a specially prepared adhesive called "joint
compound" or "mud."
[0004] The same procedure is used to repair surface defects, such
as holes and dents, and to finish openings around electrical boxes,
piping and duct work. Inside corners created by the intersection of
wallboards are also finished in a similar fashion.
[0005] In conventional drywall finishing, that is in constructions
using the conventional multi-ply paper-faced gypsum wallboard, a
drywall tape or joint tape also is used to cover seams, defects and
other openings. The tape generally adds strength and crack
resistance and also assists in preparing a smooth surface for
concealing butt joints and inside corners.
[0006] Conventionally, two types of drywall tape have been
available.
[0007] A simple Kraft paper strip is one commonly used drywall
tape. The Kraft paper tape is used by first applying an initial
layer or "bedding coat" of the of joint compound or mud to the
wallboard seam or defect, then adhering the Kraft paper strip to
the wet joint compound and finally the assembly is finished by
feathering additional joint compound on both edges of the paper
strip with subsequent sanding to form a smooth surface.
[0008] The other type of drywall tape is a woven glass fiber tape,
which usually has an adhesive backing so that it self-adheres to
the conventional paper faced wallboard. In this way, the initial
bedding step needed to finish joints, openings and other defects
when using the paper tape can be eliminated. Conventional woven
glass fiber tape is either configured with a fiberglass leno-weave
mesh or is manufactured with a cross-fiber construction that
purportedly resists stretching and wrinkles, such as supplied by
United States Gypsum Company, Chicago, Ill. Both of these prior art
weaves have a very open mesh-like construction as illustrated in
FIG. 1.
[0009] To date the newly commercialized fiberglass faced gypsum
wallboard product has been finished using the generally less
expensive paper joint tape since the adhesive back of the woven
glass fiber tape does not adhere well to the fiberglass facer
material. Thus, it has not been considered advisable to dispense
with the initial bedding layer for the joint or other defect during
the finishing operation, which eliminates one of the main
advantages recommending the use of the generally higher priced
fiberglass drywall tape.
[0010] A joint treatment system which includes reinforcing tape and
joint compound, must provide joints as strong as the gypsum board
itself. Otherwise, normal structural movement in the wall or
ceiling assembly can result in the development of cracks over the
finished joint.
[0011] One of the main advantages of the previously identified
non-woven fiberglass faced wallboard product is its resistance to
supporting mold and mildew growth. When paper tape is used for
finishing the joints and other openings with this fiberglass-faced
product, however, that advantage is potentially compromised, as the
paper at the seams, inside corners and other locations can
potentially provide a suitable surface for supporting mold and
mildew growth.
[0012] Applicant has thus developed an improved method for
finishing the joint seams, inside corners and other openings in
wall constructions using the new coated non-woven fiberglass mat
faced gypsum wallboard products, which method also resists mold and
mildew growth.
[0013] In particular, the present invention provides a drywall tape
or joint tape for covering seams, or for repairs generally in
connection with coated non-woven fiberglass faced gypsum wallboard
constructions, and a related method for finishing such joint seams
and making other repairs, that comprises a coated, non-woven
fiberglass mat similar in composition and construction to the
coated glass mat facer used in the previously identified fiberglass
faced gypsum wallboard products.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings are used to illustrate the
invention and highlight its novel features.
[0015] FIG. 1 is a photograph of a cross-fiber construction of the
fiberglass joint tape of the prior art and especially IMPERIAL.RTM.
Type P Tape manufactured for the United States Gypsum Company.
[0016] FIG. 2: is a photograph of the un-coated, non-woven
fiberglass base sheet used to manufacture the joint tape of the
present invention.
[0017] FIG. 3 is a photograph of the coated, non-woven fiberglass
mat or web used as the drywall tape or joint tape of the present
invention
[0018] FIG. 4: is a is a schematic representation of a finished
seam prepared using the coated, non-woven fiberglass joint tape of
the present invention in connection with a coated, nonwoven
fiberglass mat-faced gypsum wallboard construction.
DETAILED DESCRIPTION OF THE INVENTION
[0019] In accordance with the present invention, an improved system
and method for finishing seams and other openings in a wall
construction which uses a coated non-woven fiberglass mat-faced
gypsum wallboard is provided.
[0020] The system and method comprises applying a layer of joint
compound to the seam, inside corner or other defect in a coated,
non-woven fiberglass mat-faced gypsum wallboard assembly and then
affixing thereto a coated, non-woven glass fiber mat-based joint
tape or drywall tape. The coated, non-woven glass fiber mat drywall
tape or joint tape is applied to wet joint compound in the seam,
inside corner or other defect in a coated, fiberglass-faced gypsum
wallboard assembly using the non-coated side of the drywall
tape.
[0021] The coating on what ultimately becomes the free surface of
the coated non-woven glass fiber mat joint tape or drywall tape in
the finished seam or repair region comprises a cured (e.g., dried),
highly filled film-forming, e.g., latex, binder similar in
composition to the coating that is resident on the surface of the
coated non-woven fiberglass mat-faced gypsum wallboard itself. The
other surface of the glass fiber tape, i.e., the back surface which
is affixed to the initial layer or "bedding coat" of the joint
compound or mud consists essentially of the raw fibers of the
non-woven mat.
[0022] The present invention thus provides a drywall tape, a
drywall joint finished with the drywall tape, and a method of
preparing finished drywall joints and other opening for a gypsum
wallboard construction employing coated, non-woven fiberglass
mat-faced gypsum wallboard.
[0023] Thus, in one embodiment, the present invention relates to a
drywall joint comprising a seam region formed by two adjacent
coated glass fiber mat-faced gypsum wallboards; a drywall tape
covering said seam region, said drywall tape comprising a non-woven
web of fibers having a coating of a filled, film-forming polymer
thereon, said non-woven web of fibers forming an integral bond with
joint compound in the seam region characterized by said fibers
being embedded in dried joint compound.
[0024] In another embodiment, the present invention comprises a
finished drywall seam region or repair region, comprising an
unfinished seam region or repair region formed by a coated,
non-woven fiberglass mat-faced gypsum wallboard; a drywall tape
comprising a non-woven web of fibers having a coating of a filled,
film-forming polymer on one side and being non-coated on an
opposite side, wherein fibers on the non-coated opposite side are
embedded in dried joint compound thus forming an integral bond
between the drywall tape and joint compound in said seam region or
repair region.
[0025] In still another embodiment, the present invention comprises
a method of making a drywall joint in a seam region formed by two
adjacent coated fiberglass mat-faced gypsum wallboards comprising
applying a water-containing drying type joint compound or a setting
type to the seam region, applying a drywall tape comprising a
non-woven web of fibers having a coating of a filled, film-forming
polymer on one side and being non-coated on an opposite side onto
the joint compound to embed fibers on the non-coated opposite side
in the joint compound to form an integral bond between the drywall
tape and dried (cured) joint compound in said seam region.
[0026] With regard to the FIG. 1, a conventional fiberglass joint
tape or drywall tape construction is shown. This material is
representative of IMPERIAL.RTM. Brand Tape--Type P, commercially
available from the United States Gypsum Company. As shown, such
prior art drywall tapes have a very open mesh structure (about 100
openings per square inch), with openings clearly visible to the
natural eye. Visually, both sides of the joint tape appear
essentially identical. The side designed to be applied to the
wallboard seams and to other wallboard defects generally has a
layer of a pressure sensitive adhesive applied to it. It also is
possible that the opposite side of the glass fibers, i.e., the side
that faces away from the wallboard surface, may also be provided
with a coating of a resin or polymer. Notably, any such coating
does not alter the open nature of the mesh weave.
[0027] FIG. 1 should be contrasted with FIGS. 2 and 3 which
illustrates the construction of the joint tape for use in
connection with the present invention.
[0028] As shown in FIG. 2, the substrate or base material for the
joint tape or drywall tape for use in connection with the present
invention comprises a web or base of non-woven fibers held together
by an adhesive binder. The fibrous nature of the base non-woven
fiberglass web or mat is clearly viewed in FIG. 2. Preferably high
strength fibers are used to form the non-woven web. The fibers can
be a mineral-type material such as glass fibers, carbon fibers,
graphite fibers and/or synthetic resin fibers, such as polyester
fibers. Also, combinations of these fibers can be used. Glass
fibers are preferred. Fibers having a diameter of about 8 to 16
microns are typical, with diameters between 10 and 12 microns more
usual. Nonwoven mats are generally made from chopped strands of
fibers of a length predominately between about 1/4 and 1 inch,
though continuous fiber strands can be used satisfactorily. For the
most part, non-woven webs are less costly than woven materials.
[0029] Typically, but not exclusively, the non-woven fiber webs
used as the base substrate of the coated joint tape or drywall tape
of the present invention are made by a wet-forming process using
chopped strands of fibers and formed as a continuous non-woven web
of any workable width on a Fourdrinier-type machine. Webs having
widths of up to 240 inches or more are possible and the webs are
collected in roll form for storage and handling, e.g.,
transportation. Drywall tape having a width of about 21/4 inches
then can be cut from such larger width webs.
[0030] Non-woven fiberglass webs or mats suitable for use in the
present invention can be prepared by a wet-laid process, which is
carried out on what can be viewed as modified papermaking
machinery. Indeed, the resulting web or mat has a visual appearance
similar in many respects to paper. Descriptions of the wet-laid
process for making fiber webs or mats, generally using glass
fibers, may be found in a number of U.S. patents, including U.S.
Pat. Nos. 2,906,660, 3,012,929, 3,050,427, 3,103,461, 3,228,825,
3,760,458, 3,766,003, 3,838,995, 3,905,067, 4,112,174, 4,681,802
and 4,810,576, all of which are incorporated herein by reference.
Machines such as wire cylinders, Fourdrinier machines, Stevens
Former, Roto Former, Inver Former and Venti Former machines and the
like can be used to form the non-woven fiber web or mat.
[0031] In one of the common wet-forming processes, a very dilute
aqueous stock of the fiber material is applied over several linear
feet of an upwardly inclined wire screen, followed by several
linear feet of high vacuum water removal through the screen,
whereby the fibers in the slurry enmesh themselves into a freshly
prepared wet fiber web or mat. This is often followed by a "curtain
coater," where a fiber binder such as a urea-formaldehyde resin
binder, or in preferred practice for the present invention, an
acrylic-type binder, is applied to the wet-formed web or mat of
entangled fibers. Thereafter, the binder impregnated non-woven web
or mat is passed through an oven that removes excess water and
cures (or dries) the binder adhesive to form a coherent web or mat
structure. Generally, the binder comprises about 20 to 30% by
weight of the web or mat. With this process, fibrous webs or mats
comprising chopped, non-woven, filaments, particularly glass
fibers, oriented in a random pattern and bound together with the
resin binder are formed. This structure is evident in FIG. 2.
[0032] The individual strands of such webs or mats thus are bonded
together to form a unitary structure by the adhesive binder. The
web or mat can range in thickness, for example, from about 10 mils
(10 thousandths of an inch) to about 45 mils, with a web or mat
thickness of about 15 mils to about 40 mils generally being
suitable for the present invention.
[0033] The aforementioned fibrous webs or mats are known and are
commercially available in many forms, for example, such as those
which have been sold under the trademark DURA-GLASS by Manville
Building Materials Corporation and those which have been sold by
Elk Corporation as BUR or shingle mat. Webs or mats of this type
also are available from Owens-Corning.
[0034] Uncoated, non-woven fiber mats suitable for making the
coated joint tape or drywall tape of the present invention usually
have a basis weight between about 8 and 30 lbs. per thousand square
feet of mat surface area, more usually between about 12 and 27 lbs.
per thousand square feet and preferably between about 16 and 22
lbs. per thousand square feet.
[0035] As clearly evident in a visual comparison of FIG. 2 with
FIG. 1, non-woven, fiber webs or mats made in this way do not have
the open mesh structure of the nature shown in FIG. 1. In fact,
when viewed by the un-aided eye, such webs or mats have the visual
appearance of paper and do not appear to have an open structure at
all. However, on a microscopic level, such webs or mats do have an
open pore structure with a high percentage of fiber-fiber
interstitial space and it is possible to force air through the
pores of the web or mat.
[0036] To prepare the joint tape or drywall tape used in connection
with the present invention it is necessary to apply a coating onto
one surface of the fiber web or base. The coated mat useful as the
drywall tape of the present invention is shown in FIG. 3. A coating
is applied to the fiber web or mat using an aqueous coating
formulation. The aqueous formulation is applied in a way so that
the coating formulation coats the surface fibers of the web and
also substantially uniformly penetrates into the open-pore
structure of the fiber web without passing completely though the
thickness of the web or mat. In this way, the fibers are
substantially completely occluded by the coating on one side of the
mat or web (the coated side); while the random, overlapping and
somewhat open fiber structure is preserved on the side of the mat
opposite to the side on which the coating is applied (the
non-coated side). In other words, the coated side of the web or mat
has the appearance of FIG. 3, while the non-coated side of the
coated mat or web retains a visual appearance much like that shown
in FIG. 2.
[0037] In accordance with the present invention, the aqueous
coating is applied such that it penetrates into and envelopes the
fibers of the glass fiber web or mat preferably to a depth of from
about 30 percent to about 50 percent of the thickness of the fiber
web or mat. An amount of coating is applied so that substantially
all of the fibers on the coated side of the web or mat are embedded
or occluded in the coating. With this preferred degree of coating
penetration, the un-coated web or mat portion comprises about 50
percent to about 70 percent of the total web or mat thickness. This
uncoated portion is available for penetration by the joint compound
when a seam, corner, or other defect is finished in accordance with
the present invention.
[0038] The applied coating has a morphology characterized by a
highly-filled film which covers one surface of the web and which to
a certain extent bridges individual fibers in the web or mat.
Importantly, the coating is accompanied by a distribution of
micropores (not shown) that extend through the film coating. The
distribution of micropores in the coating is sufficient to allow
air-flow there through when the drywall tape is pressed into the
bedded layer of joint compound, thus allowing the joint compound to
fill (or facilitating the joint compound's flow into) the
fiber-fiber interstices of the non-coated side of the joint or
drywall tape. The micropores also allow the joint compound to dry
(or facilitate the drying of the joint compound) by allowing
moisture in the joint compound to evaporate in its vaporous state
through the drywall tape.
[0039] The aqueous coating composition, which is applied to one,
free surface of the above-described wet laid, non-woven fiber web
or mat (see FIG. 2) for making the coated joint tape or coated
drywall tape used in the present invention, comprises an aqueous
combination of predominately three components (1) a mineral pigment
or filler material; (2) an organic adhesive binder, preferably a
film-forming polymer and usually a film-forming latex adhesive;
and, optionally (3) an inorganic second binder or an inorganic
second adhesive.
[0040] On a dry weight basis of the two required components (100%),
the organic adhesive binder or film-forming polymer comprises at
least about 1% and usually no more than about 30% by weight of the
total coating, with the balance being the inorganic, mineral
pigment or filler. Usually, the organic adhesive binder or
film-forming polymer comprises between about 5 and 20% by weight of
the coating, on a dry weight basis. The optional inorganic second
binder comprises no more than about 20% by weight of the dried
(cured) coating. Usually, the weight ratio of the mineral pigment
or filler to the dry solids of the film-forming polymer (organic
adhesive) binder can be in excess of 15:1 and in some cases can be
in excess of 20:1, but usually is at least about 5:1.
[0041] Suitable coating compositions for making the coated joint or
drywall tape useful in the present invention thus may contain, on a
dry weight basis of the three noted components (100%), about 70 to
99 percent mineral pigment or filler, more usually about 80 to 95
percent mineral pigment or filler, about 0 to 20 percent inorganic
second adhesive, more usually about 0 to 10 percent and about 1 to
30 percent organic adhesive binder (film-forming polymer), more
usually about 5 to 20 percent.
[0042] As noted, a mineral pigment or filler comprises the major
component of the coating composition. Examples of mineral pigments
suitable for making the coated joint tape useful in the present
invention include, but are not limited to, ground limestone
(calcium carbonate), clay, sand, mica, talc, gypsum (calcium
sulfate dihydrate), aluminum trihydrate (ATH), antimony oxide, or a
combination of any two or more of these substances.
[0043] For making the aqueous coating formulation, the mineral
pigment is provided in a particulate form, preferably as a fine
powder. To be an effective mineral pigment or filler for making
coated joint or drywall tape for use in this invention, the pigment
preferably has a particle size such that at least about 95% by
weight of the pigment particles pass through a 100 mesh wire
screen, with about 75% of the particles (by number) being greater
than about 5 .mu.m. Preferably, the pigment or filler has most of,
if not all of, the very fine particles removed, especially
particles less than 1 .mu.m (i.e., particles that pass through a
screen having an opening of 1 .mu.m). The presence of an excessive
amount of very fine particles in the coating composition negatively
impacts the porosity (microporosity or micropore structure) of the
coated drywall tape. One preferred mineral pigment is a limestone
having a number average particle size of about 40 .mu.m.
[0044] The other required constituent of the coating composition is
the organic adhesive binder or film-forming polymer. The organic
adhesive binder can be anyone of a variety of film-forming
materials, generally supplied as a latex emulsion, which can be
formulated in an aqueous coating composition. For example, the
film-forming polymer can be selected, for example, from at least
one polymer derived from monomers of alkyl halides of from 2-12 C
atoms, alkene halides of from 2-12 C atoms, alkyl acrylamides of
from 2-12 C atoms, alkene acrylamides of from 2-12 C atoms, alkyl
acrylates of from 2-12 C atoms, and alkene acrylates of from 2-12 C
atoms. Some preferred polymers include those derived from at least
one monomer selected from styrene, dimethylstyrene, vinyltoluene,
chloroprene, butadiene, ethylene, acrylamide, acrylonitrile,
acrolein, methylacrylate, ethylacrylate, acrylic acid, methacrylic
acid, methyl methacrylate, n-butyl acrylate, vinylidene chloride,
vinyl ester, vinyl chloride, vinyl acetate, acrylated urethane,
hydroxyethyl acrylate, dimethylaminoethyleneacrylate, and vinyl
acrylate. For example, the film-forming polymer can be a latex
selected from at least one polymer derived from at least one
monomer comprising repeating units derived from an alkyl halide
having at least one double bond, such as a vinyl halide, e.g.,
vinyl chloride, and an alkene, such as ethylene, wherein the alkyl
halide has from 2 to 12 C atoms, and wherein the alkene has from 2
to 12 C atoms. The alkyl halide can be a vinyl halide, for
example.
[0045] A large number of suitable film-forming materials useful as
the organic adhesive binder, in addition to those identified above,
will be apparent to skilled workers and can include, as a
representative and non-limiting list, such materials as
styrene-butadiene-rubber (SBR), styrene-butadiene-styrene (SBS),
ethylene-vinyl-chloride (EVCl), poly-vinylidene-chloride (PVdC),
modified poly-vinyl-chloride (PVC), poly-vinyl-alcohol (PVOH),
ethylene-vinyl-actate (EVA), and poly-vinyl-acetate (PVA).
[0046] The binder may also be a hydrophobic, film-forming, UV
resistant, polymer or copolymer containing units of acrylic acid
and/or methacrylic acid (together usually referred to as
(meth)acrylic acids)), of their esters (usually referred to
together as ((meth)acrylates) or of acrylonitrile, including
acetate acrylic and styrene/acrylate polymer materials. The
formulation for making the coated joint tape of the present
invention should not be limited to any particular film-forming
polymer.
[0047] As noted, an optional component of the coating composition
is an inorganic adhesive binder. Examples of inorganic adhesive
binders which can be used in combination with the film-forming
polymer (organic adhesive binder(s)) in the coating composition
include, but are not limited to the following: calcium oxide,
calcium silicate, calcium sulfate (anhydrous or hemi-hydrate),
magnesium oxychloride, magnesium oxysulfate, and other complex
inorganic binders of some Group IIA elements (alkaline earth
metals), as well as aluminum hydroxide.
[0048] Inorganic pigments or filler materials will often inherently
contain some naturally occurring inorganic adhesive binder.
Examples of such fillers, some listed with the naturally occurring
binder, include (but are not limited to) the following: limestone
containing quicklime (CaO), clay containing calcium silicate, sand
containing calcium silicate, aluminum trihydrate containing
aluminum hydroxide, cementitious fly ash and magnesium oxide
containing either the sulfate or chloride of magnesium, or
both.
[0049] Obviously, to form the aqueous coating formulation, the
required binder and filler are mixed with water. Water is provided
in an amount sufficient to provide suitable rheological properties
(e.g., viscosity) to the aqueous coating composition. Other
adjuvants, such as thickeners or rheological control agents for
adjusting the viscosity of the coating composition can also be
added. A suitable rheological property is one which, given the
chosen form of application of the aqueous coating composition to
the fiber mat or web, provides for the retention of a suitable
portion of the coating formulation on the surface of the fibers of
the fiber mat and within the interstices of the fiber mat or web
preferably to a depth between 30 and 50 percent of the thickness of
the fiber mat or web from a free surface of the mat (to which the
coating formulation is applied) and also results in the formation
of the desired coating morphology (microporosity) through the
thickness of the coating. The aqueous coating composition may also
include other optional ingredients such as colorants (e.g.,
pigments and dyes), defoamers, dispersants and preservatives. When
used, the aggregate amount such other ingredients in the coating
composition is typically in the range of about 0.1 to 5% and
generally is not more than about 2% of the dry weight of the
coating formulation. Generally, a suitable aqueous coating
formulation will have a viscosity between about 8,000 and 18,000
cps. The preparation of a suitable formulation with such
ingredients to achieve such results is well within the skill of the
art.
[0050] Any suitable method for applying an aqueous coating
composition to a fiber mat or web substrate can be used for making
the coated joint or dry wall tape of the present invention and can
include such techniques as roller coating, curtain coating, knife
coating, brush coating, spray coating and the like, including
combinations thereof.
[0051] Following application of the aqueous coating composition to
the web or mat, the applied coating composition is dried (cured),
typically in a drying oven, to form the coated joint or drywall
tape. The coated web or mat is dried at a temperature and for a
time sufficient to remove water from the coating composition, to
coalesce the organic film-forming polymer adhesive on the web and
to form an adherent coating, without degrading the coating or the
web. Suitable temperatures and times will be influenced greatly by
the equipment being used and the specific nature of the coating
formulation itself and can be selected by those skilled in the art
using routine experimentation.
[0052] The coated joint or drywall tape for use in the present
invention will typically have a mass of applied coating amounting,
on a dry weight basis, to at least about 20 pounds per 1000 square
feet, more usually between about 30 and 50 lbs., per 1000 sq. ft.
of mat depending upon the thickness of the glass fiber mat. Thus,
the basis weight of the coated joint or drywall tape itself will
generally be at least about 30 pounds per 1000 sq. ft. and usually
will be between about 40 and 60 pounds per 1000 sq. ft.
[0053] With reference to FIG. 4, the use of the coated joint or
drywall tape in accordance with the present invention will now be
described. As illustrated in connection with FIG. 4, a method is
provided for preparing a drywall joint in wall constructions
featuring coated fiberglass-faced gypsum wallboards.
[0054] A particular advantage of this construction is that both the
wallboard and the joint tape are resistant to mold and mildew
growth, a property not shared by paper-based joint tape. A further
feature of this invention is that by using similar materials of
construction for both the wallboard facing and for the joint or
drywall tape, the wallboard joints (including corners and other
repaired defects) are less affected (and may be substantially
unaffected) by changing environmental factors, including changing
temperatures and humidity levels. In contrast, when the joints,
corners and other defects in coated non-woven fiberglass mat-faced
gypsum wallboards are treated in the conventional manner using
paper joint tape, changing environmental factors place stresses on
the interface between the paper and the coated fiberglass possibly
leading to the development of unsightly cracks or other
defects.
[0055] Thus, one aspect of the present invention comprises a method
for preparing a drywall joint in wall constructions featuring
coated fiberglass mat-faced gypsum wallboards in which a pair of
coated, fiberglass mat-faced gypsum wallboards are disposed in an
adjoining relationship to one another to form a seam region. A
layer of joint compound or mud, either a drying-type or a setting
type joint compound, is applied to the seam region and then the
coated, non-woven fiber joint tape of the present invention is
disposed over the seam by pressing the non-coated side of the joint
tape into the wet "mud." As noted earlier, the tape has sufficient
microscopic porosity to facilitate entry of the joint compound or
mud into the interstitial spaces of the non-woven fiber mat tape.
This incorporation of the joint compound into the tape ensures a
strong bond between the joint compound and the joint tape.
[0056] Once the first layer of joint compound dries, one or more
additional layers of joint compound (mud) can be applied usually
over the outer edges of the tape and, once dried (cured), can be
sanded (referred to as feathering) to provide a smooth finish.
[0057] As shown in FIG. 4, a flat drywall joint can be constructed
by butt joining a pair of coated, fiberglass mat-faced wallboards
18 and 17 each having a coated, fiberglass facing 12, to form a
seam region 45. The wallboards preferably are constructed in
accordance with U.S. Patent Publications 2005/0266225 and
2006/0240236, the disclosures of which are incorporated herein by
reference. Each wallboard 17 and 18 has a gypsum core 20 with a
non-woven fiberglass mat facing 13 integrally bonded to the core.
The non-woven mat has an adhered coating 14 on its outer surface. A
first layer of drying-type or setting-type joint compound or mud 19
is applied over and into the seam region 45. While the joint
compound is still wet, the joint tape 100 of the present invention
is applied, with pressure, over the joint compound so that the
joint compound or mud flows into the interstitial spaces of the
non-woven glass fiber tape 101. The joint tape 100 comprises a web
of non-woven fiber 102 with a coating 103 of a filed, film-forming
polymer. Care must be taken to provide the proper amount of joint
compound under the tape to prevent blistering of the tape. If
necessary, any excess joint compound can be removed from the edges
104 and 105.
[0058] After the first layer of joint compound 19 has dried, a
second layer of joint compound 22 is applied along the edges of the
tape. If necessary, additional water can be included in the joint
compound so as to thin it for easier application.
[0059] Similar approaches can be provided for finishing inside
corners, outside corners, horizontal flat joints, for repairing
holes and crack, and for finishing seams along electrical boxes and
switches and seams around piping and duct work.
[0060] After the second coat 22 is allowed to dry, preferably
overnight, a third layer (not shown) of drying-type joint compound
can be applied over the second coat 22, ideally with an 8 inch
knife, feathering slightly beyond the second coat. If further coats
are desired, though generally unnecessary, the third coat is
allowed to dry, and a fourth or finishing coat (also not shown) can
be applied with a 10 inch knife to the flat joints. The third coat
or fourth coat can be lightly sanded if necessary.
[0061] Joint compounds conventionally used in finishing drywall
joints and other defects can be classified as either a "drying"
type (e.g., see U.S. Pat. No. 3,998,769) or a "setting" type (e.g.,
see U.S. Pat. No. 5,653,797). In a drying-type joint compound, the
filler comprises substantially calcium carbonate. Prior to use, the
filler and the binder, along with several other known ingredients,
are mixed with water. After application, when the water dries by
evaporation, a dry, relatively hard cementitious material is left
behind. Pre-mixed drying type products also are commercially
available (known as ready mixed materials). Joint compounds or
compositions known as the "setting" type include at least a
substantial portion of calcium sulfate hemihydrate (Plaster of
Paris) in the mixture. During use of a setting-type joint compound,
the calcium sulfate hemihydrate is rehydrated to the dihydrate
state. This rehydration process normally takes place over a fairly
short period of time. Setting-type joint compounds are believed to
form a crystalline network upon setting. The present invention can
employ both the drying type and setting type joint compounds,
though for ease of application and use the drying type is usually
used in preference to the setting type.
[0062] From the foregoing it can be realized that this invention
provides drywall joints and methods of joint fabrication in a wall
construction employing coated fiberglass-faced wallboards, which
drywall joints are expected to exhibit superior properties of mold
and mildew resistance and better integrity over Kraft paper tape
joints and over other glass tape joints employing rubber based or
binder coatings.
[0063] The present invention has been described with reference to
specific embodiments for the purpose of describing, but not
limiting the invention. Various modifications, which will become
apparent to one skilled in the art, and the invention is intended
to cover those changes and substitutions that may be made by those
skilled in the art without departing from the spirit and the scope
of the invention. Unless otherwise specifically indicated, all
percentages are by weight. Throughout the specification and in the
claims the term "about" is intended to encompass + or -5% and
preferably is only about + or -2%.
* * * * *