CA 02427514 2003-05-O1
DRYWALL TAPE AND JOINT
Field of the Invention
S (0001] The present invention relates to drywall joining systems for seams or
repairs
generally, and more particularly to tape used for drywall installation and
repairs.
Background of the Invention
[0002] Walls made from gypsum wall board or drywall are conventionally
constructed by
affixing the boards to studs or joints and filling and coating the joints with
a specially
prepared adhesive called "joint compound." This process is also used to make
repairs of
defects, such as holes and dents, including those around electrical boxes,
piping and duct
work, as well as corners created by the intersection of drywall boards.
[0003] Drywall tape adds strength and crack resistance as well as smooth
concealment at
flat joints and inside corners. Conventionally, two types of drywall tape have
been
employed - a simple kraft paper strip which is adhered to the drywall surfaces
by a
bedding coat of joint compound or "mud," and glass fiber tape, which can be
applied with
joint compound or self-adhered. Kraft paper tape must be carefully positioned
a~ad care
must be taken not to discharge the mud onto non-working surfaces. In addition,
once the
paper drywall tape has been applied, one must wait as much as a day for the
compound to
dry before a final surface coat of compound can be applied. Glass fiber tape,
on the other
hand, provides exceptional wet and dry strength and resists stretching and
wrinl,;les. It
can be laid flat and resists tearing under load.
[0004] A joint treatment system which includes reinforcing tape and joint
compound,
must provide joints as strong as the gypsum board itself. Otherwise, normal
stmctural
movement in the wall or ceiling assembly can result in the development of
cracl<a over
the finished joins.
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[0005] It has been discovered that certain types of fiberglass leno-weave mesh
tape when
used with conventional joint compounds are more prone to cracking than joints
finished
with paper tape and conventional joint compounds. Because of this, some
manufacturers,
such as United States Gypsum Company, Chicago, Illinois, have manufactured
glass fiber
tapes with cross-fiber construction to provide greater drywall joint strength
than
conventional fiberglass leno-weave mesh tapes. Such tapes include Sheetrock~
brand
fiberglass drywall tape and Imperial~ brand tape. The Imperial~ brand tape
includes an
open weave of glass fibers (100 meshes per square inch) which is coated with a
binder
and slit to roll width. Spirally woven (leno) long strands and the binder
coating reduce
edge raveling and fraying and keep the loose threads from defacing finishing
surfaces.
[0006] Still another drywall tape that has been commercially accepted is
Fibatape~ glass
tape available through San Gobain Technical Fabrics, Ontario, Canada. This
product is
an SBR rubber-coated glass fiber tape with a self-adhesive backing. The tape
is self-
adhered to a drywall seam, and then covered with layers of drywall compound.
Samples
of a drywall joint made with Fibatape~ tape have been tensile tested in
accordance with
ASTM C 474 (Appendix) which measures the strength to first crack of a tape-
compound
sample coated in electrically conductive paint. The strength is measured until
the first
crack in the paint occurs, which breaks the electrical continuity along the
surface and
registers the ultimate tensile load. Failure in Fibatape~ joint tape tensile
specimens is
observed at the SBR rubber film where the joint compound separates from the
film at
failure. This suggests that typical taped joints in glass tape-drywall systems
do not
optimize the strength of the glass joint compound composite, since tensile
loads tend to
separate the glass fibers from the joint compound matrix instead of
transferring these
loads to the glass fibers themselves.
[0007] Accordingly, there is a need for creating a higher strength wall board
joint
composite system employing glass fiber tape. Such a system should be
chemically
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3
compatible with ready mixed or powder joint compound compositions and should
not
substantially detract from the already established benefits of using glass
fiber tape over
kraft paper tape.
Summarlr of the Invention
[0008] In a first embodiment of the present invention, a drywall tape suitable
for joint
compound repairs and joint covering is provided. The drywall tape includes a
web of
glass fibers and a coating disposed over a portion of the glass fibers. The
coating
comprises a resinous binder which is at least partially soluble or dispersible
in the joint
compound. The coating is further capable of forming an adhesive bond with the
joint
compound when set.
[0009] In the preferred embodiments, the joint compound and re-wettable
coating "wet
and set" together. The re-wettable coating can be chemically very similar to
the binding
resin that makes up the compound itself, or is at least soluble or dispersible
in the joint
compound. Most preferably, the re-wettable coating is soluble or dispersible
in the water
content of the joint compound so that it flows together with the compound on a
microscopic scale. Once dry, the coating most preferably becomes a very rigid
film that
is well able to transfer loads from the joint compound to the fiber. This
permits the joint
compound and drywall tape of this invention to act much like a fully
integrated
composite, which increases the mechanical properties of the joint.
[0010] Tensile testing of joints made in accordance with this invention has
revealed that
the load to first crack can be increased by as much as 16 to 65% over SBR-
coated
Fibatape samples embedded in the same joint compound composition. Note that
all
samples were coated on one side with a pressure sensitive adhesive. Testing of
plant
production samples in accordance with ASTM C474 (appendix) revealed that leno
weave
fabrics benefitted most by the new coating, with a 65% improvement, followed
by knit
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fabric (40%) and lastly, plain weaves (16 to 28%). When tapes without an
adhesive
backing are tested in accordance with ASTM C474, a similar percent increase in
tensile
load to failure can be attributed to the invention. However, the magnitude of
the results
will be about double that of the tapes that are adhesive backed. The
explanation for this is
that, in the case of the adhesive coated samples, half of the surface area of
the glass web
IO would be covered with a layer of low modulus pressure-sensitive material
that does little
to resist tensile loads placed on the sample.
[OOI 1] While standard glass tape products typically fail due to the fiber
pulling out from
the joint compound, the drywall tape of this invention with the re-wettable
coating has
been shown to fail by delamination within the joint compound itself. Along
with the
increased load to tensile failure, delamination in the joint compound suggests
that the
bond between the coating and the compound is improved since the fibers in the
sample do
not pull out. The drywall tape of this invention also produces tensile
strength results
which are approximately twice those previously measured for paper tape,
without adding
anymore basis weight or fibers to the glass fabric, over that for a
conventional glass tape,
such as Fibatape~ tape.
[0012] In further embodiments of this invention, the re-wettable coating
comprises a
soluble or dispersible resinous binder alone, or in combination with a
blocking agent,
such as a wax. A combination of a soluble binder, such as polyvinyl acetate
(PVAc), and
wax, offers a strong bond with the joint compound, while also minimizing
"blocking" in
the tape. The preferred re-wettable coating contains PVAc resin which is very
hydroscopic. Water vapor absorption can cause a roll of tape made with PVAc
resin to
block or fuse together, which causes the roll to bind. The roll of tape can
also flow
plastically and deform the shape of the tape roll. Blocking agents, such as
paravffin wax,
make the PVAc-based coating vapor resistant. Only when contacted with liquid
water,
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5 such as when the tape is applied to a wall and coated with joint compound,
does the
PVAc resin re-wet and become soluble.
[0013] In a further embodiment of this invention, a method is provided for
preparing a
drywall joint. The method includes disposing a pair of drywall boards in
adjoining
relationship to one another to form a seam region. Next, the drywall tape of
this
invention is disposed over the seam. This drywall tape includes a web of glass
fibers
having disposed thereon a resinous binder capable of re-wetting and setting
when
contacted with the joint compound. A first joint compound layer is applied
over the
drywall tape so as to re-wet the resinous binder. The first joint compound
layer ;and re-
wetted resinous binder on the tape are then dried to form an adhesive bond.
Brief Description of the Drawings
[0014] The accompanying drawings illustrate preferred embodiments of the
invention
according to the practical application of the principles thereof, and in
which:
[0015] FIG. 1: is a partial, front perspective view of the preferred drywall
tape of this
invention;
[0016] FIG. 2: is a partial, enlarged side-plan view, illustrating a coating
on the drywall
tape of FIG. 1;
[0017] FIG. 3: is a partial, top, cross-sectional view of a finished flat
drywall joint of this
invention; and
[0018] FIG. 4: is a graphical depiction of the average load to first crack for
various
drywall tape constructions, including those of the present invention.
Detailed Description of the Invention
[0019) This invention provides drywall tape, drywall joints, methods of
preparing drywall
joints, and reinforcements for cementitious materials generally. It is
understood that
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6
while the present invention is preferably related to drywall seam or repair
constructions,
the re-wettable coatings on the glass and other reinforcing fibrous webs
provide practical
solutions to reinforcing gypsum fiber board, gypsum wall board, glass-faced
gypsum
board, tilebacker boards, high impact gypsum wall board, and concrete board
constructions. The re-wettable coatings of this invention can be useful with
cementitious
materials such as gypsum, portland cement, and combinations of these materials
with
fillers or aggregate, such as mortar, cement and concrete. This invention can
be used to
enhance the performance of existing self adhesive drywall joint tapes and
patches, or
tapes and patches which do not have a pressure-sensitive adhesive on one side
of their
construction. The benefits of a re-wettable resinous binder are realized
whether a
pressure-sensitive adhesive is present on the web or not. As used herein, the
team
"drywall" includes wall board, fiberboard, glass-faced gypsum boards, and
their-
equivalents. As used herein, the term "tape" means a strip of material that
can be
provided in roll form, which may, or may not, contain an adhesive backing
layer.
[0020] With regard to the figures, and particularly to FIGS. 1-2 thereof,
there is shown a
preferred drywall tape 100 including a web of glass fibers 10 and an optional
pressure-
sensitive adhesive layer 12. When a portion of the drywall tape 100 is
magnified, as
shown in FIG. 2, the re-wettable coating 14 can be viewed. In the preferred
embodiment
of the drywall tape 100, the re-wettable coating 14 is disposed along one or
bath sides of
the web of glass fibers 10. Alternatively, the re=wettable coating 14 can be
di;;posed over
100% of the exterior surfaces of the web of glass fibers 10, over 70% of the
surface area,
or over less than SO% of the surface area. In certain constructions, the glass
fibers of the
web of glass fibers 10 are bonded together using a web adhesive binder 15,
such as vinyl
acetate acrylic, styrene/acrylate, vinyUacetate, acrylic, styrene acrylic, or
copolymers and
mixtures thereof, ete. In instances where a web adhesive binder 15 is
employed, it may or
may not be re-wettable, soluble or dispersible in liquid water. In the
preferred
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embodiment, the re-wettable coating 14 is used to also bind the fibers of the
web of glass
fibers together.
[0021] As shown in FIG. 3, a flat drywall joint can be constructed by butt
joining a pair
of drywall boards 18 and 17 to form a seam region 45. The drywall tape 100 can
be
applied with the aid of the pressure-sensitive adhesive Iayer 12, or when a
pressure-
sensitive adhesive is not employed, the drywall tape 100 can be pressed
lightly into a wet
joint compound layer which is thinly applied to the seam region 45 prior to
application of
the drywall tape 100. If joint compound is used to adhere the drywall tape 100
to the
seam region 45, care must be taken to provide sufficient joint compound under
t)he tape to
prevent blistering of the tape. While embedding the tape 100, excess joint
compound
should be removed from the edge.
(0022] Whether the tape 100 is applied with joint compound, or self-adhered, a
first coat
of joint compound 30 should applied over the tape so as to embed the tape 100
nearly
completely. While embedding the tape 100, excess joint compound is removed
from the
edge. Added water can be included in the joint compound so as to thin it for
ea:~ier
application. Similar approaches can be provided for inside corners, outside
corners,
horizontal flat joints and hole and crack repairs, finished seams along
electrical boxes and
switches and seams around piping and duct work.
[0023] After the first coat 30 is allowed to dry, preferably overnight, a
second coat 40 of
drywall compound is applied over the first coat 30, ideally with an 8 inch
knife.,
feathering slightly beyond the first coat. If further coats are desired, the
second coat 40 is
allowed to dry, and a third or finishing coat (not shown) can be applied with
a 1.0 inch
knife to the flat joints. The second coat 40 or third coat can be lightly
sanded if
necessary.
[0024] The joint compound useful in the drywall joints of this invention is
typically
classified as either a "drying" or "setting" type. In a drying-type joint
compound, the
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8
S 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 drys to evaporation, a dry, relatively hard cementitious
material is left
behind.
[0025] Joint compositions known as the "setting" type include at least a
substantial
portion of calcium sulfate hemihydrate. In order to produce calcined gypsum,
one
converts calcium sulfate dihydrate from raw gypsum to the hemihydrate state
through a
known process called calcination. This process removes 1 ~h molecules of water
from the
calcium sulfate dihydrate gypsum. The hemihydrate form of calcium sulfate is
substantially more soluble in water than the dihydxate form of calcium
sulfate. wring
1S 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. Accordingly, it is extremely difficult to produce a setting-type
joint compound
for storage in a bucket, and as such, such compounds are typically provided in
powder
form. Setting-type joint compounds also form a crystalline network upon
setting, and
provide a stronger, more durable bond.
[0026] The webs useful in manufacturing the drywall tape I00 of this invention
can be
provided as non-woven, woven or knitted fabrics, veils, mats, scrims, or
fleece. They
desirably include high strength fibers, such as glass fiber, and less
desirably may include
thermoplastic or thermosetting fibers, carbon, boron, graphite fibers or
combinations
2S thereof. In most examples of this invention, a web of glass fibers 10
having a basis
weight of about S-500 grams/m', preferably about 20-120 grams/m2, is employed.
This
web 10 can be fabricated by weaving, such as a plane or leno weave, by
knitting, by a laid
scrim process or by a non-woven process, such as resin bonding randomly
oriented glass
fibers. The webs of this invention are, desirably, at least partially porous
to wca joint
compound so as to form a good bond in the seam region 4S. Alternatively, a
veil or
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fabric could be somewhat non-porous to joint compound and still be useful as a
replacement for paper tape and, thus, be applied with a bedding coat of joint
compound.
[0027] The preferred re-wettable coating 14 applied to the web desirably has
the
properties of being soluble or dispersible in liquid water. Glass tapes of the
past were
often coated with polymers, such as SBR rubber or a resinous binder, such as
virnyl
acetate acrylic, styrene/acrylate, vinyUacetate, acrylic, styrene acrylic,
etc., which wee
specifically designed to aid in handling and slitting the reinforcements
without regard to
how the coatings interacted with joint compounds. The adhesion of traditional
rubber
based coatings such as SBR to setting or non-setting joint compounds is
minimal, and
thus, an optimum composite strength cannot be achieved, e.g., the glass fibers
tend to pull
out from compound when loaded. The preferred re-wettable coatings 14 of this
invention
set to form a strong bond between the preferred glass fibers and the set joint
compound so
that the fibers act more as an unit to resist loads. The preferred re-wettable
coating 14 of
this invention should be as inexpensive as the styrene butadiene rubber (SBR)
or joining
resin binders currently employed on glass drywall tape. This coating 14 should
be easy
and versatile to formulate and should run on pad rolls with water clean up
being; highly
desirable. It should not be significantly prone to oxidation or W light
degradation.
Ideally, the preferred re-wettable coating 14 i.s provided in a latex form
such as an
aqueous emulsion of a binder resin, blocking agent and water.
[0028] The preferred re-wettable coating 14 of this invention contains one or
more of the
resins selected from the group including: polyvinyl acetate, ethylene vinyl
acetate,
polystyrene, polyvinyl chloride, polyacrylate, ethylene acetate co-polymer,
vinyl-acrylic
co-polymer, styrene butadiene, acrylic polymer and starch; protein glues, such
as casein,
soy protein, animal glue and gelatin; vegetable-based glues, such as
cellulosics and their
chemically modified derivatives; gums (polysaccharides and carbohydrates) such
as guar
gum; resins (pine tar) which may not be water soluble; mucilages (agar,
carrageenan and
PH 1897635.1
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5 algin); inorganics such as soluble silicates (water glass) and cementitious
materi<ils
(cement, gypsum), and co-polymers and combinations of these. Most preferably,
the
resinous binder contains polyvinyl acetate (PVAc), such as Vinac 524 polyvinyl
acetate
homopolymer stabilized with polyvinyl alcohol, Airflex 401 polyvinyl
acetateJethylene
co-polymer stabilized with polyvinyl alcohol, both supplied by Air Products
and
10 Chemicals, Inc., of 7201 Hamilton Blvd., Allentown, PA 18195. The re-
wettable coating
14 preferably is provided in an aqueous emulsion or solution containing about
2.5-75 wt.
% solids. Alternatively, water soluble polymers in powder form may be applied
with
adhesive or electrostatically. Two formulations of the re-wettable coating
developed
within the context of this invention are found below:
(0029] Formulation 1
Vinac 524 Emulsion (PVAc homopolymer
stabilized with polyvinyl alcohol) 61.38%
Airflex 40I Emulsion (PVAc/ethylene
co-polymer stabilized with polyvinyl alcohol 26.30'%
Water 9.02%
Urea 0.25%
Hydrocer DP69 (paraffin wax, anti-blocking agent) 3.00%
900-103 Henkel Foamaster NXZ mixed 50/50% with water. 0.05%
30
Other pertinent formula data:
Solids level: 50%
Viscosity: about 1000 cps
PH: approximately 6.0
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S [0030] Formulation 2
Vinac S24 Emulsion (PVAc homopolymer 74.53%
stabilized with polyvinyl alcohol)
Benzoflex 9-88 (dipropylene glycol dibenzoate plasticizer
for PVAc) 7.23%
Urea 0.25%
Hydrocer DP69 (paraffin wax, anti-blocking agent) 3.00%~
Water 14.94°!~
900-103 Henkel Foamaster NXZ mixed SO/SO% with water O.OS%~
1S
(0031] As reflected above, an important ingredient for preventing the PVAc
resin from
picking up too much water during storage is an anti-blocking agent, such as
animal oils,
fats, starch, dextrine, silicone oil, waxes and combinations thereof. The
preferred anti-
blocking agent is low melting point paraffin wax. The paraffin wax can be
emulsified in
the formulations and "blooms" to the surface when the formation is dried. The
blocking
agent acts as a vapor burner to the re-wettable 14 coating on the drywall tape
100 of this
invention, so as to substantially reduce blocking in tape rolls. The anti-
blocking agent
should be less than about S-10% by weight of the formulation so that it can be
dispersed
readily when the re-wettable coating 14 is made soluble by the water in the
joint
compound. Accordingly, the re-wettable coating 14 with the above formulations
containing an anti-blocking agent and PVAc resin in solution, is capable of
being vapor
resistant when dry, but is water soluble or dispersible when contacted with
liquid water in
the joint compound.
[0032] The adhesive elements of this invention can be made of any known
pressure-
sensitive adhesive material. As used herein, the term "pressure-sensitive"
refers to any
releasable adhesive or releasable tenacious means. Adhesive compositions
suitable for
tape include, for example, the water-based pressure-sensitive adhesive such as
acrylate
adhesives, e.g., isooctyl acrylate and acrylic acid copolymer, or vinyl
acetate-2 ethyl hexyl
acrylate copolymer which can be combined with tackifiers. Alternatively, the
adhesive
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12
may comprise the rapid setting thermoplastic "hot melt" adhesives. The
adhesive
elements may also comprise a two-sided adhesive tape. It is also anticipated
that.
adhesives based on an elastomer selected from natural or synthetic rubbers
could be used.
It will be understood that alternative shapes for these adhesives, for
examples, continuous
coatings, discontinuous lines, squares, dots, circles, etc., may be employed.
IO [0033] The preferred method of manufacturing the drywall tape I00 of this
invention
shall now be described. The glass fabric knitted web of 42.1 - 52.9 grams/m2
is first
passed through a bath of latex including the Formulations 1 or 2 and then
through a set of
squeeze rollers, which sen~e to control the amount of latex picked up by the
fab>-ic,
usually about 5-20 grams/m2 of coating when dry. The rollers could be adjusted
for gap
width or pressure to perform this function, but the solids level and the
viscosity of the
latex are important factors in determining the coating weight. The saturated
fabric is then
dried either by contact with steam cans or by convection in a hot oven.
[0034] At this point, the web of glass fibers 10, now coated with a re-
wettable coating I4,
is provided with a pressure sensitive adhesive layer 12 applied to one side,
usually about
3-15 grams/m' of adhesive is applied. This may be done in a subsequent step on
a
separate finishing machine, or directly in line with the re-wettable coating
step. The
pressure-sensitive adhesive layer 12 serves to affix the drywall tape 100 to
the drywall
surface in preparation for drywall filling with drywall compound.
Altemativel;y, the web
of glass fibers 10 can be saturated and dried with the re-wettable coating 14,
then within
the same coating line, passed over a kiss coater that applies the desired
amount of latex
pressure-sensitive adhesive to the fabric. The fabric then passes into a
mechanical
convection oven for drying of the pressure-sensitive adhesive. In either case,
the web 10
is then wound into large diameter rolls for transport to a slitting department
where the roll
can be processed into tapes of any desired length and width.
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13
[0035] In still another variation of the manufacturing method, large rolls of
glass; or other
fibrous fabric which have been saturated with the re-wettable coating 14 can
then be
taken to a separate machine called a hot-melt adhesive coater. The pressure-
sensitive
adhesive can be based on one of a number of hot-melt polymer technologies
(su<;h as
those described above) rather than latex technology. The hot-melt coater
applies; a thin
film of molten adhesive to one side of the fabric. The fabric is then formed
onto a large
roll for transport to the slitting area where it is processed into tapes of
any desired length
or width. The pressure sensitive adhesive performs the same function whether
it is based
on hot-melt or latex technology. Only the method of applying the adhesive
differs in
these two systems.
[0036] The large rolls produced in accordance with the above processes can be
processed
on slitter/rewinder machines for conversion into tape. The tapes may be of any
,geometry
although most are approximately 50mm wide by about 90m long. The tapes are
subsequently wrapped, packaged and sent to customers.
Examples
[0037] Tensile testing in accordance with ASTM C 474 (appendix) was conducted
on
assemblies of joint compound and the joint tape, employing the Formulations 1
and 2, to
leno weave (46.3 grams/mz), plain weave (47.5 grams/m2) and knit fabric (52.9
grams/m2). These were compared to control samples with SBR coating and a paper
tape.
Each tape sample was applied at the butt joint of two sanded polyethylene
substrates.
Joint compound is applied in two coats, and allowed to dry for a specif ed
time. A
conductive silver paint was applied to the testing area and connected in a
series to form a
circuit. The sample is then tested under tensile load on a tensile testing
machine. When a
crack appeared, the circuit failed, and the load is noted.
PH1~$97635.1
CA 02427514 2003-05-O1
14
[0038] Tensile testing results revealed that the load to first crack could be
significantly
increased when the re-wettable coating of this invention is used on a glass
tape instead of
an SBR rubber based coating.
[0039] The data for the average load to first crack (KN) is located below in
Table 1.
Table 1: Average
Load to First
Crack (I~
ASTM-C474
(appendix)*
GLASS WEB COATING AVG. STANDARD % STANDARD % INCREASE
TYPE FORMULATION DEVIATION DEVIATION
leno weave 1 0.995350.06660 6.69117 56.4
leno weave 2 1.048330.05500 5.24635 64.7
knit fabric 1 1.145330.04948 4.31990 33.8
knit fabric 2 1.169880.07084 6.05531 36.6'!
plain weave 1 1.1815 0.11113 9.40573 15.83
plain weave 2 1.303830.04717 3.61752 27.8
light plain 2 0.9719 0.03865 3.97723 52
weave
control lightSBR 0.639470.02935 4.59053
plain
weave
control wovenSBR 0.636430.10435 16.39574
leno
control plainSBR 1.020070.02424 2.37607
weave
paper tape NIA 0.577790.06135 10.61801
control
control knit SBR 0.855980.03834 4.47865
fabric
* Current testing method allows samples to bend out of testing plane when test
is in progress.
Thus, 1 S' crack numbers may be false indication of tensile strength. Actual
force at 1 s' crack may
be higher when no bending or flexing occurs to initiate cracking.
PN 1 v897635. t
CA 02427514 2003-05-O1
5 [0040] This data is reflected in the bar chant of Fig. 4, using averages for
Formulations 1
and 2 load reading when available. It was observed in these tests that there
was at least
about a 16% increase in average load to first crack using the rewettable
coating of
Formulations 1 and 2 over SBR coatings. Note that all samples were coated on
one side
with a pressure sensitive adhesive. It would be expected that the average load
to first
10 crack would be increased by a factor of two when no adhesive is applied to
the back of
equivalent samples. The explanation for this is that, in the case of the
adhesive coated
samples, half of the surface area of the glass web would be covered with a
layer of low
modulus pressure-sensitive material that does little to resist the loads
placed on the
sample.
15 [0041] It was additionally observed that, while standard products fail by
fiber pull-out
from the joint compound, the re-wettable coatings of this invention failed by
delamination of the joint compound proximate to the coated fiber. Although the
tensile
test is conducted on polyethylene blocks, where it is expected that the
adhesion of the
joint compound to the polyethylene would be poor, real drywall testing may
demonstrate
even better results.
[0042] From the foregoing it can be realized that this invention provides
drywall joints
and methods of joint fabrication which demonstrate improved tensile properties
over kraft
tape joints and over other glass tape joints employing rubber based or binder
coatings.
The tape constructions of this invention employ a re-wettable coating
containing in the
preferred embodiment a resinous binder which is at least partially soluble or
dispersible in
the aqueous mixture of most joint compounds. Although various embodiments have
been
illustrated, this was for the purpose of describing, but not limiting the
invention. Various
modifications, which will become apparent to one skilled in the art, are
within the scope
of this invention described in the attached claims.
PH 1897635.1
