Note: Descriptions are shown in the official language in which they were submitted.
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DRYWALL TAPE AND JOINT
Field of the Invention
[O1] 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
[02] 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.
[03] 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 and 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 wrinkles.
It
can be laid flat and resists tearing under load.
[04] 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.
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[OS] 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.
[06] 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 transfernng these loads to the glass fibers
themselves.
[07] 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 compatible with ready mixed or powder joint compound compositions
and should not substantially detract from the akeady established benefits of
using
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glass fiber tape over kraft paper tape.
Summary of the Invention
[08] 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.
[09] 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 folly integrated composite, which increases
the
mechanical properties of the joint.
[O10] 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 0474 (appendix) revealed that leno weave fabrics benefitted most by the
new coating, with a 65% improvement, followed by knit 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
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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 tensile loads placed on
the
sample.
[0l 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.
[012] 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 bloclc 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 paraffin wax, make the PVAc-based
coating vapor resistant. Only when contacted with liquid water, such as when
the
tape is applied to a wall and coated with joint compound, does the PVAc resin
re-
wet and become soluble.
[013] 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
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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
[014] The accompanying drawings illustrate preferred embodiments of the
invention according to the practical application of the principles thereof,
and in
which:
[015] FIG. 1: is a partial, front perspective view of the preferred drywall
tape of
this invention;
[016] FIG. 2: is a partial, enlarged side-plan view, illustrating a coating on
the
drywall tape of FIG. 1;
[017] FIG. 3: is a partial, top, cross-sectional view of a finished flat
drywall
joint of this invention; and
[018] i 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 Descriution of the Invention
[019] This invention provides drywall tape, drywall joints, methods of
preparing
drywall joints, and reinforcements for cementitious materials generally. It is
understood that 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
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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
term
"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.
[020] 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 both sides of the web of glass fibers 10. Alternatively,
the
re-wettable coating 14 can be disposed over 100% of the exterior surfaces of
the
web of glass fibers 10, over 70% of the surface area, or over less than 50% 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, vinyl/acetate, acrylic, styrene acrylic, or copolymers and
mixtures thereof, etc. 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 embodiment, the re-wettable coating 14 is used to also bind the
fibers of
the web of glass fibers together.
[021] 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 layer 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 the tape to prevent blistering of the
tape.
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While embedding the tape 100, excess joint compound should be removed from
the edge.
[022] 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 easier 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.
[023] 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
~
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 10 inch knife to the flat joints. The second coat 40 or
third coat
can be lightly sanded if necessary.
[024] 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 filler comprises substantially calcium carbonate. Prior to use,
the
filler and the binder, along with several other lrnown ingredients, are mixed
with
water. After application, when the water drys to evaporation, a dry,
relatively
hard cementitious material is left behind.
[025] 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 %z molecules of water from the calcium sulfate dihydrate gypsum. The
hemihydrate form of calcium sulfate is substantially more soluble in water
than
the dihydrate form of calcium sulfate. During use of a setting-type joint
compound, the calcium sulfate hemihydrate is rehydrated to the dihydrate
state.
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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.
[026] The webs useful in manufacturing the drywall tape 100 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 thereof. In most examples of this invention, a
web
of glass fibers 10 having a basis weight of about 5-500 grams/m2, 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 wet joint compound so
as to
form a good bond in the seam region 45. Alternatively, a veil or 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.
[027] 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
vinyl acetate acrylic, styrene/acrylate, vinyl/acetate, 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
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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 UV light degradation. Ideally, the preferred re-wettable coating 14 is
provided
in a latex form such as an aqueous emulsion of a binder resin, blocking agent
and
water.
[028] 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 algin); inorganics
such as soluble silicates (water glass) and cementitious materials (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
acetate/ethylene co-polymer stabilized with polyvinyl alcohol, both supplied
by
Air Products and 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 25-75 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:
[029] Formulation 1
Vinac 524 Emulsion (PVAc homopolymer
stabilized with polyvinyl alcohol) 61.38%
Airflex 401 Emulsion (PVAc/ethylene
co-polymer stabilized with polyvinyl alcohol 26.30%
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Water 9.02%
Urea 0.25%
Hydrocer DP69 (paraffin wax, anti-blocking 3.00%
agent)
900-103 Henkel Foamaster NXZ mixed 50/50% 0.05%
with water.
Other pertinent formula data:
Solids level: 50%
1 Viscosity: about 1000 cps
PH: approximately 6.0
[030] Formulation 2 '
,,
Vinac 524 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 50/50% with water 0.05%
_.. . , . ,,
[O31 ] ._ As reflected above, an important ingredient for preventing the PV Ac
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- awvapor barrier to the re-
wettable
14 coating on the drywall tape 100 of this invention, so as to substantially
reduce
blocl~ing in tape rolls. The anti-blocking agent should be less than about 5-
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.
[032] The adhesive elements of this invention can be made of any known
k - ,.
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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 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.
[033] The preferred method of manufacturing the drywall tape 100 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 serve to control the amount
of
latex picked up by the fabric, 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.
[034] At this point, the web of glass fibers 10, now coated with a re-wettable
coating 14, is provided with a pressure sensitive adhesive layer 12 applied to
one
side, usually about 3-15 grams/m2 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. Alternatively, 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
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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.
[035] 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 (such 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.
[036] 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 SOmm wide by about 90m
long. The tapes are subsequently wrapped, packaged and sent to customers.
Examules
[037] 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/m2), 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 specified 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.
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[038] 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.
[039] The data for the average load to first crack (IAN) is located below in
Table
1.
Table 1: Average
Load to First
Crack (Kl~
ASTM-C474
(appendix)*
GLASS WEB COATING AVG. STANDARD % STANDARD
TYPE FORMULATION DEVIATION DEVIATION INCREASE
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 36.67
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 light SBR 0.639470.02935 4.59053
plain
weave
control woven SBR 0.636430.10435 16.39574
leno
control plain SBR 1.020070.02424 2.37607
weave
paper tape N/A 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 ire
progress. Thus, 1 S' crack numbers may be false indication of tensile
strength. Actual
force at IS' crack may be higher when no bending or flexing occurs to initiate
cracking.
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[040] This data is reflected in the bar chart 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 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.
[041] 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.
[042] 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.
14
