Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR PREPARING CARPETS HAVING POLYURETHANE
BACKINGS OBTAINED FROM POLYURETHANE LATEX FORMULATIONS
The present invention relates to polyurethane backed carpets. The
present invention particularly relates to polyurethane backed carpets and to a
process used in making same from polyurethane latex compositions.
In the manufacture of tufted carpets, a secondary adhesive backing is
required to anchor the carpet tufts to the primary backing of the carpet.
Carpets having an attached polyurethane backing can provide superior
performance in the areas of tuft bind, hand, delamination, resistance to
property loss in the presence of water, and wear resistance. Carpets and other
substrates having attached polyurethane foam layers as backing are described
in U.S. Patent Nos.: 3,755,212; 3,772,224; 3,821,130; 3,862,879; 4,022,941;
4,171,395; 4,278,482; 4,286,003; 4,296,159; 4,405,393; 4,483,894; 4,512,831;
4,515,646; 4,595,436; 4,611,044; 4,657,790; 4,696,849; 4,853,054; 4,853,280
and, 5,104,693, for example. Carpets having polyurethane backings tend to be
more expensive than carpets that incorporate other types of backings due to
the raw material costs in producing a polyurethane backing. For this reason,
polyurethanes are typically used in higher grade carpets, and are typically
not
used in low and intermediate grade carpets.
Current practice in the carpet manufacturing industry requires that
polyurethane carpet backings be prepared from an isocyanate formulation (A-
side formulation) and a polyol formulation (B-side formulation) at the carpet
manufacturing site. This is sometimes referred to as "A+B chemistry".
Preparing a polyurethane by A+B chemistry can result in unpredictable loss of
production and inefficiency due to problems that can occur in carrying out the
reaction at the manufacturing site.
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Styrene-butadiene (SB) latexes are well known. SB latex for use in
carpet is described, for example, in P. L. Fitzgerald, "Integral Latex Foam
Carpet Cushioning", J. Coat. Fab. 1977, Vol. 7 (pp.107 - 120); and in R. P.
Brentin, "Latex Coating Systems for Carpet Backing", J. Coat. Fab. 1982, Vol.
12 (pp. 82 - 91 ). SB latexes are used extensively as anchor coatings in
carpets. SB latexes can provide good tuft bind, with a relatively high degree
of
stiffness, at a relatively low investment cost. SB latexes can provide
relatively
low stiffness with reduced tuftbind properties at a relatively low investment
cost, as well. SB latexes also can provide flexibility in production costs
owing
I O to the ability to include low to high concentrations of filler component
in a low
viscosity latex. However, SB latexes with filler may not meet the rigorous
standards set for intermediate grade carpets. In addition, current technology
may require that a latex material be storage stable for a period of up to one
year. For this reason, SB latexes having solids content of greater than 55
percent are not typical of commercially available SB latexes because such
latexes generally are not storage stable.
Polyurethane/urea (PU) latexes are known and are used, for example,
as coatings for wood finishing; glass fiber sizing; textiles; adhesives; and
automotive topcoats and primers. Automotive topcoats, adhesives for food
packaging, and textiles primarily utilize aliphatic isocyanates. Wood
finishing
and topcoats primarily use aromatic isocyanates. PU latexes can be prepared
by polymerization in an organic solvent of reactants -- such as isocyanates
and
polyols, for example - useful in preparing polyurethanes, followed by
dispersion of the resulting solution in water, and optionally followed by
removal
of organic solvent. PU latexes can be prepared by various processes,
including, for example, those described in: U.S. Patent No. 4,857,565; U.S.
Patent No. 4,742,095; U.S. Patent No. 4,879,322; U.S. Patent No. 3,437,624;
U.S. Patent No. 5,037,864; U.S. Patent No. 5,221,710; U.S. Patent No.
4,237,264; and, U.S. Patent No. 4,092,286. Elimination of the use of volatile
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organic solvents from the process can be desirable from both a cost saving
standpoint and an environmental perspective.
It would be desirable to prepare polyurethane backed carpets according
to a process wherein a high performance polyurethane backing can be applied
to any grade of carpet in a cost-effective process. It would also be desirable
to
eliminate the need to prepare a polyurethane carpet backing using A+B
chemistry at a carpet manufacturing site. Further, it would be desirable to
prepare a polyurethane backed carpet by a continuous process wherein a
polyurethane latex can be applied to a carpet without the additional step of
removing a volatile organic solvent.
In one aspect, the present invention is a backed carpet having as a
backing at least one coat of polymer that is obtained from a dispersion of a
polyurethane or polyurethane-forming material in water.
In another aspect, the present invention is a process for preparing a
backed carpet comprising the steps: (1) dispersing a polyurethane prepolymer
in water to obtain an aqueous dispersion of prepolymer; (2) applying the
aqueous dispersion to the back of a carpet substrate; (3) removing the water
from the aqueous dispersion to obtain a backed carpet.
The carpet of the present invention comprises a polyurethane carpet
backing that is obtained by application of a polyurethane latex composition to
the back of a carpet substrate. In the present invention, polyurethane can
refer
to a polyurethane compound, a polyurea compound, or a mixture thereof.
Polyurethanes can be obtained by the reaction of a polyol with an
polyisocyanate. Polyureas can be obtained by the reaction of amines with
polyisocyanates. A polyurethane or polyurea can contain both urea and
urethane functionality, depending on what is included in the A-side or B-side
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formulations, or in any combination thereof. For the purposes of the present
application, no further distinction will be made herein between the polymeric
materials. The term "polyurethane" will be used generically to describe
either,
or both, polyurethane polymers and polyurea polymers. As used in the present
application, the terms "latex" and "aqueous dispersion" are used
interchangeably to describe the same material. A PU latex composition useful
in the practice of the present invention includes water, and either: a
polyurethane; a mixture capable of forming a polyurethane; or a mixture of
both. A PU latex as described herein can optionally include: chain extenders;
surfactants; fillers; dispersants; foam stabilizers; thickeners; fire
retardants, or a
combination of other optional materials that can be useful in polyurethane
formulations.
According to the practice of the present invention, a PU latex is an
aqueous dispersion of: a polyurethane; polyurethane forming materials; or a
combination thereof. Polyurethane-forming materials as used in the present
invention are materials which are capable of forming polyurethane polymers.
Polyurethane-forming materials include, for example, polyurethane
prepolymers. Prepolymers useful in the practice of the present invention are
prepared by the reaction of active hydrogen compounds with any amount of
isocyanate in excess material relative to active hydrogen material. The
isocyanate functionality can be present in an amount of from 0.2 weight
percent to 40 weight percent. A suitable prepolymer can have a molecular
weight in the range of from 100 to ~ 0,000. Prepolymers useful in the practice
of the present invention should be substantially liquid under the conditions
of
dispersal.
Active hydrogen compounds can be described as compounds having
functional groups that contain at least one hydrogen atom bonded directly to
an
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electronegative atom such as nitrogen, oxygen or sulfur. Suitable active
hydrogen compounds can be polyols of molecular weight of less than 6000.
Other latexes can be used in combination with the polyurethane latexes
of the present invention to prepare a carpet backing of the present invention.
Suitable fatexes useful for blending with polyurethane latexes of the present
invention include: styrene-butadiene latexes; styrene-butadiene-vinylidene
chloride latexes; styrene-alkyl acrylate latexes; or acrylic latexes; like
compunds and mixtures thereof.
The present invention optionally includes a chain extender. A chain
extender is used herein to build the molecular weight of the polyurethane
prepolymer by reaction of the chain extender with the isocyanate functionality
in the polyurethane prepolymer, that is, chain extend the polyurethane
prepolymer. A suitable chain extender is typically a low equivalent weight
active hydrogen containing compound having 2 or more active hydrogen
groups per molecule. The active hydrogen groups can be hydroxyl, mercaptyl,
or amino groups. An amine chain extender can be blocked, encapsulated, or
otherwise rendered less reactive. Other materials, particularly water, can
function to extend chain length and so are chain extenders for purposes of the
present invention. Polyamines are preferred chain extenders. It is
particularly
preferred that the chain extender be selected from the group consisting of
amine terminated polyethers such as, for example, Jeffamine D-400 from
Huntsman Chemical Company, amino ethyl piperazine, 2-methyl piperazine,
1,5-diamino-3-methyl-pentane, isophorone diamine, ethylene diamine,
diethylene triamine, triethylene tetramine, triethylene pentamine, ethanol
amine, lysine in any of its stereoisomeric forms and salts thereof, hexane
diamine, hydrazine and piperazine. in the practice of the present invention,
the
chain extender is often used as solution of chain extender in water.
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In preparing a polyurethane backing of the present invention, small
amounts of chain extender can be advantageously used. Generally, the chain
extender is employed at a level sufficient to react with from zero (0) to 100
percent of the isocyanate functionality present in the prepolymer, based on
one
equivalent of isocyanate reacting with one equivalent of chain extender. It
can
be desirable, under certain conditions, to allow water to act as a chain
extender
and react with some or ail of the isocyanate functionality present. A catalyst
may optionally be used to promote the reaction between a chain extender and
an isocyanate.
Suitable catalysts for use in the present invention include tertiary
amines, and organometallic compounds, like compounds and mixtures thereof.
For example, suitable catalysts include di-n-butyl tin bis(mercaptoacetic acid
isooctyl ester), dimethyltin dilaurate, dibutyltin dilaurate, dibutyltin
sulfide,
stannous octoate, lead octoate, ferric acetylacetonate, bismuth carboxylates,
triethylenediamine, N-methyl morpholine, like compounds and mixtures thereof.
An amount of catalyst is advantageously employed such that a relatively rapid
cure to a tack-free state can be obtained. If an organometallic catalyst is
employed, such a cure can be obtained using from 0.01 to 0.5 parts per 100
parts of the polyurethane-forming composition, by weight. If a tertiary amine
catalyst is employed, the catalyst preferably provides a suitable cure using
from 0.01 to 3 parts of tertiary amine catalyst per 100 parts of the
polyurethane-forming composition, by weight. Both an amine type catalyst and
an organometallic catalyst can be employed in combination.
The present invention optionally includes a filler material. The filler
material can include conventional fillers such as milled glass, calcium
carbonate, ATH, talc, bentonite, antimony trioxide, kaolin, fly ash, or other
knuwn fillers. In the practice of the present invention, a suitable filler
loading in
a PU latex can be from 100 to 1000 parts of filler per 100 parts of
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polyurethane. Preferably, filler can be loaded in an amount of at least 200
pphp, more preferably at least 300 pphp, most preferably at least 400 pphp.
The present invention also optionally includes a filler wetting agent. A
filler wetting agent generally performs the function of compatiblizing the
filler
and the polyurethane-forming composition. Useful wetting agents include
phosphate salts such as sodium hexametaphosphate. A filler wetting agent
can be included in a polyurethane-forming composition of the present invention
at a concentration of at least 0.5 parts per 100 parts of filler, by weight.
The present invention optionally includes thickeners. Thickeners are
useful in the present invention for increasing the viscosity of low viscosity
PU
latexes. Thickeners suitable for use in the practice of the present invention
are
any that are known in the art of preparing polyurethane latexes. For example,
suitable thickeners include AlcogumT"" VEP-II (trade designation of Alco
Chemical Corporation) and ParagumT"" 231 (trade designation of Para-Chem
Southern, Inc.). Thickeners can be used in any amount necessary to obtain a
dispersion of desired viscosity.
The present invention can include other optional components. For
example, a polyurethane-forming composition of the present invention can
include surfactants, blowing agents or frothing agents, fire retardant,
pigments,
antistatic agents, reinforcing fibers, antioxidants, preservatives, acid
scavengers. Examples of suitable blowing agents include gases such as air
carbon dioxide, nitrogen, argon, helium,; liquids such as water, volatile
halogenated alkanes such as the various chlorfluoromethanes and
chlorfluoroethanes; azo-blowing agents such as azobis(formamide). Preferred
in the practice of this invention is the use of a gas as a blowing or frothing
agent. Particularly preferable is the use of air as a blowing or frothing
agent. A
frothing agent can differ from a blowing agent in that frothing agents are
. , ~,~f,.~;..: ,x ...
CA 02283909 1999-09-16
43132A - --
typically introduced by mechanical introduction of a gas into a liquid to form
a froth.
Surfactants can be desirable in the present invention. Surfactants useful
herein can be cationic surfactants, anionic surfactants, or a non-ionic
surfactants.
Examples of anionic surfactants include sulfonates, carboxyiates, and
phosphates.
Examples of cationic surfactants include quaternary amines. Examples of non-
ionic surfactants include block copolymers containing ethylene oxide and
silicone
surfactants. Surfactants useful in the practice of the present invention can
be
either external surfactants or internal surfactants. External surfactants are
surfactants which do not become chemically reacted into the polymer during
latex
preparation. Internal surfactants are surfactants which do become chemically
reacted into the polymer during latex preparation. A surfactant can be
included in
a formulation of the present invention in an amount ranging from 0.01 to 20
parts
per 100 parts by weight of polyurethane component.
Generally, any method known to one skilled in the art of preparing
polyurethane latexes can be used in the practice of the present invention to
prepare a PU latex material suitable for preparing a carpet of the present
invention
with the notable exception of using an organic solvent. Substantially no
organic
solvent is used in the process of preparing the latexes of the present
invention.
Preferable, no organic solvent is used in the process of preparing the latexes
of the
present invention.
A suitable storage-stable PU latex as defined herein is any PU latex having
a mean particle size of less than 5 microns. A PU latex that is not storage-
stable
can have a mean particle size of greater than 5 microns. For example, a
suitable
dispersion can be prepared by mixing a polyurethane prepolymer with water and
dispersing the prepolymer in the water using a commercial blender.
Alternatively,
a suitable dispersion can be prepared by feeding a prepolymer into a static
mixing
' device along with water, and dispersing the water and prepolymer in the
static
~r
mixer. Continuous methods for preparing aqueous dispersions of polyurethane
are
known and can be used in the practice of the present invention. For example,
U.S.
Pat. Nos.:
_$_
AMENDED SHE~~'
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4,857,565; 4,742,095; 4,879,322; 3,437,624; 5,037,864; 5,221,710; 4,237,264;
and 4,092,286 all describe continuous processes useful for obtaining
polyurethane latexes. In addition, a polyurethane latex having a high internal
phase ratio can be prepared by a continuous process as described in U.S. Pat.
No. 5,539,021, incorporated herein by reference.
In the practice of the present invention, any of the steps used in
preparing a polyurethane carpet backing can be carried out in a continuous
manner. For example, in a first step the prepolymer can be prepared from a
suitable active hydrogen containing compound in a continuous manner; the
prepolymer can be fed, as it is obtained in the first step, into a mixing
device
with water to obtain an aqueous dispersion; the aqueous dispersion can be
applied to a carpet substrate in a continuous manner to obtain a polyurethane
backed carpet.
A polyurethane dispersion of the present invention can be stored for
later application to the back of a carpet. Storage for this purpose requires
that
the dispersion be storage-stable. Alternatively, the polyurethane latex can be
applied in a continuous manner to the back of a carpet substrate. That is, the
dispersion can be applied to the back of a carpet as the dispersion is
obtained
according to the practice of the present invention. Polyurethane latexes
applied to carpet in a continuous manner are not required to be storage-
stable,
and can have higher solids content and larger mean particle size or,
alternatively, larger mean particle size than typical storage-stable
polyurethane
latex formulations.
In preparing polymer backed carpets according to the present invention,
a polyurethane-forming composition is applied as a layer of preferably uniform
thickness onto one surface of a carpet substrate. PU latexes of the present
invention can be applied as a precoat, laminate coat or applied as a foam
coat.
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Polyurethane precoats, laminate coats, and foam coats can be prepared by
methods known in the art. Precoats, laminate coats and foam coats prepared
from iatexes are described in P. L. Fitzgerald, Glntegral Latex Foam Carpet
Cushioning", J. Coat. Fab. 1977, Vol. 7 (pp.107 - 120), and in R. P. Brentin,
"Latex Coating Systems for Carpet Backing", J. Coat. Fab. 1982, Vol. 12 (pp.
82 - 91), for example. In preparing a frothed polyurethane backing (frothing),
it
is preferred to mix all components and then blend a gas into the mixture,
using
equipment such as an Oakes or Firestone foamer.
The polyurethane-forming composition can be applied to one surtace of
a carpet substrate before it cures to a tack-free state. Alternatively, a PU
latex
containing no unreacted isocyanate functionality can be applied, thereby
removing the need to cure the polymer. Typically the polyurethane-forming
composition is applied to the surface attached to a primary backing. The
composition may be applied to the carpet substrate using equipment such as a
doctor knife, air knife, or extruder to apply and gauge the layer.
Alternatively,
the composition may be formed into a layer on a moving belt or other suitable
apparatus and dehydrated, or partially cured, or both dehydrated and partially
cured, then married to the carpet substrate using equipment such as a double
belt (also known as double band) laminator or a moving belt with an applied
foam cushion. The amount of polyurethane-forming composition used can vary
widely, from 16.95 mg per cm2 1695 mg per cm2 (5 to 500 ounces per square
yard), depending on the characteristics of the textile. After the Payer is
applied
and gauged, water is removed from the dispersion and the layer can be cured
using heat from any suitable heat source such as an infrared oven, a
convection oven, or heating plates.
The following examples are provided to illustrate the present invention.
The examples are not intended to limit the scope of the present invention and
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should not be so interpreted. Materials used in the examples are defined
below;
Voranol 4702 = 1650 equivalent weight, 16 percent EO capped triol
' Voranol 4701 = 1650 equivalent weight, 18 percent EO capped trios
Voranol 2120 = 1000 equivalent weight, PO diol
Isonate 50 = 50/50 weight/weight mixture of 2,4'-MDI and 4,4'-MDI
EXAMPLES
Example 1
The following processes were conducted at ambient temperature
(19°C). Prepolymer A was fed continuously at rate of 32.1 grams/minute
through a first arm fitted to a first T. DeSULFT"" DBS-60T surfactant (a 60
percent aqueous solution of triethanolamine dodecylbenzene sulfonate, a
Trademark of DeForest Enterprises, Inc.) was fed at a rate of
i5 1.61 grams/minute through a first arm of a second T, and merged with a
water
stream flowing at a rate of 5.5 grams/minute through the second arm of the
second T. The prepolymer stream and the wateNsurfactant stream were
merged at the first T, passed through a static mixer, and fed to the input
port of
a IKA-SD 41 SUPER-DISPAXT"" dispersing instrument (a Trademark of IKA-
WORKS, Inc.), a rotor/stator device operated at 1200 rpm.
The ratios of feeds into the dispersing instrument were 81.9 percent
prepolymer, 4.1 percent surfactant solution, and 14.0 percent water. The HIPR
emulsion formed in the dispersing instrument had a volume average particle
size of 0.265 micron and a polydispersity of 3.1, as measured by a Coulter
LS130 particle size analyzer.
Chain extension was accomplished in a LIGHTNINT"" model .025 LB in-
line blender (a Trademark of GREEY/LIGHTNIN). The HIPR emulsion from the
dispersing instrument was fed into a first arm attached to a third T and
merged
with an aqueous stream fed through a second arm of the third T at the rate of
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~,:,. ~,~
43132A CA 02283909 1999-09-16
s - .
5.1 gramslminute. The output of the combined streams was fed into one arm
' of a fourth T, which was attached to the input of the in-line blender.
Concurrently, a 10 percent aqueous piperazine solution was pumped at a
constant rate of 18.0 grams/minute (0.75 equivalents, based on the isocyanate
groups of the prepolymer) through the other arm of the fourth T. The two
streams were mixed in the in-line blender operating at 1500 rpm. The product
was collected and allowed to stand overnight to allow water to react with the
remaining isocyanate groups. The resulting stable poly(urethane/urea) latex
had a solids content of 56.0 percent by weight, a volume average particle size
of 0.256 micron, and a polydispersity of 3.5, as measured by a Coulter LS 230
particle size analyzer.
The latex was compounded by mixing 178.6 parts latex (100 parts
latexes solids) with 200 parts calcium carbonate filler. Stirring was begun
with
latex alone, then the filler was added as quickly as it was dispersed in the
liquid. Paragum~" 241 thickener (a Trademark of Para-Chem Southern, Inc.)
was added until the a viscosity of 9300 cPs (93 Ns/m2) was reached. The
carpet for testing was a nylon level loop style with a greige weight of 77.98
mg
per cm2 (23 ounces per square yard). Compound was applied to the back of
this carpet at a coating weight of 118.7 mg per cm2 (35 ounces per square
yard), followed by a polypropylene scrim, 11.19 mg per cm2 (3.3 ounces per
square yard), as a secondary backing. The carpet was dried at 132° C
for 12
minutes, then allowed to equilibrate overnight before testing.
The carpet of Example 1 had a tuftbind of 2.97 kg-meters(21.5 ft-
pounds). Tuftbind values were obtained according to ASTM D1335. The
carpet of Example 1 had a dry delamination of 1.803 kg per cm (10.1
pounds/inch) and a re-wet delamination of 892.9 kg per cm (5.0 poundslinch).
The delamination was the strength required to remove the secondary
polypropylene scrim from the fabricated carpet. It was determined by cutting a
7.62 cm by 22.86 cm (3 inch by 9 inch) strip of carpet, and peeling the
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43132A CA 02283909 1999-09-16
secondary scrim from the main portion of the carpet while measuring the force
required. The rewet delamination was determined in the same manner, except
that the carpet specimen was soaked for one minute in water, and blotted dry
prior
to testing. The carpet of Example 1 had a hand punch of 2.04 kg-meters (17.4
ft-
pounds). The hand punch was measured as the force required to push a 22.86 cm
by 22.86 cm (9 inch by 9 inch) piece of carpet 1.27 cm (0.5 inches) into a
13.97
(5.5 inch) inner diameter cylinder at a rate of 30.48 cm per minute (12.0
inches per
minute), using a 5.715 cm (2.25 inch) outer diameter solid cylinder attached
to a
load cell.
Example 2
The procedure used to prepare the latex from Example 1 was repeated,
with the following exceptions. The surfactant was DeSULFT"~ TLS-40 surfactant
(a
40 percent aqueous solution of triethanolamine lauryl sulfate, a Trademark of
DeForest Enterprises, Inc.) and the flow rates were: prepolymer,
32.0 grams/minute; surfactant, 2.4 grams/minute; and water, 3.5 grams/minute.
The ratios of the components that were fed into the disperser were prepolymer,
84.4 percent; surfactant solution, 6.3 percent; and water, 9.2 percent. The
HIPR
emulsion had a volume average particle size of 0.182 micron and a
polydispersity
of 1.6, as measured by a Coulter LS130 particle size analyzer.
The aqueous stream used to dilute the HIPR emulsion was flowed at a rate
of 4.6 grams/minute, and the piperazine solution was pumped at a rate of 17.9
grams/minute. The final poly(urethane/urea) latex had a solids content of 53.9
percent by weight, and a volume average particle size of 0.365 micron. .
~~The latex was compounded as in Example 1. Paragum 241 thickener
(supplied by Para-Chem Southern, Inc.) was added until a viscosity of between
8,000 and 10,000 cPs (80 - 100 Ns/m2) was reached. Compound was applied to
the back of the same carpet as in Example 1 at a coating weight of 121.0 mg
per
cm2 (35.7 ounces per square yard), followed by a polypropylene scrim, 11.19 mg
per cm2
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ounces per square yard), followed by a polypropylene scrim, 11.19 mg per cmz
(3.3 ounces per square yard), as a secondary backing. The carpet was dried
at 132°C for 12 minutes, then allowed to equilibrate overnight before
testing.
This carpet had a tuftbind of 2.92 kg-meters (21.1 ft-pounds), a hand punch of
2.36 kg-meters (17.1 ft-pounds), a dry delamination of 1.7679 kg per cm (9.9
pounds/inch) and a re-wet delamination of 1.3036 kg per cm (7.3 pounds/inch).
Comparative Example 3:
As a comparison, a standard, carpet grade styrene-butadiene latex
(53.3 percent solids content) was compounded with calcium carbonate and
thickener and applied as a carpet backing as in Example 1. The resulting
carpet had a coating weight of 115.6 mg per cmz (34.1 ounces per square
yard), a tuftbind of 2.24 kg-meters (16.2 ft-pounds), a deiamination of 1.7501
kg per cm (9.8 pounds/inch), a hand punch of 3.37 kg-meters (27.0 ft-pounds)
and a re-wet delamination of 1.1786 kg per cm (6.6 poundslinch).
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