Note: Descriptions are shown in the official language in which they were submitted.
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POLYURETHANE FOAM PAD AND METHODS OF MAKING AND USING SAME
Field of the Invention
[0001] The present invention relates generally to polyurethane foam pads
that
can be used, for example, in combination with textile, carpeting, or other
floor
covering applications. Also provided are methods for providing the
polyurethane
foam pads.
Background of the Invention
[0002] A backing material can be used with a carpet or textile to provide a
support,
a cushion, a contamination barrier, a moisture barrier, or to simplify
installation of the
carpet or textile. Backing or support layers often comprise a polyurethane
foam.
There are several properties of polyurethane foams which are important for
determining their usefulness in floor covering applications. These properties
include
but are not limited to resiliency, density, thickness, tear strength, tensile
strength,
dimensional stability, and cost.
[0003] Typically, polyurethane foams are manufactured using a double-belted
oven conveyer process, wherein two heated belts function as a mold, carrier,
and
gas barrier for a foam composition. During this process, a conveying foam
composition is held between an upper belt and a lower belt. The two belts
affect not
only the thickness of the foam composite, but also the density. The foam
thickness
is controlled by the spacing between the two belts. The density is affected by
the
composition of the belt itself, since as the foam formulation is conveyed to a
curing
oven, heat permeates through the two belts into the foam, resulting in a cured
foam.
Thus, the heat capacity or heat transfer capacity of a belt can directly
affect the
density of a foam product.
[0004] Unfortunately, such a belt driven process is limited in a number of
ways.
For example, the maintenance of a belt driven machine can be difficult and
costly
Belts require frequent maintenance and oftentimes frequent replacement, and
the
offline machinery time alone can present substantial economic loss.
Additionally,
since the belts themselves affect a number of properties of foam composites
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produced therefrom, the types of foam composites that can be produced using a
single
belt-driven process is inherently limited.
[0005] Accordingly, there is a need to provide improved methods and systems
for
producing foam composites with desirable densities, preferably in a cost-
effective
manner. Further, there is a need to provide improved foam composites suitable
for use
in textile and carpet applications. These needs and other needs are at least
partially
satisfied by the present invention.
Summary
[0006] Disclosed are polyurethane foam pads and methods of making and using
same.
Generally, the polyurethane foam pads comprise a cured polyurethane foam layer
having a first surface and an opposed second surface. A backing layer contacts
the first
surface, and a film layer is affixed to the second surface of the cured
polyurethane foam
layer. The polyurethane foam is formed from a mechanically frothed, chemically
blown,
or mechanically frothed/chemically blown polyurethane composition.
[0007] Also disclosed are processes for making the polyurethane foam pads.
Generally,
the polyurethane foam pads can be made by providing an uncured foamable
polyurethane composition, and applying the foamable polyurethane composition
to a
surface of a backing material. The applied polyurethane composition can be
metered to
form a substantially uniform layer of the uncured polyurethane composition
having a
predetermined thickness. A top layer can be applied to the uncured
mechanically
frothed and chemically blown polyurethane composition layer. The foamable
polyurethane composition can then be cured, to provide a polyurethane foam
pad.
Also disclosed is a composite polyurethane foam underlay, comprising:
a single mechanically frothed, chemically blown and cured polyurethane foam
layer
having a bottom surface and an opposed top surface;
a backing layer contacting to the bottom surface of the mechanically frothed,
chemically
blown and cured polyurethane foam layer, wherein the backing layer comprises a
polypropylene woven textile material; and
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a face layer comprising a gas-impermeable film affixed to the top surface of
the
mechanically frothed, chemically blown and cured polyurethane foam layer;
wherein the face layer of the composite polyurethane foam underlay is
configured to
function as a slip layer for a detached floor covering having a bottom surface
positioned
in contact with the face layer.
Further disclosed is a process for preparing a three-layer composite
polyurethane foam
underlay, comprising
providing an uncured foamable polyurethane composition;
applying the uncured foamable polyurethane composition to a surface of a
backing
material, wherein the backing layer comprises a polypropylene woven textile
material;
metering the applied uncured foamable polyurethane composition to form a
single
substantially uniform layer of the uncured polyurethane composition having a
predetermined thickness;
applying a top layer to the uncured foamable polyurethane composition layer;
mechanically frothing and chemically blowing the foamable polyurethane
composition;
and
curing the foamable polyurethane composition;
wherein the top layer of the composite polyurethane foam underlay is
configured to
function as a slip layer for a detached floor covering having a bottom surface
positioned
in contact with the face layer.
[0008] Additional embodiments of the invention will be set forth, in part, in
the detailed
description, figures, and claims which follow, and in part will be derived
from the
detailed description, or can be learned by practice of the invention. It is to
be
understood that both the foregoing general description and the following
detailed
description are exemplary and explanatory only and are not restrictive of the
invention
as disclosed.
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Brief Description of the Figures
[0009] FIG. 1 is a diagram of a cross-sectional perspective view of a
portion of a
three-layered foam composite.
[0010] FIG. 2 is a schematic drawing of a tenter machine used to a
manufacture a
disclosed composite.
Detailed Description
[0011] The present invention can be understood more readily by reference to
the
following detailed description, examples, drawings, and claims, and their
previous
and following description. However, before the present devices, systems,
and/or
methods are disclosed and described, it is to be understood that this
invention is not
limited to the specific devices, systems, and/or methods disclosed unless
otherwise
specified, as such can, of course, vary. It is also to be understood that the
terminology used herein is for the purpose of describing particular aspects
only and
is not intended to be limiting.
[0012] The following description of the invention is provided as an
enabling
teaching of the invention in its best, currently known embodiment. To this
end, those
skilled in the relevant art will recognize and appreciate that many changes
can be
made to the various aspects of the invention described herein, while still
obtaining
the beneficial results of the present invention. It will also be apparent that
some of
the desired benefits of the present invention can be obtained by selecting
some of
the features of the present invention without utilizing other features.
Accordingly,
those who work in the art will recognize that many modifications and
adaptations to
the present invention are possible and can even be desirable in certain
circumstances and are a part of the present invention. Thus, the following
description
is provided as illustrative of the principles of the present invention and not
in
limitation thereof.
[0013] As used herein, the singular forms "a," "an" and "the" include
plural
referents unless the context clearly dictates otherwise. Thus, for example,
reference
to a "surface" includes aspects having two or more such surfaces unless the
context
clearly indicates otherwise.
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[0014] Ranges can be expressed herein as from "about" one particular value,
and/or to "about" another particular value. When such a range is expressed,
another
aspect includes from the one particular value and/or to the other particular
value.
Similarly, when values are expressed as approximations, by use of the
antecedent
"about," it will be understood that the particular value forms another aspect.
It will be
further understood that the endpoints of each of the ranges are significant
both in
relation to the other endpoint, and independently of the other endpoint.
[0015] As used herein, the terms "optional" or "optionally" mean that the
subsequently described event or circumstance may or may not occur, and that
the
description includes instances where said event or circumstance occurs and
instances where it does not.
[0016] References in the specification and concluding claims to parts by
weight of
a particular element or component in a composition or article, denotes the
weight
relationship between the element or component and any other elements or
components in the composition or article for which a part by weight is
expressed.
Thus, in a composition or a selected portion of a composition containing 2
parts by
weight of component X and 5 parts by weight component Y, X and Y are present
at a
weight ratio of 2:5, and are present in such ratio regardless of whether
additional
components are contained in the composition.
[0017] A weight percent of a component, unless specifically stated to the
contrary, is based on the total weight of the formulation or composition in
which the
component is included.
[0018] As used herein, and unless the context clearly indicates otherwise,
the
term "carpet" is used to generically include broadloom carpet, carpet tiles,
and even
area rugs. To that end, "broadloom carpet" means a broadloom textile flooring
product manufactured for and intended to be used in roll form. "Carpet tile"
denotes a
modular floor covering, conventionally in 18" x 18," 24" x 24" or 36" x 36"
squares,
but other sizes and shapes are also within the scope of the present invention.
[0019] The present invention may be understood more readily by reference to
the
following detailed description of preferred embodiments of the invention and
the
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examples included therein and to the Figures and their previous and following
description.
[0020] As summarized above, in one broad aspect, the present invention
provides a composite comprising an integral foam, such as a polyurethane foam.
In
general, the disclosed composites can be used in combination with any suitable
textile or carpet material. It is contemplated that the composites can be
attached or
detached to a carpet, textile, or other floor covering. For example, a
disclosed
composite can be used as a carpet underlay or carpet or textile cushion.
[0021] It will be appreciated that the invention is based at least in part
on a novel
discovery that such a layered approach to a foam composite, when used with a
disclosed process, can provide substantially impermeable barrier layers on
portions
of the foam during the manufacturing process, such that the resulting foam
composite has a desired density, including sufficiently low densities.
[0022] In a first aspect and with reference to FIG. 1, the present
disclosure
provides generally a laminate polyurethane foam pad 100. The laminate
polyurethane foam pad 100 comprises a cured polyurethane foam layer 120 having
a first surface 122 and an opposed second surface 124. A backing layer 130 is
affixed to the first surface 122 and a laminate face layer 110 is affixed to
the second
surface 124 such that the polyurethane foam is effectively sandwiched between
the
backing layer and the laminate face layer.
[0023] The cured polyurethane foam layer 120 of the present disclosure can
be
manufactured according to any conventionally known process and formulation for
manufacturing polyurethane foam. For example, and without limitation, the
cured
polyurethane foam layer 120 can generally be prepared by admixing a first
component, such as a polyisocyanate, with a second component, such as an
active
hydrogen containing material, wherein a gas is introduced therein or produced
in situ
to form bubbles which in turn form a reduced density expanded cell-like
structure in
the cured polyurethane. The process of introducing the bubbles is known as
mechanically blowing or frothing the formulation. The process of forming
bubbles in
situ is commonly referred as chemically blowing. The greater the amount of gas
introduced into a polyurethane formulation, the lower the density of the
resultant
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foam produced therewith. But with polyurethane foams generally and with
polyurethane foams used in floor covering applications in particular, reducing
foam
density can also decrease or reduce other properties of the polyurethane foam
which
can make it a desirable material for use in floor covering applications.
[0024] In a preferred embodiment, the cured polyurethane foam layer 120 is
formed from a polyurethane composition that has been both mechanically frothed
and chemically blown, such as those disclosed and described in U.S. Patent
6,372,810.
Polyurethane foams of this nature can be prepared from formulations comprising
a
polyisocynate component in combination with relatively high levels of a
catalyst, a
surfactant, and water. The high level of water can cause a chemical blowing of
the
foam composition when the water reacts with the polyisocyanate component of
the
polyurethane formulation. The combination of the mechanical frothing and
chemical
blowing from the reaction of a polyisocyanate and water results in
polyurethane foam
having lower densities than those conventionally used in floor covering
applications,
such as carpet backings and carpet underlays. It should also be appreciated
that the
polyurethane foams so produced can have sufficiently low densities to be less
expensive than conventional polyurethane foams for carpet applications, while
maintaining sufficient resiliency and dimensional stability to be desirable
for use in
various floor covering applications. Such a low density can be achieved for
example,
by minimizing off-gassing from the polyurethane composition during the curing
process, thus providing a cured foam having an expanded cell structure
indicated by
cells 140 in FIG. 1.
[0025] In one aspect, the synergistic combination of mechanical blowing and
chemical blowing can be made possible by the inclusion of high levels of
catalyst,
water, and surfactant in the formulations used to prepare the foams. The foam
formulations used to prepare the foams of the present invention can have from
about
0.5 to about 3 parts water per hundred parts polyol, preferably from about
0.75 to
about 2.75 parts water per hundred parts polyol, and more preferably from
about 1.5
to about 2.5 parts water per hundred parts polyol. The formulations of the
present
invention also include from about 0.01 to about 3.5 parts urethane catalyst
per
hundred parts polyol, and from 1 to 2 parts surfactant per hundred parts
polyol.
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[0026] The foams can have any desired density, which will depend on the
desired
use of the foam. In one aspect, the foam can have a density of from about 2 to
about
60 pounds per cubic foot, preferably from about 3 to about 30, more preferably
from
about 6 to about 18, and even more preferably from about 6 to about 14 pounds
per
cubic foot. For use in a residential floor covering, an exemplary foam can
have a
density from about Ito about 10 pounds per cubic foot, including, for example,
2, 4,
6, or 8 pounds per cubic foot. For use in a commercial floor covering, an
exemplary
foam can have a density from about 11 to about 20 pounds per cubic foot,
including,
for example, 12, 14, 16, or 18 pounds per cubic foot. Alternatively, for use
as a
laminate flooring underlayment, an exemplary foam can have a density from
about
15 to about 25 pounds per cubic foot, including, for example, 16, 18, 20,22,
and 24
pounds per cubic foot.
[0027] The foams can also have any desired thickness, which will generally
depend on the composition of the laminate face layer, the backing layer, as
well as
the amount and composition of polyurethane deposited prior to curing.
Exemplary
embodiments have thickness of from about 80 mils to about 500 mils, including,
without limitation, embodiments having thicknesses of about 90 mils, 100 mils,
120
mils, 140 mils, 160 mils, 180 mils, 200 mils, 240 mils, 250 mils, 280 mils,
320 mils,
350 mils, 400 mils, and 450 mils.
[0028] An example formulation suitable to provide the foams includes those
formulations disclosed and described in U.S. Pat. No. 5,104,693
but additionally including
from about 0.5 to about 3 parts water per hundred parts of polyol, from about
0.01 to
about 3.5 parts urethane catalyst per hundred parts of polyol, and from 1 to 2
part
surfactant per hundred parts of polyol. In formulations of this type, the
polyol
component can be at least one isocyanate reactive material having an average
equivalent weight of about 1,000 to about 5,000 daltons.
[0029] The polyisocyanate can be any polyisocyanate sufficient to provide
an
isocyanate index of about 90 to about 130, wherein at least 30 percent by
weight of
the polyisocyanate is a soft segment prepolymer which is the reaction product
of a
stoichiometric excess of MDI or an MDI derivative and an isocyanate reactive
organic polymer having an equivalent weight from about 500 to about 5,000, the
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prepolymer having an isocyanate group content of about 10 to about 30 percent
by
weight. The underlay can be prepared by frothing the reactants with air with
further
blowing as the water reacts with isocyanate to produce carbon dioxide.
[0030] Foam formulations of the present invention can comprise a polyol
component. The polyol component of the foam formulation can be any polyol or
polyol mixture which can be used to prepare a foam which can withstand the
physical property and handling requirements of foams used in carpet or textile
applications. For example, the polyol component can be a polyol mixture having
as
one part of the mixture a polyol based on a C3-C8 alkylene oxide, which has an
equivalent weight of about 1000 to about 5000 daltons, and an internal
poly(ethylene
oxide) block or a terminal ethylene oxide cap constituting about 15 to about
30
percent of the weight of the polyol, or mixture of such polyols wherein the
polyol or
mixture thereof has an average functionality of about 1.8 to about 2.5,
preferably
from about 1.8 to about 2.4 and more preferably from about a 1.8 to about 2.3.
The
other portion of the polyol mixture is preferably a minor amount of a low
equivalent
weight compound having about 2 active hydrogen containing groups per molecule.
[0031] The polyurethane foams can be prepared with conventional
polyurethane
catalysts including, but not limited to, tertiary amine catalysts such as
triethylenediamine, N-methyl morpholine, N-ethyl morpholine, diethyl
ethanolamine,
N-coco morpholine, 1-methy1-4-dimethylaminoethyl piperazine, 3-methoxy-N-
dimethylpropylamine, N,N-diethyl-3-diethyl aminopropylamine, dimethylbenzyl
amine
and the like; organotin catalysts such as dimethyltin dilaurate, dibutyltin
dilaurate,
dioctyltin dilaurate, stannous octoate and the like; and isocyanurate
catalysts such
aliphatic and aromatic tertiary amine compounds, organotin compounds, alkali
metal
salts of carboxylic acids, phenols, symmetrical triazine derivatives, and the
like.
[0032] If an organotin catalyst is used, a suitable cure can be obtained
using from
about 0.01 to about 0.5 parts per 100 parts of the polyol, by weight. By
"suitable
cure," it is meant that a relatively rapid cure to a tack-free state is
obtained. If a
tertiary amine catalyst is used, the catalyst preferably provides a suitable
cure using
from about 0.01 to about 3 parts of tertiary amine catalyst per 100 parts of
the polyol,
by weight. Both an amine type catalyst and an organotin catalyst can be
employed
simultaneously in any combination or ratio. If a combination of amine catalyst
and
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organotin catalyst is used, the catalysts can be used in an amount of from
about 0.02
to about 3.5 parts per 100 parts of polyol, by weight.
[0033] The foams can be prepared using both mechanical and chemical blowing
agents. The mechanical blowing agent is introduced into a foam forming mixture
by a
mechanical device. The blowing agent is preferably air, however, other gasses,
such
as carbon dioxide, nitrogen, and the like can be used. The blowing agent is
preferably introduced into the polymer by frothing. A frother is a mechanical
device
which injects the blowing agent into an admixture as it agitates the
admixture.
Chemical blowing agents as used herein are volatile materials, or materials
that
produce gaseous materials as the result of a chemical reaction. Chemical
blowing
agents useful in the present invention include, for example, liquids such as
water,
volatile halogenated alkanes such as the various chlorfluoromethanes and
chlorfluoroethanes; azo-blowing agents such as azobis(formamide). Water is the
preferred chemical blowing agent.
[0034] The foams of the present invention are prepared from formulations
that
can also include fillers. The fillers can be any suitable filler, including,
for example,
aluminum oxide trihydrate (alumina), calcium carbonate, barium sulfate or
mixtures
thereof. Other fillers can also be used. The fillers can be virgin, waste
material, or
even reclaimed fillers. Examples of recycled fillers include coal fly ash,
which have
been found to be useful in amounts from about 100 to about 400 parts by
weight.
[0035] In general, the formulations used to prepare the polyurethane foams
of the
present invention include fillers at any desired level. For example, the
amount of
filler can be determined relative to parts polyol. To that end, an exemplary
polyurethane can have from about 80 parts per hundred parts of polyol to about
250
parts per hundred parts of polyol, including, without limitation, 90, 100,
120, 130, 150,
160, 190, 200, 220, and 140 parts per hundred parts of polyol. Alternatively,
the
amount of filler can be determined relative to any other desired component of
the
polyurethane composition, or even relative to the total weight of the
polyurethane
composition. For example, in an exemplary and non-limiting embodiment, a
polyurethane can comprise from about 100 to about 200 parts by weight filler,
including, for example, 110, 120, 130, 140, 150, 160, 170, 180, and 190 parts
by
weight filler, relative to the total weight of the polyurethane.
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[0036] In one aspect, the polyisocyanate component of the formulations used
to
prepare the foams can be conveniently selected from organic polyisocyanates,
modified polyisocyanates, isocyanate-based prepolymers, and mixtures thereof.
These can include aliphatic and cycloaliphatic isocyanates, aromatic and
multifunctional aromatic isocyanates. Exemplary polyisocyanates include, but
are not
limited to, 2,4- and 2,6-toluenediisocyanate and the corresponding isomeric
mixtures; 4,4'-, 2,4'- and 2,2'-diphenyl-methanediisocyanate and the
corresponding
isomeric mixtures; mixtures of 4,4'-, 2,4'- and 2,2'-
diphenylmethanediisocyanates
and polyphenyl polymethylene polyisocyanates PMDI; and mixtures of PMDI and
toluene diisocyanates. Aliphatic and cycloaliphatic isocyanate compounds are
also
useful for preparing the polyurethanes. Such examples, include 1,6-
hexamethylene-
diisocyanate; 1-isocyanato-3,5,5-trimethy1-1-3-isocyanatomethyl-cyclohexane;
2,4-
and 2,6-hexahydrotoluenediisocyanate, as well as the corresponding isomeric
mixtures; 4,4'-, 2,2'- and 2,4'-dicyclohexylmethanediisocyanate, as well as
the
corresponding isomeric mixtures.
[0037] Modified multifunctional isocyanates can also be used, La, products
which
are obtained through chemical reactions of the above diisocyanates and/or
polyisocyanates. Examples include polyisocyanates containing esters, ureas,
biurets,
allophanates and including carbodiimides and/or uretonimines; isocyanurate
and/or
urethanes containing diisocyanates or polyisocyanates. Liquid polyisocyanates
containing carbodiimide groups, uretonimine groups and/or isocyanurate rings,
having isocyanate groups (NCO) contents (42/polyisocyanate mwt) of from about
10
to about 40 weight percent, or from about 20 to about 35 weight percent, can
also be
used. These include, for example, polyisocyanates based on 4,4'-, 2,4'- and/or
2,2'-
diphenylmethane diisocyanate and the corresponding isomeric mixtures, 2,4-
and/or
2,6-toluenediisocyanate and the corresponding isomeric mixtures; mixtures of
diphenylmethane diisocyanates and PMDI and mixtures of toluenediisocyanates
and
PMDI and/or diphenylmethane diisocyanates.
[0038] Prepolymers can also be useful with the formulations used to prepare
the
foams. In one aspect, suitable prepolymers are prepolymers having NCO contents
of
from about 5 to about 40 weight percent, more preferably from about 15 to
about 30
weight percent. These prepolymers are prepared by reaction of the di- and/or
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polyisocyanates with materials such as lower molecular weight diols and
triols, but
also they can be prepared with multivalent active hydrogen compounds such as
di-
and tri-amines and di- and tri-thiols. Specific examples include aromatic
polyisocyanates containing urethane groups, having NCO contents of from about
5
to about 40 weight percent, or about 20 to about 35 weight percent, obtained
by
reaction of diisocyanates and/or polyisocyanates with, for example, lower
molecular
weight dials, trials, oxyalkylene glycols, dioxyalkylene glycols or
polyoxyalkylene
glycols having molecular weights up to about 800. These polyols can be
employed
individually or in mixtures as di- and/or polyoxyalkylene glycols. For
example,
diethylene glycols, dipropylene glycols, polyoxyethylene glycols,
polyoxypropylene
glycols and polyoxypropylenepolyoxyethylene glycols can be used.
[0039] Polyisocyanates having an NCO content of from 8 to 40 weight percent
containing carbodiimide groups and/or urethane groups, from 4,4'-
diphenylmethane
diisocyanate or a mixture of 4,4'- and 2,4'-diphenylmethane diisocyanates can
also
be used with the formulations. Additionally, prepolymers containing NCO
groups,
having an NCO content of from about 20 to about 35 weight percent, based on
the
weight of the prepolymer, prepared by the reaction of polyoxyalkylene polyols,
having a functionality of from 2 to 4 and a molecular weight of from about 800
to
about 15,000 with 4,4'-diphenylmethane diisocyanate or with a mixture of 4,4'-
and
2,4'-diphenylmethane diisocyanates and mixtures of polyisocyanates and
prepolymers; and 2,4- and 2,6-toluene-diisocyanate or the corresponding
isomeric
mixtures. PMDI in any of its forms can also be used. PMDI can have an
equivalent
weight of from about 125 to about about 300, or from about 130 to about 175,
with
an average functionality of greater than about 2. An average functionality can
also be
from about 2.5 to about 3.5. The viscosity of the polyisocyanate component can
be
from about 25 to about 5,000 centipoise (cps) (0.025 to about 5 PaYs), but
values
from about 100 to about 1,000 cps at 25° C. (0.1 to 1 PaYs) are also
useful
for ease of processing. Similar viscosities are useful where alternative
polyisocyanate components are selected. In one aspect, the polyisocyanate
component of the formulations of the present invention is selected from MDI,
PMDI,
an MDI prepolymer, a PMDI prepolymer, a modified MDI, and a combination
thereof.
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[0040] Polyfunctional active hydrogen containing materials useful with the
present
formulations can include materials other than those described above. Active
hydrogen containing compounds commonly used in polyurethane production are
those compounds having at least two hydroxyl groups. Those compounds are
referred to herein as polyols. Representatives of suitable polyols are
generally
known and are described in such publications as High Polymers, Vol. XVI,
"Polyurethanes, Chemistry and Technology" by Saunders and Frisch, Interscience
Publishers, New York, Vol. I, pp. 32-42, 44-54 (1962) and Vol. II, pp. 5-6,
198-199
(1964); Organic Polymer Chemistry by K. J. Saunders, Chapman and Hall, London,
pp. 323-325 (1973); and Developments in Polyurethanes, Vol. I, J. M. Burst,
ed.,
Applied Science Publishers, pp. 1-76 (1978). However, any active hydrogen
containing compound can be used with the present invention. Examples of such
materials include those selected from the following classes of compositions,
alone or
in admixture: (a) alkylene oxide adducts of polyhydroxyalkanes; (b) alkylene
oxide
adducts of non-reducing sugars and sugar derivatives; (c) alkylene oxide
adducts of
phosphorus and polyphosphorus acids; and (d) alkylene oxide adducts of
polyphenols. Polyols of these types are referred to herein as "base polyols".
Examples of alkylene oxide adducts of polyhydroxyalkanes useful herein are
adducts
of ethylene glycol, propylene glycol, 1,3-dihydroxypropane, 1,4-
dihydroxybutane, and
1,6-dihydroxyhexane, glycerol, 1,2,4-trihydroxybutane, 1,2,6-trihydroxyhexane,
1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, pentaerythritol,
polycaprolactone,
xylitol, arabitol, sorbitol, mannitol, and the like. Examples of alkylene
oxide adducts
of polyhydroxyalkanes are the ethylene oxide adducts of trihydroxyalkanes.
Other
useful adducts include ethylene diannine, glycerin, ammonia, 1,2,3,4-
tetrahydroxy
butane, fructose, and sucrose.
[0041] Also useful are poly(oxypropylene) glycols, triols, tetrols and
hexols and
any of these that are capped with ethylene oxide. These polyols also include
poly(oxypropyleneoxyethylene)polyols. The oxyethylene content conveniently
comprise less than about 80 weight percent of the total polyol weight, or less
than
about 40 weight percent. The ethylene oxide, if used, can be incorporated in
any way
along the polymer chain, for example, as internal blocks, terminal blocks, or
randomly distributed blocks, or any combination thereof.
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[0042] Polyamines, amine-terminated polyols, polymercaptans and other
isocyanate-reactive compounds are also suitable for use with the disclosed
formulations. Polyisocyanate polyaddition active hydrogen containing compounds
(PIPA) are particularly preferred for use with the present invention. PIPA
compounds
are typically the reaction products of TDI and triethanolamine. A method for
preparing PIPA compounds can be found in, for example, U.S. Pat. No.
4,374,209,
issued to Rowlands.
[0043] Another preferred class of polyols are "copolymer polyols", which
are base
polyols containing stably dispersed polymers such as acrylonitrile-styrene
copolymers. Production of these copolymer polyols can be from reaction
mixtures
comprising a variety of other materials, including, for example, catalysts
such as
azobisisobutyro-nitrile; copolymer polyol stabilizers; and chain transfer
agents such
as isopropanol. Polyols comprising natural oils such as soy, sunflower, and
safflower oil can be desirable in combination with standard petroleum based
polyols.
It should be appreciated that such oils can help to offset the overall carbon
footprint
of the product.
[0044] With reference again to FIG.1, the cured polyurethane foam layer 120
is
sandwiched between a backing layer 130 and a laminate face layer 110. To that
end, the backing layer 130 can be any substrate material including woven and
non-
woven textile fabrics, or a combination of woven and non-woven fabrics. In one
aspect, the backing layer comprises a thermoplastic material. Suitable
thermoplastic
materials include, without limitation, asphalt such as natural asphalt,
petroleum
asphalt, polyolefins such as polyethylene, polypropylene, ethylene-propylene
copolymer, ethylene-butene copolymer, olefin-polar monomer copolymers such as
ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, and
chlorinated
polymers such as polyvinyl chloride, and polyethylene chloride. The backing
layer
can comprise woven fabrics, bound fabrics, or nonwoven fabrics prepared from a
suitable material.
[0045] For example, according to some exemplary embodiments, the backing
layer 130 can be a woven or non-woven polymeric scrim material. Exemplary
woven
polymeric scrims can include woven polypropylene primary backing materials.
When
the backing is a woven textile fabric, such as the exemplary woven
polypropylene
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primary backing, the textile can be formed as flat weave comprised of tape
yarns,
spun yarns, or a combination of both tape and spun yarns. Still further,
suitable
woven polypropylene materials can have from 24 to 32 warp threads (threads in
the
longitudinal direction) per inch and from 10 to 22 weft threads (threads drawn
over
and under the warp threads to form the fabric weave) per inch. In an exemplary
preferred embodiment, the woven polymeric fabric comprises 28 warp threads and
weft threads per square inch of fabric. In an alternative preferred
embodiment,
the woven polymeric fabric comprises 28 warp threads and 12 weft threads per
square inch of fabric. An example of a commercially available polypropylene
material
is a (28 x 10) woven polypropylene flat weave S7704 as supplied by Sythetic
Industries (12454 N Highway 27, Chickamauga, Georgia, 30707, U.S.A.)
[0046] As noted, the backing can also be a non-woven textile material.
Exemplary non-woven textile materials include spun-bonded textiles, hydro-
entangled textiles, thermally bonded textiles, wet-laid, melt-blown, air
entangled, and
needle-punched textiles. In still other embodiments, the backing material can
be a
combination of woven and non-woven textile materials. For example, in an
embodiment the backing can be a fleeced woven primary backing material,
whereby
a polymeric woven textile is needle-punched with staple fibers to provide a
fleeced
woven backing material such as a fleeced backing material manufactured by
Propex
Fabrics, Style 4005 (24x10 FLW) (Dalton, GA U.S.A.).
[0047] The backing material can comprise virgin, recycled, waste material,
or a
combination thereof. For example, in a preferred embodiment, the backing
material
can comprise one or more polymeric materials reclaimed from prior manufactured
carpet or other floor covering components. The prior manufactured carpet or
other
floor covering can include post consumer, post commercial, post residential,
post
industrial, manufacturing remnants, quality control failures, and the like.
Such
reclaimed material can be present in the backing material in percentages
ranging
from 0 up to 100%. For example, a backing material can comprise 10%, 20%, 50%,
40%, 60%, 80%, or 100% post residential or post consumer carpet products. In
one
exemplary embodiment, a backing layer comprises at least about 50% reclaimed
material, such as post consumer carpet material, post industrial carpet
material, post
commercial carpet material, or a combination thereof.
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[0048] The backing layer can be any suitable size or weight, depending on
the
desired application of the composite. In some embodiments, the backing layer
has a
weight of about 2 to about 4 ounces per square yard. Exemplary embodiments of
the backing layer include 28 x 10 (10 pic) backings at 3 ounces per square
yard, 28 x
13 (13 pic) backings at 3.5 ounces per square yard, and 28 x 15 (15 pic)
backings at
3.75 ounces per square yard.
[0049] With reference again to composite structure depicted in FIG. 1, the
laminate face layer 110 can similarly be any one of the materials described
above as
suitable for use as the backing material. Alternatively, the laminate face
layer 110
can be any polymeric sheet material, such as a polymeric film. In a preferred
embodiment, the laminate face layer is a high density cross laminated
polyethylene
film such as product "RXHT505" commercially available from Interplast Group (9
Peach Tree Hill Road, Livingston, New Jersey 07039, U.S.A.). In an alternative
embodiment, it is contemplated that the laminate face layer can comprise a
combination of a non-woven or woven textile together with a polymer sheet
material.
For example, the laminate face layer can be a CLAF fabric available from
Atlanta
Nisseki CLAF, Inc. (ANCI) of Kennesaw, Georgia USA. The CLAF fabrics are
generally a cross laminated polyethylene open mesh non-woven fabric which
exhibit
relative high strength in both the machine and cross directions, are
relatively light
weight, exhibit a thin profile, have relatively high tear resistance, and
exhibit
dimensional stability. The CLAF fabric can optionally have good
breathability,
depending on whether or not the fabric has an extruded coating.
[0050] The laminate face layer can have any suitable weight and thickness.
In
some embodiments, the laminate face layer has a weight of from about 0.2
ounces
per square yard to about 1.0 ounce per square yard, including, without
limitation,
laminate face layers having a weight of about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,
and 0.9
ounces per square yard. In a further aspect, a laminate face layer can have a
thickness of from about 1 mil to about 3 mil, including, without limitation,
1.5 mil, 2
mil, and 2.5 mil thickness, although virtually any thickness can be used.
[0051] The composite polyurethane foam structures disclosed herein are
suitable
for use as a detached underlay for use in connection with virtually any floor
covering
application, including without limitation, wood flooring, laminate flooring,
sheet
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resilient flooring, residential carpeting, industrial carpeting, commercial
carpeting,
broadloom carpeting, carpet tiles, tufted carpets, needle-punched carpets,
hand
woven carpets, broadloom carpets, automotive carpets, carpet tiles, and even
area
rugs. Other suitable textiles include fabrics for automotive trim, and
automotive trunk
liners, synthetic playing surfaces, woven polymeric scrim, non woven polymeric
scrim, wall coverings, sheet polymers, furniture covers, and the like.
[0052] Alternatively, the composite polyurethane foam structures are also
suitable
for use as an attached pad wherein the composite structure depicted generally
in
FIG. 1 is integral to a pre-manufactured floor covering. According to this
aspect,
either the backing layer 130 or the laminate face layer 110 can be integral to
or a
component layer of a pre-manufactured floor covering material such as, for
example,
a broadloom carpet or a carpet tile.
[0053] It will be apparent that the composite polyurethane foam structures
exhibit
a number of advantages over foam structures known in the art. In one aspect,
the
composite foam structures can provide improved dimensional stability (i.e.,
the ability
of a material to retain its shape and size) to floor coverings under end-use
conditions.
A flooring underlayment lacking suitable dimensional stability tends to
ripple, buckle,
and can even change in size over time due to changes in temperature, humidity,
high traffic, heavy rolling, and the like. However, the present foam
structures feature
a laminate face layer and a backing layer affixed to the foam layer, which can
provide additional dimensional strength to the foam layer, and thereby provide
additional overall dimensional strength to the composite polyurethane foam
product.
[0054] The composite foam structures can also provide floor coverings and
floor
covering underlayers having improved humidity and moisture resistance.
Humidity
and moisture damage can damage floor coverings and can even lead to other long-
term problems, such as indoor mold. However, a disclosed three-layered
composite
structure provides a substantial barrier around the foam layer (i.e., on the
top and
bottom of the foam layer), thereby substantially preventing water permeability
into
the foam composite from the undersurface and oversurface of the floor
covering.
[0055] It will also be apparent that the present film layers can function
as an
improved slip layer for a composite structure when used as a detached underlay
for
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a floor covering. As opposed to a typical underlay, wherein the foam directly
contacts the bottom surface of the floor covering, the present composites
allow for
separation between the foam and the floor covering. Such a configuration could
be
especially desirable for foams that tend to buckle or ripple in response to
stretching
or movement of a floor covering during installation. Thus, the film layer can
function
as a more frictionless surface, allowing the floor covering to move or stretch
as
needed during installation, without disturbing the underlay.
[0056] The composite structures also provide improved resistance to
tearing,
which can have benefits during installation and during end-uses. For example,
conventional rebond polyurethane foam having no backing layer or laminate face
layer relies purely on the strength of the foam itself to remain stapled or
adhered to
a subfloor, which is often insufficient and results in tearing around or near
the point
of attachment to the subfloor. Such attachment can be achieved by stapling,
applying an adhesive layer, or any other means known in the art. However,
according to the present embodiments, the integrity of the composite product
is
improved by the presence of the more durable backing layer, laminate face
layer, or
the combination thereof, which are themselves more resistant to tearing than
the
foam layer. As a result, the tear and tensile strength of the composite is
substantially
improved relative to a conventional rebond foam having no backing or laminate
face
layer. As a specific example, a typical foam rebond material with a 6.5 lbs.
per cubic
foot density has a tensile strength of about 6.0 lbs, according to the ASTM-
D3574 or
ASTM-D2646 test, whereas tensile strengths greater than 39 lbs. have been
achieved with the present composites. To that end, a foam composite can
exhibit
any desired tensile strength, including, for example, greater than about 6,
10, 15, 20,
30, 40, 45, 50 lbs. as measured by ASTM-D3574 or ASTM-D2646 test. Tongue tear
strength is likewise improved. A typical foam rebond material with a 6.5 lbs.
per
cubic foot density exhibits a tear strength of about 1.265 lbs. whereas tear
strengths
of 28.0 lbs or greater have been achieved with the present composites,
according to
the ASTM-D5117 test. To that end, a foam composite can exhibit any desired
tongue tear strength, including, for example, greater than about 6.5, 7, 10,
12, 15, 20,
22, 25, 30, 35 lbs. as measured by ASTM-D5117.
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[0057] The composite structures can also exhibit unique properties on
opposite
sides of the composite, depending on the choice of backing and laminate face
layer
present on the composite, For example, by using different materials for the
backing
layer and the film layer, each side can exhibit different properties. Such
properties
include, without limitation, slip resistance, water permeability, heat
capacity,
impression and/or compression strength, among others. For example, the
laminate
face layer side of an 8 lbs. per cubic foot density pad, at 7/16 inches in
thickness,
can exhibit a firmness factor, measured as compression force deflection (CFD)
according to the ASTM-D3574 test, of from about 1.4 to about 1.7 lbs. per
square
inch at 25% compression, and 6.0 to 7.0 pounds per square inch at 65%
compression. In contrast, the backing layer side of the same pad can exhibit a
firmness factor of 20 to 40% greater than the firmness factor of the laminate
face
layer side. Exhibiting such dual properties can be useful in a variety of
instances.
For example, a single product can provide an end-user with a choice of
installation,
whereby the user can experience a different firmness factor depending on which
side
of the foam composite is adjacent the flooring. Further, the firmness factors
of
conventional foams are dependant on the density of the foam itself. To that
end,
conventional foams are typically more expensive as the desired density level
increases. However, by exhibiting dual properties, a foam convention as
disclosed
herein can exhibit varying firmness factors without having to increase the
cost to the
consumer.
[0058] In addition and as will be described in more detail in connection
with the
process for manufacture detailed, the pic-count of a material, such as a woven
polypropylene material, can influence the properties (e.g., thickness,
density,
compressibility, etc.) of the foam layer. In general, a material with a
tighter weave
(i.e., materials having very little spacing between warp and weft threads),
with
provide a foam composite with a lower density than a material with a looser
weave,
given that a looser weave allows more gas to escape the uncured polyurethane
foam
composition.
[0059] The present invention further provides a process for manufacturing
the
laminate polyurethane foam pads disclosed and described herein. Generally,
with
reference again to FIG. 1, the process involves applying a foam formulation to
a
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backing layer 130, adjusting the thickness of the foam formulation, and
subsequently
applying a film layer 120 to the foam formulation. Once the film layer is
applied, the
composite is cured to provide a composite as depicted in FIG. 1.
[0060] The foam formulation, as discussed above, can be an uncured
mechanically frothed and chemically blown polyurethane composition. In some
embodiments, it can be preferable to premix all of the components of the foam
formulation except polyisocyanate (and the blowing agent when a gas is used).
The
polyisocyanate and other components, as discussed above, can first be admixed
and then the blowing agent gas can be blended in using, for example, a mixer,
such
as an OAKES FROTHER* (*OAKES FROTHER is a trade designation of the E. T.
Oakes Corporation). Variable speed pumps can be used to transport the separate
components to the mixer. The composition can then be applied to a backing
layer
prior to curing.
[0061] With reference to FIG. 2, a backing material 215 can be conveyed
using a
tenter apparatus (not shown) from a roll 210. The uncured mechanically frothed
and
chemically blown polyurethane composition 220 can be applied to the backing
material 215 from a foam applicator 235. The applied foam formulation can then
be
metered to a desired thickness and uniformity using a blade 225, such as an
air
blade, a knife blade, an extruder blade, or a doctor blade, to provide an
uncured
mechanically frothed and chemically blown polyurethane composition layer 230.
The
film layer 255 can then be applied to the uncured mechanically frothed and
chemically blown polyurethane composition layer 230. Finally, the mechanically
frothed and chemically blown polyurethane layer can be cured in a curing oven
260,
at a temperature of from about 200 F to about 300 F.
[0062] The speed of the process can vary depending on the desired
properties of
the composite and/or manufacturing constraints. In preferred embodiments, the
tenter speed is held at from about 5 feet per minute to about 60 feet per
minute, or
from about 10 feet per minute to about 50 feet per minute, or from about 15
feet per
minute to about 40 feet per minute, or more preferably 25 feet per minute to
45 feet
per minute.
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[0063] The curing step can be carried out in any suitable oven, including,
without
limitation, a single, or multiple pass (including a double, or triple-pass
oven, an
infrared oven, an open flamed oven, and an open flamed forced draft convection
impingement oven, or simply with a heating plate, the selection of which can
depend,
in one aspect, on available space at a manufacturing facility. In a preferred
embodiment, the curing step is carried out in a triple-pass oven, for example,
but
without limitation, a 100 foot triple pass oven.
[0064] As will be apparent, the present composite structures are uniquely
compatible with tenter-based machinery. It should be appreciate that the use
of a
tenting apparatus can provide advantages over using other manufacturing
equipment, including belt-driven machinery. For example, a tenting apparatus
does
not require the use of a belt, which can be costly to maintain and replace,
since the
offline machinery time alone can present substantial economic loss.
[0065] In addition, the versatility of composite structures that can be
produced by
a belt-driven process is limited. With a double belt-driven process, the belts
themselves provide a gas impermeable barrier to the foam layer. The belt
coatings
provide a substantially constant gas impermeability, such that resulting foam
composites have similar densities. To replace such coatings in order to
provide
composites with varying densities would be too costly. In accordance with the
present methods, however, a backing layer and a film layer, as opposed to a
belt,
can provide gas impermeable layers when used with a tenting apparatus. As
discussed above, the backing layer and the film layer can comprise a variety
of
different materials, all with varying levels of gas permeability. Thus,
composite
structures with varying density levels can be provided by simply changing the
properties of the layer and the film layer, without substantially altering
manufacturing
conditions.
[0066] Furthermore, the present methods provide improved heat transfer from
the
curing oven to the foam layer by using a tenter apparatus in combination with
a
three-layer structure. Heat transfer is limited in a belt-driven process by
the heat
transfer capacity of the belts themselves, whereas according to the present
methods,
differing degrees of heat transfer can be accomplished by simply utilizing
different
materials as the backing layer and/or the film layer, as discussed above.
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Examples
[0067] To further illustrate the principles of the present invention, the
following
examples are put forth so as to provide those of ordinary skill in the art
with a
complete disclosure and description of how the various aspects of the
invention
disclosed herein can be made and/or evaluated. They are intended to be purely
exemplary of the invention and are not intended to limit the scope of what the
inventors regard as their invention. Efforts have been made to ensure accuracy
with
respect to numbers (e.g., amounts, temperatures, etc.); however, some errors
and
deviations may have occurred. Unless indicated otherwise, parts are parts by
weight,
temperature is degrees F or is at ambient temperature, and pressure is at or
near
atmospheric or full vacuum.
Example 1: Representative Formulation for Providing a Foam
[0068] Approximately 46 parts of a 10 percent ethylene oxide capped
propylene
oxide polyol having di-hydroxy functionality and a molecular weight of 2,000,
hereinafter referred to as "the Diol;" 46 parts of an ethylene oxide,
propylene oxide
heteropolyol wherein the ratio of ethylene oxide to propylene oxide can be
8:92 and
the polyol has tri-hydroxy functionality and a molecular weight of 3,000; and
8 parts
of diethylene glycol can be admixed. Into this mixture can be further admixed
190
parts calcium carbonate. The admixture can then be mixed and heated to 120 F.
(48.9 C.) and then allowed to cool to 72 F. (22.2 C.) and is hereinafter
referred to
as Mixture A.
[0069] 290 parts of Mixture A can be admixed with: 1.8 parts of 1.25
percent
solution of UL-6* in the Diol; 9 parts of a solution of 20 percent water
dissolved in the
Diol; 7.5 parts of a 20 percent solution of L5614 silicone surfactant*
dissolved in the
Diol; and 73 parts of an MDI prepolymer prepared by reacting a 45:55 mixture
of
dipropylene glycol and tripropylene glycol with MDI and a PMDI having an
isocyanate functionality of 2.3 and a 14 percent o'p'-MDI isomer content,
wherein the
MDI prepolymer has an isocyanate content of 27.5 percent. This admixture is
hereinafter referred to as Mixture B. *(UL-6 is a trade designation of Whitco
Chemical Corp. and is has the chemical name: diisooctylmercaptoacetate; L5614
silicone surfactant is a trade designation of OSI Specialties Inc. and is a
linear
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siloxane--polyoxyalkylene block copolymer having an average molecular weight
of
about 100,00.)
[0070] Mixture B can be frothed using compressed air and an OAKES
FROTHER* (*OAKES FROTHER is a trade designation of the E. T. Oakes
Corporation). The resulting froth has a density of about 422 g/I. The froth
can be
applied to a disclosed carrier using methods known in the art, or disclosed
methods.
Example 2: Manufacture of Polyurethane Foam Composite
[0071] A 10-plc polypropylene flat weave carrier (28 warp x 10 weft) with a
weight
of about 3 ounces per square yard was preheated at from 70 F to 196 F while
being conveyed on a tenter. A mechanically frothed/chemically blown foam
composition, such as those disclosed herein, was applied to the polypropylene
flat
weave. Approximately 39 ounces of foam was applied to each square yard of
carrier
material. The line conveying speed was kept at about 36.7 feet per minute. The
applied foam composition was metered to a thickness of about 120 mils prior to
curing. A polymer film (XF film style RX HT505), from Interplast Group, 9
Peach Tree
Hill Road, Livingston, New Jersey 07039, U.S.A.) was applied to the metered
foam
composition. The resulting pre-composite was cured in a 100 foot triple pass
oven at
a temperature of about 250 F to about 280 F. After curing, the composite had
a
thickness of about 7/16 inches (11.11 millimeters) and a density of about 8
pounds
per cubic foot.
Example 3: Fleece-Foam Composite
[0072] A fleeced-foam composite was prepared as in Example 2, with a 10-pic
fleeced woven carrier (FLW) which comprised about 3 ounches per square yard of
10-pic polypropylene flat weave and about 1.5 ounces per square yard needle-
punched fleece, for a combined carrier weight of about 4.5 ounces per square
yard.
The fleeced carrier was preheated at from 70 F to 196 F while being conveyed
on
a tenter. A mechanically frothed/chemically blown foam composition, such as
those
disclosed herein, was applied to the carrier. Approximately 39 ounces of foam
was
applied to each square yard of carrier material. The line conveying speed was
kept
at about 36.7 feet per minute. The applied foam composition was metered to a
thickness of about 120 mils prior to curing. A polymer film (XF film style RX
HT505),
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from Interplast Group, 9 Peach Tree Hill Road, Livingston, New Jersey 07039,
U.S.A.) was applied to the metered foam composition. The resulting pre-
composite
was cured in a 100 foot triple pass oven at a temperature of about 250 F to
about
280 F. After curing, the composite had a thickness of about 11/32 inches (¨
8.7
millimeters).
Example 4: Tape/Yarn-Foam Composite A
[0073] A foam composite was prepared as in Example 2, using 12-pic (28 x 12
warp-weft) tape and spun yarn polymeric woven backing, having a weight of
about
3.2 ounces per square yard. The backing was preheated at from 70 F to 196 F
while being conveyed on a tenter. A mechanically frothed/chemically blown foam
composition, such as those disclosed herein, was applied to the backing.
Approximately 39 ounces of foam was applied to each square yard of carrier
material.
The line conveying speed was kept at about 36.7 feet per minute. The applied
foam
composition was metered to a thickness of about 120 mils prior to curing. A
polymer
film (XF film style RX HT505), from Interplast Group, 9 Peach Tree Hill Road,
Livingston, New Jersey 07039, U.S.A.) was applied to the metered foam
composition.
The resulting pre-composite was cured in a 100 foot triple pass oven at a
temperature of about 250 F to about 280 F. After curing, the composite had a
thickness of about 4/32 inches (¨ 3.2 millimeters).
Example 5: Tape/Yarn-Foam Composite B
[0074] A foam composite was prepared as in Example 2, using 10-pic (28 x 10
warp-weft) tape and spun yarn polymeric woven backing, having a weight of
about 3
ounces per square yard. The backing was preheated at from 70 F to 196 F
while
being conveyed on a tenter. A mechanically frothed/chemically blown foam
composition, such as those disclosed herein, was applied to the backing.
Approximately 39 ounces of foam was applied to each square yard of carrier
material.
The line conveying speed was kept at about 36.7 feet per minute. The applied
foam
composition was metered to a thickness of about 120 mils prior to curing. A
polymer
film (XF film style RX HT505), from Interplast Group, 9 Peach Tree Hill Road,
Livingston, New Jersey 07039, U.S.A.) was applied to the metered foam
composition.
The resulting pre-composite was cured in a 100 foot triple pass oven at a
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temperature of about 250 F to about 280 F. After curing, the composite had a
thickness of about 7/64 inches (¨ 2.8 millimeters).
[0075] As can be seen from the above Examples, the backing layer and/or the
laminate face layer can affect the density (which is reflected in the
thickness) of the
resulting polyurethane foam. Without wishing to be bound by theory, it is
believed
that as the gas permeability of at least the backing layer and/or the laminate
face
layer decreases, the overall polyurethane foam composite density, reflected in
the
overall composite thickness, decreases since less gas escapes from the
foamable
composition prior to and during curing. For example, as can be seen from
Example
2, a flat weave polypropylene comprised of tape yarns, which is an example of
a
relatively less permeable (i.e., tightly weaved) backing layer, results in a
thicker
product relative to a product having a spun yarn containing backing layer as
in
Examples 4 and 5.
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