Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
RESILIENT COMPOSITE OPEN-CELL FOAM STRUCTURE
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to open-cell resilient
foam materials, and particularly to resilient foam
materials for use as a carpet cushion underlay.
prior Art
One of the outstanding advances in the plastics
industry has been the development of polyurethane foams
which are cellular plastic materials generally formed by
the reaction of long chain polyol compounds and organic
polyisacyanates. Cellular plastics are available in
carious degrees of rigidity, ranging from soft, flexible
foams useful in cushioning, clothing interliners, rug
underlays, sponges and bath mats; semi-.rigid foams, useful
particularly as crash pads; and rigid foams for structural
and insulation purposes. The final properties of the
urethane foams depend principally on the choice of
polyethers, polyesters or other long chain polyhydroxyl
compounds which are converted by the polyisocyanate into a
high molecular weight polymer which is then foamed by a
suitable foaming system, usually a reaction of water with
the free isocyanate content of the polymer, resulting in
the formation of carbon dioxide which expands 'the resin
into the desired cellular plastic. The control of
branching in the reactants permits an extremely wide range
_1_
of properties in the final foamed plastic. The density of
the foam is controlled to a great extent by the amount of
water employed. The configuration of the cell depends
principally on the equivalent weight of the long chain
polyhydroxyl materials favoring tyre production of a closed
cell structure and the higher equivalent weight
polyhydroxyl materials leading to the open-cell structure.
The degree of branching of the polyhydroxyl reactant also
influences the cell character.
The flexible and semi-°rigid foams are processed for
- the aforementioned applications in a manner such that the
foam has a low density, usually from about 1.25 to 4 pounds
per cubic foot, and preferably as low a density as is
consistent with the provisions of a product of adequate
strength, etc. Moreover, such flexible and semi-rigid
foams should have an open-celled structure for most
applications, which is to say that essentially all (i.e.,
at least about 90 per cent), of the cells are
intercommunicating since such a foam configuration is
essential to the realization of acceptable foams for
cushioning, clothing interliners, crash pads or the like.
Rigid foams, in contradistinction, may have varying density
values ranging up to 30 pounds per cubic foot or higher,
and usually have a closed cell structure.
For certain applications, including padding utilized
under carpet, however, it is often desired ~to utilize
. materials other than polyurethanes. Unfortunately,
. however, other polymer systems do not lend themselves
readily to being formed :into open-cell, resilient
structures. Generally, such structures are formed from
latexes containing the desired polymer. The two most
widely used procedures are the so-called Dunlap and 'raladay
foaming methods,
The Dunlap process utilizes a mechanical "foaming
machine°', e.g., the "oakes" foamer or "Firestone" foamer
whereby air is whipped into an aqueous latex compound
(either SBR and/or natural latex). Once frothed, a
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20~~"~03
°'gelling" agent (sodium silicon fluoride, potassium silicon
fluoride and/or ammonium acetate) is introduced to cause
the latex system to coagulate and assume a semi-solid
{putty-like) consistency which can then be subjected to
heat and allowed to cure in order to hold a desired shape.
The Dunlap process will not produce a thick foam structure
on a continuous basis. It is generally used to produce
molded pieces of various thicknesses.
The Taladay method is much like the "Dunlap Process"
except that, instead of using a chemical gelation, it
freezes the foam by introducing carbon dioxide gas into the
system to cause coagulation of the latex. Once coagulated,
the normal curing takes place.
It is almost impossible, however, to produce large or
continuous foamed materials by these methods of a thickness
greater than about 3/8 inch due to the fact that at the
greater thicknesses, the foam cells collapse, causing
uneven gauge and inferior physical properties.
The c~uali~ties of available polymers, however, such as
the compression resistance and flexibility of the synthetic
and natural rubbers, the fire-retardant properties of
polyvinyl chloride, etc., make these systems very desirable
for specific applications, e.g., padding materials,
especially carpet padding or cushion underlay.
Several prior patents disclase polyurethane foam
materials being impregnated with various compositions in
order to obtain changes in particular characteristics of
the polyurethane foam, however, none of these patents,
discussed briefly below, provides an impregnated
polyurethane foam structure having improved properties
wha.ch are particularly useful as an improved padding
material or as a cushion underlay material for use under
carpet.
U.S. Patent No. 4,008,350, issued to crawford et al,
discloses an open-celled polyurethane foam impregnated with
acrylic lances. The use described for this product is for
a lining or padding material for use between the foot or
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~~~~~r~~
leg and a ski boot. As indicated in the specification of
that patent, the resinous acrylic latices retard the
response of the foam to compressive stresses, and slaw the
tendency of the foam to recover to its original dimensions.
As such, the product is not well suited for use as a
padding in certain uses, such as a carpet cushion underlay.
U.S. Patent No. 4,169,184, issued to Pufahl, discloses
a pressure sensitive adhesive structure. The polyurethane
foam disclosed therein is to some extent (approximately
400) open-celled, but it is a high density polyurethane,
ranging from between 20-60 lbs./ft.3. The end product is
made from this high density base foam having a thickness in
the range of 15-35 mils, and is impregnated with a
po,lychloroprene (neoprene) latex. Such a product would not
yield a useful material for a padding such as a carpet
cushion underlay material.
U.S. Patent No. 4,279,953, issued to Sarden et al,
discloses a heat resistant product for use between an
automobile floorboard and the floor carpeting in the
automobile. This product is not intended to be used as a
cushion or padding, nor would it perform particularly well
in such service. This patent teaches the use of
carboxylated styrene-butadiene rubber (SPR) as an
impregnating material, and only the outer surface portions
of a polyurethane foam are impregnated. Carboxylah:ed SBR
imparts little or no resiliency to the final product, and
the less than complete impregnation of the polyurethane
foam provides no substantial improvement in resiliency of
the foam.
U.S. Patent No. 4,288,559, issued to Illger et al
discloses the use of a foam material, preferably a
polyurethane foam, impregnated with a dispersion of
aluminum hydroxide, polyurethane latex and mixing
stabilizers. The end product in this patent is touted as
providing a foam material having increased flame
resistance without impairmewt of the mechanical properties
of the foam. As indicated previously, polyurethane foam
_4_
~~~~~3
has shortcomings in several respects for use as a padding
material and especially as a carpet cushion underlay.
U.S. Patent Nos. 4,547,526 and 4,455,396, issued to
A1-Tabaqchali et al disclose a polyurethane foam
impregnated with an aqueous dispersion of an acrylate and a
flame protection agent which includes an aluminum
trihydrate. Like the Illeger et al patent discussed above,
the products disclosed are directed t:o providing increased
resistance to flame without impairment of the original
mechanical properties of the foam. The use of an acrylate
in the impregnant is indicated as providing better
resistance to aging than a polychloroprene latex would
provide.
U.S. Patent No. 4,239,571, issued to Cobb, is directed
to a polyurethane foam which is impregnated with a liquid
thermosetting resin which is cured while the foam is in
compression. The resulting composite multilayered
. structure is not open-celled and is not sufficiently
resilient for use as a padding material such as a carpet
cushion underlay. U.S. Patent No. 4,157,416, also issued
to Cobb, is directed to a similar process and product
wherein a urethane foam is employed to hold two different
resin systems while they are cured to a rigid phase.
U.S. Patent No. 4,224,374, issued to Priest, discloses
a polyurethane foam substrate impregnated with a
. carboxylated neoprene latex mixture having alumina
trihydrate included for increased fire resistance. Like
the products disclosed in the Illger et al and Al-
Tabaqchali et al patents, the object of impregnating the
foam is to impart fire or flame resistance to the foam
without affecting or impairing the mechanical properties
of the substrate.
U.S. Patent No. 4,260,688, issued to Simon, discloses
yet another approach to flame-proofing a polyurethane foam
without disturbing the physical properties of the foamed
plastic. This patent discloses an impregnant including a
carboxylated vinylidene-butadiene copolymer and aqueous
_5-
ammoniacal combinations of benzenephosphonic acid and
melamine salts.
U.S. Patent No. 4,042,746, issued to tiofer, discloses
a multilayered composite structure having a rigid foam core
member. One or more open-celled, initially resilient
palyurethane foam layers are impregnated with a
thermosetting or polymerizable liquid resin which is cured
under compression with the rigid foam core at the center
and a reinforcing fiberglass layer laminated at an outer
surface. The resulting structure is not resilient, and in
that respect it could not be used as a padding or cushion
material for carpet.
Several U.S. patents disclose processes in which a
foam material is compressed at some point during the .
processing of the foam material into a final product. U.S.
Patent No. 3,867,211, issued to Ghant, involves a process
whereby an open-cell foam sheet has a fibrous layer applied
to at least one side of the sheet, the fibrous layer and
sheet are compressed to allow a thermosetting resin to
impregnate the layer and sheet, and prior to the curing of
the resin in the foam sheet, 'the compression of the sheet
is reduced to permit the foam sheet to expand.
U.S. Patent Nos. 3,193,437 and 3,193,441, both issued
to Schafer, disclose urethane foams impregnated with
polyester resins which are compressed and cured to form
leather-like, non-porous surfaces wherein the thermosetting
resin substantially completely fills the open cells of the
polyurethane foam. The product is disclosed as being
suitable as a substitute for leather in many utiliza~tions,
and 'therefore does not appear to have any substantial
amount of resiliency which is required for a padding
material.
The systems and methods described in the above-
identified patents are found lacking in disclosing an
improved padding material having an impregnated foam
structure especially advantageously used as a carpet
cushion underlay. Further, none of the prior art systems
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CA 02068703 2002-06-27
disclose the impregnation of a foamed material with a solution
containing greater than 80$ solids, and up to 88$ solids. The
preferred ranges in these patents go up to only about 60-65~
solids, and only the Illger et al patent discusses the
possibility of using a solution having up to 80$ solids.
Further, none of the patents noted above disclose a method for
producing a resilient padding material in which the density
and resiliency of the end product are controlled by
compressing the foam carrier while the impregnant sets or is
cured.
SUMMARY OF THE INVENTION
The present invention provides an improved padding
material or carpet cushion underlay having improved mechanical
properties over unimpregnated low-density polyurethane foams
and other latex impregnated polyurethane foams. Further, the
present invention provides an improved padding structure -
having an open-celled polyurethane foam carrier impregnated
with an aqueous or non-aqueous thermosetting or thermoplastic
material which is set or cured while the foam carrier is
maintained under compression, the structure further optionally
having a substrate or scrim bonded thereto by adhesive or by
the dried impregnant. Further, the present invention provides
a method for forming a padding material including impregnating
a foam carrier with an aqueous or non-aqueous thermosetting
resin or thermoplastic material, compressing the foam carrier
by a predetermined amount, and curing the thermosetting or
thermoplastic material while the foam carrier is being held in
compression.
More particularly, the present invention provides a
padding structure especially suitable for use as a carpet
cushion underlay comprising a layer of open-cell, resilient
polyurethane foam material substantially uniformly impregnated
with a fluid
_ 7 _
composition containing a polymer which has been dried
and/or cured after impregnation, while the polyurethane
foam material is under compression, to produce a foamed
substantially open-cell, resilient structure formed
primarily of the polymer wherein the open cells thereof
partially comprise the foam material. The composite
structure further optionally comprises a substrate
laminated to the impregnated foam, the substrate preferably
being a scrim of the type customarily used as a primary
backing for the yarn of a tufted carpet.
The present invention also provides a method of making
a composite structure comprising substantially uniformly
impregnating, with a reverse roll application, for example,
a layer of open-cell, resilient foam material with an
aqueous or non-aqueous thermosetting or thermoplastic
composition, and before the composition is dried or cured,
compressing the foam material to a predetermined percentage
of its original thickness and drying or curing the
composition to produce a foamed, substantially open-cell,
resilient structure of a thickness less than the original
thickness of the foam carrier.
The method permits the material properties to be
varied, for example, the density of the padding material
which is the end product of the method may be increased
without increasing the overall weight of the padding
material by compressing the foam to a greater extent. The
method thus provides wide flexibility in producing padding
for various applications.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an elevational view of a carpet cushion
structure of the invention.
FIG. 2 is a side elevational view of an apparatus
designed to produce a carpet cushion structure in
accordance with the present invention.
FIG. 3 is a cross-sectional view of a carpet cushion
structure of the invention.
_g_
2~~~~~3
FIG, 4 is a side elevational view of an apparatus
designed to produce a cushion structure in accordance with
an alternate method of the present invention.
FIG. 5 is a side elevational view, shown substantially
in schematic form, of the heating and compressing means
employed in accordance with the alternate method of the
present invention.
DETAILED DESCPIPTION OF THE INVENTION
deferring initially to FIG. 1, a composite carpet
padding structure according to the present invention is
indicated generally as numeral 10. Carpet padding
structure 10 preferably comprises a carrier layer or base
foam material I2 which is a conventional, low-density,
open-celled, resilient foamed polyurethane (either
polyester or polyether), and most preferably the foam has a
density of less than about 1.5 lb./cu.ft.
The base foam material 12 is impregnated with a fluid
composition containing a desired polymer, preferably by
using a reverse roll applicator, in a method which will be
discussed in more detail later in the specification.
Preferably the fluid composition employed is a latex (i.e.,
water emulsion), in order that a substantially complete
impregnation or distribution throughout the foamed material
may be achieved.
The fluid composition comprises a polymeric material
compatible with the base foam material and which i.s capable
of suspension in a fluid for impregnation of the open cells
of the foam material, It will be understood by those
skilled in the art that the particular polymer selected
will depend upon the properties desired in the final
composite structure and application to which it is to be
put. Illustrative but not limitative of such polymers are
synthetic rubbers such as the styrene-butadiene copolymers,
acrylonitrile-butadiene-styrene terpolymers, etc.; natural
rubbers; acrylic and methacrylic polymer and polymers;
polyvinyl chloride or combination of these polymers.
_g_
In add ition, suitable conventional fillers (e. g.,
mineral fillers, calcium carbonates, alumina hydrate,
barytes, limestone, talc, etc.), coloring agents, curing
agents, or other adjuvants may be incorporated in the fluid
polymer composition prior to impregnation.
I~t has been determined in accordance with a first
embodiment of the present invention, directed primarily to
a carpet cushion underlay or padding, that the preferred
thermoplastic polymers for use in the latex are styrene-
butadiene rubber (SBR) in cold or non-carboxylated form,
natural rubber, or a combination of the two. The term
°°cold SBR", which is commonly used and well known in the
art, refers to a styrene-butadiene copolymer which is
cross-linked or cured with sulfur. When used to impregnate
a low density, open-celled polyurethane foam, the above-
identified preferred thermoplastic polymers yield a cushion
or padding end product, especially well-suited for' use as a
carpet padding, having substantially improved physical
properties, including compression resistance, resilience
and resistance to shear force or tearing . Instead of
retaining the mechanical properties of the base foam, as
appears to be the result in most of the prior art
impregnated foam systems, the mechanical properties of the
impregnated foam according to the preferred embodiment more
closely approximate those of a foamed product made of the
polymer contained in the latex. Thus, the foam base
material 12 may be considered a "carrier°° for the polymer
latex, providing a matrix around which the latex may be
dried into final form.
The composite carpet cushion structure 10 also
preferably has at least one substrate layer 14 laminated
thereto in the manufacturing process. Substrate 14 may be
made of one of several types of, suitable material, and is
preferably a woven scrim of the type conventionally used as
a primary backing for tufted carpet. One suitable
substrate is manufactured by Amoco, and sold, under 'the
registered 'trademark °'Action-Bac". Other woven, non-woven
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or porous sheet materials may also be suitable for use as
the substrate, examples of which include acrylics,
polypropylene, nylon, cellulose, lute, or woven or non-
woven fiberglass, having a density of approximately one
half to 4 ounces per sguare yard. The substrate 14 serves
to further improve the mechanical properties of 'the
impregnated foam structure, providing increased dimensional
stability, improved distribution of compressive forces over
. a wider area, and further improves resistance to tearing of
the padding material. The latter of these is especially
important in carpet padding which is to be secured to a
flooring surface with adhesive. The improved resistance to
tearing evidenced in the padding of the present invention
facilitates the complete removal of such padding (e.g., for
replacement) with reduced chances that the padding will
tear at the locations where the padding has been adhered to
the flooring surface. Substrates may be used on both the
upper and lower surfaces of the carpet cushion structure
10, to provide a lower surface for bonding to the flooring
and an upper surface facilitating the ability of the carpet
to slide across the surface.
Referring now to FIG. 2, a substantially diagrammatic
side elevation view is depicted of an apparatus 16 used to
produce the composite carpet padding structure of the
present invention. The polymer latex is preferably applied
in the present invention using a reverse roll applicator.
The open-celled polyurethane foam base material 12' is fed
from a roll 18 over rubber backing roll 20. Transfer roll
22 and metering roll 24 coact to load transfer roll 22 with
a predetermined amount of the polymer latex 26 from coating
dam 28, the polymer latex being applied to the polyurethane
foam 12' as the foam passes through a nip between transfer
roll 22 and rubber backing roll 20. Both transfer roll 22
and metering roll 24 are provided with doctor blades 30
which act to prevent excessive buildup of the polymer
latex. It is to be noted with respect to FIG. 2 that the
_11_
2~~~W~
arrows are included to indicate direction of travel of the
sheets and rollers.
After the polymer latex has been applied to the
polyurethane foam material, the sheet 12' is passed between
a pair of squeeze rolls 32, 34 which compress the foam and
force the latex to fully penetrate and impregnate the
entire thickness of the foam sheet 12'. The foam sheet is
then passed, prior to the drying stage, between a pair of
laminating rolls 36, 38 a~t which point a laminate substrate
14' is contacted with the foam sheet on one surface
thereof.
The laminate substrate 14' is itself fed from a roll
40, preferably across an adhesive applicator roll 42, and
brought into contact with a lower surface of impregnated
25 foam sheet 12' at laminating rolls 35, 38. The foam sheet
and substrate are pressed together between rolls 36 and 38,
and the polymer latex, which has not yet dried, i:~ pressed
between the fibers of the substrate and the latex
substantially coats the fibers as well. The composite
carpet cushion structure is then passed through a heater 44
to evaporate 'the water from the latex in forming the final
product.
It should be noted that, although the process is
described as including the application of adhesive 'to the
substrate prior to contacting 'the foam sheet material, the
latex itself may provide sufficient bonding between the
foam and the substrate for certain substrates and for
certain anticipated uses. In these instances, 'the
application of the adhesive to the substrate may be
omitted.
The impregnated foam portion of the end product 10 is
shown in cross-section in FIG. 3. There it can be seen
that the interior walls 50 of the open cells 52 of the foam
are coated with 'the impregnant composition 54 according to
the present invention. It will be understood by those
skilled in the art that the compositian of the fluid
~12~
2~f~~~~~3
polymer may be adjusted to control the density of the final
composite structure.
The composite carpet cushion product preferably should
employ a foam material 12 having a thickness in the range
of approximately 80 to 550 mils. When such a foam is
impregnated with the cold styrene-butadiene polymer,
natural rubber, or combination of the two, a carpet padding
having highly desirable properties, such as resiliency over
an extended period of time, is produced.
This preferred embodiment of the present invention is
illustrated by the following non-limiting examples.
EXAMPLE 1
A flexible, light-weight (less than 1 lb./cubic ft.
density) open-celled urethane foam layer having a thickness
of about 0.5 in. is saturated with a previously prepared
latex composition containing 22.5%, by weight, of cold
styrene-butadiene rubber. Calcium carbonate, silicates,
barytes, aluminum trihydrates, etc., ar a combination of
fillers, at.levels of 1 - 1000 parts based an 100 parts of
dry polymers in the system, curing system (as shown),
antioxidant (alkylated phenol), and soap (potassium
olea.te) are alsr~ added. The latex composition containing
80% scalids is applied to the flexible urethane foam using
the reverse roll appI:ic:~tor and squeeze rolls shown by Fig.
2 to uniformly dispense (saturate) the latex throughout the
flexible urethane foam. The saturated foam is carried on
an endless open mesh belt into a curing oven having
vertical air flow and a temperature from 120° F. to 550° F.
to dry and cure the saturated urethane foam. The resultant
flexible uniform cell structure foam exhibits all the
qualities of the latex polymer compound product which was
used to saturate the urethane foam.
'fhe use of the light-weight urethane flexible foam
only as a carrier and cell structure controller allows a
cellular product to be made from most aqueous polymers of
fluid compounds which heretofore could not easily be formed
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into foamed structures. The density of the product may be
varied between about 1.5 and 40 lbs. per cubic foot.
Thicknesses 0.0675 inch to 4.00 inches may also be
obtained. In particular., when cold or non-carboxylated
styrene-butadiene rubber, natural rubber, or a combination
of these t.wo is employed in impregnating a foam layer
between 80 and 650 mils in thickness, the cushion structure
produced will have desirable physical properties for carpet
underlay service, namely improved compression set, improved
compression resistance, and improved resistance to tearing.
FIG. 3 depicts the foamed structure 10 produced by
Example 1.
EXAMPLE 2
The procedure of Example 1 was followed utilizing the
materials and process parameters set forth below.
Dry Wet
70% Cold SBR Latex 100.00 142.86
Water Ta adjust composition
to 80% total solids
20% Potassium 0leate 3.00 15.00
Calcium Carbonate 250.00 250.00
Use polyacrylate thickener to adjust viscosity
to 1500-3000 CPS.
Add cure system prior to use.
CURE SYSTEM
Drv Wet
50% Antioxident 1.50 3.00
(Alkylated Phenols)
60% Zinc Oxide Dispersion 2.00 2.83
60% Sulfur Dispersion 1.70 2.83
50% Zinc Diethyl
Thiocarbamate Dispersion 1.00 2.00
50% ZMBT Dispersion 1.80 3.60
-14--
~~6~'~fl3
(Zinc Mercapto Benzyl Thiozole)
EXAMPLE 3
Two carpet padding samples of different density were
produced in accordance with Examples 1 and 2 of the present
invention, and were tested to measure properties of
particular importance for products used in carpet underlay
service.
Sample CPS-20
Weight 49.1 ounces per sq.yd.
Density 16.1 lbs. per cu. ft.
Thickness 0.255 in.
Aging (Heat) Pass
(24 hrs./275~ F.)
Compression Set
(22 hrs./158o F.)
30 min. recovery/70o F. 23.70
6 hr. recovery/70o F. 13,2%
Compression Resistance
(25% deflection) 5 lbs, per sq.in.
Tensile Strength
Length 86.8 lbs. force
Width 94.4 lbs, force
Percent Elongation
hength 20.7
Width 31.3n
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2~~~~~3
Sample CPS-35
Weight 81.1 ounces per sq.yd.
Density 29.6 lbs. per cu. ft.
Thickness 0.228 in.
Aging (Heat) Pass
(24 hrs./275° F.)
Compression Set
(22 hrs./158° F.)
30 min. recovery/70° F. 250
6 hr. recovery/70° F. 19.50
Compression Resistance
(25% deflection) 20 lbs. per sq.in.
FIGS. 4 and 5 are directed to an alternative padding
or cushion material and a method for making the padding or
cushion material in accordance with the present invention.
This padding material employs an open-cell foam carrier,
preferably a polyurethane foam carrier 112 as in the
previous embodiment, however, the impregnant in this
embodiment may be aqueous (latex) or non-aqueous, and may
employ a thermosetting resin or thermoplastic polymer
composition.
FIG. 4 is a substantially digrammatic representation
of an apparatus 116 which is, for the mast part, identical
to that of FIG. 2. The desired impregnawt 126 is
preferably applied using a reverse-roll applicator,
particularly when the selected impregnawt is a polymer
latex. carious other methods of applying the impregnant to
-16-
~0~~"~1~3
the foam carrier may be employed with substantial::)
equal
effectiveness. The open-celled polyurethane foam case
material 112 is fed from a roll 118 over rubber backing
roil 120. Transfer roll 122 and metering roll 124 C03ct
t0
load transfer roll 122 with a predetermined amount
of the
impregnant 126 from coating dam 128, 'the impregnant
being
applied to the polyurethane foam 112 as the foam passes
through a nip between transfer roll :122 and rubber
backing
roll 120. Both transfer roll 122 and metering roll
124 are
provided with doctor blades 130, which act to prevent
excessive buildup of the impregnant 126 on the rolls.
The
arrows included in FIG. 4 are provided to show the
direction of travel of the sheets and rollers.
After the impregnant 126 has been applied to the
polyurethane foam material, the sheet 112 may be passed
between a pair of squeeze rolls 132, 134 which temporarily
compress the foam and force the impregnant to fully
penetrate and impregnate the e:nti.r~e thickness of
foam sheet
. 1.22 The= foa.~ sheet mar ~tF~ea~ be passed between
a pair of
laminating rolls 136, 138, at which point a laminate
substrate 3.14 is contacted with the foam sheet on
one
surface thereof.
'rhe laminate substrate 114 is itself fed from a roll
140, preferably across an adhesive applicator roll
142, and
brought into contact with a lower surface of impregnated
foam sheet 112 at laminating rolls 136, 138. The foam
sheet and substrate are pressed together between rolls
136
and 138, and the impregnant 126, which has preferably
not
-17-
completely dried or cured, is pressed between the fibers of
the substrate, thereby coata.ng the fibers as well.
It should be noted that, although the process is
described as including the application of adhesive to the
substrate prior to contacting the foam sheet material, the
impregnant itself may provide sufficient bonding between
the foam and the substrate for certain substrates and for
certain anticipated uses. In these instances, the
application of the adhesive to the substrate may be
omitted.
It should also be noted that the padding structure may
be produced having a substrate adhered to both the upper
and lower surfaces, as will be evident to those skilled in
the art upon reading the present specification. Further,
the padding material may be produced without having any
substrate adhered thereto, in which case the portions of
the apparatus employed in applying the substrate may be
either idled or omitted from the apparatus entirely.
In accordance with the alternative embodiment of the
present invention, the impregnated foam sheet material is
crushed or compressed during at least a final portion of
the drying or curing of the impregnant 126, such that the
resulting composite open-cell foam product is of a reduced
thickness as compared with the original thickness o:E the
foam carrier 112. In the preferred embodiment of the
present ,invention, this is accomplished by first passing
the impregnated foam carrier through a heater 144, and
subsequently passing the foam carrier through thickness
°-18
~OG8~03
reduction means 150, depicted in FIGS. 4 and 5 as a pair of
endless belt assemblies 152 disposed on opposite sides of
the foam carrier 112 and spaced apart at a predetermined
distance substantially equal to the desired thickness of
the final padding material to be produced. It is possible
to use alternate means for compressing the impregnated
foam, for example, using one or more pairs of squeeze knips
similar to laminate rolls 136, 138.
In the somewhat more detailed view of FIG. 5, it can
be seen that each endless belt assembly 152 comprises at
least a first and a second roll 154, 156, having an endless
belt 158 extending around the rolls. At least ono of the
rolls of each belt assembly will preferably be powered or
driven, for example by a drive motor, in a manner well
known in the art. The facing surfaces of the belts 158 are
spaced apart at a predetermined desired distance, which
distance is preferably adjustable by using suitable
adjustment means disposed on the apparatus, the spacing
distance between the belts being substantially equal to the
desired end thickness of the padding material produced in
accordance with this embodiment of the invention.
After the foam carrier 112 has been saturated or
impregnated with the impregnant 126, the foam carrier is
heated, as for example, by heater 144, which may be an air-
circulating oven. The temperature to which the foam
carrier/impregnant will be heated will vary depending upon
the type of polymer employed in the impregnant. Generally,
in the case of thermoplastic polymers, the foam
_1g_
carrier/impregnant will be heated to or slightly above the
'thermoplastic temperature of the particular thermoplastic
polymer employed. Tn the case of thermosetting resins,
the foam carrier/impregnant will be heated to a temperature
just under the thermosetting temperature of the particular
thermosetting polymer employed. Again, a heater 144, such
as an air-circulating oven would be suitable for this
purpose.
Upon heating to the appropriate temperature as set
forth above, the foam carrier/impregnant is introduced into
the thickness reduction means 150, to crush or compress the
foam carrier to a desired final thickness. In the
situation where a thermoplastic impregnant is used, the
temperature of the foam carrier and impregnant is
preferably maintained until drying or curing is completed,
and the temperature is then reduced to a temperature below
the thermoplastic temperature while the foam carrier is
maintained in the state of reduced thickness. After the
impregnant is cooled below the thermoplastic temperature,
the thermoplastic polymer will no longer be in a softened,
moldable state and the influence of thickness reduction
means on the foam carrier may then be removed, either by
removing the thickness reduction means or by permitting 'the
foam carrier to exit from 'the thickness .reduction means, as
seen, for example, in ~'I~. 5. The dried or cured
impregnant serves to freeze the finished product at
substantially the 'thickness to which the foam
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carrier/impregnant was reduced in the thickness reduction
means.
It should be recognized that when a thermoplastic
material is employed as the impregnant/saturant, the
crushing to the desired finished thickness may be done
either at the time of the initial impregnation, as in the
FIG. 4 apparatus configuration, or may be done at some
later time by reheating tkie composite structure to a
temperature above the thermoplastic temperature, which
softens the thermoplastic polymer and permits the composite
structure to be deformed plastically in the sense 'that once
the foam carrier/impregnant is again subsequently cooled
below the thermoplastic temperature, the product will be
"frozen" into a configuration having the reduced thickness.
In the situation where a thermosetting material is
employed as the impregnant, the foam carrierjimpregnant is
introduced into the thickness reduction means 150 at a
temperature lower than, and preferably just below, 'the
thermosetting temperature. While the foam
carrier/impregnawt is maintained at a reduced thickness,
the temperature of the foam carrier is. raised to and held
at the thermosetting temperature until thermosetting takes
place in the impregnant. As shown in broken lines in FIG.
5, a separate heater 160 disposed at the location of 'the
thickness reduction means may be used to boast the
temperature of the foam carrier/impregnant to a temperature
at which thermosetting will oCClar. Alternatively, a single
heating means could be used to .replace both heater 1h~ and
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heater 160, and the thickness re:~~u-.:r. i ~~:a ~ ~~a ~ ~d be at
least partially disposed inside t:h~_~ ~:..rag:..F> ;aaY_ .~ means
beginning at a point where the tG:;~yc:r~.tur~> >>:f .~:~.-: foam
carrier/impregnant is just belo4: the t~exmc~.~:et :mperature.
As the crushed foam carrier 112 pr:~e~prssst s ;. nr:evh the
heater, the temperature will be raised to a te~;;~arature
above the thermosetting temperature to .induc:e t~:ermose~t in
the impregnant.
Once thermosetting of the impregnant has taken place,
the impregnant will hold the foam carrier in its crushed
(reduced thickness) configuration. The influen:c~ of the
thickness reduction means may then be removed, and no
further flowing of the ampregnant will take place. A
finished product will thus be produced having sunstantially
'the same thickness as that to which the foam carrier has
been reduced in the thickness reduction means.
The thermoplastic or thermosetting temperatures of the
various impregnants which may be used in the met~ZOd of the
,, present invention will be, for the most part, well known to
t~xose of ordinary skill in the art. However, even if the
relevant (i..e., thermoplastic ax thermosetting) temperature
of an impregnant desired to be used is not known at the
outset, fihe te~rperature may be determined in a relatively
straightforward manner by known methods.
As noted earlier, the impregnant 126 to be used in
producing an open-cell foam structure according to this
'. alternative preferred embodiment may be either aqueous
. (water based, latex) or non-aqueous, and may contain either
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a thermosetting resin or polymer, or a thermoplastic
polymer. Examples of preferred impregnants, which examples
are to be non-limiting in nature, are: synthetic rubbers
such as styrene-butadiene copolymers, acrylonitrile-
butadiene-styrene terpolymers, and other synthetic rubbers,
acrylic and methacrylic polymer and polymers, polyvinyl
chloride, PVAC, vinyl acetate, and polypropylene.
The foam structure which is the end product of the
alternate method preferably remains open-celled, in that
the foam carrier is preferably not crushed or compressed to
the extent that the impregnant completely fills all of the
voids in the open cells of the foam carrier as the finished
product loses a great deal if not all of its resiliency at
that point. Instead, compression or crushing of the foam
carrier will preferably produce an end product having a
thicker "coating" of the impregnant on the cell walls of
the foam carrier as compared to the coating present on the
open cell foam structure of the first disclosed embodiment,
which is cured or dried in an uncompressed state. The
range of crushing or compressing of the foam carrier into
an end product, set forth as a percentage of the original
foam carrier thickness, may be from about l0% to 90%, and a
preferred range will be from about 25% to 75%. The
original thickness of the polyurethane foam carrier 112 may
be any desired thickness up to about four inches, arid even
'thicker assuming substantially complete impregnation
through the thickness of the material can be achieved.
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Another parameter meriting consideration in practicing
the method for producing a compressed open-cell foam
structure having the mechanical and physical properties of
the impregnant, as opposed to the polyurethane foam
carrier, is the weight ratio of the material "added on" to
the foam carrier with respect to the total weight of the
end product. In this preferred embodiment, the add-on
material preferably constitutes from about 15% to about
99% of the total weight.
The composite open-cell structure produced by 'this
alternate preferred method may advantageously be used as a
padding material, with the amount of resiliency being
controlled to some extent by the percentage reduction in
thickness of the structure from the original 'thickness of
the foam carrier. Properties such as resiliency and the
properties identified in the examples presented directed to
the first embodiment may be varied without changing the
composition of 'the impregnant by instead changing the
amount by which the thickness of the structure is reduced.
The composite open-cell foam structure will have various
uses, such as carpet padding or underlay, or as padding or
cushioning used in bedding products, shoe foam, and other
cushioning products.
The composite structure, when used as a carpet
underlay, may advantageously be used as a padded backing
for °'carpet tiles°', which are square (or any other shape)
sections of carpet product now enjoying widespread use in
commercial applications, especially in high-rise buildings.
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2~6~~~~
The installation of these carpet section is done in a
manner similar to ceramic or linoleum tiles in that the
sections are laid next to one another to collectively form
a floor covering having a particular pattern.
While the composite open cell foam structure of the
present invention has been described above with respect to
preferred embodiments, it will be recognized by those
skilled in the art that variations and modifications may be
made without departing from the spirit and scope of the
present invention. The scope of protection is therefore to
be determined by reference to the appended claims.
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