Note: Descriptions are shown in the official language in which they were submitted.
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This invention r~lates to ~ethods of making latex foams
and more particularly to a method of ~aking no-gel latex foam free
of any backing material.
No-gel latex foams are ger.~rally made from an aqueous
emulsion or latex of a polymer that is whipped or frothed with a
foaming agent and cured in dry heat as disclosed in Reissue Patent
No. ~7,366. This is in rontrast to sellable foams ~Ihich contain
/ a gélling agent as disclosed in U. S. Patent ~o. 2,706,183 and
I are cured in the presence of s,aturated steam as disclosed in
Csnadian Patent 731,~24.
Although the no-gel latex ~oam froth contains a foam- -
ing agent to maintain the cellular sirllcture of the froth, it
, has been found beneficial to rapidly dehydrate and cure the ~oam
,' froth to help ensure formation of a uniform cell structure in
. 15 the foam product. A relatively rapid dehydration and cure can
i be obtained by simultaneously heating and dehydrating a layer of
' the no-gel latex foam froth through a lower supported sur~ace as -
, well as an upper free surface. To accomplish this the latex
¦ froth layer is supported on a water ~Japor-permeabls foraminous
support means with a vapor-permeable liner disposed between the
froth and t~e support means. The liner~ which can be a fabric
such as nylon, also pernits the no-sel latex ~oam to be easily
remoYed from
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the support means after curing.
During curing of the foam froth the fabric
liner bonds to the latex foam to form an adherent
backing that cannot be separated without causing
damage to the-cured foam. The presence of such a
fabric liner as a backing on the re~ulting foam is
in some instances highly desirable because it pro-
vides a substantial degree of stitch pullout resis-
tance when the foam is covered with an upholstery
material. But the fabric backing can also be an en-
cumbrance since it does not permit unrestricted
stretching of the foam and can cause discomfort in
those applications where the foam is used for cos-
metic padding as in brassieres.
It is thus desirable to provide a no-gel latex
foam that does not have a stretch restraining fabric
liner,
Among the several objects of the invention may
be noted the provision of a novel method for making
no-gel latex foam free of any backing material, and
a novel method of making no-gel latex foam free of
any backing material wherein the cured foam can be
easily releas~d from a foraminous support. Other
objects and features will be in part apparent and
in part pointed out hereinafter.
In accordance with the present in~ention a
foraminous water vapor-permeable supporting means
comprising a backing material is coated with a water
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vapor-permeable release agent, and a ~roth o no-gel polymer
latex is deposited onto the backing material over the release
agent. The release agent prevents the latex fro~h from adhering
to the backing material and thus functions as a parting layer
between the latex foam froth and the backing material. The
release agent also permits water vapor ~o escape from the no-gel
I latex froth through the supporting means. The deposited froth
i is dehydrated and cuxed through its upper free surface as well
I as its lower suppor~ed surface. When the no-gel latex froth
! 10 is fully cured it can be easily removed from the support means
free of any backing material.
i For continuous operation of the disclosed method the
I supporting means can comprise an elongated sheet of backing
¦ material on an endless conveyer belt. For batch operation of
the disclosed method the supporting means can comprise a
peripherally framed foraminous member of finite area.
Regardless of whether the foam is produced continuously
or in batch fashion the resultant product is substantially
smooth and free of congealed polymer skin, and has a soft feel
t 20 and hand at both the upper and lower surfaces. The foam body
has a substantially open cell structure.
i Thus the present invention provides a method for
¦ making no-gel latex foam comprising (a) coating a water vapor
I permeable supporting means with a water vapor permeable water
soluble release agent, comprising a polyethylene glycol polymer
having a molecular weight range of 1,500 to 20,000; (b) deposit-
¦ ing a froth of uncured no-gel latex foam onto the supporting
means over the coating, said no-gel latex froth being prepared
from one or more monomers each of which i5 devoid of pendant
reactive groups; (c) heating-the latex foam froth to dehydrate,
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cure and form the no-gel latex foam; and (d) separating the
fo~m from the supporting means. In a preerred embodiment
the method is provided wherein the supporting means includes
a sheet of water vapor permeable backing material. Most
' preerably, the method is provided wherein the backing material
¦ moves from a 1st location to a 2nd location and during said
¦ movement is in a consecutive fashion continuously coated with
¦ the release agent, continuously receives deposition of the
foam froth over the release agent, and the foam froth is
~ 10 continuously heated to dehydrate, cure and form the no-gel
latex foam in a continuous sheet.
The invention comprises the methods and constructions
hereinafter described, the scope of the invention being
indicated in the following claims.
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In the accompanyingr drawings in which various
embodiments of the invention are illustrated:
Fig. 1 is a simplifled schematic diagram of
an apparatus for carrying out continuous operation
of the present invention;
Figs. 2 through 8 are enlarged sectional
views taken along lines 2-2 through 8-8 respectively
of Fig. l;
Fig. 9 is an enlarged view of the fragmentary
portion 9 in Fig. 7;
Figs. 10 and 11 are enlarged views of the
fragmentary portions 10 and 11 in Fig. 8;
Fig. 12 is a simplified schemati~ diagram of
an apparatus for carrying out batch operation of the
present invention;
Fig. 13 is an enlarged sectional view taken
along the line 13-13 of Fig. 12; and
Fig. 14 is a flow diagram o~ t'ne invention
Corresponding reference characters indicate
corresponding parts throughout the several views of
the drawings.
Referring to the drawings for a detailed de-
scription of the present invention an apparatus for
carrying out continuous operation of the method for
making no-gel latex foam is generally indicated by ;~
reference number 10 in Fig. 1.
The apparatus 10 ihcludes a foraminous sup-
porting means 12 upon which a latex foam froth 14
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is deposited and upon which a release agent 16 is coated
prior to deposition of the latex foam froth 14.
The supportlng means 12 can comprise a water
vapor permeable backing mate~rial 18 di~posed on an endless
conveyor belt 20 driven in a circuitous path. The backlng
~ material 18 i~ formed of a sl~table wo~en or non-woven
; fabric such as Burlington 116 glass fabric manuI~acturedby Burlington Mills, 6135 rayon manuf'actured by Scott
Paper Co. and heat set polyester sheeting manu~actured by
Acme Mills. The bPcking material 18 is permeable to water
vapor, withstands the hot moist conditions prevalent during
` curing o~ the foam froth 14, and can be reused.
The conveyor belt 20, which is also water vapor
permeable can be ~ormed o~ any suitable material such a~
wire mesh, or metal links made by the IaPorte C~mpany. ~he
maximum size of the mesh or link openings is;not critical as
long as the conveyor ade~uately supports the bac~ing material
18 when it is layered with the no-gel latex foam ~ro~h.
- The release agent 16 is pr~erably a wzter soluble
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composition such as Carbowax, a solid ethylene~glycol polymer~
manufactured by Union Carbide and available in molecular
weight ranges of about 1500 to about 20,000. Water solutions
containing blends o~ one or more molecular weights o~ Carbowax
b'~ can be used. The Carbowax is dispensed ont:o the backing
material 18 in any suitable known manner such as from a
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conYentiona:L dispensation vat 22 having a dispensing roller
23.
A pair of metering rolls 24 and 26 coat
or impregns1;e the Carbowax into the backing material
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18. The Carbowax coating is then dried by
heating or evaporat~on (not shown) be~ore being
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covered with the no-gel latex froth 14. If desired the Carbowax
can be applied by spraying or dipping the backing material 18.
While poriions of the Carbowax, during curing of the no-gel
latex foam froth, decompose, sublirne or vaporize with the water
vapor dehydrating from the froth, the Carbowax serves to shield
the backing material 18 from the froth in i.ts adherent state.
A latex designed for use according to the present in-
vent~on is formulated of ingredients set forth in the following
table: :
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Parts by Welght,
Ingredient ~ y_Basis
Neoprene
(Type 60 or 357, DuPont) 100.00
Disodium N-octadecyl sulfosuccinamate
(CYANASOL*18, American Cyanamid) 4.00
Sodium ~exametaphosphate
(CALGON, Calgon Corp.) Q.SO
Dry gr*und nepheline syenite
(MINEX 3, American Syenite Corp.] 50.00
Alumina*trihydrate
(HYDRAL C30BF, Alcoa) 25.00
Antimony Oxide 5.00
Potassium Hydroxide 0.25
Sodium salt of sulfate monoester
of a mixture of various fatty
alcohols, chie~ly lauryl alcohol
(AQUAREX*WAQ, DuPont) 2.00
Alkylated phenol non-staining
antioxidant
(NAUGAWHITE, UNIROYAL Chemical) 1.126
Zinc Oxide 7.50
Sodium polyacrylate
(MODICOL*VD, Nopco Chemical) 0.40
Thiocarbanilide
(A-l, Monsanto) 2.00
Pyrocatechol
(Crown Zellerbach) 1.00
The neoprene latex has the following physical pro-
perties:
Total Solids 60%
pH 10.5
Surface Tension 39 dynes per cm.
Viscosity ~ambient temperature) 350 centipsises
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The latex formulation, without the ~ddition of any
gelling agent, is frothed by a suitable known apparatus
~ such as disclosed in U. ~. Patents 2,695,246, 2,706,108
,r or 2,731,253. The latex froth 14 is then poured or other-
y 5 wise deposited onto the backLng material 18 over the
release agent 16 by a suitab:Le known tra~ersing spout or
nozzle 28 such as disclosed in Canadian Patent 543,005.
A doctoring arrangment can be used~ lf desired, to
facilitate deposition of the latex froth 14 to a uniform
thickness on the backing material 18.
The cell ~tructure o~ the no-gel latex ~roth 14
is not resistant to collapse despite the presence of foam
stabilizers. It is preferable to limit the thickness of
the latex froth layer 14 to about 1-1/4 inches since de~si-
fication, cell collapse and other similar problems become
e~ident in the cured foam when this layer thickness is
exceeded. To minimize the possibility o~ cell collaps~ -
or cell densification the foam froth 14, should be cured
and dehydrated rapidly and as soon as possible after it
has been deposited onto the backing material 18. Howe~er
when the latex foam ~roth 14 is subjected to a rapid cure
cycle small fi~sures or blemishes otherwise known as sur-
face checking (not shown) can form in the foam sur~ace.
This condition is not generally objectionable but can be
-25 substantially eli-minated by preheating the latex froth 14
- before subjecting it to a rapid cure. `!
The preheating is preferably accomplished
by any suitable known means of radiant heat such
as a bank of Calrod heaters 32 (~igs. 1 and 6) near
- 30 the backing material 18, preferably directly aboYe
the latex foam froth 14 immediately be~ore a
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curing area 34. The surface temperature of the no-gel latex
froth is usually about ~0 F before bein~ preheated and about
200 F afta~.~ being preheated by for example, a five foot long
bank of the Ca1rod heaters 32. The surface temperature rise
from 70 F to 200 F can occur in a ~ime duration of about 25
seconds to about 200 5econds depending upon the composition of
the latex, the thickness of the deposited froth layer 14 and
the desired density of the cured no-gel latex foam, all of which
determine the speed of movement of the conveyor belt 20 past the
bank of Calrod heaters 32. For example a neoprene latex froth
one half inch thick is preheated for about 100 seconds. The pre-
heating effects a preliminary dehydration of the no-gel latex
froth 14 to a depth of about 1/16 to 1/8 cf an inch from the
` up~er free surface of the froth. In instances where surface
checking is a tolerable condition in the ~red foam 22 the
préheating step can be eliminated.
The latex froth 14 and the backi~ material 18 are
conveyed by the conveyor belt 20 to the cu~ng area 34 for sub-
jection to substantially dry heat at a tempErature which can
range between about 260 F to about 300 F~ depending upon the
thickness of the deposited froth layer 14, ~he desired density
of the cured foam, the heat tolerance of th~ backing material
18 and the heat tolerance of the release agE~t 16. The no-gel
latex foam froth formulations can be cured a~ temperatures in
excess of 300 F but the Carbowax decomposes at temperatures
exceeding this level.
The cure cycle duration for the no-gel latex foam
froth 14 is essentially dependent upon the ~hickness of the
froth layer and is not generally affected by t~e release agent
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16. For example d neoprene no-gel 1atex froth layer l/2 inch
thick, b~cked by an Acme 424~X polyester sheet, can be dehy-
drated and cured at about 300 F for about 75 minutes. The
release agent 16 which can have a coating density of about
5.40 grams/ft.2 is prepared as follows:
Ingredient Wei~ht Percentage
Water 64.64
Carbowax 4000 21.88
Carbowax 1500 13.13
10~ HQMME in alcohol .35
(Hydroquinone monomethyl ether,
Eastman Chemical)
100.00
The HQ~lME retards decomposition of the Carbowax. The cured
no-gel latex foam layer is chara~erized by the following
properties:
Density 7.4 lbs./ft.3
Compression 26 lbs/50 sq. in. (RMA)
Tensile 5.6 psi ~
Elongation 300% '
Tear .95 lbs/linear inch
Compression Set 10% `
(22 hrs. at 158 F)
~ based on deflected height
: Although any suitable known curing apparatus can be ,-
- used, an open-ended tunnel-type hot air oven schematically in-
dicated by reference number 36 is preferred. A relatively
~ 25 rapid cure is accomplished since the heat applied during cure - ~'
-- causes the froth 14 to dehydrate at its lower supported sur-
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~"~ face through the release agent 16 the backing material 18,
and the conveyor belt 20 as well as at its uppe,r surface as
shown in Fig. 7. A possibility of cell collapse or cell den-
, 30 sification in the cured foam 22 is thus minimized.
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After the cure cycle is completed the cured no-gel
latex foam 3~ is conveyed by the conveyor belt 20 out of the
oven 36 for stripping of the foam from the backing material 18.
The Carbowax tends to slightly adhere the foam 38 to the backing
material 18 when it cools. It is thus preferred to strip the
cured foam 38 from the backing material 18 while the release agent
16 is still hot. However hot neoprene foam is usually tender.
Therefore, to minimize the possibility of damage to the neoprene
during the stripping operation cool air is blo~n onto the upper
foam surface ~not shown~ to toughen it at the separation point.
A residue of the release agent 16 is left on the back-
ing material 18 and on the undersurface of tbe foam at the sep-
- aration point ~Fig. 11~, the residue 16 on the foam surface
usually being an insignificant amount. However cool air can be
blown against the undersurface of the str;pped foam to minimize
any tackiness between overlapplng foam surfaces as where the foam
stock is wound into a roll.
The separated foam 38, if desired, can also be cut,
or otherwise handled in preparation for its intended use.
Some applications of the no-gel latex foam product
include furniture cushions, presser pads in clothes pressing
equipment, automobile trim pads, cosmetic foam, as in brassiers,
and topper pads in mattresses, etc.
In a smilar manner the no-gel latex foam can be formed
in a batch method rather than a continuous method as previously
described. Accordingly in the batch method a supporting means
40 comprises a foraminous plate or wire screen 42 of finite area
bounded by a peripheral frame 4~ of any suitable shape and
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material mounted upon a foraminous conveyor belt 46 similar
to the conveyor 20 (Fig. 14). ~ flange 48 provided around
the frame 44 catches any latex froth 14 overflowing the
com~ines of the frame 44. The foraminous supporting means
40 is covered with a preshaped backing materlal 50 (Fig. 13)
similar to the backing material 18. The backing material
50 is precoated with the release agent 16 in any suitable
previously described manner. The frame 44, prior to use,
is treated with a suitable conventional lubricant or
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A mold release agent such as MR-Z14 manufactured by
.` Green Chemical Products of Illinois. While MR-214
provides acceptable release of the no-gel latex foam
from a metal surface after curing, it does not re-
lease the foam from a textile surface such as the
backing material 18 without causing damage to the
~; foam layer.
A nozzle 52 deposits predetermined amounts of
the latex ioam froth 14 as previously formulated onto
10 the supporting means 40 over the backing material 50
within the confineso~ the of the ~rame 44. The deposited
~roth is doctored, if desired, by a blade 54 and trans-
ported by the conveyor belt 46 into a dry air oven 56
similar to the oven 36. This arrangement permits de-
hydration of the undersurface o~ the latex foam froth
16 through the Carbowax release agent, backing mater-
: ial 50, the wire screen 42 and the conveyor belt 46.
Dehydration also occures at the upper free sur~ace of
the latex foam ~roth 1~. Curing times and temperatures
are as pre~iously described and if desired, the foam
froth can:also be preheated by the Calrod heaters 32
as disclosed.
After curing is completed the cured foam 58
. is removed ~:rom the supporting means 40 for use as is
or it can be tri~med or otherwise handled preparatory
to formation of a finished article. The resultant ~oam
: structure produced by the continuous or batch methods
is character'l~Pd by a so~t hand and feel at the upper
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and lower surfaces which are substantially smooth and
free of congealed polymer skin.
As will be apparent to those skllled in the
art the disclosed methods can be used with various
other no~gel latex formulations. For example latexes
butadiene rubber,
based on styrene-/ natural rubber and blends of
natural rubber can be used to form the no-gel latex
foam froth in accordance with the present invention.
An advantage of the present method for forming
no-gel latex foam is that the resultant product does
not have a backing material and is easily released
from the foraminous supporting means after cure.
Another advantage is the e~onomy of the disclosed
methods since the backing material is reusable.
In view of the above it will be seen that the
- several ob~ects of the invention are achieved and oth-
er advantageous results obtained.
As various changes can be made in the above
methods without departing from the scope of the in-
vention it is intended that all matter contained in
the above description shall be interpreted as illus-
trative and not in a limited sense.
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