Note: Descriptions are shown in the official language in which they were submitted.
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
STORAGE STABLE, FOAMABLE, SINGLE LATEX/EPOXY EMULSION
The invention relates to a novel single latex/epoxy emulsion.
Latex foam is a well known material. The latex is in the form of an emulsion
when
delivered to an end user. In certain applications, the emulsion is employed in
the
manufacture of flooring, wall covering, shoe lining and non-woven materials.
The end user
may add fillers to enhance desired properties prior to coating a given
substrate with a foam
layer made from the emulsion. Since products may be stored for extended
periods of time,
stable emulsions would be highly desirable. Previous attempts to provide
stable emulsions
required use of curing pastes, gelling agents, accelerators or stabilizers.
Latex emulsions
that are stable and that do not require such curing pastes, gelling agents,
accelerators or
stabilizers would be highly desirable. Especially desirable are latex
emulsions that will
cross-link in the backing process to ensure final end properties have
sufficient strength.
The present invention provides a solution to one or more of the disadvantages
and
deficiencies described above.
In one broad respect, this invention is an emulsion comprising a latex and an
epoxy
compound. The latex is preferably a carboxylated styrene-butadiene polymer
with a
bimodal particle size. The composition may also contain stabilizing
surfactants as the cross-
linking agent to improve physical properties of the resulting foam. The
composition may
employ a dual catalyst system. Furthermore, the composition may include
performance
enhancing additives, such as paraffin wax and silicone detackifier.
Advantageously, the
latex emulsion may be supplied to the point of manufacture where inorganic or
organic
filler can be added to enhance desired properties. More advantageously, no
additional
curing pastes, gelling agents, accelerators or stabilizers are required in the
practice of this
invention. The emulsion, in one non-limiting embodiment, is stable for twelve
months at
ambient temperatures. During processing, the resulting foam will cross-link in
the backing
process to improve final end properties such that the product has sufficient
strength.
Beneficially, this invention provides a simplified manufacturing process and
need not
employ any heavy metals, sulfur or nitrosamine releasing accelerators which
are
conventionally used for making such foams.
In another broad aspect, this invention is a process useful for forming an
article of
manufacture comprising applying a foam to a substrate wherein the foam is
formed from a
composition comprising a bimodal latex and an epoxy emulsion. In yet another
broad sense,
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
this invention is a process useful for forming a composition useful for
preparing a latex
foam, comprising: combining a bimodal latex and an epoxy emulsion.
The bimodal latexes used in this invention may be characterized as having two
separate and distinct particle size distributions have high solids content,
good high shear
rheology and good low shear viscosity. The large size polymer particles of the
bimodal latex
have a heterogeneous character.
The bimodal latex used in this invention may comprise a proportion of large
size
latex particles and a proportion of small size latex particles. It is
desirable to employ large
size particles whose diameter is in the range of from 2.5 to 10, most
preferably from 3 to
4, times that diameter of the small size particles. It is also desirable that
the weight
percentage of large size particles in the latex formulation exceed the weight
percentage of
the small size particles. For example, a latex composition comprised
substantially of
styrene/butadiene comprising from 50 to 98, preferably from 60 to 80, weight
percent
large size particles and from 2 to 50, preferably from 20 to 40, weight
percent small size
particles can be used. It is understood that the proportion of large size
particles and the
proportion of small size particles, the size distribution of particles, and
the amount of solids
in the formulation employed can depend on the particular latex which is
employed and/or
the particular coating device which is employed.
"The large size latex particles can vary in size from 1500 A (0.15
micrometers) to
10,000 A ( 1 micrometer), more preferably from 1800 A (0.18 micrometers) to
3,000 A (0.3
micrometers) in diameter. The small size latex particle can vary in size from
S00 A (0.05
micrometers) to 1000 A (0.1 micrometers) , more preferably from 600 A (0.06
micrometers)
to 800 A (0.08 micrometers) in diameter."
Heterogeneous polymer particles may be employed in the practice of this
invention
to provide the large size polymer particles of the bimodal latex. Of
particular interest are the
types of polymer particles disclosed in U.S. Pat. No. 4,134,872. That is, the
heterogeneous
polymer particles are characterized as having a hard resinous polymer of
interpolymer
forming a core or core-type region, and a soft preferably interpolymer shell
or shell-type
region. Also useful herein are the coalescence capable heterogeneous polymer
particles,
which particles have hard core or core-type regions and soft shell or shell-
type regions.
Broadly speaking, the large size heterogeneous polymer particles have a
relatively
soft polymer domain and a relatively hard polymer domain. It is believed that
the hard
polymer domain provides a desirable gloss characteristic to the coating
formulation; while
2
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
the soft, deformable polymer domain provides a desirable binding
characteristic to the
coating formulation.
The heterogeneous polymer particles typically comprise from 10 to 90,
preferably
40 to 75 weight percent of a hard polymer domain, and 10 to 90, preferably 25
to 60
weight percent of a soft polymer domain. Generally, the hard polymer domain
comprises
from 80 to 100 weight percent types of monomers (for example, monovinylidene
aromatic
monomers) which form a hard component of the hard polymer domain when
polymerized;
from 0 to 20 weight percent, preferably from 10 to 20 weight percent monomers
such as
open chain aliphatic conjugated dime monomers or other such monomers which
when
polymerized provide a softening character to the hard domain; and from 0 to
10, preferably
0.5 to 5 weight percent of a hydrophilic, hydrolyzable or ionizable monomer
such as acrylic
acid. Generally, the soft polymer domain comprises from 30 to 70, preferably
40 to 60
weight percent of a monoethylenically unsaturated monomer which (for example,
a
monomer which can form a hard component of the polymer domain such as a
monovinylidene aromatic monomer, or a monomer which can form a soft component
of the
soft polymer domain such as an acrylate monomer, or a combination thereof);
from 70 to
30, preferably from 60 to 40 weight percent of a soft monomer such as a
conjugated open
chain dime; and from 0.1 to 10, preferably 2 to 6 weight percent of a
hydrophilic,
hydrolyzable or ionizable monomer. Typically, the minimum film formation
temperature of
the latex composition is less than about 30°C. Preferred heterogeneous
polymer particles
comprise carboxylated monovinylidene/conjugated dime containing polymer
particles. For
example, carboxylated styrene/butadiene containing polymer particles having a
heterogeneous character are particularly useful.
The small size polymer particles of this invention are prepared from
combinations of
monomers such that the resulting particles have sufficient adhesive properties
for foam
coating applications, such as for application to a backing material to provide
for example a
resilient foam backing layer which is adhered to a second structure, the
second structure
being the subst-rate for the foam layer. Virtually any latex that can be used
as a foam
coating and can be prepared for use in a bimodal composition can be employed.
It is also
desirable that the latex be carboxylated in order to increase colloidal
stability and, hence,
the degree of binding efficiency to the paper and pigments. Examples of
suitable monomers
for providing a carboxylate character include acrylic acid, methacrylic acid,
itaconic acid
and fumaric acid. Typically, the minimum film formation temperature of the
latex
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
composition is less than about 25~ C. Representative monomers useful in
preparing the
latexes of this invention and methods for preparing the individual separate
particles are
described in U.S. Pat. Nos. 3,404,116 and 3,399,080. Examples of monomers
suitable for
preparing the latexes of this invention can include the olefins such as
ethylene and
propylene, vinyl acetate, alkyl acrylates, hydroxyalkyl acrylates, alkyl
methacrylates,
hydroxyalkyl methacrylates, acrylamide, n-methyloylacrylamides, as well as
monomers
such as vinyl chloride and vinylidene chloride. Especially preferred latexes
include
modified styrene/butadiene latexes such as, for example,
styrene/butadiene/acrylic acid,
styrene/butadiene/acrylic acid/itaconic acid, styrene/butadiene/vinylidene
chloride,
styrene/butadiene/beta-hydroxyethyl acrylate, styrene/butadiene/beta-
hydroxyethylacrylate/acrylic acid, styrene/n-butylacrylate/acrylic acid,
methyl
methacrylate/n-butylacrylate/acrylic acid, vinyl acetate/acrylic acid, vinyl
acetate/n-
buty!acrylate/acrylic acid, and/or styrene/n-butyl acrylate/butadiene/acrylic
acid. Mixtures
of carboxylic acids can be employed in the aforementioned latexes.
In the preparation of the small particle size polymer latexes, it is desirable
to use a
relatively small polymer particle (for example, a "seed" latex) in initiating
particle
formation. The latexes having separate and distinct particle sizes are then
blended together
to yield a bimodal latex composition. Alternatively, bimodal latexes can be
prepared by
intermediate addition of a seed latex during the heterogeneous particle
emulsion
polymerization process. For example, the core domain of the large size
particle can be
prepared, and either simultaneously to or after the shell domain of the large
size particle is
formed, the seed latex can be added in order to provide large size
heterogeneous polymer
particles having a hard core domain and a soft shell domain, and small size
polymer
particles having a soft character which is similar to that shell character of
the large size
particles. Any of the latex formulations can be concentrated, if desired.
In the practice of this invention, it is preferred to employ carboxylated
latex
comprised of a copolymer of a vinyl aromatic monomer and an unsaturated
carboxylic acid
monomer. In a preferred form, the copolymer may further comprise a dime
monomer.
The vinyl aromatic monomer may be selected from styrene, alpha-methylstyrene,
a,r-
methylstyrene, a,r-ethylstyrene, alpha-a,r-dimethylstyrene, a,r,a,r-
dimethylstyrene, a,r-t-
butylstyrene, vinylnaphthalene, methoxystyrene, cyanostyrene; acetylstyrene,
monochlorostyrene, dichlorostyrene, and other halostyrenes, and mixtures
thereof. The
vinyl aromatic monomer may be present in any effective amount. The vinyl
aromatic
4
CA 02392589 2002-05-24
WO 01/42358 PCT/L1S00/31618
monomer may be present in amounts of from approximately 0 to 75 percent by
weight,
based on the total weight of the polymer resin. Preferably the vinyl aromatic
monomer is
present in amounts of from approximately 35 to 70 percent by weight.
The ethylenically unsaturated carboxylic acid may be a monocarboxylic acid, or
a
dicarboxylic acid or a polycarboxylic acid, such as, for example, acrylic
acid, methacrylic
acid, fumaric acid, malefic acid, itaconic acid, derivatives thereof and
mixtures thereof.
The ethylenically unsaturated carboxylic acid monomer may be present in
amounts
of from approximately 0.5 to 25 percent by weight, based on the total weight
of the
polymeric resin. Preferably, the ethylenically unsaturated acid monomer is
present in
amounts of from approximately 1 to 5 percent by weight and, more preferably,
from 3 to 5
percent by weight, based on the total weight of the copolymer.
The dime monomer, when present, may be selected from butadiene, isoprene,
divinylbenzene, derivatives thereof and mixtures thereof. The 1,3-butadiene
monomer is
preferred. The dime monomer may be present in amounts of from approximately 0
to 85
percent by weight, preferably from approximately 30 to 65 percent by weight,
based on the
total weight of the polymer resin.
The latex may comprise an additional ethylenically unsaturated monomeric
component or components. Specific examples of such ethylenically unsaturated
compounds
include methyl methacrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-
ethylhexyl
acrylate, lauryl methacrylate, phenyl acrylate, acrylonitrile,
methacrylonitrile, ethyl-
chloroacrylate, diethyl maleate, polyglycol maleate, vinyl chloride, vinyl
bromide,
vinylidene chloride, vinylidene bromide, vinyl methyl ketone, methyl
isopropenyl ketone
and vinyl ethylester. Derivatives thereof or mixtures thereof may be included.
The latex may comprise a styrene/butadiene/-acrylic acid copolymer or a
styrene/butadiene/hydroxy-ethylacrylate/itaconic acid copolymer. The latex may
also
include a mixture of copolymers. A mixture of styrene/butadiene/acrylic acid
and
styrene/butadiene/-hydroxyethylacrylate/itaconic acid polymers in
approximately equal
amounts by weight may be used.
Such monomers are copolymerized in an aqueous emulsion containing surfactants
and modifiers under conditions of time, temperature, pressure and agitation in
accordance
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
with well known principles of emulsion polymerization.
In the practice of this invention, use of an epoxy emulsion is employed in
combination with the bimodal latex.
The epoxy resin component is suitably any compound which possesses more than
one 1,2-epoxy group. In general, the epoxy resin component is saturated or
unsaturated
aliphatic or cycloaliphatic, aromatic or heterocyclic and can be substituted
or unsubstituted.
The epoxy resins may be selected from the polyglycidyl ethers of bisphenol
compounds, the
polyglycidyl ethers of a novolac resin, and the polyglycidyl ethers of a
polyglycol. Mixtures
of two or more epoxy resins may also be used.
The preferred epoxy resins are the polyglycidyl ethers of bisphenol compounds.
The
polyglycidyl ethers of bisphenol A or bisphenol F have been found to be
suitable. The
epoxy resins may be formed as the reaction products of epichlorohydrin and
bisphenol A or
bisphenol F or derivatives thereof.
The epoxy resin component of the curable latex composition may further include
an
emulsifier or surfactant. An anionic or a nonionic surfactant may be used. A
nonionic
surfactant is preferred. An ethoxylated nonionic surfactant is more preferred.
An
ethoxylated nonionic surfactant having an HLB of approximately 16 to 20 is
most preferred.
The non-ionic surfactant sold under the trade designation "Capcure 65" and
available from
Diamond Shamrock Corporation has been found to be suitable. The emulsifying
agent or
surfactant may be present in amounts of from approximately 5 to I O percent by
weight,
based on the weight of the epoxy resin. Preferably, the emulsifying agent or
surfactant is
present in amounts of from approximately at least 8 percent by weight. It has
been found
that where a nonionic surfactant or emulsifying agent is included, the epoxy
resin emulsion
so formed provides a relatively reduced particle size. The reduced particle
size provides an
improvement in the stability of the epoxy resin and in turn in the curable
latex composition.
Desirably, in the preparation of the epoxy resin emulsion, the epoxy resin and
surfactant or emulsifier are homogenized by means of a suitable high shear
blender. The
particle size of the epoxy resin emulsion thus produced may be approximately
two to five
6
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
times that of tile latex (for example approximately three times that of the
latex (for example,
less than 1000 run)). High shear homogenization may continue during phase
inversion m
order to assist in achieving small particle size.
The level of epoxy resin employed will vary over a wide range depending upon
the
properties of the final product required, as well as the types of epoxy resin
and carboxylic
acid used.
Low viscosity resins are preferred as it is easier to produce a stable
emulsion from
them. Representative commercial epoxy resins include those sold under the
trade
designations D.E.R.~ 351-A and D.E.R.~ 330 available from The Dow Chemical
Company.
The epoxy resin emulsion component as described above comprises an organo-
soluble or organo-miscible catalyst. Suitable organo-soluble or organo-
miscible catalysts
include the phosphonium salts, such as, for example, ethyltriphenyl
phosphonium acetate
and ethyltriphenyl phosphonium phosphate and the quaternary ammonium salts,
such as, for
example, alkylbenzyl dimethyl ammonium chloride, benzyltrimethyl ammonium
chloride,
methyltrioctyl ammonium chloride, tetraethyl ammonium bromide, N-dodecyl
pyridinium
chloride and tetraethyl ammonium iodide. The preferred organo-soluble or
organo-miscible
catalysts are ethyltriphenyl phosphonium acid acetate, ethyltriphenyl
phosphonium
phosphate and methyltrioctyl ammonium chloride. Ethyltriphenyl phosphonium
phosphate
is not readily available but it can be manufactured from ethyltriphenyl
phosphonium acetate
by reaction with phosphoric acid.
The organo-soluble or organo-miscible catalyst may be present in an amount of
from
approximately 0.1 to approximately 10.0 percent, preferably from 0.3 to 2.0
percent, by
weight, based on the weight of the epoxy resin.
The water-soluble catalytic curing agent may be present in an amount of from
approximately 0.1 to approximately 15 percent by weight, based on the weight
of the
copolymer. Suitable catalytic curing agents include tridimethyl aminomethyl
phenol,
dimethyl aminomethyl phenol, dicyandiamide, polyamines such as, for example,
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
ethylenediamine, diethylenetriamine, triethylene tetramine, tetraethylene
pentamine and
isophorone diamine.
The curable latex composition according to the present invention may further
include standard compounding ingredients such as, for example, fillers,
thickening agents,
antioxidants, dispersants, pH modifiers and flame retarding agents.
An adjustment of the pH of the mixture of the reactive latex and the
coreactive
material may be made, if desired, by the addition of usual acidifying or
alkalizing agents
such as, for example, acetic acid, citric acid, dilute mineral acids, ammonium
hydroxide and
dilute aqueous solutions of alkali metal hydroxides.
The shelf life of the blend of latex and epoxy resin emulsion may be improved
by
selecting the pH of the blend such that a substantial proportion of the
carboxyl groups on
the latex copolymer are protonized. It has been found that if the pH is
maintained in the
range of approximately 6 to 6.5, extended shelf life may be achieved. The pH
may be
adjusted in any suitable manner. Addition of an approximate amount of ammonia
has been
found to be suitable for pH adjustment.
In addition to the bimodal latex, the epoxy emulsion may comprise additional
components and additives. Such additional components may include, but not
limited to, 0.1
to 10 parts per 100 dry parts of a bimodal latex, preferably about 1 to 4
parts of a paraffin
wax emulsion to improve cell tack and water resistance. The composition may
include from
0.1 to 5 parts, preferably about 1 part, of a cell detackifier, such as a
silicone based cell
detackifier, used to prevent the cell walls of the foam from sticking
together. The
composition may include from 0.1 to 5 parts, preferably about 3 parts, of a
froth stabilizer
such as a suspension of disodium N-cetostearyl sulphosuccinimate. The
composition may
include from 0.1 to 5 parts, preferably about 1 part, of a froth booster. The
composition may
include from 0.1 to about 2, preferably about 0.4 part, of a dispersant for
any filler, if
present, such as a polyphosphate dispersant added to improve dispersion of a
inorganic
(mineral) filler. The composition may include 0.1 to 5 parts, preferably about
1.5 parts, of a
catalyst or dual catalyst which improves curing time during processing, such
as a water
8
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
based mixture composed of 2,4,6-tri(dimethylaminomethyl)phenol and
ethtriphenylphosphonium acid ester. The composition may include 0.1 to 2
parts, preferably
0.5 part of ammonium sulfate to reduce viscosity. The composition may include
0.1 to 10
parts, preferably about 4 parts of the epoxy emulsion, which serves as a cross-
linker. The
composition may include a compound to improve resilience, such as 0.1 to 5
parts,
preferably 1.5 parts, of ammonium oleate. The composition may include 0.1 to S
parts of
one or more antioxidants, such as about 1.2 pans of a blend of a polymeric
hindered phenol
and ditridecyl di thio diproprionate.
The compositions of this invention may additionally comprise one or more
mineral
fillers. Examples of mineral fillers include those known in the art such as
clay, titanium
dioxide, carbon, silicates, zinc oxide, calcium carbonate, zinc sulfide,
potassium titanate and
titanate whiskers, glass flakes, clays, kaolin and glass fibers. The amount of
filler which is
employed can vary, depending upon the density of the filler and the coating
properties
desired. Each of the aforementioned components is mixed in an aqueous medium
to yield a
formulation which is about 10 to about 90 percent solids by weight.
It will be understood that the various components of the curable latex
compositions
of the present invention may be maintained separately until shortly before use
because of
their ambient temperature curing properties. In some instances, two or more
components
which do not react with each other can be premixed. For example, the latex and
the water-
soluble catalytic curing agent may be provided as one component and the epoxy
emulsion
containing the organo-soluble or organo-miscible catalyst as the other
component. The latex
may also be combined with the epoxy emulsion containing the organo-soluble or
organo-
miscible catalyst and then the water-soluble catalytic curing agent may be
added separately
immediately prior to use. Once combined, the composition may be used directly
or may be
further diluted with water depending on the solids level desired for the
particular method of
application to be employed. Advantageously, however, the composition of this
invention
containing a bimodal latex and an epoxy emulsion may be admixed and stored for
long
periods of time, for example, up to a year.
9
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
The curing temperature may be any suitable temperature above ambient
temperature.
Indeed, some curing may occur at ambient temperature, but since the reaction
time is
extremely slow, such a temperature is impractical.
The preferred temperature range is from approximately 120°C to
180°C. The
residence time is variable. Factors influencing residence time include
temperature, film
thickness, water content and the components of the curable coating
composition. With
temperatures in that range, a total residence time of approximately five to
ten minutes has
been found to be suitable.
The generality of the invention should not in any way be restricted by theory
based
on the results of our experiments; however, it can be postulated that the
water-soluble
catalytic curing agent will to some extent be transferred into the epoxy resin
phase upon
drying, and promote polymerization of the epoxy resin, as well as carboxyl-
epoxy reaction.
It also makes the latex more miscible with the epoxy resin. The organic
soluble catalyst had
shown reasonable activity for the acid-epoxy reaction only, hence resin
emulsions pre-
catalyzed with the organo-soluble catalyst yield a long shelf life. The
organic soluble
catalyst also makes the carboxylated latex polymer more miscible with the
epoxy resin. It is
therefore reasonable to assume, that the latex particles are crosslinked with
a built-in
network of homopolymerized epoxy resin.
The foaming step may be undertaken in any suitable manner conventional manner.
A foam or froth may be generated by methods well known in the art, for example
by
releasing a noncoagulating gas such as nitrogen, or by causing the
decomposition of a gas-
liberating material to chemically react with an ingredient in the mixture with
the liberation
of a non-coagulable gas as a reaction product. The mixture of the reactive
latex and the
coreactive material is also foamed by whipping or by use of apparatus having
commercially
available foam heads. Known foaming aids, such as sodium lauryl sulfate, or
foam
stabilizers, such as potassium oleate, may be added if desired. Preferably,
such added
materials should be non-reactive with the reactive group in the latex polymer
or in the
coreactive material and thus the preference may vary with the composition of
the mixture.
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
Other soaps, emulsifiers, wetting agents, and surfactants, however, may be
used, even
though they may be reactive to a limited extent.
The frothed mixture may be poured into molds, spread on a flat tray or belt,
or
coated onto substrates. For the purpose of this specification, the term
"substrate" is defined
as any material such as cloth, fabric, leather, wood, glass or metal or any
form of backing to
which the frothed mixture will adhere when applied and after it is cured.
In a preferred embodiment in which the foam is used as a textile backing, the
foam
may be applied to the textile prior to drying and curing. A typical froth
formed from the
continuous foam will have a density in the range of from approximately 200 to
400 grams
per liter in its wet state, preferably approximately 350 grams per liter. The
foam may be
applied to the substrate utilizing a doctor blade.
Once formed, the foam may be dried and cured at a temperature of approximately
110°C to 150°C. The drying and curing may be undertaken in a
forced air circulation oven.
The internal temperature of the oven should be maintained preferably at or
above
approximately 120°C.
The following examples are illustrative of this invention and are not intended
to be
limit the scope of the invention or claims hereto. Unless otherwise denoted
all percentages
are by weight.
Example
In a stainless steel reactor equipped with a nitrogen inlet, mechanical
stirrer and
condenser, 20.75 parts of bisphenol A and 68.48 parts of D.E.R. 330 epoxy
resin were
heated to 130°C with stirnng. 0.05 parts of a 70 percent solution of AI
catalyst in methanol
was added and the temperature was raised to 150°C to start the
exotherm. Under adiabatic
conditions a peak exotherm occurring at around 180°C was observed. 30
minutes after the
peak exotherm, 0.026 parts of methyl-para-toluene sulfonic ester were added
while cooling
down the resin to 120°C. 4.3 parts of Aerosol 108 (surfactant from
ICI), 5.1 parts of
Disponil TA 430 (Henkel) and 1.4 parts of Aerosol TO 75 were added and mixing
was
allowed for 30 more minutes while the temperature was further decreased to
90°C. An end
11
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
epoxy equivalent weight (EEW) value of 500 plus/minus 20 was obtained. The
resin
product was dispersed in a centrifugal pump to yield an epoxy emulsion having
volume
average particle size below 0.6 micron; an EEW value of 780-910 and a solid
content of 56-
61 percent.
An emulsion in accordance with this invention was prepared by admixing the
following
components: 100 dry parts of a bimodal carboxylated styrene-butadiene latex, 4
parts of a
paraffin wax emulsion to improve cell tack and water resistance (IMPERMAX
T940, from
Govi), 1 part of a silicone based cell detackifier used to prevent the cell
walls of the foam
from sticking together (PROSIL E70, from Stephenson Brothers), 3 parts of a
froth
stabilizer (EMPINIM MKB, a suspension of disodium N-cetostearyl
sulphosuccinimate,
from Albright and Wilson Surfactants Group), 1 part of a froth booster (SLS),
0.4 part of a
dispersant for filler (CALGON PT, a polyphosphate dispersant added to improve
dispersion
of a inorganic filler), 1.5 parts of a dual catalyst which improves curing
time during
processing (ETPPAAc/Ancamine K54, a water based mixture composed of 2,4,6-
tri(dimethylaminomethyl)phenol and ethtriphenylphosphonium acid ester, from
Morton
Performance Chemicals Europe), 0.5 part of ammonium sulfate to reduce
viscosity, 4 parts
of the epoxy emulsion which serves as a cross-linker, 1.5 parts of ammonium
oleate to
improve resilience and 1.2 parts of a blend of antioxidants (EMULSION L,
composed of a
polymeric hindered phenol (WINGSTAY L) and a secondary antioxidant, ditridecyl
di tiho
diproprionate (DTDTDP) from Great Lakes in Austria).
The emulsion was employed in a foam backing process by combining 100 parts by
dry weight of the emulsion of the preceding paragraph and 160 parts by dry
weight of
calcium carbonate filler to provide a product having a solids content of 78
percent and a
viscosity of 3,500 cps (Brookfield spindle 4 at 20 rpm). The filler was
employed to improve
resilience and strength of the final foam. Calcium carbonate was used as an
extender in the
foam manufacturing process. The calcium carbonate was preferably selected to
be readily
dispersible, exhibit low froth viscosity and stability and provide good final
foam properties
at high loadings of up to 200 parts per 100 parts dry latex. A representative
calcium
12
CA 02392589 2002-05-24
WO 01/42358 PCT/US00/31618
carbonate filler may currently be obtained from Omya as BL 200. The product
was
mechanically foamed using air to reduce density, spread onto the substrate and
the dried in
an oven at approximately 140°C to remove the water from the system.
Further modifications and alternative embodiments of this invention will be
apparent
to those skilled in the art in view of this description. Accordingly, this
description was to be
construed as illustrative only and was for the purpose of teaching those
skilled in the art the
manner of carrying out the invention. It was to be understood that the forms
of the invention
herein shown and described were to be taken as illustrative embodiments.
Equivalent
elements or materials may be substituted for those illustrated and described
herein, and
certain features of the invention may be utilized independently of the use of
other features,
all as would be apparent to one skilled in the art after having the benefit of
this description
of the invention.
13
