Note: Descriptions are shown in the official language in which they were submitted.
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WATER REPELLANT FIBERGLASS BINDER
COMPRISING A FLUORINATED POLYMER
BACKGROUND OF THE INVENTION
Field of the Invention
The subject invention pertains to polycarboxy polymer binding resins having
improved water repellancy properties. More particularly, the subject invention
pertains
to thermosetting, acrylic acid-based binder resins which cure by crosslinking
with a poly-
functional, hydroxyl group-reactive curing agent, which binders containing
such resins
exhibit minimal water absorption. Such binders are useful as replacements for
formaldehyde-based binders in non-woven fiberglass goods.
Description of the Related Art
Fiberglass binders have a variety of uses ranging from stiffening applications
where the binder is applied to woven or non-woven fiberglass sheet goods and
cured,
producing a stiffer product; thermo-forming applications wherein the binder
resin is
applied to a sheet or lofty fibrous product, following which it is dried and
optionally B-
staged to form an intermediate but yet curable product; and to fully cured
systems such
as building insulation.
Fibrous glass insulation products generally comprise matted glass fibers
bonded
together by a cured thermoset polymeric material. Molten streams of glass are
drawn
into fibers of random lengths and blown into a forming chamber where they are
randomly deposited as a mat onto a traveling conveyor. The fibers, while in
transit in
the forming chamber and while still hot from the drawing operation, are
sprayed with an
aqueous binder. A phenol-formaldehyde binder has been used throughout the
fibrous
glass insulation industry. The residual heat from the glass fibers and the
flow of air
through the fibrous mat during the forming operation are generally sufficient
to volatilize
the majority to all of the water from the binder, thereby leaving the
remaining
components of the binder on the fibers as a viscous or semi-viscous high
solids liquid.
The coated fibrous mat is transferred to a curing oven where heated air, for
example, is
blown through the mat to cure the binder and rigidly bond the glass fibers
together.
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Fiberglass binders used in the present sense should not be confused with
matrix
resins which are an entirely different and non-analogous field of art. While
sometimes
termed "binders", matrix resins act to fill the entire interstitial space
between fibers,
resulting in a dense, fiber reinforced product where the matrix must translate
the fiber
strength properties to the composite, whereas "binder resins" as used herein
are not
space-filling, but rather coat only the fibers, and particularly the junctions
of fibers.
Fiberglass binders also cannot be equated with paper or wood product "binders"
where
the adhesive properties are tailored to the chemical nature of the cellulosic
substrates.
Many such resins are not suitable for use as fiberglass binders. One skilled
in the art of
fiberglass binders would not look to cellulosic binders to solve any of the
known
problems associated with fiberglass binders.
Binders useful in fiberglass insulation products generally require a low
viscosity
in the uncured state, yet characteristics so as to form a rigid thermoset
polymeric mat for
the glass fibers when cured. A low binder viscosity in the uncured state is
required to
allow the mat to be sized correctly. Also, viscous binders tend to be tacky or
sticky and
hence they lead to accumulation of fiber on the forming chamber walls. This
accumulated fiber may later fall onto the mat causing dense areas and product
problems. A binder which forms a rigid matrix when cured is required so that a
finished
fiberglass thermal insulation product, when compressed for packaging and
shipping, will
recover to its as-made vertical dimension when installed in a building.
From among the many thermosetting polymers, numerous candidates for
suitable thermosetting fiberglass binder resins exist. However, binder-coated
fiberglass
products are often of the commodity type, and thus cost becomes a driving
factor,
generally ruling out such resins as thermosetting polyurethanes, epoxies, and
others.
Due to their excellent cost/performance ratio, the resins of choice in the
past have been
phenol/formaldehyde resins. Phenol/formaldehyde resins can be economically
produced, and can be extended with urea prior to use as a binder in many
applications.
Such urea-extended phenol/formaldehyde binders have been the mainstay of the
fiberglass insulation industry for years, for example.
Over the past several decades however, minimization of volatile organic
compound emissions (VOCs) both on the part of the industry desiring to provide
a
cleaner environment, as well as by Federal regulation, has led to extensive
investigations into not only reducing emissions from the current formaldehyde-
based
binders, but also into candidate replacement binders. For example, subtle
changes in
the ratios of phenol to formaldehyde in the preparation of the basic
phenol/formaldehyde resole resins, changes in catalysts, and addition of
different and
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multiple formaldehyde scavengers, has resulted in considerable improvement in
emissions from phenol/formaldehyde binders as compared with the binders
previously
used. However, with increasingly stringent Federal regulations, more and more
attention has been paid to alternative binder systems which are free from
formaldehyde.
One such candidate binder system employs polymers of acrylic acid as a first
component, and a polyol such as glycerine or a modestly oxyalkylated glycerine
as a
curing or "crosslinking" component. The preparation and properties of such
poly(acrylic
acid)-based binders, including information relative to the VOC emissions, and
a
comparison of binder properties versus urea formaldehyde binders is presented
in
"Formaldehyde-Free Crosslinking Binders For Non-Wovens", Charles T. Arkins et
al.,
TAPPI JOURNAL, Vol. 78, No. 11, pages 161-168, November 1995. The binders
disclosed by the Arkins article, appear to be B-stageable as well as being
able to
provide physical properties similar to those of urea/formaidehyde resins.
U.S. Patent No. 5,340,868 discloses fiberglass insulation products cured with
a
combination of a polycarboxy polymer, a. -hydroxyalkylamide, and an at least
one
trifunctional monomeric carboxylic acid such as citric acid. The specific
polycarboxy
polymers disclosed are poly(acrylic acid) polymers. See also, U.S. Patent No.
5,143,582
U.S. Patent No. 5,318,990 discloses a fibrous glass binder which comprises a
polycarboxy polymer, a monomeric trihydric alcohol and a catalyst comprising
an alkali
metal salt of a phosphorous-containing organic acid.
Published European Patent Application EP 0 583 086 Al appears to provide
details of polyacrylic acid binders whose cure is catalyzed by a phosphorus-
containing
catalyst system as discussed in the Arkins article previously cited. Higher
molecular
weight poly(acrylic acids) are stated to provide polymers exhibiting more
complete cure.
See also U.S. Patent,Nos. 5,661,213; 5,427,587; 6,136,916; and 6,221,973.
Some polycarboxy polymers have been found useful for making fiberglass
insulation products. Problems of clumping or sticking of the glass fibers to
the inside of
the forming chambers during the processing, as well as providing a final
product that
exhibits the recovery and rigidity necessary to provide a commercially
acceptable
fiberglass insulation product, have been overcome. See, for example, U.S.
Patent No.
6,331,350. The thermosetting acrylic resins have been found to be more
hydrophilic
than the traditional phenolic binders, however. This hydrophilicity can result
in
fiberglass insulation that is more prone to absorb liquid water, thereby
possibly
compromising the integrity of the product. Also, the thermosetting acrylic
resins now
being used as binding agents for fiberglass have been found to not react as
effectively
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with silane coupling agents of the type traditionally used by the industry.
The addition of
silicone as a hydrophobing agent results in problems when abatement devices
are used
that are based on incineration. Also, the presence of silicone in the
manufacturing
process can interfere with the adhesion of certain facing substrates to the
finished
fiberglass material. Overcoming these problems will help to better utilize
polycarboxy
polymers in fiberglass binders.
Accordingly, it is an objective of the present invention to provide a novel,
non-
phenol/formaldehyde binder.
Yet another object of the present invention is to provide such a binder which
allows one to prepare fiberglass insulation products which are more water
repellent and
less prone to absorb liquid water.
Still another object of the present invention is to provide a fiberglass
insulation
product which exhibits good recovery and rigidity, is formaldehyde-free, and
is more
water-proof.
These and other objects of the present invention will become apparent to the
skilled artisan upon a review of the following description and the claims
appended
hereto.
SUMMARY OF THE INVENTION
In accordance with the foregoing objectives, there is provided by the present
invention a novel fiberglass binder. The binder composition of the present
invention
comprises a polycarboxy polymer, a polyol, and a fluorinated polymer. It is
also
preferred that the binder comprise a catalyst, such as an alkaline metal salt
of a
phosphorus-containing organic acid.
An important aspect of the binder of the present invention is that the binder
composition, in addition to the polycarboxy polymer and the polyol, contains a
fluorinated polymer. The presence of the fluorinated polymer in the binder is
believed to
render the binder, and hence the fiberglass mat to which the binder is
applied,
essentially waterproof. As a result, fiberglass insulation made with the
binder of the
present invention avoids the possible problem of coming apart when subjected
to water,
as the binder of the present invention has been found to repel the water and
maintain
the integrity of the bond with the fiberglass.
Among other things, it has been discovered that by including a fluorinated
polymer in a formaldehyde free binder for glass fibers, and in particular a
polycarboxy/polyol binder, water repellency for the fiberglass mats prepared
are
achieved without adversely effecting performance or processing. The glass
fiber mats
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can be used as thermal or sound insulation, as well as filtration media in
filtering air or
liquids.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
5 The binder of interest with regard to the present invention is a
formaldehyde free
binder useful for glass fibers. Of particular interest is a binder composition
compound of
a polycarboxy polymer and a polyol. Such binder compositions are described,
for
example, in U.S. Patent No.6,331,350, which is hereby expressly incorporated
by
reference in its entirety.
The polycarboxy polymer used in the preferred binder of the present invention
comprises an organic polymer or oligomer containing more than one pendant
carboxy
group. The polycarboxy polymer may be a homopolymer or copolymer prepared from
unsaturated carboxylic acids including but not necessarily limited to, acrylic
acid,
methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, cinnamic acid,
2-
methylmaleic acid, itaconic acid, 2-methylitaconic acid, ,,-methyleneglutaric
acid, and the
like. Alternatively, the polycarboxy polymer may be prepared from unsaturated
anhydrides including, but not necessarily limited to, maleic anhydride,
methacrylic
anhydride, and the like, as well as mixtures thereof. Methods for polymerizing
these
acids and anhydrides are well-known in the chemical art.
The polycarboxy polymer of the present invention may additionally comprise a
copolymer of one or more of the aforementioned unsaturated carboxylic acids or
anhydrides and one or more vinyl compounds including, but not necessarily
limited to,
styrene, -methylstyrene, acrylonitrile, methacrylonitrile, methyl acrylate,
ethyl acrylate, n-
butyl acrylate, isobutyl acrylate, methyl methacrylate, n-butyl methacrylate,
isobutyl
methacrylate, glycidyl methacrylate, vinyl methyl ether, vinyl acetate, and
the like.
Methods for preparing these copolymers are well-known in the art.
Preferred polycarboxy polymers comprise homopolymers and copolymers of
polyacrylic acid. It is particularly preferred that the molecular weight of
the polycarboxy
polymer, and in particular polyacrylic acid polymer, is less than 10000, more
preferably
less than 5000, and most preferably about 3000 or less. The low molecular
weight
polycarboxy polymer results in a final product which exhibits excellent
recovery and
rigidity.
The formaldehyde-free curable aqueous binder composition of the present
invention also contains a polyol containing at least two hydroxyl groups. The
polyol
must be sufficiently nonvolatile such that it will substantially remain
available for reaction
with the polyacid in the composition during heating and curing operations. The
polyol
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may be a compound with a molecular weight less than about 1000 bearing at
least two
hydroxyl groups such as, for example, ethylene glycol, glycerol,
pentaerythritol,
trimethylol propane, sorbitol, sucrose, glucose, resorcinol, catechol,
pyrogallol,
glycollated ureas, 1,4-cyclohexane diol, diethanolamine, triethanolamine, and
certain
reactive polyols such as, for example,. -hydroxyalkylamides such as, for
example,
bis[N,N-di,(-hydroxyethyl)]adipamide, as may be prepared according to the
teachings of
U.S. Patent No. 4,076,917, hereby incorporated herein by reference in its
entirety, or it
may be an addition polymer containing at least two hydroxyl groups such as,
for
example, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, and
homopolymers or
copolymers of hydroxyethyl (meth) acrylate, hydroxypropyl(meth) acrylate, and
the like.
The most preferred polyol for the purposes of the present invention is
triethanolamine
(TEA).
The ratio of the number of equivalents of carboxy, anhydride, or salts thereof
of
the polyacid to the number of equivalents of hydroxyl in the polyol is from
about 1/0.01
to about 1/3. An excess of equivalents of carboxy, anhydride, or salts thereof
of the
polyacid to the equivalents of hydroxyl in the polyol is preferred, however,
thus, a more
preferred ratio of the number of equivalents of carboxy, anhydride, or salts
thereof in the
polyacid to the number of equivalents of hydroxyl in the polyol is from about
1/0.2 to
about 1/0.95, more preferably from 1/0.6 to 1/0.8, and most preferably from
1/0.65 to
1/0.75. A low ratio, approaching 1/0.7 has been found to be of particular
advantage
especially when combined with a low molecular weight polycarboxy polymer as
described above, and also preferably with a lower pH binder.
It is most preferred that the pH of the binder of the present invention also
be low,
i.e., no greater than 4.5, and preferably less than 3.5, for it has been found
that the
combination of low molecular weight polycarboxy polymer with a lowered pH
provides a
binder exhibiting minimal processing difficulties and a final product with
excellent
recovery and rigidity. Maintaining the pH in the range of from 3.5 to 4.5
allows one to
avoid serious problems with corrosion of the equipment while still realizing
the benefits
of the low pH. However, a lower pH can also be used, e.g., less than 3.5, and
is
actually preferred due to beneficial results, with appropriate handling
precautions.
An important aspect of the present invention is that the binder of the present
invention also contains a fluorinated polymer, as an additive. The presence of
the
fluorinated polymer has been found to render the polycarboxy/polyol binder of
the
present invention less prone to absorb water, while still allowing excellent
products and
good processing of those products, e.g., thermal and sound insulation products
and
filtration media in filtering air or liquids. As a result, its presence may
better maintain the
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integrity of the bond between the binder and glass fiber, and hence the
integrity of the
entire mat product, when exposed to liquid water. The binder bond, and hence
the
overall product, is more water-proof.
The preferred fluorinated polymer is a copolymer prepared from a fluorine
containing acrylate monomer with styrene or some other commonly used acrylate
comonomer. Such fluorinated polymers are available, for example, under the
trademark
ParaChem RD-F25T"'. Generally, any suitable fluorine-containing polymer in
which
fluorine has been substituted for hydrogen in an organic polymer can be
employed.
This would include the vinyl fluoride polymers and the tetrafluoroethylene
polymers.
Among the tetrafluoroethylene polymers, the homopolymers of
tetrafluoroethylene, as
well as its copolymers with hexafluoropropylene, perfluorovinylether and
ethylene can
also be used to impart hydrophobicity to the polycarboxy/polyol binder of the
present
invention.
The fluorinated polymers employed are generally added to the
polycarboxy/polyol binder as a dispersion or emulsion, and can be added
directly to the
binder composition which is then employed in the formation of the fiberglass
products.
Alternatively, the fluorinated polymer can be sprayed onto the fiberglass
product itself
once it has been formed and cured. A combination of these two events can also
be
employed. It is preferred, however, that the fluorinated polymer be added
directly to the
binder composition used in the formation of the fiberglass product.
The amount of fluorinated polymer employed is generally such that the final
fiberglass product contains from .005 to .5 wt. % of the fluorine-containing
polymer.
More preferably, the amount of fluorine-containing polymer in the final
product can
generally range from about .01 to about .3 wt. %, even more preferably from
about .04
to .1 wt. %, and most preferably in the range of about .05 to .09 wt. %. It
has been
found that the use of the fluorine-containing polymer can be at levels much
lower than
silicone materials to achieve similar water repellency, while also overcoming
the
problems often inherent in using silicone hydrophobing agents. Use of the more
preferred ranges, e.g., from .05 to .09 wt. % of the fluorine-containing
polymer, offers
excellent water repellency while using only a small amount of the additive,
thus making
the use economical as well.
It is preferred that the formaldehyde-free curable aqueous binder composition
of
the present invention also contain a catalyst. Most preferably, the catalyst
is a
phosphorous-containing accelerator which may be a compound with a molecular
weight
less than about 1000 such as, for example, an alkali metal polyphosphate, an
alkali
metal dihydrogen phosphate, a polyphosphoric acid, and an alkyl phosphinic
acid or it
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may be an oligomer or polymer bearing phosphorous-containing groups such as,
for
example, addition polymers of acrylic and/or maleic acids formed in the
presence of
sodium hypophosphite, addition polymers prepared from ethylenically
unsaturated
monomers in the presence of phosphorous salt chain transfer agents or
terminators,
and addition polymers containing acid-functional monomer residues such as, for
example, copolymerized phosphoethyl methacrylate, and like phosphonic acid
esters,
and copolymerized vinyl sulfonic acid monomers, and their salts. The
phosphorous-
containing accelerator may be used at a level of from about 1% to about 40%,
by weight
based on the combined weight of the polyacid and the polyol. Preferred is a
level of
phosphorous-containing accelerator of from about 2.5% to about 10%, by weight
based
on the combined weight of the polyacid and the polyol.
The formaldehyde-free curable aqueous binder composition may contain, in
addition, conventional treatment components such as, for example, emulsifiers,
pigments, filler, anti-migration aids, curing agents, coalescents, wetting
agents, biocides,
plasticizers, organosilanes, anti-foaming agents, colorants, waxes, and anti-
oxidants.
The formaldehyde-free curable aqueous binder composition may be prepared by
admixing the polyacid of the present invention, the polyol, and the
phosphorous-
containing accelerator using conventional mixing techniques. In another
embodiment, a
carboxyl- or anhydride-containing addition polymer and a polyoi may be present
in the
same addition polymer, which addition polymer would contain both carboxyl,
anhydride,
or salts thereof functionality and hydroxyl functionality. In another
embodiment, the salts
of the carboxy-group are salts of functional alkanolamines with at least two
hydroxyl
groups such as, for example, diethanolamine, triethanolamine, dipropanolamine,
and di-
isopropanolamine. In an additional embodiment, the polyol and the phosphorous-
containing accelerator may be present in the same addition polymer, which
addition
polymer may be mixed with the modified polyacid of the present invention. In
yet
another embodiment the carboxyl- or anhydride-containing addition polymer, the
polyol,
and the phosphorous-containing accelerator may be present in the same addition
polymer. Other embodiments will be apparent to one skilled in the art. As
disclosed
herein-above, the carboxyl groups of the polyacid may be neutralized to an
extent of
less than about 35% with a fixed base before, during, or after the mixing to
provide the
aqueous composition. Neutralization may be partially effected during the
formation of
the polyacid.
Once the composition of the polyacid, the polyol and the fluorinated polymer
has
been prepared, in a preferred embodiment, other additives, can then be mixed
in with
the composition to form the final composition to be sprayed on the fiberglass.
As molten
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streams of glass are drawn into fibers of random lengths and blown into a
forming
chamber where they are randomly deposited as a mat onto a traveling conveyor,
the
fibers, while in transit in the forming chamber, are sprayed with the aqueous
binder
composition of the present invention, which includes the modified polyacid.
More particularly, in the preparation of fiberglass insulation products, the
products can be prepared using conventional techniques. As is well known, a
porous
mat of fibrous glass can be produced by fiberizing molten glass and
immediately forming
a fibrous glass mat on a moving conveyor. The expanded mat is then conveyed to
and
through a curing oven wherein heated air is passed through the mat to cure the
resin.
The mat is slightly compressed to give the finished product a predetermined
thickness
and surface finish. Typically, the curing oven is operated at a temperature
from about
1500C to about 3250C. Preferably, the temperature ranges from about 1800 to
about
2250C. Generally, the mat resides within the oven for a period of time from
about %
minute to about 3 minutes. For the manufacture of conventional thermal or
acoustical
insulation products, the time ranges from about 3/4 minute to about 1%
minutes. The
fibrous glass having a cured, rigid binder matrix emerges from the oven in the
form of a
bat which may be compressed for packaging and shipping and which will
thereafter
substantially recover its vertical dimension when unconstrained.
The formaldehyde-free curable aqueous composition may also be applied to an
already formed nonwoven by conventional techniques such as, for example, air
or
airless spraying, padding, saturating, roll coating, curtain coating, beater
deposition,
coagulation, or the like.
The waterborne formaldehyde-free composition of the present invention, after
it
is applied to a nonwoven, is heated to effect drying and curing. The duration
and
temperature of heating will affect the rate of drying, processability and
handleability, and
property development of the treated substrate. Heat treatment at about 1200C,
to
about 4000C, for a period of time between about 3 seconds to about 15 minutes
may
be carried out; treatment at about 1500C, to about 2500C, is preferred. The
drying and
curing functions may be effected in two or more distinct steps, if desired.
For example,
the composition may be first heated at a temperature and for a time sufficient
to
substantially dry but not to substantially cure the composition and then
heated for a
second time at a higher temperature and/or for a longer period of time to
effect curing.
Such a procedure, referred to as "B-staging", may be used to provide binder-
treated
nonwoven, for example, in roll form, which may at a later stage be cured, with
or without
forming or molding into a particular configuration, concurrent with the curing
process.
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The heat-resistant nonwovens may be used for applications such as, for
example, insulation batts or rolls, as reinforcing mat for roofing or flooring
applications,
as roving, as microglass-based substrate for printed circuit boards or battery
separators,
as filter stock, as tape stock, as tape board for office petitions, in duct
liners or duct
5 board, and as reinforcement scrim in cementitious and non-cementitious
coatings for
masonry. Most preferably, the products are useful as thermal or sound
insulation. The
nonwovens can also be used as filtration media for air and liquids.
The present invention will be further illustrated by the following example,
which is
in no manner meant to be limiting in scope.
10 EXAMPLE
An emulsified copolymer of fluorine-containing acrylate monomer with styrene,
available under the trademark ParaChem RD-F25 TM, was added to a polyacrylic
acid/polyol binder in a fiberglass building product manufacturing process,
where the final
insulation product contained approximately 5% binder content by weight. The
fluorine-
containing polymer was added to the binder in several levels to produce
samples of R19
insulation containing various levels of the fluorine-containing polymer
additive. A run
was also made where a silicone hydophobing agent was added such that the final
product contained 0.09 wt. % of the silicone additive. All of the samples were
tested for
water repellency by measuring water pickup by weight. This was achieved by
taking a
6-inch by 6-inch square of the fiberglass product and placing it into a bath
of water for
five minutes. After that time, the fiberglass was removed and suspended for 30
seconds
from one corner to allow draining. After the 30 seconds, the fiberglass sample
was then
weighed. The weight gain was recorded as a percent of the original weight. The
results
are shown below:
Additive Percent
Sample based on final product) Weight Gain Percent
control (silicone additive) 0.09 70
1 0.09 38
2 0.06 63
3 0.04 245
4 0 1900
The foregoing results with regard to samples 1, 2 and 3, as compared to the
control and sample 4 (which contained no additive) demonstrate that the
fluorinated
additive of the present invention can achieve water repellency, even at
reduced levels
compared to that of silicone.
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While the invention has been described with preferred embodiments, it is to be
understood that variations and modifications may be resorted to as will be
apparent to
those skilled in the art. Such variations and modifications are to be
considered within
the purview and the scope of the claims appended hereto.
