Note: Descriptions are shown in the official language in which they were submitted.
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COATING COMPOSITION FOR CONTROLLING EFFLORESCENCE
Field of Disclosure
[001] The present disclosure relates generally to coating compositions and
more specifically to
coating compositions for controlling efflorescence in porous construction
materials.
Back2round
[002] Efflorescence is a phenomenon describing the migration and precipitation
of salts to the
surface of porous construction materials, like concrete, where the salts form
blotchy, powdery
and/or crystalline deposits. Efflorescence occurs when absorbed moisture
dissolves the salts in
the porous construction material. The salts then migrate to the surface of the
porous construction
material. Once at the surface, the water evaporates leaving the salts as a
white coating on the
surface of the porous construction material.
[003] It is known that efflorescence can be reduced by reducing water movement
in the porous
construction material. Often this can be done by coating or by impregnation
with silicon-based
materials. Silicone based impregnation provide a protection against water
penetration which is
invisible and leave the surface of the porous construction material with an un-
modified look.
However, it has been observed that silicone-based impregnation solutions are
sometimes not
efficient to protect against efflorescence.
[004] So, there is a need to protect porous construction materials to provide
protection not only
against water ingress which can lead to freeze thaw damages, swelling, warping
or weakening of
mechanical properties (such as observed for fiber cement boards), but also
against efflorescence
which can be observed, despite efficient reduction of water penetration
following treatment of
the surface with silicone based water repellent.
[005] Another approach is to use acrylic based protection in attempting to
reduce water
penetration in the porous construction material. Acrylic based protection is
based on the
formation of a film at the surface of the porous construction material and
leads to some surface
appearance modification. Even if no pigments/filler are added in the acrylic,
the surface of the
porous construction materials will have a clear visual gloss. For some
applications, there is a
need to provide protection for porous construction which leave the appearance
of the material
un-modified (i.e., to have a "natural look") and with no visual gloss.
[006] As such, there is a need in the art for a coating composition for
reducing absorption of
water and at the same time controlling efflorescence in porous construction
materials that not
only helps protect the porous construction materials from efflorescence, but
also do not change
the appearance of the porous construction material.
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Summary
[007] The present disclosure provides a coating composition for reducing
absorption of water
and at the same time for controlling efflorescence in porous construction
materials that not only
helps protect the porous construction materials from efflorescence, but also
does not change the
appearance of the porous construction material. Specifically, the coating
composition includes
an acrylic polymer waterborne emulsion, where the acrylic polymer in the
acrylic polymer
waterborne emulsion has a Tg of 15 C to 60 C, and an oil-in-water silicon-
based emulsion,
where the oil phase of the oil-in-water silicon-based emulsion based provides
the only coalescing
agent for the acrylic polymer waterborne emulsion in the coating composition.
The present
disclosure further includes an aqueous composition for controlling
efflorescence in porous
construction materials, where the aqueous composition includes the coating
composition and
water sufficient to provide the aqueous composition with a solids content of 2
to 25 weight
percent (wt.%) based on the total weight of the aqueous composition.
[008] Specifically, the coating composition for use in controlling
efflorescence in porous
construction materials includes 25 wt.% to 95 wt.% of the acrylic polymer
waterborne emulsion
based on the total weigh of the coating composition, where the acrylic polymer
in the acrylic
polymer waterborne emulsion has a Tg of 15 C to 60 C; and 75 wt.% to 5 wt.%
of the oil-in-
water silicon-based emulsion based on the total weigh of the coating
composition. The oil-in-
water silicon-based emulsion includes an oil phase formed from compounds
selected from the
group consisting of an alkoxy silane, a silicone resin, polydimethyl siloxane,
polymethyl
hydrogen siloxane and combinations thereof The oil phase of the oil-in-water
silicon-based
emulsion based provides the only coalescing agent for the acrylic polymer
waterborne emulsion
in the coating composition.
[009] The coating composition of the present disclosure can have a variety of
embodiments.
For example, the wt.% of the acrylic polymer waterborne emulsion and the oil-
in-water silicone
based emulsion in the coating composition add to 100 wt.%. So, coating
composition for use in
controlling efflorescence in porous construction materials can consist
essentially of, or can
consist of, 25 wt.% to 95 wt.% of the acrylic polymer waterborne emulsion
based on the total
weigh of the coating composition, where the acrylic polymer has a Tg of 15 C
to 60 C; and 75
wt.% to 5 wt.% of the oil-in-water silicon-based emulsion based on the total
weigh of the coating
composition, where the oil-in-water silicon-based emulsion includes an oil
phase formed from
compounds selected from the group consisting of an alkoxy silane, a silicone
resin, polydimethyl
siloxane, polymethyl hydrogen siloxane and combinations thereof, where the oil
phase of the oil-
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in-water silicon-based emulsion based provides the only coalescing agent for
the acrylic polymer
waterborne emulsion in the coating composition.
[010] In an additional embodiment, the acrylic polymer waterborne emulsion of
the coating
composition includes an acrylic polymer having a Tg of 25 C to 55 C. For the
various
embodiments, the acrylic polymer waterborne emulsion can have an acid level of
up to 2 percent
by weight of acid monomers based on a dry weight of the acrylic polymer. In
addition, the
acrylic polymer of the acrylic polymer waterborne emulsion can be formed with
non-ionic
monomers selected from the group consisting of methyl methacrylate, methyl
acrylate, ethyl
acrylate, butyl acrylate, styrene, butyl methacrylate, 2-ethylhexyl acrylate,
t-butyl acrylate, a-
methyl styrene, vinyl acetate, hexyl acrylate and combinations thereof In one
embodiment, the
acrylic polymer of the acrylic polymer waterborne emulsion is formed with non-
ionic monomers
selected from the group consisting of methyl methacrylate and butyl acrylate.
In an additional
embodiment, the acrylic polymer of the acrylic polymer waterborne emulsion is
formed with
non-ionic monomers selected from the group consisting of methyl methacrylate
and 2-ethylhexyl
acrylate. Other embodiments for the non-ionic monomers used to form the
acrylic polymer of
the acrylic polymer waterborne emulsion are also possible.
[011] For the various embodiments, the oil phase of the oil-in-water silicon-
based emulsion can
be formed from an alkoxy silane, where the alkoxy silane is selected from the
group consisting
of Si(OR)4, R1Si(OR)3, (R1)2Si(OR)2 and combinations thereof, wherein each R1
is
independently selected from an alkyl group having 1 to 20 carbon atoms, a
substituted alkyl
group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms
or a substituted
aryl group having 6 to 20 carbon atoms, and wherein each R is independently
selected from an
alkyl group having 1 to 6 carbon atoms. In a more specific embodiment, the
alkoxy silane is
R1Si(OR)3 In one embodiment, the R1 has 8 carbon atoms and R has 2 carbon
atoms to provide
triethoxy(octyl)silane.
[012] For the various embodiments, the oil phase of the oil-in-water silicon-
based emulsion can
be formed from a silicone resin, where the silicone resin is formed from a
hydrolysis-
condensation reaction of any combination of compounds selected from the group
consisting of
Si(OR)4, R1Si(OR)3, (R1)2Si(OR)2 and combinations thereof, wherein each R1 is
independently
selected from the group consisting of an alkyl group having 1 to 20 carbon
atoms, a substituted
alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon
atoms or a
substituted aryl group having 6 to 20 carbon atoms, and each R is
independently an alkyl group
having 1 to 6 carbon atoms.
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[013] For the various embodiments, the oil phase of the oil-in-water silicon-
based emulsion can
be formed from a polymethyl hydrogen siloxane, where the polymethyl hydrogen
siloxane is
selected from compounds having the formulae:
R4(R5)2Si¨(0¨SiR5H)a¨(0¨SiR5R6)b¨Si
(R5)2R4 (I); or (0SiR(R5)H)c(OSiR5R6)d (II) wherein; R4 is hydrogen or an
alkyl having 1 to 4
carbon atoms; R5 is an alkyl having 1 to 4 carbon atoms; R6 is an alkyl having
1 to 18 carbon
atoms; a is an integer from 0 to 35; b is an integer from 0 to 32; and c and d
are each
independently an integer from 1 to 10.
[014] For the various embodiments, the oil phase of the oil-in-water silicon-
based emulsion can
be formed from an organosiloxane, where the organosiloxane is selected from
compounds
having the formulae; (R7)3Si¨(0¨Si(R)2)a¨(O¨SiR7R8)b¨SiR73 (I); or
HO(R7)2Si¨(0¨
Si(R7)2)a¨(0¨SiR7R8)b¨Si(R7)20H (II) wherein; R7 is an alkyl having 1 to 4
carbon atoms; R8
is an alkyl having 1 to 18 carbon atoms; a is an integer from 0 to 35; b is an
integer from 0 to 32;
and c and d are each independently an integer from 1 to 10.
[015] Embodiments of the present disclosure also include an aqueous
composition for use in
controlling efflorescence in porous construction materials. According to the
present disclosure,
the aqueous composition includes the coating composition, as described herein,
and water in an
amount sufficient to provide the aqueous composition with a solids content of
2 to 25 wt.%
based on the total weight of the aqueous composition. For the various
embodiments, the coating
composition and the water of the aqueous composition add to 100 wt.% based on
the total weight
of the aqueous composition.
[016] The aqueous composition of the present disclosure can be used with a
porous
construction material. For example, the aqueous composition of the present
disclosure can be
used to at least partially coat the porous construction material. Examples of
porous construction
material can include an inorganic porous construction material, where the
inorganic porous
construction material can be a cement based porous construction material.
Detailed Description
[017] The present disclosure provides a coating composition for reducing
absorption of water
and at the same time controlling efflorescence in porous construction
materials that not only
helps protect the porous construction materials from efflorescence, but also
do not change the
appearance of the porous construction material. Specifically, the coating
composition includes
an acrylic polymer waterborne emulsion, where the acrylic polymer in the
acrylic polymer
waterborne emulsion has a Tg of 15 C to 60 C, and an oil-in-water silicon-
based emulsion,
where the oil phase of the oil-in-water silicon-based emulsion provides the
only coalescing agent
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for the acrylic polymer waterborne emulsion in the coating composition. The
present disclosure
further includes an aqueous composition for controlling efflorescence in
porous construction
materials, where the aqueous composition includes the coating composition and
water sufficient
to provide the aqueous composition with a solids content of 2 to 25 wt.% based
on the total
weight of the aqueous composition.
[018] When the ingredients of the coating composition are described as being
present as a
weight percent, it is understood to mean that the weight of the coating
composition is 100
percent and that all ingredients, including any optional additives, will sum
up to 100 weight
percent. For example, a coating composition having 25 wt.% to 95 wt.% of the
acrylic polymer
waterborne emulsion based on the total weigh of the coating composition and 75
wt.% to 5 wt.%
of the oil-in-water silicon-based emulsion based on the total weigh of the
coating composition is
understood to encompass a coating composition in which the amount of the
acrylic polymer
waterborne emulsion and oil-in-water silicon-based emulsion will sum up to 100
weight percent,
or the amount of acrylic polymer waterborne emulsion, oil-in-water silicon-
based emulsion and
an optional additive or additives will sum up to 100 weight percent.
Accordingly, when the
acrylic polymer waterborne emulsion is 90 weight percent, for example, the oil-
in-water silicon-
based emulsion can be any amount greater than 5 and up to 10 weight percent.
In the instances
when the oil-in-water silicon-based emulsion is less than 10 weight percent,
optional additives in
an amount sufficient to sum up to 100 weight percent are present in the
coating composition. In
addition, both the acrylic polymer waterborne emulsion and the oil-in-water
silicon-based
emulsion of the present disclosure are aqueous based continuous emulsions
comprising a
dispersed phase and a non-dispersed (continuous) phase in which the dispersed
phase is either
the acrylic polymer or silicon-based compounds and the non-dispersed phase is
water or an
aqueous solution or mixture.
[019] Apart from the oil-in-water silicon-based emulsion, the coating
composition of the
present disclosure does not include another coalescing agent. As is typical in
the art, coalescing
agents are used to assist in the formation of films in film-forming
compositions. Coalescing
agents assist in film formation by, among other things, reducing the minimum
film-forming
temperature (MFFT) of polymer(s) dispersed in the composition. Reducing the
MFFT of the
polymer(s) helps them to better coalesce, where the coalescing agent functions
as a temporary
plasticizer for the polymer(s). So, coalescing agents help with film formation
at temperatures
that are below the MFFT of the polymer(s) present in the composition.
[020] Surprisingly, the use of the oil-in-water silicon-based emulsions as
provided in the
present disclosure have not been recognized nor used as a coalescing agent in
coating
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compositions for use in controlling efflorescence in porous construction
materials. In addition,
the use of the oil-in-water silicon-based emulsions as provided in the present
disclosure
demonstrates low volatility and do not include volatile organic compounds
(VOC), features
which are both highly beneficial for the environment. As such, the coating
composition of the
present disclosure does not include any additional coalescing agent(s) besides
the oil-in-water
silicon-based emulsions as provided in the present disclosure as they are not
needed.
[021] For the present disclosure, the oil-in-water silicon-based emulsions
includes an oil phase
formed from compounds selected from the group consisting of an alkoxy silane,
a silicone resin,
polydimethyl siloxane, polymethyl hydrogen siloxane and combinations thereof,
where the oil
phase of the oil-in-water silicon-based emulsion provides the only coalescing
agent for the
acrylic polymer waterborne emulsion in the coating composition. As used
herein, the oil-in-
water silicon-based emulsion refer to an emulsion having an aqueous based
continuous phase
with the oil phase dispersed therein. As discussed herein, the oil phase is
formed from the
silicon-based compounds provided herein and the non-dispersed phase is water
or an aqueous
solution or mixture.
[022] For the various embodiments, the alkoxy silane is selected from the
group consisting of
Si(OR)4, RiSi(OR)3, (R1)2Si(OR)2 and combinations thereof, wherein each Rl is
independently
selected from an alkyl group having 1 to 20 carbon atoms, a substituted alkyl
group having 1 to
20 carbon atoms, an aryl group having 6 to 20 carbon atoms or a substituted
aryl group having 6
to 20 carbon atoms, and wherein each R is independently selected from an alkyl
group having 1
to 6 carbon atoms. In a more specific embodiment, the alkoxy silane is
R1Si(OR)3. In one
embodiment, the Rl has 8 carbon atoms and R has 2 carbon atoms to provide
triethoxy(octyl)silane. Representative, non-limiting examples of commercial
alkoxy silanes
useful for the oil-in-water silicon-based emulsion in the present disclosure
include those sold
under the tradenames DOWSILTM OFS 6341 and DOWSILTM OFS 6403.
[023] The term "substituted" as used in relation to another group, for
example, an alkyl group,
means, unless indicated otherwise, one or more hydrogen atoms in the alkyl
group has been
replaced with another substituent. Examples of such substituents include, an
alkyl group having
1 to 6 carbon atoms, halogen atoms such as chlorine, fluorine, bromine, and
iodine; halogen
atom containing groups such as chloromethyl, perfluorobutyl, trifluoroethyl,
and
nonafluorohexyl; oxygen atoms; oxygen atom containing groups such as
(meth)acrylic and
carboxyl; nitrogen atoms; nitrogen atom containing groups such as amines,
amino-functional
groups, amido-functional groups, and cyano-functional groups; sulphur atoms;
and sulphur atom
containing groups such as mercapto groups.
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[024] For the various embodiments, the silicone resin is formed from a
hydrolysis-condensation
reaction of any combination of compounds selected from the group consisting of
Si(OR)4,
RiSi(OR)3, (R1)2Si(OR)2 and combinations thereof, wherein each Rl is
independently selected
from the group consisting of an alkyl group having 1 to 20 carbon atoms, a
substituted alkyl
group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms
or a substituted
aryl group having 6 to 20 carbon atoms, and each R is independently an alkyl
group having 1 to
6 carbon atoms.
[025] The silicone resin may also contain reactive groups such as silanol
groups (hydroxy
bonded to a silicon atom) or alkoxy groups (OR groups bonded to a silicon
atom). The amount
of silanol groups present on the silicone resin may vary from 0.1 to 35 mole
percent silanol
groups, [SiOH
] SiOR groups, alternatively from 2 to 30 mole percent alkoxy groups,
alternatively from 5 to 20 mole percent alkoxy groups. The alkoxy groups may
be present on
any siloxy units within the silicone resin. The mole fractions of the various
siloxy units and
alkoxy content may be readily determined by 29Si NMR techniques.
[026] The molecular weight of the silicone resin is not limited. The silicone
resin may have a
Mn (number average molecular weight) of at least 1,000 g/mole, alternatively
Mn of at least
2,000 g/mole, or alternatively Mn of at least 5,000 g/mole. The number average
molecular
weight may be readily determined using Gel Permeation Chromatography (GPC)
techniques.
[027] Representative, non-limiting examples of commercially produced
hydrolysis-
condensation reaction useful for the oil-in-water silicon-based emulsion in
the present disclosure
include those sold under the tradenames DOWSILTM MR 2404 Resin, DOWSILTM 3037
Resin,
DOWSILTM 3074 Resin, DOWSILTM 2403 Resin and DOWSILTM 2405 Resin.
[028] For the various embodiments, the polymethyl hydrogen siloxane is
selected from
compounds having the formulae: R4(R5)2Si¨(0¨SiR5H)a¨(0¨SiR5R6)b¨Si (R5)2R4
(I); or
(0SiR(R5)H)c(OSiR5R6)d (II) wherein; R4 is hydrogen or an alkyl having 1 to 4
carbon atoms; R5
is an alkyl having 1 to 4 carbon atoms; R6 is an alkyl having 1 to 18 carbon
atoms; a is an integer
from 0 to 35; b is an integer from 0 to 32; and c and d are each independently
an integer from 1
to 10.
[029] For the various embodiments, the organosiloxane is selected from
compounds having the
formulae; (R7)3Si¨(0¨Si(R7)2)a¨(0¨SiR7R8)b¨SiR73 (I); or
HO(R7)2Si¨(0¨Si(R7)2)a¨
(0¨SiR7R8)b¨Si(R7)20H (II) wherein; R7 is an alkyl having 1 to 4 carbon atoms;
R8 is an alkyl
having 1 to 18 carbon atoms; a is an integer from 0 to 35; b is an integer
from 0 to 32; and c and
d are each independently an integer from 1 to 10. Representative, non-limiting
examples of
commercial polymethyl hydrogen siloxanes useful for the oil-in-water silicon-
based emulsion in
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the present disclosure include those sold under the tradenames DOWSILTM 6-3570
Polymer, and
Xiameter OFX-5625 fluid.
[030] As seen herein, the oil-in-water silicon-based emulsion of the present
disclosure is
formed from, more generally, a silane based emulsion, a silicone based
emulsion or a mixture of
both a silane and a silicone based emulsion. As seen above, examples of
silanes for the oil phase
of the silane based emulsions can include the alkoxy silanes, whereas examples
of the silicone
based emulsion can include the silicone resin, the polydimethyl siloxane
and/or the polymethyl
hydrogen siloxane provided herein. As noted, the coating composition of the
present disclosure
can include a combination of two or more of these compounds for the oil phase
of the oil-in-
water silicon-based emulsion of the present disclosure. For the various
embodiment, a ratio of
silane based compounds to silicone based compounds in the oil phase of the oil-
in-water silicon-
based emulsion can range from 0:1 to 1:0 (silane:silicone). Ratios within this
range are also
possible, and include 0:1, 0.01:0.99, 0.05:0.95, 0.1:0.9, 0.2:0.8, 0.3:0.7,
0.4:0.6, 0.5:0.5, 0.6:0.4,
0.7:0.3, 0.8:0.2, 0.9:0.1, 0.95:0.05, 0.99:0.01 and 1:0.
[031] Forming the oil-in-water silicon-based emulsion of the present
disclosure can include
forming a mixture by combining the desired ratio of the silane based
compound(s) to silicone
based compound(s), as provided herein, and mixing and homogenizing with water
or an aqueous
based solution to form the oil-in-water silicon-based emulsion of the present
disclosure. Water,
as used herein, can include deionized water, whereas an aqueous based solution
can include
water and one or more hydrophilic additives. Such hydrophilic additives
include, but are not
limited to, low molecular weight alcohols such as methanol, ethanol, propanol,
isopropanol and
the like. One or more of a foam control agent and/or a pH control agent can be
included with the
oil-in-water silicon-based emulsion as desired.
[032] Mixing so as to form the oil-in-water silicon-based emulsion can be
accomplished by
known methods and may occur either as a batch, a semi-continuous, or a
continuous process.
Forming the oil-in-water silicon-based emulsion of the present disclosure can
include adding
from 30 to 900 parts of water or the aqueous based solution for every 100
parts of the silane
based compound(s) and/or silicone based compound(s). This allows for the oil-
in-water silicon-
based emulsion to have an oil phase content of (e.g., a "solids" content) of
11% to 79% by
volume. The average volume particle size of the oil phase content can be from
0.3 to 10 p.m.
The viscosity of the oil-in-water silicon-based emulsion of the present
disclosure may be from 5
centipoises to 500 centipoises, as measured using a Brookfield viscometer;
viscosities
appropriate for different application methods vary considerably.
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[033] The process of combining and mixing the components for the oil-in-water
silicon-based
emulsion may occur in a single step or multiple step process. Thus, the
components may be
combined in total, and subsequently mixed via any of the techniques described
herein.
Alternatively, a portion(s) of the components may first be combined, mixed,
and followed by
combining additional quantities of the components and further mixing. One
skilled in the art
would be able to select optimal portions of the components for combing and
mixing, depending
on the selection of the quantity used and the specific mixing techniques
utilized in forming the
oil-in-water silicon-based emulsion.
[034] The coating composition of the present disclosure also includes 25 wt.%
to 95 wt.% of
the acrylic polymer waterborne emulsion based on the total weigh of the
coating composition.
As used herein acrylic polymer waterborne emulsion refers to a water based
emulsion, where the
acrylic polymer of the acrylic polymer waterborne emulsion is formed with non-
ionic monomers
selected from the group consisting of methyl methacrylate, methyl acrylate,
ethyl acrylate, butyl
acrylate, styrene, butyl methacrylate, 2-ethylhexyl acrylate, t-butyl
acrylate, a-methyl styrene,
vinyl acetate, hexyl acrylate and combinations thereof The use of the term
"meth" followed by
another term such as methacrylate refers to both acrylates and methacrylates.
Preferably, the
acrylic polymer of the acrylic polymer waterborne emulsion is formed with non-
ionic monomers
selected from the group consisting of methyl methacrylate and butyl acrylate.
Preferably, the
acrylic polymer of the acrylic polymer waterborne emulsion is formed with non-
ionic monomers
selected from the group consisting of methyl methacrylate and 2-ethylhexyl
acrylate.
[035] The acrylic polymer is substantially uncross-linked, that is the acrylic
polymer includes
less than 1 weight %, preferably less than 0.2 weight %, based on the weight
of the polymer, and
more preferably 0% of a copolymerized multi-ethylenically unsaturated monomer.
Multi-
ethylenically unsaturated monomers include, for example, ally' (meth)acrylate,
diallyl phthalate,
1,4-butylene glycol di(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate,
1,6-hexanediol
di(meth)acrylate, and divinyl benzene.
[036] The acrylic polymer waterborne emulsion has an acid level of up to 2
percent by weight
of acid monomers based on a dry weight of the acrylic polymer. Acid monomers
include
carboxylic acid monomers such as, for example, acrylic acid, methacrylic acid,
crotonic acid,
itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl
fumarate,
monobutyl fumarate, and maleic anhydride; and sulfur- and phosphorous-
containing acid
monomers. Preferred acid monomers are carboxylic acid monomers. More preferred
monomers
are (meth)acrylic acid. The acid level can be calculated by determining the
number of
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milliequivalents of acid per gram in the acrylic polymer and multiplying by
the molecular weight
of potassium hydroxide.
[037] For the various embodiments, the glass transition temperature ("Tg") of
the acrylic
polymer can be from 15 C to 60 C. In an additional embodiment, the acrylic
polymer in the
acrylic polymer waterborne emulsion has a Tg of 25 C to 55 C. The Tg of the
acrylic polymer
can be calculated by using the Fox equation (T. G. Fox, Bull. Am. Physics
Soc., Volume 1, Issue
No. 3, page 123 (1956)), where calculating the Tg of a copolymer of monomers
M1 and M2 is
determined using the equation:
1/Tg(calc)=w(M1)/Tg(M1)+w(M2)/Tg(M2)
[038] wherein Tg(calc) is the glass transition temperature calculated for the
copolymer; w(M1)
is the weight fraction of monomer M1 in the copolymer; w(M2) is the weight
fraction of
monomer M2 in the copolymer; Tg(M1) is the glass transition temperature of the
homopolymer
of Ml; Tg(M2) is the glass transition temperature of the homopolymer of M2,
all temperatures
being in degree Kelvin. The glass transition temperature of homopolymers may
be found, for
example, in "Polymer Handbook", edited by J. Brandrup and E. H. Immergut,
Interscience
Publishers. In calculating Tgs herein the contribution of copolymerized
graftlinking monomers
is excluded. The calculated Tg is calculated from the total overall
composition of the acrylic
polymer particle.
[039] The polymerization techniques used to prepare the acrylic polymer of the
acrylic polymer
waterborne emulsion include emulsion polymerization, which is well known in
the art (e.g.,
examples disclosed in U.S. Pat. Nos. 4,325,856; 4,654,397; and 4,814,373 among
others).
Conventional surfactants may be used such as, for example, anionic and/or
nonionic emulsifiers
such as, for example, alkali metal or ammonium alkyl sulfates, alkyl sulfonic
acids, fatty acids,
and oxyethylated alkyl phenols. The amount of surfactant used can be from 0.1%
to 6% by
weight, based on the weight of total monomer. Either thermal or redox
initiation processes may
be used. Conventional free radical initiators may be used such as, for
example, hydrogen
peroxide, t-butyl hydroperoxide, t-amyl hydroperoxide, ammonium and/or alkali
persulfates,
typically at a level of 0.01% to 3.0% by weight, based on the weight of total
monomer. Redox
systems using the same initiators coupled with a suitable reductant such as,
for example, sodium
sulfoxylate formaldehyde, sodium hydrosulfite, isoascorbic acid, hydroxylamine
sulfate and
sodium bisulfite may be used at similar levels, optionally in combination with
metal ions such as,
for example iron and copper, optionally further including complexing agents
for the metal. The
monomer mixture for a stage may be added neat or as an emulsion in water. The
monomer
mixture for a stage may be added in a single addition or more additions or
continuously over the
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reaction period allotted for that stage using a uniform or varying
composition; preferred is the
addition of the polymer monomer(s) emulsion as a single addition. Additional
ingredients such
as, for example, free radical initiators, oxidants, reducing agents, chain
transfer agents,
neutralizers, surfactants, and dispersants may be added prior to, during, or
subsequent to any of
the stages.
[040] The average particle diameter of the acrylic polymer particles can be
from 40 to 400
nanometers (measured with a Brookhaven Instruments particle size analyzer).
The solids content
of the acrylic polymer waterborne emulsion of the present disclosure may be
from 30% to 70%
by weight based on the total weight of the acrylic polymer waterborne
emulsion. The viscosity
of the acrylic polymer waterborne emulsion of the present disclosure may be
from 10 centipoises
to 5000 centipoises, as measured using a Brookfield viscometer; viscosities
appropriate for
different application methods vary considerably. The acrylic polymer
waterborne emulsion of
the present disclosure can have a pH of 3 to 11 as measured at 23 C.
[041] The coating composition can be prepared by techniques that are well
known in the
coatings art. The acrylic polymer waterborne emulsion and the oil-in-water
silicon-based
emulsion can be added under low shear stirring along with other coatings
adjuvants as desired.
The coating composition may contain, in addition to the acrylic polymer
waterborne emulsion
and the oil-in-water silicon-based emulsion, inorganic fillers such as quartz,
biocides when water
is present, untreated and treated silicas, metal hydroxide micropowders such
as aluminum
hydroxide micropowder, calcium hydroxide micropowder, and magnesium hydroxide
micropowder, bisamides, flake-form fillers such as mica,
dimethylpolysiloxanes, epoxy-
functional diorganopolysiloxanes, and amino-functional diorganopolysiloxanes,
as well as
pigments, curing agents, buffers, corrosion inhibitors, neutralizers,
humectants, wetting agents,
antifoaming agents, UV absorbers, fluorescent brighteners, light or heat
stabilizers, biocides,
dispersants, colorants, colorant dispersions, waxes, water-repellants,
pigments, extenders, anti-
oxidants and dyes can be added to the coating composition. Additional
components that may
also be included in the coating composition may be preservatives, freeze/thaw
additives, and
various thickeners.
[042] The present disclosure also provides for an aqueous composition for use
in controlling
efflorescence in porous construction materials. The aqueous composition
includes the coating
composition as described herein and water in an amount sufficient to provide
the aqueous
composition with a solids content of 2 to 25 wt.% based on the total weight of
the aqueous
composition. So, for the present disclosure the coating composition as
described herein can be
considered to be a concentrate form of the aqueous composition, where the
coating composition
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is diluted with water or an aqueous composition to arrive at the aqueous
composition. As with
the coating composition, an embodiment of the present disclosure includes
where the coating
composition and the water of the aqueous composition add to 100 wt.% based on
the total weight
of the aqueous composition.
[043] Mixing so as to form the aqueous composition with a solids content of 2
to 25 wt.%
based on the total weight of the aqueous composition can be accomplished by
known methods
and may occur either as a batch, a semi-continuous, or a continuous process.
Forming the
aqueous composition of the present disclosure can include water or an aqueous
composition to
the coating composition, as provided herein, to arrive at the solids content
of 2 to 25 wt.% based
on the total weight of the aqueous composition. As appreciated, arriving at
the solids content for
the aqueous composition will depend on the solids content of each of the
acrylic polymer
waterborne emulsion and the oil-in-water silicon-based emulsion.
[044] The process of combining and mixing the acrylic polymer waterborne
emulsion and the
oil-in-water silicon-based emulsion may occur in a single step or multiple
step process. Thus,
the components may be combined in total, and subsequently mixed via any of the
techniques
described herein. Alternatively, a portion(s) of the components may first be
combined, mixed,
and followed by combining additional quantities of the components and further
mixing. One
skilled in the art would be able to select optimal portions of the components
for combing and
mixing, depending on the selection of the quantity used and the specific
mixing techniques
utilized in forming the aqueous composition.
[045] As discussed herein, embodiments of the aqueous composition can be used
for
controlling efflorescence in porous construction materials. The aqueous
composition of the
present disclosure can be used with a porous construction material. For
example, the aqueous
composition of the present disclosure can be used to at least partially coat
the porous
construction material. Examples of porous construction material can include an
inorganic porous
construction material, where the inorganic porous construction material can be
a cement based
porous construction material.
[046] In providing a coating of the present disclosure the aqueous composition
of the present
disclosure is applied to the porous construction material and, dried, or
allowed to dry. The
aqueous composition is typically applied to a porous construction material
such as, for example,
wood and/or inorganic porous substrates such as those made with cement or
gypsum. Examples
of such inorganic porous substrates include concrete, stucco, drywall, and
mortar that are either
new and not previously painted or treated, previously printed, painted or
primed surfaces, or
weathered surfaces. The aqueous composition of the present disclosure may be
applied to the
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porous construction material using conventional coatings application methods
such as, for
example, paint brush, paint roller, gravure roll, curtain coater and spraying
methods such as, for
example, air-atomized spray, air-assisted spray, airless spray, high volume
low pressure spray,
and air-assisted airless spray. Drying of the aqueous composition may proceed
under ambient
conditions such as, for example, at 5 C to 35 C or the coating may be dried
at elevated
temperatures such as, for example, from 35 C to 100 C.
[047] The following examples serve to illustrate the disclosure.
Examples
[048] In the Examples, various terms and designations for materials were used
including, for
example, the following:
Table 1 List of materials
Material Description/Source Tg
( C)
DOWSILTM 520 An oil-in-water silicon-based
emulsion (silane/siloxane emulsion
blend, The Dow Chemical Company)
PRIMALTm AC- Acrylic Polymer Waterborne 26
339 Emulsion (The Dow Chemical
Company)
PRIMALTm SS- Acrylic Polymer Waterborne 33
640 Emulsion (The Dow Chemical
Company)
DOWANOLTM Coalescing Agent - dipropylene
DPnB glycol n-butyl ether (The Dow
Chemical Company)
DOWSILTM IE- Non-ionic Oil-In-Water emulsion
6682 Based on Alkoxysilane and silicone
resin (The Dow Chemical Company)
[049] High density flat fiber cement (FC) board used in the examples were
prepared using the
Hatscheck process and were air cured. The FC board has a thickness of 0.8 cm.
The FC board
was stored at room temperature (23 C) at a relative humidity of 40 to 50%.
Perform the
following coating tests at room temperature (23 C) at a relative humidity of
40 to 50%.
[050] For each of the following coating tests, impregnate the FC board with
the aqueous
composition, where the aqueous composition is formed from the coating
composition provided
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in Tables 2 and 4, below. To prepare the aqueous composition for each Example
and
Comparative Example, dilute each of the oil-in-water silicon-based emulsion
and the acrylic
polymer waterborne emulsion of the coating composition seen in Tables 2 and 4
with deionized
water to achieve the aqueous composition, where the aqueous composition has a
solids content
of 15 weight percent (wt.%) based on the total weight of the aqueous
composition. Mix the
coating composition at room temperature using an overhead stirrer with a blade
at rotation speed
of 200 RPM for approximately 5 minutes.
[051] Apply the aqueous composition formed with each Example and Comparative
Example to
the FC board to achieve a coverage amount of 150 g/m2. Allow each of the FC
boards treated
with the aqueous composition formed with each Example and Comparative Example
to dry for 7
days. After 7 day, visually inspect each of the FC boards. For the Examples
and Comparative
Examples seen in Table 1, treating the FC boards with an aqueous composition
formed with a
coating composition containing more than 50% by weight of the acrylic emulsion
(e.g., Ex 3, Ex
4 and CE C) produced a glossy appearance on the FC board. Treating the FC
board with an
aqueous composition formed with a coating composition containing from 0 to 50%
by weight of
the acrylic emulsion kept their original matte look (e.g., Ex 1 and Ex 2).
Table 2 ¨ Coating Compositions - Examples (Ex) 1-4 and Comparative Examples
(CE) A-C
Ex Silicon-Based Acrylic Ratio
Emulsion (SBE) Emulsion (AE) SBE:AE
CE (wt:wt
based
on total
wt. of
coating
comp.)
CE DOWSILTM 520 1:0
A
CE DOWSILTM 520 PRIMALTm 9:1
AC-339
Ex DOWSILTM 520 PRIMALTm 7.5:2.5
1 AC-339
Ex DOWSILTM 520 PRIMALTm 5:5
2 AC-339
Ex DOWSILTM 520 PRIMALTm 2.5:7.5
3 AC-339
Ex DOWSILTM 520 PRIMALTm 1:9
4 AC-339
CE PRIMALTm 0:1
AC-339
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Water Absorption Test
[052] Use the Cobb Test (a modified version of ISO 535-2714) to assess the
water absorption
values for each of the FC boards treated with the aqueous composition formed
with each of Ex 1-
4 and CE A-C. Water absorption into the FC boards is expressed in kg/m2 at
different contact
time with water. Assess gloss and efflorescence visually of each of the FC
boards treated with
the aqueous composition formed with each of Ex 1-4 and CE A-C. The results are
provided in
Table 3.
Resistance to Efflorescence Test
[053] Assess the resistance to efflorescence of each of the FC boards treated
with the aqueous
composition formed with each of Ex 1-4 and CE A-D as follows. Exposure of
reference or
treated FC boards to water can indeed potentially lead to penetration of the
water into the boards,
followed by dissolution of calcium hydroxide present in the board matrix and
its migration to the
surface of the board. Additionally, application of cold temperature at the top
surface of the FC
board can drive precipitation of the calcium hydroxide or calcium carbonate
(formed in situ upon
reaction of the calcium hydroxide with carbon dioxide dissolved in water),
leading to accelerated
efflorescence process. Two test methods were used in this study ¨ Forced
Condensation Method
and Forced Precipitation
Forced Condensation Method
[054] Place a FC board on top of a refrigerated cold pack having a temperature
of -18 C to
form an assembly. Place the assembly in a weather chamber in which the
relative humidity is set
> 80%. The cold surface leads to forced condensation of cold water at the
surface of the FC
boards. Replace the cold pack every day. FC boards are left for a week (7
days) in the weather
chamber. Efflorescence is visually assessed after drying the FC boards.
Forced precipitation
[055] Place a FC board horizontally on a lab bench. Apply cold water (0.5 C
from either
melting from ice or stored in a refrigerator) on the upper surface of the FC
board. The cold
temperature of the water on the upper surface forces the precipitation of
calcium hydroxide
solution (which migrates from within the FC board to the surface of the FC
board due to the
hydric conditions) or calcium carbonate (formed in situ upon reaction of the
calcium hydroxide
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with carbon dioxide dissolved in water). Efflorescence is visually assessed
overnight after
complete evaporation of the cold water that was applied to the surface of the
FC board.
[056] Assess the appearance of the FC boards after drying of the water applied
at the surface of
the boards. The results are provided in Table 3.
Table 3 - Water Absorption Results from Cobb Test and Efflorescence According
to
Forced Precipitation Test.
Time 0 1.5 3.5 6 24 Gloss Efflorescence
(hours)
CE D No +++
(untreated 0. 0.55 0.88 1.15 2.35
Fiber 0 6 0 9 9
Cement
Board)
0. 0.01 0.01 0.03 0.12 No ++
CE A 0 0 5 2 8
0. 0.02 0.02 0.04 0.12 No +
CE B 0 5 5 8 4
0. 0.01 0.01 0.04 0.11 No 0
Ex 1 0 4 8 2 3
0. 0.00 0.02 0.02 0.12 No 0
Ex 2 0 6 1 7 8
0. 0.02 0.02 0.03 0.15 Yes 0
Ex 3 0 1 1 7 2
0. 0.19 0.47 0.73 1.79 Yes 0
Ex 4 0 6 6 0 4
0. 0.35 0.61 0.85 2.10 yes 0
CE C 0 8 0 2 7
Efflorescence: +++: surface clearly white over the all surface; ++: clear
white marks on all the
surface; +: surface with some white marks. 0 : no sign of white marks)
[057] The data seen in Table 3 shows a dramatic decrease in absorption of
water by treating FC
boards with pure silane/siloxane formulation (CE A) or aqueous compositions
formed with the
coating compositions of the present disclosure (Ex 1-3), provided the acrylic
polymer content is
not larger than 75% by weight based on the total weight of the coating
composition (e.g., Ex 4).
Table 3 also demonstrates that some whitening of the surface of the FC boards
occurs as a result
of the lack of Resistance to Efflorescence Test described above. Whitening of
the surface of the
FC boards was observed with FC boards treated with nothing (CE D) and FC
boards treated with
an aqueous composition formed from a coating composition having an acrylic
polymer
waterborne emulsion content of less than 25% weight percent based on the total
weight of the
coating composition (CE B). Data in Table 3 suggests that better protection of
the FC boards
against water ingress and resultant efflorescence is obtained thanks to the
treatment with aqueous
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compositions formed with coating compositions having at least 25 wt.% of the
acrylic polymer
waterborne emulsion based on the total weight of the coating composition (Ex.
1-4).
[058] Table 4 provides an additional Example (Ex 6) and Comparative Examples
(CE E ¨ CE
H) of the coating composition. Prepare the coating compositions of each of Ex
6 and CE D
through CE G according to the ratios (ratio based on the total weight of the
coating composition)
provided in Table 4 by mixing the components at room temperature using an
overhead stirrer
with a rotation speed of 200 RPM for approximately 10 minutes. Each of CE E
through CE H
further includes 8 wt.% (based on the total weight of the polymer content in
the acrylic polymer
waterborne emulsion) of the coalescing agent. Use deionized water to prepare
aqueous
compositions having a solids content of 10% using coating compositions from
each of Ex 6 and
CE E-H seen in Table 4.
Table 4 ¨ Coating Composition - Example 6 and Comparative Examples (CE) E ¨ H
Ex / CE Silicon- Acrylic Coalescing Ratio
Based Emulsion (AE) Agent, SBE:AE
Emulsion DOWANOLTM (wt:wt
(SBE) DPnB (wt. %, based on
based on total total wt.
wt. of polymer of
content) coating
comp.)
CE E 0:0
CE F DOWSILTM PRIMALTm 8 7.5:2.5
520 SS-640
CE G DOWSILTM PRIMALTm 8 7.5:2.5
1E-6682 SS-640
CE H DOWSILTM PRIMALTm 8 5:5
1E-6682 SS-640
Ex 6 DOWSILTM PRIMALTm 0 5:5
1E-6682 SS-640
[059] For each of the following coating tests, impregnate the FC board with
the aqueous
composition prepared from the coating composition of each Ex 6 and CE E
through CE H.
Apply the aqueous composition to the FC board to achieve a coverage amount of
110 g/m2.
Allow each of the FC boards treated with the aqueous composition formed from
Ex 6 and CE E
through CE H to dry for 7 days. After 7 days, visually inspect each of the FC
boards. Each FC
board treated with the aqueous composition formed using Ex 6 and CE D through
CE G kept
their original matte look.
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Resistance to Efflorescence Test
[060] Assess the resistance to efflorescence for each of the FC boards treated
with each of the
aqueous composition formed using Ex 6 and CE E through CE H as follows. Assess
long term
durability of the FC boards treated with the aqueous compositions formed using
the coating
compositions of Ex 6 and CE E through CE H against efflorescence by submitting
the treated FC
boards to UV exposure. The FC boards treated with the aqueous compositions
described herein
are irradiated for 10 weeks in a dry closed box with an ULTRA-VITALUX High-
pressure UV
lamp (300 W, OSRAM). Assess the resistance to efflorescence after 10 weeks of
exposure to the
UV light by then testing them according to the forced precipitation
efflorescence test. The
results are provided in Table 5.
Table 5 ¨ Efflorescence Test after 10 weeks UV Exposure
Appearance of Fiber Cement Board after 10 weeks UV Efflorescence
exposure and Efflorescence Test (ice cube test).
CE E +++
CE F ++
CE G
CE H
Ex 6 0
Efflorescence: +++: surface clearly white over the all surface; ++: clear
white marks on all the
surface; +: surface with some white marks. 0 : no sign of white marks)
[061] As seen in Table 5, treating the FC board with the aqueous composition
formed with Ex 6
shows excellent resistance to efflorescence even after being exposed to UV
light for 10 weeks
prior to undergoing the forced precipitation efflorescence test. Even after 14
weeks of UV
exposure, the FC board treated with the aqueous composition formed with Ex 6
continued to
show no signs of efflorescence when tested by the forced precipitation test.
As seen for FC
boards treated with aqueous composition formed with CE E through CE H, FC
boards having
aqueous compositions containing the coalescing agent showed clear signs of
efflorescence. In
contrast, Ex 6 shows that FC boards treated with an aqueous composition
containing only the
acrylic polymer waterborne emulsion with the acrylic polymer having a Tg of
greater than 15 C
and the oil-in-water silicon-based emulsion of the present disclosure having
no additional
coalescing agent shows no sign of efflorescence.
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