CA3112956A1 - Coating composition for controlling efflorescence - Google Patents

Abstract

The present disclosure provides a coating composition for use in controlling efflorescence in porous construction materials. The coating composition includes an acrylic polymer waterborne emulsion, where the acrylic polymer in the acrylic polymer waterborne emulsion has a Tg of 15 oC to 60 oC, and an oil-in-water silicon-based emulsion. 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-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 wt.% based on the total weight of the aqueous composition.

Description

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.

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-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.

[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 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 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.

[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 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.

[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 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 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 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 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 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 Ex DOWSILTM 520 PRIMALTm 7.5:2.5 Ex DOWSILTM 520 PRIMALTm 5:5 Ex DOWSILTM 520 PRIMALTm 2.5:7.5 Ex DOWSILTM 520 PRIMALTm 1:9 CE PRIMALTm 0:1 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 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 ++

0. 0.02 0.02 0.04 0.12 No +

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 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 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 CE G DOWSILTM PRIMALTm 8 7.5:2.5 CE H DOWSILTM PRIMALTm 8 5:5 Ex 6 DOWSILTM PRIMALTm 0 5:5

[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.

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.

Claims (18)

Claims What is claimed:

1. A coating composition for use in controlling efflorescence in porous construction materials, comprising:
25 weight percent (wt.%) to 95 wt.% of an acrylic polymer waterborne emulsion based on the total weigh of the coating composition, wherein the acrylic polymer has a Tg of 15 C to 60 C; and 75 wt.% to 5 wt.% of an oil-in-water silicon-based emulsion based on the total weigh of the coating composition, wherein 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-in-water silicon-based emulsion based provides the only coalescing agent for the acrylic polymer waterborne emulsion in the coating composition.

2. The coating composition of claim 1, wherein the wt.% of the acrylic polymer waterborne emulsion and the oil-in-water silicone based emulsion in the coating composition add to 100 wt.%.

3. The coating composition of claim 1, wherein the acrylic polymer in the acrylic polymer waterborne emulsion has a Tg of 25 C to 55 C.

4. The coating composition of claim 1, wherein 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 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.

5. The coating composition of claim 4, wherein the alkoxy silane is R1Si(OR)3

6. The coating composition of claim 5, wherein Rl has 8 carbon atoms and R
has 2 carbon atoms to provide triethoxy(octyl)silane.

7. The coating composition of claim 1, wherein 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 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.

8. The coating composition of claim 1, wherein the polymethyl hydrogen siloxane is selected from compounds having the formulae:
R4(R5)25i¨(0¨SiR5H)a¨(0¨SiR5R6)b-5i (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.

9. The coating composition of claim 1, wherein the organosiloxane is selected from compounds having the formulae;
(R7)3Si¨(0¨Si(R7)2)a¨(0¨SiR7R8)b¨SiR73 (I);
or HO(R7)25i¨(0-5i(R7)2)a¨(0¨SiR7R8)b-5i(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.

10. The coating composition of any one of claims 1-9, wherein 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.

11. The coating composition of any one of claims 1-10, wherein 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

12. The coating composition of claim 11, wherein 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.

13. The coating composition of claim 11, wherein 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.

14. An aqueous composition for use in controlling efflorescence in porous construction materials, comprising:
the coating composition of any one of claims 1-13; 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.

15. The aqueous composition of claim 14, wherein the coating composition and the water of the aqueous composition add to 100 wt.% based on the total weight of the aqueous composition.

16. A porous construction material at least partially coated with the aqueous composition of any one of claims 14 or 15.

17. The porous construction material of claim 16, wherein the porous construction material is an inorganic porous construction material.

18. The porous construction material of claim 17, wherein the inorganic porous construction material is a cement based porous construction material.