Ultra-flexible nano-modified cementitious waterproofing coating and method of manufacturing

Abstract

The present invention relates to a coating composition and method of manufacturing said coating composition. The coating composition is a two-component coating composition for construction surfaces. The present coating composition is effectively bonded to the surface without an additional application of intermediate layer overcoming the existing problems associated with conventional concrete surface treatment methods.

Claims

1. A coating composition comprising a liquid component and a solid component in a weight ratio of 1:1.25 to 1:1.5; the liquid component comprises 100 parts of styrene-acrylate copolymer emulsion, 10-20 parts of water, 0.025-0.1 parts of nanoparticles, 0.25-1.0 parts of superplasticizer and 0.025-1.0 parts of defoamer to weight of the liquid component; and the solid component comprises hydraulic cement and non-hydraulic filler.

2. The coating composition of claim 1, wherein the liquid component further comprises 0.25-1.0 parts of silane coupling agent.

3. The coating composition of claim 1, wherein the solid component further comprises fibers.

4. The coating composition of claim 1, wherein the nanoparticle comprises nano-silica, nano-aluminum oxide, nano-zinc oxide, nano-boron, nano-iron oxide or nano-calcium carbonate and particle size of the nanoparticles are 5 nm to 30 nm.

5. The coating composition of claim 1, wherein the superplastizier comprises poly(melamine sulfonate), poly(naphthalene sulfonate), polycarboxylate or derivatives thereof.

6. The coating composition of claim 2, wherein the silane coupling agent comprises (3-aminopropyl) trimethoxysilane, (3-aminopropyl) triethoxysilane, (3-Glycidyloxypropyl) trimethoxysilane, (3-Glycidyloxypropyl) triethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane or N-2-aminoethyl-3-aminopropyltriethoxysilane.

7. The coating composition of claim 1, wherein the hydraulic cement comprises Portland cement or white cement and the filler comprises heavy calcium carbonate filler.

8. The coating composition of claim 1, wherein weight ratio of cement to filler is selected from 2:1, 1:1 and 1:2.

9. The coating composition of claim 3, wherein the fiber comprises polyvinyl alcohol (PVA) fibers, polyester (PET) fibers or polypropylene (PP) fibers.

10. The coating composition of claim 3, wherein the solid component comprises 0.1%-0.5% wt of fibers and the fibers are 6 mm-12 mm in length and have a diameter of 15 μm-50 μm.

11. A method of coating a surface comprising applying the coating composition of claim 1.

12. The method of claim 11, wherein the surface comprises concrete, stone, bricks, tile and cement-based surface.

Description

BRIEF DESCRIPTION OF INVENTION

(1) The above and other objects and features of the present invention will become apparent from the following description of the invention, when taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 shows elongation performance of a coat formed by the present coating composition (FIG. 1A) and tensile strength of three coats formed by coating composition according to the present invention (FIG. 1B).

(3) FIG. 2 shows maximum depth of water penetration of concrete without any coating (FIG. 2A) and coated with coating composition of the present invention (FIG. 2B) under 0.5 MPa for 72 hours.

DETAILED DESCRIPTION OF INVENTION

(4) The present invention is not to be limited in scope by any of the specific embodiments described herein. The following embodiments are presented for exemplification only.

(5) The present invention provides a novel coating composition for coating both dry and wet surfaces. The coat resulted from the present coating composition is highly waterproof with excellent elasticity and tensile strength. Additionally, the coat formed from the present coating composition adheres strongly to surfaces without any intermediate or supplementary layer. Accordingly, the present invention provides a coating composition which forms a water impermeable coat on surface with reduced delamination and cracking.

(6) The present coating composition comprises a liquid component and a solid component in a weight ratio of 1:1.25 to 1:1.5. The liquid component comprises 100 parts of styrene-acrylate copolymer emulsion, 0.25-1.0 parts of superplasticizer, 0.25-1.0 parts of defoamer, 0.025-0.1 parts of positively charged hydrophilic nanoparticles and 10-20 parts of water to weight of the liquid component. The solid component comprises hydraulic cement and non-hydraulic filler in a weight ratio selected from 2:1, 1:1 and 1:2. Optionally, the liquid component further comprises 0.25-1.0 parts of silane coupling agent and the solid component further comprises synthetic fiber. The present coating composition has a low polymer to cement weight ratio compared to conventional cementitious coating compositions. The present coating composition overcomes the problems of separation of coat from the substrate, delamination and cracking of coat or the like, which commonly exist in conventional coating compositions, by having a low polymer to cement weight ratio. The adhesiveness of the present coating composition is further enhanced by addition of silane coupling agent. The bonding strength of the present coating composition on wet surface is above 1.2 N/mm.sup.2. The liquid and solid components are mixed together before applying the present composition onto a substrate surface. The present coating composition may be applied onto wet or dry surfaces by conventional techniques readily known by one skilled in the art, such as conventional spray coating, brushing, dipping, roller coating or the like. The coat formed from the present coating composition has about 20 wt % of polymer content, and is associated with high elastic and waterproof performance. The present coating composition can be applied to inner, outer or concealed areas of civil engineering construction. The high adherence property of the present coating composition enables the coating composition to adhere onto substrate material or surfaces without an intermediate adhesive layer. The substrate includes concrete, stone, bricks, tile and cement-based substrate.

(7) The nanoparticles of the present coating composition act as a lubricant between the polymer chains; they are absorbed and anchored onto the surface of the polymer. Presence of the nanoparticles in the present coating composition enables movement between the polymers when the coat is under stress or stretched. Thus, the coat formed from the present coating composition has excellent elasticity and tensile strength. The nanoparticles of the present coating composition are hydrophilic positively charged nanoparticles. The particle size of the nanoparticles of the present invention ranges from 5 nm to 30 nm. In some embodiments, the particle size of the nanoparticles is selected from 5 nm, 13 nm, 20 nm and 30 nm. Particle size of the nanoparticles of the present coating composition may or may not be homogeneous. Examples of nanoparticles of the present composition include, but are not limited to, nano-silica, nano-aluminum oxide, nano-zinc oxide, nano-boron, nano-iron oxide and nano-calcium carbonate. In one embodiment, the particle size of the nanoparticle is 20 nm. In another embodiment, the nanoparticle is aluminum oxide nanosphere. The present composition comprises 0.025-0.1 parts of nanoparticles. In one embodiment, the present composition comprises 0.025 parts to 0.05 parts of nanoparticles. Styrene-acrylate copolymer emulsion of the present composition has excellent anti-ultraviolet performance, good durability and good chemical resistance. This co-polymer also has a favorable film forming temperature and water resistance characteristic for use as a construction coat. The copolymer emulsion is a liquid emulsion of pH 8-10.

(8) Superplasticizer, also known as water reducer, improves dispersion of the coating composition. The present composition comprises 0.25-1.0 parts of superplasticizer. In one embodiment, the composition comprises 0.25 parts to 0.5 parts of superplasticizer. Examples of superplasticizer of the present invention include, but are not limited to, poly(melamine sulfonate), poly(naphthalene sulfonate), polycarboxylate and derivatives thereof, as well as SBT®PCA-I, SBT®PCA-V, SBT JM®, OROTAN™ 1850 (Dow) and ADVA-109 (BASF). The present composition further comprises 0.25-1.0 parts of defoamer to remove micro bubbles and optionally 0.25-1.0 parts of silane coupling agent. The defoamer suitable for the present invention is a non-ionic organic silicon defoamer having a linear polysiloxiane as an active agent at room temperature. Examples of defoamer include, but are not limited to, Foamer®NXZ, Foamaster®111, Foamaster®8034A, FoamStar®A10, Foamstar ST 2446, FoamStar®A12 and FoamStar®SI 2250. Examples of silane coupling agent include, but are not limited to, (3-aminopropyl) trimethoxysilane (APTMS), (3-aminopropyl) triethoxysilane (APTES), (3-Glycidyloxypropyl) trimethoxysilane (GPTMS), (3-Glycidyloxypropyl) triethoxysilane (GPTES), N-2-aminoethyl-3-aminopropyltrimethoxysilane (AEAPTMS), N-2-aminoethyl-3-aminopropyltriethoxysilane (AEAPTES) or a combination thereof.

(9) The hydraulic cements of the solid component of the present invention are those readily used by the skilled in the art, such as Portland cement and white cement. The solid component may include one or more types of hydraulic cement. Fillers suitable for the present invention include, but are not limited to, heavy calcium carbonate fillers. The filler in the solid component of the present invention enhances the strength of the resulting coat while maintain the production cost low. One or more types of filler of different sizes are included in the solid component. In one embodiment, the filler is non-hydraulic filler and the particle size of the filler is about 250-500 mesh or lower than 60 μm. The weight ratio of cement to filler of the solid component is selected from 2:1, 1:1 and 1:2. In one embodiment, the solid component comprises 100 parts of hydraulic cement and 100 parts of non-hydraulic filler by weight.

(10) In some embodiment, the solid component further comprises fibers to enhance tear resistance and tensile strength of the present invention. Fibers are short synthetic alkali fibers, such as polyvinyl alcohol (PVA) fibers, polyester (PET) fibers and polypropylene (PP) fibers. Fibers applicable to the present invention may be 6 mm-12 mm in length and have a diameter of 15 μm-50 μm. In some embodiment, the length of short fiber is 9 mm and the diameter ranges 40 μm-50 μm. The solid component comprises 0.1%-0.5% wt of fiber.

(11) The liquid and solid components of the present composition are mixed thoroughly to become a lump-free slurry before applying onto the substrate. The lump-free slurry of the present coating composition is then applied onto surface in need thereof and when the coating composition is dried to form a waterproof and flexible coat, the coat has about 20 wt % polymer content. The substrate may be dry, wet or pre-soaked. Multiple layers of the present coating composition may be applied onto the substrate. Addition layer should be applied after the previous layer is dried. Water may be applied onto the substrate before applying the present coating composition. The present coating composition is then cured to form the resulting coat. The resulting coat is a double network composing of stiff, brittle cement-based network cross-linked by hydrated cement and a soft, ductile nano-modified polymer network.

(12) The second aspect of the present invention relates to method of preparing a water-resistant, flexible and adhesive coating composition. The method comprises modifying styrene-acrylate copolymer with nanoparticles by physical adsorption under high-speed mixing to form the liquid component. The nanoparticles are dispersed in water with the superplasticizer under rapid stirring to form an aqueous solution. The polymer emulsion is then added to the aqueous solution with fast mechanical stirring. Defoamer and optionally silane coupling agents are added last to form the liquid component. The solid component is manufactured by mixing at least one of hydraulic cement, non-hydraulic fillers, and synthetic fibers using a dry mortar production liner under high speed. Both liquid and solid component of the present invention can be packaged and stored for later application. The liquid and solid components are mixed at a weight ratio of 1:1.25 to 1:1.5 until a lump-free slurry is formed. The present coating composition is applied onto the substrate using block brushing, squeegee roller, sprayer or the like to form a 1.5-2 mm coat. The coat formed from the coating composition of the present invention has a fixed polymer content of 20 wt %.

EXAMPLES

(13) Table 1 shows examples of nano-modified polymer cementitious coating composition prepared in accordance with the present invention.

(14) TABLE-US-00001 TABLE 1 shows coating compositions according to the present invention. All constituents are represented in parts by weight ratio. Example 1 Example 2 Example 3 Example 4 Example 5 Liquid Polymer Emulsion 100 100 100 100 100 Component DI water 10 10 10 10 10 (L) Defoamer 0.5 0.5 0.5 0.5 0.5 Superplasticizer 0.25 0.5 0.5 0.5 0.5 Al.sub.2O.sub.3 Nanoparticles 0.025 0.05 0.05 0.05 0.05 Silane coupling — — 0.5 0.5 0.5 agent Solid Hydraulic cement 100 100 100 100 100 Component Calcium carbonate 100 100 100 100 100 (S) Short fiber — — — 0.2 (PET) 0.2 (PVA) L/S ratio 1:1.5 1:1.5 1:1.5 1:1.5 1:1.5

(15) Properties of example coating compositions 1-5 of the present invention (Table 1) are tested. Table 2 and Table 3 below show the physical properties of coating compositions of the present application and four commercially available concrete coating compositions.

(16) TABLE-US-00002 TABLE 2 shows physical properties of coating compositions of the present application. Tensile Elongation Bonding Impermeability strength at break strength (0.5 MP, VOC Example (N/mm2) (%) (N/mm2) 72 hrs) (g/L) 1 1.78 354 1.36 Permeation free 15.3 2 2.01 365 1.49 Permeation free 14.6 3 1.69 651 1.22 Permeation free 23.3 4 1.76 618 1.26 Permeation free 23.6 5 1.80 576 1.30 Permeation free 22.5

(17) TABLE-US-00003 TABLE 3 shows physical properties of commercially available concrete coating compositions. Elong- Imperme- Tensile ation Bonding ability strength at break strength (0.5 MP, VOC Specimen L/P (N/mm.sup.2) (%) (N/mm.sup.2) 72 hrs) (g/L) Product E 16.9:25 0.72 328 0.65 Water leakage 22 Product F 18:25 0.74 296 0.81 Water leakage 26 Product G 1:1.5 1.79 82 1.15 Water leakage 5.4 Product R 1:1.25 1.10 297 0.97 Water leakage 6.9

(18) Examples 1-5 are prepared as described above and cured for 7 days. The coating composition of the present invention is shown to have a tensile strength of 1.5-2.0 N/mm.sup.2 (FIG. 1B), 350%-650% elongation at break (FIG. 1A) and a bonding strength to concrete of 1.0-1.5 N/mm.sup.2. The waterproof performance of the coating composition is tested according to BS EN 12390-8 standards. Substrate having coated with the present coating composition is water impermeable. It is demonstrated that the maximum water penetration depth of concrete coated with coating composition of the present invention is 0 mm under 0.5 Mpa for 72 hours (FIG. 2B). On the other hand, the maximum water penetration depth of concrete with no coat is approximately 150 mm under 0.5 Mpa for 72 hours (FIG. 2A). The present coating composition is also safe; volatile organic content (VOC) of the present coating composition is less than 50 g/L.

(19) Commercially available coating products E, F, G and R which exclude nanoparticle are also tested for their physical properties (Table 3). It is showed that none of the commercially available products is water impermeable under 0.5 Mpa for 72 hours. While Products E and F shows very good elongation at break, its bonding strength and tensile strength remain weak. Product G has good bonding strength and tensile strength, but it is not flexible; tensile strength, elongation and bonding strength of Product R is weaker as compared to the coating composition of the present invention.

(20) The above examples demonstrate the present invention provides a coating composition for surfaces which is water impermeable, flexible with high tensile strength. The coating composition is effectively bonded to the surface without an additional application of intermediate layer overcoming the existing problems associated with conventional concrete surface treatment methods.

(21) If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.

(22) While the foregoing invention has been described with respect to various embodiments and examples, it is understood that other embodiments are within the scope of the present invention as expressed in the following claims and their equivalents. Moreover, the above specific examples are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. Without further elaboration, it is believed that one skilled in the art can, based on the description herein, utilize the present invention to its fullest extent. All publications recited herein are hereby incorporated by reference in their entirety.