Redispersible dry powder

Abstract

The present disclosure provides for a redispersible dry powder formed from particles of a composite structure. The composite structure consists of a lignin domain and a coating at least on a portion of the lignin domain. The coating is formed from a latex dispersion comprising vinyl acetate-based polymer particles.

Description

[0001] REDISPERSIBLE DRY POWDER

[0002] Technical Field

[0003] The present disclosure relates generally to a redispersible dry powder and more particularly to a redispersible dry powder that includes an organic filler.

[0004] Background

[0005] Hydraulic setting mixtures, like concrete and mortar, are important building products in the construction industry. However, their production generates carbon dioxide waste. To address this issue, research has explored incorporating organic materials such biochar, agricultural waste, and / or recycled organic matter into these mixtures. The goal is to reduce or offset the carbon footprint while maintaining the quality and performance of the final product. One challenge, however, is ensuring that these organic materials do not compromise the quality or performance of the resulting hydraulic setting mixture. Additionally, the cost-effectiveness of using organic materials can vary depending on specific applications.

[0006] Therefore, there is a continuing need in the art to reduce waste and carbon dioxide emissions in producing hydraulic setting mixtures while maintaining cost-effectiveness and ensuring the quality of the mixtures for the construction industry.

[0007] Summary

[0008] The aforementioned needs may be met by various aspects of the present disclosure. Embodiments of the present disclosure provide for a redispersible dry powder for use in the construction industry, and more specifically in the hydraulic setting mixtures area. When used with hydraulic setting mixtures, the redispersible dry powder of the present disclosure can help to sequester carbon dioxide while still providing cost-effectiveness and ensuring the quality of the hydraulic setting mixture.

[0009] Specifically, the present disclosure provides for a redispersible dry powder (RDP) that includes particles of a composite structure. For the various embodiments, the composite structure consists of a lignin domain and a coating at least on a portion of the lignin domain. The coating is formed from a latex dispersion comprising vinyl acetate-based polymer particles.

[0010] For the various embodiments, for the latex dispersion the vinyl acetate-based polymer particles can be formed of a copolymer formed with 50 to 95 weight percent (wt.%) vinyl acetate and 50 to 5 wt.% of a comonomer selected from the group consisting of styrene, butadiene, vinyl versatate, propionate, laurate, vinyl chloride, vinylidene chloride, ethylene, acrylates and combinations thereof, where the wt.% is based on the total weight of the copolymer. In more specific embodiments, the vinyl acetate-based polymer particles can be formed of a copolymer formed with 50 to 95 wt.% vinyl acetate and 50 to 5 wt.% of a comonomer selected from the group consisting of ethylene, vinyl versatate and combinations thereof. In a specific embodiment, the vinyl acetate-based polymer particles are formed from at least one of a vinyl acetate-ethylene copolymer and a vinyl acetate / vinyl-versatate copolymer. For the various embodiments, the vinyl acetate-based polymer particles provide the latex dispersion with a solids content of 40 to 65 wt.%, where the wt.% is based on the total weight of the latex dispersion.

[0011] For the various embodiments, the latex dispersion can include 4 to 15 wt.% of a stabilizer, where the wt.% is based on the total weight of the latex dispersion. For the various embodiments, the stabilizer can be polyvinyl alcohol having a degree of hydrolysis of 85 to 90 mole percent.

[0012] For the various embodiments, the RDP can include 5 to 40 wt.% lignin, where the wt.% is based on the total weight of the RDP. For the various embodiments, the lignin can be selected from the group consisting of a Kraft lignin, soda lignin, organosolv lignin, hydrolic lignin and combinations thereof. For the various embodiments, the lignin can have a weight average molecular weight of 1,000 to 100,000 Daltons.

[0013] For the various embodiments, the lignin domains can be solubilized in an alkali solution. For the various embodiments, the alkali solution can be a 1.0 wt.% NaOH solution in water, where the wt.% is based on the total weight of the alkali solution. For the various embodiments, the lignin domains having a mean diameter of less than about 25 pm can be encapsulated by the coating formed from the latex dispersion.

[0014] For the various embodiments, the particles are formed using a spray-drying process. For example, the present disclosure provides a method of forming particles of the RDP that includes providing lignin particles; providing a latex dispersion comprising vinyl acetate-based polymer particles; mixing the lignin particles with the latex dispersion to form a mixture, where the vinyl acetate-based polymer particles coat at least a portion of the lignin particle to form a composite structure; and spray-drying the composite structure in the mixture to form the particles of the RDP. Detailed Description

[0015] Redispersible polymers (RPs) are a type of polymer that can be dried and then redispersed in water without losing their original properties. This unique characteristic makes RPs valuable in various applications, particularly in the construction industry. In the construction industry, RPs help to enhance the properties of construction materials like tile adhesives, mortars, and other hydraulic setting mixtures by forming a continuous polymer film in the system. The formation of a continuous polymer film inside the hydraulic setting mixture has a strong influence on its physical properties, such as durability, water resistance, rheology and its adhesion between the cementitious matrix and the substrates, as well as the reduction of the water demand. On the other hand, the use of RPs can significantly contribute to the carbon footprint of the hydraulic setting mixture.

[0016] Embodiments of the present disclosure address the above identified issues by combining lignin particles with a latex dispersion to form a redispersible dry powder (RDP). For the embodiments, the particles of the RDP have a composite structure. As discussed herein, the composite structure is formed from a lignin domain and a coating on at least a portion of the lignin domain, where the coating is formed from the latex dispersion comprising vinyl acetate-based polymer particles. Such an RDP contains both the lignin and the latex in a single particle, which helps to improve the lignin’s redispersibility and homogeneity (e.g., minimizes settling and / or separation issues during storage) in the RDP all while helping to reduce the carbon footprint of the RDP of the present disclosure.

[0017] Throughout the specification, any reference to “percent” or “percent weight” is expressed in terms of dry weight of the composition, formulation or mixture unless otherwise specified.

[0018] As used herein, the term “hydraulic setting mixture” means a composition used in the construction field that can comprise a hydraulic binder, filler(s), water retention agent(s), and, further optionally, polymer containing additives such as a polymer dispersion and / or a redispersible polymer powder, such as the RDP of the present disclosure.

[0019] As used herein, the term “water soluble” refers to any compound that is soluble in water at 20 °C (e.g., forms a homogeneous solution).

[0020] As used herein, the term “hydraulic binder” refers to a mineral composition, normally of finely ground materials, which upon addition of an appropriate quantity of water forms a binding paste or slurry capable of hardening of hydration in air as well as under water and binds together the granulates.

[0021] As used herein “RDP” stands for the redispersible dry powder of the present disclosure. Embodiments of the present disclosure provide for a RDP for use in the construction industry, and more specifically in the hydraulic setting mixtures area. When used with hydraulic setting mixtures, the RDP of the present disclosure can help to sequester carbon dioxide while still providing cost-effectiveness and ensuring the quality of the hydraulic setting mixture.

[0022] Specifically, embodiments of the present disclosure provide for a redispersible dry powder (RDP) that includes particles of a composite structure. For the various embodiments, the composite structure consists of a lignin domain and a coating on at least a portion of the lignin domain. For the various embodiments, the coating is formed from a latex dispersion comprising vinyl acetate-based polymer particles. The RDP of the present disclosure helps to provide for a reduction in the carbon footprint associated with construction products as discussed herein. Specifically, the present disclosure replaces a portion of a carbon dioxide intensive component of the RPs, as discussed herein, with lignin with little to no impact on the strength and efficacy of the resulting hydraulic setting mixture. In other words, the present disclosure advantageously uses lignin to increase the bio-based content in the RDP of the present disclosure without, surprisingly, significant impact on its overall performance and characteristics of the hydraulic setting mixture. This is surprising in that it is generally known that it is difficult to incorporate lignin in construction products that require strength and resistance, without negatively impacting these properties.

[0023] As discussed herein, the coating on at least a portion of the lignin domain is formed from a latex dispersion comprising vinyl acetate-based polymer particles. For the various embodiments, the vinyl acetate-based polymer particles can be formed of a copolymer formed with 50 to 95 weight percent (wt.%) vinyl acetate and 50 to 5 wt.% of a comonomer selected from the group consisting of styrene, butadiene, vinyl versatate, propionate, laurate, vinyl chloride, vinylidene chloride, ethylene, acrylates and combinations thereof, where the wt.% is based on the total weight of the copolymer. In more specific embodiments, the vinyl acetate-based polymer particles can be formed of a copolymer formed with 50 to 95 wt.% vinyl acetate and 50 to 5 wt.% of a comonomer selected from the group consisting of ethylene, vinyl versatate and combinations thereof. In a specific embodiment, the vinyl acetate-based polymer particles are formed from at least one of a vinyl acetate-ethylene copolymer and a vinyl acetate / vinyl-versatate copolymer. For the various embodiments, the vinyl acetate -based polymer particles provide the latex dispersion with a solids content of 40 to 65 wt.%, where the wt.% is based on the total weight of the latex dispersion.

[0024] The process of preparing the vinyl acetate-based polymer particles useful in the present invention may be conducted by free-radical polymerization, such as suspension polymerization or emulsion polymerization, from the monomers described above. Emulsion polymerization is a preferred process. The total weight concentration of monomers for preparing the vinyl acetate-based polymer particles is equal to 100%. A mixture of monomers for preparing the vinyl acetate-based polymer particles may be added neat or as an emulsion in water; or added in one or more additions or continuously, linearly or nonlinearly, over the reaction period of preparing the vinyl acetate-based polymer particles. Temperatures suitable for emulsion polymerization processes may be lower than 100 °C, in the range of from 30 to 95 °C, or in the range of from 50 to 90 °C. Multistage free-radical polymerizations using the monomers described above can be used, in which at least two stages are formed sequentially.

[0025] In the polymerization process of preparing the vinyl acetate-based polymer particles, free radical initiators may be used. The polymerization process may be thermally initiated or redox initiated. Examples of suitable free radical initiators include hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ammonium and / or alkali metal persulfates, sodium perborate, perphosphoric acid, and salts thereof; potassium permanganate, and ammonium or alkali metal salts of peroxydisulfuric acid. The free radical initiators may be used typically at a level of 0.01 to 3.0% by weight, based on the total weight of monomers. Redox systems comprising the above-described initiators coupled with a suitable reductant may be used in the polymerization process. Examples of suitable reductants include sodium sulfoxylate formaldehyde, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate, hydrosulfite, sulfide, hydrosulfide or dithionite, formadinesulfinic acid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the preceding acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt may be used to catalyze the redox reaction. Chelating agents for the metals may optionally be used. In the polymerization process of preparing the vinyl acetate-based polymer particles a surfactant may be used. The surfactant may be added prior to or during the polymerization of the monomers, or combinations thereof. A portion of the surfactant can also be added after the polymerization. These surfactants may include anionic and / or nonionic emulsifiers. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfo succinate salts; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols. In some preferred embodiments, the alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates surfactant are used. The surfactant used is usually from 0.1% to 6% by weight, preferably from 0.3% to 1.5% by weight, based on the weight of total monomers used for preparing the vinyl acetate-based polymer particles.

[0026] After completing the polymerization of the vinyl acetate-based polymer particles, the obtained vinyl acetate-based polymer particles may be neutralized by one or more bases as neutralizers to a pH value, for example, at least 4, from 4 to 10, from 6 to 10. or from 7 to 9. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, zinc oxide, magnesium oxide, sodium carbonate; primary, secondary, and tertiary amines, such as triethyl amine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethyl amine, dimethyl amine, di-npropylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane. 1,2-propylenediamine, neopentanediamine, dimethylaminopropylamine, hexamethylenediamine, 4,9-dioxadodecane-l,12-diamine, polyethyleneimine or polyvinylamine; aluminum hydroxide; or mixtures thereof.

[0027] For the various embodiments, the vinyl acetate-based polymer particles of the latex dispersion can have a weight average molecular weight of 80,000 or more, 100,000 or more, or even 200,000 or more. The weight average molecular weight may be determined by SEC analysis using a polystyrene standard. For the various embodiments, the vinyl acetate-based polymer particles of the present disclosure may have a glass transition temperature (Tg) of about -30 °C to 35 °C, or from – 10 °C to 20 °C. For the various embodiments, the vinyl acetate- based polymer particles may have a particle size of from 0.1 micrometers (pm) to 2.5 pm, from 0.2 pm to 1.0 pm, or from 0.3 pm to 600 pm.

[0028] For the various embodiments, the latex dispersion can also include a stabilizer. For example, the latex dispersion can include 4 to 15 wt.% of a stabilizer, where the wt.% is based on the total weight of the latex dispersion. For the various embodiments, the stabilizer can be polyvinyl alcohol having a degree of hydrolysis of 85 to 90 mole percent. For the various embodiments, the polyvinyl alcohol can be derived from polyvinyl acetate in which 85 to 95% of the vinyl acetate groups are hydrolyzed to vinyl alcohol units. In addition, other possible stabilizers can include partially hydrolyzed cellulose derivatives such as ethyl hydroxyethyl cellulose, 2-hydroxyethyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl methyl cellulose: partially hydrolyzed rubbers such as acacia gum and xanthan gum poly(meth)acrylic acid and derivatives; and styrene maleic acid copolymers and derivatives. For the various embodiments, the stabilizer of the present disclosure can have a weight average molecular weight in a range of 10,000 to 200,000 g / mol.

[0029] Lignin is a complex organic polymer found in the cell walls of all types of plants, and is obtained as a by-product in the pulp and paper industry in different forms, depending on the process of production / extraction. While it is abundant, the use of lignin with RPs and hydraulic setting mixtures is challenging due at least in part to its heterogeneous structure, incompatibility with many adhesives and low reactivity, which makes it difficult to predict and / or control its impact on the resulting hydraulic setting mixtures.

[0030] In contrast to these general understandings, the use of lignin in the RDP of the present disclosure for use in hydraulic setting mixtures is surprisingly effective, resulting in little to no loss in the required strength and resistance properties of the examples provided herein without changing the products’ initial characteristics and current properties. In addition, lignin has a low biogenic process carbon footprint, which can contribute significantly to the reduction of carbon emissions from the RDP of the present disclosure.

[0031] For the various embodiments, the RDP of the present disclosure can include 5 to 40 wt.% lignin, where the wt.% is based on the total weight of the RDP. Preferably, the RDP of the present disclosure can include 20 to 40 wt.% lignin, where the wt.% is based on the total weight of the RDP. More preferably, the RDP of the present disclosure can include 26 to 36 wt.% lignin, where the wt.% is based on the total weight of the RDP. For the various embodiments, the lignin can have a weight average molecular weight of 1,000 to 100,000 Daltons. In additional embodiments, the lignin can have a weight average molecular weight of 5,000 to 100,000 Daltons. In further embodiments, the lignin can have a weight average molecular weight of 10,000 to 100,000 Daltons.

[0032] For the various embodiments, the lignin used in the RDP can be selected from the group consisting of a Kraft lignin, soda lignin, organosolv lignin, hydrolic lignin and combinations thereof. The lignins of the present disclosure can be produced using soft wood and / or hard wood sources. Kraft lignin is obtained from the kraft pulping process, which uses a mixture of sodium hydroxide and sodium sulfide to break down wood fibers. Kraft lignin typically has a high weight average molecular weight (e.g., 10,000 to 100,000 Daltons), and contains a high content of condensed phenolic units. Soda lignin is produced using a sodium hydroxide solution in the soda pulping process, where the resulting lignin has a high weight average molecular weight (e.g., 5,000 to 15,000 Daltons), and contains a higher proportion of guaiacyl units. Organosolv lignins are isolated using organic solvents, such as ethanol or methanol and have weight average molecular weights of 1,000 to 20,000 Daltons. Hydrolytic lignin is produced through acid hydrolysis of plant biomass and can have a weight average molecular weights in an around 1,000 Daltons.

[0033] For the various embodiments, the lignin domains of the present disclosure are characterized in that they can be solubilized in an alkali solution. For the various embodiments, the alkali solution can be a 1.0 wt.% NaOH solution in water, where the wt.% is based on the total weight of the alkali solution. For the various embodiments, the lignin domains having a mean diameter of less than about 25 pm can be encapsulated by the coating formed from the latex dispersion.

[0034] The RDP of the present disclosure, or the hydraulic setting mixture that contains the RDP, may further comprise additional components or additives. For example, for applications in which the hydraulic setting mixture should have good workability (e.g. tile adhesives), the RDP of the present disclosure, or the hydraulic setting mixture that contains the RDP, may further include one or more stabilizers selected from lime, air entraining agents (the presence of which leads to air filled voids in hydraulic mixtures), coalescents, superplasticizers, rheological modifiers and mixtures thereof. The RDP of the present disclosure, or the hydraulic setting mixture that contains the RDP, can also include an aggregate filler having a particle size of no more than 1.0 mm, such as silica sand, dolomite, limestone, perlite, expanded polystyrene, hollow glass spheres, rubber crumbs, fly ash and combinations thereof. Further additives can be selected from organic or inorganic thickening agents and / or secondary water retention agents, anti-sag agents, wetting agents, defoamers, dispersants, calcium complexing agents, retarders, accelerators, water repellents, biopolymers and fibers, all of which are well known in the art and are available from commercial sources. Preferably, when included in the RDP of the present disclosure, such additives are present in amounts from 0.001 to 5 weight percent, based on the total dry weight of the hydraulic mortar.

[0035] An anti-caking agent is often dispersed with the RDP of the present disclosure. Anticaking agents are useful when spray drying a dispersion to isolate the particles. Typical anticaking agents include mineral filler such as calcium carbonate, kaolin, barium sulphate, titanium oxide, talc, hydrated alumina, bentonite, calcium sulphoaluminate and silica. The concentration of anti-caking agent in the RDP can typically be 50 wt.% or less, preferably 20 wt.% or less, more preferably 15 wt.% or less, still more preferably 10 wt.% or less and even more preferably 5 wt.% or less relative to total RDP weight. The RDP can be free of anti-caking agent, but can contain 0.5 wt.% or more, preferably 2 wt.% or more and more preferably 5 wt.% or more relative to total RDP weight.

[0036] The RDP of the present disclosure can also be used with a hydraulic binder, where it is preferred that the hydraulic binder is cement. More preferably, the hydraulic binder is Portland cement, in particular, the types of CEM I, II, III, IV and V, and / or alumina cement (aluminate cement) and combinations thereof.

[0037] The particles of the redispersible polymer powders of the present disclosure may be formed by drying a mixture of the lignin particles, the latex dispersion comprising vinyl acetate-based polymer particles and the stabilizer. Preferably, the mixture is an aqueous mixture. For the method, forming particles of the RDP includes providing the lignin particles, as described herein; providing the latex dispersion comprising the vinyl acetate-based polymer particles; mixing the lignin particles with the latex dispersion to form a mixture, where the vinyl acetate-based polymer particles coat at least a portion of the lignin particle to form a composite structure; and spray-drying the composite structure in the mixture to form the particles of the RDP. In additional embodiments, if desired one or more of an anti-caking agent and / or a stabilizer, as provided herein, can also be present in the mixture. Spray drying can be carried out in customary spray drying plants, with atomization being carried out by means of single-fluid, two-fluid or multifluid nozzles or a rotary disc atomizer. In general, air, nitrogen or nitrogen enriched air may be employed as the drying gas, the inlet temperature of the drying gas generally not exceeding 200 °C, preferably from 110 °C to 180 °C, more preferably from 120 °C to 150 °C. The outlet temperature may generally be from 45 °C to 100 °C. preferably from 45 °C to 70 °C, depending on the plant, the Tg of the vinyl acetate-based polymer particles and the desired degree of drying. Operating nozzle pressures of the spray drying process can be in a range of 2 to 5 bar. In one example, the viscosity of the aqueous mixture to be spray-dried may be adjusted via the solids content so that a value of less than 1000 mPas (Brookfield viscosity at 20 rpm and 23 °C), preferably less than 250 mPas is obtained. The solids content of the mixture to be spray-dried may generally be from 25% to 60% by weight, preferably from 35% to 50% by weight, based on the total weight of the mixture.

[0038] Examples

[0039] All components were purchased from commercial vendors and used as received unless otherwise noted. Amounts provided for the Examples (EX) and Comparative Examples (CE) are in weight percent (wt.%) unless otherwise noted. Table 1 – Materials list

[0040] Material Description Producer Cement CEM I 42,5 R Binder Holcim

[0041] Silica sand - F32 Aggregate Quarzwerke Frechen Silica sand - F36 Aggregate Quarzwerke Frechen Walocel™ MKX 40000 PF01 Water retainer DOW™

[0042] DLP 2000 Redispersible polymer DOW™

[0043] Ecolig 101

[0044] Lignin 1 Suzano

[0045] (hardwood lignin)

[0046] Lignin 2 softwood lignin Södra

[0047] Vinyl acetate ethylene

[0048] VAE 1 DOW™

[0049] dispersion?

[0050] Vinyl acetate ethylene

[0051] VAE 2 DOW™

[0052] dispersion.b

[0053] Vinyl Acetate Vinyl

[0054] Va / VeoVa 1 DOW™

[0055]

[0056] versatate copolymerc

[0057] a. Dispersion contains copolymer of 91% vinyl acetate and 9% ethylene, 52% solids with 9% PVOH stabilize b. Dispersion contains copolymer of 75% vinyl acetate and 25% ethylene, 52% solids with 9% PVOH stabilize c. Dispersion contains copolymer of 60% vinyl acetate and 40% VeoVa10 (Hexion), 8% PVOH stabilizer

[0058] Experimental Procedures

[0059] RDP-Lignin Dry Powder Blend

[0060] The RDP-Lignin Dry Powder Blends were prepared as follows. Mix 10 wt.% of dry lignin powder with 90 wt.% of RDP powder (DLP 2000). Shake the dry mixture for two minutes in a sealed container to combine ingredients.

[0061] Lignin-RDP Dispersion Mixture

[0062] Lignin-RDP Dispersion Mixture from each RDP dispersion (e.g., VAE 1, VAE 2 or Va / VeoVa 1) and dry lignin powder was prepared as follows. The Lignin-RDP Dispersion Mixture was spray dried to form a powder as discussed herein, but could be used as a wet additive.

[0063] A mixture containing 20 wt.% lignin, based on dry weight of total solids, was prepared by mixing in a flask 24.0 g of each RDP dispersion (a 52% solids VAE dispersion) with 3.06 g dry lignin powder and 2.94 g of water. The contents of the flask were stirred for 30 min at 200 rpm using a mechanical stirrer. The resulting Lignin-RDP Dispersion Mixture had a solids content of 52.8%, (20.0 wt.% of the solids is lignin). Other wt.% lignin products were made by adjusting the basis of water and lignin added.

[0064] Alkali Lignin-RDP Dispersion Mixture

[0065] An Alkali Lignin-RDP Dispersion Mixture was prepared from RDP dispersion and an alkali solubilized lignin as follows. The Alkali Lignin-RDP Dispersion Mixture was spray dried to form a powder as discussed herein, but could also be used as a wet additive.

[0066] A 14.5 wt.% lignin solution was prepared by adding dry lignin powder to 1.0 wt.% NaOH in water. 5.0 g of the 14.5 wt.% lignin solution was added to a flask contain 5.88 g of each RDP dispersion (a 52% solids VAE dispersion). The contents of the flask were stirred for 30 min at 200 rpm using a mechanical stirrer. The resulting Alkali Lignin-RDP Dispersion Mixture had a solids content of 35.7% (20.0 wt.% of the solids is lignin). Other wt.% lignin products were made by adjusting the basis of water and lignin added.

[0067] Powder Preparation

[0068] Powders from either the Lignin-RDP Dispersion Mixture or the Alkali Lignin-RDP Dispersion Mixture were prepared using a Niro Mobile Minor spray dryer. The drier operating conditions were as follows: an inlet air temperature of 130 °C, outlet air temperature of 55 ± 1 °C, and two-phase nozzle pressure of 3 bar.

[0069] Prior to spray drying, the Lignin-RDP Dispersion Mixture or the Alkali Lignin-RDP Dispersion Mixture were well mixed under vigorous stirring. The total feed mixture was adjusted to at least 500 g to ensure a spray drying time of at least 20 min. 14.1 wt.% kaolin anticaking agent was dosed separately by adding manually into a trickle gutter at the top of the spray dryer. The pumping speed of the liquid feed was adjusted (1.4 - 2.0 rpm) based on the outlet temperature to maintain 55 °C. The dry powder was separated and collected using a cyclone. The collected powder from the cyclone was then filtered through a 500 μm sieve.

[0070] Dry Mortar Mix Preparation

[0071] Dry Mortar Mix was prepared for testing according to the following mixture, by combining the appropriate weight of each material: 35.0 wt.% cement (CEM I 42.5R, Holcim), silica sand (31.0 wt.% F32 and 31.15 wt.% F36), 0.35 wt.% cellulose ether Walocel™ MKX 40000 PF01, and 2.5 wt.% of DLP 2000 as the RDP powder. All ingredients were mixed 15 min using a bucket tumbler. If RDP lignin dry blends were used, these were prepared separately by shaken by hand for 2 min before adding to the dry mix. Powder Redispersibility

[0072] Powder redispersibility of the lignin, latex powder, and lignin-containing latex powder, as prepared above, is determined by sedimentation in a burette. For each of the lignin, latex powder, and lignin-containing latex powder, weigh 5.0 g of powder and mix with 5.0 g of deionized water using a spatula. The mixture was stirred for 30 min at 100 rpm using a blade stirrer, after which the mixture was covered and stored for 60 min. The mixture was again stirred with a spatula and 5.0 g of this mixture was transferred to a beaker containing 45.0 g of water, which was then homogenized for at least 2 minutes. Two drops of blue ink were added to aid in the readability of the sedimentation in the case of latex dispersions. The 5 wt.% redispersion was transferred into a burette and the sedimentation in mm was read after 1 and 24 h. A larger rating is unfavorable and indicates less sample remain dispersed.

[0073] Alkaline Redispersibility

[0074] Determine Alkaline Redispersibility by a similar method to the Powdered Redispersibility. Weigh 5.0 g of powder and mix with 5.0 g of an alkaline solution composed of 4.658 g deionized water and 0.35 g of a 20 wt% NaOH solution.

[0075] Digital light microscope

[0076] Images of the powder produced from the above mixtures or preparations were obtained using a Keyence digital light microscope. A thin layer of powder sample was stuck to a piece of tape and placed on a watch glass. A light platform was used to light the powder samples from underneath. Latex samples were examined by a adding a drop to a watch glass and covering the glass with a cover slip.

[0077] Particle size

[0078] Determine the particle size distribution using a Beckman-Coulter LS 13320 XR using the Universal Liquid Module. 4-6 drops of a sample were added to 15 mL of deionized water in a beaker which is subsequently well mixed to obtain a diluted sample. Drops of the diluted sample were added until the optimal concentration is obtained for measurement. After triplicate measurement, the particle size distribution was reported in terms of D10, D50, D90 and the mean. Data Analysis

[0079] Optical Microscopy

[0080] 1000x optical microscopy images of the powders showed the degree of homogeneity and mixing for the blended compositions. The descriptions are for powders prepared at 20 wt.% lignin, unless specifically noted otherwise. The descriptions refer to VAE 1 with Suzano lignin but are representative of other VAE and lignin combinations.

[0081] VAE- Lignin Blends: Images of samples obtained by mixing the dry VAE and lignin powders indicated that lignin particles did not interact with or otherwise associate with latex particles. Large, dark lignin particles are observed in images of these samples, with some lignin particles greater than 50 μm. The lignin particles observed are separated from other components. The VAE particles in this image were light and translucent.

[0082] Lignin dry method: Images of powders prepared by the dry method, where the lignin was spray dry processed with the VAE dispersion, showed partial encapsulation of lignin particles by latex and / or PVOH. This is observed by small translucent particles decorating the surface of at least a portion of the lignin particles, which is indicating a degree of association between the constituents. The VAE particles in this image were light and translucent

[0083] Lignin dissolved method: Images of dry samples obtained by the dissolved lignin method showed relatively homogeneous blends of the constituent materials. The particles are translucent but are a uniform brown across the particle. The imaged particles are approximately the same brown shade. The absence of large lignin particles suggests that the lignin has associated with the latex particles. Additionally, it was noted that using dissolved lignin allowed for more consistent homogeneous incorporation of lignin into the spray-dried powder.

[0084] A comparison of a powder with 10 wt.% lignin shows similar results with uniform particles, but which are lighter in color. The difference indicates the color contribution of lignin to the particles in this powder.

[0085] PARTICLE SIZE DISTRIBUTIONS

[0086] The particle size distributions (PSD) of the RDP-Lignin Dry Powder Blend samples (“lignin dry method”) and the Alkali Lignin-RDP Dispersion Mixture samples (“lignin dissolved method”), after spray-drying, are summarized in Table 2. Samples made using a given latex and 20 wt% lignin by the dry method display larger D90 and mean values as compared to samples made using the same latex and same overall loading of lignin by the dissolved method. Table 2 - Summary of PSDs for RDP samples made by the lignin dry method and the lignin dissolved method.

[0087] D10D50D90Mean Lignin Latex

[0088] (pm) (pm) (pm) (pm) VAE 1 0.5 0.9 21.9 6.2 VAE 2 0.6 1 17.1 4.7 Södra 20%

[0089] VA / VEOVA

[0090] Lignin 3 5.4 31.8 11.6

[0091]

[0092] Dry

[0093] VAE 1 0.5 0.9 17.6 4.5 Method

[0094] Suzano VAE 2 0.6 1 11.4 4.1 Va / VeoVa 1 3.3 5.1 23.2 9.9 VAE 1 20% 0.53 0.83 1.16 0.84 VAE 2 Lignin 0.53 0.9 1.45 0.95 Suzano

[0095] Dissolved

[0096] Va / VeoVa 1 3.34 4.9 11.39 6.48

[0097] Method

[0098]

[0099] Sbdra* NA NA < 2 < 25 < 60 VAE VAE 1 NA - - - 0.82 VAE VAE 2 NA - - - 1.06 Redispersibility *

[0100] (sedimentation ■£ in mm)

[0101]

[0102] l h 24 h VAE 1 spray

[0103] dried+20 %

[0104]

[0105] Lignin Dry

[0106] Blend

[0107] CE VAE 1 0 - Kaolin 9.3 0.6 5.8 3 9 A*

[0108] CE 0 8 +

[0109] VAE 1 10 Dry Kaolin 9.3 4.9 6 + 1 8 + 1 B*J0.1

[0110] CF 0 9 +

[0111] VAE 1 15 Dry Kaolin 9.3 4.7 8 + 0 12 + 1 C* 0.1

[0112] CF 1 0 +

[0113] VAE 1 20 Dry Kaolin 9.3 4.5 10 + 0 14 + 1 D*J0.0

[0114] CF VAE 1 20 Dry CaCO39.3 1.4 6.8 8 13 E*

[0115] 1 4 +

[0116] EX 1 VAE 1 10 Dissolved Kaolin 9.3Q ]~ 9.2 3 ± 0 4 ± 0

[0117] 1 7 +

[0118] EX 2 VAE 1 20 Dissolved Kaolin 9.3 J 9.4 2 + 0 4 + 0 CF 1 0 +

[0119] VAE 2 0 - Kaolin 9.3 “ 5.5 4 + 1 6 + 0 F* 0.2

[0120] CF 1 i

[0121] VAE 2 20 Dry Kaolin 9.3 4.6 11 + 1 14 + 1 G* 0.1

[0122] 1 7 +

[0123] EX 3 VAE 2 20 Dissolved Kaolin 9.3 Q '-9.3 2 ± 1 4 ± 0 CE VA / VEOVA 1 0 - Kaolin 9.3 0.7 ± 0.0 5.6 3 ± 0 26 ± 0 H*

[0124] VA / VFOVA 1 5 +

[0125] CE I* VA / VEOVA 1 20 Dry Kaolin 9.3 4.6 8 ± 1 19 ± 1

[0126]

[0127] VA / VEOVA 1 7 + EX 4 VA / VEOVA 1 20 Dissolved Kaolin 9.3 9.2 2 ± 1 9 ± 1

[0128]

[0129] * non-inventive example; ** “Dry” indicates dry lignin powder addition method. Dry lignin was added to VAE 1 (or VAE 2 or VA / VEOVA 1) dispersion before spray drying. The mix was then spray dried. The sediment of CE A (latex powder) consists mainly of the anti-caking agent and larger latex particles that were not able to redisperse well. This sample was a baseline measurement of the powder unmodified with lignin. Comparison of experiments CE B, CE C, and CE D to CE A show increased sedimentation (poor redispersibility) when the dry lignin powder method was used. Redispersibility worsened with more lignin, and this was attributed to less particle coverage, as was observed in the optical images. Similar comparisons can be made with EX 1 to EX 2 and CE G to EX 3, adding lignin by the dry method lowers redispersibility.

Claims

CLAIM:

1. A redispersible dry powder, comprising:particles of a composite structure, wherein the composite structure consists of a lignin domain and a coating on at least a portion of the lignin domain, wherein the coating is formed from a latex dispersion comprising vinyl acetate-based polymer particles.

2. The redispersible dry powder of claim 1, wherein the vinyl acetate-based polymer particles are formed of a copolymer formed with 50 to 95 weight percent (wt.%) vinyl acetate and 50 to 5 wt.% of a comonomer selected from the group consisting of styrene, butadiene, vinyl versatate, propionate, laurate, vinyl chloride, vinylidene chloride, ethylene, acrylates and combinations thereof, where the wt.% is based on the total weight of the copolymer.

3. The redispersible dry powder of claim 1 or claim 2, wherein the vinyl acetate-based polymer particles are formed of a copolymer formed with 50 to 95 wt.% vinyl acetate and 50 to 5 wt.% of a comonomer selected from the group consisting of ethylene, vinyl versatate and combinations thereof.

4. The redispersible dry powder of claim 1 or claim 2, wherein the vinyl acetate-based polymer particles are formed from at least one of a vinyl acetate-ethylene copolymer and a vinyl acetate / vinyl- versatate copolymer.

5. The redispersible dry powder of any one of claims 1-4, wherein the vinyl acetate-based polymer particles provide the latex dispersion with a solids content of 40 to 65 wt.%, where the wt.% is based on the total weight of the latex dispersion.

6. The redispersible dry powder of any one of claims 1-5, wherein the latex dispersion further includes 4 to 15 wt.% of a stabilizer, where the wt.% is based on the total weight of the latex dispersion.

7. The redispersible dry powder of claim 6, wherein the stabilizer is polyvinyl alcohol having a degree of hydrolysis of 85 to 90 mole percent.

8. The redispersible dry powder of any one of claims 1-7, wherein the lignin domains are solubilized in an alkali solution.

9. The redispersible dry powder of claim 8, wherein an alkali solution is a 1.0 wt.% NaOH solution in water, where the wt.% is based on the total weight of the alkali solution.

10. The redispersible dry powder of any one of claims 1-9, wherein lignin domains having a mean diameter of less than about 25 pm are encapsulated by the coating formed from the latex dispersion.

11. The redispersible dry powder of any one of claims 1-10, wherein the particles are formed using a spray-drying process.

12. The redispersible dry powder of any one of claims 1-11, wherein lignin is selected from the group consisting of a Kraft lignin, soda lignin, organosolv lignin, hydrolic lignin and combinations thereof.

13. The redispersible dry powder of any one of claims 1-12, wherein the lignin has a weight average molecular weight of 1,000 to 100,000 Daltons.

14. The redispersible dry powder of any one of claims 1-13, wherein the redispersible dry powder includes 5 to 40 wt.% lignin, where the wt.% is based on the total weight of the redispersible dry powder.

15. A method of forming particles of a redispersible dry powder, comprising:providing lignin particles;providing a latex dispersion comprising vinyl acetate-based polymer particles;mixing the lignin particles with the latex dispersion to form a mixture, wherein the vinyl acetate-based polymer particles coat at least a portion of the lignin particle to form a composite structure: andspray-drying the composite structure in the mixture to form the particles of the redispersible dry powder.

Images