Anti-blocking additives for coating formulations

Abstract

Aqueous compositions include a binder; and a C4 to C15 alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more, at a percent by weight (wt%) of the binder ranging from 0.1 wt% to 2.0 wt%. Methods include applying an aqueous composition to a substrate, the aqueous composition including a binder, and a C4 to C15 alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more; curing the aqueous composition to form a cured coating.

Description

[0001] ANTI-BLOCKING ADDITIVES FOR COATING FORMULATIONS FIELD Embodiments relate to anti-blocking additives for use in coating formulations, methods for preparing and applications utilizing same. BACKGROUND Blocking of paints and coatings refers to the undesirable adhesion between two painted surfaces when pressed against each other. While less of a problem in architectural wall paints, where the painted surfaces have little chance to stick to each other, this is a pertinent problem for windows and doors where the painted surfaces may stick together when the freshly painted window or door is closed. When the window or door is later opened, bare patches of substrate may be revealed due to blocking. Another area with blocking problems is in printing ink, for example, packaging ink. When printed packages are stacked to each other face to face, the surfaces may stick to each other, leading to loss of coating when separated apart. The blocking problems with waterborne coatings are increasing as paint and ink formulations are transitioning from solvent-borne coatings and high VOC waterborne coatings to low or even zero VOC counterparts. In this transition, the use of VOC-contributing cosolvents and coalescing agents is reduced or eliminated. To help the polymeric binders, mostly acrylic latex emulsions, to coalesce to a uniform film at or below room temperature, relatively soft (low Tg) latex and / or low-VOC (high boiling point) coalescing agents are typically used. However, one of the drawbacks is the sticky coatings these components give, which cause blocking issues. Other problems associated with low or zero VOC waterborne coatings are high surface tension, poor substrate wetting, and foaming. Various chemistries have been employed as anti-blocking additives in paint and ink formulations, including perfluorinated alkyl substances (PFAS) such as fluorosurfactants, siloxanes and waxes. While fluorosurfactants provide effective anti-blocking performance, this chemistry potentially poses significant negative impact to the environment and human health and is under increasing regulatory scrutinization. Siloxanes and waxes are often proposed as anti- blocking agents to replace fluoro-surfactants, however such additives often are inferior in preventing blocking at elevated temperatures and / or negatively affect the gloss level of the coating. Summary In an aspect, embodiments disclosed herein are directed to aqueous compositions include a binder; and a C4 to C15 alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more, at a percent by weight (wt%) of the binder ranging from 0.1 wt% to 2.0 wt%. In another aspect, embodiments are directed to methods including applying an aqueous composition to a substrate, the aqueous composition including a binder, and a C4 to C15 alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more; curing the aqueous composition to form a cured coating. Detailed Description Embodiments relate to anti-blocking additives for use in aqueous compositions, such as those used to formulate coatings, methods for preparing aqueous compositions and applications utilizing same. Anti-blocking additives include alkyl phosphates having a high concentration of monoester (e.g., >85 wt% of the total alkyl phosphate), which exhibit high water solubility and reduced phase separation in aqueous solutions. Formulated aqueous coating compositions may also be produced for generating cured coatings on a variety of substrates. When used in coating applications, alkyl phosphate esters containing high concentration of alkyl phosphate diesters (e.g., >15 wt%) are more hydrophobic and less surface active than the corresponding alkyl phosphate monoesters, which contributes to an anti-blocking additive having low water solubility (causing phase separation and haziness in aqueous solution) and slow migration to the interface. Anti-blocking additives having higher concentrations of alkyl phosphate monoesters (and monoester blends) were produced by synthetic and separation-based methodologies, which were used to produce aqueous compositions and coating compositions having good blocking resistance performance, low foam production, good color acceptance, and improved gloss properties. In some cases, aqueous compositions disclosed herein may be formulated as a coating composition, a coating layer, or a coated article for use in architectural, industrial and wood coatings in interior and exterior applications. Aqueous compositions disclosed herein may include coating formulations containing water, pigments, binder, anti-blocking additives, and other functional additives such as surfactants and dispersants. As a general guide, aqueous compositions formulated for coatings may include components in the following quantities: Table 1: Example ranges for aqueous composition components Component Weight Percent (wt%) W t 2 s) Aqu gment Volume Concentration (% PVC) ranging from 0% to 80%, or 0.1 wt% to 70 wt%.. The term “percent Pigment Volume Concentration” or “% PVC” refers to the quantity calculated by the following formula: %PVC = (volume of pigment(s) along with any fillers and extenders if used) divided by the total dry volume of paint*100 The class of applicable pigments for formulating aqueous compositions is not particularly limited and may be selected from inorganic pigments including one or more metal oxides such as titanium oxide, iron oxide, zinc oxide, and the like. Fillers may also be added, which may include calcium carbonate, clay, talc, mica, and the like. Aqueous compositions disclosed herein may include binder solids in the form of aqueous dispersions of polymers and / or copolymers particles (i.e., latexes). The class of applicable binders for use in the present invention is not particularly limited and may include homopolymers and / or copolymers and blends of polymer systems. Binder solids may be prepared from polymer systems that include acrylic, styrene-acrylic, vinyl ester-acrylic, vinyl ester-ethylene, silicone, urethane, vinylidene halide, vinyl halide polymers, and the like. Other polymer types may include epoxies, polyurethanes, polyamides, polyimides, halogenated polymers, polysilicones, polyesters, alkyds, polyolefins, (meth)acrylic resins, combinations of these and the like. Examples of binder solids include polymer and copolymers prepared from monomers such as acrylic acid, methacrylic acid, acrylate esters and methacrylate esters such as methyl acrylate, ethyl acrylate, butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, decyl acrylate, lauryl acrylate, isodecyl methacrylate, lauryl methacrylate, and butyl methacrylate; substituted acrylates and methacrylates such as hydroxyethyl acrylate, perfluorooctyl acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxyethyl methacrylate. Suitable polymers may also be prepared from monomers that include vinyl halides such as vinyl chloride, vinylidene chloride, and chloroprene; maleic anhydride; vinyl esters such as vinyl acetate and vinyl butyrate; vinyl pyrrolidone; conjugated dienes such as butadiene and isoprene; vinyl aromatic compounds such as styrene and divinyl benzene; vinyl monomers such as ethylene; acrylonitrile and methacrylonitrile; acrylamide, methacrylamide, and N-methylol acrylamide; and vinyl esters of monocarboxylic acids with up to 10 carbon atoms. Aqueous dispersions and coating compositions derived therefrom may include one or more binder compositions such as acrylic latex, vinyl acrylic latex, styrene acrylic latex, vinyl acetate ethylene latex, polyurethane dispersion, alkyd dispersion, epoxy dispersion, polyolefin dispersion, and combinations thereof. Aqueous compositions may include binder solids at a percent by weight (wt%) ranging from 5 wt% to 75 wt%, or 10 wt% to 40 wt%. Aqueous compositions may include one or more alkyl phosphate anti-blocking additives, including organophosphates generated from esterification of a phosphoric acid with one or more equivalents of a linear or branched alkyl alcohol. Alkyl phosphates may include monoesters of C4 to C15 alkyl phosphates. As used herein, “monoester alkyl phosphate” refers to an alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more, 90 wt% or more, or substantially all of the alkyl phosphate(s) content. . In some cases, anti-blocking additives may include a mixture of two or more monoesters of C4 to C15 alkyl phosphates, where the molar ratio of the two monoesters ranges from 4:1 to 1:4. In one example, an anti-blocking additive may include approximately 1:1 ratio of n-octyl phosphate:n- decyl phosphate. Alkyl phosphate anti-blocking additives may be added to an aqueous composition as an acid form, or as a potassium, sodium, amine salt. Methods to synthesize monoester-rich alkyl phosphate esters may include reacting a linear or branched C4 to C15 alcohol with an excess of phosphorylating agent such as phosphorus pentoxide, phosphoric acid, polyphosphoric acid, and the like. To increase the ratio of monoester to diester reactivity of the phosphorylating agent may be controlled by any suitable method including concentration with respect to the alkyl alcohol, temperature, or phosphorylating agent type (e.g., polyphosphoric acid). Monoester alkyl phosphate may also be obtained by physical separation of mixtures of monoester and diesters into fractions. Aqueous compositions disclosed herein may include one or more alkyl phosphate monoester anti-blocking additives at a percent by weight (wt%) ranging from 0.05 wt% to 2.5 wt%, or 0.1 wt% to 2.0 wt% based on the weight of the binder solids. Aqueous compositions disclosed may include a number of additional materials including solvents; pigments such as unencapsulated or partially or completely encapsulated TiO2; fillers; defoamers; surfactants; dispersants; thickeners; coalescents; colorants; preservatives; flow agents; leveling agents; neutralizers; additional anti-blocking agents, and the like. While formulation components have been disclosed individually, it is envisioned that component elements may be included, excluded, or combined in any manner or subcombination utilizing any of the above concentration ranges and nested subranges therein. The preparation of aqueous coating compositions of the present disclosure is not particularly limited and well known techniques may be used. Preparation techniques to prepare aqueous compositions for coating applications may include two general steps: i) pigment dispersion (so called “grinding”) and ii) let-down. During the grinding step, clusters of pigment are ground to obtain a fine particle pigment dispersion. This operation may be carried out in a high speed disperser, bead mill or similar until desired particle size (e.g., 0.3 to 5µm by laser diffraction) is achieved. During the let-down step, the pigment dispersion is combined with an aqueous dispersion of the binder and surfactant along with any other optional constituents previously mentioned using a suitable method (e.g., static mixing, dynamic mixing, dynamic and static mixing, speedmixing, low pressure mixing, overhead mixing with impellers or paint mixers, impingement mixing, and others). The final viscosity of the resulting composition may be adjusted by adding additional water or rheology modifier. The specific order of addition and selection of individual components can be readily determined by routine experimentation. A process of using the aqueous compositions may include applying the aqueous composition (e.g., as a coating composition) to a substrate by any suitable method such as brushing, dipping, rolling, spraying, and the like. In some cases, spray techniques include air- atomized spray, air spray, airless spray, high volume low pressure spray, and electrostatic spray such as electrostatic bell application, including manual or automatic methods. After coating a substrate with an aqueous composition, the coating composition can be allowed to dry (or dried by suitable means), to form a cured coating at a suitable temperature, such as room temperature (20°C to 25°C) or an elevated temperature (>25°C to 60° C). Examples The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 2 provides the materials used in the following examples.

[0002] Table 2: Materials used in the examples Component Description Supplier re re re re c. c. c. ur Example 1: Preparation of monoester alkyl phosphate samples An anti-blocking additive containing n-octyl phosphates (IE-AP8) having a high concentration of monoesters was prepared by charging a 3-neck reaction vessel with octanol (1.0 mole equivalent), fixed in a heating mantle, and capped with a condenser and an overhead stirrer with an adapter. An addition funnel was charged with polyphosphoric acid (PPA, 1.2-1.6 mole phosphorous equivalent), and placed on the remaining neck of the reaction vessel. The system was purged with dinitrogen and heated to 50°C to 60°C. PPA was added over the course of 1 to 2 hours to control the exothermic reaction, and the mixture gradually thickened and turned from clear to a faint yellow-orange over the addition. After completing the addition, the reaction mixture was heated for several hours at 90°C to 95°C. The product mixture was cooled to room temperature before transferring a storage container and further sampling. Samples of n-hexyl phosphate (IE-AP6) and a mixture of n-octyl / n-decyl (50:50 ratio) phosphates (IE-AP810) were prepared using the same methodology. To make an alkyl phosphate product in potassium salt form, 45 wt% KOH was used to neutralize the alkyl phosphate samples by slow addition with stirring to minimize heat release during the neutralization reaction. Deionized water was added to adjust the active content based on alkyl phosphate to 30 wt% unless otherwise indicated. The final pH was adjusted to 7-8. For samples IE-AP8F1 and CE-AP8F2 prepared by separation, a solid phase sorbent was used to produce monoester and diester alkyl phosphate fractions from commercially obtained mixtures. Separation was performed by combining 4 grams STEPCOTE W-877 (CE-AP8); 25 grams octadecyl-functionalized silica gel, 22-24% carbon loading, Sigma-Aldrich #553506; and 100 grams of 85:15 water:acetonitrile (Solvent A) in an 8-ounce vessel. The vessel was then shaken, and placed on horizontal roller for 2 hours. The vessel was removed from the roller and allowed to settle. To extract the monoester alkyl phosphate, the liquid phase was collected by pipette and vacuum filtered through 0.45 µm filter paper. Another aliquot of Solvent A was added and the vessel was rolled for another 2 hours. Removal of the liquid phase and application of solvent fractions was repeated and the three liquid fractions were combined as the monoester alkyl phosphate fraction “IE-AP8F1.” The extraction process was repeated using acetonitrile as a solvent to collect the diester alkyl phosphate fraction “CE-AP8F2.” Nuclear magnetic resonance (NMR) spectroscopy was used to determine the ratio of monoester to diester in the alkyl phosphate product mixtures. NMR samples were prepared by dissolving 100-200 mg of the material in 600-800 μL dimethyl sulfoxide-d6 (DMSO-d6), then transferred to 5 mm NMR tubes. NMR spectra were obtained on the Bruker Advance-III 400 spectrometer (FT 400 MHz, 1H; 101 MHz, 13C; 162 MHz, 31P). Quantitative 31P were obtained with the zgig30 pulse sequence with a relaxation delay of 38 seconds. Results are shown in Table 3. Table 3: Alkyl phosphates used in the examples Sam le Descri tion Monoester:diester wt Example 2: Solubilization properties In this example, aqueous compositions containing alkyl phosphates were prepared and the solubilization properties were characterized. Alkyl phosphates were neutralized by KOH and diluted to 30 wt% (based on active content) and the appearance (including phase separation), foaming properties, and turbidity (haziness) were analyzed. To quantify turbidity, 20 mL of the 30 wt% alkyl phosphate solution was measured on a Hach Ratio Turbidimeter for 3 replicates. The measurable range of the Turbidimeter is 0-200. For samples that are out of range, the turbidity was recorded as >200. Results are show in Table 4. Table 4: Appearance and turbidity differences of different alkyl phosphates. IE-AP8 IE-AP6 IE-AP810 CE-AP8 CE-AP6 CE- p y pp g p yl phosphates are largely different. For hexanol alkyl phosphate (IE-AP6 and CE-AP6), both samples are clear and transparent at 30% active. However, for CE-AP8 and CE-AP810 containing the higher fraction of diester, the comparative samples showed serious turbidity and phase separation, while the corresponding inventive examples (IE-AP8 and IE-AP810) are clear and transparent. The comparative examples contain high level of di-esters, which is more hydrophobic and less water-soluble than their mono-ester counterparts, which may increase turbidity and drive phase separation. Example 3: Foaming characterization Foaming is an important aspect of surfactant design and can impact composition used in manufacturing and application processes. Applications such as coatings and inks, for example, typically utilize low foam activity surfactants. For foam testing, the surfactants were diluted to 0.1 wt% in DI water. The foam test was performed using Dynamic Foam Analyzer DFA100 from Kruss GmbH with Air Sparging module. In detail, 45 mL of the surfactant solution was charged into the sample column for the foam test. The test was performed at room temperature (25 °C). Testing began by air sparging at a flow rate of 200 mL / min for 180 seconds (IE-AP6 and CE- AP6) or 30 seconds to observe foam generation. Foam decay was recorded for 180 seconds or until completely collapse after ceasing sparing air. Results are shown in Table 5. Table 5: Foam height of different 0.1 wt% alkyl phosphate solution after 30 seconds air sparging at 0.2L / min. IE AP8 IE AP6 IE AP810 CE AP8 CE AP6 CE AP810 In this example, the effect of the monoester:diester ratio (effectively monoester wt% of alkyl phosphate) of alkyl phosphate on block resistance was analyzed for a high monoester fraction (IE-AP8F1) and a low monoester fraction (CE-AP8F2) of a commercially available n-octyl phosphate. Capstone FS-63 (CE-FS), which is a comparative used for antiblocking performance, was used as positive control and samples without anti-blocking additives were used as negative control. Coating formulations were prepared with samples of the anti-blocking additives as part of the letdown as a percent by weight of the binder solids at concentrations of 0, 0.1 wt%, 0.4 wt%, and 0.8 wt%. Sample formulations are shown in Table 6.

[0003] Table 6: Coating formulations for Example 4. Total h it F ti e ur al al s t y o al al n al al al al al Block resistance test was performed according to ASTM D4946-89. Paints are drawn down with a 3-mil bird applicator. Films were dried for 1 and 7 days and 1.5” X 1.5” blocks are cut and placed face to face. A No. 8 rubber stopper and 1 kg weight were placed on the blocks, and kept in contact and under pressure for the specified time and at the specified conditions, after which the blocks were pulled apart and rated under conditions: (1) 30 minutes at room temperature; (2) 30 minutes at 120°F (50°C); and (3) 16 hours at room temperature. Qualitative block resistance performance was graded according to Table 7. Table 7: Description of tack and seal for rating block resistance Rating Description The blo c ng es resu s n ab e 8 s ow a e ow monoes er rac on sample exhibited low efficacy in block resistance while the high monoester fraction performed comparable to that of the fluorosurfactant. Organic surfactants are typically less effective than fluorosurfactants at the same use level, and the samples tested containing 0.1 % active on dry binder dosage level for the fluorosurfactant and 0.8% active for organic surfactants. Table 8: Block resistance measurements for Example 4. Additive Blank CE-FS IE-AP8F1 CE-AP8F2 Blocking was also measured for synthesized samples, along with the comparative samples, as shown in Tables 9 and 10. At the same dosage of 0.8%, the inventive samples and comparative samples did not exhibit performance differences in anti-blocking. However, the inventive samples, especially the octyl phosphate (IE-AP8) exhibited same level of block resistance even when the dosage level was reduced from 0.8% to 0.4%. Table 9: Block resistance measurements for Example 4. Block Additive Blank CE-FS CE-AP8 IE-AP8 IE-AP8 ple 4. Block Additive CE- IE-AP6 IE-AP6 CE-AP810 IE-AP810 IE-AP810 IE- AP8 and CE-AP8 with a ladder study. In this example, coatings were prepared with three dosage levels of 0.2 wt%, 0.4 wt% and 0.8 wt% for each anti-blocking additive and the blocking resistance was tested on day 1 and day 7 at 50°C. Inventive sample IE-AP8 maintained robust anti-blocking performance even at 0.2 wt%, while the comparative formulation CE-AP8 exhibits a decrease in blocking resistance as anti-blocking additive concentration decreases. Results are shown in Table 11. Table 11: Block resistance ratings for samples at 50oC P8 y) Example 5: Gloss properties for coating formulations To characterize cured coating gloss, paint drawdowns were prepared on Leneta WB charts using a 3-mil bird applicator and dried for 24 hours. Gloss was measured using a model 4563 micro-tri-gloss unit from BYK-Gardner. Results are shown in Tables 12 and 13. Table 12: Gloss testing of paints containing sample anti-blocking additives. Block Additive Blank CE-FS CE-AP8 IE-AP8 IE-AP8 ives. Block Additive CE- IE-AP6 IE-AP6 CE-AP810 IE-AP810 IE-AP810 , kyl phosphate showed a strong effect on gloss level of the paint. While a reduction in gloss level was observable when using fluorosurfactant (CE-FS), alkyl phosphate in general has a positive effect in gloss. Particularly, inventive samples containing high fractions of monoester all show significantly higher gloss level than their comparative counterparts, from 2.3 to 4.5 gloss units at the same dosage of 0.8 wt%. While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims 1. An aqueous composition comprising: a binder; and a C4 to C15 alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more, at a percent by weight (wt%) of the binder ranging from 0.1 wt% to 2.0 wt%.

2. The composition of claim 1, wherein the binder is selected from the group consisting of acrylic, styrene-acrylic, vinyl ester-acrylic, and vinyl ester-ethylene polymers.

3. The composition of claim 1, wherein the C4 to C15 alkyl phosphate comprises a monoester content of 90 wt% or more.

4. The composition of claim 1, wherein C4 to C15 alkyl phosphate is added to the aqueous composition as an acid form, or as a potassium, sodium, ammonia salt.

5. The composition of claim 1, wherein the anti-blocking additive comprises ratio of n-octyl phosphate:n-decyl phosphate ranging from 4:1 to 1:

4.

6. The composition of claim 1, wherein the anti-blocking additive comprises a n-octyl phosphate.

7. A method, comprising: applying an aqueous composition to a substrate, the aqueous composition comprising: a binder, and a C4 to C15 alkyl phosphate having a monoester content at a percent by weight (wt%) of the total alkyl phosphate of 85 wt% or more; curing the aqueous composition to form a cured coating.

8. The method of claim 7, wherein the C4 to C15 alkyl phosphate is present at a percent by weight (wt%) of the binder ranging from 0.1 wt% to 1.0 wt%.

9. The method of claim 7, wherein the cured coating has a blocking resistance rating according to ASTM D4946-89 ranging from 5 to 10.

10. The method of claim 7, wherein the blocking resistance rating is improved by at least 2 units relative to a comparative composition without the anti-blocking additive.

11. The method of claim 7, wherein the cured coating exhibits a gloss increase at 60° by at least 2 units by gloss meter relative to a comparative composition without the anti- blocking additive.

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