WO2019161190A1

WO2019161190A1 - Hydrochromic coatings and related methods

Info

Publication number: WO2019161190A1
Application number: PCT/US2019/018206
Authority: WO
Inventors: Endrit SHURDA; Yu Du; Lyle Small; Vladimir TOMOVICH
Original assignee: Chromatic Technologies, Inc.
Priority date: 2018-02-15
Filing date: 2019-02-15
Publication date: 2019-08-22

Abstract

Solvent-based coatings comprising at least one bydrochromic compound that changes color upon contact with an aqueous or polar liquid are disclosed. The hydrochromic coatings can be printed on a variety of substrates, in the form of complex graphic designs if desired, and are substantially resistant to leaching. The coatings are suitable for use as wetness indicators, for example, in absorbent personal care products that have the coating applied to at least part of the product to alert the user that the article has been exposed to water, urine or other aqueous or polar fluids. The solvent-based coatings may also be used as authenticity indicators, for example, in currency instruments, asset titles and legal instruments, such as money, checks, stock certificates, property titles, contracts, notary seals and the like.

Description

HYDROCHROMIC COATINGS AND RELATED METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application Nos. 62/631 ,374, filed February 15, 2018, and 62/693,521 , filed July 3, 2018, each of which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Many modern wetness indicators use a water-soluble pH dye formulated in a hot-melt coating. However, leaching of the dye out of the hot-melt coating tends to be problematic, and pH dyes generally do not exhibit intense color or a distinct color difference between the exposed and unexposed states. Further, printing these types of wetness indicators necessitates a multi-step process because graphic designs and hot-melt coatings require different application methods, and the multi- step process precludes printing of sophisticated graphic designs that can be smeared in subsequent processing steps.

SUMMARY

[0003] The present invention generally relates to solvent-based coatings comprising a hydrochromic compound that changes color upon contact with an aqueous or polar liquid. The solvent-based coatings disclosed herein may be used as wetness indicators, for example, in absorbent personal care products that have the coating applied to at least part of the product to alert the user that the article has been exposed to water, urine or other aqueous or polar fluids. The solvent-based coatings disclosed herein may be used as authenticity indicators, for example, in currency instruments, asset titles and legal instruments, such as paper money, checks, stock certificates, property titles, contracts, notary seals and the like. The hydrochromic coatings disclosed herein, which may be formulated as inks, lacquers, paints or the like, can be printed on a variety of substrates, in the form of complex graphic designs if desired. Further, the dried coatings are substantially resistant to leaching.

[0004] In an aspect, a solvent-based hydrocbromic coating comprises: (i) a hydrochromic compound (1 ) and/or (2);

compound (2) wherein R-i-Ru are independently selected from the group consisting of hydrogen, halo, hydroxyl, nitro, cyano, and C1-C16 linear or branched alkyl, alkenyl, alkynyl, aryl, heteroalkyl, heteroalkenyl, heteroalkynyl and heteroaryl moieties;

(ii) a transition metal-pH dye salt complex; or

(iii) a combination of (i) and (ii); and a resin; an acid or base; and a solvent.

[0005] In an embodiment, a transition metai-pH dye salt complex is selected from (3), (4), and combinations thereof,

compound (3) compound (4) wherein M is a first row transition metal and R1-R12 are independently selected from the group consisting of hydrogen, halo, hydroxyl, nitro, cyano, and C1 -C16 linear or branched alkyl, alkenyl, alkynyl, aryl, heteroalkyl, heteroalkenyl, heteroalkynyl and heteroaryl moieties. For example, M may be selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu.

[0006] In an embodiment, the hydrochromic compound is hydrophobic. For example, the hydrochromic compound may be more hydrophobic than an existing pH dye.

[0007] In an embodiment, the hydrochromic coating is substantially resistant to leaching. For example, ASTWf test method D6688-11 may be used to measure the relative resistance of printed matter to liquid chemicals. When a comparison of treated hydrochromic coating to untreated hydrochromic coating results in no, or minimal, discoloration of the treated hydrochromic coating the result is negative for leaching or shows substantial resistance to leaching.

[0008] In an embodiment, the transition metal-pH dye salt complex and/or the hydrochromic compound is present in the hydrochromic coating in an amount between 0.1 -15 wt.%, or between 0.5-15 wt.%, or between 0.5-12 wt.%, or between 1-15 wt.%, or between 2-12 wt.%, or between 5-10 wt.%.

[0009] In an embodiment, the hydrochromic compound undergoes a conjugate acid-base reaction in the presence of an aqueous solution or polar solvent. For example, the hydrochromic compound may be present as an acid in the solvent- based hydrochromic coating and contact with an aqueous solution may convert the hydrochromic compound to its conjugate base.

[0010] In an embodiment, a Zwitter ionic form of the hydrochromic compound is stabilized in the presence of water or another polar molecule. Without being bound by theory, it is contemplated that a transition between a charged Zwitter ionic state and an uncharged state may correspond to a change in color of the hydrochromic compound.

[0011] In an embodiment, a solvent-based hydrochromic coating comprises a resin present in the hydrochromic coating in an amount between 1 -50 wt.%, or between 1 -40 wt.%, or between 1 -30 wt.%, or between 2-25 wt.%, or between 4-20 wt.%, or between 5-15 wt.%, or between 8-12 wt.%. For example, the resin may be selected from the group consisting of polyvinyl butyral, polyvinyl acetate, vinyl chloride-vinyl-acetate copolymer, acrylic resin, styrene resin, polyester resin, polyurethane resin, epoxy, nitrocellulose, phenols, isocyanates and combinations thereof.

[0012] In an embodiment, a solvent-based bydrochromic coating comprises an acid or a base, such as an inorganic acid or base or an organic acid or base, which may be present in the hydrochromic coating in an amount between 1 -10 wt.%, or between 2-8 wt.%, or between 3-7 wt.%, or between 4-6 wt.%. For example, the acid may be selected from the group consisting of phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, sulfonic acid, acetic acid, tartaric acid, lactic acid, citric acid, salicylic acid, di-tert-butyl salicylic acid, C5-C20 carboxylic acids, C5-C20 aromatic acids, C4-C20 heterocyclic aromatic acids and combinations thereof, and the base may be selected from the group consisting of sodium hydroxide, potassium hydroxide, amines, amino alcohols, nitrogen-containing heterocy!ic compounds and combinations thereof.

[0013] In an embodiment, a solvent-based hydrochromic coating comprises a solvent, which may be present in the hydrochromic coating in an amount between 50-90 wt. %, or between 60-80 wt.%, or between 60-75 wt.%, or between 60-70 wt.%, or between 65-70 wt.%. For example, the solvent may be selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, butanol, octanols, acetonitrile, diacetone alcohol, benzyl alcohol, methoxy propanol, butyl glycol, glycol ethers including but not limited to ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monophenyl ether, dipropylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, and propylene glycol monophenyl ether, methoxy butanol, ethylene glycol, propylene glycol, dioxane, tetrahydrofuran, methyl cellulose, ethyl cellulose, butyl cellulose, methoxy propyl acetate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, 3-methoxybutyl acetate, butyl glycollate, butyl butoxyacetate, dibufyi 2,2’-oxybisacetate, dibasic esters, ethyl lactate, acetone, methyiethy!ketone, methylisobutylketone, cyclohexanone, terpineol, acetic acid, dimethyl sulfoxide and combinations thereof.

[0014] In an embodiment, a solvent-based hydrochromic coating further comprises an additive selected from the group consisting of surfactants, wetting agents, opacifiers, waxes, slip agents, drying rate modifiers, crosslinkers, ionic species, surface tension modifiers, matting agents, organic anhydrides, leveling agents, UV stabilizers and combinations thereof. The additive may be present in the hydrochromic coating in an amount between 0.01 - 5 wt.%, or between 0.05 - 4.5 wt.%, or between 0.1 - 4 wt.%, or between 0 2 - 3.5 wt.%, or between 0.5 - 3 wt.%, or between 0.75 - 2.5 wt.%.

[0015] Surfactants suitable for use in the coatings disclosed herein include but are not limited to solvent-free salts of unsaturated polyamine amides and lower molecular weight acidic polyesters (e.g., ANTI-TERRA@-U 100, supplied by Byk (Altana Group)).

[0016] Wetting agents suitable for use in the coatings disclosed herein include but are not limited to polymers and copolymers with pigment affinic groups (e.g., BYK⁽B⁾-9G77).

[0017] Opacifiers suitable for use in the coatings disclosed herein include but are not limited to clay, titanium dioxide, zinc oxide, calcium carbonate, talc and combinations thereof.

[0018] Waxes suitable for use in the coatings disclosed herein include but are not limited to polyethylene, polypropylene, polytetrafluoroethyiene and combinations thereof. Waxes can be natural (carnauba and montan wax), petroleum-based (paraffins, microcrystalline wax) or synthetic, derived from petroleum distillates or residues (polyethylene, polypropylene, Fischer-Tropsch wax).

[0019] Slip agents suitable for use in the coatings disclosed herein include but are not limited to polypropylene wax additives, polyether modified

dimethylpoiysiloxanes (e.g., BYK®-378) and combinations thereof.

[0020] Drying rate modifiers suitable for use in the coatings disclosed herein include but are not limited to ethyl acetate.

[0021] Crosslinkers suitable for use in the coatings disclosed herein include but are not limited to acids, amines, UV photoinitiators, cationic photoinitiators, zinc oxide, titanium chelates, mutiifunctional carbodiimides, polyfunctional aziridenes, polyethylene amines, polysiloxanes and combinations thereof.

[0022] Ionic species suitable for use in the coatings disclosed herein include but are not limited to ionic liquids, metal salts and combinations thereof. Suitable ionic liquids include but are not limited to 1 -allyl~3-methylimidazolium dicyanamide, 1 -ailyl- 3-methyiimidazoiium bis(trifiuoromethyisuifonyl)imide, 1 -ethyi-3-metbyiimidazoiium 1 , 1 ,2,2-tetrafluoroethanesulfonate, 1 -(3-cyanopropyl)-3-methylimidazolium chloride, 1 -butyl-3-methylimidazolium tetrafluoroborate, 1 -butyl-3-methylimidazoiium

hexafluorophosphate, 1 -butyl-3-methylimidazolium chloride, 1 ,3- dimethoxyimidazolium hexafluorophosphate, tetrabutylphosphonium

methanesulfonate and combinations thereof.

[0023] Surface tension modifiers suitable for use in the coatings disclosed herein include but are not limited to low-surface-tension chemicals, such as hydrocarbons (e.g., xylene, mineral spirits, mineral oils), Isopropyl acetate, polydimethylsiloxanes (ROMS) and combinations thereof.

[0024] Matting agents suitable for use in the coatings disclosed herein include but are not limited to fumed silica, synthetic amorphous silica, po!ymetby! urea resin, waxes or combinations thereof.

[0025] Organic anhydrides suitable for use in the coatings disclosed herein include but are not limited to propanoic anhydride, ethanoic anhydride, ethenoic propanoic anhydride, 1 ,2-benzendicarboxy!ic anhydride, phthalic anhydride, benzosuifonic anhydride, acetic anhydride, maleic anhydride, 1 ,8-naphthalic anhydride and combinations thereof.

[0026] Leveling agents suitable for use in the coatings disclosed herein include but are not limited to silicone, silicone glycols, fumed silica when a surface is treated with hexamethyidisi!azane, fluorosurfactants, organobentonite clay and combinations thereof.

[0027] UV stabilizers suitable for use in the coatings disclosed herein include but are not limited to UV radical scavengers, such as UV absorbers (benzotriazoles and benzophenones), HALS (hindered amines), quenchers (e.g. nickel quenchers), benzoates and combinations thereof.

[0028] In an embodiment, the additive is an additional hydrochromic compound, a pigment and/or a dye for adjusting the color of the coating. For example, the pigment or the dye may be selected from the group consisting of titanium dioxide, aluminum oxide, iron oxide, Malachite green, brilliant green, crystal violet,

erythrosine B, methyl green, methyl violet 2D, picric acid, naphthol yellow S, quinaldine red, eosine Y, metanil yellow, m-cresol purple, thymol blue, xy!enol blue, basis fuchsin, eosin B, 4-p-aminopbenol(azo)benzenesuipbonic acid-sodium salt, cresol red, martius yellow, phloxine B, methyl yellow, bromophenoi blue, congo red, methyl orange, bromochlorophenoi blue (water soluble or free acid form), ethyl orange, fluorocene WS, bromocresol green, chrysoidine, methyl red sodium salt, alizarine red S— H₂0, cochineal, chlorophenol red, bromocresol purple, 4-naphtha, alizarin, nitrazine yellow, bromothymol blue, brilliant yellow, neutral red, rosaiic acid, phenol red, 3-nitro phenol, orange II, phenoiphthalein, o-cresolphthalein, nile blue A, thymolphthalein, aniline blue WS, alizarine yellow GG, mordant orange, tropaolin 0, orange G, acid fuchsin, thiazol yellow G, indigo carmine, FD&C Blue No. 1 , FD&C Blue No. 2, FD&C Green No. 3, FD&C Red No. 40, FD&C Red No. 4, FD&C Yellow No. 5, FD&C Yellow No. 6, C.l. Food Blue 5, and C.l. Food Red 7, D&C Yellow No. 10, D&C Yellow No. 7, D&C Yellow No. 2, D&C Yellow No. 8, D&C Orange No. 4, D&C Red No. 22, D&C Red No. 28, D&C Red No. 33, D&C Green No. 8, D&C Green No. 5, D&C Brown No. 1 , Pigment Red 122, Pigment Red 53:1 , Pigment Red 48:2, Pigment Red 48:3, Pigment Red 57:1 , Pigment Red 184, Pigment Red 289, Pigment Black 7, Pigment Violet 19, Pigment Violet 23, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Green 7, Pigment Green 38, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 74, Pigment Yellow 83, Pigment Orange 5, Pigment Orange 34, Pigment Orange 36, and combinations thereof.

[0029] In an embodiment, the hydrochromic coating disclosed herein is applied to a product as a graphic design comprising intersecting and/or curved lines. In an embodiment, the product is an absorbent article. In an embodiment, the product may be selected from the group consisting of a diaper, training pants, absorbent underpants, an incontinence product, feminine hygiene products, baby wipes, household paper, bedding materials, medical absorbent articles, bandages, clothing articles, swimwear, tape, an authenticity indicating instrument, a moisture indicator label, a moisture indicator instrument, a medical device, a vessel and construction materials. In an embodiment, an authenticity indicating instrument is, for example, a currency instrument such as money, checks, stock certificates and the like, an asset title such as a property title, or a legal instrument such as a contract or notarized document.

[0030] In an embodiment, a diaper product comprises the hydrochromic coating disclosed herein as a wetness indicator printed as a graphic design comprising intersecting and/or curved lines.

[0031] In an aspect, a method of using a hydrochromic coating comprises the steps of applying the hydrochro ic coating disclosed herein to at least a portion of a substrate and curing the hydrochromic coating.

[0032] In an embodiment, the step of applying utilizes a water-free printing ink system. In an embodiment, the step of applying comprises spreading a hot melt, screen printing, stamping, flexography, intaglio printing, rotogravure, offset printing, letter press printing, electrography, lithography, inkjet printing and combinations thereof. In an embodiment, the step of applying is carried out by a water-free coating system. In an embodiment, the step of applying is carried out by an anilox coater, a flexo coater, a gravure coater, a hotmelt coater, a dip coater, a spin coater, a slot die coater, a silk screen coater and combinations thereof. In an embodiment, the step of applying produces a raised image.

[0033] In an embodiment, the step of curing comprises heating the coated substrate at a temperature between 30 °C and 80°C, or between 30 °C and 7Q°C, or between 35 °C and 60°C, or between 40 °C and 55°C for 1 to 60 seconds, or 2 to 45 seconds, or 5 to 30 seconds at a relative humidity between 0% and 80%, or between 2% and 70%, or between 4% and 65%, or between 5% and 50%. In an

embodiment, the step of curing comprises irradiating the coated substrate using electromagnetic radiation having a wavelength between 200 nm and 450 nm, or between 230 nm and 425 nm, or between 250 nm and 400 nm, or between 275 nm and 350 nm at a rate of 20 ft/min to 1000 ft/min, or 40 ft/min to 750 ft/m in, or 50 ft/m in to 500 ft/m in, or 75 ft/min to 250 ft/m in. In an embodiment, the step of curing comprises allowing the coated substrate to dry under ambient conditions for a period of 1 to 80 seconds, or 2 to 45 seconds, or 5 to 30 seconds. In an embodiment, the step of curing comprises irradiating the coated substrate using an electron beam at a rate of 10 ft/min to 1000 ft/min, or 15 ft/min to 700 ft/min, or 25 ft/min to 500 ft/min, or 50 ft/min to 250 ft/min.

[0034] In an embodiment, a substrate for use with the hydrochromic coatings disclosed herein comprises a material selected from the group consisting of plastic, textile, paper, glass, ceramic, parchment, metal and combinations thereof.

[0035] In an embodiment, a method of using a hydrochromic coating further comprises a step of exposing the cured hydrochromic coating to an aqueous solution or polar solvent and detecting a color change

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Illustrative embodiments of the present invention are described in detail below with reference to the attached drawings, wherein:

[0037] FIG. 1 is a schematic showing diaper construction and an intended printing location for a hydrochromic coating; and

[0038] FIG. 2 shows an example of hydrochromic compound printed and tested on a polyethylene substrate.

DETAILED DESCRIPTION

[0039] In general, the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art. The following definitions are provided to clarify their specific use in the context of this description.

[0040] As used herein, a“hydrochromic compound” emits radiation having a first wavelength under a first condition, such as ambient conditions, and emits radiation having a second wavelength under a second condition, such as upon exposure to water, an aqueous solution, or a non-aqueous polar solvent. In an embodiment, the first wavelength, the second wavelength or both are between 400 nm to 700 nm, thereby producing a color change detectable by the human eye. The color change may be from a first colored state to a second colored state, from a first colorless state to a second colored state, or from a first colored state to a second colorless state. In an embodiment, both the first wavelength and the second wavelength may be outside the visible portion of the electromagnetic spectrum and therefore undetectable by the human eye but detectable by instrumentation or animals other than humans.

[0041] As used herein, a“pH dye” or“pH indicator” describes a molecule, such as a bydrochromic compound, that reversibly changes color in the presence of an acid or base. Examples of pH dyes include, but are not limited to, Malachite green, brilliant green, crystal violet, erythrosine B, methyl green, methyl violet 2D, picric acid, naphthoi yellow S, quinaidine red, eosine Y, metanii yellow, m-cresoi purple, thymol blue, xyienoi blue, basis fuchsin, eosin B, 4-p- aminophenol(azo)benzenesulphonic acid-sodium salt, cresol red, martius yellow, phloxine B, methyl yellow, bromophenol blue, congo red, methyl orange,

bromochlorophenol blue (water soluble or free acid form), ethyl orange, fluorocene WS, bromocresoi green, chrysoidine, methyl red sodium salt, alizarine red S— H₂0, cochineal, chlorophenol red, bromocresoi purple, 4-naphtha, alizarin, nitrazine yellow, bromothymol blue, brilliant yellow, neutral red, rosalic acid, phenol red, 3- nitro phenol, orange II, phenolphthalein, o-cresolphthalein, nile blue A,

thymolphthalein, aniline blue WS, alizarine yellow GG, mordant orange, tropaolin O, orange G, acid fuchsin, thiazol yellow G, and indigo carmine.

[0042] As used herein, a“leuco dye” describes a molecule, such as a

hydrochromic compound, that can reversibly switch between two chemical forms, one of which is substantially colorless. The reversible transformation can be caused by heat, light or pH. When the transformation is caused by a change in pH, the leuco dye is also a pH dye.

[0043] As used herein, a“complex” or“coordination complex" comprises an atom or ion, which is usually metallic, and one or more bound molecules or ions, that are known as ligands or complexing agents. [0044] As used herein, a“coating” describes a mixture comprising at least one active component and a matrix that partially or completely encapsulates the active component.

[0045] As used herein,“weight percent” or“wt.%” is calculated as the weight of a component in a coating divided by the total weight of the coating prior to curing or drying multiplied by 100

[0046] As used herein, a“surfactant” is an inactive substance that

imparts compositions with enhanced solubility and/or wetability.

[0047] As used herein, a“wetting agent” is a compound that reduces the surface tension of a liquid to allow it to spread onto a surface.

[0048] As used herein, an“opacifier” is a compound that blocks or reduces transmission of electromagnetic energy through a chemical mixture, such as a coating.

[0049] As used herein,“waxes” are solid to semi solid materials added to a mixture to alter surface properties like water repulsion, appearance (gloss, matting, texturing), rheology, and pigment settling.

[0050] As used herein, a“slip agent” is a compound acting as an internal lubricant that migrates to the surface of a mixture to reduce friction and improve slip. Surfaces with high slip characteristics are generally resistant to scratching, soiling, and blocking.

[0051] As used herein, a“drying rate modifier” is a compound that alters the time required to reach a tack-free drying point. For example, in solvent-based inks, use of low molecular weight alcohols (e.g. ethanol) and esters (e.g. ethyl acetate) as solvents can increase the drying rate of an ink while higher molecular weight alcohols (e.g. N-propyl alcohol), acetates (e.g. N-propyl acetate), and glycol ethers (e.g. propylene glycol n-propyl ether) can decrease the drying rate.

[0052] As used herein, a“crosslinker” is a chemical moiety that covalently or ionically joins nearby molecules. Crossiinking may be present between molecules within an ink/coating and/or between a binder molecule of the ink/coating and a substrate.

[0063] As used herein, a“surface tension modifier” is a compound that improves the portability of an ink or coating, for example, by reducing surface tension

[0064] As used herein, a“matting agent” is a compound that changes the surface structure of a coating to scatter incident light and create a matte finish.

[0055] As used herein, a“leveling agent” is a compound that improves flow of a liquid product, thereby allowing the product to fill any irregularities that may be present on a surface.

[0056] As used herein, a“UV stabilizer” is a compound that combats degradation of polymers exposed to light, oxygen and/or heat and extends the life of a finished product by protecting against loss of strength, stiffness, flexibility and gloss

[0057] “Proximal” and“distal” refer to the relative positions of two or more objects, planes or surfaces. For example, an object that is close in space to a reference point relative to the position of another object is considered proximal to the reference point, whereas an object that is further away in space from a reference point relative to the position of another object is considered distal to the reference point.

[6058] The terms“direct and indirect” describe the actions or physical positions of one object relative to another object. For example, an object that“directly” acts upon or touches another object does so without intervention from an intermediary. Contrarily, an object that“indirectly” acts upon or touches another object does so through an intermediary (e.g., a third component).

[6659] FIG. 1 is a schematic showing typical diaper construction and an intended printing location for a solvent-based hydrochromic coating on a polyethylene substrate. The solvent-based hydrochromic coating is printed on a central, interior surface of a diaper. Once dried, the central, interior area of the diaper and the solvent-based hydrochromic coating are covered with layers of polyacryiate, composite fiber and polypropylene. [0060] FIG. 2 shows an example of the hydrochromic compound below printed and tested on a polyethylene substrate. The hydrochromic compound is in its acid form, which has a red color, in solvent-based ink. When the hydrochromic

compound comes into contact with water, the compound is transformed into its alkaline form, which has a yellow color.

[0061] Hydrochromic compounds suitable for use in the present hydrochromic coatings may be synthesized in accordance with the methods disclosed by Cihelnik et al. , Collect. Czech. Chem. Commum., vol. 67, (2002), pp 1779-1789, which is incorporated by reference herein. For example, Eq. 1 shows a synthetic route to preparing an exemplary hydrochromic compound.

[6062] An exemplary solvent-based hydrochromic coating formulation comprises 1-15 wt. % hydrochromic compound; 10-30 wt. % resin; 1 -10 wt. % acid; 0.01 - 5 wt. % additives (optional); and 60-80 wt. % solvent. Once these components are thoroughly mixed and dissolved, the hydrochromic coating can be stored for later use or immediately printed onto a substrate. For example, the hydrochromic coatings may be stored for at least 6 months or at least 12 months. [0063] An exemplary solvent-based bydrochromic coating formulation comprises 1-10 wt % hydrochromic compound; 10-20 vvt % resin; 1 -10 wt % organic or inorganic acid; and 60-80 wt. % solvent, such as ethanol, propanol and/or acetates. Once these components are thoroughly mixed and dissolved, the hydrochromic coating can be stored for later use or immediately printed onto a substrate.

[6664] In addition to the conjugate acid-base or Zwitter ionic complexes disclosed above, coatings comprising metai-pH dye salt complexes are disclosed herein.

[006S] Transition Metai-pH Dye Salt Complexes

[6666] pH dyes in their salt form, as shown in (A) above, are very soluble in water. Therefore, they are not very desirable for applications that require minimal leaching. However, complexing a pH dye with a first row transition metal, for example via reaction of the alkali salt with a transition metal halide, to form the transition metal-pH dye salt complex shown in (B) above increases alcohol and acetate solubility and reduces leaching of the dye in solvent-based coatings. The color transition goes from a dark color in the complexed form (B) to a light color when exposed to aqueous solutions.

(C) (D)

[0067] For the above dye, where the pH salt form (C) is converted to the transition metal-pH dye complex (D), the color changes from light when the transition metal-pH dye complex (D) is dry to a dark color when it is exposed to an aqueous solution.

[0068] In addition to the conjugate acid-base or Zwitter ionic complexes and transition metal-pH dye salt complexes disclosed above, metal-!euco dye complexes are disclosed herein.

[0069] Meial-Leuco Dye Complexes

[0070] Leuco dyes are generally not soluble in the alcohol and/or acetate solvent mixtures used for solvent-based inks. To overcome this challenge, various additives have been used in commercial leuco dye compositions. Some of these additives are disclosed in US Patent Nos. 8,791 ,045 and 9,554,948, which are incorporated by reference herein.

[0071] The present inventors have developed a technique where upon the addition of any metal complex to a leuco dye, the dye exists in its open form and becomes colored. This newly formed meta!-!euco dye complex is very soluble in the aforementioned solvent system. The colored ink can be printed and dried. After drying the substrate can be wetted with an aqueous solution and a color change occurs from the colored state to the colorless state. This procedure can be used with a variety of leuco dyes.

[6072] As an alternative to the metal chloride approach discussed above, a leuco dye (e.g., Red 40/CVL) can be dispersed with a metal complex developer (e.g., a nickel, zinc or iron complex) in a solvent-based system.

[0673] The dye interacts with the metal to take on its open form and become colored and soluble. The color disappears when a stronger ligand (e.g., water, amine) competes with the Ieuco dye for the nucleophile (Ni ion), and the dye reverts to its Ieuco (colorless) form.

STATEMENTS REGARDING INCORPORATION BY REFERENCE AND

VARIATIONS

[0074] Ail references cited throughout this application, for example patent documents including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source material; are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference)

[0075] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the invention has been specifically disclosed by preferred

embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed can be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the invention and it will be apparent to one skilled in the art that the invention can be carried out using a large number of variations of the devices, device components, and method steps set forth in the present description. As will be apparent to one of skill in the art, methods and devices useful for the present methods and devices can include a large number of optional composition and processing elements and steps. All art-known functional equivalents of materials and methods are intended to be included in this disclosure. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention. [0076] When a group of substituents is disclosed herein, it is understood that all individual members of that group and ail subgroups are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure.

II must be noted that as used herein and in the appended claims, the singular forms "a'', "an”, and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a molecule" includes a plurality of such molecules and equivalents thereof known to those skilled in the art, and so forth. As well, the terms "a" (or "an”), "one or more" and "at least one" can be used interchangeably herein. It is also to be noted that the terms "comprising",

"including", and "having" can be used interchangeably. The expression“of any of claims XX-YY” (wherein XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form, and in some embodiments is interchangeable with the expression“as in any one of claims XX-YY.”

[0078] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described.

[0079] Whenever a range is given in the specification, for example, a range of integers, a temperature range, a time range, a composition range, or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. As used herein, ranges specifically include the values provided as endpoint values of the range. As used herein, ranges specifically include all the integer values of the range. For example, a range of 1 to 100 specifically includes the end point values of 1 and 100. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein. [0080] As used herein,“comprising” is synonymous and can be used interchangeably with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of excludes any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms "comprising", "consisting essentially of and "consisting of" can be replaced with either of the other two terms. The invention illustratively described herein suitably can be practiced in the absence of any element or elements, limitation or limitations which is/are not specifically disclosed herein.

Claims

CLAIMS What is claimed is:

1. A solvent-based hydrochromic coating comprising:

(i) a hydrochromic compound (1 ) and/or (2);

compound (2) wherein R-i-Ru are independently selected from the group consisting of hydrogen, halo, hydroxyl, nitro, cyano, and C1 -C16 linear or branched alkyl, alkenyl, alkynyl, aryl, heteroalkyl, heteroalkenyl, heteroalkynyl and heteroaryl moieties;

(ii) a transitional metal-pH dye salt complex; or

2. The solvent-based hydrochromic coating of claim 1 , wherein the

transition metal-pH dye salt complex is selected from

compound (3), compound (4) and combinations thereof, wherein M is a first row transition metal and R-_I-R-12 are independently selected from the group consisting of hydrogen, halo, hydroxyl, nitro, cyano, and C1 -C16 linear or branched alkyl, alkenyl, alkynyl, aryl, heteroalkyl, heteroalkenyl, heteroalkynyl and heteroaryl moieties.

3. The solvent-based hydrochromic coating of claim 2, wherein M is

selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu.

4. The solvent-based hydrochromic coating of claim 1 , wherein the

hydrochromic coating is substantially resistant to leaching.

5. The solvent-based hydrochromic coating of claim 1 , wherein the

transition metal-pH dye salt complex and/or the hydrochromic compound is present in the hydrochromic coating in an amount between 0.1 -15 wt.%.

6. The solvent-based hydrochromic coating of claim 1 , wherein the resin is selected from the group consisting of polyvinyl butyral, polyvinyl acetate, vinyl chloride-vinyl-acetate copolymer, acrylic resin, styrene resin, polyester resin, polyurethane resin, epoxy, nitrocellulose, phenols, isocyanates and combinations thereof.

7. The solvent-based hydrochromic coating of claim 1 , wherein the resin is present in the hydrochromic coating in an amount between 1 -50 wt.%.

8. The solvent-based hydrochromic coating of claim 1 , wherein the acid or base is an inorganic acid or base.

9. The solvent-based hydrochromic coating of claim 1 , wherein the acid or base is an organic acid or base.

10. The solvent-based hydrochromic coating of claim 1 , wherein the acid is selected from the group consisting of phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, sulfonic acid, acetic acid, tartaric acid, lactic acid, citric acid, salicylic acid, di-tert-butyl salicylic acid, C5-C20 carboxylic acids, C5-C20 aromatic acids, C4-C20 heterocyclic aromatic acids and combinations thereof.

11. The solvent-based hydrochromic coating of claim 1 , wherein the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, amines, amino alcohols, nitrogen-containing heterocylic compounds and combinations thereof.

12. The solvent-based hydrochromic coating of claim 1 , wherein the acid or base is present in the hydrochromic coating in an amount between 1 - 10 wt.%.

13. The solvent-based hydrochromic coating of claim 1 , wherein the

solvent is selected from the group consisting of methanol, ethanol, n- propanol, isopropanol, butanol, octanols, acetonitrile, diacetone alcohol, benzyl alcohol, methoxy propanol, methoxy butanol, butyl glycol, glycol ethers, methoxy butanol, ethylene glycol, propylene glycol, dioxane, tetrahydrofuran, methyl cellulose, ethyl cellulose, butyl cellulose, methoxy propyl acetate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, 3-methoxybutyl acetate, butyl glycollate, butyl butoxyacetate, dibutyl 2,2’-oxybisacetate, dibasic esters, ethyl lactate, acetone, methylethylketone, methylisobutylketone, cyclohexanone, terpineol, acetic acid, dimethyl sulfoxide and combinations thereof.

14. The solvent-based hydrochromic coating of claim 1 , wherein the

solvent is present in the hydrochromic coating in an amount between 60-80 wt.%.

15. The solvent-based hydrochromic coating of claim 1 further comprising an additive selected from the group consisting of surfactants, wetting agents, opacifiers, waxes, slip agents, drying rate modifiers,

crosslinkers, ionic species, surface tension modifiers, matting agents, organic anhydrides, leveling agents, UV stabilizers and combinations thereof.

16. The solvent-based hydrochromic coating of claim 15 wherein the

additive is an additional hydrochromic compound, a pigment and/or a dye for adjusting the color of the coating.

17. The solvent-based hydrochromic coating of claim 16, wherein the

pigment or the dye is selected from the group consisting of titanium dioxide, aluminum oxide, iron oxide, Malachite green, brilliant green, crystal violet, erythrosine B, methyl green, methyl violet 2D, picric acid, naphthol yellow S, quinaldine red, eosine Y, metanil yellow, m-cresol purple, thymol blue, xylenol blue, basis fuchsin, eosin B, 4-p- aminophenol(azo)benzenesulphonic acid-sodium salt, cresol red, martius yellow, phloxine B, methyl yellow, bromophenol blue, congo red, methyl orange, bromochlorophenol blue (water soluble or free acid form), ethyl orange, fluorocene WS, bromocresol green, chrysoidine, methyl red sodium salt, alizarine red S— H₂0, cochineal, chlorophenol red, bromocresol purple, 4-naphtha, alizarin, nitrazine yellow, bromothymol blue, brilliant yellow, neutral red, rosalic acid, phenol red, 3-nitro phenol, orange II, phenolphthalein, o-cresolphthalein, nile blue A, thymolphthalein, aniline blue WS, alizarine yellow GG, mordant orange, tropaolin 0, orange G, acid fuchsin, thiazol yellow G, indigo carmine, FD&C Blue No. 1 , FD&C Blue No. 2, FD&C Green No. 3, FD&C Red No. 40, FD&C Red No. 4, FD&C Yellow No. 5, FD&C Yellow No. 6, C.l. Food Blue 5, and C.l. Food Red 7, D&C Yellow No. 10, D&C Yellow No. 7, D&C Yellow No. 2, D&C Yellow No. 8, D&C Orange No. 4, D&C Red No. 22, D&C Red No. 28, D&C Red No. 33, D&C Green No. 8, D&C Green No. 5, D&C Brown No. 1 , Pigment Red 122, Pigment Red 53:1 , Pigment Red 48:2, Pigment Red 48:3, Pigment Red 57:1 , Pigment Red 184, Pigment Red 269, Pigment Black 7, Pigment Violet 19, Pigment Violet 23, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Green 7, Pigment Green 36, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 74, Pigment Yellow 83, Pigment Orange 5, Pigment Orange 34, Pigment Orange 36, and combinations thereof.

18. The solvent-based hydrochromic coating of claim 15, wherein the ionic species is selected from the group consisting of 1 -allyl-3- methylimidazolium dicyanamide, 1 -allyl-3-methylimidazolium

bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium 1 ,1 ,2,2- tetrafluoroethanesulfonate, 1 -(3-cyanopropyl)-3-methylimidazolium chloride, 1 -butyl-3-methylimidazolium tetrafluoroborate, 1 -butyl-3- methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1 ,3-dimethoxyimidazolium hexafluorophosphate,

tetrabutylphosphonium methanesulfonate and combinations thereof.

19. The solvent-based hydrochromic coating of claim 15, wherein the

additive is present in the hydrochromic coating in an amount between 0.01 - 5 wt.%.

20. A product comprising the hydrochromic coating of any one of the

preceding claims, wherein the hydrochromic coating is applied to the product as a graphic design comprising intersecting and/or curved lines.

21. A product comprising the hydrochromic coating of any one of the

preceding claims, wherein the product is an absorbent article.

22. A product comprising the hydrochromic coating of any one of the

preceding claims, wherein the product is selected from the group consisting of a diaper, training pants, absorbent underpants, an incontinence product, feminine hygiene products, baby wipes, household paper, bedding materials, medical absorbent articles, bandages, clothing articles, swimwear, tape, an authenticity indicating instrument, a moisture indicator label, a moisture indicator instrument, a medical device, a vessel and construction materials.

23. A diaper product comprising the hydrochromic coating of any one of the preceding claims as a wetness indicator, wherein the hydrochromic coating is printed as a graphic design comprising intersecting and/or curved lines.

24. A method of using a hydrochromic coating, comprising: applying the hydrochromic coating of any one of the preceding claims to at least a portion of a substrate; and curing the hydrochromic coating.

25. The method of claim 24, wherein the substrate comprises a material selected from the group consisting of plastic, textile, paper, glass, ceramic, parchment, metal and combinations thereof.

26. The method of claim 24, wherein the step of applying utilizes a water- free printing ink system.

27. The method of claim 24, wherein the step of applying comprises

spreading a hot melt, screen printing, stamping, flexography, intaglio printing, rotogravure, offset printing, letter press printing, electrography, lithography, inkjet printing and combinations thereof.

28. The method of claim 24, wherein the step of applying is carried out by a water-free coating system.

29. The method of claim 24, wherein the step of applying is carried out by an anilox coater, a flexo coater, a gravure coater, a hotmelt coater, a dip coater, a spin coater, a slot die coater, a silk screen coater and combinations thereof.

30. The method of claim 24, wherein the step of applying produces a raised image.

31. The method of claim 24, wherein the step of curing comprises heating the coated substrate, irradiating the coated substrate using

electromagnetic radiation, allowing the coated substrate to dry under ambient conditions and/or irradiating the coated substrate using an electron beam.

2. The method of claim 24 further comprising a step of exposing the cured hydrochromic coating to an aqueous solution or polar solvent and detecting a color change.