WO2017216767A1

WO2017216767A1 - Micro-porous coating compositions

Info

Publication number: WO2017216767A1
Application number: PCT/IB2017/053593
Authority: WO
Inventors: Incorporated Hercules
Original assignee: Hickman Stuart Roy; Hercules LLC
Current assignee: Hickman Stuart Roy; Hercules LLC
Priority date: 2016-06-17
Filing date: 2017-06-16
Publication date: 2017-12-21
Anticipated expiration: 2018-12-17
Also published as: GB201610602D0

Abstract

A composition for forming a glossy, micro-porous coating on a substrate includes a coalescing agent, a binder; a crosslinking agent. Also disclosed is a printable recording medium, particularly an inkjet recording medium, comprising a substrate and an image- receiving layer wherein said image-receiving layer is a layer derived from such a coating composition.

Description

MICRO-POROUS COATING COMPOSITIONS

FIELD

[0001] The presently disclosed process(es), procedure(s), method(s), product(s), result(s), and/or concept(s) (collectively referred to hereinafter as the "present disclosure") relate generally to a micro-porous coating composition. Additionally, the present disclosure relates generally to a substrate coated with the composition and its use in inkjet printers.

BACKGROUND

[0002] An inkjet printer has become highly popular due to its high performance, and ability to produce images comparable to those of a conventional silver halide

photograph. Thus, there is a constant demand for an inkjet medium having a glossy appearance which is comparable to that of a silver halide photograph and which permits high quality image recording.

[0003] For inkjet printing, aqueous inks, which contain a high amount of water and other solvents, are typically used. The inkjet printer normally uses inkjet recording media comprising a porous image-receiving layer that is absorbent to the ink. This porous image-receiving layer is designed to absorb the liquid component in the ink quickly to reduce drying time. Thus, micro-porous inkjet recording media are widely used today for producing high quality images with fast print-speed and rapid dry-time.

[0004] However, the combination of the micro-porous inkjet recording media with other conventional coating materials used in other printing processes is generally unsatisfactory for inkjet printing. This is especially true in the case of high gloss inkjet printing.

[0005] Polymer dispersions, used as binders in dispersion paints, consist of particles finely distributed in a liquid carrier such as water and/or organic solvent(s). Coalescing agents are generally used in dispersion paints for optimizing a film formation process for the polymeric binder particles. The film formation process involves evaporation of the liquid carrier and formation of a continuous polymer film as well as the coalescence of the polymeric binder particles during and after the evaporation of the liquid carrier (e.g. , water), thereby permitting contact and fusion of adjacent polymeric dispersion particles. Typically, the coalescing agents can reduce the formation temperature and as a consequence can optimize film coherence and properties such as scrub resistance, mechanical properties as well as appearance.

[0006] On contact with printing media, the outer, aqueous phase of the inkjet fluid is separated from the internal phase by both capillary action onto the hydrophilic media surface, and by evaporation, leaving the relatively high-viscosity internal phase of the dispersion which coalesces to give a smooth sharp print image on the printing media. Traditionally, in gloss print receptive coating production (with reference to typical photo gloss paper), such coalescing effect can be achieved by using a coalescing agent such as boric acid or sodium borate (SVHC), which is toxic. There is a need to find a nontoxic coalescing agent that can provide high quality images from inkjet printers.

DETAILED DESCRIPTION

[0007] Before explaining at least one embodiment of the present disclosure in detail, it is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of the components or steps or

methodologies set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

[0008] Unless otherwise defined herein, technical terms used in connection with the present disclosure shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0009] All patents, published patent applications, and non-patent publications mentioned in the specification are indicative of the level of skill of those skilled in the art to which the present disclosure pertains. All patents, published patent applications, and non-patent publications referenced in any portion of this application are herein expressly incorporated by reference in their entirety to the same extent as if each individual patent or publication was specifically and individually indicated to be incorporated by reference.

[0010] All of the articles and/or methods disclosed herein can be made and executed without undue experimentation in light of the present disclosure. While the articles and methods of the present disclosure have been described in terms of preferred

embodiments, it will be apparent to those of ordinary skill in the art that variations may be applied to the articles and/or methods and in the steps or in the sequence of steps of the method(s) described herein without departing from the concept, spirit and scope of the present disclosure. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the present disclosure.

[0011] As utilized in accordance with the present disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings.

[0012] The use of the word "a" or "an" when used in conjunction with the term

"comprising" may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one." The use of the term "or" is used to mean "and/or" unless explicitly indicated to refer to alternatives only if the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or." Throughout this application, the term "about" is used to indicate that a value includes the inherent variation of error for the quantifying device, the method(s) being employed to determine the value, or the variation that exists among the study subjects. For example, but not by way of limitation, when the term "about" is utilized, the designated value may vary by plus or minus twelve percent, or eleven percent, or ten percent, or nine percent, or eight percent, or seven percent, or six percent, or five percent, or four percent, or three percent, or two percent, or one percent. The use of the term "at least one" will be understood to include one as well as any quantity more than one, including but not limited to, 1 , 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The term "at least one" may extend up to 100 or 1000 or more depending on the term to which it is attached. In addition, the quantities of 100/1000 are not to be considered limiting as lower or higher limits may also produce satisfactory results. In addition, the use of the term "at least one of X, Y, and Z" will be understood to include X alone, Y alone, and Z alone, as well as any combination of X, Y, and Z. The use of ordinal number terminology (i.e. , "first", "second", "third", "fourth", etc.) is solely for the purpose of differentiating between two or more items and, unless otherwise stated, is not meant to imply any sequence or order or importance to one item over another or any order of addition.

[0013] As used herein, the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. The terms "or combinations thereof and "and/or combinations thereof" as used herein refer to all permutations and combinations of the listed items preceding the term. For example, "A, B, C, or combinations thereof" is intended to include at least one of: A, B, C, AB, AC, BC, or ABC and, if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more items or terms, such as BB, AAA, AAB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

[0014] As used herein, the term "substantially" means that the subsequently described circumstance completely occurs or that the subsequently described circumstance occurs to a great extent or degree.

[0015] For purposes of the following detailed description, other than in any operating examples, or where otherwise indicated, numbers that express, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about". The numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties to be obtained in carrying out the invention.

[0016] In the present disclosure, the term "coalescing agent" is understood in a broad sense, in particular covering the functions of solvent, co-solvent, crystallization inhibitor and stripping agent. The term coalescing agent may especially denote a product that is liquid at the usage temperature, which may contribute to rendering a solid substance liquid, or to preventing or retarding the solidification or the crystallization of material in a liquid medium.

[0017] As used herein, the term "binder" refers to a compound that helps facilitate adherence of a micro-porous coating composition to a substrate. The terms binder and binder latex may be interchangeably used in the present disclosure.

[0018] As used herein, the term "pigment" refers to insoluble particles that remain suspended or dispersed when introduced into a coating composition.

[0019] As used herein, the term "wetting agent" refers to anionic, cationic, and nonionic surfactants.

[0020] As used herein, the term "gloss" refers generally to the amount of light reflected by an object's surface, such as an inkjet media surface. Gloss can be quantified, as is common in the art, and is measured relative to specific specular angles from an object surface. The specular angle is the angle equal to but opposite the angle of incidence. This specular light is responsible for the highlights visible on shiny materials. When quantifying specular gloss, it can be measured at angles of 20°, 45°, 60°, and 85° from the normal. In the present disclosure gloss is measured at 60° according to ASTM D523 using a Tri-Glossmaster (Sheen Instruments)

[0021] The present disclosure relates to a micro-porous coating composition comprising: a) a coalescing agent; b) a binder; and c) a crosslinking agent. The coalescing agent can be an esteramide compound and/or a glycol ether compound. The micro-porous coating composition is suitable for coating onto a substrate.

[0022] The esteramide compound may be represented by the general formula (I)

R¹OOC-M-CONR²R³ (I) where R¹ is a saturated or unsaturated, linear or branched, optionally cyclic, or optionally aromatic, hydrocarbon-based radical, having from 1 to 36 carbon atoms; R² and R³ are identical or different radicals and each is independently selected from saturated or unsaturated, linear or branched, optionally cyclic, optionally aromatic, or optionally substituted, hydrocarbon-based radicals, having from 1 to 36 carbon atoms, with the proviso that R² and R³ optionally form a ring member that is optionally substituted or that optionally contains a heteroatom; and M is a linear or a branched divalent alkyl radical having from 2 to 12 carbon atoms.

[0023] R¹, R² and R³ may be identical or different radicals independently selected from the group consisting of C₁-C₁₂ alkyl, aryl, alkylaryl, and arylalkyl radicals; and R² or R³ is optionally substituted.

[0024] R¹ may be selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, isoamyl, n-hexyl, cyclohexyl, 2-ethylbutyl, n-octyl, isooctyl, 2-ethylhexyl, and tridecyl radicals.

[0025] R² and R³ may be identical or different and independently selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, amyl, isoamyl, hexyl, cyclohexyl, hydroxyethyl, morpholine, piperazine and piperidine radicals.

[0026] The esteramide compound may be selected from the group consisting of CH₃— CH₂— CH₂— CH₂— CH(CH₂CH₃)— CH₂— OOC— CONMe₂, CH₃— (CH₂)1 -1 1— OOC— CONMe₂, and

C₆Hii— OOC— CONMe₂.

[0027] In a further embodiment, the esteramide compound is selected from the group consisting of methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate, methyl 2- (dimethylamino)-2-oxoacetate, ethyl 2-(dimethylamino)-2-oxoacetate, 2-ethyl-hexyl 2- (dimethylamino)-2-oxoacetate, (n-decyl 2-(dimethylamino)-2-oxoacetate, and cyclohexyl 2-(dimethylamino)-2-oxoacetate, and combinations thereof.

[0028] Additional examples of the esteramide compounds are disclosed in U.S. Pat. No. 8735324B2, which is hereby incorporated by reference herein in its entirety.

[0029] The glycol ether compound can be represented by a general formula (I I)

_R4

where R⁴ is a CrC₆ aliphatic or aromatic group; R⁵ is H, CH₃, or C₂H₅; n has a value of at least 1 ; and A comprises at least one of an ester, an amide, a hydroxyl and an ether. The value of n may be 1 , 2, 3 or 4, or the value of n may be 1 , 2 or 3. [0030] The exemplary glycol ethers can include, but are not limited to, Ci-C₆ alkylene glycol ethers such as propylene glycol butyl ether, dipropylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol propyl ether, and triethylene glycol methyl ether. Exemplary glycol ethers are commercially available under the name Dowanol® from The Dow Chemical Company. For example, n-propoxypropanol is available under the name Dowanol® PnP. Exemplary derivatives of glycol ethers include those glycol ethers modified to include an additional group or functionality such as an ester group.

[0031] The glycol ether compound may be selected from the group consisting of propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol propyl ether, triethylene glycol methyl ether, and combinations thereof.

[0032] The glycol ether may be an aromatic glycol ether such as ethylene glycol phenyl ether.

[0033] The glycol ether compound may be selected from the group consisting of propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, 3-methoxybutanol acetate, tetrahydrofurfuryl acetate, cyclohexanol acetate, and combinations thereof.

[0034] Additional examples of glycol ether compounds are disclosed in U.S. Pat. No 7879785B2, which is hereby incorporated by reference herein in its entirety.

[0035] Any suitable binder(s) can be used in the compositions of the present disclosure, including water-soluble or water-dispersible film-forming polymers and water-swellable polymers, and preferably these are selected from polymers having a hydrophilic functional group such as a hydroxyl and/or amino group.

[0036] Examples of the binders can include polymers or resin, such as, without limitation, water-soluble or water-dispersible film-forming polymers and/or latex polymers such as cellulose derivatives (for instance selected from hydroxyethyl cellulose, methyl cellulose and carboxy methyl cellulose), casein, gelatin, protein, starch (e.g. oxidized, esterified, or other modified types of starch), gum arabic, polyethylene glycol, polypropylene glycol, vinyl polymers (e.g. polyvinyl alcohol, polymers and copolymers of vinyl pyrrolidine (PVP), polymers and copolymers of vinyl acetate (including ethylene vinyl acetate), styrene butadiene and derivatives (including styrene butadiene rubbers (SBR)), styrene maleic anhydride (SMA), styrene acrylonitrile (SAN)), acrylic polymers and lattices of acrylic polymers (including acrylates and methacrylates, such as acrylate and methacrylate esters (for instance polymethyl methacrylate) and styrene-acrylic esters), polyesters, polycarbonate polymers, polyamides, polyimides, epoxy polymers, phenolic polymers, polyolefins, polyacrylamide, polyketone resins, polyurethane copolymers, and mixtures thereof. The binder is preferably not a fluoropolymer.

[0037] The composition may also comprise a UV-curable binder, typically in low concentrations. The binder may be modified to obtain desired coating characteristics, such as flexibility and durability. For example, a UV-cured binder can be employed for increased durability, while a flexible, solvent-based polymer system, such as

polyurethane, can be employed for flexibility. In other examples, a polyketone may be used for good adhesion to many substrates; a crosslinked, waterborne polymer may be used for increased water resistance.

[0038] The binders may be thermoset resins, for instance curable with heat, crosslinkings agents and/or catalysts. Examples of suitable crosslinkers can be, without limitation, melamine formaldehyde resins, urea formaldehyde resins, polyepoxide resins, and polyisocyanate curing agents. Examples of suitable catalysts can be, without limitation, amine-blocked sulfonic acid catalysts such as blocked p-toluene sulfonic acids, tin catalysts such as dibutyl tin dilaurate and dibutyl tin oxide, and tertiary amines, depending upon the particular cure reaction mechanism.

[0039] The binder may also be energy-curable, or curable by exposure to actinic radiation. Energy-curable binders may include mixtures of ethylenically unsaturated monomers and oligomers having mono-functional and poly-functional groups and photoinitiators. An energy-curable binder may alternatively or additionally include cationic curing compounds.

[0040] The crosslinking agents may be organic or inorganic materials.

[0041] The crosslinking agents may be organic materials selected from, for instance, glyoxal, glutaralaldehyde, 2,3-dihydroxy-1 ,4-dioxane, sodium bisulfate complex, bis(vinyl) sulfone, bis(vinyl) sulfone methyl ether, adipoyl dihydrazide, epichlorohydrin polyamide resins, urea-formaldehyde resins, epoxy compounds, polyepoxy compounds, aziridines, polyaziridines, melamine/formaldehyde, oxazolines, triazines,

polyisocyanates, carbodiimides, polyfunctional carbodiimides, and the like.

[0042] Examples of the inorganic crosslinking agents can include, but are not limited to, ammonium zirconium carbonate, a borate, zinc oxides, zinc ammonium carbonate, zirconium carbonate, etc.

[0043] Polyaziridines can be derived from aziridines which are trifunctional amine compounds which may be derived from ethyleneimine. Examples of commercially available polyaziridine include NeoCryl® CX 100 commercially available from DSM Coating Resins LLC and XAMA® 7 commercially available from lchemco srl. An example of a commercially available carbodimide crosslinking agent is UCARLINK XL- 29SE from Angus Chemical Co.

[0044] A variety of epoxy compounds (oxiranes) can also be used as crosslinking agents. Examples can include, but are not limited to, epoxy modified bisphenol A and epichlorohydrin epoxy resins.

[0045] Aliphatic and aromatic polyisocyanates may be used as crosslinking agents in the coating compositions. A number of such crosslinking agents are commercially available from Bayer under Desmodur®. For example, Desmodur® N3300 is an aliphatic hexamethylene diisocyanate, and Desmodur® CB-75N is an oligomeric toluene diisocyanate. Melamine formaldehyde resins are also useful crosslinking agents. An example of commercially available melamine formaldehyde is Cymel® 303 from Cytec.

[0046] A micro-porous coating composition can further comprise inorganic or organic particles, suitably bonded together by binder. The amount of particles in this type of coating is often far above the critical particle volume concentration, which results in high porosity in the coating. In this embodiment, the micro-porous coating composition may comprise from about 20% to about 100% of particles and from about 1 % to about 80% of binder, or from about 80% to about 95% of particles and from about 20% to about 5% of binder. These amounts refer to the weight % of the particles or binder by weight of the total combined weight of the particles and binder. [0047] The particles may be in granular form or incorporated into the composition in the form of a dispersion. The particles may be dispersed into the composition using any conventional method. Preferably the average particle size of the particles in the composition is from about 1 nanometer to about 1 .5 microns, preferably no more than about 500 nm, preferably no more than about 250 nm, and typically at least about 10 nm, and typically from about 50 nm to about 200 nm. Where the particles are

aggregated, these ranges preferably refer to the aggregate size.

[0048] As used herein, the term "average particle size" refers to the D₅₀ parameter, which is well-known in the art. The D₅₀ is suitably a volume parameter, i.e. a D_(v,50)- The method of establishing the D₅₀ is preferably by laser diffraction (Fraunhofer diffraction), for instance using a Mastersizer 3000 (Malvern).

[0049] One or more types of particle can be present in the composition. A

combination of one or more type(s) of inorganic particles and one or more type(s) of organic particles can be used. The particles can be pigment particles.

[0050] Examples of inorganic particles include, but are not limited to, silica including porous silica, synthetic amorphous silica, precipitated silica, fumed silica, colloidal silica and silica gels such as silica hydrogels, aerogels, xerogels, and cogels; alumina including porous alumina, fumed alumina, colloidal alumina, pseudo-boehmite, aluminum hydroxide and modified alumina; titanium dioxide; clay; kaolin; talc; glass beads; calcium carbonate (including precipitated calcium carbonate and ground calcium carbonate); calcium sulfate; barium sulfate; zinc oxide; zinc sulfide; zinc carbonate; magnesium carbonate; magnesium hydroxide; silicates, including magnesium silicate, aluminum silicate and calcium silicate; diatomaceous earth; satin white; lithopone;

zeolites; and hydrated halloysite. The inorganic pigments may be non-porous or porous. Inorganic particles having pore volumes of 0.6 cc/g or above can be used, or pore volumes of 0.6 to 3.00 cc/g can be used.

[0051] Examples of the organic pigments can include, but are not limited to, crosslinked styrene butadiene rubber (SBR) latexes, micronized polyethylene wax, micronized polypropylene wax, polystyrene, polymethyl methacrylate,

polytetrafluoroethylene, polyethylene; urea resin, melamine resin, other latexes, and mixtures thereof. [0052] Additional examples of pigments are disclosed in U.S. Pat. No 7, 172,651 B2, U.S. Pub. NO.20060137574A1 , U.S. Pat. No 5,783,038A, and PCT Pub. No.

2006049545A1 , which are hereby incorporated by reference herein in their entirety.

[0053] The micro-porous coating composition preferably also comprises a wetting agent. Any suitable wetting agent conventional in the art may be used. For instance, the wetting agents may be selected from hyper branched polymers, polyether-modified polysiloxanes (particularly polyether-modified polydimethylsiloxanes), ionic and nonionic (meth)acrylate copolymers, high molecular mass block copolymers containing groups having pigment affinity, dialkyl sulfosucci nates, and combinations thereof.

[0054] The micro-porous coating composition of the present disclosure preferably further comprises water or a mixed water-organic solvent system (for instance water and ethanol). Thus, the micro-porous coating composition is preferably an aqueous micro-porous coating composition. It will be appreciated that an aqueous micro-porous coating composition is formed before applying onto the substrate.

[0055] The aqueous micro-porous coating composition may comprise a coalescing agent in an amount of about 0.1 -50 wt%; the binder in an amount of about 0.1 -10 wt%; and the crosslinking agent in an amount of about 0.1 -5 wt%.

[0056] The aqueous micro-porous coating composition may comprise a coalescing agent in an amount of 1 -30 wt%; the binder in an amount of 0.1 -7 wt%; and the crosslinking agent in an amount of 0.1 -3 wt%.

[0057] In a further embodiment, the aqueous micro-porous coating composition comprises a coalescing agent in an amount of 2-15 wt%; the binder in an amount of 0.1 - 4 wt%; and the crosslinking agent in an amount of 0.1 -1 wt%.

[0058] The wt% ranges described immediately hereinabove refer to the weight % of the coalescing agent or binder or crosslinking agent by weight of the total weight of the micro-porous coating composition.

[0059] The micro-porous coating composition suitably comprises a solids content of from about 8 wt% to about 50 wt%, typically at least about 10 wt% and typically no more than about 40 wt% or no more than about 35 wt%, by total weight of the micro-porous coating composition. The solids content of the composition is the dry weight of the final coating, i.e. the coating after the composition has been coated and dried onto a substrate (i.e. after the volatile components such as the water or a water/organic solvent system have been removed), expressed as a percentage of the total weight of the micro-porous coating composition.

[0060] The micro-porous coating compositions of the present disclosure can be applied to any suitable substrate by any of the conventional coating techniques known to those skilled in the art. For example, a solution containing the micro-porous compositions can be coated on a surface of a substrate using a commonly known Meyer bar method, in which the solution is moved under a helically wire-wound cylindrical metal bar which remains stationary. The solution can also be coated on a surface of a substrate by any other conventional coating techniques such as rod coating, dipping, gravure coating, blade coating, slide hopper coating, slot coating or curtain coating.

[0061] The substrate suitably comprises any material capable of forming a self- supporting opaque, or transparent, film or sheet. By a "self-supporting film or sheet" as referred to herein is meant a film or sheet capable of independent existence in the absence of a supporting base. The substrate is typically a polymeric material, but may alternatively comprise paper, cardboard or other similar materials.

[0062] The paper can be an uncoated raw paper or a pre-coated paper. The raw paper may be manufactured from cellulose fibers. More specifically, the raw paper may be produced from chemical pulp, mechanical pulp, thermal mechanical pulp and/or the combination of chemical and mechanical pulp. The raw paper may also include conventional additives such as internal sizing agents and fillers. The sizing agents are added to the pulp before it is converted into a paper web or substrate. They may be chosen from conventional internal sizing agents for printing papers. The fillers may be any particular types used in conventional paper making. As non-limiting examples, the fillers may be selected from calcium carbonate, talc, clay, kaolin, titanium dioxide and combinations thereof.

[0063] Examples of pre-coated paper include, but are not limited to, inorganic pigment-coated papers and resin-coated papers. The resin coatings on resin-coated papers may be formed from polyethylene, polypropylene, polyethylene terephthalate, or other extrudable polymers. Such resin-coated papers are widely used for photographic printing.

[0064] Other suitable substrates include cloth, nonwoven fabric, felt, synthetic (non- cellulosic) papers, plastic sheets, transparent sheets, and metal sheets.

[0065] Suitable polymeric materials for the substrate include thermoplastics materials, for instance including a cellulose ester, e.g. cellulose acetate; polystyrene; a polymer or copolymer of vinyl chloride; polysulphone; a homopolymer or copolymer of a 1 -olefin, such as ethylene, propylene and buty-1 -ene; a polyamide; a polycarbonate; and, particularly, a synthetic linear polyester which may be obtained by condensing one or more dicarboxylic acids or their lower alkyl (up to 6 carbon atoms) diesters, e.g.

terephthalic acid, isophthalic acid, phthalic acid, 2,5- 2,6- or 2,7-naphthalenedicarboxylic acid, succinic acid, sebacic acid, adipic acid, azelaic acid, 4,4'-diphenyldicarboxylic acid, hexahydroterephthalic acid or 1 ,2-bis-p-carboxyphenoxyethane (optionally with a monocarboxylic acid, such as pivalic acid) with one or more glycols, particularly an aliphatic glycol, e.g. ethylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, neopentyl glycol and 1 ,4-cyclohexanedimethanol.

[0066] Non-limiting examples of thermoplastic polymeric materials which are suitable substrates include polyethylene, high density polyethylene, low density polyethylene, polypropylene, polyvinyl chloride), saran, polystyrene, high impact polystyrene, nylons, polyesters such as poly(ethylene terephthalate), copolymers of ethylene and acrylic acid, copolymers of ethylene and methacrylic acid, and mixtures thereof. If desired, all or a portion of the carboxyl groups of carboxyl-containing copolymers can be

neutralized with sodium, zinc, or the like. A non-limiting example of a metalized thermoplastic polymeric material is aluminized poly(ethylene terephthalate).

[0067] Polyester (typically polyethylene terephthalate) film is used as the substrate, especially such a film which has been biaxially oriented by sequential stretching in two mutually perpendicular directions, typically at a temperature in a range of 70 to 125° C , and preferably heat set, typically at a temperature in a range of 150 to 200° C, for example as described in GB-A-838708, which is hereby incorporated by reference herein in its entirety. [0068] Suitable polymeric materials for the substrate also include thermoset resin materials, for instance including addition-polymerization resins such as acrylics, vinyls, bis-maleimides and unsaturated polyesters: formaldehyde condensate resins such as condensates with urea, melamine or phenols; cyanate resins; functionalized polyesters; polyamides or polyimides.

[0069] Typically, the substrate is substantially non-porous.

[0070] A substantially non-porous substrate may be selected from polyvinyl chloride, propylene or oriented propylene.

[0071] The substrate suitably has a thickness in a range of 25 to 300 pm, or in a range of 50 to 175 pm, or in a range of 75 to 130 pm.

[0072] According to a further aspect of the present disclosure, there is provided a printable recording medium comprising a substrate and a porous image-receiving layer wherein said porous image-receiving layer is a layer derived from a coating composition as described hereinabove. Preferably, the printable recording medium is an inkjet recording medium.

[0073] According to a further aspect of the present disclosure, there is provided the use of the micro-porous coating composition described hereinabove as a porous image- receiving layer in a printable recording medium comprising said porous image-receiving layer disposed on a substrate, particularly wherein said printable recording medium is an inkjet recording medium, and particularly when said inkjet recording medium is suitable for producing glossy images.

[0074] According to a further aspect of the present disclosure, there is provided the use of the micro-porous coating composition described hereinabove for improving the gloss of a printable recording medium comprising a porous image-receiving layer disposed on a substrate, particularly wherein said printable recording medium is an inkjet recording medium, and particularly for improving the gloss of an image printed on said porous image-receiving layer of said printable recording medium, wherein said porous image-receiving layer comprises or is derived from said micro-porous coating composition. As used herein, the term "improving the gloss" refers to the improvement in gloss provided by the micro-porous coating composition described herein, relative to a coating composition of the prior art. [0075] According to a further aspect of the present disclosure, there is provided the use of the micro-porous coating composition described hereinabove for improving the processability of an printable recording medium comprising a porous image-receiving layer disposed on a substrate, particularly wherein said printable recording medium is an inkjet recording medium, wherein said porous image-receiving layer comprises or is derived from said micro-porous coating composition. As used herein, the term

"improving the processability" refers to the improvement in print speed and/or ink drying time provided by the micro-porous coating composition described herein, relative to a coating composition of the prior art.

[0076] According to a further aspect of the present disclosure, there is provided a method for improving the gloss of a printable recording medium comprising a porous image-receiving layer disposed on a substrate, particularly wherein said printable recording medium is an inkjet recording medium, and particularly for improving the gloss of an image printed on said porous image-receiving layer of said printable recording medium, and/or improving the processability of said printable recording medium. The method comprises providing said porous image-receiving layer as a porous image- receiving layer which comprises or is derived from the micro-porous coating

composition described hereinabove.

[0077] It will be appreciated that all features of the micro-porous coating composition described hereinabove are applicable to said uses and methods of the further aspects of the present disclosure.

[0078] The micro-porous coating composition is coated onto the substrate such that the dry coat weight of the coating may be no more than 50 g/m², or no more than 40 g/m², or no more than 35 g/m², or no more than 20 g/m², or no more than 15 g/m².The dry coat weight may be from 10 to 30 g/m², or from 12 to 15 g/m². As is conventional in the art, the term "dry coat weight" refers to the amount of coating composition per unit area of the finished coated substrate, i.e. preferably the inkjet recording medium comprising a porous image-receiving layer on a printable substrate wherein the porous image-receiving layer is derived from the micro-porous coating composition.

[0079] The substrate may be coated at ambient temperature, for instance from about 18-19 °C to about 40 °C. [0080] The coating is typically conducted at a speed of at least 1 meter per minute, or in a range of 10 to 250 meters per minute, or in a range of 20 to 200 meters per minute.

[0081] The coating is optionally dried at a temperature of about 40 to about 220 °C, or about 60 to about 180 °C, or about 80 to about 120 °C. The drying time depends on the drying temperatures and can be varied form about 1 to about 30,000 seconds, or from about 5 to about 1000 seconds, or from about 10 to about 60 seconds.

[0082] The evaporation of water and any solvents in the coating composition yields a continuous film on the substrate.

[0083] The coated substrate has a glossy surface and good inkjet recording performance.

[0084] The coated substrate is particularly suitable for use as an image-receiving medium, particularly an inkjet recording medium, particularly wherein the ink is a water- based ink.

[0085] The performance of the coated substrate as an image-receiving medium is preferably assessed by taking gloss measurements, as is conventional in the art, preferably 60° gloss measurements. Preferably, gloss readings are taken in the non- imaged areas and also in the secondary colors (red, green, blue) of imaged areas.

[0086] The present disclosure is illustrated according to the non-limiting examples set out below.

EXAMPLES

Example 1 - Preparation of Micro-porous Coating Composition

[0087] Samples 1 -6 were prepared by mixing the ingredients listed in the tables as shown below. Sample 1

(1 ) Aerodisp® W 925 - commercially available from Evontik Industries

(2) Poval™ 95-88 - commercially available from Kuraray Co. Ltd.

(3) Additiol® VXW 6503 - commercially available from Allnex S. a. r. i.

(4) Cartabond® TSI NG - commercially available from Clariant International Ltd.

Sample 2

Sample 3

(5) Rhodiasolv® Polarclean - commercially available from Solvay

Sample 4

Sample 5

Sample 6

Example 2 - Coating and Testing

[0088] Samples 1 -6 were wet-coated on oriented polypropylene (OPP),

polypropylene (PP), polyethylene terephthalate (PET) and polyvinyl chloride (PVC), respectively, using a Meyer bar method and dried. The resulting coatings were tested. Gloss at 60° was measured as described herein. Porosity of the coating was measured by ink absorption on the coating after drying, which was conducted on Evojet Office, commercially available from Lomond Trading Ltd. Three primary colors (cyan, magenta and yellow), and optionally black were used. The ink absorption is evaluated by assessing printed ink density of each colour in an ink instant dry test and expressing the results as a percentage of ink pick-up relative to the maximum density. 300% ink instant dry refers to no smearing with 300% of ink deposition, typically achieved by printing 100% of each primary color.

[0089] No films were formed when Samples 1 and 2 were wet-coated and dried. Coating conditions and testing results of Samples 3-6 are listed in Tables 1 and 2. Table 1 - Coating Conditions

Table 2 - Coating Measurements

[0090] As indicated in Table 2, the micro-porous coating composition provides good gloss levels and ink absorption.

[0091] While the present disclosure has been described with reference to certain preferred embodiments, those skilled in the art will appreciate that various

modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the present disclosure be limited only by the scope of the following claims.

Claims

What is claimed is:

1. A micro-porous coating composition comprising:

a) a coalescing agent;

b) a binder; and

c) a crossiinking agent,

wherein the coalescing agent is an esteramide compound and/or a glycol ether compound,

wherein the esteramide compound has a general formula (I)

R¹OOC-M-CONR²R³

where R¹ is a radical of saturated or unsaturated, linear or branched, optionally cyclic, or optionally aromatic hydrocarbon-based radicals, having from 1 to 36 carbon atoms; R² and R³ are identical or different radicals and each is independently selected from saturated or unsaturated, linear or branched, optionally cyclic, optionally aromatic, or optionally substituted, hydrocarbon-based radicals, having from 1 to 36 carbon atoms, with the proviso that R² and R³ optionally form a ring member that is optionally substituted or that optionally contains a heteroatom; and

M is a linear or a branched divalent alkyl radical having from 2 to 12 carbon atoms, and wherein the glycol ether compound has a general formula (II)

R-

(II)

where R⁴ is a Ci-Cs aliphatic or aromatic group; R⁵ is H, CH₃, or C2H5; n has a value of at least 1 ; and A comprises at least one of an ester, an amide, a hydroxyl and an ether.

2. The micro-porous coating composition of claim 1 , wherein R¹, R² and R³ are identical or different radicals independently selected from the group consisting of G_r C₁₂ alkyl, aryl, alkylaryl, and arylalkyl radicals; and R² or R³ is optionally substituted.

3. The micro-porous coating composition of claim 1 or 2, wherein at least one, or both, of R² and R³ are ethyl radicals.

4. The micro-porous coating composition of any one of claims 1 to 3, wherein R¹ is selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyi, isoamyi, n-hexyl, cyciohexyl, 2-ethylbutyl, n-octyi, isooctyi, 2- ethylhexyl, and tridecyi radicals,

5. The micro-porous coating composition of any one of claims 1 to 4, wherein R² and R³ are identical or different and independently selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyi, amyl, isoamyi, hexyl, cyciohexyl, hydroxyethyl, morpholine, piperazine and piperidine radicals.

6. The micro-porous coating composition of claim 1 , wherein the esteramide compound is selected from the group consisting of CH₃— CH₂— CH₂— CH₂—

CH(CH₂CH₃)— CH2—OOC— CONMe₂, CHs— (CH₂)i-n— OOC— CONMe_2l and

CeHu— OOC— CONMe₂.

7. The micro-porous coating composition of claim 1 , wherein the esteramide compound is selected from the group consisting of methyi-5-(dimethyiamino)-2-methyi- 5-oxopentanoate, methyl 2-(dimethylamino)-2-oxoacetate, ethyl 2-(dimethylamino)-2- oxoacetate, 2-ethyl-hexyl 2-(dimethylamino)-2-oxoacetate, (n-decyi 2-(dimethylamino)- 2-oxoacetafe, and cyciohexyl 2-(dimethyiamino)-2-oxoacetate, and combinations thereof.

8. The micro-porous coating composition of any one of claims 1 to 7, wherein the glycol ether compound is selected from the group consisting of propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, ethylene glycol butyl ether, diethylene glycol propyl ether, triethylene glycol methyl ether, and combinations thereof.

9. The micro-porous coating composition of any one of claims 1 to 7, wherein the glycol ether compound is selected from the group consisting of propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, 3- methoxybutanoi acetate, tetrahydrofurfuryi acetate, cyclohexanoi acetate, and combinations thereof.

10. The micro-porous coating composition of any one of claims 1 to 9, wherein the binder is selected from the group consisting of , protein, starch, casein, gelatin, gum arable, cellulose derivatives, cationic or non-ionic polyurethane dispersions, polyvinyl alcohol polymers, PVP and PVP copolymers, polymers and copolymers of vinyl acetate, styrene butadiene and derivatives, styrene maieic anhydride (SMA), styrene acryionitrile (SAN), acrylic polymers, acrylafes and methacrylates, styrene-acrylic esters,

polyacryiamide, polyethylene glycol, polypropylene glycol, polyesters, polycarbonates, polyamides, poiyimides, epoxy polymers, phenolic polymers, poiyoiefins, poiyurethanes, poiyketones, cationic latexes, anionic latexes, and combinations thereof,

1 1. The micro-porous coating composition of any one of claims 1 to 10, wherein the crosslinking agent is selected from the group consisting of giyoxal, glutaraialdehyde, 2,3-dihydroxy-1 ,4-dioxane, sodium bisulfate complex, bis(vinyi) sulfone, bis(vinyl) suifone methyl ether, adipoyl dihydrazide, epichlorohydrin poiyarnide resins, urea- formaldehyde resins, aziridines, polyaziridines, epoxy compounds, poiyepoxy

compounds, meiamine/formaidehyde, oxazoiines, triazines, aliphatic and aromatic poiyisocyanates, ammonium zirconium carbonate, borates, oxides of zinc, zinc ammonium carbonate, zirconium carbonate, carbodiimides and combinations thereof.

12. The micro-porous coating composition of any one of claims 1 to 1 1 , which is an aqueous micro-porous coating composition, preferably such that said composition further comprises water, or water and organic solvent.

13. The micro-porous coating composition of claim 12, wherein the composition comprises the coalescing agent in an amount of 0.1 -50 wt%; the binder in an amount of 0.1 -10 wt%; and the crossiinking agent in an amount of 0.1 -5 wt%.

14. The micro-porous coating composition of claim 13, wherein the composition comprises the coalescing agent in an amount of 1 -30 wt%; the binder in an amount of 0.1 -7 wt%; and the crossiinking agent in an amount of 0.1 -3 wt%.

15. The micro-porous coating composition of claim 14, wherein the composition comprises the coalescing agent in an amount of 2-15 wt%; the binder in an amount of 0.1 -4 wt%; and the crossiinking agent in an amount of 0.1 -1wt%.

16. The micro-porous coating composition of any one of claims 1 to 15, further comprising one or more type(s) of inorganic or organic particle.

17. The micro-porous coating composition of claim 16, wherein the particles are inorganic particles and selected from the group consisting of silica, silicates, alumina, titanium dioxide, clay, kaolin, talc, calcium carbonate, calcium sulfate, barium sulfate, glass beads, zinc oxide, zinc sulfide, zinc carbonate, magnesium carbonate,

magnesium hydroxide, diatomaceous earth, satin white, iithopone, zeolites, and hydrated halloysite, and combinations thereof.

18. The micro-porous coating composition of claim 16 or 17 wherein the pigment in the composition exhibits an average particle size of from 1 nanometer to 1.5 microns, or from 50 nm to 200 nm.

19. The micro-porous coating composition of any one of claims 1 to 18, further comprising a wetting agent.

20. The micro-porous coating composition of claim 19, wherein the wetting agent is selected from the group consisting of hyperbranched polymers, polyether-modified polydimethylsiloxanes, ionic and nonionic (meth)acrylate copolymers, high molecular mass block copolymers containing groups having pigment affinity,

dialkylsulfosuccinates, and combinations thereof.

21 . The micro-porous coating composition of any preceding claim comprising a solids content of from about 8 wt% to about 50 wt% by total weight of the micro-porous coating composition.

22. The micro-porous coating composition of any preceding claim for coating onto a substrate.

23. A substrate coated with the composition of any one of claims 1 to 22.

24. A printable recording medium comprising a substrate and a porous image- receiving layer wherein said porous image-receiving layer is a layer derived from a micro-porous coating composition according to any one of claims 1 to 22.

25. A printable recording medium according to claim 24 which is an Inkjet recording medium.

26. Use of the micro-porous coating composition according to any of claims 1 to 22 as a porous image-receiving layer in a printable recording medium comprising said porous image-receiving layer disposed on a substrate, particularly when said Inkjet recording medium is suitable for producing glossy images.

27. Use of the micro-porous coating composition according to any of claims 1 to 22 for improving the gloss of a printable recording medium comprising a porous image- receiving layer disposed on a substrate, particularly for improving the gloss of an image printed on said porous image-receiving layer of said printable recording medium, wherein said porous image-receiving layer comprises or is derived from said micro- porous coating composition.

28. Use of the micro-porous coating composition according to any of claims 1 to 22 for improving the processability of a printable recording medium comprising a porous image-receiving layer disposed on a substrate, wherein said porous image-receiving layer comprises or is derived from said micro-porous coating composition.

29. A method for improving the gloss of a printable recording medium comprising a porous image-receiving layer disposed on a substrate, particularly for improving the gloss of an image printed on said porous image-receiving layer of said printable recording medium, and/or improving the processability of said printable recording medium, wherein said method comprises providing said porous image-receiving layer as a porous image-receiving layer which comprises or is derived from the micro-porous coating composition according to any of claims 1 to 22.

30. Use according to any of claims 26 to 28 or method according to claim 29 wherein said printable recording medium is an Inkjet recording medium.

31 . The microporous coating composition according to claim 22 or the substrate according to claim 23 or the printable recording medium according to claim 24 or 25 or the use according to claims 26 to 28 or 30 or the method according to claim 29 or 30 wherein the substrate is a polymeric material, or comprises paper or cardboard.