Viscosity Adjusting Agent for Energy-Curable Ink

Abstract

The present invention provides an energy-curable thixotropic composition containing a small amount of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), or dipropylene glycol butyl ether (DPGBE, a mixture of isomers), or a mixture thereof. The addition of a selected solvent in an amount of about 0.5 wt% to 3 wt% reduced the low shear rate viscosity of the energy-curable thixotropic composition.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Application No. 63 / 391,085, filed Jul. 21, 2022, which is hereby incorporated by reference in its entirety.

[0002] The present invention relates to energy - curable thixotropic compositions having a low shear rate viscosity and to methods of adjusting the viscosity of energy - curable thixotropic inks and coatings. By reducing the low - shear viscosity, the flow and printability of the inks and coatings are improved.

Background Art

[0003] Printing inks are designed to function best when used at a specific viscosity. The ideal viscosity depends greatly on the type of printing. For example, lithographic inks typically have a relatively high viscosity and thixotropy, while flexographic printing inks typically have a much lower viscosity and thixotropy. Thixotropy is a well - known property to printers and ink formulators and refers to a viscous or gelled material that flows when agitated or subjected to shear stress and then returns to a viscous or gelled state when the agitation or shear stress ceases.

[0004] Certain pigments are notorious for producing high - viscosity inks at low shear rates, making them difficult to handle and print (e.g., difficult to pump into the anilox chamber of a flexographic printing press). The inventors have discovered a method to reduce the viscosity of these inks at low shear rates, making them easier to handle and print.

[0005] WO2003 / 010250 (substantially the same as EP1412441) discloses an aqueous energy - curable ink composition. Texanol is included in a list of optional additives, but there is no further description, example, or data regarding Texanol.

[0006] JP2019 - 168654 discloses an alkali - developable photosensitive composition containing a novel oxime ester photoinitiator. A solvent may optionally be added. The list of any solvents includes Texanol, but this list is long and there is no further explanation, example, or data regarding Texanol.

[0007] WO2009 / 097142 (substantially the same as EP2245075) targets low - volatile component (low - VOC) coalescing agents. It does not mention UV - curable compositions and does not recommend the use of Texanol.

[0008] Phung and colleagues (Phung et al. (2023). A study of UV - curable offset ink emulsified with an alternative isopropyl alcohol - free fountain solution. Journal of Applied Science and Engineering, vol. 27, No. 1, page 1867 - 1876) disclose a dampening aqueous solution prepared using ethylene glycol mono - butyl ether (EGME) as an alternative to isopropyl alcohol (IPA). At least 10% of EGME was required to disperse the dampening aqueous solution into the UV ink. No solvent was added to the actual ink composition.

[0009] The Printing Ink Manual states that "the selective use of non - curable solvents is possible in UV vehicle formulations, but this practice is limited." This manual further explains the use of heating ducts and cylinders to lower viscosity. Also, very low - viscosity monomers are generally not used because of their volatility and toxicity (The Printing Ink Manual, Fifth Edition, pages 641 - 642, editors: R.H. Leach, R.J. Pierce, E.P. Hickman, M.J. Mackenzie, H.G. Smith).

[0010] The citation or identification of any document in this application does not admit that such document represents prior art of the present invention. SUMMARY OF THE INVENTION

[0011] The present invention provides an energy-curable composition containing one or more high molecular weight, low volatility solvents. By including solvents, the viscosity and thixotropic properties of the energy-curable ink are surprisingly improved.

[0012] In certain embodiments, the present invention (a) one or more ethylenically unsaturated monomers, or one or more ethylenically unsaturated oligomers, or combinations thereof, and (b) a solvent selected from the group consisting of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), dipropylene glycol butyl ether (DPGBE, which mixes isomers), and mixtures thereof, to provide an energy-curable composition.

[0013] In a preferred embodiment, the solvent is present in an amount of about 0.5 wt% to about 3 wt%.

[0014] In some embodiments, the energy-curable composition is a printing ink, a coating, or a pigment dispersant. In a preferred embodiment, the composition is a flexographic printing ink.

[0015] In some embodiments, the viscosity of the energy-curable composition containing one or more of the solvents is reduced by 25% or more compared to a composition containing all the same components except the solvent.

[0016] In another aspect, the present invention is a method for reducing the viscosity of an energy-curable composition, comprising (a) providing an energy-curable composition, and (b) adding one or more solvents selected from the group consisting of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), dipropylene glycol butyl ether (DPGBE, which is a mixture of isomers), and mixtures thereof.

[0017] The present invention also provides a printed article or a coated article comprising the composition of the present invention. In some embodiments, the article is a printed label.

[0018] These and other objects, advantages, and features of the present invention will become apparent to those skilled in the art upon reading the details of the formulations and methods described below.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0020] It has surprisingly been found that certain solvents are effective in reducing the thixotropy and viscosity of energy curable inks, particularly UV curable flexographic inks, thereby improving ink flow and pumpability. Two such materials are the solvents 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Texanol, Eastman), and 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. These solvents are of high molecular weight and low in volatile organic compounds (VOCs). This discovery is surprising in that these solvents have not typically been used in energy curable ink systems and there is no prior reference actually showing the use of these solvents in such systems, particularly as viscosity / thixotropy reducers. Solvents are not normally used in energy curable inks because the press is not equipped with a long hot air oven to dry the solvent and there is a possibility that residual solvent will remain in the ink if the solvent is in the ink formulation. Further solvents which have shown surprising effectiveness as viscosity / thixotropy reducers in energy curable inks are dipropylene glycol butyl ether (DPGBE; mixed isomers). Each of these materials was tested with a finished ink or dispersant, the objective being to reduce the low shear rate viscosity of the ink or dispersant. Another unexpected result is that TXIB, and other solvents, act as pigment dispersants at very low levels.

[0021] In addition to the solvents described above, the compositions of the present invention include materials typical of energy curable ink systems. The following paragraphs provide examples of these materials.

[0022] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of any subject matter claimed.

[0023] Headings are used for organizational purposes only and are in no way intended to limit the invention.

[0024] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All patents, patent applications, published applications, and publications, websites, and other published materials referred to throughout this specification are incorporated by reference in their entirety for any purpose, unless otherwise noted. 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 are described.

[0025] Definitions As used herein, the use of the singular includes the plural unless specifically stated otherwise. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural.

[0026] As used herein, the use of "or" means "and / or" unless otherwise stated. Also, when it is clear from the context in which it is used, "and" can be interpreted as "or" in lists of alternatives where all are true at once or none can exist.

[0027] As used herein, the terms "comprises" and / or "comprising" specify the presence of the described feature, integer, step, operation, element, and / or component, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Further, the terms "includes", "having", "has", "with", "composed of", "comprised of" or variations thereof, to the extent used in either the detailed description or the claims, are intended to be included in a manner similar to the term "comprising".

[0028] When the terms "consist of", "consists of", or "consisting of" are used in the body of the claim, claim terms that are offset against "consist of", "consists of", and / or "consisting of" are limited to the elements recited immediately after "consist of", "consists of", and / or "consisting of", and are closed with respect to unrecited elements related to the terms of that particular claim. The term "combinations thereof", when included in a list of recited elements following "consist of", "consists of", and / or "consisting of", means combinations of only two or more of the recited elements.

[0029] As used herein, ranges and amounts may be expressed as "about" with respect to a particular value or range. "About" is intended to also include the exact amount. Thus, "about 5 percent" means "about 5 percent" and also means "5 percent". "About" means within typical experimental error for the intended use or purpose.

[0030] When a numerical range is recited, it is to be understood that it includes the endpoints, all values within that range, and all narrower ranges within that range, whether specifically recited or not.

[0031] Throughout this disclosure, unless otherwise specified, all parts and percentages are by weight (weight % or mass % based on total weight), and all temperatures are in °C.

[0032] As used herein, "substrate" means any surface or object to which an ink or coating can be applied. Examples of substrates include, but are not limited to, cellulosic substrates, paper, paperboard, fabric (e.g., cotton), leather, textiles, felt, concrete, masonry, stone, plastics, plastic or polymer films, spunbond nonwovens (e.g., made of polypropylene, polyester, etc.), glass, ceramics, metals, wood, composites, combinations thereof, etc. The substrate may have one or more layers of metal or metal oxide, or other inorganic materials. Nonwoven substrates are particularly preferred.

[0033] As used herein, the terms "one article" or "articles" mean a substrate or a manufactured product. Examples of articles include substrates such as cellulosic substrates, paper, paperboard, plastics, plastic or polymer films, glass, ceramics, metals, composites, etc., as well as publications (e.g., brochures), labels, and packaging materials (e.g., cardboard sheets or corrugated boards), containers (e.g., bottles, cans), polyolefins (e.g., polyethylene or polypropylene), polyesters (e.g., polyethylene terephthalate), metal foils (e.g., laminated aluminum foils), metallized polyesters, metal containers, etc., but are not limited thereto.

[0034] As used herein, the terms "composition", "the composition of the present invention", "ink and coating", "ink", and "coating" are used interchangeably and refer to the composition of the present invention or, when specified, a composition found in the prior art (comparison). In the context of the present invention, "composition" may also refer to dispersants such as pigment dispersants. Inks and coatings typically contain a resin, a solvent, and optionally a colorant. Coatings are often considered to be colorless or transparent, while inks typically contain a colorant.

[0035] As used herein, "energy curing" and "radiation curing" refer to curing achieved under exposure to an electromagnetic radiation source that produces a light effect. Such sources include, but are not limited to, electron beams, UV light, visible light, IR, or microwaves. When curing a composition under the action of UV light, then the following non-limiting UV sources may be used: low-pressure mercury lamps, medium-pressure mercury lamps, xenon lamps, excimer lamps, carbon arc lamps, metal halide lamps, UV-LED lamps, or sunlight. It should be understood by those skilled in the art that any UV light source may be used to cure the composition prepared according to the present invention. The compositions of the present invention are particularly suitable for use in compositions curable under the action of UV light and / or electron beams.

[0036] As used herein, "energy curable" and "radiation curable" refer to compositions that can be cured by exposure to one or more types of light radiation. The compositions of the present invention are particularly suitable for use in compositions curable under the action of UV light and / or electron beams.

[0037] As used herein, "(meth)acrylate" and "(meth)acrylic acid" include both acrylates and methacrylates, as well as both acrylic acid and methacrylic acid.

[0038] As used herein, "monofunctional" means having one functional group.

[0039] As used herein, "polyfunctional" means having two or more functional groups. For example, a polyfunctional monomer can be difunctional, trifunctional, tetrafunctional, or have a greater number of functional groups. The two or more functional groups can be the same or different. Unless otherwise specified, the two or more functional groups are the same, for example, a compound having two or more functional acrylate groups.

[0040] As used herein, "monomer" refers to a small molecule having one or more functional groups. Monomers, whether the same or different, react with other monomers to form monomer chains (oligomers and / or polymers). Each monomer in the chain is a monomer repeating unit. A monomer is the smallest unit that makes up an oligomer or a polymer. A monomer is a low molecular weight molecule and typically has a weight average molecular weight (Mw) of 100 Daltons or less.

[0041] As used herein, "oligomer" refers to a chain of repeating units of several monomers. An oligomer is a long chain of several monomer units and has a weight average molecular weight in the intermediate range of about 100 Daltons to about 10,000 Daltons. Oligomers can be used as ink vehicles, and added monomers react with the oligomers to form polymers.

[0042] As used herein, "polymer" refers to a macromolecule containing repeating units of multiple monomers and / or oligomers. A polymer is a high molecular weight molecule having a weight average molecular weight exceeding about 10,000 Daltons.

[0043] Energy curable composition The energy curable composition of the present invention includes one or more ethylenically unsaturated monomers, or one or more ethylenically unsaturated oligomers, or a combination thereof. The composition of the present invention includes one or more solvents selected from the group consisting of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), dipropylene glycol butyl ether (DPGBE mixes isomers), and mixtures thereof. The composition of the present invention can be an ink, a coating, or a dispersant (e.g., a pigment dispersant).

[0044] The radiation-curable composition of the present invention can be UV-cured by a light source such as UV light provided by, for example, a high-voltage mercury lamp, a medium-voltage mercury lamp, a xenon lamp, a carbon arc lamp, a metal halide lamp, a UV-LED lamp, or sunlight. The wavelength of the applied radiation irradiation is preferably in the range of about 200 to 500 nm, more preferably in the range of about 250 to 350 nm. The UV energy is preferably in the range of about 30 to 3000 mJ / cm 2 and more preferably in the range of about 50 to 500 mJ / cm 2 . In addition, the lamp can be appropriately selected according to the absorption spectrum of the radiation-curable composition. Further, the ink of the present invention can be cured under inert conditions. Inert conditions mean that the concentration of oxygen in the atmosphere is reduced or suppressed by nitrogen or some other gas in order to promote the curing of the ink. Oxygen in the atmosphere can inhibit the curing of radiation-curable inks and coatings.

[0045] Alternatively, the radiation-curable composition and ink of the present invention can be cured by an electron beam (EB). Commercially available EB dryers are available, for example, from Energy Science, Inc. (Wilmington, Mass) or from Advanced Electron Beams Inc. (AEB) (Wilmington, Mass). The absorbed energy, also known as its dose, is measured in units of kiloGray (kGy), where 1 kGy corresponds to 1,000 joules / kilogram. Usually, for complete curing, the dose of the electron beam should be in the range of 10 kGy to about 40 kGy. In the radiation-curable composition of the present invention, a radiation dose of 20 to 30 kGy at an oxygen level of less than 200 ppm is usually sufficient to obtain a dry solvent-resistant coating or ink.

[0046] The energy-curable composition of the present invention contains low levels of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), dipropylene glycol butyl ether (DPGBE, a mixture of isomers), and blends thereof. Typically, the energy-curable composition of the present invention contains one or more of these solvents in an amount of about 0.5 wt% to about 3 wt% based on the total weight of the energy-curable composition. The amount of solvent refers to the total amount of all the combined solvents, i.e., up to 3 wt% of the combined solvents is included in the composition of the present invention. Preferably, the energy-curable composition of the present invention contains about 1 wt% to about 2 wt% of total solvent.

[0047] Examples of suitable monofunctional ethylenically unsaturated monomers include isobutyl acrylate, cyclohexyl acrylate, isooctyl acrylate, n-octyl acrylate, isodecyl acrylate, isononyl acrylate, octyl / decyl acrylate, lauryl acrylate, 2-propylheptyl acrylate, tridecyl acrylate, hexadecyl acrylate, stearyl acrylate, isostearyl acrylate, behenyl acrylate, tetrahydrofurfuryl acrylate, 4-t-butylcyclohexyl acrylate, 3,3,5-trimethylcyclohexane acrylate, isobornyl acrylate, dicyclopentyl acrylate, dihydrodicyclopentadienyl acrylate, dicyclopentenyl oxyethyl acrylate, dicyclopentanyl acrylate, benzyl acrylate, phenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, alkoxylated nonylphenol acrylate, cumylphenoxyethyl acrylate, cyclic trimethylolpropane formal acrylate, 2(2-ethoxyethoxy)ethyl acrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, caprolactone acrylate, ethoxylated methoxypolyethylene glycol acrylate, methoxytriethylene glycol acrylate, tripropylene glycol monomethyl ether acrylate, diethylene glycol butyl ether acrylate, alkoxylated tetrahydrofurfuryl acrylate, ethoxylated ethylhexyl acrylate, alkoxylated phenol acrylate, ethoxylated phenol acrylate, ethoxylated nonylphenol acrylate, propoxylated nonylphenol acrylate, polyethylene glycol o-phenylphenyl ether acrylate, ethoxylated p-cumylphenol acrylate, ethoxylated nonylphenol acrylate, alkoxylated lauryl acrylate, ethoxylated tristyrylphenol acrylate, N-(acryloyloxyethyl)hexahydrophthalimide, N-butyl 1,2-(acryloyloxy)ethyl carbamate, acryloyloxyethyl hydrogen succinate, octoxypolyethylene glycol acrylate, octafluoropentyl acrylate, 2-isocyanatoethyl acrylate, acetoacetoxyethyl acrylate, 2-methoxyethyl acrylate, dimethylaminoethyl acrylate, 2-carboxyethyl acrylate, 4-hydroxybutyl acrylate, and combinations thereof are included, but not limited to. As used herein, the term ethoxylation refers to a chain extension compound through the use of ethylene oxide, propoxylation refers to a chain extension compound through the use of propylene oxide, and alkoxylation refers to a chain extension compound that uses either or both of ethylene oxide and propylene oxide. Equivalent methacrylate compounds can also be used, but those skilled in the art will understand that methacrylate compounds have lower reactivity than their equivalent acrylate counterparts.,

[0048] Examples of suitable polyfunctional ethylenically unsaturated monomers include 1,3 - butylene glycol diacrylate, 1,4 - butanediol diacrylate, neopentyl glycol diacrylate, ethoxylated neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, 2 - methyl - 1,3 - propanediyl ethoxyacrylate, 2 - methyl - 1,3 - propanediol diacrylate, ethoxylated 2 - methyl - 1,3 - propanediol diacrylate, 3 - methyl - 1,5 - pentanediol diacrylate, 2 - butyl - 2 - ethyl - 1,3 - propanediol diacrylate, 1,6 - hexanediol diacrylate, alkoxylated hexanediol diacrylate, ethoxylated hexanediol diacrylate, propoxylated hexanediol diacrylate, 1,9 - nonanediol diacrylate, 1,10 - decanediol diacrylate, ethoxylated hexanediol diacrylate, alkoxylated hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, propoxylated ethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, poly(tetramethylene glycol) diacrylate, cyclohexanedimethanol diacrylate, ethoxylated cyclohexanedimethanol diacrylate, alkoxylated cyclohexanedimethanol diacrylate, polybutadiene diacrylate, hydroxypivalyl hydroxypivalate diacrylate, tricyclodecane dimethanol diacrylate, 1,4 - butanediyl bis[oxy(2 - hydroxy - 3,1-Propanediyl)diacrylate, ethoxylated bisphenol A diacrylate, propoxylated bisphenol A diacrylate, propoxylated ethoxylated bisphenol A diacrylate, ethoxylated bisphenol F diacrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, dioxane glycol diacrylate, ethoxylated glycerol triacrylate, glycerol propoxylate triacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, caprolactone-modified trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, e-caprolactone-modified tris(2-hydroxyethyl)isocyanurate triacrylate, melamine acrylate oligomer, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, ethoxylated dipentaerythritol hexaacrylate, combinations thereof, and the like, but are not limited thereto. The term "ethoxylated" refers to a chain-extended compound through the use of ethylene oxide, "propoxylated" refers to a chain-extended compound through the use of propylene oxide, and "alkoxylated" refers to a chain-extended compound using either or both of ethylene oxide and propylene oxide. Equivalent methacrylate compounds can also be used, but those skilled in the art will understand that methacrylate compounds have lower reactivity than their equivalent acrylate counterparts.,

[0049] Other classes of functional monomers that can be used in part in these formulations include N-vinylcaprolactam, N-vinyloxazolidinone, and N-vinylpyrrolidone, and secondary or tertiary acrylamides such as N-acryloylmorpholine, diacetoneacrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-t-butylacrylamide, N-hexylacrylamide, N-cyclohexylacrylamide, N-octylacrylamide, N-t-octylacrylamide, N-dodecylacrylamide, N-benzylacrylamide, N-(hydroxymethyl)acrylamide, N-isobutoxymethylacrylamide, N-butoxymethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-propylacrylamide, N,N-dibutylacrylamide, N,N-dihexylacrylamide, N,N-dimethylaminomethylacrylamide, N,N-dimethylaminoethylacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminohexylacrylamide, N,N-diethylaminomethylacrylamide, N,N-diethylaminoethylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylaminohexylacrylamide, and cyclic lactams such as N,N'-methylenebisacrylamide.

[0050] The main classes of acrylated oligomers include epoxy acrylate, urethane acrylate, polyester acrylate, acrylic acrylate, hyperbranched polyester acrylate, aqueous UV polyurethane dispersant, and organic-inorganic hybrid materials.

[0051] The energy-curable composition of the present invention typically contains about 50% to about 90% by weight of ethylenically unsaturated monomers, ethylenically unsaturated oligomers, or combinations thereof. In some embodiments, the energy-curable composition contains about 60% to about 80% by weight, for example, about 65% to about 75% by weight of unsaturated monomers, ethylenically unsaturated oligomers, or combinations thereof.

[0052] The radiation curable composition of the present invention may contain an inert non-curable resin having no curable acrylic groups, such as poly(acrylate), poly(ester), poly(urethane), poly(amide) ketone resin, aldehyde resin, alkyd resin, phenol-formaldehyde resin, rosin resin, hydrocarbon resin, alkyd resin, or a mixture of the above, having a weight number average of 1000 to 30000 Daltons, preferably 1000 to 4000 Daltons. Such resins improve pigment wetting, gloss, rheology, and flexibility. When present, the inert resin is typically present in an amount of about 5 wt% to about 20 wt% based on the total weight of the composition.

[0053] The radiation curable composition of the present invention may contain a photoinitiator when cured by UV light. The photoinitiator may be used alone or in combination of two or more. When present, the photoinitiator is typically present in an amount of about 5 wt% to about 30 wt% based on the total weight of the composition.

[0054] There is no limitation on the type, blend, or concentration of the photoinitiator used, and any suitable type of photoinitiator can be included, such as, but not limited to, α-hydroxy ketone, acylphosphine oxide, α-amino ketone, thioxanthone, benzophenone, phenylglyoxylate, oxime ester, and combinations thereof.

[0055] Suitable α-hydroxy ketones include, but are not limited to, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-2-methyl-4'-tert-butyl-propiophenone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methyl-propiophenone, 2-hydroxy-4'-(2-hydroxypropoxy)-2-methyl-propiophenone, oligo 2-hydroxy-2-methyl-1-[4-(1-methyl-vinyl)phenyl]propanone, bis[4-(2-hydroxy-2-methylpropionyl)phenyl]methane, 2-hydroxy-1-[1-[4-(2-hydroxy-2-methylpropionyl)phenyl]-1,3,3-trimethylindan-5-yl]-2-methylpropan-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)phenoxy]phenyl]-2-methylpropan-1-one, and combinations thereof.

[0056] Suitable acylphosphine oxides include, but are not limited to, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and combinations thereof.

[0057] Suitable α-amino ketones include, but are not limited to, 2-methyl-1-[4-methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, and combinations thereof.

[0058] Suitable thioxanthones include, but are not limited to, 2-4-diethylthioxanthone, isopropylthioxanthone, 2-chlorothioxanthone, and 1-chloro-4-propoxythioxanthone, and combinations thereof.

[0059] Suitable benzophenones include, but are not limited to, benzophenone, 4-phenylbenzophenone, and 4-methylbenzophenone, methyl-2-benzoylbenzoate, 4-benzoyl-4-methyldiphenyl sulfide, 4-hydroxybenzophenone, 2,4,6-trimethylbenzophenone, 4,4-bis(diethylamino)benzophenone, benzophenone-2-carboxy(tetraethoxy)acrylate, 4-hydroxybenzophenone laurate, 1-[-4-[benzoylphenylsulfonyl]phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, and combinations thereof.

[0060] Suitable phenylglyoxylates include, but are not limited to, methyl phenylglyoxylate, 2-[hydroxy-ethoxy]-ethyl oxy-phenyl-acetate, 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl oxy-phenyl-acetate, and combinations thereof.

[0061] Suitable oxime esters include, but are not limited to, 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime, [1-(4-phenylsulfanylbenzoyl)heptylideneamino]benzoate, [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]-ethylideneamino]acetate, and combinations thereof.

[0062] Examples of other suitable photoinitiators include diethoxyacetophenone, benzyl, benzyldimethylketal, titanocene radical initiators such as titanium-bis(η5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl], 9-fluorenone, camphorquinone, 2-ethylanthraquinone, and the like.

[0063] An amine synergist may optionally also be included in the formulation. Suitable examples include aromatic amines such as 2-(dimethylamino)ethyl benzoate, N-phenylglycine; benzoic acid, 4-(dimethylamino)-, 1,1'-[(methylimino)di-2,1-ethanediyl] ester; and simple alkyl esters of 4-(N,N-dimethylamino)benzoic acid and other positional isomers of N,N-dimethylamino)benzoic acid esters, particularly preferred are ethyl, amyl, 2-butoxyethyl, and 2-ethylhexyl esters; aliphatic amines such as, for example, N-methyldiethanolamine, triethanolamine, and tri-isopropanolamine; amino acrylates and polyether acrylates modified with amines, such as EBECRYL 80, EBECRYL 81, EBECRYL 83, EBECRYL 85, EBECRYL 880, EBECRYL LEO 10551, EBECRYL LEO 10552, EBECRYL LEO 10553, EBECRYL 7100, EBECRYL P115, and EBECRYL P116 (available from ALLNEX); CN501, CN550, CN UVA421, CN3705, CN3715, CN3755, CN381, and CN386 (all available from Sartomer); GENOMER 5142, GENOMER 5161, GENOMER 5271, and GENOMER 5275 (available from RAHN); PHOTOMER 4771, PHOTOMER 4967, PHOTOMER 5006, PHOTOMER 4775, PHOTOMER 5662, PHOTOMER 5850, PHOTOMER 5930, and PHOTOMER 4250 (all available from IGM); LAROMER LR8996, LAROMER LR8869, LAROMER LR8889, LAROMER LR8997, LAROMER PO 83F, LAROMER PO 84F, LAROMER PO 94F, LAROMER PO 9067, LAROMER PO 9103, LAROMER PO 9106, and LAROMER PO77F (all available from BASF);Including, but not limited to, AGISYN 701, AGISYN 702, AGISYN 703, NeoRad P-81, and NeoRad P-85 (all available from DSM-AGI).;

[0064] For example, polymeric aminobenzoates (GENOPOL AB-1 or AB-2 from RAHN, Omnipol ASA from IGM, or Speedcure 7040 from Lambson); polymeric benzophenone derivatives (GENOPOL BP-1 or BP-2 from RAHN, Omnipol BP, Omnipol BP2702, or Omnipol 682 from IGM, or Speedcure 7005 from Lambson); polymeric thioxanthone derivatives (GENOPOL TX-1 or TX-2 from RAHN, Omnipol TX from IGM, or Speedcure 7010 from Lambson); polymeric aminoalkylphenones, for example, Omnipol 910 from IGM; polymeric benzoylformic esters, for example, Omnipol 2712 from IGM; and polymeric sensitizers Omnipol SZ from IGM are also suitable polymeric photoinitiators and sensitizers.

[0065] The energy-curable composition of the present invention may contain one or more colorants. Suitable colorants include, but are not limited to, organic or inorganic pigments and dyes. Examples of dyes include, but are not limited to, fluorescent dyes, azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, and combinations thereof. The organic pigment can be, for example, one pigment or a combination of pigments such as Pigment Yellow No. 12, 13, 14, 17, 74, 83, 114, 126, 127, 174, 188, Pigment Red No. 2, 22, 23, 48:1, 48:2, 52, 52:1, 53, 57:1, 112, 122, 166, 170, 184, 202, 266, 269, Pigment Orange No. 5, 16, 34, 36, Pigment Blue No. 15, 15:3, 15:4, Pigment Violet No. 3, 23, 27, and / or Pigment Green No. 7. The inorganic pigment can be one of the following non-limiting pigments: iron oxide, titanium dioxide, chromium oxide, ammonium ferricyanide, black ferric oxide, Pigment Black No. 7, and / or Pigment White No. 6 and 7. Similar to the combinations to achieve the desired color, other organic and inorganic pigments and dyes can also be employed. When present, the colorant is typically present in an amount of about 10 wt% to about 35 wt% based on the total weight of the composition.

[0066] Similar to most ink and coating compositions, additives can be incorporated to improve various properties. A partial listing of such additives includes, but is not limited to, adhesion promoters, silicones, light stabilizers, optical brighteners, degassing additives, ammonia, flow promoters, defoamers, antioxidants, stabilizers, surfactants, dispersants, plasticizers, rheology additives, waxes, silicones, and the like. When present, each additive is individually present in an amount of about 0.1 wt% to about 10 wt%.

[0067] Other additives are those conventionally used in energy-curable compositions and inks, and, for example, modify the fluidity, surface tension, gloss, and abrasion resistance of the coating to be cured or the ink to be printed. These additives can function as leveling agents, in-can stabilizers, wetting agents, slip agents, flow agents, dispersants, and degassing agents. Preferred additives include fluorocarbon surfactants, silicones, and organic polymer surfactants, as well as inorganic materials such as talc. By way of example, the Tegorad product line (Tegorad is a trademark and is a product of Tego Chemie, Essen, Germany, which is commercially available), and the Solsperse product line (Solsperse is a trademark and is a product of the Lubrizol Company, which is commercially available). When present, the additives are each present in an amount of from about 0.1 wt% to about 5 wt%.

[0068] The radiation-curable compositions and inks of the present invention may contain conventional extenders such as clay, talc, calcium carbonate, magnesium carbonate, or silica to adjust water absorption, misting, and color density. When present, the extender is typically present in an amount of from about 0.5 wt% to about 5 wt%.

Examples

[0069] The present invention is further illustrated by the following non-limiting examples, which are not intended to limit the scope of the present invention and should not be so construed.

[0070] Method Viscosity Viscosity was measured on an AR1000 rheometer, and the stage was set to a shear rate ramp of 25 °C, 4 cm / 2° cone, and 0 - 1000 sec -1 The viscosity value is determined by dividing the shear stress value at 100 sec -1 by the shear rate value at 100 sec -1

[0071] ​Example 1. A purple dispersant containing 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB). The purple pigment dispersant was modified by adding a small amount of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB). Table 1 shows the formulation of the modified purple dispersant, and Table 2 shows the formulation of the purple dispersant. [Table 1] [Table 2]

[0072] As can be seen from the rheology curve in Figure 1, the addition of 1% TXIB to the standard purple dispersant reduced the viscosity at 100 sec -1 by about 44% and resulted in a much more uniform flow pattern at low shear rates.

[0073] Example 2. A warm red ink modified with TXIB. The standard warm red ink (NWUV-1670, Sun Chemical) was modified with 1% TXIB. The formulation of the warm red ink of Example 2 is shown in Table 3. [Table 3]

[0074] As can be seen from the rheology curve in Figure 2, 1% TXIB significantly reduced the shear stress at low shear rates of 50 - 150 sec -1 compared to the standard unmodified ink. The reduction in viscosity at 100 sec -1 was about 66%. The box at the upper part of the curve shows the viscosity values of each experiment at a shear rate of 100 sec -1 .

[0075] Examples 3 - 7. Blue inks modified with TXIB, Texanol, or DPGBE (mixed isomers). The cyan UV flexographic printing ink (a blend of 75% NWUV-1606 / 25% NWUV-1488 from Sun Chemical) was modified with 1% TXIB, Texanol, or dipropylene glycol butyl ether (DPGBE mixed isomers). TXIB and Texanol were also tested at the 2% level. The formulations of Examples 3 - 7 are shown in Table 4.

Table 4

[0076] As can be seen in the rheology curves of Figure 3, all of the solvent materials tested reduced the low shear rate shear stress of the cyan ink (the open circle curve represents the control unmodified cyan ink). The modification that most reduced the low shear rate shear stress was 2% TXIB (the open diamond curve). The viscosity reduction by 2% TXIB at 100 sec -1 was approximately 40%.

[0077] As shown in this study, TXIB, Texanol, and DPGBE were able to reduce the thixotropy of systems with high viscosity at low shear rates. For other systems experiencing pump or low shear rate flow problems, using TXIB, Texanol, or DPGBE can result in better flow. Depending on the system and the initial low shear rate viscosity, the amount of TXIB, Texanol, or dipropylene glycol butyl ether (DPGBE mixed isomers) required to reduce viscosity and thixotropy is typically 0.5 - 3% of the formulation.

[0078] The present invention has been described in detail including its preferred embodiments. However, those skilled in the art should understand that, considering this disclosure, modifications and / or improvements can be made to the present invention that are within the scope and spirit of the present invention.

Claims

1. An energy-curable composition comprising: (a) one or more ethylenically unsaturated monomers, or one or more ethylenically unsaturated oligomers, or a combination thereof; and (b) a solvent selected from the group consisting of 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), dipropylene glycol butyl ether (DPGBE, a mixture of isomers), and blends thereof.

2. The composition according to claim 1, wherein the solvent is present in an amount of 0.5% to 3% by weight based on the total weight of the composition.

3. The composition according to any one of the preceding claims, further comprising one or more colorants.

4. The composition according to any one of the preceding claims, further comprising one or more photoinitiators.

5. The composition according to any one of the preceding claims, wherein the composition is a printing ink, a coating, or a pigment dispersant.

6. The composition according to any one of the preceding claims, wherein the composition is an energy-curable flexographic printing ink.

7. The composition according to any one of the preceding claims, wherein the viscosity is reduced by 20% or more compared to a composition containing all of the same components except the solvent.

8. The composition according to any one of the preceding claims, wherein the viscosity is reduced by 25% or more compared to a composition containing all of the same components except the solvent.

9. The composition according to any one of the preceding claims, wherein the viscosity is reduced by 30% or more compared to a composition containing all of the same components except the solvent.

10. The composition according to any one of the preceding claims, wherein the viscosity is reduced by 35% or more compared to a composition containing all of the same components except the solvent.

11. The composition according to any one of the preceding claims, wherein the viscosity is reduced by 40% or more compared to a composition containing all of the same components except the solvent.

12. A method for reducing the viscosity of an energy-curable composition, the method comprising: (a) providing an energy-curable composition; A method comprising adding one or more solvents selected from the group consisting of (b) 2,2,4-trimethyl-1,3-pentanediol isobutyrate (Texanol), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), dipropylene glycol butyl ether (DPGBE is a mixture of isomers), and blends thereof.

13. The method according to claim 12, wherein the composition is a flexographic printing ink.

14. A printed article comprising the composition according to any one or more of claims 1 to 11.

15. The article according to claim 14, wherein the article is a printed label.

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