WO2014074431A1

WO2014074431A1 - A printing form and a process for preparing a printing form

Info

Publication number: WO2014074431A1
Application number: PCT/US2013/068221
Authority: WO
Inventors: Mark E. Wagman; Helen S. M. Lu
Original assignee: E. I. Du Pont De Nemours And Company
Priority date: 2012-11-09
Filing date: 2013-11-04
Publication date: 2014-05-15

Abstract

The invention pertains to a printing form and a process for preparing it from a curable composition that includes an epoxy resin and an amine curing agent selected from primary amines and secondary amines. The process includes applying the curable composition to a supporting substrate to form a layer, curing the layer, and engraving to form at least one cell in the cured layer. Preheating the substrate to a surface temperature greater than 40C and less than about 80C results in improved surface characteristics of the printing for, such as reduction of amine blush, elimination of bubbles, and lessened surface roughness, while not accelerating the curing rate or evaporation of volatile components to an undesirable degree. The process prepares printing forms, particularly gravure printing forms, having a cured resin composition layer that is engravable, resistant to solvent inks and to mechanical wear, and capable of printing gravure-quality images.

Description

TITLE

A PRINTING FORM AND A PROCESS FOR PREPARING A PRINTING FORM

BACKGROUND OF THE INVENTION 1 . Field of the Invention

This invention pertains to a printing form and a process for preparing the printing form, and in particular, a process for preparing a gravure printing form in which one or more conventional metal layers are replaced by specified epoxy resins. 2. Description of Related Art

Gravure printing is a method of printing in which the printing form prints from an image area, where the image area is depressed and consists of small recessed cups or wells to contain the ink or printing material, and the non-image area is the surface of the form. A gravure cylinder, for example, is essentially made by electroplating a copper layer onto a base roller, and then engraving the image composed of the small recessed cells or wells digitally by a diamond stylus or laser etching machine. The cylinder with engraved cells is then overplated with a very thin layer of chrome to impart durability during the printing process. Consequently, gravure printing forms are expensive and require considerable time and material to produce.

Replacing the electroplated copper and chrome layers with a polymer-based composition has been explored, for example, by Bressler et al. (U.S. Patent No. 5,694,852), Campbell and Belser (U.S. Patent

Publication 2004/0221756), and Kellner and Sahl (UK Patent Application GB 2,071 ,574). However, a combination of several process and property requirements must be met for gravure printing forms having a polymer- based composition to succeed. For an economical process, a polymer- based coating needs to be applied to the cylinder easily ("coatability") and cured reasonably rapidly ("curability"), allowing a high-quality surface layer to be produced to the strict tolerances required for gravure engraving and printing with a minimal requirement for grinding and polishing. The surface layer needs to have a level of hardness that produces well defined print cell structure when engraved, without significant chipping or breaking

("engravability"). The surface layer also needs to possess excellent resistance to the solvents used in gravure printing inks and cleaning solutions ("durability-solvent resistance"). Also, the surface layer needs to resist the mechanical wear ("durability-mechanical wear") encountered during the printing process, e.g., wear from the scraping of the doctor blade, wear from any abrasive particles that may be in the ink, and wear from the surface onto which the image is printed. Further, in order for gravure printing forms having a polymer-based composition to replace conventional metal-covered gravure printing forms, the polymer-based printing forms should be capable of relatively long print runs and provide a consistent printed image for a minimum of 100,000 impressions, and in some embodiments at least 200,000 impressions.

However, problems sometime arise with epoxy-based resin coated systems in that the coating can develop a surface defect that manifests as oiliness or exudate; grey cloudiness; gloss reduction; greasy, waxy layer; sticky deposits; or, white crystals or patches. These defects are commonly referred to as "amine-blush" or "sweating" or "blushing", or "blooming", or "leaching", and more simply blush and bloom. The appearance of these defects can occur during cure or even after cure is completed. Severe blush or bloom will also cause significant surface irregularities resulting in an additional whitened appearance.

As a consequence, there remains a need for an improved process to produce, in an economical and environmentally-friendly manner, a printing form having a surface layer that addresses the above problems of blush and bloom as well as exhibits the necessary combination of engravability, solvent resistance, mechanical wear resistance, and print quality. SUMMARY OF THE INVENTION

The present invention provides a process for preparing a printing form including a) providing a curable composition including i) at least one epoxy resin and ii) an amine curing agent selected from primary amines and secondary amines, b) applying the curable composition onto a preheated supporting substrate, thereby forming a layer; c) curing the layer at one or more temperatures in a range of room temperature to about 250 °C; and d) engraving at least one cell in the layer resulting from step c), wherein the viscosity of the curable composition as applied to the substrate is about 400 to about 6000 cP and the substrate is preheated to a surface temperature greater than 40 °C and less than about 80 °C.

In accordance with another aspect of this invention there is provided a printing form prepared according to the process described above.

In accordance with another aspect of this invention there is provided a process for gravure printing with a printing form including a) preparing the printing form according to the process described above; b) applying a solvent ink to the at least one cell; and c) transferring ink from the cell to a printable substrate, wherein the cured layer swells < 10% based on weight of the layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the context of this disclosure, a number of terms shall be utilized.

The term "epoxy resin" means uncross-linked monomers or oligomers containing epoxy groups.

The term "epoxy novolac resin" means any of a group of epoxy resins created by the reaction of epichlorohydrin and novolac. The term "novolac" refers to any of the phenol-formaldehyde resins made with an excess of phenol in the reaction, and to any of the cresol-formaldehyde resins made with an excess of cresol in the reaction.

The term "bisphenol-based epoxy resin" means an epoxy resin created by the reaction of a bisphenol and epichlorohydrin.

The term "bisphenol-A epoxy resin" means any of a group of glycidyl ether derivatives of bisphenol A,

prepared by reaction of bisphenol A with epichlorohydrin. The term "bisphenol-F epoxy resin" means any of a group of glycidyl ether derivatives of bisphenol F, prepared by reaction of bisphenol F, i.e., a mixture of p, p', o, p', and o, o' isomers of bis(hydroxyphenyl)methane,

with epichlorohydrin.

The term "epoxy reactive diluent" refers to low viscosity epoxies that are used to modify the viscosity and other properties, such as, wetting and impregnation, of an epoxy composition that is to be cured. Herein, the term "diluent" or "reactive diluent" may be used for brevity in place of "epoxy reactive diluent."

The term "epoxy/diluent component" refers to the mixture of epoxy resins and reactive diluents in the curable composition.

The term "solvent" refers to a nonreactive component of a

composition that reduces the viscosity of the composition and has a volatility such that it is removed under the conditions (such as temperature) at which the composition is processed. A "solvent-free" composition is thus a composition that does not contain a solvent as defined above.

The term "gravure printing" means a process in which an image is created by engraving or etching one or more depressions in the surface of a printing form, the engraved or etched area is filled with ink, then the printing form transfers the ink image to a substrate, such as paper or another material. An individual engraved or etched depression is referred to as a "cell."

The term "relief printing" means a process in which a relief surface is created by engraving or etching one or more depressions in the surface of a printing form in which the image area is raised and the non-image area is the depressions, ink is applied to the raised area, and then the printing form transfers the ink image to a substrate, such as paper or another material. An individual engraved or etched depression can be referred to as a "cell." Letterpress printing is one type of relief printing. The term "printing form" means an object (e.g., in the form of a cylinder, block, or plate) used to apply ink onto a surface for printing.

The term "room temperature" or, equivalently "ambient

temperature," has its ordinary meaning as known to those skilled in the art and may include temperatures within the range of about 16°C (60 °F) to about 32 °C (90 °F).

The term "primary amine" means any of a class of organic compounds containing -NH₂ functional groups.

The term "secondary amine" means any of a class of organic compounds containing -NH- functional groups.

The term "solvent ink" means an ink that includes an organic solvent, typically the organic solvent is volatile, in contrast to water-based inks.

The term "curing" refers to hardening of a polymer material or resin by cross-linking of polymer chains, brought about by chemical additives, heat, ultraviolet radiation, or electron beam. Hardening occurs primarily by crosslinking of the polymer chains. But other interactions in the polymer material or resin, such as branching and linear chain extension, may also occur in relatively small degree compared to crosslinking of the polymer chains.

The term "curable composition" as used herein refers to the composition that is applied to a substrate and then cured. The curable composition contains at least a curable polymer material or resin and an amine curing agent, and can include additional components, for example, catalysts, reactive diluents, fillers, nanoparticles, flexibilizing components, resin modifiers, pigments, solvents and/or other additives.

The term "cured composition" as used herein refers to the composition that remains on the substrate after being applied and cured. The cured composition contains at least a curable polymer material or resin and an amine curing agent, and can include additional components, for example, catalysts, reactive diluents, fillers, nanoparticles, flexibilizing components, resin modifiers, pigments, and/or other additives, and traces of solvent (solvent is typically driven out during applying and/or curing). The cured composition may also be considered a cured layer, or engravable layer. In some instances the cured composition may be referred to as a cured layer of the curable composition.

The term "amine hydrogen equivalent weight" (AHEW) means the molecular weight of the amine-group-containing molecule divided by the number of amine hydrogens in the molecule. For example:

triethylenetetraamine ("TETA") has a molecular weight of 146 and 6 amine hydrogens, so its amine hydrogen equivalent weight is 146/6 = 24 g/equiv.

If the compound is an adduct of an amine and, e.g., an epoxy, the effective

AHEW is based on the amine component..

The term "epoxide equivalent weight" (EEW) means the weight in grams that contains 1 gram equivalent of epoxide.

The term "epoxide" means an organic compound containing a reactive group that is an "epoxide group", and the term "epoxide group" means a group that results from the union of oxygen with two carbons that are joined as indicated

- C - C -

The term "nanoparticle" means a particle having at least one dimension less than about 500 nm.

The term "molecular weight" is the weight average molecular weight, unless described otherwise in the specification.

The term "softening point" refers to a Mettler softening point, which is measured according to ASTM D-3104. It is usually reported as a temperature range. As used herein, the phrase "having a softening point less than X" means that the upper limit of the temperature range

determined by ASTM D-3104 is less than about X. A material that is a liquid at a specified temperature Y has a softening point less than Y.

Unless otherwise indicated herein, weight percent (wt%) of a component is based on the combined weight of the components, excluding solvents, of the curable composition.

The present invention includes a printing form having a print surface formed by curing a layer of a curable composition on a preheated supporting substrate, a process for preparing the printing form from a curable composition, and particularly a process for preparing a gravure printing form from a curable composition. The curable composition

includes an epoxy resin and ii) an amine curing agent selected from

primary amines and secondary amines. Surprisingly and unexpectedly, preheating the supporting substrate so that its surface temperature is

greater than 40 °C and less than about 80 °C results in improved surface characteristics of the cured layer, such as reduction of amine blush and/or bloom, elimination of bubbles, and lessened surface roughness, while not accelerating the curing rate and/or evaporation of volatile components to an undesirable degree. The optimal temperature for heating the substrate prior to application of the resin, i.e., preheating of the substrate, may be different for different resin compositions. For each composition, there is a range of temperatures where coatability is good and curing and

evaporation of volatile components are sufficiently slow. In some

embodiments, one or more of the reactive components of the resin

composition may begin to vaporize within the preheated temperature

range, and thus would not be available to react and provide suitable

degree of curing. Preheating the substrate to a temperature above 40 °C prior to application of the resin composition, improves the coatability, that is, the resin composition flows out and wets the substrate better and

bubbles do not form (or are able to escape more easily). If the substrate is preheated much above 80 °C, particularly for epoxy-based resins, the applied layer of resin may cure too quickly, or volatile components may evaporate too quickly. In some embodiments, the substrate continues to be heated following application of the resin to form a layer, and then is heated to a higher temperature to fully cure the layer of resin.

The present invention process facilitates the preparation of a

printing form in considerably less time, at reduced cost, and in a more

environmentally sound manner than conventional printing forms having one or more metal layers for gravure printing. The claimed process

prepares a printing form from the epoxy resin compositions that is capable of meeting several of the property requirements for successful

performance comparable to conventional gravure printing forms.

The present process that includes preheating of the substrate prior to application of a resin composition is particularly suited for thermally-curable resin compositions, such as epoxy-based resin compositions. The present printing form is prepared with a curable composition containing an epoxy resin and an amine curing agent. Epoxy resins suitable for use include, but are not limited to, epoxy novolac resins, bisphenol-based epoxy resins, and combinations thereof. The amine curing agents suitable for use include, but are not limited to primary amines, secondary amines, and combinations thereof. The curable epoxy resin composition can include one or more of each of the following additional

components: catalysts; epoxy-reactive diluents, including multifunctional epoxy- reactive diluents and monofunctional epoxy-reactive diluents; resin modifiers, nanoparticles; fillers; pigments; wetting additives; leveling additives; and solvents. Three embodiments of the curable composition are preferred, as described below.

A. Epoxy novolac resin compositions

In one embodiment (embodiment A), the epoxy resin is an epoxy novolac resin having an epoxide equivalent weight of about 156 to about 300 and the amine curing agent has an amine hydrogen equivalent weight of less than 60 g/equivalent.

The epoxy novolac resin that is created by the reaction of

epichlorohydrin and novolac is an intermediate molecule having a phenolic backbone having pendant epoxide groups. The novolac resin may be

prepared from unsubstituted phenols and from substituted phenols, such as cresol. Epoxy novolac resins also encompass epoxy cresol novolac

resins, wherein the cresol forms the phenolic backbone of the epoxy

novolac resin.

The epoxy novolac resins used in the processes described herein are characterized by an epoxide equivalent weight (EEW) between and

optionally including any two of the following values: 156, 160, 170, 180,

190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, and 300 g/equiv.

In one embodiment the EEW is beween about 156 and about 230

g/equivalent. If the epoxide equivalent weight is above about 300, it is

contemplated that the chemical or solvent resistance of the composition of the epoxy novolac resin would deteriorate.

In some embodiments, the epoxy novolac resins have a molecular weight between and optionally including any two of the following values: 312, 400, 600, 800, 1000, 1200, 1500, 1800, 2100, 2400, 2700, and 3000. In one embodiment the molecular weight of the epoxy novolac resin is between about 312 and about 1500. In most embodiments, the epoxy novolac resins have an average functionality greater than 2.0, which leads to higher cross-linking density upon curing. Epoxy novolac resins with higher crosslinking density have good toughness and chemical resistance, which leads to suitable wear and impact resistance and solvent resistance for use as a printing form compared to other epoxy resin compositions, such as DGEBPA and DGEBPF.

In some embodiments, the epoxy novolac resins include resins of the following formula (I)

where n can range from about 0.1 to about 20, including fractions therebetween. In some embodiments, n ranges from about 0.2 to about 5.0. In other embodiments, n ranges from about 0.2 to about 2.0.

Examples of embodiments of the epoxy novolac resins of formula (I) are D.E.N.™ 431 , D.E.N.™ 438, and D.E.N.™ 439 (available from The Dow Chemical Company, Midland, Michigan, U.S.A.); and EPON™ Resin 160, EPON™ Resin 161 (available from Momentive Specialty Chemicals, Inc., formerly Hexion Specialty Chemicals, part of Momentive Performance Materials Holdings, Inc., Columbus, Ohio, U.S. A).

In some other embodiments the epoxy novolac resins include epoxy cresol novolac resins of the following formula (Π)

where n can range from about 0.1 to about 20, including fractions therebetween. In some embodiments, n ranges from about 0.2 to about 4. Examples of embodiments of the epoxy novolac resins of formula (II) are Araldite® ECN 1280 and ECN 1273 (available from Huntsman); and EPON™ Resin 164 and EPON™ Resin 165.

In yet other embodiments the epoxy novolac resins include epoxy

where n can range from about 0 to about 1 0, including fractions

therebetween. In some embodiments, n ranges from about 0 to about 4. Examples of embodiments of the epoxy novolac resins of formula (III) are EPON™ Resin SU-2.5.

Epoxy novolac resins generally contain multiple epoxide groups.

The number of epoxide groups per molecule depends upon the number of hydroxyl groups in the starting phenolic novolac resin, the extent to which they reacted and the degree of low molecular species being polymerized during synthesis. The multiple epoxide groups allow these resins to achieve the desired degree of crosslink density. The epoxy novolac compounds of formulas (I), (II), and (III) each contain a distribution of oligomers, i.e., "-mer" units, and as such, n represents a number of -mer units in the epoxy novolac compounds, per the range of values of n for formula (I), formula (Π), and formula (ΠΙ) as indicated above. As used herein, the term "-mer" or "-mer units", encompasses epoxy novolac oligomeric compounds having more than one repeating unit that includes dimers, trimers, tetramers, pentamers, hexamers, and heptamers. In one embodiment, the distribution of -mer units in an epoxy novolac resin includes a mixture of several or all possible (i.e., di-mers through hepta- mers), such that n represents an average number of -mer units in the resin. In other embodiments, the distribution of -mer units in an epoxy novolac resin includes a mixture of several or all possible (i.e., dimers through heptamers), such that n represents the predominant species of oligomers in the mixture. As another example, the epoxy novolac of formula (I) wherein n equals 2.4, is a mixture of oligomers (i.e., a mixture of dimers, trimers, tetramers, pentamers, and hexamers, and perhaps heptamers), with the predominant species is tetramers and pentamers. For the epoxy novolac compounds represented by formulas (I), (II), and (III), n can be between and optionally include any two of the following values: 0, 0.1 , 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 .0, 1 .1 , 1 .2, 1 .3, 1 .4, 1 .5, 1 .6, 1 .7, 1 .8, 1 .9, 2.0, 2.1 , 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1 , 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1 , 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1 , 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, per the range for n that is described above. The epoxy novolac resin is present in the curable composition from about 35 to about 95% by weight, based on the combined weight of the components of the curable composition. In some embodiments, the epoxy novolac resin is present in an amount between and optionally including any two of the following values: 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, and 95% by weight, based on the combined weight of the components of the curable composition.

Mixtures of epoxy resins (i.e., more than one epoxy novolac resins, or a mixture of one or more epoxy novolac resins with one or more other epoxy resins) can also be used in the curable composition. Examples of the other epoxy resin as a second epoxy resin that can be blended with the epoxy novolac resin include, without limitation, bisphenol A diglycidyl ether, "DGEBPA" and its oligomers, of the following formula (IV)

and bisphenol F diglycidyl ether, "DGEBPF,"and its oligomers, of the following formula (V)

where x can be 0 to about 16 for their oligomers. For DGEBPA and

DGEBPF, which is non-oligomeric, x is 0. Molecular weight of oligomers of DGEBPA and DGEBPF can be up to approximately 5000 g/mol. Other epoxy resins suitable as a second epoxy resin that can be blended with the epoxy novolac resin include multifunctional epoxy-reactive diluents, such as trifunctional and tetrafunctional epoxy-reactive diluents, having viscosity greater than about 300 cP. In some embodiments, the

multifunctional epoxy-reactive diluent as the second epoxy resin can be used alone or with other multifunctional epoxy-reactive diluents having viscosity greater than about 300 cP. Examples of multifunctional epoxy- reactive diluents as the second epoxy resin include, but are not limited to, 4-glycidyloxy-N,N-diglycidylaniline which is available commercially as Ara!dite^® Y0510, and ,N,N\ ^tetraglycidyl-4,4'-methy!ene-bis- benzenamine, which is available commercially as Araidite^® Y-721 both from Huntsman International LLC (Salt Lake City, Utah, U.S.A.). When blended with at least one other epoxy resin in the curable composition, the epoxy novolac resin is present in at least 50 wt % based on the combined weight of the epoxy novolac resin and the at least one other epoxy resin.

Curing agents used in the processes described herein are primary amines and secondary amines, and thus are referred to herein as amine curing agents. Amine curing agents are primarily suitable for the present process because they increase the cure speed of the curable composition compared to other possible curing agents such as acids and/or

anhydrides, and are capable of curing the composition at moderate temperatures, e.g., room temperature to about 100°C. Amine curing agents are characterized by an amine hydrogen equivalent weight (AHEW) of less than or equal to about 60 g/equivalent. In an

embodiment, the amine hydrogen equivalent weight is between and optionally including any two of the following values: 20, 30, 40, 50, and 60 g/equivalent. In most embodiments, the amine curing agent is

characterized by an amine hydrogen equivalent weight of about 20 to 60 g/equivalent. The amine curing agent having amine hydrogen equivalent weight of less than or equal to 60 g/equivalent aids in providing a cured layer of the composition with a sufficient degree of solvent resistance such that print quality can be maintained for print run lengths of at least 100,000 impressions or more. Solvent resistance of the resin-based layer on the printing form is particularly important since many inks used in gravure printing are solvent-based inks, and attack by solvents of the resin-based layer can cause the layer to swell and thereby detrimentally impact print quality and run length. The amine curing agent is present in the curable composition from about 3 to about 30% by weight, based upon the combined weight of the components of the curable composition. In some embodiments, the amine curing agent is present in an amount between and optionally including any two of the following values: 3, 5, 10, 15, 20, 25, and 30% by weight, based on the combined weight of the components of the curable composition.

In most embodiments, the amine curing agent has 2 or more amino functionalities per molecule. The amines can be aliphatic amines (e.g., triethylenetetramine, diethylenetriamine, tetraethylenepentamine), aliphatic polyamines, modified aliphatic polyamines, cycloaliphatic amines (e.g., isophorone diamine, 1 ,2-diaminocyclohexane, 1 -(2-aminoethyl) piperazine, bis(4-aminocyclohexyl)methane), modified cycloaliphatic amines, aromatic amines (e.g., m-phenylene- diamine, 4,4'- diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone,

diethyltoluenediamine); or arylyl amines, which have cycloaliphatic or aromatic moieties from which the amine functional groups are separated by methylene groups -CH₂- (e.g., m-xylylene diamine and 1 ,3- bis(aminomethyl cyclohexane)). Epoxy curing agents are described in Epoxy Resins Chemistry and Technology, Clayton A. May editor, 2^nd edition, Marcel Dekker, In., N.Y.. An extensive list of commercial amine curing agents is also given in Table 15 on p. 730 of "Epoxy Resins," by Ha. Q. Pham and Maurice J. Marks in Encyclopedia of Polymer Science and Technology, 4th ed., Jacqueline I. Kroschwitz, exec, ed., John Wiley & Sons, Hoboken, NJ, 2004, pp. 678-804. Mixtures of amine curing agents can also be used. In some embodiments the curing agent is triethylenetetramine, diethylenetriamine, or a cycloaliphatic amine. In most embodiments, the ratio of epoxy functionality to amine hydrogen functionality is from about 0.7:1 .0 to about 1 .0:0.7, on a mole-to-mole basis.

The epoxy novolac resin can be cured in the presence of the curing agent and a catalyst, and as such the curable composition may include a catalyst. Catalytic polymerizations of epoxy occur with a variety of Lewis bases and acids as well as salts and metal complexes. Epoxy curing reactions are described in Epoxy Resins Chemistry and Technology, Clayton A. May editor, 2^nd edition, Marcel Dekker, Inc, NY. Suitable catalysts include, but are not limited to, imidazoles, 2-ethyl-4-methyl imidazole, 2,4,6-tris(dimethylaminomethyl)phenol, and nonyl phenol. The catalyst can be present in the curable composition from 0 to about 10% by weight, based on the combined weight of the components of the curable composition. In some embodiments, the catalyst is present in an amount between and optionally including any two of the following values: 0, 1 , 2, 3, 4, 5, 6, 7, 8, 9, and 10 wt%, based on the combined weight of the components of the curable composition.

The curable composition used in the processes described herein optionally contains one or more epoxy-reactive diluents. The epoxy- reactive diluents are low viscosity epoxies that are used to modify the viscosity and other properties, such as, wetting and impregnation, of the epoxy composition that is to be cured. The viscosity of the epoxy-reactive diluents is typically less than about 300 cP at room temperature. In some embodiments, the viscosity of the epoxy-reactive diluents is less than or equal to about 1000 cP at room temperature. In some other

embodiments, an epoxy-reactive diluent can have viscosity greater than about 300 cP up to about 1000 cP, and even higher (at room

temperature), particularly when the higher viscosity epoxy-reactive diluent is included in a mixture of epoxy-reactive diluents such that the viscosity of the mixture is less than about 300 cP. The epoxy-reactive diluent may be monofunctional or multifunctional (e.g., di-, tri-, or tetrafunctional, having two, three, or four epoxide groups, respectively), and may be referred to herein as reactive diluent, or functional diluent, or diluent.

Examples of monofunctional diluents include without limitation: p- tertiarybutyl phenyl glycidyl ether, cresyl glycidyl ether, 2-ethylhexyl glycidyl ether, and C₈- Ci₄ glycidyl ether. The monofunctional diluent can be used in small enough amounts, from 0 to about 20 wt% based on the combined weight of the components of the composition, that the chemical resistance of the epoxy is not impaired. In some embodiments, the monofunctional diluent is present in an amount between and optionally including any two of the following values: 0, 2, 4, 6, 8,10, 12, 14, 16, 18, and 20 wt%, based on the combined weight of the components of the curable composition.

Examples of difunctional diluents include, without limitation, 1 ,4- butanediol diglycidyl ether; neopentyl glycol diglycidyl ether; and

cyclohexane dimethanol diglycidyl ether. Difunctional diluents can be used from 0 to about 30 wt%, based on the combined weight of the components of the composition. In some embodiments, the difunctional diluent is present in an amount between and optionally including any two of the following values: 0, 1 , 3, 5, 7, 9, 1 1 , 13, 15, 17, 19, 21 , 23, 25, 27, and 30 wt%, based on the combined weight of the components of the curable composition.

Examples of trifunctional diluents include, but are not limited to, trimethylol propane triglycidyl ether, and 4-glycidyloxy-N,N- diglycidylaniline which is available commercially as Araldite^®MY0510 from Huntsman International LLC (Salt Lake City, Utah, U.S.A.). Trifunctional diluents can be used from 0 to about 30 wt%, based on the combined weight of the components of the composition. In some embodiments, the trifunctional diluent is present in an amount between and optionally including any two of the following values: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, and 30 wt%, based on the combined weight of the components of the curable composition.

Examples of tetrafunctional diluents are pentaerythritol tetraglycidyl ether, and N^^^N'-tetragiycidyl^^'-methyiene-bis-benzenamine, which is available commercially as Ara dite^®MY-721 from Huntsman

International. Tetrafunctional diluents can be used from 0 to about 20 wt%, based on the combined weight of the components of the composition. In some embodiments, the tetrafunctional diluent is present in an amount between and optionally including any two of the following values: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 wt%, based on the combined weight of the components of the curable composition.

A mixture of epoxy-reactive diluents may be used, with minimal use of a monofunctional diluent (i.e., less than 20 wt%, and preferably less than 10 wt%), to achieve desired viscosity of the curable composition while maintaining desired properties of the composition. In some embodiments, a mixture of diluents can be present from 0 to about 40% by weight, based upon the combined weight of the components of the curable composition. In some embodiments, the mixture of diluents is present in an amount between and optionally including any two of the following values: 0, 1 , 3, 5, 7, 9, 10, 1 1 , 13, 15, 17, 19, 20, 21 , 23, 25, 27, 29, 30, 31 , 33, 35, 37, and 40 wt%, based on the combined weight of the components of the curable composition.

The curable composition may also include one or more liquid compounds that aid in rendering the composition suitable to conduct the applying step of the present method. The curable composition may be dispersed or dissolved or suspended in the liquid compounds, so that the curable composition can be applied by the desired means and can form a layer of the composition on the supporting substrate. The liquid

compound is not limited and can include organic compounds and aqueous compounds. The one or more liquid compounds may be a solvent, that is a substance which is capable of dissolving another substance (i.e., resin) to form a uniform mixture. The liquid compound may be a carrier, such as the reactive diluent, that is capable of dispersing or suspending the material in the composition in solution sufficient to conduct the steps of the present method. The curable composition may include one or more liquid compounds as a solvent and/or carrier for the curable composition. In most embodiments, the liquid compound is one or more organic solvents. In most embodiments, the liquid solvent or solvent mixture is removed from the composition by evaporation after application of the composition to the supporting substrate, or most typically, during the curing step.

In the curable compositions used in the processes described herein, epoxy novolac resin is present at about 35 to about 95 wt%, the amine curing agent at about 5 to about 28 wt%, the catalyst at 0 to about 10 wt%, and the reactive diluent at 0 to about 40 wt%, based on the combined weight of epoxy novolac resin, amine curing agent, catalyst, and reactive diluent. In some embodiments the curable composition includes the epoxy novolac resin that is present at about 50 to about 95 wt%, the amine curing agent at about 5 to about 28 wt%, and the reactive diluents at 0 to about 25 wt%, based on the combined weight of epoxy novolac resin, amine curing agent, and reactive diluents. In some other embodiments of the curable compositions used in the processes described herein, epoxy novolac resin is present at about 50 to about 90 wt%, the amine curing agent at about 5 to about 25 wt%, the catalyst at about 0 to about 10 wt%, and the reactive diluent at about 0 to about 25 wt%, based on the combined weight of the components of the curable composition.

The curable composition includes at least the epoxy novolac resin having the particular EEW and the amine curing agent having the particular AHEW, as stated above. In most embodiments, the curable composition can include or can consist essentially of the epoxy novolac resin, the amine curing agent, and the catalyst. In other embodiments, the curable composition can include or can consist essentially of the epoxy novolac resin, the amine curing agent, the catalyst, and nanoparticles (as described below). In yet other embodiments, the curable composition can include or can consist essentially of the epoxy novolac resin, the amine curing agent, the catalyst, and the epoxy-reactive diluent. In yet other embodiments, the curable composition can include or can consist essentially of the epoxy novolac resin, the amine curing agent, the catalyst, the epoxy-reactive diluent, and a flexibilizing component (as described below). In yet other embodiments, the curable composition can include or can consist essentially of the epoxy novolac resin, the amine curing agent, the catalyst, the epoxy-reactive diluent, and a leveling additive (as described below). In still other embodiments, the curable composition can include or can consist essentially of the epoxy novolac resin, the amine curing agent, an additional epoxy resin (as described below), the catalyst, and the epoxy-reactive diluent. In some

embodiments, the curable compositions include the epoxy novolac resin present at about 50 to about 90 wt%, the amine curing agent at about 5 to about 25 wt%, the second epoxy resin at about 0 to about 40 wt%, the reactive diluents at about 0 to about 40 wt%, the catalyst at about 0 to about 10 wt%, the nanoparticles at about 1 to about 50 wt%, the resin modifier at about 0 to 10 wt%, the flexibilizing component at about 0 to about 15 wt%, and the leveling additive at about 0 to 10 wt%, based on the combined weight of the components of the curable composition.

In one embodiment, the epoxy novolac resin in the curable composition used for the printing form has an epoxide equivalent weight of about 156 to about 200 g/equivalent; and the amine curing agent is triethylenetetramine, diethylenetriamine, or a cycloaliphatic amine. In an embodiment, the curable composition further includes up to about 50 wt% nanoparticles; in another embodiment, up to about 20 wt% nanoparticles, such as alumina nanoparticles or silica nanoparticles. The curable epoxy novolac composition for the printing form can further include at least one additional epoxy resin, for example, bisphenol F diglycidyl ether or bisphenol A diglycidyl ether.

B. Bisphenol-based epoxy resin compositions

In another embodiment (embodiment B), the curable composition comprises i) a bisphenol-based epoxy resin; ii) an amine curing agent selected from primary amines and secondary amines, the agent having an amine hydrogen equivalent weight of less than or equal to 200 g/equivalent; and iii) at least one multifunctional epoxy-reactive diluent, which is present at 0.5 to 40 wt% based on the combined weight of the components of the curable composition, and has an epoxide equivalent weight between 55 and 400. In some embodiments, the combined weight of the components of the curable composition is based on components i), ii) and iii). In other embodiments, the combined weight of the components of the curable composition is based upon components i), ii) and iii) and one or more other optional components of the curable composition.

Various bisphenol-based epoxy resins may be used. In particular, in one embodiment the bisphenol-based epoxy resin is an intermediate molecule based on the reaction of epichlorohydrin and bisphenol A ("BPA") and/or bisphenol F ("BPF"). Bisphenol-based epoxy resins that are useful for the present invention include, but are not limited to, bisphenol A diglycidyl ether, ("DGEBPA") and its oligomers, as shown above in formula (IV), and bisphenol F diglycidyl ether, ("DGEBPF") and its oligomers, as shown above in formula (V). Molecular weight of oligomers of DGEBPA and DGEBPF can be up to approximately 6000 g/mol.

The bisphenol-based epoxy resin has a molecular weight in the range of about 298 to about 6000 g/mol. In one embodiment, the

bisphenol-based epoxy resin based on bisphenol A has a molecular weight in the range of about 340 to about 6000 g/mol. In one embodiment, the bisphenol-based epoxy resin based on bisphenol F has a molecular weight in the range of about 310 to about 6000 g/mol. In some embodiments, the bisphenol-based epoxy resins have a molecular weight between and optionally including any two of the following values: 298, 300, 310, 340, 400, 600, 800, 1000, 1200, 1500, 1800, 2100, 2400, 2700, 3000, 3300, 3600, 3900, 4200, 4500, 4800, 5100, 5400, and 6000. Since the bisphenol- based epoxy resins have 2 epoxy groups per oligomer, the bisphenol- based epoxy resins have an epoxide equivalent weight (EEW) that is generally about half of the molecular weight of the oligomer. In one embodiment, the bisphenol-based epoxy resin is present from about 40 to about 95 wt%, based on the combined weight of the bisphenol-based epoxy resin, amine curing agent, and multifunctional epoxy-reactive diluent. In another embodiment, the bisphenol-based epoxy resin is present from about 40 to about 95 wt%, based on the combined weight of the

components in the curable composition. In some embodiments, the bisphenol-based epoxy resin is present in an amount between and optionally including any two of the following values: 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, and 95 wt%, based on the combined weight of the components in the curable composition.

Examples of commercially available bisphenol A diglycidyl ether epoxy resins are Insulcast 503/504 BLK; Insulcast 504 Clear; Insulcast 125; Insulcast 333; Insulcast 136; and Insulcast 502, available (from ITW

Polymer Technologies (Glenview, Illinois, U.S.A.); EPON™ Resin 828, and EPON™ Resin 826 available from Hexion Specialty Chemicals, Inc., now Momentive Specialty Chemicals, Inc., part of Momentive Performance Materials Holdings, Inc., (Columbus, Ohio, U.S.A.). Examples of

commercially available bisphenol F diglycidyl ether epoxy resins are

Araldite® GY285, Araldite® GY281 , and Araldite® PY302-2 from Huntsman International, LLC (Salt Lake City, Utah, USA). Mixtures of bisphenol- based epoxy resins can be used in the curable composition.

The curable composition can include a combination of epoxy resins. In one embodiment, the curable composition contains a

combination of more than one bisphenol-based resin. In some

embodiments, the curable composition contains a combination of one or more bisphenol A -based epoxy resins with one or more other bisphenol- based epoxy resins. In some embodiments, the curable composition

contains a combination of one or more bisphenol F -based epoxy resins with one or more other bisphenol-based epoxy resins. In some

embodiments, when combined with one or more other bisphenol-based

epoxy resins in the curable composition, the bisphenol A and/or bisphenol F -based epoxy resins are present in at least 50 wt% based on the combined weight of all the epoxies present.

In yet other embodiments, the curable composition contains a

combination of one or more of the bisphenol-based epoxy resins with one or more other epoxy resin. The at least one other epoxy resin includes, but is not limited to, epoxy novolac resins, and epoxy cresol novolac resins.

Examples of suitable epoxy novolac resins are D.E.N.™ 431 , D.E.N.™

438, D.E.N.™ 439 (all available from the Dow Chemical Company, Midland Michigan, USA) and EPON™ Resin 160 and EPON™ Resin SU-2.5

(available from Momentive Specialty Chemicals, Inc., formerly Hexion

Specialty Chemicals, part of Momentive Performance Materials Holdings,

Inc., Columbus, Ohio, USA). When combined with at least one other epoxy resin in the curable composition, the bisphenol-based epoxy resins are

present in at least 50 wt% based on the combined weight of all the epoxies present.

Amine curing agents suitable for embodiment B of the present

invention are capable of curing the composition at moderate temperatures, e.g., room temperature to about 150 °C. In one embodiment, the amine

hydrogen equivalent weight of the curing agent is about 20 to about 200 g/equivalent. In an embodiment, the amine hydrogen equivalent weight is between and optionally including any two of the following values: 20, 30,

40, 50, 60, 70, 80, 90, 100, 1 10, 120, 130, 140, 150, 160, 170, 180, 190 and 200 g/equivalent. In most embodiments the amine curing agent has

1 .5 or more amino functionalities per molecule.

The amine curing agents can be aliphatic amines, aliphatic polyamines, modified aliphatic polyamines, cycloaliphatic amines, modified cycloaliphatic amines; aromatic amines; arylyl amines, which have cycloaliphatic or aromatic moieties from which the amine functional groups are separated by methylene groups -CH₂-, or polymeric amines. Examples of suitable amine curing agents are presented above in connection with embodiment A and in the references cited there. Mixtures of amines can also be used. In some embodiments, the amine curing agent is triethylenetetramine, diethylenetriamine, or a cycloaliphatic amine. In most embodiments, the ratio of epoxy functionality to the amine functionality is from about 0.8:1 .2 to about 1 .2:0.8, on a mole-to-mole basis. In one embodiment, the amine curing agent is present from about 5 to about 28 wt%, based on the combined weight of bisphenol-based epoxy resin, amine curing agent, and multi- reactive epoxy diluent. In another embodiment, the amine curing agent is present from about 5 to about 28 wt%, based on the combined weight of the components in the curable composition. In some embodiments, the amine curing agent is present in an amount between and optionally including any two of the following values: 5, 8, 10, 15, 20, 25, and 28 % by weight, based on the combined weight of the components of the curable composition.

The epoxy novolac resin can be cured in the presence of the curing agent and a catalyst, and as such the curable composition may include a catalyst, as described above with reference to embodiment A.

The curable composition used in the processes described herein

contains at least one multifunctional epoxy-reactive diluent, and may be

referred to herein as multi-epoxy reactive diluent, or reactive diluent. Multi- epoxy reactive diluents are epoxy compounds having more than one

epoxide group, and thus are multi-functional reactive diluents that

encompass trifunctional (i.e, having three epoxide groups) and

tetrafunctional (i.e., having four epoxide groups) epoxy compounds. The multifunctional epoxy-reactive diluents may be low viscosity epoxies that are used to modify the viscosity and other properties, such as wetting and impregnation, of the curable composition. The viscosity of the

multifunctional epoxy-reactive diluents is typically less than about 300 cP at room temperature, although it can be higher, even substantially higher such as a solid. In some embodiments, the viscosity of the epoxy-reactive

diluents is less than or equal to about 1000 cP at room temperature. In

some other embodiments, an epoxy-reactive diluent can have viscosity

greater than about 300 cP up to about 1000 cP, and even higher (at room temperature), particularly when the higher viscosity epoxy-reactive diluent is included in a mixture of epoxy-reactive diluents. Surprisingly, the presence of the multifunctional epoxy-reactive diluent in the curable composition provides improved resistance to wear and to attack by solvents for the coating of the cured composition. The presence of the

multifunctional epoxy-reactive diluents in the curable composition can provide a stiffening effect to the cured composition by crosslinking with the other components, but not so much as to render the cured composition brittle.

The multifunctional epoxy-reactive diluent has an epoxide equivalent weight (EEW) that can be from about 55 to about 400. In some

embodiments the multifunctional epoxy-reactive diluent has an EEW between about 70 to about 275. In other embodiments, the multifunctional epoxy-reactive diluent has an EEW between about 85 to about 125. In some embodiments, the multifunctional epoxy-reactive diluent has an EEW between and optionally including any two of the following values: 55, 59, 65, 70, 75, 80, 85, 87, 90, 95, 100, 105, 1 10, 120, 125, 130, 150, 180, 200, 220, 240, 260, 275, 280, 300, 320, 340, 360, 380, and 400.

In one embodiment, the multifunctional epoxy-reactive diluent is present in the curable composition at about 0.5 to about 40 wt%, based on the combined weight of bisphenol-based epoxy resin, amine curing agent, and multifunctional epoxy-reactive diluent. In another embodiment, the multifunctional epoxy-reactive diluent is present in the curable composition at about 0.5 to about 40 wt%, based on the combined weight of the components in the composition. In some embodiments, the multifunctional epoxy-reactive diluent is present in the curable composition at about 0.5 to about 20 wt%, based on the combined weight of bisphenol-based epoxy resin, amine curing agent, and multifunctional epoxy-reactive diluent. In some embodiments, the multifunctional epoxy-reactive diluent is present in the curable composition at about 0.5 to about 20 wt%, based on the combined weight of the components in the composition. In yet other embodiments, the multifunctional epoxy-reactive diluent is present in the curable composition at about 0.5 to about 10 wt%, based on the combined weight of bisphenol-based epoxy resin, amine curing agent, and

multifunctional epoxy-reactive diluent. In yet other embodiments, the multifunctional epoxy-reactive diluent is present in the curable composition at about 0.5 to about 10 wt%, based on the combined weight of the components in the composition. In some embodiments, the multifunctional epoxy-reactive diluent is present between and optionally including any two of the following values: 0.5, 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, and 40 wt%. It is possible that curable compositions containing more than the maximum amount of the multifunctional epoxy-reactive diluent may become too brittle upon curing, and in some cases even may not polymerize well.

In one embodiment, a mixture of multifunctional epoxy-reactive diluents, i.e., a mixture of a tri-epoxy reactive diluent and tetra-epoxy reactive diluent, is included in the curable composition. In other

embodiments, the curable composition includes the multifunctional epoxy- reactive diluent that is at least one tri-epoxy reactive diluent. In other embodiments, the curable composition includes the multifunctional epoxy- reactive diluent that is at least one tetra-epoxy reactive diluent. The multifunctional epoxy-reactive diluents include, but are not limited to, triglycidyl ethers, and tetraglycidyl ethers. Examples of trifunctional diluents include without limitation: 1 ,1 ,1 -trimethylolpropane triglycidyl ether

(EEW=101 ), triglycidyl-p-aminophenol (TGPAP) (EEW=97), and 4- glycidyloxy-N,N-diglycidylaniline (EEW=92), which is available

commercially as Araidite^® Y0510 from Huntsman International LLC (Salt Lake City, Utah, U.S.A.). Examples of tetrafunctional diluents include without limitation, 4,4'-methylenebis(N,N-diglycidylaniline) (EEW=106), pentaerythritol tetraglycidyl ether (EEW=90), and N,N,N'N'tetraglycidyl-4,4'- methylene-bis-benzenamine (EEW= 109), which is commercially available as Araldite MY727 from Huntsman International LLC (Salt Lake City, Utah, U.S.A.). Commercial epoxy resins, such as those described herein (e.g., Insulcast 504), often contain significant quantities of reactive diluents (both mono-epoxy and multi-epoxy functionalities which are believed to have EEW less than 400) as constituents within the bisphenol-based epoxy resin formulation.

In the curable compositions used in the processes described herein, in some embodiments the bisphenol-based epoxy resin is present at about 40 to about 95 wt%, the amine curing agent at about 5 to about 28 wt% and the multifunctional epoxy-reactive diluent at about 0.5 to about 40 wt%, based on the combined weight of bisphenol-based epoxy resin, amine curing agent, and multifunctional epoxy-reactive diluent. In some

embodiments the bisphenol-based epoxy resin is present at about 40 to about 95 wt%, the amine curing agent at about 5 to about 28 wt% and the multifunctional epoxy-reactive diluent at about 0.5 to about 40 wt%, based on the combined weight of the components of the curable composition.

In one embodiment, the curable composition can optionally contain a difunctional (i.e., having two epoxide groups) epoxy diluent compound. The difunctional epoxy has an epoxide equivalent weight (EEW) that can be from about 55 to about 400. The difunctional epoxy, which may be referred to herein as a di-epoxy reactive diluent, includes but is not limited to, diglycidyl ethers. Examples of optional difunctional epoxy reactive diluents include without limitation: 1 ,4-butanediol diglycidyl ether (EEW=101 ), neopentyl glycol diglycidyl ether (EEW=108), and cyclohexane dimethanol diglycidyl ether (EEW=1 14). In some embodiments, the difunctional epoxy- reactive diluent is present between and optionally including any two of the following values: 0, 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, and 40 wt%. In some embodiments, the di-epoxy diluent can be present at less than about 30 wt%; in other embodiments at less than about 20 wt%; and some other embodiments from about 0 to about 10 wt%, based on the combined weight of the components of the composition. The optional difunctional epoxy reactive diluent may be more suited for use in the curable composition than optional mono-functional epoxy reactive diluents. The difunctional epoxy reactive diluent contains 2 epoxide groups that provide a greater potential for crosslinking of the curable composition, and thus can aid in improving the properties of the curable composition.

In another embodiment, it is contemplated that curable compositions that contain particular di-epoxy reactive diluents could exhibit an

improvement to solvent resistance and wear resistance, and therefore the particular di-epoxy reactive diluent could effectively function in the curable composition as a multifunctional epoxy-reactive diluent. These particular di-epoxy reactive diluents should have a relatively high degree of stiffness, i.e., have a resistance to twisting along the molecular backbone (compared to the optional di-epoxy reactive diluents), and may also need to be present in the curable composition at about 10 to about 45 wt%, based on the combined weight of the components in the composition. It is expected that long-chain (> 6 methylene carbons in length) di-epoxy reactive compounds are flexible and would not be able to effectively function as the

multifunctional epoxy-reactive diluent. (See Comparative Example B which demonstrated that a curable composition absent the multi-functional reactive diluent, but containing a difunctional epoxy reactive diluent at about 5 wt% had enhanced wear resistance, but not solvent resistance.) An example of a di-epoxy reactive diluent that may be capable of functioning as the multi-reactive diluent is neopentyl glycol diglycidyl ether.

Optionally, the curable composition used in the processes described herein can contain a mono-epoxy reactive diluent. Mono-epoxy reactive diluents are epoxy compounds having one epoxide group, and thus are monofunctional epoxy-reactive diluents. Examples of mono-epoxy reactive diluents include without limitation: p-tertiarybutyl phenyl glycidyl ether, cresyl glycidyl ether, 2-ethylhexyl glycidyl ether, and C₈-C-|₄ glycidyl ethers. The monofunctional epoxy-reactive diluent has an epoxide equivalent weight (EEW) that can be less than about 275. In some embodiments, the EEW of the monofunctional epoxy-reactive diluent is less than about 225. In other embodiments, the EEW of the monofunctional epoxy-reactive diluent is less than about 200. The monofunctional epoxy-reactive diluent having an EEW less than about 275 can be used from about 0 to about 30 wt% (based on the combined weight of bisphenol-based epoxy resin, amine curing agent, and multifunctional epoxy-reactive diluent) provided that the solvent resistance of the epoxy curable composition is not impaired. In some embodiments, the monofunctional epoxy-reactive diluent having an EEW less than about 275 is present between and optionally including any two of the following values: 0, 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, and 30 wt%. In some embodiments, the mono-epoxy diluent can be present at less than about 30 wt%; and in other embodiments at less than about 20 wt%, based on the combined weight of the components of the composition. In some other embodiments, the monofunctional epoxy-reactive diluent can be used from about 0 to about 10 wt%, based on the combined weight of the components of the composition.

The curable composition may also include one or more liquid compounds that aid in rendering the composition suitable to conduct the applying step of the present method. The curable composition may be dispersed or dissolved or suspended in the liquid compounds, so that the curable composition can be applied by the desired means and can form a layer of the composition on the supporting substrate. The liquid compound is not limited and can include organic compounds and aqueous

compounds. The one or more liquid compounds may be a solvent, that is a substance which is capable of dissolving another substance (i.e., resin) to form a uniform mixture. The liquid compound may be a carrier, such as the reactive diluent, that is capable of dispersing or suspending the material in the composition in solution sufficient to conduct the steps of the present method. The curable composition may include one or more liquid compounds as a solvent and/or carrier for the curable composition. In some embodiments, the liquid compound is one or more reactive diluent. In some other embodiments, the liquid compound is the one or more organic solvents. In most embodiments, the liquid solvent or solvent mixture is removed from the composition by evaporation after application of the composition to the supporting substrate, or most typically, during the curing step.

The curable composition includes or consists essentially of at least the bisphenol-based epoxy resin, the amine curing agent selected from a primary or secondary amine and having an amine hydrogen equivalent weight of less than or equal to 200 g/equivalent, and the multifunctional epoxy-reactive diluent having an epoxide equivalent weight between 55 and 400. In most embodiments, the curable composition can include or can consist essentially of the bisphenol-based epoxy resin, the amine curing agent, and the multifunctional epoxy-reactive diluent that is selected from a tri-epoxy reactive diluent, and a tetra-epoxy reactive diluent. In some embodiments, the curable composition can include or can consist essentially of the bisphenol-based epoxy resin, the amine curing agent, and the multifunctional epoxy-reactive diluent that is selected from a di-epoxy reactive diluent having a high degree of stiffness (i.e., resistance to twisting along its molecular backbone), a tri-epoxy reactive diluent, and a tetra- epoxy reactive diluent. In some embodiments, the curable composition can include or can consist essentially of the bisphenol-based epoxy resin, the amine curing agent, the multifunctional epoxy-reactive diluent, and the pigment and/or filler. In other embodiments, the curable composition includes or consists essentially of the bisphenol-based epoxy resin, the amine curing agent, the multifunctional epoxy-reactive diluent, and the catalyst. In other embodiments, the curable composition can include or can consist essentially of the bisphenol-based epoxy resin, the amine curing agent, the multifunctional epoxy-reactive diluent, and the

nanoparticles. In yet other embodiments, the curable composition can include or can consist essentially of the bisphenol-based epoxy resin, the amine curing agent, the multifunctional epoxy-reactive diluent, the difunctional epoxy reactive diluent the monofunctional epoxy reactive diluent, and the pigment and/or filler. In still other embodiments, the curable composition can include or can consist essentially of the bisphenol- based epoxy resin, the amine curing agent, an additional epoxy resin, and the multifunctional epoxy-reactive diluent. In other embodiments, the curable composition can include or can consist essentially of the bisphenol- based epoxy resin, the amine curing agent, the multifunctional epoxy- reactive diluent, the difunctional epoxy reactive diluent, the monofunctional epoxy reactive diluent, the fillers, the pigments, and the nanoparticles.

In one embodiment, the curable compositions include the bisphenol- based epoxy resin present at about 45 to about 95 wt%, the amine curing agent at about 5 to about 25 wt%, and the multifunctional epoxy-reactive diluent at about 0.5 to about 30 wt%, based on the combined weight of the components of the curable composition. In some embodiments, the curable compositions include the bisphenol-based epoxy resin present at about 50 to about 90 wt%, the amine curing agent at about 5 to about 20 wt%, the multifunctional epoxy-reactive diluent at about 0.5 to about 20 wt%, and the nanoparticles at about 1 to about 25% based on the combined weight of the components of the curable composition. In some other embodiments, the curable compositions include the bisphenol-based epoxy resin present at about 50 to about 90 wt%, the amine curing agent at about 5 to about 20 wt%, the multifunctional epoxy-reactive diluent at about 0.5 to about 40 wt%, the monofunctional epoxy reactive diluent at about 0 to about 30 wt%, and the nanoparticles at about 1 to about 25% based on the combined weight of the components in the composition. In other embodiments, the curable compositions include the bisphenol-based epoxy resin present at about 50 to about 90 wt%, the amine curing agent at about 5 to about 20 wt%, the multifunctional epoxy-reactive diluent at about 0.5 to 40 wt%, the catalyst at about 0 to about 10 wt%, and the nanoparticles at about 1 to about 30 wt%, based on the combined weight of the components in the composition. In other embodiments, the curable compositions include the bisphenol-based epoxy resin present at about 50 to about 90 wt%, the amine curing agent at about 5 to about 20 wt%, the multifunctional epoxy-reactive diluent at about 0.5 to about 40 wt%, the filler at about 0 to about 20 wt%, pigments at about 0 to about 25 wt%, and the nanoparticles at about 1 to about 30 wt%, based on the combined weight of the

components in the composition.

In one embodiment, the curable composition includes the epoxy resin based on bisphenol A having a molecular weight of about 310 to about 6000 g/mol; the amine curing agent is an aliphatic amine,

cycloaliphatic amine, aromatic amine, or arylyl amine; and the

multifunctional epoxy-reactive diluent is selected from a di-epoxy reactive diluent, a tri-epoxy reactive diluent, or a tetra-epoxy reactive diluent, having an epoxy equivalent weight of 55 to 400.

In one embodiment, the curable composition further includes a blend of epoxy resins based on bisphenol A having a molecular weight of about 310 to about 6000 g/mol. In one embodiment, the curable

composition includes the epoxy resin based on bisphenol F having a molecular weight of about 298 to about 6000 g/mol; the amine curing agent is an aliphatic amine, cycloaliphatic amine, aromatic amine, or arylyl amine; and the multifunctional epoxy-reactive diluent that is a tri-epoxy reactive diluent or tetra-epoxy reactive diluent. In one embodiment, the curable composition further includes a blend of epoxy resins based on bisphenol F having a molecular weight of about 298 to about 6000 g/mol. In one embodiment, the curable composition includes the bisphenol-based epoxy resin having a molecular weight of about 298 to about 6000 g/mol; the

amine curing agent is triethylenetetramine, diethylenetriamine,

tetraethylenepentamine, or a cycloaliphatic amine; and the multifunctional epoxy-reactive diluent is 1 ,1 ,1 -trimethylolpropane triglycidyl ether, and

triglycidyl-p-aminophenol, 4,4'-methylenebis(N,N-diglycidylaniline), or

pentaerythritol tetraglycidyl ether. In one embodiment, the above curable compositions further include up to about 50 wt% nanoparticles, based upon the combined weight of the components of the curable composition. In

another embodiment, the above curable compositions further include up to about 10 wt% catalyst, based upon the combined weight of the components of the curable composition. In another embodiment, the above curable

compositions further include up to about 40 wt% of the difunctional epoxy- reactive diluent, based upon the combined weight of the components of the curable composition. In another embodiment, the above curable

compositions further include up to about 30 wt% of the monofunctional

epoxy-reactive diluent, based upon the combined weight of the components of the curable composition. In still another embodiment the above curable compositions further include up to about 25 wt% of a pigment, based upon the combined weight of the components of the curable composition. In yet other embodiments, the above curable compositions further include an

additional epoxy resin that is an epoxy novolac resin, where the bisphenol- based epoxy resin is present in the curable composition at least 50 wt%, based on the total of the epoxy resins. C. Solvent-free epoxy novolac/bisphenol-based epoxy resin

compositions with mono- and multifunctional reactive diluents

In a further embodiment, the curable composition is a solvent-free composition comprising i) an epoxy novolac resin having a softening point less than about 60 °C, ii) a bisphenol-A epoxy resin or a bisphenol-F epoxy resin having a softening point less than about 60 °C, iii) a monofunctional reactive diluent, iv) a multifunctional reactive diluent, and v) a stoichiometric amount of a multifunctional amine curing agent, wherein i) and ii) together are at least about 70 wt% of i), ii), iii), and iv) together; the ratio of i) to ii) is about 1 :3 to about 3:1 by weight; and the ratio of iii) to iv) is about 4:1 to about 1 :4 by weight. Surprisingly, the particular curable composition has good coatability without the need for a solvent as the composition can be applied easily to form a layer on a supporting substrate that is relatively uniform and needs only minimal grinding or polishing. The particular curable composition has good curability as the composition can be cured reasonably rapidly in less than 6 hours, and in most embodiments in less than 4 hours. Good coatability and curability allow for a high quality coating of the epoxy resin to be produced within strict tolerances needed for gravure engraving and printing with minimal after treatments. Additionally, since the high quality coating and curing can be rapidly accomplished, the claimed process is economical for time and cost such that it can compete with conventional metal-plating processes for gravure printing cylinders.

In most embodiments the curable composition includes an epoxy novolac resin that has a softening point less than about 60 °C. Epoxy novolac resins are described above with reference to embodiment A; examples include the resins according to formulas (I), (II), and (III). The application of the solvent-free curable composition to a supporting substrate at room temperature is aided by the epoxy novolac resin having a softening point less than about 60 °C. In embodiments in which the curable composition includes more than one epoxy novolac resin, it is not necessary that all the epoxy novolac resins have a softening point than about 60 °C. In other embodiments in which the curable composition includes an epoxy novolac resin in relatively small amount (compared to the bisphenol epoxy resin) the epoxy novolac resin can have a softening point equal to or greater than about 60 °C, and application of the composition may still be able to occur at room temperature. In other embodiments, if the curable composition is applied to the supporting substrate at a temperature above room temperature, the epoxy novolac resin can have a higher softening point, that is, a softening point equal to or greater than about 60 °C.

The epoxy novolac resins used in the processes described herein are characterized by an epoxide equivalent weight (EEW) between and optionally including any two of the following values: 156, 160, 170, 180, 190, 200, 210, 220,

230, 240, 250, 260, 270, 280, 290, and 300 g/equiv. In one embodiment, the

EEW is between about 156 and about 230 g/equiv. If the epoxide equivalent weight is above about 300, it is contemplated that the chemical or solvent resistance of the composition of the epoxy novolac resin would deteriorate. In some embodiments, the curable composition comprises epoxy- novolac resins having a molecular weight between and optionally including

312 and 1200 any two of the following values: 312, 400, 600, 800, 1000,

1200, 1500, 1800, 2100, 2400, 2700, and 3000. In one embodiment the

molecular weight of the epoxy novolac resin is between about 312 and

about 1000. In most embodiments, the epoxy novolac resins have an

average functionality greater than 2.0, which leads to higher cross-linking density upon curing. Epoxy novolac resins with higher crosslinking density have good toughness and chemical resistance, which leads to suitable

wear and impact resistance and solvent resistance for use as a printing

form compared to other epoxy resin compositions, such as DGEBPA of

formula (IV) and DGEBPF of formula (V).

The discussion with regard to embodiment A concerning the distribution of oligomers of epoxy resins of formulas (I) through (III) each contain a distribution of oligomers, i.e., "-mer" units, such that n represents an average number of -mer units in the resin, applies here as well and is incorporated by reference. For the bisphenol A and bisphenol F resins represented by formulas (IV) and (V) respectively, n can be between and optionally include any two of the following values: 0, 0.5, 1 .0, 1 .5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 1 1 .0, 1 1 .5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16.0, and 16.5.

In most embodiments the curable composition includes a bisphenol-A epoxy resin that has a softening point less than about 60 °C or a bisphenol-F epoxy resin that has a softening point less than about 60 °C. The application of the solvent-free curable composition to a supporting substrate at room

temperature is aided by bisphenol-A or bisphenol-F epoxy resin having a softening point less than about 60 °C. In embodiments in which the curable composition includes more than one bisphenol epoxy resin, it is not necessary that all the bisphenol epoxy resins have a softening point than about 60°C. In other embodiments in which the curable composition includes a bisphenol epoxy resin in relatively small amount (compared to the epoxy novolac resin) the bisphenol epoxy resin can have a softening point equal to or greater than about 60 °C, and application of the composition may still be able to occur at room temperature. In other embodiments, if the curable composition is applied to the supporting substrate at a temperature above room temperature, the bisphenol-A or bisphenol-F can have a higher softening point, that is, a softening point equal to or greater than about 60 °C.

Curing agents used in the processes described herein are primary amines and secondary amines, and thus are referred to herein as amine curing agents. Amine curing agents are primarily suitable for the present process because they increase the cure speed of the curable composition compared to other possible curing agents such as acids and/or anhydrides, and are capable of curing the composition at moderate temperatures, e.g., room temperature to about 150 °C. In most embodiments, amine curing

agents are characterized by an amine hydrogen equivalent weight (AHEW) of less than or equal to about 40 g/equivalent. In one embodiment, the

amine hydrogen equivalent weight is between and optionally including 20 and 40 g/equivalent. In some embodiments, the amine hydrogen

equivalent weight is between and optionally including any two of the

following values: 20, 25, 30, 35, and 40 g/equivalent. The amine curing

agent can also be provided in the form of an adduct of an amine curing

agent with one or more of the epoxy resins or reactive diluents of the

instant invention. The amine curing agent having amine hydrogen

equivalent weight of less than or equal to about 40 g/equivalents aids in

providing a cured layer of the composition with a sufficient degree of

solvent resistance such that print quality can be maintained for print run

lengths of at least 100,000 impressions or more. Solvent resistance of the resin-based layer on the printing form is particularly important since many inks used in gravure printing are solvent-based inks, and attack by solvents of the resin-based layer can cause the layer to swell and thereby

detrimentally impact print quality and run length. Amine curing agents

having an amine hydrogen equivalent weight (AHEW) of less than or equal to about 40 g/equivalent provides the curable composition with the broadest and most consistent solvent resistance to solvent-based inks. In some

embodiments, the curable composition can include amine curing agents

having an amine hydrogen equivalent weight greater than 40 g/equivalents, as the composition may still be useful in other aspects yet provide suitable solvent resistance to most solvent-based inks for gravure printing. The amine curing agent is multifunctional; that is, it has 2 or more amino functionalities per molecule. The amines can be aliphatic amines

(e.g., triethylenetetramine (TETA), diethylenetriamine (DETA),

tetraethylenepentamine, 1 ,2-diaminocyclohexane); aromatic amines (e.g., m-phenylenediamine); or arylyl amines, which have cycloaliphatic or

aromatic moieties from which the amine functional groups are separated by methylene groups -CH₂- (e.g., m-xylylene diamine and 1 ,3-bis(aminomethyl cyclohexane)). An extensive list of commercial amine curing agents is given in Table 15 on p. 730 of "Epoxy Resins," by Ha. Q. Pham and

Maurice J. Marks in Encyclopedia of Polymer Science and Technology, 4th ed., Jacqueline I. Kroschwitz, exec, ed., John Wiley & Sons, Hoboken, NJ, 2004, pp. 678-804. Mixtures of amine curing agents can also be used.

Ethyleneamine curing agents such as DETA or TETA, or adducts

containing them, are particularly preferred, though certain other amines also work either by themselves or in combination with other amines,

depending on the specific epoxy formulation. In some embodiments the curing agent is triethylenetetramine, diethylenetriamine, or

tetraethylenepentamine. A "stoichiometric" quantity of amine curing agent is used; that is to say, the ratio of the curing agent amine hydrogens to the resin epoxy functionalities in the curable composition is from about 0.95:1 .0 to about 1 .1 :1 .0, on a mole-to-mole basis and can be between and

optionally include any two of the following values: 0.95:1 .0, 0.96:1 .0,

0.97:1 .0, 0.98:1 .0, 0.99:1 .0, 1 .0:1 .0, and 1 .1 :1 .0 to about 1 .1 : .0.

A mixture of diluents is used to achieve desired viscosity of the

curable composition while maintaining desired properties of the cured

composition. Specifically, the curable composition used in the processes described herein contains a mixture of a monofunctional epoxy reactive diluent and a multifunctional epoxy reactive diluent. The epoxy reactive diluents are low viscosity epoxies that are used to modify the viscosity and other properties, such as, wetting and impregnation, of the epoxy

composition that is to be cured. The viscosity of the epoxy reactive diluents is typically less than about 300 cP at room temperature. Examples of monofunctional diluents include without limitation: p-tertiary-butyl phenyl glycidyl ether, cresyl glycidyl ether, 2-ethylhexyl glycidyl ether, C₈- Ci₄ glycidyl ether. Examples of difunctional diluents include, without limitation, 1 ,4-butanediol diglycidyl ether; neopentyl glycol diglycidyl ether; and cyclohexane dimethanol diglycidyl ether. An example of a trifunctional diluent is trimethylol propane triglycidyl ether.

In most embodiments in the mixture of diluents, the ratio of monofunctional reactive diluent to multifunctional reactive diluent is from about 4:1 to about 1 :4 by weight. Particularly in embodiments if the total amount of diluents in the mixture of diluents is equal to or greater than about 10 wt% (based on the combined weight of the epoxy/diluent component), the ratio of monofunctional reactive diluent to multifunctional reactive diluent is from about 4:1 to about 1 :4 by weight. If the total amount of diluents in the mixture of diluents is less than about 10 wt% (based on the combined weight of the epoxy/diluent component), the weight ratio of monofunctional diluent to multifunctional diluent is not particularly limited to about 4:1 to 1 :4. The ratio of the monofunctional reactive diluent to the multifunctional reactive diluent can be between and optionally include any two of the following values: 1 .0:4.0, 1 .2: 4.0, 1 .4: 4.0, 1 .6:4.0, 1 .8:4.0,

2.0:4.0, 2.2:4.0, 2.4:4.0, 2.6:4.0, 2.8:4.0, 3.0:4.0, 3.2:4.0, 3.4:4.0, 3.6:4.0, 3.8:4.0, 4.0:4.0, 4.0:3.8, 4.0:3.6, 4.0:3.4, 4.0:3.2, 4.0:3.0, 4.0:2.8, 4.0:2.6, 4.0:2.4, 4.0:2.2, 4.0:2.0, 4.0:1 .8, 4.0:1 .6, 4.0:1 .4, 4.0:1 .2, and 4.0:1 .0. The mixture of diluents is used in large enough amounts that the curable composition is coatable on a cylinder, having a viscosity in the range of about 200 to about 3500 cP at the coating temperature; and yet in small enough amounts that the chemical resistance and other properties of the cured composition are not impaired. In one embodiment, the mixture of diluents is present in the curable composition in an amount from about 4 to about 30 wt%, based on the weight of the epoxy/diluent component (i.e., the combined weight of epoxy resins (i.e., epoxy novolac resin, and bisphenol-A epoxy resin or bisphenol-F epoxy resin) and diluents (i.e., the monofunctional reactive diluent and the multifunctional reactive diluent), and can be between and optionally include any two of the following values: 4, 5, 7.5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, and 30 wt%.

In the curable compositions used in the processes described herein, the epoxy/diluent component is present at about 75 to about 95 wt% based on the combined weight of epoxy/diluent component and amine curing agent. In an embodiment, the epoxy/diluent component content can be between and optionally include any two of the following values: 75, 80, 85, 90, and 95 wt% based on the combined weight of epoxy/diluent component and amine curing agent. In the epoxy/diluent component, the epoxy novolac resin is present at about 17 to about 70 wt%, the bisphenol A epoxy resin or bisphenol F epoxy resin is present at about 17 to about 70 wt%, the monofunctional diluent is present at about 1 to about 24 wt%, and the multifunctional diluent is present at about 1 to about 24 wt%, based on the weight of the epoxy/diluent component. In an embodiment, the epoxy novolac resin content can be between and optionally include any two of the following values: 17, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70 wt% based on the weight of the epoxy/diluent component. In an embodiment, the bisphenol-A epoxy resin or bisphenol-F epoxy resin content can be between and optionally include any two of the following values: 17, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70 wt% based on the weight of the epoxy/diluent component. In an embodiment, the monofunctional diluent content can be between and optionally include any two of the following values: 1 , 3, 5, 7, 10, 12, 14, 16, 18, 20, 22, and 24 wt% based on the weight of the epoxy/diluent component. In an embodiment, the

multifunctional diluent content can be between and optionally include any two of the following values: 1 , 3, 5, 7, 10, 12, 14, 16, 18, 20, 22, and 24 wt% based on the weight of the epoxy/diluent component.

The curable composition includes at least the epoxy/diluent component and the multifunctional amine curing agent as described above. In some embodiments, the curable composition can include or can consist essentially of the epoxy/diluent component, the amine curing agent and a catalyst. In yet other embodiments, the curable composition can include or can consist essentially of the epoxy/diluent component, the amine curing agent, the catalyst, and nanoparticles (as described below). In some embodiments, the curable compositions include the epoxy resin/diluent component present at about 40 to 90 wt%, the amine curing agent at about 4 to 25 wt%, the mixture of diluents at about 3 to 30 wt%, and the nanoparticles at about 0 to 30% based on the combined weight of epoxy resins, amine curing agent, mixture of diluents, and nanoparticles. In some embodiments, the epoxy/diluent component is present at a wt% between and optionally including any two of the following values: 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, and 90 wt% based on the combined weight of epoxy resins, amine curing agent, mixture of diluents, and nanoparticles. In some embodiments, the amine curing agent is present at a wt% between and optionally including any two of the following values: 4, 7, 10, 12, 15, 17, 20, 22, and 25 wt% based on the combined weight of epoxy resins, amine curing agent, mixture of diluents, and nanoparticles. In some

embodiments, the mixture of diluents is present at a wt% between and optionally including any two of the following values: 3, 7, 10, 12, 15, 17, 20, 22, 25, 27, and 30 wt% based on the combined weight of epoxy resins, amine curing agent, mixture of diluents, and nanoparticles. In some embodiments, the nanoparticles can be present at a wt% between and optionally including any two of the following values: 0, 4, 7, 10, 12, 15, 17, 20, 22, 25, 27, and 30 wt% based on the combined weight of epoxy resins, amine curing agent, mixture of diluents, and nanoparticles.

In one embodiment, the curable composition used for the printing form can include or can consist essentially of a) an epoxy novolac resin having an epoxide equivalent weight of about 172 to about 179

g/equivalent; b) a bisphenol F epoxy resin having an epoxide equivalent weight of 163 to 172 g/equivalent; c) diethylenetriamine; d) a mixture of p- tert-butylphenyl glycidyl ether plus 1 ,4-butanediol diglycidyl ether in a weight ratio of about 3:1 , respectively; wherein the weight ratio of the epoxy novolac resin to the bisphenol F epoxy resin is about 6:7 (normalized ratio of 1 :1 .17); and mixture d) of p-tert-butylphenyl glycidyl ether plus 1 ,4- butanediol diglycidyl ether, is about 15 to 20 wt% of the epoxy/diluent component a) + b) + d). In an embodiment, the curable composition further includes up to about 30 wt% nanoparticles (as described below). ; in another embodiment, up to 20 wt% nanoparticles, such as alumina nanoparticles or silica nanoparticles. Optional ingredients in embodiments A, B, and C

Optionally, the curable compositions of embodiments A, B, and C can include up to about 50 wt% nanoparticles, i.e., particles having at least one dimension less than about 500 nm. In an embodiment, the value of the at least one dimension is between and optionally including any two of the following values: 1 , 10, 50, 75, 100, 200, 300, 400, and 500 nm. In an embodiment, the value is between about 1 and about 100 nm. The nanoparticles may be present in an amount between and optionally including any two of the following values: 0, 0.1 , 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27, 28, 29, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, and 50 wt% based on the combined weight of the components of the curable composition. The nanoparticles can provide hardness and modulus of the composition, which may lead to increased wear resistance and improved engravability of a cured layer of the composition. In one embodiment, the nanoparticles are present in an amount between about 0.1 and about 50 wt%; in some embodiments, the nanoparticles are present in an amount between about 0.1 and 30 wt%; in other embodiments, the nanoparticles are present in an amount between about 0.1 to about 20 wt%; in some embodiments, the nanoparticles are present in an amount between about 0.1 to about 10 wt%; and in some other embodiments, the nanoparticles are present in an amount between about 10 to 20 wt%, based on the combined weight of the components of the composition.

Optionally, the nanoparticles may be coated or subjected to a surface treatment with, for example, an organic onium species, to improve interaction between the nanoparticles and the resin.

Examples of suitable nanoparticles include, but are not limited to: aluminum oxides (e.g., alumina); silica (e.g., colloidal silica and fumed silica); zinc oxide; zirconium oxide; titanium oxide; magnesium oxides; tungsten oxides; tungsten carbides; silicon carbide; titanium carbide;

boron nitrides; molybdenum disulfide; clays, e.g., laponite, bentonite, montmorillonite, hectorite, kaolinite, dickite, nacrite, halloysite, saponite, nontronite, beidellite, volhonskoite, sauconite, magadite, medmonite, kenyaite, vermiculite, serpentines, attapulgite, kulkeite, alletite, sepiolite, allophane, imogolite; graphene; graphene oxide; carbon nanotubes;

carbon black; carbon filaments; and mixtures thereof.

Optionally, the curable composition may include fillers as a solid lubricant to impart improved wear characteristics of the cured composition layer. Fillers include particles having at least one dimension greater than about 500 nm, and generally between about 500 nm to about 5 micron. Examples of fillers, include but are not limited to, aluminum oxides (e.g., alumina); silica (e.g., colloidal silica and fumed silica); zinc oxide;

zirconium oxide; titanium oxide; magnesium oxides; tungsten carbides; silicon carbide; titanium carbide; boron nitrides; molybdenum disulfide; graphites; poly(tetrafluoroethylene); and mixtures thereof.

Optionally, the curable composition may include resin modifiers. Resin modifiers may be used to increase crosslinking density and/or stabilize the crosslinked network, which can provide improved end-use characteristics, such as increased solvent resistance, wear resistance, and/or improve engravability of the cured layer of the composition. Resin modifiers include, but are not limited to, acrylate monoesters of alcohols and polyols; acrylate polyesters of alcohols and polyols; methacrylate monoesters of alcohols and polyols; and methacrylate polyesters of alcohols and polyols; where the alcohols and the polyols suitable include, but are not limited to, alkanols, alkylene glycols, trimethylol propane, ethoxylated trimethylol propane, pentaerythritol, and polyacrylol oligomers. A combination of monofunctional and multifunctional acrylates or methacrylates may be used. The curable composition may include resin modifiers at up to about 10 wt%, based on the combined weight of the components of the curable composition.

The curable composition optionally may include additives, such as flexibilizing components, non-reactive diluents (such as, dibutyl phthalate), surfactants, dispersants, dyes, pigments, and wetting and leveling additives for coating uniformity and appearance. Examples of suitable surfactants include, but are not limited to, fluorinated surfactants. Epoxy may be flexibilized as described in Epoxy Resins Chemistry and

Technology, Clayton A. May editor, 2^nd edition, Marcel Dekker, Inc, NY. Suitable flexibilizing components include, but are not limited to,

polyamides, carboxylated polymers, fatty diamines, polyglycol diepoxides, polyurethane amines, and polyetherurethane amines. In some

embodiments the flexibilizing component included in the curable composition is polyurethane amine or polyetherurethane amine, such as for example, Aradur® 70BD, which is available from Huntsman

International LLC. The flexibilizing component can be present at from 0 to about 15 wt%, based on the combined weight of the components of the curable composition. In some embodiments, the flexibilizing component is present in an amount between and optionally including any two of the following values: 0, 1 , 2, 3, 4, 5, 7, 9, 1 1 , 13, and 15 wt%, based on the combined weight of the components of the curable composition.

Examples of wetting and leveling additives, which may be referred to as leveling additive, for coating uniformity and appearance are acrylic polymers, poly(dimethylsiloxane), methylalkylpolysiloxane copolymers, fluoro-modified acrylates, and fluoro-modified polyacrylate copolymers. The leveling additive can be present at from 0 to about 10 wt%, based on the combined weight of the components of the curable composition. In some embodiments, the leveling additive can be present from about 0.1 to 5 wt%, based on the combined weight of the components of the curable composition. In some embodiments, the leveling additive is present in an amount between and optionally including any two of the following values: 0, 0.1 , 1 , 2, 3, 4, 5, 7, 9, and 10 wt%, based on the combined weight of the components of the curable composition

A dispersant can be added in order to disperse the nanoparticles and/or fillers and/or pigments and avoid flocculation and agglomeration. Dispersants suitable for use are not limited, provided that the dispersant can uniformly distribute the nanoparticles and/or fillers in the layer, and is sufficiently compatible with the resin and other components in the curable composition to the extent that a suitable layer is produced. A wide range of dispersants are commercially available. One embodiment of suitable dispersants are the A-B dispersants generally described in "Use of A-B Block Polymers as Dispersants For Non-aqueous Coating Systems" by H. K. Jakubauskas, Journal of Coating Technology, Vol. 58; Number 736; pages 71 -82. Useful A-B dispersants are disclosed in U.S. Patent Nos. 3,684,771 ; 3,788,996; 4,070,388; and 4,032,698. Other useful dispersants are disclosed in U.S. Patent 6,472,463. Examples of dispersants include acrylate polymers with basic, acidic and non-ionic groups that can stabilize pigment, particulate and/or filler dispersions. The dispersant can be present in an amount of about 0.1 to 10% by weight, based on the combined weight of the components in the curable composition.

Process of Preparing

The process of preparing a printing form includes applying the curable composition onto a supporting substrate, to form a layer of the curable composition. The composition may be applied to the supporting substrate by various means that are well known in the art. The method of the present invention is particularly applicable to the application of the curable composition as a liquid to a supporting substrate that can be used as a printing roll or print cylinder in a rotogravure printing process. For application to the supporting substrate, the curable composition has a viscosity of about 400 to about 6000 cP. In some embodiments for application to the supporting substrate, the curable composition has a viscosity less than about 5000 cP. In other embodiments for application to the supporting substrate, the curable composition has a viscosity less than about 3000 cP. The supporting substrate can also include a planar support sheet that is typically composed of a metal. The supporting substrate, e.g., printing roll or print cylinder, may be made of metal (e.g., aluminum or steel), ceramic, or a polymeric material.

Prior to the application of the curable composition to the supporting substrate, an exterior surface of the supporting substrate that receives the composition may be pretreated by means of a plasma or corona pretreatment to clean and/or alter the surface (i.e., lower the surface tension) of the supporting substrate for improved film or coating wetout and bonding strengths. Additionally or alternatively, a primer solution, such as an epoxy primer solution, may be applied to the exterior surface of the supporting substrate to improve adhesion of the curable (and cured) composition to the supporting substrate.

The curable composition can be applied to the supporting substrate by any suitable method, including but not limited to, injection, pouring, liquid casting, jetting, immersion, spraying, vapor deposition, and coating. Examples of suitable methods of coating include spin coating, dip coating, slot coating, roller coating, extrusion coating, brush coating, ring coating, powder coating, and blade (e.g., doctor blade) coating, all as known in the art and described in, e.g., British Patent No. 1 ,544,748. In one

embodiment the curable composition is applied by spraying the curable composition onto the surface of the supporting substrate, such as the printing roll or cylinder. Spraying can be accomplished through the use of a nozzle by techniques known in the art. In another embodiment, the curable composition is applied to the exterior surface of the supporting substrate by brush coating in a manner similar to that described in U. S. Patent 4,007,680. In most embodiments, the curable composition is applied so as to form a continuous or seamless layer on a cylindrically- shaped supporting substrate, so as to provide a continuous print surface for the printing form (after curing and engraving).

The process of the present invention includes heating the exterior surface of the supporting substrate prior to application of the resin composition, which can be referred to herein as preheating of the substrate. The exterior surface of the supporting substrate, is preheated to a surface temperature that is greater than 40^QC and less than about 80^QC prior to application of the curable composition. In some

embodiments, the surface temperature prior to application of the curable composition is between and optionally including any two of the following values: 43^QC, 45^QC, 50^QC, 55^QC, 60^QC, 65^QC, 70^QC, 75^QC, and 80^QC. In some embodiments, the exterior surface can be preheated to a

temperature in the range of greater than 40 °C and less than about 80 °C, prior application of the resin, and maintained at that temperature or at another temperature within the range. In other embodiments, the exterior surface can be preheated to a temperature in the range of greater than 40 °C and less than about 80 °C, prior to application of the resin

composition, and the exterior surface continues to be heated but within the stated range during application. The supporting substrate can be heated by any means capable of attaining the desired exterior surface temperature, including conduction, convection, radiation, and

combinations thereof. In one embodiment, the exterior surface of the supporting substrate is preheated with infrared heating devices. In other embodiments, an electric heating blanket can be used to preheat the exterior surface of the supporting substrate.

The curable composition, as applied to the surface of the

supporting substrate, forms a layer that has a thickness between about 2 to about 300 mils (50.8 to 7620 μιτι). Optionally the thickness of the curable composition layer includes any two of the following thicknesses: 2, 4, 8, 12, 16, 20, 50, 100, 150, 200, 250, and 300 mils (50.8, 102, 203, 305, 406, 508, 1270, 2540, 3810, 5080, 6350, and 7620 μιτι).

The process of preparing a printing form includes curing the layer at one or more temperatures in the range of room temperature to about 250 °C. After the curable composition is applied to the supporting substrate, the layer of the composition is cured to harden on the

supporting substrate, so that the layer is capable of being engraved.

Hardening of the resin composition occurs by crosslinking of polymer chains of the epoxy novolac resin brought about by the reactive

components in the composition, such as the amine curing agent, optional catalyst, and optional reactive diluent, with reactive groups in the resin. Curing can be performed at ambient temperature. Although methods of curing epoxy resins include exposure to ultraviolet radiation and gelation at room temperature, for most embodiments of the present process curing includes heating the layer of the composition. Curing can be accelerated by heating the layer of the curable composition at one or more

temperatures in a range from above room temperature (i.e., ambient temperature) to about 250 °C. The curable compositions described herein are cured thermally (i.e., by heating) in less than about 6 hours. In some embodiments, the layer of the curable composition is cured thermally in less than 4 hours; in some other embodiments, the layer of the curable composition is cured thermally in about 1 hour to about 2 hours. In yet other embodiments, the layer of the curable composition is cured thermally in about 1 hour or less. Times and temperatures will depend on the specific curable composition and are readily determined by one skilled in the art. Curing at temperatures up to 250 °C also aids in driving out solvent from the curing resin layer, if solvent is present in the curable resin composition. More specifically, the temperature is in a range between and optionally including any two of the following values: 16, 30, 50, 70, 90, 1 10, 130, 150, 170, 190, 210, 230, and 250^0. Curing can be carried out at one temperature, or at two temperatures sequentially in the range, for example, 1 hour at 100°C and then 4 hours at 160°C. In an embodiment, the layer of the composition is cured by heating at about 100°C for 2 hours. In another embodiment, the layer of the composition is cured by heating at about 100 °C for 1 hour and then about 150 to 160 °C for about another 1 hour. One suitable method to determine if the layer of the curable composition is sufficiently cured is by conducting model studies of the composition based on end-use performance characteristics such as adhesion, wear resistance, and solvent resistance.

The cured layer of the curable composition (after application to the surface of the supporting substrate and cured) has a thickness that is from about 2 to about 300 mils (50.8 to 7620 μιτι). The thickness of the cured layer is between and optionally including any two of the following thicknesses: 2, 4, 8, 12, 16, 20, 50, 100, 150, 200, 250, and 300 mils (50.8, 102, 203, 305, 406, 508, 1270, 2540, 3810, 5080, 6350, and 7620 μιτι). Optionally, the cured layer can be ground and polished to desired thickness, cylindricity, and/or smoothness, prior to engraving as disclosed in U.S. Patent 5,694,852. The smoothness of the cured layer can be reported as Rz value. In most embodiments, the smoothness of the cured layer has Rz value less than about 100 microinches (2.54 μιη); and, in other embodiments, the Rz value is less than about 80 microinches (2.03 μηι).

The process of preparing a printing form includes engraving at least one cell into the cured layer of the composition on the supporting substrate. After the curable composition is applied to the substrate and cured, engraving of the cured composition layer removes the hardened composition in depth to form a plurality of individual cells in the layer for carrying ink which transfers, in whole or part, during gravure printing of the desired image. In another embodiment, engraving of cells forms recesses or recessed areas in the layer, and outermost surface of the layer carries ink which transfers, in whole or part, during relief printing of the desired image. The engraving of the plurality of cells in the cured layer on the supporting substrate provides a printing form or, equivalently, an image carrier, having a printing surface that is capable of reproducing the desired image by printing onto a substrate. The engraving may be accomplished by any of various engraving methods known in the art. Examples include, but are not limited to, electromechanical engraving (e.g., with a diamond stylus) and laser engraving. These engraving methods may be part of an electronic engraving system. In one embodiment, engraving is carried out using a diamond stylus cutting tool. In another embodiment, direct laser non-contact engraving is used for the creation of the cells. Examples of suitable lasers include, but are not limited to, C0₂ lasers, YAG lasers (based on yttrium aluminum garnet crystals), and diode lasers. The present process of preparing the printing form having a cured layer of the epoxy novolac composition is particularly advantageous in that the cured layer can be engraved using conventional engraving equipment at standard or substantially standard conditions that are used to engrave copper layer for conventional gravure cylinders.

One or more pigments may be added to the curable composition in order to enhance its laser engravability. The pigment may be present in the laser engravable composition in an amount of from about 1 wt% to about 25 wt%; and in one embodiment from about 3 wt% to about 20 wt%, based on the combined weight of the components of the curable composition. In some embodiments, the pigment is present in an amount between and optionally including any two of the following values: 0, 1 , 3, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 25 wt%, based on the combined weight of the components of the curable composition. Examples of such pigments include, but are not limited to, black silicic pigments (containing carbon-encapsulated silica particles), and carbon black.

Optionally, the engraved layer can be further treated by polishing to remove burrs, and/or by applying a coating of a fluoropolymeric

composition over the engraved layer (i.e., overcoat) to improve the ink releasability of the printing form. In some embodiments, the printing form is in the shape of a cylinder or plate. In some embodiments, the supporting substrate is metal or a polymer. In most embodiments, the printing form is suited for gravure printing. Gravure printing is a method of printing in which the printing form prints from an image area, where the image area is depressed and consists of small recessed cells (or wells) to contain the ink or printing material, and the non-image area is the surface of the form. In most embodiments, the printing surface is the cured layer of the epoxy novolac composition that is engraved to form an ink receptive cell surface suitable to carry ink for gravure printing. It is also contemplated that in some embodiments the printing form may be suited for relief printing, including use as a letterpress printing form. Relief printing is a method of printing in which the printing form prints from an image area, where the image area of the printing form is raised and the non-image area is depressed. For printing forms useful for relief printing, the engraving of at least one cell creates the non-image area that would not carry ink for printing the desired image, and the surface raised above the cell is the image area that carries ink for printing the desired image. In some embodiments the printing surface is topmost surface of raised elements of a relief surface suitable for carrying ink for relief printing.

In a further embodiment, a printing form is provided that a printing form that is prepared according to the process described above.

Preheating the substrate so that its surface temperature is greater than 40 °C and less than about 80 °C results in improved surface characteristics of the cured layer, such as reduction of amine blush, elimination of bubbles, and lessened surface roughness, while not accelerating the curing rate or evaporation of volatile components to an undesirable degree. The cured layer of the printing exhibits a level of hardness that produces well-defined print cell structures when engraved yet resists wear during printing from contact with the doctor blade and the printed substrate, and abrasive particles that may be in the ink. The cured layer of the present composition can be engraved to have cell density at resolution at least up to 200 lines per inch, with minimal or no break out of wall between adjacent cells. And yet, the cured layer of the present composition is capable of printing for relatively long print runs, i.e., at least 100,000 impressions and preferably at least 200,000 or more, with wear reduction of the cell area of no more than 10%, and in most embodiments wear of less than 5%. Furthermore, the cured layer of the present composition has excellent resistance to solvents used in printing inks and cleaning solutions, such that high quality printing can be maintained for the relatively long print runs. Since the present printing form having a cured layer of the present curable composition exhibits the necessary combination of characteristics necessary to perform gravure printing, the present printing form provides significant advance over other non-metal resin-based gravure printing forms of the prior art.

In another embodiment, a process is provided for printing with the printing form that was prepared as described above. The process for printing further includes applying an ink, typically a solvent ink, to the at least one cell that has been engraved into the cured layer of the prepared printing form, and transferring ink from the cell to a printable substrate. Suitable solvent inks include those based on organic solvents such as, without limitation, alcohols, hydrocarbons (e.g., toluene, heptane) acetates (e.g., ethyl acetate), and ketones (e.g., methyl ethyl ketone). Aqueous inks are also suitable for printing with the present printing form.

EXAMPLES

The present invention is further defined in the following Examples. It should be understood that these Examples, while indicating preferred embodiments of the invention, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions.

The meaning of abbreviations is as follows: "APS" means average particle size; "AHEW" means amine hydrogen equivalent weight; "cm" means centimeter(s); "cP" means centipoise, a viscosity equal to 0.001 pascal -second; "DETA" means diethylene triamine; "DGEBPA " means diglycidyl ether of bisphenol A; "DGEBPF " means diglycidyl ether of bisphenol F; "EEW" means epoxide equivalent weight; "equiv" means equivalent(s); "g" means gram(s); "h" means hour(s); "L" means liter(s); "Ipi" means lines per inch; "MEK" means methyl ethyl ketone; "mil" means 0.001 inch, a length equal to 0.0254 millimeters; "mg" means milligram(s); "ml_" means milliliter(s); "mm" means millimeter(s); "mPa-s" means millipascal-second(s); "millitorr" means 0.001 mm of mercury, a pressure equal to 0.13332237 pascal; "nm" means nanometer(s); "oz" means ounce(s); "P" means poise; "TETA" means triethylenetetraamine; "wt%" means weight percent(age); "μϊη" means microinch(es); and "μηΐ' means micrometer(s).

Unless otherwise indicated, the epoxide equivalent weight (EEW) cited for each of the epoxy materials is the value reported by the manufacturer, based upon each manufacturer's standard test method. Methods

Solvent Resistance

Epoxy novolac resin compositions were prepared and coated on Mylar® or Kapton® sheet support using a 10 mil (254 μιη) drawdown bar to form a polymeric film (i.e., layer) on the support. The polymeric film samples were cured as indicated in the Example, and peeled from the Mylar® or Kapton® support. Film fragments (50-100 mg) of the polymeric film samples were weighed and placed into jars containing 10-20 ml_ of specified solvent. The film fragments were immersed for one week (i.e., 7 day), then blotted dry and weighed. The wt% change of the film fragments is calculated as:

100 ^* [weight(7day) - weight(initial)] / weight(initial).

The composition had good solvent resistance if, after 7 days in the solvent, the wt% change of the fragments was less than 10%.

Engravability

Epoxy novolac resin compositions were prepared, coated onto a cylinder, cured and engraved as indicated in the Example. A cured resin sample was deemed to have good engravability if engraving of the sample to create cells at 170 to 200 lines per inch (Ipi) could be achieved with less than 15 % breakout. Engraved image resolution of 170 to 200 lines per inch corresponds to a cell width of about 1 15 to 140 μιη and a width of a cell wall of less than 25 μιη. A breakout is defined herein as a defect in which a wall adjacent to two cells has a break in it, thereby producing a connection between the two cells. The engraved area was examined

microscopically, and greater than or equal to 30 to 50 cells were examined to determine the breakout percentage.

Wear

A wear test was established to mimic the gravure printing process.

For the wear test, the cylinder, which has a cured layer of the composition, was rotated, was partially immersed in the ink tray, and was contacting a steel doctor blade once per revolution. The ink used for the test was

either Multiprint White ink (from Del Val Ink and Color Inc.), or HT Color

STR New White ink (from Hi-Tech Color Inc. (Odenton, MD, U.S.A.) . The cell area of the engraved cylinder was measured before and after 300,000 revolutions (unless otherwise noted) to monitor the extent of wear with a

Hirox KH-7700 microscope. Wear is reported as a percent reduction in cell area.

Print Quality

Print quality was determined for a long print run, i.e., greater than

100,000 impressions, and is reported in terms of number of impressions until the print quality (considering characteristics such as sharpness,

smearing, etc.) was visually unacceptable.

Surface roughness

Surface roughness of cured coatings was measured using the Pocket Surf PS1 from Mahr. This instrument measures the parameter Rz in microinches. Rz is the average of peak-to-valley heights of the surface measured on five equal travel lengths. An Rz value of 20 μίη or less has been found to be suitable for engraving and printing.

Observation of bubbles

Bubbles were viewed and photographed using a ProScope digital microscope by Bodelin Technologies. For some examples, the photographs were analysed to yield an approximate range of bubble diameters and an approximate percent of the photograph area covered by bubbles.

Materials Araldite^® DY-P (monoglycidylether of p-tert-butylphenol, CAS # 3101 -60-8), referred to herein as DY-P, was obtained from Huntsman Advanced Materials (The Woodlands, Texas, U.S.A.). EEW is 222-244 g/equiv. Its viscosity at 25 °C is 20-28 cP.

Araldite® DY-D (diglycidylether of 1 ,4-butanediol, CAS # 2425-79-8), referred to herein as DY-D, was obtained from Huntsman Advanced

Materials. EEW is 1 18-125 g/equiv. Its viscosity at 25 °C is 15-20 cP.

Araldite® DY-N (aliphatic diglycidyl ether based on neopentylglycol), referred to herein as DY-N, was obtained from Huntsman Advanced

Materials. EEW is 125-145 g/equiv. Its viscosity at 25 °C is10-18 cP.

Araldite® GY-285 (diglycidylether of bisphenol F, CAS # 2095-03-6), referred to herein as GY-285, was obtained from Huntsman Advanced Materials. EEW is 163-172 g/equiv. Its viscosity at 25 °C is 2000-3000 cP.

D.E.N.™ 431 (semi-solid epoxy novolac resin, CAS # 28064-14-4), was obtained from The Dow Chemical Company (Midland, Michigan, U.S.A.). Properties of this resin are EEW of 172-179 g/equiv, viscosity of 1 100-1700 mPa-s at 51 .7°C, and multi-epoxy functionality (± 2.8).

Insulcast 504 clear (bisphenol A epoxy), Insulcast 504 BLK

(bisphenol A epoxy with carbon black) and Insulcure 9 curing agent

(tetraethylenepentamine, CAS No. 1 12-57-2) were obtained from ITW Polymer Technologies (Glenview, Illinois, U.S.A.).

EPON™ Resin 828 (diglycidyl ether of Bisphenol A, CAS # 25068- 38-6, "DGEBPA") was obtained from Hexion Specialty Chemicals, Inc. (now Momentive Specialty Chemicals, Inc., part of Momentive

Performance Materials Holdings, Inc., Columbus, Ohio, U.S.A.).

Properties of this resin are EEW of 185-192 g/equiv, viscosity of 1 10-150 P.

EPON™ Resin 862 (diglycidyl ether of bisphenol F, "DGEBPF") was obtained from Hexion Specialty Chemicals, Inc. (now Momentive Specialty Chemicals, Inc., part of Momentive Performance Materials

Holdings, Inc., Columbus, Ohio, U.S.A.). Properties of this resin are EEW of 165-173 g/equiv, viscosity of 24-45 P.

Resiflow® flow additives were obtained from Estron Chemical, Inc. (Calvert City, Kentucky, U.S.A.) Resiflow® L-37 is a reactive polyacrylate flow additive.

Resiflow® LH-240 is a reactive, hydroxyl functional polyacrylate flow additive.

Resiflow®-S is a 50 wt% solution of an acrylic polymer in Aromatic Solvent 100 (aromatic hydrocarbons, CAS No. 64742-95-6) flow additive.

Epikure™ curing agents were obtained from Hexion Specialty Chemicals, lnc.(now Momentive Specialty Chemicals, Inc., part of

Momentive Performance Materials Holdings, Inc., Columbus, Ohio, U.S.A.).

Epikure™ 3010 is a polyamidoamine based on tall oil fatty acid and polyamines. Epikure™ 3072 is a modified polyethylene polyamine adduct. Epikure™ 3140 is a low viscosity polyamide based on dimerized fatty acid and polyamines.

Epikure™ 3175 is a modified polyamide.

Epikure™ 3274 is an aliphatic amine.

Araldite® ECN epoxy cresol novolac resin and Aradur® curing agents were obtained from Huntsman International LLC (Salt Lake City, Utah, U.S.A.).

Araldite® ECN 1273 epoxy cresol novolac resin are EEW 217-233 g/equivalent, melt viscosity of 400-800 cP at 150 °C, and 4.8 functionality.

Aradur® 355 is a cycloaliphatic amine.

Aradur® 70BD is a polyetherurethane amine.

NanoTek® nano-sized aluminum oxide, referred to as

"nanoalumina," was obtained from Alfa Aesar (catalog no.44932, Ward Hill, Massachusetts, U.S.A.). The NanoTek® nanoalumina is 99.5% AI₂O₃, Alfa Aesar 44932, 40-50 nm APS Powder, surface area of 32-40 m²/g.

The dispersant used was an acrylic graft copolymer with non-ionic functional groups.

ORGANOSILICASOL™ colloidal silica grade MEK-ST_L was obtained from Nissan Chemical America Corporation (Houston, Texas, USA). This is colloidal silica mono-dispersed in methyl ethyl ketone.

Silica is present at 30-31 wt% and the silica particle size is 40-50 nm. Tungsten (VI) oxide nanopowder was obtained from Sigma-Aldrich Corporation (St. Louis, Missouri, USA). The tungsten (VI) oxide has a particle size of <100 nm (by transmission electron microscopy).

ΒΥΚΘ-320, a solution of a polyether modified

methylalkylpolysiloxane copolymer that is used as a leveling additive with defoaming action, was obtained from BYK Additives and Instruments, a member of The ALTANA Group (Wesel, Germany).

ΒΥΚΘ-388, a solution of fluoro-modified polyacrylate-copolymer as a leveling additive was obtained from BYK Additives and Instruments, a member of The ALTANA Group (Wesel, Germany).

Butyl glycidyl ether (CAS # 2426-08-6) was obtained from Sigma- Aldrich Co. LLC (St. Louis, Missouri, U.S.A.). EEW is 130 g/equiv. ;

viscosity at 25 °C is less than 3 cP.

Diethylene triamine (CAS # 1 1 1 -40-0), referred to herein as DETA, was obtained from Sigma-Aldrich Co. LLC (St. Louis, Missouri, U.S.A.). AHEW is 20.6.

Triethylene tetramine (CAS # 1 12-24-3), referred to herein as TETA, was obtained from MP Biomedicals LLC (Solon, Ohio, U.S.A.). AHEW is approximately 27.

2,4,6-Tris(dimethylaminomethyl)phenol (CAS # 90-72-2), referred to herein as DMP-30, was obtained from Sigma-Aldrich Co. LLC.

Exact amounts of epoxy/diluent components and amine curing agents are specified in the examples. Unless otherwise indicated, the formulations in the examples have a ratio of amine hydrogen to epoxy functionality in the range of approximately 0.95 to 1 .10.

EXAMPLE 1

This example demonstrates that a solvent free epoxy formulation coated on a cylinder preheated to 60 °C results in a good coating with minimal bubble formation.

An epoxy composition was prepared by blending Epon 828 bisphenol A epoxy (20g), DY-N diluent (3.5g) and butyl glycidyl ether (2.0g).

The epoxy mixture was combined with TETA amine (3.6g) and DMP-30

(0.6g) and stirred at room temperature for 10 minutes. This mixture was used to coat a cylinder pre-heated to 60 °C. The cylinder was coated using a brush technique to deliver material to obtain the desired coating thickness (-10 mils, -254 μιτι). The coating was then cured at 100 °C for 1 hr and 160°C for 1 hr, and allowed to cool to ambient temperature gradually. The composition coated and cured to form a glossy smooth coating, with minimal bubbles on the cured coating.

COMPARATIVE EXAMPLE A

This example demonstrates that a solvent free epoxy formulation coated on a cylinder preheated to 35 °C results in a poor coating with numerous bubbles in the coating.

The same epoxy composition as in Example 1 was used to coat a cylinder pre-heated to 35 °C. The cylinder was coated using a brush technique to deliver material to obtain the desired coating thickness (-10 mils, -254 μιτι). The coating was then cured at 100°C for 1 hr and 160 C for 1 hr, and allowed to cool to ambient temperature gradually. The composition coated and cured to give a coating with numerous small bubbles throughout the coating.

EXAMPLE 2

An epoxy composition was prepared by blending Epon 828 (20g) and butyl glycidyl ether (3.5g). The epoxy mixture was combined with TETA amine (3.3g) and DMP-30 (0.6g) and stirred at room temperature for 10 minutes. This mixture was used to coat a cylinder pre-heated to 60 °C. The cylinder was coated using a brush technique to deliver material to obtain the desired coating thickness (-10 mils, -254 μιτι). The coating was then cured at 100 °C for 1 hr and 160 C for 1 hr, and allowed to cool to ambient temperature gradually. The composition coated and cured to a hard coating, with minimal bubbles on the cured polymer.

COMPARATIVE EXAMPLE B

The same epoxy composition as in Example 2 was used to coat a cylinder pre-heated to 35 °C. The cylinder was coated using a brush technique to deliver material to obtain the desired coating thickness (-10 mils, -254 μιτι). The coating was then cured at 100°C for 1 hr, 160 C for 1 hr, and allowed to cool to ambient temperature gradually. The composition coated and cured to give a coating with numerous small bubbles throughout the coating.

EXAMPLES 3. 4, AND 5; COMPARATIVE EXAMPLES C AND D

These examples demonstrate that an epoxy resin having an amine curing agent does not form bubbles upon coating under high humidity conditions provided that the substrate is preheated to greater than 60 °C prior to application of the resin composition.

28.74 g (13.1 wt% of the epoxy/diluent component) DY-P diluent, 9.67 g (4.4 wt%) DY-D diluent, 83.56 g (38.1 wt%) DEN 431 epoxy novolac, and 97.38 g (44.4 wt%) GY-285 bisphenol F epoxy were combined in a flask. The epoxy mixture was placed in a 50 °C water bath and stirred until completely uniform. The mixture was degassed under vacuum (200-1000 millitorr) to remove gas bubbles.

The following experiment was performed in a laboratory at a temperature of 22 °C. and a relative humidity in the range of 70 to 72%. A portion of the batch of epoxy mixture was combined with DETA amine in the ratio of 100 parts epoxy to 12.3 parts amine, which is equivalent to a stoichiometric ratio of amine hydrogen to epoxy of approximately 1 .03 to 1 . The mixture was stirred for approximately 10 minutes. The resulting coating solution was introduced into a metal syringe. It was then coated onto a section of a metal cylinder that had been preheated to 51 °C. The cylinder was coated using a brush technique with a combined syringe pump and translator mechanism to deliver material to obtain the desired coating thickness (6-10 mils, 152-254 μιη). The cylinder temperature was raised to 55 °C. and another section of the cylinder was coated. A second epoxy amine mixture was prepared in the same way as the first and used to coat two more sections of the cylinder at cylinder temperatures of 60 and 65 °C. Finally, a third epoxy amine mixture was prepared in the same way as the first two and used to coat another section of the cylinder at a cylinder temperature of 70 °C.

After holding for 20 minutes at 70 °C, the coating was then cured at 100°C for 1 hr and then 150°C for 1 hr and allowed to cool to ambient 5 temperature gradually.

To evaluate the quality of the five sections of cured coating on the cylinder, each was viewed with a Proscope microscope and the Rz smoothness of each was measured. The results are summarized in Table 1 .

10 Table 1

At substrate temperatures of 51 and 55 °C, a high density of bubbles and a rough coating surface were observed. At a substrate temperature of 60 °C, only very few small bubbles were observed, and the coating surface 15 has an acceptable Rz smoothness. At substrate temperatures of 65 and 70 °C, no bubbles were observed and the Rz smoothness was excellent.

EXAMPLE 6

This example demonstrates that a printing form prepared according to the instant invention exhibits good long-run print trial performance.

20 The same formulation as in Examples 4 and 5 was coated onto a metal cylinder that had been preheated to 66-70 °C to obtain a coating 8.65- 9.65 mils (220-240 μιτι) thick. The cylinder was coated using a brush technique with a combined syringe pump and translator mechanism to deliver material to obtain the desired coating thickness. The coating was then cured at 100°C for 1 hr and 150°C for 1 hr and allowed to cool to ambient temperature gradually. The composition coated and cured to form an excellent cured layer on the cylinder with no bubbles.

The cured layer on the cylinder was then machined and polished. The layer was then electromechanically engraved on an Ohio R-7100 series engraver at a cell rate of 3200 Hz with a 120 degree diamond stylus at various angles and Ipi densities according to CMYK specifications. The engraved cylinder was then used for printing with toluene-based cyan ink on C1 S paper. Initial print quality was excellent. After about 440,000 revolutions (220,000 meters), the print quality was as good as the initial print.

EXAMPLE 7

This example presents an epoxy formulation coated on a 26 inch cylinder preheated to 70-80 °C and a good coating was obtained. The cured coating was not easily scratched by finger nail along the length of the cylinder.

This example presents a solvent resistant (low-swelling) epoxy novolac with about 1 .8 wt% nanoalumina that exhibits good engravability and wear. A metal cylinder was heated to 70-80 °C and an epoxy composition is applied on the cylinder. The epoxy composition was comprised of D.E.N.™ 431 epoxy novolac, triethylenetetramine, 2,4,6- tris(dimethylaminomethyl)phenol, flow additive, dispersant, aluminum oxide (NanoTek®), xylene, and butanol. The cylinder was coated using a brush technique to deliver material to obtain the desired coating thickness (-10 mils, -254 μιτι). After the desired coating thickness of about 8 mil (203 μιτι) had been achieved, the cylinder and the coating were heated to 100°C to harden the coating. The cured layer was resistant to finger nail scratching throughout the length of the cylinder.

COMPARATIVE EXAMPLE E

This example presents an epoxy formulation coated on a cylinder preheated to about 40 °C and a good coating was obtained. The cured coating was scratched more easily on a side of the cylinder where the coating was first applied.

A metal cylinder having 26 inch length, was heated to 41 °C and the epoxy composition of Example 3 was used to coat the cylinder. The cylinder was coated using a brush technique to deliver material to obtain the desired coating thickness (-10 mils, -254 μιτι). After the desired coating thickness of about 8 mil (203 μιτι) had been achieved, the cylinder and the coating were cured as in Example 3. The cured layer was not resistant to scratching by the fingernail on a 2 inch section at the start end of the cylinder, where the coating was first applied.

Claims

CLAIMS What is claimed is:

1 . A process for preparing a printing form comprising:

a) providing a curable composition including

i) at least one epoxy resin and

ii) an amine curing agent selected from primary amines and secondary amines;

b) applying the curable composition onto a preheated supporting substrate, thereby forming a layer;

c) curing the layer at one or more temperatures in a range of room temperature to about 250 °C; and

d) engraving at least one cell in the layer resulting from step c), wherein the viscosity of the curable composition as applied to the

substrate is about 400 to about 6000 cP, and the substrate is heated to a surface temperature greater than 40 °C and less than about 80 °C prior to step b).

2. The process of Claim 1 wherein the epoxy resin is selected from epoxy novolac resins, bisphenol-based epoxy resins, and combinations thereof.

3. The process of Claim 1 wherein the epoxy resin is an epoxy novolac resin having an epoxide equivalent weight of 156 to 300 g/equivalent; and the amine curing agent has an amine equivalent weight of less than or equal to 60 g/equivalent.

4. The process of Claim 1 wherein the epoxy resin is a bisphenol-based epoxy resin; the amine curing agent has an amine hydrogen equivalent weight of less than or equal to 200 g/equivalent; and the curable composition further comprises at least one multi-epoxy reactive diluent;

wherein the multi-epoxy reactive diluent has an epoxide equivalent weight between 55 and 400 and is present at 0.5 to 40 wt% based on the combined weight of the epoxy resin, the amine curing agent, and the multi-epoxy reactive diluent.

5. The process of Claim 1 wherein the at least one epoxy resin is an epoxy novolac resin plus a bisphenol-A epoxy resin or bisphenol-F epoxy resin; the amine curing agent is a stoichiometric amount of a multifunctional amine curing agent; the curable composition further comprises a

monofunctional reactive diluent and a multifunctional reactive diluent;

wherein the epoxy resins together are at least 70 % of the total weight of the epoxy resins, the monofunctional reactive diluent, and the

multifunctional reactive diluent; and the ratio of the epoxy novolac resin to the bisphenol-A epoxy resin or bisphenol-F epoxy resin is 1 :3 to 3:1 by weight.

6. The process of Claim 1 wherein the applying step is performed by spin coating, dip coating, slot coating, roller coating, extrusion coating, brush coating, ring coating, doctor blade coating.

7. The process of Claim 1 further comprising after the curing step, grinding the layer to have a thickness from 50.8 to 7620 μιτι.

8. The process of Claim 1 wherein engraving is selected from

electromechanical engraving or laser engraving.

9. The process of Claim 1 further comprising after the engraving step conducting an additional step selected from polishing an exterior surface of the layer, or applying a coating of a fluoropolymeric composition on the layer.

10. The process of Claim 1 wherein the curable composition further comprises up to 50 wt% nanoparticles, based on the combined weight of the components of the curable composition, having at least one dimension less than 100 nm.

1 1 . The process of Claim 1 wherein the supporting substrate is in the form of a cylinder or sheet.

12. The process of Claim 1 wherein the supporting substrate is a gravure printing cylinder that is free of copper and chrome.

13. The process of Claim 1 wherein the surface of the supporting substrate is preheated by infrared radiation energy.

14. The process of Claim 1 wherein the surface of the supporting substrate is preheated by radiation, conduction, or convection.

15. The process of Claim 1 wherein the curable composition further comprises one or more leveling additives selected from acrylic polymers, poly(dimethylsiloxane), methylalkylpolysiloxane copolymers, fluoro-modified acrylates, and fluoro-modified polyacrylates.

16. A process for printing with a printing form comprising: a) preparing the printing form having at least one engraved cell in a cured layer of the curable composition according to the process of Claim 1 ; b) applying a solvent ink to the at least one cell; and c) transferring ink from the cell to a printable substrate, wherein the cured layer swells < 10% based on weight of the layer.

17. A printing form comprising a continuous print surface adjacent a supporting substrate, wherein the continuous print surface is a cured epoxy composition prepared from a curable composition comprising:

i) at least one epoxy resin and

ii) an amine curing agent selected from primary amines and secondary amines; and wherein the printing form is prepared according to the process of Claim 1 .

18. The printing form of Claim 17 wherein the curable composition further comprises up to 50 wt% nanoparticles, based on the combined weight of the components of the curable composition.

19. The printing form of Claim 17 wherein the printing form is in the shape of a cylinder or plate.

20. The printing form of Claim 17 wherein the substrate is metal or a polymer.

21 . The printing form of Claim 17 wherein the substrate is a gravure printing cylinder free of copper and chrome.

22. The printing form of Claim 17 wherein the substrate is preheated with infrared radiation energy.

23. The printing form of Claim 17 wherein the curable composition further comprises up to 10 wt% catalyst, based on the combined weight of the components of the curable composition.

24. The printing form of Claim 17 wherein the curable composition further comprises a leveling additive at up to 10 wt%, based on the combined weight of the components of the curable composition.