阅读说明：本技术 湿套印方法 (Wet overprinting method ) 是由 J·G·蒂森 K·U·高德尔 J·M·帕里斯 于 2018-03-06 设计创作，主要内容包括：本发明提供了用于将多个油墨和/或涂料层施加在基材上的方法。油墨和/或涂料层的至少一种包含一种或多种光引发剂,并且油墨和/或涂料层的至少一种不包含任何光引发剂。在某些实施方案中,所有的油墨和/或涂料层都被湿套印,并且整个印刷构造是通过在施加所有的油墨和/或涂料层之后暴露于UV辐射而固化的。在某些实施方案中,本发明的湿套印方法可以用于制备叠层。(The present invention provides a method for applying a plurality of ink and/or coating layers on a substrate. At least one of the ink and/or coating layers comprises one or more photoinitiators and at least one of the ink and/or coating layers does not comprise any photoinitiators. In certain embodiments, all of the ink and/or coating layers are wet overprinted and the entire printed construction is cured by exposure to UV radiation after all of the ink and/or coating layers are applied. In certain embodiments, the wet overprinting process of the present invention can be used to prepare laminates.)

1. A wet overprinting method for preparing a printed article comprising:

a) providing a substrate;

b) applying one or more energy curable ink or coating layers (a) onto said substrate, wherein said ink or coating layers (a) comprise one or more photoinitiators;

c) applying one or more energy curable ink or coating layers (B) onto said substrate, wherein said ink or coating layers (B) do not comprise a photoinitiator; and

d) at the end of the printing run, by curing all the coating and/or ink layers;

wherein the one or more energy curable ink or coating layers may be a primer coating; and

wherein the one or more energy curable ink or coating layers may be a top coat;

with the proviso that at least one of said ink or coating layers comprises one or more photoinitiators.

2. The method of claim 1, wherein at least one UV curable ink or coating layer comprises one or more of an acrylate, a grafted polystyrene, a vinyl compound, a cyclic lactam, or an acrylamide.

3. The method of claim 2, wherein the acrylate is an oligomeric acrylate.

4. A method according to any one of claims 1 to 3, wherein the one or more ink or coating layers are hybrid inks or coatings comprising an energy curable material and a non-energy curable material.

5. The method of claim 4, wherein at least one of the hybrid ink or coating layers comprises greater than or equal to 40 wt% energy curable material.

6. The method of any one of claims 4 or 5, wherein the hybrid ink or coating layer is dried prior to wet overprinting.

7. The method of any one of claims 4 or 6, further comprising applying heat after applying all of the ink or coating layers.

8. The process of any one of claims 1 to 7, wherein the one or more ink or coating layers (B) further comprise a small amount of a photoinitiator, in an amount of less than 10 wt%.

9. The method of any one of claims 1 to 8, wherein the one or more ink or coating layers further comprise an amine synergist.

10. The method of claim 9, wherein at least one of said amine synergists is a tertiary amine synergist.

11. The method of claim 10, wherein the tertiary amine is selected from the group consisting of UV curable materials and non-UV curable materials, and combinations thereof.

12. The method of claim 10 or 11, wherein the tertiary amine is 2-ethylhexyl-4-dimethylaminobenzoate.

13. The process of claim 10 or 11, wherein the tertiary amine is an adduct of diethylamine and tripropylene glycol diacrylate.

14. The method of any one of claims 1 to 13, wherein the photoinitiator is selected from the group consisting of type I photoinitiators, type II photoinitiators, polymeric photoinitiators, cationic photoinitiators, and combinations thereof.

15. The method of any one of claims 1 to 14, wherein the one or more photoinitiators are selected from the group consisting of ethyl michael ketone; methyl benzoyl formate; 2-oxo-phenyl acetate; phosphine oxides, phenyl bis (2,4, 6-trimethylbenzoyl), acyl phosphine oxides; 2-benzyl-2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl ] -1-butanone; 2- (4-methylbenzyl) -2- (dimethylamino) -1- (4-morpholinophenyl) butan-1-one; isopropylthioxanthone, 2, 4-diethylthioxanthone; 2-chlorothiaxanthen-9-one; 1-chloro-4-propoxythioxanthone; diphenyl (2,4, 6-trimethylbenzoyl) -phosphine oxide; ethyl (2,4, 6-trimethylbenzoyl) phenylphosphinate; and polymeric derivatives thereof.

16. The method of any one of claims 1 to 15, wherein the one or more ink or coating layers further comprise one or more materials selected from pigments, release additives, flow additives, and defoamers.

17. The method of any one of claims 1 to 16, comprising a topcoat that does not comprise ingredients prepared from bisphenol a.

18. The method of any one of claims 1 to 17, wherein the at least one ink or coating layer further comprises a non-reactive resin.

19. The method of claim 18, wherein the non-reactive resin is selected from the group consisting of modified polystyrenes, modified polyesters, ketone resins, and combinations thereof.

20. The method of claim 1, wherein only the first underlayer ink and coating layers comprise photoinitiator and all subsequent layers do not comprise photoinitiator.

21. The method of claim 1, wherein only the first underlying ink and coating layers comprise photoinitiator and none of the underlying layers comprise photoinitiator.

22. The method of claim 1 wherein 3 or more ink or coating layers are applied and the first lower ink or coating layer and the last lower ink or coating layer both comprise a photoinitiator and none of the intermediate layers comprise a photoinitiator.

23. The method of claim 1, wherein the sequence of layers is a substrate, one or more primers, one or more inks, and one or more topcoats.

24. The method of claim 1, wherein the sequence of layers is a substrate, one or more layers of ink, and one or more layers of topcoat.

25. The method of claim 1, wherein the sequence of layers is a substrate, one or more layers of a primer coating, and one or more layers of an ink.

26. The method of claim 1, wherein the sequence of layers is a substrate, and two or more layers of ink.

27. The method of claim 1, wherein the at least one layer of ink or coating covers the substrate at 100% solids coverage.

28. The method of any one of claims 1 to 27, further comprising one or more ink or coating layers that do not have an energy curable material.

29. The method of claim 28, wherein the ink or coating layer without energy curable material is dried prior to using the wet overprinting method of claim 1.

30. The method of claim 1, wherein the substrate is selected from the group consisting of paper, coated paper, paperboard, metal foil, polymeric film, and combinations thereof.

31. A printed article prepared using the method of any one of claims 1 to 30.

32. The printed article of claim 31, wherein the article is a packaging article.

33. The printed article of claim 31, wherein the article is an electronic product or component.

34. A method of printing a porous substrate comprising:

a) providing a porous substrate;

b) applying an energy curable coating (C);

c) curing said energy curable coating (C);

d) applying one or more energy curable ink or coating layers (a) and/or (B) on top of said cured coating (C);

wherein the one or more energy curable ink or coating layers are energy curable ink or coating layers (B) that do not contain a photoinitiator;

e) applying a UV curable coating layer (a) which is a top coat comprising one or more photoinitiators; and

f) and simultaneously curing the top coat and the underlying ink or coating layer.

35. The method of claim 34, wherein the one or more energy curable ink or coating layers (B) further comprise a minor amount of one or more photoinitiators in an amount of less than 10 wt%.

36. The method of any one of claims 34 or 35, wherein the porous substrate is paper or paperboard.

37. A printed substrate prepared by the method of any one of claims 34 to 37.

38. An article comprising the printed substrate of claim 38.

39. The article of claim 39 which is a publication or packaging article.

40. A wet overprinting method of making a laminated article comprising:

a) providing a first substrate and a second substrate, wherein at least one of said first and second substrates is transparent to UV radiation;

b) applying one or more energy curable ink or coating layers (a) comprising one or more photoinitiators onto at least one of said first substrate or said second substrate;

c) applying one or more energy curable ink or coating layers (B) not comprising a photoinitiator to at least one of said first substrate or said second substrate;

d) laminating said first and said second substrates with a wet surface to a wet surface, or a dry surface to a wet surface; and

e) simultaneously curing said energy curable ink or coating layer through said substrate which is transparent to UV radiation.

41. The method of claim 41, wherein said first and said second substrates are films that are transparent to UV radiation.

42. The method of claim 41, wherein one of said first or said second substrates is a film that is transparent to UV radiation and the other of said first or said second substrates is paper.

43. A method according to any one of claims 41 to 42 wherein the UV curable ink or coating layer (A) is applied to one of the first or second substrates and the UV curable ink or coating layer (B) is applied to the other of the first or second substrates.

44. A method according to any one of claims 41 to 42 wherein the UV curable ink or coating layer (A) and the UV curable ink or coating layer (B) are applied to one of the first substrate or the second substrate and the UV curable ink or coating layer is not applied to the other of the first substrate or the second substrate.

45. A method according to any one of claims 41 to 42 wherein the UV curable ink or coating layer (B) and the UV curable ink or coating (A) are applied to one of the first or second substrates and the UV curable ink or coating (B) is applied to the other of the first or second substrates.

46. A laminated article prepared by the method of any one of claims 41 to 45.

Technical Field

The present invention relates to the printing of multiple layers of inks and/or coatings on a substrate. The present invention specifically relates to a wet overprinting process for printing or applying multiple layers of inks and/or coatings onto a substrate. The invention also relates to the use of the wet overprinting process of the invention to prepare laminated articles.

Background

It is often desirable to print substrates using multiple layers of inks and/or coatings. When energy curable inks and/or coatings are used, each layer is typically cured and then the next layer is overprinted.

Many energy curable inks and/or coatings must contain a photoinitiator in order to be able to cure adequately. However, the use of photoinitiators has disadvantages. For example, photoinitiator residues remaining after curing can impair the solvent resistance of the cured ink or coating by acting as a plasticizer. Furthermore, in packaging articles, such as pharmaceuticals or cosmetics, unreacted photoinitiators and photoinitiator fragments can migrate through the printed substrate and contaminate the product contained therein. Photoinitiators are also expensive.

In an effort to reduce the amount of photoinitiators used in printing energy curable inks and/or coatings, various groups have attempted to prepare "self-initiating" energy curable polymers for use as binders in inks or coatings. To date, despite some attractive developments, none of the proposed solutions is sufficient to achieve the necessary resistance etc. after the required curing of the articles prepared using multiple layers of inks and/or coatings.

CN 105017487 discloses the preparation of siloxane polyurethanes from polyester diols using silane coupling agents and tin catalysts, wherein the tin catalysts generate free radicals under UV radiation and initiate the double bond polymerization reaction. It is not clear how the system described generates free radicals, the mechanism of which may actually be heat.

It has been shown that when electrolytes are 2-hydroxyethyl methacrylate (HEMA), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF) and TiO₂When the particles are activated by UV light, crosslinked systems can be formed (Xinhua Liu, Bin He, HaifengTang)&Qiang Wang, gauge Nanocomposite iongel-based activator exhibits robustperformance, scientific Reports,4:6673 (2014)). HEMA is acrylate, BMIMBF is ionic liquid, and TiO₂Apparently as a source of free radicals. Technically, therefore, TiO₂Acting as a source of free radicals as a photoinitiator.

It has been taught that 1-ethyl-3-methyl-imidazolium chloride ([ EMIM ] Cl), hydroxyethyl methacrylate (HEMA), chitosan and water can dissolve each other and crosslink under UV light (Xinhua Liu, Dongbei Wu, Huanglei Wang and Qigang Wang Self-recapturing Tough gel electrolyte. advanced Materials,26(25): 4370-membered 4375 (2014)). It is said that UV radicals are formed when UV light cleaves [ EMIM ] Cl to form chloride anions. Thus, [ EMIM ] Cl functions as a photoinitiator.

Another example of the claimed Self-priming System is described by Li Dan, Guo Wenxun, Gao Pen and WenAnn ("A Novel Self-initiated Waterborn UV Curable System," petrochemical technology, Volume 42, Issue 4, Pages 435-. The tin chloride catalyzed polymers of tribromoaniline and tribromophenylmaleimide exhibit UV curing properties. The photoinitiator was unknown and did not show presence, but there was no evidence of: the material can do anything but cure itself when exposed to UV.

Self-initiated and UV-cured amphiphilic macromolecular resins are described in CN 101914175. Hydroxy or amino containing coumarins are reacted with isocyanates in a molar ratio of 1:1 and dibutyltin dilaurate is used as catalyst. The product is then acrylated using a variety of monomers in specific ratios and azobisisobutyronitrile is used as an initiator. The resulting polymer cures upon exposure to UV light. The coumarins used include 4-hydroxy, 3-amino, 3-phenyl-7-amino, 7-methyl-4-hydroxy, 4-ethoxy-7-hydroxy, 6, 8-dichloro-7-hydroxy, and 6-amino-3, 4-benzo.

Yuan Hua, Guo Wenxun, and Gao Peng discuss self-initiating UV curing polymers ("Synthesis of aBelf-Initiated UV-curing Polymer," Applied Chemical Industry, Volume 40, Issue7, Pages 1180-. An unsaturated polyester-urea copolymer is produced that cures to good hardness when exposed to UV for 30-60 seconds. The components include propylene glycol, urea, phthalic anhydride, maleic anhydride and sebacic acid. Interestingly, the best curing performance occurs with an acid number of 50 and a urea content of 4% to 5%.

Other examples of Self-Initiating UV Curable Polyester Networks are discussed by GI.Ozturk, M.Zhang, and T.E.Long ("Self-Initiating UV-Curable Polyester Networks," Polymer Preprints (American chemical Society, Division of Polymer Chemistry), Volume 50, Issue 2, Pages 627-628.Journal 2009). The mechanism of formation of an interpenetrating gel network by Michael addition of the fragments after photolysis was examined. (this is also presented in the 2009ACS National Meeting in Washington, DC article).

Desousa and Khudyakov describe UV Curable amide-imide Oligomers ("ultravisible UV-Curable amide Oligomers," Industrial & Engineering Chemistry Research, Volume 45, Issue 19, Pages 6413-. The abstract is attached with the following parts: blends of UV curable oligomers based on the reaction of cyclic dianhydrides with omega-hydroxy substituted acrylates and isophorone diisocyanate (IPDI) were prepared. The cyclic dianhydrides used are benzene-1, 2,4, 5-tetracarboxylic dianhydride (PMDA) and benzophenone-3, 3',4,4' -tetracarboxylic dianhydride (BTDA). Two oligomers are poly (amide-imides). BTDA-based oligomers are reported to be self-initiating (i.e., without the addition of any photoinitiator cured by UV light). This property appears to be due to the presence of phenylpropionyl benzene fragments in the BTDA structure. The oligomers prepared using BTDA can also serve as initiators for other free radical UV light induced curing of acrylate and/or methacrylate oligomers. However, in order to use self-initiating materials in order to cure other materials (which are not sensitive to UV light per se), the materials must be intimately mixed with them in the same material layer.

Mihalic and P.Mills describe deep curing of polymers using Surface Radiation ("deep section Polymerization Initiated by Surface Radiation, Part 1Monomers," RadTechReport, Volume 13, Issue 2, Pages 28-32, Journal 1999). In acrylic systems containing typical photoinitiators, the use of peroxide (thermal) initiators and amine accelerators produces a sufficient thermal effect after brief exposure to surface UV radiation that full cure can occur even in areas where there is no line of sight to UV light. The secondary cure is stated to be non-directional. This is not predictive of the invention since a single layer coating is used, and in the previous examples, there was no layer in which there was no photoinitiator.

US6,245,827 discloses a liquid resin product with good through-cure. This is accomplished by using a cycloaliphatic epoxide, caprolactone, a cationic photoinitiator, and an "accelerator" consisting of a standard free radical type alpha-hydroxy-ketone photoinitiator (specifically Darocur 1173 or Irgacure 184) and a typical organic peroxide thermal free radical generator (Lupersol). It is claimed that the alpha-hydroxy-ketone reduces the salt fragment of the decomposed cationic photoinitiator, thereby generating the heat of reaction required to decompose the organic peroxide. This is a conventional dual cure mechanism.

For self-initiated UV curable polymersThe search of (2) has also become an academic endeavor ("Advances Inlight-induced polymerizations: I. Shadow current in free radioactive polymerizations, II. Experimental and modeling initiators of photoinitiators for effective polymerizations with LEDs." Copy 2012Hajime kit. university of Iowa. this characterization is available at Iowa research Online:http://ir.uiowa.edu/etd/4866)。

US 7,214,725 describes a series of acrylate materials which may also participate in the Michael addition reaction. Although this patent is often cited, it should be noted that it is not specifically stated to work without photoinitiators under UV exposure, but only at significantly lower levels of photoinitiators.

The resin technology of US 7,214,725 is based on the synthetic patents US 5,945,489 and US6,025,410 (same authors and priority date). These patents purportedly disclose liquid oligomers containing unsaturates that can be crosslinked using ultraviolet light without the addition of expensive photoinitiators. However, curing for the proof of concept protocol was achieved in both cases using 1.0% Irgacure 500 (CAS 118690-08-07, a mixture of itself with 1-benzoylcyclohexanol (also known as Irgacure 184CAS 947-19-3) and benzophenone CAS 119-61-9). Irgacure 500 is the requisite photoinitiator. The technique is neither truly self-initiating nor is it photoinitiator-free in any way.

Thus, there remains a need for more efficient, cost-effective methods of printing multiple layers of inks and/or coatings on a substrate.

Summary of The Invention

The present invention provides a method for printing multiple layers of inks and/or coatings on a substrate. The present invention discloses a wet overprinting process using primarily energy curable inks and coatings. The method is applicable to paste ink/coating processes (e.g. offset printing) as well as liquid ink/coating processes (e.g. flexographic printing). The invention also provides a method of printing a porous substrate wherein the pores are sealed with a cured primer coating and then the wet overprinting method of the invention is carried out.

In one aspect, the present invention provides a wet overprinting method for preparing a printed article, comprising:

a) providing a substrate;

b) applying one or more energy curable ink or coating layers (a) comprising one or more photoinitiators onto said substrate;

c) applying one or more energy curable ink or coating layers (B) onto said substrate, which do not comprise a photoinitiator; and

d) at the end of the printing run, simultaneously curing all the layers of paint and/or ink;

wherein one or more of the energy curable ink or coating layers may be a primer coating; and

wherein one or more of the energy curable ink or coating layers may be a top coat;

with the proviso that at least one of said ink or coating layers comprises one or more photoinitiators.

In another aspect, the present invention provides a method of printing a porous substrate comprising:

a) providing a porous substrate;

b) applying an energy curable coating (C);

c) curing said energy curable coating (C);

d) applying one or more energy curable ink or coating layers (a) and/or (B) on top of said cured coating (C);

(i) wherein one or more of said energy curable ink or coating layers is an energy curable ink or coating layer (B) that does not contain a photoinitiator;

e) applying a UV curable coating layer (a) which is a top coat comprising one or more photoinitiators; and

f) and simultaneously curing the top coat and the underlying ink or paint layer.

In another aspect, the present invention provides a wet overprinting method for making a laminated article, comprising:

a) providing a first substrate and a second substrate, wherein at least one of the first or second substrates is transparent to UV radiation;

b) applying one or more energy curable ink or coating layers (a) comprising one or more photoinitiators on at least one of said first substrate or said second substrate;

c) applying one or more energy curable inks or coating layers (B) that do not include a photoinitiator on at least one of the first substrate or the second substrate;

d) laminating the wet surfaces of said first and said second substrates to a wet surface, or laminating the dry surface of said first or said second substrate to a wet surface; and

e) simultaneously curing said energy curable ink or coating layer through said substrate which is transparent to UV radiation.

In certain embodiments, the present invention provides a substrate comprising a multilayer ink and/or coating printed according to the methods of the present invention.

In other embodiments, the present invention provides articles comprising substrates prepared by the methods of the present invention.

Detailed Description

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

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

The present invention provides improved methods of printing substrates and articles using multiple layers of inks and/or coatings. A wet overprinting process for printing is disclosed. The process of the present invention is particularly suitable for energy curable inks and/or coatings. The present invention also provides a process for preparing a laminated substrate by wet overprinting an ink and/or coating layer on the surface of each substrate in contact with the other substrate.

The method is equally applicable to paste-like paint/ink processes (e.g. offset printing) as it is to liquid ink/paint processes (e.g. flexographic printing). In paste inks, wet trapping can be accomplished by measuring and controlling "tack". This Method is described in ASTM Standard D4361 ("Standard Method for applying Tack of printing inks and Vehicles by a Three-Roller Tack meter") and other similar documents known to those of ordinary skill in the art. In the case of liquids, in particular flexographic inks/coatings, wet trapping can be accomplished by measuring and controlling the rheological properties of the ink/coating. These methods of measuring and controlling the rheological properties of inks/coatings are described in US 9,365,064, the disclosures of which are incorporated herein by reference in their entirety. The method of use or printing is not limited and may include, for example, offset printing, flexographic printing, ink jet printing, screen printing, gravure printing, and the like.

Definition of

In this application, the use of the singular includes the plural unless specifically stated otherwise. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the content clearly indicates otherwise.

In this application, the use of "or" means "and/or" unless stated otherwise.

As used herein, the terms "comprises," "comprising," and/or "comprising," in verb form, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Furthermore, where the terms "comprising," "having" in the present participle form, "having," "with," "consisting of … …," "formed of … …," or variants thereof are used in the detailed description or claims, such terms are intended to be inclusive in a manner similar to the term "comprising" in the participle form.

As used herein, "substrate" refers to any surface or object to which an ink or coating can be applied. Substrates include, but are not limited to, paper, fabric, leather, textiles, felts, concrete, masonry, stone, plastic or polymer films, glass, ceramic, metal, wood, composites, combinations thereof, and the like. The substrate may have one or more layers of metal or metal oxide, or other inorganic material.

As used herein, "article" or "articles" refers to a substrate or an article of manufacture. Examples of articles include, but are not limited to, substrates such as paper, fabric, leather, textiles, felts, concrete, masonry, stone, plastic or polymer films, glass, ceramics, metal, wood, composites, combinations thereof, and the like; and manufactured products such as publications (e.g., data sheets), labels, packaging materials (e.g., carton board or corrugated paper), containers (e.g., bottles, metal cans), cloths, polyolefins (e.g., polyethylene or polypropylene), polyesters (e.g., polyethylene terephthalate), metal foils (e.g., laminated aluminum foil), metallized polyesters, and metal containers, among others.

As used herein, the terms "ink and/or coating," "ink and coating," "ink or coating," "ink" and "coating" are used interchangeably.

As used herein, "energy cured" refers to curing achieved upon exposure to a variety of electromagnetic radiation sources, resulting in a photochemical effect. Such sources include, but are not limited to, electron beam, UV light, visible light, IR, or microwave. When the composition is cured by UV light, then those non-limiting UV sources can be used as follows: low-pressure mercury bulbs, medium-pressure mercury bulbs, xenon bulbs, excimer lamps, carbon rod lamps, metal halide bulbs, UV-LED lamps or daylight. It will be appreciated by those skilled in the art that any source of UV light may be used to cure the compositions prepared according to the present invention. The compositions of the invention are particularly suitable for use in compositions which cure under the action of UV light and/or electron beams.

As used herein, "coated paper" or "coated paper substrate" refers to paper having a finished product with a clay coating or similar smooth surface for papermills to print.

As used herein, "uncoated paper" or "uncoated paper substrate" refers to paper that is retained by the papermaker such that printing occurs directly on the paper fibers.

As used herein, "graft recycled polystyrene" or "rPS" refers to a polystyrene resin that is depolymerized and then copolymerized with (meth) acrylate and/or styrene and/or (meth) acrylic monomers and/or oligomers.

As used herein, ranges and amounts can be expressed as "about" a particular value or range. "about" is intended to include the exact amount as well. Thus, "about 5%" means "about 5%" and also means "5%". "about" means within typical experimental error for the intended application or purpose.

Wet overprinting method

The process of the present invention provides several benefits to conventionally used processes for printing multiple ink and/or coating layers on substrates and articles.

Coatings containing unsaturated bonds are known which can be cured to polymers by free radical addition. Various sources of free radicals have been used, including thermal generation (e.g., organic peroxides) and photogeneration (e.g., photoinitiators).

Radiation curable compositions containing acrylate groups (acrylates) may be cured by exposure to ultraviolet light (UV) or Electron Beam (EB). For fast-curing UV-curing systems, as a rule, photoinitiators are necessary which form radicals under the conditions of the use of photon radiation and initiate free-radical polymerization of the acrylate groups. This subsequently leads to drying, hardening and curing of the product. Monomers, oligomers and polymers comprising acrylate groups or other ethylenically unsaturated functional groups, for example vinyl groups, and photoinitiators, which are essential constituents of radiation-hardening systems for coatings, printing inks, adhesives or molding compositions, are also generally considered by anyone skilled in the art of the present invention.

However, UV and LED curable inks containing high levels of photoinitiators are problematic for a variety of applications in packaging (particularly food packaging). For example, high levels of unreacted photoinitiator and cleavage products resulting from degraded photoinitiator can retain prints (printed matter) and can cause problems such as migration and odor.

There is therefore a need for such prints which are fully cured and contain only small amounts or no conventional low molecular weight photoinitiators (which have a high potential for migration, odour and health risks).

In order to reduce the photoinitiator content of the ink and still obtain good curing, oxygen (a nuisance of free radical polymerization) must be reduced or eliminated, thereby avoiding oxygen inhibition. Oxygen inhibition means that oxygen as a diradical can readily react with the radical of the photoinitiator formed or with radicals on the monomer or growing polymer chain and render them inactive, usually as derivatives of peroxides. In the presence of oxygen, this can lead to inadequate drying of the ink.

In order to reduce oxygen inhibition, various measures have been proposed. The UV dryer can be inerted using nitrogen or carbon dioxide, for example. This requires precise pressure side mounting, thereby reducing the oxygen content of the curing spot, and is particularly difficult to mount for sheet-fed printing presses.

In general, it has been hypothesized that in order to cure a photo-curable (e.g., a free-radical-curable acrylate or methacrylate) it is necessary to have some combination of the following:

an ion radiation source, such as an Electron Beam (EB), that bombards the coating while it is under a layer of nitrogen or other inert gas, thereby preventing oxygen inhibition of the radical cure mechanism; or

A UV light source having a photoinitiator, wherein the photoinitiator is contained as a component in the coating material. In the absence of an inert gas blanket, sufficient photoinitiator and UV light intensity are required to fully react with the oxygen present and allow curing to proceed to completion, with atmospheric oxygen then diffusing back into the system poisons and terminating further free radical addition reactions.

In the former case (EB), the inks and coatings required for the job are usually wet overprinted and curing takes place in the EB unit at the end of the press. In the latter case (UV), the various inks or coatings are typically cured separately and the web or sheet then proceeds to the next printing station.

It has never been considered that a free base layer containing no photoinitiator can be wet overprinted between a primer layer containing a photoinitiator and a topcoat layer containing a photoinitiator, and the entire sandwich can be cured at one time with a single exposure to UV light. In particular, it was previously unknown that in the described structures it is not necessary for the individual layers to comprise a photoinitiator. It is not known that the radicals generated in adjacent layers (e.g. in the underlying primer layer or the overlying topcoat layer) can migrate into the uncured intermediate layer and cure them to a level equal to or even higher than can be achieved with a single exposure of each photoinitiated layer to a single UV lamp. The present invention shows for the first time that multiple layers of ink and/or coating can be printed by wet-overprinting layers of ink and/or coating, and curing all layers simultaneously at the end of a print run, provided that at least one of the ink and/or coating layers comprises a photoinitiator.

The benefits of this finding are enormous. The number of UV etc. required for a printing job, e.g. multi-colour application, can be reduced from one (typically equal to or even more than eight) per application/printing station to a single unit (typically a top coat) after the last printing station.

Another benefit is the elimination of photoinitiators in the intermediate layer in the print construction. This can be cost effective as the photoinitiator is typically the most expensive component of the formulation.

The method of the present invention can reduce the total loading of photoinitiators in complex printed structures. Migration of unreacted photoinitiators and photoinitiator reactive fragments is the most important area of concern in standard packaging applications, such as food packaging. Any reduction in these amounts is advantageous.

In certain embodiments, the interlayer has improved cure due to the lack of photoinitiator residues after cure. The solvent resistance of the cured product has proven to be excellent for the constructions of the present invention and those cases where the layers are cured separately before the next layer is applied. This is because the photoinitiator residues generally do not cure to the backbone of the addition-cured polymer. Instead, it acts as a plasticizer and softens the cured layer. This lack of residue significantly improves the overall ability of the cured layer to resist solvent attack.

Another potential benefit is that "universal" ink systems can be used without regard to the specific adhesion of the ink binder to the substrate, since a primer is typically present. The entire construction is commercially acceptable as long as the primer sticks to the substrate, the ink sticks to the primer, and the topcoat sticks to the ink.

In addition, the method of the present invention may provide greater flexibility in formulating inks and/or coatings. The formulation latitude of the ink and/or coating is released by removing from 7% to 10% of the formulation normally occupied by the photoinitiator. For example, the ink may be formulated with a higher pigment loading. Most printers prefer denser color inks because they print thinner and have better replication. Or the ability to place the resin/oligomer in the ink can be used to improve physical properties such as solvent resistance and adhesion.

The process of the present invention may also provide improved curing of "hard to cure color". White and black inks and coatings are notoriously difficult to cure in the UV system, but are more readily cured in the EB system. Since EB penetrates the ink layer easily independent of color, this means that the problem is not the ink chemistry itself, but that UV light cannot penetrate the ink layer completely. White and black ink pigments absorb a large amount of UV light. Formulation designers often counteract this situation and attempt to achieve good cure at the bottom of the UV light path (substrate/ink interface) by using larger amounts of photoinitiator in such formulations. However, the largest contributor to UV absorption of light attempts to pass through the ink layer and then becomes a photoinitiator itself. By removing the photoinitiator of the ink layer, a higher proportion of the UV light will pass all the way and the underlying primer reacts with the photoinitiator. Thus, curing can be performed in a "bottom-up" manner, eliminating the situation where "top-cure" is sufficient, but "ink-to-substrate adhesion" is poor. In the particular case of UV-LED lamp systems, this method cures well (not currently possible) in the case of dense yellow colors.

The process of the present invention may also provide improved solvent resistance of the ink and/or coating layers. Although the mechanism described is completely unknown, the abrasion resistance of Methyl Ethyl Ketone (MEK) solvents improves by orders of magnitude when the ink is "all-at-once cured" (e.g., sandwiched between a primer containing a photoinitiator and a topcoat containing a photoinitiator). Whereas typical UV inks containing photoinitiators yield very low MEK rub resistance (e.g., 1 to 5 double rubs), the primer/ink/topcoat system of the present invention yields good MEK rub results of greater than or equal to 100 double rubs. Typically, the commercially acceptable level of MEK rub is greater than 20, or about 100, or greater than 500. EB cured inks and topcoats are known not to have MEK abrasion resistance better than (usually worse) UV inks.

Another feature of the present invention is that it is first proposed that "stack replacement" actually become a practical proposition. Until then, the ultimate resistance (scratch, rub, oil/solvent resistance) of UV and EB inks for flexible packaging has never reached the level of the cover lay film.

In one embodiment, a primer layer of an Energy Curable (EC) material comprising a photoinitiator is deposited on the substrate, typically (but not necessarily) 100% coverage, but uncured. One or more subsequent ink layers prepared using EC curable materials (which do not contain photoinitiators) are overprinted on the primer in the desired printing sequence and pattern. Curing of configured inks and coatings by Electron Beam (EB) radiation is generally very similar to UV-cured inks and coatings, except that EB inks and coatings are configured using energy-curable materials (but without the use of photoinitiators). Accordingly, in certain embodiments, EB inks and coatings may be ideal candidates for use in the methods of the invention without a photoinitiator layer. Finally, a top coat of EC curable material containing a photoinitiator was applied at 100% coverage on all other layers. The coated substrate is passed under a UV lamp and irradiated at the desired level. The observed cure was from top to bottom of the composite structure and could be confirmed by tests such as thumb twist and solvent rub. When the appropriate levels of photoinitiator and UV radiation were used, no surface damage, cohesive failure of the inner layer, and release of the composite from the substrate were observed.

In certain embodiments, one or more inks without a photoinitiator are printed on the substrate (i.e., both the primer and the first underlying layer are inks without a photoinitiator) and a topcoat with a photoinitiator is printed on top of the inks. The structure is cured by UV radiation at the end of the printing run.

In some embodiments, a primer without a photoinitiator is applied to the substrate and then to the one or more ink layers with a photoinitiator. The structure is cured by UV radiation at the end of the printing run.

In other embodiments, one or more inks with a photoinitiator are printed on the substrate (i.e., the primer and first underlying layer are inks with a photoinitiator) and a topcoat without a photoinitiator is printed on top of the inks. The structure is cured by UV radiation at the end of the printing run.

In certain embodiments, a primer without a photoinitiator is printed on the substrate, then one or more ink layers with a photoinitiator are printed on top, and the last lower layer is a top coat without a photoinitiator. The structure is cured by UV radiation at the end of the printing run.

In some embodiments, the use of a flexible plastic film as a substrate may reduce oxygen inhibition, as the flexible plastic film acts as an oxygen barrier. However, although printing on flexible plastic film substrates is suitable for flexographic printing, it is not suitable for sheet-fed printing. Thus, there is a lack of good solutions for sheet-fed printing, mainly porous paper and paperboard for packaging materials and publications.

Furthermore, it has now surprisingly been observed that radiation curable inks cured between a paper substrate (having a surface sealed with a cured UV or EB coating) and a UV curable top coat (UV overprint varnish) require less photoinitiator, or even no photoinitiator, than the inks typically to be cured.

To seal the surface of the porous substrate from oxygen, a UV or EB curable coating is first applied to the porous paper or paperboard substrate and cured by UV or EB radiation. The UV/EB coating can be applied as a "primer", which can be, for example, a flexographic coating, a lithographic coating, or a gel coat, or another suitable type of coating having a higher viscosity.

The curing of the first coating may be performed in-line. For example, the UV coating may be applied first down and dried at an inter-station UV dryer, and then the ink applied. Alternatively, the porous material is coated off-line using EB coating and cured off-line using an EB dryer. The coating weight of the primer is preferably greater than 1g/m²More preferably 2 to 6g/m². Generally, the higher the coating weight, the better the seal of the porous substrate.

The porous material may be a mass of printing paper or cardboard commonly used in publications, or may be a single sheet of paper, a roll (which is cut into sheets and then printed on a printing press), a container (e.g. a bottle or plastic cup, etc., having a weight of 20 to 400g/m²) A packaging material in the form of. It may be uncoated or coated in a conventional manner with clay or calcium carbonate or the like. Coated or higher density paper or paperboard is preferred.

In some cases, one skilled in the art can adjust the properties of the substrate and primer coating, such as surface tension or coating weight, so that the primer coating remains on top of the porous substrate and forms after curing the effective sealing layer. It should be avoided that the coating sticks to the porous substrate, so that no sealing layer can be formed.

After the radiation curable coating (primer) is cured on top of the porous substrate, the radiation curable ink may be applied by flexographic, lithographic, inkjet, screen, gravure or other means. A preferred application is by lithography. A print density suitable for the application process is used. The photoinitiator content of the ink is 0 to 20 wt%, preferably 0 to 5 wt%, and most preferably 0 wt%. The ink may be any radiation curable ink, such as typical lithographic UV inks available from existing commercial products, such as Sun Chemical's Sun FLM, USL, ULR, with reduced photoinitiator content; or electron beam curable inks, completely free of photoinitiators, such as Sunchemical's Sunbeam ELM inks.

Finally, the wet uncured radiation curable ink is overcoated with a UV or LED flexographic coating, or a UV or LED lithographic coating. The photoinitiator content of the top coat (overprint varnish) is from 0 to 20% by weight, preferably from 1 to 10% by weight. The coating weight of the top coat is preferably greater than 1g/m²More preferably 2 to 6g/m²Or 6 to 8g/m²For high gloss applications. The ink and coating are preferably final cured together by an applied UV or LED top coat coating.

The number of radiation curable ink layers that can be applied on top of the cured primer and below the top coat depends primarily on the amount of photoinitiator in the top coat and the pigment of the ink. The more photoinitiator in the topcoat, the better the cure in the radiation curable ink layer. Typically, dark inks require a certain amount of photoinitiator, while other radiation curable inks are fully cured without a photoinitiator.

Advantageously, at the instant of UV or LED curing, the radiation curable ink is protected from oxygen entering the bottom by the encapsulating coating and from oxygen entering the top by the UV topcoat, so that the curing conditions are similar to a UV stack, which requires less photoinitiator to be cured, typically only 1/5 which is a typical initial photoinitiator concentration^thTo 1/8^th. The small amount of initiating species required for curing radiation curable inks is provided by the top coat by purposeful diffusion or incorporation.

Advantageously, the UV topcoat need not contain a photoinitiator suitable for curing pigmented inks, which is typically more precise and expensive (e.g., Irgacure 369) than photoinitiators used for non-pigmented coatings (e.g., benzophenone). In addition, since the coating is non-pigmented, the radiation can more easily address the photoinitiator and generate high levels of free radicals. Such radicals (even generated by the coating initiator) can effectively initiate free radical polymerization in the ink once they are formed in the coating and transferred to the adjacent ink layer by diffusion.

The UV curable inks and coatings of the present invention may be UV cured by any actinic light, such as UV light provided by high pressure mercury bulbs, medium pressure mercury bulbs, xenon bulbs, carbon rod lamps, metal halide bulbs, UV-LED lamps or daylight. The wavelength of the applied radiation is preferably about 200 to 500nm, more preferably about 250 to 400 nm. The UV energy is preferably about 30 to 3000mJ/cm²More preferably about 50 to 250mJ/cm². Further, the bulb may be appropriately selected according to the absorption of the radiation curable top coat.

In certain embodiments, the primer layer is printed on the substrate and cured. Such a primer layer may be curable by UV radiation and contain a photoinitiator, or it may be curable by EB radiation and contain no photoinitiator. Subsequently, using the wet overprinting process of the invention, one or more ink layers without photoinitiator are printed on top of the cured primer, and the top coat with photoinitiator is the lowest layer. The final configuration is cured by UV radiation at the end of the print run. This embodiment advantageously uses a porous substrate wherein the printed and cured primer acts to block oxygen and mitigate oxygen inhibition of the curing of subsequent layers.

In some embodiments, the wet overprinting process of the present invention can be used to laminate a first substrate to a second substrate. In the art of lamination, it is known to those skilled in the art that there are systems in which an energy curable coating or adhesive is overprinted between two substrates, typically between a film and a paper, or between two films. In all cases, at least one of the substrates must be relatively transparent to the wavelength(s) of UV energy that activate the photoinitiator(s) in the energy curable formulation.

Energy curable materials can be used as adhesives for bonding two substrates together, typically a printed layer and a non-printed layer. In most cases, this technique is used to "bury" it inside the laminated structure to protect the printed surface. In other cases, a simple and economical way is to bond a heat or chemical resistant layer to another layer, such as a sealant layer; or two layers having different chemical or gas barrier properties are bonded together.

Alternatively, a substrate may carry a graphic pattern, which is imprinted in a wet coating. After curing, the imprinted substrate is typically removed after curing, revealing the pattern. The most common example is Cast and Cure^TMBut is not limited thereto.

In some cases, it is advantageous to use two different formulations, one designed to provide good adhesion to the first substrate and the second designed to provide good adhesion to the second substrate. Heretofore, it has been impracticable to provide a photoinitiator incompatible with one or other desired substrates.

In the present invention, it has been demonstrated that curing is achieved inside a laminated structure using two different UV coating formulations in wet-on-wet contact with each other, only one of which contains a photoinitiator. Both formulations cured to fuse into a continuous layer adhered to both substrates.

In certain embodiments, one or more energy curable ink and/or coating layers (a) comprising a photoinitiator may be applied on the first and/or second substrate. One or more energy curable ink and/or coating layers (B) that do not comprise a photoinitiator may be applied on the first and/or second substrate. Advantageously, at least one of the first or second substrates is UV radiation permeable. The first and second substrates are either stacked wet on wet or dry on wet surfaces of the park and the layers of the stack are cured simultaneously with a substrate that is transparent to UV radiation.

As discussed above, oxygen inhibition is detrimental to EC cure. It is known that the presence of amines, most particularly tertiary amines, is greatly advantageous in reducing oxygen inhibition. The level of amine required must be determined empirically for each individual ink type and can vary from as low as 4% or less of the formulation (based on the weight of the material, e.g., 2-ethylhexyl-4-benzoate) to as high as 8% or more (the aminoacrylates formed as Michael adducts, e.g., diethanolamine-1, 6-HDDA or diethylamine-TPGDA). Advantageously, in the case of the outer layers (primer and top coat), the presence of the amino acrylate is highly advantageous for inhibiting the adverse effect on oxygen curing. When type II photoinitiators are used, the aminoacrylates are of dual importance as synergists in the radical generation process and as hydrogen source for the extractables (abstractable). However, even in the case of type I photoinitiators, the presence of aminoacrylates has been shown to be advantageous (Husar, et al, "Novel phosphine oxide photoinitiators," RadTech International proceedings, 2014). Although it is not strictly necessary for the amino acrylate to be present in the non-photoinitiated interlayer in order to achieve complete curing, it does appear advantageous.

It is not absolutely necessary to have a primer as the first lower layer. This is a particular case when an oxygen impermeable substrate (e.g. a polymer film) is printed. However, on oxygen permeable substrates (e.g. porous paper), the use of primers is most practical. The coated paper exhibits an intermediate condition in which a primer may or may not be required depending on the porosity of the paper. When used, the primer can regulate adhesion to the substrate independent of the ink vehicle. In theory, there is no reason to use a substrate-specific ink vehicle at all. The same ink can be used in any configuration as long as the ink sticks to the primer. Likewise, the topcoat need not be specifically formulated to adhere to the substrate. The entire composite will perform at acceptable levels as long as the top coat adheres to the ink(s) and the underlying primer.

In practice, the topcoat typically uses a blend of type I and II photoinitiators and an aminoacrylate as the initiator/synergist package. Typically, about 30% of the photoinitiator is required in order to consume the oxygen present in/around the topcoat layer. Good blends have been found to be one part form I to two parts form II. Typical initiator/synergist compositions have been found to be 3% type I photoinitiator (e.g. hydroxycyclohexyl phenyl ketone), 6% type II photoinitiator (e.g. benzophenone) and 9% aminoacrylates (e.g. the adduct of diethylamine and tripropylene glycol diacrylate (TPGDA) (e.g. Miwon Photocryl a101 or AllnexP 115)).

The middle ink layer may be formulated with or without the use of an amino acrylate, as desired, but generally up to 5% or more is advantageous as a cure accelerator. Amino acrylates are often used as standard ingredients in UV flexographic inks, and therefore in the case of liquid inks this is not a major change from current practice. For paste inks, aminobenzoates (e.g., 2-ethylhexyl-4-benzoate) have long been used successfully in lithographic ink formulations. Historically, there has been a concern that amino acrylates have an adverse effect on the water absorption value of paste ink types. However, it should be appreciated that despite the fact that there are situations: where the starting material for the preparation of the Michael adduct is an alkanolamine, there is no evidence that the same concerns are directed to alkylamines that do not contain-OH groups.

The primer layer generally works best with type I photoinitiators, which are long wave UV receivers, because these wavelengths penetrate the deepest into the material to be cured. Phosphine oxides (TPO, TPO-L and BAPO) paired with 9% aminoacrylates at 3% levels are generally sufficient for curing the primer because there is relatively little dissolved oxygen at the primer level once the primer is covered by the ink(s) and topcoat.

In another embodiment, a first layer (primer layer or ink layer) comprising photoinitiator(s) is deposited, but not cured, and then all subsequent layers are inks and/or coatings (optionally including a topcoat) that do not comprise photoinitiator(s). The entire construction is cured in a final stage comprising a UV-LED lamp or a UV mercury vapor lamp, or a combination thereof. This is said to be "bottom-up" curing.

In certain embodiments, the inks and/or coatings of the methods of the present invention are formulated according to the method of Sun Chemical U.S. Pat. No.9,365,064. US 9,365,064 describes a wet overprint printing process which minimises or eliminates "reverse overprinting". Reverse overprinting is an undesirable effect in which the first printed layer picks up the subsequent printed layer and is again deposited on subsequent plates and rollers in the press, resulting in printing defects.

Although it is preferred that the layers identified as being free of photoinitiator (i.e., the energy curable ink and/or coating layer (B)) be completely free of added photoinitiator, small amounts of photoinitiator may be added to these layers. Preferably, the amount of photoinitiator added is insufficient for the layer to react with UV light to form a rigid cured film on its own. Depending on the type of ink chosen and the actual photoinitiator, the photoinitiator content in this case is generally below 6%, or below 5%, and more preferably below 4%, or below 2%, or below 1%, and most preferably below 0.5%.

In a preferred embodiment, the process of the present invention comprises wet overprinting of inks, wherein all inks comprise at least some degree of energy curable material and optionally a photoinitiator. In one embodiment, the inks used in the wet overprinting process of the present invention are substantially all energy curable materials (and may exclude the inclusion of minor amounts of various additives and/or inert resins). In such embodiments, the energy curable material is typically present in an amount greater than or equal to 90 weight percent, preferably greater than or equal to 95 weight percent.

In certain embodiments, hybrid inks may be used that include energy curable materials and non-energy curable materials, typically used for conventional solvent-based, oil-based, and water-based inks. In the case of hybrid inks, the amount of energy curable material is typically greater than or equal to 40 wt%, or greater than or equal to 45 wt%, or greater than or equal to 50 wt%, or greater than or equal to 60 wt%, or greater than or equal to 70 wt%, or greater than or equal to 80 wt%, or greater than or equal to 90 wt%, or greater than or equal to 95 wt%, depending on the type of formulation. When using hybrid inks containing fugitive materials, the construction may be dried using heat and then cured by UV radiation at the end of the print run. However, in some embodiments, it is not necessary to heat dry the hybrid ink (e.g., one case is whether the hybrid ink contains a conventional resin, but no solvent).

The present invention generally does not encompass wet trapping of traditional solvent-based (particularly oil-based) and water-based inks (which do not contain energy curable materials). Conventional solvent-based, oil-based, and water-based inks and coatings can be defined as those that are substantially free of energy curable materials. Such inks are typically comprised of a resin, a solvent, various additives, and optionally a colorant. When wet-overprinting conventional solvent-based, oil-based, and water-based inks, they often do not adequately release enough solvent from the printed film before the next layer is printed. Therefore, they are not suitable for overprinting with subsequent ink or paint layers comprising energy curable materials, and this would compromise the integrity of the overall multi-ink layer printed construction. When solvent-based, oil-based, and water-based inks are used in conjunction with the wet overprinting process of the invention, these solvent-based, oil-based, and water-based inks are preferably completely dry (non-wet overprint) before the subsequent ink layers are subjected to the wet overprinting process of the invention.

The process of the present invention typically employs UV radiation to energy cure the inks and/or coatings. The method of the present invention is not limited to any particular wavelength range of UV radiation for which photoinitiators are currently available, about 250nm to 415nm, and generally operates over the entire UV wavelength range. However, the method of the present invention is not limited to photoinitiators within this range. With respect to the extended wavelength range of the photoinitiator (e.g. 200nm to 500nm), the method of the invention is also applicable to the extended wavelength range.

Energy curable materials can be broadly defined as those that are polymerizable when exposed to various forms of radiation (e.g., UV, EB, LED, etc.). The inks and coatings suitable for use in the wet overprinting process of the present invention are not bound by any particular formulation requirements, but they preferably both comprise energy curable materials. The most common classification of energy curable materials is listed below.

Examples of suitable monofunctional ethylenically unsaturated monomers include, but are not limited to, isobutyl acrylate; cyclohexyl acrylate; isooctyl acrylate; n-octyl acrylate; isodecyl acrylate; isononyl acrylate; octyl/decyl acrylate; dodecyl acrylate; 2-propylheptyl acrylate; tridecyl acrylate; cetyl acrylate; octadecyl acrylate; isostearyl acrylate; behenyl acrylate; tetrahydrofurfuryl acrylate; 4-tert-butylcyclohexyl acrylate; 3,3, 5-trimethylcyclohexane acrylate; isobornyl acrylate; dicyclopentyl acrylate; dihydrodicyclopentadienyl acrylate; dicyclopentenyloxyethyl acrylate; dicyclopentyl acrylate; benzyl acrylate; phenoxyethyl acrylate; 2-hydroxy-3-phenoxypropyl acrylate; alkoxylated nonylphenol acrylate; cumylphenoxyethyl acrylate; cyclic hydroxy trimethyl propane formal acrylate; 2 (2-ethoxyethoxy) ethyl acrylate; polyethylene glycol monoacrylate; polypropylene glycol monoacrylate; caprolactone acrylate; ethoxylated methoxypolyethylene glycol acrylate; methoxy triethylene glycol acrylate; tripropylene glycol monomethyl ether acrylate; diethylene glycol butyl ether acrylate; alkoxylated tetrahydrofurfuryl acrylate; ethoxylated ethylhexyl acrylate; alkoxylated phenol acrylates; ethoxylated phenol acrylates; ethoxylated nonylphenol acrylates; propoxylated nonylphenol acrylate; polyethylene glycol o-phenyl ether acrylate; ethoxylated p-cumylphenol acrylate; ethoxylated nonylphenol acrylates; alkoxylated dodecyl acrylate; ethoxylated tristyrylphenol acrylate; n- (acryloyloxyethyl) hexahydrophthalimide; n-butyl 1,2 (acryloyloxy) ethyl carbamate; acryloyloxyethyl hydrogen succinate; octyloxy polyethylene glycol acrylate; octafluoropentyl acrylate; 2-isocyanatoethyl acrylate; acetoacetoxyethyl acrylate; 2-methoxyethyl acrylate; dimethylaminoethyl acrylate; 2-carboxyethyl acrylate; 4-hydroxybutyl acrylate. Equivalent amounts of methacrylate compounds can also be used.

Examples of suitable polyfunctional ethylenically unsaturated monomers include, but are not limited to, the following 1, 3-butanediol diacrylate; 1, 4-butanediol diacrylate; neopentyl glycol diacrylate; ethoxylated neopentyl glycol diacrylate; propoxylated neopentyl glycol diacrylate; 2-methyl-1, 3-propanediyl ethoxy acrylate; 2-methyl-1, 3-propanediol diacrylate; ethoxylated 2-methyl-1, 3-propanediol diacrylate; 3 methyl 1, 5-pentanediol diacrylate; 2-butyl-2-ethyl-1, 3-propanediol diacrylate; 1, 6-hexanediol diacrylate; alkoxylated hexanediol diacrylate; ethoxylated hexanediol diacrylate; propoxylated hexanediol diacrylate; 1, 9-nonanediol diacrylate; 1,10 decanediol diacrylate; ethoxylated hexanediol diacrylate; alkoxylated hexanediol diacrylate; diethylene glycol diacrylate; triethylene glycol diacrylate; tetraethylene glycol diacrylate; polyethylene glycol diacrylate (PEG-diacrylate); propoxylated ethylene glycol diacrylate; dipropylene glycol diacrylate; tripropylene glycol diacrylate; polypropylene glycol diacrylate; poly (tetramethylene glycol) diacrylate; cyclohexane dimethanol diacrylate; ethoxylated cyclohexanedimethanol diacrylate; cyclohexane dimethanol diacrylate alkoxylates; polybutadiene diacrylate; hydroxy-tert-valeryl hydroxypivalate diacrylate; tricyclodecane dimethanol diacrylate; 1, 4-butylidenebis [ oxy (2-hydroxy-3, 1-propylene) ] diacrylate; ethoxylated bisphenol a diacrylate; propoxylated bisphenol a diacrylate; propoxylated ethoxylated bisphenol a diacrylate; ethoxylated bisphenol F diacrylate; 2- (2-ethyleneoxyethoxy) ethyl acrylate; dioxane diol diacrylate; ethoxylated glycerol triacrylate; propoxy triacrylate glycerol ester; pentaerythritol triacrylate; trimethylolpropane triacrylate; caprolactone-modified trimethylolpropane triacrylate; ethoxylated trimethylolpropane triacrylate; propoxylated trimethylolpropane triacrylate; tris (2-hydroxyethyl) isocyanurate triacrylate; e-caprolactone-modified tris (2-hydroxyethyl) isocyanurate triacrylate; a melamine acrylate oligomer; pentaerythritol tetraacrylate; ethoxylated pentaerythritol tetraacrylate; di-hydroxy-trimethylpropane tetraacrylate; polydipentaerythritol pentaacrylate; dipentaerythritol hexaacrylate; ethoxylated dipentaerythritol hexaacrylate. Equivalent amounts of methacrylate compounds can also be used.

In certain embodiments, bisphenol-a epoxy diacrylate is used as the energy curable material in one or more ink and/or coating layers suitable for use in the process of the present invention.

In other embodiments, the bisphenol-A epoxy diacrylate may be replaced with grafted polystyrene (rPS). Grafted recycled polystyrene resins are taught in WO 2017/139333. For example, depolymerized polystyrene resins can be modified using reactive monomers, oligomers, and polymers that react with free radicals induced by catalysts, initiators, and/or other depolymerization means. These monomers may include, for example, (meth) acrylic acid esters, styrene, and the like. In other embodiments, urethane acrylates or recycled polyethylene terephthalate (rPET) may be used.

Examples of other classes of functional monomers that can be used in part in these formulations include cyclic lactams, such as N-vinyl caprolactam; n-vinyl oxazolidinones and N-vinyl pyrrolidones, and secondary or tertiary acrylamides, such as acryloyl morpholine; diacetone acrylamide; n-methyl acrylamide; n-ethyl acrylamide; n-isopropylacrylamide; n-tert-butylacrylamide; n-hexyl acrylamide; n-cyclohexyl acrylamide; n-octyl acrylamide; n-tert-octylacrylamide; n-dodecyl acrylamide; n-benzyl acrylamide; n- (hydroxymethyl) acrylamide; n-isobutoxymethyl acrylamide; n-butoxymethylacrylamide; n, N-dimethylacrylamide; n, N-diethylacrylamide; n, N-propyl acrylamide; n, N-dibutylacrylamide; n, N-dihexylacrylamide; n, N-dimethylaminomethylacrylamide; n, N-dimethylaminoethylacrylamide; n, N-dimethylaminopropyl acrylamide; n, N-dimethylaminohexylacrylamide; n, N-diethylaminomethacrylamide; n, N-diethylaminoethyl acrylamide; n, N-diethylaminopropyl acrylamide; n, N-dimethylaminohexylacrylamide; and N, N' -methylenebisacrylamide. Energy curable resins, such as ketone resins, may also be used.

Oligomeric and polymeric acrylates may also be included in the energy curable inks and/or coatings. Such oligomeric and polymeric acrylates include, but are not limited to, epoxy acrylates, polyester acrylates, acrylate urethanes, acrylate polyacrylates, acrylate polyethers, acrylate polyamines, acrylate polyglycols, acrylate epoxies based on linseed oil, soybean oil, and mixtures thereof, and the like. Suitable water-soluble or water-dispersible acrylates are, for example, highly ethoxylated multifunctional acrylates, such as polyethylene oxide diacrylate or ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol triacrylate or epoxy resin acrylates, such as alkane diglycidyl ether diacrylate, polyglycerol diacrylate or aqueous acrylate urethane acrylate dispersions, for example Bayhydrol UV2280 and UV2282 (trade marks Bayer Company).

Suitable photoinitiators include, but are not limited to, alpha-hydroxy ketones, acylphosphine oxides, alpha-amino ketones, thioxanthones, benzophenones, phenylglyoxylates, oxime esters, acetophenones, benzines and their derivatives, fluorenones, anthraquinones, combinations thereof and the like.

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

Suitable acylphosphine oxide photoinitiators include, but are not limited to: 2,4, 6-trimethylbenzoyl-diphenylphosphine oxide; ethyl (2,4, 6-trimethylbenzoyl) phenylphosphinate; and bis- (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide; combinations thereof and the like.

Suitable α -aminoketone photoinitiators include, but are not limited to: 2-methyl-1- [ 4-methylthio) phenyl ] -2-morpholinopropan-1-one; 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one; and 2-dimethylamino-2- (4-methyl-benzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one; combinations thereof and the like.

Suitable thioxanthone photoinitiators include, but are not limited to: 2-4-diethylthioxanthone, isopropylthioxanthone, 2-chlorothioxanthone and 1-chloro-4-propoxythioxanthone; combinations thereof and the like.

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

Suitable benzoylformate photoinitiators include, but are not limited to: methyl phenylglyoxylate; oxy-phenyl-acetic acid 2- [ hydroxy l-ethoxy ] -ethyl ester or oxy-phenyl-acetic acid 2- [ 2-oxy-2-phenyl-acetoxy-ethoxy ] -ethyl ester; combinations thereof and the like.

Suitable oxime ester photoinitiators include, but are not limited to: 1-phenyl-1, 2-propanedione-2- (O-ethoxycarbonyl) oxime; [1- (4-phenylsulfonylbenzoyl) heptylideneamino ] benzoate, or [1- [ 9-ethyl-6- (2-methylbenzoyl) carbazol-3-yl ] -ethylideneamino ] acetate; combinations thereof and the like.

Examples of other suitable photoinitiators include diethoxyacetophenone; biphenyl acyl; benzil dimethyl ketal; titanocen free radical initiators, e.g. titanium-bis (R) ((R))5-2, 4-cyclopentadien-1-yl) -bis- [2, 6-difluoro-3- (1H-pyrrol-1-yl) phenyl](ii) a 9-fluorenone; camphorquinone; 2-ethyl anthraquinone; combinations thereof and the like.

Polymeric photoinitiators and sensitizers are also suitable, including for example: polymeric aminobenzoates (GENOPOL AB-1 or AB-2 from RAHN, Omnipol ASA from IGM, or Speedcure 7040 from Lambson); polymeric benzophenone derivatives (GENOPOL BP-1 or BP-2 from RAHN, Omnipol BP2702 or Omnipol 682 from IGM, or Speedcure 7005 from Lambson); polymeric thioxanthone derivatives (GENOPOL TX-1 or TX-2 from RAHN, Omnipol TX from IGM, or Speedcure 7010 from Lambson); polymeric aminoalkylacylbenzenes such as Omnipol 910 from IGM; polymeric benzoyl formate esters such as Omnipol 2712 from IGM; and the polymeric photosensitizer Omnipol SZ from IGM.

As discussed, the amine synergist may also be included in energy curable inks and coatings suitable for use in the method of the present invention. Suitable examples include, but are not limited to, aromatic amines, aliphatic amines, amino acrylates, and amine-modified polyether acrylates.

The inks and/or coatings may further comprise one or more additives commonly used in inks and coatings. Such additives include, but are not limited to, colorants (e.g., pigments or dyes), release additives, flow additives, defoamers, and the like.

Examples of suitable organic or inorganic pigments include, but are not limited to, carbon black, zinc oxide, titanium dioxide, phthalocyanines, anthraquinones, perylenes, carbazoles, monoazo and disazo benzimidazoles, rhodamines, indigoids, quinacridones, diazahthracenones, dinitroanilines, pyrazoles, diazahthracenones, dinityanilines, pyrazoles, anisidines, pyranthrones, tetrachloroisoindoles, dioxazines, monoazo arylides and anthrone pyrimidines. Dyes include, but are not limited to, azo dyes, anthraquinone dyes, xanthene dyes, azine dyes, combinations thereof, and the like.

Commercially available organic pigments classified according to the Color Index International include blue pigments PB1, PB15, PB15:1, PB15:2, PB15:3, PB15:4, PB15:6, PB16, PB 60; brown pigments PB5, PB23 and PB 265; green pigments PG1, PG7, PG10, and PG 36; yellow pigments PY3, PY14, PY16, PY17, PY24, PY65, PY73, PY74 PY83, PY95, PY97, PY108, PY109, PY110, PY113, PY128, PY129, PY138, PY139, PY150, PY151, PY154, PY156, PY175, PY180 and PY 213; orange pigments PO5, PO15, PO16, PO31, PO34, PO36, PO43, PO48, PO51, PO60, PO61 and PO 71; red pigments PR4, PR5, PR7, PR9, PR22, PR23, PR48, PR48:2, PR49, PR112, PR122, PR123, PR149, PR166, PR168, PR170, PR177, PR179, PR190, PR202, PR206, PR207, PR224 and PR254 purple pigments PV19, PV23, PV32, PV37 and PV 42; a black pigment.

Examples of suitable release additives include, but are not limited to, acrylated derivatives such as Evonik's tego Rad 2200N,2250,2300,2500,2600,2650&2700 and the like; or Altana's BYK UV3500,3505,3510,3530,3570 and the like; or Dow Corning's DC-31; or any other EC reactive system intended for similar action. Non-acrylated additives suitable for use in EC systems are also suitable, such as Evonik's TEGO Glide 100&440, Altana's BYK-306,307,333,337,371,373,375, & 377; dow Corning's DC-57; erbeck-1; wacker Chemie's ADDID 100,130,140,151, & 170. Other materials include all those known to those of ordinary skill in the art for high solids ink and coating modification.

Examples of suitable flow additives include, but are not limited to, acrylated additives such as Evonik's tego Rad 2100,2200N,2250, &2300 and the like; or Altana's BYK UV3500,3505,3510,3530,3570 and the like; or Dow Corning's DC-31; or any other ECI reactive system intended for similar action. Non-acrylated additives suitable for EC systems are also suitable, such as Evonik's TEGOGlide 100&440, Altana's BYK-306,307,333,337,371,373,375, & 377; dow Corning's DC-57; erbeck-1; wacker Chemie's ADDID 100,130,140,151, & 170. Other materials include all those known to those of ordinary skill in the art for high solids ink and coating modification.

Suitable defoamers include TEGO FOAMEX N, FOAMEX 1488,1495,3062,7447,800,8030,805,8050,810,815N,822,825,830,831,835,840,842,843,845,855,860 and 883, TEGOFOAMEX K3, TEGO FOAMEX K7/K8 and TEGO TWIN 4000 from EVONIK. BYK-066N,088,055,057,1790,020, BYK-A530,067A and BYK 354 from BYK are available.

In certain embodiments, one or more energy curable ink and/or coating layers may comprise one or more non-reactive resins. In some embodiments, the non-reactive resin is soluble in monomers, such as acrylates and methacrylates. Suitable examples of non-reactive resins include, but are not limited to, modified polystyrenes, modified polyesters, ketone resins, combinations thereof, and the like.

The specific formulation of the inks and/or coatings used in the method of the present invention may vary so long as the inks and/or coatings are capable of being cured by UV radiation, either because they contain a photoinitiator, or because of the wet-trap curing phenomenon described herein. The ink and/or coating can be of any type commonly used in virtually any printing process. Printing methods such as, but not limited to, offset printing, flexographic printing, gravure printing, digital (e.g., inkjet) printing, screen printing, and combinations thereof may be used.

In another embodiment, printing a build may include depositing and fully curing one or more ink and/or coating layers (UV curable, solvent based, water based, etc.) followed by subsequent application of additional ink and/or coating layers using the wet overprinting process of the present invention.

In another embodiment, printing a build may comprise applying an ink and/or coating layer using the wet overprinting method of the present invention, followed by subsequent application of one or more other ink and/or coating layers (UV curable, solvent based, water based, etc.) on top of which wet overprinting may or may not be possible.

In one embodiment, a water-based coating comprising amounts of monomers, a synergist (amine), and a photoinitiator may be used as a photo-initiated topcoat in a wet-offset process where curing is initiated in an underlying non-initiated layer.

Examples

The following examples illustrate specific aspects of the invention and are not intended to limit the scope of the invention in any respect and should not be so construed. The following examples illustrate specific aspects of the water-based coating compositions of the present invention. The described embodiments are merely exemplary and should not be construed as limiting the scope of the claimed subject matter based on this disclosure. All parts and percentages are by weight (wt% or mass% based on total weight) unless otherwise indicated.

Test method

Finger rub test

Scratch resistance was evaluated using the finger rub test. On the top layer of the cured construction, the fingers rub back and forth, with a force that is generally holding and manipulating the printed product. If the printed layer remains intact, the construction passes the finger rub test. The constructed finger rub test fails if one or more printed layers are smeared or rubbed. The main objective of this test is to evaluate the surface cure.

Thumb twisting test

The thumb was pressed hard on the top layer of the cured construct and rotated 90 degrees. If the printed layer remains intact, the construction passes the thumb twist test. If one or more of the printed layers is rubbed or damaged (typically the bond between the substrate and the ink/coating fails), the construction fails the thumb twist test. The primary purpose of this test is to evaluate through cure.

Solvent rub test

The cotton ball was dipped in Methyl Ethyl Ketone (MEK) and rubbed back and forth (i.e., double rubbed) on the top layer of the cured construction. The number of double rubs before curing constitutes a failure was recorded. Preferably, the construction is subjected to more than 50 double rubs, preferably more than 100 double rubs, more preferably more than 500 double rubs.

Adhesion test

A piece of 3M 810 tape was placed on top of the cured construct and leveled to adhere the tape to the top layer of the construct. The tape was pulled quickly at a 90 ° angle. If the printed cured layer remains adhered to the substrate, the construction passes the adhesion test. If more than 10% of the printed layer is removed from the substrate, the construction fails the adhesion test.

4 samples were prepared for each print configuration (unless otherwise noted) and the test results reported below are the average of the 4 samples.