Patent Application
20180127606
The present invention is directed to energy curable inkjet ink or coating compositions comprising at least one aminoacrylate that when cured exhibit low migration and improved adhesion to plastic surfaces and thus are useful for sensitive applications such as food packaging, pharmaceutical packaging and/or cosmetics and personal care packaging.
The present invention relates to energy curable inkjet ink or coating compositions comprising an aminoacrylate that is prepared by the Michael addition reaction of a polyacrylate with an alkanolamine. Furthermore the ink and coating compositions limit the amount of total acyl phosphine oxide photoinitator and monofunctional monomer content therein.
EP 2 671 722 is directed to industrial inkjet printing methods on packaging materials for foodstuffs and pharmaceutical compounds and liquids and describes the use of an amine modified polyetheracrylate adhesion promoter in the preparation of ultra-violet (UV) curable inkjet fluids. The fluids also contain high concentrations of silicone acrylate to increase adhesion.
WO2014/126720 is directed to pigmented free radical UV curable inkjet liquid compositions for the printing of food packaging materials and describes that cure response and a further lowering of migratable monomer can be achieved by the inclusion of suitable co-initiators such as acrylated amines and aminobenzoates.
U.S. Pat. No. 3,844,916, U.S. Pat. No. 3,914,165 and U.S. Pat. No. 3,925,349 are all directed to radiation curable non-gelled Michael addition reaction products that are obtained by reacting amines comprising at least one amino hydrogen atom with a stoichiometric excess of ethylenic material comprising a polyacrylate.
US20110159251 describes radiation curable ink compositions that contain a phenoxyethyl acrylate, a multifunctional acrylate and a pigment. Furthermore the composition may contain an amino acrylate which can be an adduct of hexandiol diacrylate (HDDA) and ethanolamine. However, the compositions use significant quantities of a monofunctional monomer, such as greater than 20% of either phenoxyethyl acrylate (PHEA) or a blend of PHEA with N-vinyl caprolactam (NVC) and high amounts of acyl phosphine oxide photoinitator.
WO2015/036615 describes radiation curable inkjet compositions for food packaging which can comprise polymeric or polymerizable aminobenzoate type co-initiators and may also include thioxanthone type photoinitiators.
Finally JP2013159707, JP2012188613, JP2011213931, JP2011213934, and JP2011213933 are all directed to energy curable inkjet compositions which contain a large proportion of monofunctional monomer.
The present invention provides an energy curable inkjet ink or coating composition comprising
HN(R1)(CnH2nOH)
wherein R1 is H or (CmH2mX);
X is H or OH;
m is 1 to 6 and n is 1 to 6.
Furthermore the present invention also provides a coated article comprising a cured ink or coating composition according to anyone of the preceding claims on the surface of the article.
Finally the present invention also provides a process for preparing a coated article comprising
These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the methods and formulations as more fully described below.
The present invention is directed to inks and compositions that use Michael reaction products based on the reaction of polyacrylates with alkanolamines that when cured exhibit low migration, improve the adhesion to plastic substrates, exhibit faster cure and lower odor.
Accordingly the present invention provides an energy curable inkjet ink or coating composition which contains at least one aminoacrylate prepared by the Michael addition reaction of a polyacrylate with an alkanolamine and contains less that 12.0% by weight of total photoinitiator.
Furthermore the ink or coating compositions contain less than 4.0% by weight of acyl phosphine oxide photoinitator and contain less than 10.0% by weight of monofunctional monomer.
It has been found that the inks or coating compositions of the present invention when cured exhibit lower levels of odor than from comparable inks comprising aminoacrylates based on aliphatic amines, such as diethylamine and dipropylamine. This is a distinct advantage for inks intended for the printing of sensitive applications such as food packaging, pharmaceutical packaging and/or cosmetics and personal care packaging.
Preferably the aminoacrylate is derived from the Michael addition reaction product of a primary or secondary alkanolamine with a stoichiometric excess of a polyacrylate.
Typically the inks and coating compositions contain between 1.0 to 50.0% by weight, preferably between 2.0 to 40% by weight and advantageously between 5.0 to 20.0% by weight of aminoacrylate.
Furthermore the amount of aminoacrylate in the ink and coating compositions preferably contain sufficient aminoacrylate such that the amine value of the ink or coating composition is greater than 1.0 mgKOH/g, more preferably greater than 3.0 mgKOH/g, and advantageously greater than 5.0 mgKOH/g.
Usually the polyacrylate is selected from dipropyleneglycol diacrylate, tripropyleneglycol diacrylate, hexanediol diacrylate, ethoxylated (2 moles) hexanediol diacrylate, ethoxylated (3 moles) hexanediol diacrylate, 3-methylpentanediol diacrylate, decanediol diacrylate, dodecanediol diacrylate, propoxylated (2 moles) neopentyl glycol diacrylate, trimethylolpropane triacrylate, ethoxylated (3 moles) trimethylolpropane triacrylate, ethoxylated (4 moles) trimethylolpropane triacrylate, ethoxylated (5 moles) trimethylolpropane triacrylate, propoxylated (3 moles) trimethylolpropane triacrylate, propoxylated (4 moles) trimethylolpropane triacrylate, propoxylated (5 moles) trimethylolpropane triacrylate propoxylated (3 moles) glyceryl triacrylate, propoxylated (4 moles) glyceryl triacrylate, propoxylated (5 moles) glyceryl triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethoxylated (4 moles) pentaerythritol tetracrylate, ethoxylated (5 moles) pentaerythritol tetracrylate, ethoxylated (6 moles) pentaerythritol tetracrylate, ethoxylated (7 moles) pentaerythritol tetracrylate, dipentaerythritol pentaacrylate, ethoxylated (5 moles) dipentaeryhtritol pentaacrylate, ethoxylated (6 moles) dipentaeryhtritol pentaacrylate, ethoxylated (7 moles) dipentaeryhtritol pentaacrylate, ethoxylated (8 moles) dipentaeryhtritol pentaacrylate, ethoxylated (9 moles) dipentaeryhtritol pentaacrylate, ditrimethylolpropane tetraacrylate, ethoxylated (4 moles) ditrimethylolpropane tetraacrylate, ethoxylated (5 moles) ditrimethylolpropane tetraacrylate, ethoxylated (6 moles) ditrimethylolpropane tetraacrylate, ethoxylated (7 moles) ditrimethylolpropane tetraacrylate, diethyleneglycol diacrylate, triethyleneglycol diacrylate, tricyclodecanedimethanol diacrylate (TCDDMDA), ethoxylated 3 and/or bisphenol A diacrylate.
Advantageously the polyacrylate is selected from hexanediol diacrylate, 3-methylpentanediol diacrylate, dipropylene glycol diacrylate, tripropyleneglycol diacrylate, ethoxylated (3 moles) trimethylolpropane triacrylate, propoxylated (3 moles) glyceryl triacrylate, neopentyl glycol diacrylate, decanediol diacrylate, ethoxylated (2 moles) hexanediol diacrylate, propoxylated (2 moles) neopentyl glycol diacrylate and/or propoxylated (3 moles) trimethylolpropane triacrylate.
Although polyacrylate monomers are preferred, the inks and coating compositions may include those Michael addition reaction products formed by the reaction of alkanolamines with ethylenically unsaturated oligomers and polymers such as; polyester acrylates, epoxy acrylates, polyurethane acrylates and/or acrylic acrylates.
Typically the alkanolamines may be selected from methanolamine, ethanolamine, diethanolamine, propanol amine, dipropanolamine, isopropanolamine, butanolamine, isobutanolamine, N-methyl ethanolamine, N-ethylethanolamine, N-methylpropanolamine and/or N-phenylethanolamine.
Preferably alkanolamine is selected from ethanolamine, diethanolamine, propanolamine and/or N-methylethanolamine.
Usually the aminoacrylates may be selected from any commercially available aminoacrylates such as Ebecryl 81, LEO10551, LEO10553 and P116 (ex. Allnex) and CN3715, CN3705, CN3735 and CN381 (ex. Sartomer), Ebecryl 7100, Ebecryl 80, Ebecryl 83, LEO10552, Ebecryl LEO10552 (ex. Allnex), CN550, CN3755, CN554 (ex. Sartomer) and Photomer 4711 and Photomer 4755 (ex. IGM).
In addition it has been found that the use of aminoacrylates as opposed to aminobenzoates as co-initiators is advantageous given that aminobenzoate co-initiators absorb strongly between 260 and 340 nm in the UV spectrum and as such they can attenuate the intensity of UV light in this region. Therefore the amount of UV light available for photoinitiators absorbing in this region to generate free radicals is restricted.
Consequently that amount of photoinitiators in the inks and coating compositions which absorb in the 260-340 nm range of the electromagnetic spectrum which include benzophenone types, hydroxyalkyl phenone (‘hydroxy ketone’) types, aminoalkylphenone types and acylphosphine oxide types can be reduced.
The use of aminoacrylates in the inks and compositions is also advantageous in that they can act as a proton donor, which facilitates the effective action of type II H-abstracting photoinitiators such as the benzophenone and thioxanthone types. Furthermore the aminoacrylates also reduce some of the deleterious effects of oxygen inhibition of the free radical curing, in air, of ethylenically unsaturated monomers and oligomers.
This is particularly advantageous given that typically high amounts of free radical photoinitators, up to and exceeding 10.0% by weight of the total ink or coating composition are employed in inkjet fluids due to the low viscosity of the fluids that allows oxygen from the atmosphere to readily diffuse into the ink film before and during the energy-curing process.
Thus the inks and coating compositions contain less than 12.0% by weight of total photoinitator, typically less than 8.0% by weight, preferably less than 6.0% by weight and advantageously less than 5.0% by weight of total photoinitiator.
Preferably the inks and coating compositions contain low migration photoinitiators and in particular photoinitiators having recognized low migration potential which are listed Group 1A and Group 1B of the current and future editions of EuPIA's (European Printing Ink Association) Suitability List of Photo-initiators for Low Migration UV Printing Inks and Varnishes.
Advantageously the photoinitiators are the difunctional, multifunctional, oligomeric, polymeric and/or polymerizable types.
Particularly favored photoinitiators include phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (‘Irgacure 819’, Cas.No. 162881-26-7), difunctional and oligomeric hydroxyl ketone types such as Irgacure 127 (Cas.No. 474510-57-1) and Esacure KIP160 (Cas.No. 71868-15-0).
Irgacure 819 (ex. BASF) Irgacure 127 (ex. BASF)
Esacure KIP160 (ex. Lamberti)
Advantageously polymeric photoinitiators, wherein the photoinitiator moieties are chemically attached to a polymeric core are used.
An example of a polymeric photoinitiator is Omnipol TX (ex. IGM Resins, CAS No.: 813452-37-8), which has the following structure;
Other commercially available polymeric thioxanthones include Genopol TX-1 (ex. Rahn) and Speedcure 7010 (ex. Lambson).
Where polymeric photoinitiators are used in the ink and coating compositions it is preferred that their total concentration is less than 4.0% by weight, preferably less than 3.0% by weight (w/w) and advantageously less than 2.0% by weight.
Finally other similar polymeric photoinitiators such as those comprising benzophenone, aminoketone, or other photoinitiator groups may also be used.
It has also been found that limiting the concentration of the acyl phosphine oxide photoinitiator also limits the amount of photodecomposition by-products that could cause contamination of the environment.
Where phosphine oxide photoinitiators, such as phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (Cas.No. 162881-26-7), are used in low migration UV curable inkjet compositions, concentrations greater than 2.5% (w/w) of the total ink composition are typically employed.
In particular, one photoinitiator class where it is useful to restrict the concentration in the ink composition is the acylphosphine oxide types. A particular acylphosphine oxide photoinitiator that is useful in the preparation of UV curable inkjet fluids, and especially those for the printing of food packaging substrates and the like is phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (Cas.No. 162881-26-7) which is available commercially as Irgacure 819 (ex. BASF).
This photoinitiator has a specific migration limit of 3.3 mg/Kg (food). However, two principal photodecomposition by-products from this photoinitiator are mesitaldehyde (2,4,6-trimethylbenzaldehyde) and 2,4,6-trimethylbenzoic acid.
Mesitaldehyde, especially, is highly prone to migrating from cured ink films and causing contamination issues. Therefore, the compositions of the present invention achieve acceptable cure with concentrations of bis(2,4,6-trimethylbenzoyl) phosphine oxide of less than 2.5% by weight of the total ink composition, more preferably less than 2.0% by weight, and advantageously less than 1.0% by weight.
When radiation curable inks and varnishes are applied to the (non-contact) surface of primary or secondary packaging intended for foodstuffs, then any contamination from the package impacting the foodstuff should fall within the guidelines set out by Article 3 of Regulation (EC) No 1935/2004, as recommended by EUPIA, requiring that materials and articles in contact with food.
In particular, EUPIA has recommended that Article 3 of this provision be followed when producing printed matter for food packaging and has produced a detailed guideline for the selection of raw materials intended for printing inks for food packaging, along with guidelines on the testing of printed matter to ensure that regulatory requirements are achieved. Furthermore, it is a requirement of the inks of this invention, that when they are cured under the action of UV light that the level of contaminants arising from the cured ink film and reaching the foodstuff should fall below the specific migration limit for any material, in the instances where specific migration limit (SML) exist for those compounds. Wherein no specific SML exists for a compound then general limits apply.
Additionally EUPIA also provides guidelines on how to measure the potential level of migratables arising from printed matter. For inks applied to the non-food contact surface of packaging (i.e. the outer surface), whether that be to the primary packaging or secondary packaging (labels and sleeves) then the most likely route for migratable species from the ink contaminating the foodstuff is by what is known as set-off migration (see
Thus, any UV-curable inkjet fluid which is applied to either the primary or secondary packaging of foodstuff should not result in contamination of that foodstuff at levels exceeding the limits detailed above.
In particular bis(2,4,6-trimethylbenzoyl) phosphine oxide and other acylphosphine oxide photoinitiators, although the parent photoinitiator has a relatively high specific migration limit of 3.3 mg/Kg (or 3,300 ppb in any foodstuff), its photodecomposition by-products are currently bounded by the 10 ppb limit.
It has been found that to guarantee that this limit, especially for mesitaldehyde, is not breached, then the inkjet fluids should contain preferably no more than 1.0% by weight, and certainly no more than 2.0% by weight of acylphosphine oxide photoinitiators.
Thus the inks and coating compositions according to present invention provides excellent UV cure response and low levels of unbound, and hence migratable, monomer from cured ink films with concentrations of phosphine oxide photoinitiator of less than 2.5% by weight of the total composition, preferably less than 2.0% by weight and advantageously less than 1.0% by weight (w/w).
In addition to the above mentioned problems adhesion of UV curable inkjet fluids to plastic surfaces can be problematic, especially when the polymerizable component of the composition consists of significant quantities of multifunctional monomers such as HDDA (hexanediol diacrylate), DPGDA (dipropyleneglycol diacrylate) and/or TMPTA (trimethylolpropane triacrylate).
Conventionally, monofunctional monomers such as NVC (N-vinyl caprolactam) and PHEA (phenoxyethyl acrylate) are used to achieve the required level of adhesion to various plastic surfaces.
However, when energy-curable inkjet fluids for the food packaging market or other sensitive produce are used the amount of monofunctional monomers must be limited, or indeed excluded, so as to minimise the risk of unreacted monomer migrating from the cured ink film and causing contamination of packaged foodstuff.
Other sensitive produce packaging includes that for pharmaceutical packaging, toys, cosmetics and/or personal care packaging. Such packaging may include substrates containing PET, LDPE, HDPE, LLDPE, polyamide, and/or CPP and in particular, substrates that are difficult to adhere to include heavier gauge plastic films and structures used in the manufacture of bags, tubes, pouches and bottles.
Consequently to achieve the required low levels of migratable species that can elute from cured inkjet films it is necessary to use polymerizable compositions based largely on multifunctional monomers and oligomers which reduces the ink or coating compositions capability of adhering to plastic surfaces.
It has surprisingly been found that the use the particular aminoacrylate according to the present invention, in conjunction with the type and amount of photoinitiator can deliver significant improvements in adhesion and migration of multifunctional inkjet fluids with low amounts of multifunctional monomer.
Consequently it is a requirement the inks and coating compositions contain less than 10.0% by weight of any monofunctional monomer, more preferably less than 5.0% by weight of monofunctional monomer, and more preferably are essentially free of any intentionally added monofunctional monomer.
Typically the inks and coating compositions further comprise multifunctional ethylenically unsaturated monomers such as 1,3-butylene glycol diacrylate; 1,4-butanediol diacrylate; neopentyl glycol diacrylate; ethoxylated neopentyl glycol diacrylate; propoxylated neopentyl glycol diacrylate; 2-methyl-1,3-propanediyl 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; diethyleneglycol diacrylate; triethylene glycol diacrylate; tetraethylene glycol diacrylate; polyethylene glycol diacrylate; propoxylated ethylene glycol diacrylate; dipropylene glycol diacrylate; tripropyleneglycol diacrylate; polypropylene glycol diacrylate; poly (tetramethylene glycol) diacrylate; cyclohexane dimethanol diacrylate; ethoxylated cyclohexane dimethanol diacrylate; alkoxylated cyclohexane dimethanol diacrylate; polybutadiene diacrylate; hydroxypivalyl hydroxypivalate diacrylate; tricyclodecanedimethanol diacrylate; 1,4-butanediylbis[oxy(2-hydroxy-3,1-propanediyl)]diacrylate; ethoxylated bisphenol A diacrylate; propoxylated bisphenol A diacrylate; propoxylated ethoxylated bisphenol A diacrylate; ethoxylated bisphenol F diacrylate; 2-(2-Vinyloxyethoxy)ethyl acrylate; dioxane glycol diacrylate; ethoxylated glycerol triacrylate; glycerol propoxylate triacrylate; pentaerythritol triacrylate; trimethylolpropane triacrylate; caprolactone modified trimethylol propane triacrylate; ethoxylated trimethylolpropane triacrylate; propoxylated trimethylol propane triacrylate; tris (2-hydroxy ethyl) isocyanurate triacrylate; e-caprolactone modified tris (2-hydroxy ethyl) isocyanurate triacrylate; melamine acrylate oligomer; pentaerythritol tetraacrylate; ethoxylated pentaerythritol tetraacrylate; di-trimethylolpropane tetra acrylate; dipentaerythritol pentaaacrylate; dipentaerythritol hexaaacrylate and/or ethoxylated dipentaerythritol hexaacrylate A, wherein term ethoxylated refers to chain extended compounds through the use of ethyleneoxide, propoxylated refers to chain extended compounds through the use of propylene oxide, and alkoxylated refers to chain extended compounds using either or both ethyleneoxide and propylene oxide.
Preferably the ink and coating compositions include highly alkoxylated monomers such as ethoxylated or propoxylated trimethylolpropane triacrylates, polyethylene glycol diacrylates and polypropylene glycol diacrylates.
Furthermore it is desirable that the average degree of alkoxylation per polymerizable (especially acrylate) moiety in the monomer/oligomer is greater than 2.0 and preferably equal to or greater than 3.0.
In the case of ethoxylated TMPTA this means that a+b+c in the chemical structure below should be greater than 6.0 and preferably equal to or greater than 9.0.
Equivalent methacrylate compounds are also capable of being used.
The inclusion of such monomers has been found to result in achieving substantially reduced levels of unbound, unreacted monomer/oligomer in the cured ink/coating film which might otherwise be free to migrate from the cured ink/coating film and hence cause contamination issues whether that be with food packaging or other sensitive applications.
Advantageously the inks and coating compositions include hybrid monomers containing both (meth)acrylate and vinyl ether polymerizable groups in the monomer molecule. A particularly preferred monomer is 2-(2-vinyloxyethoxy)ethyl acrylate (‘VEEA’).
The inks and coating compositions may further include other functional monomers which include cyclic lactam such as N-vinyl Caprolactam, N-vinyl oxazolidinone and N-vinyl pyrrolidone, and secondary or tertiary acrylamides such as acryloyl morpholine, diacetone acrylamide, N-methyl acrylamide, N-ethyl acrylamide N-isopropyl acrylamide, N-t.butyl acrylamide, N-hexyl acrylamide, N-cyclohexyl acrylamide, N-octyl acrylamide, N-t.octyl acrylamide N-dodecyl acrylamide, N-benzyl acrylamide, N-(hydroxymethyl)acrylamide, N-isobutoxymethyl acrylamide, N-butoxymethyl acrylamide, N,N-dimethyl acrylamide, N,N-diethyl acrylamide, N,N-propyl acrylamide, N,N-dibutyl acrylamide, N,N-dihexyl acrylamide, N,N-dimethylamino methyl acrylamide, N,N-dimethylamino ethyl acrylamide, N,N-dimethylamino propyl acrylamide, N,N-dimethylamino hexyl acrylamide, N,N-diethylamino methyl acrylamide, N,N-diethylamino ethyl acrylamide, N,N-diethylamino propyl acrylamide, N,N-dimethylamino hexyl acrylamide, and/or N,N′-methylenebisacrylamide.
Additionally the ink and coating compostions of the present invention may also comprise any type or blend of radiation-curable oligomers such as polyurethane acrylates, polyester acrylates, polyether acrylates and/or epoxy acrylates.
The ink and coating compositions usually have a viscosity of less than 15.0 mPa·s at 50° C., and advantageously a viscosity of less than 12.0 mPa·s at 50° C.
The ink and coating compositions may also include pigments and/or dyes such as azo dyes, anthraquinone dyes, xanthene dyes, azine dyes and combinations thereof.
Typically the organic pigments may be selected from Pigment Yellow Numbers 12, 13, 14, 17, 74, 83, 114, 126, 127, 174, 188; Pigment Red Numbers 2, 22, 23, 48:1, 48:2, 52, 52:1, 53, 57:1, 112, 122, 166, 170, 184, 202, 266, 269; Pigment Orange Numbers 5, 16, 34, 36; Pigment Blue Numbers 15, 15:3, 15:4; Pigment Violet Numbers 3, 23, 27; and/or Pigment Green Number 7. Inorganic pigments may be one of the following non-limiting pigments: iron oxides, titanium dioxides, chromium oxides, ferric ammonium ferrocyanides, ferric oxide blacks, Pigment Black Number 7 and/or Pigment White Numbers 6 and 7.
Additionally the ink and coating compositions may also contain other components which enable them to perform in their intended application. These other components include, stabilizers, wetting aids, slip agents, inert resins, antifoams, fillers, rheological aids and/or amine synergists.
Furthermore the ink and coating compositions may optionally contain an acrylic polymer or copolymer which is dissolved into the ink or coating composition, typically in a concentration of between 2.0 and 20.0% by weight.
These polymers are usually prepared by the (thermal) free radical polymerization of blends of monomers including, styrene, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, and/or isobutyl (meth)acrylate. Examples of acrylic polymers include those supplied from Dianal, Elvacite Rohm and Haas and DSM.
The acrylic polymer preferably has an average molecular weight of less than 20,000 g/mole and advantageously less than 10,000 g/mole.
Finally the ink and coating compositions are preferably essentially free of any solvent. However, if required, the ink or coating compositions can be diluted with either organic or aqueous solvents. However, the preferred maximum amount of any solvent is 10.0% by weight.
The inks and coating compositions can be energy-cured by any means. Energy-curing refers to the cure of compositions of the current invention when exposed to various electromagnetic radiation sources producing an actinic effect. Such sources include electron-beam, UV-light, visible-light, IR and microwave.
Where the inks and coating compositions are cured under the preferred action of UV light, then UV sources such as; high-voltage mercury bulb, a medium-voltage mercury bulb, a xenon bulb, a carbon arc lamp, a metal halide bulb, a UV-LED lamp or sunlight, can be used.
Usually Piezo inkjet printheads are preferred for the delivery of inks and coating compositions. However, other printhead technologies, such as continuous inkjet and thermal inkjet may also be used.
The ink and coating compositions can be applied to the non-food contact surface of food packaging including primary and secondary food packaging. The ink and coating compositions and inks of the present invention can be applied to the surface of a plastic film, paper or paperboard substrate.
The plastic film can be, for example, any of the following: polyester, polyethylene, polypropylene, polyamide, poly(lactic acid), a cellulose film and any coated or pretreated film thereof.
The plastic film can be of a flexible or rigid type and can have a thickness of less than or greater than 100 μm. A printed plastic film may subsequently be laminated to a further plastic film, to form a printed laminate film suitable for food packaging. A printed paper or paperboard substrate may subsequently be laminated to a further plastic film, to form a printed laminate suitable for food packaging.
The invention is further described by the examples given below.
The following examples illustrate specific aspects of the present invention and are not intended to limit the scope thereof in any respect and should not be so construed.
The inks were prepared by mixing the pigment dispersion with the ink components using a Silverson type disperser for 20 minutes. The inks were then filtered to remove any oversized particles that might be present in the ink.
The viscosities of the inks were measured using a Brookfield DV-II+ Pro Viscometer equipped with Spindle no. 18, at 100 rpm. In order to be suitable for jetting, it is preferred that the inks of the present invention have a viscosity ≤15.0 mPa·s at 50° C., more preferably ≤12.0 mPa·s at 50° C.
The inks were applied to 36 μm Melinex S (a polyester film) at 12 μm and then cured at 200 mJ/cm2, using a Fusion UV Systems UV-Rig equipped with a medium pressure H-bulb. The belt speed was adjusted to deliver the required UV-dose of 200 mJ/cm2, as measured by a calibrated International Light Technologies ILT 490 Profiling Belt Radiometer (covering the UV-A and UV-B ranges).
The level of unbound, unreacted monomer in a print was determined by a ‘total extraction’ test. This test involved soaking 30 cm2 of the print in 2 ml of methanol, containing 0.025% (w/w) of MEHQ (stabilizer) for 24 hours at room temperature before the methanol solution was analyzed by GC-MS. The GC-MS was calibrated with known solutions of the monomers and photoinitiator products and the results are reported as ppb, the equivalent amount of monomer that would be present in 1 Kg of food according to the EU packaging model (where it is assumed that 600 cm2 of substrate is required to package 1 Kg of food) if all the unbound monomer in the print were to migrate into and contaminate the food.
The level of contamination from a print surface was determined by a ‘set-off’ migration test. This test involved blocking 90 cm2 of the printed surface to a 30 micron sheet of LDPE (low density poly(ethene)), at 10 tonnes for a period of 72 hours at room temperature and then for a further period of 10 days at 40° C. under a load of 5 Kg. The poly(ethene) film was then extracted into 2 ml of methanol, containing 0.025% (w/w) of MEHQ (stabilizer) for 24 hours before the methanol solution was analyzed by GC-MS. Similarly, the results are reported as ppb, the amount of migratable material that would be present in 1 Kg of food according to the EU packaging model, where it is assumed that 600 cm2 of substrate is required to package 1 Kg of food.
The cure response of the inks was determined by applying 12 μm films to Leneta opacity charts (Form 2A) using calibrated K-Bars (ex. RK Print). The coated charts were then passed through a Fusion UV Systems UV-Rig equipped with a medium pressure H-bulb. The belt speed was adjusted so that the UV-dose, as measured by a calibrated International Light Technologies ILT 490 Profiling Belt Radiometer (covering the UV-A and UV-B ranges), was about 50 mJ/cm2. The number of passes through the rig to achieve both surface and through cure were then recorded allowing the UV-dose level to achieve cure to be determined. The surface cure was assessed by gently drawing a cotton wool bud across the surface of the print, full cure being determined as being the point at which no surface defects were observed. Through cure was assessed by dragging a 1.5 mm wide wooden dowel across the surface of the ink with an approximate downward load of about 5 Kg. Through cure was determined as being the point at which the dowel was not able to penetrate through to the underlying surface of the Leneta Chart.
Ink prints prepared according to the method described for extraction and migration testing were assessed for their odor. For this, 5 prints of each ink were prepared and then the coated PET films were stacked on top of each other. After 24 hours, prints from the middle of the stack were taken and assessed for odor. A score of 1 to 6 was assigned to each print, where 1 denotes strong, unpleasant odor and 6 denotes insignificant odor emanating from the print.
The inks were applied to a polyethylene laminate (ex. Albea) which had previously been treated via corona discharge to the extent that the surface energy was measured at 40-42 Dynes/cm, with Dyne pens (ex. Dyne Technology). The inks were applied at 12 microns and cured at 200 mJ/cm2, as previously described.
Firstly, the inks were assessed for adhesion according to the Cross Hatch Test according to ASTM D3359-09. A score of 0 (total adhesion loss) to 5 (no adhesion loss) was assigned as a measure of the degree of adhesion (see
A second adhesion test involved taking the print and folding it (see
The following ink examples provide comparative examples prepared according to the prior art (EP2671722 (Comparative Example 1 (C1)) and WO2014126720 (Comparative Example 2 (C2))), a further comparative example comprising an aminoacrylate based on the reaction products of alkylamines (C3) and inventive examples (I1 to I6) showing the benefits of the use of an aminoacrylate based on the reaction product of ethanolamine. Furthermore, the impact of introducing a highly alkoxylated monomer according to U.S. Application No. 61/971,562 is also shown (I3 to I6). Note that throughout the text, “C” refers to comparative examples; “I” refers to inventive examples.
The inks of Table 1 were then assessed for their extractable components according to the procedure outlined above. The results for the extraction test are provided in Table 2.
Table 5 provides the test results, other than extractables, for the examples of Tables 3 and 4.
The results provided in Table 5 show that inks comprising aminoacrylates of the current invention have faster cure responses, produce prints of lower odor and achieve superior adhesion compared with the comparative ink examples comprising aminoacrylates produced by the Michael addition reaction of polyacrylates with alkylamines.
Table 6 provides the results of the extraction test carried out on the examples of tables 3 and 4.
The results of table 6 show that ink compositions prepared according to the invention are faster curing, produce prints of lower odour and result in prints having lower levels of extractable monomer. Furthermore, Inventive examples I7 and I10 provide superior adhesion to the polyethylene laminate than do the comparative examples C4, C5 C6, C7 and C8.
Inventive examples I3 to I6 showed the benefit of the inclusion of the highly alkoxylated monomer, ethoxylated (15 moles) trimethylolpropane triacrylate in reducing the amount of extractable monomer. Table 7 provides the compositions of further inventive examples incorporating aminoacrylates of the present invention with the either of the highly alkoxylated monomers ethoxylated (15 moles) trimethylolpropane triacrylate (SR9035, ex. Sartomer) or polyethyleneglycol (400) diacrylate (SR344, ex. Sartomer). Table 7 also provides the viscosity for these inks along with the results of the odour and adhesion tests.
The results in Table 7 demonstrate that ink compositions prepared according to the invention and further comprising highly alkoxylated monomers deliver very low odour from cured prints and achieve excellent adhesion. Inventive example I11 was also applied to Fasson PE85 (white), a polyolefinic self-adhesive label, 12 micron Melinex 813, and a corona discharge treated 50 micron Melinex S film. In all 3 cases the ink passed the cross-hatch adhesion test, with a rating of 5.
Table 8 provides the results for the extraction testing on Inventive example I11 to I18
The results in Table 8 show that very low levels of extractable monomer can be achieved with a total photoinitiator concentration of only 6.0% (w/w) of the total ink composition. Furthermore, for Inventive examples I11 to I18 only 0.5% of the acyl phosphine oxide photoinitiator, Irgacure 819, was used. This ensured that low levels of the photodecomposition product mesitaldehyde were achieved in the cured print samples.
Comparative Example C2 and Inventive Example I11 were tested for their set-off migratables according to the procedure outlined above and the results are given in Table 9.
The results in table 9 demonstrate that mesitaldehyde, the photodecomposition by-product from acylphosphine oxide type photoinitiators, is highly prone to migrating from the cured ink into plastic films that come into contact with the cured ink. It confirms the benefits achievable with compositions prepared according to the invention in limiting the concentration of such photoinitiators in UV-curable inks intended for the printing of food packaging, pharmaceutical packaging, cosmetics and personal care packaging and other sensitive applications which require the need for prints having not only low odor but low levels of unbound material that could otherwise migrate from the print and cause unwanted contamination.
Note: Comparative Example C2 and Inventive Example I11 were jetted from a Xaar 1002 printhead running at 45° C., with no clogging or mis-directionality jetting problems, even after extended periods of continuous printing.
The present invention has been described in detail, including the preferred embodiments thereof. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on this invention that fall within the scope and spirit of the invention.
This application claims priority to U.S. Provisional Patent Application Ser. No. 62/161,933 filed May 15, 2015, which is hereby incorporated herein by reference in its entirety and for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US16/30659 | 5/4/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62161933 | May 2015 | US |
