WO2023079295A1 - Encre pour jet d'encre - Google Patents

Encre pour jet d'encre Download PDF

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Publication number
WO2023079295A1
WO2023079295A1 PCT/GB2022/052782 GB2022052782W WO2023079295A1 WO 2023079295 A1 WO2023079295 A1 WO 2023079295A1 GB 2022052782 W GB2022052782 W GB 2022052782W WO 2023079295 A1 WO2023079295 A1 WO 2023079295A1
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WIPO (PCT)
Prior art keywords
ink
acrylate
pigment
inkjet
monomer
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PCT/GB2022/052782
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English (en)
Inventor
Katie BORG
Sean Slater
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Fujifilm Speciality Ink Systems Limited
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Publication of WO2023079295A1 publication Critical patent/WO2023079295A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/32—Inkjet printing inks characterised by colouring agents
    • C09D11/322—Pigment inks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/10—Printing inks based on artificial resins
    • C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing

Definitions

  • Inkjet ink The present invention relates to a printing ink and in particular to a compostable inkjet ink.
  • the compostability of packaging items is now an important consideration resulting in a British Standard for compostability of packaging, BS EN 13432.
  • Packaging products that conform to the compostable criteria of this standard are suitable for composting.
  • BS EN 13432 provides five compostable criteria, where each test is undertaken according to the test methods specified in BS EN 13432. Only if a material passes every test requirement is it deemed compostable.
  • the five compostable criteria of BS EN 13432 are as follows: 1. Disintegration – the packaging sample is mixed with organic waste and maintained under test scale composting conditions for 12 weeks after which time no more than 10% of material fragments are allowed to be larger than 2 mm. 2.
  • Biodegradability a measure of the actual metabolic, microbial conversion, under composting conditions, of the packaging sample into water, carbon dioxide and new cell biomass. Within a maximum of 6 months, biodegradation of the test sample must generate an amount of carbon dioxide that is at least 90% as much as the carbon dioxide given off from the control/reference material. 3. Absence of any negative effect on the composting process. 4. Low levels of heavy metals and no adverse effect of the quality of compost produced. Upper limits, in mg/kg (ppm) of dry sample, are: zinc 150, copper 50, nickel 25, cadmium 0.5, lead 50, mercury 0.5, chromium 50, molybdenum 1, selenium 0.75, arsenic 5 and fluoride 100. 5.
  • the composted packaging material must not have adverse effect on the bulk density, pH, salinity, volatile solids, total nitrogen, total phosphorus, total magnesium, total potassium and ammonium nitrogen characteristics of the compost.
  • the substrate is typically the main focus when considering compostability of packaging as the substrate is the largest component of the item.
  • the present inventors have now considered however the effect of the printed ink layer on compostability.
  • the printed ink layer has minimal effect on the physical degradation of the packaging as it contributes a small amount to the overall mass of the item.
  • the present inventors have found however that the printed ink layer can have an effect on the levels of heavy metals in the produced compost.
  • Inkjet inks are useful for printing onto packaging because the image can be varied simply by altering the file input to the printer.
  • inkjet printing minute droplets of black, white or coloured ink are ejected in a controlled manner from one or more reservoirs or printing heads through narrow nozzles on to a substrate, which is moving relative to the reservoirs.
  • the ejected ink forms an image on the substrate.
  • the inks must flow rapidly from the printing heads, and, to ensure that this happens, they must have in use a low viscosity, typically 200 mPas or less at 25°C, although in most applications the viscosity should be 50 mPas or less, and often 25 mPas or less.
  • the ink when ejected through the nozzles, the ink has a viscosity of less than 25 mPas, preferably 5-15 mPas and most preferably between 7-11 mPas at the jetting temperature, which is often elevated to, but not limited to 40-50°C (the ink might have a much higher viscosity at ambient temperature).
  • the inks must also be resistant to drying or crusting in the reservoirs or nozzles. For these reasons, inkjet inks for application at or near ambient temperatures are commonly formulated to contain a large proportion of a mobile liquid vehicle or solvent such as water or a low-boiling solvent or mixture of solvents.
  • inkjet ink contains unsaturated organic compounds, termed monomers and/or oligomers, which polymerise when cured.
  • This type of ink has the advantage that it is not necessary to evaporate the liquid phase to dry the print; instead the print is cured, a process which is more rapid than evaporation of solvent at moderate temperatures.
  • the present inventors considered the components of inkjet inks and found that the choice of pigment can have an effect on the compostability of the printed article having the inkjet ink printed thereon. In this regard, during the drying/curing process, pigments remain in the dried/cured ink film. Pigments can be a source of heavy metals, particularly copper, and hence can be the cause of an accumulation of heavy metals in the resulting compost.
  • the present invention provides an inkjet ink comprising a radiation-curable monomer and at least one of a blue, cyan and/or green pigment, wherein the radiation-curable monomer comprises (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, wherein the ink has a viscosity of less than 100 mPas at 25°C, and wherein the amount of copper present in the ink is less than 2,000 ppm.
  • Fig.1 shows a plot of dot patch/tint % vs chroma and density for a blue ink of the invention
  • Fig.2 shows a plot of dot patch/tint % vs chroma and density for a comparative cyan ink.
  • the present inventors have surprisingly found that it is possible to provide a compostable inkjet ink with the required blue/cyan/green colour and the required properties for inkjet printing using at least one of a blue, cyan and/or green pigment and (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, wherein the ink has a viscosity of less than 100 mPas at 25°C, and wherein the amount of copper present in the ink is less than 2,000 ppm.
  • the inkjet ink of the present invention comprises at least one of a blue, cyan and/or green pigment.
  • the ink may contain: a blue pigment; a cyan pigment; a green pigment; blue and cyan pigments; blue and green pigments; cyan and green pigments; or blue, cyan and green pigments.
  • the present inventors have found that the choice of pigment can greatly affect the compostability of the printed article having the inkjet ink printed thereon.
  • pigments remain in the dried/cured ink film.
  • Pigments can be a source of heavy metals, and hence can be the cause of an accumulation of heavy metals in the resulting compost. Heavy metals of course need to be restricted according to BS EN 13432.
  • Particularly problematic pigments include phthalocyanine pigments, which are commonly employed for blue, cyan and green inks, owing to the presence of copper, and pigment yellow 150 which contains nickel. Green inks can also contain cadmium in addition to copper. Other pigments that are commonly used in the market, while not being based on heavy metals, may also contain trace amounts of heavy metals that will contribute to the total amount of heavy metal content in the printed item. Accordingly, in the present invention, the amount of copper present in the ink is less than 2,000 ppm. The present inventors have found that it is possible to maintain the same colour gamut as an ink containing a copper-based blue/cyan/green pigment whilst not compromising the compostability of the printed item.
  • the amount of copper present in the ink is 1,500 ppm or less, more preferably 1,000 ppm or less, more preferably 500 ppm or less and most preferably 50 ppm or less.
  • Copper-based phthalocyanine pigments are hence preferably absent in the ink of the present invention.
  • the ink is free of copper-based phthalocyanine pigments.
  • the amount of nickel in the ink is also restricted.
  • the amount of nickel in the ink is 600 ppm or less, preferably 400 ppm or less, more preferably 200 ppm or less and most preferably 25 ppm or less.
  • the amount of cadmium in the ink is also restricted.
  • the amount of cadmium in the ink is 20 ppm or less, more preferably 10 ppm or less, more preferably 5 ppm or less and most preferably 0.5 ppm or less.
  • the amount of zinc, chromium, lead, molybdenum, mercury, selenium and arsenic is also restricted.
  • the amount of zinc in the ink is 2,000 ppm or less, preferably 1,500 ppm or less, more preferably 1,000 ppm or less, more preferably 500 ppm or less and most preferably 150 ppm or less;
  • the amount of chromium in the ink is 1,000 or less, more preferably 400 ppm or less, more preferably 200 ppm or less and most preferably 50 ppm or less;
  • the amount of lead in the ink is 1,000 or less, more preferably 400 ppm or less, more preferably 200 ppm or less and most preferably 50 ppm or less;
  • the amount of molybdenum in the ink is 20 ppm or less, more preferably 10 ppm or less, more preferably 5 ppm or less and most preferably 1 ppm or less;
  • the amount of mercury in the ink is 20 ppm or less, more preferably 10 ppm or less, more preferably 5 ppm or less and most preferably 0.5 ppm or less;
  • the total amount of molybdenum, mercury, selenium and arsenic in the ink combined is 20 ppm or less, more preferably 10 ppm or less and most preferably 8 ppm or less.
  • the total amount of heavy metals per se is restricted and in a preferred embodiment, the ink is free of heavy metals.
  • the inkjet ink of the present invention having a restricted amount of copper present therein, preferably a restricted amount of copper and nickel, more preferably a restricted amount of copper, nickel and cadmium, and most preferably a restricted heavy metal content, does not compromise the compostability of the printed item.
  • the amount of each heavy metal present in each pigment and in the ink as a whole is determined by inductively coupled plasma atomic emission spectroscopy (ICP).
  • ICP inductively coupled plasma atomic emission spectroscopy
  • ICP uses inductively coupled plasma to produce excited atoms or ions that emit electromagnetic radiation at wavelengths characteristic of a particular element.
  • the intensity of the emissions from various wavelengths of light are proportional to the concentrations of the elements within the sample.
  • the total heavy metal content present in each pigment and hence the ink as a whole can be determined by the following method: Before commencing the analysis, the powder pigments are digested in a mixture of hydrochloric and nitric acids to ensure that the total metal content, rather than the free metal levels in the samples are correctly determined.
  • Both the dual radial and axial detectors are used. First, the calibration is run, followed by a period of blank deionised water to flush the system, the samples are then run in duplicate. Using the calibration, it is then possible to calculate the concentration of metals present. Any suitable blue, cyan and green pigments can be used provided that the ink has the restricted amount of copper present therein.
  • the pigment is dispersed in the liquid medium of the ink.
  • the pigment is typically a pigment dispersion, which is combined with the other components of the ink by mixing.
  • Dispersible pigments are well-known in the art and are commercially available, for example, under the tradenames Paliotol (available from BASF plc), Cinquasia, Irgalite (both available from Ciba Speciality Chemicals) and Hostaperm (available from Clariant UK). Pigment dispersions are commercially available for example, under the tradenames of Projet ADP (Fujifilm FFIC), Hostajet (Clariant) and SP (Fuji pigments).
  • the at least one of a blue, cyan and/or green pigment is a non-copper-based phthalocyanine pigment, such as PB16 and PB60.
  • the following commercially-available pigments classified according to Colour Index International according to the following tradenames are preferred non-limiting examples that can be used in the ink of the present invention: Blue pigments: PB22, PB24, PB25, PB28, PB50, PB56, PB60, PB61, PB61:1, PB66, PB73, PB75, PB80, PB81, PB82, PB84 and PB86.
  • Such pigments are not copper based.
  • Preferred examples include PB25, PB56, PB60 and PB61.
  • pigments including PB15.4 and PB15.3, are not suitable pigments for use in the inkjet ink of the present invention as these pigments are phthalocyanine- based pigments and have a high copper content.
  • Cyan pigments PB16, PB27, PB29 and PB79. Such pigments are not copper based.
  • Such pigments are not copper based.
  • the green pigment is an algae-based pigment or an inorganic pigment, such as Green earth or Verona green. Green earth is known commercially as PG23 and is composed of ferrous and ferric silicates of potassium, manganese and aluminium.
  • Verona green is an inorganic pigment derived from the minerals celadonite and glauconite, which has the chemical formula K[(Al,Fe 3+ ),(Fe 2+, Mg](AlSi 3 ,Si 4 )O 10 (OH) 2 .
  • Pigments other than blue, cyan and green pigments may be included in the inkjet ink of the present invention.
  • Pigments other than blue, cyan and green pigments include a yellow pigment, a magenta pigment, a black pigment, an orange pigment, a red pigment, a violet pigment, a white pigment and mixtures thereof. Such pigments are known in the art.
  • the at least one of a blue, cyan and/or green pigment is the sole pigment present in the ink. That is, the ink preferably contains no pigments other than blue, cyan and green pigments.
  • the ink may contain: a blue pigment as the sole pigment; a cyan pigment as the sole pigment; a green pigment as the sole pigment; blue and cyan pigments as the sole pigments; blue and green pigments as the sole pigments; cyan and green pigments as the sole pigments; or blue, cyan and green pigments as the sole pigments.
  • the red/green opponent colours are represented along the a* axis, with green at negative a* values and red at positive a* values.
  • the yellow/blue opponent colours are represented along the b* axis, with blue at negative b* values and yellow at positive b* values.
  • the ink can also be categorised by its chromatic attributes including the hue (or colour), the value (or lightness) and the chroma (or strength). These chromatic attributes are influenced by the chemistry of the pigment.
  • Chroma is the aspect of colour in the Munsell colour system by which a sample appears to differ from a grey of the same lightness or brightness and that corresponds to saturation of the perceived colour.
  • the ink is a blue ink.
  • the blue ink preferably has an a* value from –40 to 35 and a b* value from –75 to –20, preferably an a* value from –35 to 30 and a b* value from –70 to –25, more preferably an a* value from –30 to 25 and a b* value from –65 to –30.
  • the L* value will depend on the lightness of the blue ink.
  • the blue ink may have an L* value from 5 to 69, preferably from 10 to 67, more preferably from 15 to 65. Or the blue ink may be a lighter blue and have an L* value from 71 to 105, preferably from 73 to 100, more preferably from 75 to 95. Preferably, the blue ink preferably has a chroma from 40 to 85, more preferably from 45 to 80 and most preferably from 50 to 75. If the ink is a blue ink, the ink comprises a blue pigment.
  • the blue pigment is preferably dispersible pigment PB25, PB56, PB60 or PB61.
  • the blue pigment is the sole pigment present in the ink.
  • the ink is a cyan ink.
  • the cyan ink preferably has an a* value from –60 to –10 and a b* value from –70 to –20, preferably an a* value from –55 to –15 and a b* value from –65 to –25, more preferably an a* value from –50 to –20 and a b* value from –60 to –30.
  • the L* value will depend on the lightness of the cyan ink.
  • the cyan ink may have an L* value from 35 to 69, preferably from 40 to 67, more preferably from 42 to 65.
  • the cyan ink may be a lighter cyan and have an L* value from 71 to 105, preferably from 73 to 100, more preferably from 75 to 95.
  • the cyan ink preferably has a chroma from 40 to 85, more preferably from 45 to 80 and most preferably from 50 to 75.
  • the ink may comprise a cyan pigment.
  • the cyan pigment is the sole pigment present in the ink.
  • the cyan pigment is preferably dispersible pigment PB16, PB27, PB29 or PB79.
  • the cyan ink may comprise blue and green pigments.
  • the blue and green pigments are the sole pigments present in the ink.
  • the ink is a green ink.
  • the green ink preferably has an a* value from –105 to –55 and a b* value from –15 to 35, preferably an a* value from –100 to –60 and a b* value from –10 to 30, more preferably an a* value from –95 to –65 and a b* value from –5 to 25, most preferably an a* value from –90 to –70 and a b* value from 0 to 20.
  • the green ink has an L* value from 40 to 80, preferably from 45 to 75, more preferably from 50 to 70.
  • the green ink preferably has a chroma from 40 to 85, more preferably from 45 to 80 and most preferably from 50 to 75.
  • the ink comprises a green pigment.
  • the green pigment is the sole pigment present in the ink.
  • the green pigment is preferably dispersible pigment PG17, PG23, green 8 or green 54.
  • the green pigment is preferably an algae-based pigment or an inorganic pigment, such as Green earth or Verona green.
  • Green earth is known commercially as PG23 and is composed of ferrous and ferric silicates of potassium, manganese and aluminium.
  • Verona green is an inorganic pigment derived from the minerals celadonite and glauconite, which has the chemical formula K[(Al,Fe3+),(Fe2+,Mg](AlSi3,Si4)O10(OH)2.
  • the ink comprises a blue and/or cyan pigment. That is, the ink preferably comprises a blue pigment, a cyan pigment or blue and cyan pigments.
  • the blue and/or cyan pigment is the sole pigment present in the ink.
  • the ink comprises a blue and/or green pigment.
  • the ink preferably comprises a blue pigment, a green pigment or blue and green pigments.
  • the blue and/or green pigment is the sole pigment present in the ink.
  • the ink comprises a cyan and/or green pigment. That is, the ink preferably comprises a cyan pigment, a green pigment or cyan and green pigments.
  • the cyan and/or green pigment is the sole pigment present in the ink.
  • the ink comprises blue, cyan and green pigments.
  • the blue, cyan and green pigments are the sole pigments present in the ink.
  • Pigment particles dispersed in the ink should be sufficiently small to allow the ink to pass through an inkjet nozzle, typically having a particle size less than 8 ⁇ m, preferably less than 5 ⁇ m, more preferably less than 1 ⁇ m and particularly preferably less than 0.5 ⁇ m.
  • the pigment is preferably present in the ink in a total amount from 2 to 10% by weight and most preferably from 3 to 6% by weight, based on the total weight of the ink. That is, the total amount of blue, cyan and green pigments present in the ink is preferably from 2 to 10% by weight and most preferably from 3 to 6% by weight, based on the total weight of the ink.
  • the ink of the present invention typically contains a higher amount of pigment than an ink containing a copper-based pigment to maintain the same colour gamut. It can thus be difficult to achieve the required balance of properties for a compostable inkjet ink containing at least one of a blue, cyan and/or green pigment. It is surprising that the ink of the present invention can maintain the required balance of properties for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • the inkjet ink of the present invention comprises a radiation-curable monomer. As is known in the art, monomers may possess different degrees of functionality, which include mono, di, tri and higher functionality monomers.
  • mono and difunctional are intended to have their standard meanings, i.e. one or two groups, respectively, which take part in the polymerisation reaction on curing.
  • Multifunctional (which does not include difunctional) is intended to have its standard meaning, i.e. three or more groups, respectively, which take part in the polymerisation reaction on curing.
  • Monomers typically have a molecular weight of less than 600, preferably more than 200 and less than 450.
  • Monomers are typically added to inkjet inks to reduce the viscosity of the inkjet ink.
  • ком ⁇ онентs can be measured using an ARG2 rheometer manufactured by T.A. Instruments, which uses a 40 mm oblique / 2° steel cone at 25°C with a shear rate of 25 s -1 . Accordingly, monomer viscosities can be measured using a rotational rheometer having a 40 mm diameter / 2° steel cone at 25°C with a shear rate of 25 s -1 .
  • the radiation-curable monomer comprises (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate (MEDA/Medol-10).
  • (2-Methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate is a monofunctional (meth)acrylate monomer and has one (meth)acrylate group which takes part in the polymerisation reaction on curing. It has the following structure: (2-Methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate has a CAS no.
  • (2-methyl-2-ethyl-1,3-dioxoran-4-yl) methyl acrylate provides the ink with the required properties and in particular the viscosity required for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • (2-Methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate is preferably present in 5 to 30% by weight, more preferably 10 to 25% by weight and most preferably 15 to 20% by weight, based on the total weight of the ink.
  • the radiation-curable monomer further comprises a monofunctional monomer other than (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate.
  • Monofunctional monomers are well known in the art.
  • a radiation-curable monofunctional monomer has one functional group, which takes part in the polymerisation reaction on curing.
  • the polymerisable groups can be any group that are capable of polymerising upon exposure to radiation and are preferably selected from a (meth)acrylate group and a vinyl ether group.
  • the substituents of the monofunctional monomer other than (2-methyl-2-ethyl-1,3-dioxolane-4- yl)methyl acrylate are not limited other than by the constraints imposed by the use in an inkjet ink, such as viscosity, stability, toxicity etc.
  • the substituents are typically alkyl, cycloalkyl, aryl and combinations thereof, any of which may be interrupted by heteroatoms.
  • Non-limiting examples of substituents commonly used in the art include C1-18 alkyl, C3-18 cycloalkyl, C6-10 aryl and combinations thereof, such as C6-10 aryl- or C3-18 cycloalkyl-substituted C1-18 alkyl, any of which may be interrupted by 1-10 heteroatoms, such as oxygen or nitrogen, with nitrogen further substituted by any of the above described substituents.
  • the substituents may together also form a cyclic structure.
  • the total amount of monofunctional monomer including (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate is preferably 50-90% by weight, more preferably 55-85% by weight and most preferably 60- 80% by weight, based on the total weight of the ink.
  • the monofunctional monomer other than (2-methyl-2-ethyl-1,3-dioxolane-4- yl)methyl acrylate comprises a monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl- 1,3-dioxolane-4-yl)methyl acrylate.
  • Monofunctional (meth)acrylate monomers are well known in the art and are preferably the esters of acrylic acid.
  • (meth)acrylate is intended herein to have its standard meaning, i.e. acrylate and/or methacrylate. Mixtures of (meth)acrylates may also be used.
  • the substituents of the monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3- dioxolane-4-yl)methyl acrylate are not limited other than by the constraints imposed by the use in an inkjet ink, such as viscosity, stability, toxicity etc.
  • the monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate may be a cyclic monofunctional (meth)acrylate monomer and/or an acyclic-hydrocarbon monofunctional (meth)acrylate monomer.
  • the monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3-dioxolane- 4-yl)methyl acrylate may comprise a cyclic monofunctional (meth)acrylate monomer other than (2- methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate.
  • the substituents of the cyclic monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3- dioxolane-4-yl)methyl acrylate are typically cycloalkyl, aryl and combinations thereof, any of which may be interrupted by heteroatoms and/or substituted by alkyl.
  • substituents commonly used in the art include C3-18 cycloalkyl, C6-10 aryl and combinations thereof, any of which may substituted with alkyl (such as C1-18 alkyl) and/or any of which may be interrupted by 1-10 heteroatoms, such as oxygen or nitrogen, with nitrogen further substituted by any of the above described substituents.
  • the substituents may together also form a cyclic structure.
  • the cyclic monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3-dioxolane-4- yl)methyl acrylate may be selected from isobornyl acrylate (IBOA), phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), tetrahydrofurfuryl acrylate (THFA), 4-tert-butylcyclohexyl acrylate (TBCHA), 3,3,5-trimethylcyclohexyl acrylate (TMCHA), benzyl acrylate (BA) and mixtures thereof.
  • IBOA isobornyl acrylate
  • PEA phenoxyethyl acrylate
  • CTLCA cyclic TMP formal acrylate
  • THFA tetrahydrofurfuryl acrylate
  • TBCHA 4-tert-butylcyclohexyl acrylate
  • TMCHA 3,3,5-trimethylcyclohe
  • the cyclic monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3- dioxolane-4-yl)methyl acrylate comprises IBOA and PEA.
  • the monofunctional (meth)acrylate monomer other than (2-methyl-2-ethyl-1,3-dioxolane- 4-yl)methyl acrylate may comprise an acyclic-hydrocarbon monofunctional (meth)acrylate monomer.
  • the substituents of the acyclic-hydrocarbon monofunctional (meth)acrylate monomer are typically alkyl, which may be interrupted by heteroatoms.
  • a non-limiting example of a substituent commonly used in the art is C1-18 alkyl, which may be interrupted by 1-10 heteroatoms, such as oxygen or nitrogen, with nitrogen further substituted.
  • the acyclic-hydrocarbon monofunctional (meth)acrylate monomer contains a linear or branched C6-C20 group. It may be selected from octadecyl acrylate (ODA), 2-(2-ethoxyethoxy)ethyl acrylate, tridecyl acrylate (TDA), isodecyl acrylate (IDA), lauryl acrylate and mixtures thereof.
  • ODA octadecyl acrylate
  • TDA tridecyl acrylate
  • IDA isodecyl acrylate
  • lauryl acrylate lauryl acrylate and mixtures thereof.
  • the acyclic-hydrocarbon monofunctional (meth)acrylate monomer contains a linear C6-C20 group.
  • the monofunctional (meth)acrylate monomer other than (2- methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate is selected from isobornyl acrylate (IBOA), phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), tetrahydrofurfuryl acrylate (THFA), 4- tert-butylcyclohexyl acrylate (TBCHA), 3,3,5-trimethylcyclohexyl acrylate (TMCHA), benzyl acrylate (BA), octadecyl acrylate (ODA), 2-(2-ethoxyethoxy)ethyl acrylate, tridecyl acrylate (TDA), isodecyl acrylate (IDA), lauryl acrylate and mixtures thereof.
  • IBOA isobornyl acrylate
  • PEA phenoxyethyl acrylate
  • CCTFA
  • the ink comprises (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, IBOA and PEA.
  • the sole monofunctional (meth)acrylate monomers present in the ink are (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, IBOA and PEA. This monomer blend is particularly useful in providing the ink with the required properties for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • the total amount of monofunctional (meth)acrylate monomer including (2- methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate is preferably 30-70% by weight, more preferably 35- 65% by weight and most preferably 40-60% by weight, based on the total weight of the ink.
  • the monofunctional monomer other than (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate comprises an N-vinyl amide monomer and/or an N-(meth)acryloyl amine monomer.
  • N-Vinyl amide monomers are well-known monomers in the art.
  • N-Vinyl amide monomers have a vinyl group attached to the nitrogen atom of an amide which may be further substituted in an analogous manner to the (meth)acrylate monomers.
  • Preferred examples are N-vinyl caprolactam (NVC), N-vinyl pyrrolidone (NVP), N-vinyl piperidone, N-vinyl formamide and N-vinyl acetamide.
  • NVC N-vinyl caprolactam
  • NVP N-vinyl pyrrolidone
  • N-vinyl piperidone N-vinyl formamide
  • N-vinyl acetamide N-acryloyl amine monomers are also well-known in the art.
  • N-Acryloyl amine monomers also have a vinyl group attached to an amide but via the carbonyl carbon atom and again may be further substituted in an analogous manner to the (meth)acrylate monomers.
  • N- acryloylmorpholine ACMO
  • the ink preferably comprises NVC and/or ACMO.
  • N-Vinyl amide monomers are particularly preferred, and most preferably NVC.
  • the ink comprises an N-vinyl amide monomer and/or an N-(meth)acryloyl amine monomer present in 5-30% by weight, more preferably 5-25% by weight, based on the total weight of the ink.
  • the ink comprises (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, IBOA, PEA and NVC.
  • the sole monofunctional monomers present in the ink are (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, IBOA, PEA and NVC.
  • This monomer blend is particularly useful in providing the ink with the required properties for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • the ink may also comprise one or more N-vinyl monomers other than an N-vinyl amide monomer and/or an N-(meth)acryloyl amine monomer. Examples include N-vinyl carbazole, N-vinyl indole and N-vinyl imidazole.
  • the radiation-curable monomer further comprises a di- and/or multifunctional monomer.
  • the radiation-curable monomer further comprises a di-, tri-, tetra-, penta- or hexa- functional monomer, i.e. the radiation-curable monomer has two, three, four, five or six functional groups.
  • the radiation-curable monomer further comprises a difunctional monomer.
  • the functional group of the di- and/or multifunctional radiation-curable monomer may be the same or different but must take part in the polymerisation reaction on curing.
  • Examples of such functional groups include any groups that are capable of polymerising upon exposure to radiation and are preferably selected from a (meth)acrylate group and a vinyl ether group.
  • the di- and/or multifunctional radiation-curable monomer may possess different degrees of functionality, and a mixture including combinations of di, tri and higher functionality monomers may be used.
  • the substituents of the di- and/or multifunctional radiation-curable monomer are not limited other than by the constraints imposed by the use in an ink-jet ink, such as viscosity, stability, toxicity etc.
  • the substituents are typically alkyl, cycloalkyl, aryl and combinations thereof, any of which may be interrupted by heteroatoms.
  • Non-limiting examples of substituents commonly used in the art include C1-18 alkyl, C3-18 cycloalkyl, C6-10 aryl and combinations thereof, such as C6-10 aryl- or C3-18 cycloalkyl- substituted C1-18 alkyl, any of which may be interrupted by 1-16 heteroatoms, such as oxygen or nitrogen, with nitrogen further substituted by any of the above described substituents.
  • the substituents may together also form a cyclic structure.
  • the ink comprises 1 to 20% by weight, more preferably 5 to 15% by weight, of a di- and/or multifunctional radiation-curable monomer, based on the total weight of the ink.
  • di- and/or multifunctional radiation-curable monomer is particularly useful in maintaining the required balance of properties for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • di- and/or multifunctional monomer include difunctional (meth)acrylate monomers, multifunctional (meth)acrylate monomers, divinyl ether monomers, multifunctional vinyl ether monomers and di- and/or multifunctional vinyl ether (meth)acrylate monomers. Mixtures of di- and/or multifunctional radiation-curable monomers may also be used.
  • the di- and/or multifunctional monomer preferably comprises a (meth)acrylate monomer.
  • the ink comprises a difunctional (meth)acrylate monomer.
  • Difunctional (meth)acrylate monomers are well known in the art and a detailed description is therefore not required. Examples include hexanediol diacrylate (HDDA), 1,8-octanediol diacrylate, 1,9- nonanediol diacrylate, 1,10-decanediol diacrylate (DDDA), 1,11-undecanediol diacrylate and 1,12- dodecanediol diacrylate, polyethylene glycol diacrylate (for example tetraethylene glycol diacrylate, PEG200DA, PEG300DA, PEG400DA, PEG600DA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), tricyclodecane dimethanol diacrylate (TCDDMDA), neopentylglycol diacrylate, 3-methyl-1,5-pentane
  • HDDA
  • esters of methacrylic acid such as hexanediol dimethacrylate, 1,8-octanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, 1,11-undecanediol dimethacrylate and 1,12-dodecanediol dimethacrylate, triethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate, 1,4-butanediol dimethacrylate and mixtures thereof.
  • DDDA is particularly preferred.
  • the ink comprises DDDA.
  • the ink comprises 1 to 20% by weight, more preferably 5 to 15%, by weight of a difunctional (meth)acrylate monomer, based on the total weight of the ink. It has been found that this amount of a difunctional radiation-curable monomer is particularly useful in maintaining the required balance of properties for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • the ink may further comprise a multifunctional (meth)acrylate monomer.
  • Suitable multifunctional (meth)acrylate monomers include tri-, tetra-, penta-, hexa-, hepta- and octa-functional monomers.
  • multifunctional acrylate monomers examples include trimethylolpropane triacrylate, dipentaerythritol triacrylate, tri(propylene glycol) triacrylate, bis(pentaerythritol) hexaacrylate, and the acrylate esters of ethoxylated or propoxylated glycols and polyols, for example, ethoxylated trimethylolpropane triacrylate and ethoxylated pentaerythritol tetraacrylate (EOPETTA, also known as PPTTA), and mixtures thereof.
  • Suitable multifunctional (meth)acrylate monomers also include esters of methacrylic acid (i.e.
  • the amount of the multifunctional (meth)acrylate monomer, when present, is preferably 1-20% by weight, more preferably 5-15% by weight, based on the total weight of the ink.
  • the di- and/or multifunctional radiation-curable monomer may have at least one vinyl ether functional group.
  • the ink may further comprise a divinyl ether monomer, a multifunctional vinyl ether monomer, a difunctional vinyl ether (meth)acrylate monomer and/or a multifunctional vinyl ether (meth)acrylate monomer, preferably a difunctional vinyl ether (meth)acrylate monomer and/or a divinyl ether monomer.
  • the ink comprises 1 to 20% by weight, more preferably 5 to 15% by weight, of a divinyl ether monomer, a multifunctional vinyl ether monomer, a difunctional vinyl ether (meth)acrylate monomer and/or a multifunctional vinyl ether (meth)acrylate monomer, based on the total weight of the ink.
  • Examples of a divinyl ether monomer include triethylene glycol divinyl ether (DVE-3), diethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, bis[4-(vinyloxy)butyl] 1,6- hexanediylbiscarbamate, bis[4-(vinyloxy)butyl] isophthalate, bis[4-(vinyloxy)butyl] (methylenedi-4,1- phenylene)biscarbamate, bis[4-(vinyloxy)butyl] succinate, bis[4-(vinyloxy)butyl]terephthalate, bis[4- (vinyloxymethyl)cyclohexylmethyl] glutarate, 1,4-butanediol divinyl ether and mixtures thereof.
  • DVE-3 triethylene glycol divinyl ether
  • diethylene glycol divinyl ether 1,4-cyclohexanedimethanol diviny
  • Triethylene glycol divinyl ether (DVE-3) is particularly preferred.
  • An example of a multifunctional vinyl ether monomer is tris[4-(vinyloxy)butyl] trimellitate.
  • Examples of a vinyl ether (meth)acrylate monomer include, 2-(2-vinyloxy ethoxy)ethyl methacrylate (VEEM), 2-(2-vinyloxy ethoxy)ethyl acrylate (VEEA) and mixtures thereof.
  • VEEM 2-(2-vinyloxy ethoxy)ethyl acrylate
  • VEEA 2-(2-Vinyloxy ethoxy)ethyl acrylate
  • the di- and/or multifunctional monomer is selected from 1,10-decanediol diacrylate (DDDA), hexanediol diacrylate (HDDA), polyethylene glycol diacrylate, tripropylene glycol diacrylate (TPGDA), 3-methyl 1,5- pentanediol diacrylate (3-MPDA), dipropylene glycol diacrylate (DPGDA), tricyclodecane dimethanol diacrylate (TCDDMDA), propoxylated neopentyl glycol diacrylate (NPGPODA), trimethylolpropane triacrylate (TMPTA), di-trimethylolpropane tetraacrylate (DiTMPTA), di-pentaerythritol hexaacrylate (DPHA), ethoxylated trimethylolpropane triacrylate (EOTMPTA), ethoxylated pentaerythritol tetraacrylate (EOPETTA), tri
  • the difunctional monomer is selected from 1,10-decanediol diacrylate (DDDA), hexanediol diacrylate (HDDA), polyethylene glycol diacrylate, tripropylene glycol diacrylate (TPGDA), 3-methyl 1,5- pentanediol diacrylate (3-MPDA), dipropylene glycol diacrylate (DPGDA), tricyclodecane dimethanol diacrylate (TCDDMDA), propoxylated neopentyl glycol diacrylate (NPGPODA), triethylene glycol divinyl ether (DVE-3), 2-(2-vinyloxy ethoxy)ethyl acrylate (VEEA) and mixtures thereof.
  • DDDA 1,10-decanediol diacrylate
  • HDDA hexanediol diacrylate
  • TPGDA tripropylene glycol diacrylate
  • 3-methyl 1,5- pentanediol diacrylate 3-methyl 1,5- pentanedi
  • the difunctional monomer comprises 1,10-decanediol diacrylate (DDDA).
  • the ink comprises (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, IBOA, PEA, NVC and DDDA.
  • the sole monomers present in the ink are (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl acrylate, IBOA, PEA, NVC and DDDA.
  • This monomer blend is particularly useful in providing the ink with the required properties for inkjet printing whilst maintaining the required blue/cyan/green colour of the compostable inkjet ink.
  • the ink may further comprise a radiation-curable (i.e. polymerisable) oligomer, such as a (meth)acrylate oligomer.
  • a radiation-curable (i.e. polymerisable) oligomer such as a (meth)acrylate oligomer.
  • Any radiation-curable oligomer that is compatible with the other ink components is suitable for use in the ink of the present invention.
  • the ink comprises a (meth)acrylate oligomer.
  • the term “curable oligomer” has its standard meaning in the art, namely that the component is partially reacted to form a pre-polymer having a plurality of repeating monomer units, which is capable of further polymerisation.
  • the oligomer preferably has a molecular weight of at least 600. The molecular weight is preferably 4,000 or less.
  • Molecular weights can be calculated if the structure of the oligomer is known or molecular weights can be measured using gel permeation chromatography using polystyrene standards.
  • the oligomers may possess different degrees of functionality, and a mixture including combinations of mono, di, tri and higher functionality oligomers may be used.
  • the degree of functionality of the oligomer determines the degree of crosslinking and hence the properties of the cured ink.
  • the oligomer is preferably multifunctional meaning that it contains on average more than one reactive functional group per molecule.
  • the average degree of functionality is preferably from 2 to 6. Oligomers are typically have a viscosity of 150 mPas or above at 25oC.
  • Preferred oligomers for inclusion in the inks have a viscosity of 0.5 to 10 Pas at 50°C.
  • Oligomer viscosities can be measured using an ARG2 rheometer manufactured by T.A. Instruments, which uses a 40 mm oblique / 2° steel cone at 60°C with a shear rate of 25 s -1 . Accordingly, oligomer viscosities can be measured using a rotational rheometer having a 40 mm diameter / 2° steel cone at 60°C with a shear rate of 25 s -1 .
  • Radiation-curable oligomers comprise a backbone, for example a polyester, urethane, epoxy or polyether backbone, and one or more radiation-curable groups.
  • the polymerisable group can be any group that is capable of polymerising upon exposure to radiation.
  • the oligomers are (meth)acrylate oligomers.
  • the oligomer may include amine functionality, as the amine acts as an activator without the drawback of migration associated with low-molecular weight amines.
  • the radiation-curable oligomer is amine modified.
  • the radiation-curable oligomer is an amine-modified (meth)acrylate oligomer.
  • Particularly preferred radiation-curable oligomers are di-, tri-, tetra-, penta- or hexa-functional acrylates.
  • the radiation-curable oligomer is an amine-modified acrylate oligomer.
  • a suitable amine-modified polyester acrylate oligomer is commercially available as UVP6600.
  • a suitable amine- modified polyether acrylate oligomer is commercially available as CN3715LM.
  • Other suitable examples of radiation-curable oligomers include epoxy based materials such as bisphenol A epoxy acrylates and epoxy novolac acrylates, which have fast cure speeds and provide cured films with good solvent resistance.
  • the amount of radiation-curable oligomer, when present, is preferably 0.1-10% by weight, more preferably 0.1 to 6% by weight, based on the total weight of the ink.
  • the inkjet ink may contain one or more passive (or “inert”) resins.
  • Passive resins are resins which are not radiation-curable and hence do not undergo crosslinking under the curing conditions to which the ink is exposed. In other words, resin is not a radiation-curable material.
  • Any passive resin that is compatible with the ink components of the final inkjet ink is suitable for use in the inkjet ink of the present invention.
  • the ink formulator is able to select from a wide range of suitable passive thermoplastic resins.
  • the resin may be selected from epoxy, polyester, vinyl, ketone, nitrocellulose, phenoxy or acrylate resins, or a mixture thereof and is preferably a poly(methyl (meth)acrylate) resin.
  • the resin has a weight-average molecular weight of 20-200 KDa and preferably 20-60 KDa, as determined by GPC with polystyrene standards.
  • the resin is preferably solid at 25°C. It is preferably soluble in the liquid medium of the ink (the radiation-curable diluent and, when present, additionally the solvent).
  • the resin may improve adhesion of the ink to the substrate.
  • the resin, when present, is preferably present at 0.1 to 3% by weight, based on the total weight of the ink.
  • the ink contains 10 to 50% bio-renewable content (BRC), more preferably 20-40% BRC.
  • bio-renewable derived raw materials include plant- based materials turpenes, fatty acids and celluloses.
  • bio-sourced IBOA and DDDA are commercially available from Sartomer as Sarbio 5102 and Sarbio 5201, respectively.
  • Sarbio 5102 has a BRC fraction of 0.75 and Sarbio 5201 has a BRC fraction of 0.60.
  • Medol-10 is commercially available from Osaka and has a BRC fraction of 0.30.
  • the BRC contributed by Sarbio 5102 is 16.5%
  • the BRC contributed by Sarbio 5201 is 6.0%
  • the BRC contributed by Medol-10 is 5.2%.
  • the total BRC of the ink is therefore 27.7%. If the ink is cured by exposure to a source of actinic radiation without an inert environment, one or more photoinitiators will be required.
  • the ink may still contain a photoinitiator, although photoinitiators are not required.
  • the ink of the present invention further comprises one or more photoinitiators.
  • photoinitiators which produce free radicals on irradiation (free radical photoinitiators) such as, for example, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl phenyl (2,4,6-trimethylbenzoyl) phosphinate, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-(4- morpholinophenyl)butan-1-one, benzil dimethylketal, phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide or mixtures thereof.
  • free radical photoinitiators such as, for example, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl phenyl (2,4,6-trimethylbenzoyl) phosphinate, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2-benz
  • Such photoinitiators are known and commercially available such as, for example, under the trade names Omnirad (from IGM) and Esacure (from Lamberti). Mixtures of free radical photoinitiators can be used and preferably, the ink comprises a plurality of free radical photoinitiators. The total number of free radical photoinitiators present is preferably from one to five, and more preferably, two or more free radical photoinitiators are present in the ink.
  • the inkjet ink may also comprise one or more polymeric photoinitiators, such as Omnipol TP®. Omnipol TP® is commercially available from IGM.
  • polymeric phosphine oxide photoinitiator It is a polymeric phosphine oxide photoinitiator, and is known by the chemical name polymeric ethyl (2,4,6-trimethylbenzoyl)-phenyl phosphinate or polymeric TPO-L. It has the following structure: .
  • the total value of a, b and c of the chemical formula for polymeric TPO-L is equal to 1-20.
  • the photoinitiator if present is present from 1 to 20% by weight, preferably from 5 to 15% by weight, of the ink.
  • the presence of a photoinitiator is optional because the ink can cure without the presence of a photoinitiator by curing with a low-energy electron beam or curing by actinic radiation in an inert environment.
  • the photoinitiator may be present in an amount of less than 20% by weight, preferably less than 5% by weight, more preferably less than 3%, more preferably less than 1%, based on the total weight of the ink. Therefore, in a preferred embodiment, no photoinitiator is intentionally added to the ink. However, minor amounts of photoinitiator, which may be present as impurities in commercially available inkjet ink components, are tolerated.
  • the ink may comprise less than 0.5% by weight of photoinitiator, more preferably less than 0.1% by weight of photoinitiator, most preferably less than 0.05% by weight of photoinitiator, based on the total weight of the ink.
  • the inkjet ink may also be free of photoinitiator.
  • an inkjet ink that is cured with a low-energy electron beam or actinic radiation in an inert environment may still contain a small amount of photoinitiator such as 1 to 5% by weight of a photoinitiator, based on the total weight of the ink. This is required if the ink is first pinned with actinic radiation.
  • pinning is meant arresting the flow of the ink by treating the ink droplets quickly after they have impacted onto the substrate surface. Pinning provides a partial cure of the ink and thereby maximises image quality by controlling bleed and feathering between image areas. Pinning does not achieve full cure of the ink.
  • curing is meant fully curing the ink.
  • the inkjet ink of the present invention preferably dries primarily by curing, i.e. by the polymerisation of the monomers present, as discussed hereinabove, and hence is a curable ink.
  • the ink does not, therefore, require the presence of water or a volatile organic solvent to effect drying of the ink.
  • the inkjet ink preferably comprises less than 5% by weight of water and volatile organic solvents combined, based on the total weight of the ink.
  • the inkjet ink comprises less than 3% by weight of water and volatile organic solvent combined, more preferably less than 2 % by weight combined, more preferably less than 1% by weight combined, and most preferably the inkjet ink is substantially free of water and volatile organic solvents, where the amounts are based on the total weight of the ink.
  • substantially free is meant that only small amounts will be present, for example some water will typically be absorbed by the ink from the air and solvents may be present as impurities in the components of the inks, but such low levels are tolerated. In other words, no water or a volatile organic solvent is intentionally added to the ink.
  • the ink may comprise less than 0.5% by weight of water or a volatile organic solvent, more preferably less than 0.1% by weight of water or a volatile organic solvent, most preferably less than 0.05% by weight of water or a volatile organic solvent, based on the total weight of the ink.
  • the inkjet ink is free of water or a volatile organic solvent.
  • the ink of the present invention comprises a surfactant. The surfactant controls the surface tension of the ink. Surfactants are well-known in the art and a detailed description is not required.
  • the inkjet ink comprises an acrylated surfactant.
  • Acrylated surfactants are particularly preferred as they can be partially included in the crosslink network on cure.
  • Preferred examples of acrylated surfactants are commercially available as Tego Rad 2010 and Tego Rad 2300.
  • Adjustment of the surface tension of the inks allows control of the surface wetting of the inks on various substrates, for example, plastic substrates. Too high a surface tension can lead to ink pooling and/or a mottled appearance in high coverage areas of the print. Too low a surface tension can lead to excessive ink bleed between different coloured inks. Surface tension is also critical to ensuring stable jetting (nozzle plate wetting and sustainability).
  • the surface tension is preferably in the range of 20-40 mNm -1 and more preferably 25-35 mNm -1 .
  • the surfactant is present in each inkjet ink in an amount of 0.01 to 5% by weight, based on the total weight of the ink. The amounts by weight provided herein are based on the total weight of the ink.
  • the inkjet ink exhibits a desirable low viscosity (100 mPas or less, more preferably 50 mPas or less and most preferably 35 mPas or less at 25oC).
  • the ink most preferably has a viscosity of less than 20 mPas at 25°C.
  • Viscosity may be measured using a rotational viscometer fitted with a thermostatically controlled cup and spindle arrangement, running at 20 rpm at 25°C.
  • Other components of types known in the art may be present in the ink to improve the properties or performance. These components may be, for example, pH buffers, humectants, defoamers, dispersants, synergists, stabilisers against deterioration by heat or light, reodorants, flow or slip aids, biocides and identifying tracers.
  • the inks of the inkjet ink may be prepared by known methods such as stirring with a high-speed water- cooled stirrer, or milling on a horizontal bead-mill.
  • the present invention also provides a method of inkjet printing comprising inkjet printing the inkjet ink as defined herein onto a substrate to provide a printed ink and curing the printed ink by exposing the printed ink to a curing source.
  • the inkjet ink is inkjet printed onto a substrate.
  • the printing is performed by inkjet printing, e.g. on a single-pass inkjet printer, for example for printing (directly) onto packaging, or a multiple-pass printer where the image is built up in print swathes.
  • inkjet printing is well-known in the art and a detailed description is not required.
  • the ink is jetted from one or more printing heads through narrow nozzles on to a substrate to form a printed image.
  • Print heads account for a significant portion of the cost of an entry level printer and it is therefore desirable to keep the number of print heads (and therefore the number of inks in the ink) low. Reducing the number of print heads can reduce print quality and productivity. It is therefore desirable to balance the number of print heads in order to minimise cost without compromising print quality and productivity.
  • the substrate is not limited but include those for packaging applications. Examples include substrates composed of polyvinyl chloride (PVC), polystyrene, polyester, polyethylene terephthalate (PET), polyethylene terephthalate glycol modified (PETG) and polyolefin (e.g.
  • the substrate is a compostable substrate.
  • a substrate is compostable if it meets the criteria as set out in BS EN 13432. Examples of compostable substrates are commercially available, including Sustainex (supplied by Mondi as an alternative to PE packaging material) and Nativa (a compostable bioplastic polylactic acid (BoPLA) derived from plant sugars, supplied by Taghleef). Nativa can be derived from any sugar, such as corn starch, cassava, sugar cane, or sugar beet.
  • the substrate When discussing the substrate, it is the surface which is most important, since it is the surface which is wetted by the ink. Thus, at least the surface of substrate is composed of the above-discussed material.
  • the inks are then cured.
  • the inks are cured by exposing the inkjet ink to a curing source.
  • curing it is meant exposure to any curing means known in the art, such as exposure to actinic radiation or low- energy electron beam, to polymerise and/or crosslink the radiation-curable material.
  • the terms “dry” and “cure” are often used interchangeably in the art when referring to radiation-curable inkjet inks to mean the conversion of the inkjet ink from a liquid to solid by polymerisation and/or crosslinking of the radiation-curable material.
  • drying is meant the removal of the water by evaporation
  • curing is meant the polymerisation and/or crosslinking of the radiation-curable material.
  • the ink is cured by exposing the printed ink to a source of actinic radiation, such as UV, x-ray, electron beam etc., although UV curing is preferred.
  • the source of actinic radiation can be any source of actinic radiation that is suitable for curing radiation- curable inks but is preferably a UV source. Suitable UV sources are well known in the art and a detailed description is not required. These include mercury discharge lamps, fluorescent tubes, light emitting diodes (LEDs), flash lamps and combinations thereof. One or more mercury discharge lamps, fluorescent tubes, or flash lamps may be used as the radiation source.
  • the source of actinic radiation is a mercury discharge lamp and/or LEDs. When LEDs are used, these are preferably provided as an array of multiple LEDs.
  • the most common UV light source used to cure inkjet inks is a mercury discharge lamp.
  • the source of actinic radiation is a UV LED, i.e. the curing source is preferably a UV LED source.
  • the curing source is preferably a UV LED source.
  • These are preferably provided as an array of multiple LEDs. LEDs are increasingly used to cure inkjet inks. UV light is emitted from a UV LED source. UV LED sources comprise one or more LEDs and are well known in the art. Thus, a detailed description is not required. There are many advantages of using LEDs as the UV source.
  • LEDs are cost effective, have long maintenance intervals, have high energy efficiency and are an environmentally friendly option. LEDs have a longer lifetime and exhibit no change in the power/wavelength output over time. LEDs also have the advantage of switching on instantaneously with no thermal stabilisation time and their use results in minimal heating of the substrate. However, when LEDs are used, it can be difficult to formulate inkjet inks to obtain the required balance of properties, such as the required cure, blocking, adhesion and flexibility. In this regard, LEDs have a narrow wavelength output and reduced energy output when compared to other sources of UV radiation.
  • the compostable inkjet ink of the present invention has a desirable balance of properties, including cure, blocking, adhesion and flexibility, even when using a UV LED source as the source of actinic radiation to cure the inkjet ink. It will be understood that UV LED sources emit radiation having a spread of wavelengths. The emission of UV LED light sources is identified by the wavelength which corresponds to the peak in the wavelength distribution.
  • UV LED light sources emit UV radiation over a narrow range of wavelengths on the wavelength distribution.
  • the width of the range of wavelengths on the wavelength distribution is called a wavelength band.
  • LEDs therefore have a narrow wavelength output when compared to other sources of UV radiation.
  • a narrow wavelength band it is meant that at least 90%, preferably at least 95%, of the radiation emitted from the UV LED light source has a wavelength within a wavelength band having a width of 50 nm or less, preferably, 30 nm or less, most preferably 15 nm or less.
  • At least 90%, preferably at least 95%, of the radiation emitted from the UV LED source has a wavelength in a band having a width of 50 nm or less, preferably 30 nm or less, most preferably 15 nm or less.
  • the wavelength of the UV LED source substantially matches the absorption profile of the ink.
  • the wavelength distribution of the UV LED light peaks at a wavelength of from 360 nm to 410 nm. In a particularly preferred embodiment, the wavelength distribution of the UV LED light peaks at a wavelength of around 365 nm, 395 nm, 400 nm or 405 nm.
  • the wavelength distribution of the UV LED light peaks at a wavelength of from 360 nm to 410 nm, and at least 90%, preferably at least 95%, of the radiation has a wavelength in a band having a width of 50 nm or less, preferably 30 nm or less, most preferably 15 nm or less.
  • the wavelength distribution of the UV LED light peaks at a wavelength of around 365 nm, 395 nm, 400 nm or 405 nm, and at least 90%, preferably at least 95%, of the radiation has a wavelength in a band having a width of 50 nm or less, preferably 30 nm or less, most preferably 15 nm or less.
  • the ink may also be cured by exposing the printed ink to low-energy electron beam (ebeam).
  • the source of low-energy electron beam (ebeam) can be any source of low-energy electron beam that is suitable for curing radiation-curable inks.
  • Suitable low-energy electron beam radiation sources include commercially available ebeam curing units, such as the EB Lab from ebeam Technologies with energy of 80-300 keV and capable of delivering a typical dose of 30-50 kGy at line speeds of up to 30 m/min.
  • low-energy for the ebeam, it is meant that it delivers an electron beam having a dose at the substrate of 100 kGy or less, preferably 70 kGy or less.
  • Ebeam curing is characterised by dose (energy per unit mass, measured in kilograys (kGy)) deposited in the substrate via electrons. Electron beam surface penetration depends upon the mass, density and thickness of the material being cured. Compared with UV penetration, electrons penetrate deeply through both lower and higher density materials. Unlike UV curing, photoinitiators are not required for ebeam curing to take place. Ebeam curing is well-known in the art and therefore a detailed explanation of the curing method is not required. In order to cure the printed ink, the ink of the invention is exposed to the ebeam, which produces sufficient energy to instantaneously break chemical bonds and enable polymerisation or crosslinking.
  • the dose is more than 10 kGy, more preferably more than 20 kGy, more preferably more than 30 kGy and most preferably more than 40 kGy.
  • the dose is less than 100 kGy, more preferably less than 90 kGy, more preferably less than 80 kGy and most preferably less than 70 kGy.
  • the dose is more than 30 kGy but less than 70 kGy, more preferably more than 30 kGy but less than 60 kGy and most preferably, more than 30 kGy but 50 kGy or less. Doses above 50 kGy may cause damage to the substrate and so doses of 50 kGy or less are preferred.
  • the energy associated with these doses is 80-300 keV, more preferably 70-200 keV and most preferably 100 keV.
  • the ink cures to form a relatively thin polymerised film.
  • the ink of the present invention typically produces a printed film having a thickness of 1 to 20 ⁇ m, preferably 1 to 10 ⁇ m, for example 2 to 5 ⁇ m.
  • the present invention also provides a printed substrate obtainable by the method of inkjet printing according to the present invention.
  • the printed substrate having the inkjet ink of the present invention printed and cured thereon has a maximum amount of copper of 50 ppm.
  • the printed substrate having the inkjet ink of the present invention printed and cured thereon has a maximum amount of copper of 50 ppm and nickel of 25 ppm.
  • the printed substrate having the inkjet ink of the present invention printed and cured thereon has a maximum amount of copper of 50 ppm, nickel of 25 ppm, zinc of 150 ppm, cadmium of 0.5 ppm, lead of 50 ppm, mercury of 0.5 ppm, chromium of 50 ppm, molybdenum of 1 ppm, selenium of 0.75 ppm and arsenic of 5 ppm.
  • the present invention also provides a printed substrate having the inkjet ink as defined herein printed thereon. And a printed substrate obtainable by the method of inkjet printing as discussed above.
  • the substrate is preferably as discussed hereinabove.
  • the substrate is a compostable substrate.
  • a substrate is compostable if it meets the criteria as set out in BS EN 13432.
  • the inkjet ink is particularly suitable for composting. Accordingly, the present invention further provides a method of composting a printed substrate having the inkjet ink as defined herein printed and cured thereon comprising composting the printed substrate.
  • the criteria for composting is set out in BS EN 13432.
  • the invention will now be described with reference to the following examples, which are not intended to be limiting. Examples Example 1 An ink was prepared according to the formulation set out in Table 1. The inkjet ink formulation was prepared by mixing the components in the given amounts. Amounts are given as weight percentages based on the total weight of the ink. Table 1 The viscosity of ink 1 was 15.8 mPa ⁇ s.
  • Ink 1 was coated onto a 220 ⁇ m gloss PVC substrate using a number 2 K bar and a RK coater equipment. A wet film was deposited of approximately 12 microns. The film was cured using a Jenton mercury UV lamp 2 at 100% power and a speed of 30 m/min. Ink 1 has an L* value of 25.59, an a* value of 13.39 and a b* value of –63.13. Ink 1 has a chroma of 64.62.
  • Fig.1 shows the chroma and density for ink 1.
  • the horizontal axes represents dot patch/tint %.
  • the vertical axes shows the measurement of chroma and density.
  • the lower curve (curve interrupted by dots) shows chroma and the upper curve (uninterrupted curve) shows density.
  • the graph shows that at about 70% tint the chroma/strength plateaued.
  • PB60 pigment has a heavy metal content as set out in Table 2, as determined by ICP.
  • the total heavy metal content was determined by the following method: Before commencing the analysis, the powder pigments are digested in a mixture of hydrochloric and nitric acids to ensure that the total metal content, rather than the free metal levels in the samples are correctly determined. This is achieved by gently heating a mixture of the pigment with a 33%v/v solution of HCl and HNO3 (ratio of acids 1:3) on a hotplate until the pigment is dissolved. To obtain quantitative data for the metal levels, a calibration standard is used for each metal. Suitable certified ICP-OES metal standards can be obtained from Sigma. It is necessary to take into account the various interference bands of each metal and ensure the concentration range brackets the concentrations relevant to the application.
  • a known amount of the prepared pigment sample is combined with a known amount of deionised water to create a solution that will position the concentration of metals present roughly into the centre of the calibration range.
  • the analysis can then be conducted on a suitable ICP unit, for examples a Thermo ICS-5000 ICP-OES. Both the dual radial and axial detectors are used.
  • the calibration is run, followed by a period of blank deionised water to flush the system, the samples are then run in duplicate. Using the calibration, it is then possible to calculate the concentration of metals present.
  • Table 2 The copper content of compostable paper having ink 1 printed and cured thereon was calculated.
  • Ink 1 contains PB60 pigment in 4.5% by weight, based on the total weight of the ink.
  • ink 1 contains copper in 0.00000486% by weight, based on the total weight of the ink.
  • Ink 1 is printed onto paper having a weight of 200 gsm as a single ink lay down using a UV inkjet printer at 100% RID.
  • the printed ink is cured using a GEW Ebrick UV curing system 16-25 kW lamps.
  • the cured ink film has a weight of 10 gsm and the paper and cured ink film together have a weight of 210 gsm.
  • the weight of copper present in the cured film is therefore 0.000000486 gsm.
  • Comparative Example 2 A comparative ink was prepared according to the formulation set out in Table 3. The inkjet ink formulation was prepared by mixing the components in the given amounts. Amounts are given as weight percentages based on the total weight of the ink.
  • Table 3 The viscosity of ink 2 was 17.2 mPa ⁇ s. The viscosity was measured using a rotational viscometer fitted with a thermostatically controlled cup and spindle arrangement, running at 20 rpm at 25°C. Ink 2 was printed and cured and the L*a*b* values and chroma measured according to the methods described in Example 1. Ink 2 has an L* value of 54.24, an a* value of –36.75 and a b* value of –54.3. Ink 2 has a chroma of 65.57. Fig.2 shows the chroma and density for ink 2. As for Fig.1, the horizontal axes represents dot patch/tint %.
  • the vertical axes shows the measurement of chroma and density.
  • the lower curve (curve interrupted by dots) shows chroma and the upper curve (uninterrupted curve) shows density.
  • the graph shows that at about 70% tint the chroma/strength plateaued.
  • Figs.1 and 2 show that moving from the copper-containing cyan pigment of comparative ink 2 to the copper-free blue pigment of ink 1, the chroma can be closely matched.
  • Pigment PB 15.3 contains 11% Cu atoms, and as such contains 110,000 ppm Cu.
  • Ink 2 contains PB15:3 pigment in 1.8% by weight, based on the total weight of the ink.
  • ink 2 contains copper in 0.198% by weight, based on the total weight of the ink.
  • Ink 2 is printed onto paper having a weight of 200 gsm as a single ink lay down using a UV inkjet printer at 100% RID.
  • the printed ink is cured using a GEW Ebrick UV curing system 16-25 kW lamps.
  • the cured ink film has a weight of 10 gsm and the paper and cured ink film together have a weight of 210 gsm.
  • the weight of copper present in the cured film is therefore 0.0198 gsm.
  • the percentage of copper present in the printed paper is therefore 0.00943% or 94.3 ppm.
  • the ink of the invention provides a film which falls within the limits set out in BS EN 13432 for the copper content of 50 ppm, as it has a copper content in the printed film of 0.00231 ppm.
  • This is in marked contrast to the comparative ink which provides a film which falls outside the limits set out in BS EN 13432 for the copper content of 50 ppm, as it has a copper content in the printed film of 94.3 ppm.
  • a compostable inkjet ink can be provided that maintains the required properties for inkjet printing and has the same colour gamut as an ink containing a copper-based pigment.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)

Abstract

La présente invention concerne une encre pour jet d'encre comprenant un monomère durcissable par rayonnement et au moins un pigment bleu, cyan et/ou vert, le monomère durcissable par rayonnement comprenant de l'acrylate(2-méthyl-2-éthyl-1,3-dioxolane-4-yl)méthyle, l'encre présentant une viscosité inférieure à 100 mPas à 25 °C, et la quantité de cuivre présent dans l'encre étant inférieure à 2 000 ppm.
PCT/GB2022/052782 2021-11-05 2022-11-04 Encre pour jet d'encre WO2023079295A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080200635A1 (en) * 2007-02-15 2008-08-21 Seiko Epson Corporation Polysilane compound and synthesis method, ultraviolet-ray curable ink composition, inkjet recording method and apparatus, and ink container
WO2011021052A2 (fr) 2009-08-21 2011-02-24 Sericol Limited Encre, appareil et procédé d'impression
WO2016193728A1 (fr) * 2015-06-02 2016-12-08 Fujifilm Speciality Ink Systems Limited Encre d'impression
WO2018197852A1 (fr) * 2017-04-24 2018-11-01 Fujifilm Speciality Ink Systems Limited Encre d'impression
WO2018216484A1 (fr) * 2017-05-24 2018-11-29 Dic株式会社 Encre durcissable par rayons actiniques et procédé de production de matière imprimée
WO2021095579A1 (fr) * 2019-11-11 2021-05-20 富士フイルム株式会社 Encre de type durcissable par rayonnement actinique, ensemble d'encre, et procédé d'enregistrement d'image

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080200635A1 (en) * 2007-02-15 2008-08-21 Seiko Epson Corporation Polysilane compound and synthesis method, ultraviolet-ray curable ink composition, inkjet recording method and apparatus, and ink container
WO2011021052A2 (fr) 2009-08-21 2011-02-24 Sericol Limited Encre, appareil et procédé d'impression
WO2016193728A1 (fr) * 2015-06-02 2016-12-08 Fujifilm Speciality Ink Systems Limited Encre d'impression
WO2018197852A1 (fr) * 2017-04-24 2018-11-01 Fujifilm Speciality Ink Systems Limited Encre d'impression
WO2018216484A1 (fr) * 2017-05-24 2018-11-29 Dic株式会社 Encre durcissable par rayons actiniques et procédé de production de matière imprimée
WO2021095579A1 (fr) * 2019-11-11 2021-05-20 富士フイルム株式会社 Encre de type durcissable par rayonnement actinique, ensemble d'encre, et procédé d'enregistrement d'image

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Title
CAS , no. 69701-99-1

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