WO2013179064A1

WO2013179064A1 - Container for ink

Info

Publication number: WO2013179064A1
Application number: PCT/GB2013/051466
Authority: WO
Inventors: Sean Slater
Original assignee: Sericol Ltd
Current assignee: Sericol Ltd
Priority date: 2012-05-31
Filing date: 2013-05-31
Publication date: 2013-12-05
Anticipated expiration: 2014-11-30
Also published as: GB2518090A; GB201209685D0; GB2518090B

Description

Container for ink

This invention relates to a container for ink and in particular a pouch for containing, storing and/or dispensing an ink.

For printing inks, two main ink chemistries are used: inks that dry by solvent evaporation and inks that dry by exposure to actinic radiation, such as ultraviolet (UV) radiation. Inks that dry by solvent evaporation comprise a large proportion of a mobile liquid or solvent, such as water or a low-boiling point solvent or mixture of solvents. Inks that dry by exposure to UV radiation comprise unsaturated organic monomers or oligomers that polymerise by irradiation with UV radiation in the presence of a photoinitiator. The main advantage of UV curable inks is that it is not necessary to evaporate the liquid phase to dry the print, instead, the print is exposed to radiation to cure or harden it, a process which is more rapid than evaporation of a solvent at moderate temperatures. Packages for containing UV curable ink that are known in the art, include the "pouch type", which is essentially a collapsible bag. Pouches are typically made with a multi-laminated film that acts as a barrier to actinic radiation and vapours, including oxygen. In this regard, UV curable inks must have a container that forms a barrier to actinic radiation in order to prevent the ink from curing (or crosslinking) within the container. The materials utilised to provide such containers and are a barrier to actinic radiation, are also resistant to gas permeation and this can present a problem when storing UV inks.

Specifically, UV curable inks are inhibited from crosslinking by the presence of oxygen. When UV curable inks are prepared, the ink typically contains an amount of dissolved oxygen from the air. The presence of this oxygen can inhibit the ink from crosslinking for a considerable period of time. Therefore, the presence of oxygen can assist in the stable storage of UV curable inks in packages and containers.

However, a problem can arise in that during the storage of the ink, the oxygen is slowly consumed and so eventually, the supply of oxygen runs out and the UV curable ink can then start to become more viscous or gel-like as a result of crosslinking of the ink. This means that the UV curable ink then quickly becomes unfit for its purpose. Such an increase in viscosity or gelling is particularly problematic for inkjet inks because the viscosity of such inks must be very tightly controlled, for example, to allow good jetting from an inkjet printhead. A particularly reactive UV curable ink may only have a shelf life of six months in a standard pouch because oxygen is readily consumed by materials within the ink.

To combat this problem, it is known in the art to use a pouch formed of a gas permeable membrane. However, such pouches do not act as a barrier to actinic radiation and therefore such pouches are not suitable for UV curable ink, which cure when exposed to actinic radiation. Furthermore, an additional problem with such gas permeable membrane containers for UV curable ink is that some odorous monomer vapour from the ink can escape through this poor barrier.

There is therefore a need in the art for a pouch for containing an ink which achieves a balance between providing a barrier to actinic radiation, allowing for the supply of oxygen to the ink, whilst reducing escape of odorous vapour from the pouch.

Accordingly, the present invention provides a pouch for containing an ink comprising a chamber for containing ink and a chamber for containing an oxygen-containing gas, wherein the chamber for containing ink is surrounded by a material which is a barrier to actinic radiation, and wherein the chamber for containing ink is in communication with the chamber for containing an oxygen-containing gas via a gas permeable membrane.

The present invention will now be described with reference to the accompanying drawings in which: Fig. 1 shows an obverse and side view of a pouch of the present invention;

Fig. 2 shows a side view of the pouch of the present invention;

Fig. 3 shows an obverse and side view of a pouch of the present invention;

Fig. 4 shows an obverse and side view of a pouch of the present invention; and

Fig. 5 shows a cross-section of a portion of a pouch of the present invention showing a composite.

It has been found that the pouch of the present invention allows for oxygen to be supplied to the ink by passing from the chamber for containing an oxygen-containing gas to the chamber for containing ink through a gas permeable membrane. In this respect, the chamber for containing ink is in communication with the chamber for containing an oxygen-containing gas via a gas permeable membrane such that the oxygen-containing gas diffuses through the gas permeable membrane. This means that the oxygen can contact and mix with the ink. This inhibits the curing of a UV curable ink.

Furthermore, the chamber for containing ink is surrounded by a material which is a barrier to actinic radiation. This means that the ink is not exposed to actinic radiation. This also therefore prevents the curing of a UV curable ink via exposure to actinic radiation. The material that surrounds the chamber for containing ink also reduces the escape of odorous vapour.

According to one aspect of the invention, there is provided a pouch for containing an ink comprising a chamber for containing ink and a chamber for containing an oxygen-containing gas. The chamber for containing ink and the chamber for containing an oxygen-containing gas communicate via a gas permeable membrane. The boundary between the two chambers need not be a gas permeable membrane in its entirety, so long as oxygen-containing gas may pass through the boundary from the chamber for containing oxygen-containing gas to the chamber for containing ink. Furthermore, the chamber for containing ink should be surrounded by a material which is a barrier to actinic radiation. It is not necessary for the entire inner wall to be a gas permeable material or the entire outer wall to be a barrier to actinic radiation. This depends upon the design of the pouch and the chambers in the pouch. However, it is necessary for the chamber for containing ink to be surrounded by a material which is a barrier to actinic radiation so that the ink is protected from actinic radiation. It is also necessary for the chamber for containing ink and the chamber for containing an oxygen-containing gas to communicate via a gas permeable membrane. Hence, the barrier/boundary between the chamber for containing ink and the chamber for containing oxygen-containing gas is at least partially composed of a gas permeable material. The chamber for containing an oxygen-containing gas conveniently provides an oxygen-containing gas to the chamber for containing ink. As the oxygen within the chamber for containing ink is depleted by the presence of an ink, it is readily replaced by an oxygen-containing gas from the chamber for containing an oxygen-containing gas. Thus the lifetime of the ink is greatly increased. As can be seen in Fig. 1 , according to one aspect of the present invention there is provided a pouch for containing an ink comprising a chamber for containing ink 4 and a chamber for containing an oxygen-containing gas 5. The pouch of this aspect of the invention is defined by a double-wall structure such that the inner wall 3 comprises a gas permeable material and the outer wall 2 comprises a material which is a barrier to actinic radiation. In other words, there is an outer chamber for containing oxygen-containing gas 5 and an inner chamber for containing ink 4. The outer and inner chambers 5, 4 are separated by a boundary which comprises a gas permeable membrane 3. This allows for the supply of an oxygen-containing gas from the outer chamber 5 to the inner chamber 4 via the gas permeable membrane 3. As can be seen in Figs. 2 and 4, in a further aspect of the invention, the pouch of the invention comprises two chambers: a chamber for containing ink 4 and a chamber for containing an oxygen- containing gas 5. These chambers are divided by a boundary which comprises a gas permeable membrane 3. The outer material of the pouch is a barrier to actinic radiation 2 and a substantial barrier to vapours. The gas permeable membrane 3 allows for the supply of oxygen from the chamber for containing an oxygen-containing gas 5 to the chamber for containing ink 4. The outer material of the pouch 3 reduces the curing of the ink by being a barrier to actinic radiation. Furthermore, the outer material 3 reduces the escape of odorous vapours.

As can be seen in Fig. 3, in a further aspect of the invention, the pouch of the invention comprises two or more chambers for containing an oxygen-containing gas 5. The pouch may also comprise two or more chambers for containing ink 4. The chambers for containing ink 4 and the chambers for containing an oxygen-containing gas 5 communicate via a gas permeable membrane 3.

The chamber for containing ink 4 is in communication with the chamber for containing an oxygen- containing gas 5 via a gas permeable membrane 3. By communicate or in communication with, it is meant that the gas permeable membrane 3 allows for the diffusion of oxygen from the chamber for containing an oxygen-containing gas 5 through the gas permeable membrane 3 to the chamber for containing ink 4. In a preferred aspect of the present invention, the pouch comprises an outlet 1 . Preferably, the pouch comprises an outlet 1 from the chamber for containing ink 4 and an outlet 1 from the chamber for containing an oxygen-containing gas 5. More preferably, the chamber for containing ink 4 and the chamber for containing an oxygen-containing gas 5 are sealed separately such that an oxygen- containing gas can be replenished with the oxygen-containing gas via an outlet 1. The outlet 1 may be formed by simply cutting or piercing the pouch.

In another aspect of the present invention, the chamber for containing an oxygen-containing gas 5 is a pressurised gas container and comprises a valve for supplying gas. Therefore, an oxygen- containing gas can be supplied via other means including from pressurised gas containers. Gas can be supplied through a regulator or valve and the flow of gas can be adjusted, for example, to suit the characteristics of the ink package, ink or storage conditions.

The oxygen-containing gas may be air or oxygen. The inks may be formulated as solvent-based inks or curable inks. The solvent-based inks may contain water or volatile organic solvents. Such inks are well known in the art; see EP 0 314 403 and EP 0 424 714 for details of their formulations.

It is preferred that the inks of the present invention dry primarily by curing, i.e. by the polymerisation of the monomers present, as discussed hereinabove, and hence is a radiation-curable ink, preferably a UV curable ink. Such inks do not, therefore, require the presence of water or a volatile organic solvent to effect drying of the ink, although the presence of such components may be tolerated. The ink is preferably substantially free of water or volatile organic solvents, although some water or volatile organic solvents will typically be absorbed by the ink from the air or be present as impurities in the components of the inks, and such levels are tolerated. For example, the ink may comprise less than 5% by weight in total of water and/or volatile organic solvents, more preferably less than 2% by weight in total of water and/or volatile organic solvents and most preferably less than 1 % by weight in total of water and/or volatile organic solvents, based on the total weight of the ink. The radiation-curable inks preferably include a radiation-curable material, at least one photoinitiator and optionally at least one colouring agent.

Preferably, radiation-curable monomers are present in the ink as the radiation-curable material. Suitable free-radical polymerisable monomers are well known in the art and include (meth)acrylates, α,β-unsaturated ethers, vinyl amides and mixtures thereof. The monomers may possess different degrees of functionality, and a mixture including combinations of mono, di, tri and higher functionality monomers/oligomers may be used. Preferably, the radiation- curable material is selected from a monofunctional monomer, a multifunctional monomer and combinations thereof.

Examples of the multifunctional acrylate monomers which may be included in the inks include hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethyleneglycol diacrylate, for example, tetraethyleneglycol diacrylate), dipropyleneglycol diacrylate, tri(propylene glycol) triacrylate, neopentylglycol diacrylate, bis(pentaerythritol) hexaacrylate, and the acrylate esters of ethoxylated or propoxylated glycols and polyols, for example, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, and mixtures thereof. Particularly preferred are difunctional acrylates. Also preferred are those with a molecular weight greater than 200. A preferred combination of monomers is hexanediol diacrylate, dipropyleneglycol diacrylate and propoxylated neopentyl glycol diacrylate.

In addition, suitable multifunctional acrylate monomers include esters of methacrylic acid (i.e. methacrylates), such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, ethyleneglycol dimethacrylate, 1 ,4- butanediol dimethacrylate. Mixtures of (meth)acrylates may also be used.

Multifunctional (meth)acrylate monomers may be included at 40-80% by weight, preferably 50-70% by weight, based on the total weight of the ink. The monofunctional (meth)acrylate monomers are also well known in the art and are preferably the esters of acrylic acid. Preferred examples include phenoxyethyl acrylate, cyclic TMP formal acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, octadecyl acrylate, tridecyl acrylate, isodecyl acrylate and lauryl acrylate. Monofunctional (meth)acrylate monomers may be included at 5-30% by weight, preferably 10-20% by weight, based on the total weight of the ink.

The inks may also contain α,β-unsaturated ether monomers, such as vinyl ethers. These monomers are known in the art and may be used to reduce the viscosity of the ink formulation. Typical vinyl ether monomers which may be used in the inks of the present invention are triethylene glycol divinyl ether, diethylene glycol divinyl ether, 1 ,4-cyclohexanedimethanol divinyl ether and ethylene glycol monovinyl ether. Mixtures of α,β-unsaturated ether monomers may be used. The α,β-unsaturated ether monomer is preferably 1-20% by weight, more preferably 7-15% by weight, based on the total weight of the ink. In a preferred embodiment, the ratio of acrylate monomer to vinyl ether monomer is from 4:1 and 15:1 . N-Vinyl amides and N-acryloyl amines may also be used in the inks. N-vinyl amides are well-known monomers in the art and a detailed description is therefore not required. N-vinyl amides 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) and N- vinyl pyrrolidone (NVP). Similarly, N-acryloyl amines are also well-known in the art. N-acryloyl amines 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. A preferred example is N-acryloylmorpholine (ACMO).

N-Vinyl amides and/or N-acryloyl amines may be included at 5-30% by weight, preferably 10-20% by weight, based on the total weight of the ink.

It is possible to modify further the film properties of the inks by inclusion of oligomers or inert resins, such as thermoplastic acrylics. The oligomers may possess different degrees of functionality, and a mixture including combinations of mono, di, tri and higher functionality monomers/oligomers may be used.

Radiation-curable oligomers suitable for use in the ink comprise a backbone, for example a polyester, urethane, epoxy or polyether backbone, and one or more radiation polymerisable groups. The oligomer preferably comprises a urethane backbone. The polymerisable group can be any group that is capable of polymerising upon exposure to radiation. Preferably the oligomers are (meth)acrylate oligomers. Preferably they are multifunctional and most preferably have a functionality of 2-6.

Particularly preferred radiation-curable materials are urethane acrylate oligomers as these have excellent adhesion and elongation properties. Most preferred are tri-, tetra-, penta-, hexa- or higher functional urethane acrylates, particularly hexafunctional urethane acrylates as these yield films with good solvent resistance.

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.

Preferred oligomers have a molecular weight of 450 to 4,000, more preferably 600 to 4,000. Molecular weights (number average) can be calculated if the structure of the oligomer is known or molecular weights can be measured using gel permeation chromatography using polystyrene standards.

In one embodiment the radiation-curable oligomer polymerises by free-radical polymerisation.

Preferred oligomers for use in the invention have a viscosity of 0.5 to 20 Pa.s at 60°C, more preferably 5 to 15 Pa.s at 60°C and most preferably 5 to 10 Pa.s at 60°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 seconds^"1.

Preferably the ink comprises 10 to 30% by weight of radiation-curable material based on the total weight of the ink, preferably at least 12% by weight, more preferably 10 to 20% by weight, based on the total weight of the ink. Passive resins are resins which do not enter into the curing process, i.e. the resin is free of functional groups which polymerise under the curing conditions to which the ink is exposed. In other words, resin is not a radiation-curable material. 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 1 ,500-200,000, as determined by GPC with polystyrene standards as previously described hereinabove.

The ink preferably comprises a photoinitiator, which, under irradiation by, for example, ultraviolet light, initiates the polymerisation of the monomers. Preferred are photoinitiators which produce free radicals on irradiation (free radical photoinitiators) such as, for example, benzophenone, 1- hydroxycyclohexyl phenyl ketone, 2-benzyl-2-dimethylamino-(4-morpholinophenyl)butan-1-one, benzil dimethylketal, bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide or mixtures thereof. Such photoinitiators are known and commercially available such as, for example, under the trade names Irgacure, Darocur (from Ciba) and Lucerin (from BASF). In the case of a cationically curable system, any suitable cationic initiator can be used, for example sulfonium or iodonium based systems, e.g. diphenyliodonium fluoride and triphenylsulfonium hexafluophosphate. Examples of commercially available cationic initiators are Esacure 1064, Esacure 1 187 (Lamberti), Irgacure 250, Irgacure 270, Irgacure 290 (BASF), Uvacure 1600 (Cytec), Speedcure 992 and Speedcure 976 (Lambsons).

Preferably the photoinitiator is present from 1 to 20% by weight, preferably from 4 to 10% by weight, of the ink.

The ink may be a coloured or a colourless ink. By "colourless" is meant that the ink is free of colorant such that no colour can be detected by the naked eye. Minor amounts of colorant that do not produce colour that can be detected by the eye can be tolerated, however. Typically the amount of colorant present will be less than 0.3% by weight based on the total weight of the ink, preferably less than 0.1 %, more preferably less than 0.03%. Colourless inks may also be described as "clear" or "water white". Colourless inks may also be used as a varnish, where it is applied over a coloured ink. For the avoidance of doubt, coloured inks include white inks.

The coloured inks comprise at least one colouring agent. The colouring agent may be either dissolved or dispersed in the liquid medium of the ink. Preferably the colouring agent is a dispersible pigment, of the types known in the art and commercially available such as under the trade-names Paliotol (available from BASF pic), Cinquasia, Irgalite (both available from Ciba Speciality Chemicals) and Hostaperm (available from Clariant UK). The pigment may be of any desired colour such as, for example, Pigment Yellow 13, Pigment Yellow 83, Pigment Red 9, Pigment Red 184, Pigment Blue 15:3, Pigment Green 7, Pigment Violet 19, Pigment Black 7. Especially useful are black and the colours required for trichromatic process printing. Mixtures of pigments may be used.

In one aspect the following pigments are preferred. Cyan: phthalocyanine pigments such as Phthalocyanine blue 15.4. Yellow: azo pigments such as Pigment yellow 120, Pigment yellow 151 and Pigment yellow 155. Magenta: quinacridone pigments, such as Pigment violet 19 or mixed crystal quinacridones such as Cromophtal Jet magenta 2BC and Cinquasia RT-355D. Black: carbon black pigments such as Pigment black 7.

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 pm, preferably less than 5 pm, more preferably less than 1 pm and particularly preferably less than 0.5 pm.

The colorant is preferably present in an amount of 20 weight% or less, preferably 10 weight% or less, more preferably 8 weight% or less and most preferably 2 to 5% by weight, based on the total weight of the ink. A higher concentration of pigment may be required for white inks, however, for example up to and including 30 weight%, or 25 weight% based on the total weight of the ink.

In an alternative embodiment, the radiation-curable material is capable of polymerising by cationic polymerisation. Suitable materials include, oxetanes and epoxides (e.g. cycloaliphatic epoxides, bisphenol A epoxides and epoxy novalacs). The radiation-curable material can also comprise a combination of free-radical polymerisable and cationically polymerisable materials.

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, surfactants, defoamers, dispersants, synergists for the photoinitiator, stabilisers against deterioration by heat or light, reodorants, flow or slip aids, biocides and identifying tracers.

The inks exhibit a desirable low viscosity (less than 100 mPas, preferably less than 50 mPas and most preferably 25 mPas or less at 25°C).

(Meth)acrylate is intended herein to have its standard meaning, i.e. acrylate and/or methacrylate. Mono and multifunctional are also intended to have their standard meanings, i.e. one and two or more groups, respectively, which take part in the polymerisation reaction on curing.

The inks may be prepared by known methods such as, for example, stirring with a high-speed water- cooled stirrer, or milling on a horizontal bead-mill.

Preferably, the ink is preferably an inkjet ink. More preferably, the ink is a radiation-curable inkjet ink.

The material which acts as a barrier to actinic radiation 2 can be selected from a range of polymers and metals. In an aspect of the present invention, the material which is a barrier to actinic radiation 2 is preferably a substantially inert metal, wherein a substantially inert metal is a metal that does not react with the ink to be contained in the pouch. Preferably, the material which is a barrier to actinic radiation 2 is aluminium and/or silver. The material which is a barrier to actinic radiation 2 is preferably in the form of a foil.

The material which is a barrier to actinic radiation 2 preferably has a thickness of from 2 to 200 pm, preferably from 2 to 20 pm, more preferably from 6 to 14 pm, more preferably 6, 7, 8 or 9 pm.

The material which is a barrier to actinic radiation 2 is substantially impermeable to gas and is a barrier to the diffusion of the volatile components of the ink. Preferably, the material which is a barrier to actinic radiation 2 has a gas permeability of less than 1 x 10¹⁰ [cm³.cm]/[cm²s(cmHg)] (ASTM D 3985).

The material which is a barrier to actinic radiation 2 preferably has one or more additional layers coated thereon, such as glues and layers of polymers in order to line the barrier material. In a preferred aspect of the present invention, the material which acts as a barrier to actinic radiation 2 forms part of a composite. This permits the barrier material to be stronger and hence increased puncture resistance, permits the layer to be more easily printed thereon, allows for the layer to be increasingly impermeable to gas and/or resistant to liquid and chemicals.

The one or more additional layers are preferably selected from polyethylene, poly(ethylene terephthalate), nylon, cast polypropylene (CPP) and biaxially oriented polypropylene (BOPP). In a preferred aspect of the present invention, the barrier to actinic radiation 2 forms part of a composite, wherein the composite comprises poly(ethylene terephthalate), aluminium and polyethylene. In an alternative preferred aspect, the composite comprises poly(ethylene terephthalate), nylon, aluminium and polyethylene. Adhesive is used in between each layer to form the composite layer. Aluminium is the barrier to actinic radiation, poly(ethylene terephthalate) permits the layer to be more easily printed thereon, nylon is a has a poor gas permeability and hence helps to prevent the escape of gaseous odours and polyethylene is chemical and water resistant. Such composites are also stronger and have increased puncture resistance.

As can be seen in Fig. 5, preferably, the composite comprises the following layers in the following order: polyethylene 13, adhesive 14, poly(ethylene terephthalate) 12, adhesive 14, aluminium 15, adhesive 14 and poly(ethylene terephthalate) 12, wherein the polyethylene 13 is the inner most layer of the composite of the barrier to actinic radiation 2 of the pouch and the poly(ethylene terephthalate) 12 is the outer most layer of the composite of the barrier to actinic radiation 2 of the pouch. The total thickness of the material which is a barrier to actinic radiation 2 further comprising one or more additional layers preferably has a thickness of from 20 pm to 3 mm. The polymers used in the film may be made more durable by being halogenated, for example in order to be more resistant to effects from certain inks. The gas permeable membrane 3 can be selected from many different materials, preferably organic polymeric materials having a gas permeability of greater than 1 . More preferably, the gas permeable membrane 3 is selected from polytetrafluoroethylene (PTFE), low density polyethylene (LDPE), polypropylene, poly(isoprene), poly(chloroprene), poly(isobutylene-isoprene), poly(tetrafluoroethylene- co), poly(ethyl methacrylate) and poly(carbonate). Most preferably, the gas permeable membrane is selected from polytetrafluoroethylene (PTFE), low density polyethylene (LDPE) and polypropylene.

The gas permeable membrane 3 preferably has a permeability coefficient at 25°C of greater than 1 x 10¹⁰ [cm³.cm]/[cm²s(cmHg)] (ASTM D 3985). In this regard, we refer to Table 1 of the example of the invention which list a variety of suitable gas permeable membranes 3 for use in the present invention.

Preferably, the pouch further comprises a means for dispensing ink into an inkjet printer. A means for dispensing ink into an inkjet printer comprises an outlet 1 that is adapted to be compatible with an inkjet printer so that the ink can be dispensed from the pouch to the inkjet printer. The pouches of the present invention may be designed to conveniently fit directly into an inkjet device or machine so that ink of the desired type and quality can be provided for printing over extended periods of time.

In a further embodiment of the invention, there is provided a pouch of the invention comprising ink. The ink is preferably a radiation-curable ink, and more preferably a UV curable ink. Furthermore, the ink is preferably an inkjet ink. More preferably, the ink is a radiation-curable inkjet ink, and most preferably a UV curable inkjet ink. The ink is preferably as described hereinabove. In a further embodiment of the invention, there is provided a pouch of the invention comprising an oxygen-containing gas. The oxygen-containing gas is air or oxygen. In a further embodiment of the invention there is provided a cartridge comprising the pouch of the invention.

In a further embodiment of the invention there is provided a printer comprising the pouch of the invention.

The ink package of the present invention finds uses in connection with digital UV inks and especially with such inks having a high photoinitiator package such as those found in UV-LED curable inks or other such inks designed to be more sensitive to lower power UV sources such as low pressure mercury lamps.

The pouch of the present invention can be constructed by conventional methods of manufacture which are known in the art.

The invention will now be described, with reference to the following examples which are not intended to be limiting.

Examples

Example 1

Pouches of the present invention were prepared utilising the polymers listed in Table 1 hereinbelow as the gas permeable membrane. The permeability coefficients (P x 10¹⁰) at 25°C are provided for each material.

Table 1

Permeability Coefficient, P:

(amount of permeate). (film thickness)

P =

(surface area). (time). (pressure drop across film)

[cm³. cm]

units of P:

[cm²s (cmHg)]

Claims

1. A pouch for containing an ink comprising:

a chamber for containing ink and a chamber for containing an oxygen-containing gas,

wherein the chamber for containing ink is surrounded by a material which is a barrier to actinic radiation, and

wherein the chamber for containing ink is in communication with the chamber for containing an oxygen-containing gas via a gas permeable membrane.

2. A pouch as claimed in claim 1 , wherein the chamber for containing an oxygen-containing gas is a pressurised gas container and comprises a valve for supplying gas.

3. A pouch as claimed in any preceding claim further comprising a means for dispensing ink into an inkjet printer.

4. A pouch as claimed in any preceding claim, wherein the material which is a barrier to actinic radiation has a gas permeability of less than 1 x 10¹⁰ [cm³.cm]/[cm²s(cmHg)].

5. A pouch as claimed in any preceding claim, wherein the material which is a barrier to actinic radiation is aluminium and/or silver.

6. A pouch as claimed in any preceding claim, wherein the material which is a barrier to actinic radiation has a thickness of from 2 to 200 μηι.

7. A pouch as claimed in any preceding claim, wherein the material which acts as a barrier to actinic radiation forms part of a composite.

8. A pouch as claimed in claim 7, wherein the composite comprises the material which is a barrier to actinic radiation and one or more additional layers coated thereon, wherein the additional layer is polyethylene, poly(ethylene terephthalate), nylon, cast polypropylene (CPP) and/or biaxially oriented polypropylene (BOPP).

9. A pouch as claimed in claims 7 or 8, wherein the composite comprises poly(ethylene terephthalate), aluminium, polyethylene and optionally nylon.

10. A pouch as claimed in any of claims 7 to 9, wherein the composite has a total thickness of from 20 μηι to 3 mm.

11. A pouch as claimed in any preceding claim, wherein the gas permeable membrane has a permeability coefficient at 25 °C of greater than 1 x 10¹⁰ [cm³.cm]/[cm²s(cmHg)].

12. A pouch as claimed in any preceding claim, wherein the gas permeable membrane is polytetrafluoroethylene (PTFE), low density polyethylene (LDPE), polypropylene, poly(isoprene), poly(chloroprene), poly(isobutylene-isoprene), poly(tetrafluoroethylene-co), poly(ethyl methacrylate) and/or poly(carbonate).

13. A pouch as claimed in any preceding claim comprising ink.

14. A pouch according to claim 13, wherein the ink is an inkjet ink.

15. A cartridge comprising the pouch as claimed in any preceding claim.

16. A printer comprising the pouch as claimed in claims 1 to 14.