WO2020260352A1 - Aqueous ink compositions - Google Patents

Abstract

Provided is an ink composition, in particular an aqueous ink composition. The ink has a block copolymer having a hydrophilic block and a hydrophobic block. The hydrophilic block has triggerable cross linking groups that may be triggered by thermal or UV radiation. The ink compositions have good adhesion and water resistance properties and may be suitable for inkjet printing such as drop on demand inkjet printing.

Description

AQUEOUS INK COMPOSITIONS Related Application

The present case claims priority to, and the benefit of, GB 1909013.3 filed on 24 June 2019 (24/06/2019), the contents of which are hereby incorporated by reference in their entirety.

Field of the Invention

The present invention relates to an aqueous ink composition, in particular an aqueous inkjet ink composition.

Background of the Invention

In ink compositions a number of factors must be balanced in order to avoid or reduce the problems associated with ink compositions.

Solvent based inks refer to inks where the solvent is an organic solvent, typically a volatile organic solvent, and having low amounts or no water. Solvent based inks are the preferred formulation for a wide range of applications due to high print quality, image durability and their ability to be printed onto a range of substrates. Such inks can be formulated with either pigments or dyes. The ability to adhere to a variety of substrates and fast drying times are seen as the main benefits of solvent-based inks.

However, these systems have limitations such as the effect of volatile organic solvents on the environment and health, and the potential of fast drying inks blocking prink head nozzles.

Aqueous ink refers to inks that contain high levels of water and lower amounts of volatile organic compounds (VOCs) compared to solvent based inks.

Aqueous inks have several advantages. For example, aqueous inks use relatively inexpensive solvent (water) and are more environmentally friendly. Current aqueous inks are primarily used for desktop applications.

Aqueous inks have a number of disadvantages, particularly for commercial printing needs. For example, porous or specially treated substrates are required for good print quality using an aqueous ink. Lamination may be needed to impart durability to printed deposits formed from aqueous inks which may not be water resistant after printing. The poor adhesion of aqueous inks to non-porous substrates has provided limitations for industrial applications.

The water content of aqueous inks means increased time is needed for the ink to dry, particularly when printed on non-absorbent or non-porous substrates.

Additionally, aqueous inks have poor print quality, especially compared to solvent based inks, on hydrophobic substrates such as those commonly used in packaging materials. In particular, the printed deposit formed from an aqueous ink often shows poor water fast characteristics (i.e. is not water resistant) and poor durability (i.e. poor adhesion) after deposition.

It is an object of the present invention to provide ink compositions that have some of the above desirable characteristics. In particular, it is an object of the invention to provide an aqueous ink composition that has good water resistance and/or adhesion properties in particular when printed on non-porous substrates.

It is an alternative and/or additional object of the present invention to overcome or address the problems of prior art ink compositions by using the ink compositions of the invention or to at least provide a commercially useful alternative thereto.

Summary of the Invention

The present invention seeks to provide an aqueous ink composition which has good adhesion properties and good water resistance. In particular, the present invention seeks to provide an aqueous ink composition for use in drop on demand inkjet printing, such as piezoelectric or thermal drop on demand inkjet printing, or continuous inkjet printing.

Accordingly, in one aspect the present invention provides an aqueous ink composition comprising a block copolymer having a hydrophilic block and a hydrophobic block. The hydrophilic block has triggerable cross linking groups. The triggerable cross linking groups may be triggered by thermal or UV radiation.

It is proposed that the block copolymer forms micelles in the aqueous ink medium with the hydrophobic block at the core of the micelle and the hydrophilic block forming the shell or outer layer of the micelle. When the ink is deposited, for example on a non-porous hydrophobic substrate, the hydrophobic block contacts the hydrophobic substrate preferentially and forms an anchor point for the inks to promote adhesion. After deposition the printed deposit may be treated using the appropriate trigger (e.g. thermal or UV radiation) to initiate cross-linking of the hydrophilic block by the triggerable cross-linking groups. It is proposed that this cross linking forms a film layer that is resistant to water or other solvents.

In this way, the aqueous ink composition of the invention has good water resistance and adhesion properties, in particular when printed on hydrophobic non-porous substrates.

In another aspect the present invention provides a printed deposit formed from the aqueous ink composition of the invention. The printed deposit comprises a cured polymer film formed by crosslinking of the crosslinking groups on the hydrophilic block.

The aqueous ink composition is compatible with the components of a printer, for example an inkjet printer. The inkjet printer may be a drop on demand inkjet printer, such as a piezoelectric drop on demand inkjet printer or a continuous inkjet printer. The aqueous ink composition is suitable for application directly onto products and/or product packaging to achieve high quality images.

Preferably the aqueous ink composition described herein has a viscosity of about 0.5 to 30 mPa.s, more preferably from 1 to 20 mPa.s and even more preferably from 5 to 20 mPa.s at 25°C. Preferably the aqueous ink composition described herein has a viscosity of less than 25 mPa.s, more preferably less than 15 mPa.s at 25°C. Preferably the aqueous ink composition described herein has a viscosity of greater than 1 mPa.s, more preferably greater than 2 mPa.s, more preferably greater than 3 mPa.s, more preferably greater than 5 mPa.s, even more preferably greater than 8 mPa.s at 25°C. The viscosity of the

composition may be measured using a viscometer such as a Brookfield DV-II+ viscometer.

The Brookfield DV-II+ viscometer is a rotational viscometer which measures viscosity by measuring the torque required to turn an object in a fluid as a function of the fluid’s viscosity.

Preferably the aqueous ink composition as described herein has a surface tension from 20 to 50 mN/m, more preferably from 20 to 40 mN/m at 25°C. The surface tension of the composition may be measured using equipment such as a du Nouy ring tensiometer or using the pendant drop method on a KSV Cam 200 optical tensiometer.

Summary of Figures

Figure 1 shows a schematic of the block copolymer of the ink of the present invention.

Figure 2 shows a schematic of the deposition of an ink of the present invention. Figure 3 shows photos of inks A4 and E4 on both polyethylene terephthalate (PET) and polypropylene (PP) substrates. Figure 3(a) is A4 on PET, 3(b) is A4 on PP, 3(c) is E4 on PET and 3(d) is E4 on PP.

Detailed Description

Accordingly, in one aspect the present invention provides an aqueous ink composition comprising a block copolymer having a hydrophilic block and a hydrophobic block. The hydrophilic block has triggerable cross linking groups. The triggerable cross linking groups may be triggered by thermal or UV radiation. A representation of a block copolymer that has the features of the block copolymer present in the ink of the invention is shown in Figure 1.

It is proposed that the block copolymer forms micelles in the aqueous ink medium with the hydrophobic block at the core of the micelle and the hydrophilic block forming the shell or outer layer of the micelle (see Figure 2). When the ink is deposited, for example on a non-porous hydrophobic substrate, the hydrophobic block contacts the hydrophobic substrate preferentially and forms an anchor point for the inks to promote adhesion (see Figure 2). After deposition the printed deposit may be treated using the appropriate trigger (e.g. thermal or UV radiation) to initiate cross-linking of the hydrophilic block by the triggerable cross-linking groups. It is proposed that this cross linking forms a film layer that is resistant to water or other solvents.

In this way, the aqueous ink composition of the invention has good water resistance and adhesion properties, in particular when printed on hydrophobic non-porous substrates.

The components of the block copolymer may be controlled to control the properties of the ink for a particular application. For example, adhesion properties may be controlled by the amount or type of triggerable crosslinking groups present in the block copolymer.

The aqueous ink composition is compatible with the components of a printer, for example an inkjet printer. The inkjet printer may be a drop on demand inkjet printer, such as a piezoelectric drop on demand inkjet printer or a continuous inkjet printer. The aqueous ink composition is suitable for application directly onto products and/or product packaging to achieve high quality images.

The inks of the present invention are preferably for use with inkjet printers for example a piezoelectric inkjet printer such as a piezoelectric drop on demand inkjet printer or a continuous inkjet printer.

Preferably the aqueous ink composition described herein has a viscosity of about 0.5 to 30 mPa.s, more preferably from 1 to 20 mPa.s and even more preferably from 5 to 20 mPa.s at 25°C. Preferably the aqueous ink composition described herein has a viscosity of less than 25 mPa.s, more preferably less than 15 mPa.s at 25°C. Preferably the aqueous ink composition described herein has a viscosity of greater than 3 mPa.s, more preferably greater than 5 mPa.s, even more preferably greater than 8 mPa.s at 25°C. The viscosity of the composition may be measured using a viscometer such as a Brookfield DV-II+ viscometer.

The Brookfield DV-II+ viscometer is a rotational viscometer which measures viscosity by measuring the torque required to turn an object in a fluid as a function of the fluid’s viscosity.

Block Copolymer

The aqueous ink composition contains a block copolymer.

In this way, the present invention provides an aqueous ink composition with good adhesion to low surface energy substrates and that is water fast. A representation of a block copolymer that has the features of the block copolymer present in the ink of the invention is shown in Figure 1.

The term block copolymer refers to a polymer having two or more polymer subunits linked by covalent bonds. The union of the polymer subunits may require an intermediate non-repeating subunit, known as a junction block. Each of the polymer subunits may be a homopolymer or a copolymer. Block copolymers with two or three distinct blocks are called diblock copolymers and triblock copolymers, respectively. In the present case, diblock copolymers are preferred.

The notation used to describe the block copolymer in this application is as follows: and so on]”; or

and so on]

“P” stands for‘poly’ in the above notation. (A_n) represents the hydrophilic block and (B_m) represents the hydrophobic block. A and B represent the monomer units that make up the hydrophilic block and hydrophobic block respectively “n” and“m” are integers and represent the number of repeat monomer units making up the hydrophilic block and hydrophobic block, respectively.

(A_n) or (B_m) may each independently be a homopolymer or a copolymer.

In some preferred cases, (A_n) is a copolymer and can be represented as:

(A¹ni-C0-A² _n2) A¹ and A² represent the monomer units that make up the hydrophilic block copolymer. “n1” and“n2” are integers and represent the number of each monomer unit making up the hydrophilic block copolymer. The hydrophilic block may be composed of a statistical or random distribution of the monomer units (also referred to as statistical copolymers or random copolymers, respectively).

It is proposed that the number of monomer repeats in each of the hydrophilic and hydrophobic block may affect the properties of the block copolymer and may be used to control the properties of the resulting ink.

The hydrophobic block and hydrophilic block are joined together to form a block copolymer. The block copolymer’s hydrophobic block and hydrophilic block may each be synthesized using any known method. In particular they may be synthesized by a controlled radical polymerization reaction such as the RAFT process. Reversible addition-fragmentation chain transfer (RAFT) is a well-known process of reversible-deactivation radical polymerization. RAFT makes use of a chain transfer agent in the form of a thiocarbonylthio compound (or similar), often referred to as a RAFT agent, to provide control over the generated molecular weight and dispersity (also referred to as‘polydispersity’) during a free-radical

polymerization.

In the RAFT process the two polymer blocks (the hydrophobic block, (B_m) and the hydrophilic block (A_n)) are incorporated through sequential polymerisation processes.

Purification may be undertaken before each additional polymerisation. In this way, the structure of the block copolymer can be controlled.

The amount of block copolymer in the aqueous ink composition is 0.5 wt% or more, based on the total weight of the ink composition.

Preferably, the block copolymer is present at 1.0 wt % or more, based on the total weight of the ink composition, preferably 2 wt% or more, and even more preferably 4 wt% or more.

Preferably, the block copolymer is present at 30 wt% or less based on total weight of the ink composition, more preferably 20 wt% or less, more preferably 10 wt% or less and even more preferably 8 wt% or less.

The block copolymer may be present in an amount that is in a range with the upper and lower limits selected from the amounts described above. For example, the block copolymer may be present at 2 to 10 wt % based on total weight of the ink composition. Preferably, the block copolymer has a molecular weight, such as a weight-average molecular weight (M_w) greater than 8,000, more preferably greater than 9,000 and even more preferably greater than 10,000.

Preferably, the block copolymer has a molecular weight, such as a weight-average molecular weight (M_w) less than 45,000, more preferably less than 40,000, and even more preferably less than 37,000.

The block copolymer may have a molecular weight, such as a weight-average molecular weight (M_w) that is in a range with the upper and lower limits selected from the amounts described above. Preferably, the dye monomer has a molecular weight, such as a weight- average molecular weight (M_w) from 8,000 to 45,000, more preferably from 8,000 to 40,000, more preferably from 9,000 to 40,000, more preferably from 10,000 to 40,000 and even more preferably from 10,000 to 37,000.

The weight-average molecular weight M_w takes into account the molecular weight of a chain in determining contributions to the molecular weight average. The bigger the chain, the more the chain contributes to M_w. M_w may be measured by any suitable method, for example methods that are sensitive to the molecular size such as light scattering techniques or gel permeation chromatography (GPC).

Preferably, M_w may be measured by GPC using a Refractive Index detector and comparing to poly(methyl methacrylate) (PMMA) standards. In this case dimethylformamide (DMF) is preferably used as a solvent.

Preferably, the block copolymer has a molecular weight, such as a number-average molecular weight ( M_n ) greater than 5000, more preferably greater than 8000 and even more preferably greater than 10,000.

Preferably, the block copolymer has a molecular weight, such as a number-average molecular weight ( M_n ) less than 40,000, more preferably less than 35,000, and even more preferably less than 30,000.

The block copolymer may have a molecular weight, such as a number-average molecular weight ( M_n ) that is in a range with the upper and lower limits selected from the amounts described above. Preferably, the block copolymer has a molecular weight, such as a number-average molecular weight ( M_n ) from 5,000 to 40,000, more preferably from 5,000 to 35,000, more preferably from 8,000 to 40,000, more preferably from 8,000 to 35,000 and even more preferably from 10,000 to 30,000.

The number-average molecular weight ( _n) is the statistical average molecular weight of all the polymer chains in the sample, i.e. the total mass of all the polymer chains divided by the total number of chains. The number average molecular weight can be calculated

experimentally by gel permeation chromatography (GPC, also known as size exclusion chromatography, SEC) which separates out the chains based on size and by nuclear magnetic resonance spectroscopy where end group analysis can be utilised. Preferably, M_n may be measured by GPC using a Refractive Index detector and comparing to PMMA standards.

Preferably, the block copolymer has a dispersity (£>) greater than 1.00, more preferably greater than 1.10 and even more preferably greater than 1.15.

Preferably, the block copolymer has a dispersity (£⁾) less than 2.50, preferably less than 2.00, more preferably less than 1.50, and even more preferably less than 1.30.

The block copolymer may have a dispersity (£>) that is in a range with the upper and lower limits selected from the amounts described above. For example, the block copolymer may have a dispersity (£>) from at least 1.00 to at most 1.50.

The dispersity (£)) can be calculated using both the M_n and M_w values which can be measured as discussed above. The following equation is used to calculate dispersity:

Molecular weight dispersity, B = _w / _n

If all the polymer chains were the same size the M_n and M_w values would be identical and the dispersity would have a value of one. If a polymer has a dispersity value close to one it can be said to have a narrow molecular weight distribution; as this value increases the more dispersed the molecular weight.

Hydrophilic block

The block copolymer has a hydrophilic block having triggerable cross linking groups.

The term hydrophilic used in the present application refers to a polymer whose interactions with water and other polar substances are more thermodynamically favourable than their interactions with oil or other hydrophobic solvents. For example, the hydrophilic block may be charge-polarized or may be capable of hydrogen bonding, for example by the

incorporation of a hydroxyl group or groups.

The term triggerable cross linking group used in the present application refers to a chemical moiety which is capable of undergoing a reaction with another cross linking group, or groups, to provide a covalent bond when treated with an external trigger. In particular, in the present application the term triggerable cross linking group refers to a chemical moiety which is capable of undergoing a reaction with another cross linking group or groups to provide a covalent bond when subjected to thermal or UV radiation. It may be that an initiator is present in the composition to initiate the cross linking reactions.

The hydrophilic block comprises a number of repeat units formed by polymerization of hydrophilic monomers. The hydrophilic block may be represented as:

(An)

“A” represents the monomer or monomers forming the hydrophilic block and“n” is an integer which represents the number of monomers forming the hydrophilic block.

The hydrophilic block may be a homopolymer or a copolymer. Preferably the hydrophilic block is a copolymer and may be represented as:

(A¹ni-CO-A²n₂)

A¹ and A² represent the monomer units that make up the hydrophilic block copolymer. “n1” and“n2” are integers and represent the number of each monomer unit making up the hydrophilic block copolymer. The hydrophilic block copolymer may be a statistical or random distribution of the monomer units (also referred to as statistical copolymers or random copolymers, respectively). In some cases, the hydrophilic block is a statistical distribution of the monomer units.

The monomers, A, forming the hydrophilic block may be selected from alkenyl, alkynyl, acrylate, methacrylate, maleate, fumarate, an acrylamide functional group or a mixture thereof. Preferably, the monomers, A, are selected from acrylamides, methacrylamides, acrylates, methacrylates or a mixture thereof. The hydrophilic block monomers may be mono functional or may be multifunctional.

Suitable monomers, A, for forming the hydrophilic block may be selected from 2- hydroxybutyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy-3- phenoxypropyl acrylate, 2-acryloyloxyethylsuccinic acid, 2-acryloxyethylphthalic acid, 2- acryloxyethyl-2-hydroxyethyl-phthalic acid, hydroxy alkyl acrylamide.

When the hydrophilic block is a homopolymer, a single type of monomer, A, forms the hydrophilic block. In this case“n” is an integer from 10 to 200, preferably“n” is an integer from 20 to 150, preferably“n” is an integer from 30 to 150, preferably“n” is an integer from 50 to 150 and more preferably“n” is an integer from 70 to 130.

When the hydrophilic block is a copolymer more than one monomer forms the hydrophilic block. The more than one monomer may be referred to as A¹, A² and so on. In some cases, the hydrophilic block is formed from two monomers, A¹ and A² and is a copolymer. A¹ and A² may be selected from alkenyl, alkynyl, acrylate, methacrylate, maleate, fumarate, an acrylamide functional group or a mixture thereof. Preferably, the monomers, A¹ and A², are selected from acrylamides, acrylates or a mixture thereof, more preferably A¹ is an acrylate and A² is an acrylamide.

Suitable monomers, A¹ and A² for forming the hydrophilic block copolymer may be selected from 2-hydroxybutyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy- 3-phenoxypropyl acrylate, 2-acryloyloxyethylsuccinic acid, 2-acryloxyethylphthalic acid, 2- acryloxyethyl-2-hydroxyethyl-phthalic acid, hydroxy methyl acrylamide. Preferably, A¹ is 2- hydroxyethyl acrylate and A² is hydroxy methyl acrylamide.

“n1” and“n2” are integers and represent the number of monomer A¹ and A² respectively that make up the hydrophilic block. Preferably,“n1” is an integer from 10 to 200, preferably“n1” is an integer from 50 to 120 and more preferably“n1” is an integer from 70 to 130.

Preferably“n2” is an integer from 2 to 50, preferably“n2” is an integer from 3 to 30 and more preferably“n2” is an integer from 3 to 20.

Preferably, the ratio of n1 : n2 is from 2 : 1 to 30 : 1 , preferably from 2 : 1 to 20 : 1 and even more preferably, from 3 : 1 to 19 : 1.

The triggerable cross linking group may be selected from alkenyl, alkynyl, acrylate, methacrylate, maleate, fumarate, an acrylamide, hydroxyl, carboxylic acid, amine, epoxy, a hydroxyl alkylamide functional group or a mixture thereof.

Preferably the triggerable cross linking groups are selected from hydroxyl, carboxylic acid, amine, epoxy, a hydroxyl alkylamide functional group or a mixture thereof. For example, the triggerable cross linking groups may be hydroxyl alkylamides, such as hydroxy methylamide.

It is proposed that the cross linking groups react with other cross linking groups to form a covalent bond. The cross linking of these groups is known in the art (G. Tillet, B. Boutevin, and B. Ameduri, Prog. Polym. Sci., 36, 191-217, 201 1). The cross linking groups may be the same or different. For example, when the cross linking groups are the same a self condensation reaction occurs. Alternatively, when the cross linking groups are different, such as a amine and a carboxylic acid, a cross condensation reaction occurs.

It is proposed, that when the cross linking groups are hydroxyl alkylamides a

self-condensation reaction occur. It is known that hydroxyl alkylamides self-condense when treated with thermal radiation to form either ether bridges (releasing water) or alkylene bis-acetamides releasing water and formaldehyde as described in Tillet et. al. (G. Tillet, B. Boutevin, and B. Ameduri, Prog. Polym. Sci., 36, 191-217, 201 1). The triggerable cross linking group may be present on the monomer before the hydrophilic block is produced or the triggerable cross linking group may be added by functionalising the hydrophilic block after it is produced.

Preferably, the triggerable cross linking group may be present on the monomer before the hydrophilic block is produced. For example, a hydroxyl alkylamide triggerable cross linking group can be obtained by incorporating hydroxyl alkylacrylamide monomers into the hydrophilic block. In the case where A is a copolymer, the triggerable cross linking group may be present on only one of the monomers forming the copolymer. In this way, the amount of cross linking group can be controlled by controlling the ratio of the different monomers forming the hydrophilic block. For example, in a preferred example, the hydrophilic block is copolymer formed of two monomer units A¹ and A² where A¹ is

2-hydroxyethyl acrylate and A² is hydroxy methylacrylamide. In this case, the triggerable functional group is hydroxyl methyl amine present in the A² monomer, hydroxy

methylacrylamide. The ratio of A¹ to A² can be controlled to control the properties of the hydrophilic block and subsequently the properties of the block copolymer.

In the case where the triggerable cross linking group may be added by functionalising the hydrophilic block after it is produced, triggerable cross linking groups which may react under the conditions used to produce the hydrophilic block may be used. For example, an acrylate triggerable cross linking group may be formed by functionalising hydroxy groups on the hydrophilic block by reaction between the hydroxy groups and acryloyl chloride.

In the case where the hydrophilic block is a copolymer, a single monomer unit may contain the triggerable cross linking group or more than one monomer unit may contain the triggerable cross linking group. Preferably, a single monomer unit contains the triggerable cross linking group.

Preferably, the monomers having the triggerable cross linking groups are present in the hydrophilic block in greater than 5 mol%, more preferably greater than 8 mol% and even more preferably greater than 10 mol% based on the overall amount of monomers in the hydrophilic block.

Preferably, the monomers having the triggerable cross linking groups are present in the hydrophilic block in less than 20 mol %, more preferably less than 15 mol %, and even more preferably less than 13 mol% based on the overall amount of monomers in the hydrophilic block.

The monomers having the triggerable cross linking groups may be present in the hydrophilic block in a range with the upper and lower limits selected from the amounts described above. For example the monomers having the triggerable cross linking groups are present in the hydrophilic block at from 8 mol % to 13 mol % based on the overall amount of monomers in the hydrophilic block.

The amount of particular monomers refers to the amount of cross-linking monomer used at the start of the polymerisation. For example, the amount of monomers having the triggerable cross linking groups in the hydrophilic block refers to the amount of monomers having the triggerable cross linking groups that are used to produce the hydrophilic block.

The amount of crosslinking monomer that is incorporated into the hydrophilic block may be approximately confirmed using FTIR or other suitable method. The conversion of the monomers can be measured by NMR. These methods can be used to determine how much of the cross linking monomer is incorporated into the block.

In this way, the crosslinking of the triggerable cross linking groups can be performed in short times suitable for industrial printing.

Preferably, the hydrophilic block has a molecular weight, such as a weight-average molecular weight (M_w) greater than 8,000, more preferably greater than 10,000 and even more preferably greater than 15,000.

Preferably, the hydrophilic block has a molecular weight, such as a weight-average molecular weight (M_w) less than 40,000, more preferably less than 35,000, and even more preferably less than 30,000.

The hydrophilic block may have a molecular weight, such as a weight-average molecular weight (M_w) that is in a range with the upper and lower limits selected from the amounts described above.

The weight-average molecular weight M_w takes into account the molecular weight of a chain in determining contributions to the molecular weight average. The bigger the chain, the more the chain contributes to M_w. M_w may be measured by any suitable method, for example methods that are sensitive to the molecular size such as light scattering techniques or gas phase chromatography (GPC). Preferably, M_w may be measured by GPC using a

Refractive Index detector and comparing to PMMA standards.

Preferably, the hydrophilic block has a molecular weight, such as a number-average molecular weight ( M_n ) greater than 5000, more preferably greater than 8000 and even more preferably greater than 10,000.

Preferably, the hydrophilic block has a molecular weight, such as a number-average molecular weight ( M_n ) less than 30,000, more preferably less than 25,000, and even more preferably less than 22,000. The hydrophilic block may have a molecular weight, such as a number-average molecular weight ( M_n ) that is in a range with the upper and lower limits selected from the amounts described above.

The number-average molecular weight ( _n) is the statistical average molecular weight of all the polymer chains in the sample, i.e. the total mass of all the polymer chains divided by the total number of chains. The number average molecular weight can be calculated

experimentally by gel permeation chromatography (GPC, also known as size exclusion chromatography, SEM) which separates out the chains based on size and by nuclear magnetic resonance spectroscopy where end group analysis can be utilised. Preferably, M_n may be measured by GPC using a Refractive Index detector and comparing to PMMA standards.

Preferably, the hydrophilic block has a dispersity (£>) greater than 1.00, more preferably greater than 1.05 and even more preferably greater than 1.10.

Preferably, the hydrophilic block has a dispersity (£⁾) less than 2.50, preferably less than 2.00, more preferably less than 1.50, and even more preferably less than 1.30.

The hydrophilic block may have a dispersity (£>) that is in a range with the upper and lower limits selected from the amounts described above. For example, the hydrophilic block may have a dispersity (£>) from at least 1.00 to at most 1.50.

The dispersity (£)), M_n and M_w values can be measured as discussed above.

The length of the hydrophilic block is associated with the molecular weight and dispersity. Hydrophilic block within the ranges provided here provide block copolymers with low crosslinking times.

Hydrophobic block

The block copolymer has a hydrophobic block.

The term hydrophobic used in the present application refers to a polymer whose interactions with oil or other hydrophobic solvents are more thermodynamically favourable than their interactions with water and other polar substances. For example, the hydrophobic block may be charge neutral or non-polar. The hydrophobic block comprises a number of repeat units formed by polymerization of hydrophobic monomers. The hydrophobic block may be represented as:

(Bm)

B represents the monomer or monomers forming the hydrophobic block and“m” is an integer represent the average number of monomers forming the hydrophobic block.

“m” is an integer from 10 to 100, preferably“m” is an integer from 10 to 50 and more preferably“m” is an integer from 15 to 45.

The hydrophobic block may be a homopolymer or a copolymer. Preferably the hydrophobic block is a homopolymer (i.e. comprising repeat units of just one monomer type).

When the hydrophobic block is a homopolymer, a single type of monomer, B, forms the hydrophobic block.

When the hydrophobic block is a copolymer more than one monomer, B, forms the hydrophilic block copolymer.

The monomers, B, forming the hydrophobic block may be selected from alkenes, alkynes, acrylates, methacrylates, maleates, fumarates, acrylamides or a mixture thereof. Preferably, the monomers, B, are selected from acrylate or methacrylates.

The hydrophobic monomers may be mono functional or may be multifunctional.

Suitable example monomers, B, for forming the hydrophobic block may be selected from C3-i3-alkyl acrylates or C3-i3-alkyl methacrylates. Preferably, the monomer, B for forming the hydrophobic block is propyl methacrylate.

The term "alkyl" means the monovalent linear or branched saturated hydrocarbon moiety, consisting solely of carbon and hydrogen atoms. For example Ci-₆-alkyl means a

monovalent linear or branched saturated hydrocarbon moiety, consisting solely of carbon and hydrogen atoms having from one to six carbon atoms.

As used herein the term C3-i3-alkyl refers to any alkyl group having between 3 and 13 carbon atoms.

Preferably, the hydrophobic block has a molecular weight, such as a weight-average molecular weight (M_w) greater than 8,000, more preferably greater than 10,000 and even more preferably greater than 15,000. Preferably, the hydrophobic block has a molecular weight, such as a weight-average molecular weight (M_w) less than 40,000, more preferably less than 35,000, and even more preferably less than 30,000.

The hydrophobic block may have a molecular weight, such as a weight-average molecular weight (M_w) that is in a range with the upper and lower limits selected from the amounts described above.

The weight-average molecular weight M_w takes into account the molecular weight of a chain in determining contributions to the molecular weight average. The bigger the chain, the more the chain contributes to M_w. M_w may be measured by any suitable method, for example methods that are sensitive to the molecular size such as light scattering techniques or gel permeation chromatography (GPC). Preferably, M_w may be measured by GPC using a Refractive Index detector and comparing to PMMA standards.

Preferably, the hydrophobic block has a molecular weight, such as a number-average molecular weight ( M_n ) greater than 5000, more preferably greater than 8000 and even more preferably greater than 10,000.

Preferably, the hydrophobic block has a molecular weight, such as a number-average molecular weight ( M_n ) less than 30,000, more preferably less than 25,000, and even more preferably less than 22,000.

The hydrophobic block may have a molecular weight, such as a number-average molecular weight ( M_n ) that is in a range with the upper and lower limits selected from the amounts described above.

The number-average molecular weight ( _n) is the statistical average molecular weight of all the polymer chains in the sample, i.e. the total mass of all the polymer chains divided by the total number of chains. The number average molecular weight can be calculated

experimentally by gel permeation chromatography (GPC, also known as size exclusion chromatography, SEC) which separates out the chains based on size and by nuclear magnetic resonance spectroscopy where end group analysis can be utilised. Preferably, M_n may be measured by GPC using a Refractive Index detector and comparing to PMMA standards.

Preferably, the hydrophobic block has a dispersity (£>) greater than 1.00, more preferably greater than 1.05 and even more preferably greater than 1.10.

Preferably, the hydrophobic block has a dispersity (£⁾) less than 2.50, preferably less than 2.00, more preferably less than 1.50, and even more preferably less than 1.30. The hydrophobic block may have a dispersity (£>) that is in a range with the upper and lower limits selected from the amounts described above. For example, the hydrophobic block may have a dispersity (£>) from at least 1.00 to at most 1.50.

The dispersity (£)), M_n and M_w values can be measured as discussed above.

The length of the hydrophobic block is associated with the molecular weight and dispersity. Hydrophobic blocks within the ranges provided here provide block copolymers with good adhesion properties.

Exemplary Block Copolymers

In some cases, the block copolymer may be selected from:

Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate] (referred to as P[(HEA-co-HMAA)-Jb-PMA]:

Preferably, the block copolymer may be selected from:

P[(H EA₃₆-CO- H M AA₄)-J - PM A₅] ; P[(HEA₃₆-co-HMAA₄)-b-PMA₁₀]; P[(HEA₇₂-co-HMAA₈)-b- PMAs]; P[(HEA₇₂-co-HMAA₈)-J -PMAio]; P[(HEA₇₂-co-HMAA₈)-b-PMA₂₀]; P[(HEA₇₂-co- H M AA₈)-Jb- P M A40] ; P[(HEA₁₀₈-co-HMAA₁₂)-Jb-PMA₅]; P[(HEA₁₀₈-co-HMAA₁₂)-Jb-PMA₁₀];

P[(HEAi₀₈-co-HMAAi₂)-Jb-PMA₂₀]; P[(HEA₁₀₈-co-HMAA₁₂)-b-PMA₄₀]; P[(HEA₇₆-co-HMAA₄)-Jb- PMA_2O]; P[(HEA₆₈-co-HMAA₁₂)-Jb-PMA₂₀]; P[(HEA₆₂-co-HMAA₁₈)-Jb-PMA₂₀]; P[(HEA₇₆-co- HMAA₄)-Jb-PMA₅]; P[(HEA₇₆-co-HMAA₄)-Jb-PMA₁₀]; or P[(HEA₃₆-co-HMAA₄)-b-PMA₁₀].

Solvents

The inks of the present invention are aqueous inks. The term aqueous ink refers to ink compositions that contain water. Aqueous inks may contain substantially only water as the solvent or may contain other solvents.

Preferably, water may be present in less than 99 wt % based on total weight of the ink composition, preferably less than 97 wt %, more preferably less than 95 wt %, preferably less than 80 wt %, preferably less than 60 wt % and even more preferably less than 50 wt % based on total weight of the ink composition.

Preferably, water is present in greater than 10 wt % based on total weight of the ink composition, preferably greater than 30 wt %, preferably greater than 40 wt %, and even more preferably greater than 90 wt % based on total weight of the ink composition. Water may be present in an amount that is in a range with the upper and lower limits selected from the amounts described above. For example, water may be present in from 30 to 95 wt% based on total weight of the ink composition.

The ink compositions may contain an additional solvent such as an organic solvent.

The organic solvent may be any suitable solvent. Preferably the organic solvent, if present, is water miscible.

Suitable organic solvents selected from Ci-₆ alkyl ketones (such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone), Ci-₆ alkyl alcohol (such as ethanol, isopropanol, n-propanol, isobutanol, n-butanol, sec-butanol), Ci-₆ alkyl acetates (such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, n-amyl acetate, isoamyl acetate, isobutyl isobutyrate), tetrahydrofuran (THF), dimethylformamide (DMF) and glycol (such as ethylene glycol, propylene glycol).

Preferably, the organic solvent is a Ci-₆ alkyl alcohol, such as ethanol, isopropanol, n-propanol, isobutanol, n-butanol, sec-butanol, more preferably the organic solvent is ethanol.

In some cases, the organic solvent may be present in less than 60 wt % based on total weight of the ink composition, more preferably less than 55 wt % and even more preferably less than 50 wt %.

Preferably, the organic solvent is present in greater than 10 wt % based on total weight of the ink composition, preferably greater than 30 wt %, and even more preferably greater than 40 wt %.

The organic solvent may be present in an amount that is in a range with the upper and lower limits selected from the amounts described above.

The ratio of water : organic solvent in the ink composition may be from 10 : 1 to 1 : 10, preferably the ratio of water : organic solvent is from 2 : 1 to 1 : 2.

Colourant

The ink composition and the printed deposit may comprise a colourant. The colourant is not particularly limited and any suitable colourant known in the art may be used. The colourant may be a dye or a pigment. The pigment may be an inorganic or an organic pigment.

Preferably the pigment has an average particle size of less than 1 pm. The average particle size referred to here is the Z average particle size calculated using dynamic light scattering (DLS). This is the intensity weighted mean hydrodynamic size of the collection of particles.

The organic pigments may be selected from azo pigments (including azo lake, insoluble azo pigment, condensed azo pigment, and chelate azo pigment), polycyclic pigments (for example, phthalocyanine , perylene, perinone, anthraquinone, quinacridone , dioxazine, thioindigo, isoindolinone, and quinophthalone pigments), dye-type chelate pigment (for example, basic dye-type chelate pigments and acid dye-type chelate pigment), nitro pigments, nitroso pigments, aniline black and carbon black.

Carbon blacks for use in the ink of the present invention include carbon blacks

manufactured by Mitsubishi Chemical Corporation, for example, No. 2300, No. 900, MCF 88, No. 33, No. 40, No. 45, No.52, MA 7, MA 8, MA 100, and No. 2200 B; carbon blacks manufactured by Columbian Carbon Co., Ltd., for example, Raven 5750, Raven 5250,

Raven 5000, Raven 3500, Raven 1255, and Raven 700; carbon blacks manufactured by Cabot Corporation, for example, Regal 400 R, Regal 330 R, Regal 660 R, Mogul L, Mogul E, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, and Monarch 1400; and carbon blacks manufactured by Degussa, for example, Color Black FW 1 , Color Black FW 2, Color Black FW 2 V, Color Black FW 18, Color Black FW 200, Color Black S 150, Color Black S 160, Color Black S 170, Printex 35, Printex U, Printex V, Printex 140 U, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 and Bon Jet CW-2.

Pigments for yellow inks include C.l. Pigment Yellow 1 , C.l. Pigment Yellow 2, C.l. Pigment Yellow 3, C.l. Pigment Yellow 12, C.l. Pigment Yellow 13, C.l. Pigment Yellow 14, C.l.

Pigment Yellow 16, C.l. Pigment Yellow 17, C.l. Pigment Yellow 73, C.l. Pigment Yellow 74, C.l. Pigment Yellow 75, C.l. Pigment Yellow 83, C.l. Pigment Yellow 93, C.l. Pigment Yellow 95, C.l. Pigment Yellow 97, C.l. Pigment yellow 98, C.l. Pigment Yellow 109, C.l. Pigment Yellow 110, C.l. Pigment Yellow 114, C.l. Pigment Yellow 128, C.l. Pigment Yellow 129, C.l. Pigment yellow 138, C.l. Pigment Yellow 150, C.l. Pigment Yellow 151 , C.l. Pigment Yellow 154, C.l. Pigment Yellow 155, C.l. Pigment Yellow 180, C.l. Pigment Yellow 185, and C.l. Pigment Yellow 139.

Pigments for orange inks include C.l. Pigment Orange 64, and C.l. Pigment Orange 73. Pigments for magenta inks include C.l. Pigment Red 5, C.l. Pigment Red 7, C.l. Pigment Red 12, C.l. Pigment Red 48 (Ca), C.l. Pigment Red 48 8 (Mn), C.l. Pigment Red 57 (Ca), C.l. Pigment Red 57 : 1 , C.l. pigment Red 112, C.l. Pigment Red 122, C.l. Pigment Red 123, C.l. Pigment Red 168, C.l. Pigment Red 184, C.l. Pigment Red 202, C.l. Pigment Red 176, C.l. Pigment Red 254, C.l. Pigment Red 255, C.l. Pigment Red 272, C.l. Pigment Red 254, C.l Pigment Violet 19.

Pigments for cyan inks include C.l. Pigment Blue 1 , C.l. Pigment Blue 2, C.l. Pigment Blue 3, C.l. Pigment Blue 15 : 2, C.l. Pigment Blue 15:3, C.l. Pigment Blue 15:4, C.l. Pigment Blue 15 : 34, C.l. Pigment Blue 16, C.l. Pigment Blue 22, C.l. Pigment Blue 60, C.l. Vat Blue 4, C.l . Vat Blue 60

Pigments for green inks include C.l. Pigment Green 3 and C.l Pigment Green 7.

Pigments for violet inks include C.l. Pigment Violet 23 and C.l. Pigment Violet 37.

Pigments for white inks include C.l. Pigment White 6.

Preferably, the organic pigment is selected from C.l. Pigment Yellow 83, C.l. Pigment Yellow 138, C.l. Pigment Yellow 139, C.l. Pigment Yellow 150, C.l. Pigment Yellow 151 , Pigment Yellow 154, C.l. Pigment Yellow 155, C.l. Pigment Yellow 185, C.l. Pigment Orange 43, Pigment Orange 64, C.l. Pigment Orange 73, C.l. Pigment Red 122, C.l. Pigment Red 176, C.l. Pigment Red 254, C.l. Pigment Red 255, C.l. Pigment Red 272, C.l. Pigment Blue 15:3, C.l. Pigment Blue 15:4, C.l. Pigment Green 7, C.l. Pigment Violet 19, C.l. Pigment Violet 23, Pigment Black 7, and carbon black.

When the colourant is a pigment, the pigment may be in the form of a dispersion in the composition. The pigment dispersion may comprise a dispersant or one or more of the monomer components that is present in the ink.

The colorant may be an oil or solvent soluble dye.

Examples of yellow dyes include aryl or heteryl azo dyes having a coupling component such as a phenol, a naphthol, an aniline, a pyrazolone, a pyridone, or an open-chain active methylene compound; azomethine dyes having a coupling component such as an open- chain active methylene compound; methine dyes such as benzylidene dyes and

monomethineoxonol dyes; quinone dyes such as naphthoquinone dyes and anthraquinone dyes; and other dye species such as quinophthalone dyes, nitro/nitroso dyes, acridine dyes, and acridinone dyes.

Examples of magenta dyes include aryl or heteryl azo dyes having a coupling component such as a phenol, a naphthol, or an aniline; azomethine dyes having a coupling component such as a pyrazolone or a pyrazolotriazole; methine dyes such as arylidene dyes, styryl dyes, merocyanine dyes, and oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and xanthene dyes; quinone dyes such as naphthoquinones, anthraquinones, or anthrapyridones; and condensed polycyclic dyes such as dioxazine dyes.

Examples of cyan dyes include indoaniline dyes, indophenol dyes, and azomethine dyes having a coupling component such as a pyrrolotriazole; polymethine dyes such as cyanine dyes, oxonol dyes, and merocyanine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and xanthene dyes; phthalocyanine dyes; anthraquinone dyes; aryl or heteryl azo dyes having a coupling component such as a phenol, a naphthol, or an aniline; and indigo/thioindigo dyes.

Preferably the colourant is present in between 1 to 25 wt% based on total weight of the ink composition, more preferably 1.5 to 15 wt%, and most preferably 2 to 8 wt% based on total weight of the ink composition.

Preferably, the colourant is present in less than 25 wt% based on total weight of the ink composition, more preferably less than 15 wt% and even more preferably less than 10 wt%.

Preferably, the colourant is present in greater than 1 wt% based on total weight of the ink composition, preferably greater than 1.5 wt%, and even more preferably greater than 2 wt%.

The colourant may be present in an amount that is in a range with the upper and lower limits selected from the amounts described above.

Humectants

The ink composition and/or the printed deposit may further comprise a humectant.

In this way, the ink composition of the invention may be reliably printed.

Suitable humectants include ethylene glycol, glycerol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,4-cyclohexanedimethanol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,8-octanediol,

1 ,2-propanediol, 1 ,2-butanediol, 1 ,3-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, glycerol, 1 ,2,6-hexanetriol, sorbitol, 2-pyrrolidinone, 2-propanediol, butyrolacetone, tetrahydrofurfuryl alcohol and 1 ,2,4-butanetriol and mixtures of two or more thereof.

Preferably the humectant is glycerol, 2-pyrrolidinone, or a mixture thereof.

The ink composition may comprise up to 30 wt% of humectants in total based on the total weight of the composition. More preferably, the ink composition comprises up to 20wt% of humectants in total based on the total weight of the composition. The ink composition may comprise at least 5 wt% of humectants in total based on the total weight of the composition. Preferably, the ink composition comprises at least 10 wt%, more preferably at least 15 wt% of humectants in total based on the total weight of the

composition.

The humectant may be present in any combination of the above upper and lower limits. For example, the ink composition may comprise from 10 to 30 wt% of humectants in total based on the total weight of the compositions.

Wetting Agents

The ink composition and/or the printed deposit may further comprise a wetting agent.

In this way, the viscosity of the ink composition may be increased and the surface tension of the ink composition may be decreased.

Wetting agents for ink compositions are well-known in the art. The wetting agent may be a silicone based wetting agent, for example a silicone polyether acrylate wetting agent such as TEGO Rad 2300, BYK-333, BYK-377, BYK-378, TEGO WET 500 or a mixture thereof.

Preferably, a wetting agent is present at from 0.1 to 5 wt % based on total weight of the ink composition, more preferably at from 1 to 2 wt% based on the total weight of the ink composition.

Initiators

The aqueous ink composition may comprises an initiator. The initiator may be a thermal initiator or a photoinitiator.

The term initiator refers to a compound that undergoes a reaction due to an external stimulus producing a reactive species such as a radical. The external stimulus may be UV radiation, thermal radiation, actinic radiation or the use of an electron beam. The reactive species reacts with one or more of the monomers to initiate the polymerization reaction.

The initiator may be a photoinitiator.

The term photoinitiator refers to a compounds that undergoes a photoreaction on absorption of light, producing reactive species such as a radical. The external stimulus may be visible light or UV radiation, preferably the external stimulus is UV radiation. The reactive species produced reacts with one or more of the monomers to initiate the polymerization reaction. The photoinitiator may provide this function when irradiated with light having a wavelength within the range of 450 to 300 nm (i.e. UV radiation). This may mean that the photoinitiator has light absorption characteristics in the entire wavelength range of 450 to 300 nm.

The photoinitiaotor may be chosen to absorb light at a frequency that the chromophore does not absorb light. For example, phosphine oxides have absorption peak at around 360 to 400 nm. Red anthraquinone chromophores have absorption minima in this range. In this way, the chromophore moiety does not absorb the radiation that is applied to initiate the reaction.

Photoinitiators are well known in the art. The photoinitiator may be selected from benzil ketals, a-hydroxyalkyphenones (such as a-hydroxyacetophenones, for example, difunctional alpha hydroxyl ketone or 2-hydroxy- 1-[4-[[4-(2-hydroxy-2-methyl- propanoyl)phenyl]methyl]phenyl]-2-methyl-propan-1-one, discussed below), a--amino acetophenones, phosphine oxides (such as TPO), benzophenones, ketosulphones, thioxanthones, benzoylformate esters or a mixture thereof. Preferably, the photoinitiator is selected from TPO and benzophenone. More preferably, the photoinitiator is a mixture of TPO and benzophenone.

Preferably, the total amount of the photoinitiator is 30 wt % or less based on total weight of the ink composition, more preferably 20 wt % or less and even more preferably 17 wt % or less.

Preferably, the total amount of the photoinitiator is 5 wt % or more based on total weight of the ink composition, preferably 8 wt % or more, and even more preferably 10 wt % or more.

The total amount of the photoinitiator may be an amount that is in a range with the upper and lower limits selected from the amounts described above. For example, the total amount of the photoinitiator is 10 to 20 wt % based on total weight of the ink composition.

Methods and Uses

The present disclosure provides a method for printing markings on a substrate. The aqueous ink compositions of the invention may be printed using an inkjet printer, the method comprising the steps of directing a stream of droplets of the ink composition to a substrate.

In some cases, the method further comprises the step of curing the printed ink composition for example by treating the printed ink composition to UV or thermal radiation. The curing process triggers the triggerable cross linking groups to form cross links between the block copolymers. The ink compositions are formulated by combining the components using methods known in the art.

The curing process may be carried out by the application of thermal radiation, actinic radiation, by the use of an electron beam or by treating the printed ink composition to UV radiation. Preferably the curing process is carried out by treating the printed ink composition to thermal radiation.

The inkjet printer may be a thermal inkjet printer (i.e. a TIJ printer), a continuous inkjet printer (i.e. a CIJ printer) or a drop on demand inkjet printer (i.e. a DOD printer).

In some cases, the inkjet printer is a drop on demand inkjet printer, such as a piezo electric drop on demand inkjet printer. In some preferable cases the inks are applied to the substrate using a high resolution drop on demand printer capable of emitting a range of droplet sizes below 20 pi volume.

In some cases, the inkjet printer is continuous inkjet printing.

Once applied to the substrate, the inks of the current invention may be cured. The curing process promotes the cross linking of the triggerable cross linking groups in the ink composition to provide a printed deposit.

The curing process is initiated by the external conditions such as heat (thermal curing) or UV (radiation curing). Preferably, the external conditions promote crosslinking of the crosslinking groups and do not require any further additives or components to promote the crosslinking. In other cases, the curing process is initiated by an initiator.

The curing process may be a thermal curing process. In such cases, the thermal radiation may promote reaction of the triggerable cross linking groups without the presence of an initiator.

The curing process may be a UV curing process. In such cases, the initiator, if present, is a photoinitiator. The UV curing process may comprise a single application of UV radiation or multiple applications of UV radiation. In some cases, the UV curing process comprises two applications of UV radiation.

In some cases, the first (or only) application of UV radiation is provided by an LED. The LED preferably emits within the range 365 nm and 405 nm. Preferably, the first application of UV radiation provides a dose of 395 nm light delivered at from 20 to 500 mJ/cm², and more preferably at from 50 to 200 mJ/cm² (measured as UVA2 using an EIT Power Puck).

Preferably, the first application of UV radiation occurs immediately after printing, for example using an LED positioned immediately adjacent to the print head. In this way, the ink is at least partially cured immediately after printing and further spreading of the ink across the substrate is prevented.

In some cases, the first application of UV radiation is sufficient to cure the ink.

In other cases, additional applications of UV radiation are required. This is particularly the case at high printing speeds for example print speed print speeds up to 50 m/min, more preferably 75 m/min. In these cases, the additional application of UV radiation is preferably provided by a mercury arc source. For the additional application of UV radiation the dose of U VA is preferably from 30 to 1000m J/cm² and more preferably from 50 to 300m J/cm²⁺ (measured with an EIT Power Map).

Substrate

The present disclosure provides a method for printing markings on a substrate. Any suitable substrate may be printed in accordance with the invention.

Examples of suitable substrates include porous substrates such as uncoated paper, semi- porous substrates such as aqueous coated paper, clay coated paper, silica coated paper,

UV overcoated paper, polymer overcoated paper, and varnish overcoated paper, and non- porous substrates such as hard plastics, polymer films, polymer laminates, metals, metal foil laminates, glass, and ceramics. The paper substrates may be thin sheets of paper, rolls of paper, or cardboard. Plastics, laminates, metals, glass, and ceramic substrates may be in any suitable form such as in the form of bottles or containers, plates, rods, cylinders, etc.

The aqueous ink composition of the present invention is particularly suitable for printing on non-porous material, for example, non-porous materials used for food packaging.

In many cases the substrate will be a plastic film, paper or paperboard.

Suitable examples of plastic films include films comprising polyethylene, polypropylene, polyester, polyamide, PVC, polylactic acid, or cellulosic films. The plastic film may be pretreated or coated, for example to improve the adhesion of the inks or to render it more suitable for the application in question. Metallic films such as those used for lidding applications, glass and ceramics may also be printed.

Advantageously, using the compositions and methods described herein overcomes and/or mitigates at least some of the problems described above, providing an improved quality print.

Additives

The aqueous ink composition and/or the printed deposit may contain additional components, such as are common in the art (see for example EP2070998 and EP1788045).

The ink composition and/or the printed deposit may further comprise one or more stabilisers (e.g. photostabilizers), amine compounds, preservatives (e.g. antioxidants, anti-aging agents), surfactants, conductivity salts, , surface treatment agents, adhesion promotion additives, dispersants, tackifiers, biocides, antiseptics, crosslinking promoters,

polymerization inhibitors, plasticizers, pH adjusters, anti-foaming agents, and mixtures of two or more thereof.

Amine Functional Materials

The inks of the present invention may further comprise an amine compound.

The inks of the current formulation may have low viscosity, for example, to increase compatibility with drop on demand printers such as piezoelectric drop on demand printer.

Low viscosity formulations are particularly susceptible to oxygen inhibition because the oxygen can diffuse more rapidly into the printed film. The presence of oxygen interferes with the proper propagation of the free radical reactions so that cure may not be complete, particularly on the surface of the ink after exposure to UV light.

It is proposed that, amines provide a source of abstractable hydrogen atoms to quench reactive oxygen species. It is also proposed that amines recycle the peroxy radicals that are formed as a consequence of reaction with oxygen. This means that the radicals are not lost to the system, but are returned, via the amine, in a form that can support further

polymerisation.

In this way, the presence of an amine may improve curing performance. It is also proposed that amine compounds, in particular oligomeric amine compounds, contribute positively to the toughness and adhesion of the cured ink film. The amine compound may be any type of amine containing compound such as a small molecule amine, an amine functional oligomer or an amine functional polymer. The amine may be a primary, secondary or tertiary amine. A primary amine is an amines having one non-hydrogen substituent (i.e. NRH2); a secondary amine is an amide having two

non-hydrogen substituents (i.e. NRR’H); a tertiary amine is an amine having three non-hydrogen substituents (i.e. NRR’R”). Preferably, the amine is a secondary or tertiary amine, more preferably a tertiary amine.

Preferably, the amine compound is an amine acrylate or an amine oligomer. In some cases, the amine acrylate is an amine functional acrylate oligomer. Examples of amine functional acrylates include aminated polyether acrylate oligomers (such as Ebecryl 7100 and Ebecryl LEO10552). Examples of amine oligomers include Genomer 5695 and Genomer 5275.

Preferably, the amine compound has a molecular weight, such as a weight average molecular weight (Mw) between 200 and 10,000, more preferably between 200 and 5,000, more preferably between 500 and 5,000, more preferably between 200 and 1 ,000 and even more preferably between 500 and 1 ,000.

Preferably, the amine compound is present in less than 25 wt% based on total weight of the ink composition, more preferably less than 15 wt% and even more preferably less than 10 wt%.

Preferably, the amine compound is present in greater than 1 wt% based on total weight of the ink composition, preferably greater than 2 wt%, and even more preferably greater than 5 wt%.

The amine compound may be present in an amount that is in a range with the upper and lower limits selected from the amounts described above.

Stabilisers

Preferably, the ink composition and/or the printed deposit further comprises a stabiliser.

It is proposed that, in some cases the jetting performance of an inkjet ink is dependent on its viscosity. Undesired free radical polymerisation, for example of the acrylate or vinyl ether groups, can lead to a viscosity increase. A stabiliser may be used to prevent undesired free radical polymerisation, for example the stabiliser may acts as a polymerisation inhibitor to avoid even low levels of free radical polymerisation in the ink during storage or before use. Suitable stabilisers include p-methoxy phenol (MEHQ), butylated hydroxy toluene (BHT), quinone methide, cupferron-AI, and TEMPO.

Preferably, a stabiliser is present at from 0.1 to 5 wt % based on total weight of the ink composition.

Conductivity Additives

For continuous inkjet applications the ink composition and/or the printed deposit may further comprise a conductivity additive. The conductivity additive may be any organic salt known in the art.

Conductivity additives for ink compositions are well-known in the art.

Preferably, the organic salt is selected from quaternary ammonium or phosphonium salts. For example, the organic salt may be selected from tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium acetate, tetrabutylammonium nitrate, tetrabutylammonium

tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylphosphonium chloride and tetrabutylphosphonium bromide.

Preferably, a conductivity additive is present at from 0.1 to 5 wt % based on total weight of the ink composition.

Preservatives

The ink composition and/or the printed deposit may further comprise a preservative. The preservative may be an antioxidant or an anti-aging agent.

Suitable preservatives include sodium benzoate, benzoic acid, sorbic acid, potassium sorbate, calcium sorbate, calcium benzoate, methylparaben and mixtures of two or more thereof.

The ink composition may comprise up to 2 wt% of preservative based on the total weight of the composition. More preferably, the ink composition comprises up to 1 wt% of preservative based on the total weight of the composition. Surfactants

The ink composition and/or the printed deposit may further comprise a surfactant.

Suitable surfactants include anionic, cationic or non-ionic surfactants and mixtures of two or more thereof. Non-limiting examples of anionic surfactants include alkyl sulphate, alkylaryl sulfonate, dialkyl sulfonate, dialkyl sulphosuccinate, alkyl phosphate and polyoxyethylene alkyl ether sulphate. Non-limiting examples of cationic surfactants include alkylamine salt, ammonium salt, alkylpyridinium salt and alkylimidazolium salt. Non-limiting examples of non ionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkylaryl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerine fatty acid ester, a fluorine-containing non-ionic surfactant and a silicon-containing non-ionic surfactant. Mixtures of two or more surfactants may be used.

The ink composition may comprise up to 5 wt% of surfactant based on the total weight of the composition. More preferably, the ink composition comprises up to 1 wt% of surfactant based on the total weight of the composition.

Tackifier

The ink composition and the printed deposit may further comprise a tackifier.

In some cases the tackifier may be a binder; preferably, when the tackifier is a binder it is used in combination with a co-binder. In some cases, the tackifier is a non-film forming polymer. In some cases, the tackifier may be used in combination with other polymers to produce the desired properties.

Suitable tackifiers include resins such as rosins, terpenes and modified terpenes, aliphatic, cycloaliphatic and aromatic resins, terpene phenolic resins and silicone or mineral oils. Preferably the tackifiers are a terpene phenolic resin and/or an ester of hydrogenated rosin.

The ink composition may comprise from 0.3 to 10 wt% of tackifier based on the total weight of the composition. More preferably, the ink composition comprises from 1 to 5 wt% of tackifier based on the total weight of the composition.

Adhesion Promoter

The ink composition and the printed deposit may further comprise an adhesion promoter. An adhesion promotor is a substance which acts to promote adhesion of the ink composition to a substrate.

Suitable adhesion promotors are titanium phosphate complex, titanium acetylacetonate, triethanolamine zirconate, zirconium citrate, zirconium propanoate, organosilicon, polyketones binders, polyesters binders, or a ketone condensation resin.

Dispersant

The ink composition and the printed deposit may further comprise a pigment dispersant.

A dispersant is a substance which promotes dispersion of a component of the ink composition, for examples promotes dispersion of a pigment.

Suitable dispersants include ionic and non-ionic dispersants. Preferably the dispersant is an acrylic block copolymer.

The dispersant may be pre-mixed with the colourant for example the pigment.

The dispersant may be selected according to the nature of the colourant. The amount of dispersant is preferably from 2 wt% to 200 wt% based on the weight of pigment in the ink composition.

Definitions

As used herein the term printed deposit refers to the ink composition after it has been printed onto a suitable substrate and cured. That is the ink composition of the present invention wherein at least some of the monomers present in the ink composition are polymerized to form a film.

As used herein the term ink composition includes an ink composition suitable for use in any kind of printing, for example in inkjet printing. The ink composition is typically in the form of a liquid.

As used herein the term polymer refers to any substance having a repeat unit. Other Preferences

Each and every compatible combination of the embodiments described above is explicitly disclosed herein, as if each and every combination was individually and explicitly recited.

Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.

“and/or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example“A and/or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.

Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described.

Certain aspects and embodiments of the invention will now be illustrated by way of example and with reference to the figures described above.

References

G. Tillet, B. Boutevin, and B. Ameduri, Prog. Polym. Sci. , 36, 191-217, 201 1

Examples

The following non-limiting examples further illustrate the present invention.

All commercial chemicals were used as bought from the suppliers unless otherwise stated.

Dimethylformamide (DMF), methanol (MeOH) and hexane (all Laboratory Reagent grade) were purchased from Fisher Scientific and used as supplied.

2,2’-Azobis(isobutyronitrile) (AIBN), f-butanol, cyano-2-propyl dodecyl trithiocarbonate (CPDT) (³ 97 %) deuterium oxide (D2O), dimethylformamide (DMF) (99.8 %, anhydrous) and 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid (DCMP) (³ 97 %) were purchased from Sigma Aldrich and used without further purification.

2-Hydroxyethyl acrylate (HEA) (³ 97 %), /V-hydroxymethyl acrylamide (HMAA) (48 % wt. in H2O) and propyl methacrylate (PMA) (³ 97 %) were purchased from Sigma Aldrich. Inhibitors were removed via a basic alumina column and HMAA had water removed via freeze drying.

Bon Jet CW-2 was provided by Orient Chemicals.

Caramel dye was provided by iFC.

Brilliant Blue was provided by Sensient Chemicals.

Chloroform-d (CDCL, 99.8 % At + 0.05 % TMS Goss scientific), dimethyl sulfoxide-d₆ (DMSO-de), 99.8 % At + 0.05 % TMS Goss scientific) were used as supplied.

High-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polyethylene terephthalate) (PET) substrates were purchased from Engineering & Design Plastics.

Glycerol was provided by Sigma Aldrich.

2-pyrrolidinone was provided by Sigma Aldrich.

BYK-333, BYK-377 and BYK-378 was provided by BYK Additives.

TEGO WET 500 was provided by Evonik.

Cab-O-Jet was provided by Cabot.

433BL is a commercial ink provided by Domino Printing Sciences PLC.

¹ H NMR was carried out on a 300 MHz Bruker Avance Spectrometer. Samples were dissolved in d₆-DMSO or CDCh. ¹H NMR was used to calculate monomer conversion throughout the polymerisations.

GPC was performed on an Agilent GPC 50 plus consisting of two PL gel 5 pm 300 x 7.5 mixed-C columns as well as a guard column. The mobile phase used was degassed DMF (2.5 L) containing 2.5 g LiBr, at a flow rate of 0.8 ml/min and the column oven set to 50 °C. Calibration was carried out using near monodispersed poly(methyl methacrylate) ( M_p range = 690 to 1 ,944,000 gmol ¹). Samples were prepared by dissolving in DMF eluent (approximately 4 mg/mL) and filtered through a 0.45 pm Millipore syringe filter. Toluene was used as a flow rate marker. Cirrus GPC software (version 3.2) provided by Agilent technologies was used to analyze the data. Fourier transform infrared (FTIR) spectra of all the samples were obtained using attenuated total reflectance (ATR) on a Thermo Nicolet 380 FTIR spectrophotometer over the range 4000-500 cm^-1 for 16 scans with a resolution of 4 cm ¹.

Thermogravimetric analysis (TGA) was undertaken using a Pyris 1 thermogravimetric analyser under nitrogen atmosphere (flow rate 20 mL/min) polymer samples were heated from 30 °C to 150 °C at a rate of 10 °C/min and held for 10 minutes.

Particle size measurements were performed using a Malvern Zetasizer Nano ZS instrument. Z-average and polydispersity was measured using approximately 1 ml of solution in a polystyrene cuvette. Each sample was run 3 times with 12 scans in each run. The instrument is verified monthly using an aqueous polystyrene latex (Z- average 290 d.nm ± 10 d.nm) verification standard.

Surface tension of polymer solutions were measured using a SITA pro line t15 bubble tensiometer where the surface tension was measured over a pre-selected range of bubble lifetimes. The instrument was calibrated with deionized water before each measurement.

Viscometry measurements of polymer solutions were performed using a Brookfield ball drop tensiometer at a temperature of 25 °C unless otherwise stated. Measurements were recorded 5 times over a range of angles (20°, 30°, 40°, 50°, 60°, 70° and 80°).

Printing tests

Printing tests were carried out on a Fujifilm Dimatix inkjet (Model number DMP-2831). Crosslinking tests

Crosslinking tests were performed in both the bulk and thin film to ascertain the time required for the polymers to form an insoluble network. Polymer samples in the bulk were placed in an oven at 150 °C and samples removed at set time intervals to be tested for their solubility in methanol.

A modified thin film method was implemented in order to mimic conditions of the printing process. Drop cast films of the copolymer (from ethanol/water 50:50 w/w) on PTFE substrates were made and the cross-linking conditions investigated as with bulk samples.

All samples were left to dry for 3 hours at room temperature before heating. Adhesion tests

Adhesive performance was tested on polymer and ink formulations on substrates after drying and crosslinking. A range of industrially-designed tests were employed to qualitatively measure the adhesive properties of the block copolymers and ink formulations on various substrates [poly(ethylene terephthalate) (PET), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE) and glass].

The polymer solutions used in each of these tests is detailed below with the corresponding test results. The method of applying the polymer solution to the substrate is also detailed below with the corresponding test results.

Wetting of the polymer onto the substrate was assessed visually using a 10 x 10 grid drawn on a transparent film, which was placed on top of the draw down to calculate the approximate percentage coverage of the substrate before and after crosslinking.

The adhesive performance was qualitatively measured by the number of rubs (using a blunt, rounded surface, typically a thumb) and scratches (using a spatula) needed to remove the ink from the substrate. Approximately equal force was used each time and tests were done in triplicate.

Tape tests’ were performed whereby a 10 x 10 grid of squares (25 cm² total area) was cut into the ink/polymer. A suitable length of 3M Scotch Tape (both 610 and 810, where by 810 has a stronger adhesive force than 610) was used to cover the area surrounding the pattern as well as leaving an untethered free area of tape

(approximately 5 cm) for subsequent removal. The tape was applied carefully to avoid creases and air bubbles. One hand was used to hold the unattached tail portion of tape and the tape was removed with a swift motion that combines both lifting and pulling action, attempting to maintain consistency between samples. Again, tests were repeated two additional times to obtain suitable average values for each polymer system.

Each of these tests was assessed by a qualitative rating system (0 to 10, where 10 shows the highest adhesive performance).

Rub and scratch tests were assessed by the number of rubs (or scratches) before the ink was removed from the substrate. Greater than 10 rubs was considered excellent and has the highest score of 10, 8 - 10 rubs was considered good and has a score of 8, 5 - 8 rubs moderate and has a score of 6, 3 - 5 poor and has a score of 4 and less than 3 rubs is considered very poor and has a score of 2. For the tape tests this was assessed by the percentage of ink removed (measured from the number of squares of the grid removed) from the substrate. Where 0 - 20 % removal was considered excellent and has a score of 10, 20 - 40 % good and has a score of 8, 40 - 60% rubs moderate and has a score of 6, 60 - 80% poor and has a score of 4, and more than 80 % is considered very poor and has a score of 2. 100 % removal would have a score of zero.

Draw downs

In some worked examples of the present case, a drawdown is provided to measure properties of the deposited ink formulation.

A drawdown is a sample made by depositing a layer of the mixed ink on the surface of a substrate using a smooth-edged knife or drawdown bar or rod. A drawdown bar can be used to provide a specified ink thickness on the substrate. In the worked examples of the present case a 6 pm drawdown rod (or drawdown bar) is used to provide a wet ink thickness of approximately 6 pm which is estimated to amount of ink deposited by drop on demand printing technologies. Drawdowns are often used to mimic large printed areas.

Example 1 - Synthesis RAFT polymerisation of 2-hydroxyethyl acrylate

The following example describes the polymerisation of 2-hydroxyethyl acrylate (HEA) targeting a degree of polymerisation (D_p) of 80 [AIBN]o/[CTA]o/[HEA]o = 0.2/1/80; in methanol/DMF at 60°C. A reaction tube suitable for a R. B. Radley Co. Ltd. Carousel 12 Plus, equipped with a magnetic stirrer bar, was charged with a mixture of HEA (2 g, 17.2 mmol), CPDT (78 mg, 0.21 mmol), AI BN (7 mg, 0.04 mmol) and methanol/DMF (2 mL). The system was degassed three times via vacuum and nitrogen cycles, before the sealed tube under nitrogen atmosphere was placed into the 60 °C preheated Carousel. Samples were taken at regular intervals and the monomer conversion measured via ¹ H NMR spectroscopy and molar mass data by GPC. Termination of the reaction was achieved by unsealing the tube and rapidly cooling by placing the reaction vessel into an ice bath. The polymer was precipitated by adding to stirring hexane (300 mL) dropwise. Hexane was decanted off and the resulting polymer redissolved in methanol, transferred to a vial and the methanol evaporated off to yield a clear yellow viscous material.

Poly(2-hydroxyethyl acrylate), PHEAso:

M_n = 22,400, B = 1.11 ¹H NMR (300 MHz, de-DMSO, d ppm from TMS): 0.81 (br, 3H), 1.29 (br, 18 H), 1.62 (br, 2H), 1.79 (br, 6H), 2.26, (br, 1 H), 2.51 (br, 2H), 3.55 (br, 2H), 4.01 (br, 2H), 4.76 (br, 1 H).

FTIR assigned peaks (cm^-1): 3367 (O-H stretching), 2938 (C-H sp³ hybridised stretching), 1724 (C=0 stretching), 1449 (C-H methyl bending), 1388 (C-H gem dimethyl bending), 1241 (C=S stretching), 1160 (C-0 ester stretching), 1073 (C-0 primary alcohol stretching).

RAFT polymerization of 2-hydroxyethyl acrylate and hydroxymethyl acrylamide

The following example describes the copolymerisation of 2-hydroxyethyl acrylate (HEA) and /V-hydroxymethyl acrylamide (HMAA targeting a total degree of polymerisation (D_p) of 80 [AIBN]o/[CTA]o/[HEA]o/[HMAA]o = 0.2/1/76/4; in methanol/DMF at 60 °C. A reaction tube suitable for a R. B. Radley Co. Ltd. Carousel 12 Plus, equipped with a magnetic stirrer bar, was charged with a mixture of HEA (2 g, 17.2 mmol), HMAA (91 mg, 0.90 mmol) CPDT (82 mg, 0.22 mmol), AI BN (7 mg, 0.04 mmol) and methanol (2 ml). The system was degassed three times via vacuum and nitrogen cycles, before the sealed tube under nitrogen atmosphere was placed into the 60 °C preheated Carousel. Samples were taken at regular intervals and the monomer conversion measured via ¹ H NMR spectroscopy and molar mass data by GPC. Termination of the reaction was achieved by unsealing the tube and cooling in an ice bath. The polymer was precipitated by adding the resulting polymer solution to hexane (300 ml) dropwise. Hexane was decanted off and the resulting polymer redissolved in methanol, transferred to a vial and the methanol evaporated off to yield a clear yellow viscous material.

Poly(2-hydroxyethyl acrylate-co- /V-hydroxymethyl acrylamide) - P(HEA79-co-HMAAi):

M_n = 21 ,770, B = 1.12 ¹H NMR (300 MHz, de-DMSO, d ppm from TMS): 0.84 (br, 3H), 1.29 (br, 18 H), 1.58 (br, 2H), 1.77 (br, 6H), 2.24, (br, 1 H), 2.52 (br, 2H), 3.52 (br, 2H), 4.12 (br, 4H), 4.79 (br, 2H) FTIR assigned peaks (cm^-1): 3375 (O-H stretching), 2942 (C-H sp³ hybridised stretching), 1720 (C=0 stretching), 1540 (N-H bending), 1452 (C-H methyl bending), 1384 (C-H gem dimethyl bending), 1245 (C=S stretching), 1 157 (C-0 ester stretching), 1071 (C-0 primary alcohol stretching).

Poly(2-hydroxyethyl acrylate-co- /V-hydroxymethyl acrylamide) - P(HEA77-co-HMAA3):

M_n = 19,600, B = 1.13 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.82 (br, 3H), 1.27 (br, 18 H), 1.60 (br, 2H), 1.78 (br, 6H), 2.22, (br, 1 H), 2.53 (br, 2H), 3.54 (br, 2H), 4.14 (br, 4H), 4.80 (br, 2H)

FTIR assigned peaks (cm^-1): 3470 (O-H stretching), 2948 (C-H sp³ hybridised stretching), 1723 (C=0 stretching), 1536 (N-H bending), 1448 (C-H methyl bending), 1387 (C-H gem dimethyl bending), 1251 (C=S stretching), 1 159 (C-0 ester stretching), 1068 (C-0 primary alcohol stretching).

Poly(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide) - P(HEA76-co-HMAA4):

M_n = 19, 160, B = 1.16 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.82 (br, 3H), 1.31 (br, 18 H), 1.63 (br, 2H), 1.79 (br, 6H), 2.26, (br, 1 H), 2.51 (br, 2H), 3.55 (br, 2H), 4.16 (br, 4H), 4.78 (br, 2H)

FTIR assigned peaks (cm^-1): 3363 (O-H stretching), 2946 (C-H sp³ hybridised stretching), 1721 (C=0 stretching), 1535 (N-H bending), 1450 (C-H methyl bending), 1385 (C-H gem dimethyl bending), 1249 (C=S stretching), 1 155 (C-0 ester stretching), 1070 (C-0 primary alcohol stretching).

Poly(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide), P(HEA7_O-CO-HMAAI_O):

M_n = 21 ,300, B = 1.18 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.80 (br, 3H), 1.32 (br, 18 H), 1.65 (br, 2H), 1.82 (br, 6H), 2.28, (br, 1 H), 2.53 (br, 2H), 3.53 (br, 2H), 4.20 (br, 4H), 4.78 (br, 2H)

FTIR assigned peaks (cm^-1): 3365 (O-H stretching), 2943 (C-H sp³ hybridised stretching), 1723 (C=0 stretching), 1541 (N-H bending), 1454 (C-H methyl bending), 1385 (C-H gem dimethyl bending), 1246 (C=S stretching), 1 160 (C-0 ester stretching), 1068 (C-0 primary alcohol stretching). Poly(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide), P(HEA36-co-HMAA4):

M_n = 10,200, B = 1.17 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.78 (br, 3H), 1.29 (br, 18 H), 1.63 (br, 2H), 1.78 (br, 6H), 2.26, (br, 1 H), 2.53 (br, 2H), 3.58 (br, 2H), 4.05 (br, 4H), 4.75 (br, 2H)

FTIR assigned peaks (cm ¹): 3466 (O-H stretching), 2945 (C-H sp³ hybridised stretching), 1726 (C=0 stretching), 1540 (N-H bending), 1451 (C-H methyl bending), 1389 (C-H gem dimethyl bending), 1253 (C=S stretching), 1 161 (C-0 ester stretching), 1065 (C-0 primary alcohol stretching).

Poly(2-hydroxyethyl acrylate-co-A/-hydroxyrriethyl acrylamide), R(HEA72-oo-HMAA_d):

M_n = 17,800, B = 1.18 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.81 (br, 3H), 1.32 (br, 18 H), 1.60 (br, 2H), 1.81 (br, 6H), 2.30, (br, 1 H), 2.55 (br, 2H), 3.56 (br, 2H), 4.08 (br, 4H), 4.76 (br, 2H)

FTIR assigned peaks (cm ¹): 3368 (0-H stretching), 2943 (C-H sp³ hybridised stretching), 1723 (OO stretching), 1531 (N-H bending), 1448 (C-H methyl bending), 1381 (C-H gem dimethyl bending), 1250 (C=S stretching), 1 154 (C-0 ester stretching), 1070 (C-0 primary alcohol stretching).

Poly(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide), P(HEAio8-co-HMAAi2):

M_n = 24,700, B = 1.18 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.81 (br, 3H), 1.30 (br, 18 H), 1.62 (br, 2H), 1.83 (br, 6H), 2.26, (br, 1 H), 2.53 (br, 2H), 3.52 (br, 2H), 4.12 (br, 4H), 4.72 (br, 2H)

FTIR assigned peaks (cm ¹): 3468 (O-H stretching), 2950 (C-H sp³ hybridised stretching), 1724 (C=0 stretching), 1545 (N-H bending), 1447 (C-H methyl bending), 1390 (C-H gem dimethyl bending), 1248 (C=S stretching), 1 157 (C-0 ester stretching), 1072 (C-0 primary alcohol stretching).

RAFT polymerization of propyl methacrylate

The following example describes the polymerisation of propyl methacrylate (PMA) targeting a total degree of polymerisation (D_p) of 20 [AIBN]o/[CTA]o/[PMA]o = 0.2/1/20; in DMF at 60 °C. A reaction tube suitable for a R. B. Radley Co. Ltd. Carousel 12 Plus, equipped with a magnetic stirrer bar, was charged with a mixture of PMA (2 g, 15 mmol), CPDT (269 mg, 0.78 mmol), AIBN (24 mg, 0.15 mmol) and DMF (2 ml). The system was degassed three times via vacuum and nitrogen cycles, before the sealed tube under nitrogen atmosphere was placed into the 60 °C preheated Carousel. Samples were taken at regular intervals and the monomer conversion measured via ¹ H NMR spectroscopy and molar mass data by GPC. Termination of the reaction was achieved by unsealing the tube and cooling in an ice bath. The polymer was precipitated by adding the resulting polymer solution to methanol (300 ml) dropwise; the precipitate was filtered and washed with methanol resulting in a yellow powder.

Poly(propyl methacrylate):

M_n = 2,700, B = 1.12 ¹H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.82 (br, 3H), 1.12 (br, 3H) 1.21 (br, 3H) 1.31 (br, 18 H), 1.58 (br, 2H), 1.81 (br, 6H), 2.24, (br, 1 H), 2.55, (br, 2H), 3.55 (br, 2H), 4.01 (br, 2H)

FTIR assigned peaks (cm^-1): 2952 (C-H sp³ hybridised stretching), 1724 (C=0 stretching), 1447 (C-H methyl bending), 1392 (C-H gem dimethyl bending), 1248 (C=S stretching), 1155 (C-0 ester stretching), 1070.

Synthesis of poly[(2-hydroxyethyl acrylate-co-N-hydroxymethyl acrylamide)-b-propyl methacrylate] via RAFT polymerisation

The following example describes the diblock copolymerisation of propyl methacrylate grown from poly(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide) targeting a chain extension of 200 [AIBN]o/[macroCTA]o/[PMA]o= 0.2/1/20; in methanol at 60 °C. A round bottom flask, was charged with a mixture of PMA (128 mg, 1.06 mmol), macroCTA (1 g, 0.05 mmol), AIBN (1.6 mg, 0.01 mmol) and methanol (2 ml). The system was degassed three times via vacuum and nitrogen cycles, before the sealed tube under nitrogen atmosphere was placed into the 60 °C preheated oil bath. Samples were taken at regular intervals and the monomer conversion measured via ¹ H NMR spectroscopy and molar mass data by GPC. Termination of the reaction was achieved by unsealing the tube and cooling in an ice bath. The polymer was precipitated by adding the resulting polymer solution to hexane (300 ml) dropwise. Hexane was decanted off and the resulting polymer dissolved in methanol, transferred to a vial and the methanol evaporated off to yield a yellow viscous material. Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate],

P[(H EA36-CO- H M AA₄)-J - PM A₅] :

M_n = 10,700, B = 1.21 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.83 (br, 3H), 1.1 1 (br, 3H), 1.23 (br, 3H), 1.31 (br, 18 H), 1.61 (br, 2H), 1.83 (br, 6H), 2.22, (br, 1 H), 2.56, (br, 2H), 3.57 (br, 4H), 4.11 (br, 6H), 4.74 (br, 2H)

FTIR assigned peaks (cm ¹): 3472 (O-H stretching), 2948 (C-H sp³ hybridised stretching), 1730 (C=0 stretching), 1543 (N-H bending), 1452 (C-H methyl bending), 1388 (C-H gem dimethyl bending), 1251 (C=S stretching), 1 154 (C-0 ester stretching), 1060 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-A/-hydroxymethyl acrylamide)-Jb-propyl methacrylate], P[(HEA36-co-HMAA₄)-J -PMAio]:

M_n = 11 ,400, B = 1.24 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.81 (br, 3H), 1.08 (br, 3H), 1.24 (br, 3H), 1.35(br, 18 H), 1.65 (br, 2H), 1.79 (br, 6H), 2.25, (br, 1 H), 2.51 , (br, 2H), 3.62 (br, 4H), 4.13 (br, 6H), 4.71 (br, 2H)

FTIR assigned peaks (cm ¹): 3468 (0-H stretching), 2950 (C-H sp³ hybridised stretching), 1724 (C=0 stretching), 1545 (N-H bending), 1447 (C-H methyl bending), 1390 (C-H gem dimethyl bending), 1248 (C=S stretching), 1 157 (C-0 ester stretching), 1072 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate],

P[(H EA72-CO- H M AA₈)-J - PM A₅] :

M_n = 17,700, B = 1.21 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.87 (br, 3H), 1.13 (br, 3H), 1.27 (br, 3H), 1.34 (br, 18 H), 1.64 (br, 2H), 1.81 (br, 6H), 2.19, (br, 1 H), 2.52, (br, 2H), 3.61 (br, 4H), 4.08 (br, 6H), 4.79 (br, 2H)

FTIR assigned peaks (cm^-1): 3479 (O-H stretching), 2957 (C-H sp³ hybridised stretching), 1731 (C=0 stretching), 1552 (N-H bending), 1453 (C-H methyl bending), 1386 (C-H gem dimethyl bending), 1245 (C=S stretching), 1 156 (C-0 ester stretching), 1067 (C-0 primary alcohol stretching). Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate],

P[(H EA72-CO- H M AA₈)-J - PM A₅] :

M_n = 18,700, B = 1.23 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.79 (br, 3H), 1.14 (br, 3H), 1.27 (br, 3H), 1.38 (br, 18 H), 1.65 (br, 2H), 1.81 (br, 6H), 2.27, (br, 1 H), 2.53 (br, 2H), 3.58 (br, 4H), 4.20(br, 6H), 4.71 (br, 2H)

FTIR assigned peaks (cm^-1): 3460 (O-H stretching), 2955 (C-H sp³ hybridised stretching), 1728 (C=0 stretching), 1548 (N-H bending), 1449 (C-H methyl bending), 1382 (C-H gem dimethyl bending), 1249 (C=S stretching), 1 158 (C-0 ester stretching), 1069 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-A/-hydroxyrriethyl acrylamide)-Jb-propyl methacrylate],

P[(H EA72-CO- H M AA₈)-J - PM A20] :

M_n = 19,600, B = 1.23 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.80 (br, 3H), 1.09 (br, 3H), 1.23 (br, 3H), 1.33 (br, 18 H), 1.62 (br, 2H), 1.87 (br, 6H), 2.17, (br, 1 H), 2.51 , (br, 2H), 3.51 (br, 4H), 4.11 (br, 6H), 4.76 (br, 2H)

FTIR assigned peaks (cm^-1): 3468 (0-H stretching), 2963 (C-H sp³ hybridised stretching), 1730 (C=0 stretching), 1551 (N-H bending), 1447 (C-H methyl bending), 1378 (C-H gem dimethyl bending), 1252 (C=S stretching), 1 162 (C-0 ester stretching), 1062 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate],

P[(H EA72-CO- H M AA₈)-J - PM A40] :

M_n = 21 ,700, B = 1.25 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.79 (br, 3H), 1.14 (br, 3H), 1.26 (br, 3H), 1.40 (br, 18 H), 1.63 (br, 2H), 1.88 (br, 6H), 2.25, (br, 1 H), 2.50, (br, 2H), 3.51 (br, 4H), 4.12 (br, 6H), 4.70 (br, 2H)

FTIR assigned peaks (cm ¹): 3473 (O-H stretching), 2968 (C-H sp³ hybridised stretching), 1732 (C=0 stretching), 1547 (N-H bending), 1454 (C-H methyl bending), 1382 (C-H gem dimethyl bending), 1247 (C=S stretching), 1 165 (C-0 ester stretching), 1064 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate], P[(HEAio8-co-HMAAi₂)-J -PMA₅]: M_n = 24,600, B = 1.21 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.83 (br, 3H), 1.13 (br, 3H), 1.21 (br, 3H), 1.29 (br, 18 H), 1.58 (br, 2H), 1.80 (br, 6H), 2.21 , (br, 1 H), 2.53, (br, 2H), 3.54 (br, 4H), 4.14 (br, 6H), 4.71 (br, 2H)

FTIR assigned peaks (cm ¹): 3475 (O-H stretching), 2974 (C-H sp³ hybridised stretching), 1728 (C=0 stretching), 1549 (N-H bending), 1464 (C-H methyl bending), 1386 (C-H gem dimethyl bending), 1252 (C=S stretching), 1 168 (C-0 ester stretching), 1059 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-A/-hydroxymethyl acrylamide)-Jb-propyl methacrylate], P[(HEAio₈-co-HMAAi₂)-Jb-PMAio]:

M_n = 25,700, B = 1.23 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.84 (br, 3H), 1.17 (br, 3H), 1.27 (br, 3H), 1.33 (br, 18 H), 1.62 (br, 2H), 1.83 (br, 6H), 2.30, (br, 1 H), 2.51 (br, 2H), 3.60 (br, 4H), 4.22 (br, 6H), 4.69 (br, 2H)

FTIR assigned peaks (cm ¹): 3472 (0-H stretching), 2973 (C-H sp³ hybridised stretching), 1732 (C=0 stretching), 1547 (N-H bending), 1466 (C-H methyl bending), 1390 (C-H gem dimethyl bending), 1251 (C=S stretching), 1 170 (C-0 ester stretching), 1061 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate], P[(HEA₁₀₈-co-HMAA₁₂)-J -PMA₂o]:

M_n = 26,700, B = 1.24 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.85 (br, 3H), 1.15 (br, 3H), 1.26 (br, 3H), 1.32 (br, 18 H), 1.58 (br, 2H), 1.81 (br, 6H), 2.23, (br, 1 H), 2.52, (br, 2H), 3.60 (br, 4H), 4.19 (br, 6H), 4.71 (br, 2H)

FTIR assigned peaks (cm ¹): 3475 (O-H stretching), 2969 (C-H sp³ hybridised stretching), 1733 (C=0 stretching), 1555 (N-H bending), 1464 (C-H methyl bending), 1387 (C-H gem dimethyl bending), 1253 (C=S stretching), 1 168 (C-0 ester stretching), 1058 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate], P[(HEAi08-co-HMAAi₂)-Jb-PMA₄₀]:

M_n = 28,600, B = 1.25 ¹ H NMR (300 MHz, d₆-DMSO, d ppm from TMS): 0.84 (br, 3H), 1.12(br, 3H), 1.21 (br, 3H), 1.33 (br, 18 H), 1.61 (br, 2H), 1.81 (br, 6H), 2.22, (br, 1 H), 2.57, (br, 2H), 3.63 (br, 4H), 4.12 (br, 6H), 4.69 (br, 2H) FTIR assigned peaks (cm^-1): 3478 (O-H stretching), 2964 (C-H sp³ hybridised stretching), 1731 (C=0 stretching), 1561 (N-H bending), 1458 (C-H methyl bending), 1382 (C-H gem dimethyl bending), 1252 (C=S stretching), 1171 (C-0 ester stretching), 1054 (C-0 primary alcohol stretching).

Poly[(2-hydroxyethyl acrylate-co-N-hydroxymethyl acrylamide)-Jb-propyl methacrylate] P[(HEA₃₆-co-HMAA₄)-J -PMAio]:

M_n = 11 ,400, D = 1.24 ¹H NMR (300 MHz, DMSO-d6, d ppm from TMS): 0.81 (br, 3H), 1.08 (br, 3H), 1.24 (br, 3H), 1.35(br, 18 H), 1.65 (br, 2H), 1.79 (br, 6H), 2.25, (br, 1 H), 2.51 , (br, 2H), 3.62 (br, 4H), 4.13 (br, 6H), 4.71 (br, 2H)

FTIR assigned peaks (cm ¹): 3468 (O-H stretching), 2950 (C-H sp3 hybridised stretching), 1724 (C=0 stretching), 1545 (N-H bending), 1447 (C-H methyl bending), 1390 (C-H gem dimethyl bending), 1248 (C=S stretching), 1157 (C-0 ester stretching), 1072 (C-0 primary alcohol stretching).

Further block copolymers tested P[(HEA₇6-co-HMAA₄)-Jb-PMA2o]; P[(HEA68-co-HMAAi2)-b- PMA20]; P[( H EA₆₂-co- H M AA_{I 8})-b- PM A20] ; P[(HEA₇₆-co-HMAA₄)-b-PMA₅]; and P[(HEA₇₆-co- HMAA₄)-b-PMAio] were produced using the above methods and their structure confirmed

Example 2 - Ink Formulations

In order to test the performance of the block copolymers in continuous ink jet printing (Cl J) the block copolymers produced in Example 1 were incorporated into ink formulations.

5 wt% of each block copolymer and 1 wt% brilliant blue dye were dissolved in ethanol:water 50:50 w/w and shaken for approximately 1 hour. Ink formulations were filtered through filter paper before jetting.

Example 3 - Adhesion

Adhesive properties of ink formulation of Example 2 were studied using the methods described above.

Table 1 shows the adhesive properties of block copolymer drawn down films on PET before (Table 1a) after crosslinking (Table 1 b, after three hours at 150 °C). The numbering of the lines begins at zero (0) at the centre point of each plot increasing by two (2) for each radial line to a value of ten (10) for the outermost line.

Table 1a: PET before crosslinking; A - wetting, B - finger rub, C - nail scratch, D - tape

610 and E - tape 810.

Table 1b: PET after crosslinking; A - wetting, B - finger rub, C - nail scratch, D - tape 610 and E - tape 810.

The crosslinked polymer area (table 1b) is bigger than the non-crosslinked area (table 1a) in 5 all cases except for P(HEA36-co-HMAA4) and P[(HEA36-co-HMAA4)-b-PMA5], where the non- crosslinked polymer outperforms the crosslinked polymer in one or two of the tests, and P(HEA72-co-HMAA8), where both polymers perform equally in all tests.

Table 2 shows the adhesive properties of block copolymer drawn down films on PP before (table 2a) after cross-linking (table 2b, after three hours at 150 °C). The numbering of the lines begins at zero (0) at the centre point of each plot increasing by two (2) for each radial 5 line to a value of ten (10) for the outermost line.

Table 2a. Before crosslinking; A - wetting, B - finger rub, C - nail scratch, D - tape 610 and

E - tape 810.

Table 2b. After crosslinking; A - wetting, B - finger rub, C - nail scratch, D - tape 610 and E

- tape 810.

These screening tests show that the block copolymer with larger hydrophobic blocks give enhanced adhesive properties.

Adhesion was also studied for ink formulations containing block copolymers in which the amount of crosslinker in the hydrophilic block was varied. The formulations for this study are show in Table 3. The ink formulations were deposited as draw downs for this study.

Table 3 - Formulations of ink composition for study on the amount of the crosslinker

Tables 4 and 5 show the adhesive performance data expressed as radar graphs for draw downs on PP and PET before and after cross-linking, respectively. All tests were repeated three times and the radar plots show the average performance. The numbering of the lines begins at zero (0) at the centre point of each plot increasing by two (2) for each radial line to a value of ten (10) for the outermost line.

Table 4. Adhesion of formulations listed in Table 3 on PP and PET before crosslinking.

Table 5. Adhesion of formulations listed in Table 3 on PP and PET after crosslinking.

All formulations wetted both substrates excellently and performed well in the finger rub test with it requiring more than 10 rubs to remove any ink from the test area.

There is a difference in the adhesive performance between PP and PET. Across the series, formulations gave better adhesion on PET compared to PP; with formulations performing better for all tests on PET. For tests on PP increasing the total polymer molecular weight as well as size of the hydrophobic group from D_p 20 to 40 resulted in improved performance of the tape tests.

This trend may be caused by the increase in hydrophobicity and is also observed after cross linking.

Formulations performed better after cross-linking as the coating fixes and becomes more resilient. After cross-linking formulations on PET had less than 20 % of ink removed from the test area during the tape tests compared to between 40 and 80 % removal before cross- linking. Formulations on PP also show improvement in tape test durability after cross-link, however it is to a lesser extent than that of PET.

The adhesion performance in this study may be attributed to two factors; the size of the hydrophobic group and the polymers ability to cross-link.

Increasing the length of the hydrophobic group increase the number of pendent propyl chains incorporated into the polymer. It is proposed that increasing the number of these groups allows for greater contact between the hydrophobic segment and the substrate and therefore more anchoring points.

In order to study the effect that the amount of cross-linker has on adhesion, adhesion tests were performed using three formulations (CF5, CF6 and CF7) containing polymers where by the ratio of the hydrophilic to the hydrophobic segment was kept constant.

CF5 contains P[(HEA76-co-HMAA4)-J -PMA2o], CF6 contains P[(HEA68-co-HMAAi2)-b-PMA2o] and CF7 contains P[(HEA62-co-HMAAi8)-b-PMA2o]. The radar plots for the adhesion study are shown in Table 6. The numbering of the lines begins at zero (0) at the centre point of each plot increasing by two (2) for each radial line to a value of ten (1 0) for the outermost line.

Table 6. Adhesive properties of formulations containing block copolymers, where the ratio of the hydrophobic and hydrophilic block are kept constant but the cross-linker loading is varied.

It was observed that polymer solutions have better performance on PET over PP, this observation correlates with previous adhesion studies with different block copolymer families. Improved adhesion to the substrates was seen as the HMAA loading in the polymer was increased.

Example 4 - Amount of Crosslinker

The effect of the amount of crosslinker was studied using the hydrophilic block alone.

Bulk testing involved placing a sample of the purified dry polymer in an oven at 150 °C. Table 7a shows the results of these tests. Thin film testing involved producing drop cast films of the copolymer (from ethanol/water 50:50) on PTFE substrates. Table 7b shows the results of these tests.

Cross-linking conditions investigated by heating in an oven at 150 °C. Samples were left to dry for 3 hours at room temperature before heating.

Table la. Time taken to cross-link hydrophilic PHEA copolymers containing varying HMAA contents in bulk.

Time HEA-HMAA target D_p

[min]

Table 7b. Time taken to cross-link hydrophilic PHEA copolymers thin films containing with varying PHAA contents

Time HEA-HMAA target D_p

Each different polymer is denoted by two numbers“x-y” with x denoting the amount of 2- hydroxyethyl acrylate and y denoting the amount of /V-hydroxy methyl acrylamide. For example, 79-1 refers to P[(HEA79-CO-HMAA_I)].

“IS” refers to insoluble and indicates that the film is cross linked. “S” refers to soluble and indicates that the film is not cross linked at that time point.

The data shows that increasing the amount of HMAA decreased the required crosslinking time. Thin film samples took longer to crosslink.

The amount of HMAA refers to the amount of HMAA monomer used at the start of the polymerisation based on the total amount of monomers used to produce the hydrophilic block.

Example 5 - Hydrophobic Block and Humectants

This study was designed to look at the effects of the hydrophobic block. In particular to look at the effect of (i) the block length (size) of the hydrophobic polymer; (ii) block copolymer concentration.

This study was also designed to look at the effects of humectants. Humectants are commonly added to ink compositions to minimise solvent evaporation. In this case if an ink dries out in the nozzle, the humectant assists in the formation of a soft crust which upon printing will be less harmful to the printhead and print quality.

Components were dissolved in the appropriate solvent(s) and shaken vigorously before being filtered through a 0.2 pm filter. Viscosity was measured using a ball drop viscometer and printing tests were performed using a Dimatix printer as described above under methods.

Table 8 shows the components of each formulation expressed in weight percent (wt %) of the total formulation. Table 8 shows the components of each formulation expressed in weight percent (wt %) of the total formulation.

Results from Dimatix tests for formulations containing P[(HEA₇₆-co-HMAA₄)-J -PMA₅] and P[(HEA76-co-HMAA4)-J -PMAio] are shown in Tables 9 and 10 respectively.

Table 9 Dimatix results for ink formulations containing block copolymer R[(HEAg₆-oo-

HMAA₄)-b-PMAio].

Table 10. Dimatix results for ink formulations containing block copolymer R[(HEAgb-oo-

HMAA₄)-b-PMA₅]

Block copolymers containing a hydrophobic block of up to 10 repeat units were able to be successfully and reliably jetted in formulations with a glycerol content of at least 12% (w/w). Formulations with less than 12 % glycerol would not jet under these conditions.

Example 6 - Humectants

This study looks at the effect of mixtures of humectants. Various formulations were printed using a Dimatix printer as described above under methods.

Table 11 shows the components of each formulation expressed in weight percent (wt %) of the total formulation. Observations from Dimatix tests are shown with viscosity and surface tension measurements in Table 12.

Table 11. Formulation components looking at the effect of both glycerol and 2-pyrrolidinone used as humectants.

Table 12. Dimatix results for ink formulations containing different containing different concentrations of glycerol and 2-pyrrolidinone as well as viscosity and surface tension measurements.

As the glycerol content by using 2-pyrrolidinone may reduce the drying time. The results above show that glycerol can be reduced by 50 % and still achieve successful jetting. Viscosity measurements of A2 and B2 show that increasing the concentration of polymer in the formulation from 5 % to 10 % increases the solution viscosity by approximately 30 % (3.34 cP to 4.30 cP).

Viscosity increases for formulations containing 12 % glycerol to 4.24 cP compared to 3.34 cP with no glycerol. There is an observed decrease in viscosity as the glycerol concentration is reduces and replaced with 2-pyrrolidinone.

Example 7 - Wetting Agents

Wetting agents are typically added to ink formulation to reduce the contact angle between the pigment and binder solution and as a result, accelerate the penetration speed of the liquid into the agglomerate structure. Various formulations were tested using a Dimatix printer as described above under methods.

Four wetting agents were introduced into the formulation to test the effect on the formulation.

Table 13 shows the components of each formulation expressed in weight percent (wt %) of the total formulation. Viscosity, surface tension measurements and Dimatix printing observations are shown in Table 14. Table 13. Formulation components looking at the use of different wetting agents

Table 14. Dimatix results for ink formulations containing different containing different wetting agents.

Introducing wetting agents both increased the viscosity and decreased the surface tension of this series of formulations compared to the formulation with no wetting agents (E2).

Formulation surface tension dropped approximately 2 - 4 cP with wetting agents present.

All formulations were successfully printed onto PET and PP substrates. Differences in the wetting of the substrates were observed which correlates to the viscosity of the formulation

Wetting from best to worst: BYK-333>BYK-377 > BYK-378 > TEGO WET 500. This trend falls in line with the viscosity measurements. Increased viscosity gave better wetting performance.

Example 8 - Pigments

A black pigment Bon Jet CW-2 was tested for compatibility with the ink compositions of the invention. Various formulations were tested using a Dimatix printer as described above under methods. Table 16 shows the results of these tests.

Formulations were prepared as discussed above in Example 2 and the components of each formulation is provided below in Table 15. Values for each component are wt % based on total weight of the ink composition. Table 15. Formulation components looking at different black pigments and pigment concentration.

Table 16. Dimatix results for ink formulations containing different containing different black pigments and pigment concentrations.

A4 and B4 (formulations without polymer) and E4 and F4 (formulations with polymer) were all able to be successfully filtered and jetted. Bon Jet black was able to be introduced into the formulation up to 2 % by weight. Figure 3 shows photos of A4 and E4 on both PET and PP substrates. Figure 3(a) is E4 on PET, 3(b) is A4 on PP, 3(c) is E4 on PET and 3(d) is A4 on PP.

It can be seen that by introducing the block copolymers into solution enables better wetting with discreet droplet placement compared to the formulations without, which pooled together due to high surface energy of the substrates.

Example 9 - Printing

Ink formulations, were made up using four block copolymers and brilliant blue colourant. For this continuous inkjet printing (Cl J) study, the formulations comprise solvent and colourant with or without block copolymer at 5 wt%. The formulation of the ink compositions studied are disclosed in table 3 in Example 3 and are the ink formulations CF1 to CF4. A

commercial ink, 433BL, was also studied for comparison. 433BL is a commercial ink available from Domino Printing.

The formulations were printed using a CIJ printer onto five different polymer substrates;

PET, PP, HDPE, LDPE and glass and the adhesion measured before and after crosslinking at 150°C for 3 hours. The adhesion was measured using finger rub, nail scratch and tape test.

To ascertain the adhesive properties of the block copolymers in these formulations (CF1 to CF4), a wide range of hydrophobic substrates were employed; PP, PET, HDPE, LDPE and glass.

The results are shown below in Table 17.

Table 17. Adhesion tests after printing polymer formulations and commercial inks onto PP, PET HDPE LDPE and glass and heating at 150°C for 3 hours; A - finger rub, B - nail scratch, C - tape 610, and D - tape 810.

5

The solution properties of the formulation were also studied. P[(HEAio8-co-HMAAi2)-/> PMA₂O (contained in formulation CF1) exhibited similar droplet shapes during printing to the commercial ink formulation (i.e. without block copolymer, 433BL) and gave comparably good quality, clear prints with minimum satellites or splashes. P[(HEA72-co-HMAA8)-b-PMA2o] (in 10 CF2) also gave good clear prints; it is generally accepted that“typical” drop size and shape can be a good indication of print quality and performance, however, non-typical drop shapes can also give good prints as seen with CF2. Formulations containing the highest hydrophobic block length (PMA40, CF3 and CF4) gave the poorest prints in this study, based on visual inspection.

15

Formulations containing polymers followed the same trend as the draw down study with improved adhesive properties after thermal treatment as the polymer becomes a cross- linked network. Jetted formulations also performed better in adhesives tests on PET compared to PP. Adhesion on HDPE and LDPE were similar to that of PET.

20

The poorer adhesion on the higher energy PP, HDPE and LDPE compared to PET may be partially contributed to the wettability. If poor wettability is achieved there will be small discreet areas of cross-linked polymer rather than a large cross-linked matrix. The larger cross-linked films provide stronger adhesion as there is larger surface contact. All block copolymers showed good overall adhesion after cross-linking on glass substrates.

Formulations containing block copolymers showed better adhesive properties on all substrates compared to commercial formulations (433BL) in all cases.

It can be seen that by having ink formulations containing block copolymer resulted in superior adhesive properties in all tests. It is proposed that the pendent propyl methacrylate groups adhere to the substrate and that the polymer becomes a cross linked network resulting in increased water resistance.

Claims

Claims

1. An aqueous ink composition comprising a block copolymer having a hydrophilic block and a hydrophobic block wherein the hydrophilic block has triggerable cross linking groups.

2. The aqueous ink composition of claim 1 wherein the hydrophilic block is a copolymer represented as:

(A¹ni-CO-A²n₂) wherein A¹ and A² are monomer units and“n1” and“n2” are integers from 1 to 200.

3. The aqueous ink composition of claim 2 wherein the monomers A¹ and A² are independently selected from alkenyl, alkynyl, acrylate, methacrylate, maleate, fumarate, an acrylamide functional group or a mixture thereof.

4. The aqueous ink composition claim 3 wherein A¹ is 2-hydroxyethyl acrylate and A² is hydroxy methyl acrylamide.

5. The aqueous ink composition of any one of the previous claims wherein the triggerable cross linking groups may be selected from alkenyl, alkynyl, acrylate,

methacrylate, maleate, fumarate, an acrylamide, a hydroxylalkylamide functional group or a mixture thereof.

6. The aqueous ink composition of claim 5 wherein the triggerable cross linking groups are hydroxyl alkylamide functional groups.

7. The aqueous ink composition of any one of the previous claims wherein the amount of triggerable cross linking groups in the hydrophilic block in less than 20 mol %.

8. The aqueous ink composition of any one of the previous claims wherein the hydrophilic block has a weight-average molecular weight (M_w) greater than 8,000 to less than 40,000.

9. The aqueous ink composition of any one of the previous claims wherein the hydrophobic block is a homopolymer represented as:

(Bm) wherein B represents the monomer forming the hydrophobic block and“m” is an integer from 10 to 100.

10. The aqueous ink composition of claim 9 wherein the monomers, B, forming the hydrophobic block are selected from alkenes, alkynes, acrylates, methacrylates, maleates, fumarates, acrylamides or a mixture thereof.

1 1. The aqueous ink composition of claim 10 wherein B is propyl methacrylate.

12. The aqueous ink composition of any one of the previous claims wherein the hydrophobic block has a weight-average molecular weight (M_w) greater than 8,000 to less than 40,000.

13. The aqueous ink composition of claim 1 wherein the block copolymer is selected from poly[(2-hydroxyethyl acrylate-co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate]

14. The aqueous ink composition of claim 13 wherein the poly[(2-hydroxyethyl acrylate- co-/\/-hydroxymethyl acrylamide)-Jb-propyl methacrylate] is selected from

P[(H EA36-CO- H M AA₄)-J - PM A₅] ; R[(HEA₃₆-oo-HMAA₄)-ώ-RMA₁₀]; P[(HEA₇₂-co- HMAA₈)-Jb-PMA₅]; P[(HEA7₂-co-HMAA₈)-b-PMA₁₀]; P[(HEA7₂-co-HMAA₈)-b-PMA₂o];

P[(H EA72-CO- H M AA₈)-Jb- PM A40] ; P[(HEA_{1 0}8-co-HMAA_{1 2})-J -PMA₅]; P[(HEA_{1 08}-co-HMAA_{1 2})-J - PMA10]; P[(HEA_{1 0}8-co-HMAA_{1 2})-J -PMA₂o]; P[(HEA_{1 0}8-co-HMAA_{1 2})-J -PMA₄o]; P[(HEA₇₆-co- H M AA₄)-Jb- P M A20] ; P[(HEA68-co-HMAA_{1 2})-J -PMA₂o]; P[(HEA₆₂-co-HMAA_{1 8})-Jb-PMA₂o];

P[(H EA₇₆-CO- H M AA₄)-Jb- PM A₅] ; P[(HEA₇₆-co-HMAA₄)-Jb-PMA₁₀]; or P[(HEA₃₆-co-HMAA₄)-b- PMA10].

15. The aqueous ink composition of any one of the previous claims wherein water is present in greater than 30 wt % and less than 95 wt%, preferably less than 50 wt%.

16. The aqueous ink composition of any one of the previous claims wherein an additional solvent is present.

17. The aqueous ink composition of claim 16 wherein the additional solvent is a C1 -6 alkyl alcohol, such as ethanol.

18. An ink container containing the aqueous ink composition as defined in any one of claim 1 to 17.

19. A printing method comprising the steps of providing an ink container containing the aqueous ink composition as defined in any one of claims 1 to 17; the method comprising the steps of directing a stream of droplets of the aqueous ink composition to a substrate and curing the printed ink composition.

20. A substrate comprising a printed deposit produced by the method defined in claim 19.

21. A printed deposit comprising a cured polymer film formed by curing the aqueous ink composition of anyone of claim 1 to 17.