Primer formulation for thermoplastic material

Abstract

A primer composition for surface treatment of a polymeric substrate, comprising at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles, and water.

Description

PRIMER FORMULATION FOR THERMOPLASTIC MATERIALTECHNICAL FIELD

[0001] The present invention relates to a primer composition designed to enhance the surface properties and the printability of polymeric substrates, such as thermoplastic substrates, including, but not limited to, polymeric -based decorative coverings, tarpaulin or other shaped articles when using aqueous inks in both digital and conventional printing processes. BACKGROUND

[0002] Polymeric materials, more specifically thermoplastic materials, such as polyvinyl chloride (PVC), polyolefins (PC), and polyesters (PES) are a popular material used in various applications, including decorative coverings and functional products, prized for their durability, flexibility, and resistance to environmental factors. These decorative coverings / materials and functional products are often produced through advanced printing techniques, such as digital inkjet printing, as well as conventional methods like gravure and screen printing. Digital inkjet printing is a recording method in which liquid droplets of an inkjet ink that have been discharged from an inkjet print head are jetted directly onto a recording medium to form text or images.

[0003] However, achieving high-quality prints on thermoplastic materials can be challenging, as the print quality largely depends on how effectively the printing medium, i.e. ink, wets the substrate. Thermoplastic materials (substrates) typically have low surface energy and a hydrophobic nature, which makes them resistant to ink adhesion and uniform wetting, often requiring specialized surface treatments or primers to improve printing performance.

[0004] In recent years, advancements have enabled thermoplastic materials to be printed with two main types of printing mediums (inks): UV-curable inks and aqueous inks use a carrier system of water and humectants, which mostly evaporate during the printing process, leaving only about 9% of the ink's content on the substrate. This contrasts with the UV-curable inks, where the entire carrier system, composed of monomers, are fully polymerized during UV curing and remain therefore fully on the substrate after production. While UV-curable inks are preferred for printing on thermoplastic materials / substrates due to their fast curing and durability, they come with significant drawbacks. These include higher ink costs, reduced sustainability, and challenges in recyclability. UV inks often contain complex additives, such as photosensitizers, which can harm the environment. Photosensitizers alter light wavelengths to decompose binders in primers or inks, enabling features like easier removal of wear-resistant layers but potentially limiting recyclability. Therefore, the aqueous inks are favoured for their lower environmental impact, such as their minimal release of volatile organic compounds (VOCs) and reducedreliance on harmful chemicals. Additionally, their simpler composition and lower residue on substrates contribute to easier recyclability, aligning with sustainability goals in printing processes.

[0005] However, printing with aqueous inks on thermoplastics presents challenges such as blocking, bleeding, adhesion issues, and lamination difficulties, due to the ink formulation, the type of surface treatment, and the inherent properties of the thermoplastic substrate. Blocking occurs when printed substrates stick together under pressure, heat, or humidity, particularly if the ink or primer layer remains tacky or inadequately dried. Bleeding, on the other hand, refers to the undesirable spread of ink beyond its intended boundaries, resulting in blurry or distorted designs due to lack of ink absorption by the polymeric substrate. This results in poor edge definition and reduced print clarity, ultimately compromising the quality of the final print. Further, this issue is especially common when printing with aqueous inks, as the hydrophobic nature of thermoplastics and their smooth surface impede controlled ink absorption.

[0006] This necessitates innovative solutions to improve the interaction between the aqueous ink and the polymeric substrate, especially with low surface energy such as thermoplastic substrates.

[0007] Additionally, the extended drying time of aqueous inks complicates production, particularly when laminating a wear-resistant layer to thermoplastic substrates, as incomplete drying can compromise adhesion and result in peeling or delamination.

[0008] Therefore, there is a need to address these challenges. Effective solutions must simultaneously address lamination compatibility, in k bleeding, and blocking to ensure high- quality, durable prints on thermoplastic materials.SUMMARY OF INVENTION

[0009] The present invention aims to address problems outlined above by providing a specially formulated primer compositions for surface treatment of polymeric substrates with relatively low surface energy, such as thermoplastic substrates. A surface treatment is a preparatory step that modifies the surface properties of a material, such as a polymeric substrate, to enhance its compatibility with subsequent processes. The surface treatment may include the application of primer compositions for improved printing, coating, or bonding. This primer composition enhances the surface properties of thermoplastic substrates, improving ink adhesion, especially for aqueous ink formulations, by promoting uniform wetting, minimizing delamination, and reducing blocking and bleeding, thereby ensuring high-quality, durable prints on challenging thermoplastic materials. The present invention also concerns a primer composition formulatedto improve the print quality of inkjet-printable polymeric substrates. Preferably, the primer may reduce blocking, minimize ink bleed, promote uniform ink spread without the formation of print stripes, maintain a suitable viscosity profile, and exhibits little to no foaming during application and results in good lamination properties.

[0010] Aspects and embodiments of the invention provide a primer composition for surface treatment a polymeric substrate, a primer layer, a shaped article, a method for the preparation of the shaped article, and method of forming an image on an inkjet-printable polymeric substrates. According to an aspect of the present invention there is provided a primer composition for surface treatment of a polymeric substrate, comprising: at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles; and water.

[0011] The primer composition of the present invention is preferably suitable for application to a polymeric substrate surface prior to ink deposition in a digital printing process, and is thus an ink-receiving primer composition. The polymeric substrate can be an inkjet printable polymeric substrate. When aqueous inks are digitally printed onto polymeric substrates, such as PVC, a compatibility problem arises, as being generally non-porous and hydrophobic, As a result, ink droplets can flow across the surface after impact, causing blurred edges, colour mixing, and overall poor image quality. To overcome this issue, the primer composition of the present invention is applied to the plastic substrate before printing. The primer acts as an intermediate layer that is compatible with both the plastic substrate and the aqueous ink. Its function is to rapidly immobilize the ink droplets as soon as they land on the surface, preventing uncontrolled spreading. Specifically the primer composition comprises specifically selected binders and fillers, that fixate ink droplets by rapid capillary absorption of the carrier liquid, adsorption or anchoring of pigment or dye onto the filler surface, and immobilization within a porous primer layer network, thereby preventing ink spreading and coalescence and producing sharp, stable dots.

[0012] Preferably, there is provided a primer composition for surface treatment of a polymeric substrate for digital inkjet printing, comprising: at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles, and water.

[0013] Although the primer composition of the present invention is specifically formulated for digital printing applications, it is also compatible with conventional printing methods, such as offset printing, screen printing, gravure printing, and flexographic printing and is intended for treating the surface of thermoplastic materials or substrates.

[0014] In an embodiment, the polymeric binder is selected from one or more acrylic polymers or co-polymers. The polymeric binder can be a self-crosslinking acrylic polymer or acrylic copolymer. Further, the acrylic binder can be an acrylic self-crosslinking dispersion comprising a self-crosslinking acrylic polymer or a self-crosslinking acrylic polymer.

[0015] In an embodiment, the polymeric substrate can be a thermoplastic substrate or a thermoplastic surface. The polymeric substrate can be a thermoplastic substrate selected from the group consisting of polyvinyl chloride (PVC), polyolefin, polyester, polystyrene or polyamide.

[0016] The two distinct types of inorganic fillers are defined as a first inorganic filler and second inorganic filler. In an embodiment, the first inorganic filler comprises calcium carbonate particles. In a further embodiment, the second inorganic filler is selected from the group consisting of aluminium hydroxide oxide particles, or from inorganic particles comprising a blend of silica and kaolinite particles.

[0017] In an embodiment, the second inorganic filler of the primer composition described above is selected from aluminium hydroxide oxide particles, or from inorganic particles comprising a blend of silica and kaolinite particles, or a composite material comprising silica and kaolinite particles, wherein the silica particles are deposited on kaolinite particles, or kaolinite particles are deposited on silica particles.

[0018] In an embodiment, the blend of silica and kaolinite particles have a particle size distribution with a median diameter (D50) ranging from 0.5 pm to 10 pm, preferably from 0.5 pm to 5 pm, as determined by dynamic light scattering (DLS).

[0019] In an embodiment, the weight ratio between the first and second inorganic particles is in the range from 1 :1 to 30:1 , preferably from 1 .5:1 to 20:1 , more preferably from 1 .5:1 to 15:1 , or 3:1 to 15:1

[0020] In an embodiment, the primer composition comprises of from 5 % to 40 % by weight of first inorganic filler relative to the total weight of the primer composition, wherein the first inorganic filler is selected form calcium carbonate particles.

[0021] In an embodiment, the primer composition comprises of from 2 % to 15 % by weight of second inorganic filler relative to the total weight of the primer composition, wherein the second inorganic filler is selected form the group consisting of a blend of silica and kaolinite, or aluminium hydroxide oxide particles.

[0022] In an embodiment, the primer composition comprises of from 10 % to 80 % by weight of at least one polymeric binder relative to the total weight of the primer composition.

[0023] In some embodiments, the polymeric binder is selected from one or more acrylic polymers or acrylic co-polymers, or a blend of acrylic polymers or co-polymers with polyurethane. In some embodiments, the polymeric binder comprises a blend of polymeric binders,

[0024] In some embodiments, the polymeric binder comprises an acrylic self-crosslinking dispersion comprising a self-crosslinking acrylic polymer or co-polymer, or a blend of acrylic selfcrosslinking dispersion comprising a self-crosslinking acrylic polymer or co-polymers and polyurethane.

[0025] In some embodiments, the primer compositions of the present invention comprise a blend or mixture of a modified acrylic copolymer dispersion and polyurethane dispersion, Preferably the ratio between the acrylic copolymer and the polyurethane in the mixture is 1 :5 to 5:1 , preferably 2 :1 to 1 :2, more preferably 1 .5:1 to 1 :1 .5, even more preferably 1 .3:1 to 1 :1 .3, or 1.2:1 to 1 .2:1 , or 1 :1 .

[0026] In some embodiments, the primer composition comprises a blend or a mixture of polymeric binders comprising acrylic self-crosslinking dispersion comprising a self-crosslinking acrylic polymer or co-polymers and polyurethane, and wherein the ratio of the acrylic selfcrosslinking dispersion to polyurethane in the mixture is 1 :5 to 5:1 , preferably 2 :1 to 1 :2, more preferably 1 .5:1 to 1 :1 .5, even more preferably 1 .3:1 to 1 :1.3, or 1 .2:1 to 1 .2:1 , or 1 ;1.

[0027] In an embodiment, the calcium carbonate particles have a particle size distribution with a median diameter (D50) ranging from 0.15 pm to 15 pm, more preferably 0. 2 pm to 10 pm, even more preferably 0.2 pm to 0.5 pm .

[0028] Advantageously, the at least two inorganic fillers of the present primer composition may comprise two or more distinct types of inorganic particles selected from of silica, clay, calcium bicarbonate, aluminium oxyhydroxide, and micro chalk (calcium carbonate), alumina, or a blend of silica and kaolinite.

[0029] In an embodiment, the primer composition of the present invention has a surface tension in the range of from 20 mN / m to 80 mN / m at 20°C, as determined by ASTM D1331 -20

[0030] In some embodiments, the primer composition of the present invention has a viscosity in the range of 60 cP to 400 cP at 25°C, as measured according to ASTM D7042.

[0031] In some embodiment, the primer composition has a viscosity in the range of 60 cP (mPa-s) to 500 cP (mPa-s) at 25 °C, measured at a shear rate corresponding to 400 rpm at 25°C, as determined by ASTM D2196.

[0032] In some embodiments, the primer composition has a viscosity in the range of 60 cP (mPa-s) to 500 cP (mPa-s) at 25 °C, measured at a shear rate corresponding to 400 rpm using a rotational (Brookfield-type) viscometer. Preferably, the viscosity is in the range between 60 cP to 400 cP, more preferably 60 cP to 400 cP, and even more preferably 70 cP to 300 cP at 25 °C, as determined in accordance with ASTM D2196.

[0033] In an embodiment, the primer composition forms a surface with a surface energy of at least 30 mJ / m2upon curing, preferably with a surface energy in the range between 30 mJ / m2and 80 mJ / m2upon curing, preferably between 30 mJ / m2and 60 mJ / m2. Preferably, upon curing or drying, the primer composition is configured to form a primer layer having a surface with a surface energy of at least 30 mJ / m2upon curing, preferably with a surface energy in the range between 30 mJ / m2and 80 mJ / m2. Further, the so formed primer layer is an ink-receptive primer layer configured to receive aqueous ink composition.

[0034] The primer composition described above may further comprise one or more additives selected from poly(diallyldimethylammonium chloride) (poly(DADMAC)), polycarbodiimide (PCDI), alkyltrialkoxysilane, polyvinyl alcohol (20 % aqueous PVOH solution), additional CaCO3with a median diameter (D50) ranging from 0.15 pm to 15 pm, or any combination thereof.

[0035] In some embodiments, the primer composition of the present invention further comprises at least one addictive selected from polyvinyl alcohol (e.g 20 % PVOH solution) , and / or poly(diallyldimethylammonium chloride) (poly(DADMAC)).

[0036] In some embodiments, the primer composition of the present invention further comprises at least one additive selected from 5 wt % to 40 wt % of polyvinyl alcohol (e.g 20 % PVOH solution). In some embodiments, the primer composition described above may further optionally comprise a poly(diallyldimethylammonium chloride) (poly(DADMAC)) additive in an amount of 0.5 wt% to 5 wt% based on active poly(DADMAC), or an equivalent amount of 2.5 wt% to 25 wt% of a 20 wt% aqueous poly(DADMAC) solution, based on the total weight of the primer composition.

[0037] In some embodiments, the primer composition described above may further optionally comprise additives selected from 0.5-5 % of a poly(diallyldimethylammonium chloride) (poly(DADMAC)) or 2.5 wt% to 25 wt % in 20 % poly(DADMAC solution), 2-10% of a polycarbodiimide (PCDI), 0.5-5 % of an alkyltrialkoxysilane, 5 wt % to 40 wt % of polyvinyl alcohol when in 20 % aqueous PVOH solution, and / or additional 5-10 % extra CaCO3with a median diameter (D50) ranging from 0.15 pm to 15 pm, or any combination thereof.

[0038] In an embodiment, the primer composition has a thickness ranging of from 1 pm to 50 pm when applied wet to the thermoplastic substrate / surface.

[0039] In an embodiment, there is provided a primer layer for polymeric substrate comprising a primer composition including at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles; and water, wherein the primer layer has a surface energy of at least 30 mJ / m2, or at least 35 mJ / m2.

[0040] In an embodiment, the primer layer has a peel strength of at least 20 N / 50 mm, preferably 30 N / 50 mm, as determined in accordance with ASTM D903.

[0041] Further the present invention also provides a set of a primer composition and an aqueous ink composition compatible with the primer composition of the present invention for digital printing.

[0042] According to another aspect of the present invention there is provided an ink and primer system for image formation on a thermoplastic substrate surface comprising: a. the primer composition, the primer composition for surface treatment of a polymeric substrate prior to applying an aqueous ink composition, the primer comprising at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles; and water, and b. an aqueous ink composition comprising water and at least two different water-soluble organic solvents, wherein the at least two different water-soluble organic solvent are selected from a group consisting of alkyl diols, and wherein each water-soluble organic solvent has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C, as determined by ASTM D1331 -20.

[0043] The ink and the primer system for image formation can be preferably applied by means of digital inkjet printing.

[0044] According to a further aspect of the present invention, there is provided a shaped article comprising: a polymeric substrate, and a primer layer formed thereon. This primer layer is formed from a primer composition according to the present invention that at least partially covers the polymeric substrate, and forms the primer layer upon drying. The primer layer is preferably a micro-porous ink-receptive primer layer configured to receive aqueous inkjet droplets.

[0045] In an embodiment, the shaped article further comprises a decorative layer applied on top of the primer layer, wherein the decorative layer comprises the aqueous ink composition according to the present invention. Optionally, the shape article may further comprise a wearresistant layer applied on top of the decorative layer.

[0046] In an embodiment, the primer layer of the shaped article has a peel strength of at least 20 N / 50 mm, and a surface energy of at least 30 mJ / m2. Further, in an embodiment, the primer layer has a thickness in the range of 1 pm to 20 pm, preferably in the range of 4 pm to 10 pm .

[0047] In an embodiment, there is provided a shaped article comprising: a polymeric substrate, a primer layer applied onto the polymeric substrate, wherein the primer layer comprises the primer composition having at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles; and water, a decorative layer applied on top of the primer layer, wherein the decorative layer comprises the aqueous ink composition, wherein the aqueous ink composition comprises water and at least two different water-soluble organic solvents, wherein the at least two different water-soluble organic solvent are selected from a group consisting of alkyl diols, and wherein each water- soluble organic solvent has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C, preferably of from 15 to 75 mN / m at 20°C, more preferably 20 to 75 mN / m at 20°C (as determined by ASTM D1331 -20).

[0048] According to a further aspect of the present invention, there is provided a method for the preparation of the shaped article as described above, the method comprising providing a polymeric substrate, applying an ink and primer system (described above) by first applying the primer composition of the present invention , then printing, preferably by digital printing, a decorative layer on the primed polymeric substrate with the aqueous ink composition, drying the aqueous ink composition to form a printed polymeric substrate TERMS AND DEFINITIONS

[0049] The terms “digital inkjet printing" and “digital printing” are used herein interchangeably.

[0050] The term “surface energy” refers to a measure of the cohesive and adhesive forces at the surface of a solid material. In the context of the present invention, the surface energy of the cured primer layer refers to the surface free energy of the solid film, as determined by measuring the advancing contact angle of standard test liquids in accordance with ASTM D7334.

[0051] The term "D50" refers to a specific point in the particle size distribution of a material, representing the median particle diameter.

[0052] The term "printing substrate" refers to a material surface onto which images or text are printed, such as paper, fabric, plastic, or metal.

[0053] The term "aqueous" denotes a composition that is water-based, indicating that water serves as the primary solvent or medium.

[0054] The term “surface tension” refers to a measure of the cohesive forces within the liquid that cause it to minimize its surface area. In the context of the present invention, the primer or ink composition may exhibit a defined surface tension, which is measured in accordance with both ASTM D1331 or specifically ASTM D1331 -20.

[0055] The term “thermoplastic substrate” refers to a substrate made of a thermoplastic polymer, such as PVC, polyolefin or polyester.

[0056] The terms “polymeric substrate” and “polymeric substrate surface” are used herein interchangeably.

[0057] The term “primer" refers to a coating applied to the surface of a substrate before printing to enhance ink adhesion, durability, and print quality The terms “primer” and “primer composition”, " and “primer coating “are used herein interchangeably.

[0058] The term “dispersion” refers to a system in which particles (solids) of one substance are distributed throughout another substance, typically forming a homogeneous mixture or solution. For example, the solid(s) in a dispersion of the present invention can be within the range of from 25 wt % to 80 wt %, preferably of from 25 wt % to 50 wt %.

[0059] The term "aqueous" denotes a composition that is aqueous, indicating that water serves as the primary solvent or medium.

[0060] The term "C3to C8" refers to the length of the carbon chain, indicating that these diols contain anywhere from 3 to 8 carbon atoms.

[0061] The wet weight percentage, also described as wet-wt percent, is expressed as the wet weight of the respective component over the total wet weight of the primer composition.

[0062] The term “ASTM” stand for American Society for Testing and Materials.

[0063] The term “aqueous ink(s)" and "aqueous ink composition(s)” are used herein interchangeably.

[0064] The term "alkyl diol" or “alkane diol” refers to a class of organic compounds that contain two hydroxyl groups attached to an alkyl chain, which can vary in length and structure. As used herein, the terms “alkyl diol,” “alkane diol,” and “alkanediol” are interchangeable and refer to any linear or branched hydrocarbon diol of the general formula HO-(CH2)n-OH, in which “n”is an integer from 2 to 10.

[0065] The term micro chalk refers to calcium carbonate particles having a median diameter D50in the range of 0.001 pm to 15 pm, as determined by dynamic light scattering (DLS).

[0066] For reference, 1 cP is equal to 1 mPa-s (millipascal-second), and the two units may be used interchangeably.

[0067] As used herein, the term “ ink-receptive primer layer” is a layer formed from a primer composition that, upon curing or drying, provides a surface capable of accepting and retaining ink, such as aqueous ink composition, in a digital inkjet process and system.

[0068] The term “non-porous substrate” herein refers to a material surface that does not allow liquids or gases, like water and air, to pass through it. Although, PVC (polyvinyl chloride) is generally considered non-porous, like any polymer, can allow very small amounts of gases or liquids to diffuse through its structure, although this permeation is typically minimal and slow.

[0069] Throughout this disclosure, all parts and percentages are by weight (wt% or mass% based on the total weight) and all temperatures are in °C unless otherwise indicated.

[0070] Brief Description of the Drawings

[0071] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0072] FIG. 1 illustrates blocking results (Y-axis)of the test with different binder and inorganic fillers. 1 - acrylic self-cross linking dispersion, 2- polyurethane binder (Baybond PU 404), 3- polyurethane binder (Daotan VTW6421 ), 4-boehmite (aluminium oxide hydroxide (y-AlO(OH)) ), 5- no filler, 6- blend of silica and (lamellar) kaolinite particles; In FIG. 1 , the term "second filler" refers specifically to the second inorganic filler. It further, X-axis shows at the result at 0 , 5 and 30 wt %.

[0073] FIG. 2 illustrates an interaction plot for blocking results (Y-axis). 1 - acrylic self-cross linking dispersion, 2- polyurethane binder (Baybond PU 404), 3-polyurethane binder (Daotan VTW6421 ), 4-boehmite (aluminium oxide hydroxide (y-AlO(OH)) ), 5-no filler, 6- blend of silica and kaolinite particles. In FIG. 2, the term "second filler" refers specifically to the second inorganic filler.

[0074] FIG. 3 shows delamination results (Y-axis) of the test with different binders and inorganic fillers. 1 - acrylic self-cross linking dispersion, 2- polyurethane binder (Baybond PU 404), 3- polyurethane binder (Daotan VTW6421 ), 4-boehmite (aluminium oxide hydroxide, y-AlO(OH)), 5- no filler, 6- blend of silica and kaolinite particles (silitin Z89); In FIG. 3, the term "second filler" refers specifically to the second inorganic filler.

[0075] FIG. 4 illustrates an interaction plot for delamination results. 1 - acrylic self-cross linking dispersion, 2- polyurethane binder (Baybond PU 404), 3-polyurethane binder (Daotan VTW6421 ), 4-boehmite (aluminium oxide hydroxide, y-AlO(OH)), 5- no filler, 6- blend of silica and kaolinite particles; In FIG. 4, the term "second filler" refers specifically to the second inorganic filler.

[0076] FIG. 5 illustrates an interaction plot for blocking performance (rated 10=good, 0=bad). The comparison covers three binder systems — an acrylic polymer (e.g. Neocryl 1 131 A, Baybond PU 404® polyurethane resin, and Daotan® VTW6421 . The acrylic binder delivers the best blocking resistance, achieving the highest scores across the evaluated conditions.

[0077] Figure 6A illustrates the print quality obtained in digital inkjet printing with the primer composition comprising a single polyacrylate primer, and printed with a 4 Color (CMYK) inkjet printer.

[0078] Fig. 6B illustrates the print quality achieved using the primer composition digital inkjet printing of the present invention comprising two polymeric binders in ratio 80:20.

[0079]

[0080] Fig. 6C illustrates the print quality (showing no bleeding) achieved with primer composition on a polymeric substrate comprising two polymeric binders in ratio 50:50, using digital inkjet printing.

[0081] Figs. 7A, 7B, 7C show microscopic images of the coated / primed PVC substrates in accordance with the present invention.

[0082] FIG. 8A illustrates an image showing print quality obtained using a primer composition without (i) poly(vinyl alcohol) and without (ii) poly(diallyldimethylammonium chloride).

[0083] FIG. 8B illustrates an image showing print quality obtained using a primer composition including poly(diallyldimethylammonium chloride).

[0084] FIG. 8C is an image showing print quality obtained using a primer composition including poly(vinyl alcohol).

[0085] Figs. 9A and 9B also show image print quality from primer compositions including both (i) poly(vinyl alcohol) and (ii) poly(diallyldimethylammonium chloride).DETAILED DESCRIPTION

[0086] The present invention relates to a primer composition comprising at least one polymeric binder, two distinct types of inorganic fillers, and water. The primer composition is preferably for use in preparing a polymeric substrate for digital inkjet printing, Preferably, the primer composition is an ink -receiving primer composition for digital inkjet printing. Upon curing or drying, the primer composition preferably forms a primer layer configured to receive aqueous inkjet droplets, wherein the primer layer is preferably micro-porous and ink-receptive. Preferably, the primer layer exhibits a surface energy of at least 30 mJ / m2, thereby compensating for the inherently low surface energy of the underlying polymeric substrate and enabling sufficient wettability and adhesion for water-based inkjet-printed ink compositions in digital inkjet printing.

[0087] Although the primer composition is preferably for digital inkjet printing, it may also be suitable for other printing or surface-treatment applications, or in intermediate products associated with inkjet printing.

[0088] The primer composition is formulated for application on polymeric substrates, particularly thermoplastic substrates, and aimsto improve theprintability or print quality , adhesion, and durability, particularly when using aqueous inks in printing processes. This primer composition addresses key challenges in digital printing on thermoplastic substrates: improving lamination between substrate, ink, and wear-resistant layers, preventing blocking of the primer and ink layers, especially water-based ink layers, reducing ink bleeding, and blocking additive migration.

[0089] The primer composition of the present invention achieves these benefits through a carefully selected polymeric binder that is optimized to resolve blocking and bleeding issues. The polymeric binder can be preferably an acrylic polymeric binder that can adhere to the hydrophobic, impervious surface of thermoplastic materials and modify their surface characteristics to improve compatibility with aqueous inks. During application, the acrylic binder may form a film that provides a controlled surface texture. This texture can contribute to the formation of a micro-porous layer that can retain water temporarily, allowing the aqueous ink composition to spread and adhere properly before drying.

[0090] However, the cohesive strength (internal binding forces within the polymer film) and filmforming ability of the acrylic polymeric binders generally lower than those of polyurethane binders may not be sufficient to provide the durability needed for strong lamination, for example during and after the production of products, such as decorative coverings.

[0091] To further enhance the performance of the primer composition, blends of polymeric binders, such as a combination of acrylic polymeric binders with polyurethane, can be used. The addition of polyurethane can improve cohesive strength and mechanical stability, addressing the limitations of acrylic binders alone while maintaining sufficient flexibility. The polyurethane binder exhibits very good film-forming properties but increases blocking, whereas the polyacrylic binder reduces blocking but has inferior film-forming properties.

[0092] Moreover, such blends may lower the film-forming temperature of the binder system, enabling curing at lower temperatures and enhancing the compatibility with various substrates. This combination ensures strong adhesion, resistance to blocking, and improved lamination performance, particularly for demanding applications

[0093] Therefore, to ensure optimal lamination strength, the primer composition also incorporates inorganic fillers in precise quantities and ratios. Further, these inorganic fillers when dispersed in the acrylic polymer serving as a binder, may introduce micro-pores into the primer layer. The inorganic filler-to-polymeric binder ratio can also be critical to achieving the desired balance between adhesion, flexibility, and lamination strength. Too much inorganic filler(s) can make the primer layer brittle, while too little may compromise its effectiveness in creating a micro-porous layer. Also, the selection of specific types of inorganic fillers can also influence the primer's overall performance, including its adhesion, flexibility, and porosity.

[0094] Substrate: The substrate to be treated with the primer composition of the present invention is polymeric substrate preferably with relatively low surface energy (30-50 mN / m), such as thermoplastic substrate. The thermoplastic substrate may include polyolefins like polypropylene (PP) and polyethylene (PE), polyesters like polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Also, materials like polyamide (PA), polycarbonate (PC), fluoropolymers, and polystyrene (PS), can benefit from the primer composition to improve printability. These materials are inherently non-porous, non-absorbent (essentially water impermeable).

[0095] The primer composition can also be applied to laminate substrates, which are composed of multiple layers of different material. Also, other substrates that exhibit a thermoplastic-like surface can also be used, for example for example coated canvas and coated woven or non-woven fabrics, coated substrates, such as paper or cardboard coated or laminated with polymeric layers. These materials are widely utilized in packaging, signage, decorative coverings, and various decorative or shaped articles. The primer composition enables effective adhesion of aqueous ink compositions to these typically hydrophobic surfaces, overcoming challenges such as poor aqueous ink absorption and adhesion, by modifying the surface properties of the polymeric (thermoplastic) substrate.

[0096] The polymeric substrate might be part of various products, including floor coverings, wall coverings, ceiling coverings, or alternative surface coverings, tarpaulins, and print films.

[0097] Preferably, the primer composition of the present invention is suitable for application to a polymeric substrate surface prior to ink deposition in a digital printing process.

[0098] The primer composition of the present invention can be particularly suitable for thermoplastic surfaces such as polyvinyl chloride (PVC), but it is not limited to this application only, as previously described. Preferably, the primer composition is an ink -receiving primer composition for digital inkjet printing.

[0099] The polymeric substrate may be in form of a thermoplastic foil, film, print film, decor films; or foam layer, foamable substrate, polymer film laminates, such as flexible packaging laminates. In an embodiment, the polymeric substrate is a thermoplastic substrate selected form the groups consisting of polyolefins, such as polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polyesters, such as polyethylene terephthalate (PET), polyamide (PA) and polystyrene (PS).

[0100] In an embodiment, the polymeric substrate to be treated with the primer composition in a digital inkjet printing of the present invention is polyvinyl chloride. In a preferred embodiment, the polymeric substrate comprises polyvinyl chloride (PVC). PVC is a popular material for decorative coverings, in particular a floor covering, ceiling covering, wall covering, or alternative surface covering, tarpaulin, due to its durability, flexibility, and resistance to environmental factors. However, its non-porous and non-absorbent nature makes it a challenging substrate for aqueous inks. The non-porous and non-absorbent (essentially water impermeable) polymeric surface of the PVC does not readily absorb liquids, leading to challenges in the adherence and effective drying of aqueous inks. The relatively low surface energy of PVC, compared to other materials, further impacts its adhesion properties. To address these challenges, the primer composition of the present invention is applied to the PVC surface before the decorative layer is formed.

[0101] Polymeric Binder: In primer compositions, the binder plays a crucial role in determining the primer's performance characteristics, including adhesion, durability, print quality and compatibility with substrates and topcoats. The binder is essentially the film-forming component of the primer, responsible for holding the pigment particles together and providing adhesion to the surface being coated.

[0102] The binder is a resin or polymer that serves as the primary component in the primer composition of the present invention. It facilitates both substrate adhesion and ink absorption for jetted ink applications. Typically, polyurethane resins and / or acrylic resins can be employed either alone or in combination for these purposes. Suitable compatible binders for the primer composition may include non-ionic water-insoluble polymers in colloidal particle form, such as acrylic latexes, acrylic copolymer, acrylic self-crosslinking dispersions, polyurethane, a blend of acrylic polymers / co-polymers with polyurethane, vinyl acetate copolymer latexes, polyester, or polyamide.

[0103] The primer composition of the present invention may incorporate a blend of polyacrylate (PA) and polyurethane (PLI) as the polymer binder

[0104] As already mentioned, while the polyurethane binder provides excellent film-forming properties, it undesirably increases the blocking tendency of the coating. In contrast, the polyacrylic binder effectively reduces blocking, but its film-forming capability is comparatively poor.

[0105] Further, this blend can reduce the overall film-forming temperature of the binder blend, enabling the primer layer to cure at lower temperatures. Without being bound by any theories, a lower curing temperature allows for the formation of the primer film under milder conditions, which can significantly enhance print quality by minimizing thermal stress on the substrate. Further, despite the reduction in curing temperature, the combination of polyacrylate and polyurethane ensures sufficient blocking potential, i. e., meaning it prevents sticking to other surfaces, due to the presence of sufficient hard resin (polyacrylate) in the formulation. This ensures the primer retains its structural integrity and resistance to unwanted adhesion or transfer during processing and use. The synergistic use of polyacrylate (PA) and polyurethane (PU) binders may result in improved print quality, processability, adhesion strength, and functional durability.

[0106] In some embodiments, the modified acrylic copolymer dispersion and the polyurethane dispersion are preferably premixed to form a polymer mixture. The relative amounts of the two dispersions are expressed as a weight ratio based on the weights of the individual dispersions within this mixture. Preferably, the modified acrylic copolymer dispersion and the polyurethane dispersion can be for example in a weight ratio of 65:35, and more preferably in a substantially 1 :1 weight ratio (50:50). The resulting polymer mixture is then incorporated into the overall primer composition in the desired amount.

[0107] Furter, effective performance of the acrylic-polyurethane blend is obtained only within certain ratios of the two binders, outside of which the desirable balance of surface texture, blocking resistance, and film integrity is not achieved. For example, the ratio between the polyacrylic binder (PA) and the polyurethane binder (PU) can be in the range of 1 :2 to 2:1 , 1 : 1.5 to 1 .5: 1 , or 1 .3 :1 to 1 :1.3, more preferably 1 .1 : 1 to 1 : 1 .1 , or even more preferably about 1 : 1 . For example, a PA:PU ratio of 4:1 (equivalent to 80:20) does not achieve the required balance of properties and therefore fails to provide acceptable print quality. Additionally, certain solvents can be incorporated into the primer composition to accelerate film formation, providing an alternative to blending polyurethane with polyacrylate. These solvents can lower the film-forming temperature of the binder, accelerating film formation, especially in low-temperature environments.

[0108] In an embodiment, the polymeric binder used in the primer composition can be selected from one or more acrylic polymers or acrylic co-polymers, or a blend of acrylic polymers or copolymers with polyurethane.

[0109] The primer composition of the present invention may comprise a polymeric binder that is preferably an acrylic polymer or acrylic co-polymer. By selecting an acrylic-based resin, the issue of blocking is mitigated due to the ability of the acrylic resin to form a tough, durable, and less tacky film upon drying, as shown in Figs 1 -4. Acrylic resins often exhibit higher glass transition temperatures (Tg) than for example polyurethanes and intrinsic hardness, which contribute to improved resistance to sticking or adhering under conditions of heat and pressure.

[0110] In an embodiment, the polymeric binder is an acrylic polymer or co-polymer. Preferably, the acrylic polymer or co-polymer is a self-crosslinking acrylic polymer. The acrylic polymeric binder is well-suited for preventing blocking due to its ability to maintain high cohesive strength, and low adhesive properties. Also, the acrylic binder has an inherently polar nature and has the ability to modify the surface energy of the polymeric substrate, preferably the thermoplastic substrate.[01 1 1 ] In an alternative embodiment, the primer composition comprises a polymeric binder, wherein the polymeric binder is an acrylic self-crosslinking dispersion comprising a selfcrosslinking acrylic polymer.

[0112] Alternatively, the primer composition may comprise a polymeric binder where the polymeric binder is an acrylic self-crosslinking dispersion. The acrylic self-crosslinking dispersion is a type of polymer dispersion in water that can form a crosslinked network upon curing or drying without the need for external crosslinkers. These dispersions can be typically through emulsion polymerization, using acrylic monomers (e.g., butyl acrylate, methyl methacrylate) combined with functional monomers such as hydroxyethyl methacrylate or acrylic acid. The acrylic self-cross-linking dispersion comprises a self-crosslinking acrylic polymer.

[0113] The self-crosslinking acrylic polymer is usually in the form of an aqueous dispersion or emulsion and is typically the product of at least two monomers that react with one another. Furthermore, a self-crosslinking acrylic polymer refers to a one pack acrylic that, whilst under ambient cure, can achieve curing, typically via a carbonyl / amine reaction. This can occur between ketone groups and bi- or polyfunctional amine compounds having groups that are reactive towards carbonyl groups. These acrylic polymers exhibit enhanced resistance properties in the resultant dried film.

[0114] The self-crosslinking acrylic polymer as the polymeric binder in the primer composition, providing both film-forming properties and crosslinking functionality. These polymers can be derived from various chemistries, such as styrene-acrylic ester copolymers, styrene-acrylic ester copolymers containing acrylamide groups, or copolymers based on acrylonitrile, methacrylamide, and acrylic esters.

[0115] In one embodiment, the self-crosslinking acrylic polymer is synthesized from reactive monomers, including at least one of methyl acrylic acid (MAA), methyl methacrylate (MMA), butyl acrylate, butyl methacrylate, styrene, or methyl styrene. The resulting polymer is advantageously a styrene-acrylic ester copolymer, which provides a balance of flexibility, durability, and chemical resistance.

[0116] Depending upon the acrylic type, the cross-linking reaction, may also be initiated by the evaporation of water upon drying, a change of pH of the vehicle, or by curing at elevated temperatures where the cross-linking reaction occurs faster, or the reactive groups are deblocked.

[0117] Alternatively, the primer composition may comprise a mixture of polymeric binders where the first binder is an acrylic self-crosslinking dispersion, and the second binder is polyurethane binder. Further, the ratio between the acrylic self-crosslinking dispersion and the polyurethane binder in the primer composition 1 :1 .5 to 1 .5 :1 , even more preferably 1 .1 :1 to 1 :1 .1 . It has been found that polyurethane increases blocking, but improves the print quality, on the other hand the polyacrylate binder (acrylic self-crosslinking dispersion) reduces blocking, but decreases print quality.

[0118] Some examples polymeric binders comprising an acrylic polymer or copolymer, may include NeoCryl® A-1 127, a self-cross-linking acrylic copolymer dispersion. Joncryl® 8053, a self- cross-linking acrylic copolymer; Bayhydrol® A 2846 XP (an acrylic dispersion), Rhoplex SG-10M ( self-cross-linking acrylic emulsion); CHP 536 (an Alkylphenol Ethoxylates (APEOs),-free self- cross-linking acrylic copolymer dispersion) and Acronal® 290 D (acrylic copolymer).

[0119] Further, suitable acrylic polymers or co-polymers can be selected from Neocryl A-1 131 ( modified acrylic co-polymer white liquid emulsion / dispersion), Neocryl A-1 127, Neocryl A-1 129, Neocryl A-1 137XP, Neocryl A-1188, NeoCryl BT-20, Makrovil VI 08, NeoCryl D-2204, Exopur 4109, Vinamul 3231 , NeoCryl XK-205, and NeoCryl Al 120.

[0120] Suitable examples of polyurethanes can be selected from Baybond PU 404, Baybond PU 501 , Witcobond® W-290H, Sancure® 861 , waterborne urethane-acrylic hybrid resins.

[0121] The primer composition of the present invention in general may comprise of from 10 % to 80 % by weight of at least one polymeric binder or a blend (mixture) of polymeric binders relative to the total weight of the primer composition, preferably between 30 % to 80 % by weight, more preferably between 30 % and 80 % by weight, even more preferably between 35% and 70 % by weight, or between 35 and 60 % by weight.

[0122] In an embodiment, the primer composition of the present invention comprises of from 20 % to 80 % by weight of self-cross-linking acrylic polymer as a binder, relative to the total weight of the primer composition.

[0123] In an embodiment, the primer composition of the present invention comprises acrylic self-crosslinking dispersion in an amount comprised betweenl O % to 80 % by weight relative to the total weight of the primer composition, preferably between 30 % to 80 % by weight, more preferably between 30 wt % and 70 wt%, even more preferably between 40% and 70 % by weight.

[0124] In some embodiments, the primer composition of the present invention comprises a blend of acrylic polymer or co-polymer (e.g. acrylic dispersion) and polyurethane, in an amount comprised between 20 % to 80 % by weight relative to the total weight of the primer composition, preferably between 30 % to 80 % by weight, more preferably between 35 % and 70 % by weight, and first and a second inorganic filler, and wherein the ratio of the polyacrylic polymer and polyurethane is between 1 :2 to 2:1 ., preferably 2:1 , more preferably 1 .5:1 .

[0125] Filler: Various fillers can be used in the primer composition, e.g., inorganic fillers, organic fillers. Fillers may be used either individually or in admixture. Preferred fillers are substantially inert under the conditions encountered when the components of the invention are mixed. Preferably, at least two inorganic fillers are used in the present primer composition.

[0126] The inorganic filler is a particulate additive, solid, that is incorporated to improve mechanical performance, adjust surface characteristics, optimize application properties. The inorganic filler of the present invention comprises inorganic particles or blend of inorganic particles. In an embodiment, each inorganic filler consists of inorganic particles or blend of inorganic particles. Examples of suitable inorganic particles for use as a first and / or second inorganic filler include, but are not limited to, silica, alumina, aluminium hydroxide, aluminium hydroxide oxide particles, micro chalk, blend of silica and kaolinite, dolomite, kaolin, kaolinite, clay, wollastonite, mica, talc, calcium bicarbonate, calcium carbonate, Diatomaceous earth, calcined clay, silica gel, fumed silica, colloidal silica, talc, fumed alumina, colloidal alumina, titanium dioxide, zinc oxide, zinc sulphide and barium sulphate.

[0127] For example, commercially available inorganic fillers can be selected from Silitin Z89, Silitin V 88 , APYRAL, Socal P2 (micro-chalk), Boehmite, , Boehmite DA406, Nabaltec

[0128] The primer composition of the present invention may also comprise as at least one inorganic filler, preferably two inorganic fillers, or any dispersion(s) of inorganic material(s), including but not limited to silica, alumina, aluminium hydroxide oxide particles, blend of finely divided silica (SiO2) and lamellar kaolinite clay (a type of aluminium silicate), clay, micro chalk, calcium bicarbonate, calcium carbonate.

[0129] The particle size can vary from the nanometre range up to several microns. In preferred embodiments, the average particle size of the first inorganic filler, in particular calcium carbonate is between 0.0001 pm to 15 pm, preferably between 0.15 pm and 0.5 pm, or between 0.2 pm and 0.4 pm.

[0130] The primer composition of the present invention comprises at least two distinct types of inorganic fillers. The two distinct types of inorganic fillers are defined as a first inorganic filler and second inorganic filler. The addition of two distinct inorganic fillers in the primer composition of the present invention has a synergistic effect and improvement in print quality. The first inorganic filler is selected to provide particles that enhance mechanical anchoring and increase the surface roughness of the cured primer layer, thereby improving blocking resistance, and it additionally contributes to raising the viscosity of the primer composition. The second inorganic filler primarily functions as a viscosity regulator to maintain the primer composition within the desired rheological range, and further contributes to improved delamination performance.

[0131] Without wishing to be bound by theory, it is considered that the two inorganic fillers, differing in particle size, shape, or chemical composition, interact to enhance mechanical interlocking at the interface between the primer layer and the substrate or laminate. This interaction may strengthen the bond and improves the overall adhesion. The addition of two inorganic fillers with complementary properties can optimize the surface energy and texture, and lamination strength. This may reduce tackiness or viscosity and prevent blocking. The ratio between the two distinct inorganic fillers plays a pivotal role in achieving these technical effects.

[0132] For example, the weight ratio between the first inorganic filler and the second inorganic filler can be between 1 :1 to 50:1 , or between 1 :1 to 20:1 , or between 1 :1 and 15:1 , or between 1 :1 and 10:1 , or between 1 :1 and 8:1 . Preferably the weight ratio between the wherein the first inorganic and the second inorganic filler is 5:1 to 50:1 , or 10:1 to 50:1 .

[0133] Preferably , the weight ratio between the first and second inorganic particles can be in the range from 1 .5:1 to 30:1 , or 2:1 to 30:1 , or 3:1 to 30:1 , or 4:1 to 30:1 , 5:1 to 30:1 , 6:1 to 30:1 ,7:1 to 30:1 , 8:1 to 30:1 , 9:1 to 30:1 , or 10:1 to 30:1 , 1 1 :1 to 30:1 , 12:1 to 30:1 , 13:1 to 30:1 , 14:1 to 30:1 , 15:1 to 30:1 , 16:1 to 30:1 , 17:1 to 30:1 , 18:1 to 30:1 , 19:1 to 30:1 , 20:1 to 30:1 , 21 :1 to 30:1 , 22:1 to 30:1 , 23:1 to 30:1 , 24:1 to 30:1 , 25:1 to 30:1 , 26:1 to 30:1 , 27:1 to 30:1 , 28:1 to 30:1 , and 29:1 to 30:1.

[0134] In some embodiments, the ratio between the first inorganic filler and the second inorganic filler is 20:1 , preferably 15:1 , more preferably 10:1.

[0135] Preferably, the weight ratio between the first inorganic filler and the second inorganic filler can be between 10:1 to 50:1 ., wherein the first inorganic filler is calcium carbonate particles, and the second inorganic filler is blend of finely divided silica (SiO2) and lamellar kaolinite particles, or aluminium hydroxide oxide particles.

[0136] Particularly the first inorganic filler can be calcium carbonate or micro chalk. Preferably, the first inorganic filler can be present in an amount below 50 wt %, more preferably below 40 wt % (wet-weight percent), even more preferably below 35wt % (wet-weight percent) based on the total composition of the primer composition. The amount of the first inorganic filler is preferably at least 5 wt %, or at least 10 wt %, or at least 15 wt %, or at least 20 wt %, or at least 30 wt%. A higher amount of first inorganic filler can result in irreversible sedimentation of the inorganic particles. , whereas too low content is not effective.

[0137] For example, the primer composition may comprise a first inorganic filler in an amount of 5 to 50 wt% and a second inorganic filler in an amount of 1 to 15 wt%, based on the total weight of the composition. Preferably, the primer composition comprises a first inorganic filler in an amount of 10 to 40 wt%, and a second inorganic filler in an amount of 1 to 10 wt%, or a first inorganic filler in an amount of 15 wt % to 35 wt %, and a second inorganic filler in an amount of 1 to 8 wt %, or a first inorganic filler in an amount of 15 wt % to 30 wt %, and a second inorganic filler in an amount of 1 to 7 wt %.

[0138] The addition of two types of inorganic fillers selected for example calcium carbonate particles (micro chalk), blend of finely divided silica (SiO2) and lamellar kaolinite particles; or aluminium hydroxide oxide particles, to the primer composition increases the delamination strength of the primer layer formed on the substrate.

[0139] In an embodiment, the first inorganic filler comprises calcium carbonate particles (micro chalk particles, (CAS number 471341 )). The inclusion of calcium carbonate particles enhances the lamination strength, improving the adhesion between the thermoplastic substrate, the primer layer, the ink layer, and the wear-resistant layer.

[0140] Micro chalk, also known as micronized chalk or micro powder chalk, refers to a form of finely ground chalk, comprising as a primary component calcium carbonate (CaCO3). The micro chalk is produced through a precise grinding process that reduces the particle size to a fine powder, typically with a median diameter (D50) that may be in the range from 0.001 pm to 15 pm , or greater than 0.15 pm to 15 pm, or 0.2 pm to 10 pm, more preferably between 0.2 pm and 0.4 pm (as determined by dynamic light scattering, DLS).

[0141] The particle size of the inorganic particles, such as micro chalk, can be measured by laser diffraction (e.g. ISO 13320), dynamic light scattering (e.g. ISO 22412), or electron microscopy (e.g. SEM).

[0142] Alternatively, micro chalk (calcium carbonate with D50 of 0.001 pm to 15 pm) can be synthesized by precipitation, for example but not limited to, by mixing equimolar solutions of Na2CO3and CaCl2at different dilutions in aqueous solution, has been studied at 25°C, forming precipitated calcium carbonate with D50 of 0.001 pm to 15 pm (as determined by DLS).

[0143] Further, the micro chalk particles may optionally be surface modified to enhance their properties, for example, they may be coated. The calcium carbonate (micro chalk) particles are used as an inorganic filler and can help control the porosity of the primer layer.

[0144] Thermoplastic surfaces, such as PVC surfaces, have low porosity, which can pose challenges for primer adhesion. Calcium carbonate particles help to reduce blocking in primer compositions by enhancing surface characteristics. Its fine particles fill small voids and augment surface roughness, thereby fostering a more porous substrate surface. This increased porosity promotes better mechanical interlocking between the primer and the thermoplastic substrate, such as PVC substrate. As a result, the primer adheres more effectively to the thermoplastic substrate, reducing the likelihood of sheets sticking together during storage or handling.

[0145] In an embodiment, the particle size distribution of the calcium carbonate (micro chalk) has a median diameter (D50) of from 0.1 pm(micrometres) to about 10 pm, as determined using a Nicomp 380 Particle Sizer employing Dynamic Light Scattering (DLS) for this measurement. Very fine particles tend to agglomerate, which can create dispersion difficulties and reduce the overall effectiveness of the primer coating.

[0146] In some embodiments, the micro chalk used in the present composition is precipitated calcium carbonate with D50 in the range of 0.001 pm to 15 pm, as determined by DLS.

[0147] In an embodiment, the particle size distribution of the calcium carbonate has a median diameter (D50) of from 0.15 pm to 15 pm, or from about 0.2 pm to 10 pm, or from about 0.2 pm to5 m, or from about 0.2 m to 3 m, or form 0.2 m to 0.4 pm as determined using a Nicomp 380 Particle Sizer employing Dynamic Light Scattering (DLS) for this measurement.

[0148] Further, the CaCO3with D50 in the range of 0.001 pm to 15 pm (also referred to as micro cha used in the present invention, is preferably high purity calcium carbonate (CaCO3) having a purity greater than 97%, preferably greater than 98 %, more preferably greater than 99%, then the remaining less than 2% comprises impurities, such as magnesium, silica, iron, aluminium, and trace levels of sulphates or chlorides, typically amounting to less than 2% by weight. The calcium carbonate may be derived from natural or synthetic sources and is preferably in the form of finely divided particles with controlled morphology to enhance dispersion within the composition.

[0149] A smaller size (0.1 pm -10 pm) of inorganic particles, such as CaCO3, may lead to deeper penetration within the primer composition and / or into the pores of the substrate. This deeper penetration can reduce the availability of the particles at the surface of the primer layer, thereby diminishing their functional contribution at the surface.

[0150] Preferably, the second inorganic filler acts as a viscosity regulator, and can be present in an amount below 20 wt % (wet-weight percent), more preferably below 15 wt % (wet-weight percent), even more preferably below 12 wt % (wet-weight percent) based on the total composition of the primer composition. The wet weight percentage, also described as wet-wt percent, is expressed as the wet weight of the respective component over the total wet weight of the primer composition. The second inorganic filler can be selected from a blend of silica (SiO2) and kaolinite, preferably lamellar kaolinite, or from alumina, aluminium hydroxide, aluminium hydroxide oxide particles, or composite materials. Examples of composite materials include composite material made from a combination of silica and kaolinite particles, where silica particles can be deposited onto kaolinite particles, or vice versa.

[0151] In an embodiment, the second inorganic filler of the primer composition is selected from the group consisting of aluminium hydroxide oxide particles, or from inorganic particles comprising a blend of silica and kaolinite particles, or a composite material comprising silica and kaolinite particles, wherein silica particles are deposited on kaolinite particles, or kaolinite particles are deposited on silica particles.

[0152] The second inorganic filler can be a blend of silica and kaolinite particles with a formula: SiO2-Al2[(OH)4Si2O5] with particle size distribution (D50) of less than 2.4 pm.

[0153] The term "lamellar" refers to the plate-like or sheet-like structure of the mineral. Kaolinite is a clay mineral composed of alternating layers of silica and alumina.

[0154] In an embodiment, the second inorganic filler comprises inorganic particles consisting primarily of a natural blend of finely divided silica (SiO2) and lamellar kaolinite (a type of aluminium silicate). The material typically contains approximately 82% silicon dioxide (SiO2) and 12% aluminium oxide (Al2O3), with trace amounts of iron oxide (Fe2O3). The particle structure combines corpuscular (spherical-like) silica with plate-like kaolinite, resulting in a unique morphology. The particle size distribution d5o can be in the range between 1 .8 pm and 2.4 pm, as measured by ISO13320 (particle size was measured using laser diffraction) and electrical conductivity in the range between 70 and 100 pS / cm. Structurally, the particles exhibit a hybrid morphology, combining corpuscular silica with plate-like kaolinite. In an embodiment, the primer composition comprises an admixture of inorganic fillers, wherein the first inorganic filler comprises calcium carbonate particles (micro chalk) and wherein the second inorganic filler comprises a blend of finely divided silica (SiO2) and lamellar kaolinite (a type of aluminium silicate) (SILLITIN Z 89 by Hoffmann Mineral).

[0155] Aluminium hydroxide oxide is also known as aluminium oxide hydroxide, aluminium oxyhydroxide, or alumina hydrate and has the formula AIO(OH) (= A12O3-H2O). Preferred types of aluminium hydroxide oxide for use in the present invention can be boehmite and pseudoboehmite.

[0156] Boehmite is a mineral with an orthorhombic unit cell (a = 3.693 A, b = 12.221 A, and c = 2.865 A), classified as y-AlO(OH). Its crystal structure consists of double layers of oxygen octahedra with aluminium atoms centrally positioned within them. The outward-facing oxygen atoms are bonded via hydrogen bonds to the hydroxyl groups of adjacent octahedral layers. Due to these relatively weak hydrogen bonds, boehmite is prone to intercalation, the inclusion of small molecules, typically water, between its layers. This intercalation increases the spacing along the

[0010] direction and results in perfect cleavage perpendicular to the general direction of the hydrogen bonding. When the spacing in the

[0010] direction increases significantly, the material is referred to as pseudoboehmite, while predominantly amorphous forms are commonly known as boehmite gel.

[0157] Boehmite can occur naturally or be synthesized. It may be precipitated and grown from solutions of aluminium salts or alumina under hydrothermal conditions or produced via the hydrolysis of aluminium alkoxides.

[0158] In an alternative embodiment, the second inorganic filler comprises aluminium hydroxide oxide particles for example selected from boehmite particles, pseudo boehmite particles, and combinations thereof, and / or have a median particle size (D50) of from 0.02 to 20m, or from 0.02 pm to 10 pm , or from 0.02 pm to 5 pm , preferably from 0.03 pm to 0.3 pm, more preferably from 0.05 pm to 0.2 pm, and most preferably from 0.08 pm to 0.18 pm as determined by laser diffraction according to ISO 13320:2020-01 .

[0159] In an embodiment, the second inorganic filler of the primer composition comprises aluminium hydroxide oxide particles having a particle size distribution with a median diameter (D50) ranging from 0.5 pm to 10 pm, preferably from 0.5 pm to 5 pm, as determined by laser diffraction according to ISO 13320:2020-01 .

[0160] The D50 value is a statistical measure used to describe the particle size distribution of the ink that represents the median particle diameter, indicating that 50% of the particles in the ink are smaller than this value, and 50% are larger. Further, DLS is a technique for measuring the size distribution of small particles suspended in a liquid. It works by analysing the intensity fluctuations of laser light scattered by the particles as they undergo Brownian motion.

[0161] In an embodiment, the primer composition comprises a self-crosslinking acrylic polymer, an admixture at least two distinct types of inorganic fillers, wherein the first inorganic filler comprises calcium carbonate particles (micro chalk) and wherein the second inorganic filler comprises a blend of finely divided silica (SiO2) and lamellar kaolinite.

[0162] In an embodiment, the primer composition comprises a an acrylic self-crosslinking dispersion comprising a self-crosslinking acrylic polymer, an admixture at least two distinct types of inorganic fillers, wherein the first inorganic filler comprises calcium carbonate particles (micro chalk) and wherein the second inorganic filler comprises a blend of finely divided silica (SiO2) and lamellar kaolinite, and water, wherein the weight ratio between the first inorganic filler and the second inorganic filler is between 1 :1 and 20:1 , or between 1 :1 and 15:1 , or between 1 :1 and 10:1 , or between 1 :1 and 8:1 (wet-weight ratio).

[0163] In an alternative embodiment, the primer composition comprises a self-crosslinking acrylic polymer or a self-crosslinking acrylic co-polymer, an admixture at least two distinct types of inorganic fillers, wherein the first inorganic filler comprises calcium carbonate particles (micro chalk) and wherein the second inorganic filler comprises aluminium hydroxide oxide particles, and water.

[0164] In an embodiment, the particle size distribution of the calcium carbonate (micro chalk) has a median diameter (D50) greater than 0.1 micrometres (pm), as determined using a Nicomp 380 Particle Sizer employing Dynamic Light Scattering (DLS) for this measurement. Very fine particles tend to agglomerate, which can create dispersion difficulties and reduce the overall effectiveness of the primer coating. For example, the calcium carbonate particles can have aparticle size distribution with a median diameter (D50) ranging from 0.15 pm to 15 pm, or from 0.2 pm to 10 pm, or from 0.2 pm to 5 pm, or from 0.2 pm to 3 pm, or form 0.2 pm to 1 pm, or from 0.2 pm to 0.5 pm, or form 0.2 pm to 0.4 pm, as determined by DLS.

[0165] The ratio between the polymeric binder(s) and the two inorganic fillers is from 1 :10 to 10:1 , preferably from 1 :5 to 9:1 , more preferably from 1 :1 to 8:1 .

[0166] In an embodiment, the primer composition for thermoplastic substrate surface comprises at least one polymeric binder, wherein the polymeric binder is an acrylic selfcrosslinking dispersion comprising a self-crosslinking polymer, at least two distinct types of inorganic fillers, wherein the first inorganic filler is calcium carbonate particles , and the second inorganic filler is a blend of silica and (lamellar) kaolinite, and water, where the ratio between the polymeric binder and the two inorganic fillers is from 1 :5 to 9:1 , preferably from 1 :1 to 8:1 .

[0167] The primer composition may comprise 5 % to 40 % by weight of a first inorganic filler (calcium carbonate), preferably 10 wt% to 35 wt%, more preferably 10 wt % to 32 wt %, even more preferably 15 wt % to 30 wt%.

[0168] The primer composition may comprise based on the total weight of the primer composition: 1 to 15 %, preferably 2 % to 15 % by weight of a second inorganic filler, wherein the second inorganic filler is a blend of silica and (lamellar) kaolinite, preferably 4 wt% to 15 wt%, more preferably 5 wt % to 10 wt %.

[0169] Alternatively, the primer composition may comprise based on the total weight of the primer composition:! to 15 %, preferably 2% to 15 % by weight of a second inorganic filler, wherein the second inorganic filler is an aluminium oxide hydroxide (boehmite), preferably 4 to 15 wt%, more preferably 5 wt % to 10 wt %.

[0170] In an alternative embodiment, the primer composition for thermoplastic substrate surface comprises based on the total weight of the primer composition: 20 wt % to 80 wt % acrylic binder, wherein the polymeric binder is an acrylic self-crosslinking dispersion comprising a self-crosslinking polymer, 5 wt % to 40 wt % calcium carbonate particles, and 2 % to 15 % by weight of the second inorganic filler is a blend of silica and (lamellar) kaolinite, and the balance being water.

[0171] In some embodiments, the primer composition for thermoplastic substrate surface comprises based on the total weight of the primer composition: 20 wt % to 80 wt % acrylic binder, wherein the polymeric binder is an acrylic self-crosslinking dispersion comprising a selfcrosslinking polymer, 5 wt % to 40 wt % calcium carbonate particles, and 2 % to 15 % by weightof the second inorganic filler is a aluminium oxide hydroxide (boehmite), and the balance being water.

[0172] In some embodiments, the primer composition for thermoplastic substrate surface comprises based on the total weight of the primer composition: 10 wt % to 80 wt % of a mixture or a blend of acrylic self-crosslinking dispersion comprising a self-crosslinking polymer, and a polyurethane binder, 15 wt % to 40 wt % calcium carbonate particles, and 1 % to 15 % by weight of the second inorganic filler is a aluminium oxide hydroxide (boehmite), and the balance being water. Further, wherein the mixture in the composition comprises 1 .5: 1 to 1 :1 .5 of acrylic selfcrosslinking dispersion comprising a self-crosslinking polymer, and a polyurethane binder, preferably 1 .1 :1 to 1 :1 .1 of acrylic self-crosslinking dispersion comprising a self-crosslinking polymer, and a polyurethane binder,

[0173] Additives: The primer composition can also include other primer components (additives) such as surfactants, rheology modifiers, defoamers, optical brighteners, biocides, pH controlling agents, dyes, corrosion inhibitors, coalescing agent solvents to reduce film forming temperature of binder emulsions and the like and other additives for further enhancing the properties of the primer composition. The one or more additives present in the primer composition of the present invention can be present for example in an amount between 0.01 wt % and 50 wt %.

[0174] The primer composition of the present invention further may comprise one or more antifoaming additives in an amount comprised between 0 % and 2% by weight, preferably between 0.5 and 1 .5% by weight of the total weight of the primer formulation.

[0175] Examples of antifoaming agents are polysiloxanes, such as polymethylhydrogensiloxane or polydimethylsiloxane, polyoxyalkylene polysiloxane block copolymers, grafted polyoxyalkylene polysiloxane block copolymers and mixtures thereof with organic oils such as mineral oils such as naphthenic and paraffinic mineral oil, polypropylene oxide, polybutadiene, certain oils of vegetable or animal origin, and the like.

[0176] The primer composition of the present invention of the present invention further may comprise one or more surfactants in an amount comprised between 0 % and 2% by weight, preferably between 0.5 and 1 .5% by weight of the total weight of the primer formulation.

[0177] Examples of suitable surfactants can be a polyether modified siloxane, sodium dodecyl sulfate, polysorbate 20 (or polyoxyethylene 20 sorbitan monolaurate), Polysorbate 40 (or polyoxyethylene 20 sorbitan monopalmitate), Polysorbate 60 (or polyoxyethylene 20 sorbitan monostearate), Polysorbate 80 (or polyoxyethylene 20 sorbitan monooleate), alkylpolyglucosides, more preferably polyether modified siloxane, or Surfynol (acetylenic diol-based surfactants).

[0178] The primer composition of the present invention may further comprise one or more additives selected from 0.5-5 % of a poly(diallyldimethylammonium chloride) (further herein poly(DADMAC)), 2-10% of a polycarbodiimide (PCDI), 0.5-5 % of an alkyltrialkoxysilane, 5 wt % to 40 wt % of polyvinyl alcohol (preferably as a 20 % aqueous PVOH solution), and / or additional 5-10 % extra CaCO3with a median diameter (D50) ranging from 0.15 pm to 15 pm, or a combination thereof.

[0179] It has been discovered that the inclusion of one or more additives, such as polyvinyl alcohol and / or poly(diallyldimethylammonium chloride) (poly(DADMAC)), results in a significant improvement in print quality, when used in combination with a pigmented aqueous ink compositions in digital printing. In addition, the two compounds appear to provide a synergistic effect on print quality.

[0180] In particular, incorporation of a pigment-dispersion-destabilizing agent into the present primer composition, such as polyvinyl alcohol and / or poly(DADMAC), enhances print quality without adversely affecting other critical performance properties, including surface tension, blocking behaviour, lamination strength between the substrate and ink layer, and wear resistance, as shown in Figs 8A and 8B.

[0181] In certain embodiments, the primer composition comprises poly(diallyl dimethyl ammonium chloride) (PolyDADMAC) (e.g. poly(DADMAC 20 % solution) as a cationic fixation agent for aqueous ink compositions. PolyDADMAC possesses a high cationic charge density and is capable of rapidly interacting with anionically stabilized pigment dispersions upon contact with an ink droplet. This electrostatic fixation substantially limits pigment penetration into the substrate and suppresses lateral pigment migration. As a result, printed images exhibit increased optical density, improved colour saturation, enhanced edge acuity, and reduced bleed and feathering. The pigment fixation further decouples the pigment particles from the aqueous carrier phase of the ink, allowing the liquid components to be absorbed or evaporated independently, thereby reducing coalescence and related print artifacts. Accordingly, the primer composition comprising poly(diallyl dimethyl ammonium chloride (poly DADMAC) enables high-quality printing with aqueous ink compositions by providing rapid surface-level pigment fixation through electrostatic interaction.

[0182] In certain embodiments, the primer composition comprises polyvinyl alcohol for example PVOH 20 % solution. The primer may comprise polyvinyl alcohol (PVA), which functionsas a film-forming binder that produces a smooth and uniform coating on the substrate. The reduced surface roughness and increased surface energy of the polyvinyl alcohol -comprising primer composition may improve the aqueous ink composition wetting and droplet adhesion, resulting in controlled dot formation and enhanced image sharpness.

[0183] Without being bound by any theories, during ink drying, polyvinyl alcohol may act as a physical matrix that limits pigment mobility, promoting pigment retention near the surface and thereby increasing optical density and colour intensity. In addition, polyvinyl alcohol improves cohesion within the printed layer and adhesion to the substrate, providing enhanced mechanical durability, including improved scratch resistance and rub fastness. The barrier properties of polyvinyl alcohol further contribute to improved moisture resistance and long-term image stability. In summary, inclusion of polyvinyl alcohol in the primer composition improves print quality by promoting uniform coating formation, controlling ink droplet behaviour, retaining pigments near the surface, and enhancing the mechanical stability and durability of the printed layer.

[0184] In some embodiments, the primer composition for surface treatment of a polymeric substrate for digital inkjet printing, comprising: at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles, water, and optionally at least one additive selected from polyvinyl alcohol and po ly(dia Uy I dimethyl ammonium chloride) (poly(DADMAC). Further. The primer composition may comprises of 5 wt % to 40 wt % of polyvinyl alcohol (20 % aqueous PVOH solution), and / or 0.5-5 % of a poly(diallyl dimethyl ammonium chloride) (poly(DADMAC)) based on the total weight of the primer composition.

[0185] In some embodiments, the primer composition for surface treatment of a polymeric substrate for digital inkjet printing, comprises: 10 % to 80 % by weight of a blend of polyacrylate binder and polyurethane binder (preferably 50:50 ratio),

[0186] 5% to 40 % by weight of a first inorganic filler comprising calcium carbonate (micro chalk) with a median diameter (D50) ranging from 0.15 pm to 15 pm, and a 1 to 15 wt % of a second inorganic filler selected from boehmite or a mixture of silica and kaolinite clay, water, and optionally 5 wt % to 40 wt % of polyvinyl alcohol (20 % aqueous PVOH solution), and / or 0.5-5 % of a poly(diallyldimethylammonium chloride) (poly(DADMAC)) based on the total weight of the primer composition.

[0187] Further, the primer composition of the present invention is an aqueous primer composition, wherein the water serves as the primary solvent or carrier in the formulation.Aqueous primer compositions offer several advantages, including being more environmentally friendly due to reduced volatile organic compound (VOC) emissions.

[0188] Also, the present invention relates to a primer composition that can be used to improve the adhesion and lamination strength of aqueous inks composition applied to polymeric surfaces, preferably thermoplastic surfaces, used in decorative coverings, such as floor surface covering, ceiling surface covering, wall surface covering, and laminated flooring panels. Laminated flooring panels or floor covering elements can comprise a support layer, a foamed layer, a decorative layer adhered to the upper surface of the foam layer, a wear-resistant layer, and a backing layer. The decorative layer is an aesthetic layer comprising designs printed with aqueous ink compositions on the thermoplastic substrate. In some examples, the aqueous ink composition may be applied on the primer layer by digital printing, such in a single pass or multipass printing. Employing the primer composition of the present invention for covering elements or laminated panels serves merely as an illustration; it should not be construed as limiting the invention's applicability to these examples alone.

[0189] Further, the primer layer comprising the primer composition of the present invention may enhance the adhesion and facilitates the effective lamination of the wear-resistant layer to the thermoplastic surface of the substrate where the aqueous ink is applied. The wear-resistant layer serves as a protective topcoat or lacquer for surfaces such as laminated flooring panels or other decorative coverings, improving their durability and resistance to damage from daily use, including scratches, stains, and abrasion. In one embodiment, the wear resistant layer comprises one or more layers of a polymeric material, such as a thermoplastic and / or thermoset polymeric material. In one embodiment, the wear resistant layer comprises a transparent polyvinyl chloride layer. Other examples of the wear resistant layer include, but are not limited to, acrylic polymers, polyolefins, melamine resins and the like. The wear resistant layer can be translucent, and preferably transparent. The wear resistant layer may have a thickness of 100 pm to 1000 pm.

[0190] Surprisingly, the adhesion of the wear-resistant layer to the remainder of the multi-layer substrate may be further enhanced by the inclusion of the primer layer comprising the primer composition of the present invention that facilitates better lamination strength between the wear-resistant layer and the thermoplastic substrate, as shown in Figs. 3 and 4. Preferably, the thermoplastic substrate exhibits a peel strength between the decorative layer and the wearresistant layer of between 20 to 120 N / 50 mm, more preferably of from 25to 115 N / 50 mm, andmost preferably of from 30to 1 10 N / 50 mm, when measured for the complete product build-up including a wear-resistant layer, a primer layer, and determined according to EN 431 :1994.

[0191] Further, the primer layer of the present invention exhibits a peel strength of at least 20 N / 50 mm, preferably 30 N / 50 mm, as determined in accordance with ASTM D903. This can ensure strong adhesion between the substrate and subsequent layers.

[0192] In an embodiment, the primer composition of the present invention is formulated for treatment of polyvinyl chloride (PVC) surface / substrate. PVC is widely used as a material for decorative coverings, including floor coverings, ceiling coverings, wall coverings, and other surface coverings, due to its durability, flexibility, and resistance to environmental factors. However, its non-porous and water-impermeable nature presents challenges for the adhesion and drying of aqueous inks. Furthermore, the relatively low surface energy of PVC, typically around 35 mN / m, further hinders proper ink adhesion. The primer composition can modify the surface properties of PVC, increasing its surface energy to approximately 50 mN / m, thereby enabling improved aqueous ink wetting, adhesion, and overall print quality.

[0193] The present primer composition is particularly applicable to prepare inkjet-receptive primer layers for high-speed single pass printing or multi-pass digital printing. .

[0194] Method of application: The present invention further relates to a method of applying a primer composition to a polymeric substrate surface, specifically a thermoplastic substrate surface, such as, but not limited to, polyvinyl chloride (PVC) substrate, or a plasticized foamable PVC substrate. The primer composition is preferably for forming an inkjet-printable or inkjet - receptive primer layer.

[0195] The present invention also relates to a method for preparing a shaped article, such as a decorative covering. The method involves the following steps: providing a polymeric substrate; applying an ink and primer system as described herein, which includes first applying the primer composition of the present invention to the polymeric substrate to form a primer layer; subsequently printing a decorative layer on the primed substrate, preferably using digital printing with an aqueous ink composition; and finally, drying the aqueous ink composition to form the finished printed polymeric substrate.

[0196] The aqueous ink composition can be applied onto the cured primer layer by digital inkjet printing. High-speed digital printing processes are suitable, and the primed substrate may be printed at speeds ranging from about 5 to 300 m / min. Single-pass digital inkjet printing or multipass digital inkjet printing may be used.

[0197] After printing, thorough drying of the aqueous ink is required. Suitable drying methods include convective (hot-air) drying, contact drying, infrared (IR) drying, near-infrared (NIR) drying, or combinations thereof. Drying is typically carried out at temperatures of at least 50 °C, preferably at least 60°C.

[0198] In an embodiment, the primer composition of the present invention is applied on polyvinyl chloride (PVC) substrate / surface, followed by the printing of the aqueous ink composition.

[0199] When priming thermoplastic film substrates, the substrate may be flame or corona treated prior to coating. Such treatment of the substrate enables good adhesion of the primer layer by providing a suitable surface energy of the substrate. In general, higher surface energy is associated with better adhesion. The primer composition of the present invention, upon application and subsequent treatment, can elevate the polymeric substrate's surface energy. For example, if it is PVC substrate- to fall within the desirable range of 40 to 55 mN / m.

[0200] The primer composition can be applied to the polymeric / thermoplastic substrate by any of a number of coating methods, including flexographic, gravure, rod, spray, roll, curtain and knife coating methods. Preferred methods are flexographic, gravure and rod coating methods. The application of the primer can be on-line (directly before digital printing, as part of a continuous operation), or off-line (where the coating process occurs separately from the digital printing, allowing the primer to fully adhere and cure on the substrate without immediate printing) with the inkjet ink printing process.

[0201] The primer composition can be applied as a liquid or semi-liquid coating. The primer composition can be in a wet state, referring to its condition immediately after being applied to a polymeric substrate / surface, before any substantial drying or curing has taken place.

[0202] After being applied in a wet state, the primer composition undergoes a drying process to form a primer layer. The drying process may involve the evaporation of the volatile components from the primer composition.

[0203] The primer composition can be dried with an infrared lamp, hot air or combination thereof. In an embodiment, the primer composition is dried using an oven with hot air at a temperature ranging from 30°C to 95°C for a time in the range between about 0.5 min and 8 minutes, forming a primer layer. Subsequently, it can be printed with an aqueous ink composition forming a decorative layer on the primed surface of the polymeric substrate through methods like single-pass printing, or multi- pass printing using an aqueous ink composition, or even conventional printing. Optionally, the primed polymeric substrate, i.e the polymeric substratewith a primer layer deposited on its surface, with the decorative layer can then be laminated to another substrate or coated with an additional layer. For example, a wear-resistant layer may be applied on top of the decorative layer.

[0204] The primer layer for polymeric substrate is thus obtained by drying a primer composition according to the present invention wherein the primer layer comprises the polymeric binder and inorganic fillers of the primer composition. The surface of the primer layer is non-sticky, which means that there is no blocking or adhesion to other surfaces at room temperature or increased temperature, e.g. 50-60 °C, particularly to the backside of a substrate which is wound or roll after application and drying of the primer composition and optionally after printing.

[0205] The primer layer further refers to the solid film formed on the surface of a polymeric substrate after the application and drying of the primer composition as described in the present invention. This primer layer comprises the non-volatile components of the primer composition, including the polymeric binder and the at least two distinct inorganic fillers, while water and other volatile substances are removed during the drying process. The primer layer provides a functional surface with properties such as enhanced adhesion and a surface energy of at least 30 mJ / m2, making it suitable for subsequent processes like printing. The surface energy of the cured primer layer was determined by measuring the contact angle of standard test liquids according to ASTM D7334.

[0206] For example, the surface anergy of the primer layer can be in the range of 30-80 mJ / m2, as determined according to ASTM D7334, preferably 35 -70 mJ / m2.

[0207] The primer layer may have a thickness in the range of 1 pm to 20 pm, preferably in the range of 2 pm to 15 pm, more preferably between 4 pm to 10 pm. The primer layer may be in a form of a film, and with a peel strength of at least 20 N / 50 mm.

[0208] Further, there is provided a polymeric substrate at least partially coated with the primer composition according to the present invention forming a primer layer, the primer layer preferably comprising at least one polymeric binder and at least two types of inorganic fillers, each filler consisting of inorganic particles. In an embodiment, the primer layer may comprise from 20% to 70 % by weight acrylic polymer / acrylic co-polymer, or a blend acrylic polymer / acrylic co-polymer and polyurethane, from 15% to 80 % by weight of calcium carbonate particles, and from 3 % to 30 % by weight blend of silica and kaolinite particles. This based on the dry weight of the formulation, representing the proportions of solid materials after the evaporation of water or solvents The kaolinite particles in the blend can be a special type of lamellar kaolinite particles.

[0209] Once the primer layer is completely dried, , i.e. it contains minimal to no moisture content (see for example Table 1 and 2), and the substrate is adequately prepared, the aqueous ink composition is then printed onto the polymeric substrate. This sequential process ensures the primer composition / layer effectively prepares the thermoplastic surface, enhancing ink adhesion and resulting in superior print quality with vivid colours and sharp patterns.

[0210] After primer application, the polymeric substrate, particularly a thermoplastic substrate, exhibits two distinct surfaces: primer-treated side and untreated side. The primer-treated side is modified to exhibit high surface energy and a substantially hydrophilic nature, enabling effective adhesion of aqueous inks and coatings. In contrast, the untreated side (backside) retains its inherent low surface energy and substantially hydrophobic properties, ensuring minimal adhesion and compatibility with winding or stacking processes. In order to prevent blocking, the surface energy of the primer-treated side (frontside) and untreated side (backside) of the substrate must differ sufficiently.

[0211] Furthermore, the addition of inorganic fillers to the primer composition introduces surface roughness, which reduces the number of contact points and lowers adhesive forces. This structural modification further minimizes the risk of blocking, ensuring smoother handling and storage of the treated polymeric substrate. This, in turn, minimizes blocking when the primer- treated side comes into contact with the untreated side (backside) of the substrate.

[0212] Thus, the combination of high surface energy on the treated side of the polymeric substrate and low surface energy on the untreated side of the polymeric substrate, along with the introduction of surface roughness, may effectively prevent blocking.

[0213] In an embodiment, the primer layer may have a thickness ranging of from 1 pm to 50 pm , 1 pm to 30 pm, or 1 pm to 20 pm, or 5 pm to 15 pm when applied to the polymeric substrate surface , preferably to the thermoplastic substrate surface, more preferably to the PVC substrate surface.

[0214] In an embodiment, the thickness of the primer composition when applied on the polymeric substrate surface is between 1 pm and 20 pm, preferably between 5 pm and 18 pm, more preferably between 8 pm and 15 pm, even more preferably between 9 pm and 13 pm.

[0215] In an embodiment, the primer composition has a surface tension of 20 mN / m to 80 mN / m at 20°C, as measured by Wilhelmy plate method. The Wilhelmy plate method calculates the surface tension (y) of a liquid by measuring the force (F) exerted on a plate that is partially immersed in the liquid. The equation to determine the surface tension using the Wilhelmy plate method is: y= F / P-cos9 where: y is the surface tension of the liquid (mN / m), F is the forcemeasured by the tensiometer as the plate is either immersed in or withdrawn from the liquid (Newtons), P is the perimeter of the plate that comes in contact with the liquid (in meters (m) or centimetres (cm)), and 0 is the contact angle between the liquid and the plate. The ASTM standard for this method is ASTM D1331 , more specifically ASTM D1331 -20.

[0216] In an embodiment, the primer composition has a surface tension of 20 to 40 mN / m at 20°C, as determined by Wilhelmy plate method (as determined according to ASTM D1331 , more specifically ASTM D1331-20.)

[0217] Ink and a primer system: The primer composition of the present invention is particularly suitable for use in combination with aqueous ink compositions in digital printing, enhancing their adhesion and performance on various polymeric substrates. The application of the aqueous ink composition onto the primed polymeric (e.g. thermoplastic) substrate facilitates the creation of decorative covering elements, including but not limited to floor, ceiling, and wall surface coverings, as well as laminated flooring panels and tarpaulins.

[0218] In a further aspect of the present invention, there is provided an ink and primer system for image formation on a thermoplastic substrate surface comprising: a primer composition for surface treatment of a polymeric substrate prior to applying an aqueous ink composition, the primer composition comprising at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles; and water; and an aqueous ink composition comprising water and at least two different water-soluble organic solvents, wherein the at least two different water-soluble organic solvent are selected from a group consisting of alkyl diols, and wherein each water-soluble organic solvent has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C (as determined by ASTM D1331 ). This ink and primer system for image formation is preferably applied by means of digital inkjet printing.

[0219] Further, the primer composition of the ink and primer system described above may comprise two distinct types of inorganic fillers, denoted as a first inorganic filler and a second inorganic filler, wherein the first inorganic filler comprises calcium carbonate particles (chalk or micro chalk) and the second inorganic filler comprises a blend of silica with (lamellar) kaolinite.

[0220] In this ink and primer system, the primer composition and the aqueous ink formulation are designed to work synergistically, ensuring reliable adhesion, sharp print resolution, and longterm durability. Although inkjet or digital printing is the preferred method for applying the aqueous ink composition as part of the decorative layer, also conventional printing methods may be used for applying the aqueous ink composition.

[0221] The application of the aqueous ink composition onto the primed polymeric, preferably thermoplastic, substrate facilitates the creation of decorative covering elements, including but not limited to floor, ceiling, and wall surface coverings, as well as laminated flooring panels and tarpaulins.

[0222] The ink and primer system according to this aspect of the invention may optionally further comprise a third water soluble organic solvent selected from a group consisting of alkyl triols with a surface tension falling in the range of from 10 to 80 mN / m at 20°C, as determined in accordance with ASTM D1331 , or specifically in accordance with ASTM D1331 -20The ink and primer system can be applied to a polymeric substrate, specifically a thermoplastic substrate selected from the group consisting of polyvinyl chloride, polyolefin or polyester, more preferably a PVC substrate, preferably by means of digital inkjet printing.

[0223] Also, the present invention relates to an aqueous ink composition for forming an image by means of digital printing on a polymeric substrate, where the aqueous ink composition is used in combination with a primer composition.

[0224] In one embodiment, the aqueous ink composition is applied using a single-pass digital printing process, which employs either a substrate-wide array of stationary inkjet printing heads or multiple staggered inkjet printing heads arranged to cover the entire width of the surface. In this process, the inkjet printing heads remain stationary while the primed substrate is continuously transported beneath them.

[0225] According to an aspect of the present invention for which protection is sought, there is provided an aqueous ink and primer system for image formation, preferably by means of digital inkjet printing, on a polymeric substrate surface comprising: a primer composition for treating the polymeric substrate, wherein the primer composition comprises at least at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles, and water and an aqueous ink composition for image formation on the polymeric substrate treated with the primer composition, wherein the aqueous ink composition comprises water and at least two different water-soluble organic solvents, wherein the at least two different water-soluble organic solvent are selected from a group consisting of alkyl diols, and wherein each water-soluble organic solvent has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C, preferably of from 15 to 75 mN / m at 20°C, more preferably 20 to 75 mN / m at 20°C (as determined in accordance with ASTM D1331 , or specifically in accordance with ASTM D1331 -20).

[0226] The aqueous ink composition comprises at least two distinct (different) water-soluble organic solvents, that can be defined as a first water-soluble organic solvent and a second water- soluble organic solvent, and wherein each water-soluble organic solvent may differ in terms of carbon chain length and may include different substituents.

[0227] In an embodiment, the alkyl diols (alkane diols)in the aqueous ink composition may have carbon chain lengths ranging from C3 to C8, preferably C3 to C6.

[0228] In an embodiment, the at least two water-soluble organic solvents have a distinct boiling point falling in the range of from 50°C to 450° C at 1 atmosphere, more preferably 100°C to 350° C at 1 atmosphere.

[0229] In an embodiment, the aqueous ink composition comprises of from 5 wt % to 70 wt % of at least two water-soluble organic solvents, preferably 10 wt % to 50 wt %, more preferably of from 20 wt % to 45 wt % relative to the total weight of the aqueous ink composition.

[0230] Advantageously, the aqueous ink composition may comprise at least two alkyl diols, such as 1 ,2 propanediol, 1 ,3-propanediol, 2-methyl-1 ,3-propanediol, 1 ,2-butanediol, 1 ,3- butanediol, 1 ,4-butanediol, 1 ,2 -pentanediol, 2,3-pentanediol, 1 ,5-pentanediol, 1 ,5 hexanediol, 2,5-hexanediol, 1 ,6-hexanediol, 1 ,2-hexanediol, 2,3-hexanediol, 1 ,7- heptanediol, and 1 ,8- octanedioL

[0231] In an embodiment, the first water-soluble organic solvent is 1 ,2-hexanediol.

[0232] In an embodiment, the second water-soluble organic solvent is an alkyl diol with a carbon chain length ranging from C3 to C4, such as 1 ,3-butanediol, 1 ,2-propanediol, or 2-methyl- 1 ,3-propanediol, preferably 1 ,3-butanediol.

[0233] The aqueous ink composition of the present ink and primer system may further comprise a third water-soluble organic solvent. The third water-soluble organic solvent can be selected form the group consisting of alkyl triols. In an embodiment, the third water-soluble organic solvent is glycerol.

[0234] In an embodiment, the aqueous ink composition of the present invention comprises three different water-soluble organic solvents, each identified as a first, second, and third water- soluble organic solvents respectively. The three water-soluble organic solvents form a synergistic mixture, where their effects are being amplified or altered, leading to enhanced surface tension reduction, wetting, and ink penetration compared to what each compound could achieve individually.

[0235] In an embodiment, there is provided an aqueous ink composition for image formation on a polymeric substrate, wherein the polymeric substrate is surface treated with a primercomposition of the present invention, wherein the aqueous ink composition comprises water and three different water-soluble organic solvents, wherein the first and the second water-soluble organic solvents are alkyl diols, and the third water-soluble organic solvent is an alkyl triol, and wherein each of the first, second and third water-soluble organic solvents has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C, as determined in accordance with ASTM D1331 , or specifically in accordance with ASTM D1331 -20. In an embodiment, the aqueous ink composition comprises 1 ,2-hexanediol as the first water-soluble organic solvent, 1 ,3- butanediol as the second water-soluble organic solvent, and optionally glycerol as the third water-soluble organic solvent.

[0236] Further, the aqueous ink composition may comprise a third water-soluble organic solvent selected from a group consisting of alkyl triols with a surface tension within 10 to 80 mN / m at 20° C. Preferably, the third water-soluble organic solvent is alkyl triol, more preferably the third water soluble organic solvent is glycerol.

[0237] In an embodiment, there is provided an aqueous ink composition for image formation on a polymeric substrate as part of the ink and primer system of the present invention, wherein the polymeric substrate is treated with a primer composition of the present invention, wherein the aqueous ink composition comprises water and three different water-soluble organic solvents, wherein the first and the second water-soluble organic solvents are alkyl diols, and the third water-soluble organic solvent is an alkyl triol, and wherein each of the first, second and third water-soluble organic solvents has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C. Further, in this embodiment 1 ,2-hexanediol is indicated as a first water soluble organic solvent, 1 ,3-butanediol is indicated second waters soluble organic solvent, and glycerol is indicated as a third water soluble organic solvent.

[0238] In an embodiment, there is provided an aqueous ink composition for image formation on a polymeric substrate as part of the ink and primer system of the present invention, wherein the polymeric substrate is treated with a primer composition of the present invention, wherein the aqueous ink composition comprises water, 1 ,2-hexanediol, 1 ,3-butanediol, and glycerol.

[0239] In a further embodiment, there is provided an aqueous ink composition for image formation on a polymeric substrate, wherein the polymeric substrate is treated with a primer composition of the present invention, wherein the aqueous ink composition comprises water, three water-soluble organic solvents, an ink binder, a surfactant, one or more pigments, wherein the three water-soluble organic solvents are 1 ,3-butanediol, 1 ,2-hexanediol and glycerol. Further, in this embodiment 1 ,2-hexanediol is indicated as a first water soluble organic solvent, 1 ,3-butanediol is indicated second waters soluble organic solvent, and glycerol is indicated as a third water soluble organic solvent.

[0240] The weight ratio of glycerol to 1 ,2- hexanediol based on the total weight of the aqueous ink composition may be between 10:1 to 1 :10, preferably between 1 :1 and 1 :5. In a preferred embodiment, the aqueous ink composition of the present ink and primer system comprises 1 wt% to 3 wt % glycerol, 3 wt% to 5 wt % 1 ,2-hexanediol, and 18 to 30 wt % of 1 ,3-butanediol, and the rest water based on the total weight of the ink composition.

[0241] The aqueous ink composition may further comprise an ink composition binder, a surfactant, one or more pigments. In an exemplary embodiment, the ink composition binder is an acrylic based binder, such as a styrene-acrylic copolymer dispersion.

[0242] In a preferred embodiment, the aqueous ink composition for image formation, preferably by means of digital inkjet printing, on a polymeric substrate(e.g. PVC, polyester, or polyolefin), that is treated with a primer composition of the present invention , comprises water and three different water-soluble organic solvents, wherein the first and the second water-soluble organic solvents are alkyl diols, the third water-soluble organic solvent is alkyl triol, and wherein each of the first, second and third water-soluble organic solvents has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C, preferably 15 to 75 mN / m at 20°C.more preferably of from 20 to 75 mN / m at 20°C, even more preferably of from 24 to 73 mN / m at 20°C and wherein the aqueous ink composition comprises relative to the total weight of the composition, 20 wt% to 40 % by weight of water-soluble organic solvents, 8 wt% to 20 wt % of an ink composition binder. Further, in this embodiment 1 ,2-hexanediol is indicated as a first water soluble organic solvent, 1 ,3-butanediol is indicated second waters soluble organic solvent, and glycerol is indicated as a third water soluble organic solvent.

[0243] The aqueous ink composition of the ink and primer system in the present invention may have a viscosity in the range of from 1 .0 cP to 15.0 cP at 25°C, 3 cP to 10 cP at 25°C, 4.0 cP to 9.0 cP at 25°C, 4.0 cP to 8.0 cP at 25°C, 4 cP to 7 cP at 25°C, 4.1 to 6.6 cP at 25°C, preferably 4.8 to 6.1 cP at 25°C, more preferably 5 to 6.1 cP at 25°C, at 25°C, as measured by Anton Paar viscometer, ASTM D7042.

[0244] The aqueous ink composition of the ink and primer system in the present invention may have a surface tension in the range of from 15 mN / m to 45 mN / m at 25°C, more preferably 15 mN / m to 43 mN / m at 25°C, 15 mN / m to 40 mN / m at 25°C, 18 mN / m to 38 mN / m at 25 °C, 20mN / m to 35 mN / m at 25°C, 20 mN / m to 30 mN / m at 25°C, as measured by Wilhelmy platemethod (as determined in accordance with ASTM D1331 , or specifically in accordance with ASTM D1331 -20).

[0245] The aqueous ink composition may comprise at least one pigment. Pigments suitable for being used are those generally well-known in the art for aqueous inks. The aqueous ink composition may comprise one or more pigments for each of the CMYK (Cyan, Magenta, Yellow and black) colours and without being particularly limited to any type.

[0246] Some examples of suitable pigments are pigment dispersions that can include ProJet ADP 1000 Black (Carbon Black), ProJet ADP 1000 Cyan (Pigment Blue 15:3), ProJet ADP 1000 Yellow LF (Pigment Yellow 155), ProJet ADP 1000 Red (Pigment Red 254) and ProJet ADP 1000 Blue (Pigment Blue 60) were also used. Pro-Jet® APD 1000 pigment dispersions are available from FUJIFILM Imaging Colorants Limited.

[0247] Further, the polymeric substrate of the ink and primer system can be preferably a thermoplastic substrate selected form the group consisting of from the group consisting of polyvinyl chloride (PVC), polyolefin, polyester, polystyrene or polyamide. In an embodiment, the polymeric substrate is polyvinyl chloride (PVC).

[0248] Shaped article: The invention further pertains to a shaped article comprising a polymeric substrate and primer composition according to the present invention, wherein the primer composition at least partially covers the polymeric substrate and forms a primer layer upon drying. The polymeric substrate is preferably an inkjet printed or printable substrate. Further the primer layer is preferably an ink-receptive primer layer. In some embodiments, there is provided the ink-receptive primer layer on the polymeric substrate, the ink-receptive primer layer being obtained by the primer composition of the present invention comprising a polyacrylic binder (PA) and / or a polyurethane binder (PU), and at least two distinct types of inorganic particles.The primer composition of the shaped article comprises at least two distinct types of inorganic fillers, a first inorganic filler and a second inorganic filler. Further, the first inorganic filler preferably comprises calcium carbonate particles (chalk or micro chalk) and the second inorganic filler may preferably comprise a blend of silica with (lamellar) kaolinite. Upon drying, this primer composition forms a primer layer. The primer layer is preferably an inkjet-printable primer layer for forming an inkjet printed substrate.

[0249] This primer layer may have a peel strength of at least 20 N / 50 mm, ensuring strong adhesion, and a surface energy of at least 30 mJ / m2, which facilitates compatibility with the aqueous ink composition or other coatings. Additionally, the primer layer may have a thickness in the range of 1 pm to 20 pm, preferably in the range of 4 pm to 10 pm. Optionally, on top of theprimer layer, a decorative layer can be applied on to provide customizable designs, colours, or patterns, wherein the decorative layer comprises the aqueous ink composition according to the present invention. Further, a wear-resistant layer can be applied over the decorative layer, offering a protection against abrasion, scratches, and other forms of mechanical wear.

[0250] The shaped article may also include design flexibility, allowing it to be produced in various forms such as sheets, films, moulded components, or three-dimensional objects. Its layered construction ensures compatibility with processes like thermoforming, injection molding, or lamination.

[0251] In an embodiment, there is provided a shaped article comprising: a polymeric substrate, a primer layer applied onto the polymeric substrate. The primer layer comprises the primer composition having at least one polymeric binder, at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles; and water, a decorative layer applied on top of the primer layer. Further, the decorative layer comprises the aqueous ink composition, wherein the aqueous ink composition comprises water and at least two different water-soluble organic solvents, wherein the at least two different water-soluble organic solvent are selected from a group consisting of alkyl diols (alkane diols). Further, each water-soluble organic solvent has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C, preferably of from 15 to 75 mN / m at 20°C, more preferably 20 to 75 mN / m at 20°C.

[0252] Further, the aqueous ink composition may comprise a third water-soluble organic solvent selected from a group consisting of alkyl triols with a surface tension within 10 to 80 mN / m at 20° C. Preferably, the third water-soluble organic solvent is alkyl triol, more preferably the third water soluble organic solvent is glycerol.

[0253] Further, the polymeric substrate used in the shaped articles is preferably a thermoplastic substrate selected form the group consisting of from the group consisting of polyvinyl chloride (PVC), polyolefin, polyester, polystyrene or polyamide. The polymeric substrate is preferably an inkjet printed substrate.

[0254] In further converting steps the printed coated / primed polymeric substrate may be laminated with polymer films or polymer film laminates, papers, metal foils, or laminates comprising metal foils or it may be embossed.

[0255] The shaped article can be a decorative covering for walls, floors, or ceilings or alternative coverings. It may also be utilized in outdoor applications, such as printed tarpaulins for advertisements or weather-resistant covers. Other examples include custom-printed laminates for furniture, automotive interiors, and durable labels or signage for industrial use.

[0256] Blocking test and analysis: A laminate was formed by sequentially applying a primer composition according to the present invention, an aqueous ink composition, and wear-resistant layer onto a thermoplastic substrate. The primer composition was applied using a bar coater (K- bar), achieving a wet film thickness of approximately 12 pm. The primer composition was then dried under air ventilation forming a primer layer. A portion of the primed substrate was used for performing the blocking test.

[0257] Fig. 1 shows a main effects plot (Y, X) (Y vs. X) illustrating the results of the blocking test.

[0258] The blocking test was performed in accordance with ISO 24343-1 .

[0259] With reference to Fig. 2, the following numbers represent:! - acrylic self-cross-linking dispersion, 2- polyurethane binder (Baybond PU 404), 3-polyurethane binder (Daotan VTW6421 ), 4-boehmite, 5-no filler, 6- blend of silica and (lamellar) kaolinite particles; In the results, a higher value on the Y-axis indicates better blocking resistance. The results show that acrylic binder 1 achieves better blocking resistance compared to polyurethane binders 2 and 3, as indicated by the higher values on the Y-axis. The addition of two inorganic fillers (4 or 6) and calcium carbonate (chalk) to the acrylic binder also demonstrates a positive effect on blocking resistance. The plot demonstrates a synergistic effect in enhancing blocking resistance through the combination of calcium carbonate (chalk) and a blend of silica with kaolinite, or boehmite (aluminium oxide hydroxide) particles, and also in combination with the acrylic binder. This improvement is attributed to the creation of a rougher surface on the thermoplastic substrate.

[0260] Delamination test: A laminate was formed by sequentially applying a primer composition according to the present invention, an aqueous ink composition, and wear-resistant layer onto a thermoplastic substrate. The primer composition was applied using a bar coater (K- bar), achieving a wet film thickness of approximately 12 pm. The primer composition was then dried under air ventilation forming a primer layer. Next, the aqueous ink composition was applied to the primed thermoplastic substrate (for example by either using a K-bar or by digital printing) resulting in a wet film thickness of approximately 6 pm, followed by air-drying. Finally, a wearresistant layer was applied over the ink-coated and primed thermoplastic substrate to complete the laminate.

[0261] The laminate was subjected to delamination tests to assess the bonding strength and durability of the layered structure under various conditions.

[0262] Fig.3 demonstrates that the use of acrylic binder 1 results in higher delamination compared to polyurethane resins 1 and 2. However, the delamination observed with acrylic binder 1 significantly decreases when inorganic particles such as boehmite 4, or a blend of silicaand kaolinite particles 6 are incorporated into the primer composition. The delamination is further reduced when calcium carbonate (chalk) is added to the acrylic binder in the primer composition.

[0263] Fig. 3 shows a main effects plot (Y, X) for delamination results of the test with different binder and inorganic fillers. A higher value on the Y-axis indicates lower delamination or a higher peel strength;

[0264] With reference to Fig. 4, the following numbers represent: 1 - acrylic self-cross-linking dispersion, 2- polyurethane binder (Baybond PU 404), 3-polyurethane binder (Daotan VTW6421 ), 4-boehmite, 5-no filler, 6- blend of silica and kaolinite particles (Siltin Z89).

[0265] Fig. 5 FIG. 5 illustrates an interaction plot for blocking performance (rated 10=good, 0=bad). The comparison covers three binder systems, an acrylic polymer (e.g. Neocryl 1 131A, Baybond PU 404® polyurethane resin, and Daotan® VTW6421 . The acrylic binder delivers the best blocking resistance, achieving the highest scores across the evaluated conditions.

[0266] Figure 6A illustrates the print quality obtained in digital inkjet printing with the primer composition comprising a single polyacrylate primer (Table 1 ). The printed line shows some edge bleeding. While the primer composition performs adequately for certain applications, these observations suggest that there is room for improvement in achieving sharper, more controlled print lines.

[0267] Fig. 6B illustrates the print quality of the polyacrylate / polyurethane primer blend (ratio 80 / 20, see Table 3). Compared to the pure polyacrylate, the printed line shows reduced edge bleeding and somewhat improved definition.

[0268] Fig. 6C illustrates the print quality achieved with primer composition on a polymeric substrate, the primer composition comprising the polyacrylate / polyurethane (ratio 50 / 50, Table 3, Ex. 4) binder blend. In this formulation, the printed line appears well-defined with virtually no bleeding,

[0269] Figs. 7A, 7B, and 7C show microscopic images of coated PVC substrates obtained with a Leitz Fluovert microscope equipped with a USB-camera. The substrates were primed with the primer composition described in Table 3 and imaged under external LED illumination. These figures provide representative micrographs of the primer-coated surfaces. The observed surface features demonstrate the characteristic microstructure produced by the primer compositions of the present invention. In particular, the images reveal that the primer composition forms a microrough surface topography that enhances the suitability of the primed substrate for subsequent printing.

[0270] FIG. 8A illustrates an image showing print quality obtained using a primer composition without (i) poly(vinyl alcohol) and without (ii) poly(diallyldimethylammonium chloride).

[0271] FIG. 8B illustrates an image showing print quality obtained using a primer composition including poly(diallyldimethylammonium chloride).

[0272] FIG. 8C is an image showing print quality obtained using a primer composition including poly(vinyl alcohol).

[0273] FIG. 9A and 9B are images showing print quality obtained using a primer composition including poly(vinyl alcohol) and different concentrations of poly(diallyldimethylammonium chloride).

[0274] From the above it is clear that In particular, primer compositions may be formulated such that it exhibits no blocking at 30 kg / cm2, providing delamination resistance above 30 N / 50 mm, maintaining a viscosity of approximately between 60 -500 cP at 400 rpm, and demonstrating good spreadability under typical printing conditions.

[0275] The following examples provide illustrative and non-limiting example of primer compositions in accordance with the present disclosure.

[0276] Examples

[0277] Example I: Primer compositions (see Table 1 for exemplified primer compositions) were prepared by mixing an acrylic self-crosslinking binder dispersion, calcium carbonate particles (micro chalk)( by Socal P2, CAS 471341 ), a mixture of silica and kaolinite (Sillitin Z89), water, a defoamer (BYK016) and a surfactant. The mixture was stirred at room temperature (20-25°C) at a speed of 700-1000 rpm for 1 hour. The viscosity measured is 128 cP at shear rate of 400 rpm.

[0278] Table 1 : Typical Primer Compositions

[0279] Table 2 presents further examples of primer compositions, and the corresponding composition of the primer layer formed after the primer composition has dried.Table 2: Primer composition and dried and

[0280] Example II: Primer compositions (Table 1 B) were prepared by mixing an acrylic selfcrosslinking binder dispersion (Neocryl A-1131 ) and polyurethane (Bay bo nd PU404) as shown in Table 3. Further calcium carbonate particles (micro chalk by Socal P2, CAS 471341 ), the mixture of silica and kaolinite (Sillitin Z89), water, a defoamer (BYK016), PVOH and a surfactant were added and then stirred for 1 hour at 1000 rpm. In each case, a mixture of Neocryl A-1131 and Baybond PU404 was employed. In examples 1 , 24, 5 and 8, 50 / 50 mixture was employed; in example

[0281] Tables 3A and B show the exact compositions of the exemplified primer formulations:Table 3A: Examples 1 to 8

[0282] Some of the print quality results are visually represented in Figures 8A-8C for selected exemplary primer compositions. Specifically, Ex. 1 in Table 3 is represented by the image shown in FIG. 8A, which illustrates print quality obtained using a primer composition that does notinclude poly(vinyl alcohol) or poly(diallyldimethylammonium chloride). Ex.8 in Table 3 corresponds to FIG. 8B, which illustrates print quality obtained using a primer composition including poly(diallyldimethylammonium chloride) and demonstrates improved print definition relative to FIG. 8A. In addition, Ex. 4 in Table 3 correlates to FIG. 8A, further confirming the print quality characteristics observed for primer compositions lacking both poly(vinyl alcohol) and poly(diallyldimethylammonium chloride).

[0283] Two additional primer composition examples , Ex. 1 1 and 12 were prepared, adding 1 % and 3 %, respectively, of poly(diallyldimethylammonium chloride, thereby forming compositions comprising each poly(vinyl alcohol) and poly(diallyldimethylammonium chloride). Examples 9 and 10 are shown in Table 3B below:Table 3B: Additional examples

[0284] The print quality results are visually represented in Figures 9A and B for exemplary primer compositions 1 1 and 12. Fig. 9A corresponds to Example 11 , and Fig.9B corresponds to Example 12. A side-by-side comparison shows that by adding more polydadmac (3%), bleeding of the ink is improved, but streaks are becoming visible. Without wishing to be bound by theory, it is considered that this is due to the fact that the pigments agglomerate very fast on the surface and have little time to spread. On the other hand, by adding a lower amount of polydadmac (1 %), streaks are much less visible. Without wishing to be bound by theory, it is considered that this is due to the fact that in this example, pigments have more time to spread, but ton the other hand, bleeding becomes visible. The following example provides an illustrative and non-limiting example of an aqueous ink composition in accordance with the present invention (see Table 4).

[0285] Table 4: Example of an aqueous ink composition according to the present invention.

[0286] Table 5 presents non-limiting examples of chemical compounds and their diverse physical properties within various aqueous ink compositions. Each composition contains distinct organic solvents. In Table 1 , the vapor pressure, and viscosity (measured using an Anton Paar viscometer, ASTM D7042) of different organic solvents are specified for each non-limiting example of aqueous ink compositions. Examples 1 , 2, 7, 9, 10, 1 1 and 12 are in accordance with the present invention. Examples 3, 4, 5, 6 and 8 are comparative examples. The ink compositions are in wt %.Table 5: Use of different diolsTable-5 continuedTable 6 presents non-limiting examples of chemical compounds and their diverse physical properties within various aqueous ink compositions. Examples 1 and 2 are in accordance with the present invention. Examples 3 to 8 are comparative examples. The Examples 1 -8 are corresponding to the compositions in TABLE 5.Table 6: Results

[0287] Examples 1 and 2 in Table 7 are in accordance with the present invention. Examples 3 to 8 are comparative examples. The Examples 1 -8 correspond to the compositions in TABLE 1 .

[0288] Table 7 illustrates the results of a test where a 6 pm (micrometer) thick coating layer is dried using infrared (IR) light and the PVC substrate is passed at a speed of 50 mm / s. The table details the number of passes required to fully dry the coating under these conditions. Another Example details the duration required to evaporate 90% of the solvent under three distinct temperature conditions: 30°C, 80°C, and 120°C, all while maintaining an air flow rate of 1 m / s.Table 7: Primer Measured Data

[0289] The above examples show the uniquely effective performance of the primer compositions according to the present disclosure.

Claims

56CLAIMS1 . A primer composition for surface treatment of a polymeric substrate for digital inkjet printing, comprising:(a) at least one polymeric binder,(b) at least two distinct types of inorganic fillers, wherein each inorganic filler comprises inorganic particles, and(c) water.

2. The primer composition according to claim 1 , wherein upon curing or drying, the primer composition is configured to form a primer layer having a surface with a surface energy of at least 30 mJ / m2upon curing, preferably with a surface energy in the range between 30 mJ / m2and 80 mJ / m2, and wherein the primer layer is an ink-receptive primer layer configured to receive aqueous ink composition and wherein the primer composition is an ink -receiving primer composition3. The primer composition according to claim 2, wherein the two distinct types of inorganic fillers are defined as a first inorganic filler and second inorganic filler, wherein the first inorganic filler comprises calcium carbonate particles.

4. The primer composition according to claim 3, wherein the calcium carbonate particles have a particle size distribution with a median diameter (D50) ranging from 0.15 pm to 15 pm, more preferably 0.2 pm to 10 pm, as determined by dynamic light scattering (DLS).

5. The primer composition according to claim 3 or claim 4, wherein the second inorganic filler is selected from the group consisting of aluminium hydroxide oxide particles, or from inorganic particles comprising a blend of silica and kaolinite particles, or a composite material comprising silica and kaolinite particles, wherein the silica particles are deposited on kaolinite particles, or kaolinite particles are deposited on silica particles.

6. The primer composition according to claim 5, wherein the aluminium hydroxide oxide particles have a particle size distribution with a median diameter (D50) ranging from 0.5 pm to 10 pm, preferably from 0.5 pm to 5 pm, as determined by laser diffraction.

577. The primer composition according to claim 4 or claim 5, wherein the blend of silica and kaolinite particles have a particle size distribution with a median diameter (D50) ranging from 0.5 pm to 10 pm, preferably from 0.5 pm to 5 pm.

8. The primer composition according to any one of claims 1 to 7, having a surface tension in the range of from 20 mN / m to 80 mN / m at 20°C, as determined by ASTM D1331 .

9. The primer composition according to any one of claims 1 to 8, having a viscosity in the range of 60 cP (mPa-s) to 500 cP (mPa-s) at 25 °C, measured at a shear rate corresponding to 400 rpm at 25°C, as determined by ASTM D2196.

10. The primer composition according to any one of claims 1 to 9, comprising of from 10 % to 80 % by weight of at least one polymeric binder relative to the total weight of the primer composition, or a blend or a mixture of polymeric binders.11 . The primer composition according to any one of claims 1 to 10, comprising of from 5 % to 50 % by weight of a first inorganic filler relative to the total weight of the primer composition.

12. The primer composition according to f any one of claims 1 to 1 1 , comprising of from 2 % to 20 % by weight of a second inorganic filler relative to the total weight of the primer composition.

13. The primer composition according to any one of claims 3 to 12, wherein the weight ratio between the first and second inorganic particles is in the range from 1 :1 to 30:1 , preferably from 1.5 :1 to 20:1 , more preferably from 1 .5 :1 to 15:1 .

14. The primer composition according to any one of claims 1 to 13, wherein the polymeric binder is selected from one or more acrylic polymers or acrylic co-polymers, or a blend or mixture of acrylic polymers or co-polymers with polyurethane, wherein the ratio between the acrylic polymer or co-polymer and the polyurethane in the blend or mixture is in the range of from 1 :5 to 5:1 , preferably 2 :1 to 1 :2, wherein the acrylic polymer or acrylic co-polymer is self-crosslinking, or an acrylic self-crosslinking dispersion comprising a self-crosslinking acrylic polymer or copolymer.5815. The primer composition according to any one of claims 1 to 14, has a thickness ranging of from 1 pm to 50 pm, preferably of from 5 pm to 30 pm.

16. The primer composition according to any one of the preceding claims, further comprising one or more additives selected from poly(dia Uy I dimethyl ammonium chloride) (poly(DADMAC)), polycarbodiimide (PCDI), alkyltrialkoxysilane, polyvinyl alcohol, and / or additional CaCO3with a median diameter (D50) ranging from 0.15 pm to 15 pm as determined by DLS, or any combinations thereof.

17. The primer composition according to any one of the preceding claims, further comprising at least one additive selected from polyvinyl alcohol and / or poly(diallyl dimethyl ammonium chloride) (poly(DADMAC)).

18. Use of the primer composition according to any of any one of claims 1 to 17 for coating a polymeric substrate to obtain a primer layer configured to receive an aqueous ink composition by means of digital inkjet printing.

19. An ink and primer system for image formation on a polymeric substrate surface comprising:(a) the primer composition according to any one of any one of claims 1 to 17 for surface treatment of a polymeric substrate prior to applying an aqueous ink composition, and(b) an aqueous ink composition comprising water and at least two different water-soluble organic solvents, wherein the at least two different water-soluble organic solvent are selected from a group consisting of alkyl diols, and wherein each water-soluble organic solvent has a distinct surface tension falling in the range of from 10 to 80 mN / m at 20°C.

20. The ink and primer system according to claim 19, wherein the alkyl diols (alkane diols) have carbon chain lengths ranging from C3to C8, preferably C3to C6.21 . The ink and primer system according to any one of claims 18 to 20, wherein the alkyl diols (alkane diols) are selected from 1 ,2 propanediol, 1 ,3-propanediol, 2-methyl-1 ,3- propanediol, 1 ,2-butanediol, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,2 -pentanediol, 2,3-pentanediol, 1 ,5-pentanediol, 1 ,5 hexanediol, 2,5-hexanediol, 1 ,6-hexanediol, 1 ,2-hexanediol, 2,3-hexanediol, 1 ,7- heptanediol, and 1 ,8-octanedioL5922. The ink and primer system of any one of claims 18 to 21 , further comprising a third water- soluble organic solvent.

23. The ink and primer system of any one of claims 18 to 22, wherein the first water-soluble organic solvent is 1 ,2-hexanedioL24. The ink and primer system of claim 18 or 23, wherein the second water soluble organic solvent is 1 ,3-butanedioL25. The ink and primer system of any one of claims18 to 24, wherein the third water-soluble organic solvent, wherein the third water-soluble organic solvent is alkyl triol (alkane triol).

26. The ink and primer system of any one of claims 18 to 25, wherein each of the first, second and third water-soluble organic solvents has a distinct surface tension falling in the range of from 15 to 75 mN / m at 20°C, preferably 20 to 75 mN / m at 20°C, as determined by ASTM D1331 ..

27. The ink and primer system of any one of claims 18 to 26, wherein the third water soluble organic solvent is glycerol.

28. The ink and primer system of any one of claims 18 to 27, wherein a weight ratio of glycerol to1 ,2- hexanediol based on the total weight of the aqueous ink composition is between 10:1 to 1 :10, preferably between 1 :1 and 1 :5.

29. The ink and primer system of any one of claims 18 to 28, wherein the aqueous ink composition has a surface tension in the range of from 15 mN / m to 45 mN / m at 25°C, as determined by ASTM D1331 -20.

30. A shaped article comprising: a polymeric substrate, a primer layer formed upon drying from a primer composition according to any one of claims 1 to 16 and at least partially covering the polymeric substrate.6031 . The shaped article according to claim 30, further comprising a decorative layer applied on top of the primer layer, wherein the decorative layer comprises the aqueous ink composition according to anyone of any one of claims 18 to 29.

32. The shaped article according to any one of claims 30 or 31 , further comprising a wearresistant layer applied on top of the decorative layer.

33. The shaped article according to any one of claims 30 to 32, wherein the primer layer has a peel strength of at least 20 N / 50 mm.

34. The shaped article according to any one of claims 30 to 33, wherein the primer layer has a surface energy of at least 30 mJ / m2.

35. The shaped article according to any one of claims 30 to 34, wherein the primer layer has a thickness in the range of 1 pm to 20 pm, preferably in the range of 4 pm to 10 pm.

36. The shaped article of any one of claims 30 to 35, wherein the polymeric substrate is a thermoplastic substrate selected form the group consisting of from the group consisting of polyvinyl chloride (PVC), polyolefin, polyester, polystyrene or polyamide.

37. Method for preparation of a shaped article according to any one of claims 30 to 36, comprising providing a polymeric substrate, applying an ink and primer system according to any one of claims 19 to 29, by first applying the primer composition, then printing, preferably by digital printing, a decorative layer on the primed polymeric substrate with the aqueous ink composition, drying the aqueous ink composition to form a printed polymeric substrate.

Images