WO2025011645A1

WO2025011645A1 - Sprayable waterborne ink system

Info

Publication number: WO2025011645A1
Application number: PCT/CN2024/105207
Authority: WO
Inventors: Xueni XU; Wei Wang; Hao Shi; Ninggang SUN
Original assignee: PPG Coatings Tianjin Co Ltd
Current assignee: PPG Coatings Tianjin Co Ltd
Priority date: 2023-07-13
Filing date: 2024-07-12
Publication date: 2025-01-16
Anticipated expiration: 2026-01-13
Also published as: TW202502978A; CN119307131A

Abstract

Disclosed is a sprayable waterborne ink system, comprising a first waterborne ink composition and a second waterborne ink composition, wherein the first waterborne ink composition comprises a binder comprising a heat-activable resin which is activable at a temperature of at least 120℃, and wherein the second waterborne ink composition comprises a binder comprising a high-temperature crosslinkable resin which is crosslinkable at a temperature of at least 120℃. Also disclosed is a substrate coated with the waterborne ink system. Also disclosed is a method of treating a glass substrate, comprising: applying the waterborne ink system onto at least a part of the substrate, wherein the first waterborne ink composition is applied to the substrate prior to application of the second waterborne ink composition.

Description

SPRAYABLE WATERBORNE INK SYSTEM

TECHNICAL FIELD

The present invention relates to the field of inks, and in particular to a sprayable waterborne ink system.

BACKGROUND

Ink is usually applied by printing onto a surface of objects/substrates to be printed. However, there are limitations to printing for application onto a non-planar surface, such as, a 3D surface. With the widespread application of 3D glass in the consumer electronics industry, there is a need to develop an ink that can be applied to 3D glass substrates by spraying.

In addition, with increasingly strict national requirements for environmental protection, the use of solvent-based inks is restricted more and more, and the market demand for waterborne inks continues to expand. Therefore, how to provide a waterborne ink with excellent performances is also a research hotspot in the field of inks at the current stage.

SUMMARY

The inventor has conducted an extensive research and developed a sprayable waterborne ink system that has excellent comprehensive performances while meeting the requirements for environmental protection.

The present invention provides a sprayable waterborne ink system, comprising a first waterborne ink composition and a second waterborne ink composition, wherein the first ink composition comprises a binder comprising a heat-activable resin which is activable at a temperature of at least 120℃, and wherein the second ink composition comprises a binder comprising a high-temperature crosslinkable resin which is crosslinkable at a temperature of at least 120℃.

The present invention further provides a coated substrate, comprising a substrate and the waterborne ink system applied on at least a part of the substrate.

The invention further provides a method of treating a glass substrate, comprising:

applying the waterborne ink system to at least a part of the substrate, wherein the first waterborne ink composition is applied to the substrate prior to application of the second waterborne ink composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a 3D glass substrate coated by spraying with the waterborne ink system of Examples 1-3.

DETAILED DESCRIPTION

In the present application, unless expressly stated otherwise, the use of a singular comprises a plural and the use of a plural comprises a singular. For example, even though “a” resin is mentioned herein, one or more of such substances can be used.

In the present application, the terms such as, “comprise/comprising” , “contain/containing” and “include/including” are not intended to limit the present invention to exclude any variations or additions. Furthermore, even though the present invention has described the ink compositions, preparation methods and the like with “comprising” or similar terms, those ink compositions, preparation methods and the like can also be described as “consisting essentially of” or “consisting of” . In this case, “consisting essentially of” means that any additional components will not produce any substantive effect on the properties of the film layer formed by the ink composition.

In the present application, unless expressly stated otherwise, the use of “or” means “and/or” , even though “and/or” can be expressly used in some cases. In addition, it is to be understood that any numerical range listed herein is intended to encompass all the sub-ranges included therein. For example, a range of “1 to 10” is intended to comprise all the sub-ranges between the listed minimum value of 1 and the listed maximum value of 10 (including the end values) , namely, all the sub-ranges with a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10.

Unless described in the examples or otherwise explicitly stated, it is to be understood that all numerical values representing the quantities of ingredients or the like as used in the description and claims can vary in all substances as is modified with the term “about” . Thus, unless indicated to the contrary, the numerical parameters listed in the following description and the accompanying claims are all approximations, and can be varied depending upon the properties to be obtained by the present invention. At the least, it is not intended to limit the application of the doctrine of equivalents to the scope of claims. Each numerical parameter should at least be interpreted based on significant figures and ordinary rules of rounding.

Although the numerical ranges and parameters describing the broad scope of the present invention are approximations, the numerical records listed in the particular examples should be reported as precisely as possible. However, any one value inherently has a certain error, which is an inevitable consequence of standard deviation found in its corresponding measurement method.

As described above, the present invention relates to a sprayable waterborne ink system, comprising a first waterborne ink composition and a second waterborne ink composition, wherein the first ink composition comprises a binder comprising a heat-activable resin which is activable at a temperature of at least 120℃, and wherein the second ink composition comprises a binder comprising a high-temperature crosslinkable resin which is crosslinkable at a temperature of at least 120℃.

As used herein, the term “sprayable” means that the ink composition in the ink system is suitable for application with a spay device, in which context, the ink composition has an initial viscosity of 90 KU or less (as measured using a Brookfield KU-3 viscometer according to ASTM D562-10 2023) and can be thinned to an application viscosity of 15-35 seconds (as measured using a Zahn 3#viscosity cup) . As used herein, the "first waterborne ink composition" or "first waterborne ink" or "first ink" refers to a first waterborne ink composition prior to drying or curing, i.e., which has not undergone drying or curing yet; and the "second waterborne ink composition" or "second waterborne ink" or "second ink" refers to a second waterborne ink composition prior to drying or curing, i.e., which has not undergone drying or curing yet.

The first waterborne ink composition according to the invention is a two-package composition. The "two-package composition" means that the ingredients of the ink composition are packaged separately, and then the two packages are mixed in an accurate proportion before use.

The second waterborne ink composition according to the present invention can be a two-package composition. Alternatively, the second waterborne ink composition according to the invention can be a one-package composition. The "one-package composition" means that the ingredients of the ink are all contained in one package, and thus have an advantage of convenient use.

The first waterborne ink composition according to the present invention can be a thermoset composition. The second waterborne ink composition according to the present invention can be a thermoset composition. After curing, the thermoset coating composition will irreversibly form a coating film, which will not melt upon reheating and cannot be dissolved in a solvent. Herein, the term “curing/cured” means that at least some ingredients of the ink composition are polymerized and/or crosslinked, or have been dried to form a hardened coating film.

The first waterborne ink composition according to the present invention can be cured by heating. The second waterborne ink composition according to the present invention can be cured by heating. The first waterborne ink composition and the second waterborne ink composition according to the present invention can be cured at 140-150℃ within 20-35 min, respectively. Suitably, the first waterborne ink composition /the second waterborne ink composition according to the present invention can be fully cured at 150℃ within 30 min. By "fully cured" , it is meant that the ink layer has a MEK double wipe value of at least 50 times, such as, a MEK double wipe value of 70 times.

An ink layer formed from the first waterborne ink composition according to the present invention can have a dry film thickness of 30-40 μm. An ink layer formed from the second waterborne ink composition according to the present invention can have a dry film thickness of 15-20 μm. The "dry film thickness" refers to a thickness of fully cured ink layer.

The first waterborne ink composition according to the present invention can have a solid content of 20-35 wt%. The second waterborne ink composition according to the present invention can have a solid content of 20-35 wt%. Herein, the "solid content" refers to a ratio of a mass remaining after drying of the ink composition to the total mass of the original composition.

The first waterborne ink composition according to the present invention can have a shear thinning property. The second waterborne ink composition according to the present invention can have a shear thinning property. The shear thinning property means that the viscosity of the ink composition decreases with the increase of the shear force, that is, the ink composition has a high viscosity at low shear force, and a low viscosity at high shear force.

The first waterborne ink composition according to the present invention can have an initial viscosity at room temperature of 60-80 KU as measured using a Brookfield KU-3 viscometer according to ASTM D562-10 2023. The second waterborne ink composition according to the present invention can have an initial viscosity at room temperature of 60-80 KU as measured using a Brookfield KU-3 viscometer according to ASTM D562-10 2023. The initial viscosity refers to the storage viscosity of an ink composition, i.e., prior to any thinning/diluting process. The first waterborne ink composition according to the present invention can have an application viscosity at room temperature of 15-35 seconds as measured by a Zahn 3#viscosity cup. The second waterborne ink composition according to the present invention can have an application viscosity at room temperature of 15-35 seconds as measured by a Zahn 3#viscosity cup. The application viscosity can be measured under the following conditions: the composition is dispersed at 700-1000 rpm in a disperser for 15-30 min until fully dispersed, diluted at room temperature (at a composition-to-water mass ratio of 100 : 0-20) , and then measured. The room temperature refers to 15-30℃, such as 23℃.

The first waterborne ink composition and the second waterborne ink composition having the specific properties can be suitable for spray application, which is beneficial for coating a non-planar surface, such as, a 3D surface, and therefore can overcome the printing problem. The first waterborne ink composition and the second waterborne ink composition according to the present invention are sprayable.

As used herein, the term "waterborne" means that the solvent of the ink composition contains at least 50 wt%of water based on the total weight of the solvent. The waterborne ink system according to the present invention has a low VOC content. As used herein, the term "VOC (volatile organic compound) " refers to any organic compound having a boiling point lower than or equal to 250℃ (482°F) as measured at standard atmospheric pressure of 101.3 kPa. Organic solvents are often the main source of VOCs. Suitably, the waterborne ink system according to the present invention has a VOC content of no more than 200 g/L. Suitably, the first waterborne ink composition according to the present invention can have a VOC content of 70-80 g/L. Suitably, the second waterborne ink composition according to the present invention can have a VOC content of 80-90 g/L. The VOC values are those obtained without taking account of water, which can be obtained by detecting the contents of various organic compound ingredients in the ink composition by gas chromatography, followed by adding up the contents of the various ingredients.

Herein, the "binder" refers to an ingredient in the ink composition that can be crosslinkable/polymerizable with each other or dried to form a film, such as, a resin.

Herein, the "heat-activable resin" refers to a resin that will produce a certain viscosity and fluidity when the temperature is higher than a certain critical value (near the glass transition temperature) , which helps to provide an adhesion between the substrate and the layer.

Herein, the "high-temperature crosslinkable resin" refers to a resin that will self-crosslink or crosslink with other components at a high temperature (i.e., 120℃ or more) . Suitable high-temperature crosslinkable resins for use in the second waterborne ink composition can comprise a hydroxyl and/or carboxyl-containing resin and an amine resin.

Suitable heat-activable resins for use in the first waterborne ink can comprise a polyurethane. The polyurethane refers to a polymer containing urethane groups as repeating units. The polyurethane can comprise a polymer in which at least 50 wt%of organic units, e.g., at least 70 wt%of organic units, such as, at least 90 wt%of organic units, are linked via urethane bond. Herein, the organic units comprise one or more residues selected from simple glycols, such as, butanediol, polyester diol, polyether diol, and polycarbonate diol.

Suitably, the polyurethane can comprise an aliphatic polyurethane. The aliphatic polyurethane can be prepared from an alcohol and an aliphatic isocyanate. The aliphatic isocyanate comprises one or more selected from the group consisting of hexamethylene diisocyanate (HDI) , isophorone diisocyanate (IPDI) , and dicyclohexylmethane-4, 4'-diisocyanate (HMDI) .

Suitably, the polyurethane can have an elongation at break of 600-800%, as determined with reference to ASTM D882. For example, the polyurethane can have an elongation at break of 650%, 700%, or 750%. For example, the polyurethane can have an elongation at break of 600%or more, 650%or more, or 700%or more, and/or, 800%or less, or 750%or less. For example, the polyurethane can have an elongation at break of 650-750%, 700-750%, or within a range using any other combination of the above endpoints. The elongation at break refers to a ratio of the post-stretching elongation length to the pre-stretching length when the material is broken due to external stretching force. Suitably, the polyurethane can have a 100%modulus of 1 to 5 N/mm², as determined with reference to ASTM D882. For example, the polyurethane can have a 100%modulus of 2 N/mm², 3 N/mm², or 4 N/mm². For example, the polyurethane can have a 100%modulus of 1 N/mm² or more, 2 N/mm²or more, or 3 N/mm²or more, and/or, 5 N/mm²or less, or 4 N/mm²or less. For example, the polyurethane can have a 100%modulus of 1 to 4 N/mm², 2 to 4 N/mm², or within a range using any other combination of the above endpoints. The 100%modulus refers to a tensile strength at an elongation of 100%.

Suitably, the polyurethane can be in form of a dispersion. The polyurethane dispersion can have a solid content of 35-45 wt%, as determined according to the DIN EN ISO 3251 (2019) standard. The “solid content” refers to a percentage of the remaining mass after evaporation based on the mass of the original dispersion. Suitably, the polyurethane dispersion can have a pH of no more than 8.5, such as, 7-8.5, as determined with reference to the DIN ISO 976. Suitably, the polyurethane dispersion can have a viscosity at room temperature of no more than 220 cps, such as, 20-200 cps, as determined with reference to ISO 1652 using the Brookfield RVT Spindle 1/rpm 20/factor 5. The room temperature refers to 15-30℃, such as 23℃.

The polyurethane has suitable elongation at break and 100%modulus, which enhance the flexibility of the ink. Such characteristics of the polyurethane ensure that the ink can maintain a relatively flexible performance even at a temperature of -60℃, increasing the tensile strength that the ink can withstand. In addition, the polyurethane has a good film-forming property and a certain degree of self-crosslinking at high temperature (i.e., 120℃ or more) , so that the ink has relatively good mechanical properties (such as, good initial adhesion) even without additional crosslinking agents.

Based on the solid weight of the heat-activable resin, the heat-activable resin can comprise at least 75 wt%, suitably at least 80 wt%, such as, 85 wt%or more, e.g., 90 wt%or more, such as, 95 wt%or more, or even 100 wt%of the polyurethane resin.

Based on the total weight of the first waterborne ink composition, the polyurethane can comprise about 10 wt%or greater, suitably at least about 15 wt%, suitably at least about 20 wt%, and/or up to about 35 wt%, such as, up to about 30 wt%, suitably up to about 25 wt%of the first waterborne ink composition. Based on the total weight of the first waterborne ink composition, the polyurethane can comprise about 10-35 wt%, suitably 15-30 wt%, such as, 20-25 wt%, or in any other combinational ranges using these endpoints.

The heat-activable resin constitutes the binder of the first waterborne ink composition. Suitably, the heat-activable resin can comprise at least 80 wt%of the total solid weight of the binder of the first waterborne ink composition. For example, the heat-activable resin solid can comprises 85 wt%or more, 90 wt%or more, 95 wt%or more, or 100 wt%of the total solid weight of the binder of the first waterborne ink composition.

The first waterborne ink composition according to the present invention can further comprise a pigment/filler. The pigment/filler can provide the ink with colors, effects and/or functions, and can comprise a colored pigment and a filler (also known as an extender pigment) . Suitably, the pigment comprises an inorganic pigment. Compared with an organic pigment, the inorganic pigment improves the UV resistance of the waterborne ink. Suitably, the inorganic pigment can comprise an inorganic metal oxide, such as, titanium white, iron red, or carbon black. Suitably, the filler comprises fumed silica.

In the first waterborne ink composition, a solid weight ratio of the binder to the inorganic pigment can be 5: 2 to 5: 10. For example, the solid weight ratio of the binder to the inorganic pigment can be 5: 3, 5: 4, 5: 5, 5: 6, 5: 7, 5: 8 or 5: 9. For example, the solid weight ratio of the binder to the inorganic pigment can be 5: 2 or lower, 5: 3 or lower, 5: 4 or lower, 5: 5 or lower, or 5: 6 or lower, and/or, 5: 9 or higher, 5: 8 or higher, or 5: 7 or higher. For example, the solid weight ratio of the binder to the inorganic pigment can be 5: 2 to 5: 8, 5: 2 to 5: 7, or within a range using any other combination of the above endpoints.

Based on the total weight of the first waterborne ink composition, the pigment/filler can comprise 10-50 wt%of the first waterborne ink composition.

The first waterborne ink composition according to the present invention can further comprise an adhesion promoter. Suitably, the adhesion promoter can comprise a silane coupling agent. Suitably, the silane coupling agent comprises an epoxy functional group. Based on the total weight of the first waterborne ink composition, the adhesion promoter can comprise 1-6 wt%, such as, 2-5 wt%of the first waterborne ink composition.

The first waterborne ink composition according to the present invention can further comprise an antifoaming agent. The antifoaming agent can suppress the formation of bubbles and help generated bubbles to escape or collapse during production. Suitably, the antifoaming agent can comprise a silicone-based antifoaming agent. Based on the total weight of the first waterborne ink composition, the antifoaming agent can comprise 0-2 wt%, such as, 0.1-1.5 wt%of the first waterborne ink composition.

The first waterborne ink composition according to the present invention can further comprise a rheological aid. The rheological aid can effectively adjust the viscosity, ensure excellent workability, and avoid fat edges. Suitably, the rheological aid can comprise a polyurethane thickener. Based on the total weight of the first waterborne ink composition, the rheological aid can comprise 0-2 wt%, such as, 0.1-1.5 wt%of the first waterborne ink composition.

The first waterborne ink composition according to the present invention can further comprise a leveling agent. The leveling agent can improve flowability and processability to provide a smooth coating. Suitably, the leveling agent can comprise a silicone-based leveling agent. Based on the total weight of the first waterborne ink composition, the leveling agent can comprise 0-2 wt%, such as, 0.1-1.5 wt%of the first waterborne ink composition.

The first waterborne ink composition according to the present invention can further comprise a solvent. The solvent mainly comprises water, namely, water comprises at least 50 wt%of the solvent by mass. The solvent can further comprise an organic solvent to assist in compatibility of ingredients in the ink composition. Suitably, the organic solvent can comprise an ether solvent. Based on the total weight of the first waterborne ink composition, water can comprise 20-40 wt%of the first waterborne ink composition. Based on the total weight of the first waterborne ink composition, the organic solvent can comprise 1-10 wt% first waterborne ink composition.

Suitably, the first waterborne ink composition according to the present invention can be a two-component composition comprising at least one or more of the above components, wherein a first component comprises a polyurethane resin, a pigment/filler, optional aid (s) and a solvent, and a second component comprises an adhesion promoter. In the two-component composition, the adhesion promoter comprising silane coupling agent and the filler such as silica are packaged separately to avoid any reactions therebetween causing an influence such as increase in viscosity and/or reduce in the effect of the coupling agent, etc.

The high-temperature crosslinkable resin used in the second waterborne ink can comprise a hydroxyl and/or carboxyl-containing resin and an amine resin. The hydroxyl and/or carboxyl-containing resin can comprise a hydroxyl-functionalized (meth) acrylic-styrene polymer. By hydroxyl-functionalized, it means that the polymer contains an active hydroxyl group participating in the crosslinking reaction. The (meth) acrylic-styrene polymer refers to a polymer obtained by the polymerization of a monomer mixture comprising: a methacrylic monomer and/or an acrylic monomer, and a styrene monomer.

Suitably, the hydroxyl-functionalized (meth) acrylic-styrene polymer can have a hydroxyl value of 60-150 mgKOH/g. For example, the hydroxyl-functionalized (meth) acrylic-styrene polymer can have a hydroxyl value of 60 mgKOH/g or more, 80 mgKOH/g or more, or 110 mgKOH/g or more, and/or 150 mgKOH/g or less, 130 mgKOH/g or less, or 120 mgKOH/g or less. For example, the hydroxyl-functionalized (meth) acrylic-styrene polymer can have a hydroxyl value of 80-130 mgKOH/g, a hydroxyl value of 80-120 mgKOH/g, or within a range using any other combination of the above endpoints. The hydroxyl value refers to milligrams of potassium hydroxide (KOH) equivalent to the hydroxyl groups in 1 gram of resin. The hydroxyl value can be determined according to DIN EN ISO 469292: 2016.

Suitably, the hydroxyl-functionalized (meth) acrylic-styrene polymer can have an MFFT (minimum film forming temperature) of 40-80℃. For example, the hydroxyl-functionalized (meth) acrylic-styrene polymer can have an MFFT of 40℃ or more, or 50℃ or more, and/or, 80℃ or less, 70℃ or less, or 60℃ or less. For example, the hydroxyl-functionalized (meth) acrylic-styrene polymer can have an MFFT of 50-70℃, an MFFT of 50- 60℃, or within a range using any other combination of the above endpoints. The MFFT can be measured according to the ASTM D 2354-10 (2018) standard using the MFFT-BAR minimum film forming temperature meter (British RHOPOINT minimum film forming temperature tester MFFT-60/MFFT-90) .

Suitably, the hydroxyl-functionalized (meth) acrylic-styrene polymer can be in form of an emulsion. The hydroxyl-functionalized (meth) acrylic-styrene polymer emulsion can have a solid content of 40-45 wt%, as determined according to the DIN EN ISO 3251 (2019) standard. The "solid content" refers to a percentage of the remaining mass after evaporation based on the mass of the original emulsion. Suitably, the hydroxyl-functionalized (meth) acrylic-styrene polymer emulsion can have a pH of more than 1.0 to 3.0, as determined according to the DIN ISO 976. Suitably, the hydroxyl-functionalized (meth) acrylic-styrene polymer emulsion can have a viscosity at room temperature of 20-50 cps, as determined with reference to the ISO 1652 using the Brookfield RVT Spindle 1/rpm 20/factor 5. The room temperature refers to 15-30℃, such as 23℃.

Based on the total weight of the second waterborne ink composition, the hydroxyl-functionalized (meth) acrylic-styrene polymer can comprise about 5 wt%or greater, suitably at least about 8 wt%, suitably at least about 10 wt%, and/or up to about 20 wt%, such as, up to about 18 wt%, suitably up to about 15 wt%of the second waterborne ink composition. Based on the total weight of the second waterborne ink, the hydroxyl-functionalized (meth) acrylic-styrene polymer can comprise about 5-20 wt%, suitably 8-18 wt%, such as, 10-15 wt%of the second waterborne ink composition, or within any other combinational ranges using these endpoints.

The hydroxyl and/or carboxyl-containing resin can further comprise a polyurethane. The polyurethane can comprise a polyether polyurethane. The polyether polyurethane refers to those that can be prepared from polyisocyanate and polyether polyol. Suitably, the polyurethane can have an acid value of 10-40 mgKOH/g. For example, the polyurethane can have an acid value of 10 mgKOH/g or more, or 20 mgKOH/g or more, and/or 40 mgKOH/g or less, or 30 mgKOH/g or less. For example, the polyurethane can have an acid value of 10-30 mgKOH/g, or within a range using any other combination of the above endpoints. The "acid value” refers to milligrams of potassium hydroxide required by neutralizing the free acid in 1 gram of resin. The acid value can be determined according to DIN EN ISO 2114: 2002-06.

Suitably, the polyurethane can have a Tg (glass transition temperature) of 90-120℃. For example, the polyurethane can have a Tg of 90℃ or more, or 100 ℃ or more, and/or 120℃ or less, or 110 ℃ or less. For example, the polyurethane can have a Tg of 90-110℃, or within a range using any other combination of the above endpoints. The glass transition temperature is measured by dynamic thermomechanical analysis (DMA) using the TA Instruments Q800 instrument with frequency of 10 Hz, amplitude of 5 mm, and temperature ramp of -100℃ to 250℃, and the Tg is determined as the peak of tanδ curve according to the ASTM E1356-23.

Suitably, the polyurethane can be in form of a dispersion. The polyurethane dispersion can have a solid content of 30-35 wt%, as determined according to the DIN EN ISO 3251 (2019) standard. The “solid content” refers to a percentage of the remaining mass after evaporation based on the mass of the original dispersion. Suitably, the polyurethane dispersion can have a pH of 7.0 to 9.0, as determined according to the DIN ISO 976. Suitably, the polyurethane dispersion can have a viscosity at room temperature of 50 to 150 cps, as determined with reference to the ISO 1652 using the Brookfield RVT Spindle 1/rpm 20/factor 5. The room temperature refers to 15-30℃, such as 23 ℃.

Based on the total weight of the second waterborne ink composition, the polyurethane can comprise about 5 wt%or greater, suitably at least about 8 wt%, suitably at least about 10 wt%, and/or about 20 wt%or lower, such as, about 18 wt%or lower, suitably about 15 wt%or lower of the second waterborne ink composition. Based on the total weight of the second waterborne ink composition, the polyurethane can be about 5-20 wt%, suitably 8-18 wt%, such as, 10-15 wt%, or within any other combination ranges using these end values.

In the second waterborne ink composition, a solid weight ratio of the hydroxyl-functionalized (meth) acrylic-styrene polymer to the polyurethane can be 1: 1 to 1: 2.5, suitably, 1: 1 to 1: 2. For example, the solid weight ratio of the hydroxyl-functionalized (meth) acrylic-styrene polymer to the polyurethane can be 1: 1 or lower, 1: 1.1 or lower, 1: 1.2 or lower, 1: 1.3 or lower, 1: 1.4 or lower, or 1: 1.5 or lower, and/or 1: 2 or higher, 1: 1.9 or higher, 1: 1.8 or higher, 1: 1.7 or higher, or 1: 1.6 or higher, such as 1: 1 to 1: 1.9, or within a range using any other combination of the above endpoints. For example, the solid weight ratio of the hydroxyl-functionalized (meth) acrylic-styrene polymer to the polyurethane can be 1: 1.1, 1: 1.2, 1: 1.3, 1: 1.4, 1: 1.5, 1: 1.6, 1: 1.7, 1: 1.8, 1: 1.9 or 1: 2.

The hydroxyl and/or carboxyl-containing resin can further comprise a styrene-methacrylate polymer helping dispersion of the pigment. The styrene-methacrylate polymer is different from the hydroxyl-functionalized (meth) acrylic-styrene polymer. The styrene-methacrylate polymer refers to a polymer formed from a mixture comprising a methacrylic acid monomer and a styrene monomer via copolymerization. Suitably, the styrene-methacrylate polymer can have an MFFT (minimum film forming temperature) of 60-100℃. For example, the styrene-methacrylate polymer has an MFFT of 60℃ or higher, 70℃ or higher, or 80℃ or higher, and/or 100℃ or lower, or 90℃ or lower. For example, the styrene-methacrylate polymer has an MFFT of 70-100℃, an MFFT of 70-90℃, or within a range using any other combination of the above endpoints. The MFFT can be measured according to the ASTM D2354-10 (2018) standard using the MFFT-BAR minimum film forming temperature meter (British RHOPOINT minimum film forming temperature tester MFFT-60/MFFT-90) .

The styrene-methacrylate polymer can be in form of an emulsion. The styrene-methacrylate polymer emulsion can have a solid content of 49-51 wt%, as determined according to the DIN EN ISO 3251 (2019) standard. The "solid content" refers to a percentage of the remaining mass after evaporation based on the mass of the original emulsion. Suitably, the styrene-methacrylate polymer emulsion can have a pH of 7.0 to 8.0, as determined with reference to the DIN ISO 976. Suitably, the styrene-methacrylate polymer emulsion has a viscosity at room temperature of 700 to 1, 000 cps, as determined with reference to ISO 1652 using the Brookfield RVT Spindle 1/rpm 20/factor 5. The room temperature refers to 15-30℃, such as 23℃.

Based on the total weight of the second waterborne ink composition, the styrene-methacrylate polymer can comprise about 1 wt%or greater, suitably at least about 2 wt%, suitably at least about 3 wt%, and/or up to about 10 wt%, such as, up to about 8 wt%, suitably up to about 6 wt%of the second waterborne ink composition. Based on the total weight of the second waterborne ink composition, the styrene-methacrylate polymer can comprise about 1-10 wt%, suitably 2-8 wt%, such as, 3-6 wt%of the second waterborne ink composition, or in any other combinational ranges using these endpoints.

In the second waterborne ink composition, the solid weight ratio of the hydroxyl-functionalized (meth) acrylic acid-styrene polymer to the styrene-methacrylate polymer can be 10: 1 to 2: 1. For example, the solid weight ratio of the hydroxyl-functionalized (meth) acrylic acid-styrene polymer to the styrene-methacrylate polymer can be 10: 1 or lower, 9: 1 or lower, 8: 1 or lower, 7: 1 or lower, or 6: 1 or lower, and/or 2: 1 or higher, 3: 1 or higher, 4: 1 or higher, or 5: 1 or higher, such as 8: 1 to 2: 1, 6: 1 to 2: 1, or within a range using any other combination of the above endpoints. For example, the solid weight ratio of the hydroxyl-functionalized (meth) acrylic acid-styrene polymer to the styrene-methacrylate polymer can 9: 1, 8: 1, 7: 1, 6: 1, 5: 1, 4: 1 or 3: 1.

Suitably, the hydroxyl and/or carboxyl-containing resin in the second waterborne ink composition comprises a hydroxyl-functionalized (meth) acrylic-styrene polymer, a polyurethane and a styrene-methacrylate polymer, wherein the solid weight ratio of the hydroxyl-functionalized (meth) acrylic-styrene polymer to the polyurethane ot the styrene-methacrylate polymer can be (2-4) : (2-4) : (1-2) .

In the second waterborne ink composition, the amine resin is a resin formed by the polycondensation of an amino-containing compound, such as, urea, melamine or benzoguanamine, with a formaldehyde and an alcohol. The amine resin can comprise an urea-formaldehyde resin, a melamine formaldehyde resin and/or a benzoguanamine formaldehyde resin. Suitably, the amine resin comprises a methylated amine resin. Suitably, the amine resin has a high imino content. The high imino content means that the imino content is at least 15 mol%based on the sum of the reactive groups in the amine resin. The reactive groups refer to imino, methoxy, hydroxymethyl and methyl ether. Suitably, the amine resin can comprise a methylated amine resin with a high imino content, which comprises at least 20 wt%of imino groups based on the sum of the reactive groups in the amine resin.

The amine resin can be in form of a high-solid solvent-based amine resin, which can have a solid content of 85-95 wt%, as determined according to the DIN EN ISO 3251 (2019) standard. Suitably, the amine resin can have a viscosity at room temperature of 5, 100 to 16, 000 cps, as determined with reference to ISO 1652 using the Brookfield RVT Spindle 1/rpm 20/factor 5. The room temperature refers to 15-30℃, such as 23℃.

Based on the total weight of the second waterborne ink composition, the amine resin can comprise than about 5 wt%or greater, suitably at least about 6 wt%, suitably at least about 7 wt%, and/or up to about 15 wt%, such as, up to about 13 wt%, suitably up to about 10 wt%of the second waterborne ink composition. Based on the total weight of the second waterborne ink composition, the amine resin can comprise about 5-15 wt%, suitably 6-13 wt%, such as, 7-10 wt%of the second waterborne ink composition, or in any other combinational ranges using these endpoints.

Suitably, in the second waterborne ink composition, a solid weight ratio of the amine resin to the aforesaid resins in combination (i.e., the hydroxyl-functionalized (meth) acrylic acid-styrene polymer, polyurethane, and the styrene-methacrylate polymer) can be 1: 2 to 1: 10. For example, the solid weight ratio of the amine resin to the aforesaid resins can be 1: 2 or lower, 1: 3 or lower, 1: 4 or lower, or 1: 5 or lower, and/or, 1: 10 or higher, 1: 9 or higher, 1: 8 or higher, 1: 7 or higher, or 1: 6 or higher, such as 1: 2 to 1: 9, 1: 2 to 1: 7, or within a range using any other combination of the above endpoints. For example, the solid weight ratio of the amine resin to the aforesaid resins can be 1: 3, 1: 4, 1: 5, 1: 6, 1: 7, 1: 8 or 1: 9.

In the second waterborne ink composition, the hydroxyl and/or carboxyl-containing resin and the amine resin constitute the binder. Suitably, the hydroxyl and/or carboxyl-containing resin and the amine resin can comprise at least 80 wt%of the total solid weight of the binder of the second waterborne ink composition. For example, the hydroxyl and/or carboxyl-containing resin and the amine resin can comprise 85 wt%or higher, 90 wt%or higher, 95 wt%or higher, or even 100 wt%of the total solid weight of the binder of the second waterborne ink composition.

The second waterborne ink composition according to the present invention can further comprise a pigment/filler. The pigment/filler can provide the ink with colors, effects and/or functions, which comprises colored a pigment and a filler (also known as extender pigment) . Suitably, the pigment comprises an inorganic pigment, such as, titanium white pigment, carbon black pigment, iron red, and the like. Suitably, the filler comprises fumed silica.

In the second waterborne ink composition, a solid weight ratio of the binder to the pigment can be 2: 1 to 5: 1. For example, in the second waterborne ink composition, the solid weight ratio of the binder to the pigment can be 2: 1 or higher, 3: 1 or higher, or 3.5: 1 or higher, and/or, 5: 1 or lower, or 4: 1 or lower, such as 3: 1 to 5: 1, or within a range using any other combination of the above endpoints. For example, the solid weight ratio of the binder to the pigment can be 3: 1, 3.5: 1 or 4: 1 in the second waterborne ink composition.

Based on the total weight of the second waterborne ink composition, the pigment/filler can comprise 10-25 wt%of the second waterborne ink composition.

The second waterborne ink composition according to the present invention can further comprise an antifoaming agent. The antifoaming agent can suppress the formation of bubbles and help generated bubbles to escape or collapse during production. Suitably, the antifoaming agent can comprise a non-silicon-based organic antifoaming agent (i.e., a silicon-free organic antifoaming agent) . Based on the total weight of the second waterborne ink composition, the antifoaming agent can comprise 0-2 wt%, such as, 0.1-1.5 wt%of the second waterborne ink composition.

The second waterborne ink composition according to the present invention can further comprise a rheological aid. The rheological aid can effectively adjust the viscosity, ensure excellent workability, and avoid fat edges. Suitably, the rheological aid can comprise an inorganic bentonite-based thickener and/or a non-associative alkali swelling thickener. Based on the total weight of the second waterborne ink composition, the rheological aid can comprise 0-2 wt%, such as, 0.1-1.5 wt%of the second waterborne ink composition.

The second waterborne ink according to the present invention can further comprise a leveling agent. The leveling agent can improve flowability and processability to provide a smooth coating. Suitably, the leveling agent can comprise a silicone-based leveling agent. Based on the total weight of the second waterborne ink composition, the leveling agent can comprise 0-5 wt%, such as, 0.1-1.5 wt%of the second waterborne ink composition.

The second waterborne ink composition according to the present invention can further comprise a solvent. The solvent mainly comprises water, namely, water constitutes at least 50 wt%of the solvent by mass. The solvent can further comprise an organic solvent to assist in compatibility of ingredients in the ink composition. Suitably, the organic solvent can comprise an ether solvent. Based on the total weight of the second waterborne ink composition, water can comprise 15-25 wt%of the second waterborne ink composition. Based on the total weight of the second waterborne ink composition, the organic solvent can comprise 2-10 wt%of the second waterborne ink composition.

An ink layer formed from the waterborne ink system according to the present invention can have excellent adhesion to the substrate. Suitably, the ink layer formed from the waterborne ink system according to the present invention can have a good pull-out resistance, as determined by the method described below.

The ink layer formed according to the waterborne ink system of the present invention can have an excellent optical density (OD) . Suitably, the ink layer formed from the waterborne ink system according to the present invention can have an optical density of OD >5, as determined according to the ASTM E 1079-05 standard.

The ink layer formed according to the waterborne ink system of the present invention further can have excellent chemical resistance, moisture and heat resistance, and appearance-aging resistance.

The waterborne ink system according to the present invention can be prepared by the following method.

The preparation of a first waterborne ink composition comprises:

(1) Preparation of a first component of the first waterborne ink composition: adding raw materials (except pigment) in order under mechanical stirring (800 to 900 rpm) , and stirring continuously for at least 30 min after feeding, until that the fineness reaches 6.5 or more (as determined according to JJG 905-2010, corresponding to 20 μm or less) ; adjusting the pH to 8.0 to 9.0 with an alkali, and then adding pigments in order; after that all the raw materials are fed, stirring continuously for 15-20 min to ensure that the fineness is 6.5 or more (as determined according to JJG 905-2010, corresponding to 20 μm or less) , and then filtering with a 150 mesh filter to give the first component composition.

(2) Mixing the first component composition with a silane coupling agent to give the first waterborne ink composition having an application viscosity at room temperature of 15-35 seconds as measured by a Zahn 3#viscosity cup (15-30℃, such as 23℃) .

The preparation of a second waterborne ink composition comprises:

Adding Raw materials in order under mechanical stirring (at 800 to 900 rpm) , and stirring continuously for at least 30 min after feeding, until that the fineness reaches 6.5 or more (as determined according to JJG 905-2010, corresponding to 20 μm or less) ; adjusting the pH to 8.0 to 8.5 with an alkali, and ensuring that the fineness is 6.5 or more (as determined according to JJG 905-2010, corresponding to 20 μm or less) ; filtering the mixture with a 150 mesh filter to give the waterborne ink composition having an application viscosity at room temperature of 15-35 seconds as measured by a Zahn 3#viscosity cup (15-30℃, such as 23℃) .

The present invention further relates to a coated substrate, comprising a substrate and the waterborne ink system applied on at least a part of the substrate. The substrate can comprise a glass substrate. The substrate can comprise a non-planar surface, such as, a 3D surface. The substrate can comprise a surface of electronic product. The substrate can be a part of electronic product.

The waterborne ink system according to the present invention can be applied by spraying to a substrate. The spraying can be carried out with a commercially available spray gun. Alternatively, the waterborne ink system according to the present invention can also be applied to the substrate by printing.

The present invention further relates to use of the waterborne ink system for coating a substrate.

The invention also relates to a method of treating a glass substrate, comprising: applying the waterborne ink system to at least a part of the substrate, wherein the first waterborne ink composition is applied to the substrate prior to application of the second waterborne ink composition.

As described above, the first waterborne ink composition is a two-package composition, wherein a first package comprises a binder, and a second package comprises an adhesion promoter, the adhesion promoter comprises a silane coupling agent, and wherein the first package and the second package is mixed immediately before application to the substrate.

EXAMPLES

The following examples are provided to further illustrate the present invention, but should not be construed to limit the present invention to the details of the examples. All parts and percentages in the following examples are by weight, unless otherwise stated.

Examples 1-3:

The first waterborne ink compositions and the second waterborne ink compositions of Examples 1-3 were prepared according to the ingredients and weight ratios listed in Table 1-2. In particular, the preparation comprised:

(1) Various ingredients of the first waterborne ink composition (except the pigment and the silane coupling agent) were added in order under mechanical stirring (800 to 900 rpm) , and continuously stirred for at least 30 min after feeding, until that the fineness reached 6.5 or more. The pH was adjusted to 8.0 to 9.0 with an alkali, and then the pigment was added. After all the ingredients were fed, they were continuously mechanically stirred for 15-20 min to ensure that the fineness was 6.5 or more, and then filtered with a 150 mesh filter to give the first component composition of the first waterborne ink composition. The first component composition was mixed with the silane coupling agent (at a weight ratio of the first component composition to the silane coupling agent of 100: 5) to give the first waterborne ink composition having an application viscosity at room temperature of 15-35 seconds as measured by a Zahn 3#viscosity cup.

(2) Various ingredients of the second waterborne ink composition were added in order under mechanical stirring (800 to 900 rpm) , and continuously stirred for at least 30 min after feeding, until that the fineness reached 6.5 or more. The pH was adjusted to 8.0 to 9.0 with an alkali, and the fineness was ensured to be 6.5 or more. The mixture was filtered with a 150 mesh filter to give the second waterborne ink composition having an application viscosity at room temperature of 15-35 seconds as measured by a Zahn 3#viscosity cup.

Table 1. First Waterborne Ink Compositions of Examples 1-3

¹ Polyurethane dispersion with a solid content of 35-45 wt%, pH of 7-8.5, and viscosity at room temperature of 20 to 200 cps, wherein the polyurethane solid is an aliphatic polyurethane having an elongation at break of 600-800%and a 100%modulus of 1-5 N/mm²;

² Siloxane-based antifoaming agent;

³ Silicone-based leveling agent;

⁴ Ether-based solvent;

⁵ Polyurethane thickener;

⁶ Silane coupling agent comprising an epoxy functional group.

Table 2. Second Waterborne Ink Compositions of Examples 1-3

¹ Hydroxyl functionalized (meth) acrylic acid-styrene polymer emulsion with a solid content of 40-45wt%, pH of 1.0 to 3.0, and viscosity at room temperature of 20 to 50 cps, wherein the (meth) acrylic acid-styrene polymer solid has a hydroxyl value of 60 to 150 mgKOH/g and an MFFT of 40-80℃;

² Polyurethane dispersion with a solid content of 30-35wt%, pH of 7.0 to 9.0, a viscosity at room temperature of 50 to 150 cps, wherein the polyurethane solid has an acid value of 10 to 40 mgKOH/g and a Tg of 90-120℃;

³ Styrene-methacrylate polymer emulsion with a solid content of 49-51 wt%, pH of 7.0 to 8.0, and viscosity at room temperature of 700 to 1, 000 cps, wherein the styrene-methacrylate polymer solid has an MFFT of 60-100℃;

⁴ Non-silicon-based organic antifoaming agent;

⁵ Ether-based solvent;

⁶ High-solid solvent-based amine resin with a solid content of 85-95 wt%, and a viscosity at room temperature of 5, 100 to 16, 000 cps, wherein the amine resin solid is a methylated amine resin with a high imino content of at least 20 mol%based on the sum of the reactive groups in the amine resin;

⁷ Inorganic bentonite-based thickener and/or non-associative alkali swelling thickener; ⁸ Amine;

⁹ Silicone-based leveling agent;

¹⁰ Including carbon black, titanium dioxide, etc.

Comparative Example 1:

A commercially available ink product from TKK Company was used as the comparative example.

Performance Testing

The above-prepared first waterborne ink compositions of Examples 1-3 were applied onto a 3D glass substrate by spraying, respectively, and cured at 140-160℃ for 8-10 min. Then, the above-prepared second waterborne ink compositions of Examples 1-3 were applied onto the first waterborne ink layer by spraying, and cured at 140-160℃ for 15-30 min. The spraying was carried out using a commercially available spray gun, with the spraying parameters of: a pressure of 1-2 kg; and a spray gun caliber of 1.1 mm. The 3D glass substrate was a glass plate with upwardly tilted edges, as shown in FIG. 1.

The ink composition of the comparative example was applied to a 2D (planar) glass substrate by screen printing to superimpose 2-4 layers of ink layers, and then cured at 100-150℃ for 10-30 min.

The cured ink layers were subject to the following performance tests.

Pull-out resistance

Two glass substrates sticked together by adhesive with the ink layers facing each other, and an extrusion force was applied to the substrates at the opposite sides to the ink layers at a temperature of -60℃ until the two glass substrates sticking together were separated under the action of pressure.

Requirement: no ink film peeling under pressure.

OD:

Measured according to the ASTM E 1079-05 standard using the x-rite 341C Transmission Densitometer Model S/N. The larger the OD value, the higher the optical density, and the lower the light transmittance. The goal is OD>5.

Chemical Resistance

Determined according to the ISO 2812-4: 2017 standard.

Heat and Humidity Resistance

Determined according to the GB/T 1740-2007 standard.

Appearance Aging Resistance

Determined according to the GB/T 1856-2009 /ISO 11341: 2004 standard.

Adhesion

Determined according to the ASTM D3359-2002 standard.

The experimental results are shown in the following table:

Referring to the above experimental results, it can be seen that Examples 1-3 according to the present invention can be suitable for coating a 3D substrate by spraying. The formed ink layer has excellent comprehensive properties, meets the application requirements, and can be comparable with the ink layer printed by a commercially available ink on a 2D substrate.

Although the particular aspects of the present invention has been illustrated and described, it is obvious to persons skilled in the art that many other variations and modifications can be made without departing the spirit and scope of the present invention. Thus, the accompanying claims are intended to encompass all of these variations and modifications falling within the scope of the present invention.

Claims

A sprayable waterborne ink system, comprising a first waterborne ink composition and a second waterborne ink composition, wherein the first waterborne ink composition comprises a binder comprising a heat-activable resin which is activable at a temperature of at least 120℃, and wherein the second waterborne ink composition comprises a binder comprising a high-temperature crosslinkable resin which is crosslinkable at a temperature of at least 120℃.
The waterborne ink system of claim 1, wherein the binder of the first waterborne ink composition comprises at least 70 wt%of the heat-activable resin based on the total solid weight of the binder.
The waterborne ink system of claim 1 or 2, wherein the heat-activable resin comprises an aliphatic polyurethane.
The waterborne ink system of claim 3, wherein the aliphatic polyurethane is in a form of an aqueous dispersion with a pH of no more than 8.5 and a viscosity of no more than 220 cps.
The waterborne ink system of claim 3 or 4, wherein the aliphatic polyurethane has a 100%modulus of 1 to 5 N/mm².
The waterborne ink system of any one of claims 3-5, wherein the aliphatic polyurethane has an elongation at break of 600-800%.
The waterborne ink system of any one of claims 1-6, wherein the first waterborne ink composition further comprises an inorganic pigment.
The waterborne ink system of claim 7, wherein a solid weight ratio of the binder to the inorganic pigment in the first waterborne ink composition is 5: 2 to 5: 10.
The waterborne ink system of any one of claims 1-8, wherein the high-temperature crosslinkable resin comprises a hydroxyl and/or carboxyl-containing resin and an amine resin.
The waterborne ink system of claim 9, wherein the hydroxyl and/or carboxyl-containing resin comprises a hydroxyl-functionalized (meth) acrylic-styrene polymer.
The waterborne ink system of claim 10, wherein the hydroxyl-functionalized (meth) acrylic-styrene polymer has a hydroxyl value of 60-150 mgKOH/g.
The waterborne ink system of claim 10 or 11, wherein the hydroxyl-functionalized (meth) acrylic-styrene polymer has an MFFT of 40-80℃.
The waterborne ink system of any one of claims 9-12, wherein the hydroxyl and/or carboxyl-containing resin further comprises a polyurethane and/or a styrene-methacrylate polymer, wherein the styrene-methacrylate polymer is different from the hydroxyl-functionalized (meth) acrylic-styrene polymer.
The waterborne ink system of claim 13, wherein the polyurethane comprises a polyether polyurethane.
The waterborne ink system of claim 13 or 14, wherein the polyurethane has an acid value of 10-40 mgKOH/g.
The waterborne ink system of any one of claims 13-15, wherein the polyurethane has a Tg of 90-120℃.
The waterborne ink system of any one of claims 13-16, wherein a solid weight ratio of the hydroxyl-functionalized (meth) acrylic-styrene polymer and the polyurethane and the styrene-methacrylate polymer is (2-4) : (2-4) : (1-2) .
The waterborne ink system of any one of claims 9-17, wherein the amine resin comprises a methylated amine resin with high imino content, and the methylated amine resin with high imino content comprises at least 20 mol%of imino groups based on the total amount of reactive groups in the amine resin.
The waterborne ink system of any one of claims 1-18, wherein the first waterborne ink composition further comprises 0.5-5 wt%of a silane coupling agent based on the total weight of the first ink composition.
The waterborne ink system of any one of claims 1-19, wherein the first waterborne ink composition and/or the second waterborne ink composition has a shear thinning property.
The waterborne ink system of any one of claims 1-20, wherein the first waterborne ink composition /the second waterborne ink composition is curable at 150℃ within 30 min.
The waterborne ink system of any one of claims 1-21, wherein a coating formed by the first waterborne ink composition has a film thickness of 30-40 μm, and a coating formed by the second waterborne ink composition has a film thickness of 15-20 μm.
The waterborne ink system of any one of claims 1-22, wherein the first waterborne ink composition and/or the second waterborne ink composition are sprayable.
A coated substrate, comprising a substrate and the waterborne ink system of any one of claims 1-23 applied on at least a part of the substrate.
The coated substrate of claim 24, wherein the substrate comprises a glass substrate.
The coated substrate of claim 24 or 25, wherein the substrate is not planar.
The coated substrate of any one of claims 24-26, wherein the substrate comprises a surface of electronic products.
A method of treating a glass substrate, comprising:

applying the waterborne ink system of any one of claims 1-23 onto at least a part of a substrate, wherein the first waterborne ink composition is applied onto the substrate prior to application of the second waterborne ink composition.
The method of claim 28, wherein the first waterborne ink composition is a two-package composition, wherein a first package comprises a binder, and a second package comprises a silane coupling agent, and wherein the first package and the second package are mixed immediately before application to the substrate.