Bio-based low voc waterborne ink composition based on microbial fermentation pha and preparation method, application and printing method thereof

Abstract

The application discloses a bio-based low VOC water-based ink composition based on microbial fermentation PHA and a preparation method, application and printing method thereof, and belongs to the technical field of printing ink and water-based polymer dispersion. The ink adopts a unique unprotected colloid PHA emulsion system, supplemented by precise crosslinking equivalent regulation. Compared with conventional bio-based water-based ink on the market which needs to rely on primer or high energy consumption drying to be applied on plastic film, the application can realize excellent adhesion (0-1 level) and wet rub resistance on BOPP / BOPET substrates without primer, greatly simplifying the printing process. Under the high environmental protection standard of ensuring low VOC and no PFAS, the application significantly reduces the energy consumption of high-speed printing with lower drying heat enthalpy and solves the back sticking pain point, and at the same time, has long pot life and excellent paper-based ink removal, effectively solving the industry problem that environmental compliance and high-performance printing are difficult to be compatible.

Description

Technical Field

[0001] This invention belongs to the field of printing ink and water-based polymer dispersion technology. Specifically, it designs a bio-based low-VOC water-based ink composition based on microbial fermentation of PHA, its preparation method, application, and printing method. Background Technology

[0002] In the fields of flexographic and gravure printing, particularly in the food and consumer goods packaging industries, a core challenge has long existed: balancing printing performance with environmental and safety regulations. On the one hand, the market demands inks with excellent adhesion, durability, and high-speed printing suitability on various substrates (especially non-absorbent plastic films); on the other hand, global environmental regulations and occupational health requirements are forcing ink formulations towards low volatile organic compounds (VOCs), high bio-based content, absence of harmful substances (such as PFAS), and recyclability.

[0003] However, existing technologies cannot perfectly balance the two aspects mentioned above. The technologies in this field can be mainly classified into the following categories:

[0004] The first category is "traditional solvent-based ink systems." This has long been the mainstream technology, using strong organic solvents to dissolve resins, which effectively wets low-surface-energy plastic substrates, thus providing excellent adhesion and durability. However, the fundamental drawback of this type of technology lies in its extremely high VOC emissions, which not only pose a threat to occupational health in printing workshops but is also one of the main sources of air pollution, and has been strictly restricted worldwide.

[0005] The second category is the "energy curing (UV / EB) system". This type of technology uses ultraviolet light or electron beams to initiate monomer polymerization, contains almost no VOCs, and has a fast drying speed and high crosslinking density, thus exhibiting excellent performance. Its main drawbacks are: (1) its chemicals (such as photoinitiators and reactive monomers) pose a risk of migration into the packaging, which is strictly limited in the food packaging field; (2) the crosslinked ink layer after curing is dense, making it difficult to effectively de-ink in existing paper-based recycling processes, which is not conducive to the circular economy.

[0006] The third category is "traditional water-based ink systems." This type of technology uses water as the main solvent and has a significant advantage in low VOCs. Water-based ink technology is quite mature when applied to porous absorbent substrates such as paper and cardboard. However, when applied to non-absorbent plastic films, such as biaxially oriented polypropylene (BOPP) or biaxially oriented polyethylene terephthalate (BOPET), its fundamental shortcomings become apparent: water has a high surface tension, making it difficult to wet low-surface-energy plastic substrates. This results in ink adhesion, water resistance, and wet rub resistance often failing to meet the demands of high-end packaging. Furthermore, the high latent heat of vaporization of water leads to a significant increase in drying energy consumption.

[0007] The fourth category is "emerging bio-based latex systems." To address the aforementioned issues, the field has begun exploring the use of biodegradable polymers as binders, among which polyhydroxyalkanoates (PHAs) have attracted considerable attention due to their microbial fermentation origin and excellent barrier properties. Currently disclosed solutions mainly focus on how to prepare hydrophobic PHA into aqueous dispersions. For example, WO2020 / 036843A1 discloses a redispersible PHA emulsion stabilized by surfactants; US2007 / 0088099A1 discloses the use of polyvinyl alcohol (PVA) or starch-based substances as protective colloids to stabilize PHA aqueous dispersions; WO2012 / 149407A1 employs a melt emulsification route, but also relies on added stabilizers. The common drawback of these existing PHA dispersion technologies is that, in order to achieve dispersion stability, they introduce PVA, starch, or high content of graft / block polymeric dispersants. These hydrophilic or water-soluble protective colloidal components severely impair the adhesion and water resistance of the final ink layer on the plastic film, making it unsuitable for direct printing.

[0008] In summary, there has long been a clear technological gap in this field: that is, no water-based ink composition has been provided that can meet the environmental compliance requirements of being bio-based, low-VOC, and free of perfluorinated and polyfluoroalkyl substances (PFAS) (i.e., total organic fluorine (TOF) not detected), and can (1) not rely on PVA, starch or graft / block polymeric dispersants when preparing PHA latex, (2) achieve direct printing without primer on highly challenging films such as BOPP and BOPET (surface free energy ≥40mN / m), (3) obtain high-level adhesion and wet rubbing resistance through specific crosslinking equivalent coupling, and (4) ensure that it meets the requirements for ink removal and recycling in paper-based applications. Summary of the Invention

[0009] The purpose of this invention is to provide a bio-based low-VOC waterborne ink composition based on microbial fermentation of PHA, as well as its preparation method, application, and printing method, in order to solve the problem in the prior art that bio-based waterborne inks are difficult to balance environmental protection and direct printing performance on non-absorbent substrates.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A bio-based low-VOC waterborne ink composition based on microbial fermentation of PHA, comprising, by weight percentage of dry solids: 28 wt% to 60 wt% pigment, 35 wt% to 65 wt% binder, 0.5 wt% to 6 wt% functional additives, and 0.5 wt% to 4 wt% crosslinking agent. The binder comprises 35% to 70% PHA latex by weight of the total binder and the balance being acrylic emulsion and / or waterborne polyurethane dispersion. By controlling the pigment content within the range of 28 wt% to 60 wt%, for example 28 wt%, 28.1 wt%, 29.4 wt%, 30 wt%, 30.8 wt%, 32.3 wt%, 35 wt%, 35.1 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%, sufficient hiding power and color density of the ink are ensured. By controlling the content of the binder within the range of 35wt% to 65wt%, such as 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 57.2wt%, 59.8wt%, 60.6wt%, 61wt%, 62.2wt%, or 65wt%, excellent film-forming properties and adhesion are provided. The proportion of PHA latex in the binder is controlled within the range of 10wt% to 80wt%, such as 10wt%, 15wt%, 20wt%, 22.7wt%, 30wt%, 34.6wt%, 35wt%, 37.5wt%, 40wt%, 44.6wt%, 45wt%, 47.5wt%, 50wt%, 55wt%, 55.6wt%, 60wt%, 64.0wt%, 65wt%, or 80wt%, ensuring the bio-based content and hydrophobic properties of the ink layer. The content of functional additives is, for example, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or 6wt%, and the content of crosslinking agents is, for example, 0.5wt%, 1.0wt%, 1.7wt%, 1.9wt%, 2.0wt%, 2.2wt%, 2.5wt%, 3.0wt%, 3.7wt%, or 4.0wt%, to balance the application performance of the ink and the durability of the final film.

[0012] The composition, on a wet formulation basis, has the following properties: a total solids content of 32 wt% to 50 wt%, for example, 32 wt%, 35 wt%, 38 wt%, 39 wt%, 40 wt%, 42 wt%, 43 wt%, 45 wt%, 48 wt%, or 50 wt%; a pH value of 8.2 to 9.2, for example, 8.2, 8.4, 8.5, 8.6, 8.7, 8.8, 9.0, or 9.2; and a viscosity at 25°C of 20 mPa·s to 800 mPa·s, for example, 20 mPa·s, 40 mPa·s, 42 mPa·s, 45 mPa·s, 48 ​​mPa·s, 55 mPa·s, 100 mPa·s, 200 mPa·s, 400 mPa·s, 600 mPa·s, or... 800 mPa·s; volatile organic compound (VOC) mass fraction ≤1 wt% (i.e. 10 g / kg), for example 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%; surface tension at 25 °C is 30 mN / m to 38 mN / m, for example 30 mN / m, 30.8 mN / m, 31 mN / m, 31.5 mN / m, 31.8 mN / m, 32.5 mN / m, 33 mN / m, 35 mN / m, or 38 mN / m; and total organic fluorine (TOF) is not detected, with a method detection limit ≤5 mg / kg.

[0013] The composition contains less than 0.10 wt% of water-soluble protective colloids and grafted or block polymeric dispersants of polyvinyl alcohol (PVA), cellulose and its derivatives, starch and its derivatives, and protein and peptidoglycan residues in the PHA latex, which greatly reduces the introduction of hydrophilic components and improves water resistance.

[0014] The median particle size (D) of the PHA latex was measured according to ISO 22412:2025 and ISO 13099-2:2025 standards. 50 The wavelength range is 250 nm to 900 nm, for example, 250 nm, 260 nm, 280 nm, 300 nm, 320 nm, 350 nm, 400 nm, 450 nm, 500 nm, 600 nm, 700 nm, 800 nm, or 900 nm; the polydispersity index (PDI) is ≤0.22, for example, 0.19, 0.20, 0.21, or 0.22; the zeta potential is -35 mV to -55 mV, for example, -35 mV, -36 mV, -40 mV, -45 mV, -50 mV, -52 mV, or -55 mV; the residual solvent content in headspace gas chromatography is ≤0.15 wt%, for example, 0.02 wt%, 0.05 wt%, 0.10 wt%, or 0.15 wt%.

[0015] The ratio of the sum of the polycarbodiimide (PCD) equivalent and the oxazoline equivalent, divided by the carboxyl equivalent, is 0.72 to 1.05, for example, 0.72, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, or 1.05, based on the carboxyl equivalent in the binder. This specific equivalent ratio ensures the optimization of the crosslinking density.

[0016] The composition is suitable for direct flexographic or gravure printing without primer on polyolefin or polyester film substrates with a surface free energy greater than or equal to 40 mN / m.

[0017] The PHA is selected from at least one of the following substances or copolymers formed between monomers forming the following substances: poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), wherein the content of 3-hydroxyvalerate monomer units is from 7 mol% to 18 mol%, for example 7 mol%, 8 mol%, 10 mol%, 12 mol%, 15 mol% or 18 mol%; poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), wherein the content of 3-hydroxyhexanoate monomer units is 5 mol% to 12mol%, for example 5mol%, 6mol%, 8mol%, 10mol% or 12mol%; poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), and medium- to long-chain PHA (mcl-PHA); wherein the mcl-PHA is selected from poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3-hydroxydecanoate), poly(3-hydroxydodecanate), poly(3-hydroxytetradecanoate), poly(3-hydroxytetradecanoate), poly(3-hydroxyhexadecanoate), and poly(3-hydroxyoctadecanoate).

[0018] The acrylic emulsion has a core-shell structure and is prepared by emulsion polymerization of one or more monomers selected from butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, styrene, acrylic acid, methacrylic acid, hydroxyethyl acrylate and / or hydroxypropyl acrylate.

[0019] The pigments are selected from one or more of inorganic and organic pigments; the inorganic pigment is titanium dioxide, which is selected from anatase titanium dioxide or rutile titanium dioxide, iron oxide red, iron oxide yellow, zinc oxide, and ultramarine; the organic pigments include phthalocyanine blue, phthalocyanine green, quinacridone, benzodiimide, diimide, isoindolinone, benzimidazolone, and azo pigments, which include monoazo pigments and diazo pigments; and the pigment dispersion slurry prepared from the inorganic and / or organic pigments has a D 90 Particle size < 1µm.

[0020] The functional additive comprises wax solids selected from one or more of polyethylene wax, polypropylene wax, Fischer-Tropsch wax, carnauba wax, cactus wax, rice bran wax, beeswax, and bio-based ester waxes, and the wax solids are present in a content of 0.1 wt% to 5.0 wt% of the total dry solids of the water-based ink composition, for example, 0.1 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, or 5.0 wt%.

[0021] The functional additives include wetting and leveling agents and defoamers. The wetting and leveling agents are selected from siloxane-modified polyethers, polyether-type nonionic surfactants, and alcohol ether surfactants. The defoamers are selected from polyether-type defoamers, polyether-organosilicon composite defoamers, and mineral oil-type defoamers. All functional additives are non-fluorine-containing systems.

[0022] The total equivalent ratio of PCD to the oxazoline-containing polymer is 0.72 to 1.05, based on the carboxyl equivalent in the binder; the amount of PCD added is 0.3 wt% to 3.0 wt%, for example 0.3 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, or 3.0 wt%, based on total dry solids, with an equivalent equivalent of 140 g / eq to 300 g / eq, for example 140 g / eq, 160 g / eq, 200 g / eq, 250 g / eq, or 300 g / eq; the oxazoline-containing polymer... The amount of the substance added is from 0.5wt% to 3.0wt%, for example 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt% or 3.0wt%, with an equivalent amount of 200g / eq to 400g / eq, for example 200g / eq, 250g / eq, 300g / eq, 350g / eq or 400g / eq; the pot life at 25°C after the addition of the crosslinking agent is greater than or equal to 4 hours, for example 4 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 8 hours, 10 hours, 12 hours or 24 hours.

[0023] The composition further includes a cosolvent or film-forming aid selected from one or more of dipropylene glycol butyl ether, dipropylene glycol methyl ether, and ethyl lactate, with a total amount ≤0.8wt% on a wet formulation basis, for example 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, or 0.8wt%, and the composition has a VOC mass fraction ≤1wt%, TOF undetectable, and a method detection limit ≤5mg / kg.

[0024] The wet formulation of the composition has a surface tension of 30 mN / m to 38 mN / m at 25°C, and its storage stability meets the requirement that the viscosity change rate is ≤10% and there is no obvious stratification after 7 days of storage at 50°C.

[0025] The present invention also provides a method for preparing the water-based ink composition, the method comprising the following steps:

[0026] Step 1. Add pigment, acrylate dispersant, and neutralizer to deionized water, disperse using a high-shear disperser, and perform low-shear aging. Filter to remove coarse particles and control D. 90 Particle size <1µm, resulting in a pigment dispersion slurry;

[0027] Step 2. PHA powder is extruded using a co-rotating parallel twin-screw extruder and melt-blended with deionized water. The mixture undergoes a phase reversal within the extruder to form a crude emulsion. Subsequently, it is degassed under vacuum online and homogenized under high pressure. This high-pressure homogenization employs two-stage temperature control: an inlet temperature of 25°C to 35°C (e.g., 25°C, 28°C, 30°C, 32°C, or 35°C) and an outlet temperature <45°C, yielding PHA latex. Alternatively, it can be neutralized and dispersed in an aqueous phase, followed by high-shear and low-shear treatments to obtain PHA latex.

[0028] Step 3. Add the PHA latex obtained in Step 2, acrylic emulsion, and / or waterborne polyurethane dispersion to the pigment dispersion slurry obtained in Step 1, add water, co-solvent, and functional additives, and adjust the pH value to 8.2 to 9.2 to obtain the base ink after ink conditioning.

[0029] Step 4. 0 to 8 hours before printing, add PCD and / or oxazoline-containing polymer to the base ink obtained in Step 3 after ink adjustment, and mix with a stirrer for 10 to 30 minutes to obtain the ink composition;

[0030] Step 5. Filter the ink composition obtained in Step 4 through a 100-mesh to 200-mesh filter and then fill it to obtain the filled water-based ink composition.

[0031] After obtaining the latex via an aqueous neutralization and dispersion route, surface grafting of acrylic monomers with a content of ≤0.5wt% is performed without introducing grafted or block polymeric dispersants.

[0032] The present invention also provides an application of the water-based ink composition, which is suitable for direct flexographic or gravure printing on paper, cardboard, and biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET), treated polyethylene, or their composite substrates that have been corona- or plasma-treated to a surface free energy greater than or equal to 40 mN / m. The printing process does not rely on a primer or polyvalent metal salt pretreatment layer before printing. After printing, the ink is dried by hot air, infrared, or near-infrared at 60°C to 120°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C.

[0033] The composite material, after being printed into a film, exhibits a cross-cut adhesion rating of 0 to 1, tested according to ASTM D3359 or GB / T9286. It also withstands at least 250 wet rubs, for example, 250, 260, 280, 290, 300, 310, or 350 rubs, tested according to ASTM D3359 or GB / T9286. D5264, residual moisture content of the printing film <1.0wt%, for example 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, or 0.9wt%, and under conditions of 25°C and 50% relative humidity, the static friction coefficient of the printing film to BOPP is 0.25 to 0.45, for example 0.25, 0.30, 0.32, 0.33, 0.34, 0.35, 0.40, or 0.45, and the dynamic friction coefficient is 0.20 to 0.40, for example 0.20, 0.22, 0.24, 0.25, 0.26, 0.27, 0.30, or 0.40, and the test standard is ASTM D1894.

[0034] When the composition is used for printing on paper-based food packaging that directly or indirectly contacts food, it is used in conjunction with water-based varnish or heat-sealing coating, and the overall migration amount, specific migration amount and sensory verification are completed before it is put into use.

[0035] The composition is paper-based deinking friendly and, when evaluated according to ISO 21993 and calculated with reference to Method 11 of the International Deinking Industry Association, achieves a score of "good" or above from the European Paper Recycling Council.

[0036] The present invention also provides a printing method, the method comprising: providing the water-based ink composition; flexographic or gravure coating on the substrate; drying at 60°C to 120°C until the residual moisture content of the printed film is <1.0 wt%, and completing the printing within a crosslinking application period of 4 to 24 hours; the flexographic printing conditions using an anilox roller with an ink load of 6 cm³ / m² to 12 cm³ / m² and a line count of 79 lines / cm to 197 lines / cm; and the gravure printing selecting a process viscosity within the viscosity range of 20 mPa·s to 800 mPa·s and setting a paper feed speed to adapt to drying and adhesion requirements.

[0037] Compared with the prior art, the use of this invention can achieve the following significant beneficial effects:

[0038] Excellent direct printing performance and environmental friendliness: The composition of the present invention, through the combination of specific PHA latex and crosslinking agent, can achieve direct printing without primer on non-absorbent plastic films with surface energy greater than or equal to 40mN / m, and obtain excellent adhesion and wet scrub resistance, while maintaining extremely low VOC emissions and being PFAS-free, meeting strict environmental standards.

[0039] Highly efficient drying and processing adaptability: This ink composition has a low enthalpy of moisture evaporation, which can significantly reduce energy consumption and control residual moisture under high-speed printing conditions, preventing back adhesion. Its suitable coefficient of friction and anti-stick properties ensure smooth operation of packaging rolls on automated production lines.

[0040] Excellent circular economy compatibility: In paper-based applications, this ink composition exhibits good deinking properties during recycling, and the resulting ink fragments are easily separated by flotation without interfering with the pulp recycling process, supporting sustainable packaging waste management.

[0041] Stable onboard application period: By precisely controlling the matching window of crosslinking equivalent, this ink composition provides an onboard application period of more than 4 hours while ensuring final curing performance, solving the common problem of two-component water-based inks that cause screen clogging or application difficulties due to excessively rapid reaction. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the agricultural mulch film structure of the present invention.

[0043] In the figure, 1-wax enrichment layer; 2-ink layer body; 3-pigment particles; 4-crosslinking network; 5-interface layer; 6-substrate; 7-printed material. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. Unless otherwise stated, the raw materials used in this embodiment are commercially available industrial products or can be prepared by conventional methods. Unless otherwise specified, performance testing methods are performed according to the standards described in the invention summary section.

[0045] The structure of the present invention will be described in conjunction with the accompanying drawings: as follows Figure 1The printed matter 7 shown includes a substrate 6 and a dried ink layer attached to the substrate. The ink layer exhibits a specific layered structure at the microscopic level, wherein the outermost layer is a wax-rich layer 1 that provides slip and anti-blocking properties; the middle layer is the ink layer body 2, in which pigment particles 3 are uniformly dispersed and penetrated by a dense cross-linked network 4 formed by a cross-linking reaction, so as to give the ink layer excellent mechanical strength and toughness; and a tightly bonded interface layer 5 is formed in the area at the bottom of the ink layer in contact with the substrate 6, ensuring excellent adhesion under no-primer conditions.

[0046] Main reagents and raw materials:

[0047] Table 1. Main reagent and raw material names, product models and manufacturers:

[0048]

[0049] Main analytical and testing instruments:

[0050] Table 2 Main analytical and testing instruments:

[0051]

[0052] Main testing standards:

[0053] Table 3. Main Test Items and Test Standards:

[0054]

[0055] Measurement and Algorithm Explanation: D 50 The median diameter of the volume distribution is given; PDI is calculated using the cumulants method according to ISO 22412:2025; Zeta potential is determined at 25°C according to ISO 13099-2:2025. Crosslinking equivalent calculation: based on the -COOH equivalent in the binder, (sum of PCD equivalent and oxazoline equivalent) / -COOH equivalent is 0.72–1.05.

[0056] PHA latex preparation method 1: melt extrusion reverse method.

[0057] Step 1. Dry the PHA powder at 60°C to 80°C for 2 to 4 hours, then feed it into a co-rotating parallel twin-screw extruder. Set the barrel temperature to 140°C to 170°C depending on the PHA product, and the screw speed to 200 rpm to 400 rpm.

[0058] Step 2. Continuously introduce deionized water through the side feed port in the middle section of the extruder. The water temperature is 45℃ to 80℃, and a neutralizing agent is added simultaneously to adjust the pH of the aqueous phase to 8.5 to 9.0. Control the mass ratio of water to PHA to 0.8:1 to 2.0:1 to form a stable aqueous dispersion in the melt.

[0059] Step 3. Water is added step by step along the rear section of the barrel to increase the proportion of the aqueous phase to more than 70 wt%. Under cooling and shearing, the melt reverses to the aqueous phase. The discharged material is crushed by a perforated plate and directly enters the water bath to obtain a crude emulsion.

[0060] Step 4. The crude emulsion is degassed online under vacuum at a vacuum level of -0.08 mPa to -0.095 mPa, and then refined by high-pressure homogenization at a pressure of 90 mPa to 120 mPa, with homogenization occurring 1 to 3 times. The high-pressure homogenization employs two-stage temperature control: an inlet temperature of 25°C to 35°C and an outlet temperature <45°C. The final product is PHA latex, with a D... 50 The wavelength range is 250 nm to 900 nm, the polydispersity index (PDI) is less than or equal to 0.22, the zeta potential is -35 mV to -55 mV, and the residual solvent content in headspace gas chromatography is less than or equal to 0.15 wt%.

[0061] PHA latex preparation method two: self-neutralization and dispersion method.

[0062] Step 1. Add PHA powder to deionized water and use a neutralizing agent to adjust the pH value to 8.5 to 9.0 to obtain a neutralized mixture.

[0063] Step 2. The neutralized mixture obtained in Step 1 is treated with high shear dispersion for 12 to 18 minutes, followed by low shear aging for 40 to 55 minutes to obtain the dispersion.

[0064] Step 3. Analyze the particle size and potential of the dispersion obtained in Step 2 to confirm that the total organic fluorine is not detected, i.e., the method detection limit is <= 5 mg / kg, and the total residual protein and peptidoglycan is < 0.05 wt%. 50 PHA latex was obtained with a wavelength of 250 nm to 900 nm, a polydispersity index (PDI) of ≤0.22, a zeta potential of -35 mV to -55 mV, and a residual solvent content of ≤0.15 wt% as determined by headspace gas chromatography.

[0065] Specific preparation of PHA latex A, B, C, and D:

[0066] PHA Latex A: Prepared using the aforementioned PHA latex preparation method one, with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) powder as the raw material. The barrel temperature range was 140℃ to 165℃, and the screw speed was approximately 300 rpm. Deionized water at approximately 60℃ was introduced in the middle section, with a water-to-PHA mass ratio of approximately 1.2:1. After online vacuum degassing, it was homogenized twice under high pressure at 90 MPa to obtain PHA latex A. Its D 50 The wavelength is 320 nm, the PDI is 0.22, the Zeta potential is -45 mV, and the headspace GC residual solvent is less than or equal to 0.05 wt%.

[0067] PHA Latex B: Prepared using the aforementioned PHA latex preparation method two. In step 1, the raw material is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) powder, the pH is adjusted to 8.7, and the carboxyl neutralization degree is 75%. In step 2, high shear for 15 minutes and low shear for 45 minutes are performed. This yields PHA latex B. Its D... 50 The wavelength is 280 nm, the PDI is 0.21, the Zeta potential is -40 mV, and the headspace GC residual solvent is less than or equal to 0.02 wt%.

[0068] PHA Latex C: Prepared using the aforementioned PHA latex preparation method one, with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) powder as the raw material. The barrel temperature range was 145℃ to 170℃, and the screw speed was approximately 250 rpm. Water was added in stages at the end until the aqueous phase content was greater than or equal to 75 wt%. After online vacuum degassing, it was homogenized twice under high pressure at 90 MPa to obtain PHA latex C. Its D 50 The wavelength is 450 nm, the PDI is 0.22, the Zeta potential is -36 mV, and the headspace GC residual solvent is less than or equal to 0.05 wt%.

[0069] PHA latex D: Prepared using the aforementioned PHA latex preparation method one, with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) powder as the raw material. The barrel temperature range is 135℃ to 160℃, and the screw speed is approximately 350 rpm. Water is fed from the side, with a water-to-PHA mass ratio of approximately 1.5:1. The initial high-shear stage is followed by a cooling stage, which is the reverse. The mixture is homogenized three times under high pressure (120 MPa) to obtain PHA latex D. 50 The wavelength is 260 nm, the PDI is 0.19, the Zeta potential is -52 mV, and the headspace GC residual solvent is less than or equal to 0.05 wt%.

[0070] All the above latexes were confirmed to have no total organic fluorine in accordance with EN 14582 or ASTM D7359 standards, i.e., the method detection limit is < or equal to 5 mg / kg, and the total protein and peptidoglycan residues were confirmed to be <0.05 wt% by colorimetric method.

[0071] Preparation method of pigment dispersion slurry:

[0072] Step 1. Add the pigment powder and acrylate dispersant to deionized water, then add a neutralizing agent and adjust the pH value to 8.5 to 9.0 to obtain the slurry to be dispersed.

[0073] Step 2. Disperse the slurry obtained in Step 1 using a high-shear disperser for 10 to 30 minutes, then switch to low-shear aging for 20 to 40 minutes to obtain a dispersion.

[0074] Step 3. Sieve the dispersion obtained in Step 2 to remove coarse particles and control D. 90Particle size <1µm yields pigment dispersion slurry.

[0075] Preparation method of water-based ink composition:

[0076] Step 1. Prepare the pigment dispersion slurry according to the aforementioned method.

[0077] Step 2. Prepare PHA latex using PHA powder as raw material according to either PHA latex preparation method one or PHA latex preparation method two described above.

[0078] Step 3. Add the PHA latex obtained in Step 2, acrylic emulsion, and / or waterborne polyurethane dispersion to the pigment dispersion slurry obtained in Step 1, add water, co-solvent, and functional additives, and adjust the pH value to 8.2 to 9.2 to obtain the base ink after ink preparation.

[0079] Step 4. 0 to 8 hours before printing, add polycarbodiimide and / or an oxazoline-containing polymer to the base ink obtained in Step 3, and mix with a stirrer for 10 to 30 minutes to obtain the ink composition.

[0080] Step 5. Filter the ink composition obtained in Step 4 through a 100-mesh to 200-mesh filter and then fill it to obtain the filled water-based ink composition.

[0081] Examples and Comparative Examples:

[0082] Example 1: This example provides a flexographic black ink for cardboard printing. Its wet formulation has a total solids content of 42wt% ± 1wt%, and the testing standard is based on ISO 3251. The raw material composition is as follows: 30.31 parts of carbon black dispersion paste, which has a total solids content of 45wt% and is prepared according to the aforementioned method for preparing pigment dispersion paste; 35.0 parts of PHA latex A, with a total solids content of 40wt%; 25.0 parts of acrylic emulsion A, with a total solids content of 45wt%; 5.11 parts of wax emulsion, with a total solids content of 30wt%; 0.3 parts of co-solvent, which is a mixture of dipropylene glycol butyl ether and dipropylene glycol methyl ether in a 1:1 mass ratio; 0.6 parts of wetting and leveling agent; 0.4 parts of defoamer; 2.01 parts of polycarbodiimide, a dispersion with a total solids content of 40wt%, equivalent to 0.804 parts of active solids; and 1.8 parts of deionized water, used to adjust the total solids content to 42wt% ± 1wt%. Pigment: Carbon black; 32.3 wt% on dry solids. Functional solids: 6 wt%. Crosslinking solids: 1.9 wt% (derived from polycarbodiimide). In this embodiment, the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent in the binder to the carboxyl equivalent is 0.95.

[0083] Example 2: This example provides a biaxially oriented polypropylene surface gravure blue ink. Its wet formulation has a total solids content of 40wt%±1wt%, and the testing standard is based on ISO 3251. The raw material composition is as follows: 25.80 parts of CIPB15:3 pigment dispersion, with a total solids content of 45wt%; 28.0 parts of PHA latex B, with a total solids content of 45wt%; 22.0 parts of waterborne polyurethane dispersion, with a total solids content of 35wt%; 12.0 parts of acrylic emulsion B, with a total solids content of 45wt%; 4.60 parts of wax emulsion; 0.5 parts of cosolvent, composed of dipropylene glycol butyl ether and ethyl lactate mixed in a 1:1 mass ratio; 0.7 parts of wetting and leveling agent; 0.4 parts of defoamer; 5.10 parts of oxazoline polymer, an aqueous dispersion, equivalent to 1.53 parts of active solids; and 5.6 parts of deionized water, used to adjust the total solids content to 40wt%±1wt%. Pigment: CIPB15:3; 28.1 wt% on dry solids. Functional solids: 6 wt%. Crosslinking solids: 3.7 wt% (derived from oxazoline-containing polymers). In this embodiment, the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent in the binder to the carboxyl equivalent is 0.95.

[0084] Example 3: This example provides a biaxially oriented polyethylene terephthalate (PET) surface printing white ink. Its wet formulation has a total solids content of 43wt% ± 1wt%, and the testing standard is based on ISO 3251. The raw material composition is as follows: 18.21 parts of titanium dioxide pigment dispersion, with a total solids content of 70wt%; 30.0 parts of PHA latex A, with a total solids content of 40wt%; 25.0 parts of waterborne polyurethane dispersion, with a total solids content of 35wt%; 10.0 parts of acrylic emulsion B, with a total solids content of 45wt%; 4.95 parts of wax emulsion; 0.4 parts of cosolvent, which is dipropylene glycol methyl ether; 0.6 parts of wetting and leveling agent; 0.4 parts of defoamer; 2.28 parts of polycarbodiimide, a dispersion with a total solids content of 40wt%, equivalent to 0.912 parts of active solids; and 3.5 parts of deionized water, used to adjust the total solids content to 43wt% ± 1wt%. Pigment: Titanium dioxide (anatase / rutile); 30.8 wt% on dry solids. Functional solids: 6 wt%. Crosslinking solids: 2.2 wt% (derived from polycarbodiimide). In this embodiment, the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent in the binder to the carboxyl equivalent is 0.95.

[0085] Example 4: This example provides a flexographic red ink for paper bags with a high PHA ratio. Its wet formulation has a total solids content of 39wt% ± 1wt%, and the testing standard is based on ISO 3251. The raw material composition is as follows: 34.52 parts of CIPR57:1 pigment dispersion, with a total solids content of 40wt%; 45.0 parts of PHA latex C, with a total solids content of 40wt%; 10.0 parts of acrylic emulsion A, with a total solids content of 45wt%; 5.20 parts of wax emulsion; 0.3 parts of cosolvent, which is dipropylene glycol methyl ether; 0.5 parts of wetting and leveling agent; 0.3 parts of defoamer; 1.67 parts of polycarbodiimide, a dispersion with a total solids content of 40wt%, equivalent to 0.67 parts of active solids; and 2.0 parts of deionized water, used to adjust the total solids content to 39wt% ± 1wt%. Pigment: CIPR57:1; 35.1wt% on a dry solids basis. Functional solids: 6wt%. Crosslinked solids: 1.7 wt% (derived from polycarbodiimide). In this embodiment, the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent to the carboxyl equivalent in the binder to the carboxyl equivalent is 0.95.

[0086] Example 5: This example provides a thin-film surface-printing blue ink using low-particle-size PHA latex. Its wet formulation has a total solids content of 38wt% ± 1wt%, and the testing standard is based on ISO 3251. The raw material composition is as follows: 26.14 parts of CIPB15:3 pigment dispersion, with a total solids content of 45 wt%; 20.0 parts of PHA latex D, with a total solids content of 40 wt%; 40.0 parts of waterborne polyurethane dispersion, with a total solids content of 35 wt%; 5.0 parts of acrylic emulsion, with a total solids content of 45 wt%; 3.67 parts of wax emulsion; 0.6 parts of cosolvent, which is ethyl lactate; 0.8 parts of wetting and leveling agent; 0.5 parts of defoamer; 2.00 parts of polycarbodiimide, which is a dispersion with a total solids content of 40 wt%, equivalent to 0.8 parts of active solids; 2.64 parts of oxazoline-containing polymer, which is an aqueous dispersion, equivalent to 0.8 parts of active solids; and 6.0 parts of deionized water, used to adjust the total solids content to 38 wt% ± 1 wt%. Pigment: CIPB15:3; 29.4 wt% on a dry solids basis. Functional solids: 6 wt%. Crosslinked solids: 4.0 wt% (derived from polycarbodiimide and oxazoline-containing polymers). This example is a dual crosslinking agent system. Based on the carboxyl equivalent in the binder, the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent to the carboxyl equivalent is 0.95.

[0087] Example 6: This example is used for equivalence window verification. Its wet formulation components are the same as in Example 2, with a total solids content of 40wt% ± 1wt%. Pigment: CIPB15:3; 28.1wt% on a dry solids basis. Functional solids: 6wt%. Crosslinking solids: 3.7wt% (derived from an oxazoline-containing polymer). In this example, the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent divided by the carboxyl equivalent is adjusted to 0.95.

[0088] Comparative Example 1: This comparative example is a PHA-free system. Based on Example 2, PHA latex B was removed and replaced with an acrylic emulsion and an aqueous polyurethane dispersion with the same total solids content. The crosslinking agent used was the same as in Example 2. The total solids content was 40 wt% ± 1 wt%. Pigment: CIPB15:3; 28.1 wt% on dry solids. Functional solids: 6 wt%. Crosslinking solids: 3.7 wt% (derived from an oxazoline-containing polymer).

[0089] Comparative Example 2: This comparative example is a non-crosslinked system. Based on Example 1, polycarbodiimide was removed, while the remaining components remained unchanged. The total solids content was 42wt% ± 1wt%. Pigment: Carbon black; 32.3wt% on dry solids. Functional solids: 6wt%. Crosslinking solids: 0wt% (no crosslinking agent added).

[0090] Comparative Example 3: This comparative example uses a fluorinated additive system. Based on Example 2, a fluorinated surfactant was used instead of the wetting and leveling agent, while the remaining components remained unchanged. The total solids content was 40wt% ± 1wt%. Pigment: CIPB15:3; 28.1wt% on dry solids. Functional solids: 6wt%. Crosslinking solids: 3.7wt% (derived from an oxazoline-containing polymer).

[0091] Comparative Example 4: This comparative example is a coarsely dispersed latex system. Based on Example 1, PHA latex A was replaced with median particle size D. 50 This is a coarsely dispersed emulsion with a wavelength of 1000 nm to 1500 nm. The emulsion is printable but produces a loose ink layer, while the other components remain unchanged. The total solids content is 42 wt% ± 1 wt%. Pigment: Carbon black; 32.3 wt% on a dry solids basis. Functional solids: 6 wt%. Crosslinking solids: 1.9 wt% (derived from polycarbodiimide).

[0092] Comparative Example 5: This comparative example is a system with a low crosslinking equivalent. Based on Example 2, only the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent divided by the carboxyl equivalent was adjusted to 0.50, while the other components remained unchanged. The total solids content was 40wt% ± 1wt%. Pigment: CIPB15:3; 29.3wt% on a dry solids basis. Functional solids: 6wt%. Crosslinking solids: 2.5wt% (derived from the oxazoline-containing polymer).

[0093] Comparative Example 6: This comparative example is a system with a relatively high crosslinking equivalent. Based on Example 2, only the ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent divided by the carboxyl equivalent was adjusted to 1.30, while the other components remained unchanged. The total solids content was 40wt% ± 1wt%. Pigment: CIPB15:3; 27.0wt% on a dry solids basis. Functional solids: 6wt%. Crosslinking solids: 4.8wt% (derived from the oxazoline-containing polymer).

[0094] Formula Overview Table:

[0095] Table 4 Key component ratios of the examples and comparative examples (by mass percentage of dry solids):

[0096]

[0097] Note: Top layer = pigment solids + binder solids + functional solids + crosslinking solids.

[0098] Table 5 General physicochemical properties (25℃) of the wet formulations of the examples and comparisons:

[0099]

[0100] Application example:

[0101] General instructions: Particle size (DLS) and zeta (ELS) are tested at 25°C; surface tension is determined according to ISO 1409:2020 (25°C, Wilhelmy); viscosity is determined according to GB / T 2794-2022 (25°C).

[0102] Application Example 1: Flexographic printing performance on paper / paperboard.

[0103] Experimental Description: This experiment aims to systematically evaluate the printability and physicochemical stability of different water-based ink compositions on porous cellulose substrates. The test substrate was industrial standard 150g / m² kraft paper, and the printing equipment was a modular flexographic printing press. During the experiment, the anilox roller parameters were strictly set to an ink load of 8 cm³ / m² and a line count of 157 lines / cm to ensure consistent ink transfer across all samples. The printing speed was fixed at 150 m / min, and the drying unit temperature was set to 90°C. Ink samples from Examples 1 to 6 and Comparative Examples 1 to 6 were selected for testing. After printing, the samples were equilibrated in a constant temperature and humidity environment of 25°C and 50% RH for 24 hours. Subsequently, ink adhesion was tested using the tape tear test according to ASTM D3359, and wet rubbing resistance (4 lb load) was tested using a friction tester according to ASTM D5264. The residual volatile organic compound content and residual moisture content of the printed product were also determined. In addition, the viscosity change rate of the ink after 7 days of storage at 50℃ was recorded. The criteria for passing this experiment are as follows: ink adhesion grade ≤ 1, wet rubbing resistance ≥ 250 times, residual water content of the printing film < 1.0 wt%, viscosity change rate after 7 days of storage at 50℃ ≤ 10%, and no obvious stratification observed after static observation; samples that meet all the above indicators are considered qualified, otherwise they are considered unqualified.

[0104] Table 6. Flexographic printing performance of paper / paperboard:

[0105]

[0106] Analysis: Statistical results of the experimental data show that Examples 1 to 6, containing PHA latex, all formed continuous and tightly bonded ink layers on the paper substrate surface, and all performance indicators met the qualified standards. Specifically, the adhesion level of the example groups was stable at 0–1, and the number of wet rubs ranged from 260 to 310, indicating that the introduction of hydrophobic bio-based polyester components effectively reduced the penetration rate of water to the ink layer interface. In contrast, although Comparative Example 1, which did not contain PHA latex, showed no significant difference in drying speed, its wet rub resistance was only 130 times, its adhesion dropped to 3, and its viscosity change rate reached 12%, failing to meet the qualified requirements. This indicates that relying solely on acrylic emulsion on the porous substrate surface is insufficient in terms of film density and system stability. Comparative Example 4 used large particle size (D 50Latex particles larger than 1000 nm resulted in reduced ink layer packing density, adhesion degradation to level 5, and a residual water content as high as 3.2%, confirming the crucial role of latex particle size control in microscopic film formation quality. Furthermore, Comparative Example 5 (equivalent ratio 0.50) and Comparative Example 6 (equivalent ratio 1.30), with deviations in the crosslinking agent equivalent ratio, both exhibited decreased durability. The former suffered from weakened abrasion resistance due to insufficient crosslinking density, while the latter experienced increased ink layer brittleness due to excessive crosslinking, thus affecting adhesion strength. The data indicate that specific component formulation and process window are necessary conditions for ensuring satisfactory paper-based printing performance.

[0107] Application Example 2: Printability of Plastic Films (BOPP Standard).

[0108] Experimental Description: This experiment focuses on investigating the wetting and spreading ability, interfacial adhesion, and environmental compliance of the ink composition on a non-absorbent hydrophobic substrate. A 30µm thick biaxially oriented polypropylene (BOPP) film was used as the substrate. Before the experiment, the surface free energy of the film was increased to above 40mN / m using an online corona treatment device. Gravure printing was used. The viscosity of all samples was uniformly adjusted to 35mPa·s (25℃), and the printing speed was set to 120m / min. The drying system used a combination of 100℃ hot air and infrared radiation (IR). All examples and comparative examples were tested. After printing, the samples underwent a 24-hour curing period, followed by multiple performance characterizations: including cross-cut adhesion testing according to ASTM D3359, wet rubbing resistance and 95% ethanol rubbing resistance testing using a rubbery tester, and surface tension determination of the wet ink using the Wilhelmy dipstick method. Simultaneously, the total organic fluorine content in the dry film was determined using combustion ion chromatography. The criteria for passing this experiment are as follows: ink adhesion grade ≤ 1, total organic fluorine (TOF) not detected (method detection limit ≤ 5 mg / kg), and volatile organic compound (VOC) mass fraction ≤ 1 wt%; only samples that meet all three of the above criteria are judged to be qualified for BOPP direct printing.

[0109] Table 7. Gravure Printing Performance of Thin Films (BOPP):

[0110]

[0111] Analysis: On the corona-treated BOPP substrate, Examples 1 to 6 exhibited satisfactory wetting and film-forming properties, with surface tension controlled between 30.8 and 32.5 mN / m, adhesion reaching grade 0–1, and total organic fluorine levels were undetectable, meeting environmental compliance requirements. This indicates that, without introducing fluorinated surfactants, the wetting problem of water-based inks on plastic films can be effectively solved through the synergistic effect of surface energy matching of the resin system and an appropriate amount of non-fluorinated wetting and leveling agents. Although Comparative Example 3 reduced the surface tension to 26.5 mN / m and achieved good abrasion resistance by introducing fluorinated additives, it was deemed unqualified based on the criterion due to the detection of residual total organic fluorine (>5 mg / kg). Comparative Example 1, lacking the hydrophobic framework provided by PHA latex, had a wet abrasion resistance of only 60 cycles, an alcohol resistance of only 30 cycles, and an adhesion grade of 4, indicating that ordinary acrylic resin cannot provide sufficient interfacial bonding without a primer. Comparative Example 2, in the absence of a crosslinking agent, showed a normal film appearance but significantly reduced chemical resistance, confirming the necessity of a post-crosslinking strategy for constructing a durable network structure. Overall data trends indicate that the introduction of bio-based latex, combined with precise control of crosslinking equivalence, is an effective way to achieve satisfactory direct printing performance of films.

[0112] Application Example 3: Paper-based ink removal and EPRC scoring.

[0113] Experiment Description: This experiment aims to quantitatively evaluate the deinking efficiency of printed materials in a standard waste paper recycling process and its impact on the quality of recycled pulp, based on the relevant standards of the European Paper Recycling Council (EPRC). The experiment strictly followed the ISO 21993:2020 standard and the INGEDE Method 11 test method. First, the printed samples prepared in Application Example 1 underwent artificial aging treatment, and then were placed in a Hobart N50 pulper for pulping in a chemical medium containing sodium hydroxide, sodium silicate, hydrogen peroxide, and sodium oleate. The pulp suspension was then fed into a Voith Delta 25 laboratory flotation tank, where ink particles were removed by bubble adsorption. During the experiment, an image analysis system was used to monitor changes in pulp brightness (ΔL*), color change (Δa*), and the total area of ​​ink particles larger than 250µm remaining on the filter paper after deinking. Finally, the EPRC score was calculated based on each indicator. The criteria for determining the pass / fail status of this experiment are as follows: an EPRC score of ≥71 points calculated according to INGEDE Method 11 (i.e., achieving a rating of "good" or above); samples that meet this score requirement are deemed to have qualified ink removal performance, while those that do not are deemed unqualified.

[0114] Table 8. Ink removal indexes and EPRC scores:

[0115]

[0116] Analysis: According to the test results, the EPRC scores of Examples 1 to 6 ranged from 84 to 90 points, all exceeding the passing score of 71 points. Furthermore, the pulp exhibited high whiteness after deinking, with fewer large residual ink particles. This satisfactory deinking performance is primarily attributed to the physical properties of PHA latex. Under alkaline pulping conditions, it neither completely dissolves (avoiding increased wash water color due to dissolved dyes) nor forms large, difficult-to-break adhesive particles. Instead, it tends to form hydrophobic fragments of suitable size that are easily captured by air bubbles and separated by flotation. In contrast, Comparative Example 1 (pure acrylic system), while achieving the passing score, showed a slightly lower improvement in brightness compared to the Example groups. Notably, Comparative Example 6 (high crosslinking equivalent) had an EPRC score below 70 points, deemed unqualified. This is because the excessively high crosslinking density enhanced the cohesion and alkali resistance of the ink film, making it difficult to effectively peel off from the fiber surface during mechanical pulping, or resulting in excessively large, difficult-to-float flakes after peeling. Data analysis shows that, while ensuring printability, controlling the degree of crosslinking and the hydrophilic-hydrophobic balance of the polymer are key factors in ensuring that paper-based packaging meets recyclability standards.

[0117] Application Example 4: Coefficient of friction and resistance to adhesion of film rolls.

[0118] Experimental Description: This experiment focuses on evaluating the tribological properties and anti-blocking performance of the ink printing film surface to verify its suitability for roll-to-roll processing and high-speed automated packaging lines. The BOPP printing sample prepared in Application Example 2 was conditioned for 24 hours in a standard environment of 25°C and 50%RH. The static coefficient of friction (μ) between the printing film surfaces was measured using a precision friction coefficient tester according to ASTM D1894 standard. s ) and coefficient of kinetic friction (μ k Simultaneously, according to ASTM D4946 standard, the adhesive resistance test was conducted: the printed samples were stacked back to back, a standard load of 0.91 kg was applied, and the samples were kept in a 40°C environment for 30 minutes. After cooling, the samples were manually peeled off, and a grade of 0–10 was assigned based on the ease of peeling and the extent of ink layer damage. Samples that could not complete the test due to poor adhesion causing ink layer detachment were recorded as "not applicable". The pass / fail criteria for this test are as follows: static friction coefficient (μ) s The coefficient of kinetic friction (μ) is between 0.25 and 0.45. k The coefficient of friction must be between 0.20 and 0.40, and the resistance level must be ≥ 8. Only samples that meet both the coefficient of friction range and resistance level requirements are considered qualified.

[0119] Table 9. Friction coefficient and adhesion resistance:

[0120]

[0121] Analysis: Test data shows that the static friction coefficients of Examples 1 to 6 range from 0.30 to 0.35, and the dynamic friction coefficients range from 0.22 to 0.27, with all achieving a resistance level of 9 or 10. All indicators fall within the set acceptable range. This specific friction coefficient range meets the technical requirements for the smoothness of packaging materials in conventional vertical and horizontal automatic packaging machines, preventing film feeding stoppages due to excessive friction and avoiding roll misalignment or loosening due to insufficient friction. The excellent resistance performance is attributed to the surface migration and enrichment of the wax emulsion during film formation, as well as the high crystallinity and glass transition temperature of the PHA material itself, ensuring that the ink layer does not soften and stick under heat and pressure. In contrast, Comparative Example 4 (coarsely dispersed latex) has static / dynamic friction coefficients as high as 0.46 / 0.41, and a resistance level of only 6, which is deemed unacceptable. This indicates that the rough surface morphology is not conducive to the effective distribution of slip additives. For Comparative Examples 1, 2, 5, and 6, due to their poor adhesion to the BOPP substrate, large-area peeling of the ink layer occurred during the test, making it impossible to obtain effective tribological data. This confirms that good adhesion is a prerequisite for achieving functional performance indicators.

[0122] Application Example 5: Energy consumption and residual water in high-speed gravure printing.

[0123] Experiment Description: This experiment aims to quantify the drying efficiency and energy consumption of ink under simulated high-speed industrial printing conditions to evaluate its practical production applicability. The experiment was conducted on a gravure printing press equipped with three independent temperature control zones (hot air + IR), using BOPP film as the printing substrate. The paper feed speed was increased to 180 m / min, and the temperature of each drying zone was set to 100℃. The active power of each drying unit and the substrate throughput time were recorded using a power analyzer, and the energy consumption index per unit printing area (kJ / m²) was calculated using a formula. Simultaneously, printed samples were taken from the rewinding section, sealed, and preserved. The residual moisture content (wt%) in the printed film was determined using headspace gas chromatography. The experiment also examined whether the ink layer could be sufficiently dried under high-speed conditions to prevent tackiness. Samples that could not form a complete roll due to adhesion failure or ink layer damage were marked as unmeasurable. The pass / fail criteria for this experiment are as follows: residual moisture content of the printed film < 1.0 wt%; samples meeting this indicator are considered to have qualified drying performance, otherwise they are considered unqualified.

[0124] Table 10 Energy Consumption Index and Residual Water (180 m³ / min; Three-zone hot air + IR; Drying setting 100℃):

[0125]

[0126] Analysis: Under high-speed printing conditions of 180 m / min, the residual water content of the printed films in Examples 1 to 6 was all controlled below 0.8 wt%, meeting the qualified standard of <1.0 wt%, with corresponding energy consumption indices between 110 and 130 kJ / m². Among them, Example 5 exhibited the lowest energy consumption (110 kJ / m²) and the lowest residual water content (0.5 wt%), which is related to the higher solid content and optimized solvent evaporation characteristics in this formulation. Compared with traditional high water-to-water ratio ink systems, the system of this invention significantly reduces the total enthalpy required for water evaporation by reducing the proportion of water (partially replaced by low latent heat organic co-solvents) and utilizing the mechanism of water repulsion by hydrophobic resins. In contrast, Comparative Example 4, due to the tendency of large-particle latex to cause interparticle water encapsulation during film formation, resulted in a residual water content as high as 1.6% under the same drying energy input, which was deemed unqualified. This not only increased production energy consumption but also greatly increased the risk of back adhesion after winding. The samples in Comparative Example 1 could not be effectively tested due to ink layer detachment under high wind speed and high tension. Data analysis shows that by designing the polymer microstructure and increasing the solid content of the formulation, the drying efficiency of water-based inks can be effectively improved, achieving the goal of low energy consumption. At the same time, the risk of back adhesion caused by moisture retention is avoided, verifying the practical application potential of this system in high-speed printing production lines.

[0127] Application Example 6: Pot life after crosslinking.

[0128] Experimental Description: This application example aims to evaluate the chemical stability of the water-based ink composition after actual printing press preparation, i.e., its pot life. Since this invention employs a two-component curing strategy with the addition of a post-crosslinking agent, evaluating its viscosity stability in the ink bath is crucial for ensuring continuous printing operations. The experiment was conducted strictly according to ISO standards and actual printing conditions. The specific operating steps were as follows: First, a certain amount of the base ink samples from Examples 1 to 6 and Comparative Examples 1 to 6 were accurately weighed and placed in a constant temperature environment (25±1℃). Subsequently, according to the equivalence ratio set for each formulation, metered amounts of polycarbodiimide and / or an oxazoline-containing polymer crosslinking agent were added. A magnetic stirrer was used to continuously stir at a speed of 300–500 rpm for 10–30 min to ensure that the crosslinking agent was uniformly dispersed in the system without localized excessive concentrations. The initial viscosity was recorded immediately after stirring and used as the starting time point (T0). Subsequently, under a constant temperature of 25°C, the sample viscosity was measured every 30 minutes using a rotational viscometer (AMETEK Brookfield DV2T LV, equipped with #2 or #1 rotor, 60 rpm) until the test was completed. The endpoint of the pot life was defined as: the sample viscosity rising to twice the initial viscosity, or the sample exhibiting obvious gelation, layering, or loss of flowability. The pass / fail criterion set for this experiment was: at 25°C, the ink pot life must be ≥4 hours. This duration is a key indicator for ensuring stable ink condition, consistent cell transfer, and avoiding downtime for cleaning the printing rollers during industrial continuous printing. Samples with a pot life <4 hours were deemed unqualified.

[0129] Table 11 Pot life after crosslinking (25℃):

[0130]

[0131] Analysis: Based on the experimental data in Table 11, a clear structure-property relationship conclusion can be drawn. First, the pot life of the ink compositions in Examples 1 to 6 after the addition of the crosslinking agent is distributed between 5.5 and 7.0 hours, fully meeting the qualification criterion of greater than or equal to 4 hours. This indicates that within the set carboxyl group / crosslinking agent equivalent ratio range (0.72–1.05), a kinetic balance is formed between the carboxyl group distribution density on the PHA latex surface and the active groups of the crosslinking agent. This balance ensures both the rheological stability of the ink during the printing process and the crosslinking density after drying and film formation.

[0132] In contrast, Comparative Example 6 increased the crosslinking agent equivalent ratio to 1.30, resulting in an excess of active groups in the system and a significantly accelerated reaction kinetics. The data primarily showed a drastically shortened pot life to 2.0 hours, rendering it unacceptable. In practical applications, this rapid viscosity increase can lead to cell clogging (screen blockage), poor transfer, and color variation fluctuations in printed products, severely impacting production efficiency. Conversely, while Comparative Example 5 had a longer pot life (9.0 hours), data from the aforementioned application examples showed that insufficient crosslinking density resulted in a sacrifice of the final ink layer's resistance (such as wet rubbing resistance).

[0133] Furthermore, while Comparative Example 1 (pure acrylic system) performed well in terms of its pot life, its main drawback was its inability to provide sufficient adhesion to the film substrate. Comparative Example 4 (coarsely dispersed PHA), although possessing acceptable chemical stability, suffered from decreased film-forming physical properties due to its excessively large particle size. Therefore, this invention, by precisely controlling the matching window between the surface charge characteristics (Zeta potential) of the PHA latex and the crosslinking equivalent, successfully found the optimal balance between the contradictory indicators of "on-board stability" and "curing reactivity," demonstrating the necessity and scientific validity of a specific equivalent ratio window (0.72–1.05) for achieving high-performance bio-based waterborne inks.

[0134] Experimental Results and Analysis:

[0135] Analysis of the impact of key components on performance:

[0136] The ratio of PHA latex to auxiliary resin: This invention balances the adhesion, durability and processing performance of the ink layer by adjusting the ratio of PHA latex to acrylic emulsion / waterborne polyurethane dispersion.

[0137] When the proportion of PHA latex in the binder is high, such as in Example 4 (approximately 64%), the ink layer exhibits a high paper base deinking score (EPRC score of 85) and acceptable adhesion, but the energy consumption index under high-speed drying conditions is slightly higher (128 kJ / m²).

[0138] When the proportion of PHA latex in the binder is low, such as in Example 5 (about 37%), the coating exhibits the lowest drying energy consumption (110 kJ / m²) and the highest wet rub resistance (350 times) when combined with a higher proportion of waterborne polyurethane dispersion.

[0139] Examples 1 and 2 demonstrate a comprehensive balance of adhesion (0–1 grade), wet rubbing resistance, and drying efficiency on BOPP film substrates.

[0140] The data from Comparative Examples 1 and 4 reveal the results of deviating from the technical concept: completely eliminating PHA latex (Comparative Example 1) resulted in a decrease in adhesion to uncoated BOPP to level 4 and a significant reduction in wet rubbing resistance (60 times); while the use of large-particle-size PHA latex (Comparative Example 4) affected the film density, leading to an increase in the coefficient of friction (COF > 0.4) and a decrease in the resistance level (level 6).

[0141] Control of crosslinking equivalent window:

[0142] This invention limits the ratio of (polycarbodiimide equivalent + oxazoline equivalent) to carboxyl equivalent to 0.72 to 1.05. Examples 1 to 6 all achieved simultaneous compliance with pot life (≥5.5 h) and wet rubbing resistance (≥260 cycles) within this range. Data indicate that this equivalent range is beneficial for forming an effective interpenetrating network structure.

[0143] Experimental results outside this range showed that when the ratio was too low (0.50 for Comparative Example 5), the crosslinking density was insufficient, resulting in a decrease in wet rubbing resistance to 150 cycles; when the ratio was too high (1.30 for Comparative Example 6), although the durability was acceptable, the pot life was shortened to 2.0 hours, and the paper base ink removal score dropped to below 70 points (unqualified) due to excessive crosslinking density.

[0144] Sustainability and compliance analysis:

[0145] The test results of all examples showed that total organic fluorine (TOF) was not detected (<5 mg / kg), meeting the requirements of the non-fluorinated technology route. A comparison with Comparative Example 3 (dependent on fluorinated additives, TOF detected) shows that the surface energy characteristics of bio-based resins, combined with non-fluorinated additives, can replace fluorinated surfactants. Furthermore, the paper deinking test results showed that the EPRC scores of Examples 1 to 6 in the recycling process all reached "Good" or higher (≥84 points), and the generated ink residue was mainly composed of easily removable fragments by flotation, indicating that the crosslinking system did not negatively impact paper fiber recycling.

[0146] Comprehensive evaluation of processing and application performance:

[0147] The industrial suitability of the formulation was verified through evaluation of high-speed printing energy consumption, coefficient of friction (COF), resistance to tack, and pot life. The example samples, at a printing speed of 180 m / min, maintained a residual water content below 0.8 wt% and an energy consumption index between 110 and 130 kJ / m², lower than Comparative Example 4 (high energy consumption due to high residual water). Simultaneously, the coefficient of friction of the example samples remained stable within the range of 0.25–0.45, and the resistance to tack rating was ≥9, indicating that its surface properties are suitable for the processing requirements of automated packaging lines.

[0148] In summary, the experimental data show that by controlling the ratio of micronized PHA latex to auxiliary resin and combining it with a specific crosslinking equivalent range, the water-based ink prepared by this invention has achieved the set technical indicators in terms of film adhesion, resistance, ink removal and processing adaptability, and meets the requirements of fluorine-free environmental protection.

[0149] Those skilled in the art should understand that the above embodiments are merely exemplary and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the technical solutions of the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bio-based low-VOC waterborne ink composition based on microbial fermentation of PHA, characterized in that, The composition, by weight percentage of dry solids, comprises: 28 wt% to 60 wt% pigment, 35 wt% to 65 wt% binder, 0.5 wt% to 6 wt% functional additives, and 0.5 wt% to 4 wt% crosslinking agent, wherein the binder comprises 10 wt% to 80 wt% of polyhydroxyalkanoate latex and the balance being acrylic emulsion and / or aqueous polyurethane dispersion. The composition, based on a wet formulation, has the following properties: total solids content of 32% to 50%, pH value of 8.2 to 9.2, viscosity at 25°C of 20 mPa·s to 800 mPa·s, volatile organic compound mass fraction ≤1 wt%, surface tension at 25°C of 30 mN / m to 38 mN / m, and total organic fluorine not detected, with a method detection limit ≤5 mg / kg; The content of water-soluble protective colloids and grafted or block polymeric dispersants of polyvinyl alcohol, cellulose and its derivatives, starch and its derivatives in the composition is all <0.10wt%, and the total residual amount of protein and peptidoglycan in the polyhydroxyalkanoate latex is <0.05wt%. The median particle size D of the polyhydroxyalkanoate latex was measured according to ISO 22412:2025 and ISO 13099-2:2025 standards. 50 The wavelength range is 250 nm to 900 nm, the polydispersity index is ≤0.22, the zeta potential is -35 mV to -55 mV, and the residual solvent content measured by headspace gas chromatography is ≤0.15 wt%. The ratio of the sum of the polycarbodiimide equivalent and the oxazoline equivalent, divided by the carboxyl equivalent, is 0.72 to 1.05, based on the carboxyl equivalent in the binder. The composition is suitable for direct flexographic or gravure printing without primer on polyolefin or polyester film substrates with a surface free energy greater than or equal to 40 mN / m. The functional additives include wetting and leveling agents and defoamers. The wetting and leveling agents are selected from siloxane-modified polyethers, polyether-type nonionic surfactants, and alcohol ether surfactants. The defoamers are selected from polyether-type defoamers, polyether-organosilicon composite defoamers, and mineral oil-type defoamers. All functional additives are non-fluorine-containing systems. The composition further includes a cosolvent, which is selected from one or more of dipropylene glycol butyl ether, dipropylene glycol methyl ether, and ethyl lactate, with a total amount ≤0.8wt% based on wet formulation, and the composition has a volatile organic compound mass fraction ≤1wt%, and the total organic fluorine is not detected, with a method detection limit ≤5mg / kg.

2. The water-based ink composition according to claim 1, characterized in that, The polyhydroxy fatty acid ester is selected from at least one of the following substances or copolymers formed between monomers forming the following substances: poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and medium- and long-chain polyhydroxy fatty acid esters. The medium- and long-chain polyhydroxy fatty acid esters are selected from poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3-hydroxydecanoate), poly(3-hydroxydodecanate), poly(3-hydroxydodecanate), poly(3-hydroxytetradecanoate), poly(3-hydroxyhexadecanoate), and poly(3-hydroxyhexadecanoate).

3. The water-based ink composition according to claim 1, characterized in that, The acrylic emulsion has a core-shell structure and is prepared by emulsion polymerization of one or more monomers selected from butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, styrene, acrylic acid, methacrylic acid, hydroxyethyl acrylate and / or hydroxypropyl acrylate.

4. The water-based ink composition according to claim 1, characterized in that, The pigment is selected from one or more of inorganic and organic pigments; The inorganic pigments are selected from titanium dioxide, iron oxide red, iron oxide yellow, zinc oxide, and ultramarine. The titanium dioxide is selected from anatase titanium dioxide or rutile titanium dioxide; The organic pigments include phthalocyanine blue, phthalocyanine green, quinacridone, benzodiimide, diimide, isoindolinone, benzimidazolone, and azo pigments, wherein the azo pigments include monoazo pigments and diazo pigments; Furthermore, the D of the pigment dispersion slurry prepared from the inorganic pigments and / or organic pigments is... 90 Particle size < 1µm.

5. The water-based ink composition according to claim 1, characterized in that, The functional additives comprise wax solids selected from one or more of polyethylene wax, polypropylene wax, Fischer-Tropsch wax, carnauba wax, cactus wax, rice bran wax, beeswax, and bio-based ester waxes, and the content of the wax solids is from 0.1 wt% to 5.0 wt% of the total dry solids of the water-based ink composition.

6. The water-based ink composition according to claim 1, characterized in that, The total equivalent ratio of polycarbodiimide to oxazoline-containing polymer is 0.72 to 1.05 based on the carboxyl equivalent in the binder; the amount of polycarbodiimide added is 0.3 wt% to 3.0 wt% based on total dry solids, with an equivalent equivalent of 140 g / eq to 300 g / eq, and the amount of oxazoline-containing polymer added is 0.5 wt% to 3.0 wt%, with an equivalent equivalent of 200 g / eq to 400 g / eq; the pot life at 25°C after adding the crosslinking agent is greater than or equal to 4 hours.

7. The water-based ink composition according to claim 1, characterized in that, The wet formulation of the composition has a surface tension of 30 mN / m to 38 mN / m at 25°C, and its storage stability meets the requirement that the viscosity change rate is ≤10% and there is no obvious stratification after 7 days of storage at 50°C.

8. A method for preparing the water-based ink composition according to claim 1, characterized in that, The preparation method includes the following steps: Step 1. Add pigment, acrylate dispersant, and neutralizer to deionized water, disperse using a high-shear disperser, and perform low-shear aging. Filter to remove coarse particles and control D. 90 Particle size <1µm, resulting in a pigment dispersion slurry; Step 2. Polyhydroxyalkanoate powder is melt-mixed with deionized water via co-rotating parallel twin-screw extruder. The mixture undergoes phase reversal within the extruder to form a crude emulsion. Subsequently, it is degassed online under vacuum and homogenized under high pressure. The high-pressure homogenization employs two-stage temperature control: an inlet temperature of 25°C to 35°C and an outlet temperature <45°C, to obtain polyhydroxyalkanoate latex. Alternatively, it can be neutralized and dispersed in an aqueous phase, followed by high-shear and low-shear treatments to obtain polyhydroxyalkanoate latex. Step 3. Add the polyhydroxyalkanoate latex obtained in Step 2, acrylic emulsion, and / or aqueous polyurethane dispersion to the pigment dispersion slurry obtained in Step 1, add water, co-solvent, and functional additives, and adjust the pH value to 8.2 to 9.2 to obtain the base ink after ink preparation. Step 4. 0 to 8 hours before printing, add polycarbodiimide and / or oxazoline-containing polymer to the base ink obtained in Step 3, and mix with a stirrer for 10 to 30 minutes to obtain the ink composition. Step 5. Filter the ink composition obtained in Step 4 through a 100-mesh to 200-mesh filter and then fill it to obtain the filled water-based ink composition.

9. The preparation method according to claim 8, characterized in that, After obtaining the latex via an aqueous neutralization and dispersion route, surface grafting of acrylic monomers with a content of ≤0.5wt% is performed without introducing grafted or block polymeric dispersants.

10. An application of the water-based ink composition according to claim 1, characterized in that, The composition is suitable for direct flexographic or gravure printing on paper, cardboard, and biaxially oriented polypropylene, biaxially oriented polyethylene terephthalate, treated polyethylene or their composite substrates with a surface free energy greater than or equal to 40 mN / m after corona or plasma treatment. The printing process does not rely on a primer or polyvalent metal salt pretreatment layer before printing. After printing, the material is dried with hot air, infrared or near-infrared at 60°C to 120°C.

11. The application according to claim 10, characterized in that, The composite material, after being printed into a film, exhibits a cross-cut adhesion rating of 0 to 1, as tested according to ASTM D3359 or GB / T 9286. It also withstands ≥250 wet rub cycles, as tested according to ASTM D5264. The residual moisture content of the printed film is <1.0 wt%. Furthermore, under conditions of 25°C and 50% relative humidity, the static friction coefficient of the printed film against biaxially oriented polypropylene is 0.25 to 0.45, and the dynamic friction coefficient is 0.20 to 0.40, as tested according to ASTM D1894.

12. The application according to claim 10, characterized in that, When the composition is used for printing on paper-based food packaging that directly or indirectly contacts food, it is used in conjunction with water-based varnish or heat-sealing coating, and the overall migration amount, specific migration amount and sensory verification are completed before it is put into use.

13. A printing method, characterized in that, The method includes: providing the water-based ink composition of claim 1; applying flexographic or gravure coating to the substrate of claim 10; drying at 60°C to 120°C until the residual moisture content of the printed film is <1.0 wt%, and completing the printing within a crosslinking application period of 4 to 24 hours; the flexographic printing conditions using an anilox roller with an ink load of 6 cm³ / m² to 12 cm³ / m² and a line count of 79 lines / cm to 197 lines / cm; and the gravure printing selecting a process viscosity within the viscosity range of 20 mPa·s to 800 mPa·s as described in claim 1 and setting the paper feed speed to suit the drying and adhesion requirements.

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