Method for improving the storage stability of liquid coating compositions

Abstract

The present application relates to a method for improving the storage stability of a liquid coating composition comprising a film-forming resin and two or more high molecular co-agents, wherein at least one high molecular co-agent is immiscible with the dispersion system of the liquid coating composition, the method comprising: i) providing the surface energy of the high molecular co-agent and the film-forming resin, the surface energy being obtained according to the measurement of the contact angle; ii) providing the interfacial energy between the high molecular co-agent and the film-forming resin and between the high molecular co-agents; iii) providing the wetting factor between the high molecular co-agent and the film-forming resin; iv) adjusting the feeding sequence of the high molecular co-agents according to the obtained wetting factor.

Description

Technical Field

[0001] This invention relates to a method for improving the storage stability of coating compositions, and more particularly to a method for improving the storage stability of liquid coating compositions. Background Technology

[0002] The application of coating additives is indispensable for improving coating production processes, ensuring the stability of coatings during storage and transportation, enhancing coating compatibility and overcoming coating defects, and improving coating application performance.

[0003] Special auxiliary materials added in small quantities to achieve specific requirements in coating production processes and coating performance are called coating additives, including polymeric additives. Coatings are combinations of various materials, and additives are essential for coating production. When a coating contains multiple additives, the compatibility between the additives and the base material, the synergy between additives, and the balance between the additives used to coordinate the contradictory performance requirements of the coating are all issues that need attention. Polymeric additives refer to additives that are themselves polymers or high-molecular-weight polymers. When a coating contains one or more polymeric additives, particular attention must be paid to the overall compatibility of the additives used. For example, with temperature changes, liquid coating compositions containing multiple polymeric additives face the problem of additive precipitation and clumping during storage, such as the typical floating wax phenomenon, which brings many inconveniences to construction and greatly increases the difficulty of construction. Currently, the main solutions to the problem of floating wax in liquid coating compositions during storage are to add additives that can eliminate the generated foam, such as defoamers, or to use physical defoaming methods such as nitrogen purging, installing rake devices, physical sweeping or puncturing defoaming, and spray defoaming. The solution implemented in the above manner not only increases the complexity and instability of the system, but also inevitably increases the cost.

[0004] Therefore, the coatings industry urgently needs a simple method to improve the storage stability of liquid coating compositions so that the resulting coating compositions can meet application requirements. Summary of the Invention

[0005] To fill the aforementioned gaps, the inventors of this invention conducted extensive experiments and data processing, and for the first time revealed that surface energy and interfacial energy can be used to evaluate the compatibility of raw materials, identify the wetting factors of different types of polymeric additives and the main resin, thereby providing a method for improving the storage stability of liquid coating compositions by using physical parameters through modeling.

[0006] Therefore, according to embodiments of the present invention, a method for improving the storage stability of a liquid coating composition is provided, the liquid coating composition comprising a film-forming resin and two or more polymeric additives, wherein at least one polymeric additive is immiscible with the dispersion system of the liquid coating composition, the method comprising:

[0007] i) Provide the surface energy of the polymeric additive and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle;

[0008] ii) Provide interfacial energy between the polymeric additive and the film-forming resin, as well as between the polymeric additives;

[0009] iii) Provides a wetting factor between the polymeric additive and the film-forming resin;

[0010] iv) Adjust the feeding sequence of the polymeric additives according to the obtained wetting factor.

[0011] In an embodiment of the present invention, the interface can be obtained according to the following formula:

[0012]

[0013] Where γ i It is the surface energy of component i, γ i d and γ i p These represent the contributions of dispersion and polarity to the surface energy of component i, respectively.

[0014] In an embodiment of the present invention, the wetting factor is obtained according to the following formula: Where γ A-B γ A-树脂 and γ 树脂-B These are polymeric additives, specifically A.

[0015] Preferably, in the method for improving the storage stability of a liquid coating composition according to the present invention, the step of adjusting the feeding sequence of the polymeric additives according to the obtained wetting factor includes: when ωa>1, pre-mixing polymeric additive A with film-forming resin, and finally adding polymeric additive B.

[0016] Preferably, in the method for improving the storage stability of a liquid coating composition according to the present invention, the step of adjusting the feeding order of the polymeric additives according to the obtained wetting factor includes: when the ωa of multiple polymeric additives is greater than 1, preferentially adding the polymeric additive with the highest ωa to the film-forming resin.

[0017] Preferably, in the method for improving the storage stability of a liquid coating composition according to the present invention, the liquid coating composition comprises an aqueous coating composition or a solvent-based coating composition, preferably an aqueous coating composition.

[0018] The inventors of this invention were surprised to discover that the method for improving the storage stability of liquid coating compositions according to this invention can model the data of polymeric additives and standardize the process. The method and model proposed by this invention help reduce the number of experiments and workload. Through the method and model proposed by this invention, the wetting factors of different types of polymeric additives and film-forming resins can be identified, and the process sequence can be formulated and optimized. This method is superior to other methods such as simply adding defoamers and physical purging defoaming, in terms of saving materials and energy consumption, making the method for improving storage stability simpler and easier to implement.

[0019] definition

[0020] Unless otherwise stated herein, the terms “a” or “an” as used in the context of describing the invention should be understood to include the plural.

[0021] When a composition is described as having, including, or containing specific components, or when a method is described as having, including, or containing specific process steps, it is anticipated that the composition of the present invention is substantially composed of or consisting of the components involved, or that the method of the present invention is substantially composed of or consisting of the process steps involved.

[0022] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0023] The terms "preferred" and "ideally" refer to embodiments of the invention that provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. Attached Figure Description

[0024] Figure 1The stability of a single wax additive in a liquid coating composition was demonstrated.

[0025] Figure 2 The stability of various combinations of wax additives in liquid coating compositions is shown.

[0026] Figure 3 The stability of a single wax additive in water is shown.

[0027] Figure 4 A schematic diagram showing the interactions between a) lanolin and carnauba wax, b) PE / PTFE wax and carnauba wax, and c) PE / PTFE wax and lanolin is shown.

[0028] Figure 5 and Figure 6 The relevant FTIR and DSC test results are shown respectively.

[0029] Figure 7 and Figure 8 Scaled-up experiments according to embodiments of the present invention are shown respectively.

[0030] Figure 9 A liquid coating composition without the addition of any surfactants is shown.

[0031] Figure 10 Liquid coating compositions prepared by changing the feed order of silwet@L7500 or PE / PTFE wax are shown.

[0032] Figure 11 A liquid coating composition prepared by adding BYK-019 is shown. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Improvements and adjustments made by those skilled in the art based on the present invention in practical applications still fall within the scope of protection of the present invention.

[0034] This invention provides a method for improving the storage stability of a liquid coating composition, the liquid coating composition comprising a film-forming resin and two or more polymeric additives, wherein at least one polymeric additive is immiscible with the dispersion system of the liquid coating composition, the method comprising:

[0035] i) Provide the surface energy of the polymeric additive and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle;

[0036] ii) Provide interfacial energy between the polymeric additive and the film-forming resin, as well as between the polymeric additives;

[0037] iii) Provides a wetting factor between the polymeric additive and the film-forming resin;

[0038] iv) Adjust the feeding sequence of the polymeric additives according to the obtained wetting factor.

[0039] Contact angle measurement is a traditional and effective method for assessing the surface energy of solids. The surface energy of a solid or liquid, as well as its dispersion and polar composition, can be calculated from contact angle data using the Owens-Wendt method (Equations (1) and (2)):

[0040]

[0041]

[0042] Where θ is the contact angle, γ is the surface energy, the subscripts 's' and 'l' represent solid and liquid respectively, and the superscripts 'd' and 'p' represent dispersed component and polar component respectively.

[0043] Generally, in order to obtain the surface energy γ of the solid from equations (1) and (2) s At least two liquids are required, and typically one polar liquid and one non-polar liquid should be used.

[0044] Contact angle testing was performed on a DSA100 instrument (Krüss GmbH, Germany) based on the handleless droplet method, where a drop of test liquid is deposited onto the sample surface. Each sample was tested at least six times to ensure the repeatability of the measurement data.

[0045] In the method according to the present invention, the interface can be obtained according to the following formula:

[0046]

[0047] Where γ 12 It is the interfacial energy between the two components, γ i It is the surface energy of component i, γ i d and γ i p These represent the contributions of dispersion and polarity to the surface energy of component i, respectively.

[0048] In the method according to the invention, the wetting factor is obtained according to the following formula: Where γ A-B γ A-树脂 and γ 树脂-B These are the interfacial energies between polymeric additives A and B, between polymeric additive A and the resin, and between the resin and polymeric additive B, respectively.

[0049] In the method according to the present invention, the step of adjusting the feeding sequence of the polymeric additive according to the obtained wetting factor includes:

[0050] When ωa>1, polymeric additive A is premixed with film-forming resin, and finally polymeric additive B is added.

[0051] In the method according to the present invention, the step of adjusting the feeding sequence of the polymeric additive according to the obtained wetting factor includes:

[0052] When the ωa of multiple polymeric additives is greater than 1, the polymeric additive with the highest ωa should be added to the film-forming resin first.

[0053] As an example, the liquid coating composition applicable to the method of the present invention includes an aqueous coating composition or a solvent-based coating composition, preferably an aqueous coating composition.

[0054] In the above-described liquid coating composition, a film-forming resin constitutes its main component. In the context of this application, the term "film-forming resin" refers to a resin component that can be coated onto a substrate or coating film and wherein the resin contained therein is dried, crosslinked, or otherwise hardened with a suitable curing agent as needed, thereby forming a non-sticky, continuous film on the substrate or coating film. As an example, the film-forming resin includes at least one of epoxy resins, chlorinated resins, alkyd resins, phenolic resins, polyurethanes, polysiloxanes, polyester resins, and acrylic resins, preferably at least one of acrylic resins and polyester resins. This application does not impose any particular limitation on the type of film-forming resin, as long as it can be used in the liquid coating composition. In addition to the resin components described above, the liquid coating composition also contains solvents (including but not limited to water, water-miscible organic solvents, or combinations thereof) and optional additional additives. These additional additives do not adversely affect the liquid coating composition or the coating obtained therefrom. Suitable additives include, for example, those agents that improve the processing or manufacturing properties of the liquid coating composition, or improve specific functional properties or characteristics of the composition or the coating obtained therefrom (such as adhesion to a substrate or undercoat). Possible additives include, for example, solubilizers, anti-migration agents, antibacterial agents, wetting agents, biocides, plasticizers, defoamers, antioxidants, adhesion promoters, UV stabilizers, or combinations thereof. The amounts of each optional component are sufficient to achieve the intended purpose, but preferably, such amounts will not adversely affect the liquid coating composition or the coating obtained therefrom.

[0055] In the above-mentioned liquid coating composition, the polymeric additives include at least one of wetting and dispersing agents, plasticizers, defoamers, leveling agents, anti-settling agents, adhesion promoters, matting agents, and slip agents.

[0056] Preferably, the polymeric additive is a wax additive, and preferably includes natural waxes and synthetic waxes. The natural waxes include paraffin wax, beeswax, cetacean wax, lanolin, carnauba wax, candelilla wax, Japanese wood wax, and combinations thereof; the synthetic waxes include Fischer-Tropsch wax, polyethylene wax, polypropylene wax, polyethylene / polypropylene wax, polytetrafluoroethylene wax, polyamide wax, oxidized polyethylene wax, grafted polypropylene wax, EVA wax, and combinations thereof.

[0057] In the method according to the invention, the liquid coating composition includes packaging coatings, coil coatings, industrial wood coatings, and other coating compositions containing polymeric additives, especially wax additives.

[0058] Therefore, in some preferred embodiments, the liquid coating composition is an aqueous coating composition, and the polymeric additive is a wax additive, preferably including lanolin, carnauba wax, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, and combinations thereof.

[0059] For liquid coating compositions, after storage for 3 days, preferably 5 days, more preferably 30 days, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition is reduced by at least 20%, preferably at least 25%, more preferably at least 30%, compared to the original liquid coating composition when the feed sequence of the polymeric additives is adjusted according to the method of the present invention.

[0060] The solubility or dispersibility of polymeric additives in liquids (such as water or other solvents) is more or less affected by temperature. Therefore, the method for improving the storage stability of liquid coating compositions according to the present invention is preferably applicable to regions with large temperature variations, preferably temperate and frigid zones.

[0061] It is evident that there are many methods for improving the storage stability of liquid coating compositions in the coatings industry. The inventors of this invention have surprisingly discovered that the method for improving the storage stability of liquid coating compositions according to this invention enables data modeling and process standardization of polymeric additives; the proposed method and model establishment help reduce the number of experiments and workload; through the proposed method and model establishment, the wetting factors of different types of polymeric additives and the main resin are identified, and the process sequence is formulated and optimized. This method, unlike other methods such as simply adding defoamers and physical purging defoaming, demonstrates superiority in terms of material and energy savings, making the method for improving storage stability simpler and easier to implement.

[0062] Surface energy and interfacial energy are used to evaluate the compatibility of various raw materials used in coating formulations.

[0063] In some embodiments of the present invention, the inventors, through extensive experiments and data analysis, have discovered that surface energy and interfacial energy can be used to evaluate the compatibility of various raw materials used in coating formulations. Specifically, in embodiments illustrated by way of example, liquid coating compositions, such as waterborne polyester coating compositions (e.g., 16VC020), are selected that contain a variety of wax additives listed in Table 1 below. After a period of storage, a waxy coating often appears.

[0064] Because 16VC020 contains three types of wax additives, the compatibility of each wax additive with the film-forming resin was evaluated. The resin's compatibility with water was initially studied by using a control group in which no wax additives were added to the liquid coating composition. Figure 1 As shown in Figure a, no phase separation was observed after 5 days, indicating that the film-forming resin used in the coating formulation has good miscibility and compatibility with water. However, this is not the case for liquid coating compositions containing wax additives, especially multiple wax additives. The presence of lanolin and PE / PTFE wax led to significant phase separation after 2 days. Lanolin was found on the top layer, while PE / PTFE wax was at the bottom, which may be due to their relative density with water (…). Figure 1 (b and 1c). When carnauba wax (hereinafter referred to as carnauba wax) was introduced into the liquid coating composition, phase separation was observed after 4 days. Figure 1 d). The extended time may be due to the higher stability of palm wax, as it is prepared in the form of a wax emulsion. This is in contrast to liquid coating compositions containing all wax additives. Figure 2 d) In contrast, introducing individual wax additives into the liquid coating composition did not result in the formation of wax lumps, which either floated on the surface of the liquid coating composition or adhered to the sidewalls of the bottle, even though the wax additives were unstable and tended to precipitate in the liquid coating composition. This indicates that no wax floating occurred, and therefore the interaction between wax additives may have played a role in the wax floating problem.

[0065] To investigate the interactions between wax additives, different combinations of three wax additives were added to liquid coating compositions, and the presence of floating wax was examined after 2 days. When lanolin and carnauba wax were added to the liquid coating composition, no obvious wax lumps were found on the sidewalls of the container. Furthermore, compared to the sample containing only lanolin (…), Figure 1 (b) Phase separation was not obvious, indicating that lanolin is more stable in the presence of carnauba wax. Figure 2 a) A similar situation occurs when PE / PTFE wax and carnauba wax are added to liquid coating compositions. For example... Figure 2 As shown in b, no wax lumps precipitated on the sidewalls or floated on the surface of the liquid coating composition. It should be noted that phase separation did occur after two days; however, unlike that observed in samples containing only PE / PTFE wax, the white powder settled to the bottom. Figure 1 c). Therefore, this may mean that palm wax can interact with lanolin and PE / PTFE wax, resulting in greater stability of both wax additives in liquid coating compositions. Conversely, when lanolin and PE / PTFE wax coexist in a liquid coating composition ( Figure 2 c) Significant wax deposition occurs on the sidewalls, and wax clumps are observed on the surface of the liquid coating composition. The wax float problem is even worse than that occurring in liquid coating compositions containing all wax additives. Figure 2 d). Clearly, lanolin and PE / PTFE wax have a synergistic effect on the wax floatation problem. The combination of wax auxiliaries exhibits different behavior in causing the wax floatation problem compared to samples using a single wax auxiliary agent. Therefore, the underlying mechanism behind this problem needs to be investigated.

[0066] Because wax additives are immiscible with water, they are more likely to precipitate from water-based coating compositions without the aid of resins. Unlike carnauba waxes, lanolin and PE / PTFE waxes can be dissolved or dispersed in organic solvents. Therefore, carnauba waxes are well miscible with water, while lanolin and PE / PTFE waxes are unstable in water (see [link to product description]). Figure 3 In this case, the potential for wetting by the film-forming resin is key to the retention of wax additives in the coating composition, and this possibility can be assessed by the interfacial energy between the film-forming resin and the wax additive. The water contact angle is used to measure the surface energy of the wax additive and the film-forming resin used in the waterborne coating composition, and the interfacial energy is obtained according to the following formula:

[0067]

[0068] Where γ 12 It is the interfacial energy between the two components, γ i It is the surface energy of component i, γ i d and γ i p These represent the contributions of dispersion and polarity to the surface energy of component i, respectively. The results are listed in Table 1.

[0069] Table 1: Surface energy and corresponding interfacial energy of film-forming resins, carnauba wax, PE / PTFE wax and lanolin

[0070]

[0071] As shown in Table 1, the interfacial energy between PE / PTFE wax and the film-forming resin is the highest. This indicates that the wax additive is unlikely to be wetted by the film-forming resin, resulting in the worst stability of PE / PTFE wax in liquid coating compositions. Furthermore, its interfacial energy is almost an order of magnitude higher than that of lanolin, so when lanolin and PE / PTFE wax are present together in a liquid coating composition, the film-forming resin tends to adhere to the lanolin, leaving the PE / PTFE wax uncoated. Consequently, the PE / PTFE wax is carried to the surface by air bubbles generated during the preparation of the liquid coating composition, leading to the problem of wax floating.

[0072] The inventors discovered that the wetting factor, defined by the following formula, can better explain the interactions between film-forming resins and different wax additives, as well as among different wax additives:

[0073] Where γ A-B γ A-树脂 and γ 树脂-B These are the interfacial energies between polymeric additives A and B, between polymeric additive A and the film-forming resin, and between the film-forming resin and polymeric additive B, respectively. Previously, ωa was widely used to predict the thermodynamic equilibrium distribution of particles in polymer mixtures, but this is the first time it has been used to evaluate or even improve the storage stability of liquid coating compositions.

[0074] When ωa > 1, particles of polymeric additive A exist only in the polymeric additive B phase; when ωa < -1, particles of polymeric additive A selectively concentrate in the resin phase; and when -1 < ωa < 1, particles of polymeric additive A exist at the interface between the polymeric additive B phase and the resin phase. In samples containing palm wax / lanolin and palm wax / polyethylene wax, the values ​​of ωa are -0.15 and -0.23, respectively, indicating that the wax particles are located at the interface between the two phases composed of film-forming resin and other wax additives. This allows the wax additive to interact with the resin, making it possible for the wax particles to be stabilized with the help of the resin (see...). Figure 4 (a and 4b). However, for lanolin and PE / PTFE wax, the result ωa is greater than 1 (see a and 4b). Figure 4 c). This indicates that PE / PTFE wax preferentially accumulates in the lanolin phase, resulting in less interaction with the film-forming resin. Therefore, PE / PTFE wax is unstable in liquid coating compositions and is easily carried to the surface by air bubbles. Liquid coating compositions containing lanolin and PE / PTFE wax exhibit an accelerated wax floating process, while no wax floating occurs in samples containing other types of wax additives.

[0075] In addition, the applicant used FTIR and DSC to determine the composition of the wax block. From Figure 5 PTFE (1202 and 1145cm) can be excluded in FTIR testing.-1 It may contain PE wax, carnauba wax, and lanolin; while from Figure 6 DSC testing at 120°C clearly showed the presence of PE wax. In other words, the FTIR and DSC results indicate that the main component of the wax block is polyethylene wax (PE wax), but no PTFE was found, possibly due to its higher density than water. The predominance of PE wax in the wax block may be related to its poorest stability in liquid coating compositions, which is supported by the mechanism mentioned above. However, it is also possible that more PE wax is introduced into the liquid coating composition relative to other waxes, thus causing this problem. Therefore, to determine the amount of wax in the wax block, the inventors conducted further DSC measurements. The actual weight ratio of wax in the wax block was estimated by DSC analysis of combinations of waxes with different weight ratios (Table 2), and the results are shown in Table 3. The weight ratios in Table 3 refer to the simplified internal ratios of the three wax additives—PE wax, palm wax, and lanolin—in the formulation. Using PE as the baseline (3), the ratio of PE wax: palm wax: lanolin in the formulation is 3:1:1.6. DSC peak area analysis of the actual enriched samples indicates that the actual PE: palm wax: lanolin ratio is approximately 3:0.6:<0.6. This set of experiments demonstrates that the enrichment of PE wax is not due to the high amount of PE added in the formulation. Compared to the weight ratios provided in the liquid coating composition, less palm wax and lanolin wax aggregated in the wax blocks. This indicates that PE wax precipitates more easily than other waxes; rather than dissolving more in solution, it has poor compatibility, resulting in a large amount of PE wax floating on the surface of the liquid coating composition and subsequently forming viscous lumps. This observation is consistent with the above mechanism, thus concluding that the interaction between various wax additives and resins can be predicted using interfacial energy and wetting coefficients, which is beneficial for future coating formulation design.

[0076] Table 2: DSC measurements of combinations of different wax additives with specific weight ratios

[0077]

[0078] Table 3: Actual weight ratio of wax additives in wax blocks analyzed by DSC

[0079] PE 3 3 palm wax 1 ～0.6 Lanolin 1.6 <0.6

[0080] Because PE / PTFE wax is abundant in wax blocks, stabilizing these wax additives is thought to alleviate the problem of wax float. In the original liquid coating composition, PE / PTFE wax was added last in the preparation process, while other wax additives and water were present in the liquid coating composition. This resulted in insufficient time for the PE / PTFE wax to interact with the film-forming resin. However, the highest interfacial energy of PE / PTFE wax indicates that these wax additives are difficult to wet with the film-forming resin, making it impossible for the PE / PTFE wax to be completely encapsulated in the film-forming resin. Without the help of the film-forming resin, these suspended wax particles tend to move towards the surface of the liquid coating composition in the presence of air bubbles. Furthermore, it is well known that the generation of air bubbles is unavoidable in liquid coating composition systems, and the number of air bubbles generated in this process can be correlated with the stirring speed. When there is a large amount of water in the liquid coating composition, the stirring speed is high, and the applicant found that PTFE can induce more air bubbles during stirring, possibly due to its low surface tension. Therefore, it can be expected that adding PE / PTFE wax to liquid coating compositions, especially water-based coating compositions, may lead to the problem of wax float.

[0081] To address this issue, one approach is to premix the PE / PTFE wax with the film-forming resin. In the waterborne polyester coating composition 16VC020, three film-forming resins were used, thus allowing for the selection of different weight ratios of film-forming resins and wax additives. To optimize wetting conditions, the interfacial properties of the wax additives and film-forming resins were evaluated, and the results are shown in Tables 4 and 5.

[0082] Table 4: Interfacial energies between premixed resins and wax additives with different combinations

[0083]

[0084] Table 5: Interfacial energies between resins and wax additives premixed with resins #2 and #4 at different weight ratios

[0085]

[0086]

[0087] As shown in Table 4, not all combinations of waxes and film-forming resins exhibit the lowest interfacial energy. Therefore, the problem of wax float may not be alleviated by randomly selecting film-forming resins to coat wax particles. For example, premixing the wax additive with all film-forming resins (i.e., #1 / #2 / #4) results in the highest interfacial energy, while using resins #2 and #4 can lower the interfacial energy. Therefore, the interaction between such film-forming resins and wax particles should be utilized. Compared to the sample prepared according to the original coating formulation, the bubble height decreased from 1.1 cm to 0.8 cm after adding pretreated PE / PTFE wax (i.e., premixing PE / PTFE wax with film-forming resin). This is likely due to the enhanced surface tension and better compatibility of the improved wax additive. The reduction in bubble height indicates a lower risk of inducing wax float. It should be noted that the bubble height did not decrease significantly, so it can be reasonably estimated that premixing the wax with the film-forming resin can only alleviate this problem to a certain extent.

[0088] Since premixing wax additives has limited effect on mitigating the problem of wax floating, an alternative method was proposed: changing the feeding order of PE / PTFE wax by introducing it before adding lanolin. This allows the PE / PTFE wax more time to interact with the film-forming resin, resulting in more wax being encapsulated within it. In the initial experiment, only PE / PTFE wax was added to the liquid coating composition. After changing the wax addition order, the bubble height was significantly reduced, and less wax precipitated at the bottom. This indicates that the PE / PTFE wax becomes relatively stable, and the wax floating phenomenon can be effectively alleviated.

[0089] Inspired by the expected results, the next step was to add all the waxes to the liquid coating composition while rearranging the feed sequence of the PE / PTFE waxes. After preparation, fewer bubbles were observed, and the residence time of bubbles was shortened after modifying the feed sequence of the coating formulation. Furthermore, the foam height was almost halved, and the phase separation process slowed down after 5 days, indicating a more stable liquid coating composition. This again demonstrates that changing the feed sequence can be a potential way to help solve the problem of floating wax, which was also confirmed by the fewer wax clumps found on the sidewalls after improving the preparation sequence.

[0090] Therefore, the present invention relates to a method for improving the storage stability of a liquid coating composition comprising a film-forming resin and two or more polymeric additives, wherein at least one polymeric additive is immiscible with the dispersion system of the liquid coating composition, the method comprising:

[0091] i) Provide the surface energy of the polymeric additive and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle;

[0092] ii) Provide interfacial energy between the polymeric additive and the film-forming resin, as well as between the polymeric additives;

[0093] iii) Provides a wetting factor between the polymeric additive and the film-forming resin;

[0094] iv) Adjust the feeding sequence of the polymeric additives according to the obtained wetting factor.

[0095] Furthermore, the inventors conducted further experiments to confirm the efficiency of the proposed method in solving this problem, particularly during scaling up. Similar results were obtained when the total amount of raw materials was increased from 1 kg to 3 kg. Adjusting the feeding sequence of the raw materials resulted in fewer bubbles being generated. Figure 7 ).

[0096] Another scale-up experiment was conducted using 15 kg of raw material, and the laboratory parameters were adjusted accordingly. To better simulate the factory preparation process, the position of the HSD disk and the stirring speed were changed. For example... Figure 8 As shown in Figure a, after 3 days, the sample prepared according to the original coating formulation's feed order exhibited approximately 3 times the bubble height of the sample obtained using the modified feed order. Furthermore, wax was visible throughout the surface of the liquid coating composition, while after adjusting the order of introducing the PE / PTFE wax, wax was only seen in a few locations. Figure 8 (b) So far, it can be concluded that rearranging the feed sequence helps to minimize the risk of wax floatation. Moreover, this is consistent with the predictions made by the interfacial energy mechanism mentioned above.

[0097] Preferably, in the method for improving the storage stability of a liquid coating composition according to the present invention, the step of adjusting the feeding sequence of the polymeric additives according to the obtained wetting factor includes: when ωa>1, pre-mixing polymeric additive A with film-forming resin, and finally adding polymeric additive B.

[0098] Preferably, in the method for improving the storage stability of a liquid coating composition according to the present invention, the step of adjusting the feeding order of the polymeric additives according to the obtained wetting factor includes: when the ωa of multiple polymeric additives is greater than 1, preferentially adding the polymeric additive with the highest ωa to the film-forming resin.

[0099] Preferably, in the method for improving the storage stability of a liquid coating composition according to the present invention, the liquid coating composition comprises an aqueous coating composition or a solvent-based coating composition, preferably an aqueous coating composition.

[0100] As indicated by the wetting factor above, lanolin and PE / PTFE wax are preferably in the same phase. To avoid interactions between these two wax additives, the feed order of the raw materials can be further adjusted during sample preparation, introducing lanolin last while keeping the PE / PTFE wax in an earlier stage. This reduces the expected interaction time between the wax additives, thus minimizing the interaction. Compared to samples where only the feed order of PE / PTFE wax is changed, altering the feed order of lanolin and PE / PTFE wax significantly improves the stability of the wax additives in the liquid coating composition and prevents wax floating.

[0101] For liquid coating compositions, after storage for 3 days, preferably 5 days, more preferably 30 days, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition is reduced by at least 20%, preferably at least 25%, more preferably at least 30% compared to the original liquid coating composition when the feed sequence of the polymeric additives is adjusted according to the method.

[0102] The solubility or dispersibility of polymeric additives in liquids (such as water or other solvents) is more or less affected by temperature. Therefore, the method for improving the storage stability of liquid coating compositions according to the present invention is preferably applicable to regions with large temperature variations, preferably temperate and frigid zones.

[0103] It is evident that there are many methods for improving the storage stability of liquid coating compositions in the coatings industry. The inventors of this invention have surprisingly discovered that the method for improving the storage stability of liquid coating compositions according to this invention enables data modeling and process standardization of polymeric additives; the proposed method and model establishment help reduce the number of experiments and workload; through the proposed method and model establishment, the wetting factors of different types of polymeric additives and the main resin are identified, and the process sequence is formulated and optimized. This method, unlike other methods such as simply adding defoamers and physical purging defoaming, demonstrates superiority in terms of material and energy savings, making the method for improving storage stability simpler and easier to implement.

[0104] Other experiments to solve the problem of floating wax

[0105] It has been shown that the presence of air bubbles causes wax additives to float, therefore, removing air bubbles during stirring is key to mitigating this problem. However, additives in liquid coating compositions, such as waterborne polyester coating composition 16VC020, such as surface wetting agents, leveling agents, and defoamers, can affect the generation and stability of air bubbles. To assess their effects, no surfactants were added to the liquid coating composition, and large air bubbles were observed after preparing the liquid coating composition. Figure 9a). Furthermore, the bubbles persisted for at least three days. This was expected given the absence of a defoamer in the liquid coating composition. After 7 days, a significant amount of wax additive clumped on the sidewalls and floated on the surface of the liquid coating composition. Conversely, by adjusting the order of addition of the PE / PTFE wax, fewer bubbles were generated, and their residence time was also shortened. Figure 9 b). Although some wax particles floated on the surface, the prepared samples showed better results. Figure 9 c). This result further confirms that adjusting the feeding sequence of wax additives can reduce wax floatation.

[0106] The addition of defoamers plays a crucial role in reducing bubbles; without them, many large bubbles are generated and do not dissipate quickly. In the waterborne polyester coating composition 16VC020, silwet@L7500 can be used as a defoamer. To achieve better defoaming performance after preparation, silwet@L7500 was introduced at the end, resulting in a slight reduction in foam height from 1.1 cm to 0.8 cm. Figure 10 The results indicate that readjusting the feed order of silwet@L7500 helps suppress foam formation. For comparison, the feed order of PE / PTFE wax was also readjusted, resulting in a foam height of 0.55 cm. Notably, the foam height was somewhat lower than that of samples prepared by simply changing the feed order of PE / PTFE wax. Therefore, readjusting the feed order of the wax additives, rather than the feed order of the defoamer silwet@L7500, may have a greater impact on resolving the wax floatation problem. Furthermore, similar results were obtained by adding 0.2 wt% of BYK-019, a novel defoamer, to the liquid coating composition. Figure 11 As shown, the foam height decreased from 1.1 cm to 0.95 cm, indicating that BYK-019 had a limited effect on preventing wax blockage. Since the waterborne polyester coating composition 16VC020 is a relatively mature and long-used formulation, the introduction of new raw materials is not considered. Therefore, the method according to the invention provides a simple and effective approach without requiring changes to the existing coating formulation.

[0107] The inventors of this invention were surprised to discover that the method for improving the storage stability of liquid coating compositions according to this invention can model the screening data of polymeric additives and standardize the process. The method and model proposed by this invention help reduce the number of experiments and workload. Through the method and model proposed by this invention, the wetting factors of different types of polymeric additives and the main resin can be identified, and the process sequence can be formulated and optimized. This method is superior to other methods such as simply adding defoamers and physical purging defoaming, in terms of saving materials and energy consumption, making the method for improving storage stability simpler and easier to implement.

[0108] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for improving the storage stability of a liquid coating composition, said liquid coating composition comprising a film-forming resin and two or more polymeric additives, wherein at least one polymeric additive is immiscible with the dispersion system of said liquid coating composition, said method comprising: i) Provide the surface energy of the polymeric additive and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle; ii) Provide interfacial energy between the polymeric additive and the film-forming resin, and between the polymeric additives themselves; iii) Provides a wetting factor between the polymeric additive and the film-forming resin; iv) Adjust the feeding sequence of the polymeric additives according to the obtained wetting factor; The interface can be obtained according to the following formula: Where γ i It is the surface energy of component i, γ i d and γ i p These are the contributions of dispersion and polarity to the surface energy of component i, respectively. The wetting factor is obtained according to the following formula: , where γ A-B γ A-树脂 and γ 树脂-B These are the interfacial energies between polymeric additives A and B, between polymeric additive A and resin, and between resin and polymeric additive B, respectively. The step of adjusting the feeding sequence of the polymeric additives based on the obtained wetting factor includes: When ωa > 1, polymeric additive A is premixed with film-forming resin, and finally polymeric additive B is added to the liquid coating composition.

2. The method for improving the storage stability of a liquid coating composition according to claim 1, wherein, The steps for adjusting the feeding sequence of the polymeric additives based on the obtained wetting factor include: When the ωa of multiple polymeric additives is greater than 1, the polymeric additive with the highest ωa should be added to the film-forming resin first.

3. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The liquid coating composition includes a water-based coating composition or a solvent-based coating composition.

4. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The liquid coating composition is a water-based coating composition.

5. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The polymeric additives include at least one of wetting and dispersing agents, plasticizers, defoamers, leveling agents, anti-settling agents, adhesion promoters, matting agents, and slip agents.

6. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The polymeric additive is a wax additive.

7. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The polymeric additives include natural waxes and synthetic waxes.

8. The method for improving the storage stability of a liquid coating composition according to claim 7, wherein, The natural waxes include paraffin wax, beeswax, cetacean wax, lanolin, carnauba wax, candelilla wax, Japanese wood wax, and combinations thereof; the synthetic waxes include Fischer-Tropsch wax, polyethylene wax, polypropylene wax, polyethylene / polypropylene wax, polytetrafluoroethylene wax, polyamide wax, oxidized polyethylene wax, grafted polypropylene wax, EVA wax, and combinations thereof.

9. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The liquid coating composition includes packaging coatings, coil coatings, industrial wood coatings, and other coating compositions containing polymeric additives.

10. The method for improving the storage stability of a liquid coating composition according to claim 9, wherein, The liquid coating composition includes other coating compositions containing wax additives.

11. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 3 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 20% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

12. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 3 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 25% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

13. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 3 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 30% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

14. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 5 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 20% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

15. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 5 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 25% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

16. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 5 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 30% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

17. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 30 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 20% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

18. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 30 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 25% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

19. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, After 30 days of storage, measured by the bubble method according to ASTM E 2407 04 (2015), the bubble height of the liquid coating composition was reduced by at least 30% compared to the original liquid coating composition when the feed sequence of the polymeric additives was adjusted according to the method.

20. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The method described is applicable to areas with large temperature variations.

21. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The method is applicable to both temperate and frigid zones.

22. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The liquid coating composition also includes a solvent and optional additional additives.

23. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The film-forming resin includes at least one of epoxy resin, chlorinated resin, alkyd resin, phenolic resin, polyurethane, polysiloxane, polyester resin and acrylic resin.

24. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein, The film-forming resin includes at least one of acrylic resins and polyester resins.

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