Method for improving 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 polymeric aids wherein at least one polymeric aid is immiscible with a dispersed system of the liquid coating composition, the method comprises the following steps: i) providing surface energy of the high-molecular auxiliary agent and the film-forming resin, wherein the surface energy is obtained according to a measured contact angle; ii) providing interfacial energy between the polymer aids and the film-forming resin and between the polymer aids; iii) providing a wetting factor between the polymer additive and the film-forming resin; and iv) adjusting the feeding sequence of the polymer additive according to the obtained wetting factor.

Description

Technical Field

[0001] The present invention relates to a method for improving the storage stability of a coating composition, and more particularly to a method for improving the storage stability of a liquid coating composition. Background Art

[0002] The strengthening of the coating production process, the stability of the coating during storage and transportation, the matching of the coating and the overcoming of coating defects, and the improvement and enhancement of the coating construction performance are all inseparable from the application of coating additives.

[0003] Some auxiliary special materials added in small amounts to meet certain specific requirements of the coating production process and coating performance are called coating additives, including polymer additives. Coatings are a combination of multiple materials, and additives are essential materials for coating production. When the coating contains multiple additives, the compatibility between the additives and the base material, the synergy between the additives, and the balance between the contradictions between the coating performance requirements with the additives are all issues that need attention. Polymer additives refer to additives that are macromolecules or polymers. When the coating contains one or more polymer additives, it is particularly important to pay attention to the overall matching of the additive application. For example, as the temperature changes, the liquid coating composition containing multiple polymer additives faces the problem of additive precipitation and agglomeration during storage, such as the typical wax floating phenomenon, which brings many inconveniences to the construction and greatly increases the difficulty of construction. So far, the main solution to the problem of wax floating faced by liquid coating compositions during storage is to add some additives that can eliminate the generated foam, such as some defoamers, to the coating composition, or to physically purge and defoam by nitrogen, install a rake device, physically sweep or puncture defoam, spray defoam, etc. 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 field urgently needs a simple method for improving the storage stability of a liquid coating composition so that the obtained coating composition can meet application requirements. Summary of the invention

[0005] In order to fill the above-mentioned gaps, the inventors of the present invention conducted a large number of experiments and data collation, and revealed for the first time that surface energy and interfacial energy can be used to evaluate the compatibility of raw materials and identify the wetting factors of different types of polymer additives and the main resin, thereby providing a method for improving the storage stability of liquid coating compositions using physical parameters in a modeling manner.

[0006] Therefore, according to an embodiment of the present invention, there is provided 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 polymer additives, wherein at least one polymer additive is immiscible with the dispersion system of the liquid coating composition, the method comprising:

[0007] i) providing the surface energy of the polymer auxiliary agent and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle;

[0008] ii) providing interfacial energy between the polymer additive and the film-forming resin and between the polymer additives;

[0009] iii) providing a wetting factor between the polymer auxiliary agent and the film-forming resin;

[0010] iv) adjusting the feeding sequence of the polymer additives according to the obtained wetting factors.

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

[0012]

[0013] where γ i is the surface energy of component i, γ i d and γ i p are the dispersion and polarity contributions to the surface energy of component i, respectively.

[0014] In an embodiment according to 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 They are polymer additive A respectively.

[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 order of the polymer additive according to the obtained wetting factor comprises: when ωa>1, pre-mixing the polymer additive A with the film-forming resin, and finally adding the polymer 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 polymer additives according to the obtained wetting factor comprises: when ωa of multiple polymer additives is greater than 1, preferentially adding the polymer 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 the present invention were surprised to find that the method for improving the storage stability of a liquid coating composition according to the present invention can model the data of polymer additives and standardize the process; the proposal of the method of the present invention and the establishment of the model can help reduce the number of experiments and workload; the proposal of the method of the present invention and the establishment of the model can identify the wetting factors of different types of polymer additives and film-forming resins, formulate and optimize the process sequence, which is different from other methods such as purely adding defoaming agents and physical blowing defoaming, and is superior in 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" used in the context of describing the present invention should be understood to include the plural.

[0021] Where a composition is described as having, comprising, or consisting of particular components, or where a method is described as having, comprising, or consisting of particular process steps, it is contemplated that the composition of the invention consists essentially of, or consists of, the referenced components, or that the method of the invention consists essentially of, or consists of, the referenced process steps.

[0022] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0023] The terms "preferred" and "preferably" refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the recitation of one or more preferred embodiments does not mean that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The stability of a single wax adjuvant in a liquid coating composition is shown.

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

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

[0027] Figure 4 Schematic diagrams showing the interactions between a) lanolin and palm wax, b) PE / PTFE wax and palm wax, and c) PE / PTFE wax and lanolin.

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

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

[0030] Fig. 9 A liquid coating composition without any added surfactant is shown.

[0031] Fig.10 The liquid coating compositions prepared by changing the silwet@L7500 or changing the feeding sequence of PE / PTFE wax are shown.

[0032] Fig.11 Shown is a liquid coating composition prepared with the addition of BYK-019. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. Improvements and adjustments made by those skilled in the art in practical applications according to the present invention still belong to the scope of protection of the present invention.

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

[0035] i) providing the surface energy of the polymer auxiliary agent and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle;

[0036] ii) providing interfacial energy between the polymer additive and the film-forming resin and between the polymer additives;

[0037] iii) providing a wetting factor between the polymer auxiliary agent and the film-forming resin;

[0038] iv) adjusting the feeding sequence of the polymer additives according to the obtained wetting factors.

[0039] Contact angle measurement is a traditional and effective method for evaluating the surface energy of solids. The surface energy of a solid or liquid and its dispersive and polar components 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’ denote solid and liquid, respectively, and the superscripts ‘d’ and ‘p’ denote dispersed and polar components, respectively.

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

[0044] The contact angle measurements were performed on a DSA100 instrument (Krüss GmbH, Germany) based on the sessile drop method, where a drop of the test liquid is deposited on the sample surface. At least six replicates were performed for each sample to ensure the reproducibility of the measurement data.

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

[0046]

[0047] where γ 12 is the interfacial energy between the two components, γ i is the surface energy of component i, γ i d and γ i p are 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 They are the interfacial energies between polymer additives A and B, between polymer additive A and resin, and between resin and polymer additive B.

[0049] In the method according to the present invention, the step of adjusting the feeding order of the polymer additive according to the obtained wetting factor comprises:

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

[0051] In the method according to the present invention, the step of adjusting the feeding order of the polymer additive according to the obtained wetting factor comprises:

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

[0053] As an illustrative example, the liquid coating composition suitable for use in 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-mentioned liquid coating composition, film-forming resin constitutes its main part. In the context of the present application, the term "film-forming resin" refers to a resin component, which can be applied to a substrate or a paint film and the resin contained therein is dried, crosslinked or otherwise hardened with a suitable curing agent as required, thereby forming a non-sticky continuous film on the substrate or the paint film. As an exemplary illustration, the film-forming resin includes at least one of epoxy resin, chlorinated resin, alkyd resin, phenolic resin, polyurethane, polysiloxane, polyester resin and acrylic resin, preferably including at least one of acrylic resin and polyester resin. The present application has no particular restrictions on the type of film-forming resin, as long as it can be used for liquid coating compositions. In addition to the above-mentioned resin component, the liquid coating composition also includes a solvent (including but not limited to water, water-miscible organic solvents or combinations thereof) and optional additional additives. These additional additives will not adversely affect the liquid coating composition or the coating obtained therefrom. Suitable additives include, for example, those reagents that can improve the processing properties or manufacturing properties of the liquid coating composition or improve the specific functional properties or characteristics (such as adhesion to substrates or lower coatings) of the composition or the coating obtained therefrom. The additives that may be included are, for example, cosolvents, anti-migration aids, antimicrobial agents, wetting agents, biocides, plasticizers, defoamers, antioxidants, adhesion promoters, UV stabilizers, or combinations thereof. The content of each optional component is sufficient to achieve its intended purpose, but preferably, such content does not adversely affect the liquid coating composition or the coating obtained therefrom.

[0055] In the above liquid coating composition, the polymer additive includes at least one of a wetting and dispersing agent, a plasticizer, a defoaming agent, a leveling agent, an anti-settling agent, an adhesion promoter, a matting agent and a slip agent.

[0056] Preferably, the polymer additive is a wax additive, preferably including natural wax and synthetic wax. The natural wax includes paraffin, beeswax, spermaceti, lanolin, carnauba wax, candelilla wax, Japanese wood wax and combinations thereof; the synthetic wax includes 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 present invention, the liquid coating composition includes packaging coatings, coil coatings, industrial wood coatings and other coating compositions containing polymer additives, especially wax additives.

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

[0059] For the liquid coating composition, after storage for 3 days, preferably 5 days, more preferably 30 days, measured by the bubble method according to ASTME 2407 04 (2015), compared with the original liquid coating composition, after adjusting the feeding sequence of the polymer additive according to the method described in the present invention, the bubble height of the liquid coating composition is reduced by at least 20%, preferably at least 25%, more preferably at least 30%.

[0060] The solubility or dispersibility of polymer 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 suitable for areas with large temperature changes, preferably temperate and cold zones.

[0061] Obviously, in the field of coatings, there are many methods for improving the storage stability of liquid coating compositions. The inventors of the present invention were surprised to find that the method for improving the storage stability of liquid coating compositions according to the present invention can model the data of polymer additives and standardize the process; the method of the present invention and the establishment of the model can help reduce the number of experiments and workload; the method of the present invention and the establishment of the model can identify the wetting factors of different types of polymer additives and the main resin, formulate and optimize the process sequence, which is different from other methods such as the addition of defoaming agents and physical purge defoaming, and is superior in saving materials and energy consumption, making the method for improving storage stability simpler and easier to implement.

[0062] Evaluate the compatibility of various raw materials used in coating formulations through surface energy and interfacial energy

[0063] In some embodiments according to the present invention, the inventors have found through a large number of experiments and data analysis that the compatibility of various raw materials used in the coating formulation can be evaluated using surface energy and interfacial energy. Specifically, in an exemplary embodiment, a liquid coating composition, such as a water-based polyester coating composition (e.g., 16VC020), is selected, which contains a variety of wax additives listed in Table 1 below. After being stored for a period of time, wax floating phenomenon often occurs.

[0064] Since there are three types of wax additives in 16VC020, the compatibility of each wax additive with the film-forming resin was evaluated. The compatibility of the resin with water was first studied by not adding any wax additive to the liquid coating composition as a control. Figure 1 As shown in Figure 5a, no phase separation was observed after 5 days, indicating that the film-forming resins used in the coating formulation have good miscibility and compatibility with water. However, this is not the case for liquid coating compositions with wax additives, especially multiple wax additives. The presence of lanolin and PE / PTFE waxes resulted in a clear phase separation after 2 days. Lanolin was found in the top layer, while PE / PTFE waxes were 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 since it is prepared in the form of a wax emulsion. Compared with the liquid coating composition containing all wax additives ( Figure 2 d), the introduction of 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 side walls of the bottle, even though the wax additives were unstable and tended to settle out in the liquid coating composition. This indicates that wax floating did not occur, and thus interactions between the wax additives may play a role in the wax floating problem.

[0065] To investigate the interaction between the wax additives, different combinations of three wax additives were added to the liquid coating composition and wax floating 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 side walls of the container. In addition, compared to the sample with only lanolin ( Figure 1 b), the phase separation is not obvious, indicating that lanolin is more stable in the presence of palm wax ( Figure 2 a) When PE / PTFE wax and palm wax were added to the liquid coating composition, a similar situation occurred. Figure 2 As shown in Fig. 2a, no wax lumps settled 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, it was not like the white powder that sank to the bottom as observed in the sample with only PE / PTFE wax (Fig. Figure 1 c). Therefore, this may mean that palm wax can interact with lanolin and PE / PTFE wax, thereby making the two wax additives have higher stability in the liquid coating composition. In contrast, when lanolin and PE / PTFE wax coexist in the liquid coating composition ( Figure 2 c), a large amount of wax was deposited on the sidewalls, and wax lumps were observed on the surface of the liquid coating composition. The wax floating problem was even worse than what occurred in the liquid coating composition containing all wax additives ( Figure 2 d). It is clear that lanolin and PE / PTFE wax have a synergistic effect on the wax floating problem. The combination of wax additives shows different behavior in causing wax floating problems compared to the samples using individual wax additives. Therefore, the potential mechanism behind this problem needs to be investigated.

[0066] Since wax additives are not miscible with water, they are more likely to precipitate from waterborne coating compositions without the aid of resins. Unlike palm wax, lanolin and PE / PTFE waxes can be dissolved or dispersed in organic solvents. Therefore, palm wax can be mixed well with water, while lanolin and PE / PTFE waxes are unstable in water (see Figure 3 ). In this case, the possibility of being wetted by the film-forming resin is the key to the retention of the wax additive in the coating composition, and this possibility can be evaluated 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 water-based coating composition. The interfacial energy is obtained according to the following formula:

[0067]

[0068] where γ 12 is the interfacial energy between the two components, γ i is the surface energy of component i, γ i d and γ i p are 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 resin, palm wax, PE / PTFE wax and lanolin

[0070]

[0071] As can be seen from Table 1, the interfacial energy between PE / PTFE wax and 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 the liquid coating composition. In addition, the value of 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 the liquid coating composition, the film-forming resin tends to stay with the lanolin, leaving the PE / PTFE wax uncoated by the resin. Therefore, the PE / PTFE wax will be brought to the surface by the bubbles generated when preparing the liquid coating composition, and the problem of floating wax will arise.

[0072] The inventors have found that the interaction between the film-forming resin and different wax additives and between different wax additives can be better explained by using the wetting factor defined by the following formula:

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

[0074] When ωa>1, the particles of polymer additive A exist only in the polymer additive B phase; when ωa<-1, the particles of polymer additive A are selectively concentrated in the resin phase, and when -1<ωa<1, the particles of polymer additive A exist at the interface between the polymer additive B phase and the resin phase. In samples containing liquid coating compositions of 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 of the two phases consisting of the film-forming resin and other wax additives. This enables 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 waxes, the results are greater than 1 (see Figure 4 c). This indicates that the PE / PTFE wax preferentially accumulates in the lanolin phase, resulting in less interaction with the film-forming resin. Therefore, the PE / PTFE wax is unstable in the liquid coating composition and is easily brought to the surface by bubbles. The liquid coating composition containing lanolin and PE / PTFE wax has an accelerated wax floating process, while no wax floating phenomenon occurs for samples containing other types of wax additives.

[0075] In addition, the applicant used FTIR and DSC to determine the composition of the wax block. Figure 5 PTFE (1202 and 1145 cm-1 ), may contain PE wax, palm wax and lanolin; and from Figure 6 From the DSC test, it can be clearly seen that there is PE wax (120°C). In other words, the results of FTIR and DSC show that the main component in the wax block is polyethylene wax (PE wax), but no PTFE is found, which may be due to its greater density than water. The reason why PE wax is in the majority in the wax block may be related to their worst stability in the liquid coating composition, which is also supported by the above mechanism, but it is also possible that more PE wax is introduced into the liquid coating composition relative to other waxes, which causes this problem. Therefore, it is necessary to determine the amount of wax in the wax block, and the inventors conducted more DSC measurements. Combinations of waxes with different weight ratios (Table 2) were analyzed by DSC to estimate the actual weight ratio of wax in the wax block, and the results are shown in Table 3. The weight ratio in Table 3 refers to the internal simplified ratio of the three wax additives of PE wax, palm wax and lanolin in the formula. Taking PE as the basis (3), the ratio of PE wax: palm wax: lanolin in the formula is 3:1:1.6. The DSC peak area analysis of the actual enriched sample shows that the ratio of PE: palm wax: lanolin in the actual sample is about 3:0.6:<0.6. This set of experiments shows that the enrichment of PE wax is not caused by the large amount of PE added in the formula. Compared with the weight ratio provided in the liquid coating composition, less palm wax and lanolin wax are gathered in the wax block. This shows that PE wax is easier to precipitate than other waxes. It is not more soluble in the solution, but has poor compatibility, resulting in a large amount of PE wax floating on the surface of the liquid coating composition and then forming a sticky block. This observation is also consistent with the above mechanism. Therefore, it can be concluded that the use of interfacial energy and wetting coefficient can predict the interaction between various wax additives and resins, which is beneficial to the future design of coating formulations.

[0076] Table 2: DSC measurements of combinations of different wax additives at certain weight ratios

[0077]

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

[0079] Theoretical weight ratio Actual weight ratio PE 3 3 Palm wax 1 ～0.6 Lanolin 1.6 <0.6

[0080] Since PE / PTFE wax is abundant in the wax block, stabilizing these wax additives is believed to alleviate the problem of wax floating. In the original liquid coating composition, PE / PTFE wax is added at the end of the preparation process, and other wax additives and water are present in the liquid coating composition. This results in insufficient time for PE / PTFE wax to react with the film-forming resin. However, the highest interfacial energy of PE / PTFE wax indicates that these wax additives are difficult to be wetted by the film-forming resin, making it impossible for PE / PTFE wax to be completely enclosed in the film-forming resin. Without the help of the film-forming resin, these suspended wax particles tend to move to the surface of the liquid coating composition in the presence of bubbles. In addition, it is well known that the generation of bubbles is inevitable in the liquid coating composition system, and the number of bubbles generated in this process can be related to 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 bubbles when stirring, which may be due to its low surface tension. Therefore, it can be expected that the addition of PE / PTFE wax to liquid coating compositions, especially water-based coating compositions, may cause the problem of wax floating.

[0081] To solve this problem, 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, so different weight ratios of film-forming resin to wax additives could be selected. To optimize the wetting conditions, the interfacial energy of the wax additive and the film-forming resin was evaluated, and the results are shown in Tables 4 and 5.

[0082] Table 4: Interfacial energy 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 wax and film-forming resins present the lowest interfacial energy, and therefore, the wax floating problem may not be alleviated by randomly selecting a film-forming resin to coat the wax particles. For example, premixing the wax additive with all the film-forming resins (i.e., #1 / #2 / #4) resulted in the highest interfacial energy, while using #2 and #4 resins reduced the interfacial energy. Therefore, such interactions between the film-forming resin and the wax particles should be utilized. Compared with the sample prepared according to the original coating formulation, the bubble height decreased from 1.1 cm to 0.8 cm after adding the pretreated PE / PTFE wax (i.e., premixing the PE / PTFE wax with the film-forming resin), which may be due to the enhanced surface tension and better compatibility of the improved wax additive. The reduction in bubble height indicates a lower risk of initiating wax floating problems. It should be noted that there was no significant decrease in the bubble height, so it is reasonable to estimate that premixing the wax with the film-forming resin can only alleviate this problem to a certain extent.

[0088] Since premixing of wax additives has limited effect on alleviating the wax floating problem, an alternative method is proposed, which is to change the feeding order of PE / PTFE wax and introduce PE / PTFE wax before adding lanolin. Therefore, PE / PTFE wax has a longer time to interact with the film-forming resin, with the purpose of making more wax encapsulated in the film-forming resin. In the first test, only PE / PTFE wax was added to the liquid coating composition. After changing the order of adding wax, the height of the bubble was much smaller and less wax precipitated at the bottom. This shows that PE / PTFE wax becomes relatively stable and the wax floating phenomenon can be well alleviated.

[0089] Inspired by the expected results, the next step was to add all the waxes to the liquid coating composition while rearranging the feeding order of the PE / PTFE waxes. After preparation, fewer bubbles were observed and the residence time of the bubbles was reduced after modifying the feeding order of the coating formulation. In addition, the height of the foam was almost reduced by half and the phase separation process was slower after 5 days, indicating that the liquid coating composition was more stable. This again shows that changing the order of raw material feeding can be a potential way to help solve the floating wax problem, which is also confirmed by the fewer wax lumps found on the sidewalls after the modified preparation order.

[0090] Thus, the present invention relates to 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:

[0091] i) providing the surface energy of the polymer auxiliary agent and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle;

[0092] ii) providing interfacial energy between the polymer additive and the film-forming resin and between the polymer additives;

[0093] iii) providing a wetting factor between the polymer auxiliary agent and the film-forming resin;

[0094] iv) adjusting the feeding sequence of the polymer additives according to the obtained wetting factors.

[0095] In addition, the inventors conducted more experiments to confirm the efficiency of the proposed method in solving this problem, especially in the process of scale-up. Similar results were obtained after increasing the total amount of raw materials from 1 kg to 3 kg. Adjusting the feeding order of the raw materials produced fewer bubbles ( Figure 7 ).

[0096] Another scale-up test was conducted with 15 kg of raw material and the laboratory parameters were adjusted accordingly. The position of the HSD disk and the stirring speed were changed to better mimic the conditions in the plant preparation process. Figure 8 As shown in Figure 1, after 3 days, the sample prepared according to the feed sequence of the original coating formulation exhibited a bubble height that was about 3 times that of the sample obtained using the modified feed sequence. In addition, wax was seen everywhere on the surface of the liquid coating composition, while after adjusting the order of introducing the PE / PTFE wax, wax was seen in a few places ( Figure 8 b). So far, it can be concluded that rearranging the feeding sequence helps to minimize the risk of wax floating. Moreover, this is consistent with the prediction of 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 order of the polymer additive according to the obtained wetting factor comprises: when ωa>1, pre-mixing the polymer additive A with the film-forming resin, and finally adding the polymer 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 polymer additives according to the obtained wetting factor comprises: when ωa of multiple polymer additives is greater than 1, preferentially adding the polymer 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 shown in the wetting factors above, lanolin and PE / PTFE wax are preferably in the same phase. In order to avoid interaction between the two wax additives, the feed order of the raw materials can be further adjusted when preparing the sample, introducing lanolin at the end and keeping the PE / PTFE wax at the early stage. In this way, the interaction is expected to be minimized with a shortened mixing time between the wax additives. Changing the feed order of lanolin and PE / PTFE wax can greatly improve the stability of the wax additives in the liquid coating composition and prevent wax floating compared to the sample in which only the feed order of PE / PTFE wax is changed.

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

[0102] The solubility or dispersibility of polymer 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 suitable for areas with large temperature changes, preferably temperate and cold zones.

[0103] Obviously, in the field of coatings, there are many methods for improving the storage stability of liquid coating compositions. The inventors of the present invention were surprised to find that the method for improving the storage stability of liquid coating compositions according to the present invention can model the data of polymer additives and standardize the process; the method of the present invention and the establishment of the model can help reduce the number of experiments and workload; the method of the present invention and the establishment of the model can identify the wetting factors of different types of polymer additives and the main resin, formulate and optimize the process sequence, which is different from other methods such as the addition of defoaming agents and physical purge defoaming, and is superior in saving materials and energy consumption, making the method for improving storage stability simpler and easier to implement.

[0104] Other tests to solve the wax float problem

[0105] It has been proven that the presence of bubbles can trigger the floating of wax additives, so removing bubbles during the stirring process is key to alleviating this problem. However, additives in liquid coating compositions, such as the waterborne polyester coating composition 16VC020, such as surface wetting agents, leveling agents, and defoamers, can affect the generation and stability of bubbles. In order to evaluate their effects, no surfactant was added to the liquid coating composition, and large bubbles were found after the liquid coating composition was prepared ( Fig. 9a). In addition, the bubbles persisted for at least three days. This is expected due to the absence of defoamers in the liquid coating composition. After 7 days, a large amount of the wax additive had agglomerated on the sidewalls and floated on the surface of the liquid coating composition. In contrast, by adjusting the order of addition of the PE / PTFE wax, fewer bubbles were generated and their residence time was shortened ( Fig. 9 b). Although there are some wax pieces floating on the surface, the prepared sample shows better results ( Fig. 9 c). This result once again confirms that adjusting the feeding sequence of wax additives can reduce floating wax.

[0106] Adding defoamers plays a key role in reducing bubbles. Without defoamers, many large bubbles will be generated and will not disappear in a short time. In the waterborne polyester coating composition 16VC020, silwet@L7500 can be used as a defoamer. In order to have better defoaming performance after preparation, silwet@L7500 was introduced at the end. As a result, the height of the foam was slightly reduced from 1.1 cm to 0.8 cm ( Fig.10 ), indicating that readjusting the feeding order of silwet@L7500 helps to suppress the formation of foam. For comparison, the feeding order of PE / PTFE wax was also readjusted, resulting in a foam height of 0.55 cm. It is worth noting that the value of the foam height is reduced to a certain extent compared with the sample made by only changing the feeding order of PE / PTFE wax. Therefore, rearranging the feeding order of wax additives rather than the feeding order of defoaming agent silwet@L7500 may have a greater impact on solving the floating wax problem. In addition, similar results were obtained by adding 0.2wt% BYK-019, a new defoaming agent, to the liquid coating composition. As Fig.11 As shown in the figure, the height of the foam is reduced from 1.1 cm to 0.95 cm, and it seems that BYK-019 has limited effect on preventing the formation of wax blocks. Since the waterborne polyester coating composition 16VC020 is a relatively mature formula that has been used for many years, the introduction of new raw materials is not considered. Therefore, the method according to the present invention provides a simple and effective method without changing the existing coating formulation.

[0107] The inventors of the present invention were surprised to find that according to the method for improving the storage stability of a liquid coating composition of the present invention, the screening data of polymer additives can be modeled and the process can be standardized; the proposal of the method of the present invention and the establishment of the model can help reduce the number of experiments and workload; through the proposal of the method of the present invention and the establishment of the model, the wetting factors of different types of polymer additives and the main resin can be identified, and the process sequence can be formulated and optimized, which is different from other methods such as purely adding a defoaming agent and physical blowing defoaming, and is superior in 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 only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present 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, the liquid coating composition comprising a film-forming resin and two or more polymer additives, wherein at least one polymer additive is immiscible with a dispersion of the liquid coating composition, the method comprising: i) providing the surface energy of the polymer auxiliary agent and the film-forming resin, wherein the surface energy is obtained by measuring the contact angle; ii) providing interfacial energy between the polymer additive and the film-forming resin and between the polymer additives; iii) providing a wetting factor between the polymer auxiliary agent and the film-forming resin; iv) adjusting the feeding sequence of the polymer additives according to the obtained wetting factors.

2. The method for improving the storage stability of a liquid coating composition according to claim 1, wherein: The interface can be obtained according to the following formula: where γ i is the surface energy of component i, γ i d and γ i p are the dispersion and polarity contributions to the surface energy of component i, respectively.

3. The method for improving the storage stability of a liquid coating composition according to claim 1 or 2, wherein: The wetting factor is obtained according to the following formula: where γ A-B , γ A-树脂 and γ 树脂-B They are the interfacial energies between polymer additives A and B, between polymer additive A and resin, and between resin and polymer additive B.

4. The method for improving the storage stability of a liquid coating composition according to claim 3, wherein: The step of adjusting the feeding order of the polymer additive according to the obtained wetting factor comprises: When ωa>1, the polymer additive A is pre-mixed with the film-forming resin, and finally the polymer additive B is added to the liquid coating composition.

5. The method for improving the storage stability of a liquid coating composition according to claim 4, wherein: The step of adjusting the feeding order of the polymer additive according to the obtained wetting factor comprises: When the ωa of multiple polymer additives is greater than 1, the polymer additive with the highest ωa should be added to the film-forming resin preferentially.

6. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 5, wherein: The liquid coating composition includes an aqueous coating composition or a solvent-based coating composition, preferably an aqueous coating composition.

7. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 6, wherein: The polymer auxiliary agent includes at least one of a wetting and dispersing agent, a plasticizer, a defoaming agent, a leveling agent, an anti-settling agent, an adhesion promoter, a matting agent and a slip agent.

8. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 7, wherein: The polymer additive is a wax additive, preferably including natural wax and synthetic wax.

9. The method for improving the storage stability of a liquid coating composition according to claim 8, wherein: The natural waxes include paraffin, beeswax, spermaceti, lanolin, carnauba wax, candelilla wax, Japan 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.

10. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 9, wherein: The liquid coating composition includes packaging coatings, coil coatings, industrial wood coatings and other coating compositions containing polymer additives, especially wax additives.

11. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 10, wherein: After storage for 3 days, preferably 5 days, more preferably 30 days, the bubble height of the liquid coating composition is measured by the bubble method according to ASTM E 2407 04 (2015), compared with the original liquid coating composition, when the feeding sequence of the polymer additive is adjusted according to the method, The bubble height of the liquid coating composition is reduced by at least 20%, preferably at least 25%, more preferably at least 30%.

12. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 11, wherein: The method is suitable for areas with large temperature changes, preferably temperate and frigid zones.

13. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 12, wherein: The liquid coating composition also comprises a solvent and optionally additional additives.

14. The method for improving the storage stability of a liquid coating composition according to any one of claims 1 to 13, 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, and preferably includes at least one of acrylic resin and polyester resin.

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