Use of dendrimer compounds as Anti-skinning agents

Abstract

This invention relates to the use of dendrimer compounds or their derivatives as anti-skinning agents in paints and coatings, specifically for encapsulating metal driers to prevent skin formation. Also, the present invention provides an oxime- free anti-skinning composition for encapsulating metal driers to prevent skin formation in paints and coatings, which comprises a dendrimer compound or its derivative.

Description

[0001] USE OF DENDRIMER COMPOUNDS AS ANTI-SKINNING AGENTS

[0002] Technical Field

[0003] This invention relates to the use of dendrimer compounds or their derivatives as anti-skinning agents in paints and coatings, specifically for encapsulating metal driers to prevent skin formation.

[0004] Background of the Invention

[0005] Dendrimers are synthesized through stepwise polymerization, resulting in highly branched, tree-like structures. These macromolecules have a spherical shape with hollow interiors, making them suitable for encapsulating metal ions. The high molecular weight and non-volatile nature of dendrimers make them ideal candidates for replacing traditional volatile anti-skinning agents.

[0006] Dendrimers have been explored for various applications due to their unique properties, such as their well-defined structure, high degree of branching, and multivalency. Some of the key uses of dendrimers in known technology include drug delivery and gene delivery. Dendrimers have been extensively studied for drug delivery applications. Their ability to encapsulate drug molecules within their structure and their surface groups make them excellent carriers for targeted drug delivery. For example, dendrimers have been used to deliver anticancer drugs to tumor sites, improving the efficacy and reducing side effects of the treatment (EP4069307A2). Dendrimers are also used in gene delivery systems due to their ability to form complexes with DNA and protect genetic material from degradation. This property is utilized to deliver genes into cells for gene therapy applications. US2021121580A1 discloses DNA dendrimer having one or more DNA sequences linked thereto and methods for treating diseases and conditions of cells by delivering the dendrimers to the cells. However, it is not known the use of dendrimer in coating, paint or ink compositions.

[0007] In this type of compositions, the formation of skin during storage is a significant problem affecting product quality and shelf life. Metal driers, such as cobalt, manganese, and zirconium, are commonly used in paint formulations to accelerate the drying process. Herein, the binder contains unsaturation between carbon atoms, where oxidation initiates the formation of free radicals. These free radicals start a polymerization process, which is catalyzed by the metal driers, leading to skin formation. As a result, the presence of metal driers can cause premature skin formation when exposed to air, deteriorating the paint's quality and usability.

[0008] Traditional anti-skinning agents, such as oximes, have been widely used to mitigate this issue. Methyl ethyl ketoxime (MEKO) is a conventional antiskinning agent known for its effectiveness in delaying skin formation. However, MEKO and similar oxime-based agents require higher usage rates and are volatile, potentially leading to harmful vapor exposure. The volatility of these agents also raises environmental and health concerns, prompting the need for safer and more efficient alternatives.

[0009] Therefore, there is a need for a safe, non-toxic, low-volatility, and environmentally friendly anti-skinning agent that can effectively prevent skin formation in paints while maintaining paint stability and performance.

[0010] Detailed Description of the Invention

[0011] The present invention provides dendrimer compounds, or their derivatives which are used as anti- skinning agents to encapsulate metal driers and prevent skin formation in paints and coatings. The term "dendrimer" as used herein refers to a molecular structure comprising an inner core, successive layers (or "generations") of repeating units attached to this core, and an outer surface formed by terminal groups attached to the outermost generation. In other words, a dendrimer is a highly structured macromolecule characterized by its uniform, multi-branched three-dimensional architecture. This intricate system is formed through a repetitive series of chemical reactions, where each cycle adds a new generation, resulting in a progressively larger dendrimer.

[0012] The molecular weight of the dendrimer compound is an important parameter in this invention. It has been found that the molecular weight of the dendrimer is preferably between 100 to 10,000 Da. More preferably, the molecular weight should be between 250 to 7,500 Da, and most preferably, between 400 to 5,000 Da. These specific ranges of molecular weights ensure optimal performance in encapsulating metal driers and preventing skin formation. Lower molecular weight dendrimers tend to have a more compact and flexible structure, which allows them to form a more effective encapsulation around metal driers. This encapsulation prevents the metal driers from prematurely reacting with oxygen in the air, which is a primary cause of skin formation in paints and coatings. Higher molecular weight dendrimers, while more branched, can become too bulky and less efficient in creating a tight encapsulation around the driers. Additionally, the solubility and dispersibility of dendrimers in the paint or coating matrix are influenced by their molecular weight. Dendrimers within the disclosed molecular weight range dissolve and disperse more uniformly throughout the formulation. This uniform distribution ensures that the anti-skinning effect is consistent throughout the entire volume of the paint or coating.

[0013] The dendrimer compound utilized in this invention can be selected from a variety of dendrimer families. Specifically, it may be chosen from the group consisting of poly amidoamine (PAM AM) dendrimers, polypropyleneimine (PPI) dendrimers, polyethyleneimine (PEI) dendrimers, polyether dendrimers, polylysine (PLL) dendrimers, polypeptide dendrimers, poly glycerol dendrimers, carbosilane dendrimers, polyester dendrimers, poly thioether dendrimers, polyphosphorhydrazone (PPH) dendrimers, DNA-based dendrimers, and triazine dendrimers. Preferably, the dendrimer compound is selected from the group consisting of polyamidoamine (PAMAM) dendrimers, polypropyleneimine (PPI) dendrimers, polyethyleneimine (PEI) dendrimers, polyether dendrimers, polylysine (PLL) dendrimers, and combinations thereof.

[0014] According to the present invention, the dendrimer compounds used in this invention may also be characterized by the presence of chelating functional groups. These functional groups enhance the dendrimers' ability to bind with metal ions. The chelating functional groups can be selected from the group consisting of amines, carboxylates, thiols, phosphines, hydroxyl groups, imidazole groups, pyridine groups, phenolic groups, and combinations thereof. Preferably, the chelating functional groups are selected from amines, carboxylates, thiols, phosphines, and combinations thereof.

[0015] These chelating groups are strategically positioned on the surface of the dendrimers, maximizing their interaction with metal ions. When a dendrimer with chelating groups encounters metal ions within the paint or coating formulation, the chelating groups effectively bind to these ions, forming stable complexes. This binding prevents the metal ions from participating in undesirable reactions that lead to skin formation.

[0016] According to the present invention, dendrimer compounds are preferably produced by a method comprising the steps of reacting a core molecule with monomer building blocks to synthesize dendrimers outward from the core by sequentially adding layers. The method includes an initial round of synthesis that adds a single layer, or “generation,” of monomer building blocks to the core, with each monomer building block having at least one free, reactive terminus. Each subsequent round of polymerization expands the dendrimer by one layer, increasing the number of free, reactive termini and the generation of the dendrimer. This process is repeated multiple times to produce dendrimers of the desired diameter or mass. As the density of the branches increases, the outermost branches arrange themselves in the form of a sphere surrounding a lower density core.

[0017] According to the present invention, monomer building block may be selected from the group consisting of ethylenediamine, methyl acrylate, propyleneimine, ethyleneimine, glycidol, ethylene oxide, lysine, various amino acids, chlorosilanes, 2,2-bis(hydroxymethyl)propionic acid (bis-MPA), thiols, alkenes, phosphorhydrazine, aldehydes, nucleotides, cyanuric chloride and its combination thereof.

[0018] According to the present invention, core molecule may be selected from the group consisting of ethylenediamine, ammonia, pentaerythritol, trimesic acid, silicon compounds, triazine, sorbitol, peptides, proteins, polyethylene glycol (PEG) and its combination thereof.

[0019] The dendrimer compounds used in this invention can be of various generations, which refers to the number of branching points in the dendrimer structure. In other words, each generation of a dendrimer represents a new layer of branches radiating from the central core. The generation number increases with the addition of these branching layers. Specifically, the dendrimer compound can be a first to fifth-generation dendrimer, a reduced first to fifth-generation dendrimer, a methylated first to fifth-generation dendrimer, or a methylated and reduced first to fifth-generation dendrimer. More preferably, the dendrimer compound is a first to third-generation dendrimer, a reduced first to third-generation dendrimer, a methylated first to third-generation dendrimer, or a methylated and reduced first to third-generation dendrimer. Most preferably, the dendrimer compound is a first to third-generation dendrimer.

[0020] In one embodiment of the present invention, the first-generation dendrimer corresponds to the following formula 1 :

[0021] Formula 1 wherein R’ is each independently a hydrogen atom, a Cl -Cl 8 alkyl radical, aromatic radical which is branched or straight chain, and wherein m is an integer from 1 to 8, preferably 1 to 4. In one embodiment of the present invention, the second-generation dendrimer corresponds to the following formula 2:

[0022] Formula 2 wherein R’ is each independently a hydrogen atom, a C1-C18 alkyl radical, aromatic radical which is branched or straight chain, and wherein m is an integer from 1 to 8, preferably 1 to 4 and p is an integer from 0 to 7 and preferably 1 to 4.

[0023] According to the present invention, the reduced second-generation dendrimer corresponds to the following formula 3; the reduced and methylated second- generation dendrimer corresponds to the following formula 4; and the methylated second-generation dendrimer corresponds to the following formula 5 :

[0024] Formula 4

[0025] Formula 5 wherein R and R’ are each independently a hydrogen atom, a Cl -Cl 8 alkyl radical, aromatic radical which is branched or straight chain, and wherein m is an integer from 1 to 8, preferably 1 to 4 and p is an integer from 0 to 7 and preferably 1 to 4.

[0026] As illustrative example, the first-generation dendrimer is shown in Formula 6:

[0027] Formula 6

[0028] According to the present invention, dendrimer compound is preferably liquid. For optimal application in paints and coatings, the viscosity of the dendrimer compound is preferably in the range of 1 to 5000 cP and preferably 25 to 3000 cP (measured using a Brookfield viscometer). This range of viscosity ensures that the dendrimer can be easily mixed into the paint or coating formulation without adversely affecting the application properties of the final product. The amount of dendrimer compound used in the paint or coating may also be important. It is found that the dendrimer compound is preferably used in an amount between 0.001% and 1% by weight of the paint or coating. More preferably, the amount should be between 0.01% and 0.5%, and most preferably, between 0.05% and 0.2%. These amounts ensure that the dendrimer compound is effective in preventing skin formation without negatively impacting the performance of the paint or coating.

[0029] In another embodiment, the present invention provides an anti-skinning composition for encapsulating metal driers to prevent skin formation in paints and coatings, which comprises a dendrimer compound or its derivative. This composition is oxime-free. This composition may further include at least one metal drier. The amount of dendrimer compound in this composition is preferably between 1% and 15% by weight of the metal drier. More preferably, the amount is between 2% and 10% by weight of the metal drier.

[0030] According to the present invention, the metal drier is metal drier is selected from the group consisting of carboxylic acid having 2 to 20 carbons or preferably having 3 to 12 carbons of cobalt, manganese, zirconium, calcium, zinc, iron, copper, strontium or aluminium. The metal drier is selected from the group consisting of cobalt naphthenate, cobalt octoate, cobalt linoleate, cobalt neodecanoate, cobalt versates, cobalt isononanoate, manganese naphthenate, manganese octoate, manganese linoleate, manganese neodecanoate, manganese versates, manganese isononanoate, lead naphthenate, lead octoate, lead linoleate, zirconium naphthenate, zirconium octoate, zirconium linoleate, zirconium neodecanoate, zirconium versates, zirconium isononanoate, calcium naphthenate, calcium octoate, calcium linoleate, calcium neodecanoate, calcium versates, calcium isononanoate, zinc naphthenate, zinc octoate, zinc linoleate, zinc neodecanoate, zinc versates, zinc isononanoate, strontium naphthenate, strontium octoate, strontium linoleate, copper naphthenate, copper octoate, copper linoleate, iron naphthenate, iron octoate, iron linoleate, aluminum naphthenate, aluminum octoate, aluminum linoleate and its combination thereof. More preferably, the metal drier is selected from the group consisting of cobalt octoate, cobalt linoleate, cobalt neodecanoate, cobalt versates, cobalt isononanoate, zirconium naphthenate, zirconium octoate, zirconium linoleate, zirconium neodecanoate, zirconium versates, zirconium isononanoate, calcium naphthenate, calcium octoate, calcium linoleate, calcium neodecanoate, calcium versates, calcium isononanoate and its combination thereof.

[0031] According to the present invention, the anti-skinning composition may further comprise a solvent.

[0032] In another embodiment, the present invention provides a paint or coating composition comprising the anti-skinning composition according to the present invention.

[0033] EXAMPLES

[0034] Example 1

[0035] The first-generation (GO) dendrimer synthesis: a) Ethylenediamine (0.17 mol) and methyl methacrylate (1.04 mol) are charged to the reactor. b) A vertical condenser is used during the reaction. c) Reaction is stirred at 60 °C until the reaction ends. The reaction is checked with Infrared analysis. When the reaction ends, NH2peak above 3000 cm'1disappears. Until this disappearance, the reaction continues. d) After the reaction is completed, excess methacrylate is removed from the reaction environment by distillation. Then the final product is pure. 0.17 mol of first-generation dendrimer is obtained.

[0036]

[0037] Example 2

[0038] The second-generation (Gl) dendrimer synthesis: a) The first-generation dendrimer obtained in Example 1 (0.17 mol) and ethylenediamine (1.04 mol) are charged to the reactor. b) This reaction lasts around 8 hours at 75 °C. c) The progress of the reaction is followed with Infrared analysis. In Infrared analysis, the disappearance of the ester carbonyl peak and emergence of the amide carbonyl are monitored. If two carbonyl peaks are visible, the reaction is continuing. When only the amide peak is visible the reaction is complete. d) The reaction is carried out with a condenser. Towards the end of the reaction, a yellow-orange viscous product is formed. e) Then, excess ethylenediamine is removed by vacuum distillation. f) Then the pure product is ready for use. 0.17 mol of first-generation dendrimer is obtained. Example 3

[0039] Reduced second-generation (GIA) dendrimer synthesis: a) The second-generation dendrimer obtained in Example 2 (0.17 mol) is dissolved in THF (7 mol) in the reactor by stirring. b) (7 mol) Lithium aluminum hydride (LiAlH4) is added into reaction environment at ambient temperature. c) The reaction continues overnight at 55 °C. d) Water is added to discompose excess lithium aluminum hydride (LiAlEL). e) The final product is filtered to remove precipitated by-products, and the aqueous solution is evaporated to obtain pure product. f) Yield is 100%.

[0040] Example 4

[0041] Methylated to second-generation (GIB) dendrimer synthesis: a) Second-generation dendrimer obtained in Example 2 (0.17 mol) is charged to the reactor. Mixing is supplied. b) Dichloromethane (7 mol) is charged. Stirring is supplied and the reaction temperature is set to 40 °C. c) Liquid sodium hydroxide (1.3 mol) is added drop by drop to the reaction environment. d) Dimethyl carbonate (2 mol) is charged to the reactor. e) The reaction continues for 7 hours under reflux at 50 °C. f) It is filtered by using filter paper after 7 hours when the reaction completed. g) Dichloromethane is evaporated, and pure product is obtained. Example 5

[0042] Reduced and methylated second-generation (G1C) dendrimer synthesis: a) The reduced dendrimer obtained in Example 3 (0.38 mol) is charged to the reactor, water (2 gram) is charged and mixed at ambient temperature. b) Formaldehyde (1.3 mol) is charged dropwise to the reactor. c) Mixing is started. d) Formic acid (0.39 mol) is added dropwise to the reactor. e) Effective cooling must be provided with a vertical condenser during the reaction. f) The reaction temperature is set at between 60-70 °C and, continues at this temperature until the reaction ends. g) The end point of the reaction is monitored by infrared analysis. When the reduced dendrimer is fully methylated, the sharp peaks above 3000 cm'1disappear, and the product is obtained.

[0043]

[0044] Example 6

[0045] Use of dendrimer technology in paint as anti-skinning agent to encapsulate metals:

[0046] A long oil alkyd-based, white, glossy, and decorative base paint was used as the starting material. The formulation is as follows:

[0047] To this paint, Calcium Oct 10 and Zirconium Oct 18 were added, and the mixture was stirred for 30 minutes. Following this, Cobalt Oct 10 was added and mixed until the blue-purple color in the white paint was no longer visible. Three samples were prepared using this method. As anti-skinning agents, methyl ethyl ketoxime (MEKO) as a reference, first generation dendrimer (GO), and second-generation dendrimer (Gl) were added to the previously prepared paint samples in sequence. The details of the samples are shown in the table below:

[0048] 5 *EGEDry®Cobalt Oct 10: EGE KIMYA commercial catalysis bearing 10% cobalt. The catalysis is cobalt 2ethylhexanoic acid complex.

[0049] EGEDry®Calcium Oct 10: EGE KIMYA commercial catalysis bearing 10% calcium. The catalysis is Calcium 2ethylhexanoic acid complex.

[0050] 10

[0051] EGEDry ©Zirconium Oct 18: EGE KIMYA commercial catalysis bearing 10% zirconium. The catalysis is Zirconium 2ethylhexanoic acid complex.

[0052] The fastest way to compare the performance of anti- skinning agents is through 15 the open-lid test. In this test, paint samples are kept at room temperature with their lids open. As oxygen penetrates the samples, drying (skin formation) is expected in the paints after a certain period. An effective anti-skinning agent added to the paint will delay this skin formation (drying). While the most accurate method is the closed can test, it is not always practical due to the long shelf life of some paints, which can be up to 5 years. Therefore, the open can method is often used as a guide.

[0053] This test was conducted comparatively with all samples 1 , 2 and 3 and skin day results are shown in the table below:

[0054] Initially, dendrimer samples demonstrated anti-skinning effects similar to the reference sample (MEKO). In comparative testing, it was observed that all dendrimer samples effectively delayed skin formation in the paint. Notably, sample 3, which contained the G1 dendrimer, exhibited an even better antiskinning performance than the reference. While the reference sample formed a skin at a certain point, sample 3 delayed this skin formation by an additional day, forming a skin only on the 7th day. This indicates that the G1 dendrimer is not only comparable to MEKO but may actually provide superior protection against skin formation in alkyd-based paints.

[0055] Example 7

[0056] Use of dendrimer technology in paint as anti-skinning agent to encapsulate metals: (ASTM5890 Test)

[0057] The paint drying performance test was conducted to evaluate the effectiveness of the dendrimer samples in paint applications. Upon initial application, dendrimer class compounds interact with the paint by complexing or encapsulating the metal ions responsible for the drying process. This complexation or encapsulation plays a crucial role in regulating the catalytic activity of these metals. By controlling the availability and reactivity of the metal ions, dendrimers can modulate the drying rate of the paint. This regulation ensures a more controlled and desirable drying performance, preventing premature skin formation and improving the overall quality and longevity of the paint coating. Here the table below shows the type of sample used in this test: Results:

[0058] During the fresh application, the reference paint demonstrated a more predictable drying pattern. Sample 1 showed significantly delayed drying times, indicating potential over-complexation or encapsulation. Sample 2 exhibited improved leveling and intermediate drying times compared to the reference. A delay in drying performance was observed in the earlier stage, up to two weeks. After 20 days, the drying times for the reference remained relatively stable. Sample 2 showed a reduction in drying times and surface dryness was not seen. Sample 3 achieved better tack-free and surface dry times compared to the fresh application, indicating possible stabilization over time. After 70 days, the reference paint experienced increased drying times, indicating degradation or changes over time. Sample 2 continued to show extended through dry times. Sample 3 maintained consistent and improved drying times, showing the best performance among the samples. The drying performance of the dendrimer derivatives was similar to the previous drying control, with performances increasing after 20 and 70 days of aging.

Claims

AMENDED CLAIMS received by the International Bureau on 14 Oct 2025(14.10.2025)1. Use of a dendrimer compound or its derivative as anti-skinning agent for encapsulating metal driers to prevent skin formation in paints and coatings.

2. Use of a dendrimer compound according to claim 1, wherein the molecular weight of dendrimer compound is between 100 to 10,000 Da.

3. Use of a dendrimer compound according to claim 1 or 2, wherein the molecular weight of dendrimer compound is between 250 to 7,500 Da.

4. Use of a dendrimer compound according to any one of claims 1 to 3, wherein the molecular weight of dendrimer compound is between 400 to 5,000 Da.

5. Use of a dendrimer compound according to any one of preceding claims, wherein the dendrimer compound is selected from the group consisting of poly amidoamine (PAM AM) dendrimers, polypropyleneimine (PPI) dendrimers, polyethyleneimine dendrimers (PEI), polyether dendrimers, polylysine dendrimers (PLL), polypeptide dendrimers, polyglycerol dendrimers, carbosilane dendrimers, polyester dendrimers, polythioether dendrimers, polyphosphorhydrazone (PPH) dendrimers, DNA-based dendrimers, triazine dendrimers and its combination thereof.

6. Use of a dendrimer compound according to claim 5, wherein the dendrimer compound is selected from the group consisting of polyamidoamine (PAM AM) dendrimers, polypropyleneimine (PPI) dendrimers, polyethyleneimine dendrimers (PEI), polyether dendrimers, polylysine dendrimers (PLL) and its combination thereof.

7. Use of a dendrimer compound according to any one of preceding claims, wherein the dendrimer compound is liquid.

8. Use of a dendrimer compound according to any one of preceding claims, wherein the dendrimer compound comprises chelating functional groups.

9. Use of a dendrimer compound according to any one of preceding claims, wherein chelating functional groups are selected from the group consisting of amines, carboxylates, thiols, phosphines, hydroxyl groups, imidazole groups, pyridine groups, phenolic groups and its combination thereof.10.Use of a dendrimer compound according to claim 9, wherein chelating functional groups are selected from the group consisting of amines, carboxylates, thiols, phosphines and its combination thereof.11.Use of a dendrimer compound according to any one of preceding claims, wherein the viscosity of dendrimer compound is in the range of between 1 to 5000 cP.12.Use of a dendrimer compound according to claim 11, wherein the viscosity of dendrimer compound is in the range of between 25 to 3000 cP.

13. Use of a dendrimer compound according to any one of preceding claims, wherein the dendrimer compound is used in an amount of between 0.001% and 1 % by weight of the paint or coating.

14. Use of a dendrimer compound according to claim 13, wherein the dendrimer compound is used in an amount of between 0.01% and 0.5% by weight of the paint or coating.

15. Use of a dendrimer compound according to claim 14, wherein the dendrimer compound is used in an amount of between 0.05% and 0.2% by weight of the paint or coating.16.Use of a dendrimer compound according to any one of preceding claims, wherein the dendrimer compound is a first to fifth-generation dendrimer, a reduced first to fifth-generation dendrimer, a methylated first to fifthgeneration dendrimer, or a methylated and reduced first to fifth-generation dendrimer.17.Use of a dendrimer compound according to claim 16, wherein the dendrimer compound is a first to third-generation dendrimer, a reduced first to third-generation dendrimer, a methylated first to third-generation dendrimer, or a methylated and reduced first to third-generation dendrimer.18.Use of a dendrimer compound according to claim 17, wherein the dendrimer compound is a first to third-generation dendrimer.

Images