High degassing powder paint and method of obtaining a high degassing powder paint

Abstract

The present invention relates to a high degassing powder paint comprising 20 to 50 wt.% of a polyester resin, 20 to 50 wt.% of an epoxy resin, 0.1 to 6 wt.% of a degassing additive, 0.7 to 4.0 wt.% supplementary additives and 0 to 40 wt.% fillers and pigments, in relation to the total weight of the composition. The present invention also relates to a method of obtaining a high degassing powder paint.

Description

HIGH DEGASING POWDER PAINT AND METHOD FOR OBTAINING HIGH DEGASING POWDER PAINT Field of application

[0001] The present invention relates to the field of coating, paint, and varnish compositions characterized by their physical nature or the effects produced, more specifically, powder compositions. The present invention also relates to a method for obtaining the corresponding powder paint coating. Introduction

[0002] The invention relates to powder paint-based coating compositions, in particular, a powder paint composition with high degassing and low curing temperature for forming a coating. Likewise, the present invention relates to a method for producing the corresponding powder paint for application to heat-sensitive substrates with high moisture content, such as wood substrates in general. Fundamentals of the invention

[0003] Liquid paints and varnishes are commonly used to protect and decorate a wide variety of surfaces, including wood, plastic, metal, and other substrates. However, powder paints offer several advantages over liquid products, as they are applied as a dry, fluid powder. Unlike liquid paints, powder paints do not require water or solvents and, therefore, do not emit volatile organic compounds during the curing process, eliminating solvent waste and minimizing their environmental impact.

[0004] Furthermore, powder paints have better performance rates, since all the powder can be reused, generating a much lower residue. These coatings offer a solid surface finish that is more resistant than that achieved by conventional liquid paint, resulting in good chemical and mechanical resistance.

[0005] Powder coatings are composed of finely divided particles that remain that way during storage under appropriate conditions, being chemically and physically stable at room temperature. The manufacture of these powder coatings generally involves dry mixes of solid resin, additives, pigments, and fillers. The choice of resin is crucial, as it determines the properties of the paints and the desired physical and chemical characteristics of the coating, being responsible for film formation and adhesion to the substrate. The most commonly used resins are epoxy, polyester, hybrid epoxy / polyester, acrylic, or polyurethane.

[0006] However, although powder coatings offer notable economic and environmental advantages, some disadvantages are associated with the use of conventional powder coatings. For example, the application of powder coatings on heat-sensitive substrates with high moisture content is often limited due to the need for high temperatures, between 180°C and 200°C, to cure the coating. Additionally, these substrates may require a heating step prior to the paint application process to remove moisture, since the poor degassing of water vapor present in some substrates leads to the formation of defects in the cured coating film, such as blistering, cracking, cratering, and / or boiling.

[0007] The challenge, therefore, lies in manufacturing high-outgassing powder coating compositions that can cure at low temperatures, generating less thermal stress on the substrate. In addition, coatings suitable for application on heat-sensitive substrates with high oxide content moisture that provide chemical and mechanical protection to the coated surface. State of the art

[0008] There are, in the state of the art, solutions designed to obtain coatings based on hybrid powder paints for application on heat-sensitive substrates.

[0009] An example of a known prior art solution is patent document CN 100347250 C, which discloses and describes a powder coating composition prepared by extrusion at different temperatures. The composition comprises a mixture of epoxy resin, vibrin, and epoxy-silicone, a crosslinking agent, a curing agent, a leveling agent, a degassing agent, an optical brightener, a silicon reinforcing agent, and a filler. Although the disclosed invention is suitable for application in the field of coatings for heat-sensitive materials, the use of a large number of components, including a curing agent, is required to achieve the disclosed effect.

[0010] The powder coating composition disclosed in patent document CN 110343445 B is prepared from carboxyl-terminated polyester, epoxy, and hyperbranched polymer resins, a flow agent, a leveling agent, an isocyanate curing agent, a curing accelerator, a dispersing agent, pigments, and fillers. This coating is described for application to heat-sensitive substrates such as glass, paper, plastic, and wood, with curing performed by medium-wave infrared radiation. However, the use of components containing isocyanates may be considered harmful to the user's health during the coating application process.

[0011] Other patent documents also disclose powder paint compositions with low curing temperature, as is the case of patent document WO 2006005136 Al which describes a powder coating composition prepared from epoxy resin modified with suitable rubber for application in wood derivatives, especially for medium-density fiberboard (MDF). As well as, patent document CN 112831247 A which, in turn, reveals a powder paint composed of a mixture of epoxy resins, linear and hyperbranched polyesters, curing agent, leveling agent, degassing agent, pigments and / or fillers, which is used to coat heat-sensitive parts, without specifying the material of the parts in question.

[0012] However, in the prior art, most powder coatings use additional curing agents, catalysts, and crosslinkers, which increase the cost of the process and can, in some cases, be toxic to the user. Furthermore, powder coatings often use curing temperatures of 180°C to 200°C, limiting the range of substrate selection and potentially causing coating failures when applied to substrates with higher moisture contents. Furthermore, the need for prior substrate surface preparation, including heating or not, for the application of powder coating compositions, and the possibility of application to substrates with high moisture contents, are not disclosed.

[0013] As can be inferred from the above, there is room and demand for a powder coating composition solution with degassing capabilities that allows coating heat-sensitive and / or high-moisture substrates without the need for preheating the part, overcoming the disadvantages of the current state-of-the-art technology. Similarly, a powder coating with low toxicity, good processability, and resistance properties can be cured at low temperatures, resulting in low thermal stress on the substrate and low defect formation in the cured coating. Objectives of the invention

[0014] An object of the present invention is to provide a high outgassing powder paint coating for application to heat-sensitive substrates. heat, according to the characteristics of claim 1 of the attached table of claims.

[0015] Another objective of the present invention is to provide a method for obtaining high degassing powder paint, according to the characteristics of claim 9 of the attached claim table.

[0016] Other characteristics and details of the characteristics are represented by dependent claims. Brief description of the figures

[0017] For better understanding and visualization of the object of the present invention, it will be described with reference to the attached figures, representing the technical effect obtained by means of an exemplary embodiment that does not limit the scope of the present invention. Figure 1: shows a graph of the powder paint curing window according to a preferred embodiment of the present invention; and Figure 2: shows a wooden handle after applying a layer of powder paint according to an embodiment of the present invention in an infrared curing process. Detailed description of the invention

[0018] This invention relates to hybrid-based, high-outgassing powder coating compositions and a method for preparing and using them. These powder coatings comprise a mixture of epoxy and polyester resins with additives, pigments, and fillers. The resulting material can be used to coat and protect heat-sensitive substrates, including wood, from chemical and mechanical damage.

[0019] The powder paint composition according to the present invention comprises at least two resins, i.e. polymeric compositions suitable for powder coatings, such as thermoplastic or thermosetting resins, particularly epoxy and polyester resins.

[0020] The epoxy resin may be selected from a variety of aliphatic or aromatic epoxy resins for powder coatings, including but not limited to epoxy resin produced by the reaction of epichlorohydrin and phenolic compounds, e.g., bisphenol A and bisphenol F, preferably bisphenol A (2,2-bis(4-hydroxyphenyl)propane).

[0021] The polyester resin may be selected from a variety of polyester resins for powder coatings, including but not limited to polyester resins typically obtained by the condensation polymerization reaction between a saturated polybasic acid or anhydride thereof and a polyalcohol, for example, carboxy-functional polyester resins and hydroxy-functional polyester resins, more preferably carboxylated polyester resin.

[0022] The epoxy-polyester hybrid system of the present invention therefore includes a preferred blend of a carboxylated polyester resin and a bisphenol A epoxy resin in a polyester:epoxy mixing ratio of 60:40 or 70:30 or 50:50, preferably a mixing ratio of 50:50, and acidity of 15 mgKOH / g to 100 mgKOH / g, preferably of 70 mgKOH / g to 85 mgKOH / g.

[0023] The composition of the present invention further comprises the addition of degassing additives, including, but not limited to, one or more micronized waxes, preferably polyethylene- and amide-based micronized waxes. The introduction of these additives is essential to help air, vapor, or gases escape from the film during the curing process, thereby preventing the formation of defects on the coating surface, such as blistering, cracking, cratering, and / or boiling.

[0024] Supplemental additives may also be introduced into formulations, for example, surface additives, including silicone, acrylate, fluorocarbon and / or hydrocarbon-based leveling agents; and / or additives to improve sprayability, including anti-caking agents such as calcium and magnesium stearates, silicas and silicates, starch and talc; and / or matting additives, including silica-based matting agents, waxes and fillers; and / or antioxidant additives, including antioxidants derived from amines, lactones, phosphites, phenolics, thioethers and mixtures thereof.

[0025] Furthermore, the powder coating composition of the present invention may include the use of pigments and fillers. The pigments may comprise micro- to nanoscale particles of organic or inorganic origin in a natural, synthetic, and / or functionalized state. For example, inorganic pigments include, but are not limited to, metal oxides of aluminum, iron, titanium, zinc, barium, copper, and silicon, or a mixture thereof, and salts such as sulfates, carbonates, silicates, silicas, titanates, chromates, and phosphates; and organic pigments include, but are not limited to, compounds with azo groups, phthalocyanine, and carbon blacks. Fillers are used to reinforce the coating and improve barrier protection properties, including, but not limited to, carbonates, sulfates, silicas, and silicates.

[0026] In one embodiment of the present invention, the general composition of the disclosed powder paint includes from 20 to 50% by weight of a polyester resin, from 20 to 50% by weight of an epoxy resin, from 0.1 to 6% by weight of degassing additives, from 0.7 to 4.0% by weight of supplemental additives, and from 0 to 40% by weight of fillers and pigments. In the context of the present invention, "% by weight" refers to the weight percentage based on the total weight of the powder paint composition described in the present invention.

[0027] The powder coating compositions of the present invention may also include additives and auxiliaries other than those described above, depending on the intended purpose of the product, including, but not limited to, texturizing agents, adhesion promoters, anti-crater additives, anti-stain additives, colorants, and masterbatch, among others. Furthermore, the powder coating of the present invention does not require the addition of an infrared-absorbing raw material for the coating curing process.

[0028] The invention also relates to a method of preparing the powder paint composition according to the present invention comprising the steps of: a) Weighing and pre-mixing the components in the amounts specified by the formulation; b) Heating and melting the pre-mixture, preferably in an extruder; c) Cooling the material to obtain a solid material; d) Grinding the solid material into smaller particles; e) Classifying and sieving the particles obtained.

[0029] In a more detailed description of the above steps, step a) involves a preferred order of addition of the components, consisting of adding the resins first, followed by the additives, and finally the pigments and fillers. The premixing can then be done manually or with a mechanical stirrer, continuing until the components are homogenized.

[0030] Step b), in turn, aims to achieve complete homogenization of the mixture components, preferably in an extruder. The premix is ​​heated to a temperature of approximately 110°C, an extruder screw speed between 400 and 500 rpm, and a feeder speed between 15 and 50 rpm, causing the composition to melt and behave as a semi-liquid, allowing the ingredients to be better mixed. After leaving the extruder as a high-consistency paste, the material is cooled in step c), passing through cooling calenders. This process converts the material into sheets, which are broken into flakes or chips using a mechanical shredder or manually using a hammer or similar tools.

[0031] If necessary, the brightness, color, appearance and impact resistance characteristics of the material can be evaluated and adjusted during the extrusion process, steps b) and c). Optionally, an additional extrusion process can be applied to improve the characteristics of the mixture, as well as its degree of homogenization, by repeating steps b) and c) of the method.

[0032] In step d), the material is milled or micronized to reduce particle size to achieve the desired particle size and ensure adequate fluidization of the material for good paint application. This step is preferably performed using a hammer or disc mill. To obtain the material according to the invention, the maximum temperature during milling should not exceed 35°C, and the average particle size obtained should preferably be 25 to 60 microns (pm).

[0033] Finally, the material undergoes a particle classification and sieving stage (step e), in which classification is performed using a cyclone, followed by sieving through a steel or nylon mesh, preferably using a rotary or vibrating screen. After classification, the material is ready for packaging and use.

[0034] Surfaces and substrates suitable for the powder paint coating of the present invention are preferably prepared by cleaning and removing potential surface contaminants. Additional treatments, such as preheating the part, are not necessary for the application of the powder paint due to the characteristics of the disclosed formulation.

[0035] The powder coating of the present invention can be applied to the surface of the substrate by methods known in the art, for example, by means of a fluidized bed, triboelectric gun, or electrostatic gun, preferably by means of a corona-type electrostatic gun. The coating is preferably applied in a single layer, achieving a dry film thickness of 10 pm to 150 pm, preferably from 20 pm to 100 pm, and more preferably from 30 pm to 50 pm.

[0036] After application, regardless of the method used, the paint must be cured to achieve the best physical and chemical characteristics. To this end, the composition is cured in convection ovens, stationary ovens, or under infrared radiation, preferably under infrared radiation. The curing temperature range is 110°C to 180°C, with low or ultra-low temperature curing being preferred, specifically 120°C to 140°C (Figure 1, Table 1), depending on the substrate material. An advantage of the present invention is that the coating can cure in a range of 2 to 30 minutes, depending on the temperature conditions and curing method used, for example, as shown in Table 1 for curing using convection ovens. Table 1 - Values ​​determined, in convection ovens, for the preferential curing window of the powder paint coating of the present invention.

[0037] The coating finish can range from 5 gloss units, a matte finish, to values ​​above 80 gloss units, a glossy finish, with gloss adjustments being made during the composition preparation process. Similarly, the texture of the coating obtained with the powder paint of the present invention can be adjusted according to the intended purpose during preparation, preferably being smooth.

[0038] The application of the powder coating according to the present invention is particularly effective on heat-sensitive and / or high-moisture substrates, more specifically, on wood substrates in general, including MDF. An advantage of the present invention is that the powder coating can be applied to low- to high-density wood and to substrates with a preferred moisture content of up to 25%. Commercial applications of the powder coating of the invention include, for example, wood parts in the furniture, construction, and tooling industries.

[0039] The ability to use powder coatings on a wider variety of heat-sensitive substrates, including those with high moisture content, is attributed to the improved composition disclosed in the present invention. For example, the addition of components with lower melting points and outgassing capabilities prevents defects in the cured coating without affecting the final gloss of the coating and without the need for preheating the substrate before applying the coating.

[0040] For a better understanding of the objectives and advantages of present invention, exemplary embodiments thereof will be described below, representing the technical effect obtained without limiting the scope of the present invention.

[0041] In one embodiment of the present invention, the powder paint composition comprises the example formulations set forth in Table 2, for a colorless powder paint formulation (Formulation 1) and a gold-tinted powder paint formulation (Formulation 2), which were prepared and processed as described above. Table 2 - Example formulations for a colorless powder paint (Formulation 1) and a gold-tinted powder paint (Formulation 2).

[0042] The formulations obtained were applied and cured, according to the present invention, on wood and aluminum sheet to evaluate their properties and characteristics.

[0043] Formulation 1 powder paint, when applied to wood, presented a smooth texture on the substrate surface, with a layer thickness of 35 pm to 50 pm, without the presence of defects in the coating. The same was observed for Formulation 2. Similar properties were also observed when applying the powder coatings of Formulations 1 and 2 to aluminum sheets, presenting gloss properties at 60° above 80 gloss units, an impact resistance (ISO 6272-2) >50 kg-cm, a flexibility on a conical mandrel (NBR 10545) of 0 mm and an adhesion to the substrate (NBR 11003) of GrO, that is, no area of ​​the coating was detached. The powder material of the example formulations also presented an approximate gel time of 150 seconds at 120°C and 114 seconds at 130°C.

[0044] To further evaluate the curing ability of the powder paint coating compositions of the present invention, 5 samples of low and high density pine and eucalyptus wood handles were coated with example Formulations 1 and 2 (Table 3) in layers of 20 pm to 50 pm. The coating was applied using a corona-type electrostatic gun and cured using infrared radiation catalytic panels.

[0045] For this purpose, each sample was placed between two infrared radiation catalytic panels, for heating and curing of the applied coating, with an average distance between the samples and the catalytic panels varying between 22 cm and 35 cm (Figure 2) and heating exposure times varying between 2 minutes and 5 minutes for each sample according to Table 3. The samples were subjected to temperatures between 120°C and 130°C and rotated manually and constantly to maintain homogeneity in the exposure to the applied temperature. Table 3 - Conditions and results of the curing test of wooden handles applied with the powder paint coating of Formulations 1 and 2.

[0046] The curing test in the presence of catalytic panels showed that the samples under all conditions evaluated, distance and curing time, presented a cured coating without apparent defects at temperatures of 120°C to 130°C. However, it is important to emphasize that the use of infrared radiation is not necessary to obtain the cured coating of the present invention, and it is possible to cure the developed powder paint coating by means of conventional heating methods known in the prior art. Conclusion

[0047] It will be understood by those skilled in the art that modifications can be made to the present invention without departing from the concepts set forth in the description above. Such modifications should be considered as falling within the scope of the present invention. Consequently, the particular embodiments described in detail above are merely illustrative, exemplary, and not limiting of the scope of the present invention, which should be given the full scope of the appended claims and any and all equivalents thereof.

Claims

CLAIMS 1. High degassing powder paint, characterized by the fact that it comprises: - from 20 to 50% by weight of a polyester resin, - from 20 to 50% by weight of an epoxy resin, - from 0.1 to 6% by weight of degassing additives, - from 0.7 to 4.0% by weight of supplementary additives, and - from 0 to 40% by weight of fillers and pigments, in relation to the total weight of the composition.

2. High degassing powder paint, according to claim 1, characterized by the fact that it comprises a hybrid system of epoxy-polyester resins, preferably carboxy-functional polyester resins and hydroxy-functional polyester resins, preferably a carboxylated polyester resin and an epoxy resin produced by the reaction of epichlorohydrin and phenolic compounds, including bisphenol A and bisphenol F, preferably bisphenol A.

3. High degassing powder paint, according to claim 1, characterized by the fact that it comprises a hybrid epoxy-polyester resin system with a polyester:epoxy mixing ratio of 60:40 or 70:30 or 50:50, preferably 50:

50.

4. High degassing powder paint, according to claim 1, characterized by the fact that it comprises a hybrid system of epoxy-polyester resins with acidity of 15 mgKOH / g to 100 mgKOH / g, preferably 70 mgKOH / g to 85 mgKOH / g.

5. High degassing powder paint according to claim 1, characterized in that the degassing additive includes one or more micronized waxes, preferably polyethylene-based micronized waxes. and amide.

6. High degassing powder paint, according to claim 1, characterized by the fact that it comprises supplementary additives and / or additional auxiliaries, preferably antioxidant and / or anti-caking and / or leveling additives.

7. High degassing powder paint, according to claims 1 to 6, characterized in that the coating is cured at a temperature of 110°C to 180°C, preferably 120°C to 140°C.

8. High degassing powder paint, according to claims 1 to 6, characterized by the fact that it is applied in the absence of preheating on a heat-sensitive substrate and / or with a high moisture content, preferably wooden substrates.

9. Method of obtaining a high degassing powder paint, characterized by the fact that it comprises the steps of: a) Weighing and pre-mixing the components in the quantities specified by the formulation; b) Heating and melting the pre-mixture, preferably in an extruder; c) Cooling the material to obtain a solid material; d) Grinding the solid material into smaller particles; e) Classification and sieving of the particles obtained.

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