Coated particles and methods for their production

Abstract

The coating particles according to an embodiment of the present invention comprise: a core comprising a (meth)acrylate resin; and an anti-stick coating formed on the surface of the core, the anti-stick coating comprising an alkali metal salt. The content of the alkali metal salt is from 3 ppm to 7000 ppm of the total weight of the core and the anti-stick coating. A method for preparing the coating particles according to an embodiment of the present invention involves preparing a coating solution comprising an alkali metal salt and a solvent. A core comprising a (meth)acrylate resin is mixed with the coating solution to prepare preliminary coating particles. The preliminary coating particles are dried to prepare coated particles. The content of the alkali metal salt is from 0.03% to 5% by weight of the total weight of the coating solution.

Description

Technical Field

[0001] This invention provides a coating particle and a method for preparing the same. Background Technology

[0002] Acrylic resins, as polymer resins, are transparent resins used in various fields requiring transparency due to their excellent transparency, weather resistance, and superior mechanical and physical properties.

[0003] Acrylic resins are produced, stored, and distributed, for example, in granular form. However, the ester or carboxyl groups contained in acrylic resins are functional groups with high polarity indices. They can react and bind to each other on the surface between particles, forming aggregates of particles. Therefore, the processability of acrylic resin granules may be reduced, and their marketability during long-term storage may be significantly reduced, making them potentially unusable.

[0004] Techniques have been proposed to prevent particle aggregation (caking or blocking). For example, techniques have been proposed to prepare particles by mixing an anti-blocking agent during particle formation or to treat the surface of the particles with an anti-blocking agent. However, these techniques cannot prevent clumping when acrylic resin particles are stored for a long time, or they may lead to a decrease in marketability due to particle discoloration. Summary of the Invention

[0005] (a) Technical problems to be solved One technical problem of the present invention is to provide coating particles whose aggregation is suppressed.

[0006] One technical problem of the present invention is to provide a method for preparing the coating particles.

[0007] (II) Technical Solution The coating particles according to the invention comprise: a core comprising a (meth)acrylate resin; and an anti-stick coating formed on the surface of the core, the anti-stick coating comprising an alkali metal salt. The content of the alkali metal salt is from 3 ppm to 7000 ppm of the total weight of the core and the anti-stick coating.

[0008] In an exemplary embodiment, the content of the alkali metal salt can be from 3 ppm to 3000 ppm of the total weight of the core and the anti-stick coating.

[0009] According to an exemplary embodiment, the (meth)acrylic resin may include repeating units derived from (meth)acrylic acid.

[0010] According to an exemplary embodiment, the content of the repeating unit derived from (meth)acrylic acid can be from 10% to 30% by weight of the total weight of the (meth)acrylic acid-based resin.

[0011] According to an exemplary embodiment, the content of the repeating unit derived from (meth)acrylic acid can be from 10% to 20% by weight of the total weight of the (meth)acrylic acid-based resin.

[0012] According to an exemplary embodiment, the alkali metal salt may include a sodium salt.

[0013] According to an exemplary embodiment, the alkali metal salt may include an alkali metal phosphate.

[0014] According to an exemplary embodiment, the alkali metal salt may not include alkali metal carboxylates.

[0015] According to an exemplary embodiment, the alkali metal salt may include at least one selected from trisodium phosphate, sodium sulfite, sodium silicate, and sodium octanoate.

[0016] According to an exemplary embodiment, the (meth)acrylate resin may include repeating units derived from (meth)acrylate monomers, wherein the (meth)acrylate monomers may include one or more selected from alkyl (meth)acrylates, hydroxyl-containing (meth)acrylates, carboxyl-containing (meth)acrylates, and alkoxy-containing (meth)acrylates.

[0017] According to an exemplary embodiment, the pH of the alkali metal salt may be higher than the pH of the (meth)acrylic resin.

[0018] According to the present invention, a coating solution comprising an alkali metal salt and a solvent is prepared. A core comprising a (meth)acrylate resin is mixed with the coating solution to prepare preliminary coating particles. The preliminary coating particles are dried to prepare coated particles. The content of the alkali metal salt is from 0.03% to 5% by weight of the total weight of the coating solution.

[0019] According to an exemplary embodiment, the content of the alkali metal salt can be from 0.03% by weight to 0.5% by weight of the total weight of the coating solution.

[0020] According to an exemplary implementation, the drying process can last for 20 to 30 hours.

[0021] According to an exemplary embodiment, the drying can be carried out at 20°C to 30°C.

[0022] (III) Beneficial Effects The coated particles according to an exemplary embodiment of the present invention do not stick together even when stored under high pressure. Therefore, particle agglomeration can be prevented, and the operability and storeability of the particles can be improved.

[0023] The method for preparing coated particles according to an exemplary embodiment of the present invention can reduce the adhesion between particles in a simple way. Detailed Implementation

[0024] According to an exemplary embodiment of the present invention, a coated particle comprising a core with a surface coated is provided. Furthermore, a method for preparing the coated particle is provided.

[0025] The present invention will now be described in detail. However, this is merely an exemplary description, and the present invention is not limited to the specific embodiments described herein.

[0026] The coating particles according to an exemplary embodiment comprise a core and an anti-stick coating. The core comprises a (meth)acrylate resin, and the anti-stick coating is formed on the surface of the core and comprises an alkali metal salt.

[0027] The core can be prepared as a (meth)acrylate resin core and without an anti-stick coating. The core can be prepared by methods known in the art or by purchasing commercially available products.

[0028] The (meth)acrylate resin may comprise a polymer or copolymer formed by polymerizing (meth)acrylate monomers or a mixture of monomers containing (meth)acrylate monomers. The (meth)acrylate resin may comprise repeating units derived from (meth)acrylate monomers.

[0029] The "(meth)acrylate monomer" may include compounds containing acrylic acid groups (CH2=CH-C(=O)-O-) or methacrylic acid groups (CH2=C(CH3)-C(=O)-O-) as (meth)acrylate or (meth)acrylate ester monomers. The (meth)acrylate resin can be formed by polymerization through the breaking of carbon-carbon double bonds in the (meth)acrylate groups contained in the (meth)acrylate monomer.

[0030] The (meth)acrylate monomer is not particularly limited as long as it contains a (meth)acrylate group, but for example, the (meth)acrylate monomer may include alkyl (meth)acrylates, (meth)acrylates containing hydroxyl groups, (meth)acrylates containing carboxyl groups, (meth)acrylates containing alkoxy groups, etc. These can be used alone or in combination of two or more.

[0031] The (meth)acrylic acid monomer may include, for example, acrylic acid, methacrylic acid, etc.

[0032] Alkyl (meth)acrylates can be listed as, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, 1,3-dimethylbutyl acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, heptaethyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tetrate (meth)acrylate, and n-tetradecyl (meth)acrylate. These can be used alone or in combination of two or more.

[0033] Examples of hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylaurate (meth)acrylate, and methyl (4-hydroxymethylcyclohexyl)methacrylate. These can be used alone or in combination of two or more.

[0034] Examples of (meth)acrylates containing a carboxyl group include carboxyethyl (meth)acrylate and carboxypentyl (meth)acrylate. These can be used alone or in combination of two or more.

[0035] Examples of (meth)acrylates containing alkoxy groups include 2-methoxyethyl acrylate and acrylates containing polyethers.

[0036] In addition to the (meth)acrylates listed above, the monomer mixture may further comprise polymerizable monomers having unsaturated groups.

[0037] For example, the polymerizable monomers may include: aromatic alkenyl monomers such as styrene, α-methylstyrene, p-methylstyrene, and p-methoxystyrene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; and unsaturated aliphatic monomers such as butadiene, ethylene, and propylene.

[0038] In some embodiments, the (meth)acrylic resin may comprise repeating units derived from (meth)acrylic acid monomers. For example, the (meth)acrylic resin may comprise a polymer comprising a mixture of monomers of (meth)acrylic acid and ethylene.

[0039] In an exemplary embodiment, the content of the repeating unit derived from (meth)acrylic acid may be from 10% to 30% by weight of the total weight of the (meth)acrylic acid-based resin. In some embodiments, the content of the repeating unit derived from (meth)acrylic acid may be from 13% to 27% by weight, 13.5% to 25% by weight, or 18% to 23% by weight of the total weight of the (meth)acrylic acid-based resin.

[0040] Within the aforementioned range, the anti-caking and anti-sticking properties of the following anti-stick coating can be more effectively exhibited.

[0041] In an exemplary embodiment, the (meth)acrylic resin may comprise an ethylene-acrylic resin. The (meth)acrylic resin may comprise repeating units derived from ethylene and repeating units derived from acrylic acid. In the total weight of the ethylene-acrylic resin, the content of repeating units derived from acrylic acid may be from 10% to 30% by weight, and the content of repeating units derived from ethylene may be from 70% to 90% by weight.

[0042] According to an exemplary embodiment, the anti-tacking coating comprises an alkali metal salt. The alkali metal salt functions as an anti-tacking agent.

[0043] The alkali metal salt contains an alkali metal with a high ionization tendency, which can increase the polarity index of the anti-stick coating, thereby enabling the (meth)acrylic resin to bond firmly to the anti-stick coating.

[0044] Furthermore, the alkali metal salt can be readily ionized, and the anti-stick coating can contain a large number of cations. Therefore, repulsive forces can act between the anti-stick coating particles on their surfaces, thereby preventing particle agglomeration.

[0045] According to an exemplary embodiment, the alkali metal salt may contain sodium, potassium, rubidium, etc., as alkali metals.

[0046] According to an exemplary embodiment, the alkali metal salt may include a sodium salt. Sodium has a high ionization tendency, thereby forming monovalent cations. Protons can migrate rapidly on the particle surface, thereby forming strong metal-ionic bonds on the particle surface. Therefore, the repulsive force between metal cations between particles can be increased, thereby preventing particle agglomeration.

[0047] In addition, sodium salts can have higher solubility in water-based solvents than calcium salts, and can improve the efficiency of the coating particle preparation process.

[0048] The alkali metal salt may contain inorganic anions such as silicate, sulfite, sulfate, phosphate, polyphosphate, and bisulfite, or organic anions such as octanoate and citrate. In one embodiment, the alkali metal salt may contain inorganic anions.

[0049] According to an exemplary embodiment, the pH of the alkali metal salt can be 5 or higher. According to some embodiments, the pH of the alkali metal salt can be 6 or higher, 7 or higher, 8 or higher, 9 or higher, 10 or higher, or 11 or higher. Within the above ranges, the pH of the alkali metal salt can be higher than the pH of the (meth)acrylate resin.

[0050] According to an exemplary embodiment, the alkali metal salt may include an alkali metal phosphate. Phosphate is a trivalent anion, which can bind with more cations, thereby further improving the anti-stick properties of the anti-stick coating.

[0051] According to an exemplary embodiment, the alkali metal salt may include at least one selected from trisodium phosphate, sodium sulfite, sodium silicate, and sodium octanoate. In one embodiment, the alkali metal salt may include trisodium phosphate.

[0052] According to an exemplary embodiment, the alkali metal salt may not include an alkali metal carboxylate. The carboxylate may react with the carboxyl or ester groups contained in the (meth)acrylate resin, potentially promoting agglomeration.

[0053] According to an exemplary embodiment, the content of the alkali metal salt is from 3 ppm to 7000 ppm of the total weight of the core and the anti-stick coating. In some embodiments, the content of the alkali metal salt can be from 3 ppm to 6000 ppm or from 3 ppm to 3000 ppm of the total weight of the core and the anti-stick coating.

[0054] When the content of the alkali metal salt is less than 3 ppm, it cannot prevent the adhesion between particles. When the content of the alkali metal salt exceeds 7000 ppm, the alkali metal salt may precipitate during the preparation process of the coated particles, which may form an uneven coating on the particle surface, and the precipitate may block the pipes of the preparation equipment.

[0055] According to an exemplary embodiment, when the content of the repeating unit derived from (meth)acrylic acid in the total weight of the (meth)acrylic resin of the core is 10% to 20% by weight, the content of the alkali metal salt can be 3 ppm to 2000 ppm or 10 ppm to 1500 ppm of the total weight of the core and the anti-stick coating.

[0056] According to an exemplary embodiment, when the content of the repeating unit derived from (meth)acrylic acid in the total weight of the (meth)acrylic resin of the core is more than 20% by weight and less than 30% by weight, the content of the alkali metal salt can be 3 ppm to 6500 ppm or 4.5 ppm to 6000 ppm of the total weight of the core and the anti-stick coating.

[0057] According to an exemplary embodiment, the average particle size of the coated particles is not particularly limited, and the coating can be introduced to prevent agglomeration between resin particles of various sizes.

[0058] According to the present invention, a method for preparing the coating particles is provided.

[0059] According to an exemplary embodiment, a coating solution comprising the alkali metal salt and a solvent is prepared. The alkali metal salt can be any alkali metal salt as described above, and the solvent is not particularly limited, but can be an aqueous solvent capable of dissolving the alkali metal salt. For example, the solvent can be water.

[0060] According to an exemplary embodiment, the content of the alkali metal salt is from 0.03% to 5% by weight of the total weight of the coating solution. According to some embodiments, the content of the alkali metal salt can be from 0.03% to 0.5% by weight of the total weight of the coating solution.

[0061] Within the aforementioned range, the color and physical properties of the particles can be maintained while preventing surface adhesion between particles.

[0062] When the content of the alkali metal salt is less than 0.03% by weight, particle adhesion cannot be prevented. When the content of the alkali metal salt exceeds 5% by weight, the precipitates of the alkali metal salt may clog the pipes of the preparation equipment during the coating particle preparation process, and productivity may be reduced.

[0063] According to an exemplary embodiment, the core comprising a (meth)acrylate resin is mixed with the coating solution to prepare preliminary coated particles. The (meth)acrylate resin may be a (meth)acrylate resin as described above.

[0064] The nucleus can be added to the coating solution and stirred for approximately 10 to 60 minutes. After mixing, preliminary coating particles can be obtained by filtration.

[0065] According to an exemplary embodiment, the preliminary coating particles are dried to prepare coated particles. In the preliminary coating particles, the solvent may remain on the surface of the core. By performing the drying process, the residual solvent can be removed, and an anti-stick coating can be formed on the surface of the core.

[0066] According to an exemplary embodiment, the drying process can last for 20 to 30 hours. For example, the drying can be carried out at 20°C to 30°C.

[0067] The coated particles do not stick together even when stored at high temperatures for extended periods. In an exemplary embodiment, multiple coated particles do not stick together even when stored at temperatures between 40°C and 70°C for more than 10 hours. In one embodiment, multiple coated particles do not stick together even when stored at temperatures between 45°C and 60°C for more than 15 hours.

[0068] The coated particles do not stick together even under high temperature and high pressure conditions. In an exemplary embodiment, multiple coated particles do not stick together even after storage for more than 10 hours at a pressure of more than about 0.4 bar (gauge pressure) and a temperature of 40°C to 70°C. In some embodiments, multiple coated particles do not stick together even after storage for more than 15 hours at a pressure of more than about 0.5 bar (gauge pressure) and a temperature of 45°C to 60°C.

[0069] The embodiments of the present invention will be further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only for illustrating the present invention and are not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and its technical concept, which is obvious to those skilled in the art, and such variations and modifications naturally fall within the scope of the claims.

[0070] Preparation Example 1 A monomer mixture comprising ethylene and acrylic acid in a weight ratio of 79.3:20.7, along with an initiator, was added to a reactor and reacted for less than one minute at a pressure of approximately 26,700 psig and a temperature of 245°C to 260°C. After the reaction, unreacted monomers were separated by a depressurization process to obtain an acrylic resin core.

[0071] Preparation Example 2 A monomer mixture comprising ethylene and acrylic acid in a weight ratio of 86.5:13.5, along with an initiator, was added to a reactor and reacted for less than one minute at a pressure of approximately 31,000 psig and a temperature of 235°C to 240°C. After the reaction, unreacted monomers were separated by a depressurization process to obtain an acrylic resin core.

[0072] Example 1 Prepare an aqueous solution containing 0.03% by weight of trisodium phosphate as an alkali metal salt. Add 5 parts by weight of the acrylic resin core of Preparation Example 1 to 100 parts by weight of the aqueous solution and stir for 30 minutes. Obtain preliminary coated particles by filtration, and then dry at room temperature (25°C) for 24 hours to obtain coated particles.

[0073] Examples 2 to 28 and Comparative Examples 1 to 6 Coated particles were prepared using the same method as in Example 1, except that the type and content of alkali metal salts in the aqueous solution and the type of acrylic resin core were changed, as shown in Table 1 below.

[0074] For the coated particles of the examples and comparative examples, the content of alkali metal salts contained in the coated particles was measured using an inductively coupled plasma (ICP) analyzer.

[0075] Specifically, approximately 0.55 g of the coating particles from the examples and comparative examples were mixed with sulfuric acid and then heated to carbonize them. The samples were then cooled to room temperature and ashed in a two-step process at 250°C and 600°C in an electric furnace. After ashing, the samples were cooled to room temperature, nitric acid was added, and the mixture was heated to dissolve the residue, thereby preparing a solution. The content of alkali metal salts was measured using an ICP analyzer for the diluted solutions prepared from the original solution.

[0076] [Table 1] The meanings of the abbreviations in Table 1 are as follows.

[0077] TSP: Trisodium phosphate SS: Sodium silicate SP: Sodium Caprylate A-1: Preparation of the ethylene-acrylic resin core of Example 1 (acrylic acid content is 20.7% by weight) A-2: Preparation of the ethylene-acrylic resin core of Example 2 (acrylic acid content is 13.5% by weight) Experimental Example Approximately 5 g of the coated particles from the examples and comparative examples were added to a stainless steel cup and stored in an oven at 50°C for 17 hours under pressure applied using a 4.5 kg weight (approximately 0.55 bar (bar.g)). After removing the cup from the oven, it was inverted, and the percentage of the weight of the particles that fell from the cup relative to the initial addition of 5 g was calculated. For example, when all particles fell from the cup, the evaluation value was 100%, and when all particles aggregated and did not fall from the cup, the evaluation value was 0%. The evaluation results are shown in Table 2 below.

[0078] [Table 2] Referring to Table 2, it can be confirmed that the coating particles of Examples 1 to 7, which used trisodium phosphate as an alkali metal salt and the ethylene-acrylic resin core of Preparation Example 1, exhibited higher evaluation values ​​and thus less aggregation compared to the coating particles of Comparative Examples 1 and 2. Furthermore, it can be confirmed that in Examples 8 to 12, which used the ethylene-acrylic resin core of Preparation Example 2, less aggregation occurred compared to Comparative Example 3.

[0079] In the coated particles of Examples 13 to 18, which used sodium silicate as an alkali metal salt and the ethylene-acrylic resin core of Preparation Example 1, higher evaluation values ​​were observed compared to the coated particles of Comparative Example 4, thus confirming that less aggregation occurred. Furthermore, in Examples 19 to 26, which used the ethylene-acrylic resin core of Preparation Example 2, higher evaluation values ​​were observed compared to Comparative Example 5.

[0080] In Examples 27 and 28, which used sodium octanoate as an alkali metal salt and the ethylene-acrylic resin core of Preparation Example 2, higher evaluation values ​​were obtained compared to Comparative Example 6, thus confirming that aggregation was reduced and agglomeration was suppressed.

[0081] The above description is merely an example of applying the principles of this invention, and other configurations may be further included without departing from the scope of this invention.

Claims

1. A coating particle, wherein, The coating particles comprise: The core comprises a (meth)acrylate resin; as well as An anti-stick coating is formed on the surface of the core, and the anti-stick coating comprises an alkali metal salt. The content of the alkali metal salt is 3 ppm to 7000 ppm of the total weight of the core and the anti-stick coating.

2. The coating particles according to claim 1, wherein, The content of the alkali metal salt is 3 ppm to 3000 ppm of the total weight of the core and the anti-stick coating.

3. The coating particles according to claim 1, wherein, The (meth)acrylic resin comprises repeating units derived from (meth)acrylic acid.

4. The coating particles according to claim 3, wherein, The content of the repeating unit derived from (meth)acrylic acid is from 10% to 30% by weight of the total weight of the (meth)acrylic acid-based resin.

5. The coating particles according to claim 4, wherein, The content of the repeating unit derived from (meth)acrylic acid is 10% to 20% by weight of the total weight of the (meth)acrylic acid-based resin.

6. The coating particles according to claim 1, wherein, The alkali metal salts include sodium salts.

7. The coating particles according to claim 1, wherein, The alkali metal salts include alkali metal phosphates.

8. The coating particles according to claim 1, wherein, The alkali metal salts do not include alkali metal carboxylates.

9. The coating particles according to claim 1, wherein, The alkali metal salt includes at least one selected from trisodium phosphate, sodium sulfite, sodium silicate, and sodium octanoate.

10. The coating particles according to claim 1, wherein, The (meth)acrylate resin comprises repeating units derived from (meth)acrylate monomers, wherein the (meth)acrylate monomers comprise one or more selected from alkyl (meth)acrylates, hydroxyl-containing (meth)acrylates, carboxyl-containing (meth)acrylates, and alkoxy-containing (meth)acrylates.

11. The coating particles according to claim 1, wherein, The pH of the alkali metal salt is higher than the pH of the (meth)acrylic resin.

12. A method for preparing coating particles, wherein, The preparation method includes the following steps: Prepare a coating solution containing alkali metal salts and solvents; A core containing a (meth)acrylic resin is mixed with the coating solution to prepare preliminary coating particles; and The preliminary coating particles are dried to prepare the coating particles. The content of the alkali metal salt is 0.03% to 5% by weight of the total weight of the coating solution.

13. The method for preparing coating particles according to claim 12, wherein, The content of the alkali metal salt is from 0.03% to 0.5% by weight of the total weight of the coating solution.

14. The method for preparing coating particles according to claim 12, wherein, The drying process takes 20 to 30 hours.

15. The method for preparing coating particles according to claim 12, wherein, The drying is carried out at 20°C to 30°C.

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