Polymer bead composition, polymer beads comprising same, and method for manufacturing polymer beads

Abstract

The present specification relates to: a polymer bead composition comprising an aromatic vinyl-based monomer, a crosslinking agent, an initiator, and a phosphorus-based flame retardant; polymer beads comprising same; and a method for manufacturing polymer beads.

Description

Polymer bead composition, polymer beads comprising the same, and method for manufacturing polymer beads

[0001] Cross-citation with related application(s)

[0002] The present application claims the benefit of the filing date of Patent No. 10-2024-0200210 filed with the Korean Intellectual Property Office on December 30, 2024 and Patent No. 10-2025-0210395 filed with the Korean Intellectual Property Office on December 16, 2025, the contents of which are incorporated herein.

[0003] This specification relates to a polymer bead composition, a polymer bead comprising the same, and a method for manufacturing a polymer bead.

[0004] Conventional polymer beads are generally manufactured through suspension polymerization, dispersion polymerization, and emulsion polymerization processes. Among these methods, suspension polymerization, in particular, forms polymer beads by dispersing monomers in an aqueous solution using mechanical force. However, beads manufactured in this manner have the following disadvantages.

[0005] 1) Non-uniformity of particle size distribution: Since it depends on mechanical dispersion, the particle size distribution of polymer beads tends to widen. This can degrade the optical and physical properties of the product.

[0006] 2) Lack of flame retardancy: The polymers used in existing acrylic-based sound barriers have low flame retardancy ratings, which increases the risk in the event of a fire. Due to this problem, acrylic sound barriers are gradually being replaced by polycarbonate (PC), which has a high flame retardancy rating.

[0007] 3) Light pollution problem: Transparent acrylic sound barriers can cause light pollution in adjacent areas, such as residential areas, due to light reflection.

[0008] 4) Deterioration of processability: Adding a large amount of flame retardant lowers the Melt Index (MI) during masterbatch manufacturing, causing problems during the molding process.

[0009] To solve the above problem, it is necessary to develop polymer beads that have a uniform particle size distribution and excellent optical or flame-retardant properties.

[0010] This specification relates to a polymer bead composition, a polymer bead comprising the same, and a method for manufacturing a polymer bead.

[0011] The present invention provides a polymer bead composition comprising an aromatic vinyl monomer; a crosslinking agent; an initiator; and a phosphorus-based flame retardant.

[0012] In addition, the present invention provides a polymer bead comprising: a polymer matrix derived from the above-described polymer bead composition and derived from the aromatic vinyl monomer; and a phosphorus-based flame retardant encapsulated within the polymer matrix.

[0013] In addition, the present invention provides a method for manufacturing polymer beads comprising the steps of: preparing the polymer bead composition described above; stirring the polymer bead composition at a stirring speed of 3,000 rpm or more and 15,000 rpm or less to prepare a suspension; and suspending polymerizing the suspension at a temperature of 30°C or more and 100°C or less.

[0014] By utilizing the polymer bead composition of the present invention, polymer beads having a uniform particle size can be manufactured.

[0015] By utilizing the polymer bead composition of the present invention, polymer beads with excellent flame retardancy can be manufactured.

[0016] By utilizing the polymer bead composition of the present invention, polymer beads with reduced light reflection can be manufactured.

[0017] Figures 1 to 4 are the results of the appearance comparison of Experimental Example 1.

[0018] The present invention will be described in detail below.

[0019] In this specification, the 'polymer bead composition' can be used for the purpose of manufacturing polymer beads through a polymerization process.

[0020] In this specification, 'encapsulation' means surrounding a specific substance with another substance. For example, that a flame retardant is encapsulated within a polymer matrix may mean that the polymer matrix surrounds part or all of the surface of the flame retardant.

[0021] In this specification, 'Particle Size' refers to the diameter of an individual particle. In cases where the particle is not spherical, it may refer to the diameter of a virtual, perfect sphere having the same volume as the particle. Alternatively, it may refer to the diameter of a virtual circle having the same area as the cross-section of the particle as confirmed by an optical microscope image, such as a scanning electron microscope; the maximum inscribed circle diameter that can be contained within the cross-section of the particle as confirmed by the optical microscope image; or the diameter of the smallest circle that completely encloses the cross-section of the particle as confirmed by the optical microscope image.

[0022] In this specification, 'Mean Particle Size' refers to a statistical representative value representing a sample containing several particles. For example, it may be the Number Mean Particle Size calculated by dividing the sum of the diameters of individual particles in the sample by the number of particles, or it may be the Mean Particle Size (Dn) derived by a method using a particle size analyzer as described below.

[0023] The above method for measuring particle size or average particle size may use a method using a particle size analyzer (PSD) or a scanning electron microscope image analysis method.

[0024] The method using the particle size analyzer described above is a laser diffraction analysis method that irradiates a dispersion containing dispersed polymer beads with a laser and analyzes the pattern of scattered light using an optical model. It enables statistical analysis of the entire sample and allows for fast and automated analysis. By utilizing the particle size analyzer, it is possible to derive and analyze volume distribution curves or volume accumulation distribution curves in order from smallest to largest particle sizes.

[0025] Unless otherwise stated in this specification, the particle size or average particle size may be measured using the particle size analyzer. For example, the average particle size of the polymer beads may be obtained by analyzing a dispersion in which the polymer beads are dispersed using a particle size analyzer. Additionally, the average particle size of the polymer beads may be obtained by analyzing a dispersion in which a plurality of polymer beads are dispersed using a particle size analyzer.

[0026] In this specification, 'Dn' refers to the particle size at the n% point of the cumulative volume distribution according to particle size. That is, D 50 is the particle size at the 50% point of the cumulative volume distribution according to particle size, and D 90 The particle size at the 90% point of the cumulative volume distribution according to particle size is D 10 Dn is the particle size at the 10% point of the cumulative volume distribution according to particle size. The above Dn can be measured using the Laser Diffraction Method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) to calculate the particle size distribution by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam. By calculating the particle diameters at the points corresponding to 10%, 50%, and 90% of the cumulative volume distribution according to particle size in the measuring device, D 10 , D 50 and D 90 It can measure.

[0027] In this specification, the 'alkyl group' is an aliphatic saturated hydrocarbon group and may be linear or branched.

[0028] In this specification, 'aryl group' refers to a substituent comprising an aromatic ring, which may include a single ring or a multi-ring structure. For example, it may include a phenyl group.

[0029] In this specification, the 'alkyl group and aryl group' may each be substituted or unsubstituted. The term 'substitution' may mean that any hydrogen bonded to a carbon of a hydrocarbon group is substituted with at least one substituent, and examples of the substituents include a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkyl halide group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a thioalkoxy group having 1 to 6 carbon atoms, a vinyl group, a hydroxyl group, a primary to tertiary amine group, an imine group, a thiol group, and a sulfide group.

[0030] The present invention provides a polymer bead composition comprising an aromatic vinyl monomer; a crosslinking agent; an initiator; and a phosphorus-based flame retardant.

[0031] In the present invention, the polymer bead composition comprises a phosphorus-based flame retardant. The phosphorus-based flame retardant is a compound containing phosphorus (P) and is included to improve the flame retardancy of the polymer beads. The phosphorus-based flame retardant can suppress combustion through dehydration and the formation of a non-combustible layer during thermal decomposition. Specifically, the phosphorus-based flame retardant forms a protective film (carbonized layer) with an oxygen-blocking effect during the thermal decomposition of the polymer beads, thereby suppressing heat transfer and reducing the combustion rate, resulting in a highly efficient flame retardant effect. Furthermore, it has the advantage of being environmentally friendly as it does not emit harmful gases during combustion, and it has the effect of exhibiting a flame retardant effect regardless of the substrate of the object to be combusted.

[0032] The polymer bead composition of the present invention contains a phosphorus-based flame retardant to improve flame retardancy. The polymer bead composition can be manufactured into polymer beads through a polymerization process. At this time, the phosphorus-based flame retardant is encapsulated within the polymer beads to prevent the flame retardant from decomposing or reacting prematurely, and the effect of the flame retardant can be maintained for a long time even at high temperatures. The encapsulation effect of the flame retardant can be achieved by adjusting the content of the flame retardant, the size of the polymer beads, the manufacturing conditions of the polymer beads, etc., as described below in this specification.

[0033] In the present invention, the content of the phosphorus-based flame retardant may be 1 part by weight or more and 20 parts by weight or less, based on 100 parts by weight of the aromatic vinyl monomer. Preferably, it may be 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, or 11 parts by weight or more. Additionally, it may be 18 parts by weight or less, 16 parts by weight or less, 14 parts by weight or less, or 12 parts by weight or less. If the above numerical range is exceeded, the flame retardant may leak into the solvent during the encapsulation process and be adsorbed onto the surface of the polymer beads, resulting in uneven encapsulation and inconsistent tension on the surface of the polymer beads. On the other hand, if it falls below the above numerical range, the inherent flame retardant effect of the phosphorus-based flame retardant may be reduced. That is, within the above numerical range, the flame retardancy of the polymer beads can be exhibited, and mechanical strength and flexibility can be balanced, thereby improving the physical properties of the polymer beads. In addition, the coefficient of variation described later can be controlled to be small, and the phosphorus-based flame retardant can be uniformly encapsulated in the polymer matrix.

[0034] In the present invention, the content of the phosphorus-based flame retardant may be 100 parts by weight or more and 900 parts by weight or less, based on 100 parts by weight of the crosslinking agent. Preferably, it may be 150 parts by weight or more, 200 parts by weight or more, 250 parts by weight or more, 300 parts by weight or more, 350 parts by weight or more, 400 parts by weight or more, 450 parts by weight or more, 500 parts by weight or more, or 550 parts by weight or more. Additionally, it may be 850 parts by weight or less, 800 parts by weight or less, 850 parts by weight or less, or 800 parts by weight or less. If the above numerical range is exceeded, the content of the crosslinking agent is low, causing the polymer matrix to have a loose crosslinked structure, and there is a problem in that the phosphorus-based flame retardant easily escapes between the loose polymer matrix. On the other hand, if it falls below the above numerical range, the inherent flame retardant effect of the phosphorus-based flame retardant may be reduced. That is, within the above numerical range, the flame retardancy of the polymer beads can be exhibited, and mechanical strength and flexibility can be balanced, thereby improving the physical properties of the polymer beads. In addition, the coefficient of variation described later can be controlled to be small, and the phosphorus-based flame retardant can be uniformly encapsulated in the polymer matrix.

[0035] In the present invention, the phosphorus-based flame retardant may include a phosphazene-based compound, a phosphate-based compound, or a combination thereof.

[0036] In the present invention, the phosphazene compound may include a cyclic phosphazene compound, a chain-type phosphazene compound, a cross-linked phosphazene compound, or a combination thereof. The phosphazene compound has a backbone in which double bonds between phosphorus and nitrogen are repeated, and phosphorus and nitrogen are bonded to each other in one molecule. In this case, when combusted, the nitrogen component generates a non-combustible gas (nitrogen gas), which pushes out oxygen and causes the char formed by the phosphorus component to swell, thereby forming a protective film with excellent thermal insulation effect.

[0037] In the present invention, the phosphazene compound may be represented by the following chemical formula 1. The phosphorus and nitrogen bonds of the following chemical formula 1 form a ring structure, and when a fire occurs, they stick together to form a three-dimensional network structure. In this case, the formed char is dense, so the thermal insulation effect can be further improved.

[0038] [Chemical Formula 1]

[0039]

[0040] In the above chemical formula 1,

[0041] X 1 To X 3 Each is independently Cl, Br, or F, and

[0042] R 1 to R 3 Each is independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 20 carbon atoms, and

[0043] n, m, and k are each independently 0, 1, or 2.

[0044] In the above chemical formula 1, n, m, and k can each be independently 0, 1, or 2, and can be the same or different from each other.

[0045] In the present invention, the phosphate-based compound may be represented by the following chemical formula 2. In this case, the phosphate-based compound has high miscibility with other polymer components included in the polymer bead composition and excellent processability, thereby further enhancing the flame-retardant effect. Through this, a low afterglow time may be observed.

[0046] [Chemical Formula 2]

[0047]

[0048] In Chemical Formula 2,

[0049] A1 to A4 are identical or different, and each is an independently substituted or unsubstituted aryl group, and

[0050] L1 is a divalent linker connected to a phosphate group through an aromatic carbon atom.

[0051] In the present invention, A1 to A4 may be the same or different and each may be an aryl group having 6 to 12 carbon atoms that is independently substituted or unsubstituted.

[0052] In the present invention, A1 to A4 may be the same or different and each may be an independently substituted or unsubstituted phenyl group.

[0053] In the present invention, L1 may be a divalent linker comprising one aromatic ring selected from the group consisting of bisphenol A, bisphenol AP, bisphenol B, bisphenol BP, bisphenol C, bisphenol E, bisphenol F, bisphenol G, bisphenol M, bisphenol S, bisphenol P, bisphenol PH, bisphenol TMC, bisphenol Z, and resorcinol.

[0054] In the present invention, the phosphorus-based flame retardant may be a diphosphate ester of a difunctional phenolic compound selected from the group consisting of bisphenol A, bisphenol AP, bisphenol B, bisphenol BP, bisphenol C, bisphenol E, bisphenol F, bisphenol G, bisphenol M, bisphenol S, bisphenol P, bisphenol PH, bisphenol TMC, bisphenol Z, and resorcinol.

[0055] In the present invention, the aromatic vinyl monomer may include a styrene monomer. The styrene monomer may be styrene, which is advantageous for forming a polymer with a high glass transition temperature and can improve the strength and durability of the manufactured beads. In addition, styrene facilitates free radical polymerization, which has the effect of enabling mass production.

[0056] In the present invention, the aromatic vinyl monomer may be a compound having an aromatic ring and a vinyl group. In this case, the aromatic ring has the advantage of providing electronic stability, strength, heat resistance, and chemical resistance, and the vinyl group can form a polymer chain.

[0057] In the present invention, the aromatic vinyl monomer may include one or more benzene rings and one to five vinyl groups bonded to the benzene rings.

[0058] In the present invention, the aromatic vinyl monomer may include a styrene monomer, divinylbenzene, or a combination thereof.

[0059] In the present invention, the polymer bead composition may further include one or more selected from the group consisting of (meth)acrylic acid alkyl ester monomers having 1 to 20 carbon atoms and (meth)acrylic acid fluoroalkyl ester monomers having 1 to 20 carbon atoms.

[0060] In the present invention, the polymer bead composition may include one or more selected from the group consisting of methyl methacrylate, divinylbenzene, butyl methacrylate, trimethylolmethane tetraacrylate, trimethylolmethane triacrylate, trimethylolpropane triacrylate, trimethylolbutane triacrylate, and ethylene glycol dimethacrylate.

[0061] In the present invention, the crosslinking agent is suitable for inducing crosslinking during the manufacture of polymer beads to form a three-dimensional network structure.

[0062] In the present invention, the crosslinking agent may be an acrylic crosslinking agent having an acrylate group as a reactive group. In this case, the high reactivity results in a faster polymerization rate, and the physical stability and chemical resistance of the manufactured polymer beads can be improved.

[0063] In the present invention, the crosslinking agent comprises 1,2-ethanediol diacrylate, 1,3-propanediol diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, divinylbenzene, ethylene glycol diacrylate, propylene glycol diacrylate, butylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polybutylene glycol diacrylate, allyl acrylate, 1,2-ethanediol dimethacrylate, 1,3-propanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, It may be one or more selected from the group consisting of 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, butylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylpropane triacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butylene glycol dimethacrylate, triethylene glycol methacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate, allyl methacrylate, and diallyl malate. Preferably, it may be 1,4-butanediol dimethacrylate. In this case, it has high reactivity and can improve the physical stability and chemical resistance of the polymer beads produced.

[0064] In the present invention, the content of the crosslinking agent may be 0.1 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the aromatic vinyl monomer. Preferably, it may be 0.5 parts by weight or more, 0.7 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 1.8 parts by weight or more. Additionally, it may be 4 parts by weight or less, 3 parts by weight or less, or 2.5 parts by weight or less. Within the above numerical range, the size of the polymer beads can be uniformly controlled, and the polymerization reaction rate can be maintained excellently. Furthermore, the physical strength of the polymer beads produced can be improved.

[0065] In the present invention, the initiator may include a radical initiator. The initiator can react with a monomer to initiate the growth of a polymer chain and can control the size and distribution of polymer beads by providing uniform reaction conditions.

[0066] In the present invention, the initiator may include a lipid-soluble initiator or a water-soluble initiator.

[0067] In the present invention, the lipid-soluble initiator may include one or more selected from the group consisting of benzoyl peroxide, azobis isobutyronitrile, azobisphenylbutyronitrile, and azobiscyclohexanecarbonitrile.

[0068] In the present invention, the water-soluble initiator may include one or more selected from the group consisting of potassium sulfate, sodium sulfate, ammonium persulfate, and azo-based water-soluble initiators.

[0069] In the present invention, the content of the initiator may be 0.1 parts by weight or more and 3 parts by weight or less based on 100 parts by weight of the aromatic vinyl monomer. Preferably, it may be 0.3 parts by weight or more, 0.5 parts by weight or more, 0.7 parts by weight or more, or 0.9 parts by weight or more. Additionally, it may be 2.5 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, or 1 part by weight or less. Within the above numerical range, the size of the polymer beads can be uniformly controlled, and the polymerization reaction rate can be maintained excellently.

[0070] In the present invention, the polymer bead composition may further include one or more additives selected from the group consisting of chain transfer agents, antioxidants, and solvents.

[0071] In the present invention, the chain transfer agent removes radicals generated from the unsaturated bonds of the terminal vinyl groups of aromatic vinyl monomers, thereby reducing the unequal termination reactions of the terminal vinyl groups and unreacted monomers, and thus removing monomers that decompose at high temperatures, which can improve heat resistance.

[0072] In the present invention, the chain transfer agent may be represented by Chemical Formula 3.

[0073] [Chemical Formula 3]

[0074] R 4 -SH

[0075] In the above chemical formula 3,

[0076] R 4 It may be a straight-chain or branched-chain alkyl group having 10 to 30 carbon atoms.

[0077] In the present invention, the chain transfer agent may include one or more selected from the group consisting of 1-dodecanethiol, t-dodecyl mercaptan, and t-hexadecyl mercaptan.

[0078] In the present invention, the content of the chain transfer agent may be 0.1 parts by weight or more and 0.8 parts by weight or less based on 100 parts by weight of the aromatic vinyl monomer. Preferably, it may be 0.2 parts by weight or more or 0.3 parts by weight or more. Additionally, it may be 0.6 parts by weight or less, 0.5 parts by weight or less, or 0.4 parts by weight or less. Within the above numerical ranges, heat resistance and polymerization stability may be improved.

[0079] In the present invention, the solvent may include ion-exchanged water. The ion-exchanged water used in the present invention is preferably as low in cations as possible, and is more preferably ultrapure water with a resistance of 5 MΩ or higher under a nitrogen stream generated by passing through an ion exchanger. At this time, the ion-exchanged water may be added as the remaining amount excluding the total content of monomers, silane monomers, chain transfer agents, crosslinking agents, initiators, etc., with respect to the entire composition, and preferably, the amount may be adjusted to a level suitable for performing a process of manufacturing polymer beads through suspension polymerization of the composition.

[0080] The present invention provides a polymer bead comprising: a polymer matrix derived from the above-described polymer bead composition and derived from the aromatic vinyl monomer; and a phosphorus-based flame retardant encapsulated within the polymer matrix.

[0081] In the present invention, the phosphorus-based flame retardant may be dispersed within a polymer matrix in the form of fine capsules. That is, the polymer matrix may surround part or all of the surface of the phosphorus-based flame retardant. In this case, the leaching of the flame retardant to the outside is prevented, thereby preventing chemical decomposition, exposure to moisture, or thermal deformation of the flame retardant.

[0082] In the present invention, the coefficient of variation of the polymer beads calculated by the following mathematical formula 1 may be 30% or less. Preferably, it may be 25% or less, 23% or less, 20% or less, 18% or less, 17% or less, 16% or less, 15.7% or less, or 14.9% or less. Additionally, it may be 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, or 9% or more. Within the above numerical range, the shape of the polymer bead particles is formed as a uniform sphere, so excellent optical performance can be maintained. Additionally, the afterglow effect may be enhanced.

[0083] [Mathematical Formula 1]

[0084] Coefficient of Variation (%) = (Standard deviation of polymer bead particle size / Average particle size of polymer beads) * 100 (%)

[0085] The standard deviation of the polymer bead particle size may be obtained by measuring the distribution of polymer bead particle sizes ranging from 10 to 10,000 and measuring the standard deviation. In this case, the number of polymer beads may be 10, 100, 200, 300, or 500.

[0086] In the present invention, the average particle size of the polymer beads may be 10 μm or more and 100 μm or less. Preferably, it may be 11 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, 14.5 μm or more, 15 μm or more, or 15.5 μm or more. Additionally, it may be 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. Within the above numerical range, the stability of the polymer beads can be improved by preventing the flame retardant from leaking out of the polymer beads, and the flame retardant effect can be improved by sufficiently dispersing the flame retardant within the polymer beads. Furthermore, it is possible to prevent an excessive increase in glossiness within the above numerical range. Additionally, the aforementioned coefficient of variation can be controlled to be small.

[0087] In the present invention, the polymer beads may have flame retardant properties of grade V-2 as a result of a flame retardant test by the UL-94 method. In this case, the result may be obtained by repeating the flame retardant test by the UL-94 method five times. Under the above conditions, there is an effect of excellent flame retardant performance.

[0088] In the present invention, when the polymer beads undergo a flame retardant test by the UL-94 method five times, the sum of the afterburner times after the first flame contact (t1, unit: s) and the sum of the afterburner times after the second flame contact (t2, unit: s) (t1+t2) may be 180 seconds or less. Preferably, it may be 160 seconds or less, 150 seconds or less, 130 seconds or less, 125 seconds or less, 120 seconds or less, 115 seconds or less, 110 seconds or less, 105 seconds or less, 100 seconds or less, 95 seconds or less, 90 seconds or less, 85 seconds or less, or 80 seconds or less. Under the above conditions, there is an effect of excellent flame retardant performance. For the purposes of the present invention, since a low afterburner time indicates excellent flame retardant performance, the lower limit is not specifically limited, but it may be 1 second or more or 10 seconds or more.

[0089] The present invention provides a method for manufacturing polymer beads comprising the steps of: preparing the polymer bead composition described above; stirring the polymer bead composition at a stirring speed of 3,000 rpm or more and 15,000 rpm or less to produce a suspension; and suspending polymerizing the suspension at a temperature of 30°C or more and 100°C or less.

[0090] In the present invention, the step of preparing the suspension is a step of dispersing the raw materials of the polymer bead composition at high speed to disperse them into uniform sizes.

[0091] In the present invention, the stirring speed of the step of preparing the suspension may be 3,000 rpm or more and 15,000 rpm or less. Preferably, it may be 3,000 rpm or more, 3,500 rpm or more, 4,000 rpm or more, 4,500 rpm or more, 5,000 rpm or more, 5,500 rpm or more, 6,000 rpm or more, 6,500 rpm or more, or 6,800 rpm or more. Additionally, it may be 13,000 rpm or less, 11,000 rpm or less, 10,000 rpm or less, 9,000 rpm or less, 8,000 rpm or less, or 7,500 rpm or less. Within the above numerical range, the phosphorus-based flame retardant can be uniformly encapsulated by dispersing the raw materials of the polymer bead composition into a fine and uniform size.

[0092] In the present invention, the stirring time of the step of preparing the suspension may be 5 minutes or more and 1 hour or less. Preferably, it may be 6 minutes or more, 8 minutes or more, 10 minutes or more, 12 minutes or more, 14 minutes or more, 16 minutes or more, or 18 minutes or more. Additionally, it may be 50 minutes or less, 40 minutes or less, 30 minutes or less, or 25 minutes or less. Within the above numerical ranges, the phosphorus-based flame retardant can be uniformly encapsulated by dispersing the raw materials of the polymer bead composition into a fine and uniform size.

[0093] In the present invention, the step of preparing the suspension may be performed under temperature conditions of 40°C or lower. Preferably, it may be 38°C or lower, 36°C or lower, 34°C or lower, 32°C or lower, 30°C or lower, 28°C or lower, or 26°C or lower. Additionally, it may be 5°C or higher, 10°C or higher, 15°C or higher, or 20°C or higher. Within the above numerical ranges, the initiation of a polymerization reaction is prevented, and the raw materials can be easily mixed.

[0094] In the present invention, the suspension polymerization step is a process of applying heat / temperature to convert liquid droplets in a suspension into solid polymer beads through polymerization.

[0095] In the present invention, the temperature of the suspension polymerization step may be 30°C or higher and 100°C or lower. Preferably, it may be 35°C or higher, 40°C or higher, 45°C or higher, 50°C or higher, 55°C or higher, or 58°C or higher. Additionally, it may be 90°C or lower, 80°C or lower, 75°C or lower, 70°C or lower, or 65°C or lower. Within the above numerical ranges, polymerization stability and polymerization processability may be improved.

[0096] In the present invention, the stirring speed of the suspension polymerization step may be 10 rpm or more and 2,000 rpm or less. Preferably, it may be 30 rpm or more, 50 rpm or more, 100 rpm or more, 150 rpm or more, 160 rpm or more, 180 rpm or more, 200 rpm or more, 220 rpm or more, or 240 rpm or more. Additionally, it may be 1,500 rpm or less, 1,000 rpm or less, 800 rpm or less, 600 rpm or less, 400 rpm or less, or 300 rpm or less. Within the above numerical ranges, there is an effect of preventing side reactions and enabling stable polymerization.

[0097] In the present invention, the suspension polymerization step may be performed for a polymerization time of 1 hour or more and 20 hours or less. Preferably, it may be 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, or 6 hours or more. Additionally, it may be 18 hours or less, 16 hours or less, 14 hours or less, 12 hours or less, 10 hours or less, or 8 hours or less. Within the above numerical ranges, there is an effect of preventing side reactions and enabling stable polymerization.

[0098] In the present invention, the suspension polymerization step may be performed under an inert gas atmosphere. Specifically, it may be a nitrogen atmosphere. In this case, stable polymerization can be induced by preventing the initiator from being activated by oxygen at the beginning of the reaction.

[0099] In the present invention, the step of preparing the polymer bead composition may include the step of pre-stirring the polymer bead composition.

[0100] In the present invention, the stirring speed of the preliminary stirring step may be 100 rpm or more and 2,000 rpm or less. Preferably, it may be 300 rpm or more, 400 rpm or more, 500 rpm or more, or 600 rpm or more. Additionally, it may be 1,500 rpm or less, 1,000 rpm or less, or 800 rpm or less. Within the above numerical range, the materials in the polymer bead composition may be sufficiently mixed to the extent that a reaction is not initiated.

[0101] In the present invention, the stirring time of the preliminary stirring step may be 1 minute or more and 1 hour or less. Preferably, it may be 5 minutes or more, 10 minutes or more, 15 minutes or more, or 20 minutes or more. Additionally, it may be 50 minutes or less, 40 minutes or less, or 35 minutes or less. Within the above numerical ranges, the materials in the polymer bead composition may be sufficiently mixed to the extent that a reaction is not initiated.

[0102] In the present invention, the step of preparing the polymer bead composition may be performed under a temperature condition of 40°C or lower. Preferably, it may be 38°C or lower, 36°C or lower, 34°C or lower, 32°C or lower, 30°C or lower, 28°C or lower, or 26°C or lower. Additionally, it may be 5°C or higher, 10°C or higher, 15°C or higher, or 20°C or higher. Within the above numerical ranges, the initiation of a polymerization reaction is prevented, and the raw materials can be easily mixed.

[0103] In the present invention, the method for manufacturing the polymer beads may further include, after the step of polymerizing the polymer bead composition, a step of filtration; a step of drying; a step of washing; a step of grinding; or a combination thereof.

[0104] In the present invention, the washing step may use ion-exchanged water. At this time, the ion-exchanged water may be applied with a washing frequency of 1 to 10 times. The washing frequency may be 2 times or more or 3 times or more, and 8 times or less, 6 times or less, or 4 times or less.

[0105] In the present invention, the drying step may be performed under vacuum drying conditions. At this time, unnecessary side reactions are suppressed.

[0106] In the present invention, the drying step may be performed for a drying time of 1 hour or more and 40 hours or less under a drying temperature condition of 30°C or more and 90°C or less.

[0107] In the present invention, the drying temperature may be 40°C or higher, 50°C or higher, 60°C or higher, or 65°C or higher. Additionally, it may be 85°C or lower, 80°C or lower, or 75°C or lower. Within the above numerical range, moisture within the polymer beads is sufficiently removed, and the polymer beads are not thermally decomposed.

[0108] In the present invention, the drying time may be 3 hours or more, 5 hours or more, 8 hours or more, 10 hours or more, 15 hours or more, or 20 hours or more. Additionally, it may be 35 hours or less, 30 hours or less, or 25 hours or less. Within the above numerical range, moisture within the polymer beads is sufficiently removed, and the polymer beads are not thermally decomposed.

[0109] In the present invention, the drying step may be performed under vacuum or inert gas conditions. At this time, the occurrence of side reactions can be prevented.

[0110] In the present invention, the grinding step is a step of adjusting the polymer beads to a required particle size. A grinder such as a jet mill, a ball mill atomizer, or a hammer mill may be used.

[0111] The present invention will be explained in more detail below through examples.

[0112] <Preparation Example>

[0113] <Preparation of Phosphorus-based Flame Retardants>

[0114] Phosphorus-based flame retardant A>

[0115] A phosphazene compound was prepared.

[0116] Phosphorus-based flame retardant B

[0117] Bisphenol A bis(diphenylphosphate) (BDP) was prepared. The trade name was P-639.

[0118] Phosphorus-based flame retardant C

[0119] Resorcinol bis(di-2,6-xylyl phosphate, RDP) was prepared. The trade name was Mflam PX-220.

[0120] <Examples and Comparative Examples>

[0121] <Example 1>

[0122] 542.786 g of ion-exchanged water as a solvent, 214.02 g of styrene as an aromatic vinyl monomer, 4.3 g of 1,6-hexanediol diacrylate as a crosslinking agent, 2.0 g of azobisisobutyronitrile as an initiator, and 4.92 g of phosphorus-based flame retardant A were mixed, placed in a reactor, and stirred for 30 minutes at a preliminary stirring speed of 700 rpm to prepare a polymer bead composition.

[0123] <Example 2>

[0124] A polymer bead composition was prepared in the same manner as in Example 1, except that the content of phosphorus-based flame retardant A was changed to 14.76 g.

[0125] <Example 3>

[0126] A polymer bead composition was prepared in the same manner as in Example 1, except that the content of phosphorus-based flame retardant A was changed to 24.6g.

[0127] <Example 4>

[0128] A polymer bead composition was prepared in the same manner as in Example 1, except that 4.92g of phosphorus-based flame retardant B was used instead of 4.92g of phosphorus-based flame retardant A.

[0129] <Example 5>

[0130] A polymer bead composition was prepared in the same manner as in Example 1, except that 14.76g of phosphorus-based flame retardant C was used instead of 4.92g of phosphorus-based flame retardant A.

[0131] <Comparative Example 1>

[0132] A polymer bead composition was prepared in the same manner as in Example 1, except that it did not contain a phosphorus-based flame retardant.

[0133] <Experimental Example 1: Appearance Comparison>

[0134] In the examples and comparative examples, the polymer bead compositions prepared were discharged from the reactor and vigorously stirred in a homomixer at a stirring speed of 7,000 rpm for 20 minutes to prepare a suspension in which the raw materials were dispersed.

[0135] The above suspension was introduced into a 2L reactor and heated to an internal temperature of 60℃ while stirring at a stirring speed of 250 rpm under a nitrogen stream, and then the suspension polymerization reaction was carried out at 60℃ for 7 hours.

[0136] Afterwards, the solid was filtered from the suspension, washed three times with ion-exchanged water, dehydrated, and then dried for 24 hours at 70°C and under vacuum conditions to produce polymer beads.

[0137] The appearance of polymer beads prepared using the polymer bead compositions of the examples and comparative examples was observed using a scanning electron microscope (SEM). This is shown in Fig. 1 (Example 1), Fig. 2 (Example 2), Fig. 3 (Example 4), and Fig. 4 (Comparative Example 1).

[0138] Meanwhile, at least 10 polymer beads were selected, their particle sizes were measured, and the average particle size and standard deviation were calculated. Subsequently, the coefficient of variation calculated using the following mathematical formula 1 was derived and recorded in Table 1 below.

[0139] [Mathematical Formula 1]

[0140] Coefficient of Variation (%) = (Standard deviation of polymer bead particle size / Average particle size of polymer beads) * 100 (%)

[0141] <Experimental Example 2: Flame Retardancy Test>

[0142] Polymer beads were prepared in the same manner as in Experimental Example 1, and a 3 mm thick specimen was prepared using the prepared polymer beads and left for 48 hours under conditions of 23°C and 50% RH relative humidity before the experiment.

[0143] Flame retardancy was tested using the UL 94:2023, 20mm Vertical Burning Test method. Specifically, the specimen was fixed vertically, a flame was applied to the bottom of the specimen for 10 seconds, then removed, and the time the flame remained (t1) was measured.

[0144] Afterwards, when the fire went out, the flame was applied again for 10 seconds and then removed, and the time the flame remained (t2) and the time the embers remained (t3) were measured.

[0145] The experiment was conducted on five samples of the same type of polymer beads using the same method, and the sum of t1 and t2 below was calculated as the total afterglow time and recorded in Table 1 below.

[0146] Grades (V-0, V-1, and V-2) were assigned according to the standards specified in UL 94.

[0147] t1: Total afterglow time after the first flame contact (s)

[0148] t2: Total afterglow time after the second flame contact (s)

[0149] t3: Total residual time after the second flame contact (s)

[0150] Classification Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Crosslinking Agent Content 2 2 2 2 2 Initiator Content 0.9 3 0.9 3 0.9 3 0.9 3 0.9 3 0.9 3 Phosphorus-based Flame Retardant Type Flame Retardant A Flame Retardant A Flame Retardant A Flame Retardant B Flame Retardant C Non-included Content 2.3 6.9 1 1.4 9 2.3 6.9 Non-included Experimental Example 1 Average Particle Size (㎛) 16.3 1 6.2 1 5.8 1 5.7 7 1 8.7 1 1 5.0 Coefficient of Variation (%) 15.6 2 6.4 1 4.8 1 9.6 1 5.9 Experimental Example 2 Total Afterglow Time (s) 1 2 4 1 2 9 7 2.4 9 8 8 4 1 8 1.1 Grade V-2 V-2 V-2 V-2 V-2 V-2 V-2

[0151] In Table 1, the content of the crosslinking agent, initiator, and phosphorus-based flame retardant is based on 100 parts by weight of aromatic vinyl monomer.

[0152] From the above results, polymer beads prepared using a polymer bead composition containing a phosphorus-based flame retardant had a small coefficient of variation and a uniform particle size (Examples 1 to 5).

[0153] In addition, it was confirmed that the after-salt time was short and the grade of the after-salt test results was high (Examples 1 to 5).

Claims

1. Aromatic vinyl monomer; Crosslinking agent; Initiator; and Polymer bead composition containing a phosphorus-based flame retardant.

2. In Claim 1, A polymer bead composition in which the content of the above-mentioned phosphorus-based flame retardant is 1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of the above-mentioned aromatic vinyl monomer.

3. In Claim 1, A polymer bead composition in which the content of the above-mentioned phosphorus-based flame retardant is 100 parts by weight or more and 900 parts by weight or less, based on 100 parts by weight of the above-mentioned crosslinking agent.

4. In Claim 1, The above-mentioned phosphorus-based flame retardant is a polymer bead composition comprising a phosphazene-based compound, a phosphate-based compound, or a combination thereof.

5. In Claim 4, A polymer bead composition wherein the above-mentioned phosphazene compound comprises a cyclic phosphazene compound, a chain-type phosphazene compound, a cross-linked phosphazene compound, or a combination thereof.

6. In Claim 4, Polymer bead composition in which the above-mentioned phosphazene-based compound is represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, X 1 To X 3 Each is independently Cl, Br, or F, and R 1 to R 3 Each is independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 20 carbon atoms, and n, m, and k are each independently 0, 1, or 2.

7. In Claim 4, A polymer bead composition wherein the above-mentioned phosphate-based compound is represented by the following chemical formula 2: [Chemical Formula 2] In Chemical Formula 2, A1 to A4 are identical or different, and each is an independently substituted or unsubstituted aryl group, and L1 is a divalent linker connected to a phosphate group through an aromatic carbon atom.

8. In Claim 1, A polymer bead composition in which the above aromatic vinyl monomer comprises a styrene monomer.

9. Derived from a polymer bead composition according to any one of claims 1 to 8, and A polymer matrix derived from the above aromatic vinyl monomer; and Polymer beads comprising a phosphorus-based flame retardant encapsulated within the polymer matrix.

10. In Claim 9, Polymer beads having a coefficient of variation of 30% or less calculated by the following mathematical formula 1: [Mathematical Formula 1] Coefficient of Variation (%) = (Standard deviation of polymer bead particle size / Average particle size of polymer beads) * 100 (%) 11. In Claim 9, Polymer beads having an average particle size of 10㎛ or more and 100㎛ or less.

12. In Claim 9, Polymer beads having V-2 flame retardant properties as a result of a flame retardant test by the UL-94 method.

13. In Claim 9, A polymer bead having a total sum (t1+t2) of the sum of the after-flame times after the first flame contact (t1, unit: s) and the sum of the after-flame times after the second flame contact (t2, unit: s) of 180 seconds or less when the flame retardancy test by the UL-94 method is repeated 5 times.

14. A step of preparing a polymer bead composition according to any one of claims 1 to 8; A step of preparing a suspension by stirring the above polymer bead composition at a stirring speed of 3,000 rpm or more and 15,000 rpm or less; and A method for manufacturing polymer beads comprising the step of suspending and polymerizing the above suspension at a temperature of 30°C or higher and 100°C or lower.

15. In Claim 14, A method for manufacturing polymer beads, wherein the stirring speed of the suspension polymerization step is 10 rpm or more and 2,000 rpm or less.

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