Expandable resin particles, expanded resin particles, foamed resin molded product, and method for manufacturing the same

Abstract

To provide novel expandable resin particles, expanded resin particles, foamed resin molded articles and manufacturing methods thereof.SOLUTION: Provided is a styrene-modified polyethylene-based expandable resin particle, the expandable resin particle comprising a polyethylene resin and a polystyrene resin, wherein based on 100 wt.% of the polyethylene resin and the polystyrene resin, the content of the polyethylene resin is in a range of 5 wt.% to 30 wt.%, and the content of the polystyrene resin is in a range of 70 wt.% to 95 wt.%; the polystyrene resin is in the form of grains dispersed in the polyethylene resin; and an average grain size of the grains of the polystyrene resin is in a range of 0.02 μm to 0.15 μm in a surface region of the expandable resin particle and 0.20 μm to 0.60 μm in a center region of the expandable resin particle. Furthermore, an expanded resin particle and a foamed resin molded article prepared by the expandable resin particle are also provided. Yet further, a method for manufacturing the expandable resin particle is also provided.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Taiwan Patent Application No. 113104963, filed February 7, 2024, the subject matter of which is incorporated herein by reference.

[0002] The present disclosure relates to expandable resin particles, expanded resin particles, foamed resin molded articles, and methods for manufacturing the same, and more specifically, the present disclosure relates to styrene-modified polyethylene-based expandable resin particles, styrene-modified polyethylene-based expanded resin particles, foamed resin molded articles, and methods for manufacturing the same. [Background technology]

[0003] Due to their excellent cushioning properties, foamed resin molded articles are widely used in packaging materials, building materials, and shock absorbing materials. Generally, expandable resin particles are first prepared into expanded resin particles, and then these expanded resin particles are melted together in a mold to form a foamed resin molded article.

[0004] The expandable resin particles may be made of polyethylene, polypropylene, or polystyrene. However, foamed resin molded products made of polystyrene have the disadvantage of low restorability after compression. Furthermore, foamed resin molded products made of polyethylene or polypropylene have the disadvantage of insufficient rigidity.

[0005] Therefore, it is desirable to provide novel expandable resin particles, expanded resin particles, foamed resin molded articles, and methods for producing the same that overcome the above disadvantages. Summary of the Invention

[0006] The present disclosure provides styrene-modified polyethylene-based expandable resin particles, the expandable resin particles comprising a polyethylene resin and a polystyrene resin, the polyethylene resin content being 5% to 30% by weight and the polystyrene resin content being 70% to 95% by weight, based on 100% by weight of the polyethylene resin and the polystyrene resin. The polystyrene resin is in the form of particles dispersed in the polyethylene resin, the average particle size of the polystyrene resin particles being 0.02 μm to 0.15 μm in the surface region of the expandable resin particles, the surface region of the expandable resin particles being a region from 1.5 μm from the surface of the expandable resin particles to the surface of the expandable resin particles, the average particle size of the polystyrene resin particles being 0.20 μm to 0.60 μm in the central region of the expandable resin particles, and the central region of the expandable resin particles being a region at least 500 μm away from the surface of the expandable resin particles.

[0007] The present disclosure also provides styrene-modified polyethylene-based expanded resin particles produced from the expandable resin particles through a foaming process.

[0008] The present invention further provides a foamed resin molded product manufactured by the expanded resin particles through a molding process, wherein the foamed resin molded product can be used as a material for a transport container or a transport device.

[0009] Generally, in expanded resin particles containing polyethylene resin and polystyrene resin, or foamed resin molded products produced using such expanded resin particles, if the content of polystyrene resin is too high, the rigidity (compressive strength) increases but the compression recovery (compression set) decreases, while if the content of polyethylene resin is too low, the expanded resin particles or foamed resin molded products have insufficient recovery. Therefore, in the present disclosure, the obtained expanded resin particles or foamed resin molded products have appropriate rigidity and compression recovery when the content of polyethylene resin is in the range of 5% by weight to 30% by weight and the content of polystyrene resin is in the range of 70% by weight to 95% by weight, based on 100% by weight of polyethylene resin and polystyrene resin.

[0010] For example, based on the total of the polyethylene resin content and the polystyrene resin content being 100% by weight, the polyethylene resin content may be, for example, 8% by weight, 10% by weight, 12% by weight, 14% by weight, 16% by weight, 18% by weight, 20% by weight, 22% by weight, 24% by weight, 26% by weight, or 28% by weight, with the remainder being polystyrene resin.

[0011] In one embodiment, based on 100% by weight of polyethylene resin and polystyrene resin, the content of polyethylene resin is in the range of 5% by weight to 25% by weight, and the content of polystyrene resin is in the range of 75% by weight to 95% by weight. In one embodiment, based on 100% by weight of polyethylene resin and polystyrene resin, the content of polyethylene resin is in the range of 5% by weight to 20% by weight, and the content of polystyrene resin is in the range of 80% by weight to 95% by weight. In one embodiment, based on 100% by weight of polyethylene resin and polystyrene resin, the content of polyethylene resin is in the range of 5% by weight to 15% by weight, and the content of polystyrene resin is in the range of 85% by weight to 95% by weight.

[0012] In one embodiment, the polystyrene resin is in the form of particles dispersed in the polyethylene resin. The shape of the polystyrene resin particles is not particularly limited, and the polystyrene resin particles may be spherical, ellipsoid, spherical-like, ellipsoid-like, or other irregular particles.

[0013] In one embodiment, the average particle size of the polystyrene resin particles in the surface region of the expandable resin particle is in the range of 0.02 μm to 0.15 μm, e.g., 0.02 μm to 0.14 μm or 0.02 μm to 0.13 μm. For example, the average particle size of the polystyrene resin particles in the surface region of the expandable resin particle may be approximately 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.10 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, or 0.15 μm. Here, the average particle size of the polystyrene resin particles in the surface region of the expandable resin particle shows a positive correlation with the 50% compression set of the foamed resin molded product (e.g., molded plate). If the average particle size of the polystyrene resin particles in the surface region of the expandable resin particles is too large, the 50% compression set of the foamed resin molded product (e.g., molded plate) will increase, and the recovery of the foamed resin molded product (e.g., molded plate) will be reduced.

[0014] In one embodiment, the average particle size of the polystyrene resin particles in the central region of the expandable resin particles is in the range of 0.20 μm to 0.60 μm, such as 0.20 μm to 0.50 μm or 0.20 μm to 0.45 μm. For example, the average particle size of the polystyrene resin particles in the central region of the expandable resin particles may be approximately 0.20 μm, 0.25 μm, 0.30 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.50 μm, 0.55 μm, or 0.60 μm. The average particle size of the polystyrene resin particles in the central region of the expandable resin particles is positively correlated with the flexural strength of a foamed resin molded product (e.g., a molded plate). If the average particle size of the polystyrene resin particles in the central region of the expandable resin particles is too small, the flexural strength of the foamed resin molded product (e.g., a molded plate) will not be ideal.

[0015] In one embodiment, in the surface region of the expandable resin particle, the number of polystyrene resin particles with a particle size of 0.01 μm to 0.1 μm is 50% or more of the total number of polystyrene resin particles, and may be, for example, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more of the total number of polystyrene resin particles.

[0016] In one embodiment, in the surface region of the expandable resin particles, the number of polystyrene resin particles with a particle size of 0.02 μm to 0.08 μm is 50% or more of the total number of polystyrene resin particles, and may be, for example, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, or 80% or more of the total number of polystyrene resin particles.

[0017] In one embodiment, in the central region of the expandable resin particle, the number of polystyrene resin particles with a particle size of 0.1 μm to 0.6 μm is 70% or more of the total number of polystyrene resin particles, and may be, for example, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more of the total number of polystyrene resin particles.

[0018] In one embodiment, in the central region of the expandable resin particle, the number of polystyrene resin particles with a particle size of 0.2 μm to 0.5 μm is 60% or more of the total number of polystyrene resin particles, and may be, for example, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more of the total number of polystyrene resin particles.

[0019] In one embodiment, the skewness of the curve of the particle size and number distribution of the polystyrene resin particles in the surface region of the expandable resin particle can be -0.5 to 8, for example, -0.5 to 8, -0.4 to 8, -0.4 to 7, -0.4 to 6, -0.4 to 5, -0.4 to 4, -0.4 to 3, -0.3 to 3, -0.2 to 3, -0.1 to 3, 0.0 to 3, 0.1 to 3, 0.2 to 3, 0.3 to 3, or 0.4 to 3. Here, the skewness of the curve of the particle size and number distribution of the polystyrene resin particles in the surface region of the expandable resin particle shows a negative correlation with the 50% compression set of the foamed resin molded product (e.g., molded plate). If the skewness of the curve of the particle size and number distribution of the polystyrene resin particles in the surface region is outside the above range, the 50% compression set of the foamed resin molded product (e.g., molded plate) may increase. Therefore, in one embodiment, if the skewness of the curve of the particle size and quantity distribution of the polystyrene resin particles in the surface region is within the above range, the foamed resin molded product (for example, a molded plate) can have good recovery properties.

[0020] In one embodiment, the kurtosis of the curve of the particle size and number distribution of polystyrene resin particles in the surface region of the expandable resin particle can be -1.5 to 120, for example, -1.5 to 100, -1.5 to 80, -1.5 to 60, -1.5 to 40, -1.5 to 20, -1.5 to 10, -1.0 to 10, -0.5 to 10, -0.3 to 10, or 0.0 to 10. Here, the kurtosis of the curve of the particle size and number distribution of polystyrene resin particles in the surface region of the expandable resin particle shows a positive correlation with the tensile elongation of a foamed resin molded product (e.g., a molded plate). In one embodiment, if the kurtosis of the curve of the particle size and number distribution of polystyrene resin particles in the surface region of the expandable resin particle is within the above range, the foamed resin molded product (e.g., a molded plate) has good tensile elongation.

[0021] In one embodiment, the skewness of the curve of the particle size and number distribution of the polystyrene resin particles in the central region of the expandable resin particles can be -0.7 to 0.7, for example, -0.6 to 0.7, -0.6 to 0.6, -0.5 to 0.6, -0.5 to 0.5, -0.4 to 0.5, -0.3 to 0.5, -0.2 to 0.5, -0.1 to 0.5, or 0.0 to 0.5. Here, the skewness of the curve of the particle size and number distribution of the polystyrene resin particles in the central region of the expandable resin particles shows a negative correlation with the compressive strength or tensile strength of a foamed resin molded product (e.g., a molded plate). In one embodiment, if the skewness of the curve of the particle size and number distribution of the polystyrene resin particles in the central region of the expandable resin particles is within the above range, the compressive strength or tensile strength of the foamed resin molded product (e.g., a molded plate) will be good.

[0022] In one embodiment, the kurtosis of the curve of the particle size and number distribution of the polystyrene resin particles in the central region of the expandable resin particles can be -1.0 to 2.5, for example, -1.0 to 2.0, -0.5 to 2.0, -0.5 to 1.5, or -0.5 to 1.0. Here, in the central region of the expandable resin particles, the kurtosis of the curve of the particle size and number distribution of the polystyrene resin particles shows a positive correlation with the flexural strength or flexural modulus of a foamed resin molded product (e.g., a molded plate), but shows a negative correlation with the tensile elongation of the foamed resin molded product (e.g., a molded plate). In one embodiment, if the kurtosis of the curve of the particle size and number distribution of the polystyrene resin particles in the central region of the expandable resin particles is within the above range, the foamed resin molded product (e.g., a molded plate) will have good flexural strength, flexural modulus, or tensile elongation.

[0023] In one embodiment, the 698 cm infrared absorption spectrum obtained from the surface of the expandable resin particle -1 and 2850 cm -1 The absorbance ratio (D 698 / D 2850 ) may be 1.0 or more, for example, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, or 2.5 or more. In one embodiment, the 698 cm -1 and 2850 cm -1 may be in the range of 1.0 to 6.0, for example, 1.2 to 6.0, 1.4 to 6.0, 1.6 to 6.0, 1.8 to 6.0, 2.0 to 6.0, 2.2 to 6.0, 2.4 to 6.0, or 2.5 to 6.0. Here, the infrared absorption spectrum of the surface of the expandable resin particle may be an attenuated total reflection (ATR) infrared absorption spectrum.

[0024] When the surface of the expandable resin particle is detected by infrared absorption spectroscopy, D 698 / D 2850 D may reflect the proportion of polystyrene in the region of the expandable resin particle several micrometers (μm) deep from its surface. 698 / D2850 is negatively correlated with the tensile elongation of the foamed resin molded product (e.g., molded plate). 698 / D 2850 If D is higher than the above range, the proportion of polyethylene in the surface area becomes too small, which may cause the expanded resin particles to be unable to undergo subsequent molding to form a foamed resin molded article, or the chemical resistance and elongation of the foamed resin molded article may be insufficient. 698 / D 2850 If the surface area is less than the above range, the proportion of polystyrene in the surface area will be too small, which may result in insufficient rigidity (compression strength).

[0025] In one embodiment, the average particle size of the expandable resin particles can be in the range of 1.0 mm to 2.0 mm, e.g., 1.1 mm to 2.0 mm, 1.1 mm to 1.9 mm, 1.2 mm to 1.9 mm, 1.2 mm to 1.8 mm, 1.3 mm to 1.8 mm, 1.3 mm to 1.7 mm, or 1.4 mm to 1.7 mm. If the average particle size of the expandable resin particles is too small, it becomes difficult to retain the blowing agent, which does not contribute to reducing the density of the foamed resin molded product. If the average particle size of the expandable resin particles is too large, the size of the expandable resin particles also increases, which reduces the effectiveness of filling the mold during the molding process and makes it difficult to form a thin foamed resin molded product. However, the present disclosure is not limited thereto, and the average particle size of the expandable resin particles can be adjusted as needed.

[0026] In one embodiment, the polystyrene resin has a non-crosslinked portion, and the molecular weight of the non-crosslinked portion is in the range of 30,000 to 80,000, for example, 35,000 to 80,000, 40,000 to 80,000, 45,000 to 80,000, 50,000 to 80,000, 50,000 to 75,000, 55,000 to 75,000, 55,000 to 70,000, or 60,000 to 70,000. The molecular weight of the non-crosslinked portion can be measured by gel permeation chromatography (GPC). In the present disclosure, the molecular weight of the non-crosslinked portion of the polystyrene resin shows a negative correlation with the 50% compression set. When the molecular weight of the polystyrene resin is relatively large, when expanded resin particles or a foamed resin molded article are deformed by force, the intermolecular displacement can be small, and the expanded resin particles or foamed resin molded article have good recovery and are less likely to deform. Therefore, if the molecular weight of the non-crosslinked portion of the polystyrene resin is within the above range, the resulting foamed resin molded article will have good recovery properties.

[0027] In one embodiment, the polymer dispersion index (PDI) of the non-crosslinked portion of the polystyrene resin may be less than 4.0. Here, the polymer dispersion index of the non-crosslinked portion of the polystyrene resin is negatively correlated with the extensibility of a foamed resin molded product (e.g., a molded plate). This may be because the non-uniform network size distribution of the polystyrene may deteriorate the bonding of the expanded resin particles, resulting in reduced extensibility of the foamed resin molded product. Therefore, if the polymer dispersion index of the non-crosslinked portion of the polystyrene resin is within the above range, the foamed resin molded product may have good extensibility.

[0028] In one embodiment, the expandable resin particles include xylene-insoluble matter and acetone-insoluble matter. The xylene-insoluble matter is a portion of polyethylene together with polyethylene, polystyrene, or polystyrene that forms a three-dimensional network structure through a chemical reaction, and is insoluble in xylene. Here, the expandable resin particles can be subjected to Soxhlet extraction with xylene to obtain a xylene-insoluble portion, and this portion becomes the xylene-insoluble portion of the expandable resin particles. Furthermore, the acetone-insoluble matter is a portion of polyethylene together with polystyrene or polystyrene that forms a loose two-dimensional network structure through a chemical reaction, and is insoluble in acetone. Here, the xylene-soluble portion of the expandable resin particles obtained by Soxhlet extraction with xylene can be extracted with acetone to obtain an acetone-insoluble portion, and this portion becomes the acetone-insoluble portion of the expandable resin particles.

[0029] In one embodiment, the xylene insoluble content of the expandable resin particles may be 70% by weight or less (including 0% by weight), for example, in the range of 1% to 70% by weight, 5% to 70% by weight, 10% to 70% by weight, 15% to 70% by weight, 20% to 70% by weight, 20% to 65% by weight, 25% to 65% by weight, 25% to 60% by weight, or 30% to 60% by weight. Here, the xylene insoluble content of the expandable resin particles has a positive correlation with 50% compression set. When the xylene insoluble content of the expandable resin particles is within the above range, the resulting foamed resin molded article still has good recovery and is resistant to deformation, while maintaining other desired properties.

[0030] In one embodiment, the content of acetone insoluble matter in the expandable resin particles may be in the range of 10% by weight to 60% by weight, for example, 11% by weight to 60% by weight, 12% by weight to 60% by weight, 13% by weight to 60% by weight, 14% by weight to 60% by weight, 15% by weight to 60% by weight, 15% by weight to 55% by weight, 15% by weight to 50% by weight, 15% by weight to 45% by weight, or 15% by weight to 40% by weight. Here, the acetone insoluble matter in the expandable resin particles has a negative correlation with compressive strength. This may be because the two-dimensional network structure of the expandable resin particles tends to form a laminated structure. Furthermore, the acetone insoluble matter in the expandable resin particles shows a negative correlation with the tensile strength of the resulting foamed resin molded product. This may be because the two-dimensional network structure of the expandable resin particles tends to form a laminated structure, resulting in low strength in other dimensions. Therefore, if the content of acetone insoluble matter in the expandable resin particles is within the above range, the resulting foamed resin molded article will have good compressive strength (rigidity) and tensile strength.

[0031] In one embodiment, the ratio of the xylene insoluble matter content to the acetone insoluble matter content in the expandable resin particles (xylene insoluble matter content / acetone insoluble matter content) can be in the range of 0.01 to 5, for example, 0.01 to 4.5, 0.01 to 4.0, 0.01 to 3.5, 0.05 to 3.5, 0.1 to 3.5, 0.1 to 3.0, 0.15 to 3.0, 0.15 to 2.5, 0.2 to 2.5, 0.2 to 2.0, 0.25 to 2.0, 0.25 to 1.5, or 0.3 to 1.5. Here, the ratio of the xylene insoluble matter content to the acetone insoluble matter content is positively correlated with the 50% compression set. When the ratio of the xylene insoluble matter content to the acetone insoluble matter content in the expandable resin particles is within the above range, the resulting foamed resin molded article will still have good recovery and will be less likely to deform, while retaining other necessary properties.

[0032] In one embodiment, the total content of acetone insoluble matter and xylene insoluble matter in the expandable resin particles can be in the range of 40% to 90% by weight, for example, 42% to 90% by weight, 45% to 90% by weight, 50% to 90% by weight, 51% to 90% by weight, 52% to 90% by weight, 53% to 90% by weight, 54% to 90% by weight, 55% to 90% by weight, 56% to 90% by weight, 57% to 90% by weight, 58% to 90% by weight, 59% to 90% by weight, or 60% to 90% by weight. Here, the total content of acetone insoluble matter and xylene insoluble matter is positively correlated with 50% compression set. When the total content of acetone insoluble matter and xylene insoluble matter in the expandable resin particles is within the above range, the resulting foamed resin molded article has good recovery and is less likely to deform.

[0033] In one embodiment, the expandable resin particles may further contain acetone-soluble matter, and the sum of the acetone-insoluble matter content, the xylene-insoluble matter content, and the acetone-soluble matter content may be 100% by weight. In one embodiment, the acetone-soluble matter content may be in the range of 10% to 60% by weight, for example, 10% to 58% by weight, 10% to 55% by weight, 10% to 50% by weight, 10% to 49% by weight, 10% to 48% by weight, 10% to 47% by weight, 10% to 46% by weight, 10% to 45% by weight, 10% to 44% by weight, 10% to 43% by weight, 10% to 42% by weight, 10% to 41% by weight, or 10% to 40% by weight.

[0034] In one embodiment, the swelling ratio of the expandable resin particles may be 2.5 or less, for example, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, or 1.6 or less. When the swelling ratio of the expandable resin particles is within the above range, the expanded resin particles or foamed resin molded products obtained using the expandable resin particles will simultaneously have excellent resilience (compression set) and excellent rigidity. This may be because, when the swelling ratio of the expandable resin particles is within the above range, the two-dimensional or three-dimensional resin structure will have a high density. Therefore, when the resin structure is deformed by force, it is less likely to collapse and can exhibit good resilience (recovery).

[0035] In this disclosure, the swelling ratio of expandable resin particles is the swelling ratio of a mixture of acetone-insoluble and xylene-insoluble expandable resin particles in an organic solvent (e.g., methyl ethyl ketone) at room temperature (e.g., 23°C). The swelling ratio (swelling degree) of cross-linked polyethylene resin immersed in an organic solvent is related to the cross-linked structure (three-dimensional network structure) of the resin. Furthermore, the higher the density of the network structure, the lower the organic solvent absorption rate and the smaller the swelling ratio. Furthermore, non-cross-linked polyethylene resin hardly swells in organic solvents.

[0036] In the present disclosure, expandable resin particles having a large swelling ratio of a mixed insoluble matter of xylene (crosslinked polyethylene resin component) and acetone (crosslinked polyethylene resin component, non-crosslinked polyethylene resin component, and polyethylene resin component having graft-polymerized styrene monomer) compared to expandable resin particles containing a mixed insoluble matter with a small swelling ratio comprise a polyethylene resin containing a crosslinked three-dimensional network structure with numerous coarse meshes.

[0037] When the expandable resin particles are foamed, the polyethylene resin containing a cross-linked three-dimensional network structure with a coarse mesh can be sufficiently stretched to maintain its strength, resulting in the formation of foam cell walls with high strength. Furthermore, when the expandable resin particles are compressed, the polyethylene resin is relatively flexible and sufficiently deformable, so that the foam cell walls of the expanded particles can maintain a closed cell structure without rupture, even if the content of polystyrene resin is high. Therefore, if the swelling ratio of the expandable resin particles is within the above range, expanded resin particles and foamed resin molded products with high rigidity and resilience can be obtained.

[0038] Furthermore, the present disclosure further provides a method for producing styrene-modified polyethylene-based expandable resin particles, the method comprising the steps of: providing a mixture containing polyethylene resin particles; and mixing the mixture containing polyethylene resin particles with a styrene monomer and a polymerization initiator to obtain the styrene-modified polyethylene-based expandable resin particles.

[0039] In the present disclosure, in the step of mixing a mixture containing polyethylene resin particles with a styrene monomer and a polymerization initiator, the styrene monomer (and the polymerization initiator) can be added to the mixture containing polyethylene resin particles once or multiple times. When the styrene monomer (and the polymerization initiator) is added to the mixture containing polyethylene resin particles multiple times, polystyrene aggregation can be reduced.

[0040] In the present disclosure, when a mixture containing polyethylene resin particles is mixed with styrene monomer and a polymerization initiator, the reaction mixture can be heated to an appropriate temperature (e.g., 115°C to 125°C) to allow the polymerization of the styrene monomer to proceed. If the polymerization reaction temperature of the styrene monomer is outside the range of 115°C to 125°C, it will affect the content of xylene insolubles, which in turn will affect the properties of the resulting foamed resin molded product. Furthermore, the polymerization reaction time of the styrene monomer is not particularly limited and can be adjusted depending on the reaction conditions.

[0041] In the present disclosure, the polyethylene resin particles may comprise low density polyethylene (LDPE), high density polyethylene, or a combination thereof. Low density polyethylene includes linear low density polyethylene or branched low density polyethylene. In one embodiment, the polyethylene resin particles may comprise branched low density polyethylene. In one embodiment, "low density polyethylene" refers to a polyethylene having a viscosity of 0.915 g / cm 3 ~0.935g / cm 3 This refers to polyethylene with a density in the range of

[0042] In the present disclosure, styrene monomers may include, for example, styrene, methylstyrene, ethylstyrene, dimethylstyrene, methoxystyrene, n-butylstyrene, tert-butylstyrene, chlorostyrene, tribromostyrene, divinylbenzene, styrene sulfonic acid, sodium styrene sulfonate, or combinations thereof.

[0043] In the present disclosure, in addition to the polyethylene resin particles, the mixture comprising the polyethylene resin particles may further comprise a suspending agent, a surfactant, a polymerization inhibitor, a solvent, or a combination thereof.

[0044] In the present disclosure, a suspending agent may be used as an abrasive or to prevent the formation of clumps of resin. The suspending agent may be a particulate inorganic suspending agent, such as tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, ferric hydroxide, titanium hydroxide, magnesium hydroxide, barium phosphate, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, talc, kaolin, or bentonite. The above suspending agents may be used alone or in combination of two or more. In one embodiment, the suspending agent may be sodium pyrophosphate (Na4P2O7) and magnesium nitrate (Mg(NO3)2). Magnesium pyrophosphate (Mg2P2O 7(s) ) can be obtained after the reaction, however, the present disclosure is not limited thereto.

[0045] Furthermore, the solids content of the suspending agent can be 0.05 to 10 parts by weight, such as 0.3 to 5 parts by weight, based on 100 parts by weight of the aqueous medium of the suspension polymer system. For example, water can be used as the aqueous medium solvent. If too little suspending agent is used, it can be difficult to suspend and stabilize the styrene monomer, resulting in the formation of clumped resin. If too much suspending agent is used, production costs increase and the particle size distribution becomes broader.

[0046] In the present disclosure, a surfactant can reduce surface tension (or interfacial tension). The surfactant can be, for example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, or a zwitterionic surfactant. Specific examples of surfactants include, but are not limited to, sodium alkyl sulfonate, sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecylbenzene sulfonate (SDBS), or sodium dodecylphenyloxide disulfonate. The surfactants may be used alone or in combination of two or more. In one embodiment, the surfactant can be SDBS, but the present disclosure is not limited thereto.

[0047] In the present disclosure, the polymerization inhibitor can reduce the polystyrene content on the surface of the expandable resin particles. The polymerization inhibitor can be an aqueous polymerization inhibitor such as sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, or citric acid. The polymerization inhibitors can be used alone or in combination of two or more. In one embodiment, the polymerization inhibitor can be sodium nitrite, although the present disclosure is not limited thereto.

[0048] The aqueous polymerization inhibitor hardly penetrates into the core particles (polyethylene resin particles) and dissolves in the aqueous medium. Therefore, in the aqueous medium, the polymerization of the styrene-based monomer microdroplets that do not penetrate into the core particles but are near the surface of the core particles and absorbed therein can be inhibited, while the styrene-based monomer that has penetrated into the core particles is polymerized. Therefore, the amount of polystyrene resin in the surface portion of the expandable resin particles can be reduced compared to the center portion.

[0049] The amount of aqueous polymerization inhibitor used may be 0.001 to 0.1 parts by mass, for example, 0.002 to 0.02 parts by mass, per 100 parts by mass of the aqueous medium (for example, water as a solvent). If the amount of aqueous polymerization inhibitor used is excessive, the amount of residual styrene monomer increases, making it impossible to obtain a good foamed resin molded product formed by expanded resin particles.

[0050] In the present disclosure, a polymerization initiator is used for the polymerization of polystyrene. Polymerization initiators used in the suspension polymerization of styrene monomers, such as peroxides, can be used as the polymerization initiator. Specific examples of peroxides used as polymerization initiators include, but are not limited to, cumene hydroperoxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate (Perbutyl® E), t-butyl peroxybenzoate (TBPB), benzoyl peroxide, t-butyl peroxyisopropyl carbonate, t-amyl peroxy-2-ethylhexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, lauroyl peroxide, and azo compounds (e.g., azobisisobutyronitrile). The above polymerization initiators may be used alone or in combination of two or more. In one embodiment, the polymerization initiator may be t-butyl peroxy-2-ethylhexanoate. In another embodiment, the polymerization initiator may be t-butyl peroxybenzoate. However, the present disclosure is not limited to these.

[0051] Furthermore, the amount of the polymerization initiator can be 0.01 to 3 parts by mass per 100 parts by mass of the styrene monomer. If the amount of the polymerization initiator is outside the above range, it will affect the content of xylene insolubles, thereby affecting the properties of the foamed resin molded product prepared.

[0052] In the present disclosure, the solvent can be water.

[0053] The present disclosure further provides a method for producing styrene-modified polyethylene-based expanded resin particles, the method comprising: mixing the styrene-modified polyethylene-based expandable resin particles with a blowing agent to perform a foaming process to obtain styrene-modified polyethylene-based expanded resin particles. Specific examples of the blowing agent include, but are not limited to, propane, butane, pentane, dimethyl ether, or carbon dioxide. In one embodiment, the blowing agent can be carbon dioxide.

[0054] Furthermore, the present disclosure also provides a method for producing a foamed resin molded product, the method comprising the steps of: providing a mold; and carrying out a molding process in which the styrene-modified polyethylene-based expanded resin particles are filled into the mold to obtain a foamed resin molded product. More specifically, the molding process includes heating the styrene-modified polyethylene-based expanded resin particles to perform secondary foaming, whereby the expanded resin particles are melted and connected together, making it possible to obtain a foamed resin molded product of a desired shape.

[0055] In this specification, when a component is described as having a certain element, this means that the component may contain one or more of the element, and does not mean that the component has only one of the element, unless otherwise specified.

[0056] In this specification, unless otherwise specified, feature A "or" feature B means the presence of feature A or the presence of feature B. Feature A "and / or" feature B means the presence of feature A, the presence of feature B, or the presence of both features A and B. Feature A "and" feature B means the presence of both features A and B. The terms "comprise," "comprising," "include," "including," "have," and "having" mean "comprise / comprise / comprising, but not limited to."

[0057] In this disclosure, unless otherwise specified, the terms "nearly," "approximately," and "about" refer to an acceptable error in a particular value that would normally be specified by one of ordinary skill in the art, the error depending on how the numerical value is measured or specified. In certain embodiments, the terms "nearly," "approximately," and "about" refer to within 1, 2, 3, or 4 standard deviations. In certain embodiments, the terms "nearly," "approximately," and "about" refer to within ±20%, ±15%, ±10%, ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.05%, or less of a given value or range. Quantities given herein are approximate quantities, i.e., without specifying "nearly," "approximately," and "about," "nearly," "approximately," and "about" may still be implied. Furthermore, the phrases "within a range of a first value to a second value," "from a first value to a second value," etc., mean that the range includes the first value, the second value, and other values ​​between the first and second values.

[0058] Other novel features of the present disclosure will become more apparent from the following detailed description. [Brief explanation of the drawings]

[0059] [Figure 1] FIG. 1 is a schematic cross-sectional view of a styrene-modified polyethylene expandable resin particle according to an example of the present disclosure, showing a morphology thereof. [Figure 2] FIG. 2 is a TEM photograph of the surface region of a styrene-modified polyethylene expandable resin particle according to Example 1 of the present disclosure. [Figure 3] FIG. 3 is a TEM photograph of the central region of a styrene-modified polyethylene expandable resin particle according to Example 1 of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0060] Various embodiments of the present disclosure are provided in the following description. These embodiments are intended to explain the technical content of the present disclosure, but do not limit the scope of the present disclosure. The features described in the embodiments can be applied to other embodiments by appropriate modification, substitution, combination, or separation.

[0061] The present disclosure will be described in more detail through embodiments, but these embodiments do not limit the scope of the present disclosure. Unless otherwise specified, in the following preparation examples, examples and comparative examples, the temperature is in degrees Celsius, and the numerical parts and percentages are by weight. The relationship between parts by weight (or mass) and parts by volume is the same as the relationship between kilograms and liters.

[0062] Preparation of core particles - polyethylene resin particles Using an extruder (type ZE40A manufactured by Berstorff Corp., φ43 mm and L / D=37.5, twin-screw extruder), polyethylene resin (trade name: "NA248" manufactured by Asia Polymer Corporation, density = 0.916 g / cm) was extruded. 3 ) was melt-kneaded at a temperature of 230 to 250°C and cut into 0.4 to 0.6 mg / particle (average: 0.5 mg / particle) using a standard cutting method to obtain core particles (polyethylene resin particles). [Example]

[0063] Example 1 - Preparation of styrene-modified polyethylene-based expandable resin particles In a 20 L autoclave equipped with a stirrer ("Series 2246" manufactured by Amar Equipment Pvt. Ltd.), 8000 g of RO water, 103.3 g of magnesium nitrate hexahydrate and 48.1 g of sodium pyrophosphate as suspending agents, 11.5 g of sodium dodecylbenzenesulfonate as a surfactant, 1.2 g of sodium nitrite as an aqueous polymerization inhibitor, and then 600.0 g of the prepared polyethylene resin core particles were added. The mixture was then stirred at 430 rpm at room temperature for 30 minutes.

[0064] Heating was then initiated and the temperature was raised to 100° C. After reaching a temperature of 100° C., a first portion of the polymerization initiator (13.8 g of t-butylperoxy-2-ethylhexyl monocarbonate (trade name: "Perbutyl® E" manufactured by NOF Corp.)) and a first portion of the styrene monomer (867.5 g) were added to the autoclave. The temperature was then increased and maintained at 120° C. for 3 hours (i.e., at the constant reaction temperature and time in the first stage shown in Table 2).

[0065] After the temperature was reduced to 100° C., the second portion of styrene monomer (2549.4 g) was added to the autoclave, after which the temperature was increased and maintained at 120° C. for 6 hours (i.e., at the constant reaction temperature and time in the second stage shown in Table 2).

[0066] After the temperature was lowered, the product was removed from the autoclave, dehydrated and rinsed using a centrifuge, and water adhering to the surface was removed using an airflow dryer to obtain styrene-modified polyethylene expandable resin particles having an average particle size of about 1.37 mm. [Example]

[0067] Example 2 - Preparation of styrene-modified polyethylene-based expandable resin particles The preparation method of the styrene-modified polyethylene-based expandable resin particles of this example was the same as that of Example 1, except that the second portion of the polymerization initiator (13.8 g of t-butylperoxy-2-ethylhexyl monocarbonate) was added while adding the second portion of 2550 g of styrene monomer, and the obtained styrene-modified polyethylene-based expandable resin particles had an average particle size of about 1.36 mm.

[0068] The styrene-modified polyethylene-based expandable resin particles of Examples 3 to 19 were prepared according to the following Tables 1 and 2. The preparation methods for the styrene-modified polyethylene-based expandable resin particles of Examples 3 to 19 were the same as those of Examples 1 or 2, and will not be described again. Furthermore, in Examples 10 to 19, in addition to changing the amounts added according to Tables 1 and 2, the internal volume of the autoclave was changed from 20 L to 250 L.

[0069] Table 1: Raw materials used in Examples 1 to 19 and their amounts (unit: grams (g)) (hereinafter, Examples will be abbreviated as Ex.) [Table 1]

[0070] Table 2: Reaction conditions and product properties of Examples 1 to 19 [Table 2] *Solid content (SC) is calculated as follows: SC (%) = (amount of styrene monomer + amount of core particles) / total amount of all raw materials × 100%

[0071] Preparation of styrene-modified polyethylene-based expanded resin particles 5000 g of styrene-modified polyethylene-based expandable resin particles prepared in Examples 1 to 19 were each packed into a 30 L sealed container (pressure-resistant container) equipped with a stirrer along with 2000 g of RO water as a dispersion medium. 50 g of kaolin as a dispersant and 50 g of sodium alkylbenzene sulfonate as a surfactant were added to the dispersion medium. Next, the temperature inside the sealed container was raised to an expansion temperature of 166°C while stirring at a stirring speed of 300 rpm. Carbon dioxide (CO2) as an inorganic physical foaming agent was then injected into the sealed container under pressure so that the pressure inside the sealed container was 4.5 to 8.0 MPa (G: gauge pressure). The expandable resin particles were maintained at the same temperature (166°C) for 30 minutes, allowing the carbon dioxide to penetrate the expanded resin particles, resulting in expanded resin particles. Next, the expanded resin particles were discharged from the sealed container together with the dispersion medium, and the pressure was returned to atmospheric pressure, resulting in a pressure of approximately 45 kg / m. 3 As a result, styrene-modified polyethylene expanded resin particles having a density of 1000 MPa were obtained.

[0072] Preparation of foamed resin molded products First, the styrene-modified polyethylene-based expanded resin particles obtained as described above were aged at room temperature for one day. Next, using a molding machine (Jiuh-Shin Machinery Co., Ltd., JSM-HVA-P-400 / 300), the expanded resin particles were molded into a rectangular parallelepiped molded article measuring 400 mm x 300 mm x 60 mm. The molded article was dried at 60 °C for one day and then aged at room temperature for at least one day.

[0073] Method for detecting styrene-modified polyethylene-based expandable resin particles

[0074] Detection of xylene insolubles, acetone insolubles and swelling ratio First, approximately 1 g of expandable resin particles was collected and its weight (Wo) was measured to four decimal places. The measured expandable resin particles were placed in a 150-mesh wire mesh bag. Next, approximately 200 ml of xylene was poured into a 200 ml round flask, and the sample placed in the wire mesh bag was placed in a Soxhlet extraction tube. Soxhlet extraction was performed by applying heat to the flask using a heating mantle for 24 hours. After extraction, the extraction tube was cooled by air cooling. After cooling, the wire mesh was removed from the extraction tube, and the sample and wire mesh were rinsed with approximately 600 ml of acetone. Next, the acetone was evaporated, and the sample was dried at a temperature of 120 °C. The sample recovered from the wire mesh after drying was the "xylene insoluble matter."

[0075] The xylene solution obtained after Soxhlet extraction was added to 600 ml of acetone. The components that did not dissolve in acetone were then filtered using No. 5A filter paper specified in JIS P3801 and collected. The collected material was evaporated to dryness under reduced pressure. The resulting solid matter is the "acetone insoluble matter." Furthermore, the weight of the "acetone soluble matter" can be obtained by subtracting the weights of the "xylene insoluble matter" and "acetone insoluble matter" from the weight of the expandable resin particles (Wo).

[0076] The weight (Wa) of the mixed insoluble matter of "xylene-insoluble matter" and "acetone-insoluble matter" obtained above was measured to four decimal places. In some examples, when the weight of the mixed insoluble matter was less than 0.2 g, the above procedure was repeated until 0.2 g or more of the mixed insoluble matter was obtained in order to obtain a sufficient amount of the mixed insoluble matter.

[0077] Next, the mixed insoluble material was immersed in 50 ml of methyl ethyl ketone and maintained at a temperature of 23°C for 24 hours. After that, the mixed insoluble material was removed from the methyl ethyl ketone and slowly wiped with filter paper, and the weight (Wb) of the mixed insoluble material was measured to four decimal places. The swelling ratio was then calculated from the following formula based on the weight (Wb / Wa) of the mixed insoluble material before and after immersion in methyl ethyl ketone. S=Wb / Wa (1) Here, S is the swelling ratio, Wa is the weight of the mixed insoluble matter before immersion in methyl ethyl ketone, and Wb is the weight of the mixed insoluble matter after immersion in methyl ethyl ketone.

[0078] Weight average molecular weight (Mw) of the non-crosslinked portion of polystyrene resin Soxhlet extraction was performed in the same manner as described above. The extracted xylene solution was then added to 600 ml of acetone, followed by decantation and evaporation to dryness under reduced pressure. As a result, polystyrene resin was obtained as an acetone-soluble substance. The acetone-soluble substance of the obtained polystyrene resin was subjected to the following detection to obtain the weight-average molecular weight of the non-crosslinked portion of the polystyrene resin.

[0079] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polystyrene resin were measured by gel permeation chromatography (GPC) (polymer assay mixed gel column) using polystyrene as the standard. Specifically, a Waters APC was used. The measurement was performed under the following conditions: eluent: tetrahydrofuran (THF), flow rate: 0.7 ml / min, sample concentration: 0.22 wt%, and columns: Waters Acquity XT 900 (2.5 μm) / 450 (2.5 μm) / 125 (2.5 μm) / 45 (1.7 μm), 4.6 × 30 mm × 1 + 4.6 × 150 mm × 3 connected in series. More specifically, the acetone-soluble portion of the polystyrene resin was dissolved in tetrahydrofuran, and the resultant was measured by gel permeation chromatography (GPC). The weight-average molecular weight was obtained by correcting using standard polystyrene. This makes it possible to obtain the weight average molecular weight (Mw) and number average molecular weight (Mn) of the non-crosslinked portion of the polystyrene resin, as well as the polymer dispersity index (PDI) (i.e., Mw / Mn) of the non-crosslinked portion of the polystyrene resin.

[0080] 698cm -1 and 2850 cm -1 The absorbance ratio (D 698 / D 2850 ) ATR infrared spectroscopy is widely used to analyze the surfaces of various materials, including organic materials such as polymers. The spectrum can be measured simply by bonding the sample and ATR prism, and surfaces up to a depth of several micrometers can be analyzed.

[0081] 698 cm obtained from the infrared absorption spectrum -1 Absorbance D at 698 is 698 cm , which is derived from the out-of-plane deformation vibration of the benzene ring mainly contained in polystyrene resins. -1 Furthermore, the height of the peak that appears around 2850 cm obtained from the infrared absorption spectrum -1 Absorbance D at 2850 is the 2850 cm band resulting from the CH stretching vibration of methylene groups contained in both polyolefin-based resins and polystyrene-based resins. -1 This is the height of the peak that appears around it.

[0082] Absorbance ratio (D 698 / D 2850 ) was measured in the following manner. Surface analysis of 10 randomly selected expandable resin particles was performed by ATR infrared spectroscopy to obtain their infrared absorption spectra. From each infrared absorption spectrum, each absorbance ratio (D 698 / D 2850 ) was calculated, excluding the minimum and maximum absorbance ratios. The arithmetic mean of the remaining eight absorbance ratios was then calculated as the absorbance ratio (D 698 / D 2850 The absorbance ratio (D 698 / D 2850 ) was measured using, for example, a measuring device available from Nicolet Instrument Corp. under the trade name "Thermo Scientific Nicolet iS10."

[0083] Nuclear magnetic resonance ( 13 CNMR)-Polystyrene content (wt%) Approximately 0.3 g of sample was weighed into a 10 mm NMR tube and approximately 0.7 g of xylene was added. Oxygen was reduced by nitrogen purging via an insertion pipette for 1 minute. The tube was stoppered and placed in the aluminum heating block of the sample preparation unit and heated to 105°C for 2 hours. The sample was periodically checked for homogeneity and manually mixed as needed. Mixture homogeneity was evident by observation of uniform distribution of polymer in solution, with no obvious regions of high solvent concentration or air pockets. Data were collected using a JEOL JNM-ECZ400S / L1 400 MHz with a ROYALPROBE™ HFX. 13 For C NMR, the following experimental conditions were used: spectral width = 20,000 Hz, relaxation delay = 10 s, number of scans = 4,000, and inverse gate decoupling at a sample temperature of 105 °C. All measurements were performed on unspun samples in locked mode. Samples were allowed to thermally equilibrate for 10 min before data acquisition. Polyethylene (PE) was identified by the peaks at 29-31 ppm, and polystyrene (PS) by the peaks at 145-148 ppm.

[0084] The PE / PS relative content is 13 The mole fractions were calculated based on the specific chemical shifts (δc) in the C NMR spectrum. For PS, the δc at 145–148 ppm represents the quaternary carbon of the benzene ring, while the δc at 29.0–31.2 ppm represents the two secondary carbons (–CH2–) of PE. To convert mole fractions to weight fractions, multiply each mole fraction by the molecular weight of ethylene (28) and styrene (140).

[0085] The formulas and definitions are as follows: definition PS (mol): δc 145-148 ppm integral value PE (mol): Divide the integral value of δc 29.0 to 31.2 ppm by 2 PS (weight): multiply the moles of PS by the molecular weight of styrene PE (weight): multiply the moles of PE by the molecular weight of ethylene formula PS(weight%): [PS(weight) / PS(weight)+PE(weight)]×100% PE(weight%): [PE(weight) / PS(weight)+PE(weight)]×100%

[0086] Morphological detection of styrene-modified polyethylene-based expandable resin particles Styrene-modified polyethylene-based expandable resin particles were prepared, and the expandable resin particles were cut in half from the surface through the central region using a cutting machine to obtain test samples. The test samples were embedded in epoxy resin, stained with ruthenium tetroxide, and ultrathin sections were prepared using an ultramicrotome.

[0087] 1 is a schematic cross-sectional view of a styrene-modified polyethylene-based expandable resin particle according to an example of the present disclosure, in which the region from 1.5 μm from the surface 11 a of the expandable resin particle 1 (i.e., the distance D1 is about 1.5 μm) to the surface 11 a of the expandable resin particle 1 is the surface region 11 of the expandable resin particle 1, and the region at least 500 μm away from the surface 11 a of the expandable resin particle 1 (to the center of the expandable resin particle) (i.e., the distance D2 is about 500 μm) is the central region 12 of the expandable resin particle 1.

[0088] The ultrathin sections were placed on a grid, and cross-sectional photographs (TEM photographs) were taken at 3,000x or 10,000x magnifications using a transmission electron microscope (JEM-2100F manufactured by JOEL Ltd.). The cross-sectional morphologies of the surface region 11 and central region 12 of the expandable resin particle 1 were observed. From the TEM photographs, the morphologies of the polyethylene resin (PE) phase and polystyrene resin (PS) phase of the expandable resin particle 1 were visually observed. For example, Figures 2 and 3 are TEM photographs of the surface region and central region, respectively, of a styrene-modified polyethylene-based expandable resin particle according to Example 1 below of the present disclosure. It can be seen that the polystyrene resin is dispersed in the polyethylene resin in the form of particles, and the polystyrene resin particles include spherical, ellipsoid, spherical-like, ellipsoid-like, or other irregular particles.

[0089] Furthermore, the captured images were analyzed using image processing software (MacView, MOUNTECH CO., Ltd.), and the particle size and quantity of the polystyrene resin particles were recorded to obtain a particle size (X axis) and quantity (Y axis) distribution curve of the polystyrene resin particles. The average particle size and standard deviation, as well as the skewness and kurtosis of the particle size and quantity curve of the distribution were calculated.

[0090] The standard deviation describes the spread of the distribution around the mean grain size. It is often written as s, and s 2 It is the square root of the sample variance, denoted as , and can be calculated as follows:

number

number

number

[0091] The skewness of the distribution grain size and quantity curve is calculated based on third moments about the mean value (ie, the average grain size) as follows:

number

number

number

[0092] If the data distribution is symmetric, the skewness is 0. If the skewness is greater than 0, the distribution is right-skewed, i.e., the distribution has a long tail on the right. If the skewness is less than 0, the distribution is left-skewed, i.e., the distribution has a long tail on the left. At the same time, the larger the absolute value of the skewness, the more significant the deviation of the distribution.

[0093] The kurtosis of the distribution grain size and quantity curve is calculated based on the fourth moment about the mean value (ie, the average grain size) as follows:

number

number

[0094] Detection method for foam resin molded products Compressive strength at 10%, 25%, 50% and 75% strain and 50% compression set were measured according to ASTM D3575. Flexural strength and flexural modulus were measured according to ASTM D790IA. Tensile strength and tensile elongation were measured according to ISO 1798:2008.

[0095] The analysis results of the polystyrene resin particles in the surface region and the central region of the styrene-modified polyethylene expandable resin particles are shown in Tables 3 and 4 below.

[0096] Table 3: Analysis results of polystyrene resin particles in the surface region [Table 3] JPEG0007777166000012.jpg74142

[0097] Table 4: Analysis results of polystyrene resin particles in the central region [Table 4] JPEG0007777166000014.jpg55143

[0098] The average particle size and standard deviation of the polystyrene resin particles, as well as the skewness and kurtosis of the particle size and number distribution curves of the particles in the surface and central regions of the expandable resin particles, are shown in Table 5 below.

[0099] Table 5: Statistical results of the mean particle size and standard deviation of polystyrene resin particles and the skewness and kurtosis of the particle size and quantity distribution curves of polystyrene resin particles [Table 5]

[0100] The detection results of the styrene-modified polyethylene expandable resin particles and the foamed resin molded articles prepared as described above are shown in Tables 6 and 7 below, respectively.

[0101] Table 6: Detection results of styrene-modified polyethylene-based expandable resin particles [Table 6]

[0102] Table 7: Detection results for foamed resin molded products [Table 7]

[0103] The above results indicate that if the average particle size of the polystyrene resin particles in the surface and central regions of styrene-modified polyethylene-based expandable resin particles is within a specific range, the foamed resin molded product prepared therefrom will have appropriate rigidity and compression recovery. If the skewness or kurtosis of the curve of the particle size and quantity distribution of the polystyrene resin particles in the surface and central regions of styrene-modified polyethylene-based expandable resin particles is within a specific range, the foamed resin molded product prepared therefrom will have appropriate rigidity and compression recovery. If the content of xylene insolubles, the content of acetone insolubles, their ratio, or their total in the styrene-modified polyethylene-based expandable resin particles is within a specific range, the foamed resin molded product prepared therefrom will have appropriate rigidity and compression recovery. Furthermore, the swelling ratio of the styrene-modified polyethylene-based expandable resin particles, the molecular weight of the non-crosslinked portion of the polystyrene resin, or the absorbance ratio (D) of the infrared absorption spectrum can be measured. 698 / D 2850 ) is within a specific range, the foamed resin molded article prepared thereby also has appropriate rigidity and compression recovery. Therefore, the styrene-modified polyethylene-based expandable resin particles, expanded resin particles, and foamed resin molded article provided by the present disclosure improve the disadvantage of polystyrene foamed resin molded articles, which is low in recovery after compression, and also improve the disadvantage of polyethylene foamed resin molded articles, which is insufficient in rigidity, and are applicable to various cushioning materials such as materials for transportation containers or transportation devices.

[0104] Although the present disclosure has been described in connection with embodiments thereof, it will be understood that many other possible variations and modifications can be made without departing from the spirit and scope of the present disclosure as hereinafter claimed.

Claims

1. Styrene-modified polyethylene-based expandable resin particles, comprising a polyethylene resin and a polystyrene resin, Based on 100% by weight of the polyethylene resin and the polystyrene resin, the content of the polyethylene resin is in the range of 5% by weight to 30% by weight, and the content of the polystyrene resin is in the range of 70% by weight to 95% by weight, the polystyrene resin is in the form of particles dispersed in the polyethylene resin; the average particle size of the polystyrene resin particles is in the range of 0.02 μm to 0.15 μm in the surface region of the expandable resin particle, and the surface region of the expandable resin particle is a region from 1.5 μm from the surface of the expandable resin particle to the surface of the expandable resin particle; The average particle size of the polystyrene resin particles is in the range of 0.20 μm to 0.60 μm in a central region of the expandable resin particle, and the central region of the expandable resin particle is a region at least 500 μm away from the surface of the expandable resin particle; Expandable resin particles, wherein the number of the polystyrene resin particles having a particle size of 0.01 μm to 0.1 μm is 50% or more of the total number of the polystyrene resin particles in the surface region of the expandable resin particles.

2. The expandable resin particles according to claim 1, wherein the number of the polystyrene resin particles having a particle size of 0.02 μm to 0.08 μm is 50% or more of the total number of the polystyrene resin particles in the surface region of the expandable resin particles.

3. The expandable resin particles according to claim 1, wherein the number of the polystyrene resin particles having a particle size of 0.1 μm to 0.6 μm is 70% or more of the total number of the polystyrene resin particles in the central region of the expandable resin particles.

4. The expandable resin particles according to claim 1, wherein the number of the polystyrene resin particles having a particle size of 0.2 μm to 0.5 μm is 60% or more of the total number of the polystyrene resin particles in the central region of the expandable resin particles.

5. 2. The expandable resin particle according to claim 1, wherein the skewness of the curve of the particle size and number distribution of the polystyrene resin particles is −0.5 to 8 in the surface region of the expandable resin particle.

6. The expandable resin particles according to claim 1, wherein the kurtosis of the curve of particle size and number distribution of the polystyrene resin particles is -1.5 to 120 in the surface region of the expandable resin particles.

7. The expandable resin particles according to claim 1, wherein the skewness of the curve of the particle size and number distribution of the polystyrene resin particles is −0.7 to 0.7 in the central region of the expandable resin particles.

8. The expandable resin particles according to claim 1, wherein the kurtosis of the curve of the particle size and number distribution of the polystyrene resin particles is −1.0 to 2.5 in the central region of the expandable resin particles.

9. The expandable resin particles according to claim 1, wherein the expandable resin particles contain xylene insolubles and acetone insolubles, and the ratio of the content of the xylene insolubles to the content of the acetone insolubles is in the range of 0.01 to 5.

10. The expandable resin particles according to claim 9, wherein the content of the acetone insoluble matter is in the range of 10% by weight to 60% by weight.

11. The expandable resin particles according to claim 9, wherein the content of the xylene insoluble matter is 70% by weight or less.

12. The expandable resin particles according to claim 9, wherein the sum of the content of the acetone insoluble matter and the content of the xylene insoluble matter is in the range of 40% by weight to 90% by weight.

13. The expandable resin particles according to claim 1 , wherein the swelling ratio of the expandable resin particles is 2.5 or less.

14. 2. The expandable resin particles according to claim 1, wherein the polystyrene resin has a non-crosslinked portion, and the molecular weight of the non-crosslinked portion is in the range of 30,000 to 80,000.

15. 698 cm obtained from the infrared absorption spectrum of the surface of the expandable resin particle －１ and 2850 cm －１ The expandable resin particles according to claim 1 , wherein the absorbance ratio at

16. 10. Styrene-modified polyethylene-based expanded resin particles produced by foaming the expandable resin particles of claim 1.

17. 17. A foamed resin molded product produced by the expanded resin particles of claim 16 through a molding process.

18. The foamed resin molded article according to claim 17, which is used as a material for a transport container or a transport device.

19. A method for producing the expandable resin particles according to claim 1, comprising the steps of: providing a mixture comprising polyethylene resin particles; mixing the mixture containing the polyethylene resin particles with a styrene monomer and a polymerization initiator to obtain the expandable resin particles according to claim 1; A method for providing the above.

20. 20. The method of claim 19, wherein the mixture containing the polyethylene resin particles is mixed with the styrene monomer and the polymerization initiator and then heated to 115°C to 125°C to obtain the expandable resin particles of claim 1.

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