Foamable and foamable resin particles, foamable resin molded article, and method for producing same

Abstract

The invention provides styrene modified polyethylene foamable resin particles. The styrene modified polyethylene foamable resin particles comprise polyethylene resin and polystyrene resin, wherein based on 100 wt% of the polyethylene resin and the polystyrene resin, the content of the polyethylene resin is 5 wt% to 30 wt%, and the content of the polystyrene resin is 70 wt% to 95 wt%; the polystyrene resin is dispersed in the polyethylene resin in a granular form; in the surface area of the foamable resin particles, the average particle size of the polystyrene resin particles is 0.02-0.15 [mu] m; in the middle area of the foamable resin particles, the average particle size of the polystyrene resin particles is between 0.20 [mu] m and 0.60 [mu] m. In addition, the present invention also provides foamable resin particles obtained from the foamable resin particles, a foamable resin molded article, and a method for producing the foamable resin particles.

Description

Technical Field

[0001] The present invention relates to a foamable resin particle, a foamable resin particle, a foamable resin molded body and a preparation method thereof, and in particular to a styrene-modified polyethylene foamable resin particle, a foamable resin particle, a foamable resin molded body and a preparation method thereof. Background Art

[0002] Foamed resin molded articles are widely used in packaging, construction, and shock-absorbing materials due to their excellent cushioning properties. Generally speaking, foamed resin molded articles are made by preparing expandable resin particles into foamable resin particles. These expandable resin particles are then fused together in a mold to form the foamed resin molded article.

[0003] The material of the foamable resin particles may include polyethylene, polypropylene or polystyrene. However, the foamed resin molded body made from polystyrene has the disadvantage of poor recovery after compression; the foamed resin molded body made from polyethylene or polypropylene has the disadvantage of insufficient rigidity.

[0004] In view of this, there is an urgent need to develop a novel foamable resin particle, a foamable resin particle, a foamed resin molded body and a preparation method thereof to improve the aforementioned shortcomings. Summary of the Invention

[0005] The present invention provides styrene-modified polyethylene foamable resin particles, comprising polyethylene resin and polystyrene resin. Based on 100 wt% of the polyethylene resin and the polystyrene resin, the polyethylene resin content is 5 wt% to 30 wt%, and the polystyrene resin content is 70 wt% to 95 wt%. The polystyrene resin is dispersed in the polyethylene resin in the form of particles. In the surface region of the foamable resin particles, the average particle size of the polystyrene resin particles is between 0.02 μm and 0.15 μm, wherein the surface region of the foamable resin particles is the region from 1.5 μm to the surface of the foamable resin particles. In the middle region of the foamable resin particles, the average particle size of the polystyrene resin particles is between 0.20 μm and 0.60 μm, wherein the middle region of the foamable resin particles is the region at least 500 μm away from the surface of the foamable resin particles.

[0006] The present invention further provides styrene-modified polyethylene foamable resin particles, which are obtained by subjecting the aforementioned foamable resin particles to a foaming process.

[0007] The present invention also provides a foamed resin molded body obtained by molding the aforementioned foamable resin particles, wherein the foamed resin molded body can be used as a material for a loading container or a transport device.

[0008] Generally speaking, in expandable resin particles comprising polyethylene resin and polystyrene resin, or in expandable resin molded articles produced using these expandable resin particles, excessive polystyrene resin content increases rigidity (compressive strength) but degrades compressive recoverability (compression set). Excessively low polyethylene resin content can lead to insufficient recoverability in the expandable resin particles or expandable resin molded articles. Therefore, in the present invention, based on 100 wt% of the polyethylene resin and polystyrene resin, a polyethylene resin content of 5 wt% to 30 wt% and a polystyrene resin content of 70 wt% to 95 wt% can achieve appropriate rigidity and compressive recoverability in the expandable resin particles or expandable resin molded articles.

[0009] For example, based on the sum of the polyethylene resin content and the polystyrene resin content as 100 wt%, the polyethylene resin content may be, for example, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt% or 28 wt%, with the remainder being polystyrene resin.

[0010] In one embodiment, based on 100 wt% of the polyethylene resin and the polystyrene resin, the polyethylene resin content is 5 wt% to 25 wt% and the polystyrene resin content is 75 wt% to 95 wt%. In another embodiment, based on 100 wt% of the polyethylene resin and the polystyrene resin, the polyethylene resin content is 5 wt% to 20 wt% and the polystyrene resin content is 80 wt% to 95 wt%. In another embodiment, based on 100 wt% of the polyethylene resin and the polystyrene resin, the polyethylene resin content is 5 wt% to 15 wt% and the polystyrene resin content is 85 wt% to 95 wt%.

[0011] In one embodiment, the polystyrene resin is dispersed in the polyethylene resin in the form of particles. The shape of the polystyrene resin particles is not particularly limited and can be spherical, elliptical, quasi-spherical, quasi-elliptical or other irregular particles.

[0012] In one embodiment, the average particle size of the polystyrene resin particles in the surface region of the foamable resin particles is between 0.02 μm and 0.15 μm, for example, between 0.02 μm and 0.14 μm or between 0.02 μm and 0.13 μm. For example, the average particle size of the polystyrene resin particles in the surface region of the foamable resin particles 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. The average particle size of the polystyrene resin particles in the surface region of the foamable resin particles is positively correlated with the 50% compression set of the foamed resin molded article (e.g., a formed sheet). When the average particle size of the polystyrene resin particles in the surface area of the foamable resin particles is too large, the 50% compression set rate of the foamed resin molded body (e.g., a formed board) may increase, resulting in poor rebound (resilience) recovery of the foamed resin molded body (e.g., a formed board).

[0013] In one embodiment, in the middle region of the foamable resin particles, the average particle size of the polystyrene resin particles is between 0.20 μm and 0.60 μm, for example, between 0.20 μm and 0.50 μm or between 0.20 μm and 0.45 μm. For example, in the middle region of the foamable resin particles, the average particle size of the polystyrene 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 middle region of the foamable resin particles is positively correlated with the bending strength of the foamed resin molded body (e.g., a formed plate). When the average particle size of the polystyrene resin particles in the middle region of the foamable resin particles is too small, the bending strength of the foamed resin molded body (e.g., a formed plate) may be unsatisfactory.

[0014] In one embodiment, in the surface area of the foamable resin particles, the number of polystyrene resin particles having a particle size between 0.01 μm and 0.1 μm may be 50% or more of the total number of polystyrene resin particles, 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.

[0015] In one embodiment, in the surface area of the foamable resin particles, the number of polystyrene resin particles having a particle size between 0.02 μm and 0.08 μm may be 50% or more of the total number of polystyrene resin particles, for example, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, or 80% or more.

[0016] In one embodiment, in the middle region of the foamable resin particles, the number of polystyrene resin particles having a particle size between 0.1 μm and 0.6 μm may be 70% or more of the total number of polystyrene resin particles, for example, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more.

[0017] In one embodiment, in the middle region of the foamable resin particles, the number of polystyrene resin particles having a particle size between 0.2 μm and 0.5 μm may be 60% or more of the total number of polystyrene resin particles, for example, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, or 90% or more.

[0018] In one embodiment, the skewness of the distribution curve of the particle size and number of the polystyrene resin particles in the surface region of the expandable resin particles may be between -0.5 and 8, for example, between -0.5 and 8, -0.4 and 8, -0.4 and 7, -0.4 and 6, -0.4 and 5, -0.4 and 4, -0.4 and 3, -0.3 and 3, -0.2 and 3, -0.1 and 3, 0.0 and 3, 0.1 and 3, 0.2 and 3, 0.3 and 3, or 0.4 and 3. The skewness of the distribution curve of the particle size and number of the polystyrene resin particles in the surface region of the expandable resin particles is negatively correlated with the 50% compression set of the foamed resin molded article (e.g., a molded sheet). If the skewness of the distribution curve of the particle size and number of the polystyrene resin particles in the surface region is outside the aforementioned range, the 50% compression set of the foamed resin molded article (e.g., a molded sheet) may increase. Therefore, in one embodiment, when the skewness of the distribution curve of the particle size and number of polystyrene resin particles in the surface region is within the aforementioned range, the resilience of the foamed resin molded article (eg, molded plate) is good.

[0019] In one embodiment, the kurtosis of the distribution curve of the particle size and number of the polystyrene resin particles in the surface region of the expandable resin particles may be between -1.5 and 120, for example, between -1.5 and 100, -1.5 and 80, -1.5 and 60, -1.5 and 40, -1.5 and 20, -1.5 and 10, -1.0 and 10, -0.5 and 10, -0.3 and 10, or 0.0 and 10. The kurtosis of the distribution curve of the particle size and number of the polystyrene resin particles in the surface region of the expandable resin particles is positively correlated with the tensile elongation of the foamed resin molded article (e.g., a formed sheet). In one embodiment, when the kurtosis of the distribution curve of the particle size and number of the polystyrene resin particles in the surface region is within the aforementioned range, the foamed resin molded article (e.g., a formed sheet) exhibits good tensile elongation.

[0020] In one embodiment, the skewness of the distribution curve of the particle size and number of the polystyrene resin particles in the middle region of the foamable resin particles may be between -0.7 and 0.7, for example, between -0.6 and 0.7, -0.6 and 0.6, -0.5 and 0.6, -0.5 and 0.5, -0.4 and 0.5, -0.3 and 0.5, -0.2 and 0.5, -0.1 and 0.5, or 0.0 and 0.5. The skewness of the distribution curve of the particle size and number of the polystyrene resin particles in the middle region of the foamable resin particles is negatively correlated with the compressive strength or tensile strength of the foamed resin molded article (e.g., a formed sheet). In one embodiment, when the skewness of the distribution curve of the particle size and number of the polystyrene resin particles in the middle region is within the aforementioned range, the foamed resin molded article (e.g., a formed sheet) has good compressive strength or tensile strength.

[0021] In one embodiment, the kurtosis of the distribution curve of the particle size versus number of the polystyrene resin particles in the middle region of the foamable resin particles may be between -1.0 and 2.5, for example, between -1.0 and 2.0, -0.5 and 2.0, -0.5 and 1.5, or -0.5 and 1.0. The kurtosis of the distribution curve of the particle size versus number of the polystyrene resin particles in the middle region of the foamable resin particles is positively correlated with the flexural strength or flexural modulus of the foamed resin molded article (e.g., formed sheet), but negatively correlated with the tensile elongation of the foamed resin molded article (e.g., formed sheet). In one embodiment, when the kurtosis of the distribution curve of the particle size versus number of the polystyrene resin particles in the middle region is within the aforementioned range, the foamed resin molded article (e.g., formed sheet) exhibits good flexural strength, flexural modulus, or tensile elongation.

[0022] In one embodiment, the infrared absorption spectrum of the surface of the expandable resin particles is at 698 cm -1 and 2850cm-1 The ratio of the absorbance (D 698 / D 2850 ) may be greater than or equal to 1.0, for example, may be greater than or equal to 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4 or 2.5. In one embodiment, the infrared absorption spectrum of the surface of the expandable resin particles is at 698 cm -1 and 2850cm -1 The ratio of the absorbance of the expandable resin particles to the absorbance of the expandable resin particles may be between 1.0 and 6.0, for example, between 1.2 and 6.0, 1.4 and 6.0, 1.6 and 6.0, 1.8 and 6.0, 2.0 and 6.0, 2.2 and 6.0, 2.4 and 6.0, or 2.5 and 6.0. The infrared absorption spectrum of the surface of the expandable resin particles may be an attenuated total reflectance (ATR) infrared absorption spectrum.

[0023] When the surface of the expandable resin particles is detected by infrared absorption spectrometer, D 698 / D 2850 It can reflect the proportion of polystyrene in the area with a depth of several microns (μm) from the surface of the foamable resin particles, where D 698 / D 2850 It is negatively correlated with the tensile elongation of the foamed resin molded body (e.g., a molded plate). In one embodiment, if D 698 / D 2850 If the polyethylene content in the surface area is greater than the above range, the polyethylene content in the surface area is too low, which may result in the foaming resin particles being unable to smoothly undergo the subsequent molding process to obtain a foamed resin molded body; or the chemical resistance and elongation of the foamed resin molded body are not ideal. In one embodiment, if D 698 / D 2850 If the content is less than the aforementioned range, the proportion of polystyrene in the surface area is too low, which may result in insufficient rigidity (compressive strength).

[0024] In one embodiment, the average particle size of the foamable resin particles may be between 1.0 mm and 2.0 mm, for example, between 1.1 mm and 2.0 mm, 1.1 mm and 1.9 mm, 1.2 mm and 1.9 mm, 1.2 mm and 1.8 mm, 1.3 mm and 1.8 mm, 1.3 mm and 1.7 mm or 1.4 mm and 1.7 mm. When the average particle size of the foamable resin particles is too small, the foaming agent is not easy to maintain, which is unfavorable for reducing the density of the foamed resin molded body. When the average particle size of the foamable resin particles is too large, the size of the foamable resin particles also increases, and the effect of filling the metal mold in the die casting process is poor, and it is difficult to form a thin foamed resin molded body. However, the present invention is not limited thereto, and the average particle size of the foamable resin particles may also be adjusted according to demand.

[0025] In one embodiment, the polystyrene resin may have a non-crosslinked portion, and the molecular weight of the non-crosslinked portion may be between 30,000 and 80,000, for example, between 35,000 and 80,000, 40,000 and 80,000, 45,000 and 80,000, 50,000 and 80,000, 50,000 and 75,000, 55,000 and 75,000, 55,000 and 70,000, or 60,000 and 70,000. The molecular weight of the non-crosslinked portion can be measured by gel permeation chromatography (GPC). The molecular weight of the non-crosslinked portion of the polystyrene resin is negatively correlated with the 50% compression set. When the molecular weight of the polystyrene resin is relatively high, the resulting foamable resin particles or foamable resin molded articles experience less intermolecular displacement when subjected to stress and deformation, resulting in the resulting foamable resin particles or foamable resin molded articles having better resilience and being less susceptible to deformation. Therefore, when the molecular weight of the non-crosslinked portion of the polystyrene resin is within the aforementioned range, the resulting foamable resin molded articles exhibit excellent resilience.

[0026] In one embodiment, the polymer dispersity index (PDI) of the non-crosslinked portion of the polystyrene resin may be less than 4.0. The PDI of the non-crosslinked portion of the polystyrene resin is negatively correlated with the elongation of the foamed resin molded article (e.g., a formed sheet). This may be due to the uneven distribution of the polystyrene network size, which results in poor bonding of the foamed resin particles and a decrease in the elongation of the foamed resin molded article. Therefore, when the PDI of the non-crosslinked portion of the polystyrene resin is within the aforementioned range, the foamed resin molded article can have good elongation.

[0027] In one embodiment, the expandable resin particles include a xylene-insoluble component and an acetone-insoluble component. The xylene-insoluble component is the portion of polyethylene, polystyrene, or polyethylene and polystyrene that is insoluble in xylene due to a chemical reaction to form a three-dimensional network structure. The expandable resin particles can be subjected to Soxhlet extraction with xylene to obtain a xylene-insoluble portion, which is the xylene-insoluble component of the expandable resin particles. Furthermore, the acetone-insoluble component is the portion of polystyrene, or polyethylene and polystyrene that is insoluble in acetone due to a chemical reaction to form a loose two-dimensional network structure. The xylene-soluble portion obtained by Soxhlet extraction with xylene can be extracted with acetone to obtain an acetone-insoluble portion, which is the acetone-insoluble component of the expandable resin particles.

[0028] In one embodiment, the content of xylene-insoluble components in the foamable resin particles may be less than or equal to 70 wt% (including 0 wt%), for example, 1 wt% to 70 wt%, 5 wt% to 70 wt%, 10 wt% to 70 wt%, 15 wt% to 70 wt%, 20 wt% to 70 wt%, 20 wt% to 65 wt%, 25 wt% to 65 wt%, 25 wt% to 60 wt%, or 30 wt% to 60 wt%. The xylene-insoluble components in the foamable resin particles are positively correlated with the 50% compression set. When the content of xylene-insoluble components in the foamable resin particles is within the aforementioned range, the resulting foamed resin molded article can have good resilience and resistance to deformation while retaining other desired properties.

[0029] In one embodiment, the content of the acetone-insoluble component in the foamable resin particles may be between 10wt% and 60wt%, for example, between 11wt% and 60wt%, 12wt% and 60wt%, 13wt% and 60wt%, 14wt% and 60wt%, 15wt% and 60wt%, 15wt% and 55wt%, 15wt% and 50wt%, 15wt% and 45wt% or 15wt% and 40wt%. Wherein, the acetone-insoluble component in the foamable resin particles is negatively correlated with the compressive strength. The possible reason is that the two-dimensional network structure of the foamable resin particles is easier to form a layered laminated structure. In addition, the acetone-insoluble component in the foamable resin particles is negatively correlated with the tensile strength of the obtained foamed resin molded body. The possible reason is that the two-dimensional network structure of the foamable resin particles is easier to form a layered laminated structure, and the other dimension strength is poor. Therefore, when the content of the acetone-insoluble component in the expandable resin particles is within the aforementioned range, the obtained expanded resin molded article can have good compressive strength (rigidity) and tensile strength.

[0030] In one embodiment, the ratio of the xylene-insoluble content to the acetone-insoluble content in the expandable resin particles (xylene-insoluble content / acetone-insoluble content) may be between 0.01 and 5, for example, between 0.01 and 4.5, 0.01 and 4.0, 0.01 and 3.5, 0.05 and 3.5, 0.1 and 3.5, 0.1 and 3.0, 0.15 and 3.0, 0.15 and 2.5, 0.2 and 2.5, 0.2 and 2.0, 0.25 and 2.0, 0.25 and 1.5, or 0.3 and 1.5. The ratio of the xylene-insoluble content to the acetone-insoluble content is positively correlated with the 50% compression set. When the ratio of the content of xylene-insoluble components to the content of acetone-insoluble components in the foamable resin particles is within the aforementioned range, the obtained foamed resin molded body can have good rebound (resilience) and is not easily deformed while retaining other desired properties.

[0031] In one embodiment, the sum of the acetone-insoluble content and the xylene-insoluble content in the expandable resin particles may be between 40 wt % and 90 wt %, for example, between 42 wt % and 90 wt %, 45 wt % and 90 wt %, 50 wt % and 90 wt %, 51 wt % and 90 wt %, 52 wt % and 90 wt %, 53 wt % and 90 wt %, 54 wt % and 90 wt %, 55 wt % and 90 wt %, 56 wt % and 90 wt %, 57 wt % and 90 wt %, 58 wt % and 90 wt %, 59 wt % and 90 wt %, or 60 wt % and 90 wt %. The sum of the acetone-insoluble content and the xylene-insoluble content is positively correlated with the compression set of 50%. When the sum of the content of the acetone-insoluble component and the content of the xylene-insoluble component in the expandable resin particles is within the aforementioned range, the obtained foamed resin molded article can have good resilience and is less likely to deform.

[0032] In one embodiment, the expandable resin particles may further include an acetone-soluble component, wherein the sum of the acetone-insoluble component, the xylene-insoluble component, and the acetone-soluble component is 100 wt %. In one embodiment, the acetone-soluble component may be in the range of 10 wt % to 60 wt %, for example, 10 wt % to 58 wt %, 10 wt % to 55 wt %, 10 wt % to 50 wt %, 10 wt % to 49 wt %, 10 wt % to 48 wt %, 10 wt % to 47 wt %, 10 wt % to 46 wt %, 10 wt % to 45 wt %, 10 wt % to 44 wt %, 10 wt % to 43 wt %, 10 wt % to 42 wt %, 10 wt % to 41 wt %, or 10 wt % to 40 wt %.

[0033] In one embodiment, the swelling ratio of the foamable resin particles may be less than or equal to 2.5, for example, less than or equal to 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, or 1.6. When the swelling ratio of the foamable resin particles is within the aforementioned range, the foamable resin particles or foamed resin molded bodies obtained using the foamable resin particles may have excellent recoverability (compression set rate) and at the same time excellent rigidity. This may be because when the swelling ratio of the foamable resin particles is within the aforementioned range, the two-dimensional or three-dimensional structure of the resin is denser, so when subjected to force deformation, the resin structure is less likely to collapse and can exhibit good recovery.

[0034] Here, the swelling degree of expandable resin particles refers to the swelling degree of the mixed insoluble components (acetone-insoluble and xylene-insoluble) in the expandable resin particles in an organic solvent (e.g., methyl ethyl ketone) at room temperature (e.g., 23°C). The swelling degree (degree of swelling) of a cross-linked polyethylene resin immersed in an organic solvent is correlated with the resin's cross-linked structure (three-dimensional network). Furthermore, a denser network structure results in lower organic solvent absorption and, consequently, lower swelling. Furthermore, non-cross-linked polyethylene resin hardly swells in organic solvents.

[0035] In the present invention, compared with the expandable resin particles having a smaller swelling degree of the mixed insoluble components, the expandable resin particles having a larger swelling degree of the mixed insoluble components of xylene (cross-linked polyethylene resin component) and acetone insoluble components (cross-linked polyethylene resin component, uncross-linked polyethylene resin component and polyethylene resin component of grafted polymerized styrene monomer) contain a polyethylene resin with a cross-linked three-dimensional network structure having a larger coarse mesh.

[0036] During foaming, the polyethylene resin, which contains a coarse-meshed, cross-linked, three-dimensional network structure, allows for moderate stretching while retaining its strength, thereby forming a highly robust foam wall. Furthermore, when the foamable resin particles are compressed, the polyethylene resin is relatively flexible and fully deformable. Even with a high polystyrene resin content, the foam wall of the foamable particles maintains a closed-cell structure without rupturing. Therefore, when the degree of swelling of the foamable resin particles is within the aforementioned range, foamable resin particles and foamable resin molded articles having high rigidity and resilience can be obtained.

[0037] In addition, the present invention also provides a method for preparing styrene-modified polyethylene foamable resin particles, comprising the following steps: providing a mixture containing polyethylene resin particles; mixing the mixture containing polyethylene resin particles with styrene monomer and a polymerization initiator to obtain the aforementioned styrene-modified polyethylene foamable resin particles.

[0038] In the present invention, the mixture containing polyethylene resin particles is mixed with styrene monomer and a polymerization initiator. The styrene monomer (and polymerization initiator) can be added to the mixture containing polyethylene resin particles in one portion or in multiple portions. When the styrene monomer (and polymerization initiator) is added to the mixture containing polyethylene resin particles in multiple portions, the occurrence of polystyrene aggregation and clumping can be reduced.

[0039] In the present invention, after mixing the mixture containing polyethylene resin particles with styrene monomer and a polymerization initiator, the reaction mixture can be heated to an appropriate temperature (e.g., 115 to 125°C) to polymerize the styrene monomer. When the polymerization temperature of the styrene monomer is outside the range of 115 to 125°C, the content of xylene-insoluble components can be affected, thereby affecting the properties of the resulting foamed resin molded article. Furthermore, the polymerization reaction time of the styrene monomer is not particularly limited and can be adjusted according to the reaction conditions.

[0040] In the present invention, the polyethylene resin particles may include 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 be branched low-density polyethylene. Here, the so-called "low-density polyethylene" refers to a polyethylene having a density range of 0.915 g / cm 3 to 0.935g / cm 3 of polyethylene.

[0041] In the present invention, the styrene monomer may include, for example, styrene, methylstyrene, ethylstyrene, dimethylstyrene, methoxystyrene, n-butylstyrene, tert-butylstyrene, chlorostyrene, tribromostyrene, divinylbenzene, styrenesulfonic acid, sodium styrenesulfonate, or a combination thereof.

[0042] In the present invention, the mixture containing polyethylene resin particles may further include a suspending agent, a surfactant, a polymerization inhibitor, a solvent or a combination thereof in addition to the polyethylene resin particles.

[0043] In the present invention, a suspending agent can serve as a grinding agent or prevent the formation of lumpy resin. The suspending agent can 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. These suspending agents can be used alone or in combination. In one embodiment, sodium pyrophosphate (Na₄P₂Oₐ) and magnesium nitrate (Mg(NO₃)₂) can be used as the suspending agent. The reaction of these two suspending agents yields magnesium pyrophosphate (Mg₂P₂Oₐ(s)), but the present invention is not limited thereto.

[0044] In addition, the solid content of the amount of suspending agent used can be 0.05 to 10 parts by mass, for example 0.3 to 5 parts by mass, relative to 100 parts by mass of the aqueous medium of the suspension polymer system (for example, water as a solvent). When the amount of suspending agent used is too small, it is difficult to suspend and stabilize the styrene monomer, and a blocky resin may be generated. When the amount of suspending agent used is too much, the manufacturing cost is increased, and the distribution of particle size is also broadened.

[0045] In the present invention, the 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 alkyl benzenesulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecyl benzenesulfonate (SDBS) or sodium dodecylphenyloxide disulfonate. The above surfactants can be used alone or in combination of two or more. In one embodiment, the surfactant can be SDBS; however, the present invention is not limited thereto.

[0046] In the present invention, a polymer inhibitor can reduce the polystyrene content on the surface of the expandable resin particles. The polymer inhibitor can be an aqueous polymer inhibitor, such as sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, or citric acid. These polymer inhibitors can be used alone or in combination. In one embodiment, the polymer inhibitor can be sodium nitrite; however, the present invention is not limited thereto.

[0047] The aqueous polymer inhibitor hardly penetrates into the core particles (polyethylene resin particles) and dissolves in the aqueous medium. Thus, the droplet polymerization in the aqueous medium of the styrene monomer that is not impregnated into the core particles and the styrene monomer adsorbed near the surface of the core particles in the core particles can be suppressed, while the polymerization of the styrene monomer that is impregnated into the core particles is carried out. Therefore, the amount of polystyrene resin on the surface portion of the expandable resin particles can be reduced compared to the center portion.

[0048] The amount of the aqueous polymer inhibitor added may be 0.001 to 0.1 parts by mass, for example, 0.002 to 0.02 parts by mass, relative to 100 parts by mass of the aqueous medium (e.g., water as a solvent). If the amount of the aqueous polymer inhibitor is too high, the residual styrene monomer may increase, and a good foamed resin molded article formed from the foamable resin particles may not be obtained.

[0049] In the present invention, the polymerization initiator is used for the polymerization of polystyrene. The polymerization initiator can be a polymerization initiator used in the suspension polymerization method of styrene monomer, such as a peroxide. Specific examples of peroxides as polymerization initiators include, but are not limited to, cumene hydroperoxide, dicumyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxybenzoate (TBPB), benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, lauroylperoxide, and azo compounds (e.g., azobisisobutyronitrile). The above polymerization initiators can be used alone or in combination. In one embodiment, the polymerization initiator can be t-butyl peroxy-2-ethylhexanoate; in another embodiment, the polymerization initiator can be t-butyl peroxybenzoate; but the present invention is not limited thereto.

[0050] In addition, the amount of the polymerization initiator can be 0.01 to 3 parts by mass relative to 100 parts by mass of the styrene monomer. When the amount of the polymerization initiator is outside the aforementioned range, the content of the xylene insoluble component will be affected, thereby affecting the properties of the prepared foamed resin molded body.

[0051] In the present invention, the solvent may be water.

[0052] The present invention also provides a method for preparing styrene-modified polyethylene foamable resin particles, comprising the steps of: mixing the aforementioned styrene-modified polyethylene foamable resin particles with a blowing agent to perform a foaming process, thereby obtaining styrene-modified polyethylene foamable 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 may be carbon dioxide.

[0053] The present invention also provides a method for producing a foamed resin molded article, comprising the steps of: providing a mold; and filling the mold with the aforementioned styrene-modified polyethylene foamable resin particles to perform a molding process to obtain the foamed resin molded article. Specifically, the molding process includes heating the styrene-modified polyethylene foamable resin particles to perform secondary foaming, thereby fusing the particles together to form a single body, thereby obtaining a foamed resin molded article having a desired shape.

[0054] It should be noted that, in this specification, unless otherwise specified, "having a" component is not limited to having a single component, and may include one or more components.

[0055] In this specification, unless otherwise specified, the so-called feature A “or” feature B means that A exists alone or B exists alone; the so-called feature A “and / or” feature B means that A exists alone, B exists alone, or A and B exist simultaneously; the so-called feature A “and” feature B, feature A “and” feature B, or feature A “and” feature B means that A and B exist simultaneously; the so-called “include”, “comprise”, “have”, and “contain” means “including but not limited to”.

[0056] As used herein and unless otherwise indicated, the terms "about" or "approximately" refer to an acceptable error for a particular value as determined by one skilled in the art, which depends in part on how the value is measured or determined. In certain embodiments, the terms "about" or "approximately" mean within 1, 2, 3, or 4 standard deviations. In certain embodiments, the terms "about" and "approximately" mean 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. A given quantity is an approximate quantity, meaning that even without the specific indication of "about," "approximately," "substantially," or "substantially," the meaning of "about," "approximately," "substantially," or "substantially" may be implied. Furthermore, the phrases "ranging from a first value to a second value" or "ranging between a first value and a second value" mean that the range includes the first value, the second value, and any values therebetween.

[0057] Other novel features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A schematic cross-sectional view of the morphology detection of styrene-modified polyethylene foamable resin particles according to an embodiment of the present invention is shown;

[0059] Figure 2 A transmission electron microscope image of the surface area of the styrene-modified polyethylene foamable resin particles of Example 1 of the present invention is shown;

[0060] Figure 3 A transmission electron microscope image of the middle region of the styrene-modified polyethylene-based expandable resin particles of Example 1 of the present invention is shown.

[0061] [Description of Reference Numerals]

[0062] 1. Foamable resin particles;

[0063] 11a surface;

[0064] 11 surface area;

[0065] 12 middle area;

[0066] D1, D2 distance. DETAILED DESCRIPTION

[0067] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and effects of the present invention from the disclosure herein. The present invention may also be implemented or applied through other different specific embodiments, and the details in this specification may be modified and altered to suit different viewpoints and applications without departing from the spirit of the present invention.

[0068] The present invention will be further illustrated by way of examples, which are not intended to limit the scope of the invention. Unless otherwise indicated, in the following examples and comparative examples, temperatures are in degrees Celsius, and parts and percentages are by weight. Parts by weight are related to parts by volume in the same way that kilograms are related to liters.

[0069] Preparation of core particles-polyethylene resin particles

[0070] An extruder (Model ZE40A manufactured by Berstorff Corp.; L / D = 37.5 twin-screw extruder), polyethylene resin (trade name: "NA248", density 0.916 g / cm 3 , manufactured by Asia Polymer Corporation) were melt-kneaded at 230 to 250° C. and cut into 0.4 to 0.6 mg / piece (average 0.5 mg / piece) by a chain cutting method to obtain core particles (polyethylene resin particles).

[0071] Example 1

[0072] Preparation of styrene-modified polyethylene foamable resin particles

[0073] In a 20 L autoclave equipped with a stirring device ("Series 2246," manufactured by Amar Equipment Pvt. Ltd.), 8,000 g of deionized 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, and 1.2 g of sodium nitrite as an aqueous polymer inhibitor were added. Then, 600.0 g of the polyethylene resin core particles prepared above were added. The mixture was then stirred at 430 rpm at room temperature for 30 minutes.

[0074] Then, heating was started and the temperature was raised to 100° C. After reaching the temperature of 100° C., 13.8 g of tert-butylperoxy-2-ethylhexyl monocarbonate (trade name: E", manufactured by NOF Corp.) and 867.5 g of the first portion of styrene monomer were added to the autoclave. Then, the temperature was raised and maintained at 120°C for 3 hours (the first stage isothermal reaction temperature and time in Table 2).

[0075] After the temperature was lowered to 100° C., 2549.4 g of the second portion of styrene monomer was added to the autoclave. The temperature was then raised and maintained at 120° C. for 6 hours (the second stage of isothermal reaction temperature and time shown in Table 2).

[0076] After cooling, the contents were removed from the autoclave. The product was then dehydrated and washed using a centrifuge, and the water attached to the surface of the product was removed using a flash dryer to obtain styrene-modified polyethylene expandable resin particles with an average particle size of approximately 1.37 mm.

[0077] Example 2

[0078] Preparation of styrene-modified polyethylene foamable resin particles

[0079] The preparation method of the styrene-modified polyethylene foamable resin particles of this embodiment is similar to that of Example 1, except that 13.8 g of tert-butylperoxy-2-ethylhexyl monocarbonate as a second polymerization initiator is also added at the same time as the addition of 2550 g of the second styrene monomer; and the average particle size of the obtained styrene-modified polyethylene foamable resin particles is about 1.36 mm.

[0080] According to Table 1 and Table 2 below, styrene-modified polyethylene foamable resin particles of Examples 3 to 19 were prepared; the preparation method of styrene-modified polyethylene foamable resin particles of Examples 3 to 19 was similar to that of Example 1 or 2 and will not be repeated here.

[0081] Table 1: Raw materials and amounts used in Examples 1 to 19 (unit: gram (g))

[0082]

[0083]

[0084] Table 2: Reaction conditions and product characteristics of Examples 1 to 19

[0085]

[0086] *Solid content (SC) is calculated as follows:

[0087] SC (%) = (weight of styrene monomer + weight of core particles) / total weight of all components × 100% Preparation of styrene-modified polyethylene foamable resin particles

[0088] 5000g of the styrene-modified polyethylene foamable resin particles prepared in Examples 1 to 19 were respectively loaded into a 30L sealed container (pressure-resistant container) equipped with a stirrer together with 2000g of deionized water as a dispersion medium. In addition, 50g of kaolin as a dispersant and 50g of sodium alkylbenzene sulfonate as a surfactant were added to the dispersion medium. Next, while stirring the inside of the sealed container at a stirring speed of 300rpm, the temperature was raised to an expansion temperature of 166°C. Then, carbon dioxide (CO2) as an inorganic physical foaming agent was pressurized and injected into the sealed container so that the pressure inside the sealed container became 4.5 to 8.0MPa (G: gauge pressure). The foamable resin particles were impregnated with carbon dioxide and kept at the same temperature (166°C) for 30 minutes to obtain foamable resin particles. Next, the foamable resin particles were discharged from the sealed container together with the dispersion medium to atmospheric pressure to obtain a density of about 45kg / m 3 Styrene-modified polyethylene foamable resin particles.

[0089] Preparation of foamed resin molded body

[0090] First, the styrene-modified polyethylene foamable resin particles obtained above were allowed to stand at room temperature for one day. Next, using a molding machine (JSM-HVA-P-400 / 300, manufactured by Jiuh-Shin Machinery Co., Ltd.), the foamable resin particles were molded into a rectangular parallelepiped shaped article measuring 400 mm × 300 mm × 60 mm. The resulting article was dried at 60°C for one day and then allowed to stand at room temperature for at least one day.

[0091] Detection method for styrene-modified polyethylene foamable resin particles

[0092] Detection of xylene-insoluble components, acetone-insoluble components and swelling

[0093] First, take about 1g of expandable resin particles, weigh their weight (Wo) to the fourth decimal place, and place the weighed expandable resin particles in a 150-mesh mesh bag. Next, pour about 200ml of xylene into a 200ml round flask, and place the sample placed in the mesh bag in a Soxhlet extraction tube. Use a jacket heater to heat the flask for 24 hours to perform Soxhlet extraction. After extraction, cool the extraction tube naturally. After cooling, remove the wire mesh from the extraction tube and rinse the sample and mesh bag with about 600ml of acetone. Next, evaporate the acetone and dry the sample at 120°C. After drying, recover the sample from the mesh bag to obtain the "xylene insoluble component".

[0094] The xylene solution obtained after Soxhlet extraction was added to 600 ml of acetone. The acetone-insoluble components were then filtered using No. 5A filter paper as specified in JIS P3801 and evaporated to dryness under reduced pressure. The resulting solid matter was designated as the "acetone-insoluble component." Furthermore, the weight of the "xylene-insoluble component" and "acetone-insoluble component" was subtracted from the weight of the expandable resin particles (Wo) to obtain the weight of the "acetone-soluble component."

[0095] The mixed insoluble component of the "xylene-insoluble component" and the "acetone-insoluble component" obtained above was weighed to the fourth decimal place (Wa). It should be noted that in some examples, when the weight of the mixed insoluble component was less than 0.2 g, the above steps were repeated until 0.2 g or more of the mixed insoluble component was obtained to obtain a sufficient amount of the mixed insoluble component.

[0096] Next, the mixed insoluble matter was immersed in 50 ml of methyl ethyl ketone and maintained at 23°C for 24 hours. The mixed insoluble matter was then removed from the methyl ethyl ketone, gently wiped with filter paper, and the weight of the mixed insoluble matter (Wb) was measured to the fourth decimal place. The degree of swelling was then calculated using the following formula (1) based on the weight of the mixed insoluble matter before and after immersion in methyl ethyl ketone (Wb / Wa).

[0097] S = Wb / Wa (1)

[0098] Here, S is the degree of swelling, Wa is the weight of the mixed insoluble components before immersion in methyl ethyl ketone, and Wb is the weight of the mixed insoluble components after immersion in methyl ethyl ketone.

[0099] Weight average molecular weight of the non-crosslinked portion of the polystyrene resin (Mw)

[0100] Soxhlet extraction was performed in the same manner as described above. The extracted xylene solution was then added to 600 ml of acetone, washed, and evaporated to dryness under reduced pressure to obtain a polystyrene resin as an acetone-soluble component. The resulting acetone-soluble polystyrene resin was subjected to the following assay to determine the weight average molecular weight of the non-crosslinked portion of the polystyrene resin.

[0101] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polystyrene resin were measured using gel chromatography (GPC) (a mixed gel column for polymer measurement) using polystyrene as a standard substance. Specifically, a Waters APC instrument was used under the following conditions: eluent: tetrahydrofuran (THF), flow rate: 0.7 ml / min, sample concentration: 0.22 wt%, columns: 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 columns connected in series. More specifically, the acetone-soluble fraction of polystyrene resin was dissolved in tetrahydrofuran and measured using a gel chromatography analyzer. Calibration was performed using polystyrene standards to obtain the weight-average molecular weight and number-average molecular weight. This yields the polydispersity index (PDI), or Mw / Mn.

[0102] At 698cm -1 and 2850cm -1 The ratio of the absorbance (D 698 / D 2850 )

[0103] ATR infrared spectroscopy is widely used to analyze the surfaces of various substances, including organic substances such as polymers. Its detection method is quite simple. Just attach the sample and the ATR prism to analyze the spectrum from the surface to a depth of several microns.

[0104] The 698 cm-1 ray obtained from infrared absorption spectroscopy -1 Absorbance D 698 Refers to 698cm -1 The height of the peak appearing near 2850 cm is derived from the out-of-plane deformation vibration of the benzene ring mainly contained in the polystyrene resin. -1 Absorbance D 2850 Refers to the 2850cm -1 The height of the peak appearing near φ is derived from the stretching vibration between CH of the methylene groups contained in both the polyolefin-based resin and the polystyrene-based resin.

[0105] The absorbance ratio (D698 / D 2850 ) is determined as follows. The surface of 10 randomly selected expandable resin particles is analyzed by ATR infrared spectroscopy to obtain infrared absorption spectra. The absorbance ratio (D 698 / D 2850 ), and exclude the minimum absorbance ratio and the maximum absorbance ratio. Then, the arithmetic mean of the remaining 8 absorbance ratios is regarded as the absorbance ratio (D 698 / D 2850 For example, the absorbance ratio (D ) can be measured using a measuring device provided by Nicolet Instrument Corp. under the trade name "Thermo Scientific Nicolet iS10". 698 / D 2850 ).

[0106] Nuclear magnetic resonance (NMR) 13 C NMR)-polystyrene content (wt%)

[0107] About 0.3 g of sample was weighed into a 10 mm NMR tube and about 0.7 g of xylene was added. Oxygen was reduced by purging with nitrogen through the inserted pipette for 1 minute. The tube was capped and placed in the aluminum heating block of the sample preparation apparatus and heated at 105 ° C for two hours. The homogeneity of the sample was checked regularly and manually mixed as needed. It was obvious that the mixture was homogeneous by observing the uniform distribution of polymer in the solution, with no obvious high solvent concentration or air pockets. TM The data were collected using a JEOL JNM-ECZ400S / L1 400MHz HFX. The following experimental conditions were used for 13 C NMR, spectral width = 20000 Hz, relaxation delay = 10 s, scan number = 4000, and inverse gated decoupling with a sample temperature of 105°C. All measurements were performed in locked mode on non-rotating samples. The samples were allowed to thermally equilibrate for 10 minutes before data acquisition. Polyethylene (PE) was identified by the peak at 29-31 ppm, while polystyrene (PS) was identified by the peak at 145-148 ppm.

[0108] PE / PS relative content 13 The assigned chemical shifts (δ C ) calculation. For PS, δ at 145-148ppm C The quaternary carbon of the benzene ring, δ CThe two secondary carbon atoms (-CH2-) of PE are present. To convert the mole fraction to a weight fraction, multiply the mole fraction by the molecular weight of ethylene (28) and the molecular weight of styrene (140).

[0109] The formula and definition are as follows.

[0110] definition

[0111] PS(mole):δ C Integration of 145-148 ppm

[0112] PE(mole):δ C The integral of 29.0-31.2 ppm is divided by 2

[0113] PS (wt): PS moles multiplied by styrene molecular weight

[0114] PE (wt): PE moles multiplied by ethylene molecular weight

[0115] formula

[0116] PS(wt%):[PS(wt) / PS(wt)+PE(wt)]×100%

[0117] PE(wt%):[PE(wt) / PS(wt)+PE(wt)]×100%

[0118] Morphology Analysis of Styrene-Modified Polyethylene Expandable Resin Particles

[0119] A styrene-modified polyethylene foamable resin particle was cut in half from its surface through the middle using a cutting machine to obtain a test sample. The test sample was then embedded in epoxy resin, stained with ruthenium tetraoxide, and ultrathin sections were prepared using an ultramicrotome.

[0120] Figure 1 The figure is a schematic cross-sectional view of the morphology of styrene-modified polyethylene foamable resin particles according to an embodiment of the present invention. The region from approximately 1.5 μm (i.e., distance D1 of approximately 1.5 μm) from the surface 11a of the foamable resin particle 1 to the surface 11a of the foamable resin particle 1 is the surface region 11 of the foamable resin particle 1, and the region from at least approximately 500 μm (i.e., distance D2 of approximately 500 μm) from the surface 11a of the foamable resin particle 1 (to the center of the foamable resin particle) is the middle region 12 of the foamable resin particle 1.

[0121] The ultrathin section was placed on a grid, and a cross-sectional photograph (transmission electron microscope (TEM) image) was taken at a magnification of 3000 times or 10000 times using a transmission electron microscope (JEM-2100F manufactured by JEOL Ltd.), and the cross-sectional morphology of the surface region 11 and the middle region 12 of the expandable resin particle 1 was observed. From the TEM image, the morphology of the polyethylene resin (PE) phase and the polystyrene resin (PS) phase in the expandable resin particle 1 was visually observed. For example, Figure 2 and Figure 3 As shown, they are TEM images of the surface area and the central area of the styrene-modified polyethylene foamable resin particles of Example 1 below, respectively. It can be observed that the polystyrene resin is dispersed in the polyethylene resin in the form of particles, and the polystyrene resin particles include spherical, elliptical, quasi-spherical, quasi-elliptical or other irregular particles.

[0122] In addition, the extracted images were analyzed using image processing software (MacView from MOUNTECH Co., Ltd.). The particle size and number of the polystyrene resin particles were recorded to obtain a distribution curve of the particle size (X-axis) and number (Y-axis) of the polystyrene resin particles. The average particle diameter and standard deviation, as well as the skewness and kurtosis of the particle size and number distribution curve were calculated.

[0123] The standard deviation is used to calculate the degree of dispersion from the average particle size, usually expressed as s, which is the sample variation (expressed as s 2 ). Calculated as follows.

[0124]

[0125] in, N is the number of samples, w i is the weight term (=1 means that all weights are the same), x i is the i-th value, is the weighted mean.

[0126] The skewness of the particle size versus number distribution curve is based on the third moment about the mean (ie, the average particle size) and is calculated as follows.

[0127]

[0128] Where N is the number of samples, w i is the weight item (=1 means that all items have the same weight), x i is the i-th value, is the mean value and s is the standard deviation.

[0129] If the data distribution is symmetrical, the skewness is 0. If the skewness is greater than 0, the distribution is right-skewed, that is, the distribution has a long tail on the right; if the skewness is less than 0, the distribution is left-skewed, that is, the distribution has a long tail on the left; at the same time, the larger the absolute value of the skewness, the more serious the degree of deviation of the distribution.

[0130] The kurtosis of the particle size versus number distribution curve is based on the fourth moment about the mean (ie, the average particle size) and is calculated as follows.

[0131]

[0132] Where N is the number of samples, w i is the weight term (=1 means that all weights are the same), x i is the i-th value, is the mean, and s is the standard deviation. Using this formula, the kurtosis of a normal distribution is 0. This formula is often referred to as excess kurtosis.

[0133] If the kurtosis is close to 0, it means that the kurtosis of the distribution is normal; if the kurtosis is greater than 0, it means that the kurtosis of the distribution is steep (high and pointed); if the kurtosis is less than 0, it means that the kurtosis of the distribution is flat (short and fat).

[0134] Testing methods for foamed resin molded bodies

[0135] Compressive strength at strains of 10%, 25%, 50%, and 75%, and compression set at a strain of 50% are measured according to ASTM D3575. Flexural strength and flexural modulus can be measured according to ASTM D790IA. Furthermore, tensile strength and elongation can be measured according to ISO 1798:2008.

[0136] The analysis results of the polystyrene resin particles in the surface region and the middle region of the styrene-modified polyethylene-based expandable resin particles are shown in Tables 3 and 4 below.

[0137] Table 3: Surface area analysis results of polystyrene resin particles

[0138]

[0139]

[0140] Table 4: Analysis results of polystyrene resin particles in the middle area

[0141]

[0142]

[0143] The statistical results of the average particle size and standard deviation of the polystyrene resin particles in the surface area and the middle area of the styrene-modified polyethylene foamable resin particles, as well as the skewness and kurtosis of the distribution curve of the particle size and number are shown in Table 5 below.

[0144] Table 5: Statistical results of the average particle size and standard deviation of polystyrene resin particles, as well as the skewness and kurtosis of the distribution curve of particle size and number

[0145]

[0146]

[0147] The test results of the styrene-modified polyethylene foamable resin particles and the foamed resin molded bodies prepared therefrom are shown in Tables 6 and 7 below, respectively.

[0148] Table 6: Test results of styrene-modified polyethylene foamable resin particles

[0149]

[0150] Table 7: Test results of foamed resin molded articles

[0151]

[0152]

[0153] The above results show that when the average particle size of the polystyrene resin particles in the surface area and the middle area of the styrene-modified polyethylene foamable resin particles is between a specific range, the foamed resin molded body prepared under this condition has appropriate rigidity and compression recoverability. When the skewness or kurtosis of the distribution curve of the particle size and number of the polystyrene resin particles in the surface area and the middle area of the styrene-modified polyethylene foamable resin particles is between a specific range, the foamed resin molded body prepared under this condition has appropriate rigidity and compression recoverability. When the content of the xylene insoluble component, the content of the acetone insoluble component, the ratio thereof or the sum thereof of the styrene-modified polyethylene foamable resin particles is between a specific range, the foamed resin molded body prepared under this condition has appropriate rigidity and compression recoverability. In addition, when the swelling degree of the styrene-modified polyethylene foamable resin particles, the molecular weight of the non-crosslinked part of the polystyrene resin, or the absorbance ratio (D 698 / D 2850 ) is within a specific range, the foamed resin molded article produced under these conditions can also have appropriate rigidity and compression recoverability. Therefore, the styrene-modified polyethylene-based expandable resin particles, expandable resin particles, and foamed resin molded articles provided by the present invention can improve the shortcomings of polystyrene foamed resin molded articles, such as the poor recovery after compression, and the insufficient rigidity of polyethylene foamed resin molded articles. Thus, they can be used in various cushioning materials, such as those used in containers or transportation equipment.

[0154] Although the present invention provides related embodiments, it should be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as claimed.

Claims

1. A styrene-modified polyethylene foamable resin particle comprising: Polyethylene resin and polystyrene resin; The invention is characterized in that, based on 100 wt % of the polyethylene resin and the polystyrene resin, the content of the polyethylene resin is 5 wt % to 30 wt %, and the content of the polystyrene resin is 70 wt % to 95 wt %; Wherein, polystyrene resin is dispersed in polyethylene resin in the form of particles; In the surface region of the expandable resin particles, the average particle size of the polystyrene resin particles is between 0.02 μm and 0.15 μm, wherein the surface region of the expandable resin particles is an area from 1.5 μm to the surface of the expandable resin particles; In the middle region of the expandable resin particle, the average particle size of the polystyrene resin particles is between 0.20 μm and 0.60 μm, wherein the middle region of the expandable resin particle is a region at least 500 μm away from the surface of the expandable resin particle.

2. The expandable resin particles according to claim 1, wherein In the surface region of the expandable resin particles, the number of polystyrene resin particles having a particle diameter of 0.01 μm to 0.1 μm accounts for 50% or more of the total number of polystyrene resin particles.

3. The expandable resin particles according to claim 1, wherein In the surface region of the expandable resin particles, the number of polystyrene resin particles having a particle diameter of 0.02 μm to 0.08 μm accounts for 50% or more of the total number of polystyrene resin particles.

4. The expandable resin particles according to claim 1, wherein In the middle region of the expandable resin particles, the number of polystyrene resin particles having a particle diameter of 0.1 μm to 0.6 μm accounts for 70% or more of the total number of polystyrene resin particles.

5. The expandable resin particles according to claim 1, wherein In the middle region of the expandable resin particles, the number of polystyrene resin particles having a particle diameter of 0.2 μm to 0.5 μm accounts for 60% or more of the total number of polystyrene resin particles.

6. The expandable resin particles according to claim 1, wherein In the surface region of the expandable resin particles, the skewness of the distribution curve of the particle size and number of the polystyrene resin particles is between -0.5 and 8.

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

8. The expandable resin particles according to claim 1, wherein In the middle region of the expandable resin particles, the skewness of the distribution curve of the particle size and number of the polystyrene resin particles is between -0.7 and 0.

7.

9. The expandable resin particles according to claim 1, wherein In the middle region of the expandable resin particles, the kurtosis of the distribution curve of the particle size and number of the polystyrene resin particles is between -1.0 and 2.

5.

10. The expandable resin particles according to claim 1, wherein The expandable resin particles include a xylene insoluble component and an acetone insoluble component, and the ratio of the xylene insoluble component to the acetone insoluble component is between 0.01 and 5.

11. The expandable resin particles according to claim 10, wherein The content of the acetone insoluble component is between 10 wt % and 60 wt %.

12. The expandable resin particles according to claim 10, wherein The content of the xylene insoluble component is less than or equal to 70 wt %.

13. The expandable resin particles according to claim 10, wherein The total content of the acetone insoluble component and the xylene insoluble component is between 40 wt % and 90 wt %.

14. The expandable resin particles according to claim 1, wherein The expandable resin particles have a degree of swelling less than or equal to 2.

5.

15. The expandable resin particles according to claim 1, wherein The polystyrene resin has a non-crosslinking portion, and the molecular weight of the non-crosslinking portion is between 30,000 and 80,000.

16. The expandable resin particles according to claim 1, wherein The infrared absorption spectrum of the surface of the expandable resin particles is at 698 cm -1 and 2850cm -1 The absorbance ratio is greater than or equal to 1.

0.

17. A styrene-modified polyethylene foamable resin particle, characterized in that: The foamable resin particles according to claim 1 are obtained by subjecting the foamable resin particles to a foaming process.

18. A foamed resin molded body, characterized in that: The foamable resin particles according to claim 17 are obtained by a molding process.

19. The foamed resin molded article according to claim 18, wherein Can be used as material for loading containers or transport devices.

20. A method for preparing expandable resin particles according to claim 1, characterized in that: The preparation method comprises the following steps: providing a mixture comprising polyethylene resin particles; and The mixture containing polyethylene resin particles is mixed with a styrene monomer and a polymerization initiator to obtain the expandable resin particles according to claim 1.

21. The preparation method according to claim 20, characterized in that The mixture containing the polyethylene resin particles is mixed with a styrene monomer and a polymerization initiator, and then heated to 115° C. to 125° C. to obtain the expandable resin particles according to claim 1 .

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