Foam bead and method for manufacturing the same

Abstract

To provide: a foam bead designed to inhibit deterioration of cushioning properties even when used for a long period of time or used repetitively; and a method for manufacturing the foam bead.SOLUTION: A foam bead is a bead for a cushion loaded into a cushion, a pillow, or the like. The foam bead is obtained by foaming a resin bead impregnated with an organic blowing agent. The foam bead has a mean particle diameter of 0.5-5.0 mm, and is not subjected to mechanical rotary processing during particle transportation. The foam bead has an expansion ratio of 30-45 times, and a settling rate of 8.0% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to foam beads and a method for producing the same. [Background technology]

[0002] Resin foams such as polystyrene foam are excellent in terms of light weight, cushioning properties, and moldability, and are used in various industrial fields such as containers for agricultural and marine products, cushioning materials for various products, and building materials. Resin foams are obtained by molding foam beads in a mold. In recent years, the foam beads themselves have also been used as cushion beads for cushions and pillows, and demand for them is increasing.

[0003] A bead cushion is known, which is made by filling a sewn bag with foamed beads. When using this type of cushion, the foamed beads inside flow due to body pressure, and disperse the body pressure by deforming to fit the shape of the body. As a result, it creates a snug fit that envelops the body, providing comfort.

[0004] Expanded beads are generally produced through an expansion step in which raw material beads (expandable particles) are expanded, a granulation step, and an aging step (see, for example, Patent Document 1). The outline of this production method will be described with reference to FIG.

[0005] In FIG. 7, the expansion step is first performed using a pre-expansion machine 21. The raw material beads are resin beads impregnated with an organic foaming agent such as pentane or butane. The pre-expansion machine 21 has an input hopper 22, a pre-expansion tank 23, an agitator 24, and a motor 25 for rotating the agitator 24. The raw material beads input from the input hopper 22 into the pre-expansion tank are expanded to a predetermined expansion ratio by being heated by steam at atmospheric pressure or under pressure while being agitated by the agitator 24. The obtained expanded particles are discharged from a discharge port 23a provided at the bottom of the pre-expansion tank 23 to a discharge hopper 26.

[0006] In the subsequent granulation process, the obtained expanded particles are sent to a silo 29. The discharge hopper 26 and the silo 29 are connected by a granulation pipe 27, and the expanded particles are delivered by a granulation blower 28 with fins. The granulation blower 28 is provided midway through the granulation pipe 27, and has a rotor 28a such as a fin. The expanded particles introduced into the granulation pipe 27 are mechanically rotated by the rotation of the rotor 28a of the granulation blower 28, delivered to the silo 29, and supplied into the silo from a supply port 30 provided in the ceiling of the vertical silo 29.

[0007] The foamed beads supplied to the silo 29 contain not only air but also organic gas (such as butane gas) derived from the organic foaming agent. Therefore, in the silo 29, maturation is carried out to replace the organic gas with air. The maturation period is about one to two days. After maturation, the foamed beads are taken out from an outlet 31 provided at the bottom of the silo 29. These foamed beads are used as a raw material for resin foams or as a filler for cushions, etc. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-5256 Summary of the Invention [Problem to be solved by the invention]

[0009] For example, the average particle size of cushion beads is about 0.5 mm to 5.0 mm from the viewpoint of the fit to the body and internal fluidity. When a bead cushion filled with such cushion beads is used for a long time or repeatedly, the foamed beads inside are subjected to load each time. As a result of the repeated load, the foamed beads may become sagging, leading to a decrease in cushioning properties.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide foamed beads in which the decrease in cushioning properties is suppressed even after long-term or repeated use, and a method for producing the same. [Means for solving the problem]

[0011] The foamed beads of the present invention are formed by foaming resin beads impregnated with an organic foaming agent, and are characterized in that the foamed beads have an average particle size of 0.5 mm or more and 5.0 mm or less and are not subjected to a mechanical rotation process during feeding.

[0012] In the present invention, the term "not having been subjected to a mechanical rotation treatment during feeding" means that the expanded beads have not been subjected to a treatment in which the expanded beads pass through a rotating rotor during feeding and are subjected to mechanical shear stress by violently colliding with the rotor body or the surrounding pipe wall surface. The absence of such treatment can be confirmed, for example, by observing the presence or absence of wrinkles on the surface of the beads using an electron microscope.

[0013] The above-mentioned expanded beads are characterized in that the expansion ratio is 30 to 45 times and the settling rate is 8.0% or less.

[0014] The foamed beads are characterized in that they are beads for cushioning.

[0015] The method for producing the expanded beads of the present invention is a method for producing the expanded beads of the present invention, which comprises an expansion step in which the resin beads impregnated with the organic blowing agent are expanded to form expanded beads, a feeding step in which the expanded beads are fed to a silo, and an aging step in which the fed expanded beads are aged in the silo to obtain the expanded beads, and is characterized in that in the feeding step, the expanded beads are fed without being subjected to mechanical rotation processing by a rotating body in the feeding path to the silo.

[0016] The silo has an exhaust device that sucks in air within the silo and exhausts it to the outside, and the expanded particles are fed while the air within the silo is sucked in by the exhaust device.

[0017] The foamed particles are supplied from a supply port provided on a side surface of the silo, and the exhaust device is provided on the side surface of the silo.

[0018] In the above-mentioned pelletizing step, the expanded pellets are fed at a temperature of 40°C to 80°C. Effect of the Invention

[0019] The foamed beads of the present invention are made by foaming resin beads impregnated with an organic foaming agent, have an average particle size of 0.5 mm to 5.0 mm, and are not subjected to mechanical rotation processing during feeding, so that the surface of the beads is prevented from being scratched by mechanical shear stress during the processing. This prevents the beads from becoming easily worn down due to scratches, and the foamed beads have reduced deterioration of cushioning properties even after long-term or repeated use. These foamed beads are particularly suitable for cushioning beads.

[0020] The above-mentioned expanded beads have an expansion ratio of 30 to 45 times and a settling rate of 8.0% or less, so that settling during repeated use can be suitably suppressed, as shown in the examples described later.

[0021] The method for producing expanded beads of the present invention includes an expansion step, a granulation step, and an aging step, and in the granulation step, the expanded beads are transported without being subjected to mechanical rotation processing by a rotor in the granulation path to the silo, so that the beads are prevented from being subjected to mechanical shear stress during the processing, which would cause scratches on the surface of the beads. This prevents the beads from becoming easily sagging due to scratches, and expandable beads having reduced cushioning properties can be obtained even after long-term or repeated use.

[0022] The silo has an exhaust device that sucks in air inside the silo and exhausts it to the outside, and the expanded particles are fed while the exhaust device sucks in the air inside the silo, so that the fluidity of the expanded particles is easily maintained when fed. In addition, the expanded particles are supplied from a supply port provided on a side surface of the silo, and the exhaust device is provided on the same side surface of the silo, so that the suction force of the exhaust device can be easily applied to the expanded particles, making it easy to feed the expanded particles to the silo.

[0023] In the above-mentioned granulation step, the expanded beads are granulated at a temperature of 40° C. to 80° C., which helps to reduce the odor of the expanded beads. In addition, granulation at a high temperature makes the expanded beads susceptible to damage and deformation due to impact during granulation, but the manufacturing method of the present invention helps to prevent such phenomena. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a process schematic diagram showing an example of a method for producing foamed beads of the present invention. [Diagram 2] 1 is an overall schematic diagram showing an example of a method for producing foamed beads of the present invention. FIG. [Diagram 3] FIG. 2 is a schematic cross-sectional view of the silo of FIG. [Figure 4] FIG. 2 is a schematic cross-sectional view showing another embodiment of the silo. [Diagram 5] FIG. 1 is a schematic diagram showing a sag test of foam beads. [Figure 6] FIG. 2 is a diagram showing electron microscope photographs of the foamed beads of Example 1 and Comparative Example 1. [Figure 7] FIG. 1 is a schematic diagram of a conventional method for producing foam beads. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The foamed beads of the present invention are foamed beads obtained by foaming resin beads impregnated with an organic foaming agent. The average particle size of the foamed beads is 0.5 mm or more and 5.0 mm or less, and preferably 0.5 mm or more and 3.0 mm or less. The average particle size is the particle size at which the cumulative value is 50% when the particle size distribution is a cumulative distribution on a volume basis, and is a value measured by a laser diffraction / scattering method.

[0026] The foamed beads of the present invention are particularly suitable as beads for cushions. Beads for cushions are roughly classified into small particle types with an average particle size of 0.5 mm or more and less than 1.0 mm, and large particle types with an average particle size of 1.0 mm or more and 3.0 mm or less. The large particle types are more likely to have their surfaces scratched during feeding than the small particle types due to their size, but the foamed beads of the present invention are not subjected to mechanical rotation processing during feeding, so even such large particle type foamed beads are more likely to be prevented from becoming worn.

[0027] The fact that the expanded beads have not been subjected to mechanical rotation processing during feeding can be confirmed, for example, by observing the expanded beads with an electron microscope. For example, if no wrinkles are found on the surface of the expanded beads when magnified 80 times with an electron microscope, it can be determined that the expanded beads have not been subjected to mechanical rotation processing. These wrinkles refer to grooves with a certain depth or more that are formed on the surface of the expanded beads.

[0028] The expansion ratio of the expanded beads of the present invention is, for example, 30 to 70. Since the resistance to settling decreases as the expansion ratio increases, the expansion ratio is preferably 30 to 50, more preferably 30 to 45, may be 30 to 40, or may be 35 to 40.

[0029] The settling rate of the foamed beads is, for example, less than 8.5%, and more preferably 8.0% or less. The lower limit of the settling rate is, for example, 4.0%, and preferably 5.0%. The settling rate is measured by the method described in the Examples below.

[0030] A preferred form of the expanded beads is one in which the expansion ratio is 30 to 45 times and the settling rate is 8.0% or less.

[0031] Fig. 1 is a process schematic diagram showing an example of the method for producing expanded beads of the present invention. The production method in Fig. 1 includes (1) an expansion step in which resin beads impregnated with an organic blowing agent are expanded to form expanded beads, (2) a disintegration step in which blocked expanded beads are disintegrated, (3) a granulation step in which the expanded beads are sent to a silo, and (4) an aging step in which the sent expanded beads are aged in the silo to obtain expanded beads. The disintegration step may be omitted as necessary.

[0032] The resin beads (expandable particles) used as the raw material in the above manufacturing method can be obtained by impregnating a thermoplastic resin with an organic blowing agent using a known method. For example, polystyrene resin beads impregnated with the organic blowing agent can be obtained by stirring and polymerizing styrene monomer in water and adding the organic blowing agent thereto.

[0033] Examples of the thermoplastic resin include polystyrene resins, polyolefin resins such as polypropylene resins and polyethylene resins, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polylactic acid, polycarbonate resins, and copolymers thereof. In addition, a combination of multiple resins can be used as the thermoplastic resin. For example, a combination of polystyrene resins and polyolefin resins can be used.

[0034] Examples of organic blowing agents include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, and hexane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; halogenated hydrocarbons such as ethyl chloride and methylene chloride; and dialkyl ethers such as dimethyl ether and diethyl ether.

[0035] The resin beads may further contain, as additives other than the thermoplastic resin and the organic foaming agent, a cell regulator, an antioxidant, a colorant, a lubricant, a flame retardant, etc. Commercially available products may also be used as the resin beads used in the present invention.

[0036] Each step will be described below with reference to FIG.

[0037] (1) Foaming process In this step, the resin beads are expanded to form expanded particles. The expansion method used in the present invention is not particularly limited, and any known method can be used. For example, there is a method of heating the resin beads with steam or the like to expand and expand the organic foaming agent dissolved in the resin beads (heat expansion), and a method of suddenly releasing the atmosphere from a high pressure to a low pressure to expand and foam the organic foaming agent dissolved in the resin beads.

[0038] The foaming conditions are not particularly limited as long as they can foam the resin to the above-mentioned predetermined range of foaming ratio, and the pressurizing conditions, heating conditions, etc. The foaming ratio is determined by the amount of resin beads added, heating time, etc.

[0039] In the expansion process shown in FIG. 2, a pre-expanding machine 1 is used to perform heat expansion. The pre-expanding machine 1 has an input hopper 2, a pre-expanding tank 3, an agitating blade 4, and a motor 5 for rotating the agitating blade 4. After the resin beads A are input from the input hopper 2 into the pre-expanding tank, steam or a mixture of steam and air is introduced into the pre-expanding tank 3 while stirring with the agitating blade 4, and heating is continued under certain conditions. After the resin beads A reach a predetermined expansion ratio, heating is stopped. For example, the resin beads are heated at 80°C to 95°C under steam pressure. Then, the expanded beads B are discharged from a discharge port 3a provided at the bottom of the pre-expanding tank 3 into a discharge hopper 6. Immediately after discharge, the expanded beads B are blocked.

[0040] (2) Granulation process This step is a step of deflocculating the blocked expanded particles B. The deflocculating method is not particularly limited, but for example, the particles are deflocculated by stirring with a stirrer 6a provided in the discharge hopper 6. The particle temperature of the expanded particles B is about 80°C in the pre-expanding tank 3, but immediately after discharge, it is lowered to, for example, about 50°C to 60°C by stirring at room temperature, and then the particles are introduced into the particle sending pipe 7.

[0041] (3) Particle sending process This process is a process of sending the expanded particles to a silo. As shown in Fig. 2, the discharge hopper 6 and the silo 9 are connected by a particle sending pipe 7. A blower 8 for sending compressed air is provided at the end of the particle sending pipe 7 on the discharge hopper side. The expanded particles B introduced into the particle sending pipe 7 are air-fed while being suspended only by air.

[0042] In Figure 2, the blower 8 is provided at the end of the granulation pipe 7, and no rotating body (e.g., fins) is provided along the granulation path of the granulation pipe 7 through which the expanded beads pass. Therefore, unlike the conventional technology shown in Figure 7, this manufacturing method is configured such that the expanded beads are not subjected to a mechanical rotation process during granulation. Also, while a rotating body (e.g., fins) is sometimes provided at the supply port 10 in the conventional technology, this is not provided in this manufacturing method. Therefore, the number of collisions and impacts that the expanded beads B receive during granulation are reduced, making them less likely to be scratched.

[0043] In addition, the expanded particles can be fed smoothly by sucking air from inside the silo with the exhaust device 12 installed in the silo. In addition, the exhaust device 12 is preferably installed near the supply port 10, taking into consideration the air flow caused by the exhaust device 12.

[0044] In the granulation step, the expanded particles B are preferably granulated at a temperature three to four times higher than room temperature. Specifically, it is preferable to granulate the expanded particles B to the silo 9 at 40°C to 80°C (more preferably 50°C to 60°C). The particle temperature of the expanded particles B when they are moved from the discharge hopper 6 to the granulation pipe 7 is about 50°C to 60°C, and they are supplied to the silo 9 while maintaining this temperature. When they are moved from the discharge hopper 6 to the granulation pipe 7, the expanded particles B are in a wet state due to the moisture of steam. If they are dried at room temperature in the silo while remaining in a wet state, odorous components derived from the organic blowing agent contained in the moisture are likely to adhere to the surface of the particles. Therefore, by sending the expanded particles at a temperature higher than room temperature, they are easily dehydrated completely before being put into the silo 9 (for example, just before being put into the silo 9), and the odor of the expanded beads is easily reduced.

[0045] As described above, the purpose of feeding the expanded particles at a high temperature is to vaporize and dry the wet expanded particles all at once. For example, as described below, by providing an exhaust device 12 such as a ventilation fan near the supply port 10 of the silo 9, it is possible to create an air flow to the outside and simultaneously dehydrate and deodorize the expanded particles B just before feeding them into the silo 9. Since the expanded particles fed are at a high temperature and the flow of air at room temperature promotes their vaporization, the configuration with the exhaust device 12 is preferable in terms of dehydration and deodorization as well as smooth feeding.

[0046] It is preferable that the granule transport pipe 7 has a thermal insulation structure up to the supply port 10. For example, a thermal insulation pipe having a thermal insulation layer may be used as the granule transport pipe 7, or the outer periphery of the granule transport pipe 7 may be covered with a thermal insulation material. In addition, it is preferable that the blower 8 is provided with a heater function so as to be able to blow hot air of about 40°C to 80°C.

[0047] (4) Aging process In this process, the expanded beads B are dried while being aged in the silo 9 to obtain expanded beads C. In FIG. 2, the silo 9 is a horizontal type extending horizontally and has a substantially rectangular parallelepiped shape extending in the X direction. The X direction in FIG. 2 is the extension direction. In the silo 9, a supply port 10 is provided at one end side in the extension direction, and an outlet 11 is provided at the other end side in the extension direction. In this maturing process, the expanded beads B are supplied from the supply port 10 at one end side, and the expanded beads C are taken out from the outlet 11 at the other end side. As described above, the expanded beads B are preferably fed into the silo 9 in a high temperature and dehydrated state by being fed at a high temperature. In the maturing process, the expanded beads B are also cooled and further dried.

[0048] As an example of the operation of the aging process, the expanded beads B are supplied to the silo 9, leaving about 10 to 50% of the internal volume of the silo. The expanded beads B are then aged in the silo for about 24 to 48 hours. This aging process is preferably performed while exhausting the air in the silo with an exhaust device 12 described later. The aging process is not limited to a batch process, and may be performed continuously. For example, the aging process may be performed continuously by repeatedly feeding a portion of the expanded beads and removing a portion of the expanded beads in a certain time cycle. In the case of a continuous process, the expanded beads in the silo gradually move in a substantially horizontal direction from one end to the other end. In the case of a continuous process, it is also preferable that the fed expanded beads are aged in the silo for about 24 to 48 hours.

[0049] The structure of the silo will be further described with reference to FIG. 3. FIG. 3 is a schematic cross-sectional view of the silo in FIG. 2, showing the state during the maturation period. The material of the silo 9 may be metal or resin. The internal volume of the silo 9 is not particularly limited, but may be, for example, 100 m 3 ~500m 3 It is.

[0050] As shown in Fig. 3, the supply port 10 is provided on a side surface 9a, which is one end of the silo 9 in the extension direction. In this case, the foamed particles are supplied to the silo 9 from the side. On the other hand, the discharge port 11 is provided on the other end of the silo 9 in the extension direction, specifically, on a bottom 9c near a side surface 9b, which is the end opposite to the side surface 9a. The discharge port 11 is provided with an openable and closable lid or the like.

[0051] A part of the bottom surface 13 inside the silo 9 is inclined downward toward the outlet 11. Due to such an inclination, the foamed particles can easily move toward the outlet 11 even though the silo 9 is a horizontal type.

[0052] Moreover, the silo 9 preferably has an exhaust device 12 that exhausts the air inside to the outside. In Fig. 2, the exhaust device 12 is provided directly below the supply port 10 on the side surface 9a. This creates a flow of air to the outside, and for example, the expanded particles can be simultaneously dehydrated and deodorized just before they are fed into the silo 9. Furthermore, since the vaporized organic gas has a high specific gravity, the organic gas can be efficiently exhausted by the exhaust device 12 directly below the supply port 10.

[0053] The height at which the exhaust device 12 is installed in the silo 9 is not particularly limited, but it is preferable that the exhaust device 12 is installed in a height region where the foamed particles do not accumulate, since air flow is likely to occur within the silo. For example, the exhaust device 12 is installed in a height region that is 1 / 3 or more of the height of the side surface 9a on one end side of the silo 9. This height region may be 1 / 2 or more, or 2 / 3 or more, of the height of the side surface 9a. The exhaust device 12 blows air on the foamed particles before they cool (while they are still at a high temperature), making it easier to remove organic gases.

[0054] Even if the exhaust device 12 is provided at a height where the foamed beads are accumulated, the air is exhausted through the gaps between the foamed beads, so that a large amount of air can come into contact with the foamed beads. As a result, it is considered that the organic gas remaining in the foamed beads can be easily removed.

[0055] As the exhaust device 12, for example, an exhaust fan (ventilation fan) such as a propeller fan or a sirocco fan can be used.

[0056] The horizontal dimension L (length along the extension direction) of the silo 9 is, for example, 5 m to 30 m, and preferably 10 m to 30 m. The horizontal dimension L is larger than the vertical dimension (length along the vertical direction), and the ratio of the vertical dimension to the horizontal dimension L is, for example, (1:2) to (1:6), and preferably (1:2.5) to (1:5).

[0057] Figure 4 shows a schematic cross-sectional view of another type of silo. Silo 9A shown in Figure 4(a) is rectangular parallelepiped, and a bottom member 14 is provided inside the silo. This results in a configuration in which a part of the bottom surface inside the silo is inclined downward toward the outlet 11. In Figure 4(a), the bottom surface 13 inside the silo is composed of a flat surface and an inclined surface.

[0058] In addition, the silo 9B shown in FIG. 4(b) has a different position of the supply port 10 and the discharge port 11 from the silo 9 shown in FIG. 3. In the silo 9B, the supply port 10 is provided at one end side in the extension direction, specifically, in the ceiling part 9d near the side surface 9a. In addition, an exhaust device 12 is provided near the supply port 10 at the upper part of the side surface 9a. In addition, the discharge port 11 is provided at the side surface 9b, which is the other end in the extension direction. In the silo 9B, the bottom surface 13 inside the silo is formed only of an inclined surface, and the entire bottom surface 13 is inclined downward from one end side to the other end side, and is excellent in dischargeability. In addition, the bottom surface 13 inside the silo may be formed of a plurality of inclined surfaces with different inclination angles.

[0059] The configurations of the silo used in the maturation step are shown in Figures 3 and 4, but the configurations (such as the arrangement of the supply port and the discharge port) in these configurations can be combined with each other. The silo is not limited to the configurations shown in Figures 3 and 4, and for example, the silo may be provided with a vent hole penetrating the inside and outside of the silo. In this case, for example, the vent hole may be provided on the opposite side to the position where the exhaust device is provided (for example, side surface 9b in Figure 3).

[0060] The silo may be of a vertical type extending vertically as shown in Fig. 7. A horizontal type is preferable from the viewpoint of increasing the area where the expanded beads come into contact with the air in the silo, promoting the replacement of the organic gas remaining in the expanded beads with air, and reducing the odor of the expanded beads, while a vertical type is preferable from the viewpoint of saving space relative to the site area, for example.

[0061] The method for producing foamed beads of the present invention is not limited to the embodiment shown in the drawings above. EXAMPLES

[0062] Example 1 After polystyrene resin beads were expanded at an expansion ratio of 38 times in a preliminary expansion tank, the expanded particles were sent to the configuration shown in Figure 2 and aged in a silo for 24 to 48 hours to obtain expanded beads that were not subjected to mechanical rotation treatment during the sending process. The average particle size of the expanded beads was 0.5 mm to 3.0 mm.

[0063] Comparative Example 1 After polystyrene resin beads were expanded at an expansion ratio of 38 times in a preliminary expansion tank, the expanded particles were sent to the configuration shown in Figure 7 and aged in a silo for 24 to 48 hours to obtain expanded beads that were subjected to a mechanical rotation treatment during the sending process. The average particle size of the expanded beads was 0.5 mm to 3.0 mm.

[0064] [Settling test] Using the foamed beads obtained above, a sag test was carried out according to the following procedure. The outline of the test is shown in Figure 5. 1: 330 ml of foam beads were placed in a cylindrical container (φ78 mm). 2: A compressive load of 650 N (66.3 kgf) was applied to the foamed beads 16 from the upper part of the cylindrical container 15 at a compression speed of 10 mm / min. 3: The above procedure was repeated 100 times. 4: After step 3 above was completed, the foamed beads were transferred to a measuring cylinder and the volume was measured. The settling rate was calculated using the following formula. The calculated settling rates are shown in Table 1. Settling rate (%) = (volume reduction / volume before test) x 100

[0065] [Table 1]

[0066] As a result of the above sag test, although the expansion ratio was the same, the sag rate was reduced in Example 1 compared to Comparative Example 1. That is, in the expanded beads of Example 1, sag resistance against repeated load was improved.

[0067] [External appearance observation using an electron microscope] The appearance of the foamed beads of Example 1 and Comparative Example 1 was observed before and after the sag test. Photographs taken using an electron microscope at 80x magnification are shown in FIG. 6. As shown in FIG. 6, in Comparative Example 1, wrinkles were observed in the foamed beads before the sag test, similar to those observed after the sag test. The photograph also shows that the foamed beads after the sag test were significantly wrinkled and crushed. On the other hand, in Example 1, no wrinkles were observed in the foamed beads before the sag test, and the wrinkles and crushing of the foamed beads after the sag test were suppressed. It is believed that the difference in the state of the foamed beads before the sag test influenced the results, such as the sag rate. [Industrial Applicability]

[0068] The foamed beads of the present invention can be widely used as foamed beads, since the deterioration of cushioning properties is suppressed even when used for a long time or repeatedly, and are particularly suitable for foamed beads used as a filler for products such as bead cushions. [Explanation of symbols]

[0069] 1 Pre-foaming machine 2 Input hopper 3 Pre-foaming tank 4 Mixing blade 5 Motor 6 Discharge hopper 7 Granule feeding tube 8. Blower 9, 9A, 9B Silos 10 Supply inlet 11 Outlet 12 Exhaust system 13 Bottom 14 Bottom member 15 Container 16 Foam Beads A Resin beads B. Foam particles C. Foam beads

Claims

1. The foamed beads are obtained by foaming resin beads impregnated with an organic foaming agent, The foamed beads have an average particle size of 0.5 mm or more and 5.0 mm or less, and are not subjected to a mechanical rotation treatment during feeding.

2. 2. The foamed beads according to claim 1, wherein the foamed beads have an expansion ratio of 30 to 45 times and a settling rate of 8.0% or less.

3. 3. The foam beads according to claim 1, wherein the foam beads are beads for cushioning.

4. A method for producing the foamed beads according to claim 1 or 2, comprising the steps of: The manufacturing method includes an expansion step of expanding the resin beads impregnated with the organic blowing agent to form expanded beads, a feeding step of feeding the expanded beads to a silo, and an aging step of aging the fed expanded beads in the silo to obtain the expanded beads, A method for producing expanded beads, characterized in that in the granulation step, the expanded beads are transported without being subjected to mechanical rotation treatment by a rotor on the transport path to the silo.

5. The method for producing expanded beads according to claim 4, characterized in that the silo has an exhaust device that sucks in air inside the silo and exhausts it to the outside, and the expanded beads are fed while the air inside the silo is sucked in by the exhaust device.

6. 6. The method for producing expanded beads according to claim 5, wherein the expanded beads are supplied from a supply port provided on a side surface of the silo, and the exhaust device is provided on the side surface of the silo.

7. 5. The method for producing expanded beads according to claim 4, wherein the expanded beads are fed at a temperature of 40° C. to 80° C. in the feeding step.

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