Deodorizing method for polystyrene beads

Abstract

To provide a method for deodorizing a foam bead which reduces odor derived from an organic foaming agent.SOLUTION: A method for deodorizing a foam bead includes a foaming step of foaming resin beads A impregnated with an organic foam agent and forming foamed particles B, and an aging step of aging the foam particles B by a silo 9 and obtaining foamed beads C, wherein the silo 9 is a horizontal type extending in a horizontal direction, and in the aging step, the foamed particles are supplied from a supply port 10 provided on one end side in the extension direction of the silo 9, and are taken out from a take-out port 11 provided on the other end side in the extension direction of the silo 9.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for deodorizing foamed beads, and particularly to a method for deodorizing cushion beads used as a filling material for cushions.

Background Art

[0002] Resin foams such as foamed styrene are excellent in lightweight, cushioning properties, and molding processability, and are used in various industrial fields such as storage containers for agricultural and marine products, cushioning materials for various products, and building materials for construction. The resin foam can be obtained by in-mold forming using foamed beads. In recent years, foamed beads themselves are also used as filling materials for cushions and pillows, and the demand is increasing.

[0003] As a cushion, a bead cushion in which a bag body is sewn and filled with foamed beads is known. In this type of cushion, during use, the foamed beads filled inside flow due to body pressure, deform along the body shape, and disperse the body pressure. As a result, a fitting feeling that wraps around the body is generated, providing comfort.

[0004] Generally, foamed beads are manufactured through a foaming process of foaming raw material beads (foamable particles) and an aging process of aging the obtained foamed particles (see, for example, Patent Document 1). The outline of this manufacturing method will be described based on FIG. 4.

[0005] In FIG. 4, first, the foaming process is performed using a pre-foaming machine 21. As the raw material beads, for example, resin beads impregnated with an organic foaming agent such as pentane or butane are used. The pre-foaming machine 21 has a charging hopper 22, a pre-foaming tank 23, a stirring blade 24, and a motor 25 for rotating the stirring blade 24. The raw material beads charged into the pre-foaming tank from the charging hopper 22 are heated by steam under atmospheric pressure or pressure while being stirred by the stirring blade 24, and foamed to a predetermined foaming ratio. The obtained foamed particles are discharged from the discharge port 23a provided at the lower part of the pre-foaming tank 23 to the discharge hopper 26.

[0006] In the subsequent maturation process, the foamed particles obtained in the foaming process are transferred to silo 29 for maturation. The discharge hopper 26 and silo 29 are connected by a granule delivery pipe 27, and the foamed particles are delivered by a blower 28 located at the end of the granule delivery pipe 27. In Figure 4, the foamed particles are supplied into the silo from a supply port 30 located at the top of the vertical silo 29. These foamed particles contain not only air but also organic gases (such as butane gas) derived from the organic foaming agent, so maturation takes place in silo 29 to replace the air with these organic gases. The maturation period is approximately 1 to 2 days. After maturation, the foamed beads are removed from an outlet 31 located at the bottom of silo 29. These foamed beads are used as raw materials for resin foams or as fillers for cushions and other materials. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 55-148134 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Incidentally, with the conventional methods described above, organic gases derived from organic blowing agents may still remain in the foamed beads after they are removed from the silo. In that case, the foamed beads may emit an odor derived from the organic blowing agent, which could affect products such as cushions that use those foamed beads.

[0009] This invention has been made in view of these circumstances, and aims to provide a method for deodorizing foamed beads in which odors derived from organic foaming agents are reduced. [Means for solving the problem]

[0010] The present invention provides a method for deodorizing foamed beads, comprising a foaming step of foaming resin beads impregnated with an organic foaming agent to form foamed particles, and a maturation step of maturing the foamed particles in a silo to obtain foamed beads, wherein the silo is horizontal and extends in the horizontal direction, and in the maturation step, the foamed particles are supplied from a supply port provided on one end of the silo in the direction of extension and removed from an outlet provided on the other end of the silo in the direction of extension.

[0011] In this invention, one end of the silo in the direction of extension refers to the portion (including the end) that is closer to one end in the direction of extension than the central part of the silo, and the other end of the silo in the direction of extension refers to the portion (including the other end) that is closer to the other end in the direction of extension than the central part of the silo.

[0012] The silo described above has an exhaust device for discharging the air inside the silo to the outside, and the maturation process is characterized by maturing the foamed particles while exhausting the air inside the silo using the exhaust device.

[0013] The exhaust device described above is characterized by being installed on the side of one end of the silo.

[0014] The above-mentioned supply port is provided on the side of one end of the silo, and the exhaust device is provided directly below the supply port.

[0015] The silo is characterized in that all or part of its bottom surface is sloped downward toward the outlet.

[0016] The foamed particles are characterized by being transported at a temperature of 40°C to 80°C after the foaming process described above and supplied to the silo.

[0017] The above organic blowing agent is characterized by being an aliphatic hydrocarbon.

[0018] The above-mentioned foam beads are characterized by being cushion beads. [Effects of the Invention]

[0019] The deodorization method of the foamed beads of the present invention has a foaming step of foaming resin beads impregnated with an organic foaming agent to form foamed particles, and an aging step of aging the foamed particles in a silo to obtain foamed beads. The silo is a horizontal type extending in the horizontal direction. In the aging step, the foamed particles are supplied from a supply port provided at one end side in the extending direction of the silo and taken out from a take-out port provided at the other end side in the extending direction of the silo. Therefore, the contact area between the foamed particles and air in the silo increases, and the replacement of the organic gas remaining in the foamed particles with air can be promoted. As a result, foamed beads with a reduced odor derived from the organic foaming agent can be obtained.

[0020] The silo has an exhaust device for discharging the air inside the silo to the outside. The aging step ages the foamed particles while exhausting the air inside the silo by the exhaust device. Therefore, by increasing the chance of the foamed particles contacting new air, the replacement of the organic gas remaining in the foamed particles with air can be further promoted.

[0021] Moreover, since the exhaust device is provided on the side surface of one end side of the silo, for example, air can be easily discharged through the foamed particles deposited in the silo, and it becomes easy to remove the organic gas remaining in the foamed particles. Also, the air flow inside the silo is likely to occur.

[0022] The supply port is provided on the side surface of one end side of the silo, and the exhaust device is provided directly below the supply port. Therefore, due to the air flow, dehydration and the like are likely to be performed when the foamed particles are introduced into the silo. Furthermore, the organic gas (such as butane gas) with a heavy vaporized specific gravity can be efficiently discharged, and the odor can be easily reduced.

[0023] Since all or part of the bottom surface inside the silo is inclined downward toward the take-out port, the foamed particles can easily move toward the take-out port, ensuring the take-out property, and the odor derived from the organic foaming agent can be reduced.

Brief Description of the Drawings

[0024] [Figure 1] It is a schematic diagram showing an example of a method for deodorizing foamed beads of the present invention. [Figure 2] It is a schematic cross-sectional view of the silo in FIG. 1. [Figure 3] It is a schematic cross-sectional view showing another form of the silo. [Figure 4] It is a schematic diagram of a conventional method for deodorizing foamed beads.

Embodiments for Carrying Out the Invention

[0025] The method for deodorizing foamed beads of the present invention comprises: (1) a foaming step of foaming resin beads impregnated with an organic foaming agent to form foamed particles; and (2) an aging step of aging the foamed particles in a silo to obtain foamed beads.

[0026] The resin beads (foamable particles) used as the raw material for the above deodorizing method can be obtained by impregnating a thermoplastic resin with an organic foaming agent by a well-known method. For example, styrene monomer is stirred and polymerized in water, and an organic foaming agent is added thereto, whereby polystyrene resin beads impregnated with the organic foaming agent are obtained.

[0027] As the thermoplastic resin, polystyrene-based resins; polyolefin-based resins such as polypropylene-based resins and polyethylene-based resins; polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polylactic acid; polycarbonate-based resins; copolymers thereof, etc. can be used. Also, as the thermoplastic resin, a plurality of resins can be used in combination. For example, a combination of a polystyrene-based resin and a polyolefin-based resin can be used.

[0028] 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. Aliphatic hydrocarbons tend to remain in the foaming beads and can easily cause unpleasant odors as organic gases, but the deodorization method of the present invention can effectively reduce odors caused by aliphatic hydrocarbons.

[0029] The resin beads may further contain additives other than thermoplastic resin and organic foaming agent, such as foam regulators, antioxidants, colorants, lubricants, and flame retardants. Commercially available resin beads can also be used in this invention.

[0030] An example of the present invention's method for deodorizing foamed beads is explained with reference to Figure 1. The deodorization method of the present invention is particularly useful for filler beads (especially cushion beads) where odor is a problem. Although this deodorization method can also be applied to molding beads as odor remains, molding beads are ultimately heated to, for example, about 80°C during in-mold molding, so the resin foam (finished product) does not have an odor.

[0031] One example of a bead used as a filler is cushion beads, which have seen increasing demand recently. Cushion beads can be broadly classified into two types: 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 average particle size is measured by laser diffraction and scattering. Small-particle types have a small surface area and are easy to dry by air drying at room temperature (15°C to 25°C), making them easy to deodorize. On the other hand, large-particle types have a large surface area and are difficult to dry, so odors tend to adhere to the surface of the particles. According to the deodorization method of the present invention, even large-particle foamed beads can be deodorized.

[0032] (1) Foaming process In this process, the resin beads described above are foamed to form foamed particles. The foaming method used in the present invention is not particularly limited, and well-known methods can be employed. For example, this could involve heating with steam or the like to expand and foam the organic foaming agent dissolved in the resin beads (heat foaming), or rapidly releasing from a high-pressure atmosphere to a low-pressure atmosphere to expand and foam the organic foaming agent dissolved in the resin beads.

[0033] The foaming conditions are not limited to any conditions that allow foaming to reach a predetermined foaming ratio (e.g., 30 to 70 times), but rather to any conditions that allow foaming to occur. The pressure conditions and heating conditions are not particularly limited. The foaming ratio is determined by the amount of resin beads added and the heating time.

[0034] In the foaming process shown in Figure 1, heating and foaming are performed using a pre-foaming machine 1. The pre-foaming machine 1 includes an input hopper 2, a pre-foaming tank 3, a stirring blade 4, and a motor 5 that rotates the stirring blade 4. After introducing resin beads A into the pre-foaming tank from the input hopper 2, steam or a mixture of steam and air is introduced into the pre-foaming tank 3 while stirring with the stirring blade 4, and heating is continued under constant conditions until the resin beads A reach a predetermined foaming ratio, at which point heating is stopped. For example, heating is performed at 80°C to 95°C using steam pressure. The foamed particles B are then discharged into the discharge hopper 6 from a discharge port 3a located at the bottom of the pre-foaming tank 3.

[0035] Immediately after discharge, the foamed particles B are blocked. These are then delivered to the particle delivery pipe 7 by agitator (not shown) in the discharge hopper 6, for example, while being stirred, and by air from a blower (not shown). The particle temperature of foamed particles B is about 80°C in the pre-foaming tank 3, but immediately after discharge, it drops to about 50°C to 60°C due to room temperature stirring and air from the blower.

[0036] (2) Aging process In this process, foamed particles B are dried and matured in silo 9 to obtain foamed beads C. The discharge hopper 6 and silo 9 are connected by a conveying pipe 7, and for example, a blower 8 that supplies compressed air is provided at the discharge hopper end of the conveying pipe 7. The foamed particles B introduced into the conveying pipe 7 are transported by air while being suspended by compressed air. Note that the method of delivering the foamed particles B is not limited to the method shown in Figure 1.

[0037] It is preferable that the foamed particles B are delivered at a temperature 3 to 4 times that of room temperature. Specifically, it is preferable that they be delivered to the silo 9 at 40°C to 80°C (more preferably 50°C to 60°C). The particle temperature of the foamed particles B at the time of transfer from the discharge hopper 6 to the delivery pipe 7 is approximately 50°C to 60°C, and this temperature is maintained when they are supplied to the silo 9. At the time of transfer from the discharge hopper 6 to the delivery pipe 7, the foamed particles B are wet due to the moisture from the steam. If they are dried at room temperature in the silo while still wet, odor components contained in the moisture are more likely to adhere to the surface of the particles. Therefore, by delivering them at a temperature higher than room temperature, even the large-particle type foamed beads described above can be easily dewatered before being put into the silo 9 (for example, just before being put into the silo 9), making it easier to reduce odor.

[0038] As described above, the purpose of transporting the granules at high temperature is to vaporize and dry the moist foamed particles all at once. For example, as will be described later, by installing an exhaust device 12 such as a ventilation fan near the supply port 10 of the silo 9, an airflow to the outside can be created, and the foamed particles B can be dehydrated and deodorized simultaneously just before being put into the silo 9. Since the transported foamed particles are at a high temperature and vaporization is promoted by the airflow at room temperature, the configuration with the exhaust device 12 is preferable in terms of dehydration and deodorization.

[0039] It is preferable that the granule delivery pipe 7 has an insulating structure up to the supply port 10. For example, an insulating pipe having an insulating layer may be used as the granule delivery pipe 7, or the outer circumference of the granule delivery pipe 7 may be covered with insulating material. Furthermore, it is preferable that the blower 8 is equipped with a heater function so that it can blow warm air at a temperature of about 40°C to 80°C.

[0040] As shown in Figure 1, the silo 9 is horizontal and extends horizontally, and has a roughly rectangular parallelepiped shape extending in the X direction. The X direction in Figure 1 is the extension direction. In the silo 9, a supply port 10 is provided on one end in the extension direction, and an outlet port 11 is provided on the other end in the extension direction. In the maturation process, foamed particles B are supplied from the supply port 10 on one end, and foamed beads C are removed from the outlet port 11 on the other end. As described above, it is preferable that the foamed particles B are introduced into the silo 9 at a high temperature and dehydrated by being delivered at a high temperature. In addition, the foamed particles B are cooled and further dried during the maturation process.

[0041] In the conventional maturation process, a silo 29 was used, as shown in Figure 4. The silo 29 in Figure 4 is vertical, and the foamed particles supplied from the supply port 30 at the top of the silo 29 are deposited and matured inside the vertical silo. They are then removed as foamed beads from the outlet 31 at the bottom of the silo 29.

[0042] In contrast, the deodorization method of the present invention, as shown in Figure 1, uses a horizontal silo 9, which increases the surface area of ​​the foam particles in contact with air within the silo compared to conventional silos, and facilitates the replacement of residual organic gases in the foam particles with air. This makes it possible to further reduce the odor of the foam beads C. Furthermore, since odor removal can be achieved earlier with this method, a shortening of the maturation period can also be expected.

[0043] As an example of the maturation process, foam particles B are supplied to silo 9, leaving approximately 10-50% of its internal volume empty. The foam particles B are then matured in the silo for approximately 24-48 hours. This maturation process is preferably carried out while exhausting the air from the silo using the exhaust device 12, which will be described later. The maturation process is not limited to a batch process; it may also be carried out continuously. For example, it may be carried out continuously by repeatedly adding a portion of the foam particles and removing a portion of the foam beads in a fixed time cycle. In the case of a continuous process, the foam particles in the silo gradually move in a substantially horizontal direction from one end to the other. Even in the case of a continuous process, it is preferable that the added foam particles are matured in the silo for approximately 24-48 hours.

[0044] The silo's structure will be further explained using Figure 2. Figure 2 is a schematic cross-sectional view of the silo shown in Figure 1, illustrating its state during the maturation period. The silo 9 can be made of materials such as metal or resin. The internal volume of the silo 9 is not particularly limited, but for example, 100 m³ 3 ~500m 3 That is the case.

[0045] As shown in Figure 2, the supply port 10 is located on the side surface 9a, which is one end of the silo 9 in the direction of its extension. In this case, the foamed particles are supplied to the silo 9 from the side. On the other hand, the outlet 11 is located on the other end of the silo 9 in the direction of its extension, specifically on the bottom 9c near the side surface 9b, which is the end opposite to the side surface 9a. The outlet 11 is provided with an openable and closable lid or the like.

[0046] A portion of the bottom surface 13 inside the silo 9 is sloped downward toward the outlet 11. This slope allows the foam particles to move more easily toward the outlet 11, even though the silo 9 is a horizontal type.

[0047] Furthermore, it is preferable that the silo 9 has an exhaust device 12 that discharges the internal air to the outside. In Figure 2, the exhaust device 12 is located on the side 9a directly below the supply port 10. This creates an airflow to the outside, allowing for simultaneous dewatering and deodorization of the foamed particles just before they are introduced into the silo 9. Also, since the vaporized organic gas has a high specific gravity, the exhaust device 12 directly below the supply port 10 can efficiently discharge the organic gas.

[0048] In silo 9, the height at which the exhaust device 12 is installed is not particularly limited, but it is preferable to install it in a height region where foam particles do not accumulate, for example, because it is easier to create airflow within the silo. For example, it is installed in a height region of 1 / 3 or more of the height of the side surface 9a on one end of silo 9. This height region may be 1 / 2 or more of the height of the side surface 9a, or 2 / 3 or more of the height. The exhaust device 12 makes it easier to remove organic gases by blowing air on the foam particles before they cool down (while they are still at a high temperature).

[0049] Furthermore, even if the exhaust device 12 is installed in the height region where the foam particles accumulate, the air will be discharged through the gaps between the foam particles, allowing for greater contact between the foam particles and the air. As a result, it is believed that it will be easier to remove any organic gases remaining on the foam particles.

[0050] As the exhaust device 12, for example, an exhaust fan (ventilation fan) such as a propeller fan or a centrifugal fan can be used.

[0051] The horizontal dimension L (length along the extension direction) of silo 9 is, for example, 5m to 30m, preferably 10m to 30m. Furthermore, the horizontal dimension L is greater 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), preferably (1:2.5) to (1:5).

[0052] Figure 3 shows schematic cross-sectional views of other silo configurations. Silo 9A shown in Figure 3(a) is rectangular in shape and has a bottom member 14 inside. As a result, a portion of the bottom surface inside the silo is sloped downward toward the outlet 11. In Figure 3(a), the bottom surface 13 inside the silo is composed of a flat surface and an inclined surface.

[0053] Furthermore, the silo 9B shown in Figure 3(b) has different positions for the supply port 10 and outlet port 11 compared to the silo 9 shown in Figure 2. In silo 9B, the supply port 10 is located on one end in the extending direction, specifically on the ceiling portion 9d near the side surface 9a. An exhaust device 12 is also provided near the supply port 10 at the top of the side surface 9a. The outlet port 11 is located on the other end in the extending direction, on the side surface 9b. In silo 9B, the bottom surface 13 inside the silo is formed solely of inclined surfaces, with the entire bottom surface 13 inclined downward from one end to the other, resulting in excellent retrieval performance. The bottom surface 13 inside the silo may be formed of multiple inclined surfaces with different inclination angles.

[0054] The silo configurations used in the present invention are shown in Figures 2 and 3 above, but the various components in these configurations (such as the arrangement of supply ports and outlets) can be combined with each other. Furthermore, the silo is not limited to the configurations shown in Figures 2 and 3 above; for example, the silo may be provided with ventilation holes that penetrate through the inside and outside of the silo. In this case, for example, the ventilation holes may be provided on the opposite side from where the exhaust device is installed (for example, side 9b in Figure 2).

[0055] The deodorization method of the present invention is not limited to the embodiments shown in Figures 1 to 3 above. [Industrial applicability]

[0056] The deodorizing method of the present invention can reduce the odor derived from organic foaming agents in foamed beads, and therefore can be widely used as a deodorizing method for foamed beads. It is particularly suitable for deodorizing foamed beads used as a filling material in products such as bead cushions. [Explanation of symbols]

[0057] 1. Reserve foaming machine 2. Input hopper 3. Pre-foaming tank 4. Agitator blades 5 Motors 6. Discharge hopper 7 Grain feed tube 8. Blower 9, 9A, 9B silos 10 supply ports 11 Outlet 12 Exhaust system 13. Base 14 Bottom member A resin beads B Foaming particles C. Foam beads

Claims

1. The process comprises a foaming step of foaming resin beads impregnated with an organic foaming agent to form foamed particles, and a maturation step of maturing the foamed particles in a silo (excluding a fluidized bed dryer) to obtain foamed beads. A method for deodorizing foamed beads, characterized in that the silo is horizontal and extends in the horizontal direction, and in the maturation process, the foamed particles are supplied from a supply port provided on one end of the silo in the direction of extension, accumulated and matured inside the silo, and removed from an outlet provided on the other end of the silo in the direction of extension.

2. The method for deodorizing foamed beads according to claim 1, characterized in that the silo has an exhaust device for discharging the air inside the silo to the outside, and the maturation process matures the foamed particles while exhausting the air inside the silo with the exhaust device.

3. The method for deodorizing foamed beads according to claim 2, characterized in that the exhaust device is provided on the side of one end of the silo.

4. The method for deodorizing foamed beads according to claim 3, characterized in that the supply port is provided on the side of one end of the silo, and the exhaust device is provided directly below the supply port.

5. The method for deodorizing foamed beads according to any one of claims 1 to 4, characterized in that all or part of the bottom surface inside the silo is inclined downward toward the outlet.

6. The method for deodorizing foamed beads according to any one of claims 1 to 5, characterized in that, after the foaming step, the foamed particles are delivered at a temperature of 40°C to 80°C and supplied to the silo.

7. The method for deodorizing foamed beads according to any one of claims 1 to 6, characterized in that the organic foaming agent is an aliphatic hydrocarbon.

8. The method for deodorizing foamed beads according to any one of claims 1 to 7, characterized in that the foamed beads are cushion beads.

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