Expanded beads manufacturing apparatus and manufacturing method

Abstract

To simplify cleaning of a facility even in a production of various types of foamed particles.SOLUTION: A manufacturing device (10) of the present invention comprises: a pressure vessel (1); at least two types foaming lines (2A, 2B) for transporting foamed thermoplastic resin particles from the pressure vessel (1); and a recovery line (3) that is connected to a lower portion of the pressure vessel (1), and is provided as a different line from the foaming lines (2A, 2B) for recovering un-foamed thermoplastic resin particles in the pressure vessel (1).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for producing expanded beads. [Background technology]

[0002] It is known that expanded beads made of thermoplastic resins can be produced by dispersing thermoplastic resin particles in water containing a dispersant in a pressure-resistant vessel, adding a volatile blowing agent, maintaining the particles under high temperature and high pressure to allow the volatile blowing agent to be impregnated, and then releasing the particles into a low-pressure atmosphere (hereinafter referred to as the depressurization foaming method).

[0003] A manufacturing device for expanded thermoplastic resin beads is generally composed of major devices such as a pressure vessel, a discharge valve, a separator (e.g., a centrifuge) for separating liquid, and a storage tank (dryer) for drying the expanded beads. A manufacturing device for expanded beads using the depressurization expansion method is disclosed in, for example, Patent Document 1.

[0004] FIG. 6 is a diagram showing a schematic configuration of the expanded bead manufacturing apparatus disclosed in Patent Document 1. As shown in FIG. 6, the expanded bead manufacturing apparatus disclosed in Patent Document 1 includes a pressure vessel 303, a valve 304, an orifice 305, a low-pressure vessel 306, a transport medium supply unit 311, a dry intake air blower 318, and an air heater 319. In the pressure vessel 303, resin particles 301 made of a polyolefin resin composition are dispersed in an aqueous dispersion medium 302. In the pressure vessel 303, the resin particles 301 are heated to a temperature equal to or higher than the softening temperature of the resin particles 301, and become water-containing resin particles. The resin particles 301 are then released into a low-pressure vessel 306, the internal pressure of which is lower than that of the pressure vessel 301, and are expanded. When the valve 304 is opened, the resin particles 301 pass through the orifice 305 and are released into the low-pressure vessel 306 (released particles 307).

[0005] Saturated steam is blown into the low-pressure vessel 306 from a steam blowing port 308, and the released particles 307, which are expanded particles, come into contact with the saturated steam. The released particles 307 and the dispersion medium 310 are separated in a filtration section 312. The dispersion medium 310 is discharged from an outlet 309. The released particles 307 are transported to a dryer 315 through an outlet 313 of the low-pressure vessel 306 together with a transport medium 314 supplied from a transport medium supply section 311. The transport medium 314 is saturated steam. The line along which the released particles 307 are transported from the pressure-resistant vessel 301 through the low-pressure vessel 306 to the dryer 315 constitutes the expansion line of the expanded particles. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-290420 A Summary of the Invention [Problem to be solved by the invention]

[0007] The manufacturing device described in Patent Document 1 has only one expansion line for expanded beads, so there is room for improvement in terms of efficiently manufacturing a wide variety of expanded beads with different colors or expansion ratios. When using the device described in Patent Document 1 to manufacture such a wide variety of expanded beads, careful cleaning of the main equipment of the manufacturing device is required to prevent mixing of expanded beads of a different variety from the variety being manufactured. This reduces the production efficiency of expanded beads.

[0008] In addition, from the viewpoint of the capital investment required for the production equipment and the balance between production capacity and sales volume, it is difficult to provide a system of expansion lines for each type of expanded beads.

[0009] Therefore, even in the production of a wide variety of expanded beads, there is a demand for a production apparatus in which the main components are easy to clean.

[0010] An object of one aspect of the present invention is to provide an expanded bead production apparatus and method that allows easy cleaning of the equipment even when producing a wide variety of expanded bead varieties. [Means for solving the problem]

[0011] In order to solve the above problems, an expanded bead manufacturing apparatus according to one embodiment of the present invention is characterized in that it comprises a pressure-resistant container for expanding thermoplastic resin particles, at least one expansion line for transporting the expanded thermoplastic resin particles from the pressure-resistant container, and a recovery line connected to the lower part of the pressure-resistant container and separate from the expansion line for recovering unexpanded thermoplastic resin particles in the pressure-resistant container.

[0012] In order to solve the above problems, a method for producing expanded beads according to another embodiment of the present invention includes an expansion step of supplying a foaming agent into a pressure vessel, heating and pressurizing a dispersion containing thermoplastic resin particles and water in the pressure vessel to a temperature equal to or higher than the softening temperature of the thermoplastic resin particles, and then releasing the dispersion into an atmosphere under a lower pressure than the internal pressure of the pressure vessel, thereby expanding the dispersion; a transport step of transporting the expanded thermoplastic resin particles from the pressure vessel through a foaming line; and a recovery step of recovering unfoamed thermoplastic resin particles in the pressure vessel through a recovery line separate from the foaming line. Effect of the Invention

[0013] According to each aspect of the present invention, cleaning of the equipment is easy even when producing a wide variety of expanded beads. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 shows a schematic configuration of an expanded bead manufacturing apparatus according to a first embodiment of the present invention, in which 101 is a side view and 102 is a top view. [Diagram 2] FIG. 2 shows a schematic configuration of an expanded bead manufacturing apparatus according to a second embodiment of the present invention, in which 201 is a side view and 202 is a top view. [Diagram 3]FIG. 11 is a side view showing a schematic configuration of a modified example of the expanded beads manufacturing apparatus according to the second embodiment of the present invention. [Figure 4] FIG. 4 shows a schematic configuration of an expanded bead manufacturing apparatus according to a third embodiment of the present invention, in which 401 is a side view and 402 is a top view. [Diagram 5] FIG. 11 is a side view showing a schematic configuration of an expanded bead manufacturing apparatus according to a fourth embodiment of the present invention. [Figure 6] FIG. 1 is a diagram showing a schematic configuration of an expanded bead manufacturing apparatus disclosed in Patent Document 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Embodiment 1] (Foam bead manufacturing equipment) An embodiment of the present invention will be described in detail below. Fig. 1 shows a schematic configuration of an expanded bead manufacturing apparatus 10 according to this embodiment, in which 101 is a side view and 102 is a top view.

[0016] As shown in 101 and 102 in Fig. 1, the manufacturing apparatus 10 according to this embodiment includes a pressure-resistant container 1, foaming lines 2A and 2B, and a recovery line 3. The manufacturing apparatus 10 may include one foaming line, and preferably includes at least two foaming lines. In this embodiment, a case where the manufacturing apparatus includes two foaming lines, 2A and 2B, will be described as an example.

[0017] The pressure vessel 1 is a vessel for producing expanded particles by the depressurization foaming method, and has a semi-elliptical lower portion. For example, thermoplastic resin particles, mini-pellets containing an inorganic dispersant and a dispersion aid, and CO2 as a foaming agent are charged into the pressure vessel 1 together with water. Then, the pressure vessel 1 is heated to adjust the contents in the pressure vessel 1 to a temperature equal to or higher than the softening temperature of the thermoplastic resin particles, and then the pressure in the pressure vessel 1 is adjusted to a predetermined pressure. As a result, the thermoplastic resin particles in the pressure vessel 1 are impregnated with the foaming agent.

[0018] The expansion lines 2A and 2B are lines for transporting the expanded beads released from the pressure-resistant container 1. The manufacturing apparatus 10 is provided with two expansion lines 2A and 2B for transporting the expanded beads for one pressure-resistant container 1. Expanded beads A are transported to the expansion line 2A, while expanded beads B, which is a different type from the expanded beads A, are transported to the expansion line 2B.

[0019] The foaming lines 2A and 2B are provided with valves 21A and 21B, foaming cylinders 4A and 4B (low pressure atmosphere), and transport lines 5A and 5B, respectively.

[0020] When expanding beads A are manufactured, the thermoplastic resin particles, which are the raw material of the expanded beads A and impregnated with the blowing agent, are released and expanded into the expansion tube 4A, which has a pressure lower than the internal pressure of the pressure-resistant container 1, by opening the valve 21A (depressurization expansion method), to obtain the expanded beads A. The expanded beads A in the expansion tube 4A are transported to the transport line 5A. The expanded beads A are transported from the transport line 5A together with the transport air, and are stored in a predetermined storage tank after undergoing at least cleaning treatment, drainage treatment, dehydration treatment, and drying treatment. When expanding beads B are manufactured, the thermoplastic resin particles, which are the raw material of the expanded beads B, are released and expanded into the expansion tube 4B by the depressurization expansion method, to obtain the expanded beads B. In the expansion line 2B, the expanded beads B in the expansion tube 4B are transported to the transport line 5B.

[0021] In the expansion line 2A, the expanded particles A are transported from the transport line 5A together with the transport air, and are stored in a predetermined storage tank after undergoing at least cleaning, drainage, dehydration, and drying treatments. In the expansion line 2B, the expanded particles B are stored in a predetermined storage tank after undergoing the same treatments as above.

[0022] The various equipment constituting the foaming lines 2A and 2B are not particularly limited as long as they are capable of performing at least the above-mentioned cleaning treatment, drainage treatment, dehydration treatment, and drying treatment. The foaming lines 2A and 2B applicable to the manufacturing apparatus 10 according to this embodiment are shown in, for example, Figures 6 and 7 of International Publication WO2020 / 158061.

[0023] In this way, the manufacturing apparatus 10 is provided with two expansion lines 2A and 2B for one pressure vessel 1, and is therefore capable of manufacturing different types of expanded beads A and B. The post-processing equipment such as a dehydrator and dryer following the pressure vessel 1 is relatively low-cost equipment. Therefore, when manufacturing a wide variety of expanded beads, the manufacturing apparatus 10 can be configured to share the pressure vessel 1 and have two expansion lines 2A and 2B following the pressure vessel 1, thereby keeping the capital investment for the manufacturing apparatus 10 low.

[0024] Furthermore, since the manufacturing apparatus 10 is provided with the recovery line 3, cleaning of the facilities of the manufacturing apparatus 10 becomes easy.

[0025] The recovery line 3 is connected to the lower part of the pressure vessel 1 and is a line separate from the foaming lines 2A and 2B. The recovery line 3 is a line for recovering unfoamed thermoplastic resin particles in the pressure vessel 1. The recovery line 3 is equipped with a discharge valve 3a. The discharge valve 3a is an on-off valve for discharging the contents in the pressure vessel 1.

[0026] For example, when expanding beads B are manufactured after expanding beads A are manufactured, when the mini-pellets and the blowing agent, which are the raw materials of the expanded beads B, are charged into the pressure vessel 1, the thermoplastic resin particles, which are the raw materials of the expanded beads A, may remain in the pressure vessel 1 in an unfoamed state. Therefore, when the expanded beads B are manufactured, it is necessary to remove the unfoamed thermoplastic resin particles (sometimes called resin pellets) in the pressure vessel 1. According to the manufacturing apparatus 10, the resin pellets in the pressure vessel 1 can be easily discharged outside the pressure vessel 1 by switching the discharge valve 3a of the recovery line 3 from a closed state to an open state. Therefore, according to the manufacturing apparatus 10 according to this embodiment, in the manufacture of various kinds of expanded beads, the resin pellets in the pressure vessel 1 can be easily removed, and cleaning of the equipment becomes easy. As a result, the production efficiency of the expanded beads A and B is improved.

[0027] The connection point of the pressure-resistant container 1 to the recovery line 3 is not particularly limited as long as the contents in the pressure-resistant container 1 can be transported to the recovery line 3 by opening the discharge valve 3a. Preferably, as shown in FIG. 1, the recovery line 3 is connected to the lowest part 1a. The lowest part 1a corresponds to the apex of the semi-elliptical shape that constitutes the lower part of the pressure-resistant container 1. In the pressure-resistant container 1, the resin pellets gather at the lowest part 1a. Therefore, by connecting the discharge valve 3a to the lowest part 1a of the pressure-resistant container 1 in this manner, it becomes possible to evenly discharge the resin pellets in the pressure-resistant container 1.

[0028] (Method of manufacturing expanded beads) The manufacturing method of the expanded beads according to the present embodiment includes an expansion step, a transport step, and a recovery step. In the expansion step, the expanded beads are manufactured by a so-called depressurization expansion method. That is, in the expansion step, a foaming agent is supplied into a pressure vessel, and a dispersion containing thermoplastic resin particles and water is heated and pressurized in the pressure vessel to a temperature equal to or higher than the softening temperature of the thermoplastic resin particles, and then released into an atmosphere with a lower pressure than the internal pressure of the pressure vessel, thereby expanding the dispersion. In the transport step, the expanded thermoplastic resin particles obtained in the expansion step are transported. That is, in the transport step, the expanded thermoplastic resin particles are transported from the pressure vessel through a foaming line. In addition, in the recovery step, the unexpanded thermoplastic resin particles in the pressure vessel are recovered through a recovery line that is separate from the foaming line.

[0029] In the foaming step, at least two types of expanded beads are produced in one pressure vessel by a depressurization foaming method. Therefore, the foaming step includes a plurality of foaming stages in which at least two types of expanded beads are produced by a depressurization foaming method. In the transporting step, a foaming line is provided for the expanded beads produced in each foaming stage, and various types of expanded beads are transported through each foaming line. The recovering step is carried out between the above-mentioned plurality of foaming stages. When a certain foaming stage is carried out, unexpanded thermoplastic resin particles remaining in the pressure vessel in the foaming stage carried out before the certain foaming stage are recovered in the recovering step.

[0030] Therefore, the manufacturing method according to the present embodiment can be said to be a method including a first expansion step, a first transport step, a second expansion step, a second transport step, and a recovery step K. In the first expansion step, a foaming agent is supplied into a pressure vessel, and a dispersion containing first thermoplastic resin particles and water is heated and pressurized in the pressure vessel to a temperature equal to or higher than the softening temperature of the first thermoplastic resin particles, and then released into a lower pressure atmosphere than the internal pressure of the pressure vessel. In the first transport step, the thermoplastic resin foamed particles produced in the first expansion step are transported from the pressure vessel through a first expansion line. In the second expansion step, after the first transport step, a foaming agent is supplied into the pressure vessel, and a dispersion containing second thermoplastic resin particles and water is heated and pressurized in the pressure vessel to a temperature equal to or higher than the softening temperature of the second thermoplastic resin particles, and then released into a lower pressure atmosphere than the internal pressure of the pressure vessel. In the second transport step, the thermoplastic resin expanded particles produced in the second expansion step are transported from the pressure container via a second expansion line that is a separate system from the first expansion line. The recovery step K is carried out between the first transport step and the second expansion step. In the recovery step K, unexpanded thermoplastic resin particles remaining in the pressure container in the first expansion step are recovered via a recovery line that is a separate system from the first and second expansion lines.

[0031] According to the manufacturing method of this embodiment, even in the manufacturing of many kinds of expanded beads, the resin pellets in the pressure-resistant container can be easily removed, and cleaning of the equipment becomes easy. The manufacturing method of this embodiment is not particularly limited as long as it includes the above-mentioned steps. For example, the manufacturing method of this embodiment is a method for manufacturing expanded beads using a manufacturing apparatus 10 shown in FIG. 1. Hereinafter, the manufacturing method of this embodiment will be described by taking the method using the manufacturing apparatus 10 shown in FIG. 1 as an example.

[0032] In the manufacturing method according to the present embodiment, first, an expansion step is performed to manufacture the expanded beads A. In the expansion step, resin pellets as the raw materials of the expanded beads A and a blowing agent are charged together with water into a pressure vessel 1. Then, the pressure vessel 1 is heated to adjust the temperature of the contents in the pressure vessel 1 to a temperature equal to or higher than the softening temperature of the thermoplastic resin particles as the raw material of the expanded beads A, and the pressure in the pressure vessel 1 is adjusted to a predetermined pressure. Then, the valve 21A is opened to release and expand the contents into the expansion tube 4A, which has a pressure lower than the internal pressure of the pressure vessel 1, to obtain the expanded beads A.

[0033] Next, a transport step is performed to transport the expanded beads A through the expansion line 2A. In the transport step, the expanded beads A in the expansion cylinder 4A are transported to the transport line 5A, and the expanded beads A are transported from the transport line 5A together with the transport air, and are stored in a predetermined storage tank after undergoing at least a cleaning treatment, a drainage treatment, a dehydration treatment, and a drying treatment.

[0034] Next, in order to produce expanded beads B, a recovery step is carried out before the resin pellets and the blowing agent, which are the raw materials of expanded beads B, are charged into the pressure vessel 1. In the recovery step, the discharge valve 3a of the recovery line 3 is switched from a closed state to an open state, thereby discharging the resin pellets, which are the raw materials of expanded beads A, from the pressure vessel 1 to outside the pressure vessel 1.

[0035] After the recovery step, the resin pellets and the blowing agent, which are the raw materials of the expanded beads B, are charged into the pressure-resistant container 1 to carry out the expansion step of producing the expanded beads B. This expansion step is the same as the expansion step of producing the expanded beads A described above, and therefore a description thereof will be omitted.

[0036] Next, a transport step is performed to transport the expanded beads B through the expansion line 2B. This transport step is similar to the transport step of transporting the expanded beads A described above, and therefore a description thereof will be omitted.

[0037] (About foam particles) Here, the raw materials of each of the various kinds of expanded beads used in this embodiment may be raw materials that can be expanded by the above-mentioned depressurization expansion method, and include at least a crystalline thermoplastic resin and a foaming agent. In addition, various additives can be added as necessary as raw materials for the expanded beads, in addition to the crystalline thermoplastic resin and the foaming agent, depending on the type of the expanded beads. For example, flame retardants, heat stabilizers, radical generators, processing aids, weather resistance stabilizers, nucleating agents, foaming aids, antistatic agents, radiation heat transfer inhibitors, and colorants can be mentioned. These additives can be used alone or in combination of two or more.

[0038] The thermoplastic resin used in the present embodiment is not particularly limited as long as it is a crystalline thermoplastic resin having a general known foaming property. Examples of the thermoplastic resin include polyolefin resin, polyester resin, polyphenylene ether resin, polyamide resin, and mixtures thereof. The thermoplastic resin is preferably a polyolefin resin or a polyester resin.

[0039] Examples of polyester resins include aliphatic polyester resins, aromatic polyester resins, and aliphatic aromatic polyester resins. Specific examples of polyester resins include polyhydroxyalkanoate, polybutylene succinate (PBS), poly(butylene adipate-co-butylene terephthalate) (PBAT), and polyethylene terephthalate (PET). The polyhydroxyalkanoate is at least one selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate).

[0040] The polyolefin resin is not particularly limited, and examples thereof include the polyolefin resins exemplified in International Publication WO2020 / 158061.

[0041] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0042] Fig. 2 is a schematic diagram showing the schematic configuration of the expanded bead manufacturing apparatus 10A according to this embodiment, in which 201 is a side view and 202 is a top view. As shown in 201 and 202 of Fig. 2, the manufacturing apparatus 10A according to this embodiment differs from the first embodiment mainly in that the expansion lines 2A and 2B are provided branching off from the recovery line 3.

[0043] The manufacturing apparatus 10A includes one expansion cylinder 4 for expanding the expanded particles A and B. The expansion cylinder 4 forms a common low-pressure space for the expansion lines 2A and 2B. By sharing the expansion cylinder 4 in this way, the number of pieces of equipment can be reduced.

[0044] The discharge valve 3a is provided upstream of a branching portion 23 between the foaming lines 2A and 2B and the recovery line 3. The discharge valve 3a is an on-off valve for discharging the contents in the pressure-resistant container 1. In addition, on the downstream side of the branching portion 23, an on-off valve 3b (first valve) and an on-off valve 3c (second valve) are provided.

[0045] The on-off valve 3b is provided in the pipe 2c branched from the branching portion 23 to the foaming cylinder 4. The on-off valve 3b is a valve that switches between opening and closing the foaming line including the foaming lines 2A and 2B. On the other hand, the on-off valve 3c is provided in a pipe branched from the branching portion 23 in a direction different from the pipe 2c. The on-off valve 3c is a valve that switches between opening and closing the recovery line 3.

[0046] The manufacturing apparatus 10A also includes a relay pipe 6 that relays the foaming cylinder 4 and the transport lines 5A and 5B. The relay pipe 6 extends from the foaming cylinder 4 and is configured to connect to both the transport line 5A of the foaming line 2A and the transport line 5B of the foaming line 2B. The relay pipe 6 is configured to be able to switch between the connection state between the foaming cylinder 4 and the transport line 5A and the connection state between the foaming cylinder 4 and the transport line 5B. For example, when the transport lines 5A and 5B are arranged parallel to each other and the foaming cylinder 4 is arranged at equal intervals with respect to both the transport lines 5A and 5B, the relay pipe 6 has the following configuration. That is, in this case, the relay pipe 6 is configured to be able to rotate between the transport lines 5A and 5B around the foaming cylinder 4.

[0047] In the manufacturing method using the manufacturing apparatus 10A, first, resin pellets as raw materials for the expanded particles A and a foaming agent are charged together with water into the pressure-resistant container 1, and the contents are released into the foaming cylinder 4 by a depressurization foaming method to obtain the expanded particles A (foaming step). At this time, the discharge valve 3a and the on-off valve 3b are opened, while the on-off valve 3c is closed.

[0048] Next, after connecting a relay pipe 6 to a transport line 5A of the process system of the expansion line 2A, the expanded particles A in the expansion cylinder 4 are transported to the transport line 5A, and then transported via the expansion line 2A (transportation process).

[0049] Next, in order to produce expanded beads B, a recovery step is carried out before the resin pellets and the blowing agent, which are the raw materials of expanded beads B, are charged into the pressure-resistant container 1. In the recovery step, the discharge valve 3a and the on-off valve 3c of the recovery line 3 are switched from a closed state to an open state, and the on-off valve 3b is switched from an open state to a closed state. This causes the resin pellets, which are the raw materials of expanded beads A, in the pressure-resistant container 1 to be discharged out of the pressure-resistant container 1.

[0050] After the recovery step, the resin pellets and the foaming agent, which are the raw materials of the expanded particles B, are charged into the pressure-resistant container 1, and an expansion step is carried out to manufacture the expanded particles B. After switching the connection of the relay pipe 6 from the transport line 5A of the process system of the expansion line 2A to the transport line 5B of the process system of the expansion line 2B, the expanded particles B in the expansion tube 4 are transported to the transport line 5B, and the expanded particles A are transported via the expansion line 2B (transport step).

[0051] Even with the configuration of the manufacturing apparatus 10A according to this embodiment, in the production of various types of expanded beads, the resin pellets inside the pressure-resistant container 1 can be easily removed, and cleaning of the equipment becomes easy.

[0052] 3 is a side view showing a schematic configuration of a modified example of the manufacturing apparatus 10A. As shown in FIG. 3, the manufacturing apparatus 10B as this modified example differs from the configuration shown in FIG. 2 in the shape of the lower part of the pressure-resistant vessel 1A.

[0053] As shown in Fig. 3, the lower part of the pressure-resistant container 1A has a conical shape. The shape of the lower part of the pressure-resistant container 1A may be either a conical shape or a pyramidal shape as long as it is a conical shape. Furthermore, when the shape of the lower part of the pressure-resistant container 1A is a conical shape, the lowest part 1a corresponds to the apex of the conical shape. Since the lower part of the pressure-resistant container 1A has a conical shape, the contents tend to collect at the lowest part 1a.

[0054] [Embodiment 3] Further, for the sake of convenience, the same reference numerals are given to the members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0055] Fig. 4 shows a schematic configuration of the expanded bead manufacturing apparatus 10C according to this embodiment, where 401 is a side view and 402 is a top view. As shown in 401 and 402 in Fig. 4, the manufacturing apparatus 10C according to this embodiment differs from the second embodiment in that it is provided with a three-way valve 8.

[0056] The three-way valve 8 is provided at a branching portion 23 between the foaming lines 2A and 2B and the recovery line 3. The three-way valve 8 is a valve having the functions of the three valves, namely, the discharge valve 3a, the on-off valve 3b, and the on-off valve 3c, in the manufacturing apparatus 10A according to the embodiment 2. The three-way valve 8 enables, with one valve, the same switching operation as the on-off switching of the discharge valve 3a, the on-off valve 3b, and the on-off valve 3c in the manufacturing apparatus 10A.

[0057] Even with the configuration of the manufacturing apparatus 10C according to this embodiment, in the production of various types of expanded beads, the resin pellets inside the pressure-resistant container 1 can be easily removed, and cleaning of the equipment becomes easy.

[0058] [Embodiment 4] Further, for the sake of convenience, the same reference numerals are given to the members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0059] Fig. 5 is a side view showing a schematic configuration of an expanded bead manufacturing apparatus 10D according to this embodiment. As shown in Fig. 5, the manufacturing apparatus 10D according to this embodiment is different from the manufacturing apparatus 10B shown in Fig. 3 of the second embodiment in that the manufacturing apparatus 10D according to this embodiment is provided with expansion cylinders 4A and 4B corresponding to the expansion lines 2A and 2B, respectively.

[0060] In the manufacturing apparatus 10D, the relay pipe 6 extends from the on-off valve 3b. The relay pipe 6 is configured to be able to switch between the connection between the on-off valve 3b and the foaming cylinder 4A and the connection between the on-off valve 3b and the foaming cylinder 4B.

[0061] Even with the configuration of the manufacturing apparatus 10D according to this embodiment, in the production of various types of expanded beads, the resin pellets inside the pressure-resistant vessel 1A can be easily removed, and cleaning of the equipment becomes easy.

[0062] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0063] 〔summary〕 The expanded bead manufacturing apparatus 10 according to embodiment 1 of the present invention comprises a pressure-resistant container 1 for expanding thermoplastic resin particles, at least one expansion line 2A, 2B for transporting the expanded thermoplastic resin particles from the pressure-resistant container 1, and a recovery line 3 connected to the lower part of the pressure-resistant container 1 and separate from the expansion lines 2A and 2B, for recovering unexpanded thermoplastic resin particles in the pressure-resistant container 1.

[0064] The manufacturing apparatus 10 according to aspect 2 of the present invention is configured in such a manner that, in aspect 1, the recovery line 3 is provided with a discharge valve 3a for discharging the contents within the pressure-resistant vessel 1, and the discharge valve 3a is connected to the lowest part 1a of the pressure-resistant vessel 1.

[0065] The manufacturing apparatus 10A according to aspect 3 of the present invention is configured in such a manner that, in aspect 1 or 2, the foaming lines 2A, 2B are branched off from the recovery line 3, a discharge valve 3a for discharging the contents of the pressure-resistant container is provided upstream of the branch point 23 between the foaming lines 2A, 2B and the recovery line 3, and a first valve (on-off valve 3b) for switching the foaming lines 2A, 2B between on-off and on-off, and a second valve (on-off valve 3c) for switching the recovery line 3 between on-off and on-off are provided downstream of the branch point 23 between the foaming lines 2A, 2B and the recovery line 3.

[0066] The manufacturing apparatus 10C according to the fourth aspect of the present invention is configured in any one of the first to third aspects, in which the foaming lines 2A, 2B are branched off from the recovery line 3, and a three-way valve 8 is provided at a branching portion 23 between the foaming lines 2A, 2B and the recovery line 3.

[0067] The manufacturing apparatus 10, 10A to 10D according to a fourth embodiment of the present invention is configured in such a way that in any one of the first to fourth embodiments, the lower part of the pressure-resistant vessel 1 has a semi-elliptical or conical shape.

[0068] The method for producing expanded beads according to embodiment 6 of the present invention includes an expansion step of supplying a blowing agent into a pressure vessel 1, heating and pressurizing a dispersion containing thermoplastic resin particles and water in the pressure vessel 1 to a temperature equal to or higher than the softening temperature of the thermoplastic resin particles, and then releasing the dispersion into an atmosphere (expansion cylinders 4A, 4B) under a lower pressure than the internal pressure of the pressure vessel 1 to cause expansion; a transport step of transporting the expanded thermoplastic resin particles from the pressure vessel 1 via expansion lines 2A and 2B; and a recovery step of recovering unexpanded thermoplastic resin particles in the pressure vessel 1 via a recovery line 3 which is a system separate from the expansion lines 2A and 2B.

[0069] The method for producing expanded beads according to a seventh aspect of the present invention is a method in which the production apparatus 10, 10A to 10D according to any one of the first to fifth aspects is used in the sixth aspect. [Explanation of symbols]

[0070] 1. 1A pressure vessel 1a Bottom 2A, 2B foaming line 3. Collection Line 3a Exhaust valve 3b On-off valve (first valve) 3c On-off valve (second valve) 4, 4A, 4B Foaming cylinder (low pressure atmosphere) 8. Three-way valve 10, 10A, 10B, 10C, 10D manufacturing equipment 23 Branching section

Claims

1. a pressure vessel for foaming the thermoplastic resin particles; At least two foaming lines for transporting the thermoplastic resin foam particles from the pressure-resistant container; a recovery line connected to a lower portion of the pressure vessel and separate from the expansion line for recovering unexpanded thermoplastic resin particles remaining in the pressure vessel after the thermoplastic resin expanded particles are produced; The expanded thermoplastic resin beads are transported through at least two expansion lines, and the types of the expanded thermoplastic resin beads are different.

2. the recovery line is provided with a discharge valve for discharging the contents of the pressure vessel; The expanded beads manufacturing apparatus according to claim 1 , wherein the discharge valve is connected to a lowermost portion of the pressure vessel.

3. The foaming line is provided branching off from the recovery line, a discharge valve for discharging the contents of the pressure-resistant container is provided upstream of a branch point between the foaming line and the recovery line, 3. The expanded beads manufacturing apparatus according to claim 1, further comprising: a first valve for switching the expansion line on and off; and a second valve for switching the expansion line on and off, the first valve being disposed downstream of a branch point between the expansion line and the recovery line.

4. The foaming line is provided branching off from the recovery line, 3. The expanded beads manufacturing apparatus according to claim 1, further comprising a three-way valve provided at a branch point between said expansion line and said recovery line.

5. 5. The expanded bead manufacturing apparatus according to claim 1, wherein the lower part of the pressure vessel has a semi-elliptical or conical shape.

6. a foaming step of supplying a foaming agent into a pressure vessel, heating and pressurizing a dispersion containing thermoplastic resin particles and water to a temperature equal to or higher than the softening temperature of the thermoplastic resin particles in the pressure vessel, and then releasing the dispersion into an atmosphere under a lower pressure than the internal pressure of the pressure vessel, thereby foaming the dispersion; A transporting step of transporting the thermoplastic resin foam particles from the pressure vessel through at least two foaming lines; and a recovery step of recovering unexpanded thermoplastic resin particles remaining in the pressure vessel after the production of expanded thermoplastic resin particles through a recovery line separate from the expansion line, A method for producing expanded beads, wherein the types of expanded thermoplastic resin beads transported in at least two expansion lines are different.

7. A method for producing expanded beads according to claim 6, which uses the expanded bead production apparatus according to any one of claims 1 to 5.

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