Method and apparatus for manufacturing tubular molded body

Abstract

To enhance the continuous extrusion stability of a molten resin tube by suppressing the shaking of the molten resin tube in the preliminary water tank of the front stage of a reduced pressure water tank.SOLUTION: In the method for manufacturing a tube-shaped molded body, the cooling step includes a charging step of charging the molten resin tube (P) into a reserve water tank (20) to which cooling water is continuously supplied and a decompression water tank (30) connected to the reserve water tank (20) in this order, and a suppressing step of installing a jig (40) in the reserve water tank (20) and suppressing a flow of the cooling water from directly hitting the molten resin tube (P) by the jig (40).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for producing a tubular formed body and an apparatus for producing a tubular formed body. [Background technology]

[0002] Patent Document 1 discloses a technique for cooling a molten resin tube extruded from a die during extrusion molding, in which the molten resin tube is introduced into a spare water tank and a reduced-pressure water tank connected to the spare water tank. A sizing die is installed near the entrance of the reduced-pressure water tank. The technique disclosed in Patent Document 1 allows the cooling water in the spare water tank and the molten resin tube to be sucked into the reduced-pressure water tank, thereby achieving a sizing effect by using a sizing die installed near the entrance of the reduced-pressure water tank to improve the roundness of the molten resin tube.

[0003] In the technology of Patent Document 1, the cooling water is supplied into the auxiliary water tank in a direction coaxial with and opposite to the extrusion direction of the molten resin composition. This prevents the flow of cooling water from directly hitting the extruded molten resin tube. This prevents the molten resin tube from wobbling due to the flow of cooling water in the auxiliary water tank located upstream of the reduced pressure water tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-97580 Summary of the Invention [Problem to be solved by the invention]

[0005] However, simply setting the flow direction of the cooling water in the auxiliary water tank, as in the technology of Patent Document 1, is insufficient to prevent the molten resin tube from wobbling. For example, if the flow rate of the cooling water is high, the flow of the cooling water may be turbulent, causing the molten resin tube to wobble. Furthermore, because a large amount of cooling water is supplied to the auxiliary water tank, if the cooling water supply direction is coaxial with and opposite to the extrusion direction of the molten resin composition, the cooling water may hit the inlet wall or outlet wall of the auxiliary water tank, and the rebounded cooling water may hit the molten resin tube, causing it to wobble. If the molten resin tube wobbles in the auxiliary water tank, the continuous extrusion stability of the molten resin tube may deteriorate.

[0006] One aspect of the present invention aims to provide a method for manufacturing a tubular molded product and an apparatus for manufacturing a tubular molded product that can suppress the wobbling of a molten resin tube in a preliminary water tank located before a reduced pressure water tank and improve the continuous extrusion stability of the molten resin tube. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one embodiment of the present invention provides a method for producing a tubular molded product, comprising: an extrusion step of extruding a molten resin composition through an annular die to form a molten resin tube; and a cooling step of cooling the molten resin tube, wherein the cooling step comprises: an introduction step of introducing the molten resin tube, in the order of a reserve water tank to which cooling water is continuously supplied, and a reduced-pressure water tank connected to the reserve water tank; and a suppression step of installing a jig in the reserve water tank and using the jig to suppress the flow of cooling water from directly hitting the molten resin tube.

[0008] In order to solve the above problems, one embodiment of the present invention provides an apparatus for manufacturing tubular molded products, comprising: an extrusion section having an annular die for extruding a molten resin composition into a tube; and a cooling section for cooling the molten resin tube extruded from the annular die; the cooling section comprises a reserve water tank and a reduced pressure water tank connected to the reserve water tank, and is configured so that the molten resin tube is fed into the reserve water tank and then the reduced pressure water tank in that order; the reserve water tank comprises a supply section for continuously supplying cooling water into the reserve water tank; and a jig is installed in the reserve water tank, which prevents the flow of cooling water from the supply section from directly hitting the molten resin tube. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to suppress the wobbling of the molten resin tube in the preliminary water tank located before the reduced pressure water tank, thereby improving the stability of continuous extrusion of the molten resin tube. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a basic configuration of a manufacturing apparatus for a tubular molded article according to an embodiment of the present invention. [Figure 2] 201 is a cross-sectional view perpendicular to the height direction, and 202 is a cross-sectional view perpendicular to the length direction, in order to explain the fluctuation of a molten resin tube in a spare water tank in the manufacturing apparatus having the basic configuration shown in FIG. [Figure 3] 1 is a perspective view showing an example of a jig provided in a manufacturing apparatus for a tubular molded article according to an embodiment of the present invention. [Figure 4] 4 is a cross-sectional view perpendicular to the height direction, illustrating the effect of the jig 40 shown in FIG. 3 in suppressing the wobbling of the molten resin tube P. FIG. [Figure 5] 4 is a cross-sectional view perpendicular to the length direction, illustrating the effect of the jig 40 shown in FIG. 3 in suppressing the wobbling of the molten resin tube P. FIG. [Figure 6] 4 is a perspective view for explaining the effect of the jig 40 shown in FIG. 3 in suppressing the wobbling of the molten resin tube P. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0012] [Embodiment 1] Hereinafter, one embodiment of the present invention will be described in detail.

[0013] (Apparatus for manufacturing a tubular molded article according to this embodiment) FIG. 1 is a cross-sectional view showing the basic configuration of a manufacturing apparatus 100 for a tubular molded article according to this embodiment.

[0014] As shown in Fig. 1, as a basic configuration, a manufacturing apparatus 100 includes a melt extruder 10 (extrusion section) that extrudes a molten resin tube P, and a cooling section C. The molten resin tube P extruded from the melt extruder 10 moves to the cooling section C. The cooling section C cools the molten resin tube P extruded from the melt extruder 10. The molten resin tube P is cooled in the cooling section C to form a tubular molded product.

[0015] As shown in Figure 1, in this specification, the length direction (axial direction) of the molten resin tube P is referred to as the LD direction, with one side (front side) in the LD direction being the LDa side and the other side (rear side) being the LDb side. Furthermore, the direction (height direction) perpendicular to the LD direction and the horizontal plane is referred to as the HD direction, with one side (upper side) in the HD direction being the HDa side and the other side (lower side) being the HDb side. Furthermore, the direction (width direction) perpendicular to both the LD and HD directions is referred to as the WD direction.

[0016] In the manufacturing apparatus 100, the LD direction is the same as the extrusion direction of the molten resin tube P, and it can be said that the LDb side is the downstream side in the extrusion direction of the molten resin tube P, and the LDa side is the upstream side in the extrusion direction of the molten resin tube P. That is, in the manufacturing apparatus 100, the molten resin tube P extruded from the melt extruder 10 moves from the LDb side to the LDa side.

[0017] The melt extruder 10 melts and kneads the resin composition to produce a molten resin composition. Any conventionally known melt extruder can be used as the melt extruder 10 as long as it is capable of melt-kneading the resin composition to produce a molten resin composition. The melt extruder 10 has an annular die 11 for extruding the molten resin composition into a tubular shape. By being extruded through the annular die 11, the molten resin composition becomes tubular, and a molten resin tube P is obtained. The annular die 11 is attached to the tip of the HDa side of the melt extruder 10.

[0018] The cooling section C includes a spare water tank 20 and a reduced pressure water tank 30 connected to the spare water tank 20. The cooling section C is configured so that the molten resin tube P is introduced into the spare water tank 20 and then the reduced pressure water tank 30 in that order. In the cooling section C, the spare water tank 20 is connected to an inlet 31a on the LDb side of the reduced pressure water tank 30.

[0019] The spare water tank 20 is a water tank that pre-cools the molten resin tube P before it is sucked into the decompression water tank 30. The spare water tank 20 has an inlet 21 on the LDb side. The molten resin tube P is introduced into the spare water tank 20 through the inlet 21. The spare water tank 20 also has a supply unit 22. The supply unit 22 continuously supplies cooling water into the spare water tank 20. The supply unit 22 is provided on one wall of the spare water tank 20 in the WD direction. The supply unit 22 is configured to discharge cooling water into the spare water tank 20. The supply direction (discharge direction) of the cooling water by the supply unit 22 is the WD direction, which is different from the LD direction. Therefore, the supply of cooling water by the supply unit 22 causes a flow of cooling water in the WD direction within the spare water tank 20.

[0020] The auxiliary water tank 20 is also equipped with a sizing die 23. The sizing die 23 is provided at the connection between the auxiliary water tank 20 and the inlet 31a of the reduced pressure water tank 30. The auxiliary water tank 20 and the reduced pressure water tank 30 are connected to each other via the sizing die 23. Therefore, the molten resin tube P and cooling water in the auxiliary water tank 20 are sucked under reduced pressure through the sizing die 23 and flow into the reduced pressure water tank 30. Therefore, in the auxiliary water tank 20, in addition to the flow of cooling water from the supply unit 22, a flow of cooling water toward the sizing die 23 is generated.

[0021] The reduced pressure water tank 30 is a water tank for further cooling and solidifying the molten resin tube P that has been pre-cooled in the spare water tank 20. The reduced pressure water tank 30 contains cooling water to the extent that the molten resin tube P is immersed in the water. The reduced pressure water tank 30 is equipped with a vacuum pump (not shown) that sucks in only air. The reduced pressure inside the reduced pressure water tank 30 is maintained under reduced pressure by this vacuum pump.

[0022] In the manufacturing apparatus 100, the molten resin tube P extruded from the annular die 11 is pre-cooled in the auxiliary water tank 20. Then, the molten resin tube P, together with the cooling water in the auxiliary water tank 20, is introduced into the reduced pressure water tank 30 from the inlet 31a by vacuum suction and is discharged from the outlet 31b. When the molten resin tube P is introduced into the reduced pressure water tank 30 by vacuum suction, the molten resin tube P is sized by the sizing die 23 so that its diameter is reduced, thereby improving the roundness of the molten resin tube P (sizing effect).

[0023] Figure 2 is a diagram for explaining the wobble of the molten resin tube P in the spare water tank 20 in the manufacturing apparatus 100 as the prerequisite configuration shown in Figure 1, where 201 in Figure 2 is a cross-sectional view perpendicular to the HD direction, and 202 in Figure 2 is a cross-sectional view perpendicular to the LD direction.

[0024] 2, the supply direction (discharge direction) of cooling water from supply unit 22 is the WD direction, which is different from the LD direction. Furthermore, a large amount of cooling water is supplied from supply unit 22 into spare water tank 20 to pre-cool the molten resin tube P. Therefore, the flow of cooling water from supply unit 22 directly hits the molten resin tube P being extruded in the LD direction in spare water tank 20, causing the molten resin tube P to wobble in the WD direction.

[0025] As shown in 202 in FIG. 2, in the manufacturing apparatus 100 as a prerequisite configuration, the spare water tank 20 may include a supply unit 24 in addition to the supply unit 22. The supply unit 24 is provided on the lower surface (the surface on the HDb side) of the spare water tank 20 and is configured to discharge cooling water from the HDb side to the HDa side. In the configuration shown in 202 in FIG. 2, the supply direction (discharge direction) of cooling water by the supply unit 24 is the HD direction. In the configuration shown in 202 in FIG. 2, the flow of cooling water from the supply unit 24 directly hits the molten resin tube P being extruded in the LD direction in the spare water tank 20, causing the molten resin tube P to wobble in the HD direction.

[0026] As described above, the wobbling of the molten resin tube P deteriorates the stability of continuous extrusion of the molten resin tube P. Furthermore, the position at which the molten resin tube P enters the sizing die 23 is unstable, which deteriorates the sizing effect of the molten resin tube P.

[0027] Therefore, the manufacturing apparatus 100 according to this embodiment is configured such that a jig is installed in the auxiliary water tank 20, and the jig prevents the flow of cooling water from the supply unit 22 or 24 from directly hitting the molten resin tube P. This configuration prevents the molten resin tube P from wobbling in the auxiliary water tank 20, improving the stability of continuous extrusion of the molten resin tube P. Furthermore, with the above configuration, the position at which the molten resin tube P enters the sizing die 23 is stabilized, improving the sizing effect of the molten resin tube P.

[0028] In the manufacturing apparatus 100 according to this embodiment, the jig may be installed in the spare water tank 20 and may be designed appropriately depending on the direction of the cooling water flow, etc., as long as it is configured to prevent the cooling water flowing in directions other than the LD direction from directly hitting the molten resin tube P. The jig may have a wall portion that receives the cooling water flow.

[0029] Fig. 3 is a perspective view showing an example of a jig 40 provided in the manufacturing apparatus 100 according to this embodiment. Figs. 4 to 6 are diagrams for explaining the effect of suppressing the wobbling of the molten resin tube P by the jig 40 shown in Fig. 3, Fig. 4 is a cross-sectional view perpendicular to the HD direction, Fig. 5 is a cross-sectional view perpendicular to the LD direction, and Fig. 6 is a perspective view.

[0030] As shown in Fig. 3, the jig 40 has a passage 41. The passage 41 has two side walls 41a and a bottom wall 41b. The bottom wall 41b connects the two side walls 41a. The two side walls 41a and the bottom wall 41b form a groove with a U-shaped cross section that extends in the LD direction and is open on the HDa side. The jig 40 has, for example, a trough-shape as the passage 41.

[0031] As shown in FIGS. 4 and 5, the jig 40 has a passage 41 that guides the molten resin tube P to the reduced-pressure tank. In other words, the jig 40 is installed in the spare tank 20 so that the molten resin tube P fits within the passage 41. The length of the jig 40 in the LD direction is smaller than the distance between two inner wall surfaces of the spare tank 20 that face each other in the LD direction. As shown in FIG. 4, the jig 40 is arranged so that the inlet on the LDb side of the passage 41 is in contact with the inlet 21 of the spare tank 20. For this reason, a gap D is formed between the passage 41 of the jig 40 and the inner wall surface on the LDa side of the spare tank 20.

[0032] Next, the effect of the jig 40 in suppressing the wobbling of the molten resin tube P will be described. Note that in FIGS. 4 to 6, the flow of cooling water in the spare water tank 20 is indicated by arrows. As shown in FIG. 4, the side wall portion 41a receives the flow of cooling water from the supply portion 22. This prevents the flow of cooling water from the supply portion 22 from directly hitting the molten resin tube P. Furthermore, as shown in FIG. 5, the bottom wall portion 41b receives the flow of cooling water from the supply portion 24. This prevents the flow of cooling water from the supply portion 24 from directly hitting the molten resin tube P.

[0033] As described above, according to this embodiment, the jig 40 is arranged so that the molten resin tube P is contained within the passage portion 41, thereby preventing the flow of cooling water from the supply portions 22 and 24 from directly hitting the molten resin tube P. This prevents the molten resin tube P from wobbling in the spare water tank 20, improving the stability of continuous extrusion of the molten resin tube P. Furthermore, the position at which the molten resin tube P enters the sizing die 23 is stabilized, improving the sizing effect of the molten resin tube P.

[0034] Furthermore, the cooling water supplied to the auxiliary water tank 20 flows into the passage 41 and cools the molten resin tube P. Although this cooling water indirectly hits the molten resin tube P, it does not affect the wobbling of the molten resin tube P. Specifically, the cooling water from the supply units 22 and 24 flows into the passage 41 of the jig 40 through the gap D and indirectly hits the molten resin tube P. Furthermore, because a large amount of cooling water is supplied to the auxiliary water tank 20, the cooling water flows into the passage 41 beyond the end face (top surface) on the HDa side of the passage 41 and indirectly hits the molten resin tube P. The cooling water that flows into the passage 41 in this manner is affected by the decompression suction caused by the decompression water tank. Therefore, since the flow direction of this cooling water is approximately in the LD direction, it does not affect the wobbling of the molten resin tube P.

[0035] Furthermore, it is sufficient that the spare water tank 20 includes at least one of the supply units 22 and 24. For example, if the spare water tank 20 includes only the supply unit 22, depending on the amount of cooling water, the effect of the cooling water directly hitting the molten resin tube P from the HDb may be small. In such a case, the passage unit 41 of the jig 40 does not need to include the bottom wall unit 41b. However, even if the spare water tank 20 includes only the supply unit 22, it is preferable that the passage unit 41 include the bottom wall unit 41b from the viewpoint of reducing the effect of the cooling water directly hitting the molten resin tube P.

[0036] Furthermore, cooling water in the spare water tank 20 flows into the passage 41, and the molten resin tube P accommodated in the passage 41 is pre-cooled. The passage 41 is not limited to the configuration shown in FIGS. 3 to 6 as long as it is configured to allow the inflow of cooling water. For example, the passage 41 may be configured so that the HDa side is open and no gap D is formed. Alternatively, the passage 41 may be configured so that the HDa side is closed by an upper wall portion and a gap D is formed.

[0037] (Method of manufacturing a tubular molded article according to this embodiment) The method for producing a tubular molded product according to this embodiment includes an extrusion step and a cooling step. The extrusion step is a step of extruding a molten resin composition through an annular die to form a molten resin tube, and the cooling step is a step of cooling the molten resin tube. In the method for producing a tubular molded product according to this embodiment, the cooling step includes a charging step and a charging step. The charging step is a step of charging the molten resin tube, in this order, into a spare water tank to which cooling water is continuously supplied and a reduced-pressure water tank connected to the spare water tank, and the suppression step is a step of installing a jig in the spare water tank and using the jig to suppress the flow of cooling water from directly hitting the molten resin tube.

[0038] The method for producing a tubular molded article according to this embodiment is not particularly limited as long as it includes the extrusion step and the cooling step, and the cooling step includes the introducing step and the suppressing step. For example, the method for producing a tubular molded article according to this embodiment can be a method using the above-described manufacturing apparatus 100. Hereinafter, various steps of the method for producing a tubular molded article according to this embodiment will be described using the method using the manufacturing apparatus 100 as an example.

[0039] First, in the extrusion step, a molten resin composition is extruded through an annular die 11 to form a molten resin tube P. In this extrusion step, the resin composition is melt-kneaded by a melt extruder 10 and transferred to the annular die 11, and the resulting molten resin composition is extruded through the annular die 11.

[0040] The manner in which the resin composition is melt-kneaded by the melt extruder 10 is not particularly limited as long as a melt-kneaded resin composition can be obtained. Specific examples of the melt-kneading method include the following methods (a1) and (a2): (a1) A method in which a resin composition containing a thermoplastic resin is prepared by mixing or blending using a mixer or the like, and then the resin composition is supplied to a melt extruder 10 and melt-kneaded; (a2) A method in which raw materials for a resin composition containing a thermoplastic resin are supplied to a melt extruder 10, a resin composition is prepared (completed) in the melt extruder 10, and the resin composition is melt-kneaded.

[0041] In the method (a1), the order in which the raw materials for the resin composition are mixed or blended (dry blended) is not particularly limited. In the method (a2), the order in which the raw materials for the resin composition are supplied to the melt extruder 10 is not particularly limited.

[0042] In the method (a1), the mixing device is not particularly limited, and examples thereof include a ribbon blender, a flash blender, a tumbler mixer, and a super mixer.

[0043] In the methods (a1) and (a2), a kneader, a Banbury mixer, a roll, and the like can be used as the melt-kneading device in addition to the melt extruder 10. From the viewpoint of superior productivity and convenience, the melt-kneading device is preferably the melt extruder 10. Furthermore, the melt extruder 10 is preferably a twin-screw extruder.

[0044] The temperature at which the resin composition is melt-kneaded cannot be generally defined because it depends on the physical properties (melting point, weight-average molecular weight, etc.) of the thermoplastic resin used as the raw material and the type of additives used. When a polyhydroxyalkanoic acid resin (described below) is used as the thermoplastic resin, the temperature at which the resin composition is melt-kneaded is preferably 155°C to 175°C, and more preferably 165°C to 173°C, for example. If the composition temperature is 155°C or lower, unmelted polyhydroxyalkanoic acid resin may be generated. On the other hand, if the composition temperature is 175°C or higher, the polyhydroxyalkanoic acid resin may be thermally decomposed.

[0045] In the cooling process, the molten resin tube P extruded from the annular die 11 is cooled. In the charging process of the cooling process, the molten resin tube P is charged, in this order, into the auxiliary water tank 20 to which cooling water is continuously supplied, and then into the reduced pressure water tank 30 connected to the auxiliary water tank 20. In this charging process, the molten resin tube P, together with the cooling water in the auxiliary water tank 20, is charged into the reduced pressure water tank 30 from the inlet 31a by reduced pressure suction. When charged into the reduced pressure water tank 30 by reduced pressure suction, the molten resin tube P is sized by the sizing die 23 so that its diameter is reduced, improving the roundness of the molten resin tube P (sizing effect).

[0046] In the suppression process, a jig 40 is placed in the spare water tank 20, and the jig 40 prevents the flow of cooling water from directly hitting the molten resin tube P. This prevents the molten resin tube P from wobbling in the spare water tank 20, improving the stability of continuous extrusion of the molten resin tube P. Furthermore, the position at which the molten resin tube P enters the sizing die 23 is stabilized, improving the sizing effect of the molten resin tube P.

[0047] In the manufacturing method of the tubular molded article according to this embodiment, the jig 40 preferably has a passage 41 that guides the molten resin tube P to the reduced pressure water tank 30. In the suppression step, the jig 40 is preferably installed so that the side wall 41a of the passage 41 receives the flow of cooling water. This further prevents the molten resin tube P from wobbling in the spare water tank 20.

[0048] In the manufacturing method of a tubular molded article according to this embodiment, the inflow rate of cooling water supplied to the preliminary water tank 20 is not particularly limited as long as it is an amount that can pre-cool the molten resin tube P. For example, when a polyhydroxyalkanoic acid resin, which will be described later, is used as the raw material for the molten resin tube P, the inflow rate of cooling water supplied to the preliminary water tank 20 is preferably 30 mL / sec or more, and more preferably 60 mL / sec or more. The upper limit of the inflow rate of cooling water supplied to the preliminary water tank 20 is not particularly limited, but is preferably 150 mL / sec or less, and more preferably 100 mL / sec or less. In particular, when a polyhydroxyalkanoic acid resin, which will be described later, is used as the raw material for the molten resin tube P, the polyhydroxyalkanoic acid resin has a slow solidification rate, so the molten resin tube P is easily deformed. For this reason, the inflow rate of cooling water supplied to the preliminary water tank 20 is large, as in the above-mentioned numerical range. In such a state where the inflow rate of cooling water is large, simply setting the discharge direction of cooling water from supply section 22 so that molten resin tube P is coaxial with molten resin tube P makes it difficult to suppress the flow of cooling water to an extent that can suppress wobbling of molten resin tube P. According to the manufacturing method for a tubular molded body of this embodiment, even if the inflow rate of cooling water supplied to reserve water tank 20 is large, as in the above numerical range, because jig 40 is installed in the suppression step, wobbling of molten resin tube P in reserve water tank 20 can be prevented.

[0049] The temperature of the cooling water supplied to the preliminary water tank 20 may be any temperature that can pre-cool the molten resin tube P, and can be set appropriately depending on the raw material of the molten resin tube P. For example, when a polyhydroxyalkanoic acid resin described below is used as the raw material of the molten resin tube P, the temperature of the cooling water is preferably 5°C to 60°C, and more preferably 20°C to 60°C.

[0050] (Resin composition used in the method for producing a tubular molded article according to this embodiment) The resin composition used in the method for producing a tubular molded article according to this embodiment, i.e., the resin composition constituting the raw material of the molten resin tube P, contains a thermoplastic resin. The thermoplastic resin is not particularly limited. Preferred thermoplastic resins include general-purpose resins such as polypropylene, polyethylene, polyvinyl chloride, polyvinyl acetate, polyacetal, polycarbonate, polyamide, acrylonitrile, butadiene, polystyrene, and acrylic polymers, as well as biodegradable resins such as P3HA resin, polylactic acid, polyglycolic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polybutylene succinate terephthalate, and polycaprolactone. The thermoplastic resins may be used alone or in combination of two or more.

[0051] In particular, the resin composition preferably contains an aliphatic polyester resin. Furthermore, the aliphatic polyester resin is preferably a poly(3-hydroxyalkanoate) resin (hereinafter, sometimes referred to as a P3HA resin). In this specification, the term "P3HA resin" refers to a 3-hydroxyalkanoic acid repeating unit represented by the general formula: [-CHR-CH2-CO-O-] (wherein R is C n H 2n+1 and n is an integer of 1 or more and 15 or less.) as a repeating unit.

[0052] More specifically, the P3HA-based resin preferably contains 3-hydroxybutyrate (3HB) units. The P3HA-based resin containing 3HB units is preferably selected from the group consisting of poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). The P3HA resin may contain only one type, or may contain two or more types.

[0053] The P3HA resin is preferably a P3HA resin produced by a microorganism (a microbially produced P3HA resin). A microbially produced P3HA resin is usually composed only of D-form (R-form) polyhydroxyalkanoate monomer units. Among the microbially produced P3HA resins, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferred because of ease of industrial production, with P3HB, P3HB3HH, P3HB3HV, and P3HB4HB being more preferred.

[0054] P3HA-based resins can also be produced by, for example, the method described in WO 2010 / 013483. Commercially available P3HA-based resins include Kaneka Biodegradable Polymer PHBH (registered trademark) manufactured by Kaneka Corporation.

[0055] Furthermore, the P3HA-based resin contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin account for 65.0 to 99.0 mol % of all repeating units (100 mol %), preferably 68.0 to 98.5 mol %, more preferably 70.0 to 98.5 mol %, and even more preferably 70.0 to 98.0 mol %.

[0056] When the composition ratio of 3HB repeating units is 90.0 mol% or more, the rigidity of the P3HA-based resin is improved, the crystallization rate is accelerated, flash is reduced, and productivity tends to be improved. On the other hand, when the composition ratio of 3HB repeating units is 99.0 mol% or less, the melting point is below the thermal decomposition temperature, enabling stable and continuous production. The monomer composition ratio of the P3HA-based resin can be measured by gas chromatography or the like (see, for example, WO 2014 / 020838).

[0057] The molecular weight of the P3HA resin is not particularly limited as long as it exhibits substantially sufficient physical properties for the intended application. The weight-average molecular weight of the P3HA resin is preferably in the range of 100,000 to 1,000,000, more preferably 150,000 to 700,000, even more preferably 200,000 to 500,000, and particularly preferably 250,000 to 450,000. A weight-average molecular weight of 100,000 or more ensures adequate mechanical strength. Furthermore, a molecular weight of 1,000,000 or less can suppress an increase in melt viscosity, resulting in excellent moldability.

[0058] The weight-average molecular weight can be measured using gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) with a polystyrene gel column (Shodex K-804 manufactured by Showa Denko K.K.) and chloroform as the mobile phase, and can be calculated as a polystyrene-equivalent molecular weight. A calibration curve is prepared using polystyrenes with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. A column suitable for measuring the molecular weight can be used for the GPC.

[0059] The resin composition may also contain additives that can be used with the thermoplastic resin, provided that the effects of the present invention are not impaired. Examples of such additives include inorganic fillers such as talc, calcium carbonate, mica, and silica; colorants such as pigments and dyes; odor absorbers such as activated carbon and zeolite; fragrances such as vanillin and dextrin; plasticizers; antioxidants; weather resistance improvers; ultraviolet absorbers; crystal nucleating agents; lubricants; release agents; water repellents; antibacterial agents; and sliding properties improvers. Only one type of additive may be contained, or two or more types may be contained. The content of these additives can be appropriately determined by those skilled in the art depending on the intended use.

[0060] According to this embodiment, when a P3HA-based resin is used as a raw material for the tubular molded body, marine pollution due to waste can be suppressed, thereby contributing to the achievement of Sustainable Development Goals (SDGs) such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and sustainably use the oceans and marine resources for sustainable development."

[0061] The tubular molded article produced by the production method according to this embodiment may be any tubular molded article that can be produced by extrusion molding. Examples of such tubular molded articles include straws, pipes, hollow fibers, etc., with straws being preferred.

[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] That is, one embodiment of the present invention is as follows.

[0064] <1> an extrusion step of extruding the molten resin composition through an annular die 11 to form a molten resin tube P; a cooling step of cooling the molten resin tube P, The cooling step a step of introducing the molten resin tube P into a spare water tank 20 to which cooling water is continuously supplied and a reduced pressure water tank 30 connected to the spare water tank 20, in that order; A method for manufacturing a tubular molded body, comprising: a suppression step of placing a jig (40) in the preliminary water tank (20) and using the jig (40) to suppress the flow of cooling water from directly hitting the molten resin tube (P).

[0065] <2> The jig 40 has a passage 41 that guides the molten resin tube P to the reduced pressure water tank 30, In the suppression step, the jig 40 is installed so that the side wall portion 41a of the passage portion 41 receives the flow of the cooling water. <1> A method for producing a tubular molded article.

[0066] <3> The jig 40 has a trough shape. <2> A method for producing a tubular molded article.

[0067] <4> The inflow rate of the cooling water supplied to the spare water tank 20 is 30 mL / sec or more. <1> ~ <3> 1. A method for producing the tubular molded article according to any one of the preceding claims.

[0068] <5> an extrusion section (melt extruder 10) having an annular die 11 for extruding a molten resin composition into a tubular shape; a cooling section C for cooling the molten resin tube P extruded from the annular die 11, The cooling section C includes a spare water tank 20 and a reduced pressure water tank 30 connected to the spare water tank 20, and is configured so that the molten resin tube P is introduced into the spare water tank 20 and then the reduced pressure water tank 30, The auxiliary water tank 20 is provided with supply units 22 and 24 that continuously supply cooling water into the auxiliary water tank 20, A jig 40 is installed in the spare water tank 20, and the jig 40 prevents the flow of cooling water from the supply sections 22, 24 from directly hitting the molten resin tube P, in this tubular molded body manufacturing apparatus.

[0069] <6> The jig 40 has a passage 41 for guiding the molten resin tube P to the reduced pressure water tank 30, The passage portion 41 includes a side wall portion 41a that receives the flow of cooling water from the supply portion 22. <5> A manufacturing apparatus for tubular moldings.

[0070] <7> The jig 40 has a trough shape. <6> A manufacturing apparatus for tubular moldings. [Example]

[0071] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0072] The substances used in the examples and comparative examples are shown below.

[0073] [Poly(3-hydroxyalkanoate) resin] Copolymer (A): P3HB3HH-30: P3HB3HH (average content ratio of 3HB / 3HH = 70.5 / 29.5 (mol% / mol%), weight average molecular weight is 640,000 g / mol) Produced in accordance with the method described in Example 9 of WO 2019 / 142845.

[0074] Copolymer (B): P3HB3HH-11H: P3HB3HH (Kaneka Biodegradable Polymer PHBH (registered trademark)) (average content ratio 3HB / 3HH = 89.0 / 11.0 (mol % / mol %), weight average molecular weight 750,000 g / mol) It was produced according to the method described in WO 2008 / 010296.

[0075] Poly(3-hydroxybutyrate) (C1): PHB: Poly(3-hydroxybutyrate) (weight average molecular weight: 300,000 g / mol) It was produced according to the method described in Comparative Example 1 of WO 2004 / 041936.

[0076] Copolymer (C2): P3HB3HH-3: P3HB3HH (average content ratio of 3HB / 3HH = 97.1 / 2.9 (mol% / mol%), weight average molecular weight is 300,000 g / mol) It was produced in accordance with the method described in Example 2 of WO 2019 / 142845. P3HB3HH-6: P3HB3HH (average content ratio of 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 500,000 g / mol) It was produced according to the method described in WO 2008 / 010296.

[0077] Copolymer (C3): P3HB3HH-13: P3HB3HH (Kaneka Biodegradable Polymer PHBH (registered trademark)) (average content ratio 3HB / 3HH = 87.1 / 12.9 (mol% / mol%), weight average molecular weight 330,000 g / mol) [Additives] Additive-1: Behenamide (Nippon Fine Chemical Co., Ltd.: BNT-22H) Additive-2: Erucic acid amide (Neutron-S, manufactured by Nippon Fine Chemical Co., Ltd.).

[0078] [Plasticizer] Plasticizer: Glycerin diacetomonolaurate (BIOCIZER, manufactured by Riken Vitamin Co., Ltd.).

[0079] The evaluation methods used in the examples and comparative examples are described below.

[0080] [Evaluation of dizziness] During tube molding, the position of the molten resin tube extruded from the annular die in the auxiliary water tank was visually confirmed. If the molten resin tube moved 2 mm or more in a direction perpendicular to the extrusion direction, it was evaluated as "wobble (present)," and if it moved less than 2 mm, it was evaluated as "no wobble (absent)."

[0081] [Evaluation of stable moldability] Tube molding was carried out, and if molding could be continued for 10 minutes or more, the stable molding was evaluated as good, and if molding ceased in less than 10 minutes, the stable molding was evaluated as poor.

[0082] Example 1 To obtain the resin composition shown in Table 1, 0.494 kg of P3HB3HH-30, 0.094 kg of P3HB3HH-11H, 0.248 kg of PHB, 0.87 kg of P3HB3HH-3, 0.292 kg of P3HB3HH-13, 20 g of additive-1, and 10 g of additive-2 were mixed and blended.

[0083] The blend was melt-extruded using a φ26 mm co-rotating twin-screw extruder. The cylinder temperature and die temperature of the co-rotating twin-screw extruder were both set to 150°C. The extruded strand-like resin material was passed through a water bath filled with warm water at 40°C and cut using a pelletizer to obtain resin composition pellets.

[0084] The resin composition pellets were then used as raw material to form a tube using a φ50 mm single-screw extruder. A circular die (outer diameter 15 mm, inner diameter 13.5 mm) was connected to the extruder, and the cylinder temperature and die temperature were both set to 160°C. The water tank was filled with warm water at 40°C. The position of the water tank was adjusted so that the distance from the die to the water tank entrance was 50 mm. The flow rate of cooling water supplied to the auxiliary water tank (referred to as "water flow rate" in Table 1) was set to 30 ml / sec, and the jig shown in Figure 3 was installed inside the auxiliary water tank.

[0085] The screw rotation speed of the extruder was adjusted so that the extrusion rate was 10 kg / hour, and the take-off speed of the take-off machine was set to 10 m / min. After that, the molten resin tube was taken up, and after waiting for 5 minutes for the take-off to stabilize, evaluation of wobbling and extrusion stability was carried out.

[0086] (Examples 2 to 3, Comparative Example 1) Except for the flow rate of the cooling water supplied to the spare water tank and whether or not a jig was installed, the tube was formed in the same manner as in Example 1, and the same evaluations were carried out as in Example 1. The results are summarized in Table 1.

[0087] [Table 1]

[0088] As can be seen from Table 1, in Examples 1 to 3 in which a jig was installed in the spare water tank, the wobbling of the molten resin tube was suppressed, and the molding stability (continuous extrusion stability) of the molten resin tube was improved. [Industrial Applicability]

[0089] The present invention can be used in the field of extrusion molding of tubular molded articles. [Explanation of symbols]

[0090] 10 Melt extruder (extrusion section) 11 Circular Dies 20 Spare tank 22, 24 Supply section 30 Decompression Tank 40 Jig 41 Passage section 41a Side wall part 41b Bottom wall 100 Manufacturing equipment P Melt Resin Tube

Claims

1. an extrusion step of extruding the molten resin composition through an annular die to form a molten resin tube; a cooling step of cooling the molten resin tube, The cooling step a step of introducing the molten resin tube into a spare water tank to which cooling water is continuously supplied and a reduced-pressure water tank connected to the spare water tank, in that order; a suppression step of placing a jig in the preliminary water tank and using the jig to suppress the flow of cooling water from directly hitting the molten resin tube.

2. the jig has a passage portion that guides the molten resin tube to a reduced-pressure water tank, The method for producing a tubular formed article according to claim 1 , wherein in the suppression step, the jig is placed so that a side wall of the passage receives the flow of the cooling water.

3. The method for producing a tubular formed article according to claim 2 , wherein the jig has a trough shape.

4. The method for producing a tubular molded article according to claim 1, wherein the inflow rate of the cooling water supplied to the preliminary water tank is 30 mL / sec or more.

5. an extrusion section having an annular die for extruding the molten resin composition into a tubular shape; a cooling unit that cools the molten resin tube extruded from the annular die, the cooling unit includes a spare water tank and a reduced-pressure water tank connected to the spare water tank, and the molten resin tube is introduced into the spare water tank and then the reduced-pressure water tank, the auxiliary water tank includes a supply unit that continuously supplies cooling water into the auxiliary water tank; A jig is installed in the preliminary water tank, and the jig prevents the flow of cooling water from the supply section from directly hitting the molten resin tube, in this tubular molded body manufacturing apparatus.

6. the jig has a passage portion for guiding the molten resin tube to the reduced-pressure water tank, The tubular molding manufacturing apparatus according to claim 5 , wherein the passage portion has a side wall portion that receives the flow of cooling water from the supply portion.

7. The apparatus for manufacturing a tubular molding according to claim 6 , wherein the jig has a trough shape.

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