Method for manufacturing extruded articles

Abstract

Provided is a method for manufacturing an extruded body, which can stably and continuously manufacture a PHA extruded body using a polyhydroxyalkanoate (PHA) powder granulate. 【Solution means】The method for manufacturing an extruded body includes extruding polyhydroxyalkanoate (PHA) using an extruder. The extrusion molding includes melting a powder granulate containing PHA powder at a plasticizing melting temperature T P (unit: °C) to obtain a melt, extruding the melt from a die, and cooling and solidifying the extruded melt. The plasticizing melting temperature T P is represented by formula (1) T M -10 < T P ≦ T M +20 (1) (wherein, T M (unit: °C) represents the highest melting peak temperature observed in differential scanning calorimetry in which the powder granulate is heated from room temperature at a rate of 10 °C / min in a nitrogen atmosphere.) is satisfied.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing an extruded article. [Background technology]

[0002] Polyhydroxyalkanoates (PHAs) are biopolyester resins produced by microorganisms within their bodies and are known for their biodegradability in marine environments. However, PHAs also decompose easily with heat; for example, thermal decomposition progresses significantly at temperatures above 180°C. Furthermore, although PHAs are crystalline polymers, their slow crystallization rate leads to problems in extrusion molding, such as adhesion to cooling rolls, fusion of extruded bodies, and instability of shape and dimensions due to post-shrinkage. For this reason, in PHA extrusion molding, pellets made by melt-kneading raw PHA powder (hereinafter sometimes referred to as "molten pellets") to which a crystallization nucleating agent is added, or molten pellets made by compounding PHA with other resins are sometimes used as the molding material. However, crystallization nucleating agents can cause the extruded material to stick to the cooling rolls and generate deposits on the die (called eye discharge), hindering continuous molding. Moreover, the production of PHA molten pellets by the melt-kneading process requires a large amount of electricity. Products manufactured using molten pellets made by compounding PHA with other resins generally tend to have a slower ocean decomposition rate.

[0003] Patent Document 1 discloses a powder granule that can be manufactured without melting and kneading. The powder granule is manufactured with less thermal history and less power consumption than molten pellets.

[0004] Patent Document 2 discloses a powder granule that can exhibit excellent crystallization properties due to the "melt memory effect" without the addition of a crystallization nucleating agent. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 7387950 [Patent Document 2] Patent No. 7454097 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] This disclosure provides a method for manufacturing extruded articles that can stably and continuously produce PHA extruded articles using PHA powder granules. [Means for solving the problem]

[0007] The forms of this disclosure include the following: [Aspect 1] A method for manufacturing an extruded article, This includes extruding polyhydroxyalkanoate (PHA) using an extrusion molding machine. The aforementioned extrusion molding process plasticizes the powder granules containing PHA powder at a melting temperature T P The process includes melting at (unit: °C) to obtain a molten material, extruding the molten material from a die, and cooling the extruded molten material to solidify it. The plasticizing melting temperature T P However, equation (1) T M -10 <T P ≦T M +20 (1) (In the formula, T M (Unit: °C) represents the highest melting peak temperature observed in differential scanning calorimetry, where the powder granules are heated from room temperature at a rate of 10 °C / min in a nitrogen atmosphere. A method to satisfy the requirements. [Aspect 2] The method according to embodiment 1, wherein the powder granules have a melt memory effect. [Aspect 3] The method according to embodiment 1 or 2, wherein the powder granules are compressed granules. [Aspect 4] The method according to aspect 3, wherein the powder granule has an outer wall portion formed by melting and solidifying at least a part of the PHA powder located at the outer edge of the powder granule, and the PHA powder compressed inside the outer wall portion is contained therein. [Aspect 5] The die is a T-shaped die, The method according to any one of aspects 1 to 4, wherein the melt extruded from the die is cooled by at least one cooling roll. [Aspect 6] The at least one cooling roll includes a first roll and a second roll that sandwich the melt, The cooled melt is conveyed along the surface of the second roll, The surface temperature T of the first roll R1 (unit: °C), the surface temperature T of the second roll R2 (unit: °C), and the crystallization temperature T of the powder granule C satisfy equations (2), equation (3), and equation (4) T C -80 < T R1 ≤ T C (2) T C -60 < T R2 ≤ T C (3) T R1 < T R2 (4) and satisfy The crystallization temperature T of the powder granule C is defined as the peak temperature of the crystallization exothermic peak observed during cooling in differential scanning calorimetry in which the powder granule is heated from room temperature to 180 °C at a rate of 10 °C / min, held at 180 °C for 2 minutes, and then cooled at a rate of 10 °C / min in a nitrogen atmosphere. The method according to aspect 5. [Aspect 7] The surface temperature T of the second roll R2 is 50 °C to 80 °C. The method according to aspect 6. [Aspect 8] The method according to any one of aspects 1 to 7, wherein the extrusion molding machine has a single-screw flight screw having a supply zone, a compression zone, and a metering zone. [Aspect 9] The method according to embodiment 8, wherein the extrusion molding is performed at a screw rotation speed of 100 rpm or less. [Aspect 10] Crystallization temperature T of the aforementioned powder granules C The temperature (in degrees Celsius) is 80°C or higher. The crystallization temperature T of the powder granules C The method according to any one of embodiments 1 to 9, wherein the powder granules are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, and the peak temperature of the crystallization exothermic peak observed during cooling is defined as the peak temperature of the crystallization exothermic peak observed during cooling. [Aspect 11] The method according to any one of embodiments 1 to 4, or embodiments 8 to 10 that reference embodiments 1 to 4, wherein the extruded article has a tubular shape. [Aspect 12] The crystallization temperature T of the extruded body CA (Unit: °C) and the crystallization temperature T of the powder granules. C (Unit: °C) is given by equation (5) 0.8≦T CA / T C ≤1.2 (5) Satisfying the conditions, The crystallization temperature T of the powder granules C However, in differential scanning calorimetry where the powder granules are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, the peak temperature of the crystallization exothermic peak observed during cooling is defined as follows: The crystallization temperature T of the extruded body CA The method according to any one of embodiments 1 to 11, wherein the extruded body is heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, and the peak temperature of the crystallization exothermic peak observed during cooling is defined as the peak temperature of the crystallization exothermic peak. [Aspect 13] Melt flow rate (MFR) of the PHA powder ORI (Unit: g / 10min), Melt flow rate MFR of the powder granules. GRN(Unit: g / 10min), and the melt flow rate (MFR) of the extruded product. ART (Unit: g / 10min) is given by formulas (a), (b), and (c) 1 ≤ MFR GRN / MFR ORI ≤5 (a) 1 ≤ MFR ART / MFR GRN ≤5 (b) 1 ≤ MFR ART / MFR ORI ≤10 (c) The melt flow rate MFR of the PHA powder satisfies the following conditions. ORI , the melt flow rate MFR of the powder granules GRN , and the melt flow rate MFR of the extruded product ART However, the method according to any one of embodiments 1 to 12, measured at 165°C and a load of 5 kg in accordance with ISO 1133. [Effects of the Invention]

[0008] This disclosure provides a method for manufacturing extruded articles that enables the stable and continuous production of PHA extruded articles using PHA powder granules. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing an example of an extrusion molding machine used in the method according to the embodiment. [Figure 2] These are the temperature-induced DSC curves for the PHA powder and PHA powder granules used in the examples. [Figure 3] These are the temperature cooling DSC curves for the PHA powder and PHA powder granules used in the examples. [Modes for carrying out the invention]

[0010] A. Powder granules First, the powder granules used as the extrusion molding material in the method for manufacturing an extruded article according to the embodiment will be described.

[0011] The powder granules contain polyhydroxyalkanoate (PHA) powder, preferably containing PHA powder as the main component, more preferably essentially consisting of PHA powder, and even more preferably consisting of PHA powder. In this specification, "contains" and "includes" mean that additional components or elements may be included unless otherwise specified, and encompass "essentially consisting of" and "consisting of." "Essentially consisting of" means that additional components or elements may be included that do not substantially adversely affect the product. "Consisting of" means that only the materials or elements described are included, but does not exclude the inclusion of unavoidable impurities.

[0012] Powder granules are produced by granulating PHA powder. Such powder granules have a melt memory effect. Powder granules can preferably be produced by powder compression granulation (hereinafter also referred to as compression granulation). Details of the method for producing powder granules will be described later.

[0013] In this specification, a powder granule having a melt memory effect means a powder granule having the following characteristics i) and ii). i) The powder granules are processed in a nitrogen atmosphere at a rate of 10°C / min from room temperature to a first holding temperature T H1 The temperature is raised to the first holding temperature T H1 In a first differential scanning calorimetry (DSC) measurement, where the sample is held for 2 minutes and then cooled at a rate of 10°C / min, the first hold temperature T at which the crystallization exothermic peak of PHA is observed during cooling is H1 (Unit: °C) It has the first hold temperature T H1 The highest melting peak temperature T M It is higher than this. Here, the highest melting peak temperature T M (Unit: °C) is defined as the highest peak temperature of the melting peak observed in differential scanning calorimetry when a powder granule is heated from room temperature at a rate of 10 °C / min in a nitrogen atmosphere. ii) The powder granules are processed in a nitrogen atmosphere at a rate of 10°C / min from room temperature to a second holding temperature T H2 The temperature is raised to the second holding temperature TH2 In a second DSC (Dynamic Stabilization Spectroscopy) where the sample is held for 2 minutes and then cooled at a rate of 10°C / min, the second hold temperature T is such that no crystallization exothermic peak of PHA is observed during the cooling process. H2 (Unit: °C) Second hold temperature T H2 The first hold temperature T H1 It's higher than that.

[0014] The melt memory effect refers to the phenomenon in which a pseudo-crystalline phase structure order remains in the molten material when a crystalline polymer is heated and melted (thermoplasticized) above its melting point. The melt memory effect is a unique phenomenon that can occur in crystalline polymers, where, even in a temperature range above the melting point, a region remains that does not immediately become disordered and random due to the long relaxation time required for the material to change to a random aggregated state due to thermal disturbance. Hereinafter, the pseudo-crystalline phase structure order produced by the melt memory effect may be referred to as the melt memory structure. Such powder granules are described in Japanese Patent No. 7454097 and can be manufactured by the method described in Japanese Patent No. 7454097.

[0015] The melt memory effect of powder granules can be evaluated by the method described in Japanese Patent No. 7454097. Specifically, the peak temperature of the crystallization exothermic peak (i.e., the crystallization temperature of the powder granules) is observed in the cooling DSC curve obtained by differential scanning calorimetry (DSC) after heating the powder granules to a temperature above the melting point of PHA and then cooling them at a rate of 10°C / min. C If the temperature (in °C) is higher than the crystallization temperature of PHA powder measured in the same manner, the powder granules have a high melt memory effect. When powder granules have a high melt memory effect, the crystallization exothermic peak of the powder granules often has a smaller half-width at half maximum than the crystallization exothermic peak of PHA powder measured in the same manner. The above DSC can be performed, for example, by raising the temperature of the sample from room temperature to 180 °C at a rate of 10 °C / min in a nitrogen atmosphere, then holding it at 180 °C for 2 minutes, and immediately after, cooling the sample in a nitrogen atmosphere at a rate of 10 °C / min.

[0016] When a powder granule exhibiting the melt memory effect is heated and melted, the melt memory structure of PHA remaining in the molten material functions as a crystallization nucleus during cooling. Since the melt memory structure is a pseudo-crystalline phase structure of PHA itself, the crystallization temperature T of the powder granule that crystallizes using the melt memory structure as a nucleus is determined. C The crystallization temperature is higher than that of molten pellets to which a crystallization nucleating agent has been added. Furthermore, the melt memory effect of powder granules exhibits excellent persistence with respect to molten residence time. On the other hand, if the melt memory structure in the molten material is lost due to thermal disturbance and leads to a random aggregated state, crystallization will not proceed easily during cooling.

[0017] A method for manufacturing an extruded article using powder granules with a melt memory effect as the extrusion molding material may have the following advantages compared to a conventional method for manufacturing an extruded article using molten pellets containing a crystallization nucleating agent as the extrusion molding material.

[0018] i) As described in Japanese Patent No. 7454097, the powder granules are manufactured under conditions where the temperature of the granules immediately after granulation is below the melting point of PHA. Therefore, thermal decomposition of PHA during the granulation process and the resulting decrease in molecular weight are suppressed. As a result, the PHA contained in the powder granules may have a larger molecular weight than the PHA contained in the molten pellets. Consequently, the PHA in the extruded molded body produced from the powder granules can also have a larger molecular weight, thereby enabling the extruded molded body to have superior physical properties.

[0019] ii) The process for producing powder granules uses significantly less electricity than the melt-mixing granulation process using an extruder for producing molten pellets. Therefore, by producing extruded molded products from powder granules, the total amount of electricity used can be greatly reduced.

[0020] iii) By advantageously utilizing the melt memory effect of powder granules, the range of molding conditions (set temperatures of the extrusion molding machine and cooling rolls, screw rotation speed, etc.) can be expanded, making it easier to control the appearance and degree of crystallinity of the extruded product, and also increasing the degree of freedom in the shape of the extruded product (thickness of the extruded product, etc.).

[0021] iv) By using powder granules, extruded articles that do not contain crystallization nucleating agents can be manufactured. Since there is no risk of crystallization nucleating agents leaching out of the manufactured extruded articles, they can be used in applications such as food and medical use. Furthermore, crystallization nucleating agents can cause problems such as adhesion to cooling rolls, the formation of eye discharge, and increased tackiness of the extruded material and / or extruded articles, leading to the extruded material sticking to the cooling rolls and the extruded articles fusing together, thus hindering continuous extrusion molding. By performing extrusion molding using powder granules that do not contain crystallization nucleating agents, these problems can be avoided, making continuous extrusion molding easier.

[0022] In one embodiment, the powder granules have an outer wall portion formed by the melting and solidification of at least a portion of the PHA powder located at the outer edge of the powder granules, and compressed PHA powder is contained inside the outer wall portion. In this application, melting and solidification means solidification after melting. The outer wall portion is located at the outer edge of the powder granules. In this specification, the outer wall portion is also referred to as the shell portion. The compressed PHA powder inside the outer wall portion may be melted and solidified and welded in place to at least a portion, or it may not be melted and solidified to at least a portion. The compressed PHA powder inside the outer wall portion may be in an unmelted state. That is, at least a portion of the compressed PHA powder inside the outer wall portion may include an unmelted compressed powder form, or it may include a partially melted and solidified form. The partially melted and solidified form is intended to be a form in which the constituent components of the PHA powder are partially melted and solidified, but it does not form a welded structure strong enough to hold the PHA powder like the outer wall portion. In this specification, the inside of the outer wall portion is also referred to as the core portion. The core portion inside the outer wall contains compressed PHA powder. In this specification, "compressed" means that the density of the PHA powder located in the core portion is higher than the bulk density of the PHA powder before granulation. Such powder granules are described in Japanese Patent No. 7387950 and can be manufactured by the method described in Japanese Patent No. 7387950. Furthermore, such powder granules have the melt memory effect described above.

[0023] The outer wall (shell) has a dense structure containing molten and solidified PHA powder. On the other hand, the inner core, although compressed, has a looser structure compared to the dense structure (welded structure) of the outer wall containing the molten and solidified PHA powder. Because the outer wall containing the molten and solidified PHA powder holds the compressed PHA powder present in the core, the powder granules can have a stable structure, less powder shedding, and excellent handling and safety, and can also lead to an improved working environment for the manufacture of extruded molded products.

[0024] The outer wall portion (shell portion) has a welded structure in which at least a portion of the thermoplastic resin powder located at the outer edge of the powder granules is melted and solidified. The outer wall portion may be smooth enough to have a glossy appearance. Alternatively, the outer wall portion may be formed by the melting of some of the components of the thermoplastic resin powder and partial welding with adjacent components, even if the melting is not complete enough to form a smooth surface. The outer wall portion can be formed during compression granulation, for example, at the contact surface with the die hole, by the melting of at least a portion of the PHA powder due to frictional heat with the wall surface or heat transfer from the wall surface. The thickness of the outer wall portion can vary depending on the manufacturing conditions of the PHA powder granules.

[0025] The core is the part located inside the outer wall and contains compressed thermoplastic resin powder. The PHA powder in the core may be porous, or it may have a non-welded structure because heat is not transferred to the core during granulation. The core may have a structure in which the PHA powder maintains its powder shape (i.e., a non-welded structure or a powdery structure), or a structure in which it is partially welded but the shape of the PHA powder remains.

[0026] In this specification, for the sake of simplicity of explanation, the terms "outer wall (shell)" and "core" are used. However, as mentioned above, the outer wall is formed when the PHA powder melts due to the heat during granulation, so in reality, there is no clear boundary between the outer wall (shell) and the core. The outer wall (shell) refers to the part that includes the welded structure of the PHA powder and is located on the outer edge of the powder granules, contributing to maintaining a certain shape of the powder granules. The core refers to the part located inside the outer wall (shell).

[0027] The shape of the powder granules is preferably approximately cylindrical or approximately rectangular prismatic, and it is preferable that the powder granules have an outer wall portion on the side surface. In this disclosure, the powder granules have an approximately cylindrical or approximately rectangular prismatic shape, and it is preferable that an outer wall portion is formed on the side surface of the powder granules having an approximately cylindrical or approximately rectangular prismatic shape.

[0028] Because powder granules with this shape can be directly supplied to extrusion molding machines for thermoplastic resins, they can be used as extrusion molding materials.

[0029] Powder granules can take on any suitable shape. Typically, when powder granules are manufactured by compression granulation of powder and granulation is performed by passing the powder through a circular die hole, the basic shape of the powder granules is a cylindrical pellet shape.

[0030] In this specification, the term "die" used in the manufacture of powder granules refers collectively to tools equivalent to molds used to compress and shape PHA powder granules.

[0031] When the powder granules are approximately cylindrical in shape, the diameter of the powder granules is, for example, 2 mm to 7 mm, preferably 3 mm to 5 mm. The length (height) of the powder granules is, for example, 1 mm to 10 mm, preferably 2 mm to 7 mm. Such a shape results in powder granules that are easy to handle. The diameter of the powder granules can be adjusted, for example, by the diameter of the die holes in the disc plate (die plate) during granulation, and the length can be adjusted by the distance between the disc plate and the cutter. This distance can be any appropriate distance. The distance between the disc plate and the cutter is, for example, 1 mm to 30 mm, preferably 2 mm to 20 mm, preferably 3 mm to 10 mm.

[0032] The fracture strength of the powder granules, based on measurements using a Kiya hardness tester, is preferably 1.0 kg or more, preferably 2.0 kg or more, preferably 3.0 kg or more, preferably 4.0 kg or more, preferably 5.0 kg or more, preferably 6.0 kg or more, preferably 7.0 kg or more, preferably 8.0 kg or more, preferably 9.0 kg or more, and preferably 10.0 kg or more. The upper limit may exceed the measurement limit of the Kiya hardness tester (10 kg is the measurement limit for the "WPF1600-B" manufactured by Shiro Sangyo Co., Ltd.). Within this range, powder granules with excellent handling properties and melt processability can be obtained. Here, fracture strength refers to the average fracture stress (fracture load) measured by crushing powder granules with 20 or more particles (preferably 25 or more particles) in a direction perpendicular to the longitudinal direction (extrusion direction) of the powder granules. In powder granulation, the shell portion is composed of molten resin, making it possible to maintain a stable shape as a granule despite it being a powder granule. The diameter of the pressure surface of the pressure attachment of the Kiya hardness tester is, for example, 5 mm.

[0033] The bulk density of the powder granules can be any appropriate bulk density, but is preferably 0.3 kg / L to 2.0 kg / L, and more preferably 0.5 kg / L to 1.0 kg / L. Increasing the bulk density improves the supply speed and supply stability of the powder granules to the extrusion molding machine.

[0034] The bulk density of powder granules is calculated by allowing the powder granules to fall naturally into a 1-liter measuring cup until it is level, accurately measuring out 1 liter of powder granules, and then measuring its mass (unit: kg / L).

[0035] B.PHA powder The PHA powder, which is the raw material for powder granules, is a powdered polyhydroxyalkanoate (PHA) resin. PHA can be a compound produced in the body of microorganisms, for example, by feeding on carbohydrates, oils, etc. Such PHA is primarily extracted from microorganisms as a powdered polymer.

[0036] PHA contains hydroxyalkanoic acid as a polymerization component and has at least repeating units derived from hydroxyalkanoic acid. PHA may be artificially synthesized or biosynthesized by microorganisms. Examples of hydroxyalkanoic acid include glycolic acid, 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynanoate, 3-hydroxydecanoate, 3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate, 4-hydroxybutyrate, 4-hydroxyvalerate, 5-hydroxyvalerate, or 6-hydroxyhexanoate. The number of carbon atoms in hydroxyalkanoic acid may be 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or 8 or more, preferably 3 or more. The number of carbon atoms in the hydroxyalkanoic acid may be 15 or less, 12 or less, 10 or less, 8 or less, 6 or less, or 4 or less, preferably 10 or less, and particularly 6 or less. The hydroxyalkanoic acid may be used alone or in combination of two or more types.

[0037] Preferred PHAs include poly(3-hydroxyalkanoate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0038] In PHA powder, the weight-average molecular weight (Mw) of PHA is 200,000 or more, preferably 300,000 or more, preferably 500,000 or more, and preferably 700,000 or more. The melt memory effect is manifested by a time delay in the process in which polymer molecular chains transition from a crystalline ordered state to a random state in the molten state. Therefore, the larger the molecular weight, the longer the relaxation time (transition time to random chains), which is advantageous in terms of the persistence of the effect. A weight-average molecular weight of 200,000 or more of PHA is preferable because it can effectively delay the decrease or deactivation of the melt memory effect due to thermal disturbance. On the other hand, if the molecular weight of PHA becomes too large, the viscosity becomes too high, which is disadvantageous for causing solid-phase deformation, and powder granulation tends to become difficult. For this reason, the weight-average molecular weight of PHA is preferably 3 million or less, preferably 2 million or less, preferably 1.5 million or less, and preferably 1 million or less.

[0039] The weight-average molecular weight (Mw) mentioned above can be determined as the weight-average molecular weight in terms of polystyrene by gel permeation chromatography (GPC). For example, evaluation can be performed using a Showa Denko "Showdex GPC-101" as the GPC apparatus, polystyrene gel (Showa Denko "Showdex K-804") as the column packing material, and an organic solvent mobile phase (e.g., chloroform). The column apparatus, column packing material, and organic solvent mobile phase can be selected as appropriate, but chloroform can be used, for example.

[0040] PHA powder may be a powdered resin obtained through its manufacturing process, i.e., a powder due to the manufacturing process, or it may be obtained by pulverizing a non-powdered PHA resin such as pellets, lumps, or molded articles. PHA powder can be obtained, for example, by pulverizing molded articles, pellets, trimming scraps generated in extrusion molding, or sprues or runners generated in injection molding at room temperature, or after cooling with dry ice or liquid nitrogen as necessary, using a pulverizer (for example, Dalton products, trade names "Nearmill," "Sylpheedmill," "Atomizer," or "Impactmill," etc.).

[0041] The particle size of the PHA powder can be any appropriate particle size depending on its form, as long as the effects of this embodiment are obtained. Preferably, the maximum particle size of the PHA powder before granulation is 5 mm or less, and the minimum particle size is 0.0001 mm or more.

[0042] The average particle size of the PHA powder is, for example, 0.001 mm or more and 1.0 mm or less. Preferably, the average particle size of the PHA powder is 1.0 mm or less, preferably 0.01 mm or more and 0.8 mm or less, and preferably 0.1 mm or more and 0.5 mm or less. In this specification, the average particle size may be measured by laser diffraction. The average particle size of the PHA powder may be the median diameter (d50) which is the cumulative 50% in the cumulative particle size distribution on a volume basis. The median diameter (d50) may be a mixture of primary particles and aggregated particles. The PHA powder may be used alone or in combination of two or more types.

[0043] The PHA powder before granulation may have any bulk density, but the bulk density of the PHA powder is preferably 0.05 kg / L to 1.0 kg / L, more preferably 0.1 kg / L to 0.8 kg / L, and even more preferably 0.2 kg / L to 0.6 kg / L. When the bulk density of the PHA powder is within this range, compression granulation is easily performed.

[0044] The bulk density of PHA powder is calculated by letting the PHA powder fall naturally into a 1-liter measuring cup until it is level, accurately measuring out 1 liter of PHA powder, and then measuring its mass (unit: kg / L).

[0045] Other components contained in C.PHA powder granules The powder granules may contain any suitable additives as needed. The additives may be in solid form, such as powder, or in liquid form. Examples of additives include binders, dispersants, crystallization nucleating agents, antioxidants, light stabilizers, foaming agents, UV absorbers, antiblocking agents, heat stabilizers, impact modifiers, antibacterial agents, compatibilizers, processing aids, lubricants, coupling agents, hydrolysis inhibitors, oxygen scavengers, or colorants (dyes and pigments). Additives may be used individually or in combination of two or more.

[0046] The additive content in the powder granules is, for example, 10.0% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, and more preferably 1.0% by mass or less.

[0047] Powder granules may contain binders as additives. Here, "binder" refers collectively to compounds that exist between PHA powder particles, in addition to the constituent components of the raw material PHA powder, and that bind the powder particles together, thereby increasing the fracture strength of the granules. Various compounds that exhibit a binding effect, preferably water-dispersible or water-soluble polymer compounds, polysaccharides, etc., can be appropriately selected and used as binders as needed.

[0048] In one embodiment, it is preferable to melt and bind a portion of the components of the PHA powder to form a powder granule, and it is preferable not to include a binder.

[0049] The binder content is typically 10.0% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, preferably 1.0% by mass or less, preferably 0.5% by mass or less, preferably 0.1% by mass or less, and preferably 0% by mass (undetectable), based on the total mass of the PHA powder granules.

[0050] In one embodiment, a dispersant is preferably used as an additive. A surfactant is preferably used as the dispersant. The hydrophilic / hydrophobic balance of the dispersant (surfactant) can be controlled by adjusting the degree of esterification of the compound that becomes the dispersant, the type of fatty acid (e.g., presence or absence of hydroxyl groups, saturated or unsaturated fatty acids, alkyl chain length), the degree of polymerization, etc. The use of a dispersant can bring about effects such as improving the productivity (discharge rate) of powder granules, reducing frictional heat during granulation, and improving the cleanability of the granulation equipment.

[0051] Examples of dispersants include fatty acids, fatty acid metal salts, fatty acid sulfonates, fatty acid amides, acrylamides, polyhydric alcohol fatty acid esters, and polyglycerol fatty acid esters. Dispersants may be used individually or in combination of two or more.

[0052] In one embodiment, the dispersant is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerol fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids.

[0053] Polyhydric alcohol fatty acid esters are ester compounds composed of a polyhydric alcohol and a fatty acid. Examples of polyhydric alcohol fatty acid esters include esters of polyhydric alcohols such as pentaerythritol and glycerol, and fatty acids having 8 or more carbon atoms (preferably 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms).

[0054] Fatty acid amides are compounds that have a structure formed by the dehydration condensation of a fatty acid with ammonia or a primary or secondary amine. Examples of fatty acid amides include saturated fatty acid monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide.

[0055] Polyglycerol fatty acid esters are ester compounds composed of polyglycerol and fatty acids. Examples of polyglycerol fatty acid esters include diglycerol palmitate, diglycerol stearate, diglycerol oleate, decaglycerol palmitate, decaglycerol stearate, and decaglycerol oleate.

[0056] The dispersant content is typically 0% to 10.0% by mass, preferably 0.01% to 9.0% by mass, preferably 0.1% to 7.0% by mass, and more preferably 0.3% to 5.0% by mass, relative to the total mass of the powder granules. Furthermore, the dispersant content is typically 10.0% or less by mass, preferably 5.0% or less by mass, preferably 3.0% or less by mass, preferably 1.0% or less by mass, preferably 0.5% or less by mass, preferably 0.1% or less by mass, and preferably 0% by mass (undetectable), relative to the total mass of the powder granules.

[0057] Crystallization nucleating agents can be added as additives to powder granules. Examples of crystallization nucleating agents that can be added to powder granules include organometallic salt compounds such as phosphate ester metal salts, benzoate metal salts, pimephosphate metal salts, rosin metal salts, oxalate metal salts, and fatty acid metal salts; aliphatic organic esters, triallyl phosphate, polyalkylene glycol or its derivatives, aliphatic polyesters, and organic compounds such as benzylidene sorbitol; dyes and pigments such as pentaerythritol, quinacdrin, cyanine blue, and carbon black; minerals such as talc, mica, kaolin, clay, carbonate minerals, metal oxides, and metal sulfates; ionomers; and polymer compounds such as high-melting-point polyamides.

[0058] In one embodiment, talc, mica, kaolin, or calcium carbonate are used as crystallization nucleating agents. One type of crystallization nucleating agent may be used alone, or two or more types may be used in combination.

[0059] The content of the crystallization nucleating agent in the powder granules is, for example, 0.1% by mass or more and 10.0% by mass or less, preferably more than 0.1% by mass and less than 10.0% by mass, preferably 0.2% by mass or more and 7.0% by mass or less, and preferably 0.3% by mass or more and 5.0% by mass or less.

[0060] In one embodiment, the powder granules substantially do not contain a crystallization nucleating agent. Because the powder granules can exhibit a melt memory effect, they can achieve excellent crystallization characteristics in molding processes even without the use of a crystallization nucleating agent.

[0061] "Substantially free of crystallization nucleating agents" means, for example, that the content of crystallization nucleating agents in the powder granules is 0.1% by mass or less, preferably less than 0.1% by mass, preferably 0.01% by mass or less, preferably 0.005% by mass or less, preferably 0.001% by mass or less, and preferably 0% by mass (undetectable) of crystallization nucleating agents in the powder granules.

[0062] Furthermore, those skilled in the art should understand that powder granules may contain a crystallization nucleating agent or that powder granules may be used together with a crystallization nucleating agent. When powder granules contain a crystallization nucleating agent or when powder granules are used together with a crystallization nucleating agent, in addition to the crystallization-promoting effect due to the melt memory effect, a crystallization-promoting effect due to the crystallization nucleating agent can be obtained.

[0063] Method for producing D.PHA powder granules Powder granules can be manufactured using various powder granulators, but preferred granulators include compression granulators such as disc pelletizers, screw extrusion machines, briquetting machines, compaction machines, and tableting machines. Powder granules manufactured by compression granulators are thought to have an outer wall containing oriented crystals due to the strong shear stress from the die hole walls during the granulation process. Therefore, powder granules manufactured by compression granulation (i.e., compression granules) can have a particularly high melt memory effect.

[0064] Among the examples given above, the disc pelletizer method is preferred from the viewpoint of granulation productivity and the quality and shape uniformity of the resulting powder granules. In the disc pelletizer method, a semi-wet granulation method can be employed, which involves incorporating an appropriate amount of moisture into the PHA powder. In some cases, granulation can be performed without using water. When granulation is performed without using water, the post-granulation drying treatment described later may become unnecessary. When granulation is performed without using water, the amount of energy required in the drying process can be reduced, and the amount of carbon dioxide emitted during the manufacturing process can be significantly reduced.

[0065] As mentioned above, PHA powder granules can be advantageously obtained by the granulation method described in Japanese Patent No. 7454097 or Japanese Patent No. 7387950.

[0066] When the powder granules are a mixture containing two or more types of PHA powder raw materials, or contain any components other than PHA, it is preferable to mix them uniformly using any suitable mixer. Examples of mixers include Henschel mixers, Nauter mixers, powder kneaders (KDH, KDA, CKD, CPM) (Dalton), Spartan mixers (SPM) (Dalton), and SP granulators (SPG) (Dalton). To obtain a desirable mixture with excellent granulation properties, it is preferable to use a mixing and stirring device equipped with appropriate stirring blades. For example, when using a Henschel mixer type mixer, it is preferable to use a combination of upper and lower blades, with the upper blade being a Y1 blade (product name, manufactured by Nippon Coke Industries Co., Ltd.) and the lower blade being an S0 blade (product name, manufactured by Nippon Coke Industries Co., Ltd.). It is also preferable to install a deflector in the stirring tank and mix the materials. In other words, using a mixing device that can uniformly disperse each component throughout the mixture is advantageous in improving the productivity and quality stability of the final powder granules.

[0067] When producing powder granules using the semi-wet granulation method described above, the amount of water added can be any appropriate amount depending on the properties of the powder (e.g., water absorption). In this case, the amount of water added is 3 to 30 parts by mass, preferably 5 to 25 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of crystalline polymer powder. The semi-wet method can be used to improve the stability of granulation.

[0068] In the granulation process of powder granules, localized heat generation can lead to die clogging. Therefore, incorporating an appropriate amount of moisture into the PHA powder during granulation and using the heat of vaporization of water to suppress excessive temperature rise during granulation can be advantageous for continuous granulation.

[0069] The powder granules can be dried after granulation, but the final moisture content of the powder granules is preferably 10% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, preferably 1.0% by mass or less, and preferably 0.5% by mass or less. The final moisture content of the powder granules can be appropriately selected depending on the intended use.

[0070] It is preferable that the powder granules are granulated without the addition of water. If the moisture content of the powder granules is low, post-granulation drying may not be necessary. If granulation can be performed without using water, drying is unnecessary, which can significantly reduce the amount of carbon dioxide emitted during the powder granulation process.

[0071] The moisture content of the granulated powder without the addition of water is, for example, 1.0% by mass or less, preferably 0.5% by mass or less, preferably 0.3% by mass or less, and preferably 0.2% by mass or less.

[0072] When producing powder granules using a screw extrusion compression granulator, it is easy to install a temperature control device on the compression granulator, and compression granulation can be performed at low screw rotation speeds, thus reducing localized heat generation due to rapid shear heat generation during granulation. When producing powder granules using a bricketing, compaction, or tableting compression granulator, the shear stress on the powder from the die hole walls is smaller compared to the disc pelletizer method, thus reducing localized heat generation during granulation. Therefore, with the screw extrusion, bricketing, compaction, and tableting methods, powder granules can be produced continuously and stably without causing die clogging due to localized heat generation, even without the addition of water. When granulation is performed without the addition of water, post-granulation drying is unnecessary, thus simplifying the manufacturing process and reducing energy consumption for drying.

[0073] The moisture content of powder granules is measured using an infrared moisture meter.

[0074] A disc pelletizer type granulator has, as a basic structure, one (flat die) or two discs (indicating cylindrical dies) with numerous holes ranging from 2 mm to 30 mm in diameter, and rollers for pressurizing the raw material into the holes of the discs. PHA powder (which may contain moisture) supplied between the disc and the roller, or between two discs, is pressed into the holes of the discs as the roller rotates, forming a cylindrical extruded product. The extruded product is cut on the back surface of the disc with a cutter or the like to obtain pelletized powder granules. The length of the granules can be adjusted by the distance between the back surface of the disc and the cutter, the rotation speed of the roller, etc. The distance between the disc plate and the cutter can be any appropriate distance. For example, the distance between the disc plate and the cutter is 1 mm to 30 mm, more preferably 2 mm to 20 mm, and even more preferably 3 mm to 10 mm.

[0075] More specifically, disc pelletizer systems include roller-disc die systems, roller-ring die systems, double die systems, and flat die systems. A commercially available disc pelletizer granulator is, for example, the Dalton F-series disc pelletizer.

[0076] The powder granules may be thoroughly dried immediately before use as an extrusion molding material. This effectively suppresses the decrease in molecular weight of PHA and / or defects in the appearance of the extruded product that occur during extrusion molding. The moisture content of the powder granules immediately before use as an extrusion molding material is preferably 0.3% by mass or less, 0.1% by mass or less, 0.05% by mass or less, 0.03% by mass or less, or 0.02% by mass or less. Drying is usually carried out at 70°C to 110°C, 75°C to 100°C, or 80°C to 90°C until the predetermined moisture content is reached. The moisture content of the powder granules is measured using an infrared moisture meter.

[0077] E. Method for manufacturing extruded articles by extrusion molding The method for manufacturing an extruded article according to the embodiment includes using powder granules containing PHA as a molding material and extruding the PHA using an extruder. Extrusion molding includes melting the powder granules fed into the extruder to obtain a molten material, extruding the molten material from a die, and cooling the extruded molten material to solidify it. The extruded article may have a sheet-like or tubular shape, but is not limited to these.

[0078] In this specification, "die" used in extrusion molding is a general term for a tool that corresponds to a mold for extruding molten PHA into a desired shape.

[0079] E-1. Method for manufacturing sheet-like extruded articles When manufacturing a sheet-like extruded product, for example, the extruded product can be manufactured using the extruder 1 shown in Figure 1. The extruder 1 comprises an extruder 10, at least one cooling roll 30, at least one conveying roll 50, and a winding roll 70. The extruder 10 comprises a cylinder 12, a screw 14 housed within the cylinder 12, a hopper 16 for supplying powder granules 92 to the cylinder 12, a die head 17, an adapter 19, and a T-type die 18. The hopper 16 is located at the uppermost part of the extruder 10. The die head 17, adapter 19, and T-type die 18 are connected in this order downstream of the cylinder 12. The T-type die 18 is located at the lowermost part of the extruder 10. The cooling roll 30 is located below the T-type die 18 in the direction of gravity. In the extrusion molding machine 1 shown in Figure 1, at least one cooling roll 30 consists of a first roll 32 and a second roll 34, and at least one conveying roll 50 consists of a third roll 52 located downstream of the second roll 34, and a pair of pinch rolls 54 located downstream of the third roll 52. The temperature of each part of the extrusion molding machine 1 can be controlled by heating heaters (not shown) and / or cooling units (not shown) provided in each part.

[0080] The powdered granules 92 fed into the hopper 16 are supplied into the cylinder 12. The powdered granules 92 are heated and melted inside the cylinder 12. The molten material is sent to the T-type die 18 via the die head 17 and adapter 19 by the rotating screw 14, and a sheet-like molten material 94 is continuously extruded from the T-type die 18.

[0081] Plasticization and melting temperature T of powder granules 92 in extruder 10 P (Unit: °C) is given by formula (1) T M -10 <T P ≦T M +20 (1) (In the formula, T M (Unit: °C) represents the highest melting peak temperature observed in differential scanning calorimetry (DSC) when granulated powder is heated from room temperature at a rate of 10 °C / min in a nitrogen atmosphere. It satisfies the condition.

[0082] Note that the highest melting peak temperature T M If multiple melting peaks are observed by DSC, this refers to the highest peak temperature among those melting peaks. If only one melting peak is observed by DSC, this refers to the peak temperature of that melting peak.

[0083] In this specification, the plasticization melting temperature T P This is defined as the temperature of the molten material inside the die head 17. The temperature of the molten material inside the die head 17 is measured by a thermocouple attached to the die head 17.

[0084] Plasticization melting temperature T P By satisfying equation (1), the loss of the melt memory effect of the powder granules 92 due to thermal disturbances, mechanical mixing, etc., can be suppressed, thereby enabling extrusion molding that effectively utilizes the melt memory effect.

[0085] Plasticization melting temperature T P Preferably, T M -8 <T P ≦TM +15 To satisfy and comfortably T M -5 <T P ≦T M +10 Satisfying the following, and more preferably, T M -5 <T P ≦T M +5 It satisfies the condition.

[0086] In conventional extrusion molding using molten PHA pellets as a molding material, the plasticizing melt temperature T P If the temperature is set below the melting peak temperature of the molten pellets, it not only places an excessive load on the extruder, but also results in insufficient plasticization, which can lead to residual unmelted material being mixed into the extruded molded product, and insufficient flow causing defects in the extruded molded product such as shrinkage, poor transfer, uneven flow, uneven thickness, and orange peel texture.

[0087] In contrast, in the method according to this embodiment, which uses PHA powder granules 92 as a molding material, the load on the extruder 10 is reduced due to the large porosity of the powder granules 92, so the plasticization melting temperature T P is T M -10 <T P <T M Even when this condition is met, the powder granules 92 can be sufficiently plasticized and extruded without placing an excessive load on the molding machine.

[0088] Inside the extruder 10, a flow field is formed as the screw 14 rotates for plasticization metering. The maximum temperature at which the melt memory effect is maintained in the flow field may be lower than the maximum temperature at which the melt memory effect is maintained in the stationary field. Plasticization melt temperature T P However, T P >T MIf the condition +20 is met, the melt memory effect decreases or disappears due to the action of the flow field, slowing down the crystallization and solidification of the molten material 94 extruded from the T-type die 18. This can lead to various problems such as poor release from the cooling roll 30, sticking of extruded molded bodies to each other, resulting deformation of the extruded molded bodies, difficulty in thinning the extruded molded bodies, reduction of effective sheet width, and post-shrinkage, potentially reducing productivity. The effective sheet width refers to the width of the region within the sheet-shaped extruded molded body that has a thickness within a set range.

[0089] In one embodiment, the screw 14 is a single-screw flight screw. The single-screw flight screw has a supply zone, a compression zone, and a metering zone in the flow direction of the powder granules and their molten material, from upstream to downstream. Such a single-screw flight screw can suppress the reduction or disappearance of the melt memory effect due to the flow field caused by thermal disturbance and / or mechanical mixing. When the screw of the extrusion machine is a single-screw flight screw, the rotational speed S of the screw 14 R The rotational speed S of the screw 14 is preferably 100 rpm or less, 80 rpm or less, 60 rpm or less, 50 rpm or less, or 30 rpm or less. R By reducing this, the reduction or disappearance of the melt memory effect caused by the flow field generated by mechanical mixing can be suppressed. The rotational speed S of the screw 14. R The rotation speed may be 10 rpm or higher.

[0090] The sheet-like molten material 94 extruded from the T-type die 18 is drawn down between the first roll 32 and the second roll 34, which constitute the cooling roll 30. The molten material 94 is sandwiched between the first roll 32 and the second roll 34 and then conveyed along the surface of the second roll 34. During this time, the molten material 94 is cooled by the cooling roll 30 and crystallizes and solidifies. This forms a sheet-like extruded molded body 96. The extruded molded body 96 is conveyed to the winding roll 70 via the conveying roll 50 and wound up by the winding roll 70. The winding speed of the extruded molded body 96 can be controlled by the rotational speed of the second roll 34.

[0091] The first roll 32 may have an outermost layer made of an elastomer. When the outermost layer of the first roll 32 is made of an elastomer, the first roll 32 can be deformed to press the entire melt 94 against the second roll 34, and the thickness of the extruded molded body 96 can be efficiently controlled. The surfaces of the first roll 32 and / or the second roll 34 may be mirror surfaces, or may have irregularities of a predetermined shape. The surface shape of the first roll 32 and / or the second roll 34 can be transferred to the surface of the extruded molded body 96.

[0092] The surface temperatures of the cooling rolls 30 (i.e., the first roll 32 and the second roll 34) and the conveying roll 50 can be set as appropriate. The surface temperature T R1 of the first roll 32 and the surface temperature T R2 of the second roll 34 are preferably controlled independently of each other. The surface temperature T R1 of the first roll 32 and the surface temperature T R2 of the second roll 34 may be controlled integrally. The surface temperature T R2 of the second roll 34 may be controlled integrally with the surface temperature T R3 of the third roll 52. The surface temperature of each roll can be controlled by a temperature control device (e.g., a water cooling device, an oil cooling device, a heater) provided on each roll. A plurality of rolls may share one temperature control device, whereby the surface temperatures of the plurality of rolls are controlled integrally. The surface temperature of each roll is measured by a contact thermometer (e.g., a thermocouple) provided on the surface of each roll.

[0093] In one embodiment, the surface temperature T R1 (unit: °C) of the first roll 32, the surface temperature T R2 (unit: °C) of the second roll 34, and the crystallization temperature T C (unit: °C) of the powder granulated product 92 are given by formulas (2), (3), and (4) T C -80 < T R1 ≦ T C (2) T C -60 < T R2 ≦ T C (3) T R1 < TR2 (4) The following conditions may be met. Note that the crystallization temperature T C This is defined as the peak temperature of the crystallization exothermic peak observed during cooling in differential scanning calorimetry (DSC) in which powder granules 92 are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min.

[0094] Surface temperature T of the first roll 32 R1 The surface temperature of the second roll 34 is T R2 By being lower than the surface temperature of the second roll 34, the molten material 94 is prevented from sticking to the first roll 32, and the molten material 94 is conveyed along the surface of the second roll 34 with high reliability. R2 and the surface temperature T of the first roll 32 R1 The difference (T R2 -T R1 The temperature range may be 5°C to 60°C, 10°C to 50°C, or 20°C to 40°C.

[0095] Surface temperature T of the first roll 32 R1 , the surface temperature T of the second roll 34 R2 , and the crystallization temperature T of the powder granules 92 C Preferably, T C -75 <T R1 ≦T C , and T C -60 <T R2 ≦T C more, T C -70 <T R1 ≦T C , and T C -55 <T R2 ≦T C More preferably, T C -70 <T R1 ≦T C , and T C -50 <T R2 ≦T C Particularly preferred, T C -70 <T R1 ≦T C , and T C -45 <T R2 ≦T C It satisfies the condition.

[0096] Surface temperature T of the second roll 34 R2 The crystallization temperature of powder granules 92 is T C By doing the following, the crystallization solidification of the molten material 94 extruded from the T-type die 18 can be accelerated, and extruded molded products 96 with excellent quality and appearance can be manufactured with high productivity. The crystallization temperature T of the powder granules 92 having the melt memory effect as described above. C Since this is higher than the crystallization temperature of molten pellets to which a crystallization nucleating agent has been added, when extrusion molding is performed using powder granules 92 having a melt memory effect as a molding material, the surface temperature T of the second roll 34 is higher compared to conventional extrusion molding using molten pellets. R2 The surface temperature T of the second roll 34 can be increased. R2 A high crystallinity is advantageous for improving the crystallinity of the extruded article 96 produced. Improved crystallinity leads to the production of an extruded article 96 with high heat resistance, high elastic modulus (rigidity), and high shape and dimensional stability, as well as fewer appearance defects. High heat resistance means a high thermal shrinkage onset temperature. High shape and dimensional stability means that the extruded article 96 shrinks little or no after production, does not warp, and if shrinkage occurs, its anisotropy is small.

[0097] In one embodiment, the highest melting peak temperature T of the powder granules 92 M The temperature is above 140°C, and the powder granules 92 have a high crystallization temperature of above 80°C due to the melt memory effect. C It may have the following. In this case, the surface temperature T of the second roll 34 R2By maintaining a high temperature of 50°C to 80°C, the molten material 94 in contact with the second roll 34 can be rapidly crystallized and solidified. As a result, the extruded molded product 96 does not adhere to the second roll 34, and an extruded molded product 96 with excellent quality and appearance can be manufactured with high productivity.

[0098] For example, the powder granules used in the examples described later have a maximum melting peak temperature T M The temperature is 147°C, and the crystallization temperature is T C The temperature is 95°C. When extrusion molding is performed using this powder granule, the surface temperature T of the second roll 34 is 95°C. R2 By maintaining a temperature of 63°C, the molten material 94 in contact with the second roll 34 can be rapidly crystallized and solidified. As a result, the extruded product 96 does not adhere to the second roll 34, and an extruded product 96 with excellent quality and appearance can be manufactured with high productivity.

[0099] The surface temperature of each roll in the extrusion molding machine 1 is the crystallization temperature T of the powder granules 92. C The temperature can be set as appropriate depending on the circumstances. For example, the crystallization temperature T of the powder granules 92. C If the temperature is between 95°C and 100°C, the surface temperature of the first roll 32 is T R1 The temperature is preferably 20°C to 60°C, more preferably 30°C to 50°C, and the surface temperature T of the second roll 34 is R2 The temperature is preferably 50°C to 95°C, more preferably 55°C to 90°C, even more preferably 58°C to 85°C, and most preferably 60°C to 80°C.

[0100] For example, the crystallization temperature T of the powder granule 92 C If the temperature is between 80°C and 95°C, the surface temperature of the first roll 32 is T R1 The temperature is preferably 10°C to 50°C, more preferably 20°C to 45°C, and the surface temperature T of the second roll 34 is R2 The temperature is preferably 50°C to 85°C, more preferably 40°C to 80°C, even more preferably 40°C to 80°C, and most preferably 40°C to 70°C.

[0101] Thus, the crystallization temperature T of powder granulesC Depending on the surface temperature T of the first roll 32, R1 The surface temperature T of the second roll 34 R2 By appropriately selecting the elements, the melt memory effect can be effectively utilized to rapidly crystallize the molten material 94. This results in various advantages, such as improved release properties from the cooling roll 30, prevention of sticking between extruded bodies 96, prevention or reduction of deformation of the extruded bodies 96, improved ease of thinning the extruded bodies 96, increased effective sheet width, and reduced shrinkage after extrusion molding, enabling efficient extrusion molding. Furthermore, the manufactured extruded bodies 96 can have a high degree of crystallinity, thus possessing high heat resistance, elastic modulus, and stability of shape and dimensions, and exhibiting fewer appearance defects.

[0102] Surface temperature T of the second roll 34 R2 However, the crystallization temperature T of the powder granule 92 C If the temperature is 60°C or more lower than the specified temperature, the extruded article 96 produced may not have sufficient crystallinity, and shrinkage after extrusion may reduce the dimensional and shape stability of the extruded article 96, as well as increase appearance defects such as sheet warping, transfer defects, and uneven thickness.

[0103] In the method according to this embodiment, a powder granule 92 that does not contain a crystallization nucleating agent can be used as the molding material. Crystallization nucleating agents can cause problems such as adhering to the cooling roll, generating eye discharge, and increasing the stickiness of the extruded product and / or extruded molded product, leading to the extruded product sticking to the cooling roll and the extruded molded product fusing together, which can hinder continuous extrusion molding. Furthermore, crystallization nucleating agents can also be a factor in reducing the heat resistance of the manufactured extruded molded product. These problems can be avoided by performing extrusion molding using a powder granule that does not contain a crystallization nucleating agent.

[0104] In one embodiment, the crystallization temperature T of the extruded body 96 CA (Unit: °C) and crystallization temperature T of powder granule 92 C (Unit: °C) is given by formula (5) 0.8≦T CA / T C≤1.2 (5) The following conditions are met. Note that the crystallization temperature T of the powder granules 92 C T is defined as the peak temperature of the crystallization exothermic peak observed during cooling in a DSC (Deep Stem Cell) in which powder granules 92 are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min. CA This is defined as the peak temperature of the crystallization exothermic peak observed during cooling in a DSC (Dynamic Stem Cell Spectroscopy) in which an extruded body 96 (specifically, a measurement piece cut from the extruded body 96) is heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min.

[0105] Equation (5) above represents the crystallization temperature T of the extruded body 96. CA The crystallization temperature T of the powder granule 92 C This indicates that the crystallization temperature change due to extrusion molding is small, meaning that the melt memory effect of the powder granules 92 was effectively utilized during extrusion molding. As mentioned above, effectively utilizing the melt memory effect is advantageous for improving the degree of crystallization of the extruded body 96, and as a result, the extruded body 96 can have a large effective sheet width, reduced shrinkage after extrusion molding, and high heat resistance.

[0106] Crystallization temperature T of extruded body 96 CA The crystallization temperature T of the powder granule 92 C It may be higher than that. In that case, the extruded product 96 is thought to have a higher melt memory effect than the powder granules 92, which may be advantageous when further molding the extruded product 96.

[0107] In one embodiment, the powder granules 92 are manufactured under conditions where the temperature of the granules immediately after granulation is below the melting point of PHA, and in this case, the melt flow rate (MFR) of the PHA powder is ORI (Unit: g / 10min), Melt flow rate MFR of powder granule 92 GRN (Unit: g / 10min), and the melt flow rate (MFR) of the extruded body 96. ART(Unit: g / 10min) is given by formulas (a), (b), and (c) 1 ≤ MFR GRN / MFR ORI ≤5 (a) 1 ≤ MFR ART / MFR GRN ≤5 (b) 1 ≤ MFR ART / MFR ORI ≤10 (c) The melt flow rate (MFR) of PHA powder can be satisfied. ORI Melt flow rate MFR of powder granule 92 GRN , and the melt flow rate MFR of the extruded body 96 ART It is measured at 165°C and under a load of 5 kg in accordance with ISO 1133.

[0108] Formulas (a), (b), and (c) above indicate that the decrease in molecular weight of PHA during the process of producing the PHA extruded article 96 from PHA powder was sufficiently suppressed. By suppressing the decrease in molecular weight of PHA, it is possible to produce an extruded article 96 with superior mechanical properties.

[0109] E-2. Method for manufacturing tubular extruded articles Examples of tubular extruded articles include elongated cylindrical molded products with a hollow interior, such as straws and pipes. Extruded articles have a roughly circular cross-sectional shape.

[0110] A tubular extruded body can be manufactured using an extruder equipped with a cylinder, a screw housed within the cylinder, a hopper for supplying powdered granules to the cylinder, and an annular die. The extruder has the same configuration as the extruder 10 described above shown in Figure 1, except that it is equipped with an annular die instead of a T-shaped die. The plasticization melt temperature in this extruder is the plasticization melt temperature T in the extruder shown in Figure 1. P The settings are the same as above. A tubular extruded body can be manufactured by melting powder granules in a cylinder, extruding the tubular molten material from an annular die into water, and cooling the molten material in water to solidify it into crystals.

[0111] When an extruded body is used as a drinking straw, from the viewpoint of ease of drinking, the extruded body preferably has an outer diameter of 2 mm to 10 mm, more preferably 4 mm to 8 mm, even more preferably 5 mm to 7 mm, and preferably an average thickness of 0.005 mm to 0.5 mm, more preferably 0.01 mm to 0.3 mm, even more preferably 0.02 mm to 0.2 mm, even more preferably 0.03 mm to 0.15 mm, and particularly preferably 0.04 mm to 0.10 mm. In the method according to the embodiment, by effectively utilizing the melt memory effect of the powder granules, the molten material can be rapidly crystallized and solidified even without a crystallization nucleating agent, so that an extruded body having such a small average thickness (for example, an average thickness of 0.1 mm or less) and sufficient thickness accuracy, rigidity, and heat resistance can be manufactured. When an extruded body is used as a drinking straw, it is preferable that the cross-section of the extruded body is as close to a perfect circle as possible.

[0112] When an extruded product is used as a drinking straw, the extruded product may be subjected to secondary processing to form a stopper portion and / or a bellows portion, etc.

[0113] E-3. Extruded bodies of other shapes An extruded molded body usable as a bottle or container can also be manufactured by the method according to the embodiment. Specifically, an extruder equipped with a cylinder, a screw housed in the cylinder, a hopper for supplying powdered granules to the cylinder, and an annular die is used to melt the powdered granules in the cylinder, extrude the tubular molten material through the annular die, and send it into an open mold. The mold is closed to seal one end of the tubular molten material, air is blown into the molten material to make it adhere to the mold, and the molten material is cooled and crystallized. This makes it possible to manufacture an extruded molded body usable as a bottle or container.

[0114] The applications of the extruded articles produced by the method according to this embodiment are not particularly limited. The extruded articles can be used in a variety of applications, such as medical supplies, tableware supplies, agricultural supplies, fishery supplies, forestry supplies, office automation parts, home appliance parts, automotive parts, daily necessities, stationery, and bottle molding preforms. The powder granules used in the method according to this embodiment can be manufactured with less energy than molten pellets used in conventional extrusion molding. Furthermore, the extruded articles produced by the method according to this embodiment have excellent physical properties and appearance, as well as being biodegradable in seawater. Therefore, the method according to this embodiment can contribute to reducing greenhouse gas emissions and improving environmental problems caused by the dumping of plastics into the ocean. [Examples]

[0115] The embodiment will be described in detail below with reference to examples, but the embodiment is not limited in any way by these examples. Unless otherwise specified, parts and percentages are based on mass.

[0116] Example 1 (1) Preparation of raw material powders A commercially available copolymer polyester of 3-hydroxybutyrate and 3-hydroxyhexanoic acid, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), was prepared as a powder (PHA powder). The hydroxyhexanoate content of the PHA powder was 6 mol%, the bulk density was 0.33 kg / L, the maximum melting peak temperature was 145°C, the crystallization temperature was 85°C, and the melt flow rate (MFR) was 0.33 kg / L. ORI The concentration was 3.0 g / 10 min. The weight-average molecular weight of PHBH was 500,000 (polystyrene equivalent).

[0117] The bulk density of the PHA powder was measured using the same method as that used for the bulk density of the powder granules described later.

[0118] The maximum melting peak temperature and crystallization temperature of PHA powder were determined using 5 mg of PHA powder, and the maximum melting peak temperature T of the powder granules described later was used. M and crystallization temperature T CThe measurements were taken in the same manner (see Figures 2 and 3).

[0119] PHA powder melt flow rate MFR ORI The measurement was performed in accordance with ISO 1133, using a melt indexer (Yasuda Seiki Seisakusho Co., Ltd. "No. 120-FWP"), with a cylinder set temperature of 165°C, a load of 5 kg, and preheating for 4 minutes.

[0120] (2) Manufacturing of powder granules 100 parts by mass of PHA powder were placed into an FM mixer (manufactured by Nippon Coke Industries Co., Ltd., product name "5FM5C / I"; processing volume: 5L), and 20 parts by mass of tap water were continuously sprayed in for 5 minutes while the stirring blades were rotated at a speed of 2,000 rpm to obtain a water-containing powder.

[0121] A water-containing powder was fed into a disc pelletizer (Dalton Co., Ltd., product name "Disc Pelletizer F-5 / 11-175"), and a roughly cylindrical granular precursor was produced under conditions of a roller rotation speed of 108 rpm. The thickness of the die plate of the disc pelletizer was 15 mm, and the hole diameter was 3 mmφ. The length of the water-containing powder that receives compressive stress from the die hole wall inside the die plate (referred to as the effective length) was 10 mm. The granulation rate was 43 kg / h.

[0122] The obtained granular precursor was dried at 100°C for 4 hours using a hot air circulating dryer (manufactured by ESPEC, product name "PH-402") to obtain powdered granules.

[0123] (3) Evaluation of powder granules i) Bulk density The bulk density of the powder granules was calculated by measuring the mass of 1 liter of powder granules obtained by allowing the dried powder granules to fall naturally into a 1-liter measuring container. The bulk density of the powder granules was 0.40 kg / L.

[0124] ii) Moisture content The amount of moisture remaining in the powder granules was measured using an infrared moisture meter (FD-660, manufactured by Kett Scientific Laboratories). The moisture content of the powder granules was 0.5% by mass.

[0125] iii) Fracture stress The fracture stress (in kg) of 25 powder granules was measured using a Kiya-type hardness tester (manufactured by Shiro Sangyo Co., Ltd., product name "WPF1600-B"), and the average of the measured values ​​was calculated. The fracture stress was measured by setting the powder granule with its side facing downwards in the hardness tester and crushing it from the side using a 5 mm diameter cylindrical press. In other words, the fracture stress was measured by crushing the powder granule perpendicular to its longitudinal direction (extrusion direction). The average fracture stress of the powder granules was 1.5 kg, indicating that the powder granules had excellent handling properties.

[0126] iv) Maximum melting peak temperature T M and crystallization temperature T C A 5 mg sample was obtained by cutting the powder granules perpendicular to the longitudinal direction (extrusion direction) with a razor blade. Differential scanning calorimetry (DSC) was performed on the sample using a SII Nanotechnology "DSC6220". Specifically, the sample was heated from room temperature to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then DSC was performed while cooling at a rate of 10°C / min to obtain the DSC curves shown in Figures 2 and 3. In the DSC curve during heating shown in Figure 2, a melting endothermic peak was observed, and its highest peak temperature (i.e., the highest melting peak temperature) T M The temperature was 147°C. In the DSC curve during cooling shown in Figure 3, a clear crystallization exothermic peak was observed, and its peak temperature (i.e., crystallization temperature) T C The temperature was 95°C. Crystallization temperature T of powder granules C The temperature was higher than the crystallization temperature of the raw material PHA powder (85°C). Furthermore, when the sample was heated from room temperature to 200°C at a rate of 10°C / min in a nitrogen atmosphere, held at 200°C for 2 minutes, and then cooled at a rate of 10°C / min while DSC was performed, no crystallization exothermic peak was observed. These results indicate that a high melt memory effect is present in the powder granules. In addition, the full width at half maximum (FWHM) of the crystallization exothermic peak of the powder granules was smaller than that of the crystallization exothermic peak of the PHA powder.

[0127] v) Melt Flow Rate (MFR) GRN Melt flow rate (MFR) of powder granules GRN The melt flow rate (MFR) of the powder granules was measured in accordance with ISO 1133, using a melt indexer (Yasuda Seiki Seisakusho Co., Ltd. "No. 120-FWP"), with a cylinder setting temperature of 165°C, a load of 5 kg, and preheating for 4 minutes. GRN The concentration was 3.0g / 10min.

[0128] (4) Extrusion The powder granules were dried at 100°C for 8 hours using a dryer (ESPEC, product name "PH-402") to reduce the moisture content of the powder granules to 0.05% by mass or less. After drying, the powder granules were molded using an extruder as shown in Figure 1. The extruder consisted of a pair of cooling rolls, a first roll and a second roll, a conveying roll consisting of a third roll located downstream of the second roll and a pair of pinch rolls located downstream of the third roll, and a winding roll. A 40mmφ single-screw extruder (GSI Creos, product name "691C-EF049") equipped with a full-flight screw with L / D=28 was used as the extruder. For the first roll, a roll with a silicone rubber outer layer was used. The surface temperature of the first roll was controlled by water cooling. For the second and third rolls, metal mirror-finish rolls with chrome-plated surfaces were used. The second and third rolls share a hot water temperature control system, allowing for integrated control of the surface temperatures of both rolls.

[0129] The extruder cylinder was divided into five regions C1 to C5 in the direction of flow of the granulated powder and its molten material, from upstream to downstream, and the temperature of each region was controlled independently. Region C1 was the region below the hopper into which the granulated powder was fed. The T-die was divided into three regions D1 to D3 in the width direction of the molten material extruded from the T-die, and the temperature of each region was controlled independently. Region D2 was the region sandwiched between regions D1 and D3, including the center of the T-die. The set temperatures for regions C1 to C5 of the cylinder, the die head (HD) and adapter (AD) attached to the tip of the cylinder, and regions D1 to D3 of the T-die were as shown in Table 1 below.

[0130] [Table 1]

[0131] The temperature of the molten material inside the die head, i.e., the plasticizing melt temperature T, is measured by a thermocouple attached to the die head. P The results were as shown in Table 5.

[0132] Screw rotation speed S R At 30 rpm, a sheet of molten material was continuously extruded from a T-type die with a die width of 300 mm. The molten material was then cooled by sandwiching it between a pair of cooling rolls, consisting of a first roll and a second roll, positioned directly below the T-type die. The surface temperature of the first roll was set to 20°C. The surface temperature of the first roll, measured with a contact thermocouple (ST-41-K-1000-3C / A, manufactured by Rika Kogyo Co., Ltd.), was 30°C. The surface temperatures of the second and third rolls were set to 70°C. The surface temperatures of the second and third rolls, measured with the same contact thermocouple, were both 63°C. Upon contact with the second roll, the molten material cooled rapidly to 63°C, yielding a single-layer sheet (extruded product) with a thickness of 80 μm. The sheet was fed to a winding roll via the third roll and pinch rolls and wound up. The winding speed of the sheet was set to 1.3 m / min. The winding speed was controlled by the rotation speed of the second roll, thereby controlling the thickness of the sheet.

[0133] (5) Evaluation of extruded products i) Resistance to sticking to the second roll The degree to which the sheets adhered to the second roll was evaluated according to the following criteria. The results are shown in Table 5.

[0134] A: The sheet did not stick to the second roll. B: The sheet stuck to the second roll, or was prone to sticking to it.

[0135] ii) Effective width The width (hereinafter referred to as "effective width") of the area in the sheet having a thickness within ±10 μm of the design thickness (80 μm in Example 1) was measured. Here, width refers to the length in the direction perpendicular to the conveying direction (machine direction, MD) (TD). The results are shown in Table 5.

[0136] iii) Crystallization temperature T CA A 5 mg sample was cut from the center of the sheet using a razor blade. The crystallization temperature T of the sheet was determined using the same method as described above for the melt memory effect of powder granules. CA The following was measured. The results are shown in Table 5. Crystallization temperature T of the sheet. CA The temperature is 99°C, and the crystallization temperature of powder granules is T C It was 4°C higher than (95°C).

[0137] iv) Melt flow rate (MFR) ART A sample is cut from the sheet, and the melt flow rate (MFR) of the sheet is measured using that sample. ART The following measurements were taken. The measurements were performed in accordance with ISO 1133, using a melt indexer (Yasuda Seiki Seisakusho Co., Ltd. "No. 120-FWP"), with a cylinder set temperature of 165°C, a load of 5 kg, and preheating for 4 minutes. The results are shown in Table 5.

[0138] v) Appearance The appearance of the sheets was evaluated according to the following criteria. In these criteria, "defective appearance" refers to issues such as waviness and orange peel texture. The results are shown in Table 5.

[0139] AA: There were almost no cosmetic defects. A+: Some cosmetic defects were observed (the defects were minor). A: Cosmetic defects were easily observed (the cosmetic defects were moderate). B: The exterior was severely damaged.

[0140] vi) Heat shrinkage A 120mm x 120mm square piece was cut from the sheet, and two lines were drawn on its surface. The two lines intersected perpendicularly at the center of the piece and each had a length of 100mm. One of the two lines was parallel to the sheet's conveying direction (machine direction, MD), and the other line was parallel to the direction perpendicular to MD (TD). The piece was placed in an oven set to 150°C, near the melting point of PHA, or 170°C, above the melting point of PHA, for 30 minutes. Afterward, the length of the lines drawn on the piece was measured to determine the amount of sheet shrinkage in both the MD and TD directions. The results are shown in Table 5.

[0141] As shown in Table 5, the sheet could be wound stably onto the second roll without sticking. The sheet had a stable shape and dimensions with virtually no cosmetic defects. The sheet did not shrink when heated.

[0142] Example 2 Except for setting the sheet winding speed to 1.5 m / min and the design thickness of the sheet to 50 μm during extrusion molding, the sheet was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 5. The sheet was able to be wound stably without sticking to the second roll. The sheet had a stable shape and dimensions with almost no appearance defects. The sheet did not shrink when heated.

[0143] Example 3 Except for setting the sheet winding speed to 3.0 m / min and the design thickness of the sheet to 30 μm during extrusion molding, the sheet was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 5. The sheet was able to be wound stably without sticking to the second roll. The sheet had a stable shape and dimensions with almost no appearance defects. The sheet did not shrink when heated.

[0144] Example 4 In extrusion molding, the set temperatures for the cylinder regions C1-C5, the die head (HD) and adapter (AD) attached to the tip of the cylinder, and the T-type die regions D1-D3 are as shown in Table 2 below, and the plasticizing melt temperature T P Except for setting the temperature to 160°C and the winding speed to 1.2 m / min, the sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 5. The sheet could be wound stably without sticking to the second roll. The sheet had minor cosmetic defects. The sheet did not shrink when heated.

[0145] [Table 2]

[0146] Example 5 In the extrusion molding process, a sheet was produced in the same manner as in Example 1, except that the surface temperature of the second and third rolls was set to 40°C. The measured surface temperatures of both the second and third rolls were 37°C. The obtained sheet was evaluated in the same manner as in Example 1. The results are shown in Table 5. The sheet could be wound stably without sticking to the second roll. The sheet had moderate surface defects. The sheet did not shrink when heated.

[0147] Comparative Example 1 In extrusion molding, the set temperatures for the cylinder regions C1-C5, the die head (HD) and adapter (AD) attached to the tip of the cylinder, and the T-type die regions D1-D3 are as shown in Table 3 below, and the plasticizing melt temperature T P Except for setting the temperature to 170°C, a sheet was prepared in the same manner as in Example 1, and the degree of adhesion of the sheet to the second roll and the crystallization temperature T were measured. CA The appearance and other aspects were evaluated in the same manner as in Example 1. The results are shown in Table 5. The sheet stuck to the second roll and could not be wound up stably.

[0148] [Table 3]

[0149] Comparative Example 2 In extrusion molding, the set temperatures for the cylinder regions C1-C5, the die head (HD) and adapter (AD) attached to the tip of the cylinder, and the T-type die regions D1-D3 are as shown in Table 4 below, and the plasticizing melt temperature T P A sheet was prepared in the same manner as in Example 1, except that the temperature was set to 135°C. Unmelted PHA was present in the molten material extruded from the T-die, and the resulting sheet had wrinkles and holes.

[0150] [Table 4]

[0151] Comparative Example 3 Except for using commercially available PHA molten pellets (BluePHA Co., Ltd., product name "BP-330-05") with a crystallization nucleating agent added instead of powder granules, a sheet was prepared in the same manner as in Example 1, and the degree of adhesion of the sheet to the second roll and the crystallization temperature T were evaluated. CA Melt flow rate MFR ART The appearance and other aspects were evaluated in the same manner as in Example 1. The maximum melting peak temperature T of the molten pellet. M , crystallization temperature T C , and melt flow rate MFR PLTThe results were as shown in Table 5. The evaluation results are shown in Table 5. The sheet stuck to the second roll and could not be wound continuously.

[0152] Comparative Example 4 In the extrusion molding process, the sheets were manufactured in the same manner as in Comparative Example 3, except that the surface temperature of the second and third rolls was set to 40°C, the sheet winding speed was set to 2.0 m / min, and the design thickness of the sheet was set to 80 μm. The measured surface temperatures of the second and third rolls were both 37°C. The obtained sheets were evaluated in the same manner as in Example 1. The results are shown in Table 5. The sheets sometimes stuck to the second roll, but it was barely possible to manufacture sheets continuously. However, the sheets had a small effective width, were wavy, and had poor shape and dimensional stability. In addition, the sheets shrank at MD and stretched at TD at 170°C, showing poor heat resistance.

[0153] [Table 5]

[0154] In this specification, a numerical range represented by the symbol "~" includes the numbers before and after the symbol "~" as the lower and upper limits, respectively, unless otherwise specified. Furthermore, the upper and / or lower limits of the numerical ranges described in this specification can be arbitrarily combined to define a preferred range. For example, a preferred range can be defined by arbitrarily combining the upper and lower limits of a numerical range, by arbitrarily combining the upper limits of a numerical range, and by arbitrarily combining the lower limits of a numerical range.

[0155] In this application, the term "and / or" refers to at least one of the enumerated items and all possible combinations thereof.

[0156] Although this embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and any design changes that do not depart from the gist of this disclosure are also included in this disclosure. [Explanation of Symbols]

[0157] 1 Extrusion molding machine, 10 Extruder, 12 Cylinder, 14 Screw, 16 Hopper, 17 Die head, 18 T-type die, 19 Adapter, 30 Cooling roll, 32 First roll, 34 Second roll, 50 Conveyor roll, 52 Third roll, 54 Pinch roll, 70 Winding roll, 92 Powder granules, 94 Molten material, 96 Extruded molded body

Claims

1. A method for manufacturing an extruded article, This includes extruding polyhydroxyalkanoate (PHA) using an extrusion molding machine. The aforementioned extrusion molding process plasticizes the powder granules containing PHA powder at a melting temperature T Ｐ The process includes melting at (unit: °C) to obtain a molten material, extruding the molten material from a die, and cooling the extruded molten material to solidify it. The plasticizing melting temperature T Ｐ However, equation (1) T Ｍ -10<T Ｐ ≦T Ｍ +20 (1) (In the formula, T Ｍ (Unit: °C) represents the highest melting peak temperature observed in differential scanning calorimetry, where the powder granules are heated from room temperature at a rate of 10 °C / min in a nitrogen atmosphere. A method to satisfy the requirements.

2. The method according to claim 1, wherein the powder granules have a melt memory effect.

3. The method according to claim 1 or 2, wherein the powder granules are compression granules.

4. The method according to claim 3, wherein the powder granules have an outer wall portion formed by the melting and solidification of at least a portion of the PHA powder located at the outer edge of the powder granules, and compressed PHA powder is contained inside the outer wall portion.

5. The die is a T-type die, The method according to claim 1 or 2, wherein the molten material extruded from the die is cooled by at least one cooling roll.

6. The at least one cooling roll includes a first roll and a second roll that sandwich the molten material, The cooled molten material is conveyed along the surface of the second roll. The surface temperature T of the first roll Ｒ１ (unit: °C), the surface temperature T of the second roll Ｒ２ (unit: °C), and the crystallization temperature T of the powder granule Ｃ satisfy formula (2), formula (3), and formula (4) T Ｃ -80<T Ｒ１ ≦T Ｃ (2) T Ｃ -60<T Ｒ２ ≦T Ｃ (3) T Ｒ１ <T Ｒ２ (4) Satisfying the conditions, The crystallization temperature T of the powder granules Ｃ The method according to claim 5, wherein the powder granules are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, and the peak temperature of the crystallization exothermic peak observed during cooling is defined as the peak temperature of the crystallization exothermic peak observed during cooling.

7. Surface temperature T of the second roll Ｒ２ The method according to claim 6, wherein the temperature is 50°C to 80°C.

8. The method according to claim 1 or 2, wherein the extrusion molding machine has a single-screw flight screw having a supply zone, a compression zone, and a metering zone.

9. The method according to claim 8, wherein the extrusion molding is performed at a screw rotation speed of 100 rpm or less.

10. The aforementioned powder granules have a crystallization temperature T Ｃ The temperature (in degrees Celsius) is 80°C or higher. The crystallization temperature T of the powder granules Ｃ The method according to claim 1 or 2, wherein the powder granules are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, and the peak temperature of the crystallization exothermic peak observed during cooling is defined as the peak temperature of the crystallization exothermic peak observed during cooling.

11. The method according to claim 1 or 2, wherein the extruded article has a tubular shape.

12. Crystallization temperature T of the extruded body ＣＡ (Unit: °C) and the crystallization temperature T of the powder granules. Ｃ (Unit: °C) is given by equation (5) 0.8≦T ＣＡ / T Ｃ ≦1.2 (5) Satisfying the conditions, The crystallization temperature T of the powder granules Ｃ However, in differential scanning calorimetry where the powder granules are heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, the peak temperature of the crystallization exothermic peak observed during cooling is defined as follows: The crystallization temperature T of the extruded body ＣＡ The method according to claim 1 or 2, wherein the extruded body is heated to 180°C at a rate of 10°C / min in a nitrogen atmosphere, held at 180°C for 2 minutes, and then cooled at a rate of 10°C / min, and the peak temperature of the crystallization exothermic peak observed during cooling is defined as the peak temperature of the crystallization exothermic peak observed during cooling.

13. The melt flow rate MFR of the PHA powder ＯＲＩ (Unit: g / 10 min), Melt flow rate MFR of the powder granules ＧＲＮ (Unit: g / 10 min), and the melt flow rate MFR of the extruded product. ＡＲＴ (Unit: g / 10 min) is given by formulas (a), (b), and (c) 1≦MFR ＧＲＮ / MFR ＯＲＩ ≦5 (a) 1≦MFR ＡＲＴ / MFR ＧＲＮ ≦5 (b) 1≦MFR ＡＲＴ / MFR ＯＲＩ ≦10 (c) The melt flow rate MFR of the PHA powder satisfies the following conditions. ＯＲＩ , the melt flow rate MFR of the powder granules ＧＲＮ , and the melt flow rate MFR of the extruded product ＡＲＴ The method according to claim 1 or 2, wherein the measurement is performed at 165°C and a load of 5 kg in accordance with ISO 1133.

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