Manufacturing method for molded products

Abstract

Provided is a method for manufacturing a PHA molded body by injection molding, effectively utilizing the melt memory effect of a polyhydroxyalkanoate (PHA) powder granulate. 【Solution means】The method for manufacturing a molded body includes injection molding PHA by an injection molding machine. The injection molding includes melting a powder granulate containing PHA powder at a plasticizing melting temperature T P (unit: °C) to obtain a melt, injecting the melt into a mold, and cooling and solidifying the melt. The plasticizing melting temperature T P is represented by formula (1) T M -20 < T P ≤ T M + 20 (1) (In the formula, 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 a molded 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 are also easily decomposed by heat; for example, thermal decomposition progresses significantly at temperatures above 180°C. Furthermore, although PHAs are crystalline polymers, their crystallization rate is slow, making them difficult to crystallize within the mold during injection molding. For this reason, in PHA injection molding, pellets made by melting and kneading raw PHA powder (hereinafter sometimes referred to as "molten pellets") with added crystallization nucleating agents are sometimes used as the molding material. However, crystallization nucleating agents can adhere to the mold surface, hindering continuous molding. Moreover, the production of PHA molten pellets by the melting and kneading process requires a large amount of electricity.

[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.

[0005] Patent Document 3 discloses a method for injection molding PHA using a molding material that does not contain a crystallization nucleating agent. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7387950 [Patent Document 2] Patent No. 7454097 [Patent Document 3] Patent No. 7525489 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In injection molding of PHA, the crystallization and solidification of PHA can be accelerated by effectively utilizing the melt memory effect of PHA powder granules, even without substantially incorporating a crystallization nucleating agent. Therefore, this disclosure provides a method for manufacturing a PHA molded article by injection molding by effectively utilizing the melt memory effect of PHA powder granules. [Means for solving the problem]

[0008] The forms of this disclosure include the following: [Aspect 1] A method for manufacturing a molded article, This includes injection molding of polyhydroxyalkanoate (PHA) using an injection molding machine. The injection molding process plasticizes the powder granules containing PHA powder at a melting temperature T P This includes melting at (unit: °C) to obtain a molten material, pouring the molten material into a mold, and cooling the molten material to solidify it. The plasticization melting temperature T P However, equation (1) T M -20 <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 granulate 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 granulate, and the PHA powder compressed inside the outer wall portion is contained therein. [Aspect 5] The maximum melting peak temperature T of the powder granulate M is 140°C or higher, The injection molding is performed according to formula (2) 10≦S R ×V I ≦5,000 (2) for screw rotation speed S R (unit: rpm) and injection speed V I (unit: mm / sec), according to the method described in any one of aspects 1 to 4. [Aspect 6] The method according to any one of aspects 1 to 5, wherein the injection molding machine has a single-screw flight screw having a supply zone, a compression zone, and a metering zone. [Aspect 7] The injection molding is performed at a screw rotation speed S of 100 rpm or less R according to the method described in aspect 6. [Aspect 8] The injection molding is performed at an injection speed V of 100 mm / sec or less I according to the method described in any one of aspects 1 to 7. [Aspect 9] The set temperature T of the mold MOLD (unit: °C) and the crystallization temperature T of the powder granulate C satisfy the formula (3) T C -60<T MOLD ≦T C (3) and the crystallization temperature T of the powder granulate C is defined as the peak temperature of the crystallization heat generation peak observed during cooling in differential scanning calorimetry in which the powder granulate 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, according to the method described in any one of aspects 1 to 8. [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 set temperature T of the mold MOLD The method according to embodiment 10, wherein the temperature is 60°C to 80°C. [Aspect 12] The crystallization temperature T of the molded body CA (Unit: °C) and the crystallization temperature T of the powder granules. C (Unit: °C) is given by equation (4) 0.8≦T CA / T C ≤1.2 (4) 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 molded body CA The method according to any one of embodiments 1 to 11, wherein the molded 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. [Aspect 13] The method according to any one of embodiments 1 to 12, wherein the molded body has a load deflection temperature of 100°C or higher, and the load deflection temperature is measured at a load of 0.45 MPa in accordance with ISO 75. [Aspect 14] 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 molded body. 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 molded body ART However, the method according to any one of embodiments 1 to 13, measured at 165°C and a load of 5 kg in accordance with ISO 1133. [Effects of the Invention]

[0009] This disclosure provides a method for manufacturing a PHA molded article by injection molding, which effectively utilizes the melt memory effect of PHA powder granules. [Brief explanation of the drawing]

[0010] [Figure 1] These are the temperature-induced DSC curves for the PHA powder and PHA powder granules used in the examples. [Figure 2] 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]

[0011] A. Powder granules First, we will describe the powder granules used as injection molding material in the method for manufacturing a molded article according to the embodiment.

[0012] 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.

[0013] 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. Details of the production method will be described later.

[0014] 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 is 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 T H2In 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] A method for manufacturing molded articles using powder granules with a melt memory effect as an injection molding material may have the following advantages compared to a conventional method for manufacturing molded articles using molten pellets containing a crystallization nucleating agent as an injection molding material.

[0019] 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 molded body produced from the powder granules can also have a larger molecular weight, thereby enabling the molded body to have superior physical properties.

[0020] 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 molded products from powder granules, the total amount of electricity used can be greatly reduced.

[0021] iii) By advantageously utilizing the melt memory effect of powder granules, the range of molding conditions (setting temperature of injection molding machine and mold, injection speed, screw rotation speed, etc.) can be expanded, making it easier to control the appearance and crystallinity of the molded product.

[0022] iv) By using powder granules, molded 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 molded articles, they can be used for food applications, medical applications, and other uses. Furthermore, the crystallization nucleating agents will not adhere to the molding dies and hinder continuous molding.

[0023] 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.

[0024] 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 molded products.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] 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.

[0029] Because powder granules with this shape can be directly supplied to injection molding machines for thermoplastic resins, they can be used as injection molding materials.

[0030] 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.

[0031] In this specification, "die" refers collectively to tools equivalent to molds used to compress and shape PHA powder granules.

[0032] 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.

[0033] 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.

[0034] 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 injection molding machine.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] Preferred PHAs include poly(3-hydroxyalkanoate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0039] 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.

[0040] 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.

[0041] 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 products. PHA powder can be obtained, for example, by pulverizing molded products, pellets, or sprues or runners generated in injection molding at room temperature, or after cooling them with dry ice or liquid nitrogen as needed, using a pulverizer (for example, Dalton products, trade names "Nearmill," "Sylpheedmill," "Atomizer," or "Impactmill," etc.).

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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).

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] "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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] The moisture content of powder granules is measured using an infrared moisture meter.

[0075] 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.

[0076] 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.

[0077] The powder granules may be thoroughly dried immediately before use as an injection molding material. This effectively suppresses the decrease in molecular weight of PHA and / or defects in the appearance of the molded product that occur during injection molding. The moisture content of the powder granules immediately before use as an injection 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.

[0078] E. Method for manufacturing molded articles by injection molding The method for manufacturing a molded article according to the embodiment includes using powder granules containing PHA as a molding material and injection molding the PHA using an injection molding machine. The injection molding includes melting the powder granules put into the injection molding machine to obtain a molten material, injecting the molten material into a mold, and cooling the molten material to solidify it. More specifically, the powder granules are heated and melted in the cylinder of the injection molding machine, the molten material is injected into a mold through a nozzle attached to the tip of the cylinder, and the molten material is cooled and solidified in the mold to obtain a molded article.

[0079] Injection molding machine plasticizes powder granules at melting temperature T P It is melted at the plasticizing melt temperature T. P (Unit: °C) is given by formula (1) T M -20 <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.

[0080] 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.

[0081] In this specification, the plasticization melting temperature T P This is defined as the set temperature of the cylinder. If the set temperature differs depending on the part (zone) of the cylinder, generally the temperature is set higher in the downstream part in the flow direction of the powder granules and their molten material, so the plasticizing melt temperature T P This is defined as the set temperature at the point closest to the nozzle (i.e., the downstream point of the cylinder). Note that the nozzle's set temperature is generally the same as or lower than the downstream set temperature of the cylinder. Plasticization melting temperature T PThis is generally approximately equal to the temperature of the molten material immediately before it is poured into the mold. The temperature of the molten material immediately before it is poured into the mold can be measured with a contact thermometer (e.g., a thermocouple).

[0082] Plasticization melt temperature T that satisfies equation (1) P By melting the powder granules, the loss of the melt memory effect of the powder granules due to thermal disturbances, mechanical mixing, etc., can be suppressed, thereby enabling injection molding that effectively utilizes the melt memory effect.

[0083] Plasticization melting temperature T P Preferably, T M -15 <T P ≦T M +15 To satisfy and comfortably T M -10 <T P ≦T M +10 Satisfying the following, and more preferably, T M -5 <T P ≦T M +5 It satisfies the condition.

[0084] In conventional injection 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 pellet, it not only places an excessive load on the molding machine, but also results in insufficient plasticization, making the injection-molded product prone to surface defects such as sink marks or flow marks due to insufficient flow.

[0085] In contrast, in the method according to this embodiment, which uses PHA powder granules as a molding material, the load on the molding machine is reduced due to the large porosity of the powder granules, so the plasticization melt temperature T P is T M -20 <T P <T M Even when these conditions are met, the powder granules can be sufficiently plasticized and injection molded without placing an excessive load on the molding machine.

[0086] Inside an injection molding machine, a flow field is formed along with the rotation of the screw for plasticization and metering and the piston movement of the screw for injection. The maximum temperature at which the melt memory effect in the flow field is maintained can be lower than the maximum temperature at which the melt memory effect in the stationary field is maintained. The plasticizing melt temperature T P is such that T P >T M + 20. When this condition is satisfied, the melt memory effect is reduced or disappears due to the action of the flow field, and the crystal solidification in the mold becomes slow. As a result, problems such as poor mold release from the mold, deformation of the molded body associated therewith, and lengthening of the molding cycle occur, and productivity may decrease.

[0087] In one embodiment, the maximum melting peak temperature T M of the powder granulate is 140°C or higher, and the screw rotation speed S R (unit: rpm) and the injection speed V I (unit: mm / sec) of the injection molding machine satisfy the following formula (2) 10 ≦ S R × V I ≦ 5,000 (2) is satisfied.

[0088] S R × V I The value of is preferably 4,000 or less, more preferably 3,000 or less, still more preferably 2,500 or less, and most preferably 2,000 or less. Also, the value of S R × V I is preferably 50 or more, more preferably 100 or more, still more preferably 200 or more, and still more preferably 300 or more.

[0089] S R × V I By setting the value of to be 10 or more and 5,000 or less, an injection molded body of PHA with excellent quality and appearance can be manufactured with high productivity.

[0090] In one embodiment, the injection speed V Iis preferably 100 mm / sec or less, 80 mm / sec or less, 60 mm / sec or less, 50 mm / sec or less, or 30 mm / sec or less.

[0091] In one embodiment, the screw of the injection molding machine is a single-screw flight screw. The single-screw flight screw has a supply zone, a compression zone, and a metering zone from upstream to downstream in the flow direction of the powder granulate and its melt. 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 injection molding machine is a single-screw flight screw, the rotational speed S of the screw R is preferably 100 rpm or less, 80 rpm or less, 60 rpm or less, 50 rpm or less, or 30 rpm or less. The rotational speed S of the screw R By reducing the rotational speed S of the screw, the reduction or disappearance of the melt memory effect due to the flow field caused by mechanical mixing can be suppressed. The rotational speed S of the screw R may be 10 rpm or more.

[0092] In one embodiment, the set temperature T of the mold MOLD (unit: °C) and the crystallization temperature T of the powder granulate C (unit: °C) satisfy the formula (3) T C -60 < T MOLD ≦ T C (3) The crystallization temperature T C is defined as the peak temperature of the crystallization exothermic peak observed during the temperature decrease in a differential scanning calorimetry (DSC) in which the powder granulate 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.

[0093] The set temperature T of the mold MOLD and the crystallization temperature T of the powder granulate C are preferably T C -50 < T MOLD ≦ T C More preferably, T C -45 <T MOLD ≦T C More preferably, T C -40 <T MOLD ≦T C Particularly preferred, T C -30 <T MOLD ≦T C It satisfies the condition.

[0094] Mold setting temperature T MOLD The crystallization temperature of powder granules T C By keeping the temperature below (°C), the crystallization solidification of PHA in the mold can be accelerated, enabling the production of molded products with superior quality and appearance with high productivity. The melt memory effect of powder granules originates from the pseudo-crystalline phase structure of PHA itself, therefore the crystallization temperature of powder granules T C This can be higher than the crystallization temperature of molten pellets to which a crystallization nucleating agent has been added. Therefore, when performing injection molding using powder granules with a melt memory effect as a molding material, the mold set temperature T can be higher compared to conventional injection molding using molten pellets. MOLD The set temperature of the mold can be increased. MOLD A high is advantageous for improving the crystallinity of the molded article, making it possible to manufacture molded articles with high dimensional accuracy that have a high temperature of deflection under load (DTUL), flexural modulus (rigidity), and flexural strength, while also having fewer surface defects such as sink marks, flow marks, and orange peel texture.

[0095] For example, T C If the temperature is between 95°C and 100°C, the mold set temperature T MOLD The temperature is preferably 50°C to 95°C, more preferably 55°C to 90°C, even more preferably 60°C to 85°C, and most preferably 65°C to 80°C.

[0096] For example, T C If the temperature is between 80°C and 95°C, the mold set temperature T MOLDThe temperature is preferably 35°C to 80°C, more preferably 40°C to 75°C, even more preferably 45°C to 73°C, and most preferably 50°C to 70°C.

[0097] Thus, the crystallization temperature T of powder granules C Depending on the setting temperature of the mold, MOLD By appropriately selecting the elements, the melt memory effect can be effectively utilized to improve the crystallinity of the molded article, making it possible to manufacture molded articles with high dimensional accuracy that have a high load deflection temperature, flexural modulus, and flexural strength, as well as fewer surface defects such as sink marks, flow marks, and orange peel texture.

[0098] Mold setting temperature T MOLD However, T MOLD ≦T C If the temperature is -60°C, the molded article produced may not have sufficient crystallinity, which can lead to a decrease in the load deflection temperature and / or flexural strength of the molded article, as well as an increase in appearance defects.

[0099] The highest melting peak temperature T of powder granules M If the temperature is 140°C or higher, the powder granules will have a high crystallization temperature of 80°C or higher due to the melt memory effect. C (Unit: °C) may have a maximum melting peak temperature T. 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 performing injection molding using this powder granule, the mold setting temperature T MOLD By maintaining a high temperature of around 70°C (for example, 60°C to 80°C), the molten powder granules can be crystallized and solidified within the mold, enabling the production of molded products with excellent quality and appearance with high productivity.

[0100] In the method according to the embodiment, powder granules that do not contain crystallization nucleating agents can be used as the molding material. Crystallization nucleating agents can cause problems such as adhering to the mold and hindering continuous molding, reducing the bending strength and / or load deflection temperature of the molded body, and causing stickiness in the molded body, making it difficult to remove the molded body from the mold. By using powder granules that do not contain crystallization nucleating agents as the molding material, these problems can be avoided.

[0101] In one embodiment, the crystallization temperature of the molded body T CA (Unit: °C) and crystallization temperature T of powder granules C (Unit: °C) is given by formula (4) 0.8≦T CA / T C ≤1.2 (4) The following conditions are met. Note that the crystallization temperature T of the powder granules is also specified. C T is defined as the peak temperature of the crystallization exothermic peak observed during cooling in a DSC (Dynamic Stem Cell) where 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. CA This is defined as the peak temperature of the crystallization exothermic peak observed during cooling in a DSC (Dynamic Stem Cell Spectroscopy) where a molded body (specifically, a measurement piece cut from the molded 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.

[0102] Equation (4) above represents the crystallization temperature T of the molded body. CA The crystallization temperature of powder granules T C This indicates that the crystallization temperature is almost equivalent to that of the previous formula, meaning that the change in crystallization temperature due to injection molding is small, and that the melt memory effect of the powder granules was effectively utilized in injection molding. Molded articles manufactured by effectively utilizing the melt memory effect have a high degree of crystallinity, as described above. Therefore, molded articles that satisfy equation (4) can have a high load deflection temperature, bending strength, bending modulus, dimensional accuracy, and excellent appearance.

[0103] In one embodiment, the powder granules are manufactured under conditions that the temperature of the granules immediately after granulation is below the melting point of PHA, in which case the melt flow rate (MFR) of the PHA powder is... ORI (Unit: g / 10min), Melt flow rate (MFR) of powder granules GRN (Unit: g / 10min), and the melt flow rate (MFR) of the molded 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 PHA powder can be satisfied. ORI Melt flow rate (MFR) of powder granules GRN , and the melt flow rate (MFR) of the molded product ART It is measured at 165°C and under a load of 5 kg in accordance with ISO 1133.

[0104] Formulas (a), (b), and (c) above indicate that the decrease in molecular weight of PHA during the process of manufacturing a molded article of PHA from PHA powder was sufficiently suppressed. By suppressing the decrease in molecular weight of PHA, it is possible to manufacture a molded article with superior mechanical properties.

[0105] In one embodiment, the molded article produced has a load deflection temperature of 100°C or higher. The load deflection temperature is measured at a load of 0.45 MPa in accordance with ISO 75.

[0106] The applications of the molded articles produced by the method according to this embodiment are not particularly limited. The molded articles can be used in a variety of applications, such as medical supplies, tableware supplies, agricultural supplies, fishing 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 compared to molten pellets used in conventional injection molding. Furthermore, the molded 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]

[0107] 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.

[0108] 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 0.30 kg / L, the maximum melting peak temperature was 145°C, the crystallization temperature was 85°C, and the melt flow rate (MFR) was 0.30 kg / L. ORI The concentration was 3.0g / 10min.

[0109] 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.

[0110] 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 C The measurements were taken in the same manner (see Figures 1 and 2).

[0111] 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.

[0112] (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 15 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.

[0113] 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 12 mm. The granulation rate was 70 kg / h.

[0114] The obtained granular precursor was dried at 100°C for 9 hours using a hot air circulating dryer (manufactured by ESPEC, product name "PH-402") to obtain powdered granules.

[0115] (3) Evaluation of powder granules i) Structural observation The obtained powder granules were cut perpendicular to the extrusion direction from the die hole using a razor blade to obtain observation pieces with a thickness of 0.5 mm, and the cut surface was observed with an optical microscope. A partially molten outer wall structure (shell structure) of PHA powder was observed at the outer edge of the cut surface, and the original form of unmolten PHA powder was observed inside the outer wall structure (core). From these observation results, it was confirmed that powder granules with a core-shell structure similar to those described in Japanese Patent No. 7387950 were manufactured.

[0116] ii) 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 0.45 kg / L.

[0117] iii) 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 0.05% by mass.

[0118] iv) 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 7 kg, indicating that the powder granules had excellent handling properties.

[0119] v) 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 1 and 2. In the DSC curve during heating shown in Figure 1, 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 2, 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 CThe 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. The full width at half maximum (FMAX) of the crystallization exothermic peak of the powder granules was smaller than that of the crystallization exothermic peak of the PHA powder.

[0120] vi) 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.

[0121] (4) Injection molding 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 0.02% by mass or less. After drying, the powder granules were fed into an injection molding machine (Toyo Machinery & Metal Co., Ltd., "SI-80IV-D150B", clamping force 80 tons) to produce dumbbell-shaped molded bodies (4 mm thick) for ISO testing.

[0122] The injection molding machine's screw was a single-screw flight screw having a supply zone, a compression zone, and a metering zone, arranged from upstream to downstream in the flow direction of the powder granules and their molten material. The injection molding machine's cylinder was divided into four zones, from upstream to downstream in the flow direction of the powder granules and their molten material: a region below the hopper where the powder granules are fed (zone 1), a region corresponding to the screw's supply zone (zone 2), a region corresponding to the screw's compression zone (zone 3), a region corresponding to the screw's metering zone (zone 4), and a region corresponding to the tip of the screw (zone 5). The temperatures of zones 1 to 5 and the nozzle attached to the tip of the cylinder were controlled independently. The set temperature for zone 1 was 40°C, and the set temperatures for zones 2 to 5 and the nozzle were all 160°C. In this case, the plasticizing melt temperature T P The temperature was 160°C. Furthermore, the temperature of the molten material immediately before it was injected into the mold from the nozzle was measured using a contact thermocouple and was also 160°C.

[0123] Screw rotation speed S R The rotation speed is 30 rpm, and the injection speed is V. I The speed is 40 mm / s, and the mold setting temperature is T MOLD The temperature was set to 70°C, and the cooling time was 60 seconds.

[0124] (5) Evaluation of the molded product i) Ease of removal from the mold Multiple injection molding cycles were performed, and the ease of removing the molded parts from the mold was evaluated according to the following criteria. The results are shown in Table 1.

[0125] A: The crystallization was sufficient, and the material could be easily ejected from the mold using an ejector pin. B: Although crystallization was progressing, there were times when the ejector pins could not eject the material from the mold. C: Crystallization was insufficient, and the material could not be ejected from the mold using the ejector pin.

[0126] ii) Crystallization temperature T CA A 5 mg sample was cut from the center of the molded body using a razor blade. The crystallization temperature T of the molded body was determined using the same method as described above for the melt memory effect of powder granules. CA The crystallization temperature of the molded body T was measured. The results are shown in Table 1. CA The temperature is 98°C, and the crystallization temperature of powder granules is T C It was 3 degrees Celsius higher than (95 degrees Celsius).

[0127] iii) Melt flow rate (MFR) ART A measurement piece is cut from the molded body, and the melt flow rate (MFR) of the molded body is measured using this measurement piece. 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 1.

[0128] iv) Appearance The appearance of the molded articles was evaluated according to the following criteria. The results are shown in Table 1.

[0129] AA: There were almost no cosmetic defects such as sink marks, flow marks, or orange peel texture. A+: Some cosmetic defects such as shrinkage, flow marks, and orange peel texture were observed (the cosmetic defects were minor). A: Surface defects such as shrinkage, flow marks, and orange peel texture were easily observed (the surface defects were moderate). B: There were severe cosmetic defects such as sink marks, flow marks, and orange peel texture.

[0130] Furthermore, since sink marks are indentations caused by the shrinkage of the molded product, molded products with sink marks are considered to have inferior dimensional accuracy.

[0131] v) Bending test In accordance with ISO 178, the bending strength (in MPa) and flexural modulus (in MPa) of the molded body were measured in a constant temperature room at 23°C at a speed of 2 mm / min using an Autograph (Shimadzu Corporation "AG-X"). For the measurements, 80 mm long strip-shaped test pieces cut from a dumbbell-shaped molded body were used. The results are shown in Table 1.

[0132] vi) Temperature of deflection under load In accordance with ISO 75, the deflection temperature was measured in a constant temperature chamber at 23°C using an HDT (3M-2, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a load of 0.45 MPa and a heating rate of 120°C / h. For the measurement, 80 mm long strip-shaped test pieces cut from a dumbbell-shaped molded body were used. The results are shown in Table 1.

[0133] As shown in Table 1, the molded articles could be easily removed from the mold and possessed excellent appearance, high flexural strength, high flexural modulus, and high load deflection temperature. These indicate that the molded articles had a sufficient degree of crystallinity.

[0134] Example 2 Except for setting the injection molding speed to 10 mm / second, a dumbbell-shaped molded body was produced in the same manner as in Example 1, and the ease of removal of the molded body and the crystallization temperature T were evaluated. CA Melt flow rate MFR ART Appearance, bending strength, bending modulus, and temperature of deflection under load were evaluated in the same manner as in Example 1. The results are shown in Table 1. The molded articles could be easily removed from the mold and had excellent appearance, high bending strength, high bending modulus, and high temperature of deflection under load.

[0135] Example 3 In injection molding, the plasticizing melt temperature T is set to 150°C for all zones 2-5 and the nozzle. P Set the temperature to 150°C and the screw rotation speed S R Except for setting the rotation speed to 100 rpm, a dumbbell-shaped molded body was fabricated in the same manner as in Example 1. Ease of removal of the molded body, crystallization temperature T CA Melt flow rate MFRART Appearance, bending strength, bending modulus, and temperature of deflection under load were evaluated in the same manner as in Example 1. The results are shown in Table 1. The molded articles could be easily removed from the mold and had excellent appearance, high bending strength, high bending modulus, and high temperature of deflection under load.

[0136] Example 4 In injection molding, the plasticization melt temperature T is set to 140°C for all zones 2-5 and the nozzle. P Set the temperature to 140°C and the screw rotation speed S R Except for setting the rotation speed to 100 rpm, a dumbbell-shaped molded body was produced in the same manner as in Example 1, and the ease of removing the molded body and the crystallization temperature T were examined. CA Melt flow rate MFR ART Appearance, bending strength, bending modulus, and temperature of deflection under load were evaluated in the same manner as in Example 1. The results are shown in Table 1. The molded articles could be easily removed from the mold and had excellent appearance, high bending strength, high bending modulus, and high temperature of deflection under load.

[0137] Example 5 In injection molding, injection speed V I Except for setting the temperature to 80 mm / s, a dumbbell-shaped molded body was prepared in the same manner as in Example 1, and the ease of removing the molded body and the crystallization temperature T were examined. CA Melt flow rate MFR ART Appearance, bending strength, bending modulus, and temperature of deflection under load were evaluated in the same manner as in Example 1. The results are shown in Table 1. In some cases, the molded articles could not be removed from the mold with ejector pins. Appearance defects were observed in the molded articles.

[0138] Example 6 In injection molding, the mold setting temperature T MOLD Except for setting the temperature to 40°C, a dumbbell-shaped molded body was prepared in the same manner as in Example 1, and the ease of removing the molded body and the crystallization temperature T were examined. CA Melt flow rate MFR ARTAppearance, bending strength, bending modulus, and load deflection temperature were evaluated in the same manner as in Example 1. The results are shown in Table 1. The molded article had sufficient appearance, bending strength, bending modulus, and load deflection temperature, but compared to the molded article of Example 1, it showed more sink marks and a lower load deflection temperature. In Example 6, the mold setting temperature T MOLD The temperature is 40℃, and the mold setting temperature T of Example 1 MOLD Because the temperature was lower than that of Example 1, the crystallization and solidification of PHA inside the mold was slower, resulting in inferior appearance and load deflection temperature compared to Example 1.

[0139] Example 7 In injection molding, screw rotation speed S R Except for setting the rotation speed to 100 rpm, a dumbbell-shaped molded body was produced in the same manner as in Example 1, and the ease of removing the molded body and the crystallization temperature T were examined. CA Melt flow rate MFR ART Appearance, bending strength, bending modulus, and temperature at which deflection under load were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0140] The molded body could not be removed from the mold with an ejector pin. The molded body removed from the mold manually had a good appearance, high bending strength, high bending modulus, and high load deflection temperature, but compared to the molded body of Example 1, it had a worse appearance with more orange peel texture and sink marks, and a lower load deflection temperature. In Example 7, the screw rotation speed S R Because the value was greater than in Example 1, the melt memory effect was reduced by the flow field, resulting in inferior ease of removal, appearance, and load deflection temperature of the molded product compared to Example 1. A broad exothermic peak was observed in the cooling DSC curve of the molded product, and its peak temperature was approximately 73°C. This is because the crystallization temperature T of the powder granules was lowered. C This result differs significantly from (95℃), indicating that the crystallization temperature was not maintained during the injection molding process. This result also suggests that a large screw rotation speed S is not suitable. R This suggests that the melt memory effect was reduced due to the influence of the fluid field.

[0141] Comparative Example 1 In injection molding, the plasticization melt temperature T is set to 170°C for all zones 2-5 and the nozzle. P A dumbbell-shaped molded body was prepared in the same manner as in Example 1, except that the temperature was set to 170°C. The molded body was not sufficiently crystallized and could not be removed from the mold with an ejector pin. Therefore, the molded body was removed from the mold manually, and the crystallization temperature of the molded body T CA The appearance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0142] The molded product exhibited severe orange peel texture and shrinkage. Furthermore, a broad exothermic peak was observed in the cooling DSC curve of the molded product, with a peak temperature of approximately 73°C. This corresponds to the crystallization temperature T of the powder granules. C This differs significantly from (95℃), indicating that the crystallization temperature was not maintained during the injection molding process.

[0143] [Table 1]

[0144] 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.

[0145] In this application, the term "and / or" refers to at least one of the enumerated items and all possible combinations thereof.

[0146] 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.

Claims

1. A method for manufacturing a molded article, This includes injection molding of polyhydroxyalkanoate (PHA) using an injection molding machine. The injection molding process plasticizes the powder granules containing PHA powder at a melting temperature T Ｐ This includes melting at (unit: °C) to obtain a molten material, pouring the molten material into a mold, and cooling the molten material to solidify it. The plasticizing melting temperature T Ｐ However, equation (1) T Ｍ -20<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 highest melting peak temperature T of the powder granules Ｍ The temperature is 140°C or higher. The injection molding described above is performed according to formula (2) 10≦S Ｒ ×V Ｉ ≦5,000 (2) Screw rotation speed S that satisfies this condition Ｒ (Unit: rpm) and injection speed V Ｉ The method according to claim 1 or 2, performed in (unit: mm / second).

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

7. Screw rotation speed S of 100 rpm or less Ｒ The method according to claim 6, wherein the injection molding is performed.

8. The injection molding is performed at an injection speed V of 100 mm / second or less. Ｉ The method according to claim 1 or 2, performed in [location].

9. The set temperature T of the mold ＭＯＬＤ (Unit: °C) and the crystallization temperature T of the powder granules. Ｃ However, equation (3) T Ｃ -60<T ＭＯＬＤ ≦T Ｃ (3) Satisfying the conditions, The crystallization temperature T of the aforementioned 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.

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 aforementioned 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 set temperature T of the mold ＭＯＬＤ The method according to claim 10, wherein the temperature is 60°C to 80°C.

12. The crystallization temperature T of the molded body ＣＡ (Unit: °C) and the crystallization temperature T of the powder granules. Ｃ (Unit: °C) is given by equation (4) 0.8≦T ＣＡ / T Ｃ ≦1.2 (4) Satisfying the conditions, The crystallization temperature T of the aforementioned 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 molded body ＣＡ The method according to claim 1 or 2, wherein the molded 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 method according to claim 1 or 2, wherein the molded body has a load deflection temperature of 100°C or higher, and the load deflection temperature is measured at a load of 0.45 MPa in accordance with ISO 75.

14. 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 molded body. 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 molded body 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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