Method for producing molded body containing poly-3-hydroxybutyric acid-based resin and use thereof

Abstract

The present invention aims to provide a novel production method capable of obtaining a molded body containing a P3HB-based resin using an injection blow molding method and a technology using the same. The present invention solves the above problem by providing a production method of a molded body containing a P3HB-based resin, the method comprising the following steps (A) to (C): (A) a step of plasticizing a resin composition containing a P3HB-based resin, (B) a step of injection molding the plasticized resin composition obtained by the above step (A) to obtain a preform, and (C) a step of blow molding the preform obtained by the above step (B) to obtain a molded body.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a molded article comprising a poly-3-hydroxybutyrate resin and its use. Background Technology

[0002] Currently, with the need to reduce plastic waste and fossil fuels, biodegradable resins and bio-based resins are receiving significant attention as raw materials for containers / bottles. Among these, poly-3-hydroxybutyrate resins (hereinafter sometimes referred to as "P3HB resins," meaning "poly-3-hydroxybutyrate resins" and "P3HB resins" have the same meaning in this specification), especially poly-3-hydroxybutyrate, can be manufactured from bio-based raw materials through microbial cultivation and exhibits excellent biodegradability in soil and oceans. Therefore, it is expected to be a key material for solving the aforementioned problems. However, P3HB resins crystallize slowly, and once crystallized, they are difficult to remelt. Furthermore, due to their high melting point, they are difficult to manufacture containers / bottles using injection blow molding.

[0003] To address the aforementioned issues, methods for manufacturing P3HB-type resins based on injection molding (Patent Document 1), methods for manufacturing biodegradable containers by injection blow molding (Patent Document 2), and methods for manufacturing hollow molded articles based on injection blow molding using polyester resins containing polyethylene terephthalate and polyethylene naphthalate as molding materials (Patent Document 3) have been reported.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 94 / 28061

[0007] Patent Document 2: Japanese Patent Application Publication No. 2000-6230

[0008] Patent Document 3: Japanese Patent Application Publication No. 9-52277 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, none of the aforementioned patent documents describe a specific method for injection blow molding using P3HB-type resin. That is, none of the aforementioned patent documents describe manufacturing molded articles containing P3HB-type resin using injection blow molding.

[0011] The present invention was made in view of the above-mentioned problems, and its object is to provide a new manufacturing method and technology for obtaining molded articles containing P3HB resin (especially molded articles containing P3HB resin with excellent appearance) by injection blow molding.

[0012] Methods for solving problems

[0013] In order to solve the above-mentioned problems, the inventors conducted in-depth research and discovered the following new insights: In the injection blow molding method, by adjusting the thickness of the preform obtained by injection molding and the surface temperature of the preform before blow molding, it is possible to manufacture a molded body containing P3HB resin with excellent appearance, thereby completing the present invention.

[0014] Therefore, one aspect of the present invention is a method for manufacturing a molded article comprising a P3HB-type resin (hereinafter referred to as "this manufacturing method"), which includes the following steps (A) to (C): (A) a step of plasticizing a resin composition comprising a P3HB-type resin, (B) a step of injection molding the plasticized resin composition obtained in step (A) to obtain a preform, and (C) a step of blow molding the preform obtained in step (B) to obtain a molded article, wherein the thickness of the preform is 2.5 mm or more and 10 mm or less, and the surface temperature of the preform supplied for blow molding in step (C) is 110°C or more and 165°C or less.

[0015] Another aspect of the present invention is a marine-degradable molded body (hereinafter referred to as "this molded body"), which is manufactured by a manufacturing method comprising the following steps (A) to (C): (A) a step of plasticizing a resin composition containing a P3HB type resin, (B) a step of injection molding the plasticized resin composition obtained by step (A) to obtain a preform, and (C) a step of blow molding the preform obtained by step (B) to obtain a molded body, wherein the thickness of the preform is 2.5 mm or more and 10 mm or less, and the surface temperature of the preform supplied for blow molding in step (C) is 110°C or more and 165°C or less.

[0016] The effects of the invention

[0017] According to one aspect of the present invention, a novel manufacturing method using injection blow molding can achieve the effect of obtaining molded articles containing P3HB-type resin with excellent appearance. Detailed Implementation

[0018] The following describes one embodiment of the present invention in detail. It should be noted that, unless otherwise specified, in this specification, "A to B" indicating a numerical range means "A or more and B or less". Furthermore, all documents described in this specification are incorporated herein by reference.

[0019] [1. Content of this invention]

[0020] Representative resins used in containers / bottles, such as polyethylene terephthalate and polypropylene, can be blow-molded around or below their melting points. On the other hand, P3HB resins exhibit poor elasticity below their melting points and become low-viscosity above their melting points, making blow molding difficult. This property differs significantly from typical polyester resins such as polyethylene terephthalate described in Patent Document 3, making the molding of P3HB resins technically challenging.

[0021] To address this issue, the inventors conducted in-depth research on a method for manufacturing molded articles containing P3HB-type resin using injection blow molding. The inventors discovered that by utilizing the slow crystallization of P3HB-type resin, the preform is extracted from the injection mold while its surface is cured but its interior remains hot and uncured, and then blow molded at a temperature below the melting point of P3HB-type resin, thereby enabling the manufacture of molded articles containing P3HB-type resin. Furthermore, the inventors found that the aforementioned state of the preform (i.e., surface cured but interior uncured) can be controlled by the thickness of the preform obtained from injection molding and the surface temperature of the preform before blow molding. Moreover, the inventors discovered that if the surface temperature of the preform before blow molding does not reach a certain temperature, a molded article containing P3HB-type resin can be manufactured by reheating the preform.

[0022] In existing technologies, the molding of P3HB resins mainly focuses on the composition of the resin as a raw material and the conditions for injection blow molding. In contrast, the inventors have focused on the properties of P3HB resins and successfully manufactured molded articles containing P3HB resins using these properties. This technology, based on such a concept, is unprecedented and surprising.

[0023] Therefore, according to the present invention, P3HB type resins, which have high melting points and are difficult to process, can be easily processed. The structure of this manufacturing method will be described in detail below.

[0024] [2. Method for manufacturing molded articles containing P3HB type resin]

[0025] This manufacturing method includes the following steps (A) to (C) as necessary steps.

[0026] • Process (A): The process of plasticizing a resin composition containing P3HB resin.

[0027] • Process (B): The process of injection molding the plasticized resin composition obtained in process (A) above to obtain a preform.

[0028] • Process (C): The process of blow molding the preform obtained through process (B) to obtain the molded body.

[0029] (Process (A))

[0030] In step (A) of this manufacturing method, a resin composition containing P3HB-type resin (hereinafter sometimes simply referred to as "resin composition") is plasticized. Step (A) can also be referred to as a step of melting the resin composition containing P3HB-type resin. Through step (A), the resin composition can be made into a liquid state, and therefore, a preform of the desired shape can be obtained in step (B).

[0031] <P3HB type resin>

[0032] In this specification, "P3HB resin" refers to an aliphatic polyester resin that can be produced by microorganisms, with 3-hydroxybutyrate as the repeating unit.

[0033] In one embodiment of the present invention, the P3HB resin may be a poly(3-hydroxybutyrate) with 3-hydroxybutyrate as the repeating unit only, or it may be a copolymer of 3-hydroxybutyrate and other hydroxyalkyl esters.

[0034] In one embodiment of the present invention, the P3HB resin can be a mixture of homopolymer and one or more copolymers, or a mixture of two or more copolymers. The copolymerization form is not particularly limited and can be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc.

[0035] In one embodiment of the present invention, examples of P3HB-type resins include: poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-copoly-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-copoly-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-copoly-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-copoly-3-hydroxydecanoate) (P3HB3HD), and poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate-copoly-3-hydroxyhexanoate) (P3HB3HV3HH). From the perspective of ease of industrial production, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred.

[0036] In one embodiment of the present invention, the P3HB resin may be selected from poly-3-hydroxybutyrate, poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate), poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-4-hydroxybutyrate), and combinations thereof.

[0037] Furthermore, by changing the composition ratio of the repeating units, the melting point and crystallinity can be altered, resulting in changes to properties such as Young's modulus and heat resistance. Moreover, it can impart properties between polypropylene and polyethylene. As mentioned above, it is easily produced industrially and, from the viewpoint of a resin with useful physical properties, P3HB3HH, a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred. Particularly among P3HB-type resins, which are prone to thermal decomposition upon heating to 180°C or higher, P3HB3HH is preferred from the viewpoint of lowering the melting point and enabling low-temperature molding processing.

[0038] P3HB resins can be produced by microorganisms, for example. There are no particular limitations on the microorganisms that produce P3HB resins; any microorganism capable of producing P3HB resins can be used. For example, the earliest known P3HB-producing bacterium is *Bacillus megaterium*, discovered in 1925. Other examples include *Cupriavidus necator* (formerly classified as *Alcaligenes eutrophus* and *Ralstonia eutropha*) and *Alcaligenes latus*, among other naturally occurring microorganisms. In these microorganisms, P3HB is known to accumulate within the bacterial cells.

[0039] In addition, known microorganisms that produce copolymers of hydroxybutyrate and other hydroxyalkyl esters include *Aeromonas caviae* as a producer of P3HB3HV and P3HB3HH, and *Alcaligenes eutrophus* as a producer of P3HB4HB. Especially regarding P3HB3HH, to improve the productivity of P3HB3HH, *Alcaligenes eutrophus* strain AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) with genes introduced into the P3HA synthase group is preferred. These microorganisms can be cultured under appropriate conditions, and microbial cells containing accumulated P3HB3HH can be used. In addition to the above, recombinant microorganisms with various P3HB resin synthesis-related genes can be used depending on the desired P3HB resin production, as long as the culture conditions, including the type of substrate, are optimized.

[0040] Alternatively, P3HB3HH can also be manufactured using the method described in International Publication No. 2010 / 013483. Commercially available products of P3HB3HH include, for example, "Kaneka Biodegradable Polymer PHBH (registered trademark)" from Kaneka Corporation (e.g., X131N used in the examples).

[0041] In one embodiment of the present invention, regarding the composition ratio of the repeating units of P3HB3HH, from the viewpoint of balancing softness and strength, the composition ratio of 3-hydroxybutyrate units to 3-hydroxyhexanoate units is preferably 80 / 20 to 99 / 1 (mol / mol), more preferably 75 / 15 to 97 / 3 (mol / mol). When the composition ratio of 3-hydroxybutyrate units to 3-hydroxyhexanoate units is 80 / 20 (mol / mol) or more and 99 / 1 (mol / mol) or less, the moldability is improved.

[0042] In one embodiment of the present invention, the weight-average molecular weight (hereinafter sometimes referred to as "Mw") of the P3HB resin is not particularly limited, but is preferably 150,000 to 800,000, more preferably 200,000 to 700,000, and even more preferably 250,000 to 600,000. When the weight-average molecular weight is 150,000 or higher, sufficient mechanical properties can be obtained, and when it is 800,000 or lower, sufficient crystallization rate can be obtained, enabling good molding and processability. The weight-average molecular weight of the P3HB resin can be determined by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko Corporation), using polystyrene gel (Shodex K-804 manufactured by Showa Denko Corporation) in a column, and using chloroform as the mobile phase, after polystyrene conversion.

[0043] <Resin Composition>

[0044] The resin composition in step (A) may contain only P3HB resin, or it may contain other resins besides P3HB resin. There are no particular limitations on such other resins, but biodegradable aliphatic polyester resins other than P3HB resins are preferred. Examples include polybutylene succinate (PBS) resins, polycaprolactone (PCL) resins, and polyhydroxyalkanoate resins (excluding P3HB resins). Examples of the aforementioned polybutylene succinate (PBS) resins include polybutylene succinate (PBS) and polybutylene adipate succinate (PBSA). Polyhydroxyalkanoate resins other than P3HB resins refer to polyhydroxyalkanoate resins that do not contain 3-hydroxybutyrate as a monomer component; for example, polyglycolic acid, polylactic acid, and poly4-hydroxybutyrate resins can be used. As for poly4-hydroxybutyrate resins, they can be poly(4-hydroxybutyrate) with 4-hydroxybutyrate as the only repeating unit, or they can be copolymers of 4-hydroxybutyrate and other hydroxyalkanoates. From the perspective of balancing drop strength, molding processability and biodegradability, PBSA-type resin is preferred.

[0045] PBSA-type resins are aliphatic polyester polymers containing 1,4-butanediol, succinic acid, and adipic acid in their structural units. In one embodiment of the present invention, as a PBSA-type resin, any diol, dicarboxylic acid, or hydroxyalkyl ester other than 1,4-butanediol, succinic acid, and adipic acid may be included in the structural units without impairing biodegradability. Examples include: polybutylene adipate succinate, copolymers of polybutylene adipate succinate and lactic acid, copolymers of polybutylene adipate succinate and terephthalic acid, copolymers of polybutylene adipate succinate and malic acid, copolymers of polybutylene adipate succinate and sebacic acid, and copolymers of polybutylene adipate succinate and azelaic acid.

[0046] For the resin composition in step (A), from an industrial availability point of view, polybutylene adipate succinate is preferred among the aforementioned PBSA-type resins. Furthermore, if the resin composition contains polybutylene adipate succinate, it can achieve a good balance of high biodegradability and drop strength.

[0047] In one embodiment of the present invention, without impairing the effects of the present invention, the PBSA-type resin may contain diols and dicarboxylic acids other than those described above. Examples of such diols include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanediol. Examples of such dicarboxylic acids include octanoic acid, sebacic acid, dodecanoic acid, succinic anhydride, and adipic anhydride.

[0048] In one embodiment of the invention, the content of PBSA-type resin in the resin composition is not particularly limited, but is based on the weight of the resin composition, for example, 49% by weight or less, preferably 45% by weight or less, and more preferably 40% by weight or less. The lower limit of the content of PBSA-type resin in the resin composition is not particularly limited and can be 0% by weight. When the content of PBSA-type resin in the resin composition is 50% by weight or less, moderate marine degradability can be maintained.

[0049] In one embodiment of the present invention, commercially available products such as BioPBS (registered trademark) FD92PM, FD92PB, FD72PM, FD72PB manufactured by PTTMCC Biochem Co., Ltd., Bionolle (registered trademark) manufactured by Showa Denko Co., Ltd., and SMB (a mixture of PHBH resins containing 50% by weight of PBSA) can be used.

[0050] In one embodiment of the present invention, the content of P3HB resin in the resin composition is not particularly limited, and is based on the weight of the resin composition, for example, 51% by weight or more, preferably 55% by weight or more, and more preferably 60% by weight or more. The upper limit of the content of P3HB resin in the resin composition is not particularly limited, and can be 100% by weight.

[0051] The shape of the resin in the resin composition in step (A) is not particularly limited; for example, it can be in powder, granule, fragment, or flake form. From the viewpoint of efficient manufacturing, the shape of the resin in the resin composition is preferably granular.

[0052] Furthermore, the resin composition in step (A) may contain other components besides those mentioned above. For example, organic or inorganic fillers may be included, provided that the effects of the present invention are not compromised. Examples of organic fillers, from the viewpoint of biodegradability and carbon neutrality of the resulting molded article, preferably include wood-based materials such as wood chips, wood flour, cellulose powder, nanocellulose, and sawdust, as well as naturally derived materials such as grains, rice flour, starch, corn starch, rice straw, wheat straw, and natural rubber. Examples of inorganic fillers include: talc, kaolin, calcium carbonate, bentonite, mica, sericite, glass powder, graphite, magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, zinc borate, hydrated calcium borate, alumina, magnesium oxide, wollastonite, calcium silicate, sepiolite, whiskers, glass fiber, glass powder, metal powder, beads, silica hollow spheres, Shirasu sand hollow spheres, and organic hollow spheres. The content of these organic or inorganic fillers can be appropriately set and is not particularly limited. Organic or inorganic fillers can be used alone or in combination of two or more.

[0053] In addition to the organic or inorganic fillers mentioned above, without impairing the effects of the present invention, the material may also include one or more of the following: pigments, dyes, and other colorants commonly used as additives; odor absorbers such as activated carbon and zeolite; fragrances such as vanillin and dextrin; antioxidants; weather resistance modifiers; ultraviolet absorbers; water repellents; antibacterial agents; slip modifiers; and other minor additives. The content of these additives can also be appropriately set.

[0054] <Plasticizer>

[0055] There are no particular limitations on the methods of plasticizing; for example, it can be done using an electric injection molding machine, a hydraulic injection molding machine, etc.

[0056] The heating temperature during plasticizing is not particularly limited, as long as it is sufficient to completely melt the resin composition without thermal decomposition. For example, it is 120–180°C, preferably 130–175°C, and more preferably 140–170°C. The heating time is also not particularly limited, for example, from 10 seconds to 5 minutes. In one embodiment of the invention, plasticizing can be performed using the method described in the examples below.

[0057] (Process (B))

[0058] In step (B) of this manufacturing method, the plasticized resin composition obtained in step (A) is injection molded to obtain a preform. Specifically, the resin composition plasticized in step (A) can be filled into a barrel, melted and mixed by a roller, and then injected from a nozzle into a mold for the preform, where it is cooled to produce a preform.

[0059] In this specification, "preform" refers to an object of any shape obtained by injection molding of resin that has been plasticized by heating. In other words, a preform can also be referred to as an intermediate obtained during the manufacturing process of this manufacturing method.

[0060] In step (B), it is preferable not to allow the preform to cool and solidify to the interior. That is, the preform is preferably supplied to step (C) for blow molding in a state where it has not cooled and solidified to the interior. By using a preform in a state where the surface of the preform is solidified but the interior is not solidified for blow molding in step (C), a molded body with excellent appearance can be obtained. There is no particular limitation on the method for confirming that the interior has not cooled and solidified. For example, it can be determined by cutting the removed preform and observing the cross-section, or by rapidly cooling the removed preform to below the glass transition temperature to crystallize and freeze it, and then measuring the crystallinity of the surface and interior of the preform.

[0061] In another embodiment of the present invention, step (B) can also be described as a step of injection molding the plasticized resin composition obtained by step (A) to obtain a preform with a surface that is cured but an interior that is not.

[0062] In step (B), there is no particular limitation on the method of injection molding, and examples include using an injection molding machine. Examples of injection molding machines include electric injection molding machines and hydraulic injection molding machines. From the viewpoint of excellent injection accuracy and obtaining a molded body with a good appearance, it is preferable to use an electric injection molding machine with injection blow molding function.

[0063] The conditions for injection molding are not particularly limited as long as the desired preform can be obtained. For example, when using an electric injection molding machine, the barrel temperature can be, for example, 140-180°C at the nozzle, 130-170°C at the front, 120-160°C at the middle, and 110-150°C at the rear.

[0064] In the case of manufacturing multiple preforms in a single injection molding process, a hot runner system is typically used to improve production efficiency. The hot runner is located within a hot runner assembly that forms part of the mold for the preform. The hot runner temperature can be set, for example, to 140–180°C.

[0065] The velocity at which the above-mentioned resin composition is injected from the nozzle into the mold can be, for example, 5-60% or 5-50 mm / sec. In addition, the holding pressure in the mold can be, for example, 5-150 MPa, and the holding pressure time can be, for example, 0-30 seconds.

[0066] In one embodiment of the invention, the conditions for injection molding can be those described in the embodiments described later.

[0067] The shape of the preform can be determined by the mold used during injection molding. From the viewpoint of facilitating blow molding as described later, the shape of the preform is preferably hollow, and more preferably a hollow cylindrical shape.

[0068] The thickness of the preform is 2.5 mm or more, preferably 3 mm or more, more preferably 3.5 mm or more, and even more preferably 4 mm or more. When the thickness of the preform is 2.5 mm or more, the internal temperature of the preform is less likely to drop, and it is easier to cool and solidify to the interior. Alternatively, the thickness of the preform is, for example, 10 mm or less, preferably 8 mm or less, and even more preferably 6 mm or less. When the thickness of the preform is 10 mm or less, it is easier to process during blow molding. In one embodiment of the present invention, the thickness of the preform is 2.5 mm or more and 10 mm or less, preferably 3 mm or more and 8 mm or less, more preferably 3.5 mm or more and 6 mm or less, and even more preferably 4 mm or more and 6 mm or less.

[0069] The mold temperature for the preform can be any temperature at which the resin composition does not fully cure; there are no particular limitations. For example, the mold temperature for the preform can be 50–100°C. Alternatively, setting it to 35–60°C improves productivity and sometimes makes it easier to obtain molded parts with fewer burrs.

[0070] The resin composition ejected from the nozzle is cooled within the mold of the preform. Cooling is performed within a range where the preform is not fully cured to the interior, but only the surface is cured. Specifically, the surface temperature of the preform is 110°C or higher, preferably 115°C or higher, and more preferably 120°C or higher. Furthermore, the upper limit of the surface temperature of the preform is 165°C or lower, preferably 160°C or lower, and more preferably 155°C or lower. When the temperature is within the above range, the molded part is less likely to break during blow molding in step (C). In one embodiment of the invention, the surface temperature of the preform is 110°C or higher and 165°C or lower, preferably 115°C or higher and 160°C or lower, and more preferably 120°C or higher and 155°C or lower. The surface temperature of the preform can be measured, for example, using a laser. The surface temperature of the preform is preferably maintained within the above range until the start of step (C) described later. The cooling time is not particularly limited as long as the surface temperature of the preform is within the above range; for example, it can be 5 to 30 seconds.

[0071] (Process (C))

[0072] In step (C) of this manufacturing method, the preform obtained in step (B) is blow-molded to obtain a molded body. Specifically, the preform obtained in step (B) can be transferred to a blow molding mold having a desired shape, the preform is expanded using compressed air to seal it within the mold, and then cooled to obtain the molded body.

[0073] In this specification, "molded body" refers to an object of any shape obtained by blow molding the above-described preform. In other words, the molded body can also be referred to as a finished product obtained by this manufacturing method.

[0074] In step (C), the surface temperature of the preform supplied for blow molding is 110°C or higher, preferably 115°C or higher, and more preferably 120°C or higher. Furthermore, the upper limit of the surface temperature of the preform is 165°C or lower, preferably 160°C or lower, more preferably 155°C or lower, further preferably 150°C or lower, and particularly preferably 140°C or lower. When the surface temperature of the preform is within the above range, the molded body is less likely to break during blow molding in step (C). In one embodiment of the present invention, the surface temperature of the preform is 110°C or higher and 165°C or lower, preferably 115°C or higher and 160°C or lower, and more preferably 120°C or higher and 155°C or lower. It should be noted that the "surface temperature of the preform supplied for blow molding" in step (C) can also be referred to as the "surface temperature of the preform before (just before) blow molding."

[0075] In process (C), there is no particular limitation on the method of blow molding, and examples include, for instance, using an injection blow molding machine.

[0076] The conditions for blow molding are not particularly limited as long as the desired molded part can be obtained. For example, when using an injection blow molding machine, the mold temperature for blow molding can be 20–80°C, and the compressed air pressure can be 0.3–10 MPa. In one embodiment of the present invention, the conditions for blow molding can be those described in the embodiments described later.

[0077] (Process (B'))

[0078] In one embodiment of the invention, the manufacturing method may further include a step of heating the preform (hereinafter referred to as "step (B')") between step (B) and step (C). Step (B') may also be referred to as a reheating step of the preform.

[0079] Step (B') is performed, for example, when the surface temperature of the preform obtained by step (B) is below 110°C. That is, in this manufacturing method, step (B') is applied so that the surface temperature of the preform supplied for blow molding in step (C) reaches 110°C or higher.

[0080] By including process (B'), even when the surface temperature of the preform obtained by process (B) is low (e.g., below 110°C), it is possible to obtain a molded body with excellent appearance.

[0081] In step (B'), the method of reheating is not particularly limited. Any method such as a heater, infrared radiation, or ultrasound can be used for reheating. From a simplicity point of view, a heating vessel equipped with a heater is preferred. Reheating can be performed indirectly using the heater or directly by bringing the part into contact with the heater. Preferably, the preform obtained in step (B) is removed from the injection molding machine and reheated indirectly using a heating vessel equipped with a heater.

[0082] The conditions for reheating are simply that the surface temperature of the preform supplied for blow molding in step (C) is 110°C or higher, and there are no particular limitations. For example, when heating is performed in a heating vessel, the surface temperature of the non-contact heating core can be 150–300°C, the surface temperature of the heating vessel can be 150–300°C, and the reheating time can be 0–40 seconds. In one embodiment of the invention, the conditions for reheating can be those described in the embodiments described later.

[0083] [3. Molded body]

[0084] This molded body can be manufactured using this manufacturing method. In one embodiment of the present invention, the molded body is marine degradable and is manufactured by a manufacturing method comprising the following steps (A) to (C): (A) a step of plasticizing a resin composition containing a P3HB type resin; (B) a step of injection molding the plasticized resin composition obtained in step (A) to obtain a preform; and (C) a step of blow molding the preform obtained in step (B) to obtain a molded body, wherein the thickness of the preform is 2.5 mm or more and 10 mm or less, and the surface temperature of the preform supplied for blow molding in step (C) is 110°C or more and 165°C or less.

[0085] As described above, this manufacturing method includes a step (step (C)) of blow molding a preform. Therefore, in one embodiment of the invention, the molded body is preferably hollow inside.

[0086] This molded body is not particularly limited as long as it is manufactured by this manufacturing method. Examples include: tubes, containers (e.g., bottle containers), bags, parts, conduits, cans, musical instruments, tool shells, etc.

[0087] The shape of this molded body is not particularly limited, and examples include: wide-mouthed, flat, round, complex shapes, etc.

[0088] The diameter, length, and capacity of this molded body are not particularly limited and can be appropriately set according to the usage method, etc.

[0089] In this manufacturing method, as described above, a resin composition comprising a P3HB-type resin having biodegradable / marine-degradable properties is used. Therefore, in one embodiment of the invention, the molded article is preferably marine-degradable.

[0090] This invention is not limited to the above-described embodiments. Various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this invention.

[0091] That is, one embodiment of the present invention is shown below.

[0092] <1> A method for manufacturing a molded article comprising P3HB type resin, the method comprising the following steps (A) to (C):

[0093] (A) The process of plasticizing a resin composition containing P3HB resin.

[0094] (B) The process of injection molding the plasticized resin composition obtained through step (A) to obtain a preform, and

[0095] (C) The process of blow molding the preform obtained through the above process (B) to obtain the molded body.

[0096] The thickness of the aforementioned preform is 2.5 mm or more and 10 mm or less.

[0097] In the above process (C), the surface temperature of the preform supplied for blow molding is above 110°C and below 165°C.

[0098] <2> According to the manufacturing method described in <1>, the preform is supplied to the blow molding process (C) in a state where it has not been cooled and solidified to the interior.

[0099] <3> The manufacturing method according to <1> or <2> further includes a step of heating the preform between the above-mentioned step (B) and the above-mentioned step (C).

[0100] <4> The manufacturing method according to any one of <1> to <3>, wherein the above-mentioned P3HB type resin is selected from poly-3-hydroxybutyrate, poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate), poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-4-hydroxybutyrate), and combinations thereof.

[0101] <5> The manufacturing method according to any one of <1> to <4>, wherein the above-mentioned P3HB resin is poly(3-hydroxybutyrate-copolymer-3-hydroxyhexanoate).

[0102] <6> The manufacturing method according to any one of <1> to <5>, wherein the resin composition further comprises polybutylene adipate.

[0103] <7> A molded body manufactured by any one of the manufacturing methods described in <1> to <6>.

[0104] <8> The molded body described in <7> is a marine-degradable molded body.

[0105] <9> A marine-degradable molded body, manufactured by the following method,

[0106] The manufacturing method includes the following steps (A) to (C):

[0107] (A) The process of plasticizing a resin composition containing P3HB resin.

[0108] (B) The process of injection molding the plasticized resin composition obtained through step (A) to obtain a preform, and

[0109] (C) The process of blow molding the preform obtained through the above process (B) to obtain the molded body.

[0110] The thickness of the aforementioned preform is 2.5 mm or more and 10 mm or less.

[0111] In the above process (C), the surface temperature of the preform supplied for blow molding is above 110°C and below 165°C.

[0112] Example

[0113] The following description is based on specific embodiments, but the present invention is not limited to these embodiments.

[0114] [Measurement and Evaluation Methods]

[0115] The measurements and evaluations in the examples and comparative examples were performed using the following methods.

[0116] (Injection blow molding)

[0117] The shape (appearance) of the molded body when a preform is blow-molded into a container shape using an injection blow molding machine ASB12N / 10T (manufactured by Nissei ASB Machinery Co., Ltd.) was evaluated. In the evaluation, containers with good appearance were rated as "○", containers with holes in the blow molding process were rated as "×B", containers that could not be transferred to the blow molding process due to sagging were rated as "×C", and containers that were torn or had poor thickness uniformity were rated as "×D".

[0118] (Drop test)

[0119] The containers manufactured in the examples and comparative examples were dropped from a height of 1.7m. In the evaluation, cases that broke were rated as "×", and cases that did not break were rated as "○".

[0120] [Example 1]

[0121] Particles of Kaneka's biodegradable polymer PHBH (registered trademark) X131N (manufactured by Kaneka Corporation) were fed into an injection blow molding machine ASB12N / 10T (manufactured by Nissei ASB Machinery Co., Ltd.) to plasticize the resin.

[0122] Next, the obtained plasticized resin was injection molded to obtain a preform. For the barrel temperature during injection molding, the nozzle was 165°C, the front section 155°C, the middle section 145°C, and the rear section 135°C. The injection speed was 40%, and a pressure of 4 MPa was maintained for 13 seconds. Furthermore, the hot runner temperature was 165°C for the components, spool, and nozzle. For the mold of the preform, mold A was used, with a core-side temperature and cavity-side temperature of 90°C and a cooling time of 10 seconds. The preform thickness was 4.5 mm, and the volume of the blow-molded part was 320 mL.

[0123] Then, the obtained preform was reheated. The surface temperature of the non-contact heating core was set to 275°C and the surface temperature of the heating vessel was set to 180°C for 25 seconds. It should be noted that the surface temperature of the preform before reheating was 109°C.

[0124] Next, the preform, with a reheated surface temperature of 124°C, was blow-molded to obtain the container (molded body). The mold temperature during blow molding was 35°C, and the air pressure was 0.4 MPa.

[0125] [Example 2]

[0126] As the resin, a mixture of X131N and SMB (a PHBH resin mixture containing 50 wt% PBSA and 50 wt% X131N) was used. X131N particles and SMB particles were packed into a bag at a weight ratio of X131N:SMB = 4:6, crushed by hand, and stirred until homogeneous to obtain the above mixture. The resulting resin mixture was then subjected to resin plasticization under the same conditions as in Example 1.

[0127] Next, the core-side temperature and cavity-side temperature of the mold were set to 60°C. Otherwise, injection molding was performed using the same method as in Example 1 to obtain a preform. The thickness of the preform was 4.5 mm, and the volume of the blow-molded part was 320 mL.

[0128] Then, the obtained preform was reheated under the same conditions as in Example 1. It should be noted that the surface temperature of the preform before reheating was 90°C.

[0129] Next, the preform, with a reheated surface temperature of 119°C, was blow-molded to obtain the container. The mold temperature during blow molding was 30°C, and the air pressure was 0.4 MPa.

[0130] [Example 3]

[0131] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0132] Next, mold C was used as the mold for the preform, and injection molding was performed using the same method as in Example 1 to obtain the preform. The thickness of the preform was 6.5 mm, and the volume of the blow-molded part was 320 mL.

[0133] Then, the obtained preform was reheated under the same conditions as in Example 1. It should be noted that the surface temperature of the preform before reheating was 126°C.

[0134] Next, using the preform with a reheated surface temperature of 136°C, a blow molding process was performed under the same conditions as in Example 1 to obtain the container.

[0135] [Example 4]

[0136] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0137] Next, mold C was used as the mold for the preform, and injection molding was performed using the same method as in Example 1 to obtain the preform. The thickness of the preform was 6.5 mm, and the volume of the blow-molded part was 320 mL.

[0138] Without reheating the preform, the container was obtained by blow molding using a preform with a surface temperature of 126°C under the same conditions as in Example 1.

[0139] [Comparative Example 1]

[0140] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0141] Next, mold B was used as the mold for the preform, and injection molding was performed using the same method as in Example 1 to obtain the preform. The thickness of the preform was 2 mm, and the volume of the blow-molded body was 200 mL.

[0142] Then, without reheating, the container was obtained by blow molding using a preform with a surface temperature of 98°C under the same conditions as in Example 1.

[0143] [Comparative Example 2]

[0144] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0145] Next, mold B was used as the mold for the preform, and injection molding was performed using the same method as in Example 1 to obtain the preform. The thickness of the preform was 2 mm, and the volume of the blow-molded body was 200 mL.

[0146] Then, the obtained preform was reheated under the same conditions as in Example 1. It should be noted that the surface temperature of the preform before reheating was 98°C.

[0147] Next, using the preform with a reheated surface temperature of 108°C, a blow molding process was performed under the same conditions as in Example 1 to obtain the container.

[0148] [Comparative Example 3]

[0149] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0150] Next, mold B was used as the mold for the preform, and injection molding was performed using the same method as in Example 1 to obtain the preform. The thickness of the preform was 2 mm, and the volume of the blow-molded body was 200 mL.

[0151] Then, the surface temperature of the non-contact heating core was set to 295°C and the surface temperature of the heating vessel was set to 200°C. Otherwise, the obtained preform was reheated under the same conditions as in Example 1. It should be noted that the surface temperature of the preform before reheating was 98°C.

[0152] Next, using the preform with a reheated surface temperature of 123°C, a blow molding process was performed under the same conditions as in Example 1 to obtain the container.

[0153] [Comparative Example 4]

[0154] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0155] Next, injection molding was performed using the same method as in Example 1 to obtain a preform. The preform had a thickness of 4.5 mm, and the volume of the blow-molded part was 320 mL.

[0156] Then, without reheating, the preform with a surface temperature of 109°C was blow-molded under the same conditions as in Example 1 to obtain the container.

[0157] [Comparative Example 5]

[0158] Plasticization of the resin was performed using the same resin as in Example 1, under the same conditions as in Example 1.

[0159] Next, mold A was used as the mold for the preform, and the preform was obtained by injection molding using the same method as in Example 1. The thickness of the preform was 4.5 mm, and the volume of the blow-molded part was 320 mL.

[0160] Then, the surface temperature of the non-contact heating core was set to 400°C, and the surface temperature of the heating vessel was set to 400°C. Otherwise, the obtained preform was reheated under the same conditions as in Example 1. It should be noted that the surface temperature of the preform before reheating was 109°C.

[0161] Next, using a preform with a reheated surface temperature of 167°C, we attempted to blow mold it under the same conditions as in Example 1, but drawdown occurred, and we were unable to obtain a container (molded body).

[0162] [result]

[0163] Table 1 shows the results of evaluating the injection blow molding properties of Examples 1-4 and Comparative Examples 1-5, as well as the results of drop tests conducted on Examples 1-4. In the table, "PF" refers to "preform". Furthermore, PF temperature refers to the surface temperature of the preform supplied to each process (in other words, the surface temperature of the preform before each process). It should be noted that for Comparative Examples 1-5, drop tests were not conducted because containers with excellent appearance were not obtained.

[0164]

[0165] According to Table 1, Examples 1-4 exhibited good injection blow molding properties. Furthermore, Example 2, which used a specific resin mixture, showed good impact resistance in addition to good injection blow molding properties. In Example 4, where no reheating was performed, injection blow molding properties were also good. On the other hand, Comparative Examples 1-2, where the preform thickness was 2 mm and the surface temperature of the preform before blow molding was below 110°C, resulted in openings in the container during blow molding. Additionally, even when the temperature of the preform before blow molding was above 110°C, the container thickness was uneven when the preform thickness was 2 mm. Moreover, even when the preform thickness was 4.5 mm, openings occurred in the container when the temperature of the preform before blow molding was below 110°C. Furthermore, when the surface temperature of the preform exceeded 165°C, the container failed to form due to resin sagging.

[0166] Therefore, it can be seen that if the thickness of the preform exceeds 2 mm and the surface temperature of the preform before blow molding is above 110°C and below 165°C, a container with a good appearance can be manufactured. Furthermore, it can be seen that by using specific resin mixtures, containers that not only have a good appearance but also excellent impact resistance can be manufactured.

[0167] Industrial applicability

[0168] This manufacturing method can produce biodegradable molded bodies with excellent appearance and can be suitable for the manufacture of various molded bodies (especially containers).

Claims

1. A method for manufacturing a molded article comprising a poly-3-hydroxybutyrate resin, the method comprising the following steps (A) to (C): (A) A process for plasticizing a resin composition containing poly-3-hydroxybutyrate resin. (B) The process of injection molding the plasticized resin composition obtained through step (A) to obtain a preform, and (C) The process of blow molding the preform obtained through process (B) to obtain the molded body. The thickness of the preform is 2.5 mm or more and 10 mm or less. In step (C), the surface temperature of the preform supplied for blow molding is above 110°C and below 165°C. The content of poly-3-hydroxybutyrate resin in the resin composition is 51% by weight or more. The mold temperature of the preform is 35-100℃.

2. The manufacturing method according to claim 1, wherein, The preform is supplied to the blow molding process (C) in a state where it has not been cooled and solidified to the interior.

3. The manufacturing method according to claim 1 or 2, further comprising: The process of heating the preform between process (B) and process (C).

4. The manufacturing method according to claim 1 or 2, wherein, The poly-3-hydroxybutyrate resins are selected from poly-3-hydroxybutyrate, poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate), poly(3-hydroxybutyrate-copoly-3-hydroxyvalerate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate), poly(3-hydroxybutyrate-copoly-4-hydroxybutyrate), and combinations thereof.

5. The manufacturing method according to claim 1 or 2, wherein, The poly-3-hydroxybutyrate resin is poly(3-hydroxybutyrate-copoly-3-hydroxyhexanoate).

6. The manufacturing method according to claim 1 or 2, wherein, The resin composition further comprises polybutylene adipate.

7. A molded body manufactured by the manufacturing method according to any one of claims 1 to 6.

8. The molded article according to claim 7, wherein it is a marine degradable molded article.

9. A marine-degradable molded body, manufactured by the following method, The manufacturing method includes the following steps (A) to (C): (A) A process for plasticizing a resin composition containing poly-3-hydroxybutyrate resin. (B) The process of injection molding the plasticized resin composition obtained through step (A) to obtain a preform, and (C) The process of blow molding the preform obtained through process (B) to obtain the molded body. The thickness of the preform is 2.5 mm or more and 10 mm or less. In step (C), the surface temperature of the preform supplied for blow molding is above 110°C and below 165°C. The content of poly-3-hydroxybutyrate resin in the resin composition is 51% by weight or more. The mold temperature of the preform is 35-100℃.

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