Method for producing molded articles containing poly-3-hydroxybutyrate resin and its use

Abstract

The objective of the present invention is to provide a novel production method allowing a molded body containing a P3HB-based resin to be obtained using an injection blow molding method, and a technique for using the same. The above problem is solved by providing a method for producing a molded body containing a P3HB-based resin, the method comprising the steps (A) to (C): (A) the step of plasticizing a resin composition containing a P3HB-based resin; (B) the step of injection molding the plasticized resin composition obtained in the previous step (A), to obtain a preform; and (C) the step of blow-forming the preform obtained in the previous step (B), to obtain a molded body.

Description

Technical Field

[0001] The present invention relates to a method for producing a molded article containing a poly-3-hydroxybutyrate resin and its utilization.

Background Art

[0002] Currently, there is a demand for solving the problem of plastic waste and reducing dependence on fossil fuels, and biodegradable resins and bio-based resins have attracted attention as raw materials for containers and bottles. Among them, poly-3-hydroxybutyrate resins (hereinafter sometimes referred to as "P3HB-based resins"; that is, in this specification, "poly-3-hydroxybutyrate resins" and "P3HB-based resins" are treated as synonyms), particularly poly-3-hydroxybutyrate, can be produced from bio-based raw materials by microbial culture and exhibits excellent biodegradability in soil and sea. Therefore, it is expected as a key material for solving the above problems. However, P3HB-based resins have a slow crystallization rate and are difficult to remelt once crystallized. In addition, due to their high melting point, there is a problem that it is difficult to manufacture containers and bottles by injection blow molding.

[0003] In order to solve the above problems, a method for producing a P3HB-based resin by injection molding (Patent Document 1), a method for producing a biodegradable container by an injection blow molding method (Patent Document 2), a method for producing a hollow molded article by injection blow molding using a polyester resin composed of polyethylene terephthalate and polyethylene naphthalate as a molding material (Patent Document 3), etc. have been reported.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0005] However, the aforementioned patent documents do not describe a specific method for injection blow molding using P3HB resin. In other words, none of the aforementioned patent documents describe the production of molded articles containing P3HB resin by injection blow molding.

[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a novel manufacturing method and utilization technology that can obtain a molded article containing a P3HB resin (in particular, a molded article containing a P3HB resin with excellent appearance) using an injection blow molding method. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have discovered a novel finding that, in injection blow molding, it is possible to produce molded articles containing P3HB resin with excellent appearance by adjusting the thickness of the preform obtained by injection molding, the surface temperature of the preform before blow molding, etc., and have completed the present invention.

[0008] Accordingly, one aspect of the present invention is a method for producing a molded article containing a P3HB resin (hereinafter referred to as "the present manufacturing method"), comprising the following steps (A) to (C): (A) a step of plasticizing a resin composition containing a P3HB 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 subjected to blow molding in step (C) is 110°C or more and 165°C or less.

[0009] Another aspect of the present invention is a molded article manufactured by the following manufacturing method, comprising the steps (A) to (C): (A) a step of plasticizing a resin composition containing a P3HB 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 subjected to blow molding in step (C) is 110°C or more and 165°C or less, and the molded article is marine biodegradable (hereinafter referred to as "the molded article"). [Effects of the Invention]

[0010] According to one aspect of the present invention, a novel manufacturing method using injection blow molding can be used to obtain a molded article containing a P3HB resin with excellent appearance. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B". Furthermore, all references cited in this specification are incorporated herein by reference.

[0012] [1. Outline of the present invention] Polyethylene terephthalate and polypropylene, which are typical resins used in containers and bottles, can be blow-molded around or below their melting point. On the other hand, P3HB resins have poor elasticity below their melting point and become low viscosity above their melting point, making blow molding difficult. This property differs significantly from that of general polyester resins such as polyethylene terephthalate described in Patent Document 3 mentioned above, and this property has made molding P3HB resins technically difficult.

[0013] To solve these problems, the inventors diligently investigated a method for manufacturing molded articles containing P3HB resin using injection blow molding. The inventors found that by taking advantage of the slow crystallization of P3HB resin, a molded article containing P3HB resin can be manufactured by removing the preform from the injection mold when its surface is solidified but its interior is still hot and not yet solidified, and then blow molding it at a temperature lower than the melting point of the P3HB resin. Furthermore, the inventors found that the above state of the preform (i.e., the surface is solidified but the interior is not) is controlled by the thickness of the preform obtained by injection molding, the surface temperature of the preform before blow molding, etc. In addition, the inventors found that if the surface temperature of the preform before blow molding has not reached a certain temperature, a molded article containing P3HB resin can be manufactured by reheating the preform.

[0014] Conventional technologies focused primarily on the composition of the raw resin and the conditions of injection blow molding when molding P3HB resins. In contrast, the inventors focused on the properties of P3HB resins and succeeded in manufacturing molded articles containing P3HB resins by utilizing these properties. This type of innovative technology is unprecedented and remarkable.

[0015] Therefore, according to the present invention, P3HB resins, which have a high melting point and are relatively difficult to process, can be easily processed. The configuration of this manufacturing method will be described in detail below.

[0016] [2. Method for manufacturing molded articles containing P3HB resin] This manufacturing method includes the following steps (A) to (C) as essential steps. • Process (A): Process for plasticizing a resin composition containing P3HB resin. • Step (B): A step in which the plasticizer resin composition obtained in step (A) is injection molded to obtain a preform. • Step (C): A step of blow molding the preform obtained in step (B) to obtain a molded body.

[0017] (Process (A)) In Process (A) of this manufacturing method, a resin composition containing a P3HB-based resin (hereinafter, may be simply referred to as "resin composition") is plasticized. Process (A) can also be paraphrased as a process of melting the resin composition containing the P3HB-based resin. By Process (A), since the resin composition can be made into a liquid state, a preform having a desired shape can be obtained in Process (B).

[0018] <P3HB-based resin> In this specification, "P3HB-based resin" is an aliphatic polyester resin that can be produced from microorganisms and has 3-hydroxybutyrate as a repeating unit.

[0019] In one embodiment of the present invention, the P3HB-based resin may be poly(3-hydroxybutyrate) having only 3-hydroxybutyrate as a repeating unit, or may be a copolymer of 3-hydroxybutyrate and another hydroxyalkanoate.

[0020] In one embodiment of the present invention, the P3HB-based resin may be a mixture of a homopolymer and one or more copolymers, or may be a mixture of two or more copolymers. The form of copolymerization is not particularly limited and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc.

[0021] In one embodiment of the present invention, examples of the P3HB-based resin include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), and the like. Among them, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are industrially easy to produce.

[0022] In one embodiment of the present invention, the P3HB-based resin can be selected from the group consisting of poly-3-hydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and combinations thereof.

[0023] Further, by changing the composition ratio of the repeating units, the melting point and crystallinity can be changed, and as a result, physical properties such as Young's modulus and heat resistance can be changed, and it is possible to impart physical properties between polypropylene and polyethylene. From the viewpoint that it is industrially easy to produce and is a physically useful resin as described above, P3HB3HH, which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred. In particular, among P3HB-based resins having the property of being easily thermally decomposed under heating at 180°C or higher, P3HB3HH is also preferred from the viewpoint that it can lower the melting point and enable molding processing at low temperatures.

[0024] P3HB resins can be produced, for example, by microorganisms. The microorganisms that produce P3HB resins are not particularly limited as long as they have the ability to produce P3HB resins. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925, and other examples include natural microorganisms such as Cupriavidus necator (formerly classified as Alcaligenes eutrophus, Ralstonia eutropha), and Alcaligenes latus. It is known that P3HB accumulates within the cells of these microorganisms.

[0025] Furthermore, known microorganisms that produce copolymers of hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with respect to P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T.Fukui, Y.Doi, J.Bateriol., 179, p4821-4830 (1997)), into which genes for the P3HA synthase group have been introduced, are more preferred in order to increase the productivity of P3HB3HH. Microbial cells that have been cultured under appropriate conditions to accumulate P3HB3HH within the cell are used. In addition to the above, genetically modified microorganisms into which various P3HB resin synthesis-related genes can be introduced to suit the P3HB resin to be produced, or the culture conditions, including the type of substrate, can be optimized.

[0026] Furthermore, P3HB3HH can also be produced by methods described, for example, in International Publication No. 2010 / 013483. Examples of commercially available P3HB3HH include Kaneka Corporation's "Kaneka Biodegradable Polymer PHBH®" (e.g., X131N used in the examples).

[0027] In one embodiment of the present invention, the composition ratio of the repeating units of P3HB3HH is preferably such that the ratio of 3-hydroxybutyrate units to 3-hydroxyhexanoate units is 80 / 20 to 99 / 1 (mol / mol), and more preferably 75 / 15 to 97 / 3 (mol / mol), from the viewpoint of balancing flexibility and strength. 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, moldability is improved.

[0028] 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. If the weight-average molecular weight is 150,000 or more, sufficient mechanical properties can be obtained, and if it is 800,000 or less, a sufficient crystallization rate can be obtained, and good moldability can be achieved. The weight-average molecular weight of the P3HB resin can be determined by gel permeation chromatography (GPC) (Shoda Denko's "Shodex GPC-101") using polystyrene gel (Shoda Denko's "Shodex K-804") as the column and chloroform as the mobile phase, and is expressed as the molecular weight in terms of polystyrene.

[0029] <Resin composition> The resin composition in step (A) may contain only a P3HB resin, or it may contain other resins in addition to the P3HB resin. While not particularly limited, such other resins are preferably biodegradable aliphatic polyester resins other than the P3HB resin. Examples include polybutylene succinate (PBS) resins, polycaprolactone (PCL) resins, and polyhydroxyalkanoate resins (excluding the P3HB resin). Examples of the polybutylene succinate (PBS) resin include polybutylene succinate (PBS) and polybutylene succinate adipate (PBSA). Polyhydroxyalkanoate resins other than the P3HB resin refer to polyhydroxyalkanoate resins that do not contain 3-hydroxybutyrate as a monomer component, and examples include polyglycolic acid, polylactic acid, and poly-4-hydroxybutyrate resins. The poly-4-hydroxybutyrate resin may be poly(4-hydroxybutyrate) in which only 4-hydroxybutyrate is repeated as the unit, or it may be a copolymer of 4-hydroxybutyrate and other hydroxyalkanoates. Among these, PBSA resins are preferred from the viewpoint of balancing drop strength, moldability, and biodegradability.

[0030] PBSA-based resins are aliphatic polyester polymers having 1,4-butanediol, succinic acid, and adipic acid as structural units. In one embodiment of the present invention, the PBSA-based resin may have any diol, dicarboxylic acid, or hydroxyalkanoate other than 1,4-butanediol, succinic acid, and adipic acid as structural units, as long as biodegradability is not impaired. Examples include polybutylene succinate adipate, a copolymer of polybutylene succinate adipate and lactic acid, a copolymer of polybutylene succinate adipate and terephthalic acid, a copolymer of polybutylene succinate adipate and malic acid, a copolymer of polybutylene succinate adipate and sebacic acid, and a copolymer of polybutylene succinate adipate and azelaic acid.

[0031] The resin composition in step (A) is preferably polybutylene succinate adipate from among the PBSA-based resins mentioned above, from the viewpoint of industrial availability. In addition, if the resin composition contains polybutylene succinate adipate, it is possible to achieve a good balance between high biodegradability and drop strength.

[0032] In one embodiment of the present invention, the PBSA-based resin may contain diols other than those mentioned above, dicarboxylic acids other than those mentioned above, to the extent that the effects of the present invention are not impaired. 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-cyclohexanedimethanol. Examples of such dicarboxylic acids include superiric acid, sebacic acid, dodecanoic acid, succinic anhydride, and adipic anhydride.

[0033] In one embodiment of the present invention, the content of PBSA-based resin in the resin composition is not particularly limited, but is, for example, 49% by weight or less, preferably 45% by weight or less, and more preferably 40% by weight or less, based on the weight of the resin composition. The lower limit of the content of PBSA-based resin in the resin composition is not particularly limited and may be 0% by weight. If the content of PBSA-based resin in the resin composition is 50% by weight or less, a moderate level of biodegradability is maintained.

[0034] In one embodiment of the present invention, the PBSA-based resin may be a commercially available product, for example, BioPBS® FD92PM, FD92PB, FD72PM, FD72PB manufactured by PTT MCC Biochem, Bionore® manufactured by Showa Denko, SMB (a PHBH resin mixture containing 50% by weight of PBSA), etc.

[0035] In one embodiment of the present invention, the content of P3HB resin in the resin composition is not particularly limited, but is, for example, 51% by weight or more, preferably 55% by weight or more, and more preferably 60% by weight or more, based on the weight of the resin composition. The upper limit of the content of P3HB resin in the resin composition is not particularly limited and may be 100% by weight.

[0036] The shape of the resin in the resin composition in step (A) is not particularly limited and may be, for example, powder, pellet, fragment, or flake. From the viewpoint of efficient manufacturing, the shape of the resin in the resin composition is preferably pelletized.

[0037] Furthermore, the resin composition in step (A) may contain other components not mentioned above. For example, it may contain organic or inorganic fillers, etc., to the extent that they do not impede the effects of the present invention. Examples of organic fillers include, from the viewpoint of the biodegradability and carbon neutrality of the resulting molded article, wood-based materials such as wood chips, wood flour, cellulose powder, nanocellulose, and sawdust, and naturally derived materials such as rice husks, 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 flakes, graphite, magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, zinc borate, hydrated calcium borate, alumina, magnesia, wollastonite, xonotlite, sepiolite, whiskers, glass fibers, glass flakes, metal powders, beads, silica balloons, shirasu balloons, organic balloons, etc. The content of the organic or inorganic filler can be set as appropriate and is not particularly limited. The organic or inorganic filler can be used alone or in combination of two or more types.

[0038] In addition to the organic or inorganic fillers described above, the present invention may also contain one or more of the following additives, to the extent that they do not impair the effects of the present invention: colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, antioxidants, weather-resistant modifiers, UV absorbers, water-repellent agents, antibacterial agents, sliding modifiers, and other secondary additives. The content of these additives can also be set as appropriate.

[0039] <Plasticization> The method of plasticization is not particularly limited, but it can be carried out by, for example, an electric injection molding machine, a hydraulic injection molding machine, etc.

[0040] The heating temperature during plasticization is not particularly limited as long as it can completely melt the resin composition without causing thermal decomposition, but is, for example, 120 to 180°C, preferably 130 to 175°C, and more preferably 140 to 170°C. The heating time is also not particularly limited, but is, for example, 10 seconds to 5 minutes. In one embodiment of the present invention, plasticization may be carried out by the method described in the examples below.

[0041] (Process (B)) In step (B) of this manufacturing method, a preform is obtained by injection molding the plasticized resin composition obtained in step (A). Specifically, the resin composition plasticized in step (A) is filled into a barrel, melted and mixed in a cylinder, then injected from a nozzle into a preform mold, and cooled to produce the preform.

[0042] In this specification, "preform" means an object of any shape obtained by injection molding a resin that has been plasticized by heating. In other words, a preform can also be said to be an intermediate obtained during the manufacturing process of this manufacturing method.

[0043] In step (B), it is preferable not to allow the preform to cool and solidify completely inside. That is, it is preferable that the preform be subjected to blow molding in step (C) while it is not cooled and solidified completely inside. By performing blow molding in step (C) using a preform whose surface is solidified but whose interior is not, a molded body with excellent appearance can be obtained. There are no particular limitations on how to confirm that the preform is not cooled and solidified completely inside, but 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 its glass transition temperature to freeze the crystallization and measuring the degree of crystallinity of the preform surface and interior.

[0044] Furthermore, in one embodiment of the present invention, step (B) can also be rephrased as a step of injection molding the plasticizer resin composition obtained in step (A) to obtain a preform in which the surface is solidified but the interior is not solidified.

[0045] In process (B), the method of injection molding is not particularly limited, but 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 obtaining a molded product with excellent injection accuracy and good appearance, it is preferable to use an electric injection molding machine equipped with an injection blow molding function.

[0046] The conditions for performing 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 temperatures may be, for example, 140-180°C at the nozzle, 130-170°C at the front, 120-160°C in the middle, and 110-150°C at the rear.

[0047] When manufacturing multiple preforms in a single injection molding cycle, a hot runner system is typically employed to improve production efficiency. The hot runner is located within a hot runner block, which forms part of the mold for the preform. The hot runner temperature can be set, for example, to 140-180°C.

[0048] The injection speed of the above resin composition from the nozzle into the mold may be, for example, 5-60% or 5-50 mm / sec. The holding pressure in the mold may be, for example, 5-150 MPa, and the holding time may be, for example, 0-30 seconds.

[0049] In one embodiment of the present invention, the conditions for performing injection molding may be those described in the examples below.

[0050] The shape of the preform described above can be determined by the mold used when performing injection molding. From the viewpoint of facilitating blow molding as described later, the shape of the preform is preferably hollow, and more preferably hollow cylindrical.

[0051] 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. If the thickness of the preform is 2.5 mm or more, the temperature inside the preform does not drop easily, and it does not cool and solidify easily to the inside. Also, the thickness of the preform is, for example, 10 mm or less, preferably 8 mm or less, and more preferably 6 mm or less. If 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.

[0052] The mold temperature for the preform is not particularly limited as long as it is a temperature at which the resin composition does not completely solidify. The mold temperature for the preform may be, for example, 50 to 100°C. In addition, setting the temperature to 35 to 60°C may improve productivity and make it easier to obtain molded products with fewer burrs.

[0053] The resin composition injected from the nozzle is cooled within the mold of the preform. At this time, the cooling is carried out within a range in which only the surface hardens, and the preform does not completely solidify inside. 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. If the temperature is within the above range, the molded body will be less likely to break during blow molding in process (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. The surface temperature of the preform can be measured, for example, by a laser. It is preferable that the surface temperature of the preform be maintained within the above range until process (C) described later is started. The cooling time is not particularly limited as long as the surface temperature of the preform is within the above range, but it could be, for example, 5 to 30 seconds.

[0054] (Process (C)) In step (C) of this manufacturing method, a molded body is obtained by blow molding the preform obtained in step (B). Specifically, the preform obtained in step (B) is transferred to a blow molding die having the desired shape, the preform is inflated using compressed air and made to adhere tightly to the inside of the die, and then cooled to obtain a molded body.

[0055] In this specification, "molded article" means an object of any shape obtained by blow molding the above-mentioned preform. In other words, a molded article can also be said to be a finished product obtained by this manufacturing method.

[0056] The surface temperature of the preform subjected to blow molding in step (C) 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, even more preferably 150°C or lower, and particularly preferably 140°C or lower. If the surface temperature of the preform is within the above range, the molded body will be less likely to be damaged 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. Note that "surface temperature of the preform subjected to blow molding" in step (C) can also be rephrased as "surface temperature of the preform before (immediately before) blow molding".

[0057] In process (C), the method of blow molding is not particularly limited, but examples include using an injection blow molding machine.

[0058] The conditions for performing blow molding are not particularly limited as long as the desired molded product can be obtained. For example, when using an injection blow molding machine, the mold temperature for blow molding may be 20 to 80°C, and the compressed air pressure may be 0.3 to 10 MPa. In one embodiment of the present invention, the conditions for performing blow molding may be those described in the examples described later.

[0059] (Process (B')) In one embodiment of the present invention, the manufacturing method may further include a step of heating the preform between step (B) and step (C) (hereinafter referred to as "step (B')"). Step (B') can also be referred to as a preform reheating step.

[0060] Step (B') is performed, for example, when the surface temperature of the preform obtained in step (B) is below 110°C. In other words, in this manufacturing method, step (B') is applied so that the surface temperature of the preform subjected to blow molding in step (C) is 110°C or higher.

[0061] By including step (B'), it becomes possible to obtain a molded product with excellent appearance even when the surface temperature of the preform obtained in step (B) is low (for example, below 110°C).

[0062] The method of reheating in step (B') is not particularly limited. Any method can be applied for reheating, such as a heater, infrared radiation, or ultrasound. From the viewpoint of simplicity, it is preferable to use a heating pot equipped with a heater. Reheating can be performed indirectly using a heater, or directly by bringing the material into contact with a heater. Preferably, the preform obtained in step (B) is removed from the injection molding machine and reheated indirectly using a heating pot equipped with a heater.

[0063] The conditions for reheating are not particularly limited, as long as the surface temperature of the preform subjected to blow molding in step (C) reaches 110°C or higher. For example, when heating is performed in a heating pot, the surface temperature of the non-contact heating core may be 150 to 300°C, the surface temperature of the heating pot may be 150 to 300°C, and the reheating time may be 0 to 40 seconds. In one embodiment of the present invention, the conditions for reheating may be those described in the examples described later.

[0064] [3. Molded body] The molded article is manufactured by the present manufacturing method. In one embodiment of the present invention, the molded article is manufactured by the following manufacturing method, which includes the steps (A) to (C): (A) a step of plasticizing a resin composition containing a P3HB 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 subjected to blow molding in step (C) is 110°C or more and 165°C or less, and is marine biodegradable.

[0065] As described above, this manufacturing method includes a step of blow molding a preform (step (C)). Therefore, in one embodiment of the present invention, it is preferable that the molded article is hollow inside.

[0066] The molded product is not particularly limited as long as it is manufactured by this manufacturing method, but examples include tubes, containers (e.g., bottles), bags, parts, pipes, tanks, musical instruments, tool cases, etc.

[0067] The shape of the molded body is not particularly limited, but examples include wide-mouthed, flat, round, and complex shapes.

[0068] The diameter, length, and capacity of this molded body are not particularly limited and can be set as appropriate depending on the intended use.

[0069] As described above, this manufacturing method uses a resin composition containing a P3HB resin that has biodegradable and marine biodegradable properties. Therefore, in one embodiment of the present invention, it is preferable that the molded article is marine biodegradable.

[0070] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0071] In other words, one embodiment of the present invention is as follows: <1> The following steps (A) to (C): (A) A process of plasticizing a resin composition containing P3HB resin, (B) A step of injection molding the plasticizer resin composition obtained in step (A) to obtain a preform, and (C) A step of blow molding the preform obtained in step (B) above to obtain a molded body, Includes, The thickness of the aforementioned preform is 2.5 mm or more and 10 mm or less. A method for producing a molded article containing a P3HB resin, wherein the surface temperature of the preform subjected to blow molding in step (C) is 110°C or higher and 165°C or lower. <2> The preform is subjected to blow molding in step (C) while it has not cooled and solidified completely inside. <1> The manufacturing method described above. <3> Furthermore, the process includes a step of heating the preform between step (B) and step (C), <1> or <2> The manufacturing method described above. <4> The P3HB resin is selected from the group consisting of poly-3-hydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and combinations thereof. <1> ~ <3> A manufacturing method described in any of the following. <5> The P3HB resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). <1> ~ <4> A manufacturing method described in any of the following. <6> The resin composition further comprises polybutylene succinate adipate. <1> ~ <5> A manufacturing method described in any of the following. <7> <1> ~ <6> A molded article manufactured by any of the manufacturing methods described in one of the following. <8> It is marine biodegradable. <7> The molded body described above. <9> The following steps (A) to (C): (A) A process of plasticizing a resin composition containing P3HB resin, (B) A step of injection molding the plasticizer resin composition obtained in step (A) to obtain a preform, and (C) A step of blow molding the preform obtained in step (B) above to obtain a molded body, Includes, The thickness of the aforementioned preform is 2.5 mm or more and 10 mm or less. A molded article manufactured by a manufacturing method in which the surface temperature of the preform subjected to blow molding in the above step (C) is 110°C or higher and 165°C or lower, and which is marine biodegradable. [Examples]

[0072] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0073] [Measurement and evaluation methods] Measurements and evaluations in the examples and comparative examples were performed using the following methods.

[0074] (Injection blow type) The shape (appearance) of molded products was evaluated when preforms were blow-molded into container shapes using an injection blow molding machine ASB12N / 10T (manufactured by Nissei ASB Machinery Co., Ltd.). The evaluation criteria were as follows: a container with a good appearance was marked "○", a container with a hole during blow molding was marked "×B", a container that could not proceed to the blow molding process due to drawdown was marked "×C", and a container that tore or had poor thickness uniformity was marked "×D".

[0075] (Drop test) The containers manufactured in the examples and comparative examples were dropped from a height of 1.7m. The evaluation was as follows: "×" indicated that the container broke, and "〇" indicated that it did not break.

[0076] [Example 1] Pellets of Kaneka Biodegradable Polymer PHBH (registered trademark) X131N (manufactured by Kaneka Corporation) were placed in an injection blow molding machine ASB12N / 10T (manufactured by Nissei ASB Machinery Co., Ltd.) and the resin was plasticized.

[0077] Next, the obtained plasticizer resin was injection molded to obtain a preform. The barrel temperatures during injection molding were 165°C at the nozzle, 155°C at the front, 145°C in the middle, and 135°C at the rear. The injection speed was 40%, and the holding pressure was 4 MPa for 13 seconds. Furthermore, the hot runner temperature was 165°C for the block, spool, and nozzle. Mold A was used for the preform, with core and cavity temperatures of 90°C, and a cooling time of 10 seconds. The preform thickness was 4.5 mm, and the volume of the molded body after blow molding was 320 mL.

[0078] Subsequently, the obtained preform was reheated. During reheating, the surface temperature of the non-contact heating core was set to 275°C and the surface temperature of the heating pot to 180°C, and heating was performed for 25 seconds. The surface temperature of the preform before reheating was 109°C.

[0079] Next, a container (molded body) was obtained by blow molding using the preform with a surface temperature of 124°C after reheating. The mold temperature during blow molding was 35°C and the air pressure was 0.4 MPa.

[0080] [Example 2] As the resin, a mixture of X131N and SMB (a PHBH resin mixture containing 50% by weight of PBSA and 50% by weight of X131N) was used. The above mixture was obtained by placing X131N pellets and SMB pellets in a bag in a weight ratio of X131N:SMB=4:6, crushing them by hand, and stirring until homogenized. The obtained resin mixture was plasticized under the same conditions as in Example 1.

[0081] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that the core and cavity temperatures of the mold were set to 60°C. The thickness of the preform was 4.5 mm, and the volume of the molded body after blow molding was 320 mL.

[0082] Subsequently, the obtained preform was reheated under the same conditions as in Example 1. The surface temperature of the preform before reheating was 90°C.

[0083] Next, a container was obtained by blow molding using the preform with a surface temperature of 119°C after reheating. The mold temperature during blow molding was 30°C and the air pressure was 0.4 MPa.

[0084] [Example 3] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0085] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that mold C was used as the mold for the preform. The thickness of the preform was 6.5 mm, and the volume of the molded body after blow molding was 320 mL.

[0086] Subsequently, the obtained preform was reheated under the same conditions as in Example 1. The surface temperature of the preform before reheating was 126°C.

[0087] Next, a container was obtained by blow molding using a preform with a surface temperature of 136°C after reheating, under the same conditions as in Example 1.

[0088] [Example 4] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0089] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that mold C was used as the mold for the preform. The thickness of the preform was 6.5 mm, and the volume of the molded body after blow molding was 320 mL.

[0090] Without reheating the preform, a container was obtained by blow molding using a preform with a surface temperature of 126°C under the same conditions as in Example 1.

[0091] [Comparative Example 1] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0092] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that mold B was used as the mold for the preform. The thickness of the preform was 2 mm, and the volume of the molded body after blow molding was 200 mL.

[0093] Subsequently, without reheating, a container was obtained by blow molding using a preform with a surface temperature of 98°C under the same conditions as in Example 1.

[0094] [Comparative Example 2] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0095] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that mold B was used as the mold for the preform. The thickness of the preform was 2 mm, and the volume of the molded body after blow molding was 200 mL.

[0096] Subsequently, the obtained preform was reheated under the same conditions as in Example 1. The surface temperature of the preform before reheating was 98°C.

[0097] Next, using the preform with a surface temperature of 108°C after reheating, a container was obtained by blow molding under the same conditions as in Example 1.

[0098] [Comparative Example 3] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0099] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that mold B was used as the mold for the preform. The thickness of the preform was 2 mm, and the volume of the molded body after blow molding was 200 mL.

[0100] Subsequently, the obtained preform was reheated under the same conditions as in Example 1, except that the surface temperature of the non-contact heating core was set to 295°C and the surface temperature of the heating pot to 200°C. The surface temperature of the preform before reheating was 98°C.

[0101] Next, using the preform with a surface temperature of 123°C after reheating, a container was obtained by blow molding under the same conditions as in Example 1.

[0102] [Comparative Example 4] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0103] Next, a preform was obtained by injection molding in the same manner as in Example 1. The thickness of the preform was 4.5 mm, and the volume of the molded body after blow molding was 320 mL.

[0104] Subsequently, without reheating, a container was obtained by blow molding using a preform with a surface temperature of 109°C under the same conditions as in Example 1.

[0105] [Comparative Example 5] The same resin as in Example 1 was used, and the resin was plasticized under the same conditions as in Example 1.

[0106] Next, a preform was obtained by injection molding in the same manner as in Example 1, except that mold A was used as the mold for the preform. The thickness of the preform was 4.5 mm, and the volume of the molded body after blow molding was 320 mL.

[0107] Subsequently, the obtained preform was reheated under the same conditions as in Example 1, except that the surface temperature of the non-contact heating core and the surface temperature of the heating pot were set to 400°C. The surface temperature of the preform before reheating was 109°C.

[0108] Next, we attempted to perform blow molding using a preform with a surface temperature of 167°C after reheating, under the same conditions as in Example 1. However, drawdown occurred, and we were unable to obtain a container (molded body).

[0109] [result] Table 1 shows the results of the injection blow performance evaluation for Examples 1-4 and Comparative Examples 1-5, as well as the results of the drop test for Examples 1-4. In the table, "PF" means "preform." The PF temperature refers to the surface temperature of the preform used in each process (in other words, the surface temperature of the preform before each process). Note that for Comparative Examples 1-5, a drop test was not performed because a container with a good appearance could not be obtained.

[0110] [Table 1] Table 1 shows that Examples 1-4 exhibited good injection blow properties. Example 2, which used a specific resin mixture, also showed good impact resistance in addition to good injection blow properties. Example 4, which did not undergo reheating, also exhibited good injection blow properties. On the other hand, Comparative Examples 1-2, where the preform thickness was 2 mm and the preform surface temperature before blow molding was less than 110°C, resulted in holes in the containers during blow molding. Furthermore, even when the preform temperature before blow molding was 110°C or higher, a preform thickness of 2 mm resulted in uneven container thickness. Additionally, even with a preform thickness of 4.5 mm, a preform temperature below 110°C before blow molding resulted in holes in the containers. Moreover, when the preform surface temperature exceeded 165°C, the containers could not be molded due to resin drawdown.

[0111] Therefore, it was found that if the preform thickness exceeds 2 mm and the surface temperature of the preform before blow molding is between 110°C and 165°C, a container with a good appearance can be manufactured. Furthermore, it was found that by using a specific resin mixture, a container with excellent impact resistance in addition to a good appearance can be manufactured. [Industrial applicability]

[0112] This manufacturing method can produce biodegradable molded articles with excellent appearance, and therefore can be suitably used in the manufacture of various molded articles (especially containers).

Claims

1. The following steps (A) to (C): (A) A step of plasticizing a resin composition containing a poly-3-hydroxybutyrate resin, (B) A step of injection molding the plasticizer resin composition obtained in step (A) to obtain a preform, and (C) A step of blow molding the preform obtained in step (B) above to obtain a molded body, Includes, The thickness of the aforementioned preform is 2.5 mm or more and 10 mm or less. In step (C) above, the surface temperature of the preform subjected to blow molding is 110°C or higher and 165°C or lower. A method for producing a molded article containing a poly-3-hydroxybutyrate resin, wherein the mold temperature of the preform is 35 to 100°C.

2. The manufacturing method according to claim 1, wherein the preform is subjected to blow molding in step (C) while it has not been cooled and solidified to the interior.

3. Furthermore, the manufacturing method according to claim 1 or 2, further comprising a step of heating the preform between step (B) and step (C).

4. The manufacturing method according to any one of claims 1 to 3, wherein the poly-3-hydroxybutyrate resin is selected from the group consisting of poly-3-hydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and combinations thereof.

5. The manufacturing method according to any one of claims 1 to 4, wherein the poly-3-hydroxybutyrate resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

6. The manufacturing method according to any one of claims 1 to 5, wherein the resin composition further comprises polybutylene succinate adipate.

7. A molded article manufactured by the manufacturing method described in any one of claims 1 to 6.

8. The molded article according to claim 7, which is marine biodegradable.

9. The following steps (A) to (C): (A) A step of plasticizing a resin composition containing a poly-3-hydroxybutyrate resin, (B) A step of injection molding the plasticizer resin composition obtained in step (A) to obtain a preform, and (C) A step of blow molding the preform obtained in step (B) above to obtain a molded body, Includes, The thickness of the aforementioned preform is 2.5 mm or more and 10 mm or less. In step (C) above, the surface temperature of the preform subjected to blow molding is 110°C or higher and 165°C or lower. A molded article manufactured by a manufacturing method in which the mold temperature of the preform is 35 to 100°C, and which is biodegradable in marine environments.

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