Method and apparatus for manufacturing a press-molded body

Abstract

To suppress generation of bubbles in a press-molded body of P3HA-based resin.SOLUTION: A press molded body manufacturing method of the present invention includes: a heating step of heating a resin composition containing P3HA-based resin to form a molten resin composition; a resin supply step of supplying the molten resin composition between a pair of molds by discharging it from a discharge part; and a molding step of closing the pair of molds, press-molding the flowable molten resin composition, and cooling it. Molding surfaces of the pair of molds are surface-treated with a fluororesin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for producing a press-molded article of a poly(3-hydroxyalkanoate) resin (hereinafter, sometimes referred to as a "P3HA resin"). [Background technology]

[0002] In recent years, there has been growing interest in the use of biodegradable plastics to combat marine pollution caused by plastics. However, a report compiled by the United Nations Environment Programme in 2015 pointed out that compostable plastics such as polylactic acid cannot be expected to decompose in a short period of time in the cold ocean, and therefore cannot be used to combat marine pollution.

[0003] In this context, P3HA-based resins are attracting attention as a material that can solve the above problems because they are biodegradable even in seawater.

[0004] On the other hand, a technique is known in which a thermoplastic biodegradable resin is heated to form a molten resin, the molten resin is fed into a mold, the mold is closed to perform press molding, and then cooled to obtain a molded product. For example, Patent Document 1 discloses a technique for forming a biodegradable resin plate by preforming an amorphous biodegradable resin plate and compression molding the obtained biodegradable resin plate at a temperature above the glass transition temperature and below the melting point. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-181782 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a P3HA-based resin is used as the biodegradable resin and press molding is carried out as in the technique described in Patent Document 1, it has been found that the following problems arise.

[0007] That is, when press molding is performed using a metal or metal alloy mold, it has been found that the aesthetics of the resulting press-molded body can be an issue, particularly when bubbles are generated on the side surfaces of the resulting press-molded body, causing the body to become cloudy.

[0008] An object of one aspect of the present invention is to provide a method and apparatus for producing a press-molded body of a P3HA-based resin, which can suppress the generation of bubbles in the press-molded body. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, one embodiment of the present invention provides a method for producing a press-molded body, which comprises a heating step of heating a resin composition containing a poly(3-hydroxyalkanoate)-based resin to form a molten resin composition, a resin supply step of supplying the molten resin composition between a pair of molds by discharging it from a discharge portion, and a molding step of closing the pair of molds and press-molding and cooling the flowable molten resin composition, wherein the molding surfaces of the pair of molds are surface-treated with a fluorine-based resin.

[0010] In addition, in order to solve the above-mentioned problems, one embodiment of the present invention provides a press-molded body manufacturing apparatus that is equipped with a pair of molds into which a molten resin composition containing a poly(3-hydroxyalkanoate)-based resin is filled, and that includes a molten resin generation section that heats the poly(3-hydroxyalkanoate)-based resin composition to generate a molten resin composition, a supply section that has a discharge section that discharges the molten resin composition and supplies the molten resin composition between the pair of molds by the discharge section, and a molding section that closes the pair of molds to press-mold and cool the flowable molten resin composition, and that is configured such that the molding surfaces of the pair of molds are surface-treated with a fluorine-based resin. [Effects of the Invention]

[0011] According to one aspect of the present invention, it is possible to suppress the generation of bubbles in a press-molded body of a P3HA-based resin. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing a schematic configuration of a press-molded body manufacturing apparatus according to an embodiment of the present invention; [Figure 2] 1 is a diagram illustrating a schematic configuration of a molding unit of a manufacturing apparatus for a press-molded body according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0014] [Technical philosophy] When press-molding a P3HA-based resin as a biodegradable resin, the inventors adopted Method B, in which the molten resin obtained by heating the P3HA-based resin is press-molded while still in a molten state that allows it to flow within the mold, rather than Method A, in which a flat plate made of P3HA-based resin is press-molded using a mold.

[0015] While conducting research into the production of press-molded products using the above-mentioned method B, the present inventors discovered a new problem: when press-molding is performed using a metal or metal alloy die, the press-molded product becomes cloudy, mainly at its side surfaces. It was also discovered that this cloudiness is likely to occur particularly in the relatively thin-walled portions (thickness 0.2 mm to 0.3 mm) of the side surfaces of the press-molded product. Furthermore, it was discovered that the cloudy portions appear cloudy due to the accumulation of fine air bubbles.

[0016] However, this problem does not occur when a flat plate is heated to soften it and then press-molded (Method A above). Furthermore, when polyethylene resin, which is commonly used in press molding, is press-molded using a metal or metal alloy mold, the cloudiness described above does not occur. Therefore, it can be said that this problem is specific to press-molding a molten P3HA-based resin composition while it is in a flowable molten state within a mold.

[0017] Therefore, the present inventors conducted extensive research to solve the above-mentioned problems and discovered that the cloudiness caused by the fine bubbles described above can be prevented by treating the molding surface of a mold with a fluororesin.

[0018] A method for producing a press-molded body according to one embodiment of the present invention (hereinafter sometimes referred to as the present production method) was obtained based on the above findings, and comprises a heating step of heating a resin composition containing a poly(3-hydroxyalkanoate)-based resin to form a molten resin composition, a resin supply step of supplying the molten resin composition between a pair of molds by discharging it from a discharge portion, and a molding step of closing the pair of molds and press-molding the flowable molten resin composition and cooling it, wherein the molding surfaces of the pair of molds are surface-treated with a fluorine-based resin.

[0019] According to this manufacturing method, it is possible to suppress the generation of bubbles in a press-molded article of a P3HA-based resin, and therefore, according to one embodiment of the present invention, it is possible to obtain a press-molded article with excellent surface beauty.

[0020] Furthermore, this manufacturing method can reduce marine pollution caused by waste disposal, thereby contributing to the achievement of Sustainable Development Goals (SDGs) such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and sustainably use the oceans and marine resources for sustainable development." This manufacturing method is described in detail below.

[0021] [Method for manufacturing press-molded body] As described above, this manufacturing method includes the heating step, the resin supplying step, and the press-molding step, and produces a press-molded body of a P3HA-based resin through the heating step, the resin supplying step, and the press-molding step.

[0022] In the heating step, a resin composition containing a P3HA resin is heated to form a molten resin composition. Any conventionally known method can be used to heat the resin composition, as long as it can form a molten resin composition containing a P3HA resin. Preferably, the heating step includes a melt-kneading step of melt-kneading the resin composition containing a P3HA resin.

[0023] The mode of the melt-kneading step is not particularly limited as long as a melt-kneaded resin composition can be obtained. Specific examples of the melt-kneading step include the following (a1) and (a2): Methods include: (a1) A method in which a resin composition containing a P3HA-based resin is prepared by mixing or blending using a mixer or the like, and then the resin composition is supplied to a melt-kneading device and melt-kneaded; (a2) A method in which raw materials for a resin composition containing a P3HA-based resin are supplied to a melt-kneading device, and a resin composition is prepared (completed) in the melt-kneading device, and the resin composition is melt-kneaded.

[0024] In the method (a1), the order in which the raw materials for the resin composition containing the P3HA resin are mixed or blended (dry blended) is not particularly limited.In the method (a2), the order in which the raw materials for the resin composition containing the P3HA resin are supplied to the melt-kneading device is not particularly limited.

[0025] In the method (a1), the mixing device is not particularly limited, and examples thereof include a ribbon blender, a flash blender, a tumbler mixer, and a super mixer.

[0026] In the methods (a1) and (a2), the melt-kneading device is not particularly limited and examples thereof include an extruder, a kneader, a Banbury mixer, a roll, etc. From the viewpoint of excellent productivity and convenience, the melt-kneading device is preferably an extruder, and more preferably a twin-screw extruder.

[0027] In the melt-kneading step, the temperature at which the resin composition is melt-kneaded cannot be generally defined because it depends on the physical properties of P3HA (e.g., melting point, weight-average molecular weight) and the types of additives used. Regarding the temperature at which the resin composition is melt-kneaded, for example, the temperature of the melt-kneaded resin composition discharged from the discharge port (hereinafter sometimes referred to as the composition temperature) is preferably 140°C to 190°C, more preferably 150°C to 180°C, and even more preferably 160°C to 170°C. If the composition temperature is 150°C or lower, unmelted P3HA-based resin may be generated. On the other hand, if the composition temperature is 180°C or higher, the P3HA-based resin may be thermally decomposed.

[0028] In the resin supplying step, the molten resin composition is supplied between the pair of molds by being discharged from a discharge portion. Remains in a molten state The molten resin composition is discharged from the discharge portion into a pair of molds, thereby supplying the molten resin composition in a molten state between the pair of molds.

[0029] The method for supplying the molten resin composition between the molds is not particularly limited as long as the molten resin composition discharged from the discharge portion can be supplied between the pair of molds. From the viewpoint of reliably supplying the molten resin composition between the pair of molds, it is preferable to first discharge the molten resin composition from the discharge portion into the lower mold, supply a predetermined amount of the molten resin composition to the lower mold, and then place the upper mold on the lower mold, thereby supplying the molten resin composition between the pair of molds.

[0030] Furthermore, in the resin supplying step, the configuration of the discharge section is not particularly limited as long as it is capable of discharging the molten resin composition, and any conventionally known configuration can be used. From the viewpoint of improving the productivity of the press-molded body, it is preferable that the discharge section be configured to be able to quantitatively discharge the molten resin composition. Examples of such a discharge section configuration include a configuration equipped with a gear pump and a configuration equipped with an automatic opening and closing nozzle. Specific examples of the discharge section include a plunger-type discharger, a pre-plunger-type discharger, and a screw-type discharger.

[0031] In the press molding step, the pair of dies are closed, and the flowable molten resin composition is press-molded and cooled. In the resin supply step, the molten resin composition is supplied between the pair of dies in a molten state, so that the molten resin composition can flow in the space between the pair of dies even when the pair of dies are closed in the press molding step.

[0032] In the resin supplying step, the molten resin composition in a molten state is supplied between a pair of molds, and then in the press molding step, the pair of molds are subjected to heat pressing using a heat press molding machine. Then, the pair of molds after the heat pressing is cooled, thereby performing press molding. After press molding, the pair of molds are opened to obtain a press-molded product.

[0033] The heat press molding machine used in the resin supplying step is not particularly limited as long as it is configured to be able to heat press the pair of dies to which the molten resin composition has been supplied. Any conventionally known device can be used as the heat press molding machine.

[0034] In addition, in order to allow the molten resin composition supplied between the pair of dies to flow, the pair of dies are preferably preheated. The heating temperature of the pair of dies may be any temperature that can maintain the composition temperature of the molten resin composition, preferably within ±30°C of the composition temperature of the molten resin composition, and more preferably the same temperature as the composition temperature of the molten resin composition.

[0035] The pressure applied by the pair of dies in the heat press molding machine is not particularly limited, but is preferably 50 KN to 300 KN, and more preferably 100 KN to 200 KN. Setting the pressure within the above range has the advantage of making it easier to obtain a press-molded body with a uniform thickness.

[0036] The pressing time of the pair of dies in the heat press molding machine is not particularly limited, but is preferably 5 to 60 seconds, and more preferably 10 to 30 seconds. Setting the pressing time within the above range has the advantage of making it easier to obtain a press-molded product with a uniform thickness.

[0037] The method for cooling the pair of molds after the hot pressing is not particularly limited, and examples thereof include a method in which the pair of molds after the hot pressing is sandwiched between a pair of cooling plates and subjected to cold pressing.

[0038] In this method, the pressing pressure during cold pressing is not particularly limited, but is preferably 10 KN to 100 KN, and more preferably 30 KN to 50 KN. Setting the pressing pressure within the above numerical range has the advantage of producing a press-molded product with a uniform thickness.

[0039] The pressing time during cold pressing is not particularly limited, but is preferably 60 to 600 seconds, and more preferably 120 to 300 seconds. Setting the pressing time within the above range has the advantage that the P3HA resin is sufficiently solidified, making it easy to remove the press-molded body.

[0040] The temperature of the cooling plate used in the cooling press is not particularly limited, but is preferably 10° C. to 60° C., and more preferably 20° C. to 50° C. Setting the temperature of the cooling plate within the above range has the advantage that the P3HA resin is sufficiently solidified, making it easy to remove the press-molded body.

[0041] The present production method is characterized in that the molding surfaces of the molds are surface-treated with a fluororesin. As a result, the press-molded product produced by this production method does not exhibit the cloudiness caused by the fine bubbles. Here, the "molding surfaces" refer to the surfaces of the pair of molds that come into contact with the molten resin composition, and can also be referred to as the opposing surfaces of the pair of molds.

[0042] The molding surface is present on each of a pair of molds (upper and lower molds). The surface treatment with a fluororesin may be applied to the molding surface of at least one of the pair of molds, and preferably to both of the pair of molds.

[0043] Furthermore, the region of the molding surface to which the surface treatment is applied is not particularly limited, as long as it is a region of the molding surface corresponding to the location in the press-molded body where the clouding phenomenon may occur. For example, when the press-molded body has a concave shape with a recess or a cylindrical shape with a bottomless hole, the molding surface corresponding to the side wall of the press-molded body in a pair of dies is generally a surface that rises above the horizontal plane. In other words, in press molding, the side wall of the press-molded body is generally the portion that rises from the horizontal plane in the pressing direction. The clouding phenomenon occurs particularly in the thin-walled portion of the side wall of the press-molded body. Therefore, it is preferable that the region of the molding surface to which the surface treatment is applied includes at least the region corresponding to the thin-walled portion of the side wall of the press-molded body, and more preferably the entire molding surface.

[0044] Furthermore, the press-molded product suitable for this production method is not particularly limited, but is a molded product having a rising portion (for example, a side wall portion of the press-molded product) that rises in the pressing direction with a thickness of 0.1 mm to 0.4 mm, preferably 0.2 mm to 0.3 mm. By keeping the thickness of the rising portion within the above numerical range, the occurrence of cloudiness can be significantly suppressed.

[0045] The fluorine-based resin used in the surface treatment is not particularly limited, but examples thereof include perfluoroalkoxyalkane (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), and the like.

[0046] The surface treatment may be combined with a metal surface coating treatment. That is, the coating formed by the surface treatment may be a composite film of a metal coating and a fluororesin coating. The metal constituting the metal coating is not particularly limited, but examples thereof include nickel-based metals, chromium-based metals, iron-based metals, and alumina-based metals.

[0047] [Press-molded body manufacturing device] An apparatus for manufacturing a press-molded body according to one embodiment of the present invention (hereinafter sometimes referred to as the present manufacturing apparatus) is configured to realize the present manufacturing method. Fig. 1 is a diagram showing a schematic configuration of the present manufacturing apparatus. Fig. 2 is a diagram showing a schematic configuration of the molding section of the present manufacturing apparatus.

[0048] As shown in Fig. 1, a press-molded product manufacturing apparatus 10 according to one embodiment of the present invention includes a pair of dies into which a molten resin composition containing a P3HA resin is filled. Fig. 1 shows the lower die of the pair of dies. The manufacturing apparatus 10 includes a molten resin generation section 1 and a supply section 2.

[0049] The molten resin production section 1 heats the P3HA-based resin composition to produce a molten resin composition. The molten resin production section 1 is equipped with a raw material input section for inputting raw materials for the P3HA-based resin composition. The molten resin production section 1 is also equipped with a melt-kneading device that melts and kneads the raw materials input from the raw material input section. The molten resin production section 1 may also be equipped with a mixing device that mixes the raw materials, as necessary. Examples of the melt-kneading device and mixing device include the devices described above.

[0050] The supply section 2 has a discharge section 2a that discharges the molten resin composition produced in the molten resin production section 1. The discharge section 2a can have the same configuration as the discharge section described above. The supply section 2 supplies the molten resin composition between the pair of molds by the discharge section 2a. In the configuration shown in FIG. 1, the supply section 2 is configured to discharge the molten resin composition from the discharge section 2a to the lower mold. After a predetermined amount of molten resin composition is supplied to the lower mold, the upper mold is placed on the lower mold, and the molten resin composition is supplied between the pair of molds.

[0051] As shown in FIG. 2, the manufacturing apparatus 10 also includes a molding unit 30. The molding unit 30 closes a pair of molds 31 to press-mold and cool the flowable molten resin composition. The molding unit 30 includes a heat press molding machine that heat-presses the pair of molds 31, and a cooling device that cools the pair of molds 31 after the heat press is complete. Any device used in press molding can be used for the heat press machine and the cooling device. For example, the cooling device may include a pair of cooling plates that sandwich the pair of molds 31, and the cooling plates may be used to cold-press the pair of molds 31.

[0052] 2 is a mold for molding a press-molded body having a concave shape with a recess. The pair of molds 31 includes a lower mold 32 and an upper mold 33.

[0053] In the manufacturing apparatus 10, the molding surfaces of the pair of dies 31 are surface-treated with a fluororesin. As a result, the press-molded body manufactured by the manufacturing apparatus 10 does not suffer from the cloudiness caused by the fine bubbles described above.

[0054] Here, the molding surface can be said to be the surface that constitutes the molding space formed by the lower mold 32 and the upper mold 33. The surface treatment with a fluororesin may be applied to the molding surface of at least one of the lower mold 32 and the upper mold 33, and is preferably applied to both the lower mold 32 and the upper mold 33.

[0055] The molding surface of lower mold 32 has raised surfaces 32a and 32b, and the molding surface of upper mold 33 has raised surfaces 33a and 33b. Raised surfaces 32a and 33a and raised surfaces 32b and 33b are molding surfaces that respectively constitute the thin-walled portions of the press-molded body that rise in the pressing direction. On the molding surface of paired molds 31, the region to be subjected to the surface treatment is preferably a region that includes at least raised surfaces 33a and 33b and / or raised surfaces 33a and 33b, and more preferably the entire molding surface.

[0056] Furthermore, the thickness of the thin-walled portion of the raised portion of the press-molded body is determined by the distance between the raised surfaces 32a and 33a and the distance between the raised surfaces 32b and 33b in the pair of dies 31. The distance between these raised surfaces in the pair of dies 31 is determined so that the thickness of the raised portion of the press-molded body is 0.1 mm to 0.4 mm, preferably 0.2 mm to 0.3 mm.

[0057] (P3HA resin) The resin composition used in this production method contains a P3HA-based resin. In this specification, "P3HA-based resin" refers to a biodegradable aliphatic polyester (preferably, a polyester containing no aromatic ring). A P3HA-based resin contains 3-hydroxyalkanoic acid repeating units represented by the general formula: [-CHR-CH2-CO-O-] (wherein R is C n H 2n+1 and n is an integer of 1 or more and 15 or less.) as a repeating unit.

[0058] The P3HA resin contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin account for 94.5 to 98.5 mol %, preferably 95.0 to 98.5 mol %, more preferably 96.0 to 98.5 mol %, and even more preferably 96.5 to 98.0 mol %, of all repeating units (100 mol %).

[0059] When the composition ratio of 3HB repeating units is 94.5 mol% or more, the rigidity of the P3HA-based resin is improved, the crystallization rate is accelerated, flash is reduced, and productivity tends to be improved. On the other hand, when the composition ratio of 3HB repeating units is 98.5 mol% or less, the melting point is below the thermal decomposition temperature, enabling stable and continuous production. The monomer composition ratio of the P3HA-based resin can be measured by gas chromatography or the like (see, for example, WO 2014 / 020838).

[0060] More specifically, P3HA-based resins include copolymers of 3HB with other hydroxyalkanoates, such as poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate).

[0061] P3HA resins produced by microorganisms (microorganism-produced P3HA resins) are usually P3HA resins composed only of D-form (R-form) polyhydroxyalkanoic acid monomer units. Among microbially produced P3HA resins, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferred, with P3HB, P3HB3HH, P3HB3HV, and P3HB4HB being more preferred, due to ease of industrial production.

[0062] Microorganisms that produce microbially produced P3HA resins are not particularly limited as long as they are capable of producing P3HA resins. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925. Other examples include naturally occurring microorganisms such as Cupriavidus necator (formerly classified as Alcaligenes eutrophus and Ralstonia eutropha) and Alcaligenes latus. These microorganisms are known to accumulate P3HB within their cells.

[0063] Known bacteria that produce copolymers of hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, for P3HB3HH, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)), which has been introduced with genes encoding P3HA resin synthases, is preferred for increasing P3HB3HH productivity. These microorganisms are cultured under appropriate conditions to accumulate P3HB3HH within the cells. In addition to the above, genetically modified microorganisms into which various P3HA resin synthesis-related genes have been introduced may be used depending on the P3HA resin to be produced, and culture conditions, including the type of substrate, may be optimized.

[0064] The molecular weight of the P3HA resin is not particularly limited as long as it exhibits substantially sufficient physical properties for the intended application. The weight-average molecular weight of the P3HA resin is preferably in the range of 100,000 to 1,000,000, more preferably 150,000 to 700,000, even more preferably 200,000 to 500,000, and particularly preferably 250,000 to 450,000. A weight-average molecular weight of 100,000 or more ensures adequate mechanical strength. Furthermore, a molecular weight of 1,000,000 or less can suppress an increase in melt viscosity, resulting in excellent moldability.

[0065] The weight-average molecular weight can be measured using gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) with a polystyrene gel column (Shodex K-804 manufactured by Showa Denko K.K.) and chloroform as the mobile phase, and can be calculated as a polystyrene-equivalent molecular weight. A calibration curve is prepared using polystyrenes with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. A column suitable for measuring the molecular weight can be used for the GPC.

[0066] The resin composition used in this production method may contain a second P3HA resin in addition to the P3HA resin. The second P3HA resin contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the poly(3-hydroxyalkanoate) resin preferably contains 65.0 to 90.0 moles of 3HB units, more preferably 68.0 to 88.0 moles, and even more preferably 70.0 to 85.0 moles. When the resin composition further contains the second P3HA resin, the toughness of the molded article is excellent.

[0067] The second P3HA-based resin is not particularly limited as long as it is different from the P3HA-based resin. Examples of the second P3HA-based resin include the resins exemplified above as the P3HA-based resin.

[0068] The content of the second P3HA resin is not particularly limited, but is preferably 50 parts by weight or less, more preferably 45 parts by weight or less, and even more preferably 40 parts by weight or less, relative to 100 parts by weight of the total P3HA resin. The lower limit of the content of the second P3HA resin is not particularly limited, and may be 0 parts by weight. The P3HA resins described above can be used as the second P3HA resin. In this specification, "total P3HA resins" refers to all P3HA resins contained in the resin composition produced by this production method.

[0069] The resin composition may contain other resins besides the P3HA resin, provided that the effects of the present invention are not impaired. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate. The other resins may be contained alone or in combination.

[0070] The content of the other resin is not particularly limited, but is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and even more preferably 30 parts by weight or less, relative to 100 parts by weight of the total P3HA resin. The lower limit of the content of the other resin is not particularly limited, and may be 0 part by weight.

[0071] The resin composition does not necessarily contain an inorganic filler, but preferably further contains an inorganic filler, which has the effect of improving the strength of the press-molded body.

[0072] The inorganic filler is not particularly limited, but examples thereof include talc, diatomaceous earth, white clay, clay, calcium carbonate, manganese carbonate, magnesium carbonate, barium sulfate, mica, silica, alumina, zircon, iron oxide, zinc oxide, titanium oxide, silicon nitride, boron nitride, aluminum nitride, silicon carbide, graphite, carbon black, ferrite, graphite, quartz, glass fiber, glass particles, etc. These may be used alone or in combination of two or more.

[0073] The content of the inorganic filler is, for example, 0 to 60 parts by weight, preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight, and particularly preferably 15 to 35 parts by weight, relative to 100 parts by weight of the total P3HA resin. When the content of the inorganic filler is within the above range, sufficient strength of the press-molded body can be ensured.

[0074] When an inorganic filler is contained in the resin composition, a press-molded article produced by a manufacturing method other than the manufacturing method according to the present embodiment is likely to have a cloudy side surface, which may cause problems with the appearance. However, according to the manufacturing method according to the present embodiment, a press-molded article with a good appearance can be obtained.

[0075] The resin composition may also contain additives that can be used with the P3HA resin, provided that the effects of the present invention are not impaired. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding properties improvers. Only one type of additive may be contained, or two or more types may be contained. The content of these additives can be appropriately determined by those skilled in the art depending on the intended use.

[0076] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0077] That is, one embodiment of the present invention is as follows. <1> a heating step of heating a resin composition containing a poly(3-hydroxyalkanoate)-based resin to form a molten resin composition; a resin supplying step of supplying the molten resin composition between a pair of molds by discharging it from a discharge portion; a molding step of closing the pair of molds to press-molde and cool the flowable molten resin composition, The method for producing a press-molded body, wherein the molding surfaces of the pair of molds are surface-treated with a fluorine-based resin. <2> The press-molded body has a thickness of 0.1 mm to 0.4 mm at the rising portion rising in the pressing direction. <1> A method for producing the press-molded body according to claim 1. <3> The poly(3-hydroxyalkanoate) is one or more selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). <1> or <2> A method for producing the press-molded body according to claim 1. <4> An apparatus for producing a press-molded product, comprising a pair of molds into which a molten resin composition containing a poly(3-hydroxyalkanoate)-based resin is filled, a molten resin producing section for heating a poly(3-hydroxyalkanoate)-based resin composition to produce a molten resin composition; a supply section having a discharge section that discharges the molten resin composition and supplies the molten resin composition between the pair of molds by the discharge section; a molding section that closes the pair of molds to press-molde and cool the flowable molten resin composition, The press-molded body manufacturing apparatus has the molding surfaces of the pair of molds treated with a fluororesin. [Example]

[0078] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0079] Example 1 Using a tabletop plunger-type melt extrusion machine (manufactured by Nakatsuji Mold Industry Co., Ltd.), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (sometimes referred to as PHBH) (weight-average molecular weight Mw 400,000, 3HH ratio 6 mol%) was heated to 165°C to form a molten resin. The molten PHBH resin was then extruded into a lower mold preheated to 165°C, thereby supplying the molten PHBH resin to the lower mold. The lower mold to which the molten PHBH resin had been supplied was then closed with an upper mold also heated to 165°C, thereby supplying the molten resin between the pair of molds. The pair of molds to which the molten PHBH resin had been supplied were subjected to heat pressing using a heat press molding machine (manufactured by Mikado Technos Co., Ltd., VS38-2525) at a pressure of 125 KN and a press time of 20 seconds. Immediately after the hot pressing, the pair of molds was sandwiched between upper and lower cooling plates cooled to 25°C, and press molding was performed by applying a pressure of 30 KN and a pressing time of 300 seconds. After press molding, the molds were opened and the pressed compact was removed.

[0080] The pair of dies 31 shown in Fig. 2 was used. Here, the upper and lower dies were made of aluminum alloy (A7075) as the die material. The molding surfaces of both the upper and lower dies were surface-treated with fluorine-based resin (PTFE).

[0081] Example 2 Press molding was carried out in the same manner as in Example 1, except that the temperature of the pair of dies was heated to 150°C.

[0082] (Comparative Example 1) Press molding was performed in the same manner as in Example 1, except that a pair of dies made of aluminum alloy (A7075), both of which had not been surface-treated with fluororesin (PTFE) on their molding surfaces, were used.

[0083] (Comparative Example 2) All examples are based on the use of a pair of molds made of aluminum alloy (A7075), both of which had no fluororesin (PTFE) surface treatment applied to the molding surfaces of the upper and lower molds, and which were heated to a temperature of 150°C. 1 Press molding was carried out in the same manner as above.

[0084] (Reference example 1) Press molding was carried out in the same manner as in Example 1, except that low-density polyethylene (Mirason, manufactured by Mitsui-Dow Polychemicals Co., Ltd.) was used as the molding resin instead of PHBH.

[0085] (Reference example 2) Press molding was performed in the same manner as in Example 1, except that instead of PHBH, low-density polyethylene (Mirason, manufactured by Mitsui Dow Polychemicals Co., Ltd.) was used as the molding resin, the temperature of the molten resin was set to 200°C, and the temperature of the pair of molds was heated to 200°C.

[0086] (Evaluation method) The press-molded articles of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Examples 1 and 2 were visually inspected for the presence or absence of bubbles in the thin-walled portions of the side walls, and were evaluated as follows. 〇: No bubbles, ×: Bubbles are present.

[0087] The evaluation results are shown in Table 1.

[0088] [Table 1]

[0089] As is clear from the results shown in Table 1, in Comparative Examples 1 and 2, in which PHBH was press-molded using an aluminum alloy die without surface treatment, bubbles were generated in the thin-walled portions of the side walls of the press-molded body, and the obtained molded body had poor appearance.

[0090] On the other hand, in Reference Examples 1 and 2, in which low-density polyethylene was used as the molding resin, no bubbles were generated in the thin-walled portions of the side walls of the press-molded body, even when a mold made of aluminum alloy was used.

[0091] This suggests that the problem of bubbles forming in the thin-walled portions of the side walls that occurred in the press-molded bodies of Comparative Examples 1 and 2 is a problem specific to the use of PHBH as the molding resin.

[0092] Compared to Comparative Examples 1 and 2, in Examples 1 and 2, which used a mold whose molding surface was surface-treated with a fluorine-based resin (PTFE), no bubbles were observed in the thin-walled parts of the side walls, and press-molded bodies with good appearance were obtained. [Industrial Applicability]

[0093] The present invention can be suitably used in the field of producing press-molded articles using P3HA-based resins, as well as in other fields. [Explanation of symbols]

[0094] 1. Molten resin generating section 2 Supply section 2a Discharge part 30 Molding section 31 Pair of molds 32 Lower mold 33 Upper mold 10 Manufacturing equipment (press molding manufacturing equipment)

Claims

1. a heating step of heating a resin composition containing a poly(3-hydroxyalkanoate)-based resin to form a molten resin composition; a resin supplying step of supplying the molten resin composition between a pair of molds by discharging it from a discharge portion; a molding step of closing the pair of molds to press-molde and cool the flowable molten resin composition, the molding surfaces of the pair of molds are surface-treated with a fluorine-based resin, The press-molded body has a thickness of 0.1 mm to 0.4 mm at a rising portion rising in the pressing direction.

2. The poly(3-hydroxyalkanoate) is one or more selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). The method for producing a press-molded body according to claim 1, wherein the poly(3-hydroxyalkanoate) is one or more selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxydecanoate).

3. An apparatus for producing a press-molded product, the apparatus comprising a pair of molds into which a molten resin composition containing a poly(3-hydroxyalkanoate)-based resin is filled, a molten resin producing section for heating a poly(3-hydroxyalkanoate)-based resin composition to produce a molten resin composition; a supply section having a discharge section that discharges the molten resin composition and supplies the molten resin composition between the pair of molds by the discharge section; a molding section that closes the pair of molds to press-molde and cool the flowable molten resin composition, the molding surfaces of the pair of molds are surface-treated with a fluorine-based resin, The press-molded body manufacturing apparatus has a rising portion of the press-molded body that rises in the pressing direction having a thickness of 0.1 mm to 0.4 mm.

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