Resin supply device, press molding device, resin supply method, and method for manufacturing press-molded products

Abstract

This enables quantitative transfer of the molten resin composition even when the intermittent transfer time is prolonged. [Solution] The resin supply device (10) is provided in the molding apparatus and includes a raw material supply unit (6) that supplies the resin composition to the extruder (1), a transfer unit (2) that intermittently transfers the molten resin composition (11) from the extruder (1) to the discharge unit (3), a pressure measuring unit (7) that measures the pressure between the extruder (1) and the transfer unit (2), and a control unit (8) that controls the amount of resin composition supplied from the raw material supply unit (6) to the extruder (1) so that the pressure value measured by the pressure measuring unit (7) is within a predetermined range.

Description

Technical Field

[0001] The present invention relates to a resin supply device, a press molding device, a resin supply method, and a method for manufacturing a press molded product.

Background Art

[0002] There is known a technique in which a thermoplastic resin is heated by an extruder or the like to prepare a molten resin composition, and the molten resin composition discharged from a discharge portion is quantitatively supplied to a mold, and a product is manufactured by press molding or injection molding.

[0003] For example, Patent Document 1 discloses a technique for molding a plastic product by attaching an injection molding machine, which is a secondary molding machine operating intermittently, to a continuously operating extruder.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in molding methods such as press molding and extrusion molding as described above, there is known a technique in which a gear pump is used to intermittently and quantitatively transfer a molten resin composition prepared by an extruder to a discharge portion.

[0006] In such intermittent transfer using a gear pump, when the time of intermittent transfer becomes long, it may be difficult to quantitatively transfer the molten resin composition, and there is room for improvement.

[0007] One aspect of the present invention aims to realize a resin supply device, a press molding device, a resin supply method, and a method for manufacturing a press molded product capable of quantitatively transferring a molten resin composition even when the time of intermittent transfer becomes long.

Means for Solving the Problems

[0008] To solve the above problems, a resin supply device according to one aspect of the present invention is a resin supply device provided in a molding apparatus, characterized by comprising: a melting unit that melts a resin composition containing a thermoplastic resin to produce a molten resin composition; a raw material supply unit that supplies the resin composition to the melting unit; a discharge unit for intermittently discharging the molten resin composition to a mold; a transfer unit that intermittently transfers the molten resin composition from the melting unit to the discharge unit; a pressure measuring unit that measures the pressure between the melting unit and the transfer unit; and a control unit that controls the amount of resin composition supplied from the raw material supply unit to the melting unit so that the pressure value measured by the pressure measuring unit is within a predetermined range.

[0009] To solve the above problems, another aspect of the present invention provides a resin supply method performed during molding, characterized by comprising: a raw material supply step of supplying a resin composition containing a thermoplastic resin to a melting section; a melting step of melting the resin composition supplied in the raw material supply step in the melting section to produce a molten resin composition; a transfer step of intermittently transferring the molten resin composition to a discharge section via a transfer section; a pressure measurement step of measuring the pressure between the melting section and the transfer section; and a control step of controlling the amount of resin composition supplied to the melting section in the raw material supply step so that the pressure value measured in the pressure measurement step falls within a predetermined range. [Effects of the Invention]

[0010] According to these embodiments of the present invention, quantitative transfer of the molten resin composition is possible even when the intermittent transfer time is extended. [Brief explanation of the drawing]

[0011] [Figure 1] This figure schematically shows the general configuration of a resin supply device according to one embodiment of the present invention. [Figure 2] Figure 1 shows a schematic graph illustrating the relationship between the primary pressure P of the gear pump, measured by the pressure measurement unit, and the operating time T of the resin supply device. [Figure 3] This is a process diagram showing an example of a resin supply method according to one embodiment of the present invention. [Modes for carrying out the invention]

[0012] 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.

[0013] (Configuration of the resin supply device) Figure 1 is a schematic diagram showing the general configuration of the resin supply device 10 according to this embodiment. As shown in Figure 1, the resin supply device 10 is a device that supplies a molten resin composition 11 to a mold 5. The resin supply device 10 comprises an extruder 1 (melting section), a transfer section 2, a discharge section 3, a heating and cutting section 4, a raw material supply section 6, a pressure measuring section 7, and a control section 8. The resin supply device 10 is installed in a molding apparatus.

[0014] Extruder 1 corresponds to the melting section, which melts a resin composition containing a thermoplastic resin to produce a molten resin composition 11. In extruder 1, the resin composition is fed in through the inlet 1a. The resin composition fed in through the inlet 1a is then melted and kneaded to become the molten resin composition 11. Note that the melting section is not limited to the extruder 1 shown in Figure 1, but can be any device capable of melting a resin composition.

[0015] The transfer unit 2 intermittently transfers the molten resin composition 11 from the extruder 1 to the discharge unit 3. In the transfer unit 2, the molten resin composition 11 is intermittently and quantitatively transferred to the discharge unit 3. The transfer unit 2 comprises a metering pump that intermittently and quantitatively discharges the molten resin composition 11 toward the discharge unit 3, and a transfer unit body that transfers the molten resin composition 11 discharged from the metering pump to the discharge unit 3. Specifically, the transfer unit 2 comprises a gear pump 2a as the metering pump and a hot hose 2b as the transfer unit body. The gear pump 2a is connected to the extruder 1 and intermittently discharges the molten resin composition 11 toward the discharge unit 3 by intermittent drive. The gear pump 2a is the drive source for the transfer unit 2 to intermittently transfer the molten resin composition 11 to the discharge unit 3. The hot hose 2b of the transfer unit 2 is a hose that relays between the gear pump 2a and the discharge unit 3. In the transfer section 2, the molten resin composition 11 is intermittently and quantitatively discharged by the gear pump 2a and transferred to the discharge section 3 via the hot hose 2b. The quantitative pump is not limited to the gear pump 2a; any known device can be used as long as it is configured to intermittently and quantitatively discharge the molten resin composition 11. In addition to the gear pump, the quantitative discharge section can be, for example, a shot pump (note: a pump that repeatedly suctions and discharges at a constant volume, like a syringe), a manifold block, etc. Furthermore, the transfer section body is not limited to the hot hose 2b; any known component can be used as long as it is configured to transfer the molten resin composition 11.

[0016] Thus, the resin supply device 10 is equipped with a transfer unit 2 that intermittently transfers the molten resin composition 11 from the extruder 1 to the discharge unit 3, thus ensuring smooth transfer from the extruder 1 to the discharge unit 3. Furthermore, since the transfer unit 2 of the resin supply device 10 is equipped with a gear pump 2a, the molten resin composition 11 can be intermittently and quantitatively discharged toward the discharge unit 3.

[0017] The discharge unit 3 is for intermittently discharging the molten resin composition 11 into the mold 5. The discharge unit 3 is equipped with an on / off nozzle 31. The mold 5 has a molding section 5a that constitutes the molding space of the molded product. The on / off nozzle 31 of the discharge unit 3 intermittently discharges the molten resin composition 11 into the molding section 5a of the mold 5. The on / off nozzle 31 is provided at the tip of the discharge unit 3. The molten resin composition 11 is intermittently and quantitatively discharged from the on / off nozzle 31 into the mold 5. The discharge unit 3 is not particularly limited as long as it is configured to intermittently discharge the molten resin composition 11, and known devices can be used. Also, in the configuration shown in Figure 1, one molding section 5a was formed in one mold 5. However, the mold 5 is not limited to the configuration shown in Figure 1. Two or more molding sections 5a may be formed in one mold 5.

[0018] The heating and cutting section 4 heats and cuts the molten resin composition 11 discharged from the opening / closing nozzle 31 to the mold 5 without contact and instantaneously. The heating and cutting section 4 is equipped with a hot air heater 4a (hot air supply section) that supplies hot air to the molten resin composition 11. With the resin supply device 10, even if the heating and cutting section 4 cuts the stringy portion 11a of the molten resin composition 11 between the opening / closing nozzle 31 and the mold 5, no new stringy portion is generated, and the molten resin composition 11 can be supplied to the mold 5 with good quantitative accuracy.

[0019] The raw material supply unit 6 supplies a resin composition containing a thermoplastic resin, which is a raw material of the molten resin composition 11, to the extruder 1. (Hereinafter, it is referred to as the raw material resin composition). The raw material supply unit 6 is a so-called feeder device. The raw material supply unit 6 supplies a set fixed amount of the raw material resin composition to the extruder 1. The raw material supply unit 6 is roughly classified into a volumetric type and a gravimetric type as the raw material supply method. The volumetric type is a method of supplying a fixed volume of the raw material resin composition per unit time by a screw or the like that rotates at a fixed rotation speed inside the raw material supply unit 6. Further, the gravimetric type is a method of supplying a fixed weight of the raw material resin composition per unit time measured by a weighing unit when supplying the raw material resin composition by a screw or the like that rotates inside the raw material supply unit 6. In the gravimetric type, it is necessary to control the rotation speed of the screw in order to supply a fixed weight of the raw material resin composition. In the resin supply device , the raw material supply method of the raw material supply unit 6 may be the gravimetric type or the volumetric type. From the viewpoint of being able to more easily control the supply amount of the raw material resin composition to a fixed amount, it is preferable that the raw material supply method is the volumetric type.

[0020] Note that the raw material supply unit 6 is provided with a supply amount adjustment unit (not shown) for adjusting the supply amount of the raw material resin composition to the extruder 1. The raw material supply unit 6 is configured such that the supply adjustment unit inputs a control signal from the control unit 8 and adjusts the supply amount of the raw material resin composition to the extruder 1 based on the control signal.

[0021] The pressure measurement unit 7 is a device that measures the pressure between the extruder 1 and the transfer unit 2. The pressure measurement unit 7 is disposed at the pressure between the extruder 1 and the gear pump 2a. The pressure measurement unit 7 measures the pressure on the upstream side of the gear pump 2a, that is, the suction pressure (primary pressure) of the molten resin composition 11 by the gear pump 2a. The pressure measurement unit 7 may be any device that can measure the primary pressure of the gear pump 2a, and a conventionally known pressure measuring instrument can be adopted. It is preferable that the pressure measurement unit 7 is a device that outputs an analog signal as the pressure measurement value.

[0022] The control unit 8 controls the supply amount of the raw material resin composition from the raw material supply unit 6 to the extruder 1. The control unit 8 inputs the output signal (pressure measurement value) of the pressure measurement unit 7, and based on the output signal, outputs a control signal to the supply adjustment unit of the raw material supply unit 6. The raw material supply unit 6 controls the supply amount of the raw material resin composition to the extruder 1 based on the control signal from the control unit 8.

[0023] In the resin supply device 10 according to the present embodiment, the control unit 8 performs feedback control on the supply amount of the raw material resin composition to the extruder 1 based on the primary pressure measurement value of the gear pump 2a measured by the pressure measurement unit 7.

[0024] (Control method by the control unit) Hereinafter, referring to FIGS. 1 and 2, the control method by the control unit 8 will be described.

[0025] In the intermittent driving operation of the gear pump 2a in the resin supply device 10, the primary pressure of the gear pump 2a is maintained at a constant pressure or higher. FIG. 2 is a graph schematically showing the relationship between the primary pressure P of the gear pump 2a measured by the pressure measurement unit 7 and the operating time T of the resin supply device 10.

[0026] The intermittent driving operation of the gear pump 2a is performed periodically. As shown in FIG. 2, in the intermittent driving operation of the gear pump 2a, the primary pressure P shows a waveform behavior with a certain period. In FIG. 2, the period of the waveform of the primary pressure P is indicated by a double arrow line. In the waveform of the primary pressure P shown in FIG. 2, the primary pressure P shows a lower limit peak value at the drive stop point ("discharge end" in FIG. 2) and an upper limit peak value at the drive start point ("discharge start" in FIG. 2).

[0027] In the intermittent drive operation of the gear pump 2a, a slight difference arises between the amount of molten resin composition 11 sucked in by the gear pump 2a (sometimes referred to as the resin supply amount) and the amount of molten resin composition 11 discharged by the gear pump 2a (sometimes referred to as the resin discharge amount). As the operating time T of the resin supply device 10 increases (long-run operation), the slight difference between the resin supply amount and the resin discharge amount accumulates, causing the baseline of the primary pressure P waveform to fluctuate. That is, the lower limit peak value or upper limit peak value in the primary pressure P waveform does not remain constant but fluctuates. As a result, the primary pressure P waveform may fall below the set lower limit value P1 of the primary pressure P, as shown in Figure 2A, or exceed the set upper limit value P2 of the primary pressure P, as shown in Figure 2B. If the primary pressure P falls below the set lower limit value P1, uneven discharge of the molten resin composition 11 from the gear pump 2a may occur, and if the primary pressure P exceeds the set upper limit value P2, a pressure resistance abnormality of the extruder 1 may occur. Thus, in the intermittent drive operation of the gear pump 2a, if the intermittent transfer time becomes long, quantitative transfer of the molten resin composition 11 may become difficult.

[0028] Therefore, in the resin supply device 10 according to this embodiment, the control unit 8 controls the amount of raw material resin composition supplied from the raw material supply unit 6 to the extruder 1 so that the pressure value measured by the pressure measurement unit 7 (primary pressure P of the gear pump 2a) is within a predetermined range. The "predetermined range" here refers to the range from the set lower limit value P1 to the set upper limit value P2 shown in Figure 2.

[0029] According to the resin supply device 10 of this embodiment, the control unit 8 controls the amount of raw resin composition supplied to the extruder 1 so that the primary pressure P of the gear pump 2a is within a predetermined range. Therefore, even if the intermittent transfer time by the gear pump 2a is long, uneven discharge of the molten resin composition 11 from the gear pump 2a and abnormal pressure resistance of the extruder 1 can be suppressed. Thus, according to the resin supply device 10 of this embodiment, quantitative transfer of the molten resin composition 11 is possible even if the intermittent transfer time is long.

[0030] The control unit 8 can use any control method to control the amount of raw material resin composition supplied to the raw material supply unit 6, as long as the primary pressure P of the gear pump 2a is controlled to be within a predetermined range. Preferably, the control unit 8 controls the supply of raw material resin composition from the raw material supply unit 6 to the extruder 1 in the following ways: (i) when the pressure value measured by the pressure measuring unit 7 (primary pressure P of the gear pump 2a) is lower than the predetermined range, it increases the amount of raw material resin composition supplied from the raw material supply unit 6 to the extruder 1; and (ii) when the pressure value measured by the pressure measuring unit 7 (primary pressure P of the gear pump 2a) is higher than the predetermined range, it decreases the amount of raw material resin composition supplied from the raw material supply unit 6 to the extruder 1. Furthermore, in the case of the above controls (i) and (ii), the control unit 8 preferably includes a storage unit that stores a set lower limit value P1 and a set upper limit value P2.

[0031] In the case of the control described in (i) above, the control unit 8 determines whether the primary pressure P is lower than the predetermined range based on a comparison between the lower limit peak value and the set lower limit value P1 in the waveform of the primary pressure P of the gear pump 2a. If, based on the above comparison result, it is determined that the primary pressure P is lower than the predetermined range, the control unit 8 outputs a control signal to the raw material supply unit 6 to increase the amount of raw material resin composition supplied to the extruder 1. If, based on the above comparison result, it is determined that the primary pressure P of the gear pump 2a is within the predetermined range, it is determined that the primary pressure P of the gear pump 2a is within the predetermined range.

[0032] Furthermore, in the case of the control described in (ii) above, the control unit 8 determines whether the primary pressure P is higher than the predetermined range based on the comparison result between the upper limit peak value and the set upper limit value P2 in the waveform of the primary pressure P of the gear pump 2a. If, based on the above comparison result, it is determined that the primary pressure P is higher than the predetermined range, the control unit 8 outputs a control signal to the raw material supply unit 6 that reduces the amount of raw material resin composition supplied to the extruder 1. If, based on the above comparison result, it is determined that the primary pressure P is not higher than the predetermined range, it is determined that the primary pressure P of the gear pump 2a is within the predetermined range.

[0033] The criteria for determining whether the primary pressure P is lower than the predetermined range, based on a comparison between the lower limit peak value and the set lower limit value P1, can be appropriately set according to the settings of the intermittent transfer operation, the performance of various components of the resin supply device 10, the properties of the molten resin composition 11, etc. Similarly, the criteria for determining whether the primary pressure P is higher than the predetermined range, based on a comparison between the upper limit peak value and the set upper limit value P2, can be appropriately set according to the settings of the intermittent transfer operation, the performance of various components of the resin supply device 10, the properties of the molten resin composition 11, etc.

[0034] For example, the number of times the upper limit peak value of the primary pressure P exceeds the set upper limit value P2 can be set as a criterion for determining whether the primary pressure P is higher than the predetermined range. Similarly, the number of times the lower limit peak value of the primary pressure P falls below the set lower limit value P1 can be set as a criterion for determining whether the primary pressure P is lower than the predetermined range. For either criterion, the number of reference counts can be appropriately set according to the settings of the intermittent transfer operation, the performance of various components of the resin supply device 10, the properties of the molten resin composition 11, etc.

[0035] Furthermore, it is possible to appropriately set a provision for how much the supply amount of the raw resin composition to the extruder 1 should be increased or decreased when the primary pressure P is determined to be lower or higher than the predetermined range. In other words, the rate of change in the supply amount of the raw resin composition to the extruder 1 when the primary pressure P of the gear pump 2a is determined to be outside the predetermined range can be appropriately set according to the setting of the intermittent transfer operation, the performance of various components of the resin supply device 10, the properties of the molten resin composition 11, etc.

[0036] Furthermore, in the intermittent drive operation of the gear pump 2a (intermittent transfer operation of the transfer unit 2), the lower the primary pressure P of the gear pump 2a, the more likely it is that discharge irregularities will occur. The setting lower limit P1 that defines the above predetermined range can be set based on whether or not discharge irregularities occur in the intermittent drive operation of the gear pump 2a. Therefore, the setting lower limit P1 is the lower limit at which discharge irregularities do not occur in the intermittent drive operation of the gear pump 2a, and can be set appropriately according to the setting of the intermittent transfer operation, the performance of various components of the resin supply device 10, the properties of the molten resin composition 11, etc. Specifically, the setting lower limit P1 is 4 MPa.

[0037] Furthermore, in the intermittent drive operation of the gear pump 2a, the higher the primary pressure P of the gear pump 2a, the more likely it is that pressure abnormalities will occur in the extruder 1. The setting upper limit P2 that defines the above predetermined range can be set based on whether or not pressure abnormalities occur in the extruder 1 during the intermittent drive operation of the gear pump 2a. That is, the setting upper limit P2 can be set considering the pressure upper limit P3 of the extruder 1 shown in Figure 2. The setting upper limit P2 is a value lower than the pressure upper limit P3 and can be set appropriately according to the settings of the intermittent transfer operation, the performance of various components of the resin supply device 10, the properties of the molten resin composition 11, etc. The setting upper limit P2 is preferably 25 MPa less than the pressure upper limit P3, and more preferably 24 MPa less than the pressure upper limit P3. Specifically, if the pressure upper limit P3 is 22 MPa, the setting upper limit P2 is 15 MPa.

[0038] Furthermore, the control unit 8 may be implemented by logic circuits (hardware) formed on an integrated circuit (IC chip), or it may be implemented by software using a CPU (Central Processing Unit). By providing such a control unit 8, automatic control of the raw material supply unit 6 can be realized.

[0039] In this case, the resin supply device 10 according to this embodiment includes a CPU that executes instructions for a program, which is software that realizes each function; a ROM (Read Only Memory) or storage device (collectively referred to as a "recording medium") on which the program and various data are recorded in a way that can be read by a computer (or CPU); and a RAM (Random Access Memory) for loading the program. The object of this disclosure is achieved when the computer (or CPU) reads the program from the recording medium and executes it. As the recording medium, a "non-temporary tangible medium" such as tape, disk, card, semiconductor memory, or programmable logic circuit can be used. The program may also be supplied to the computer via any transmission medium capable of transmitting the program (such as a communication network or broadcast waves). The present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

[0040] (molding equipment) The molding to which the resin supply device according to this embodiment is applied is all molding using a molten resin composition, and may be injection molding or press molding. Therefore, the molding apparatus to which the resin supply device according to this embodiment is applied can be a conventionally known molding apparatus, as long as it is configured to supply a molten resin composition to a mold, and may be an injection molding apparatus or a press molding apparatus. Preferably, the molding apparatus to which the resin supply device according to this embodiment is applied is a press molding apparatus.

[0041] The press molding apparatus according to this embodiment comprises the resin supply device and molds described above. Referring to Figure 1, the press molding apparatus includes a resin supply device 10 and a pair of molds: a lower mold 5 to which the molten resin composition 11 is supplied, and an upper mold (not shown) that is paired with mold 5. In the press molding apparatus, the pair of molds filled with the molten resin composition 11 are press-molded, and the molds are opened to obtain a press-molded product. The press molding apparatus includes, for example, a hot press molding machine that performs hot pressing on the mold 5, and a cooling press machine that cools and presses the hot-pressed mold 5.

[0042] The above-mentioned hot press molding machine and cold press molding machine are not particularly limited as long as they are configured to perform hot press and cold press on a pair of molds filled with the molten resin composition 11. Conventional known devices can be used for the hot press molding machine and cold press molding machine.

[0043] (thermoplastic resin) The raw material resin composition used in this embodiment includes a thermoplastic resin. The thermoplastic resin is not particularly limited. Preferred thermoplastic resins include general-purpose resins such as polypropylene, polyethylene, polyvinyl chloride, polyvinyl acetate, polyacetal, polycarbonate, polyamide, acrylonitrile, butadiene, polystyrene, and acrylic polymers, as well as biodegradable resins such as P3HA resins, polylactic acid, polyglycolic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polybutylene succinate terephthalate, and polycaprolactone. Depending on the melting conditions of the resin composition, the molten resin composition of these resins may exhibit the stringing phenomenon described above when cut with a cutter. Furthermore, it is preferable that the resin composition used in this embodiment includes a thermoplastic resin that can be used in press molding.

[0044] In particular, the thermoplastic resin is preferably a biodegradable resin, and more preferably a poly(3-hydroxyalkanoate) resin (hereinafter sometimes referred to as "P3HA resin"). In this specification, "P3HA resin" means a biodegradable aliphatic polyester (preferably a polyester that does not contain aromatic rings). The P3HA resin is a 3-hydroxyalkanoic acid represented by the general formula: [-CHR-CH2-CO-O-] (wherein R is C n H 2n+1 The alkyl group represented by , where n is an integer between 1 and 15. is a polyhydroxyalkanoate containing ) as a repeating unit. According to this embodiment, when a P3HA resin is used as the thermoplastic resin, marine pollution due to waste can be suppressed, 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, seas and marine resources for sustainable development."

[0045] Furthermore, 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 constitute 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 the total repeating units (100 mol%).

[0046] When the composition ratio of 3HB repeating units is 94.5 mol% or higher, the rigidity of the P3HA resin is further improved, the crystallization rate is increased, burrs are reduced, and productivity tends to improve. On the other hand, when the composition ratio of 3HB repeating units is 98.5 mol% or lower, the melting point is below the thermal decomposition temperature, enabling stable and continuous production. The monomer composition ratio of the P3HA resin can be measured by gas chromatography, etc. (see, for example, International Publication No. 2014 / 020838).

[0047] More specifically, the P3HA resin is preferably one or more selected from the group consisting of 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).

[0048] Furthermore, P3HA resins produced by microorganisms (microbially produced P3HA resins) are typically P3HA resins composed only of D-isomer (R-isomer) polyhydroxyalkanoic acid monomer units. Among microbially produced P3HA resins, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferred due to their ease of industrial production, and P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are more preferred.

[0049] The microorganisms that produce microbially produced P3HA resins are not particularly limited as long as they are microorganisms capable of producing P3HA 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.

[0050] 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 of the P3HA resin synthase group have been introduced, are more preferred in order to increase the productivity of P3HB3HH. Microbial cells that have accumulated P3HB3HH in their cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, genetically modified microorganisms into which various P3HA resin synthesis-related genes can be introduced can be used, depending on the P3HA resin to be produced, or the culture conditions, including the type of substrate, can be optimized.

[0051] 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 range of the P3HA resin is preferably 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 provides adequate mechanical strength. Furthermore, a molecular weight of 1,000,000 or less suppresses the increase in melt viscosity and provides excellent moldability.

[0052] The weight-average molecular weight can be determined using gel permeation chromatography (GPC) (Shodex GPC-101, Showa Denko Corporation), with a polystyrene gel column (Shodex K-804, Showa Denko Corporation) and chloroform as the mobile phase, expressed as the molecular weight in polystyrene equivalent. Calibration curves are created using polystyrene with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000. Any column suitable for measuring the aforementioned molecular weights can be used in the GPC.

[0053] The raw material resin composition used in this embodiment may contain a second P3HA-based resin in addition to the P3HA-based resin. The second P3HA-based resin contains at least one copolymer of 3HB units and other hydroxyalkanoate units, and the amount of 3HB units in the poly(3-hydroxyalkanoate)-based resin is preferably 65.0 to 90.0 moles, more preferably 68.0 to 88.0 moles, and even more preferably 70.0 to 85.0 moles. The inclusion of the second P3HA-based resin in the raw material resin composition results in superior toughness of the molded article.

[0054] The second P3HA-based resin is not particularly limited, as long as it is different from the aforementioned P3HA-based resin. Examples of the second P3HA-based resin include the resins exemplified above as the aforementioned P3HA-based resin.

[0055] 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, per 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 resin described above can be used as the second P3HA resin. In this specification, "total P3HA resin" refers to all P3HA resin contained in the raw material resin composition.

[0056] The raw material resin composition may contain other resins besides P3HA resins, as long as 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 composition may contain only one or two or more of these other resins.

[0057] The content of the other resins is not particularly limited, but is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, per 100 parts by weight of the total P3HA resin. Even more preferably 30 parts by weight or less. The lower limit of the content of the other resins is not particularly limited and may be 0 parts by weight.

[0058] The aforementioned raw material resin composition does not necessarily have to contain inorganic fillers, but it is preferable that it further contains inorganic fillers. The inclusion of inorganic fillers in the resin composition improves the crystallization rate, resulting in effects such as reduced burrs and improved production cycles.

[0059] The inorganic filler is not particularly limited, but examples 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, and glass particles. These may be used individually or in combination of two or more types.

[0060] The inorganic filler content 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, per 100 parts by weight of the total P3HA resin. When the inorganic filler content is within the above range, it is possible to achieve both a sufficient crystallization rate and toughness.

[0061] Furthermore, the raw material resin composition may contain additives that can be used together with the P3HA resin, to the extent that they do not impair the effects of the present invention. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolites, fragrances such as vanillin and dextrin, plasticizers, antioxidants, weather resistance modifiers, ultraviolet absorbers, crystal nucleating agents, lubricants, mold release agents, water repellents, antibacterial agents, and sliding properties modifiers. Only one type of additive may be included, or two or more types may be included. The content of these additives can be appropriately determined by those skilled in the art depending on the intended use.

[0062] (Resin supply method) The resin supply method according to this embodiment (hereinafter referred to as "this resin supply method") is a resin supply method performed during molding, and includes: a raw material supply step of supplying a resin composition containing a thermoplastic resin to a melting section; a melting step of melting the resin composition supplied in the raw material supply step in the melting section to produce a molten resin composition; a transfer step of intermittently transferring the molten resin composition to a discharge section via a transfer section; a pressure measurement step of measuring the pressure between the melting section and the transfer section; and a control step of controlling the amount of resin composition supplied to the melting section in the raw material supply step so that the pressure value measured in the pressure measurement step falls within a predetermined range. This makes it possible to quantitatively transfer the molten resin composition 11 even if the intermittent transfer time is long. The molding to which this resin supply method is applied is all molding using a molten resin composition, and may be injection molding or press molding.

[0063] The resin supply method is not particularly limited as long as it includes the above-mentioned raw material supply step, melting step, transfer step, discharge step, pressure measurement step, and control step, but an example is the resin supply method using the resin supply device 10 described above. Figure 3 is a process diagram showing an example of the resin supply method. As shown in Figure 3, the resin supply method includes a raw material supply step 100, a melting step 101, a transfer step 102, a discharge step 103, a pressure measurement step 104, a control step 105, and a heating and cutting step 106.

[0064] In the raw material supply step 100, the raw material resin composition is supplied to the melting and kneading apparatus, which serves as the melting section. The method of supplying the raw material resin composition to the melting and kneading apparatus is not particularly limited, and conventionally known supply methods can be used. In the raw material supply step 100, the raw material resin composition may be prepared (completed) by mixing or blending using a mixing device or the like, and then supplied to the melting and kneading apparatus. The mixing device is not particularly limited, and examples include ribbon blenders, flash blenders, tumbler mixers, and super mixers. Alternatively, various materials of the raw material resin composition may be supplied to the melting and kneading apparatus, and the resin composition may be prepared within the melting and kneading apparatus. Preferably, the raw material resin composition is supplied to the melting and kneading apparatus, which serves as the melting section, using the raw material supply section 6 (see Figure 1) described above.

[0065] In the melting step 101, the raw material resin composition supplied in the raw material supply step is melted to produce a molten resin composition. The method for melting the raw material resin composition can be any conventionally known method, as long as it can form a molten resin composition containing a thermoplastic resin. Preferably, the melting step includes a melt-kneading step in which the resin composition containing the thermoplastic resin is melt-kneaded.

[0066] The form of the melt-kneading process is not particularly limited, as long as a melt-kneaded resin composition can be obtained. Specific examples of the melt-kneading process include, for example, the following methods (a1) and (a2): (a1) A raw material resin composition is prepared by mixing or blending using a mixing device or the like. The raw material resin composition is then supplied to a melt-kneading device and melt-kneaded (the melting step 101 is performed after the raw material supply step 100); (a2) A method of supplying raw materials for a resin composition containing a thermoplastic resin to a melt-kneading apparatus, preparing (completing) the resin composition within the melt-kneading apparatus, and melt-kneading the resin composition (the raw material supply process 100 and the melting process 101 are carried out simultaneously).

[0067] In method (a1) above, the order in which the various materials of the raw resin composition are mixed or blended (dry blended) is not particularly limited. In method (a2) above, the order in which the various materials of the raw resin composition are supplied to the melt kneading apparatus is not particularly limited.

[0068] In the methods described in (a1) and (a2) above, the melting and kneading apparatus is not particularly limited and includes extruders, kneaders, Banbar mixers, and rolls. Extruders are preferred as the melting and kneading apparatus due to their superior productivity and convenience, and twin-screw extruders are even more preferred.

[0069] In the melt-mixing process, for example, if the thermoplastic resin is a P3HA-based resin, the temperature at which the resin composition is melt-mixed cannot be specified in general, as it depends on the physical properties of the P3HA-based resin (melting point, weight-average molecular weight, etc.) and the type of additives used. Regarding the temperature at which the resin composition is melt-mixed, for example, the temperature of the molten resin composition discharged from the discharge unit (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 undergo thermal decomposition.

[0070] In the transfer step 102, the molten resin composition is intermittently transferred to the discharge section via the transfer unit. The method for intermittently transferring the molten resin composition to the discharge section is not particularly limited, and known transfer methods can be employed. Preferably, in the transfer step 102, the molten resin composition is quantitatively and intermittently transferred to the discharge section. In this case, the transfer device only needs to be capable of quantitatively and intermittently transferring the molten resin composition, and examples include a shot pump (note: a pump that repeatedly sucks and discharges at a constant volume, like a syringe), a manifold block, and a gear pump. Among these, it is preferable to use a gear pump as the transfer device. That is, in the transfer step 102, it is preferable to use a gear pump to intermittently transfer the molten resin composition to the discharge section. The gear pump is not particularly limited as long as it is capable of quantitatively and intermittently transferring the molten resin composition to the discharge section, and conventionally known devices can be employed.

[0071] Furthermore, in the transfer process 102, a transfer body may be provided between the transfer device and the discharge section, and the molten resin composition may be intermittently transferred from the transfer device to the discharge section via the transfer body. The transfer body is not particularly limited as long as it is configured to transfer the molten resin composition. Preferably, the transfer body is a hot hose. The hot hose is configured to transfer the molten resin composition having the above-mentioned composition temperature, and is composed of, for example, a heater, an insulating layer, and an inner tube. Among these, from the viewpoint of pressure resistance and heat resistance, the material of the inner tube in the hot hose is preferably Teflon®.

[0072] In the discharge process 103, the molten resin composition is intermittently discharged from the discharge unit to the mold. The method of intermittently discharging the molten resin composition from the discharge unit to the mold is not particularly limited. Preferably, from the viewpoint of mass production of press-molded products, the discharge unit is installed directly above the mold, and the molten resin composition is intermittently discharged to the mold by discharging and dropping from the discharge unit into the mold.

[0073] In the discharge step 103, it is preferable to perform intermittent discharge, particularly for molten resin compositions with relatively high viscosity. This improves the quantitative accuracy of the supply of molten resin composition to the mold. In the discharge step 103, it is preferable that the discharge section has an open / close nozzle. An open / close nozzle capable of intermittently discharging the molten resin composition can be realized, for example, by an open / close mechanism that opens and closes the discharge port. By alternately opening and closing the discharge port using the open / close mechanism, the open / close nozzle intermittently discharges the molten resin composition.

[0074] Furthermore, the intermittent dispensing of the molten resin composition may be performed periodically, with the dispensing operation being executed and stopped alternately, or it may be performed aperiodically. When the dispensing operation is performed periodically, the period of execution and stopping of the dispensing operation can be appropriately set according to the composition temperature, the tackiness of the molten resin composition, etc.

[0075] In the pressure measurement step 104, the pressure between the melting section and the transfer section is measured. More specifically, the suction pressure (primary pressure) of the molten resin composition by the transfer section is measured. Preferably, a gear pump is used as the transfer device in the transfer step 102, and in the pressure measurement step 104, the pressure upstream of the gear pump, i.e., the suction pressure (primary pressure) of the molten resin composition by the gear pump is measured. The pressure measuring instrument used in the pressure measurement step can be any instrument capable of measuring the primary pressure of the transfer section, and conventionally known pressure measuring instruments can be used. Preferably, the pressure measuring instrument used in the pressure measurement step is an instrument that outputs an analog signal as the pressure measurement value.

[0076] In the control step 105, the amount of resin composition supplied to the melting section in the raw material supply step 100 is controlled so that the pressure value measured in the pressure measurement step 104 falls within a predetermined range. The method for controlling the amount of resin composition supplied to the melting section in the control step 105 is the same as described in the section (Control method by the control unit) above, so the explanation is omitted.

[0077] In the heating and cutting step 106, the molten resin composition discharged from the discharge unit to the mold is heated and cut instantaneously without contact. In this way, when supplying the molten resin composition to the mold, the molten resin composition between the discharge unit and the mold is heated and cut instantaneously without contact, allowing for a quantitative supply of the molten resin composition to the mold.

[0078] Here, "heating and cutting without contact" means heating and cutting the molten resin composition without bringing the heat source for heating into contact with the molten resin composition. The distance between the heat source and the molten resin composition is not particularly limited, as long as the molten resin composition can be heated and cut instantaneously. "Heating and cutting instantaneously" means cutting the molten resin composition at the same time as heating by the heat source. Here, "at the same time as heating by the heat source" means simultaneously within the measurement limit, and is intended to be within 3 seconds, preferably within 1 second, from heating by the heat source.

[0079] The method for heating and cutting the molten resin composition in the heating and cutting step 106 is not particularly limited, as long as it can heat and cut the molten resin composition non-contact and instantaneously. For example, the radiant heat of a heat source may be used to heat and cut the molten resin composition non-contact and instantaneously. In this case, hot air may be used to heat and cut the molten resin composition non-contact and instantaneously. It is preferable to use a hot air heater as the heat source for supplying hot air to the molten resin composition. By adopting a heating and cutting method using hot air in this way, the occurrence of new stringing phenomena due to the cut molten resin composition becomes less likely. Therefore, the molten resin composition can be cut at the same location each time during each discharge operation. As a result, the effect of quantitatively supplying the molten resin composition to the mold is achieved.

[0080] Furthermore, in the heating and cutting step 106, a hot wire (heated metal wire) may be used to heat and cut the molten resin composition instantaneously and without contact. In this case, the hot wire, as a heat source, is brought close to the molten resin composition without contact, and the molten resin composition is instantaneously heated and cut by the radiant heat from the hot wire.

[0081] (Method of manufacturing molded products) The molding to which this resin supply method is applied is all molding using a molten resin composition, and may be injection molding or press molding. Therefore, the manufacturing method of a molded product to which this resin supply method is applied can be a conventionally known manufacturing method, as long as it includes a step of supplying a molten resin composition to a mold, and may be a manufacturing method for injection molded products or a manufacturing method for press molded products. Preferably, the manufacturing method of a molded product to which this resin supply method is applied is a manufacturing method for press molded products.

[0082] The method for manufacturing a press-molded product according to this embodiment includes the resin supply method described above as one step. In this method for manufacturing a press-molded product, a pair of molds is used, consisting of a lower mold to which the molten resin composition is supplied by the resin supply method described above, and an upper mold that is paired with the lower mold. The method for manufacturing a press-molded product includes a press molding step in which the pair of molds are closed and press molding is performed on the molten resin composition supplied to the molds by the resin supply method described above.

[0083] In the above press forming process, the pair of molds are subjected to hot pressing using a hot press forming machine. Then, the pair of molds that have been hot-pressed are cooled and pressed to perform press forming. After press forming, the pair of molds are opened to obtain the press-formed product.

[0084] The hot press molding machine and cold press molding machine used in the above press molding process are not particularly limited, as long as they are configured to perform hot and cold pressing on the pair of molds to which the molten resin composition is supplied. Conventional known devices can be used for the hot press molding machine and cold press molding machine.

[0085] 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.

[0086] In other words, one embodiment of the present invention is as follows:

[0087] <1> A resin supply device provided in a molding apparatus, comprising: a melting unit that melts a resin composition containing a thermoplastic resin to produce a molten resin composition; a raw material supply unit that supplies the resin composition to the melting unit; a discharge unit for intermittently discharging the molten resin composition to a mold; a transfer unit for intermittently transferring the molten resin composition from the melting unit to the discharge unit; a pressure measuring unit that measures the pressure between the melting unit and the transfer unit; and a control unit that controls the amount of resin composition supplied from the raw material supply unit to the melting unit so that the pressure value measured by the pressure measuring unit is within a predetermined range.

[0088] <2> The control unit increases the amount of resin composition supplied from the raw material supply unit to the melting unit when the pressure value measured by the pressure measuring unit is lower than the predetermined range, and decreases the amount of resin composition supplied from the raw material supply unit to the melting unit when the pressure value measured by the pressure measuring unit is higher than the predetermined range. <1> A resin supply device.

[0089] <3> The transfer unit includes a gear pump. <1> A resin supply device.

[0090] <4> The aforementioned thermoplastic resin is a biodegradable resin. <1> A resin supply device.

[0091] <5> The aforementioned thermoplastic resin is a poly(3-hydroxyalkanoate) resin. <1> A resin supply device.

[0092] <6> <1> ~ <5> A press molding apparatus comprising one of the following resin supply devices and a mold.

[0093] <7> A resin supply method performed during molding, comprising: a raw material supply step of supplying a resin composition containing a thermoplastic resin to a melting section; a melting step of melting the resin composition supplied in the raw material supply step in the melting section to produce a molten resin composition; a transfer step of intermittently transferring the molten resin composition to a discharge section via a transfer section; a pressure measurement step of measuring the pressure between the melting section and the transfer section; and a control step of controlling the amount of resin composition supplied to the melting section in the raw material supply step so that the pressure value measured in the pressure measurement step falls within a predetermined range.

[0094] <8> <7> A method for manufacturing a press-molded product, comprising a resin supply method as one step. [Industrial applicability]

[0095] The present invention can be suitably used, for example, in the field of manufacturing press-molded articles using P3HA-based resins, and in other fields. [Explanation of Symbols]

[0096] 1. Extruder 2 Transfer section 2a Gear pump 3 Discharge part 5. Mold 6 Raw material supply department 7. Pressure measurement unit 8 Control Unit 10 Resin supply device 11. Molten resin composition 100 Raw material supply process 101 Melting process 102 Transfer process 103 Discharge process 104 Pressure measurement process 105 Control process 106 Heat cutting process

Claims

1. A resin supply device provided in a molding apparatus, A melting section that melts a resin composition containing a thermoplastic resin to produce a molten resin composition, A raw material supply unit that supplies the resin composition to the molten section, A dispensing unit for intermittently dispensing the molten resin composition into a mold, A transfer unit intermittently transfers the molten resin composition from the melting section to the discharge section, A pressure measuring unit for measuring the pressure between the melting section and the transfer section, A resin supply device comprising: a control unit that controls the amount of resin composition supplied from the raw material supply unit to the melting unit so that the pressure value measured by the pressure measuring unit falls within a predetermined range; and a control unit that controls the amount of resin composition supplied from the raw material supply unit to the melting unit.

2. The control unit, If the pressure value measured by the pressure measuring unit is lower than the predetermined range, the amount of resin composition supplied from the raw material supply unit to the melting unit is increased. The resin supply apparatus according to claim 1, wherein if the pressure value measured by the pressure measuring unit is higher than the predetermined range, the amount of resin composition supplied from the raw material supply unit to the melting unit is reduced.

3. The resin supply device according to claim 1, wherein the transfer unit is equipped with a gear pump.

4. The resin supply device according to claim 1, wherein the thermoplastic resin is a biodegradable resin.

5. The resin supply device according to claim 1, wherein the thermoplastic resin is a poly(3-hydroxyalkanoate) resin.

6. A press molding apparatus comprising a resin supply device according to any one of claims 1 to 5, and a mold.

7. A method for supplying resin during molding, A raw material supply process for supplying a resin composition containing a thermoplastic resin to the melting section, A melting step in which the resin composition supplied in the raw material supply step is melted in the melting section to produce a molten resin composition, A transfer step in which the molten resin composition is intermittently transferred to the discharge section via a transfer section, A pressure measurement step for measuring the pressure between the melting section and the transfer section, A resin supply method comprising a control step of controlling the amount of resin composition supplied to the molten section in the raw material supply step so that the pressure value measured in the pressure measurement step falls within a predetermined range.

8. A method for manufacturing a press-molded product, comprising the resin supply method described in claim 7 as one step.

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