Molded foam production method

Abstract

The problem addressed is to provide a molded foam production method capable of providing a molded foam having excellent internal fusibility. The molded foam production method includes: a one-side heating step and an opposite-side heating step in which, with both drain valves (13A and 13B) closed, water vapor is supplied through one steam valve (12A or 12B) into a molding space (21); and a both-sides heating step in which, with the two drain valves (13A and 13B) closed, water vapor is supplied through the two steam valves (12A and 12B) into the molding space (21).

Description

Method for producing foamed molded article

[0001] The present invention relates to a method for producing a foamed molded article.

[0002] Large amounts of petroleum-derived plastics are discarded every year, and the resulting lack of landfill sites and environmental pollution have become serious issues. In recent years, microplastics have become a major problem in the marine environment. For this reason, biodegradable plastics that are decomposed by the action of microorganisms in (a) environments such as the sea and soil, and (b) landfills and compost, have attracted attention. Development of biodegradable plastics is underway with the aim of achieving a wide range of applications, including (a) agricultural, forestry, and fishery materials used in the environment, and (b) food containers, packaging materials, sanitary products, garbage bags, and other products that are difficult to recover and reuse after use. Furthermore, foam molded articles made from biodegradable plastics are expected to be used in packaging cushioning, agricultural product boxes, fish boxes, automotive components, building materials, civil engineering materials, and other applications.

[0003] Among the biodegradable plastics, poly(3-hydroxyalkanoate) (hereinafter sometimes referred to as "P3HA") has attracted attention as a plant-derived plastic due to its excellent biodegradability and carbon neutrality.

[0004] As techniques relating to foam molded articles using the above-mentioned biodegradable plastics, for example, the techniques described in Patent Documents 1 and 2 are known.

[0005] Japanese Patent Publication No. 2013-176886 Japanese Patent Publication No. 2012-214636

[0006] However, the above-mentioned conventional techniques are not sufficient from the viewpoint of the internal fusion properties of the resulting foamed molded article, and there is room for further improvement.

[0007] One embodiment of the present invention has been made in consideration of the above-mentioned problems, and its object is to provide a novel method for producing a foamed molded article that can provide a foamed molded article with excellent internal fusion.

[0008] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0009] That is, a method for producing a foamed molded article according to one embodiment of the present invention includes a filling step of filling a molding space formed by a fixed mold having a fixed-side steam valve and a fixed-side drain valve, and a movable mold having a movable-side steam valve and a movable-side drain valve, with aliphatic polyester-based resin foamed particles; and a step of, with the fixed-side drain valve and the movable-side drain valve closed, introducing a water vapor pressure Pf １ a one-side heating step in which steam of a pressure Pf is supplied into the molding space while the fixed-side drain valve and the movable-side drain valve are closed, and a steam pressure Pf is supplied through the steam valve that was not used in the one-side heating step among the fixed-side steam valve and the movable-side steam valve. ２ a reverse heating step of supplying steam of a pressure Pf into the molding space, and a step of supplying steam of a pressure Pf through the fixed side steam valve and the movable side steam valve with the fixed side drain valve and the movable side drain valve closed. ３ and a double-sided heating step of supplying steam of the above formula (1) into the molding space.

[0010] According to one embodiment of the present invention, it is possible to provide a novel method for producing a foamed molded article, which can provide a foamed molded article having excellent internal fusion properties.

[0011] 1 is a schematic diagram showing a molding apparatus for producing a foam molded article according to one embodiment of the present invention. 2 is a schematic diagram showing a foam molded article according to an example of the present invention.

[0012] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, the term "A to B" representing a numerical range means "greater than or equal to A (including and greater than A) and less than or equal to B (including and less than B)."

[0013] In this specification, the "method for producing a foam molded article according to one embodiment of the present invention" may be referred to as the "present production method," and the "expanded aliphatic polyester resin beads" may be referred to as "expanded beads." The foam molded article obtained by the present production method may also be referred to as an "aliphatic polyester resin foam molded article."

[0014] In this specification, a repeating unit derived from an X monomer may be referred to as an “X unit.” A repeating unit may also be referred to as a structural unit.

[0015] 1. Technical Concept of One Embodiment of the Present Invention As a result of extensive research by the present inventors, it has been found that the techniques described in the above-mentioned Prior Art Documents 1 and 2 have room for further improvement in terms of the internal fusion properties of the resulting foamed molded article.

[0016] The present inventors conducted extensive research to solve the above-mentioned problems. Specifically, the present inventors conducted extensive research to develop a novel method for producing a molded foam that can provide a molded foam with excellent internal fusion. In a method for producing a molded foam using a molding machine equipped with a fixed mold and a movable mold, the step of supplying steam to only one of the fixed mold and the movable mold through a steam valve equipped therein is referred to as the "one-sided heating step." The step of supplying steam to only the mold other than the mold to which steam was supplied in the one-sided heating step through a steam valve equipped therein is referred to as the "reverse one-sided heating step." The step of supplying steam to both the fixed mold and the movable mold through their respective steam valves is referred to as the "double-sided heating step." During the course of extensive research, the present inventors discovered the novel finding that a molded foam with excellent internal fusion can be obtained by performing the one-sided heating step and the reverse one-sided heating step with both the fixed-side drain valve and the movable-side drain valve closed. In the past, in the one-way heating step and the reverse one-way heating step of producing a foamed molded article, steam was typically supplied to the mold while the drain valve of the mold opposite the mold supplying steam through a steam valve was open. In other words, performing both the one-way heating step and the reverse one-way heating step with both the fixed-side drain valve and the movable-side drain valve closed is a method that would not normally be possible for a person skilled in the art. The present inventors have surprisingly discovered a novel finding that, when such a method is adopted, foamed molded articles with excellent internal fusion can be obtained. This finding could not have been predicted from the prior art, in which one-way heating / reverse one-way heating is typically performed with the drain valve of the mold opposite the mold supplying steam open.

[0017] 2. Method for manufacturing a foamed molded article A method for manufacturing a foamed molded article according to one embodiment of the present invention includes a filling step of filling a molding space formed by a fixed mold having a fixed-side steam valve and a fixed-side drain valve, and a movable mold having a movable-side steam valve and a movable-side drain valve, with aliphatic polyester-based resin foamed particles; and a step of, with the fixed-side drain valve and the movable-side drain valve closed, introducing a water vapor pressure Pf １a one-side heating step in which steam of a pressure Pf is supplied into the molding space while the fixed-side drain valve and the movable-side drain valve are closed, and a steam pressure Pf is supplied through the steam valve that was not used in the one-side heating step among the fixed-side steam valve and the movable-side steam valve. ２ a reverse heating step of supplying steam of a pressure Pf into the molding space, and a step of supplying steam of a pressure Pf through the fixed side steam valve and the movable side steam valve with the fixed side drain valve and the movable side drain valve closed. ３ and a double-sided heating step of supplying steam of the above formula (1) into the molding space.

[0018] The present manufacturing method has the above-mentioned configuration, and therefore has the advantage of being able to provide a foamed molded article with excellent internal fusion properties.

[0019] Furthermore, because this production method uses a biodegradable aliphatic polyester resin, the resulting foamed molded articles can suppress soil pollution due to disposal. This can contribute to the achievement of Sustainable Development Goals (SDGs), such as Goal 12, "Ensure sustainable consumption and production patterns." Furthermore, when P3HA-based resin foam particles containing a P3HA-based resin, which is an aliphatic polyester-based resin that is both soil-degradable and marine-degradable, are used, the resulting foamed molded articles can suppress not only soil pollution due to disposal but also marine pollution. This can contribute to the achievement of Goal 12, "Ensure sustainable consumption and production patterns," as well as Goal 14, "Conserve and sustainably use the oceans and marine resources for sustainable development."

[0020] The materials (raw materials) used in this manufacturing method will be explained below, followed by an explanation of each step.

[0021] (Aliphatic polyester resin expanded particles) The aliphatic polyester resin expanded particles used in the present production method are obtained by expanding aliphatic polyester resin particles obtained from an aliphatic polyester resin. Further, a foamed molded article is obtained by molding the expanded beads (e.g., in-mold foam molding). It can also be said that the aliphatic polyester resin expanded particles are obtained by expanding aliphatic polyester resin particles containing an aliphatic polyester resin.

[0022] Specifically, the aliphatic polyester resin particles can be obtained, for example, by the following methods: (1) mixing an aliphatic polyester resin with a bubble adjuster such as talc and other additives such as amide to obtain a mixture; (2) melt-kneading the obtained mixture while heating, for example, using an extruder, to obtain a molten resin composition; (3) cooling the obtained resin composition with water and cutting it to obtain aliphatic polyester resin particles.

[0023] Specifically, the expanded aliphatic polyester resin particles can be obtained by, for example, expanding aliphatic polyester resin particles using the following method: (1) Mixing a dispersion medium such as water, aliphatic polyester resin particles, and, if necessary, a crosslinking agent such as 1,1-di(t-butylperoxy)cyclohexane (TBCH), a dispersant such as calcium phosphate tribasic, and a dispersion aid such as sodium alkanesulfonate in a container; (2) Stirring the resulting mixture with a stirrer or the like, adding a blowing agent such as carbon dioxide, ethanol, or mixed butane (e.g., a mixture of normal butane and isobutane) to the container to prepare a dispersion; (3) Heating the dispersion to a foaming temperature and, if necessary, applying pressure to increase the pressure in the container to a foaming pressure; (4) Maintaining the temperature and pressure in the container near the foaming temperature and foaming pressure, respectively, for a certain period of time; (5) Next, releasing the dispersion from the container to atmospheric pressure to obtain expanded particles. The dispersion (mixture) in the container is continuously stirred with a stirrer or the like from (2) to (5) until the dispersion is completely released. The steps (1) and (2) may be collectively referred to as a "dispersion step."

[0024] The expanded beads thus obtained may be washed with an aqueous solution of sodium hexametaphosphate or the like, if necessary.

[0025] Alternatively, the aliphatic polyester-based resin particles may be impregnated with a foaming gas (foaming agent) in a pressure-resistant container, and then the aliphatic polyester-based resin particles may be placed in a pre-expansion machine and pre-expanded with water vapor or the like to obtain expanded particles.

[0026] The shape of the expanded beads is not particularly limited, but may be, for example, spherical or approximately spherical.

[0027] (Aliphatic polyester resin) As described above, expanded aliphatic polyester resin particles are obtained by expanding aliphatic polyester resin particles containing an aliphatic polyester resin. In other words, expanded aliphatic polyester resin particles contain an aliphatic polyester resin as a resin component. In this specification, the "resin component" in the expanded beads refers to the resin component that substantially constitutes the expanded beads, excluding blowing agents, cell control agents, and other additives, among the components contained in the expanded beads.

[0028] The resin component of the expanded aliphatic polyester resin beads contains, for example, more than 50 wt%, more preferably 60 wt% or more, more preferably 70 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, even more preferably 95 wt% or more, and particularly preferably 100 wt% of the resin component, of the expanded aliphatic polyester resin. In other words, it is particularly preferable that the resin component of the expanded aliphatic polyester resin beads is composed only of an aliphatic polyester resin. The higher the content of the aliphatic polyester resin in the resin component of the expanded aliphatic polyester resin beads, the more advantageous it is that soil pollution due to disposal of the resulting foamed molded article can be suppressed.

[0029] Examples of the aliphatic polyester resin include one or more selected from the group consisting of poly(3-hydroxyalkanoate) resins, polylactic acid, polyethylene succinate, polybutylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate polyethylene succinate adipate, polybutylene succinate adipate, polyethylene adipate terephthalate, polybutylene adipate terephthalate, polyethylene succinate terephthalate, polybutylene succinate terephthalate, polyethylene oxalate, polybutylene oxalate, polyneopentyl oxalate, polyethylene sebacate, polybutylene sebacate, polyhexamethylene sebacate, and polycaprolactone.

[0030] Among aliphatic polyester resins, poly(3-hydroxyalkanoate) resins are preferred because they are biodegradable in both soil and water. In other words, the resin component of the expanded aliphatic polyester resin particles preferably contains a poly(3-hydroxyalkanoate) resin.

[0031] The resin component of the expanded aliphatic polyester resin beads preferably contains more than 50% by weight of poly(3-hydroxyalkanoate) resin based on 100% by weight of the resin component. In this specification, expanded beads containing more than 50% by weight of "X" resin based on 100% by weight of the resin component may be referred to as "X resin expanded beads." For example, expanded beads containing more than 50% by weight of poly(3-hydroxyalkanoate) resin based on 100% by weight of the resin component may also be referred to as "poly(3-hydroxyalkanoate) resin expanded beads." The expanded aliphatic polyester resin beads are preferably poly(3-hydroxyalkanoate) resin expanded beads. This configuration has the advantage of being able to suppress (reduce) soil and marine pollution due to the disposal of foamed molded articles.

[0032] The resin component of the expanded aliphatic polyester resin beads preferably contains 60 wt% or more of poly(3-hydroxyalkanoate) resin, more preferably 70 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, even more preferably 95 wt% or more, and particularly preferably 100 wt% of the resin component, based on 100 wt% of the resin component. In other words, it is particularly preferable that the resin component of the expanded aliphatic polyester resin beads is composed solely of poly(3-hydroxyalkanoate) resin. A higher content of poly(3-hydroxyalkanoate) resin in the resin component of the expanded aliphatic polyester resin beads has the advantage of being able to suppress soil and / or marine pollution due to disposal of the resulting foamed molded articles.

[0033] (Poly(3-hydroxyalkanoate)-based resin) In this specification, "poly(3-hydroxyalkanoate)-based resin" may be referred to as "poly(3-hydroxyalkanoate)" or "P3HA." P3HA will be described below.

[0034] P3HA is a polymer having a 3-hydroxyalkanoate unit as an essential constituent unit (monomer unit). In this specification, "3-hydroxyalkanoate" may also be referred to as "3HA." Specifically, P3HA is preferably a polymer containing a repeating unit represented by the following general formula (1): [-CHR-CH ２ -CO-O-]... (1). In the general formula (1), R is C ｎ H ２ｎ＋１ where n is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. n is preferably 1 to 10, and more preferably 1 to 8.

[0035] As P3HA, P3HA produced by a microorganism is particularly preferred. P3HA produced by a microorganism is poly[(R)-3HA] in which all 3HA units are (R)-3HA.

[0036] P3HA preferably contains 3HA units (particularly repeating units of general formula (1)) in an amount of 50 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, of the total 100 mol% of repeating units of P3HA. Furthermore, the repeating units (monomer units) may be 3HA units only, or may contain, in addition to 3HA units, repeating units derived from monomers other than 3HA (e.g., 4-hydroxyalkanoate units, etc.).

[0037] Specific examples of 3HA units include 3-hydroxybutyrate units, 3-hydroxyvalerate units, and 3-hydroxyhexanoate units. 3-Hydroxybutyrate has a melting point and tensile strength close to those of propylene. Therefore, it is preferable that P3HA according to one embodiment of the present invention contains a 3-hydroxybutyrate unit. In this specification, "3-hydroxybutyrate" may also be referred to as "3HB."

[0038] P3HA preferably contains 3HB units (monomer units) in an amount of 80 mol% or more, and more preferably 85 mol% or more, of the total repeating units (100 mol%) of P3HA. As P3HA, a polymer containing 3HB units, in which all 3HB is (R)-3HB (a polymer produced by a microorganism) is particularly preferred.

[0039] When P3HA contains two or more types of repeating units, the monomer from which the repeating units other than the repeating unit with the largest content are derived is referred to as a comonomer. In this specification, a "repeating unit derived from a comonomer" may also be referred to as a "comonomer unit."

[0040] The comonomer is not particularly limited, but is preferably 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH) or 4-hydroxybutyrate (hereinafter sometimes referred to as 4HB).

[0041] Specific examples of P3HA include poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (hereinafter, may be referred to as "P3HB3HV"), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter, may be referred to as "P3HB3HH"), poly Examples of suitable poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (hereinafter, may be referred to as "P3HB4HB"). In particular, from the viewpoints of processability and the physical properties of foamed molded articles, poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) are preferred. In one embodiment of the present invention, the above-mentioned P3HA may be used alone or in combination of two or more.

[0042] It should be noted that "-co-X" is intended to include X units as comonomer units.

[0043] It is preferable that P3HA has a 3HB unit as an essential repeating unit (structural unit) and also has a comonomer unit. That is, P3HA is preferably a copolymer having a 3HB unit and a comonomer unit. A case where P3HA has a 3HB unit and a comonomer unit will be described. In this case, the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of all repeating units in P3HA is preferably 99 / 1 (mol% / mol%) to 80 / 20 (mol% / mol%), more preferably 97 / 3 (mol% / mol%) to 80 / 20 (mol% / mol%), and even more preferably 95 / 5 (mol% / mol%) to 85 / 15 (mol% / mol%). When the ratio of comonomer units in 100 mol% of all repeating units of P3HA is 1 mol% or more, the melt-kneadable temperature range and the thermal decomposition temperature range of P3HA are sufficiently separated, which has the advantage that the resulting expanded beads have excellent processability. On the other hand, if the ratio of the comonomer units to 100 mol% of all repeating units of P3HA is 20 mol% or less, the P3HA composition crystallizes quickly during melt-kneading, resulting in high productivity. P3HA having such a ratio of each monomer unit can be produced according to methods known to those skilled in the art, for example, the method described in International Publication WO 2009 / 145164.

[0044] The ratio of each monomer unit in P3HA can be determined by a method known to those skilled in the art, for example, the method described in WO 2013 / 147139.

[0045] In one embodiment of the present invention, the method for producing P3HA is not particularly limited, and may be a production method by chemical synthesis or a production method using a microorganism. Among these, a production method using a microorganism is preferred. Known methods can be applied to the production method of P3HA using a microorganism.

[0046] Specific examples of bacteria that produce copolymers of 3HB and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) is more preferred, in which P3HB3HH productivity has been improved by introducing genes encoding the P3HA synthase group. In the method for producing P3HA, microbial cells obtained by culturing microorganisms such as Alcaligenes eutrophus AC32 strain under appropriate conditions and allowing P3HB3HH to accumulate within the cells are preferably used. In addition to the copolymer-producing bacteria described above, genetically modified microorganisms into which various P3HA synthesis-related genes have been introduced may also be used depending on the P3HA to be produced. Furthermore, various culture conditions for the microorganisms (bacteria), including the type of substrate, may be optimized depending on the P3HA to be produced.

[0047] In one embodiment of the present invention, the method for culturing a microorganism that produces P3HA is not particularly limited, and for example, the method described in International Publication No. WO2019 / 142717 can be used.

[0048] The resin component of the expanded aliphatic polyester resin particles may contain a resin other than the aliphatic polyester resin, such as polypropylene, polyethylene, polystyrene, modified starch, or modified cellulose.

[0049] In addition to the resin component containing the aliphatic polyester resin, the expanded beads may contain additives, such as a crystal nucleating agent, a cell regulator, a crosslinking agent, a crosslinking aid, a blowing agent, a dispersant, and a dispersing aid, that may be used during the production of the aliphatic polyester resin particles and / or the expanded beads. The expanded beads may also contain other components that can be used in addition to the above, as long as they do not impair the effects of one embodiment of the present invention. Examples of other components 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 other component may be contained, or two or more types may be contained. The content of these other components can be appropriately determined by those skilled in the art depending on the intended use. Regarding the types and amounts of such additives, foam regulators, crosslinking agents, crosslinking aids, foaming agents, dispersants, dispersing aids, and other components, the types and amounts disclosed in WO 2021 / 002092 can be used as an example.

[0050] As the crosslinking agent, for example, an organic peroxide is preferred. By using a crosslinking agent in the process of producing aliphatic polyester resin particles and / or expanded beads, crosslinked expanded beads can be obtained. In other words, it is preferred that the expanded aliphatic polyester resin beads are crosslinked by an organic peroxide.

[0051] The organic peroxide used as a crosslinking agent preferably has a one-hour half-life temperature of 90°C to 160°C, more preferably 110°C to 160°C, even more preferably 110°C to 125°C, and particularly preferably 114°C to 124°C, although this will vary depending on the type of aliphatic polyester resin used. Specific examples of such organic peroxides include benzoyl peroxide (BPO, one-hour half-life temperature: 92°C), t-butylperoxy-2-ethylhexyl carbonate (TBEC, one-hour half-life temperature: 121°C), and 1,1-di(t-butylperoxy)cyclohexane (TBCH, one-hour half-life temperature: 116°C). The use of an organic peroxide with a one-hour half-life temperature of 90°C or higher has the advantage of tending to produce expanded beads with a desired gel fraction. On the other hand, when an organic peroxide having a one-hour half-life temperature of 160° C. or less is used, there is an advantage that unreacted crosslinking agent is less likely to remain in the final product.

[0052] When a crosslinking agent is used, the amount used is not particularly limited. The amount of crosslinking agent used may be appropriately determined based on the desired degree of crosslinking and closed cell content in the resulting expanded beads. Furthermore, the amount of crosslinking agent used is positively correlated with the gel fraction of the expanded beads and significantly affects the gel fraction value of the expanded beads. Therefore, it is also desirable to strictly determine the amount of crosslinking agent used taking into account the gel fraction of the resulting expanded beads.

[0053] The gel fraction of the expanded aliphatic polyester resin beads is preferably 30% by weight to 85% by weight, more preferably 50% by weight to 80% by weight, and even more preferably 60% by weight to 75% by weight, based on 100% by weight of the expanded beads. When the gel fraction of the expanded beads is (a) 30% by weight or more, based on 100% by weight of the expanded beads, there is an advantage that the molding temperature range of the expanded beads that can provide high-quality expanded molded articles when molding them into expanded articles is wide, thereby improving productivity, and when the gel fraction is (b) 85% by weight or less, there is an advantage that expanded molded articles with excellent internal fusion properties can easily be obtained at low molding pressures.

[0054] The present manufacturing method will be described below with reference to FIG. 1. FIG. 1 is a plan view showing an example of a molding apparatus used in the present manufacturing method. Note that the molding apparatus 10 shown in FIG. 1 is merely an example, and the molding apparatus used in the present manufacturing method is not limited to that shown in FIG. 1. For example, the molding apparatus may be equipped with conventionally known parts and equipment such as a drain restrictor (drain bypass). Specifically, the present manufacturing method is carried out by the steps shown below.

[0055] (i) A step (filling step) of filling a molding space 21 of a mold consisting of a fixed mold 11A and a movable mold 11B as shown in Fig. 1 with expanded aliphatic polyester resin particles through a filling machine 16. Fixed-side steam valves 12A and 12B, and fixed-side drain valves 13A and 13B are connected to the fixed mold 11A and the movable mold 11B, respectively. The fixed mold 11A and the movable mold 11B are also provided with conventionally known core vents or cut holes for passing steam through the molding space 21, but these are omitted from Fig. 1 .

[0056] (ii) A process (preheating process) in which the fixed side steam valve 12A and the fixed side drain valve 13A are opened, and the movable side steam valve 12B and the movable side drain valve 13B are opened, and steam is allowed to flow from the fixed side steam valve 12A and the movable side steam valve 12B, thereby expelling air present in the mold chambers 14A and 14B of the fixed mold 11A and the movable mold 11B and heating the entire mold.

[0057] (iii) The moving-side steam valve 12B, the fixed-side drain valve 13A, and the moving-side drain valve 13B are closed, and the steam pressure Pf is released through the fixed-side steam valve 12A. １ a step of heating the air present among the expanded aliphatic polyester resin particles filled in the molding space 21 and the expanded particles by supplying the water vapor of the above into the molding space 21 (one-side heating step).

[0058] (iv) Next, the moving-side steam valve 12B is opened and the fixed-side steam valve 12A is closed (the fixed-side drain valve 13A and the moving-side drain valve 13B are already closed). ２a step of heating the air and the foamed particles present among the expanded aliphatic polyester resin particles filled in the molding space 21 by supplying the water vapor of the above into the molding space 21 (reverse one-way heating step).

[0059] (v) The fixed side steam valve 12A is opened (the fixed side drain valve 13A and the movable side drain valve 13B are already closed). The water vapor pressure Pf ３ This step supplies steam into the molding space 21 to raise the temperature until the surfaces of the expanded aliphatic polyester resin beads filled in the molding space 21 are softened, thereby molding the expanded aliphatic polyester resin beads into a foamed molded article (double-sided heating step).

[0060] (vi) A process of spraying water from cooling water supply nozzles 15A, 15B (the nozzles shown in FIG. 1 are only a part of the nozzles) to cool the fixed mold 11A and the movable mold 11B, opening the molds, and removing the foam molded article (cooling and removal process).

[0061] In this manufacturing method, in both the one-way heating step (iii) and the reverse one-way heating step (iv), with both the fixed-side drain valve 13A and the movable-side drain valve 13B closed, the water vapor pressure Pf is applied through the fixed-side steam valve 12A or the movable-side steam valve 12B. １ or Pf ２ is supplied into the molding space 21. This makes it possible to produce a foamed molded article with excellent internal fusion.

[0062] In the one-way heating step (iii) and the reverse one-way heating step (iv), the steam valves through which the steam passes may be different from each other, and the steam may be supplied into the molding space 21 through a steam valve reverse to the steam valve described above. That is, in the one-way heating step (iii), the fixed side steam valve 12A, the fixed side drain valve 13A, and the movable side drain valve 13B are closed, and the steam pressure Pf １ In the reverse heating of (iv), the fixed side steam valve 12A is opened, the moving side steam valve 12B is closed, and the steam pressure Pf ２The water vapor may be supplied into the molding space 21.

[0063] <2-1. Filling Step> The filling step of this manufacturing method is a step of filling a molding space consisting of a fixed mold connected to a fixed steam valve and a fixed drain valve, and a movable mold connected to a movable steam valve and a movable drain valve, with expanded aliphatic polyester resin particles. The method for filling the expanded aliphatic polyester resin particles into the molding space may be, for example, using a filling machine connected to the fixed mold.

[0064] In the filling process, the fixed mold and the movable mold are closed to form a molding space, and then aliphatic polyester resin foam particles are filled. However, to improve filling properties, a gap (cracking) large enough to prevent leakage of the foam particles during mold closing may be intentionally left, and the mold may be completely closed after filling with the foam particles. This allows the foam particles to be filled while the air used during filling is discharged through the gap between the fixed mold and the movable mold, which tends to improve filling properties. The gap size (cracking amount) in this case is preferably 1% to 40% of the foam molded body size in the mold opening (mold closing) direction of the foam molded body to be in-mold foam-molded, and more preferably 2% to 35%. Furthermore, when filling with the foam particles, the internal pressure of the foam particles may be increased to above atmospheric pressure using a conventional method, or the foam particles may be used at atmospheric pressure. The foam particles may be filled using, for example, a filling machine.

[0065] <2-2. One-side heating step> In the one-side heating step of this manufacturing method, with both the fixed-side drain valve and the moving-side drain valve closed, a steam pressure Pf １ This is a step of supplying water vapor into the molding space. This makes it possible to provide a foamed molded article with excellent internal fusion.

[0066] Water vapor pressure Pf １ The value of Pf is not particularly limited as long as it is greater than 0. １ The value of 0 MPa (G) < Pf １≦0.07 MPa (G), and 0 MPa (G) < Pf １ It is more preferable that Pf≦0.06 MPa(G), and 0 MPa(G)<Pf １ It is more preferable that Pf≦0.05 MPa(G), and 0 MPa(G)<Pf １ It is more preferable that Pf≦0.04 MPa(G), and 0.01 MPa(G)≦Pf １ ≦0.03 MPa(G), and more preferably 0.02 MPa(G)≦Pf １ It is particularly preferable that the water vapor pressure Pf is ≦0.03 MPa (G). １ When the water vapor pressure Pf is 0.07 MPa (G) or less, the foamed particles near the surface (the surface in contact with the mold) do not fuse together in the early stages of molding, which has the advantage that the foamed particles can be heated to the inside. As a result, a foamed molded article with excellent internal fusion properties can be obtained. １ When the water vapor pressure Pf is 0.04 MPa (G) or less, it is particularly advantageous that the internal foam particles can be heated. As a result, a foamed molded article with even better internal fusion properties can be obtained. １ When the pressure is 0.02 MPa (G) or more, it has the advantage that the internal foam particles can be heated. As a result, a foamed molded article with even better internal fusion properties can be obtained. In this specification, "(G)" indicates that the pressure unit is "gauge pressure."

[0067] The heating step time is not particularly limited, but is preferably 3 to 20 seconds, more preferably 4 to 15 seconds, even more preferably 5 to 13 seconds, and particularly preferably 5 to 10 seconds. When the heating step time is within the above-mentioned range, the expanded beads can be heated sufficiently. As a result, a foamed molded article with excellent surface and internal fusion properties can be obtained.

[0068] <2-3. Reverse one-way heating step> In the reverse one-way heating step of this manufacturing method, with both the fixed-side drain valve and the moving-side drain valve closed, a steam pressure Pf ２This is a step of supplying water vapor into the molding space. This makes it possible to provide a foamed molded article with excellent internal fusion.

[0069] Water vapor pressure Pf ２ The value of Pf is not particularly limited as long as it is greater than 0. ２ The value of 0 MPa (G) < Pf ２ ≦0.07 MPa (G), and 0 MPa (G) < Pf ２ It is more preferable that Pf≦0.06 MPa(G), and 0 MPa(G)<Pf ２ It is more preferable that Pf≦0.05 MPa(G), and 0 MPa(G)<Pf ２ It is more preferable that Pf≦0.04 MPa(G), and 0.01 MPa(G)≦Pf ２ ≦0.03 MPa(G), and more preferably 0.02 MPa(G)≦Pf ２ It is particularly preferable that the water vapor pressure Pf is ≦0.03 MPa (G). ２ When the water vapor pressure Pf is 0.07 MPa (G) or less, the foamed particles on the surface (the surface in contact with the mold) do not fuse together in the early stages of molding, which has the advantage that the foamed particles inside can be heated as well. As a result, a foamed molded article with excellent internal fusion properties can be obtained. ２ When the water vapor pressure Pf is 0.04 MPa (G) or less, it is particularly advantageous that the internal foam particles can be heated. As a result, a foamed molded article with even better internal fusion properties can be obtained. ２ When the water vapor pressure Pf is 0.02 MPa (G) or more, it has the advantage that the internal foam particles can be heated. As a result, a foamed molded article having even better internal fusion properties can be obtained. １ and Pf ２ may be the same or different.

[0070] The duration of the one-way heating step is not particularly limited, but is preferably 3 to 20 seconds, more preferably 4 to 15 seconds, even more preferably 5 to 13 seconds, and particularly preferably 5 to 10 seconds. When the duration of the one-way heating step is within the above-mentioned range, the expanded beads can be heated sufficiently. As a result, a foamed molded article with excellent surface and internal fusion properties can be obtained.

[0071] The duration of the reverse one-way heating step is preferably the same as or shorter than the duration of the one-way heating step. This configuration has the advantage that the foamed particles inside can be sufficiently heated. As a result, a foamed molded article with excellent internal fusion properties can be obtained.

[0072] <2-3. Double-sided heating step> In the double-sided heating step of the present manufacturing method, with both the fixed-side drain valve and the moving-side drain valve closed, a water vapor pressure Pf ３ This is a process of supplying water vapor into the molding space.

[0073] Water vapor pressure Pf ３ The value of Pf is not particularly limited as long as it is greater than 0. ３ The value of 0.05 MPa (G) ≦ Pf ３ ≦0.30 MPa(G), and preferably 0.08 MPa(G)≦Pf ３ ≦0.25 MPa(G), and more preferably 0.10 MPa(G)≦Pf ３ It is more preferable that Pf≦0.23 MPa(G), and 0.13 MPa(G)≦Pf ３ It is particularly preferable that the water vapor pressure Pf is ≦0.20 MPa (G). ３ When the water vapor pressure Pf is 0.05 MPa (G) or more, there is an advantage that a molded product having excellent fusion properties can be obtained. ３ When the water vapor pressure Pf is 0.30 MPa (G) or less, there is an advantage that the surface properties of the obtained molded body are not deteriorated. ３ is Pf １ and / or Pf ２ may be the same as or different from.

[0074] Water vapor pressure Pf １ The value of water vapor pressure Pf ３The quotient obtained by dividing by the value of is preferably greater than 0 and less than 0.50, more preferably greater than 0 and 0.40 or less, even more preferably 0.05 to 0.30, and particularly preferably 0.10 to 0.25. This configuration has the particular advantage that it is possible to heat the foamed particles even to the interior. As a result, a foamed molded article with even better internal fusion properties can be obtained.

[0075] Water vapor pressure Pf ２ The value of water vapor pressure Pf ３ The quotient obtained by dividing by the value of is preferably greater than 0 and less than 0.50, more preferably greater than 0 and 0.40 or less, even more preferably 0.05 to 0.30, and particularly preferably 0.10 to 0.25. This configuration has the particular advantage that it is possible to heat the foamed particles even to the interior. As a result, a foamed molded article with even better internal fusion properties can be obtained.

[0076] Conventionally, water vapor pressure Pf １ and water vapor pressure Pf ２ is the water vapor pressure Pf ３ or the water vapor pressure Pf １ and Pf ２ The values ​​of these are the water vapor pressure Pf ３ On the other hand, in the course of intensive research, the inventor has found that in addition to performing one-way heating and reverse one-way heating with both drain valves closed, the water vapor pressure Pf １ and water vapor pressure Pf ２ The value of water vapor pressure Pf ３ Surprisingly, we have independently obtained the novel finding that by setting the water vapor pressure Pf to a value less than half the value of Pf, it is possible to provide a foamed molded article with superior internal fusion properties. １ or water vapor pressure Pf ２ The value of water vapor pressure Pf ３ When the quotient obtained by dividing by the value of Pf is within the above-mentioned range, the water vapor pressure Pf １ or water vapor pressure Pf ２ Since the value of can be set low, there is also the advantage that production costs can be kept low.

[0077] The duration of the double-sided heating step is not particularly limited, but is preferably 1 to 60 seconds, more preferably 2 to 45 seconds, and even more preferably 3 to 30 seconds. When the duration of the double-sided heating step is 1 second or longer, it has the advantage of obtaining a molded product with superior fusion properties. When the duration of the double-sided heating step is 60 seconds or shorter, it has the advantage of obtaining a molded product with superior fusion properties and surface properties.

[0078] 1, in one embodiment of the present invention, the manufacturing method may include a one-sided heating step, an opposite one-sided heating step, a preheating step carried out before or after the double-sided heating step, a cooling and removal step, etc. In addition, the method may include a conventionally known step, such as a heat retention step (steaming step) in which the fixed-side steam valve and the movable-side steam valve are closed after the double-sided heating step.

[0079] The water vapor pressure, duration, and the like in the preheating step, the cooling and removal step, and the like, which are performed before and after the double-sided heating step, can be determined as appropriate. For example, the water vapor pressure in the preheating step may be 0.01 to 0.04 MPa (G), and the heating time may be 1 to 30 seconds. The temperature of the water sprayed in the cooling and removal step may be 1 to 60°C, and the cooling time may be 1 to 500 seconds.

[0080] [3. Foam Molded Article] The present manufacturing method can produce a foam molded article (hereinafter referred to as "the present foam molded article") made from an aliphatic polyester resin. Because the present foam molded article is manufactured by the present manufacturing method, it has excellent internal fusion properties.

[0081] The internal fusion property of the foamed molded article can be evaluated by the method described in the Examples below. The internal fusion property of the foamed molded article is preferably greater than 70%, more preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more. There is no particular upper limit for the internal fusion property of the foamed molded article, and 100% is most preferred.

[0082] In one embodiment of the present invention, the present foam molded article preferably includes a molded portion having a thickness of 40 mm to 500 mm. More preferably, the present foam molded article includes a molded portion having a thickness of 50 mm to 500 mm. Furthermore, in one embodiment of the present invention, the present foam molded article may be a foam molded article having an item storage space and a partition portion that divides the item storage space. In other words, the present foam molded article may be a molded article having a portion with a T-shaped cross section. An example of such a foam molded article is a foam molded article 1 having a shape as shown in FIG. 2. The shape shown in FIG. 2 is also the shape of a foam molded article produced in the Examples of the present application. In the foam molded article 1 shown in FIG. 2, the thickness of the bottom portion 3 is 50 mm. Furthermore, the foam molded article 1 shown in FIG. 2 has a partition portion 4, i.e., a portion with a T-shaped cross section.

[0083] When a foam molded article including a molded portion having a thickness of 40 mm to 500 mm (sometimes referred to as a "thick portion"), such as the foam molded article 1 shown in Figure 2, is produced by a conventional manufacturing method, it has been difficult to achieve a sufficient level of internal fusion (for example, a value greater than 70%), particularly in the thick portion (bottom portion 3). However, according to the present manufacturing method, a foam molded article having excellent internal fusion in the thick portion (bottom portion 3) can be obtained, and therefore, by forming the foam molded article into the shape described above, the effects of the present manufacturing method can be fully obtained.

[0084] The foamed molded article may have a shape other than that shown in Fig. 2, for example, one or more handles, or may have additional partitions, ribs, grooves, or irregularities on the inner wall surface. Furthermore, the thickness of the vertical wall, bottom, partition, etc. may be partially changed, or a notch may be provided on the side or bottom surface, or any other known shape may be used.

[0085] The foamed molded article can be suitably used, for example, as a cushioning material for packaging (e.g., cushioning material for packaging home appliances such as refrigerators, freezers, air conditioner bodies and their outdoor units, washing machines, air purifiers, humidifiers, rice cookers, microwave ovens, ovens, toasters, electric fans, and storage battery units; cushioning material for packaging automotive goods such as transmissions, roofs, hoods, doors, batteries, and engines), logistics materials (e.g., agricultural product boxes, fish boxes, etc.), heat insulating materials, civil engineering and construction components, and automotive components (e.g., toolboxes, bulkheads, seat cores, bumper cores, tibia pads, door trims, etc.). Among these, when the foamed molded article has a partition (having a portion with a T-shaped cross section), it is preferably used as a cushioning material for packaging, logistics materials, and automotive components because of its excellent durability and surface properties.

[0086] An embodiment of the present invention may have the following configuration.

[0087] [1] A filling step of filling a molding space formed by a fixed mold having a fixed-side steam valve and a fixed-side drain valve, and a movable mold having a movable-side steam valve and a movable-side drain valve with aliphatic polyester resin foamed particles, and a step of supplying a water vapor pressure Pf through the fixed-side steam valve or the movable-side steam valve while the fixed-side drain valve and the movable-side drain valve are closed. １ a one-side heating step in which steam of a pressure Pf is supplied into the molding space while the fixed-side drain valve and the movable-side drain valve are closed, and a steam pressure Pf is supplied through the steam valve that was not used in the one-side heating step among the fixed-side steam valve and the movable-side steam valve. ２ a reverse heating step of supplying steam of a pressure Pf into the molding space, and a step of supplying steam of a pressure Pf through the fixed side steam valve and the movable side steam valve with the fixed side drain valve and the movable side drain valve closed. ３ and a double-sided heating step of supplying the water vapor of the above formula (1) into the molding space.

[0088] [2] In the one heating step, 0 MPa (G) < Pf １ The method for producing a foamed molded article according to [1], wherein the compressive strength is ≦0.04 MPa (G).

[0089] [3] In the reverse one-way heating step, 0 MPa (G) < Pf ２ The method for producing a foamed molded article according to [1] or [2], wherein the compressive strength is ≦0.04 MPa (G).

[0090] [4] In the double-sided heating step, 0.05 MPa (G)≦Pf ３ The method for producing a foamed molded article according to any one of [1] to [3], wherein the compressive strength is ≦0.30 MPa (G).

[0091] [5] The method for producing a foam molded article according to any one of [1] to [4], wherein the foam molded article includes a molded portion having a thickness of 40 mm to 500 mm.

[0092] [6] The method for producing a foamed molded article according to any one of [1] to [5], wherein the expanded aliphatic polyester resin particles are expanded poly(3-hydroxyalkanoate) resin particles.

[0093] [7] The water vapor pressure Pf １ The value of the water vapor pressure Pf ３ [7] The method for producing a foamed molded article according to any one of [1] to [6], wherein the quotient obtained by dividing by the value of

[0094] [8] The water vapor pressure Pf ２ The value of the water vapor pressure Pf ３ [8] The method for producing a foamed molded article according to any one of [1] to [7], wherein the quotient obtained by dividing by the value of

[0095] [9] In the one heating step, 0 MPa (G) < Pf １ ≦0.04 MPa (G), and in the reverse one-way heating step, 0 MPa (G) < Pf ２ ≦0.04 MPa (G), and in the double-sided heating step, 0.05 MPa (G) ≦ Pf ３ The method for producing a foamed molded article according to any one of [1] to [8], wherein the compressive strength is ≦0.30 MPa (G).

[0096]

[10] The method for producing a foam molded article according to any one of [1] to [9], wherein the foam molded article has an internal fusion property of more than 70%.

[0097] Hereinafter, one embodiment of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto. One embodiment of the present invention can be carried out by appropriately modifying the following examples within the scope of the above and below-described aims. All embodiments carried out by appropriately modifying the following examples are included within the technical scope of the present invention.

[0098] [Materials] The materials used in the examples and comparative examples are shown below.

[0099] (Aliphatic polyester resin) P3HA: The P3HA is P3HB3HH (the monomer ratio is 3HB / 3HH=95 / 5 (mol% / mol%), and the melting point is 145.0°C), and was produced in accordance with the method described in paragraphs

[0064] to

[0125] of International Publication WO2009 / 145164.

[0100] (Nucleating agent) Pentaerythritol (Neuraizer P manufactured by Mitsubishi Chemical Corporation) (Lubricant) Behenic acid amide (manufactured by Tokyo Chemical Industry Co., Ltd.) Erucic acid amide (manufactured by Tokyo Chemical Industry Co., Ltd.) (Foaming agent) Talc (Talc Powder PKS manufactured by Hayashi Chemical Industry Co., Ltd.) (Crosslinking agent (organic peroxide)) 1,1-di(t-butylperoxy)cyclohexane (TBCH: Perhexa C manufactured by NOF Corporation) (Foaming agent) Carbon dioxide (manufactured by Air Water Inc.) (Dispersing agent) Tricalcium phosphate (manufactured by Taihei Chemical Industry Co., Ltd., specific gravity 3.1 / pH 6) (Dispersing aid) Sodium alkanesulfonate (Latemul PS manufactured by Kao Corporation) (Cleaning agent) Sodium hexametaphosphate (manufactured by Taihei Chemical Industry Co., Ltd.).

[0101] [Measurement and Evaluation Methods] The measurement and evaluation methods carried out in the examples and comparative examples will be explained below.

[0102] (Measurement of apparent density of expanded beads) The apparent density of expanded beads was measured by the following methods (1) to (3): (1) A measuring cylinder containing ethanol was prepared, and expanded beads with a weight Wd (g) were submerged in the ethanol; (2) The volume of the expanded beads read from the rise in the water level of the ethanol was determined as Vd (cm ３(3) The apparent density of the expanded beads was calculated by the following formula: Apparent density of expanded beads (g / cm ３ )=Wd / Vd.

[0103] (Calculation of Expansion Ratio of Expanded Beads) The density of unexpanded P3HB3HH before expansion was 1.2 g / cm ３ Therefore, the expansion ratio of the expanded beads was calculated by the following formula: Expansion ratio (times) of expanded beads = 1.2 / apparent density of expanded beads.

[0104] (Fusion property of foam molded article) The shape of the foam molded article 1 obtained in this example is shown in Figure 2. The foam molded article 1 has a box-like shape with a partition (external dimensions: length 730 mm x width 800 mm x height 110 mm, thickness of the upright wall 2 and partition 4 20 mm, thickness of the bottom 3 50 mm).

[0105] The evaluation of fusion properties was carried out according to the following (1) to (4): (1) An incision was made with a cutter in the thickness direction of the bottom 3 (direction perpendicular to the outer bottom surface) on the outer bottom surface of the foam molded article 1 (the outer surface of the bottom 3 that was in contact with the fixed mold and the filling machine) with a length (depth) of 1 / 20 to 1 / 10 of the thickness of the bottom 3 (50 mm); (2) The foam molded article was then broken by hand along the incision; (3) The portion of the resulting fracture surface excluding the incision (observation surface) was visually observed, and the portion from the movable mold side surface (the inner surface of the bottom 3 that was in contact with the movable mold, also known as the "inner bottom surface") to 10 mm in the thickness direction of the bottom 3 was observed as surface fusion, and the portion from the movable mold side surface to 10 mm in the thickness direction of the bottom 3 was observed as internal fusion. The total number of expanded beads present within each observation surface of the surface fusion evaluation section and the internal fusion evaluation section, and the number of expanded beads that were broken within the observation surface other than at the boundary between the expanded beads (i.e., expanded beads in which the expanded beads themselves were broken), were counted; (4) the respective fusion rates were calculated based on the following formula: Fusion rate (%) = (number of expanded beads that were broken within the observation surface other than at the boundary between the expanded beads / total number of expanded beads present within the observation surface) × 100.

[0106] Examples 1 to 4, Comparative Examples 1 to 4 Preparation of Expanded Beads (Expanded P3HA Resin Beads) (1) Preparation of P3HA Resin Beads 100 parts by weight of P3HA resin, 1.0 part by weight of pentaerythritol, 0.50 parts by weight of behenamide, 0.50 parts by weight of erucamide, and 0.10 parts by weight of talc were weighed and dry-blended to prepare a P3HA resin composition. The prepared P3HA resin composition was fed into a twin-screw extruder (TEM-26SX manufactured by Toshiba Machine Co., Ltd.), and melt-kneaded at a cylinder temperature of 130°C to 160°C (melt-kneading step). The melt-kneaded P3HA resin composition at 179°C was extruded from the nozzle of a die attached to the tip of the extruder. The extruded P3HA-based resin composition was cooled with water at 50°C and then cut into cylindrical P3HA-based resin particles each weighing 3.5 mg and having a length / diameter ratio of 2.0 (resin particle molding step). The P3HA-based resin particles had a melting point of 145.0°C.

[0107] (2) Preparation of P3HA-Based Expanded Resin Beads 100 parts by weight (2.5 kg) of the resulting P3HA-based resin particles, 200 parts by weight of pure water as an aqueous dispersion medium, 2.0 parts by weight of 1,1-di(t-butylperoxy)cyclohexane (TBCH) as a crosslinking agent (organic peroxide), 1.0 part by weight of tricalcium phosphate as a dispersant, and 0.05 parts by weight of sodium alkanesulfonate as a dispersing aid were supplied to a pressure-resistant vessel with an internal volume of 10 L and equipped with a stirring blade. The stirring blade was rotated at 260 rpm to stir the raw materials in the pressure-resistant vessel. Thereafter, the contents (dispersion) in the pressure-resistant vessel were continuously stirred until the release of the dispersion was completed.

[0108] Nitrogen was introduced into the pressure vessel, and then evacuation was performed to remove oxygen from the pressure vessel. Furthermore, carbon dioxide was supplied as a blowing agent into the pressure vessel to prepare a dispersion (dispersion step). The temperature inside the pressure vessel was then raised to a foaming temperature of 129.0°C. Further, carbon dioxide was supplied to the pressure vessel to raise the pressure inside the pressure vessel to a foaming pressure of 3.3 MPa (gauge pressure) (temperature-pressure increase step). Next, the temperature and pressure inside the pressure vessel were maintained near the foaming temperature and foaming pressure, respectively, for 30 minutes (holding step). After the holding step, the valve at the bottom of the pressure vessel was opened, and the dispersion inside the pressure vessel was released into atmospheric pressure through an orifice with a diameter of 3.6 mm, yielding expanded P3HA resin particles (release step).

[0109] The resulting expanded beads were washed with an aqueous solution of sodium hexametaphosphate and water to remove the dispersant and other substances adhering to the surface of the expanded beads, and then dried at 75°C. The resulting expanded beads had a length / diameter ratio of 1.0 and a spherical or nearly spherical shape. The resulting expanded beads had a gel fraction of 67% by weight and an apparent density of 0.076 g / cm. ３ (Expansion ratio: 16 times).

[0110] <Molding of foam molded article> Molds (fixed mold and movable mold) capable of producing a box-shaped foam molded article 1 having a partition (external dimensions: length 730 mm × width 800 mm × height 110 mm, thickness of upright wall 2 and partition 4 20 mm, thickness of bottom 3 50 mm) were mounted on a molding machine (DABO DPM-1300). Using this molding machine, a foam molded article (in-mold foam molded article) was obtained as follows. The molds were mounted on the molding machine so that the outer bottom surface of the foam molded article 1 was molded by the fixed mold. Furthermore, the in-mold foam molding was performed such that the mold opening and closing directions of the fixed mold and the movable mold were horizontal to the ground, and the height direction of the box-shaped foam molded article 1 was horizontal.

[0111] (1) A mold consisting of a fixed mold and a movable mold was opened and then closed until the mold gap in the mold opening / closing direction became 7 mm.

[0112] (2) The expanded beads were impregnated with pressurized air in a pressure vessel, and the internal pressure was adjusted to 0.17 MPa (absolute pressure). The expanded beads were then filled into the molding space of the mold through a filling machine 16 without flowing out of the mold system (filling step). The positional relationship between the filling machine and the fixed mold was the same as that shown in Figure 2.

[0113] (3) The mold was closed so that the mold gap was 0 mm.

[0114] (4) A preheating step was carried out for 6 seconds with steam at 0.03 MPa (gauge pressure) from the fixed side steam valve and 0.03 MPa (gauge pressure) from the moving side steam valve.

[0115] (5) Steam pressure Pf listed in Table 1 from the fixed side steam valve １ The one-sided heating step was carried out for 5 seconds with steam at a pressure of 1000 (gauge pressure). The open / close states of the fixed-side drain valve and the movable-side drain valve at this time are also shown in Table 1.

[0116] (6) Steam pressure Pf from the moving side steam valve to the water vapor pressure Pf listed in Table 1 ２ The inverse heating step was carried out for 5 seconds with steam at a pressure of 1000 psi (gauge pressure). The open / closed states of the fixed-side drain valve and the movable-side drain valve at this time are also shown in Table 1.

[0117] (7) From the fixed side steam valve and the moving side steam valve, the water vapor pressure Pf listed in Table 1 ３ The double-sided heating step was carried out for 15 seconds with steam of 1000 kJ / min. The open / close states of the fixed-side drain valve and the movable-side drain valve at this time are also shown in Table 1.

[0118] (8) Water was sprayed from the cooling water supply nozzle for 180 seconds to cool the fixed mold and the movable mold, and then the molds were opened and the foam molded articles were removed (cooling and removal step). The surface fusion property and internal fusion property of each foam molded article were measured according to the methods described above. The results are shown in Table 1.

[0119] One embodiment of the present invention can be suitably used for a variety of applications, such as food containers, packaging materials, sanitary products, automotive components (particularly toolboxes, etc.), cushioning materials for packaging (particularly for home appliances), agricultural product boxes, fish boxes, logistics materials, heat insulating materials, and civil engineering and construction components.

[0120] REFERENCE SIGNS LIST 1 foam molded body 2 standing wall portion 3 bottom portion 4 partition portion 10 molding device 11A fixed mold 11B movable mold 12A fixed side steam valve 12B movable side steam valve 13A fixed side drain valve 13B movable side drain valve 14A, 14B mold chamber 15A, 15B cooling water supply nozzle 16 filling machine 21 molding space

Claims

1. a filling step of filling a molding space formed by a fixed mold having a fixed-side steam valve and a fixed-side drain valve and a movable mold having a movable-side steam valve and a movable-side drain valve with aliphatic polyester-based resin foamed particles; With the fixed-side drain valve and the movable-side drain valve closed, a water vapor pressure Pf is applied through the fixed-side steam valve or the movable-side steam valve. １ a one-way heating step of supplying water vapor into the molding space; With the fixed-side drain valve and the movable-side drain valve closed, a water vapor pressure Pf is applied through the steam valve that was not used in the one-side heating step among the fixed-side steam valve and the movable-side steam valve. ２ a one-way heating step of supplying the steam into the molding space; With the fixed-side drain valve and the movable-side drain valve closed, a water vapor pressure Pf is applied through the fixed-side steam valve and the movable-side steam valve. ３ and a double-sided heating step of supplying steam into the molding space, In the one-side heating step, 0 MPa (G) < Pf 1 ≦ 0.04 MPa (G), In the one-way heating step, 0 MPa (G) < Pf 2 ≦ 0.04 MPa (G), The method for producing a foamed molded article, wherein in the double-side heating step, 0.05 MPa(G)≦Pf 3 ≦0.30 MPa(G).

2. The method for producing a foam molded article according to claim 1, wherein the foam molded article includes a molded portion having a thickness of 40 mm to 500 mm.

3. 2. The method for producing a foamed molded article according to claim 1, wherein the expanded aliphatic polyester resin particles are expanded poly(3-hydroxyalkanoate) resin particles.

4. The water vapor pressure Pf １ The value of the water vapor pressure Pf ３ The method for producing a foamed molded article according to claim 1, wherein the quotient obtained by dividing the value of

5. The water vapor pressure Pf ２ The value of the water vapor pressure Pf ３ The method for producing a foamed molded article according to claim 1, wherein the quotient obtained by dividing the value of

6. The method for producing a foam molded article according to any one of claims 1 to 5, wherein the foam molded article has an internal fusion property of more than 70%.