Method for producing aliphatic polyester foamed particles

Abstract

The present invention addresses the problem of providing novel aliphatic polyester-based foamed particles having a low apparent density. The problem is solved by a method for producing aliphatic polyester-based foamed particles, the method comprising: a dispersion step for dispersing aliphatic polyester-based resin particles and a foaming agent in an aqueous dispersion medium in a container; and a release step in which one end of the container is opened, and the dispersion liquid in the container is released to a region having a pressure lower than that in the container and having a specific temperature and water vapor amount.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing aliphatic polyester-based foamed particles. Background Art

[0002] Plastics derived from petroleum are discarded in large quantities every year, and the shortage of landfill sites and environmental pollution caused by these large amounts of waste have become serious problems. In addition, in recent years, microplastics have become a major problem in the marine environment. Therefore, biodegradable plastics that are decomposed by the action of microorganisms in (a) environments such as the sea and soil, and (b) landfills and composts have attracted attention.

[0003] For the purpose of widespread application to (a) materials for the agricultural, forestry, and fisheries industries used in the environment, and (b) food containers, packaging materials, sanitary products, garbage bags, etc. that are difficult to recycle and reuse after use, the development of biodegradable plastics is underway. In addition, the use of foams made of biodegradable plastics is expected in packaging cushioning materials, agricultural boxes, fish boxes, automotive components, building materials, civil engineering materials, etc.

[0004] From the viewpoints of excellent biodegradability and carbon neutrality, among the above biodegradable plastics, poly(3-hydroxyalkanoate) (hereinafter sometimes referred to as "P3HA"), which is a plastic derived from plant raw materials, has attracted attention.

[0005] Heretofore, the development of technologies for biodegradable plastics has been actively carried out. For example, the technologies described in Patent Documents 1 and 2 are known.

[0006] In addition, as a technology for polyethylene-based resin foamed particles, the technology described in Patent Document 3 is also known.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: WO2019 / 146555

[0010] Patent Document 2: WO2021 / 002092

[0011] Patent Document 3: WO2016 / 147775 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] Here, in the case of foamed particles, a low apparent density is sometimes required depending on their use.

[0014] In view of the above-described circumstances, an object of an embodiment of the present invention is to provide a new method for manufacturing aliphatic polyester-based expanded particles, which can provide aliphatic polyester-based expanded particles having a low apparent density.

[0015] Means for Solving the Problem

[0016] That is, the method for manufacturing aliphatic polyester-based expanded particles according to an embodiment of the present invention includes: a dispersion step of dispersing aliphatic polyester-based resin particles containing an aliphatic polyester-based resin and a foaming agent in an aqueous dispersion medium; and a release step of opening one end of the container and releasing the dispersion liquid in the container to a region where the pressure is lower than the pressure in the container, the temperature of the region being 65°C to 95°C and the amount of water vapor being 144 g / m 3 ~502 g / m 3 .

[0017] In addition, the aliphatic polyester-based expanded particles according to an embodiment of the present invention are (i) containing an aliphatic polyester-based resin; (ii) not containing a plasticizer, or containing more than 0 part by weight and 4 parts by weight or less of the plasticizer relative to 100 parts by weight of the aliphatic polyester-based resin; (iii) having a gel fraction of 60% by weight or more; and (iv) having an apparent density of 64 g / L or less.

[0018] In addition, the aliphatic polyester-based expanded molded article according to an embodiment of the present invention is (i) containing an aliphatic polyester-based resin; (ii) not containing a plasticizer, or containing more than 0 part by weight and 4 parts by weight or less of the plasticizer relative to 100 parts by weight of the aliphatic polyester-based resin; (iii) having a gel fraction of 50% by weight or more; and (iv) having a density of 44 g / L or less.

[0019] Effects of the Invention

[0020] According to one aspect of the present invention, it is possible to provide a new aliphatic polyester-based expanded particle having a low apparent density. Detailed Embodiments

[0021] The following describes an embodiment of the present invention, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications can be made within the scope shown in the claims. In addition, 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. It should be noted that all the academic literatures and patent literatures described in this specification are incorporated herein by reference. In addition, unless otherwise specified in this specification, the numerical range "A to B" means "A or more (including A and greater than A) and B or less (including B and less than B)".

[0022] In this specification, the repeating unit derived from the X monomer is sometimes referred to as "X unit". The repeating unit may also be referred to as a structural unit.

[0023] In this specification, the "method for producing aliphatic polyester-based foamed particles" is sometimes referred to as the "production method", and the "method for producing aliphatic polyester-based foamed particles according to an embodiment of the present invention" is sometimes referred to as the "present production method". In this specification, the "aliphatic polyester-based resin particles" are sometimes referred to as "resin particles", the "aliphatic polyester-based foamed particles" are sometimes referred to as "foamed particles", the "aliphatic polyester-based foamed particles according to an embodiment of the present invention" are sometimes referred to as the "present foamed particles", the "aliphatic polyester-based foamed molded article" is sometimes referred to as the "foamed molded article", and the "aliphatic polyester-based foamed molded article according to an embodiment of the present invention" is sometimes referred to as the "present foamed molded article".

[0024] 〔1. Technical idea of an embodiment of the present invention〕

[0025] The present inventors conducted intensive research to obtain aliphatic polyester-based foamed particles having a low apparent density by a hitherto unknown new method. In particular, the present inventors focused on the specific conditions in the method for producing aliphatic polyester-based foamed particles, rather than the materials and compositions used to produce the aliphatic polyester-based foamed particles.

[0026] As a result of intensive research, the present inventors independently found that: in the step of releasing a dispersion liquid in which aliphatic polyester-based resin particles are dispersed in a container to a region having a pressure lower than that in the container, by setting the temperature and the amount of water vapor in this region within a specific range, it is surprisingly possible to reduce the apparent density of the obtained aliphatic polyester-based foamed particles, thereby completing the present invention.

[0027] 〔2. Method for producing aliphatic polyester-based foamed particles〕

[0028] A method for manufacturing aliphatic polyester-based expanded particles according to an embodiment of the present invention includes: a dispersion step of dispersing aliphatic polyester-based resin particles containing an aliphatic polyester-based resin and a foaming agent in an aqueous dispersion medium; and a release step of opening one end of the container and releasing the dispersion liquid in the container to a region where the pressure is lower than the pressure in the container, the temperature of the region being 65°C to 95°C and the amount of water vapor being 144 g / m 3 ~502 g / m 3 .

[0029] Due to the above configuration, this manufacturing method has the advantage of being able to provide aliphatic polyester-based expanded particles with a low apparent density.

[0030] In addition, in this manufacturing method, an aliphatic polyester-based resin, which is a biodegradable resin, is used. Therefore, the obtained expanded particles and the expanded molded article formed from the expanded particles can suppress soil pollution caused by waste. Thus, for example, it can contribute to the achievement of sustainable development goals (SDGs) such as Goal 12, "Ensure sustainable consumption and production patterns". Furthermore, in the case of an aliphatic polyester-based resin containing a P3HA-based resin that has not only soil degradability but also marine degradability, the obtained expanded particles and the expanded molded article formed from the expanded particles can suppress not only soil pollution caused by waste but also marine pollution. Thus, for example, in addition to Goal 12, "Ensure sustainable consumption and production patterns", it can also contribute to the achievement of the sustainable development goal (SDG) of Goal 14, "Conserve and sustainably use the oceans, seas and marine resources for sustainable development".

[0031] Hereinafter, after explaining the materials (raw materials) in this manufacturing method, each step will be explained.

[0032] (2-1. Aliphatic polyester-based resin particles)

[0033] (Aliphatic polyester-based resin)

[0034] The resin particles contain an aliphatic polyester resin as a resin component. Specific examples of the aliphatic polyester resin include poly(3-hydroxyalkanoate) resins, polylactic acid, polybutylene succinate, polybutylene adipate succinate, polybutylene terephthalate adipate, polybutylene terephthalate succinate, polycaprolactone, etc. Among the aliphatic polyester resins, a poly(3-hydroxyalkanoate) resin having marine degradability in addition to soil degradability is preferred. In other words, the aliphatic polyester resin preferably contains a poly(3-hydroxyalkanoate) resin. Further, from the viewpoint of providing a foam molded article with excellent flexibility, the aliphatic polyester resin preferably contains polybutylene terephthalate adipate. That is, in one embodiment of the present invention, as the aliphatic polyester component, the resin particles preferably contain a poly(3-hydroxyalkanoate) resin or polybutylene terephthalate adipate, more preferably contain a poly(3-hydroxyalkanoate) resin and polybutylene terephthalate adipate.

[0035] In 100% by weight of the aliphatic polyester resin, the aliphatic polyester resin preferably contains 50% by weight or more of a poly(3-hydroxyalkanoate) resin, more preferably 60% by weight or more, still more preferably 70% by weight or more, still more preferably 80% by weight or more, further preferably 90% by weight or more, and still further preferably 95% by weight or more. In 100% by weight of the aliphatic polyester resin, the aliphatic polyester resin particularly preferably contains 100% by weight of a poly(3-hydroxyalkanoate) resin. In other words, the aliphatic polyester resin is particularly preferably composed only of a poly(3-hydroxyalkanoate) resin. The greater the content of the poly(3-hydroxyalkanoate) resin in the aliphatic polyester resin, the more advantageous it is in terms of being able to suppress marine pollution and / or soil pollution caused by the disposal of the obtained foam particles and foam molded articles.

[0036] (Poly(3-hydroxyalkanoate) resin)

[0037] The resin particles preferably contain a poly(3-hydroxyalkanoate) resin as a resin component. In this specification, the "poly(3-hydroxyalkanoate) resin" is sometimes referred to as "poly(3-hydroxyalkanoate)" or "P3HA". P3HA will be described below.

[0038] P3HA is a polymer having a 3-hydroxyalkanoate unit as an essential constituent unit (monomer unit). In this specification, the "3-hydroxyalkanoate" is also sometimes referred to as "3HA". Specific examples of P3HA preferably include a polymer containing a repeating unit represented by the following general formula (1):

[0039] [-CHR-CH 2 -CO-O-]…(1).

[0040] In the general formula (1), R represents an alkyl group represented by C n H 2n+1 and n represents an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl. As n, it is preferably 1 to 10, more preferably 1 to 8.

[0041] As P3HA, P3HA produced by microorganisms is particularly preferred. P3HA produced by microorganisms is poly[(R)-3HA] in which all 3HA units are (R)-3HA.

[0042] In 100 mol% of all the repeating units of P3HA, P3HA preferably contains 50 mol% or more of 3HA units (particularly the repeating units of the general formula (1)), more preferably 70 mol% or more, and still more preferably 80 mol% or more. In addition, as the repeating units (monomer units) containing P3HA, it may be only 3HA units, or may contain repeating units derived from monomers other than 3HA (for example, 4-hydroxyalkanoate units, etc.) in addition to 3HA units.

[0043] Specific examples of the 3HA unit include 3-hydroxybutyrate unit, 3-hydroxypentanoate unit, and 3-hydroxyhexanoate unit, etc. The melting point and tensile strength of 3-hydroxybutyrate are close to those of propylene. Therefore, the P3HA of one embodiment of the present invention preferably contains 3-hydroxybutyrate units. In this specification, "3-hydroxybutyrate" is sometimes referred to as "3HB".

[0044] When P3HA contains two or more types of repeating units, the monomer that is the source of the repeating units other than the repeating unit with the highest content is called a comonomer. In this specification, the "repeating unit derived from the comonomer" is sometimes referred to as the "comonomer unit".

[0045] The comonomer is not particularly limited, and 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH) or 4-hydroxybutyrate (hereinafter sometimes referred to as 4HB) is preferred, etc.

[0046] P3HA is preferably at least one selected from poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). If it is this configuration, it is possible to more easily provide aliphatic polyester-based expanded particles having a high closed-cell ratio of the expanded particles and excellent compressive strength of the obtained expanded molded article. From the viewpoints of processability and physical properties of the expanded molded article, among these, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) are more preferable.

[0047] In one embodiment of the present invention, the method for producing P3HA is not particularly limited and may be a production method based on chemical synthesis or a production method based on microorganisms. Among them, a production method based on microorganisms is preferred. Regarding the production method of P3HA based on microorganisms, a known method can be applied, and preferably includes a cultivation step, a purification step, and a drying step.

[0048] The method for culturing microorganisms that produce P3HA in the cultivation step is not particularly limited. For example, the method described in International Publication No. WO2019 / 142717 can be used.

[0049] As a copolymer-producing bacterium of 3HB and other hydroxyalkanoate esters, specifically, the following can be cited: Aeromonas caviae as a P3HB3HV and P3HB3HH-producing bacterium, Alcaligenes eutrophus as a P3HB4HB-producing bacterium, etc. In particular, regarding P3HB3HH, Alcaligenes eutrophus AC32 strain (Alcaligenes eutrophus AC32, FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) etc. whose productivity of P3HB3HH has been improved by introducing genes of P3HA synthase group is more preferably used. In the method for producing P3HA, microbial cells in which P3HB3HH is accumulated in the cells by culturing microorganisms such as Alcaligenes eutrophus AC32 strain under appropriate conditions can be appropriately used. In addition, regarding the copolymer-producing bacterium, in addition to the above, genetically recombinant microorganisms into which various genes related to P3HA synthesis have been introduced according to the desired P3HA to be produced can also be used. In addition, for the culture conditions of the microorganism (bacterium), various culture conditions including the type of substrate can be optimized according to the desired P3HA to be produced.

[0050] The method for purifying P3HA obtained by microbial culture in the purification process is not particularly limited, and known physical treatment and / or chemical treatment, and / or biological treatment can be applied. For example, the purification method described in International Publication No. 2010 / 067543 can be preferably applied.

[0051] The method for drying P3HA obtained by microbial culture and purification in the drying process is not particularly limited, and spray drying, fluidized bed drying, pneumatic drying, rotary drying, vibratory drying, belt drying can be applied. For example, the drying method described in International Publication 2018 / 070492 can be preferably applied.

[0052] (2-2. Additives)

[0053] In addition to the aliphatic polyester resin, the resin particles may further contain additives (other additives). As other additives, for example, crosslinking agents, crystal nucleating agents, bubble regulators, lubricants, plasticizers, antistatic agents, flame retardants, conductive agents, heat insulating agents, antioxidants, ultraviolet absorbers, colorants, inorganic fillers, organic fillers, hydrolysis inhibitors, nonionic water-soluble polymers, etc. can be cited. For various purposes, other additive materials can be used alone or in combination of two or more. As other additives, those having biodegradability are particularly preferred.

[0054] Examples of the crystallization nucleating agent include, for example, pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, boron nitride, etc. One of these crystallization nucleating agents can be used alone, or two or more thereof can be used in combination. In addition, when two or more crystallization nucleating agents are used in combination, the mixing ratio can be appropriately adjusted according to the purpose.

[0055] Examples of the foaming regulator include, for example, talc, silica, calcium silicate, calcium carbonate, alumina, titanium dioxide, diatomaceous earth, clay, baking soda, bauxite, barium sulfate, alumina, bentonite, etc. Among these foaming regulators, talc is preferred from the viewpoint of particularly excellent dispersibility in the aliphatic polyester resin. One of these foaming regulators can be used alone, or two or more thereof can be used in combination. In addition, when two or more foaming regulators are used in combination, the mixing ratio can be appropriately adjusted according to the purpose.

[0056] Examples of the lubricant include, for example, behenic acid amide, oleic acid amide, erucic acid amide, stearic acid amide, palmitic acid amide, N-stearoyl behenic acid amide, N-stearoyl erucic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, ethylene bislauric acid amide, ethylene bisdecanoic acid amide, p-phenylene bisstearic acid amide, copolycondensate of ethylenediamine, stearic acid and sebacic acid, etc. Among them, behenic acid amide and erucic acid amide are preferred from the viewpoint of particularly excellent lubricant effect on the aliphatic polyester resin.

[0057] Examples of the antistatic agent include, for example, coconut oil fatty acid diethanolamide, etc. The content of the antistatic agent in the resin particles is not particularly limited.

[0058] From the viewpoint of being able to reduce the apparent density and / or being able to improve the compatibility with the aliphatic polyester resin, the resin particles preferably further contain a nonionic water-soluble polymer. In other words, the resin particles preferably contain a nonionic water-soluble polymer. A nonionic water-soluble polymer refers to a polymer that does not ionize to generate ions when dissolved in water.

[0059] (2-2. Resin particle preparation process)

[0060] This manufacturing method preferably includes a resin particle preparation step of preparing aliphatic polyester resin particles containing an aliphatic polyester resin before the dispersion step. The resin particle preparation step can also be said to be a step of shaping the resin into a shape that is easily usable for foaming. The method of the resin particle preparation step is not particularly limited as long as resin particles can be obtained. As the method of the resin particle preparation step, for example, a method including the following steps can be cited: a melt-kneading step of melt-kneading a resin composition containing an aliphatic polyester resin and optionally used other additives, and a particle shaping step of shaping the melt-kneaded resin composition into a shape that is easily usable for foaming.

[0061] In the melt-kneading step, the temperature during melt-kneading the resin composition varies depending on the physical properties (such as melting point, weight-average molecular weight, etc.) of the aliphatic polyester resin and the types of additives used, and cannot be generalized. Regarding the temperature during melt-kneading the resin composition, for example, the temperature of the melt-kneaded resin composition discharged from the die nozzle (hereinafter, sometimes referred to as the composition temperature.) is preferably 150°C to 200°C, more preferably 160°C to 195°C, and further preferably 170°C to 190°C. When the composition temperature is 150°C or higher, there is no risk of insufficient melt-kneading of the resin composition. On the other hand, when the composition temperature is 200°C or lower, there is no risk of thermal decomposition of the aliphatic polyester resin.

[0062] As the method of the particle shaping step, the melt-kneaded resin composition is not particularly limited as long as it can be shaped into a desired shape. By using a melt-kneading device equipped with a die and a cutting device as the above-mentioned melt-kneading device, in the particle shaping step, the melt-kneaded resin composition can be easily shaped into a desired shape. Specifically, the melt-kneaded resin composition is ejected from the die nozzle of the melt-kneading device, and by cutting the resin composition using the cutting device while or after ejection, it can be shaped into a desired shape. The shape of the obtained resin particles is not particularly limited, and from the perspective of being easily usable for foaming, it is preferably cylindrical, elliptical cylindrical, spherical, cubic, rectangular parallelepiped, etc.

[0063] In the particle shaping step, the resin composition ejected from the die nozzle can be cooled. In the case of cooling the resin composition ejected from the die nozzle, the resin composition can be cut using the cutting device while or after cooling the resin composition.

[0064] (2 - 3. Dispersion step)

[0065] The dispersion step is a step of dispersing (a) aliphatic polyester resin particles containing an aliphatic polyester resin, (b) a foaming agent, and, if necessary, (c) a crosslinking agent, a dispersing agent, a crosslinking aid, a dispersing aid, and / or a plasticizer in an aqueous dispersion medium in a container. The dispersion step can also be considered as a step of preparing a dispersion liquid in which (a) aliphatic polyester resin particles containing an aliphatic polyester resin, (b) a foaming agent, and, if necessary, (c) a crosslinking agent, a dispersing agent, a crosslinking aid, a dispersing aid, and / or a plasticizer are dispersed in a container. It should be noted that in the dispersion liquid, (a) the crosslinking agent and the crosslinking aid are consumed by reacting with the aliphatic polyester resin in the resin particles and may not be present. (b) The foaming agent and the plasticizer are impregnated in the resin particles and may not be present in a dispersed state.

[0066] The container is not particularly limited, and a container capable of withstanding the foaming temperature and foaming pressure described below is preferred. For example, a pressure-resistant container is preferred.

[0067] As the aqueous dispersion medium, as long as it can uniformly disperse at least the resin particles and the foaming agent, there is no particular limitation. As the aqueous dispersion medium, for example, tap water and / or industrial water can be used. From the viewpoint of stably producing foamed particles, as the aqueous dispersion medium, pure water such as RO water (water purified by the reverse osmosis membrane method), distilled water, deionized water (water purified by an ion exchange resin), and ultrapure water are preferably used.

[0068] Examples of the foaming agent include inorganic gases such as nitrogen, carbon dioxide, and air; saturated hydrocarbons having 3 to 5 carbon atoms such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane; ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether; halogenated hydrocarbons such as chloromethane, dichloromethane, and dichlorodifluoroethane; and water. As the foaming agent, at least one or more selected from the above inorganic gases, saturated hydrocarbons having 3 to 5 carbon atoms, ethers, halogenated hydrocarbons, and water can be used. Among them, from the viewpoints of environmental burden and foaming power, nitrogen or carbon dioxide is preferably used as the foaming agent. These foaming agents can be used alone or in combination of two or more. In addition, when using two or more foaming agents in combination, the mixing ratio can be appropriately adjusted according to the purpose.

[0069] In this manufacturing method, a dispersant is preferably used. By using a dispersant, mutual adhesion between resin particles can be suppressed, and there is an advantage that foamed particles can be stably manufactured. Examples of the dispersant include inorganic substances such as tricalcium phosphate, trimagnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, clay, alumina, titanium oxide, and aluminum hydroxide. One of these dispersants can be used alone, or two or more of them can be used in combination. In addition, when two or more dispersants are used in combination, the mixing ratio can be appropriately adjusted according to the purpose.

[0070] In this manufacturing method, in order to improve the effect of suppressing mutual adhesion between resin particles, a dispersion aid can also be used. Examples of the dispersion aid include anionic surfactants such as sodium alkyl sulfonate, sodium alkylbenzene sulfonate, and α-olefin sulfonate. One of these dispersion aids can be used alone, or two or more of them can be used in combination. In addition, when two or more dispersion aids are used in combination, the mixing ratio can be appropriately adjusted according to the purpose.

[0071] In this manufacturing method, a crosslinking agent is preferably used. By using a crosslinking agent, the aliphatic polyester-based resin in the obtained foamed particles becomes an aliphatic polyester-based resin having a crosslinked structure. When a crosslinking agent is used in this manufacturing method, it can be a method of using a crosslinking agent in the above resin particle preparation step and not using a crosslinking agent in the dispersion step (hereinafter, also referred to as "Method A"); it can also be a method of not using a crosslinking agent in the above resin particle preparation step and using a crosslinking agent in the dispersion step (hereinafter, also referred to as "Method B"); it can also be a method of using a crosslinking agent in both the above resin particle preparation step and the dispersion step (hereinafter, also referred to as "Method C").

[0072] Methods A and C will be described. In the resin particle preparation step, by melt-kneading an aliphatic polyester-based resin and a resin composition containing a crosslinking agent simultaneously, crosslinked aliphatic polyester-based resin particles containing an aliphatic polyester-based resin can be obtained. In the resin particle preparation step, the method of pre-producing crosslinked aliphatic polyester-based resin particles containing an aliphatic polyester-based resin is not particularly limited to the above method, etc. For example, the methods described in JP-A-2009 / 061753 and JP-A-2020 / 158613 can be adopted.

[0073] When it is Method A, the dispersion step can also be considered as a step of dispersing (a) crosslinked aliphatic polyester-based resin particles containing an aliphatic polyester-based resin, (b) a foaming agent, and, if necessary, (c) a crosslinking agent, a dispersant, a crosslinking aid, a dispersion aid, and / or a plasticizer in an aqueous dispersion medium in a container.

[0074] When it is Mode B, the dispersion step can also be considered as a step of dispersing (a) aliphatic polyester resin particles containing an aliphatic polyester resin, (b) a foaming agent, (c) a crosslinking agent, and, if necessary, (d) a dispersant, a crosslinking aid, a dispersion aid, and / or a plasticizer in an aqueous dispersion medium in a container.

[0075] When it is Mode C, the dispersion step can also be considered as a step of dispersing (a) crosslinked aliphatic polyester resin particles containing an aliphatic polyester resin, (b) a foaming agent, (c) a crosslinking agent, and, if necessary, (d) a dispersant, a crosslinking aid, a dispersion aid, and / or a plasticizer in an aqueous dispersion medium in a container.

[0076] When it is Modes B and C, in the dispersion step, the foaming agent and the crosslinking agent may not be added simultaneously. For example, in the dispersion step, uncrosslinked resin particles, or crosslinked resin particles and a crosslinking agent are dispersed in an aqueous dispersion medium in a container to prepare crosslinked resin particles. It may be (i) thereafter, dispersing the foaming agent in the container; or it may be (ii) thereafter, taking out the crosslinked resin particles in the container and dispersing the crosslinked resin particles and the foaming agent in an aqueous dispersion medium in another container.

[0077] In addition, when it is Mode B, in the dispersion step, first, the resin particles containing an aliphatic polyester resin and the crosslinking agent react in an aqueous dispersion medium to obtain crosslinked aliphatic polyester resin particles containing an aliphatic polyester resin. As a result, even in the dispersion step of Mode B, similar to the dispersion step of Mode A, a dispersion liquid in which (a) crosslinked aliphatic polyester resin particles containing an aliphatic polyester resin, (b) a foaming agent, and, if necessary, (c) a crosslinking agent, a dispersant, a crosslinking aid, a dispersion aid, and / or a plasticizer are dispersed in an aqueous dispersion medium is obtained.

[0078] As the crosslinking agent, any compound can be used as long as it can crosslink the aliphatic polyester resin, and there is no particular limitation. As the crosslinking agent, an organic peroxide is preferably used. In other words, the aliphatic polyester-based foamed particles are preferably aliphatic polyester-based foamed particles crosslinked with an organic peroxide. The organic peroxide can be used in (a) the resin particle preparation step; it can also be used in (b) the dispersion step; it can also be used in both (c) the resin particle preparation step and the dispersion step. More specifically, in order to react the organic peroxide with the aliphatic polyester resin, the organic peroxide and the aliphatic polyester resin can be melt-kneaded in (a) the resin particle preparation step; the resin particles and the organic peroxide can also be dispersed in an aqueous dispersion medium in (b) the dispersion step; or while melt-kneading the organic peroxide and the aliphatic polyester resin, the resin particles and the organic peroxide can be further dispersed in an aqueous dispersion medium. In the dispersion step, by dispersing the resin particles produced in the resin particle preparation step and the organic peroxide in an aqueous dispersion medium, the organic peroxide can be impregnated into the resin particles and react with them. For these reasons, in this manufacturing method, it is preferable to use an organic peroxide as the crosslinking agent. It should be noted that when using an organic peroxide as the crosslinking agent, a crosslinked structure is formed by direct bonding (without passing through the structure derived from the crosslinking agent) between the molecular chains of the aliphatic polyester resin.

[0079] Depending on the type of aliphatic polyester resin used, etc., the organic peroxide used as a crosslinking agent is preferably an organic peroxide having a 1-hour half-life temperature of 90°C to 160°C, more preferably an organic peroxide having a 1-hour half-life temperature of 115°C to 125°C. Specific examples of such organic peroxides include: benzoyl peroxide (1-hour half-life temperature: 92°C), tert-butyl peroxy-2-ethylhexyl carbonate (1-hour half-life temperature: 121°C), tert-butyl peroxyisopropyl carbonate (1-hour half-life temperature: 118°C), tert-amyl peroxy-2-ethylhexyl carbonate (1-hour half-life temperature: 117°C), tert-amyl peroxyisopropyl carbonate (1-hour half-life temperature: 115°C), tert-butyl peroxyisobutyrate (1-hour half-life temperature: 93°C), tert-butyl peroxy-2-ethylhexanoate (1-hour half-life temperature: 95°C), tert-butyl peroxyisononanoate (1-hour half-life temperature: 123°C), tert-butyl peroxyacetate (1-hour half-life temperature: 123°C), tert-butyl diperoxybenzoate (1-hour half-life temperature: 125°C), tert-amyl peroxyisobutyrate (1-hour half-life temperature: 93°C), tert-amyl peroxy-2-ethylhexanoate (1-hour half-life temperature: 92°C), tert-amyl peroxyisononanoate (1-hour half-life temperature: 114°C), tert-amyl peroxyacetate (1-hour half-life temperature: 120°C), tert-amyl peroxybenzoate (1-hour half-life temperature: 122°C), dicumyl peroxide (1-hour half-life temperature: 137°C), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (1-hour half-life temperature: 140°C), di-tert-butyl peroxide (1-hour half-life temperature: 149°C), etc. When using an organic peroxide having a 1-hour half-life temperature of 90°C or higher, there is an advantage in that there is a tendency to obtain foamed particles having a desired gel fraction. On the other hand, when using an organic peroxide having a 1-hour half-life temperature of 160°C or lower, there is an advantage in that there is no need to worry about unreacted crosslinking agent remaining in the final product.

[0080] The amount of the crosslinking agent used is not particularly limited, and the amount of the crosslinking agent used has a positive correlation with the gel fraction of the obtained foamed particles. In other words, the more the amount of the crosslinking agent used increases, the more the gel fraction of the obtained foamed particles tends to increase. Therefore, it is desirable to set the amount of the crosslinking agent used in consideration of the gel fraction of the obtained foamed particles. In addition, the less the amount of the crosslinking agent used, in other words, the lower the gel fraction of the obtained foamed particles, the more the foamed particles with a low apparent density tend to be obtained. On the other hand, the more the amount of the crosslinking agent used, in other words, the higher the gel fraction of the obtained foamed particles, the more the moldability and physical properties (e.g., compressive strength, impact strength, heat resistance, etc.) of the obtained foamed particles tend to be improved. According to one embodiment of the present invention, there is an advantage that even when a certain amount or more of the crosslinking agent is used, in other words, even when the gel fraction of the obtained foamed particles is a certain value or more, foamed particles with a low apparent density can be obtained. That is, according to one embodiment of the present invention, there is an advantage that foamed particles with a low apparent density and good moldability and physical properties can be obtained.

[0081] With respect to 100 parts by weight of the aliphatic polyester resin, the amount of the crosslinking agent used is preferably, for example, 1.6 parts by weight to 5.0 parts by weight, more preferably 1.7 parts by weight to 3.0 parts by weight, and still more preferably 1.8 parts by weight to 2.5 parts by weight. When the amount of the crosslinking agent used is 1.6 parts by weight or more with respect to 100 parts by weight of the resin particles, foamed particles having a sufficient gel fraction (e.g., 60% by weight) can be obtained. As a result, there is an advantage that the moldability and / or physical properties (e.g., compressive strength, impact strength, and heat resistance, etc.) of the obtained foamed particles are improved. Here, the "amount of the crosslinking agent used" in this specification means the amount of the crosslinking agent in the resin particle preparation step in Method A; in Method B, it means the amount of the crosslinking agent in the dispersion step; and in Method C, it means the total amount of the crosslinking agent in the resin particle preparation step and the dispersion step. It should be noted that when a commercially available product is used as the crosslinking agent, the amount of the crosslinking agent used refers to the amount of the organic peroxide contained in the commercially available product used.

[0082] In this production method, in order to improve the crosslinking efficiency of the aliphatic polyester resin, a crosslinking aid may also be used. Examples of the crosslinking aid include compounds having at least 1 unsaturated bond in the molecule. As the crosslinking aid, allyl esters, acrylate esters, methacrylate esters, divinyl compounds, etc. are particularly preferred. These crosslinking aids can be used alone or in combination of two or more. In addition, when two or more crosslinking aids are used in combination, the mixing ratio can be appropriately adjusted according to the purpose.

[0083] The amount of the crosslinking aid used is not particularly limited, and relative to 100 parts by weight of the resin particles, it is preferably 0.01 to 3.00 parts by weight, more preferably 0.03 to 1.50 parts by weight, and still more preferably 0.05 to 1.00 parts by weight. When the amount of the crosslinking aid used is 0.01 part by weight or more relative to 100 parts by weight of the resin particles, sufficient effects can be exhibited as a crosslinking aid.

[0084] In the dispersion step, when the crosslinking agent and, if necessary, the crosslinking aid are impregnated into the resin particles and react, in order to improve the crosslinking efficiency of the aliphatic polyester resin, it is preferable to reduce the oxygen concentration in the container and the dissolved oxygen amount in the dispersion liquid. As methods for reducing the oxygen concentration in the container and the dissolved oxygen amount in the dispersion liquid, examples include replacing the gas dissolved in the container and the dispersion liquid with an inorganic gas such as carbon dioxide and nitrogen, and evacuating the gas in the container by vacuum suction.

[0085] A plasticizer can also be used in this production method. In this production method, when using a plasticizer, the plasticizer can be used in the resin particle preparation step described above and not used in the dispersion step (hereinafter also referred to as "Method D"); it can also be not used in the resin particle preparation step described above and used in the dispersion step (hereinafter also referred to as "Method E"); it can also be used in both the resin particle preparation step and the dispersion step described above (hereinafter also referred to as "Method F").

[0086] Examples of the plasticizer include, for example, glyceride compounds such as glycerol diacetyl monolaurate, citrate compounds such as tributyl acetylcitrate; sebacate compounds such as dibutyl sebacate; adipate compounds; polyether ester compounds; benzoate compounds; phthalate compounds; isosorbide compounds; polycaprolactone compounds; dicarboxylate compounds such as benzylmethyl diethylene glycol adipate, etc. Among them, from the viewpoint of excellent plasticizing effect on the aliphatic polyester resin, glyceride compounds, citrate compounds, sebacate compounds, and dicarboxylate compounds are preferred. These plasticizers can be used alone or two or more of them can be mixed and used. In addition, when two or more plasticizers are mixed and used, the mixing ratio can be appropriately adjusted according to the purpose.

[0087] The amount of the plasticizer used is not particularly limited. The more the plasticizer is used, the more likely it is to obtain foamed particles with a low apparent density. On the other hand, the less the plasticizer is used, the more likely it is to increase the strength (e.g., compressive strength) of the foamed molded body formed from the obtained foamed particles. According to one embodiment of the present invention, there is an advantage that foamed particles with a low apparent density can be obtained without using a large amount of the plasticizer. That is, according to one embodiment of the present invention, there is an advantage that foamed particles with a low apparent density can be obtained and a foamed molded body with good strength can be provided.

[0088] With respect to 100 parts by weight of the aliphatic polyester resin, the amount of the plasticizer used is preferably 4 parts by weight or less, more preferably 3 parts by weight or less, further preferably 2 parts by weight or less, still more preferably 1 part by weight or less, and particularly preferably 0 part by weight. In other words, in this manufacturing method, it is particularly preferred not to use the plasticizer. That is, in this manufacturing method, it is preferred not to use the plasticizer or to use more than 0 part by weight and 4 parts by weight or less of the plasticizer with respect to 100 parts by weight of the above-mentioned aliphatic polyester resin. When the amount of the crosslinking agent used is 4 parts by weight or less with respect to 100 parts by weight of the resin particles, there is an advantage that foamed particles capable of providing a foamed molded body with good strength can be obtained. Here, in this specification, "the amount of the plasticizer used" means the amount of the plasticizer in the resin particle preparation step in Method D; in Method E, it means the amount of the plasticizer in the dispersion step; and in Method F, it means the total amount of the plasticizer in the resin particle preparation step and the dispersion step.

[0089] (2-5. Heating - pressure increasing step and holding step)

[0090] This manufacturing method preferably includes: a heating - pressure increasing step of heating the temperature inside the container to a certain temperature and increasing the pressure inside the container to a certain pressure between the dispersion step and the release step, following the dispersion step; and a holding step of holding the temperature and pressure inside the container at a certain temperature and a certain pressure.

[0091] The heating - pressure increasing step is preferably carried out after the dispersion step, and the holding step is preferably carried out after the heating - pressure increasing step. In this specification, sometimes (a) the certain temperature in the heating - pressure increasing step and the holding step is referred to as the foaming temperature, and (b) the certain pressure is referred to as the foaming pressure.

[0092] The foaming temperature varies depending on the type of aliphatic polyester resin, the type of foaming agent, the degree of plasticization of the aliphatic polyester resin, the desired apparent density of the foamed particles, etc., and thus cannot be generalized. The foaming temperature is preferably, for example, 100.0°C to 140.0°C, more preferably 110.0°C to 135.0°C, and even more preferably 115.0°C to 133.0°C. When the foaming temperature is 100°C or higher, there is a tendency to obtain foamed particles with a low apparent density. On the other hand, when the foaming temperature is 140°C or lower, there is no risk of hydrolysis of the resin particles in the container.

[0093] In the heating - pressurizing process, as the rate of temperature rise to the desired foaming temperature (hereinafter sometimes referred to as the heating rate), it is preferably 1.0°C / min to 3.0°C / min, more preferably 1.5°C / min to 3.0°C / min. When the heating rate is 1.0°C / min or higher, the productivity is excellent. On the other hand, when the heating rate is 3.0°C / min or lower, there is no risk of the foaming agent impregnating into the resin particles during heating, and no risk of insufficient reaction between the cross - linker and the aliphatic polyester resin.

[0094] The foaming pressure is preferably 1.0 MPa to 10.0 MPa (gauge pressure), more preferably 2.0 MPa to 5.0 MPa (gauge pressure), and even more preferably 2.5 MPa to 4.0 MPa. When the foaming pressure is 1.0 MPa (gauge pressure) or higher, foamed particles with a low apparent density can be obtained.

[0095] It should be noted that the higher the foaming pressure, the lower the apparent density of the foamed particles that can be obtained. On the other hand, when the foaming pressure is too high (for example, exceeding 4.0 MPa (gauge pressure)), a container capable of withstanding a higher pressure is required, that is, expensive equipment is needed. Therefore, from the perspective of not requiring expensive equipment, the foaming pressure is preferably 1.0 MPa to 4.0 MPa (gauge pressure), more preferably 2.0 MPa to 3.7 MPa (gauge pressure), and even more preferably 2.5 MPa to 3.5 MPa.

[0096] (2 - 6. Release process)

[0097] The release process is carried out after the dispersion process, and is preferably carried out after the heating - pressurizing process or the holding process that may optionally follow the dispersion process. Through the release process, the resin particles can be foamed, and as a result, foamed particles are obtained.

[0098] In the discharging step, the "region where the pressure is lower than the pressure inside the container" means "a region at a pressure lower than the pressure inside the container" or "a space at a pressure lower than the pressure inside the container", and can also be regarded as "under an atmosphere where the pressure is lower than the pressure inside the container". The region where the pressure is lower than the pressure inside the container only needs to have a pressure lower than the foaming pressure, and there is no particular limitation. For example, it can be a region under atmospheric pressure. In addition, when performing the heating - pressure increasing step, the "pressure inside the container" in the discharging step can also be referred to as the "foaming pressure".

[0099] In the discharging step, when discharging the dispersion liquid into a region where the pressure is lower than the pressure inside the container, for the purpose of adjusting the flow rate of the dispersion liquid and reducing the deviation of the apparent density of the obtained foamed particles, etc., the dispersion liquid can also be discharged through an opening hole with a diameter of 1 mm to 5 mm.

[0100] In the discharging step, the temperature of the region where the pressure is lower than the pressure inside the container (hereinafter also simply referred to as the "region") is set to 65°C to 95°C, and the water vapor amount in the region is set to 144 g / m 3 ~502 g / m 3 . By setting the temperature and water vapor amount in the region within the above ranges, foamed particles with a low apparent density can be obtained.

[0101] The temperature of the region is preferably 65°C to 95°C, more preferably 70°C to 93°C, further preferably 75°C to 91°C, and particularly preferably 80°C to 90°C. Based on this configuration, there are the following advantages: foamed particles with a low apparent density and no mutual adhesion and shrinkage or extremely little mutual adhesion and shrinkage can be obtained. It should be noted that the temperature of the region can be adjusted by the amount of water vapor input into the region, the amount of outside air blown into the region, the conveying air volume of the foamed particles, and the temperature of the conveying air of the foamed particles, etc.

[0102] The water vapor amount in the region is preferably 144 g / m 3 ~502 g / m 3 , more preferably 178 g / m 3 ~468 g / m 3 , further preferably 217 g / m 3 ~437 g / m 3 , particularly preferably 263 g / m 3 ~421 g / m 3 . Based on this configuration, there is the advantage that foamed particles with a low apparent density and no mutual adhesion and shrinkage or extremely little mutual adhesion and shrinkage can be obtained.

[0103] In the release process, a cleaning agent can be used after foaming the resin particles. Examples of the cleaning agent include, for example, warm water, sodium hexametaphosphate, etc. By using the cleaning agent, the amount of the dispersant attached to the surface of the foamed particles can be adjusted.

[0104] (2-7. Secondary foaming process)

[0105] As a method for obtaining foamed particles with a low apparent density, there is a method (process) of further expanding the foamed particles obtained in a series of processes from the dispersion process to the release process. The process involved is also referred to as the "secondary foaming process". In the case of performing the secondary foaming process, sometimes the series of processes including the above-mentioned dispersion process to the above-mentioned release process is referred to as the primary foaming process, and the foamed particles obtained in the primary foaming process are referred to as primary foamed particles.

[0106] As the secondary foaming process, for example, the following method can be cited: (c1) supplying the foamed particles obtained in the foaming process into a container; (c2) supplying an inorganic gas such as air or carbon dioxide into the container to increase the pressure inside the container; (c3) impregnating the inorganic gas into the foamed particles through the above-mentioned (c2) to make the pressure inside the foamed particles higher than the atmospheric pressure; (c4) thereafter, heating the foamed particles with steam or the like to further expand them to obtain foamed particles with a desired apparent density.

[0107] As described above, the secondary foaming process is a complicated process. In the case of performing the secondary foaming process, not only the number of processes but also the manufacturing cost will increase. One embodiment of the present invention has the following advantages: without performing the secondary foaming process and only performing the primary foaming process, foamed particles with a low apparent density can also be provided.

[0108] The internal pressure of the foamed particles in the secondary foaming process is preferably 0.15 MPa to 0.60 MPa (absolute pressure), more preferably 0.20 MPa to 0.50 MPa (absolute pressure).

[0109] In the secondary foaming process (in the above-mentioned (c2) and (c3)), as the temperature inside the container when impregnating the inorganic gas into the foamed particles, it is preferably 10 °C to 90 °C, more preferably 20 °C to 90 °C, more preferably 30 °C to 90 °C, and further preferably 40 °C to 90 °C.

[0110] In the secondary foaming process (in the above-mentioned (c4)), the pressure of steam or the like for heating the foamed particles (hereinafter sometimes referred to as the "secondary foaming pressure".) varies depending on the characteristics of the foamed particles used and the desired apparent density, and cannot be generalized. The secondary foaming pressure is preferably 0.01 MPa to 0.17 MPa (gauge pressure), more preferably 0.03 MPa to 0.11 MPa (gauge pressure).

[0111] As the gel fraction of the secondary foamed particles, it is preferably the same as the gel fraction of the foamed particles. That is, as the gel fraction of the secondary foamed particles, the description of the above item (gel fraction) can be appropriately cited.

[0112] (Physical properties of aliphatic polyester-based foamed particles)

[0113] (Apparent density)

[0114] The apparent density of the foamed particles is not particularly limited, and a low value is preferred. For example, the apparent density of the foamed particles is preferably 20 g / L to 64 g / L, more preferably 22 g / L to 63 g / L, still more preferably 25 g / L to 62 g / L, still more preferably 25 g / L or more and less than 62 g / L, still more preferably 27 g / L to 61 g / L, still more preferably 28 g / L to 60 g / L, and further preferably 30 g / L to 59 g / L. Based on this configuration, an aliphatic polyester-based foamed molded article that is light in weight and has good strength (compressive strength) can be obtained.

[0115] (Heat on the high-temperature side)

[0116] The heat on the high-temperature side of the foamed particles is not limited, and is preferably 0.1 J / g to 20.0 J / g, more preferably 0.3 J / g to 18.0 J / g, and further preferably 0.5 J / g to 15.0 J / g. Based on this configuration, aliphatic polyester-based foamed particles can be produced in which the aliphatic polyester-based foamed particles obtained in the foaming process do not adhere to each other and the in-mold foaming moldability is excellent. In addition, the greater the heat on the high-temperature side of the foamed particles, the higher the apparent density of the foamed particles tends to be; the smaller the heat on the high-temperature side of the foamed particles, the lower the apparent density of the foamed particles tends to be. Mainly, the heat on the high-temperature side of the foamed particles can be controlled by adjusting parameters such as the conditions during foaming (especially, the foaming temperature and foaming pressure), and the time for holding the resin particles in a container (for example, a pressure-resistant container) before foaming. For example, when the foaming temperature is increased, the heat on the high-temperature side tends to become smaller, and conversely, when the foaming temperature is decreased, the heat on the high-temperature side tends to become larger. This is because the amount of un-melted crystals changes with different foaming temperatures. In addition, when the foaming pressure is increased, the heat on the high-temperature side tends to become smaller, and conversely, when the foaming pressure is decreased, the heat on the high-temperature side tends to become larger. This is because the plasticization condition changes based on the foaming pressure (the amount of foaming agent), and the amount of un-melted crystals changes. In addition, the longer the time for holding the resin particles in the container before foaming, the greater the heat on the high-temperature side tends to be. This is because the growth amount of un-melted crystals changes with different holding times of the resin particles in the container. The temperature for holding the resin particles in the container before foaming is usually at the same level as the foaming temperature.

[0117] (Gel fraction)

[0118] The gel fraction of the foamed particles is not particularly limited, and from the viewpoints of moldability and physical properties (for example, compressive strength, impact strength, heat resistance, etc.), a high value is preferred. For example, the gel fraction of the foamed particles is preferably 60% by weight or more, more preferably 63% by weight or more, further preferably 67% by weight or more, and particularly preferably 70% by weight or more.

[0119] [3. Aliphatic polyester-based foamed particles]

[0120] Regarding the aliphatic polyester-based foamed particles of an embodiment of the present invention, (i) they contain an aliphatic polyester-based resin; (ii) they do not contain a plasticizer, or contain more than 0 part by weight and 4 parts by weight or less of the plasticizer relative to 100 parts by weight of the above aliphatic polyester-based resin; (iii) the gel fraction is 60% by weight or more; and (iv) the apparent density is 64 g / L or less.

[0121] These foamed particles can be suitably obtained by the production method described in the above item [2. Production method of aliphatic polyester-based foamed particles].

[0122] In addition, since each aspect (for example, aliphatic polyester-based resin, gel fraction, apparent density, etc.) related to these foamed particles is the same as that described in the above item [2. Production method of aliphatic polyester-based foamed particles], the relevant description is incorporated herein by reference and the description is omitted here.

[0123] [4. Aliphatic polyester-based foamed molded article]

[0124] An aliphatic polyester-based foamed molded article of an embodiment of the present invention is formed from the aliphatic polyester-based foamed particles of an embodiment of the present invention. It can also be considered that an aliphatic polyester-based foamed molded article of an embodiment of the present invention is made of the aliphatic polyester-based foamed particles of an embodiment of the present invention. An aliphatic polyester-based foamed molded article of an embodiment of the present invention may also contain the aliphatic polyester-based foamed particles of an embodiment of the present invention. With this configuration, an aliphatic polyester-based foamed molded article with a low density can be provided.

[0125] The production method of this foamed molded article (that is, the molding method of the foamed particles) is not particularly limited, and a known method can be applied. For example, the following methods of in-mold foaming molding (A) to (D) etc. are not particularly limited:

[0126] (A) A method of pressurizing these foamed particles with an inorganic gas in a container, impregnating the inorganic gas into the foamed particles, and after giving a given internal pressure to the foamed particles, filling the foamed particles into a mold and heating with steam;

[0127] (B) After filling the foamed particles into a metal mold, compress the volume in the metal mold by 10% to 75% using steam heating;

[0128] (C) Compress the foamed particles by gas pressure and fill them into a metal mold, and use the restoring force of the foamed particles with steam heating;

[0129] (D) Without special pretreatment, fill the foamed particles into a metal mold and use steam heating.

[0130] In the production of the present foamed molded article, the pressure of the steam for heating the foamed particles (hereinafter sometimes referred to as the molding pressure) varies depending on the characteristics of the foamed particles used, etc., and cannot be generalized. The molding pressure is preferably 0.05 MPa to 0.30 MPa (gauge pressure), more preferably 0.08 MPa to 0.25 MPa (gauge pressure), and further preferably 0.10 MPa to 0.20 MPa (gauge pressure).

[0131] In the production method of the present foamed molded article, as the inorganic gas in the above method (A), at least one selected from air, nitrogen, oxygen, carbon dioxide, helium, neon, argon, etc. can be used. Among these inorganic gases, air and / or carbon dioxide are preferred.

[0132] In the production method of the present foamed molded article, as the temperature in the container when impregnating the inorganic gas into the foamed particles in method (A), it is preferably 10°C to 90°C, more preferably 20°C to 90°C, more preferably 30°C to 90°C, and further preferably 40°C to 90°C.

[0133] In the production method of the present foamed molded article, the internal pressure of the foamed particles in the above method (A) is preferably 0.10 MPa to 0.30 MPa (absolute pressure), more preferably 0.11 MPa to 0.25 MPa (absolute pressure), and further preferably 0.12 MPa to 0.20 MPa (absolute pressure). The measurement of the internal pressure of the foamed particles can be carried out as long as it is in accordance with the measurement method described in the following examples.

[0134] The compression strength of the present foamed molded article varies depending on the type of aliphatic polyester resin, the density of the molded article, etc., and thus cannot be uniformly defined, but the strength at 50% compression is preferably 0.18 MPa or more, more preferably 0.19 MPa or more, and further preferably 0.20 MPa or more. Based on this configuration, an aliphatic polyester-based foamed molded article with high compression strength can be provided.

[0135] The gel fraction of the present foamed molded article is as high as that of the present foamed particles. In contrast, the gel fraction of the foamed molded article has a tendency to be significantly lower than that of the foamed particles. It is presumed that this is because the aliphatic polyester resin undergoes hydrolysis during molding and drying, but one embodiment of the present invention is not limited by any of these presumptions.

[0136] The density of the present foamed molded article is as low as the apparent density of the present foamed particles. Additionally, the density of the foamed molded article has a tendency to be significantly lower than the apparent density of the foamed particles. It is presumed that this is because the foamed particles further expand due to heating during molding, but one embodiment of the present invention is not limited by any of these presumptions.

[0137] One embodiment of the present invention's aliphatic polyester-based foamed molded article may have the following constitution:

[0138] An aliphatic polyester-based foamed molded article, which (i) contains an aliphatic polyester resin; (ii) does not contain a plasticizer, or contains more than 0 parts by weight and 4 parts by weight or less of the plasticizer relative to 100 parts by weight of the above aliphatic polyester resin; (iii) has a gel fraction of 50% by weight or more; and (iv) has a density of 44 g / L or less.

[0139] The above-mentioned aliphatic polyester-based foamed molded article of one embodiment of the present invention can be suitably obtained by molding the aliphatic polyester-based foamed particles obtained by the manufacturing method described in the above item of 〔2. Manufacturing method of aliphatic polyester-based foamed particles〕 and / or the aliphatic polyester-based foamed particles described in the above item of 〔3. Aliphatic polyester-based foamed particles〕.

[0140] 〔5. Uses〕

[0141] One embodiment of the present invention can be suitably used in packaging cushioning materials (for example, cushioning materials for home appliances such as refrigerators, freezers, air conditioner main bodies and their outdoor units, washing machines, air purifiers, humidifiers, rice cookers, microwave ovens, ovens, toasters, electric fans, battery units, etc.; cushioning materials for automotive items such as transmissions, car hoods, engine hoods, car doors, batteries, engines, etc.); automotive components (for example, bumper cores, headrests, trunks, toolboxes, floor partitions, seat cores, child seat cores, sun visor cores, knee airbags, etc.); heat insulation materials (for example, constant temperature storage containers, constant temperature transportation containers, etc.), foundry mold applications; agricultural product boxes; fish boxes; building materials and civil engineering materials, etc.

[0142] 〔Others〕

[0143] One embodiment of the present invention may include the following constitution.

[0144] [1] A method for manufacturing aliphatic polyester-based foamed particles, the method comprising:

[0145] A dispersion step of dispersing aliphatic polyester-based resin particles containing an aliphatic polyester-based resin and a foaming agent in an aqueous dispersion medium in a container;

[0146] A release step of opening one end of the container and releasing the dispersion liquid in the container to a region where the pressure is lower than the pressure in the container,

[0147] wherein the temperature of the region is 65°C to 95°C and the amount of water vapor is 144 g / m 3 to 502 g / m 3 .

[0148] [2] The method for manufacturing aliphatic polyester-based foamed particles according to [1], wherein

[0149] the aliphatic polyester-based resin contains a poly(3-hydroxyalkanoate)-based resin.

[0150] [3] The method for manufacturing aliphatic polyester-based foamed particles according to [1] or [2], wherein

[0151] the aliphatic polyester-based resin contains polybutylene adipate terephthalate.

[0152] [4] The method for manufacturing aliphatic polyester-based foamed particles according to any one of [1] to [3], wherein

[0153] the gel fraction of the aliphatic polyester-based foamed particles is 60% by weight or more.

[0154] [5] The method for manufacturing aliphatic polyester-based foamed particles according to any one of [1] to [4], wherein

[0155] in the dispersion step, a crosslinking agent is further dispersed in the aqueous dispersion medium.

[0156] [6] The method for manufacturing aliphatic polyester-based foamed particles according to any one of [1] to [5], wherein

[0157] in the dispersion step, a plasticizer is not used or, based on 100 parts by weight of the aliphatic polyester-based resin, more than 0 part by weight and 4 parts by weight or less of the plasticizer is used.

[0158] [7] An aliphatic polyester-based foamed particle, wherein

[0159] (i) contains an aliphatic polyester-based resin;

[0160] (ii) It does not contain a plasticizer, or contains more than 0 parts by weight and 4 parts by weight or less of the plasticizer relative to 100 parts by weight of the aliphatic polyester resin;

[0161] (iii) The gel fraction is 60% by weight or more; and

[0162] (iv) The apparent density is 64 g / L or less.

[0163] [8] The aliphatic polyester-based expanded particles according to [7], wherein

[0164] the aliphatic polyester resin contains a poly(3-hydroxyalkanoate) resin.

[0165] [9] The aliphatic polyester-based expanded particles according to [7] or [8], wherein

[0166] the aliphatic polyester resin contains polybutylene adipate terephthalate.

[0167]

[10] An aliphatic polyester-based expanded molded article formed from the aliphatic polyester-based expanded particles according to any one of [7] to [9].

[0168]

[11] An aliphatic polyester-based expanded molded article, wherein

[0169] (i) It contains an aliphatic polyester resin;

[0170] (ii) It does not contain a plasticizer, or contains more than 0 parts by weight and 4 parts by weight or less of the plasticizer relative to 100 parts by weight of the aliphatic polyester resin;

[0171] (iii) The gel fraction is 50% by weight or more; and

[0172] (iv) The density is 44 g / L or less.

[0173] Examples

[0174] Hereinafter, the present invention will be specifically described based on examples, and the technical scope of the present invention is not limited by these examples.

[0175] [Materials]

[0176] The substances used in the examples and comparative examples are as follows.

[0177] (Aliphatic polyester resin)

[0178] P3HA: P3HA produced by the method of Production Example 1 described later

[0179] PBAT: Poly(butylene adipate-co-terephthalate) (Ecoflex F Blend C1200 manufactured by BASF).

[0180] (Non-ionic water-soluble polymer)

[0181] Non-ionic water-soluble polymer: Polyoxyalkylene (Plonon #208 manufactured by NOF Corporation, 80 wt% ethylene oxide, average molecular weight 10,000, hydrophobic group is oxypropylene group)

[0182] (Bubble regulator)

[0183] Bubble regulator: Talc powder (Micro Ace K-1 manufactured by Nippon Talc Co., Ltd.)

[0184] (Crystallization nucleating agent)

[0185] Crystallization nucleating agent: Pentaerythritol (Neulizer P manufactured by Mitsubishi Chemical Corporation)

[0186] (Lubricant)

[0187] Lubricant - 1: Behenamide (Crodamide® BR manufactured by CRODA), Lubricant - 2: Erucamide (Crodamide® ER manufactured by CRODA)

[0188] (Dispersant)

[0189] Dispersant: Tricalcium phosphate (manufactured by Taihei Chemical Industry Co., Ltd.)

[0190] (Dispersion aid)

[0191] Dispersion aid: Sodium alkyl sulfonate (Latemul® PS manufactured by Kao Corporation)

[0192] (Crosslinking agent)

[0193] Crosslinking agent: 1,1 - bis(tert - butylperoxy)cyclohexane (Perhexa® C - 80(S) manufactured by NOF Corporation, purity 80%)

[0194] (Cleaning agent)

[0195] Cleaning agent: Sodium hexametaphosphate (manufactured by WUXI LOTUS ESSENCE Co., Ltd.)

[0196] (Antistatic agent)

[0197] Antistatic agent: Coconut oil fatty acid diethanolamide (Profan 128Extra manufactured by Sanyo Chemical Industries, Ltd.)

[0198] [Measurement method]

[0199] The evaluation methods carried out in the examples and comparative examples are described below.

[0200] (Measurement of the melting point of aliphatic polyester resin particles)

[0201] Using a differential scanning calorimeter (DSC7020 manufactured by Hitachi High-Tech Science Corporation), approximately 5 mg of aliphatic polyester resin particles was weighed. In the DSC curve obtained when the aliphatic polyester resin particles were heated from 10°C to 190°C at a heating rate of 10°C / minute, the highest-temperature melting peak temperature was taken as the melting point.

[0202] (Measurement of the MFR of aliphatic polyester resin particles)

[0203] Using a melt flow index tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the measurement was carried out according to JIS K7210 under the following conditions: a load of 5 kg, and the measurement temperature was the melting end temperature + 5°C to 10°C read from the DSC curve obtained through the above (Measurement of the melting point of aliphatic polyester resin particles).

[0204] (Measurement of the average weight per one aliphatic polyester resin particle)

[0205] One hundred aliphatic polyester resin particles were prepared, and the weight Wp (mg) was measured. The average weight per one particle was calculated as Wp / 100 (mg).

[0206] (Measurement of the temperature and water vapor amount in the low-pressure region during the release process)

[0207] The temperature and relative humidity in the low-pressure region were measured using a temperature and humidity transmitter (HMT330 manufactured by VAISALA) and a probe. The water vapor amount at that temperature was calculated using the measured temperature and relative humidity values.

[0208] (Measurement of the apparent density of aliphatic polyester foamed particles)

[0209] The method for measuring the apparent density of aliphatic polyester foamed particles is as described in the following (1) to (3): (1) Prepare a graduated cylinder filled with ethanol, and sink aliphatic polyester foamed particles with a weight of Wd (g) into the ethanol; (2) Let the volume of the aliphatic polyester foamed particles read from the rising amount of the ethanol water level (immersion method) be Vd (cm 3 ); (3) The apparent density ρd of the aliphatic polyester foamed particles was calculated by the following formula;

[0210] Apparent density ρd (g / L) = (Wd / Vd) × 1000.

[0211] (Evaluation of the Apparent Density of Aliphatic Polyester Foamed Particles)

[0212] The apparent density of the aliphatic polyester foamed particles was evaluated according to the following criteria.

[0213] ○ (Good): The apparent density of the aliphatic polyester foamed particles is 64 g / L or less.

[0214] × (Poor): The apparent density of the aliphatic polyester foamed particles exceeds 64 g / L.

[0215] (Evaluation of the Mutual Adhesion of Aliphatic Polyester Foamed Particles)

[0216] The mutual adhesion of the aliphatic polyester foamed particles was evaluated according to the following criteria.

[0217] ○ (Good): In 100 g of the aliphatic polyester foamed particles, the weight of two or more foamed particles sticking together is less than 1 g.

[0218] × (Poor): In 100 g of the aliphatic polyester foamed particles, the weight of two or more foamed particles sticking together is 1 g or more.

[0219] (Measurement of the Shrinkage Rate of Aliphatic Polyester Foamed Particles)

[0220] The method for measuring the shrinkage rate of the aliphatic polyester foamed particles is as described in the following (1) to (7): (1) Prepare a 300 ml graduated cylinder-type vacuum container, and put the aliphatic polyester foamed particles with a weight of Wbd (g) into this container; (2) Read the volume Vat (cm 3 ) of the aliphatic polyester foamed particles; (3) Calculate the bulk density BD of the aliphatic polyester foamed particles under atmospheric pressure by the following formula;

[0221] Bulk density BD (g / cm 3 ) = Wbd / Vat;

[0222] (4) Use a vacuum pump to adjust the inside of the container containing the above-mentioned aliphatic polyester foamed particles to a reduced pressure state; (5) Read the volume Vvc (cm 3 ) of the aliphatic polyester foamed particles under reduced pressure; (6) Calculate the bulk density VBD of the aliphatic polyester foamed particles under reduced pressure by the following formula;

[0223] Bulk density VBD (g / cm 3 ) = Wbd / Vvc;

[0224] (7) Calculate the shrinkage rate of the aliphatic polyester foamed particles by the following formula;

[0225] Shrinkage rate (%) = (1 - (VBD / BD)) × 100.

[0226] (Evaluation of shrinkage of aliphatic polyester-based foamed particles)

[0227] Based on the shrinkage rate, the shrinkage of the aliphatic polyester-based foamed particles was evaluated according to the following criteria.

[0228] ○ (Good): The shrinkage rate of the aliphatic polyester-based foamed particles is less than 5%.

[0229] △ (Qualified): The shrinkage rate of the aliphatic polyester-based foamed particles is 5% - 10%.

[0230] × (Defective): The shrinkage rate of the aliphatic polyester-based foamed particles exceeds 10%.

[0231] (Determination of gel fraction of aliphatic polyester-based foamed particles)

[0232] The method for determining the gel fraction of the aliphatic polyester-based foamed particles is as described in the following (1) - (5): (1) Add 0.5 g of the aliphatic polyester-based foamed particles and 50 ml of chloroform to a 100 ml flask; (2) Heat and reflux the mixture in the flask at 62 °C under atmospheric pressure for 8 hours; (3) Filter the heat-treated product obtained using a suction filtration device equipped with a 100-mesh wire mesh; (4) Dry the filtered product on the wire mesh in an oven at 80 °C under vacuum for 8 hours, and measure the weight Wg (g) of the dried product; (5) Calculate the gel fraction by the following formula:

[0233] Gel fraction (wt%) = (Wg / 0.5) × 100.

[0234] (Determination of high-temperature side heat of aliphatic polyester-based foamed particles)

[0235] The high-temperature side heat of the aliphatic polyester-based foamed particles was measured using a differential scanning calorimeter (DSC 7020 manufactured by Hitachi High-Tech Science Corporation). The specific operation sequence is as described in the following (1) - (5): (1) Weigh approximately 5 mg of the aliphatic polyester-based foamed particles; (2) Heat the aliphatic polyester-based foamed particles from 10 °C to 190 °C at a heating rate of 10 °C / minute to melt the aliphatic polyester-based foamed particles; (3) In the DSC curve obtained through the above process (2), connect the point representing the temperature before the start of melting and the point representing the temperature after the end of melting with a straight line to make a baseline; (4) Draw a straight line perpendicular to the X-axis through the maximum point between the melting peak on the high-temperature side or the highest-temperature melting peak and the adjacent melting peak; (5) Take the heat calculated from the area on the high-temperature side surrounded by the straight lines passing through the baseline and the maximum point and the DSC curve as the high-temperature side heat.

[0236] (Measurement of the internal pressure of aliphatic polyester-based foamed particles)

[0237] The method for measuring the internal pressure of aliphatic polyester-based foamed particles is as described in the following (1) to (5): (1) The weight W1 (g) of the aliphatic polyester-based foamed particles after the pressurization process was measured; (2) The foamed particles were heated at 150 °C for 30 minutes to dissipate the inorganic gas inside the foamed particles; (3) For the aliphatic polyester-based foamed particles after the dissipation of the inorganic gas, the weight W2 (g) of the foamed particles was measured again; (4) The weight of the inorganic gas (ΔW) was calculated from the weight difference (W1 - W2) of the aliphatic polyester-based foamed particles before and after the dissipation of the inorganic gas; (5) The internal pressure P (MPa) of the aliphatic polyester-based foamed particles was calculated by the ideal gas state equation (specifically shown in the following formula):

[0238] Internal pressure P (MPa) = (1 + ΔW / M × 0.082 × (273 + T) × (ρd × 1000 / W2)) / 9.87:

[0239] In the above formula, M is the average molar molecular weight; T is the temperature (room temperature) (°C) when measuring the weight of the aliphatic polyester-based foamed particles after the pressurization process; ρd is the apparent density (g / cm 3 )

[0240] (Measurement of the density of aliphatic polyester-based foamed molded articles)

[0241] The method for measuring the density of aliphatic polyester-based foamed molded articles is as described in the following (1) to (4): (1) The longitudinal (mm), transverse (mm), and thickness direction lengths (mm) of the aliphatic polyester-based foamed molded article measured using a digital caliper (manufactured by Mitutoyo Corporation) were used to calculate the volume V (mm 3 ) of the aliphatic polyester-based foamed molded article; (2) The weight W (g) of the foamed molded article was measured; (3) The density ρ of the aliphatic polyester-based foamed molded article was calculated by the following formula: Density ρ (g / L) = (W / V) × 1000000

[0242] (Measurement of the gel fraction of aliphatic polyester-based foamed molded articles)

[0243] The method for measuring the gel fraction of an aliphatic polyester-based foamed molded body is as described in the following (1) to (6): (1) Cut out a 0.5 g rectangular parallelepiped with a length of 5 mm, a width of 5 mm, and a height of 5 mm from the surface of the aliphatic polyester-based foamed molded body; (2) Add 0.5 g of the rectangular parallelepiped cut from the aliphatic polyester-based foamed molded body and 50 ml of chloroform to a 100 ml flask; (3) Under atmospheric pressure, heat and reflux the mixture in the flask at 62 °C for 8 hours; (4) Filter the obtained heat-treated product using a suction filtration device equipped with a 100-mesh wire mesh; (5) Dry the filtered product on the wire mesh in an oven at 80 °C for 8 hours under vacuum conditions, and measure the weight Wgm (g) of the dried product; (6) Calculate the gel fraction by the following formula:

[0244] Gel fraction (wt%) = (Wgm / 0.5) × 100.

[0245] (Measurement of the compressive strength of an aliphatic polyester-based foamed molded body)

[0246] The method for measuring the compressive strength of an aliphatic polyester-based foamed molded body is as follows: Using a tensile-compression testing machine (TG-50kN manufactured by Minebea), in accordance with JIS K 6767, the compressive strength at 50% distortion was determined.

[0247] 〔Production Example 1〕Production of P3HA

[0248] P3HA was produced according to the method described in International Publication No. 2018 / 070492. At this time, 1 part by weight of a nonionic water-soluble polymer (Plonon #208 manufactured by NOF Corporation) was used relative to 100 parts by weight of P3HA. The obtained P3HA contained: (a) P3HB3HH with a monomer ratio of 3HB / 3HH = 95 / 5 (mol% / mol%) and a weight-average molecular weight of 600,000; and (b) 1 part by weight of a nonionic water-soluble polymer relative to 100 parts by weight of this P3HB3HH.

[0249] 〔Example 1〕

[0250] (Production of aliphatic polyester-based resin particles)

[0251] Weigh using P3HA such that the P3HA is 100 parts by weight, the bubble regulator is 0.10 part by weight, the crystallization nucleating agent is 1.0 part by weight, lubricant - 1 is 0.30 part by weight, and lubricant - 2 is 0.30 part by weight, and make a mixture using a high - speed stirring and dispersing machine (SMV(G)-100 manufactured by Kawata Corporation). Use a twin - screw extruder (TEM - 26SX manufactured by Toshiba Machine Co., Ltd.) to melt - knead the mixture at a cylinder set temperature of 130 °C to 160 °C and make it spray out from the die nozzle installed at the front end of the extruder. After cooling the melted P3HA - based composition at 179 °C ejected from the nozzle with water at 43 °C, apply a trace amount of antistatic agent diluted with water to the surface of the strand of the P3HA - based composition (100 parts by weight), and then cut the strand. The obtained aliphatic polyester - based resin particles have an average weight of 1.6 mg per particle, a melting point of 145 °C, and an MFR of 2.3 g / 10 min measured at 160 °C - 5 kgf after drying at 80 °C.

[0252] (Manufacture of aliphatic polyester - based foamed particles)

[0253] While stirring, add 100 parts by weight of the obtained aliphatic polyester - based resin particles, 200 parts by weight of pure water, 1.0 part by weight of a dispersant, 0.1 part by weight of a dispersion aid, and 2.7 parts by weight of a cross - linker into a pressure - resistant container, and then thoroughly aerate with carbon dioxide to remove the oxygen in the pressure - resistant container. Then, introduce carbon dioxide into the pressure - resistant container as a foaming agent. After that, heat the dispersion liquid in the pressure - resistant container to a foaming temperature of 128.5 °C. Then, additionally introduce carbon dioxide and increase the pressure to a foaming pressure of 3.3 MPa (gauge pressure), and maintain it for 40 minutes near this foaming temperature and near this foaming pressure. After that, open the valve at the bottom of the pressure - resistant container, and release the dispersion liquid in the pressure - resistant container through an opening hole with a diameter of 3.6 mm to an area where the pressure is lower than the pressure inside the container (specifically, atmospheric pressure), the temperature is 90 °C, and the water vapor amount is 379 g / m 3 to obtain aliphatic polyester - based foamed particles. Remove the dispersant adhering to the surface of the foamed particles to a certain extent with a cleaning agent diluted with water and at a certain temperature, and dry at 80 °C. At this time, spray a trace amount of antistatic agent diluted with water to suppress the static electricity of the aliphatic polyester - based foamed particles. The obtained aliphatic polyester - based foamed particles have an apparent density of 58 g / L, a gel fraction of 73% by weight, and a heat quantity on the high - temperature side of 5 J / g. In addition, for the obtained aliphatic polyester - based foamed particles, the evaluation of mutual adhesion is 〇, and the evaluation of shrinkage is △. The composition, manufacturing method, and physical properties of the aliphatic polyester - based foamed particles are summarized in Table 1.

[0254] (Manufacture of aliphatic polyester - based foamed molded body)

[0255] The obtained aliphatic polyester-based foamed particles were added into a pressure-resistant container heated to 80 °C, and the internal pressure of the aliphatic polyester-based foamed particles was adjusted to 0.16 MPa (absolute pressure) by pressurizing with air. The foamed particles were filled into a metal mold with a length of 370 mm, a width of 320 mm, and a thickness of 60 mm of a molding machine (EP-900L-M5 manufactured by DAISEN Co., Ltd.). Then, the aliphatic polyester-based foamed particles were heated with heated steam at a pressure of 0.15 MPa (gauge pressure) for 5 to 10 seconds to obtain an aliphatic polyester-based foamed molded body, and then the foamed molded body was dried at 75 °C. The evaluation results of the aliphatic polyester-based foamed molded body are summarized in Table 1.

[0256] [Examples 2 and 3, Comparative Examples 1 to 6]

[0257] In the release process, the dispersion liquid in the pressure-resistant container was released into an area where the pressure was lower than the pressure in the container (specifically, atmospheric pressure), and the temperature and the amount of water vapor were the conditions shown in Table 1. Except for this, aliphatic polyester-based foamed particles and an aliphatic polyester-based foamed molded body were produced by the same method as in Example 1, and the same evaluation as in Example 1 was carried out. The manufacturing method, physical properties of the foamed particles, and the evaluation results of the foamed molded body are summarized in Table 1.

[0258] [Example 4]

[0259] Aliphatic polyester-based foamed particles were produced using a mixture of 90 parts by weight of P3HA and 10 parts by weight of PBAT instead of 100 parts by weight of P3HA. Except for this, aliphatic polyester-based foamed particles and an aliphatic polyester-based foamed molded body were produced by the same method as in Example 2, and the same evaluation as in Example 1 was carried out. The manufacturing method, physical properties of the foamed particles, and the evaluation results of the foamed molded body are summarized in Table 1.

[0260] [Comparative Example 7]

[0261] Aliphatic polyester-based foamed particles were produced using a mixture of 90 parts by weight of P3HA and 10 parts by weight of PBAT instead of 100 parts by weight of P3HA. In the release process, the dispersion liquid in the pressure-resistant container was released into an area where the pressure was lower than the pressure in the container, and the temperature and the amount of water vapor were the conditions shown in Table 1. Except for this, aliphatic polyester-based foamed particles and an aliphatic polyester-based foamed molded body were produced by the same method as in Example 1, and the same evaluation as in Example 1 was carried out. The manufacturing method and physical properties of the foamed particles, and the evaluation results of the foamed molded body are summarized in Table 1.

[0262]

[0263] Industrial Applicability

[0264] The present invention can be suitably used in the fields of packaging cushioning materials (for example, cushioning materials for 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, battery units, etc.; cushioning materials for automotive item packaging such as transmissions, car hoods, engine hoods, car doors, batteries, engines, etc.); automotive components (for example, bumper cores, headrests, trunks, toolboxes, floor partitions, seat cores, child seat cores, sun visor cores, knee airbags, etc.); heat insulation materials (for example, containers for constant temperature storage, containers for constant temperature transportation, etc.), foundry mold applications; agricultural boxes; fish boxes; building materials and civil engineering materials, etc.

Claims

1. A method for manufacturing aliphatic polyester-based foamed particles, the method comprises: a dispersion step of dispersing aliphatic polyester-based resin particles containing an aliphatic polyester-based resin and a foaming agent in an aqueous dispersion medium in a container; a release step of opening one end of the container and releasing the dispersion liquid in the container to a region where the pressure is lower than the pressure in the container, Among them, the temperature of the region is 65°C to 95°C, and the water vapor amount is 144 g / m 3 ~502 g / m 3 .

2. The method for manufacturing aliphatic polyester-based foamed particles according to claim 1, wherein, the aliphatic polyester-based resin contains a poly(3-hydroxyalkanoate)-based resin.

3. The method for manufacturing aliphatic polyester-based foamed particles according to claim 1 or 2, wherein, the aliphatic polyester-based resin contains polybutylene adipate terephthalate.

4. The method for manufacturing aliphatic polyester-based foamed particles according to claim 1 or 2, wherein, the gel fraction of the aliphatic polyester-based foamed particles is 60% by weight or more.

5. The method for manufacturing aliphatic polyester-based foamed particles according to claim 1 or 2, wherein, a crosslinking agent is further used in the manufacturing method.

6. The method for manufacturing aliphatic polyester-based foamed particles according to claim 1 or 2, wherein, in the manufacturing method, a plasticizer is not used, or the plasticizer is used in an amount of more than 0 part by weight and 4 parts by weight or less relative to 100 parts by weight of the aliphatic polyester-based resin.

7. An aliphatic polyester-based foamed particle, wherein, (i) contains an aliphatic polyester-based resin; (ii) does not contain a plasticizer, or contains the plasticizer in an amount of more than 0 part by weight and 4 parts by weight or less relative to 100 parts by weight of the aliphatic polyester-based resin; (iii) has a gel fraction of 60% by weight or more; and (iv) has an apparent density of 64 g / L or less.

8. The aliphatic polyester-based foamed particle according to claim 7, wherein, the aliphatic polyester-based resin contains a poly(3-hydroxyalkanoate)-based resin.

9. The aliphatic polyester-based foamed particle according to claim 7, wherein, the aliphatic polyester-based resin contains polybutylene adipate terephthalate.

10. An aliphatic polyester-based foamed molded article formed by molding the aliphatic polyester-based foamed particles according to any one of claims 7 to 9.

11. An aliphatic polyester-based foamed molded article, wherein, (i) contains an aliphatic polyester-based resin; (ii) does not contain a plasticizer, or contains the plasticizer in an amount of more than 0 part by weight and 4 parts by weight or less relative to 100 parts by weight of the aliphatic polyester-based resin; (iii) has a gel fraction of 50% by weight or more; and (iv) has a density of 44 g / L or less.

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