Method for producing molded body

Abstract

This method for producing a molded body containing a poly(3-hydroxyalkanoate)-based resin includes carrying out: a step for heating and melting a composition containing a poly(3-hydroxyalkanoate)-based resin; and a step for cooling and solidifying the molten composition to obtain a molded body. The cooling and solidifying step includes: a first cooling step for cooling at a temperature T1; and a second cooling step for cooling at a temperature T2. T1 and T2 satisfy equations (1) to (2) below. Equation (1): T1<T2. Equation (2): 35ºC≤T2≤60ºC

Description

Manufacturing method of molded body

[0001] The present invention relates to a method for producing a molded article containing a poly(3-hydroxyalkanoate) resin.

[0002] In recent years, the separate collection and composting of food waste has been promoted, particularly in Europe, and there is a demand for plastic products that can be composted together with food waste. Furthermore, with marine pollution caused by microplastics coming to the forefront, there is hope for the development of plastics that can be decomposed in seawater.

[0003] Poly(3-hydroxyalkanoate) resins are thermoplastic polyesters that are produced and accumulated as energy storage substances within the cells of many microbial species. Because they are biodegradable not only in soil but also in seawater, they have attracted attention as a material that can solve the above-mentioned problems.

[0004] To produce a molded article containing a poly(3-hydroxyalkanoate) resin as a main component, a resin-containing composition is first heated and melted in an extruder or the like, the melt is extruded from the outlet of the extruder, and the melt is then cooled, for example, by passing it through a water tank or the like to crystallize and solidify. The following cooling conditions for crystallization and solidification have been reported.

[0005] For example, Patent Document 1 describes that, in producing pellets or tubes composed of a poly(3-hydroxyalkanoate) resin, the molten resin after extrusion is passed through a water tank filled with hot water at 40°C to cool and solidify it (see Examples).

[0006] Furthermore, Patent Document 2 discloses that, in producing straws made of polyhydroxyalkanoate, two water tanks are provided as water tanks for cooling and solidifying the melted material, with the temperature of the second water tank set lower than that of the first water tank. Specifically, the document discloses that the straw is passed through a first water tank containing water at a temperature of 125 to 175°F (approximately 52 to 80°C), and then cooled through a second water tank containing water at a temperature of 70 to 90°F (approximately 21 to 32°C).

[0007] International Publication No. 2022 / 009717 U.S. Patent Application Publication No. 2020 / 0367682

[0008] It is known that poly(3-hydroxyalkanoate) resins generally have a low crystallization temperature, and therefore, even when the molten resin is cooled, it takes a long time for the molten resin to be completely crystalline and solidified. According to the cooling conditions described in Patent Documents 1 and 2, it takes a long time for the molten resin to be crystalline and solidified, which results in a problem of low productivity of molded articles.

[0009] In view of the above-mentioned current situation, an object of the present invention is to provide a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, which can shorten the cooling time required for crystallization and solidification after melting.

[0010] As a result of intensive research to solve the above-mentioned problems, the inventors of the present invention found that when melting and then cooling a poly(3-hydroxyalkanoate)-based resin-containing composition, the time required for crystallization and solidification can be shortened by first cooling the composition at a temperature lower than the temperature suitable for crystallization of the resin, and then cooling the composition at a temperature suitable for crystallization, thereby completing the present invention.

[0011] That is, the present invention relates to a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, which comprises the steps of heating and melting a poly(3-hydroxyalkanoate)-based resin-containing composition and cooling and solidifying the melted composition to obtain a molded article, wherein the cooling and solidifying step comprises a first cooling step of cooling the composition to a temperature T1 and a second cooling step of cooling the composition to a temperature T2, and wherein T1 and T2 satisfy the following formulas (1) and (2): Formula (1): T1<T2 Formula (2): 35°C≦T2≦60°C

[0012] According to the present invention, it is possible to provide a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, which can shorten the cooling time required for crystallization and solidification after melting. The shortening of the cooling time after melting can increase the productivity of poly(3-hydroxyalkanoate)-based resin-containing molded articles and also enable the production line to be made more compact.

[0013] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment. This embodiment is a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, which includes a step of heating and melting a poly(3-hydroxyalkanoate)-based resin-containing composition and a step of cooling and solidifying the molten composition to obtain a molded article, and the cooling and solidifying step includes a first cooling step of cooling at temperature T1 and a second cooling step of cooling at temperature T2. First, the poly(3-hydroxyalkanoate)-based resin will be described.

[0014] [Poly(3-hydroxyalkanoate)-based resin] Poly(3-hydroxyalkanoate)-based resin (hereinafter also referred to as P3HA) is a general term for polymers containing at least 3-hydroxyalkanoic acid as a monomer unit. The 3-hydroxyalkanoic acid constituting P3HA is not particularly limited, but examples include 3-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid. P3HA may be a homopolymer or a copolymer containing two or more types of monomer units.

[0015] Furthermore, P3HA may be a copolymer containing, as a monomer unit, at least one of the above-mentioned 3-hydroxyalkanoic acids and other hydroxyalkanoic acids (for example, 4-hydroxyalkanoic acids such as 4-hydroxybutanoic acid). Only one type of P3HA may be used, or two or more types may be used in combination, but a combination of two or more types is preferred.

[0016] A raw material composition containing P3HA or a molded article produced according to the present disclosure preferably contains 50% by weight or more of P3HA, more preferably 70% by weight or more, even more preferably 80% by weight or more, and even more preferably 90% by weight or more. By using P3HA as the main component, good biodegradability can be exhibited.

[0017] [Poly(3-hydroxyalkanoate) copolymer (A)] The raw material composition containing P3HA preferably contains at least a poly(3-hydroxyalkanoate) copolymer (A) as P3HA. The poly(3-hydroxyalkanoate) copolymer is a copolymer having at least one or two or more types of 3-hydroxyalkanoate units. The 3-hydroxyalkanoate unit is preferably represented by the following general formula (1): [-CHR-CH ２ -CO-O-] (1)

[0018] In the general formula (1), R is C ｐ H ２ｐ＋１ where p is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. p is preferably an integer of 1 to 10, and more preferably an integer of 1 to 8.

[0019] As the poly(3-hydroxyalkanoate) copolymer (A), a poly(3-hydroxyalkanoate) copolymer produced by a microorganism is particularly preferred. In the poly(3-hydroxyalkanoate) copolymer produced by a microorganism, all of the 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0020] The poly(3-hydroxyalkanoate) copolymer (A) preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more of all structural units (monomer units). The poly(3-hydroxyalkanoate) copolymer (A) may contain only two or more types of 3-hydroxyalkanoate units as structural units of the polymer, or may contain other units (e.g., 4-hydroxyalkanoate units) in addition to one or more types of 3-hydroxyalkanoate units.

[0021] The poly(3-hydroxyalkanoate) copolymer (A) is preferably a copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units and other hydroxyalkanoate units, and the 3-hydroxybutyrate units are preferably all (R)-3-hydroxybutyrate units.

[0022] The other hydroxyalkanoate units may be 3-hydroxyalkanoate units other than 3HB units, or may be hydroxyalkanoate units other than 3-hydroxyalkanoate units (for example, 4-hydroxyalkanoate units). Only one type of other hydroxyalkanoate unit may be included, or two or more types may be included.

[0023] Specific examples of the poly(3-hydroxyalkanoate) copolymer (A) include poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3- Examples of suitable poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), etc. In particular, from the viewpoints of productivity and mechanical properties of molded articles, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) being particularly preferred.

[0024] The poly(3-hydroxyalkanoate) copolymer (A) may consist of only one type of poly(3-hydroxyalkanoate) copolymer, but from the viewpoint of the balance between productivity and mechanical properties of the molded article, it may contain at least two types of poly(3-hydroxyalkanoate) copolymers differing from each other in crystallinity, more specifically, it may contain at least two types of poly(3-hydroxyalkanoate) copolymers differing from each other in the types of constituent monomers and / or the content ratios of the constituent monomers.

[0025] Specifically, the poly(3-hydroxyalkanoate) copolymer (A) may comprise a copolymer (A1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 1 to 5 mol %, and a copolymer (A2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 24 mol % or more. Such a resin composition can impart a good elastic modulus to a molded article and increase the productivity of the molded article.

[0026] In addition to the copolymer (A1) and the copolymer (A2), the copolymer may further contain a copolymer (A3) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of the other hydroxyalkanoate units is 6 mol % or more but less than 24 mol %, which makes it easier to achieve a better elastic modulus and productivity.

[0027] The raw material composition containing P3HA may contain, as P3HA, poly(3-hydroxybutyrate) (B) in addition to the poly(3-hydroxyalkanoate) copolymer (A), which can increase the solidification rate of the entire P3HA and improve the productivity of molded articles.

[0028] Poly(3-hydroxybutyrate) (B) refers to a homopolymer of 3-hydroxybutyrate, but may contain a small amount of monomer units other than 3-hydroxybutyrate units. Specifically, poly(3-hydroxybutyrate) (B) preferably has an average content of 3-hydroxybutyrate units of more than 99 mol% and not more than 100 mol% relative to 100 mol% of all constituent monomer units.

[0029] The monomer units other than the 3-hydroxybutyrate units contained in the poly(3-hydroxybutyrate) (B) are not particularly limited as long as they are copolymerizable with the 3-hydroxybutyrate units, and examples thereof include 3-hydroxyalkanoate units other than 3-hydroxybutyrate units and hydroxyalkanoate units other than 3-hydroxyalkanoate units (e.g., 4-hydroxyalkanoate units). Specific examples include the units described above with respect to the poly(3-hydroxyalkanoate) copolymer.

[0030] The P3HA contained in the raw material composition preferably has an average content of 3-hydroxybutyrate units of 100 mol % of all constituent monomer units contained in the entire P3HA, of 80 mol % or more and 98.5 mol % or less, more preferably 85 mol % or more and 96 mol % or less, and even more preferably 88 mol % or more and 95 mol % or less, from the viewpoint of achieving both strength and productivity of the molded article.

[0031] The average content of each monomer unit in P3HA can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of WO 2013 / 147139. The average content means the molar ratio of each monomer unit to all constituent monomer units contained in the entire P3HA.

[0032] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is not particularly limited, but from the viewpoint of achieving both strength of the molded body and productivity, it is preferably 200,000 to 2,000,000, more preferably 250,000 to 1,500,000, and even more preferably 300,000 to 1,000,000.

[0033] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin can be measured in terms of polystyrene using gel permeation chromatography (HPLC GPC system manufactured by Shimadzu Corporation) using a chloroform solution. As the column for the gel permeation chromatography, a column appropriate for measuring the weight-average molecular weight may be used.

[0034] The method for producing poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a production method using chemical synthesis or a production method using a microorganism. Among these, a production method using a microorganism is preferred. Known methods can be applied to the production method using a microorganism. For example, known bacteria that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, in order to increase the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) or the like into which genes encoding P3HA synthases have been introduced is more preferred, and microbial cells obtained by culturing these microorganisms under appropriate conditions and allowing P3HB3HH to accumulate within the cells can be used. In addition to the above, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may be used depending on the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0035] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis. Alternatively, a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, or the like, or by dissolving two or more resins in a solvent, mixing, and drying the resins.

[0036] (Other Resins) The raw material composition may contain other resins besides the poly(3-hydroxyalkanoate)-based resin, as long as the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester-based resins such as polybutylene succinate adipate, polybutylene succinate, polycaprolactone, and polylactic acid, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebacate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0037] The content of the other resin is not particularly limited, but is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, even more preferably 10 parts by weight or less, and particularly preferably 5 parts by weight or less, relative to a total of 100 parts by weight of the poly(3-hydroxyalkanoate) resin. It may even be 1 part by weight or less. The lower limit of the content of the other resin is not particularly limited, and may even be 0 part by weight.

[0038] (Plasticizer) The raw material composition preferably contains a plasticizer in addition to the poly(3-hydroxyalkanoate) resin. By adding a plasticizer, the productivity of molded articles can be improved.

[0039] The plasticizer is not particularly limited, but from the viewpoint of compatibility with the poly(3-hydroxyalkanoate) resin, it is preferable to use an ester compound having an ester bond in the molecule.

[0040] Examples of ester compounds that can be used as plasticizers include modified glycerin compounds, dibasic acid ester compounds, adipate compounds, polyether ester compounds, benzoate ester compounds, citrate ester compounds, isosorbide ester compounds, and polycaprolactone compounds. Among these, modified glycerin ester compounds, dibasic acid ester compounds, adipate ester compounds, polyether ester compounds, and isosorbide ester compounds are preferred. The ester compounds can be used alone or in combination of two or more. When two or more compounds are used in combination, the mixing ratio of the ester compounds can be appropriately adjusted.

[0041] As the modified glycerin compound, a glycerin ester compound is preferred. As the glycerin ester compound, any of glycerin monoesters, diesters, and triesters can be used, but from the viewpoint of compatibility with poly(3-hydroxyalkanoate) resins, glycerin triesters are preferred. Among glycerin triesters, glycerin diacetomonoester is particularly preferred. Specific examples of glycerin diacetomonoesters include glycerin diacetomonolaurate, glycerin diacetomonooleate, glycerin diacetomonostearate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate. Examples of the modified glycerin compound include Riken Vitamin Co., Ltd.'s "Rikemal" PL series and "BIOCIZER."

[0042] Specific examples of dibasic acid ester compounds include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl) azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, diethyl succinate, and mixed-group dibasic acid ester compounds.

[0043] Examples of the adipate compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0044] Examples of polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0045] As the ester compound, a modified glycerin-based compound is preferred from the viewpoints of cost, versatility, and high biomass content. In particular, from the viewpoint of food contact, a glycerin triester is more preferred, a glycerin diacetomonoester is even more preferred, and glycerin diacetomonolaurate is particularly preferred.

[0046] The amount of plasticizer to be added can be appropriately determined taking into consideration the moldability and strength of the molded product, but is preferably 0.1 parts by weight or more and 10 parts by weight or less relative to a total of 100 parts by weight of the poly(3-hydroxyalkanoate) resin. The lower limit of the amount of plasticizer to be added is preferably 1 part by weight or more, more preferably 2 parts by weight or more, and even more preferably 3 parts by weight or more. The upper limit is preferably 8 parts by weight or less, more preferably 6 parts by weight or less.

[0047] (Additives) The raw material composition may contain additives as long as the effects of the invention are not impaired. Examples of additives that can be used depending on the purpose include crystallization nucleating agents, lubricants, plasticizers, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, UV absorbers, colorants, inorganic fillers, organic fillers, and hydrolysis inhibitors. Biodegradable additives are particularly preferred.

[0048] Examples of the crystallization nucleating agent include sugar alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, boron nitride, etc. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, because they are particularly effective in promoting the crystallization of poly(3-hydroxyalkanoate) resins.

[0049] The amount of the crystallization nucleating agent used is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, relative to 100 parts by weight of the total poly(3-hydroxyalkanoate) resin. One type of crystallization nucleating agent may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

[0050] However, the raw material composition may be substantially free of sugar alcohols such as pentaerythritol. Substantially free of sugar alcohols means that the amount of sugar alcohols added is less than 0.1 parts by weight per 100 parts by weight of the total poly(3-hydroxyalkanoate) resin. It may even be less than 0.01 parts by weight. In an embodiment in which sugar alcohols are not added substantially, it is possible to avoid the problems of sugar alcohols bleeding out from the molded product and the resulting contamination of the manufacturing equipment.

[0051] When sugar alcohols are not substantially blended, it is preferable to blend talc and / or fatty acid amide as a nucleating agent, and it is particularly preferable to blend both talc and fatty acid amide.By using these nucleating agents, even when sugar alcohols are not substantially blended, the productivity of the molded body can be improved.In addition, specific examples of fatty acid amides are as follows: as a lubricant.Fatty acid amides can function as both a nucleating agent and a lubricant.

[0052] Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauricamide, ethylenebiscapricamide, p-phenylenebisstearamide, polycondensates of ethylenediamine, stearic acid, and sebacic acid, etc. Among these, behenamide and erucamide are preferred because of their particularly excellent lubricating effect on poly(3-hydroxyalkanoate) resins.

[0053] The amount of lubricant used is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, relative to 100 parts by weight of the total poly(3-hydroxyalkanoate) resin. One type of lubricant may be used, or two or more types may be used, and the usage ratio can be adjusted appropriately depending on the purpose.

[0054] The raw material composition containing the poly(3-hydroxyalkanoate) resin may be a blend of the respective components, or may be a mixture of the respective components that has been mixed and then homogenized by heating and melting. The shape of the raw material composition is not particularly limited, and may be, for example, pellets or powder.

[0055] [Melt-Kneading Step] In the method for producing a molded article according to the present disclosure, first, a raw material composition containing a poly(3-hydroxyalkanoate) resin is heated and melted. A general processing machine can be used to heat and melt the raw material composition. Such a processing machine is not particularly limited, and known machines can be used, but examples include a Banbury mixer, a roll mill, a kneader, and a single-screw or multi-screw extruder. In particular, it is preferable to use an extruder.

[0056] The composition temperature during heating and melting may be equal to or higher than the melting point (Tm) of the raw material composition, specifically, within the range of 140°C to 190°C, preferably 150 to 185°C, and more preferably 160 to 180°C.

[0057] [Cooling and Solidification Step] Next, the heated and melted raw material composition is cooled and solidified to obtain a molded product. When the heated and melted raw material composition is heated and melted using an extruder, the molten composition discharged from the outlet of the extruder may be cooled and solidified.

[0058] In the present disclosure, cooling and solidification refers to a process performed on a melt of a resin composition, in which the melt is cooled to crystallize and solidify, thereby forming a molded product having a predetermined shape. This cooling and solidification does not include a stretching treatment or a heating treatment that is performed after producing a molded product such as a film or fiber.

[0059] In this embodiment, the cooling and solidifying step comprises at least two cooling steps, including a first cooling step in which the raw material composition is cooled at a temperature T1 and a second cooling step in which the raw material composition is cooled at a temperature T2. The first and second cooling steps can be carried out sequentially. That is, the heated and melted raw material composition is cooled to a temperature T1 in the first cooling step to obtain a semi-solidified composition, and then the semi-solidified composition is immediately cooled to a temperature T2 in the second cooling step to promote crystalline solidification and obtain a molded body. The first and second cooling steps are preferably carried out continuously. In particular, when the process from heating and melting to obtaining a molded body is carried out continuously on a production line, it is preferable to carry out both steps continuously on the production line.

[0060] The cooling temperature T1 in the first cooling step is lower than the cooling temperature T2 in the second cooling step. That is, formula (1): T1 < T2 is satisfied. In this embodiment, the material is first cooled to a temperature T1 lower than the temperature suitable for crystallization, and then cooled to a temperature T2 suitable for crystallization, thereby shortening the total cooling time required for crystallization and solidification. Conversely, if T1 is higher than T2, it is difficult to achieve the effect of shortening the cooling time.

[0061] The cooling temperature T1 in the first cooling step is preferably higher than the glass transition temperature of P3HA (near about 0°C) so as not to inhibit the crystallization of P3HA, more preferably 10°C or higher, and even more preferably 20°C or higher.

[0062] In the second cooling step, a cooling temperature suitable for crystallization is adopted to increase the crystallinity of the composition that has been semi-solidified in the first cooling step. As such a temperature, the cooling temperature T2 in the second cooling step satisfies the formula (2): 35°C ≦ T2 ≦ 60°C. The lower limit of the formula (2) may be 40°C or higher. The second cooling step reduces the temperature of the melt to a temperature close to a temperature suitable for crystallization, thereby promoting crystalline solidification.

[0063] The temperature difference between cooling temperature T1 and cooling temperature T2 can be set as appropriate, but is preferably within a range that satisfies formula (3): 5°C≦T2−T1≦40°C. When the temperature difference is 5°C or more, the effect of shortening the cooling time by providing the first cooling step is easily obtained. Furthermore, when the temperature difference is 40°C or less, the crystallization of P3HA is less likely to be inhibited by the first cooling step. The lower limit of the temperature difference is preferably 10°C or more, and the upper limit is preferably 35°C or less, more preferably 30°C or less.

[0064] The cooling temperatures T1 and T2 do not refer to the actual temperatures of the composition, but rather to the temperatures of the medium used for cooling. For example, when cooling is performed in a liquid bath, they refer to the temperature of the liquid in the liquid bath, and when cooling is performed in a mold, they refer to the set temperature of the mold.

[0065] The cooling time in each cooling step cannot be generally defined because it differs depending on the shape and size of the molded body, the molding method, the cooling method, the type of cooling medium, etc., but the ratio of the cooling time in the first cooling step to the cooling time in the second cooling step may be about 0.1 to 10, preferably 0.2 to 5, and more preferably 0.2 to 2.

[0066] Although not particularly limited, the cooling time in the first cooling step is preferably 2 to 20 seconds, more preferably 5 to 15 seconds. When the cooling time in the first cooling step is 2 seconds or more, the effect of providing the first cooling step is easily obtained. Furthermore, when the cooling time in the first cooling step is 20 seconds or less, the crystallization of P3HA is less likely to be inhibited by the first cooling step.

[0067] Furthermore, the cooling time in the second cooling step is preferably 2 to 30 seconds, more preferably 5 to 25 seconds, and even more preferably 8 to 20 seconds. When the cooling time in the second cooling step is 2 seconds or more, the melt can be cooled to a temperature close to that suitable for crystallization by the second cooling step, and crystalline solidification can be easily achieved. When the cooling time in the second cooling step is 30 seconds or less, the effect of shortening the total cooling time can be easily obtained.

[0068] According to this embodiment, the total cooling time in the first cooling step and the second cooling step can be shortened, specifically, to 40 seconds or less, or 35 seconds or less, or even 30 seconds or less.

[0069] The cooling methods in the first cooling step and the second cooling step are not particularly limited, and any cooling method used in the field of resin melt processing can be used as appropriate. Examples include a method of cooling by passing the molten composition through a liquid tank, a method of cooling by contacting the molten composition with a cooling roll or a cooling belt, a method of injecting the molten composition into a mold and cooling it in the mold, and a method of cooling by blowing cold air onto the molten composition. Among these, the method of cooling in a liquid tank is preferred because it allows for efficient cooling.

[0070] The first cooling step and the second cooling step may use the same cooling method or different cooling methods. However, it is preferable to use the same cooling method because it simplifies the production process. In particular, it is preferable to use a method in which cooling is performed in a liquid tank for both the first cooling step and the second cooling step.

[0071] When cooling in a liquid tank, the liquid in the liquid tank is not particularly limited, and water, an organic solvent, or the like can be used as appropriate. Water and an organic solvent may also be used in combination. Water is preferred because it is easy to handle and has an excellent cooling effect.

[0072] [Molded Product] The molded product produced by the manufacturing method according to this embodiment is not particularly limited, and may be a pellet, an injection molded product, an extrusion molded product, a blow molded product, an inflation molded product, a fiber, an extrusion foam, or a bead foam. Since the molded product can be produced by cooling in a liquid tank, the molded product is preferably a pellet or a tube. The obtained molded product can be further subjected to thermoforming by heating, vacuum forming, press molding, or the like.

[0073] When the molded article produced by the production method according to this embodiment is in the form of pellets, the pellets can be used to produce a molded article of any shape by a known molding method. Applicable molding methods include, but are not limited to, film molding, sheet molding, tube molding, injection molding, blow molding, fiber spinning, extrusion foaming, and bead foaming. Specific examples of film molding include, but are not limited to, T-die extrusion molding, calendar molding, roll molding, and inflation molding.

[0074] Molded articles obtained according to the present disclosure can be suitably used in agriculture, fisheries, forestry, horticulture, medicine, hygiene products, the food industry, clothing, non-clothing, packaging, automobiles, building materials, and other fields. Specific applications are not particularly limited, but examples include tableware, agricultural materials, office automation parts, home appliance parts, automobile components, daily necessities, stationery, molded bottles, extruded sheets, and profile extrusion products. Furthermore, because the resin component of the molded article obtained according to the present disclosure is primarily composed of poly(3-hydroxyalkanoate)-based resin, it is seawater degradable, and therefore can solve environmental problems caused by the dumping of plastics into the ocean.

[0075] The following items list preferred aspects of the present disclosure, but the present invention is not limited to them. [Item 1] A method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, comprising: a step of heating and melting a poly(3-hydroxyalkanoate)-based resin-containing composition; and a step of cooling and solidifying the melted composition to obtain a molded article, wherein the cooling and solidifying step comprises a first cooling step of cooling to a temperature T1 and a second cooling step of cooling to a temperature T2, wherein T1 and T2 satisfy the following formulas (1) and (2): Formula (1): T1<T2 Formula (2): 35°C≦T2≦60°C [Item 2] A method for producing a molded article according to item 1, wherein T1 and T2 further satisfy the following formula (3): Formula (3): 5°C≦T2−T1≦40°C [Item 3] A method for producing a molded article according to item 1 or 2, wherein the cooling time in the first cooling step is 2 to 20 seconds. [Item 4] A method for producing a molded body according to any one of items 1 to 3, wherein the cooling time in the second cooling step is 2 to 30 seconds. [Item 5] A method for producing a molded body according to any one of items 1 to 4, wherein the sum of the cooling time in the first cooling step and the cooling time in the second cooling step is 40 seconds or less. [Item 6] A method for producing a molded body according to any one of items 1 to 5, wherein the first cooling step and / or the second cooling step is carried out in a liquid bath. [Item 7] A method for producing a molded body according to any one of items 1 to 6, wherein the first cooling step and the second cooling step are carried out continuously. [Item 8] A method for producing a molded body according to item 6 or 7, wherein the liquid bath contains water. [Item 9] A method for producing a molded body according to any one of items 1 to 8, wherein the molded body is in the form of a pellet or a tube. [Item 10] A method for producing a molded body according to any one of items 1 to 9, wherein the poly(3-hydroxyalkanoate) resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. [Item 11] The method for producing a molded article according to Item 10, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

[0076] The present invention will be specifically explained below with reference to examples, but the technical scope of the present invention is not limited to these examples.

[0077] The substances used in the examples and comparative examples are as follows: [Poly(3-hydroxyalkanoate)-based resin] P3HB3HH-6:P3HB3HH (average content ratio 3HB / 3HH=93.8 / 6.2 (mol % / mol %), weight-average molecular weight 560,000 g / mol) Produced in accordance with the method described in Example 1 of WO 2019 / 142845.

[0078] [Additives] Additive: Behenic acid amide (manufactured by Nippon Fine Chemical Co., Ltd.: BNT-22H)

[0079] Example 1 4.50 g of P3HB3HH-6 and 0.045 g of additive were placed in a small kneader (DSM Xplore 5 Model 2005) and kneaded for 5 minutes under conditions of a barrel temperature of 170 ° C. and a screw rotation speed of 100 rpm. After kneading was completed, the molten strand-shaped resin composition was discharged from the die and immediately placed in a first water bath set at 20 ° C. for 5 seconds (first cooling step). After removing from the first water bath, it was immediately placed in a second water bath set at 50 ° C., and the time required for crystalline solidification was measured (second cooling step). Crystallization was judged by the timing when a spatula was pressed against the resin composition and no longer deformed. The time required for crystalline solidification was 20 seconds. In total, crystalline solidification took 25 seconds.

[0080] (Examples 2 to 5, Comparative Examples 2 and 3) The time required for crystallization and solidification in the second cooling step was measured in the same manner as in Example 1, except that the set temperatures of the first and second water baths or the cooling time of the first water bath were changed as shown in Table 1. The results are summarized in Table 1.

[0081] Comparative Example 1 The time required for crystallization and solidification in the second water bath was measured in the same manner as in Example 1, except that the first water bath was not provided and the molten strand-shaped resin composition extruded from the die was directly poured into a second water bath set at 50° C. The results are summarized in Table 1.

[0082]

[0083] As can be seen from Table 1, in Comparative Example 1, when the first cooling step was not carried out and only the second cooling step was carried out, the time required for crystallization and solidification was 42 seconds.

[0084] On the other hand, in Examples 1 to 5, the first cooling step, in which cooling was performed at a lower temperature, was followed by the second cooling step, and therefore the total time required for crystallization and solidification was shortened to a maximum of 31 seconds.

[0085] In Comparative Examples 2 and 3, the cooling temperature in the first cooling step was set higher than that in the second cooling step, so the total time required for crystallization and solidification was not shortened and was approximately the same as or longer than that of Comparative Example 1.

Claims

1. A method for producing a molded article containing a poly(3-hydroxyalkanoate) resin, comprising the steps of: heating and melting a poly(3-hydroxyalkanoate) resin-containing composition; and cooling and solidifying the melted composition to obtain a molded article, wherein the cooling and solidifying step comprises a first cooling step of cooling to a temperature T1 and a second cooling step of cooling to a temperature T2, wherein T1 and T2 satisfy the following formulas (1) and (2): Formula (1): T1<T2 Formula (2): 35°C≦T2≦60°C 2. The method for producing a molded article according to claim 1, wherein T1 and T2 further satisfy the following formula (3): 5°C≦T2−T1≦40°C.

3. The method for producing a molded body according to claim 1 or 2, wherein the cooling time in the first cooling step is 2 to 20 seconds.

4. The method for producing a molded body according to claim 1 or 2, wherein the cooling time in the second cooling step is 2 to 30 seconds.

5. The method for producing a molded body according to claim 1 or 2, wherein the total cooling time in the first cooling step and the second cooling step is 40 seconds or less.

6. A method for producing a molded body according to claim 1 or 2, wherein the first cooling step and / or the second cooling step is carried out in a liquid tank.

7. A method for producing a molded body according to claim 1 or 2, wherein the first cooling step and the second cooling step are carried out continuously.

8. The method for producing a molded body according to claim 6, wherein the liquid bath contains water.

9. The method for producing a molded body according to claim 1 or 2, wherein the molded body is in the form of a pellet or a tube.

10. The method for producing a molded article according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

11. The method for producing a molded article according to claim 10, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

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