Method for producing molded body

Abstract

Provided is a method for producing a molded body containing a poly(3-hydroxyalkanoate)-based resin, wherein the following steps are carried out: a step in which a composition containing a poly(3-hydroxyalkanoate)-based resin having a melting point Tm is melt kneaded at a temperature T1; a step in which the temperature of the molten composition is maintained at a temperature T2 for 10-240 seconds; and a step in which, after maintaining this temperature, the composition is extruded and solidified by cooling to obtain a molded body. Tm, T1 and T2 satisfy equations (1) to (3). Equation (1): Tm≤T1. Equation (2): T2≤T1. Equation (3): Tm-30ºC≤T2≤Tm+10ºC.

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] However, poly(3-hydroxyalkanoate) resins have a slow crystallization rate, and therefore, after the resin is heated and melted during molding, it takes a long time for it to crystallize and solidify, which poses a problem of low productivity of molded articles produced by melt processing.

[0005] As one method for addressing such problems, for example, Patent Document 1 describes that a melt-processable composition having excellent solidification properties can be produced by heating and extruding a poly(3-hydroxybutyrate)-based resin exhibiting specific melting characteristics within a specific temperature range.

[0006] International Publication No. 2021 / 010327

[0007] The technology disclosed in Patent Document 1 improves the solidification properties of poly(3-hydroxyalkanoate) resins and increases the molding speed. However, the solidification properties are still insufficient, and there is room for further improvement. In particular, there is a need to increase the cooling crystallization temperature (Tcc), which is an index of the solidification speed.

[0008] 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 that exhibits high Tcc.

[0009] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a poly(3-hydroxyalkanoate)-based resin-containing molded article exhibiting a high Tcc can be obtained by melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition, maintaining the temperature of the molten composition at a specific temperature near the melting point of the composition for a specific period of time, and then cooling and solidifying the composition, thereby completing the present invention.

[0010] That is, the present invention relates to a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, comprising the steps of melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition having a melting point Tm at a temperature T1, maintaining the temperature of the molten composition at a temperature T2 for 10 to 240 seconds, and extruding the composition after the maintenance, and cooling and solidifying it to obtain a molded article, wherein Tm, T1, and T2 satisfy the following formulas (1) to (3): Formula (1): Tm≦T1 Formula (2): T2≦T1 Formula (3): Tm−30°C≦T2≦Tm+10°C

[0011] According to the present invention, it is possible to provide a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article that exhibits a high Tcc.

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. This embodiment is a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, and includes the steps of melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition having a melting point Tm at temperature T1, maintaining the temperature of the molten composition at temperature T2 for 10 to 240 seconds, and extruding the composition after the maintenance and cooling and solidifying it to obtain a molded article. First, the poly(3-hydroxyalkanoate)-based resin will be described.

[0013] [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.

[0014] 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.

[0015] 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.

[0016] [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)

[0017] In the general formula (1), R is C ｐ H ２ｐ＋１where 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] From the viewpoint of productivity and mechanical properties of the molded article, the poly(3-hydroxyalkanoate) copolymer (A) preferably contains at least two types of poly(3-hydroxyalkanoate) copolymers differing from each other in crystallinity, and more preferably contains 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.

[0024] Specifically, the poly(3-hydroxyalkanoate) copolymer (A) preferably comprises 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 molded articles and increase the productivity of molded articles.

[0025] 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.

[0026] Copolymer (A1) is a highly crystalline poly(3-hydroxyalkanoate) resin, while copolymer (A2) is a low-crystalline poly(3-hydroxyalkanoate) resin. Copolymer (A3) is a medium-crystalline poly(3-hydroxyalkanoate) resin whose crystallinity is intermediate between that of copolymer (A1) and copolymer (A2).

[0027] In general, highly crystalline poly(3-hydroxyalkanoate) resins have excellent productivity but poor mechanical properties, while low-crystalline poly(3-hydroxyalkanoate) resins have poor productivity but excellent mechanical properties. By using two or three of the above-mentioned resins in combination, a molded product with an excellent balance between productivity and mechanical properties can be obtained.

[0028] The content of other hydroxyalkanoate units in the copolymer (A1) is 1 mol% or more and 5 mol% or less. From the viewpoint of productivity of the molded article, the lower limit of this content is preferably 2 mol% or more, and the upper limit is preferably 4 mol% or less.

[0029] The copolymer (A1) is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate), more preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0030] The content of other hydroxyalkanoate units in copolymer (A2) is 24 mol% or more. From the viewpoint of the strength of the molded article, the lower limit of this ratio is preferably 26 mol% or more, more preferably 28 mol% or more. Furthermore, from the viewpoint of the productivity of copolymer (A2), the upper limit of this ratio is preferably 99 mol% or less, more preferably 50 mol% or less, even more preferably 40 mol% or less, and particularly preferably 30 mol% or less.

[0031] The copolymer (A2) is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate), more preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0032] The ratio of copolymer (A1) to copolymer (A2) is not particularly limited, but from the viewpoint of the productivity of copolymer (A2) and the balance between productivity and mechanical strength of the molded article, the weight ratio of copolymer (A1) to copolymer (A2) is preferably 1.5 or more and 4.5 or less. The lower limit of this weight ratio is preferably 2.0 or more. The upper limit is preferably 4.0 or less, more preferably 3.5 or less.

[0033] The content of other hydroxyalkanoate units in copolymer (A3) is 6 mol% or more and less than 24 mol%. From the viewpoint of productivity of copolymer (A3) and productivity of molded articles, the upper limit of this ratio is preferably 20 mol% or less, more preferably 15 mol% or less. The lower limit of this ratio is preferably 8 mol% or more, more preferably 10 mol% or more.

[0034] The copolymer (A3) is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate), more preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0035] The proportion of copolymer (A3) relative to the total of copolymer (A1), copolymer (A2), and copolymer (A3) is preferably 0 to 45% by weight, from the viewpoint of the balance between productivity and mechanical properties of the copolymer or molded article. By setting the proportion of copolymer (A3) to 45% by weight or less, a good elastic modulus can be imparted to the molded article. The proportion is more preferably 40% by weight or less, even more preferably 30% by weight or less, and even more preferably 20% by weight or less.

[0036] [Poly(3-hydroxybutyrate) (B)] The raw material composition containing P3HA preferably contains poly(3-hydroxybutyrate) (B) as P3HA in addition to the poly(3-hydroxyalkanoate) copolymer (A). This can increase the solidification rate of the entire P3HA and improve the productivity of molded articles. Furthermore, in the holding step, fine high-melting-point crystals derived from poly(3-hydroxybutyrate) (B) are more likely to be produced, making it easier to increase the Tcc of the resulting molded article.

[0037] 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, the average content of 3-hydroxybutyrate units in poly(3-hydroxybutyrate) (B) based on 100 mol % of all constituent monomer units is preferably more than 99 mol % and 100 mol % or less. The lower limit may be 99.5 mol % or more.

[0038] 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.

[0039] The content of poly(3-hydroxybutyrate) (B) may be set as appropriate, but it is preferable that the proportion of poly(3-hydroxybutyrate) (b) be 1 wt% or more and 20 wt% or less out of a total of 100 wt% of the poly(3-hydroxyalkanoate) copolymer (A) and poly(3-hydroxybutyrate) (B). A content of 1 wt% or more can increase the solidification rate of the entire P3HA, further increasing the Tcc of the resulting molded body. The lower limit of the content is more preferably 3 wt% or more, and even more preferably 5 wt% or more. Furthermore, a content of 20 wt% or less can easily suppress the generation of foreign matter caused by poly(3-hydroxybutyrate) (B). The upper limit is more preferably 15 wt% or less.

[0040] 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.

[0041] 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.

[0042] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is not particularly limited, but from the viewpoint of achieving both strength and productivity of the molded article, 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.

[0043] The weight-average molecular weights of copolymer (A1), copolymer (A2), copolymer (A3), and poly(3-hydroxybutyrate) (B) are not particularly limited. However, from the viewpoint of achieving both strength and productivity of molded articles, the weight-average molecular weights of copolymer (A1) and poly(3-hydroxybutyrate) (B) are each preferably 200,000 to 1,000,000, more preferably 220,000 to 800,000, and even more preferably 250,000 to 700,000. On the other hand, from the viewpoint of achieving both strength and productivity of molded articles, the weight-average molecular weights of copolymer (A2) and copolymer (A3) are each preferably 200,000 to 2,500,000, more preferably 250,000 to 2,300,000, and even more preferably 300,000 to 2,000,000.

[0044] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin, copolymer (A1), copolymer (A2), copolymer (A3), or poly(3-hydroxybutyrate) (B) 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.

[0045] 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.

[0046] 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.

[0047] (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.

[0048] 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.

[0049] (Plasticizer) The raw material composition preferably contains a plasticizer in addition to the poly(3-hydroxyalkanoate) resin. By adding a plasticizer, productivity of the molded article can be improved.

[0050] 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.

[0051] 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.

[0052] 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."

[0053] 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.

[0054] Examples of the adipate compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0055] Examples of polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0056] 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.

[0057] 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.

[0058] (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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] [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 melt-kneaded at a temperature T1. A general processing machine can be used to melt-knead 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.

[0067] The temperature T1 in the melt-kneading step refers to the maximum temperature that the raw material composition actually reaches during melt-kneading. The temperature T1 during melt-kneading is a temperature equal to or higher than the melting point Tm of the raw material composition so that the raw material composition is sufficiently melted. That is, the formula (1): Tm≦T1 is satisfied. If T1 is lower than Tm, a large amount of resin component that does not melt during the melt-kneading step is generated, making it difficult to obtain a uniform molded product.

[0068] The melting point Tm of a raw material composition refers to the peak temperature of a melting peak detected in a DSC curve obtained by using a uniformly mixed raw material composition and a differential scanning calorimeter during temperature rise. When multiple melting peaks are detected, the peak temperature of the melting peak detected on the highest temperature side is taken as Tm.

[0069] The temperature T1 during melt-kneading may be equal to or higher than the melting point Tm of the raw material composition, but is preferably equal to or higher than a temperature 1°C higher than Tm (Tm + 1°C), and more preferably equal to or higher than a temperature 3°C higher than Tm (Tm + 3°C).

[0070] The upper limit of the temperature T1 during melt-kneading is not particularly limited, but since this makes it easier to achieve the effects of the holding step described below, it is preferably equal to or lower than a temperature 30°C higher than the melting point Tm of the raw material composition (Tm + 30°C), i.e., T1 ≦ Tm + 30°C. More preferably, T1 ≦ Tm + 25°C, and even more preferably, T1 ≦ Tm + 20°C. Alternatively, T1 ≦ Tm + 10°C may be acceptable. If the upper limit of T1 is within the above range, it becomes easier to generate fine resin crystals in the molten resin in the subsequent holding step, and as a result, the Tcc of the resulting molded body can be further increased.

[0071] The temperature T1 during melt-kneading can be determined in relation to the melting point Tm of the raw material composition as described above, and therefore no specific numerical value is set. However, the temperature may be, for example, within a range of 140°C to 190°C, preferably 150 to 185°C, and more preferably 160 to 180°C.

[0072] [Retention Step] After the melt-kneading step, a step is carried out in which the temperature of the molten composition is maintained at temperature T2 for 10 to 240 seconds. This step may cause some polymer chains to orient in the molten poly(3-hydroxyalkanoate) resin, resulting in the formation of fine resin crystals. It is presumed that these fine resin crystals may act as a crystal nucleating agent, thereby increasing the Tcc of the resulting molded article.

[0073] The temperature T2 in the holding step refers to the actual temperature measured on the composition during the holding step or immediately after extrusion after the holding step. The temperature T2 during the holding step is a temperature equal to or lower than the temperature T1 during melt-kneading. That is, it satisfies the formula (2): T2≦T1. T1 and T2 may be the same temperature. If T2 exceeds T1, it becomes difficult to achieve the effect of increasing Tcc by the holding step.

[0074] The temperature difference (T1-T2) between the temperature T1 during melt-kneading and the temperature T2 during the holding step is not particularly limited, but is preferably 0 to 30°C, more preferably 0 to 20°C, and even more preferably 0 to 15°C. It may also be 0 to 10°C.

[0075] Furthermore, the temperature T2 during the holding step is a temperature near the melting point Tm of the composition, and is in a range that satisfies formula (3): Tm - 30°C ≦ T2 ≦ Tm + 10°C. Therefore, the composition as a whole remains in a molten state during the holding step. If T2 is a temperature lower than "Tm - 30°C", the viscosity of the molten resin increases, making it difficult to control the resin temperature. On the other hand, if T2 is a temperature higher than "Tm + 10°C", the polymer chains relax, making it difficult to increase Tcc.

[0076] The lower limit of T2 is preferably not less than "Tm-20°C", more preferably not less than "Tm-15°C", and even more preferably not less than "Tm-10°C". The upper limit of T2 is preferably not more than "Tm+8°C", and more preferably not more than "Tm+6°C".

[0077] As described above, the temperature T2 during the holding step can be determined in accordance with the relationship between the temperature T1 during melt-kneading and the melting point Tm of the raw material composition, and therefore no specific numerical value is set. However, the temperature T2 may be, for example, within a range of 130°C to 185°C, preferably 140 to 180°C, and more preferably 150 to 170°C.

[0078] In the holding step, the temperature T2 of the composition is held for 10 to 240 seconds. If the holding time is less than 10 seconds, the polymer chains are not sufficiently oriented, making it difficult to increase the Tcc. Furthermore, if the holding time exceeds 240 seconds, decomposition of the resin begins to occur, which is undesirable. The holding time is preferably 20 seconds or more, more preferably 30 seconds or more. Since this further increases the Tcc of the molded article, a holding time of 45 seconds or more is preferred, more preferably 60 seconds or more, and particularly preferably 80 seconds or more. The upper limit of the holding time may be 200 seconds or less, 150 seconds or less, or 120 seconds or less.

[0079] In the holding step, the composition may be left stationary without being kneaded, but it is preferable to hold the temperature while melt-kneading the composition, which allows fine resin crystals to be formed evenly throughout the composition, thereby enabling the Tcc of the molded product to be uniformly increased.

[0080] The melt-kneading step and the holding step may be carried out sequentially in a single kneading extruder, but it is preferable to carry out each step in a separate device, since this makes it easier to control the holding step. In particular, it is preferable to prepare a kneader and an extruder connected to the outlet of the kneader, carry out the melt-kneading step in the kneader, transfer the molten composition as it is to the extruder, carry out the holding step in the extruder, and then extrude the composition from the outlet of the extruder.

[0081] [Cooling and solidification step] The composition that has been through the melt-kneading step and the holding step can be extruded and cooled and solidified by a conventional method to obtain a molded product. The cooling and solidification method is not particularly limited, and the composition that has been through the holding step may be cooled by passing it through a liquid tank, by contacting it with a cooling roll or a cooling belt, or by cooling it in a mold, or by applying cold air.

[0082] The temperature during cooling may be selected as appropriate, but may be, for example, about 30 to 70°C, and preferably about 40 to 60°C.

[0083] [Molded body] The molded body produced by the manufacturing method according to this embodiment is not particularly limited, and may be a pellet, an injection molded body, an extrusion molded body, a blow molded body, an inflation molded body, a fiber, an extrusion foam, or a bead foam. The molded body produced according to this embodiment exhibits a high Tcc and good solidification properties. The obtained molded body can be further subjected to thermoforming by heating, vacuum forming, press molding, etc.

[0084] The Tcc exhibited by the molded article produced by the production method according to this embodiment varies depending on the constitution of the poly(3-hydroxyalkanoate) resin, but can be, for example, 80° C. or higher, 85° C. or higher, 90° C. or higher, or 95° C. or higher. There is no particular upper limit, and the Tcc is below the melting point of the poly(3-hydroxyalkanoate) resin.

[0085] When the molded article produced by the production method according to this embodiment is a pellet, the pellet can be used to produce a molded article of any shape by a known molding method. Because the pellets exhibit a high Tcc, molded articles can be produced from the pellets with high productivity. Applicable molding methods are not particularly limited, and include film molding, sheet molding, tube molding, injection molding, blow molding, fiber spinning, extrusion foaming, bead foaming, and the like. Specific examples of film molding are also not particularly limited, and include, for example, T-die extrusion molding, calendar molding, roll molding, and inflation molding.

[0086] 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.

[0087] 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 the steps of melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition having a melting point Tm at temperature T1, maintaining the temperature of the molten composition at temperature T2 for 10 to 240 seconds, and extruding the composition after the maintenance and cooling and solidifying it to obtain a molded article, wherein Tm, T1, and T2 satisfy the following formulas (1) to (3): Formula (1): Tm≦T1 Formula (2): T2≦T1 Formula (3): Tm−30°C≦T2≦Tm+10°C [Item 2] The method for producing a molded article according to item 1, wherein the melt-kneading step is carried out in a kneader, and the maintaining step is carried out in an extruder connected to the outlet of the kneader. [Item 3] The method for producing a molded article according to item 1 or 2, wherein the composition is melt-kneaded in the holding step. [Item 4] The method for producing a molded article according to any one of items 1 to 3, wherein formula (1) satisfies Tm≦T1≦Tm+30°C. [Item 5] The method for producing a molded article according to any one of items 1 to 4, wherein the poly(3-hydroxyalkanoate) resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. [Item 6] The method for producing a molded article according to item 5, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

[0088] 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.

[0089] The substances used in the examples and comparative examples are as follows. [Poly(3-hydroxyalkanoate)-based resin] P3HB: Poly(3-hydroxybutyrate) (weight average molecular weight: 300,000 g / mol) Produced in accordance with the method described in Comparative Example 1 of WO 2004 / 041936. P3HB3HH-2: P3HB3HH (average content ratio 3HB / 3HH = 96.9 / 1.9 (mol% / mol%), weight average molecular weight: 600,000 g / mol) Produced in accordance with the method described in Comparative Example 2 of WO 2019 / 142845. P3HB3HH-3: P3HB3HH (average content ratio 3HB / 3HH = 96.9 / 3.1 (mol% / mol%), weight average molecular weight is 300,000 g / mol) Produced in accordance with the method described in Example 2 of WO 2019 / 142845. P3HB3HH-28: P3HB3HH (average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight average molecular weight is 660,000 g / mol) Produced in accordance with the method described in Example 9 of WO 2019 / 142845.

[0090] [Additives] Additive-1: Behenic acid amide (manufactured by Nippon Fine Chemicals Co., Ltd.: BNT-22H) Additive-2: Erucic acid amide (manufactured by Nippon Fine Chemicals Co., Ltd.: Neutron S)

[0091] [Plasticizer] Plasticizer: Glycerin diacetomonolaurate (BIOCIZER, manufactured by Riken Vitamin Co., Ltd.)

[0092] The evaluation methods used in the examples and comparative examples are described below. [Method for measuring Tm] Using a differential scanning calorimeter (DSC Polymer 214 manufactured by NETZSCH), approximately 2 mg of the resin composition was weighed and heated from -30°C to 180°C at a heating rate of 10°C / min. In the DSC curve obtained, the peak temperature of the melting peak detected on the highest temperature side was determined as Tm.

[0093] [Method of Measuring Tcc] Using a differential scanning calorimeter (DSC Polymer 214 manufactured by NETZSCH), approximately 2 mg of the resin composition was weighed, heated from -30°C to 180°C at a heating rate of 10°C / min, held at 180°C for 1 minute, and then cooled to -30°C at a heating rate of 10°C / min. The peak temperature of the cooling crystallization temperature detected in the DSC curve obtained when the temperature was lowered was determined as the cooling crystallization temperature Tcc. Generally, the cooling crystallization temperature Tcc is used as an index of solidification rate, and in particular, the smaller the difference between the melting point and the cooling crystallization temperature of a material, the faster the crystallization and solidification.

[0094] Example 1 10 parts by weight of P3HB, 10 parts by weight of P3HB3HH-2, 60 parts by weight of P3HB3HH-3, 20 parts by weight of P3HB3HH-28, 1 part by weight of Additive-1, 0.5 parts by weight of Additive-2, and 4.3 parts by weight of plasticizer were blended. The blended resin material was placed in a Φ55 mm co-kneader (Buss) as a melt-kneading process and kneaded so that the resin temperature T1 was 166 ° C. At this time, a portion of the kneaded resin composition was recovered, and Tm was measured, which was 160 ° C. Thereafter, the molten mixture in the co-kneader was transferred directly to a Φ70 mm oblique-axis counter-rotating twin-screw extruder directly connected to the co-kneader, and in the extruder, the resin temperature T2 was melt-kneaded and extruded as a holding process so that the resin temperature T2 was 166 ° C. and the holding time was 33 seconds. The extruded resin material was passed through a water tank filled with warm water at 50°C to crystallize and solidify the strands, which were then cut with a pelletizer to obtain resin composition pellets. The Tcc of the obtained resin composition pellets was measured and found to be 80°C.

[0095] (Examples 2 to 10, Comparative Example 2) Resin composition pellets were prepared in the same manner as in Example 1, except that the same raw materials were used and the discharge amount, the resin temperature T1 in the melt-kneading step, and the resin temperature T2 and holding time in the holding step were changed as shown in Table 1, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 1.

[0096] Comparative Example 1 Resin composition pellets were prepared in the same manner as in Example 2, except that the twin-screw extruder was not connected to the co-kneader and the resin material was extruded from the co-kneader, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 1.

[0097] Comparative Example 3 An attempt was made to produce resin composition pellets under the same conditions as in Example 1, except that the holding time in the holding step was changed to 300 seconds. However, the molecular weight was significantly reduced due to thermal decomposition of the resin, and it was not possible to obtain resin composition pellets of a quality that could be used for producing a molded product, etc.

[0098] Comparative Example 4 An attempt was made to produce resin composition pellets under the same conditions as in Example 1, except that the resin temperature T2 in the holding step was changed to 125° C. However, because crystallization was promoted in the extruder, it was not possible to continuously obtain resin composition pellets of consistent quality due to shear heating and the like.

[0099]

[0100] From Table 1, it can be seen that in Comparative Example 1, the resin composition was pelletized directly without being subjected to a holding step after melt-kneading, and therefore the Tcc of the obtained resin composition pellets was as low as 70°C.

[0101] On the other hand, in Examples 1 to 10, the resin composition was melt-kneaded at a resin temperature T1, and then held at a resin temperature T2 lower than T1 for 10 to 240 seconds. As a result, the Tcc of the resulting resin composition pellets was 80°C or higher, which was significantly improved compared to Comparative Example 1.

[0102] However, in Comparative Example 2, the resin temperature T2 in the holding step was set to a temperature higher than the resin temperature T1 during melt-kneading, exceeding "Tm + 10°C", so the Tcc of the obtained resin composition pellets was similar to that of Comparative Example 1, and no effect was obtained from the holding step.

[0103] In Comparative Example 3, the holding time was set to a long time of 300 seconds, and therefore the molecular weight of the resin was reduced during the holding step, and good quality resin pellets could not be obtained.

[0104] In Comparative Example 4, the resin temperature T2 in the holding step was set to a temperature lower than Tm-30°C, which made it difficult to control the resin temperature in the holding step, and it was not possible to continuously obtain resin composition pellets of consistent quality.

Claims

1. A method for producing a poly(3-hydroxyalkanoate) resin-containing molded article, comprising the steps of melt-kneading a poly(3-hydroxyalkanoate) resin-containing composition having a melting point Tm at temperature T1, maintaining the temperature of the molten composition at temperature T2 for 10 to 240 seconds, and extruding the composition after the temperature has been maintained, and cooling and solidifying it to obtain a molded article, wherein Tm, T1, and T2 satisfy the following formulas (1) to (3): Formula (1): Tm≦T1 Formula (2): T2≦T1 Formula (3): Tm-30°C≦T2≦Tm+10°C 2. The method for producing a molded article according to claim 1, wherein the melt-kneading step is carried out in a kneader, and the holding step is carried out in an extruder connected to the outlet of the kneader.

3. The method for producing a molded article according to claim 1 or 2, wherein the composition is melt-kneaded in the holding step.

4. The method for producing a molded body according to claim 1 or 2, wherein the formula (1) satisfies Tm≦T1≦Tm+30°C.

5. 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.

6. The method for producing a molded article according to claim 5, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

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