Method for producing molded body

Abstract

This method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded body comprises: a step for melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition (A) having a melting point Tm1; a step for adding a non-molten poly(3-hydroxyalkanoate)-based resin-containing composition (B) having a melting point Tm2 (where Tm2 is a temperature higher than Tm1) to the molten composition (A) having a composition temperature of lower than Tm2, thereby obtaining a poly(3-hydroxyalkanoate)-based resin-containing composition (C); a step for holding the temperature of the composition (C) at a temperature of Tm1 to Tm2; and a step for extruding the composition (C) after the holding step and cooling and solidifying the resultant to obtain a molded body.

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 a desire to develop plastics that can decompose 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. They are also biodegradable not only in soil but also in seawater, and are therefore attracting attention as materials 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] Furthermore, Patent Document 2 discloses that the crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) can be increased by blending 0.1 to 20 parts by weight of poly(3-hydroxyalkanoate) having a melting point 20°C or more higher than that of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with 100 parts by weight of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0007] International Publication No. 2021 / 010327 Japanese Patent Application Laid-Open No. 2004-161802

[0008] The techniques disclosed in Patent Documents 1 and 2 can improve the solidification properties of poly(3-hydroxyalkanoate) resins and increase the molding speed. However, the solidification properties are still insufficient, and there is room for further improvement.

[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 is capable of improving the molding speed.

[0010] As a result of intensive research to solve the above-mentioned problems, the present inventors discovered that the molding speed can be improved by melt-kneading a first poly(3-hydroxyalkanoate)-based resin-containing composition, then adding a second poly(3-hydroxyalkanoate)-based resin-containing composition in an unmolten state, which has a higher melting point, to the molten composition, and then carrying out a step of maintaining a temperature between the melting points of both compositions, followed by cooling and solidifying, 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, comprising the steps of: melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition (A) having a melting point Tm1; adding a non-molten poly(3-hydroxyalkanoate)-based resin-containing composition (B) having a melting point Tm2 (provided that Tm2 is higher than Tm1) to the molten composition (A) having a composition temperature lower than Tm2 to obtain a poly(3-hydroxyalkanoate)-based resin-containing composition (C); maintaining the temperature of the composition (C) at a temperature equal to or higher than Tm1 and equal to or lower than Tm2; and extruding the composition (C) after the maintaining step, and cooling and solidifying it to obtain a molded article.

[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 improve the molding speed.

[0013] An embodiment of the present invention will be described below, but the present invention is not limited to the following embodiment. This embodiment relates to a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, including the steps of melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition (A) having a melting point Tm1, adding a non-molten poly(3-hydroxyalkanoate)-based resin-containing composition (B) having a melting point Tm2 to the molten composition (A) whose composition temperature is lower than Tm2 to obtain a poly(3-hydroxyalkanoate)-based resin-containing composition (C), maintaining the temperature of the composition (C) at a temperature equal to or higher than Tm1 and equal to or lower than Tm2, ​​and extruding the composition (C) after the maintaining step and cooling and solidifying it to obtain a molded article. First, the poly(3-hydroxyalkanoate)-based resin, which is the main component of the composition (C) or the molded article, 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] The P3HA-containing composition (C) or the molded article produced by 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 P3HA-containing composition (C) 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 constituent units (monomer units). The poly(3-hydroxyalkanoate) copolymer (a) may contain only two or more types of 3-hydroxyalkanoate units as constituent 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] 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.

[0025] 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.

[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 and less than 24 mol %, which makes it easier to achieve a better elastic modulus and productivity.

[0027] 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).

[0028] 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.

[0029] The content of other hydroxyalkanoate units in copolymer (a1) is 1 mol% or more and 5 mol% or less. From the viewpoint of productivity of molded articles, the lower limit of this ratio is preferably 2 mol% or more, and the upper limit is preferably 4 mol% or less.

[0030] 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).

[0031] 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.

[0032] 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).

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] [Poly(3-hydroxybutyrate) (b)] The P3HA-containing composition (C) preferably contains, as P3HA, poly(3-hydroxybutyrate) (b) in addition to the poly(3-hydroxyalkanoate) copolymer (a). This can increase the solidification rate of the entire poly(3-hydroxyalkanoate) resin and improve the productivity of molded articles.

[0038] 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% based on 100 mol% of all constituent monomer units. The lower limit may be 99.5 mol% or more.

[0039] The monomer units other than the 3-hydroxybutyrate units contained in 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.

[0040] The content of poly(3-hydroxybutyrate) (b) may be set as appropriate, but it is preferable that the proportion of poly(3-hydroxybutyrate) (b) is 1% by weight or more and 20% by weight or less out of a total of 100% by weight of the poly(3-hydroxyalkanoate)-based copolymer (a) and poly(3-hydroxybutyrate) (b). A content of 1% by weight or more can increase the solidification rate of the entire poly(3-hydroxyalkanoate)-based resin, thereby improving the productivity of molded articles. The lower limit of the content is more preferably 3% by weight or more, and even more preferably 5% by weight or more. Furthermore, a content of 20% by weight or less can easily suppress the generation of foreign matter caused by poly(3-hydroxybutyrate) (b). The upper limit is more preferably 15% by weight or less.

[0041] The P3HA contained in the P3HA-containing composition (C) preferably has an average content of 3-hydroxybutyrate units in 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.

[0042] 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.

[0043] 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.

[0044] Furthermore, the weight-average molecular weights of the copolymer (a1), the copolymer (a2), the copolymer (a3), and the poly(3-hydroxybutyrate) (b) are not particularly limited. However, from the viewpoint of achieving both the strength and productivity of the molded article, the weight-average molecular weights of the copolymer (a1) and the 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 the strength and productivity of the molded article, the weight-average molecular weights of the copolymer (a2) and the 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] (Other Resins) The P3HA-containing composition (C) 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.

[0049] 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.

[0050] (Plasticizer) The P3HA-containing composition (C) preferably contains a plasticizer in addition to the poly(3-hydroxyalkanoate) resin. By adding a plasticizer, the productivity of molded articles can be improved.

[0051] 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.

[0052] 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.

[0053] 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."

[0054] 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.

[0055] Examples of the adipate compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0056] Examples of polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0057] 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.

[0058] 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.

[0059] (Additives) The P3HA-containing composition (C) may contain additives as long as the effects of the present 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.

[0060] 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.

[0061] 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.

[0062] However, the P3HA-containing composition (C) 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 poly(3-hydroxyalkanoate) resin in total. 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] [P3HA-Containing Composition (A)] The P3HA-containing composition (A) preferably contains at least one or more poly(3-hydroxyalkanoate) copolymers (a). In addition, it may further contain other resins, plasticizers, additives, etc., as described above. Furthermore, it may or may not contain poly(3-hydroxybutyrate) (b).

[0067] From the viewpoint of the balance between the mechanical properties and productivity of the molded article, the P3HA contained in the P3HA-containing composition (A) preferably has an average content of 3-hydroxybutyrate units of 80 mol% or more and less than 98.5 mol%, more preferably 85 mol% or more and 96 mol% or less, and even more preferably 88 mol% or more and 95 mol% or less, based on 100 mol% of all constituent monomer units contained in the entire P3HA.

[0068] The P3HA-containing composition (A) may be a blend of the components, or may be a mixture of the components that has been mixed and then heated to melt and homogenize. The shape of the composition (A) is not particularly limited, and may be, for example, pellets or powder.

[0069] [P3HA-Containing Composition (B)] The P3HA-containing composition (B) has a melting point Tm2 that is higher than the melting point Tm1 of the P3HA-containing composition (A). Generally, the poly(3-hydroxybutyrate) (b) described above has a higher melting point than the copolymer (a). Therefore, it is preferable that the P3HA-containing composition (B) contains at least poly(3-hydroxybutyrate) (b). The composition (B) may be composed solely of poly(3-hydroxybutyrate) (b), or may further contain, in addition to poly(3-hydroxybutyrate) (b), the copolymer (a) and other resins, plasticizers, additives, etc., as described above, so long as the composition (B) has a higher melting point than the composition (A).

[0070] In order to configure P3HA-containing composition (B) so that it has a higher melting point than P3HA-containing composition (A), it is desirable to select each P3HA so that the average content of 3-hydroxybutyrate units in 100 mol% of all constituent monomer units contained in the entire P3HA of composition (B) is higher than the average content of 3-hydroxybutyrate units in 100 mol% of all constituent monomer units contained in the entire P3HA of composition (A).

[0071] The P3HA contained in the P3HA-containing composition (B) preferably has an average content of 3-hydroxybutyrate units of 98.5 mol% or more and 100 mol% or less, based on 100 mol% of all constituent monomer units contained in the entire P3HA. Within this range, composition (B) having a higher melting point than composition (A) can be formed. The lower limit may be more than 99 mol%, or may be 99.5 mol% or more.

[0072] The P3HA-containing composition (B) may be a blend of the components, or may be a mixture of the components mixed together and then heated and melted to homogenize. The shape of the composition (B) is not particularly limited, and may be, for example, pellets or powder. From the viewpoint of dispersibility, powder is preferred.

[0073] The difference (Tm2-Tm1) between the melting point Tm1 of the P3HA-containing composition (A) and the melting point Tm2 of the P3HA-containing composition (B) is not particularly limited, but is preferably 5°C or higher and 70°C or lower. When the melting point difference is within this range, the effect of improving the molding speed by the holding step is easily achieved. The lower limit is preferably 8°C or higher. The upper limit is not particularly limited, but may be 50°C or lower, 30°C or lower, 20°C or lower, or 15°C or lower.

[0074] The melting point Tm1 of the P3HA-containing composition (A) or the melting point Tm2 of the P3HA-containing composition (B) refers to the peak temperature of the melting peak detected in a DSC curve obtained by heating the homogeneously mixed compositions with a differential scanning calorimeter. When multiple melting peaks are detected, the peak temperature of the melting peak detected on the highest temperature side is designated as Tm.

[0075] The proportions of P3HA-containing composition (A) and P3HA-containing composition (B) used may be set as appropriate, but it is preferable that the proportion of composition (B) be 1 wt% or more and 20 wt% or less out of a total of 100 wt% of composition (A) and composition (B). A proportion of 1 wt% or more can increase the solidification rate of the entire P3HA, improving the productivity of molded articles. The lower limit of this proportion is more preferably 3 wt% or more, and even more preferably 5 wt% or more. Furthermore, a proportion of 20 wt% or less can easily suppress the generation of foreign matter due to the high-melting-point resin component contained in composition (B). The upper limit is more preferably 15 wt% or less.

[0076] [Melt-Kneading Step] In the method for producing a molded article according to the present disclosure, first, the P3HA-containing composition (A) is melt-kneaded to form a molten state. A general processing machine can be used to melt-knead the composition (A). Such a processing machine is not particularly limited, and known machines can be used, including, for example, a Banbury mixer, a roll mill, a kneader, a single-screw or multi-screw extruder, etc. In particular, it is preferable to use an extruder.

[0077] The temperature during melt-kneading is not particularly limited as long as the P3HA-containing composition (A) melts, but is preferably equal to or higher than the melting point of the composition (A) and equal to or lower than the decomposition temperature of P3HA. Specifically, the temperature is preferably in the range of 140°C to 190°C, more preferably 150 to 185°C, and even more preferably 160 to 180°C.

[0078] [Addition Step] Next, non-molten P3HA-containing composition (B) is added to molten P3HA-containing composition (A) to form P3HA-containing composition (C). The temperature of composition (A) at the time composition (B) is added is preferably lower than the melting point Tm2 of composition (B). If the temperature is higher than Tm2, ​​composition (B) will tend to melt immediately after being added, making it difficult to achieve the effect of improving the molding speed by the holding step.

[0079] When the temperature of composition (A) reaches a temperature equal to or higher than the melting point Tm2 of composition (B) in the melt-kneading step, it is preferable to carry out a step of lowering the temperature of composition (A) to below Tm2 before adding composition (B).

[0080] The P3HA-containing composition (B) can be suitably introduced by introducing the composition (B) from the side feed section of the extruder.

[0081] [Maintaining Step] After the P3HA-containing composition (B) is added, a step is carried out in which the temperature of the P3HA-containing composition (C) is maintained in a range from the melting point Tm1 of the P3HA-containing composition (A) or higher to the melting point Tm2 of the P3HA-containing composition (B). By carrying out this step, the molding speed of the composition (C) can be increased. In this step, while the composition (C) is melted as a whole, melting of all of the high-melting-point component, composition (B), is avoided, and a portion of it can remain in the molten composition (C) as fine resin crystals. It is presumed that these fine resin crystals act as a crystal nucleating agent, thereby improving the molding speed of the composition (C).

[0082] If the temperature of composition (C) in the holding step exceeds the melting point Tm2 of composition (B), most of composition (B) will melt, making it difficult to achieve the effects of the holding step. On the other hand, if the temperature of composition (C) in the holding step is less than the melting point Tm1 of composition (A), compositions (A) and (B) will not melt sufficiently, resulting in the formation of a large amount of insoluble matter, making it difficult to obtain a uniform molded product.

[0083] The temperature of the P3HA-containing composition (C) during the holding step refers to the actual temperature measured for the composition (C) during the holding step or immediately after extrusion after the holding step. The temperature during the holding step (hereinafter also referred to as the holding temperature) may be equal to or higher than the melting point Tm1 of composition (A) and equal to or lower than the melting point Tm2 of composition (B), but from the viewpoint of suppressing insoluble content, a higher temperature is preferable. Specifically, it is preferably equal to or higher than a temperature 15°C lower than Tm2 (Tm2-15°C), and more preferably equal to or higher than a temperature 10°C lower than Tm2 (Tm2-10°C). Furthermore, from the viewpoint of increasing the molding speed, a low holding temperature is preferable. Specifically, it is preferably equal to or lower than a temperature 3°C lower than Tm2 (Tm2-3°C), more preferably equal to or lower than a temperature 5°C lower than Tm2 (Tm2-5°C), and even more preferably equal to or lower than a temperature 8°C lower than Tm2 (Tm2-8°C).

[0084] The holding temperature can be determined based on the relationship between the melting point Tm1 of composition (A) and the melting point Tm2 of composition (B) as described above, and therefore no specific numerical value is set. However, the holding temperature may be, for example, within a range of 140°C to 185°C, preferably 150 to 180°C, and more preferably 155 to 170°C.

[0085] The time for which the holding temperature is maintained (hereinafter also referred to as the holding time) is not particularly limited, but is preferably 20 to 180 seconds in terms of the balance between the effect achieved by the holding step and productivity. If the holding time is 20 seconds or more, the effect of improving the molding speed by the holding step is easily achieved. Furthermore, if it is 180 seconds or less, the effect of improving the molding speed commensurate with the holding time can be achieved. The lower limit is preferably 30 seconds or more, more preferably 50 seconds or more, even more preferably 80 seconds or more, and particularly preferably 100 seconds or more. The upper limit may be 150 seconds or less.

[0086] In the holding step, the composition (C) may be in a stationary state without being kneaded, but it is preferable to hold the temperature while melt-kneading the composition (C). This allows fine resin crystals to be evenly dispersed throughout the composition (C), making it easier to improve the molding speed and form molded products of stable quality. In this case, in order to suppress heat generation due to shear and make it easier to control the holding temperature, it is preferable to carry out the holding step in an extruder that does not have a kneading section.

[0087] The melt-kneading step and the holding step may be carried out sequentially in separate devices, but it is preferable to carry out the steps from melt-kneading of composition (A) to extrusion of composition (C) sequentially in the same extruder, since this simplifies the production method. In this case, it is preferable to provide a kneading section in the first half of the extruder for carrying out the melt-kneading, and not provide a kneading section in the second half of the extruder for carrying out the holding step.

[0088] [Cooling and solidification step] The composition (C) 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 after 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.

[0089] 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.

[0090] [Molded Product] The molded product produced by the manufacturing method according to this embodiment is not particularly limited, and may be any of pellets, injection molded products, extrusion molded products, blow molded products, inflation molded products, fibers, extruded foams, and bead foams. Such molded products can be obtained at an improved molding speed. The obtained molded product can be further subjected to thermoforming by heating, vacuum molding, press molding, etc.

[0091] 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 high solidification properties, molded articles can be produced from the pellets with high productivity. 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.

[0092] 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.

[0093] The following items list preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] A method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, comprising: a step of melt-kneading a poly(3-hydroxyalkanoate)-based resin-containing composition (A) having a melting point Tm1; a step of adding a non-molten poly(3-hydroxyalkanoate)-based resin-containing composition (B) having a melting point Tm2 (provided that Tm2 is higher than Tm1) to the molten composition (A) having a composition temperature lower than Tm2 to obtain a poly(3-hydroxyalkanoate)-based resin-containing composition (C); a step of maintaining the temperature of the composition (C) at a temperature equal to or higher than Tm1 and equal to or lower than Tm2; and a step of extruding the composition (C) after the maintaining step, and cooling and solidifying it to obtain a molded article. [Item 2] The method for producing a molded body according to item 1, further comprising a step of lowering the temperature of composition (A) to less than Tm2 after melt-kneading composition (A) and before adding composition (B). [Item 3] The method for producing a molded body according to item 1 or 2, wherein composition (C) is melt-kneaded in the holding step. [Item 4] The method for producing a molded body according to any one of items 1 to 3, wherein the holding temperature in the holding step is at least a temperature 15°C lower than Tm2. [Item 5] The method for producing a molded body according to any one of items 1 to 4, wherein the holding time in the holding step is 20 to 180 seconds. [Item 6] The method for producing a molded body according to any one of items 1 to 5, wherein Tm1 and Tm2 satisfy the formula: 5°C≦Tm2−Tm1≦70°C. [Item 7] The method for producing a molded body according to any one of items 1 to 6, wherein composition (A) contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. [Item 8] The method for producing a molded article according to Item 7, wherein the poly(3-hydroxyalkanoate) resin contained in the composition (A) has an average content of 3-hydroxybutyrate units of 80 mol% or more and less than 98.5 mol% based on 100 mol% of all constituent monomer units.[Item 9] The method for producing a molded article according to any one of Items 1 to 8, wherein the poly(3-hydroxyalkanoate) resin contained in composition (B) has an average content of 3-hydroxybutyrate units of 98.5 mol% or more and 100 mol% or less based on 100 mol% of all constituent monomer units. [Item 10] The method for producing a molded article according to any one of Items 1 to 9, wherein the proportion of composition (B) is 1 to 20 wt% based on a total of 100 wt% of compositions (A) and (B). [Item 11] The method for producing a molded article according to any one of Items 1 to 10, wherein the holding step is carried out in an extruder that does not have a kneading section. [Item 12] The method for producing a molded article according to any one of Items 1 to 11, wherein steps from melt-kneading of composition (A) to extrusion of composition (C) are carried out in the same extruder.

[0094] 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.

[0095] 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.

[0096] [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)

[0097] [Plasticizer] Plasticizer: Glycerin diacetomonolaurate (BIOCIZER, manufactured by Riken Vitamin Co., Ltd.)

[0098] The evaluation methods used in the examples and comparative examples are described below. [Method for evaluating tube molding speed] The cylinder temperature and die temperature of a φ50 mm single-screw extruder connected to an annular die (outer diameter 15 mm, inner diameter 13.5 mm) were set to 165°C, and resin composition pellets were added and extruded into a tube. The extruded tube was passed through a 50°C water bath located 100 mm away from the annular die, then taken up by a take-up machine and cut to a length of 200 mm. To evaluate moldability, the screw rotation speed was arbitrarily changed, and the maximum take-up speed at which a tube with an outer diameter of 6 mm, a wall thickness of 0.2 mm, and a length of 200 mm could be molded was defined as the tube molding speed.

[0099] [Method for measuring Tm1 or Tm2] Using a differential scanning calorimeter (DSC Polymer 214 manufactured by NETZSCH), approximately 2 mg of each resin composition (A) or (B) (however, for resin composition (A), the blend after extruder kneading was used as a sample) was weighed, and the DSC curve obtained by heating from -30°C to 180°C at a heating rate of 10°C / min was obtained, and the peak temperature of the melting peak detected on the highest temperature side was determined as Tm1 or Tm2. The results are shown in Table 1.

[0100] Example 1 A blend of 11.1 parts by weight of P3HB3HH-2, 66.7 parts by weight of P3HB3HH-3, and 22.2 parts by weight of P3HB3HH-28 was prepared to obtain the resin composition shown in Table 1, and this was then further blended with 1 part by weight of Additive-1, 0.5 parts by weight of Additive-2, and 4 parts by weight of a plasticizer.

[0101] The blended resin material (resin mixture) was fed into a φ26 mm co-rotating twin-screw extruder (manufactured by Shibaura Machinery) through the main feed section to form a molten composition (A), and 10 parts by weight of unmolten P3HB (powder having a primary particle diameter of approximately 2 μm) was fed into the side feed section as composition (B) and kneaded, followed by extrusion of composition (C).

[0102] The conditions from the addition of P3HB to the extrusion of composition (C) were such that the temperature of composition (A) at the time of addition of composition (B) and the holding temperature of composition (C) were 165°C and the holding time was 63 seconds, and the screw configuration and cylinder temperature were adjusted. A kneading section was provided before the side feed section of the co-rotating twin-screw extruder, but no kneading section was provided after the side feed section.

[0103] The extruded resin material was passed through a water tank filled with hot water at 40°C to solidify the strands, which were then cut with a pelletizer to obtain resin composition pellets made of resin composition (C). The tube forming speed was evaluated using the obtained resin composition pellets, and the tube forming speed was found to be 55 m / min.

[0104] (Examples 2 to 6 and Comparative Examples 1 and 2) Resin composition pellets were prepared in the same manner as in Example 1, except that the temperature of composition (A) when composition (B) was added, the holding temperature or holding time of composition (C), or the amount of composition (B) added was 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.

[0105] Comparative Example 3 Resin composition pellets were prepared in the same manner as in Example 1, except that composition (B) was not fed through the side feed section, and P3HB was added to the resin material fed through the main feed section according to the resin composition shown in Table 1, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 1.

[0106]

[0107] As can be seen from Table 1, in Examples 1 to 6, composition (B) was added to composition (A) in a molten state, and then the temperature was maintained at not less than the melting point Tm1 (160°C) of composition (A) and not more than the melting point Tm2 (170°C) of composition (B), and therefore the tube forming speed was increased to 50 m / min or more.

[0108] On the other hand, in Comparative Example 1, the holding temperature of composition (C) was 175°C, which was higher than the melting point Tm2 (170°C) of composition (B), and therefore the effect of carrying out the holding step after adding composition (B) was not fully exhibited, and the tube forming speed was less than 50 m / min.

[0109] In Comparative Example 2, the holding temperature of composition (C) was 150°C, which was lower than the melting point Tm1 (160°C) of composition (A), so the resin did not melt sufficiently and a large amount of insoluble matter was produced, making it impossible to mold a tube.

[0110] In Comparative Example 3, composition (B) was not added to composition (A) in a molten state, but was dry-blended with composition (A) in a non-molten state and then melted. Therefore, the effect of carrying out the holding step was not fully exerted, and the tube molding speed was less than 50 m / min.

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 (A) having a melting point Tm1; adding a non-molten poly(3-hydroxyalkanoate) resin-containing composition (B) having a melting point Tm2 (provided that Tm2 is higher than Tm1) to the molten composition (A) having a composition temperature lower than Tm2 to obtain a poly(3-hydroxyalkanoate) resin-containing composition (C); maintaining the temperature of the composition (C) at a temperature between Tm1 and Tm2; and extruding the composition (C) after the maintaining step, and cooling and solidifying it to obtain a molded article.

2. The method for producing a molded body according to claim 1, further comprising a step of lowering the temperature of composition (A) to below Tm2 after melt-kneading composition (A) and before adding composition (B).

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

4. A method for producing a molded body according to claim 1 or 2, wherein the holding temperature in the holding step is at least 15°C lower than Tm2.

5. The method for producing a molded article according to claim 1 or 2, wherein the holding time in the holding step is 20 to 180 seconds.

6. The method for producing a molded article according to claim 1 or 2, wherein Tm1 and Tm2 satisfy the formula: 5°C≦Tm2−Tm1≦70°C.

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

8. A method for producing a molded article according to claim 7, wherein the poly(3-hydroxyalkanoate) resin contained in composition (A) has an average content of 3-hydroxybutyrate units of 80 mol% or more but less than 98.5 mol% of all constituent monomer units (100 mol%).

9. A method for producing a molded article according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) resin contained in composition (B) has an average content of 3-hydroxybutyrate units of 98.5 mol% or more and 100 mol% or less out of 100 mol% of all constituent monomer units.

10. The method for producing a molded article according to claim 1 or 2, wherein the proportion of composition (B) is 1 to 20% by weight out of a total of 100% by weight of composition (A) and composition (B).

11. The method for producing a molded article according to claim 1 or 2, wherein the holding step is carried out in an extruder having no kneading section.

12. The method for producing a molded article according to claim 1 or 2, wherein the steps from melt-kneading of composition (A) to extruding of composition (C) are carried out in the same extruder.

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