Method for producing molded body

Abstract

Provided is a method for producing a molded body comprising a poly(3-hydroxyalkanoate)-based resin, the method comprising: melting and kneading a resin composition comprising the poly(3-hydroxyalkanoate)-based resin in a kneader; and discharging the kneaded composition under a condition where the shear rate at a discharge port is 200 (1 / s) or higher. The poly(3-hydroxyalkanoate)-based resin preferably comprises a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

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 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.

[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 with improved solidification properties.

[0009] As a result of intensive research to solve the above-mentioned problems, the inventors have discovered that the solidification properties of a poly(3-hydroxyalkanoate)-based resin-containing composition can be improved by melt-kneading the poly(3-hydroxyalkanoate)-based resin-containing composition in a kneader and controlling the shear rate at the discharge port to a certain value or higher when the composition is discharged from the discharge port, and have thus completed the present invention.

[0010] That is, the present invention relates to a method for producing a molded article containing a poly(3-hydroxyalkanoate)-based resin, which comprises the steps of melting and kneading a resin composition containing a poly(3-hydroxyalkanoate)-based resin in a kneader, and discharging the resin composition under conditions in which the shear rate at the discharge port calculated by the following formula is 200 (1 / s) or higher. Formula: Shear rate (1 / s) = 4 × Q / (π × R ３ ) (where Q is the discharge amount per discharge port (cm ３ / s), π represents the ratio of the circumference of a circle to its diameter, and R represents the radius (cm) of the outlet hole.

[0011] According to the present invention, it is possible to provide a method for producing a poly(3-hydroxyalkanoate) resin-containing molded article having improved solidification properties.

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The present embodiments relate to a method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, which includes the steps of melting and kneading a resin composition containing a poly(3-hydroxyalkanoate)-based resin in a kneader and discharging the resin composition under conditions such that the shear rate at the discharge port is 200 (1 / s) or more. 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 resin 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 a main component, good biodegradability can be exhibited.

[0016] [Poly(3-hydroxyalkanoate) copolymer (A)] A resin composition containing P3HA preferably contains at least a poly(3-hydroxyalkanoate) copolymer (A) as P3HA. A 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 ratio 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 resin composition containing P3HA may contain, as P3HA, poly(3-hydroxybutyrate) (B) in addition to the poly(3-hydroxyalkanoate) copolymer (A). This can increase the solidification rate of the entire P3HA, further improving the productivity of molded articles.

[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) is 1% by weight or more and 20% by weight or less out of a total of 100% by weight of poly(3-hydroxyalkanoate) copolymer (A) and poly(3-hydroxybutyrate) (B). A content of 1% by weight or more can increase the solidification rate of the entire P3HA. 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.

[0040] However, a resin composition containing P3HA does not necessarily contain poly(3-hydroxybutyrate) (B). According to the method for producing a molded article according to the present disclosure, even if poly(3-hydroxybutyrate) (B) is not contained, the solidification property of the poly(3-hydroxyalkanoate) copolymer (A) can be improved by controlling the shear rate, thereby improving the productivity of molded articles.

[0041] The P3HA contained in the resin 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.

[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] 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.

[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 resin 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.

[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 resin 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.

[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 resin 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.

[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 resin 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 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] However, the resin composition may be substantially free of lubricants. "Substantially free of lubricants" means that the lubricant content is less than 0.01 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. According to the method for producing a molded article according to the present disclosure, even if the resin composition is substantially free of lubricants, the solidification properties of the poly(3-hydroxyalkanoate) resin are improved, thereby improving the productivity of molded articles.

[0067] The resin 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 resin composition is not particularly limited, and may be, for example, pellets or powder.

[0068] [Melt-Kneading Step] In the method for producing a molded article according to the present disclosure, first, a resin composition containing a poly(3-hydroxyalkanoate) resin is melt-kneaded in a kneader. A general kneader can be used for melt-kneading the resin composition. Such a kneader is not particularly limited, but for example, a single-screw or multi-screw extruder, kneader, etc. can be used.

[0069] In the manufacturing method according to the present disclosure, a melt-kneaded resin composition is discharged from a discharge port connected to a kneader. The discharge is performed under conditions where the shear rate at the discharge port is 200 (1 / s) or higher. This improves the solidification properties of the resin composition containing a poly(3-hydroxyalkanoate)-based resin, thereby increasing the productivity of poly(3-hydroxyalkanoate)-based resin-containing molded articles. It is presumed that the application of high shear elongates and orients the molecular chains of the resin, and that the oriented molecular chains more easily induce crystallization of the poly(3-hydroxyalkanoate)-based resin.

[0070] The higher the shear rate, the better, and it is preferably 300 (1 / s) or more, more preferably 400 (1 / s) or more, even more preferably 500 (1 / s) or more, even more preferably 700 (1 / s) or more, and particularly preferably 900 (1 / s) or more. The upper limit of the shear rate is not particularly limited, but from the viewpoint of ease of control, it is preferably 3000 (1 / s) or less, more preferably 2000 (1 / s) or less, and even more preferably 1000 (1 / s) or less.

[0071] The shear rate at the discharge port can be controlled by adjusting the discharge rate of the kneader and the number and diameter of the holes at the discharge port. For example, the shear rate can be increased by reducing the number of holes or the diameter of the holes. The shear rate at the discharge port is calculated by the following formula: Shear rate (1 / s) = 4 x Q / (π x R ３ ) Q: Discharge volume per discharge port (cm ３ / s), π: pi, R: radius of the outlet hole (cm)

[0072] Although the temperature of the resin composition during discharge is not particularly limited, a lower temperature makes it more likely that molecular chains oriented by high shear will be relaxed, and therefore crystallization will be promoted. From this viewpoint, the temperature of the resin composition measured at the discharge port is preferably 180°C or less, more preferably 176°C or less, even more preferably 170°C or less, and particularly preferably 166°C or less.

[0073] The lower limit of the temperature of the resin composition during extrusion is not particularly limited as long as the resin composition can be melt-extruded, but may be, for example, 140° C. or higher, preferably 150° C. or higher, more preferably 160° C. or higher, and particularly preferably 165° C. or higher. According to the production method of the present disclosure, even if the temperature of the resin composition during extrusion is relatively high, good solidification properties can be achieved by increasing the shear rate.

[0074] The diameter of the discharge port is not particularly limited as long as the resin can be discharged, but is preferably 1.2 mm or more. If the diameter is less than 1.2 mm, pressure loss increases and the stability of melt extrusion of the resin tends to decrease. From the viewpoint of such stability, the diameter of the discharge port is more preferably 1.5 mm or more, and even more preferably 2 mm or more. There is no particular upper limit, but it may be, for example, 10 mm or less, 5 mm or less, or 3 mm or less. Here, the diameter of the discharge port refers to the diameter of the hole of the discharge port. The shape of the discharge port may be circular or may be other than circular.

[0075] [Cooling and solidification step] The molten resin composition extruded from the discharge port can be cooled and solidified by a conventional method to obtain a molded product. The cooling and solidification method is not particularly limited, and the resin composition may be cooled by passing it through a liquid tank, by contacting it with a cooling roll or a cooling belt, by cooling it in a mold, or by applying cold air.

[0076] 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.

[0077] [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. This method is particularly suitable for the manufacture of extrusion molded products including pellets, tubes, and films. The molded product produced by this embodiment exhibits good solidification properties. The obtained molded product can be further subjected to thermoforming by heating, vacuum forming, press molding, etc.

[0078] When the molded article produced by the production method according to this embodiment is in the form of pellets, the pellets can be used to produce a molded article of any shape by a known molding method. Applicable molding methods include, but are not limited to, film molding, sheet molding, tube molding, injection molding, blow molding, fiber spinning, extrusion foaming, and bead foaming. Specific examples of film molding include, but are not limited to, T-die extrusion molding, calendar molding, roll molding, and inflation molding.

[0079] 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.

[0080] The following items enumerate preferred aspects of the present disclosure, but the present invention is not limited to the following items. [Item 1] A method for producing a molded article containing a poly(3-hydroxyalkanoate)-based resin, comprising the steps of melting and kneading a resin composition containing a poly(3-hydroxyalkanoate)-based resin in a kneader, and discharging the resin composition under conditions in which the shear rate at a discharge port calculated by the following formula is 200 (1 / s) or higher. Formula: Shear rate (1 / s) = 4 × Q / (π × R ３ ) (where Q is the discharge amount per discharge port (cm ３ / s), π represents the ratio of the circumference of a circle to its diameter, and R represents the radius (cm) of the hole in the discharge port. [Item 2] A method for producing a molded article according to item 1, wherein the poly(3-hydroxyalkanoate) resin contains a copolymer of a 3-hydroxybutyrate unit and another hydroxyalkanoate unit. [Item 3] A method for producing a molded article according to item 2, wherein the other hydroxyalkanoate unit is a 3-hydroxyhexanoate unit. [Item 4] A method for producing a molded article according to any one of items 1 to 3, wherein the temperature of the resin composition during the discharge is 180°C or less. [Item 5] A method for producing a molded article according to any one of items 1 to 4, wherein the molded article is an extrusion-molded article. [Item 6] A method for producing a molded article according to any one of items 1 to 5, wherein the molded article is a pellet. [Item 7] A method for producing a molded article according to any one of items 1 to 6, wherein the diameter of the discharge port is 1.2 mm or more.

[0081] 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.

[0082] The substances used in the examples and comparative examples are as follows: [Poly(3-hydroxyalkanoate)-based resin] P3HB3HH-6: P3HB3HH (average content ratio 3HB / 3HH = 94.0 / 6.0 (mol% / mol%), weight-average molecular weight 610,000 g / mol) Produced in accordance with the method described in Example 1 of WO 2019 / 142845.

[0083] [Additives] Additive-1: Behenic acid amide (manufactured by Nippon Fine Chemical Co., Ltd.: BNT-22H)

[0084] Example 1: 100 parts by weight of P3HB3HH-6 and 0.5 parts by weight of Additive-1 were blended. The blended resin material was placed in the hopper of a loss-in-weight feeder (KUBOTA: CE-W-1E type). The resin material was fed from the feeder at a rate of 10 kg / hr to a co-rotating twin-screw extruder (Shibaura Machine: TEM26SX) equipped with a die having two 2 mm diameter outlets. The molten resin discharged from the die was subjected to a shear rate of 1474 (1 / s) and melt-kneaded under conditions such that the resin temperature reached 176°C. The molten resin discharged from the die was immersed in a water bath filled with 40°C warm water, and the time to crystallization and solidification was measured, which was 17 seconds. The end of crystallization and solidification was determined when the tip of a spatula was pressed against the resin and no longer deformed.

[0085] (Examples 2 to 5, Comparative Example 1) Resin composition pellets were prepared in the same manner as in Example 1, except that the same raw materials were used, the number and diameter of the holes in the discharge port were changed as shown in Table 1 while maintaining the discharge amount, and the shear rate at the discharge port 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.

[0086] Example 6 Resin composition pellets were prepared in the same manner as in Example 1, except that Additive-1 was not added, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 1.

[0087]

[0088] From Table 1, it can be seen that in Comparative Example 1, where the shear rate at the discharge port was less than 200 (1 / s), the solidification time of the resin composition was 38 seconds, whereas in Examples 1 to 5, where the shear rate was controlled to 200 (1 / s) or more, the solidification time was shortened to less than 30 seconds in all cases. It can also be seen that the solidification time shortens as the shear rate value increases.

[0089] (Examples 7 to 11, Comparative Example 2) Resin composition pellets were prepared in the same manner as in Example 1, except that the same raw materials were used, the number and diameter of the holes in the discharge port were changed as shown in Table 2 while maintaining the discharge amount, and the shear rate and resin temperature at the discharge port were changed as shown in Table 2, and evaluations were carried out in the same manner as in Example 1. The results are summarized in Table 2.

[0090]

[0091] Table 2 also shows that the solidification time was shorter in Examples 7 to 11, in which the shear rate at the discharge port was controlled to 200 (1 / s) or more, compared to Comparative Example 2, in which the shear rate at the discharge port was less than 200 (1 / s).

Claims

1. A method for producing a molded article containing a poly(3-hydroxyalkanoate) resin, comprising the steps of melting and kneading a resin composition containing a poly(3-hydroxyalkanoate) resin in a kneader, and discharging the resin composition under conditions such that the shear rate at the discharge port is 200 (1 / s) or higher, as calculated by the following formula: Shear rate (1 / s) = 4 x Q / (π x R ３ ) (where Q is the discharge amount per discharge port (cm ３ / s), π represents the ratio of the circumference of a circle to its diameter, and R represents the radius (cm) of the outlet hole.

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

3. The method for producing a molded article according to claim 2, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

4. The method for producing a molded article according to any one of claims 1 to 3, wherein the temperature of the resin composition during the extrusion is 180°C or less.

5. The method for producing a molded article according to any one of claims 1 to 3, wherein the molded article is an extrusion molded article.

6. The method for producing a molded body according to any one of claims 1 to 3, wherein the molded body is in the form of a pellet.

7. The method for producing a molded article according to any one of claims 1 to 3, wherein the diameter of the discharge port is 1.2 mm or more.

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