WO2025177972A1 - Method for producing molded body - Google Patents

Abstract

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

Description

Manufacturing method of molded body

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

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 along with food waste. Furthermore, with marine pollution caused by microplastics coming to the forefront, there is hope for the development of plastics that can decompose in seawater.

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 in soil and seawater, making them attractive as a material that can solve the above problems.

To manufacture a molded article whose main component is a poly(3-hydroxyalkanoate) resin, the resin-containing composition is first heated and melted in an extruder or the like, the molten material is extruded from the extruder's outlet, and the molten material is then cooled, for example, by passing it through a water tank, causing it to crystallize and solidify. The following cooling conditions have been reported for crystallizing and solidifying.

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

Furthermore, Patent Document 2 describes how, when producing straws made from polyhydroxyalkanoate, two water tanks are provided for cooling and solidifying the material after melting, with the temperature of the second water tank set lower than that of the first water tank. Specifically, it discloses that the material is passed through a first water tank containing water at a temperature of 125-175°F (approximately 52-80°C), and then cooled through a second water tank containing water at a temperature of 70-90°F (approximately 21-32°C).

International Publication No. 2022/009717 US Patent Application Publication No. 2020/0367682

Poly(3-hydroxyalkanoate) resins generally have a low crystallization temperature, so it is known that even when the molten resin is cooled, it takes a long time for the molten resin to completely crystallize and solidify. The cooling conditions described in Patent Documents 1 and 2 require a long time for the molten resin to crystallize and solidify, resulting in the problem of low productivity for molded articles.

In light of the current situation, the present invention aims to provide a method for producing molded articles containing poly(3-hydroxyalkanoate) resins that can shorten the cooling time required for crystallization and solidification after melting.

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

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

The present invention provides a method for producing molded articles containing poly(3-hydroxyalkanoate) resins that can shorten the cooling time required for crystallization and solidification after melting. Reducing the cooling time after melting increases the productivity of molded articles containing poly(3-hydroxyalkanoate) resins and also allows for more compact production lines.

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

[Poly(3-hydroxyalkanoate)-based resin]
Poly(3-hydroxyalkanoate) 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 that constitutes 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.

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

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

[Poly(3-hydroxyalkanoate) copolymer (A)]
The raw material composition containing P3HA preferably contains, as P3HA, at least a poly(3-hydroxyalkanoate) copolymer (A). 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)

In general formula (1), R represents an alkyl group represented by C _p H _2p+1 , and p represents 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 1 to 10, and more preferably 1 to 8.

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

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). Poly(3-hydroxyalkanoate) copolymer (A) may contain only two or more types of 3-hydroxyalkanoate units as structural units of the polymer, or it may contain other units (e.g., 4-hydroxyalkanoate units) in addition to one or more types of 3-hydroxyalkanoate units.

The poly(3-hydroxyalkanoate) copolymer (A) is preferably a copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units and other hydroxyalkanoate units. It is preferable that all of the 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units.

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.

Specific examples of poly(3-hydroxyalkanoate) copolymers (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), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB) are listed. In particular, from the standpoint 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.

The poly(3-hydroxyalkanoate) copolymer (A) may consist of only one type of poly(3-hydroxyalkanoate) copolymer. However, from the viewpoint of balancing the productivity and mechanical properties of the molded product, it may also contain at least two types of poly(3-hydroxyalkanoate) copolymers with different crystallinity. More specifically, it may contain at least two types of poly(3-hydroxyalkanoate) copolymers with different types of constituent monomers and/or different content ratios of constituent monomers.

Specifically, the poly(3-hydroxyalkanoate) copolymer (A) may include a copolymer (A1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 1 to 5 mol %, and a copolymer (A2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units 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.

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

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

Poly(3-hydroxybutyrate) (B) refers to a homopolymer of 3-hydroxybutyrate, but may contain small amounts of monomer units other than 3-hydroxybutyrate units. Specifically, it is preferable that the average content of 3-hydroxybutyrate units in poly(3-hydroxybutyrate) (B) is more than 99 mol% and not more than 100 mol% of all constituent monomer units (100 mol%).

The monomer units other than 3-hydroxybutyrate units contained in poly(3-hydroxybutyrate) (B) are not particularly limited as long as they are copolymerizable with 3-hydroxybutyrate units, but examples 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 for poly(3-hydroxyalkanoate) copolymers.

The P3HA contained in the raw material composition preferably has an average content of 3-hydroxybutyrate units out 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 perspective of achieving both strength and productivity of the molded product.

The average content of each monomer unit in P3HA can be determined by methods known to those skilled in the art, such as the method described in paragraph [0047] of WO 2013/147139. The average content refers to the molar proportion of each monomer unit among all constituent monomer units contained in the entire P3HA.

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

The weight-average molecular weight of poly(3-hydroxyalkanoate) resins can be measured in polystyrene equivalent terms using gel permeation chromatography (Shimadzu Corporation HPLC GPC system) with a chloroform solution. A column suitable for measuring weight-average molecular weights should be used as the column for gel permeation chromatography.

The method for producing poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a chemical synthesis method or a microbial production method. Of these, microbial production methods are preferred. Known methods can be applied to microbial production methods. 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 the P3HA synthase group 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 are used. In addition to the above, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may also be used depending on the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

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

(Other resins)
The raw material composition may contain other resins besides the poly(3-hydroxyalkanoate)-based resin, provided that 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.

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, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin in total. It may be 1 part by weight or less. There is no particular lower limit for the content of the other resin, and it may be 0 parts by weight.

(Plasticizer)
The raw material composition preferably contains a plasticizer in addition to the poly(3-hydroxyalkanoate) resin, which can improve the productivity of molded articles.

The plasticizer is not particularly limited, but from the standpoint of compatibility with poly(3-hydroxyalkanoate) resins, it is preferable to use an ester compound having an ester bond within the molecule.

Examples of ester compounds that can be used as plasticizers include modified glycerin compounds, dibasic acid ester compounds, adipate ester 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. Furthermore, the ester compounds can be used alone or in combination of two or more. When using a combination of two or more, the mixing ratio of the ester compounds can be adjusted as appropriate.

Glycerin ester compounds are preferred as modified glycerin compounds. While any of glycerin monoesters, diesters, and triesters can be used as glycerin ester compounds, glycerin triesters are preferred from the standpoint of compatibility with poly(3-hydroxyalkanoate) resins. Of the glycerin triesters, glycerin diacetomonoesters are particularly preferred. Specific examples of glycerin diacetomonoesters include glycerin diacetomonolaurate, glycerin diacetomonooleate, glycerin diacetomonostearate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate. Examples of modified glycerin compounds include Riken Vitamin Co., Ltd.'s "Rikemal" PL series and "BIOCIZER."

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.

Examples of adipate ester compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

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

As the ester compound, modified glycerin compounds are preferred because they are cost-effective, versatile, and have a high biomass content. From the standpoint of food contact in particular, glycerin triesters are more preferred, glycerin diacetomonoesters are even more preferred, and glycerin diacetomonolaurate is particularly preferred.

The amount of plasticizer to be added can be set appropriately taking into consideration the moldability and strength of the molded product, but is preferably 0.1 to 10 parts by weight per 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, and more preferably 6 parts by weight or less.

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

Crystallization nucleating agents include, for example, sugar alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, sugar alcohols are preferred, with pentaerythritol being particularly preferred, as they are particularly effective in promoting the crystallization of poly(3-hydroxyalkanoate) resins.

The amount of 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, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin in total. Furthermore, one type of crystallization nucleating agent may be used, or two or more types may be used, and the usage ratio can be adjusted appropriately depending on the purpose.

However, the raw material composition may be substantially free of sugar alcohols such as pentaerythritol. "Substantially free of sugar alcohols" means that the amount of sugar alcohols added is less than 0.1 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin in total. It may also 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 problem of sugar alcohols bleeding out from the molded product and the resulting contamination of the manufacturing equipment.

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

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

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, per 100 parts by weight of poly(3-hydroxyalkanoate) resin in total. Furthermore, 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.

The raw material composition containing the poly(3-hydroxyalkanoate) resin may be a blend of the individual components, or may be a mixture of the individual components that has been mixed and then homogenized by heating and melting. There are no particular limitations on the shape of the raw material composition, and it may be, for example, pellets or powder.

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

The temperature of the composition when heated and melted should be equal to or higher than the melting point Tm of the raw material composition. Specifically, it may be in the range of 140°C to 190°C, preferably 150 to 185°C, and more preferably 160 to 180°C.

[Cooling solidification process]
The heated and melted raw material composition is then cooled and solidified to obtain a molded product. When the raw material composition is heated and melted using an extruder, the molten composition may be discharged from the outlet of the extruder and then cooled and solidified.

In this disclosure, cooling and solidification refers to a process performed on a molten resin composition, in which the molten material is cooled to crystallize and solidify, forming a molded product having a predetermined shape. This cooling and solidification does not include stretching or heating processes that are performed after the production of molded products such as films or fibers.

In this embodiment, the cooling and solidifying step is composed of at least two cooling steps, including a first cooling step in which cooling is performed at a temperature T1 and a second cooling step in which cooling is performed at a temperature T2.
The first cooling step and the second cooling step can be carried out sequentially, i.e., the heated and melted raw material composition is cooled to a temperature T1 in the first cooling step to obtain a semi-solidified composition, and then the semi-solidified composition is immediately cooled to a temperature T2 in the second cooling step to promote crystallization and obtain a molded product.
The first cooling step and the second cooling step are preferably carried out continuously. In particular, when the processes from heat-melting to obtaining a molded body are carried out continuously on a production line, it is preferable to carry out both steps continuously on the production line.

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

The cooling temperature T1 in the first cooling step is preferably higher than the glass transition temperature of P3HA (approximately 0°C) so as not to inhibit the crystallization of P3HA. It is more preferable that it be 10°C or higher, and even more preferable that it be 20°C or higher.

In the second cooling step, a cooling temperature suitable for crystallization is adopted to increase the degree of crystallization of the composition that has been semi-solidified in the first cooling step. The cooling temperature T2 in the second cooling step satisfies formula (2): 35°C≦T2≦60°C. The lower limit of formula (2) may be 40°C or higher. The second cooling step lowers the temperature of the molten material to a temperature close to a temperature suitable for crystallization, allowing crystalline solidification to proceed.

The temperature difference between cooling temperature T1 and cooling temperature T2 can be set as appropriate, but it is preferable that it be within a range that satisfies formula (3): 5°C≦T2-T1≦40°C. If the temperature difference is 5°C or more, the effect of shortening the cooling time by providing a first cooling step is likely to be achieved. Furthermore, if it is 40°C or less, the crystallization of P3HA is less likely to be inhibited by the first cooling step. The lower limit of the temperature difference is preferably 10°C or more, and the upper limit is preferably 35°C or less, with 30°C or less being more preferable.

Cooling temperature T1 and cooling temperature T2 do not refer to the actual temperature of the composition, but to the temperature of the medium used for cooling. For example, if cooling is performed in a liquid bath, they refer to the temperature of the liquid in the liquid bath, and if cooling is performed in a mold, they refer to the set temperature of the mold.

The cooling time for each cooling step cannot be generally determined as it varies depending on the shape and size of the molded body, the molding method, the cooling method, the type of cooling medium, etc., but the ratio of the cooling time for the first cooling step to the cooling time for the second cooling step may be approximately 0.1 to 10, with 0.2 to 5 being preferable, and 0.2 to 2 being more preferable.

Although not particularly limited, the cooling time in the first cooling step is preferably 2 to 20 seconds, and more preferably 5 to 15 seconds. If the cooling time in the first cooling step is 2 seconds or more, the effects of providing the first cooling step are more likely to be achieved. Furthermore, if the cooling time in the first cooling step is 20 seconds or less, the crystallization of P3HA is less likely to be inhibited by the first cooling step.

Furthermore, the cooling time in the second cooling step is preferably 2 to 30 seconds, more preferably 5 to 25 seconds, and even more preferably 8 to 20 seconds. If the cooling time in the second cooling step is 2 seconds or more, the melt can be cooled to a temperature close to that suitable for crystallization, making it easier to achieve crystalline solidification. If the cooling time in the second cooling step is 30 seconds or less, the effect of shortening the total cooling time is likely to be achieved.

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

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

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

When cooling in a liquid tank, there are no particular restrictions on the liquid in the tank, and water or an organic solvent can be used as appropriate. Water and an organic solvent can also be used in combination. Water is preferred because it is easy to handle and has an excellent cooling effect.

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

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

The molded articles obtained according to this 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 equipment 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 articles obtained according to this disclosure is primarily composed of poly(3-hydroxyalkanoate)-based resin, they are seawater degradable, which could potentially solve environmental problems caused by the dumping of plastics into the ocean.

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:
The method includes a step of heating and melting a poly(3-hydroxyalkanoate)-based resin-containing composition, and a step of cooling and solidifying the melted composition to obtain a molded product,
The cooling and solidifying step includes a first cooling step of cooling at a temperature T1 and a second cooling step of cooling at a temperature T2,
A method for producing a molded body, wherein T1 and T2 satisfy the following formulas (1) and (2):
Formula (1): T1<T2
Formula (2): 35℃≦T2≦60℃
[Item 2]
Item 2. The method for producing a molded body according to item 1, wherein T1 and T2 further satisfy the following formula (3):
Formula (3): 5℃≦T2-T1≦40℃
[Item 3]
3. The method for producing a molded body according to item 1 or 2, wherein the cooling time in the first cooling step is 2 to 20 seconds.
[Item 4]
4. The method for producing a molded body according to any one of items 1 to 3, wherein the cooling time in the second cooling step is 2 to 30 seconds.
[Item 5]
5. The method for producing a molded body according to any one of items 1 to 4, wherein the total cooling time in the first cooling step and the second cooling step is 40 seconds or less.
[Item 6]
6. The method for producing a molded body according to any one of items 1 to 5, wherein the first cooling step and/or the second cooling step are carried out in a liquid tank.
[Item 7]
7. The method for producing a molded body according to any one of items 1 to 6, wherein the first cooling step and the second cooling step are carried out continuously.
[Item 8]
8. The method for producing a molded body according to item 6 or 7, wherein the liquid bath contains water.
[Item 9]
Item 9. The method for producing a molded body according to any one of items 1 to 8, wherein the molded body is a pellet or a tube.
[Item 10]
10. The method for producing a molded article according to any one of items 1 to 9, wherein the poly(3-hydroxyalkanoate)-based resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.
[Item 11]
Item 11. The method for producing a molded article according to item 10, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.

The present invention will be explained in detail below using examples, but the technical scope of the present invention is not limited to these examples.

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

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

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

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

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

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

In contrast, in Examples 1 to 5, the first cooling step, which involved cooling at a lower temperature, was followed by the second cooling step, shortening the total time required for crystallization to a maximum of 31 seconds.

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

Claims (11)

A method for producing a poly(3-hydroxyalkanoate)-based resin-containing molded article, comprising:
The method includes a step of heating and melting a poly(3-hydroxyalkanoate)-based resin-containing composition, and a step of cooling and solidifying the melted composition to obtain a molded product,
The cooling and solidifying step includes a first cooling step of cooling at a temperature T1 and a second cooling step of cooling at a temperature T2,
A method for producing a molded body, wherein T1 and T2 satisfy the following formulas (1) and (2):
Formula (1): T1<T2
Formula (2): 35℃≦T2≦60℃ The method for producing a molded body according to claim 1 , wherein T1 and T2 further satisfy the following formula (3):
Formula (3): 5℃≦T2-T1≦40℃ The method for producing a molded body according to claim 1 or 2, wherein the cooling time in the first cooling step is 2 to 20 seconds. The method for producing a molded body according to claim 1 or 2, wherein the cooling time in the second cooling step is 2 to 30 seconds. The method for producing a molded body according to claim 1 or 2, wherein the total cooling time in the first cooling step and the second cooling step is 40 seconds or less. The method for producing a molded body according to claim 1 or 2, wherein the first cooling step and/or the second cooling step are carried out in a liquid tank. The method for producing a molded body according to claim 1 or 2, wherein the first cooling step and the second cooling step are carried out continuously. The method for manufacturing a molded body according to claim 6, wherein the liquid tank contains water. The method for manufacturing a molded body according to claim 1 or 2, wherein the molded body is a pellet or a tube. The method for producing a molded article according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) resin contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units. The method for producing a molded article according to claim 10, wherein the other hydroxyalkanoate units are 3-hydroxyhexanoate units.