WO2024111463A1

WO2024111463A1 - Method for manufacturing poly(3-hydroxyalkanoate)-based resin molded body

Info

Publication number: WO2024111463A1
Application number: PCT/JP2023/040843
Authority: WO
Inventors: 郁弥迫; 拓野村; 信雄中村; 遼大橋
Original assignee: 株式会社カネカ
Priority date: 2022-11-25
Filing date: 2023-11-14
Publication date: 2024-05-30

Abstract

The present invention addresses the problem of suppressing mutual adhesion of molded bodies and adhesion of a molded body to a cutter and manufacturing a P3HA-based resin molded body with high productivity. The problem is solved by a method for manufacturing a P3HA-based resin molded body, the method comprising: (i) a step for melting and extruding a resin composition; (ii) a step for cooling the melted resin composition with a water bath to obtain a strand; (iii) a step for cutting off the strand while adding water to a cutter; and (iv) a step for retaining a cut-off molded body at a specific temperature.

Description

Method for producing molded body of poly(3-hydroxyalkanoate) resin

The present invention relates to a method for producing molded bodies of poly(3-hydroxyalkanoate)-based resins (hereinafter sometimes referred to as "P3HA-based resins").

Biodegradable resins such as P3HA-based resins (for example, polyhydroxyalkanoic acid (hereinafter, sometimes referred to as "PHA" or "P3HA")) are being increasingly used in various environmentally friendly applications due to their biodegradability. When using P3HA-based resins, they may be molded into pellets for transportation or processing. For example, Patent Document 1 describes a method for producing polyester resin molded products by melt extruding a polyester resin composition, in which immediately after melt extrusion, the polyester resin composition is cooled in a medium in which PHA fine particles are dispersed to produce PHA pellets, etc.

Japanese Patent Publication No. 2016-169374

The above technologies are excellent, but there is still room for improvement in terms of productivity, etc.

The present invention aims to provide a technology that can suppress adhesion of molded bodies to each other and to the cutter, and can efficiently manufacture molded bodies of P3HA-based resin.

The inventors conducted extensive research to solve the above problems, and discovered that by adding water to the strands (hereinafter sometimes simply referred to as "strands") obtained from a resin composition containing a P3HA-based resin (hereinafter sometimes referred to as a "P3HA-based resin composition") when cutting the strands, the molded bodies can be prevented from sticking to each other and to the cutter and the molded body discharge section. The inventors also discovered that by holding the molded bodies after cutting in a holding tank (agitation tank), the molded bodies can be prevented from sticking to each other more reliably, and this led to the completion of the present invention.

Therefore, one aspect of the present invention is a method for producing a molded product of a P3HA-based resin (hereinafter referred to as "this manufacturing method"), comprising: (i) a melt extrusion step in which a resin composition containing a P3HA-based resin is melted and extruded in an extruder; (ii) a stranding step in which the molten resin composition obtained in step (i) is cooled in a water bath to obtain strands; (iii) a cutting step in which the strands obtained in step (ii) are cut while adding water to a cutter; and (iv) a holding step in which the cut molded product obtained in step (iii) is held at Tc-25°C to Tc+15°C (where Tc represents the crystallization temperature of the resin composition containing the P3HA-based resin).

One aspect of the present invention provides a technology that can suppress adhesion of molded bodies to each other and to the cutter, and can efficiently manufacture molded bodies of P3HA-based resin.

One embodiment of the present invention is described in detail below. Note that unless otherwise specified in this specification, "A to B" indicating a numerical range means "A or more, B or less." In addition, all documents described in this specification are incorporated herein by reference.

1. Overview of the Invention
In conventional molding of P3HA resin, in the cooling process after melt extrusion of a resin composition containing P3HA resin, it was generally necessary to set the strand bath long (for example, Patent Document 1). When the strand bath is short, the solidification of the molten resin becomes insufficient, and as a result, in a normal pelletizer, problems may occur such as the cut molded bodies adhering to each other (adhering to each other) or the molded bodies adhering to the cutter or the molded body discharge part and not being separated due to poor cutting of the strands. When such adhesion of the molded bodies to each other or adhesion of the molded bodies to the cutter or the molded body discharge part occurs, the piping or pelletizer is clogged, and productivity is significantly reduced. On the other hand, there is also a problem that the installation area of the equipment becomes large when the strand bath is made long. On the other hand, measures such as adding an agent to prevent adhesion to each other can be considered to solve the above problem, but this is not preferable from the viewpoint of containing impurities.

The inventors therefore conducted extensive research to solve the above problems, and have succeeded in obtaining the following findings.

(1) When cutting the strands obtained from a resin composition containing a P3HA-based resin, adding water to the strands and cutter can prevent the molded bodies from adhering to each other and to the cutter or the molded body discharge section.

(2) By holding the cut molded bodies in a holding tank (mixing tank), adhesion of the molded bodies to each other can be more reliably prevented.

(3) It is possible to manufacture molded bodies containing P3HA resin without adding an anti-adhesion agent.

This manufacturing method is extremely advantageous in the manufacture of molded bodies of P3HA-based resin, since it suppresses adhesion between the molded bodies and adhesion to the cutter, and allows molded bodies of P3HA-based resin to be manufactured with high productivity. Furthermore, this manufacturing method does not require the addition of an agent to prevent adhesion between the molded bodies, and therefore molded bodies with high biodegradability can be obtained. Therefore, with the above-mentioned configuration, the amount of plastic waste generated can be reduced, which can contribute to the achievement of Sustainable Development Goals (SDGs), such as Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and sustainably use the oceans and marine resources for sustainable development". The configuration of this manufacturing method is explained in detail below.

2. Method for producing molded body of P3HA resin
The present production method includes the following steps:
Step (i): A melt extrusion step in which a resin composition containing a P3HA-based resin is melted and extruded in an extruder. Step (ii): A stranding step in which the molten resin composition obtained in step (i) is cooled in a water bath to obtain strands. Step (iii): A cutting step in which the strands obtained in step (ii) are cut while adding water to a cutter. Step (iv): A holding step in which the cut molded body obtained in step (iii) is held at Tc-25°C to Tc+15°C (here, Tc indicates the crystallization temperature of the resin composition containing the P3HA-based resin. In this specification, the "crystallization temperature of the resin composition" is a temperature measured by the method described in the Examples).

In one embodiment of the present invention, the production method preferably includes the following step in addition to the above steps (i) to (iv).
Step (v): A drying step of drying the molded body obtained in the step (iv) at 40 to 120°C.

By including the above steps (i) to (iv) or (i) to (v), this manufacturing method can suppress adhesion of the molded bodies to each other and to the cutter, and can produce molded bodies of P3HA-based resin with high productivity.

(2-1. Step (i))
Step (i) is a melt extrusion step in which a resin composition containing a P3HA-based resin (hereinafter, sometimes referred to as "the resin composition") is melted in an extruder and extruded.

<P3HA Resin>
In this specification, the term "P3HA-based resin" refers to a P3HA-based resin having the following formula (1):
[—O—CHR—CH ₂ —CO—] (1)
(wherein R is an alkyl group represented by C _n H _2n+1 , and n is an integer of 1 to 15.) means a copolymer having one or more 3-hydroxyalkanoate repeating units as essential structural units. In this specification, the "P3HA-based resin" may also be referred to as "P3HA". The P3HA-based resin is not particularly limited as long as it is included in the above formula (1). The P3HA-based resin may be a copolymer consisting of two or more types of 3-hydroxyalkanoate repeating units, or a copolymer consisting of a 3-hydroxyalkanoate repeating unit and other repeating units. In this specification, the "P3HA-based resin" means a polymer (copolymer) containing 50 mol % or more of the 3-hydroxyalkanoate repeating units out of the total monomer repeating units (100 mol %). The P3HA-based resin may be a copolymer consisting of only 3-hydroxyalkanoate repeating units, or a copolymer containing a 3-hydroxyalkanoate repeating unit and other repeating units.

The P3HA resin according to the present production method preferably contains a 3-hydroxybutyrate repeating unit (a repeating unit in which R is _CH3 in the above formula (1)) as the 3-hydroxyalkanoate repeating unit. The P3HA resin according to the present production method may be a poly(3-hydroxybutyrate) containing only 3-hydroxybutyrate as a repeating unit, or may be a copolymer of 3-hydroxybutyrate and another hydroxyalkanoate.

In one embodiment of the present invention, the P3HA-based resin may be a homopolymer, a mixture of a homopolymer and one or more types of copolymers, or a mixture of two or more types of copolymers. The type of copolymerization is not particularly limited, and may be random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization, etc.

In one embodiment of the present invention, examples of P3HA-based resins include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxypropionate) (P3HB3HP), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). Poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), etc. are included. From the viewpoint of being able to adjust the melting point low and widen the processing range, P3HB3HH, P3HB4HB, and P3HB3HP are preferred. Among them, P3HB3HH and P3HB4HB are particularly preferred because they are easy to produce industrially. From the viewpoint of industrial productivity, in addition to the above, P3HB and P3HB3HV are also preferred.

The P3HA resin is preferably produced by a microorganism. The microorganism that produces the P3HA resin is not particularly limited as long as it is a microorganism capable of producing the P3HA resin. For example, the first P3HB3HH-producing bacterium was Bacillus megaterium, which was discovered in 1925, and other natural microorganisms include Cupriavidus necator (formerly classified as Alcaligenes eutrophus and Ralstonia eutropha) and Alcaligenes latus. It is known that P3HB3HH accumulates within the cells of these microorganisms.

In addition, as a producer of copolymers of hydroxybutyrate and other hydroxyalkanoates, Aeromonas kiabiei, which produces P3HB3HH, is known.
caviae, and P3HB4HB-producing bacterium Alcaligenes eutrophus. In particular, with regard to P3HB3HH, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) into which genes of the P3HB3HH synthase group have been introduced in order to increase the productivity of P3HB3HH is more preferred, and microbial cells in which P3HB3HH has been accumulated by culturing these microorganisms under appropriate conditions are used. In addition to the above, genetically modified microorganisms into which various P3HA resin synthesis-related genes have been introduced may be used according to the P3HA resin to be produced, and culture conditions including the type of substrate may be optimized.

P3HB3HH can also be produced by the method described in, for example, International Publication No. 2010/013483. Commercially available products of P3HB3HH include Kaneka Biodegradable Polymer PHBH (registered trademark) manufactured by Kaneka Corporation.

In one embodiment of the present invention, the P3HA resin contains 3-hydroxybutyrate units (hereinafter also referred to as "3HB units"), and the content of 3HB units out of 100 mol% of all repeating units in the P3HA resin is preferably 82 mol% or more, more preferably 84 mol% or more, and even more preferably 86 mol% or more. When the content of 3HB units in the P3HA resin is 82 mol% or more, excellent effects are achieved in terms of the physical properties of the resin composition containing the P3HA resin.

In one embodiment of the present invention, the P3HA resin contains 3HB units, and the content of 3HB units in 100 mol% of all repeating units in the P3HA resin is preferably 99 mol% or less, more preferably 97 mol% or less, and even more preferably 95 mol% or less. When the content of 3HB units in the P3HA resin is 99 mol% or less, excellent effects are achieved in terms of the physical properties of the resin composition containing the P3HA resin. Note that when the resin composition is a blend of multiple P3HA resins, it is intended that the average 3HB unit content of all the P3HA resins contained in the resin composition be within this range.

In one embodiment of the present invention, the weight average molecular weight (hereinafter sometimes referred to as Mw) of the P3HA resin is not particularly limited, but is preferably 50,000 to 3 million, more preferably 100,000 to 2.5 million, even more preferably 150,000 to 2 million, and most preferably 150,000 to 1 million. When the weight average molecular weight of the P3HA resin is 50,000 to 3 million, the mechanical properties such as strength are sufficient and the moldability is excellent.

The method for measuring the weight-average molecular weight of P3HA-based resin is not particularly limited, but for example, the weight-average molecular weight can be calculated as polystyrene equivalent by using chloroform as the mobile phase, a Waters GPC system as the system, and Showa Denko Shodex K-804 (polystyrene gel) as the column.

<Resin composition containing P3HA-based resin>
In the present resin composition, the P3HA-based resin may be, for example, any of those described above in the section P3HA-based resin. As the P3HA-based resin, the above-mentioned resins may be used alone or in combination of two or more kinds.

In one embodiment of the present invention, the content of the P3HA-based resin in the resin composition is preferably 80 parts by weight or more, more preferably 85 parts by weight or more, and even more preferably 90 parts by weight or more, per 100 parts by weight of the resin composition. When the content of the P3HA-based resin in the resin composition is 80 parts by weight or more, the effect of having high biodegradability is achieved. The upper limit is not particularly limited, and may be, for example, 100 parts by weight.

[Biodegradable resins other than P3HA-based resins]
In one embodiment of the present invention, the resin composition may contain a biodegradable resin other than the P3HA-based resin. Examples of such resins include, but are not limited to, polybutylene adipate terephthalate (PBAT), polybutylene succinate adipate (PBSA), polybutylene succinate (PBS), polybutylene succinate terephthalate (PBST), polybutylene succinate adipate terephthalate (PBSAT), polybutylene sebacate terephthalate (PBSeT), polybutylene azelate terephthalate (PBAzT), polycaprolactone (PCL), polylactic acid (PLA), etc.

In one embodiment of the present invention, the content of biodegradable resins other than P3HA-based resins in the resin composition is, for example, 30 parts by weight or less, preferably 20 parts by weight or less, and more preferably 10 parts by weight or less, relative to 100 parts by weight of the resin composition. When the content of biodegradable resins other than P3HA-based resins in the resin composition is 30 parts by weight or less, an effect of exhibiting good moldability is achieved. The lower limit is not particularly limited, and may be, for example, 0 parts by weight.

In one embodiment of the present invention, when the resin composition is composed of a P3HA-based resin and a biodegradable resin other than the P3HA-based resin, the amounts of both resins can be adjusted so that the sum of the P3HA-based resin and the biodegradable resin other than the P3HA-based resin is 100 parts by weight.

[Nucleating agents/lubricants]
In one embodiment of the present invention, the resin composition may further contain a crystal nucleating agent and/or a lubricant. When the resin composition contains a crystal nucleating agent, the molding processability, productivity, etc. are improved. When the resin composition contains a lubricant, the surface smoothness of the molded product is improved.

In one embodiment of the present invention, the crystal nucleating agent and/or lubricant are incorporated into the aliphatic polyester resin composition by melt-kneading with the P3HA resin.

The crystal nucleating agent is not particularly limited as long as it has the above-mentioned effect, but examples thereof include inorganic substances such as pentaerythritol, boron nitride, titanium oxide, talc, layered silicates, calcium carbonate, sodium chloride, and metal phosphates; sugar alcohol compounds derived from natural products such as erythritol, galactitol, mannitol, and arabitol; polyvinyl alcohol, chitin, chitosan, polyethylene oxide, aliphatic carboxylic acid amides, aliphatic carboxylic acid salts, aliphatic alcohols, aliphatic carboxylic acid esters, dimethyl adipate, dibutyl adipate, and diisodecyl ether. Examples of suitable crystal nucleating agents include dicarboxylic acid derivatives such as butyl adipate and dibutyl sebacate; cyclic compounds having a functional group C=O and a functional group selected from NH, S, and O in the molecule, such as indigo, quinacridone, and quinacridone magenta; sorbitol derivatives such as bisbenzylidene sorbitol and bis(p-methylbenzylidene) sorbitol; compounds containing a nitrogen-containing heteroaromatic nucleus, such as pyridine, triazine, and imidazole; phosphate ester compounds, bisamides of higher fatty acids, and metal salts of higher fatty acids; branched polylactic acid; and low molecular weight poly(3-hydroxybutyrate). These crystal nucleating agents may be used alone or in combination of two or more.

The content of the crystal nucleating agent is not particularly limited as long as it can promote the crystallization of the P3HA resin, but is preferably 0.1 to 2.0 parts by weight, more preferably 0.6 to 1.8 parts by weight, even more preferably 0.7 to 1.6 parts by weight, and particularly preferably 0.8 to 1.5 parts by weight, per 100 parts by weight of the resin composition. When the content of the crystal nucleating agent is 0.5 parts by weight or more per 100 parts by weight of the resin composition, a sufficient effect as a crystal nucleating agent can be obtained. Furthermore, when the content of the crystal nucleating agent is 2.0 parts by weight or less per 100 parts by weight of the resin composition, an appropriate viscosity is maintained during processing, and the effect on the physical properties of the molded product is also reduced.

In one embodiment of the present invention, the lubricant contains at least one selected from the group consisting of behenic acid amide, stearic acid amide, erucic acid amide, and oleic acid amide. This provides the resulting molded article with lubricity (particularly external lubricity). Of behenic acid amide, stearic acid amide, erucic acid amide, and oleic acid amide, it is preferable to contain behenic acid amide or erucic acid amide from the viewpoint of improving processability and productivity.

In one embodiment of the present invention, the lubricant may be behenic acid amide, stearic acid amide, erucic acid amide, oleic acid amide, or a combination of two or more of these, or may be a combination with a lubricant other than behenic acid amide, stearic acid amide, erucic acid amide, or oleic acid amide (hereinafter referred to as "other lubricants"). As other lubricants, for example, those described in WO 2022/014408 can be used.

The amount of lubricant (the total amount when multiple lubricants are used) is not particularly limited as long as it can provide lubricity, but is preferably 0.1 to 2.0 parts by weight, more preferably 0.2 to 1.6 parts by weight, even more preferably 0.3 to 1.4 parts by weight, and particularly preferably 0.4 to 1.2 parts by weight, per 100 parts by weight of the resin composition. When the amount of lubricant is 0.1 part by weight or more per 100 parts by weight of the resin composition, a sufficient effect as a lubricant can be obtained. Furthermore, when the amount of lubricant is 2.0 parts by weight or less per 100 parts by weight of the resin composition, bleeding out onto the surface of the molded product is avoided, and a molded product with excellent appearance can be obtained.

[Other ingredients]
In addition to the P3HA resin, the crystal nucleating agent, and the lubricant, the resin composition may contain other components such as plasticizers, inorganic fillers, antioxidants, ultraviolet absorbers, colorants such as dyes and pigments, and antistatic agents, as long as the effects of the present invention are not impaired. Examples of the above components include those described in International Publication No. WO 2022/014408.

The content of each of the above components is not particularly limited as long as the effects of the present invention can be achieved, and can be appropriately determined by those skilled in the art.

[others]
In one embodiment of the present invention, from the viewpoint of biodegradability, it is preferable that the resin composition does not contain an anti-adhesion agent.

<Melt Extrusion>
The melt extrusion in step (i) may be carried out by any apparatus known in the art, including, but not limited to, a twin-screw extruder (e.g., TEM-26SX manufactured by Toshiba Machine Co., Ltd.), a single-screw extruder, and the like.

The melting temperature in step (i) may vary depending on the composition of the resin composition, the type of P3HA-based resin contained in the resin composition, etc., but is, for example, 120 to 200°C, and preferably 140 to 180°C.

(2-2. Step (ii))
Step (ii) is a stranding step in which the molten resin composition obtained in step (i) is cooled in a water bath to obtain strands. In this step, the resin composition is cooled in a water bath in a strand bath to promote crystallization of the resin composition and obtain strands. In step (ii), lowering the temperature of the strand bath enables more efficient (space-saving) strand cutting in step (iii). In addition, lowering the temperature of the strand bath allows the strands coming out of the extruder to be rapidly cooled, and the residence time in the strand bath can be shortened (the size of the strand bath can be reduced).

The temperature of the water bath in step (ii) is preferably 20 to 60°C, more preferably 22 to 50°C, and even more preferably 25 to 40°C. In this manufacturing method, even if the temperature of the water bath in step (ii) is set to a low temperature of 20 to 60°C, molded bodies of P3HA-based resin can be manufactured with good productivity. When the temperature of the water bath is 20 to 60°C, the residence time in the water bath can be shortened, which has the advantage of allowing the strand bath to be made smaller.

The diameter of the strand obtained in step (ii) is preferably 0.5 to 10.0 mm, more preferably 0.6 to 5.0 mm, and even more preferably 0.8 to 3.0 mm. When the diameter of the strand is 0.5 to 10.0 mm, the strand can be cooled efficiently in step (ii) without being broken.

(2-3. Step (iii))
Step (iii) is a cutting step in which the strand obtained in step (ii) is cut while adding water to the cutter. In step (iii), by adding water to the cutter when cutting the strand, adhesion of the molded bodies to each other and to the cutter or the molded body discharge part can be suppressed.

In this specification, "while adding water to the cutter" means that cutting is performed while water is applied to at least the strand and the blade of the cutter. More preferably, in addition to the above, cutting is performed while water is also applied to the formed body discharge section. Even more preferably, water is continued to be added from the strand cutter to the holding tank. This has the effect of preventing adhesion to the formed body discharge section and suppressing clogging of the formed body discharge section.

In one embodiment of the present invention, it is preferable that the addition of water in step (iii) is performed on all of the strands, the cutter, and the molded body discharge section.

In this manufacturing method, by introducing a combination of equipment used in the cutting step (iii) (e.g., a wet pelletizer) and a crystallization holding tank (agitation tank) used in the holding step (iv) downstream of the strand bath used in the stranding step (ii), it is possible to prevent the compacts from sticking together and to significantly reduce the equipment installation area.

In step (iii), the temperature of the water added to the cutter is preferably Tc-25°C to Tc+15°C, more preferably Tc-20°C to Tc+10°C, and even more preferably Tc-10°C to Tc+5°C. Here, Tc indicates the crystallization temperature of the resin composition containing the P3HA-based resin. When the temperature of the water added to the cutter is Tc-25°C to Tc+15°C, sufficient crystallization occurs.

The absolute temperature of the water added in step (iii) is preferably 50 to 90°C, and more preferably 60 to 80°C. When the absolute temperature of the water added is 50 to 90°C, sufficient crystallization occurs.

(2-4. Step (iv))
Step (iv) is a holding step in which the cut molded bodies obtained in step (iii) are held at Tc-25°C to Tc+15°C (wherein Tc represents the crystallization temperature of the resin composition containing the P3HA resin). In this step, after the P3HA resin-containing strands are cut, the cut molded bodies are dispersed in water in a crystallization holding tank (stirring tank) to crystallize the molded bodies while preventing adhesion between the molded bodies. In this step, by cooling in the crystallization holding tank (stirring tank), it is possible to more reliably prevent the molded bodies from adhering to each other.

The holding temperature in step (iv) is Tc-25°C to Tc+15°C, preferably Tc-20°C to Tc+10°C, and more preferably Tc-10°C to Tc+5°C. Here, Tc indicates the crystallization temperature of the resin composition containing the P3HA-based resin. If the holding temperature is Tc-25°C to Tc+15°C, sufficient crystallization occurs.

The absolute temperature of the holding temperature in step (iv) is preferably 50 to 90°C, and more preferably 60 to 80°C. When the absolute temperature of the holding temperature is 50 to 90°C, sufficient crystallization occurs.

In one embodiment of the present invention, step (iv) is preferably carried out while stirring the cut molded body obtained in step (iii).

The stirring speed during the stirring is not particularly limited, but is, for example, 50 to 800 rpm, and preferably 200 to 600 rpm.

The mixing time (residence time in the mixing tank) is not particularly limited, but is, for example, 1 to 10 minutes, and preferably 1.5 to 5 minutes.

The device used for the stirring is not particularly limited, but for example, a vertical stirrer, a horizontal stirrer, etc. may be used.

(2-5. Step (v))
Step (v) is a drying step in which the molded body obtained in step (iv) is dried at 40 to 120° C. By this step, a molded body can be obtained as a dried product.

The drying temperature in step (v) is preferably 40 to 120°C, more preferably 60 to 100°C, and even more preferably 70 to 90°C. If the drying temperature is 40 to 120°C, moisture can be sufficiently removed.

The drying time in step (v) can be changed as appropriate depending on the drying temperature, etc., but is, for example, 3 to 10 hours, and preferably 4 to 6 hours.

The device used for drying in step (v) is not particularly limited, but for example, a box dryer, a hopper dryer, etc. may be used.

The molded articles obtained by this manufacturing method can be used, for example, as paper, films, sheets, tubes, plates, rods, containers (e.g., bottle containers), food trays, bags, parts, etc.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments.

That is, one embodiment of the present invention is as follows.
<1> (i) a melt extrusion step of melting and extruding a resin composition containing a P3HA-based resin in an extruder;
(ii) a stranding step in which the molten resin composition obtained in the step (i) is cooled in a water bath to obtain strands;
(iii) a cutting step of cutting the strand obtained in the step (ii) while adding water to a cutter; and (iv) a holding step of holding the cut molded body obtained in the step (iii) at Tc-25°C to Tc+15°C (wherein Tc represents the crystallization temperature of the resin composition containing the P3HA-based resin).
A method for producing a molded article of a P3HA resin having the above structure.
<2> The manufacturing method according to <1>, wherein in the step (iii), the temperature of the water added to the cutter is Tc-25°C to Tc+15°C (wherein Tc represents the crystallization temperature of the resin composition containing the P3HA-based resin).
<3> The method according to <1> or <2>, wherein in the step (ii), the temperature of the water bath is 20 to 60° C.
<4> The manufacturing method according to any one of <1> to <3>, wherein the P3HA resin contains 3HB units and the content of 3HB units in the P3HA resin is 82 mol% or more.
<5> The method according to any one of <1> to <4>, wherein the P3HA-based resin is one or more selected from poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and poly(3-hydroxybutyrate-co-3-hydroxypropionate).
<6> The method according to any one of <1> to <5>, wherein the strand has a diameter of 0.5 to 10.0 mm.
<7> The method according to any one of <1> to <6>, further comprising: (v) drying the molded body obtained in the step (iv) at 40 to 120° C.
<8> The method according to any one of <1> to <7>, wherein the resin composition contains a crystal nucleating agent and/or a lubricant.
<9> The method according to any one of <1> to <8>, wherein the step (iv) is performed while stirring the cut molded body obtained in the step (iii).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Raw materials used]
(P3HA resin)
・ P3HA-1: P3HB3HH (monomer ratio is 3HB / 3HH = 85 / 15 (mol / mol)), molecular weight 660,000 P3HA-2: P3HB3HH (monomer ratio is 3HB / 3HH = 94 / 6 (mol / mol)), molecular weight 480,000 P3HA-1 was prepared by the method described in Example 1 of WO2022 / 091685, and P3HA-2 was prepared by the method described in Example 1 of WO2021 / 085534.

(others)
Lubricant: Behenic acid amide (Nippon Fine Chemical Co., Ltd.)
- Nucleating agent: pentaerythritol (Nippon Synthetic Chemical Industry Co., Ltd.).

[Measurement and evaluation methods]
(Adhesion to the blade)
The adhesion of the molded article to the blade was evaluated visually.

(Crystallization Temperature)
The crystallization temperature of the P3HA resin composition is a temperature measured using the following apparatus, conditions and method.
Measurement method: Differential Scanning Calorimetry (DSC)
Measurement equipment: Hitachi Hightech Science, EXSTAR6000 series DSC6200
Measurement sample: 5 to 10 mg of P3HA was placed in an aluminum pan, the lid was placed on and crimped.
Measurement conditions: The temperature is increased from 25° C. to 180° C. at 10° C./min, and then decreased at 10° C./min to 25° C. During the measurement, nitrogen gas is flowed at 50 mL/min.
Identification of crystallization temperature: The exothermic peak observed during the temperature drop is taken as the crystallization peak, and the peak top is taken as the crystallization temperature.

(Strand diameter)
The strands emerging from the strand bath were cut with scissors and measured using a ruler.

(mutual rate)
The compacts discharged from the pelletizer or the mixing tank were extracted and their weights were measured. Among the extracted compacts, those that were not cut were selected and their weights were measured. Then, the mutual adhesion rate (%) of the compacts was calculated based on [weight of the uncut compacts among the extracted compacts]/[weight of all the extracted compacts]×100.

Example 1
(Melt Extrusion (Step (i)))
A twin-screw extruder (TEM-26SX manufactured by Toshiba Machine Co., Ltd.) was used for melt-kneading the P3HA-based resin composition. 60 parts by weight of P3HA-1, 40 parts by weight of P3HA-2, 0.5 parts by weight of behenic acid amide, and 1 part by weight of pentaerythritol were weighed and dry-blended to prepare a P3HA-based resin composition. The adjusted P3HA-based resin composition was fed to the twin-screw extruder, and the P3HA-based resin composition was melt-kneaded at a cylinder temperature of 175°C. The melt-kneaded P3HA-based resin composition at 185°C (crystallization temperature: 70°C) was discharged from the nozzle of the die attached to the tip of the extruder.

(Preparation of Molded Body)
The P3HA-based resin composition discharged from the extruder was immersed in a strand bath adjusted to a water temperature of 55° C. for 5 seconds, and then supplied to a wet pelletizer (Tanaka Corporation) (step (ii)). The strands (diameter 3 mm) of the wet pelletizer were cut while supplying water at 60° C. to the blades and strands (diameter 3 mm) of the wet pelletizer (step (iii)). The cut molded body was supplied to a holding tank (stirring tank) and retained in water at 60° C. (step (iv)). After that, the molded body was dehydrated and dried at 80° C. to obtain a molded body (step (v)). By the above method, the adhesion to the blades and the mutual adhesion rate of the molded body were measured and evaluated.

Example 2
A molded article was produced in the same manner as in Example 1, except that the water temperature in the strand bath was 33° C. and the residence time was 1.5 seconds.

Comparative Example 1
A molded body was produced in the same manner as in Example 1, except that in the production of the molded body, water was not added to the blades and strands of the wet pelletizer, and retention in the holding tank was not performed.

Comparative Example 2
A molded body was produced in the same manner as in Example 1, except that retention in a holding tank was not performed in the production of the molded body.

Comparative Example 3
The molded bodies were produced in the same manner as in Example 1, except that the temperature of water added to the blades and strands of the wet pelletizer and the retention temperature in the holding tank were 30°C.

Comparative Example 4
A molded body was produced in the same manner as in Example 2, except that retention in a holding tank was not performed in the production of the molded body.

Comparative Example 5
The molded bodies were produced in the same manner as in Example 2, except that the temperature of water added to the blades and strands of the wet pelletizer and the retention temperature in the holding tank were set to 30°C.

Comparative Example 6
The molded bodies were produced in the same manner as in Example 2, except that the temperature of water added to the blades and strands of the wet pelletizer and the retention temperature in the holding tank were 40°C.

〔result〕
The results of Examples 1 and 2 and Comparative Examples 1 to 6 are shown in Table 1.

〔result〕
As can be seen from Table 1, in Examples 1 and 2, there was no adhesion to the blade, and the adhesion rate of the molded body was low. On the other hand, adhesion of the molded body to the blade was observed in Comparative Example 1. In Comparative Examples 2 to 6, there was no adhesion to the blade, but the adhesion rate of the molded body was high.

The above shows that the method for producing molded bodies of P3HA-based resin according to one embodiment of the present invention can suppress adhesion of the molded bodies to each other and to the cutter, and can produce molded bodies of P3HA-based resin with high productivity.

Furthermore, a comparison of Example 2 with Comparative Examples 4 to 6 showed that even if the residence time in the strand bath was shortened, there was no adhesion to the blades and the adhesion rate of the molded bodies was also reduced.

The manufacturing method of the present invention can be suitably used in the fields of agriculture, fishing, forestry, horticulture, medicine, hygiene products, clothing, non-clothing, packaging, automobiles, building materials, and other fields.

Claims

(i) a melt extrusion step of melting and extruding a resin composition containing a poly(3-hydroxyalkanoate)-based resin in an extruder;
(ii) a stranding step in which the molten resin composition obtained in the step (i) is cooled in a water bath to obtain strands;
(iii) a cutting step of cutting the strand obtained in the step (ii) while adding water to a cutter, and (iv) a holding step of holding the cut molded body obtained in the step (iii) at Tc-25°C to Tc+15°C (wherein Tc represents the crystallization temperature of the resin composition containing the poly(3-hydroxyalkanoate)-based resin).
The present invention relates to a method for producing a molded article of a poly(3-hydroxyalkanoate) resin having the above formula:
The manufacturing method according to claim 1, wherein in step (iii), the temperature of the water added to the cutter is Tc-25°C to Tc+15°C (where Tc represents the crystallization temperature of the resin composition containing the poly(3-hydroxyalkanoate)-based resin).
The method of claim 1, wherein the temperature of the water bath in step (ii) is 20 to 60°C.
The method according to claim 1, wherein the poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units, and the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin is 82 mol% or more.
The method of claim 1, wherein the poly(3-hydroxyalkanoate)-based resin is one or more selected from poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and poly(3-hydroxybutyrate-co-3-hydroxypropionate).
The manufacturing method according to claim 1, wherein the diameter of the strand is 0.5 to 10.0 mm.
The method of claim 1 further includes (v) a drying step of drying the molded body obtained in step (iv) at 40 to 120°C.
The manufacturing method according to claim 1, wherein the resin composition contains a crystal nucleating agent and/or a lubricant.
The manufacturing method according to any one of claims 1 to 8, wherein the step (iv) is carried out while stirring the cut molded body obtained in the step (iii).