Granulated body and method for producing same

Abstract

Provided is a granulated body that contains an aliphatic polyester and has a high bulk density and high fluidity. The problem is solved by a method for producing a granulated body containing an aliphatic polyester, the method comprising a step for compressing and granulating a powder containing an aliphatic polyester and having a bulk density of 0.30-0.50 g / cm3.

Description

Technical Field

[0001] The present invention relates to a granulated body and a method for producing the same. Background Art

[0002] Biodegradable resins such as polyhydroxyalkanoic acid (PHA) are biodegradable and are therefore used in various applications. For example, PHA is used as a dry powder for transportation and processing. In the past, a method for producing PHA powder by spray drying a PHA suspension has been developed (for example, Patent Document 1).

[0003] However, a method for preparing a plastic composition is known, wherein the plastic composition comprises at least one polyester, a biological entity having polyester decomposing activity and at least one acid-resistant filler, wherein the biological entity accounts for less than 11% (by weight) based on the total weight of the plastic composition, and the mixing step is carried out at a temperature at which the polyester is partially or entirely in a molten state and / or in an extruder, preferably a twin-screw extruder, more preferably a co-rotating twin-screw extruder (for example, Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2018 / 070492

[0007] Patent Document 2: Japanese Patent Application Publication No. 2021-119240 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, the bulk density of the PHA powder obtained by spray drying described in Patent Document 1 is low and the fluidity may be poor, so there is room for improvement.

[0010] Furthermore, the technique described in Patent Document 2 is a technique for mixing using an extruder, and therefore has problems such as a decrease in the molecular weight of the aliphatic polyester.

[0011] An object of one embodiment of the present invention is to provide granules containing an aliphatic polyester having a high bulk density and high fluidity.

[0012] Solutions to the problem

[0013] The present inventors have conducted intensive research to solve the above problems and have found for the first time that aliphatic polyesters having high bulk density and fluidity can be produced by including the following steps: the step of compressing and granulating powders containing aliphatic polyesters and having a bulk density within a specific range, thereby completing the present invention.

[0014] Therefore, one embodiment of the present invention comprises a bulk density of 0.30 g / cm 3 ~0.50g / cm 3 A method for producing granules containing aliphatic polyester (hereinafter, "a method for producing granules containing aliphatic polyester according to one embodiment of the present invention" is referred to as "this production method"), comprising the step of compressing and granulating a powder containing aliphatic polyester.

[0015] Another embodiment of the present invention is a granulated body having a bulk density exceeding 0.50 g / cm 3 And 0.70g / cm 3 and the content of the aliphatic polyester is 90 wt % or more (hereinafter referred to as "the present granules").

[0016] Effects of the Invention

[0017] According to one embodiment of the present invention, there can be provided granules comprising an aliphatic polyester having a high bulk density and high fluidity. DETAILED DESCRIPTION

[0018] A mode for implementing the present invention is described in detail below. It should be noted that, in this specification, unless otherwise specified, "A to B" indicating a numerical range means "A or more and B or less". In addition, all documents recorded in this specification are cited as references in this specification.

[0019] [1. Summary of the present invention]

[0020] The PHA powder obtained by spray drying as described in Patent Document 1 is granulated by a compounding process described later. Granulating the PHA powder improves the operability when it is supplied to a molding machine, and the transportability is improved due to the increase in the apparent bulk density. However, the present inventors have found that the bulk density of the obtained PHA powder is low in the conventional method described in Patent Document 1, so the fluidity of the PHA powder is reduced, resulting in a problem of reduced production efficiency in the above-mentioned compounding process. In addition, when the fluidity of the PHA powder is reduced, the transportability of the powder is also deteriorated.

[0021] In addition, the present inventors have found that, in the technique using an extruder as described in Patent Document 2, when an aliphatic polyester having poor fluidity is used, it is difficult to put it into the extruder, resulting in a problem of reduced production speed. In addition, it has been found that when the screw speed of the extruder is increased to increase the production speed, the temperature rises excessively, so that the aliphatic polyester is thermally decomposed, resulting in a problem of reduced molecular weight. In particular, since the melting point and decomposition temperature of the above-mentioned PHA are close, the molecular weight is easily reduced when heated to increase fluidity.

[0022] Therefore, the present inventors conducted intensive studies to solve the above-mentioned problems and, as a result, succeeded in obtaining the following findings.

[0023] ･By compressing and granulating a low bulk density powder containing aliphatic polyester, granules with high bulk density and excellent fluidity can be obtained.

[0024] ･The granules obtained by the present production method have a high bulk density and are therefore excellent in transportability.

[0025] ･According to the present production method, granules containing aliphatic polyester can be produced without using a binder.

[0026] ･According to the present production method, it is not necessary to use a plasticizer or the like during compression granulation, so that impurities are reduced and granules having a high aliphatic polyester content can be obtained.

[0027] In particular, the technical concept of compressing and granulating a powder containing an aliphatic polyester having a low bulk density to obtain a granule having a high bulk density is unprecedented and the present invention is extremely excellent. The granules obtained by the present production method have a high bulk density and excellent fluidity, and can be advantageously used as a raw material for granules containing an aliphatic polyester.

[0028] In the present specification, "powder" means a particle having a median diameter of less than 0.5 mm, and "granules" means particles obtained by granulating a powder, and particularly means a particle having a median diameter of 0.5 mm to 10.0 mm.

[0029] According to the scheme described above, plastic products can be efficiently manufactured, thereby contributing to the realization of Sustainable Development Goals (SDGs), such as Goal 12 "Ensuring sustainable consumption and production patterns" and Goal 14 "Conserving and sustainably using the oceans, seas and marine resources for sustainable development". The scheme of the present manufacturing method is described in detail below.

[0030] [2. Method for producing aliphatic polyester granules]

[0031] The manufacturing method comprises: 3~0.50g / cm 3 The present production method comprises a step of compressing and granulating the aliphatic polyester powder. By having the above-mentioned structure, the present production method can obtain aliphatic polyester granules having high bulk density and excellent fluidity.

[0032] (2-1. Powder containing aliphatic polyester)

[0033] The bulk density of the powder containing aliphatic polyester in the present production method is 0.30 g / cm 3 ~0.50g / cm 3 The bulk density of the above powder is preferably 0.32 g / cm 3 ~0.48g / cm 3 , more preferably 0.34 g / cm 3 ~0.46g / cm 3 , more preferably 0.36 g / cm 3 ~0.44g / cm 3 In the present production method, by using a powder containing an aliphatic polyester having a bulk density within the above range, an aliphatic polyester granule having a high bulk density and excellent fluidity can be obtained. In the present specification, the above bulk density is a value measured by the method described in the examples described later.

[0034] The powder contains aliphatic polyester. The aliphatic polyester is not particularly limited, and examples thereof include poly(3-hydroxyalkanoate) (hereinafter also referred to as "P3HA"), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate succinate, polybutylene adipate terephthalate, polybutylene succinate terephthalate, polycaprolactone, etc. Among them, from the perspective of industrial productivity, the aliphatic polyester is preferably P3HA. The powder may contain one of the aliphatic polyesters, or two or more of the aliphatic polyesters.

[0035] The aliphatic polyester contained in the powder preferably contains 50% by weight or more of P3HA in 100% by weight of the aliphatic polyester, more preferably 60% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, and further preferably 95% by weight or more. The aliphatic polyester contained in the powder particularly preferably contains 100% by weight of P3HA in 100% by weight of the aliphatic polyester.

[0036] The median particle size of the above-mentioned powder is preferably 60 to 200 μm, more preferably 80 to 180 μm, and further preferably 100 to 170 μm. The yellowness (YI) of the above-mentioned powder is preferably 40 or less, more preferably 35 or less, and further preferably 30 or less. It should be noted that the lower the YI, the lower the yellowness, and the lower limit is not particularly limited, for example, it can be 5 or more. The thermal stability of the above-mentioned powder is preferably 70 to 100%, more preferably 75 to 95%, and further preferably 77 to 85%. These median particle size, YI, and thermal stability can be measured by the method described in the embodiments described later.

[0037] The powder containing aliphatic polyester in the present production method preferably contains 90% by weight or more of aliphatic polyester, more preferably 95% by weight or more, further preferably 97% by weight or more, and most preferably 99% by weight or more. The upper limit of the content of aliphatic polyester in the above powder is not particularly limited, and for example, it may be 100% by weight or less, or 100% by weight.

[0038] The melting point of the aliphatic polyester contained in the powder is preferably 50 to 200° C., more preferably 60 to 180° C., further preferably 70 to 170° C., and particularly preferably 80 to 160° C. When the melting point of the aliphatic polyester is within the above range, the powder can be melt-bonded during compression granulation without heating, so the amount of binder used can be reduced.

[0039] In one embodiment of the present invention, the powder containing aliphatic polyester does not contain a binder. The present manufacturing method can manufacture granules containing aliphatic polyester without using a binder by including a step of compressing and granulating the powder containing aliphatic polyester. In this specification, "binder" refers to a substance that makes aliphatic polyesters such as plasticizers, cellulose, and water adhere to each other, or promotes their adhesion. In addition, in this specification, the powder containing aliphatic polyester "does not contain a binder" means that the powder containing aliphatic polyester does not contain a binder at all, and also means that it does not substantially contain a binder. The powder containing aliphatic polyester "substantially does not contain a binder" means that, relative to 100% by weight of the powder containing aliphatic polyester, for example, it contains less than 1% by weight of a binder, more preferably less than 0.1% by weight, and further preferably 0.01% by weight. The less the content of the binder, the lower the manufacturing cost.

[0040] Hereinafter, one embodiment of the present production method will be described in detail using poly(3-hydroxyalkanoate) as an example of an aliphatic polyester, including a method for producing a powder containing an aliphatic polyester.

[0041] <p3ha>

[0042] The P3HA of the present production method is a polymer having a 3-hydroxyalkanoate unit as a structural unit (monomer unit). In this specification, "3-hydroxyalkanoate" is sometimes referred to as "3HA". Specifically, the P3HA is preferably a polymer containing a repeating unit represented by the following general formula (1):

[0043] [-CHR-CH 2 -CO-O-]･･･(1).

[0044] In the general formula (1), R represents C n H 2n+1 , n represents an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl. n is preferably 1 to 10, more preferably 1 to 8.

[0045] More specifically, examples of PHA 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) (P3HB4HB), 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), and the like. Among them, P3HB, P3HB3HH, P3HB3HV, P3HB4HB, and P3HB3HP are preferred from the viewpoint of easy industrial production.

[0046] In addition, by changing the composition ratio of the repeating units, the melting point and crystallinity can be changed, and as a result, the physical properties such as Young's modulus and heat resistance can be changed. In addition, it is possible to impart physical properties between those of polypropylene and polyethylene, and to make it a physically useful plastic that is easy to produce on an industrial scale as described above. From the above viewpoints, P3HB3HH, which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred.

[0047] More specifically, P3HA is a copolymer having a 3-hydroxybutyrate unit and a comonomer unit, and the ratio of the 3HB unit to the comonomer unit in 100 mol% of all repeating units of the copolymer (3HB unit / comonomer unit) is preferably 70 / 30 (mol% / mol%) to 99 / 1 (mol% / mol%), more preferably 75 / 25 (mol% / mol%) to 97 / 3 (mol% / mol%), and further preferably 80 / 20 (mol% / mol%) to 95 / 5 (mol% / mol%).

[0048] P3HA having such a ratio of each monomer unit can be prepared by a method known to those skilled in the art, for example, the method described in International Publication No. 2009 / 145164. The ratio of each monomer unit in P3HA (i.e., the above-mentioned (3HB unit / comonomer unit)) can be obtained by the method described in the Examples.

[0049] <Method for producing powder containing P3HA>

[0050] In one embodiment of the present invention, the method for producing a powder containing P3HA (hereinafter sometimes referred to as "P3HA powder") is not particularly limited, and may be a method based on chemical synthesis or a method based on microorganisms. Among them, a method based on microorganisms is preferred. Regarding the method for producing P3HA powder based on microorganisms, a known method can be used, preferably including a culturing step, a purification step, and a drying step.

[0051] The method for culturing the P3HA-producing microorganism in the culturing step is not particularly limited, and for example, the method described in International Publication No. 2019 / 142717 can be used.

[0052] The microorganism producing P3HA is not particularly limited as long as it can produce PHA in the cell. For example, microorganisms isolated from nature and microorganisms preserved in strain preservation institutions (e.g., IFO, ATCC, etc.), or mutants and transformants that can be prepared from them can be used. For example, the bacterial cell of P3HB, which is an example of producing PHA, was first discovered in 1925 as Bacillus megaterium. Other natural microorganisms include Cupriavidus necator (old classification: Alcaligenes eutrophus, Ralstonia eutropha), Alcaligenes latus, etc. It is known that PHA accumulates in the bacterial cells of these microorganisms.

[0053] In addition, as an example of PHA, a bacterial cell that produces a copolymer of hydroxybutyrate and other hydroxyalkanoates includes Aeromonas caviae as a P3HB3HV and P3HB3HH producing bacterium, Alcaligenes eutrophus as a P3HB4HB producing bacterium, and the like. In particular, regarding P3HB3HH, in order to improve the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain, FERM BP-6038 (Alcaligenes eutrophus AC32, FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) and the like are more preferably introduced with genes of the PHA synthase group. In addition to the above, genetically modified microorganisms introduced with various PHA synthesis-related genes can also be used depending on the PHA to be produced.

[0054] The method for purifying P3HA obtained by culturing microorganisms in the purification step is not particularly limited, and known physical treatments and / or chemical treatments and / or biological treatments can be applied. For example, the purification method described in International Publication No. 2010 / 067543 is preferably applied.

[0055] The method for drying P3HA obtained by microbial culture and purification in the drying step is not particularly limited, and spray drying, fluidized bed drying, airflow drying, rotary drying, vibration drying, belt drying, plate drying, etc. can be applied. For example, the drying method described in International Publication No. 2018 / 070492 can be preferably applied.

[0056] As a method of spray drying, for example, an aqueous suspension containing P3HA (hereinafter also referred to as "P3HA aqueous suspension") is supplied to a dryer in the form of fine droplets, and dried while in contact with hot air in the dryer. The method (atomizer) for supplying the P3HA aqueous suspension in the form of fine droplets to the dryer is not particularly limited, and examples thereof include a method using a rotating disk, a method using a nozzle, and other known methods. The contact method between the droplets and the hot air in the dryer is not particularly limited, and examples thereof include: a co-current method, a counter-current method, and a method of using a combination of these methods.

[0057] The drying temperature during the spray drying can be any temperature that can remove most of the aqueous medium from the droplets of the P3HA aqueous suspension, and can be appropriately set under the following conditions: it can be dried to the target moisture content and the quality deterioration (molecular weight reduction, color tone reduction) and melting can be avoided as much as possible. In addition, the air volume of the hot air in the dryer can be appropriately set according to the size of the dryer, etc.

[0058] The method for producing P3HA powder may also include a step of further drying the obtained P3HA after the spray drying. In addition, the method for producing P3HA may also include other steps (for example, a step of adding various additives to the P3HA aqueous suspension, etc.).

[0059] (2-2. Compression granulation process)

[0060] The present production method includes a step of compressing and granulating the powder containing the aliphatic polyester (hereinafter also referred to as "compression granulation step"). By compressing and granulating the powder, a granulate containing the aliphatic polyester having a high bulk density and excellent fluidity can be obtained. Since the fluidity of the granulate is improved, the raw material supplied to the device (in the present production method, the powder containing the aliphatic polyester) is not easily pushed back by the raw material already supplied, which is called "feed neck", and the production efficiency of the product is improved. In addition, by the compression granulation step, granulation can be performed even when the powder does not contain the binder, so the production cost can be reduced.

[0061] The present inventors infer that the reason why the granules containing aliphatic polyester with high bulk density can be obtained by the compression granulation step is that the heat (friction heat) generated in the compression granulation step causes the aliphatic polyesters to melt and bond to each other and solidify. As described above, according to the present production method, the powder can be solidified without heating, so it is not necessary to use the above-mentioned binder. As a result, there is an advantage that the production cost can be reduced.

[0062] In the compression granulation step, the pressure during compression is preferably 10 kN to 60 kN, more preferably 15 kN to 50 kN, and even more preferably 17 kN to 47 kN. When the pressure is 10 kN or more, the powder can be fully melted and bonded. In addition, when the pressure is 60 kN or less, the granulator is less likely to have excessive torque, and the raw material can be prevented from being completely melted.

[0063] In the present production method, granules with high bulk density can be produced without heating in the compression granulation step. Therefore, in one embodiment of the present invention, the compression granulation step is preferably performed at 50°C or less, more preferably at 40°C or less, and further preferably at 30°C or less. In addition, the lower limit of the temperature is not particularly limited, and may be, for example, 0°C or more. By performing the compression granulation step within the above temperature range, the aliphatic polyester is less likely to be thermally decomposed, and thus the molecular weight reduction of the aliphatic polyester can be suppressed.

[0064] The temperature of the raw material in the compression granulation step is not particularly limited. The temperature of the raw material can be, for example, 0 to 100° C. In addition, the raw material can be heated or non-heated. That is, in the present production method, the powder can be granulated regardless of the temperature of the raw material. From the viewpoint of preventing thermal decomposition of the aliphatic polyester from occurring, it is preferred not to heat the raw material.

[0065] In the present production method, the method of compression granulation is not particularly limited, and it can be carried out using, for example, a known compression granulation device. The type of compression granulation device is not particularly limited, and examples thereof include: a plate-shaped type, a sheet-shaped type, a roll extrusion type ( )、Compression type( ), screw extrusion type, roll foot extrusion type, paddle extrusion type, moving model, piston extrusion type, etc. Among them, from the viewpoint of both the quality and productivity of the granulated body containing aliphatic polyester, a roll extrusion type granulator is preferred. As a roll extrusion type granulator, a roll extruder (Briquette Machine, manufactured by HOSOKAWA MICRON Co., Ltd.), Briketta (registered trademark) BSS type (manufactured by Shinto Industry), BM-2 type (Keihan), etc. can be used.

[0066] There is no particular limitation on the method of supplying the above-mentioned powder as a raw material to the above-mentioned compression granulation device. For example, the above-mentioned powder can be stored in a hopper and directly supplied to the granulation device through a conveyor belt attached to the hopper; or supplied to the compression granulation device from the hopper conveyor belt through a belt conveyor, a bucket conveyor, etc.

[0067] In the roller extrusion type compression granulation device, the supplied powder is longitudinally extruded by a screw, and the pressed powder is compressed from the left and right using a pair of rollers to produce granules. Examples of the rollers include a ring roll, a segment roll, and a compact roll.

[0068] When the above-mentioned double-roll extrusion type compression granulation device is used, the roll rotation speed is preferably 5 rpm to 20 rpm, more preferably 7 rpm to 15 rpm, and further preferably 10 rpm to 14 rpm. The compression force is preferably 10 kN to 60 kN, more preferably 15 kN to 50 kN, and further preferably 17 kN to 47 kN. The roll support pressure is preferably 3 MPa to 15 MPa, more preferably 4 MPa to 10 MPa, and further preferably 4.5 MPa to 9 MPa.

[0069] The compression granulation step may be performed separately as a compression step and a crushing (granulation) step. That is, the powder may be compressed and then crushed to granulate. Specifically, for example, a compressed tablet containing aliphatic polyester may be produced by compressing the powder and then the compressed tablet may be crushed.

[0070] In one embodiment of the present invention, the compression granulation step may include the following steps:

[0071] (a) The bulk density is 0.30 g / cm 3 ~0.50g / cm 3 A step of compressing a powder containing an aliphatic polyester to obtain a flake-shaped aliphatic polyester; and

[0072] (b) A step of crushing the flaky aliphatic polyester obtained in the above step (a).

[0073] The method of the above-mentioned crushing process is not particularly limited as long as the obtained compressed granules can be crushed, and it can be carried out by a known crusher. As the device that can be used in the crushing process, various crushers such as jaw crushers, roller crushers, rotor crushers (flake crushers) are preferably used; various mills such as roller mills, shear mills, cutting mills, and vibrating screens with added crushing media are preferably used. In addition, these crushers can also be used in combination. As the above-mentioned rotor crusher, for example, Feather mill (manufactured by HOSOKAWA MICRON Co., Ltd.), ROTOPLEX (manufactured by HOSOKAWA MICRON Co., Ltd.), etc. can be used.

[0074] The present production method may further include the steps of sizing and classifying the obtained granules as necessary. The sizing step using a sizing machine and the classification step using a classifier may be performed by known methods.

[0075] The method of transporting the powder and granules in each step is not limited, and natural fall, conveyor belt transport, air transport, etc. can be used. For example, after the raw material is transported to the granulator by a conveyor belt, it is preferably transported to the crusher / granulator / classifier by natural fall.

[0076] [3. Granules containing aliphatic polyester]

[0077] The bulk density of the present granules exceeds 0.50 g / cm 3 And 0.70g / cm 3 The content of the aliphatic polyester is 90% by weight or more. The granules have improved fluidity, transportability, etc. by having the above-mentioned structure. It should be noted that, with respect to "aliphatic polyester", the matters described in [2. Method for producing aliphatic polyester granules] can be appropriately cited.

[0078] The bulk density of the present granules exceeds 0.50 g / cm 3 And 0.70g / cm 3 Below, preferably 0.51 g / cm 3 ~0.65g / cm 3 , more preferably 0.52 g / cm 3 ~0.60g / cm 3 , more preferably 0.53 g / cm 3 ~0.57g / cm 3 When the bulk density of the present granules is within the above range, the present granules are excellent in fluidity and transportability.

[0079] The content of the aliphatic polyester in the present granules is 90% by weight or more, preferably 95% by weight or more, more preferably 97% by weight or more, and further preferably 99% by weight or more. When the content of the aliphatic polyester in the present granules is within the above range, the processability is excellent. The upper limit of the content of the aliphatic polyester in the present granules is not particularly limited, and for example, it may be 100%.

[0080] The median particle size of the present granules is preferably 0.5 mm to 4.0 mm, more preferably 0.7 mm to 3.8 mm, further preferably 1.0 mm to 3.5 mm, and particularly preferably 1.3 mm to 3.2 mm. When the median particle size of the present granules is 0.5 mm or more, the fluidity of the present granules increases. In addition, when the median particle size of the present granules is 4.0 mm or less, clogging in the piping, etc. can be suppressed, and it is easier to be bitten by the screw of the extruder, etc. during processing, thereby improving productivity. The median particle size of the granules can be measured by the method described in the embodiments described later.

[0081] The hardness of the granules is preferably 5kgf~35kgf, more preferably 7kgf~30kgf, and further preferably 10kgf~25kgf. When the hardness of the granules is 5kgf or more, the breakage during transportation can be suppressed, so the transportability and fluidity increase. In addition, when it is below 35kgf, it becomes easier to crush by screw etc., so the processability is excellent. The hardness of the granules can be measured by the method described in the embodiments described later.

[0082] The moisture content of the present granules is preferably 5% or less, more preferably 1% or less, further preferably 0.5% or less, and particularly preferably 0.3% or less. The lower the moisture content, the better, for example, it may be 0%. When the moisture content of the present granules is within the above range, the hardness and fluidity of the obtained granules are increased.

[0083] The yellowness (YI) of the present granules is, for example, preferably 40 or less, more preferably 35 or less, and further preferably 30 or less. It should be noted that the lower the YI, the lower the yellowness, and the lower limit is not particularly limited, for example, it may be 5 or more. When the YI of the present granules is within the above range, it can be evaluated that the mixing of impurities is suppressed to a certain amount or less, thereby ensuring a certain quality. The YI can be measured by the method described in the examples described later.

[0084] The thermal stability of the granules is, for example, 70% or more, preferably 73% or more, and more preferably 75% or more. When the thermal stability is within the above range, it can be used as a raw material for granules with excellent thermal stability. The higher the thermal stability, the better, for example, it can be 100%.

[0085] In one embodiment of the present invention, the present granules are produced by the present production method.

[0086] The granules can be used for various purposes such as paper, film, sheet, tube, plate, rod, container (for example, bottle container), bag, and member.

[0087] The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0088] That is, one embodiment of the present invention is as follows.

[0089] <1> A method for producing a granulate, wherein the granulate contains an aliphatic polyester, the method comprising:

[0090] For aliphatic polyesters with a bulk density of 0.30 g / cm 3 ~0.50g / cm 3 The powder is compressed and granulated.

[0091] <2> according to <1> The method for producing granules, wherein:

[0092] The compression granulation step is performed at 50°C or below.

[0093] <3> according to <1> or <2> The method for producing granules, wherein:

[0094] The compression granulation step is carried out using a double roll extrusion type granulator.

[0095] <4> according to <1> ~ <3> The method for producing granules, wherein:

[0096] In the compression granulation step, the pressure during compression is 10 kN to 60 kN.

[0097] <5> according to <1> ~ <4> The method for producing granules according to any one of the preceding claims, wherein

[0098] The aliphatic polyester is poly(3-hydroxyalkanoate).

[0099] <6> according to <1> ~ <5> The method for producing granules according to any one of the preceding claims, wherein

[0100] The aliphatic polyester is one or more selected from poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0101] <7> A granulate comprising an aliphatic polyester, wherein the bulk density of the granulate exceeds 0.50 g / cm 3 And 0.70g / cm 3 The content of the aliphatic polyester is 90 wt % or more.

[0102] <8> according to <7> The granules, wherein

[0103] The aliphatic polyester is poly(3-hydroxyalkanoate).

[0104] <9> according to <7> or <8> The granules, wherein

[0105] The aliphatic polyester is one or more selected from poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0106] <10> according to <7> ~ <9> The granules described in any one of the above, wherein the median particle size is 0.5 mm to 4.0 mm.

[0107] <11> according to <7> ~ <10> The granules described above have a hardness of 5 kgf to 35 kgf.

[0108] <12> according to <7> ~ <11> The granules described above have a water content of 5% or less.

[0109] Example

[0110] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0111] [Measurement method]

[0112] (Water content)

[0113] The water content of the aliphatic polyester powder and granules was measured using a heat-drying moisture meter (trade name: MS-70, manufactured by A&D Corporation).

[0114] 〔Composition ratio〕

[0115] The composition ratio of the 3HB unit and the comonomer unit of the aliphatic polyester (copolymer) in the aliphatic polyester powder was calculated as follows (the above-mentioned (3HB unit / comonomer unit)). 1 ml of a sulfuric acid-methanol mixture (15:85) and 1 ml of chloroform were added to about 20 mg of dry bacteria cultured for the production of aliphatic polyester powder, and the mixture was sealed and heated at 100°C for 140 minutes to obtain the methyl ester of the PHA decomposition product. After cooling, 0.5 ml of deionized water was added thereto and mixed thoroughly, and then allowed to stand until the aqueous layer and the organic layer were separated. Thereafter, the monomer unit composition of the PHA decomposition product in the separated organic layer was analyzed by capillary gas chromatography. The gas chromatograph used was Shimadzu Corporation's GC-17A, and the capillary column used was GL Science's NEUTRA BOND-1 (column length 25 m, column inner diameter 0.25 mm, liquid film thickness 0.4 μm). He was used as the carrier gas, the column inlet pressure was set to 100 kPa, and 1 μl of the sample was injected. The temperature condition is to increase the temperature to an initial temperature of 50-200°C at a rate of 8°C / min, and then increase the temperature to 200-290°C at a rate of 30°C / min.

[0116] (Yellowness)

[0117] The yellowness (YI) of the aliphatic polyester powder and granules was measured in accordance with JIS K 7373 using a colorimeter (trade name: CM-5, manufactured by Konica Minolta Co., Ltd.).

[0118] (Molecular weight)

[0119] The weight average molecular weight of the aliphatic polyester in the aliphatic polyester powder and granules was determined by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko Industries) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko Industries) in a column and chloroform as a mobile phase, and the weight average molecular weight was determined in terms of polystyrene.

[0120] (Bulk density)

[0121] The bulk density of the aliphatic polyester powder and granules was measured using a bulk density tester (trade name: Standard Bulk Specific Gravity Tester, manufactured by Zonte Scientific Instruments) in accordance with JIS K 7365:1999.

[0122] (hardness)

[0123] The hardness of the aliphatic polyester granules was measured using a hardness tester (trade name: Kiya hardness tester, manufactured by Fujiwara Seisakusho).

[0124] (Median particle size of aliphatic polyester powder)

[0125] The median particle size of the aliphatic polyester powder was measured using a laser diffraction / scattering particle size distribution measuring device LA-950 (manufactured by HORIBA Corporation). 0.05 g of sodium dodecyl sulfate was added as a surfactant to 20 mL of ion exchange water to obtain a surfactant aqueous solution. Next, 0.2 g of aliphatic polyester powder was added to the surfactant aqueous solution as a measurement object, and the aliphatic polyester powder was dispersed in the surfactant aqueous solution to obtain a dispersion for measurement. The prepared dispersion was introduced into the laser diffraction / scattering particle size distribution measuring device and measured.

[0126] (Median particle size of granules)

[0127] The median particle size of the aliphatic polyester granules was measured using a metal mesh sieve in accordance with JIS Z 8801-1:2000.

[0128] (Thermal stability)

[0129] The thermal stability of aliphatic polyester powder and granules was measured using a small heat press (trade name: H300-01, manufactured by AS ONE Co., Ltd.) Pressing was performed at 160°C and 13 MPa for 20 minutes, and the ratio of molecular weight change before and after heating was taken as thermal stability.

[0130] (Liquidity)

[0131] The fluidity of aliphatic polyester powder and granules was measured using an extruder TEM26SS (manufactured by Toshiba Machine). A certain amount of powder or granules was fed into the extruder, and the screw speed was measured until feed blockage occurred. The processing volume corresponding to the speed was further calculated and compared to evaluate the fluidity.

[0132] [Example 1]

[0133] (Compression granulation)

[0134] By the method described in Example 1 of International Publication No. 2021 / 085534, a P3HB3HH powder (dry powder) having a 3HH ratio described in Table 1 was obtained. The obtained powder was supplied to a double-roll extruder (manufactured by HOSOKAWA MICRON) which is a double-roll extrusion granulator having a longitudinal screw and two rotating rollers for compression to obtain a compressed tablet. The obtained compressed tablet was crushed and granulated using a Feather mill (manufactured by HOSOKAWA MICRON) having a longitudinal screw and a rotating roller to obtain a granulate. The roller speed of the compression granulator was set to 14 rpm, the compression force was set to 40 kN, and the roller support pressure was set to 9 MPa. In addition, the manufacture of the granules was carried out at room temperature (23°C) and the raw material temperature was 22°C. The granules had a moisture content of 0.21%, a molecular weight of 420,000, a bulk density of 0.57, a median particle size of 1.8 mm, a YI of 14, a hardness of 10 kgf, a thermal stability of 85%, and a P3HB3HH content of 99% by weight.

[0135] [Example 2]

[0136] By the method described in Example 1 of International Publication No. 2022 / 091685, a P3HB3HH powder (dry powder) having a 3HH (commonomer unit) ratio described in Table 1 was obtained. The obtained powder was supplied to the above-mentioned double-roll extruder (manufactured by HOSOKAWA MICRON) to obtain a compressed sheet. The obtained sheet was crushed using the above-mentioned Feather mill (manufactured by HOSOKAWA MICRON) to obtain a granulate. The roller speed of the compression granulator was set to 10 rpm, the compression force was set to 17 kN, and the roller support pressure was set to 4.5 MPa. In addition, the manufacture of the granules was carried out at room temperature (23°C) and the raw material temperature was 22°C. The moisture content of the granules was 0.09%, the molecular weight was 650,000, the bulk density was 0.53, the median particle size was 3.2 mm, the YI was 26, the hardness was 18 kgf, the thermal stability was 77%, and the P3HB3HH content was 99% by weight.

[0137] [Example 3]

[0138] The method of culturing the bacteria was changed to the method described in Example 2 of International Publication No. 2019 / 142845. In addition, a P3HB3HH powder (dried powder) having a 3HH ratio described in Table 1 was obtained by the same method as in Example 1. The obtained powder was supplied to the above-mentioned double-roll extruder (manufactured by HOSOKAWA MICRON) to obtain a sheet. The obtained sheet was crushed using a Feather mill (manufactured by HOSOKAWA MICRON) equipped with a longitudinal screw and a rotating roller to obtain a granulate. The roller speed of the compression granulator was set to 14rpm, the compression force was set to 45kN, and the roller support pressure was set to 9MPa. In addition, the manufacture of the granules was carried out at room temperature (23°C) and the raw material temperature was 22°C. The moisture content of the granules was 0.20%, the molecular weight was 650,000, the bulk density was 0.53, the median particle size was 3.2mm, the hardness was 14kgf, the thermal stability was 55%, and the P3HB3HH content was 99% by weight.

[0139] [Example 4]

[0140] The culture method of the bacteria was changed to the method described in Example 2 of International Publication No. 2019 / 142845. In addition, a P3HB3HH powder (dry powder) having a 3HH ratio described in Table 1 was obtained by the same method as in Example 1. The obtained powder was supplied to the above-mentioned double-roll extruder (manufactured by HOSOKAWA MICRON) to obtain a sheet. The obtained sheet was crushed using a ROTOPLEX (manufactured by HOSOKAWA MICRON) having a fixed blade and a rotating blade to obtain a granulate. The roller speed of the compression granulator was set to 10.7 rpm, the compression force was set to 25 kN, and the roller support pressure was set to 4.5 MPa. In addition, the manufacture of the granules was carried out at room temperature (27°C) and the raw material temperature was 26°C. The granules had a moisture content of 0.09%, a molecular weight of 650,000, a bulk density of 0.54, a median particle size of 2.8 mm, a YI of 26, a hardness of 20 kgf, a thermal stability of 80%, and a P3HB3HH content of 99% by weight.

[0141] [Example 5]

[0142] A dispersed slurry was obtained by the same method as (cleaning 2) of Example 1 of International Publication No. 2022 / 091685. It was dehydrated using a filter cloth and dried using a plate dryer (manufactured by Andritz) to obtain a P3HB3HH powder (dried powder) having a 3HH ratio described in Table 1. The obtained powder was supplied to the above-mentioned double-roll extruder (manufactured by HOSOKAWA MICRON) to obtain a sheet. The obtained sheet was crushed using a ROTOPLEX (manufactured by HOSOKAWA MICRON) having a fixed blade and a rotating blade to obtain a granulate. The roller speed of the compression granulator was set to 11.5 rpm, the compression force was set to 36 kN, and the roller support pressure was set to 9 MPa. In addition, the manufacture of the granules was carried out at room temperature (28°C) and the raw material temperature was 28°C. The granules had a moisture content of 0.17%, a molecular weight of 450,000, a bulk density of 0.57, a median particle size of 2.5 mm, a YI of 14, a hardness of 14 kgf, a thermal stability of 83%, and a P3HB3HH content of 99% by weight.

[0143] [Example 6]

[0144] A dispersed slurry was obtained by the same method as (cleaning 2) of Example 1 of International Publication No. 2022 / 091685. It was dehydrated using a filter cloth and dried using a plate dryer (manufactured by Andritz) to obtain a P3HB3HH powder (dried powder) having a 3HH ratio described in Table 1. The obtained powder was supplied to the above-mentioned double-roll extruder (manufactured by HOSOKAWA MICRON) to obtain a sheet. The obtained sheet was crushed using a ROTOPLEX (manufactured by HOSOKAWA MICRON) having a fixed blade and a rotating blade to obtain a granulate. The roller speed of the compression granulator was set to 14.4 rpm, the compression force was set to 13 kN, and the roller support pressure was set to 4.1 MPa. In addition, the manufacture of the granules was carried out at room temperature (11°C) and the raw material temperature was 60°C. The granules had a moisture content of 0.28%, a molecular weight of 700,000, a bulk density of 0.52, a median particle size of 2.5 mm, a YI of 23, a hardness of 24 kgf, a thermal stability of 83%, and a P3HB3HH content of 99% by weight.

[0145] [Comparative Example 1]

[0146] The powder (dried powder) of Example 1 was used as Comparative Example 1. The powder of Comparative Example 1 contained 3HH as a comonomer, had a moisture content of 0.21%, (3HB unit / 3HH unit) of 94.8 / 5.2 (mol% / mol%), a weight average molecular weight of 420,000, a bulk density of 0.42, a median particle size of 163 μm, a YI of 14, and a thermal stability of 84%.

[0147] [Comparative Example 2]

[0148] The powder (dried powder) of Example 2 was used as Comparative Example 2. The powder of Comparative Example 2 contained 3HH as a comonomer, had a moisture content of 0.09%, (3HB unit / 3HH unit) of 82 / 18 (mol% / mol%), a weight average molecular weight of 650,000, a bulk density of 0.44, a median particle size of 163 μm, a YI of 26, and a thermal stability of 77%.

[0149] [Comparative Example 3]

[0150] The powder (dried powder) of Example 3 was used as Comparative Example 3. The powder of Comparative Example 3 contained 3HH as a comonomer, had a moisture content of 0.20%, (3HB unit / 3HH unit) of 96.3 / 3.7 (mol% / mol%), a weight average molecular weight of 330,000, a bulk density of 0.36, a median particle size of 113 μm, and a thermal stability of 55%.

[0151] [Comparative Example 4]

[0152] The powder (dried powder) of Example 4 was used as Comparative Example 4. The powder of Comparative Example 4 contained 3HH as a comonomer, had a moisture content of 0.09%, (3HB unit / 3HH unit) of 82 / 18 (mol% / mol%), a weight average molecular weight of 650,000, a bulk density of 0.44, a median particle size of 163 μm, a YI of 26, and a thermal stability of 77%.

[0153] [Comparative Example 5]

[0154] The powder (dried powder) of Example 5 was used as Comparative Example 5. The powder of Comparative Example 5 contained 3HH as a comonomer, had a moisture content of 0.17%, (3HB unit / 3HH unit) of 94.9 / 5.1 (mol% / mol%), a weight average molecular weight of 450,000, a bulk density of 0.32, a median particle size of 2.9 μm, a YI of 14, and a thermal stability of 83%.

[0155] [Comparative Example 6]

[0156] The powder (dried powder) of Example 6 was used as Comparative Example 6. The powder of Comparative Example 6 contained 3HH as a comonomer, had a moisture content of 0.28%, (3HB unit / 3HH unit) of 87.5 / 12.5 (mol% / mol%), a weight average molecular weight of 700,000, a bulk density of 0.35, a median particle size of 26.1 μm, a YI of 23, and a thermal stability of 83%.

[0157] The physical properties of the granules of Examples 1 to 6 and the powders of Comparative Examples 1 to 6 are shown in Table 1. The powders of Comparative Examples 1 to 6 were so soft that they could be crushed by hand, and therefore the hardness was not measured.

[0158]

[0159] The results of the flowability tests of Examples 1 and 3 and Comparative Examples 1 and 3 are shown in Table 2. In Table 2, "FN" means feed blocking.

[0160]

[0161] 〔result〕

[0162] As shown in Table 1, the bulk density of any of the granules in Examples 1 to 6 exceeds 0.50 g / cm 3 , having a higher bulk density than the powders of Comparative Examples 1 to 6. In addition, as can be seen from Table 2, compared with the powders of Comparative Examples 1 and 3, the granules of Examples 1 and 3 have a low screw speed for FN and a larger processing volume, and therefore have excellent fluidity. In addition, there is no significant change in thermal stability and YI between the examples and the comparative examples. Therefore, compared with the dry powder produced by spray drying, the granules of the present invention produced by compression granulation do not show a difference in quality. The above results show that according to the production method of one embodiment of the present invention, granules with high bulk density, high fluidity and containing aliphatic polyester can be produced.

[0163] Industrial Applicability

[0164] The granules obtained by the production method of the present invention can be suitably used in agriculture, fishery, forestry, horticulture, medicine, sanitary products, clothing, non-clothing materials, packaging, automobiles, building materials, and other fields.

Claims

1. A method for producing a granulate, wherein the granulate comprises an aliphatic polyester, the method comprising: For aliphatic polyesters with a bulk density of 0.30 g / cm 3 ~0.50g / cm 3 The powder is compressed and granulated.

2. The method for producing granules according to claim 1, wherein The compression granulation step is performed at 50°C or below.

3. The method for producing granules according to claim 1, wherein The compression granulation step is carried out using a double roll extrusion type granulator.

4. The method for producing granules according to claim 1, wherein In the compression granulation step, the pressure during compression is 10 kN to 60 kN.

5. The method for producing granules according to any one of claims 1 to 4, wherein The aliphatic polyester is poly(3-hydroxyalkanoate).

6. The method for producing granules according to claim 5, wherein The aliphatic polyester is one or more selected from poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

7. A granulate comprising an aliphatic polyester, wherein the bulk density of the granulate exceeds 0.50 g / cm 3 And 0.70g / cm 3 The content of the aliphatic polyester is 90 wt % or more.

8. The granules according to claim 7, wherein The aliphatic polyester is poly(3-hydroxyalkanoate).

9. The granules according to claim 8, wherein The aliphatic polyester is one or more selected from poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

10. The granules according to any one of claims 7 to 9, wherein the median particle size is 0.5 mm to 4.0 mm. 11 . The granules according to claim 7 , which have a hardness of 5 kgf to 35 kgf.

12. The granules according to any one of claims 7 to 9, which have a water content of 5% or less.

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