Granulated product and method for producing same

Abstract

The present invention addresses the problem of providing a granulated product that contains an aliphatic polyester and has a high bulk density and high fluidity. The abovementioned problem is solved by a method for producing a granulated product that contains an aliphatic polyester, the method including a step for compressing and granulating a powder that contains an aliphatic polyester and has a bulk density of 0.30 g / cm3 to 0.50 g / cm3.

Description

Granules and their manufacturing method

[0001] The present invention relates to a granule and a method for producing the same.

[0002] Biodegradable resins such as polyhydroxyalkanoic acid (PHA) are being increasingly used in a variety of applications due to their biodegradability. For example, PHA is transported or processed as a dried powder when used. A method for producing PHA powder by spray-drying a PHA suspension has been developed (see, for example, Patent Document 1).

[0003] Meanwhile, there is known a technology for preparing a plastic composition comprising at least one polyester, a biological entity having polyester-degrading activity, and at least one antacid filler, wherein the biological entity accounts for less than 11% (by weight) of the total weight of the plastic composition, in which the mixing step is carried out at a temperature at which the polyester is partially or wholly molten and / or in an extruder, preferably a twin-screw extruder, more preferably a co-rotating twin-screw extruder (e.g., Patent Document 2).

[0004] International Publication No. 2018 / 070492 Specification Japanese Patent Application Laid-Open No. 2021-119240

[0005] However, the PHA powder obtained by the spray drying method described in Patent Document 1 has a low bulk density and may have poor flowability, so there is room for improvement.

[0006] Furthermore, the technique described in Patent Document 2 involves mixing using an extruder, which has the problem of reducing the molecular weight of the aliphatic polyester.

[0007] An object of one aspect of the present invention is to provide a granule containing an aliphatic polyester that has a high bulk density and high flowability.

[0008] The present inventors have conducted extensive research to solve the above problems, and as a result, have found that an aliphatic polyester having high bulk density and flowability can be produced by including a step of compressing and granulating a powder containing an aliphatic polyester and having a bulk density within a specific range, thereby completing the present invention.

[0009] Therefore, one aspect of the present invention is a granular material having a bulk density of 0.30 g / cm ３ ~0.50 g / cm ３ The present invention relates to a method for producing a granule containing an aliphatic polyester, the method comprising the step of compressing and granulating a powder containing an aliphatic polyester (hereinafter, the "method for producing a granule containing an aliphatic polyester according to one embodiment of the present invention" will be referred to as the "present production method").

[0010] In another aspect of the present invention, a bulk density of 0.50 g / cm ３ Super, 0.70g / cm ３ The granules (hereinafter referred to as "the granules") have a molecular weight of 1000 or less and an aliphatic polyester content of 90% by weight or more.

[0011] According to one aspect of the present invention, a granule containing an aliphatic polyester having a high bulk density and high fluidity can be realized.

[0012] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more, B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0013] [1. Overview of the Invention] PHA powder obtained by spray drying or the like as described in Patent Document 1 is then pelletized in a compounding process or the like. Pelletizing the PHA powder improves handling when feeding it into a molding machine, and increases the apparent bulk density, thereby improving transportability. However, the inventors have discovered that the conventional method described in Patent Document 1 results in a problem in that the bulk density of the resulting PHA powder is low, resulting in low fluidity of the PHA powder and reduced production efficiency in the compounding process or the like. Furthermore, reduced fluidity of the PHA powder also leads to the problem of poor transportability of the powder.

[0014] The present inventors have also found that the technique of using an extruder described in Patent Document 2, when using an aliphatic polyester with poor fluidity, causes a problem of difficulty in entering the extruder, resulting in a decrease in production rate. Furthermore, they have also found that increasing the screw rotation speed of the extruder to increase the production rate causes an excessive rise in temperature, resulting in thermal decomposition of the aliphatic polyester and a decrease in molecular weight. In particular, since the melting point and decomposition temperature of the above-mentioned PHA are close, the molecular weight is likely to decrease when heated to increase fluidity.

[0015] Therefore, the present inventors conducted extensive research to solve the above problems, and as a result, they succeeded in making the following discoveries: - By compressing and granulating a powder containing an aliphatic polyester and having a low bulk density, granules with a high bulk density and excellent flowability can be obtained. - The granules obtained by this production method have a high bulk density and therefore excellent transportability. - According to this production method, granules containing an aliphatic polyester can be produced without using a binder. - According to this production method, there is no need to use a plasticizer or the like during compression granulation, so that granules with a high aliphatic polyester content can be obtained with fewer impurities.

[0016] In particular, the technical idea of ​​obtaining granules with a high bulk density by compressing and granulating a powder containing an aliphatic polyester with a low bulk density has not been realized to date, and the present invention is therefore extremely superior. The granules obtained by this production method have a high bulk density and excellent flowability, and can therefore be advantageously used as a granule raw material containing an aliphatic polyester.

[0017] In this specification, the term "powder" refers to a material having a median diameter of less than 0.5 mm, and the term "granules" refers to particles obtained by granulating powder, particularly those having a median diameter of 0.5 mm to 10.0 mm.

[0018] According to the above-mentioned configuration, plastic products can be efficiently manufactured, which can contribute to the achievement of the 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 will be described in detail below.

[0019] [2. Method for producing aliphatic polyester granules] This production method is for producing aliphatic polyester granules having a bulk density of 0.30 g / cm ３ ~0.50 g / cm ３ The present production method includes a step of compressing and granulating a powder containing an aliphatic polyester, the powder being of the formula:

[0023] By virtue of the above-described configuration, it is possible to obtain aliphatic polyester granules having a high bulk density and excellent flowability.

[0020] (2-1. Powder containing aliphatic polyester) The powder containing aliphatic polyester in this production method has a bulk density of 0.30 g / cm ３ ~0.50 g / cm ３ The bulk density of the powder is preferably 0.32 g / cm ３ ~0.48g / cm ３ and more preferably 0.34 g / cm ３ ~0.46g / cm ３ , more preferably 0.36 g / cm ３ ~0.44 g / cm ３In this production method, by using a powder containing an aliphatic polyester having a bulk density within the above range, it is possible to obtain aliphatic polyester granules having a high bulk density and excellent flowability. In this specification, the bulk density is a value measured by the method described in the examples below.

[0021] The powder contains an aliphatic polyester. The aliphatic polyester is not particularly limited, but examples thereof include poly(3-hydroxyalkanoate) (hereinafter also referred to as "P3HA"), polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate, polybutylene adipate terephthalate, polybutylene succinate terephthalate, and polycaprolactone. Among these, P3HA is preferred as the aliphatic polyester from the viewpoint of industrial productivity. The powder may contain one type of aliphatic polyester, or two or more types thereof.

[0022] The aliphatic polyester contained in the powder preferably contains 50% by weight or more of P3HA relative to 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, even more preferably 90% by weight or more, and even more preferably 95% by weight or more. The aliphatic polyester contained in the powder particularly preferably contains 100% by weight of P3HA relative to 100% by weight of the aliphatic polyester.

[0023] The median diameter of the powder is preferably 60 to 200 μm, more preferably 80 to 180 μm, and even more preferably 100 to 170 μm. The yellowness index (YI) of the powder is preferably 40 or less, more preferably 35 or less, and even more preferably 30 or less. The lower the YI, the lower the yellowness, and although there are no particular restrictions on the lower limit, it may be, for example, 5 or more. The thermal stability of the powder is preferably 70 to 100%, more preferably 75 to 95%, and even more preferably 77 to 85%. The median diameter, YI, and thermal stability can be measured by the methods described in the Examples below.

[0024] The powder containing the aliphatic polyester in the present production method preferably contains 90% by weight or more of the aliphatic polyester, more preferably 95% by weight or more, even more preferably 97% by weight or more, and most preferably 99% by weight or more. The upper limit of the aliphatic polyester content in the powder is not particularly limited, and may be, for example, 100% by weight or less, or even 100% by weight.

[0025] 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-mentioned range, the powder can be fused without heating during compression granulation, and therefore the amount of binder used, which will be described later, can be reduced.

[0026] In one embodiment of the present invention, the powder containing an aliphatic polyester does not contain a binder. This production method includes a step of compressing and granulating the powder containing an aliphatic polyester, thereby enabling the production of granules containing an aliphatic polyester without using a binder. In this specification, the term "binder" refers to a substance that bonds or promotes the adhesion of aliphatic polyesters to each other, such as a plasticizer, cellulose, or water. Furthermore, in this specification, the term "binder-free" for a powder containing an aliphatic polyester refers to a powder containing no binder at all, as well as a powder containing substantially no binder. The term "substantially binder-free" for a powder containing an aliphatic polyester refers to a powder containing, for example, 1 wt % or less, more preferably 0.1 wt % or less, and even more preferably 0.01 wt % or less of a binder, based on 100 wt % of the powder containing the aliphatic polyester. The lower the binder content, the lower the production costs.

[0027] Hereinafter, one embodiment of the present production method will be described in detail, including a method for producing a powder containing an aliphatic polyester, using poly(3-hydroxyalkanoate) as an example of an aliphatic polyester.

[0028] <P3HA> P3HA in this production method is a polymer having a 3-hydroxyalkanoate unit as a constituent unit (monomer unit). In this specification, "3-hydroxyalkanoate" may also be referred to as "3HA". Specifically, P3HA is preferably a polymer containing a repeating unit represented by the following general formula (1): [-CHR-CH ２ -CO-O-]...(1).

[0029] In the general formula (1), R is C ｎ H ２ｎ＋１ where n is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. n is preferably 1 to 10, and more preferably 1 to 8.

[0030] 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), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB 4HB), 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. Among these, P3HB, P3HB3HH, P3HB3HV, P3HB4HB, and P3HB3HP are preferred because of ease of industrial production.

[0031] Furthermore, by changing the composition ratio of the repeating units, it is possible to change the melting point and degree of crystallinity, and as a result, it is possible to change physical properties such as Young's modulus and heat resistance, and it is possible to impart physical properties between those of polypropylene and polyethylene.In addition, from the viewpoint that it is easy to produce industrially as described above and is a physically useful plastic, P3HB3HH, which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, is more preferred.

[0032] More specifically, P3HA is a copolymer having 3-hydroxybutyrate units and comonomer units, and the ratio of 3HB units to comonomer units (3HB units / comonomer units) in 100 mol% of all repeating units in the copolymer is preferably 70 / 30 (mol% / mol%) to 99 / 1 (mol% / mol%), more preferably 75 / 25 (mol% / mol%) to 97 / 3 (mol% / mol%), and even more preferably 80 / 20 (mol% / mol%) to 95 / 5 (mol% / mol%).

[0033] P3HA having such a ratio of each monomer unit can be produced according to 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 determined by the method described in the Examples. <Method for producing a powder containing P3HA>

[0034] 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 production method by chemical synthesis or a production method using a microorganism. Of these, a production method using a microorganism is preferred. Known methods can be applied to the microbial production method of P3HA powder, but it is preferable that the method include a culture step, a purification step, and a drying step.

[0035] The method for culturing the microorganism that produces P3HA in the culturing step is not particularly limited, and for example, the method described in WO 2019 / 142717 can be used.

[0036] The microorganism that produces P3HA is not particularly limited as long as it is a microorganism that can produce PHA intracellularly. For example, microorganisms isolated from nature and deposited in a depository institution for strains (e.g., IFO, ATCC, etc.), or mutants and transformants that can be prepared from them, can be used. For example, the first microorganism to produce P3HB, an example of PHA, was Bacillus megaterium, 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 PHA accumulates intracellularly in these microorganisms.

[0037] Examples of bacteria that produce copolymers of hydroxybutyrate and other hydroxyalkanoates, which are examples of PHA, include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, more preferred is Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)), into which genes encoding PHA synthases have been introduced, in order to increase the productivity of P3HB3HH. In addition to the above, the bacterial cells may be genetically modified microorganisms into which various PHA synthesis-related genes have been introduced depending on the PHA to be produced.

[0038] The method for purifying the P3HA obtained by microbial culture in the purification step is not particularly limited, and known physical treatments, chemical treatments, and / or biological treatments can be applied. For example, the purification method described in WO 2010 / 067543 can be preferably applied.

[0039] The method for drying the P3HA obtained by microbial culture and purification in the drying step is not particularly limited, and spray drying, fluidized bed drying, flash drying, rotary drying, vibration drying, band drying, plate drying, etc. can be applied. For example, the drying method described in WO 2018 / 070492 can be preferably applied.

[0040] An example of a spray drying method is a method in which an aqueous suspension containing P3HA (hereinafter referred to as "P3HA aqueous suspension") is supplied into a dryer in the form of fine droplets and dried while being brought into contact with hot air in the dryer. The method (atomizer) for supplying the P3HA aqueous suspension into the dryer in the form of fine droplets is not particularly limited, and examples include known methods such as a method using a rotating disk or a method using a nozzle. The method for contacting the droplets with the hot air in the dryer is not particularly limited, and examples include a parallel flow method, a countercurrent method, and a method combining these.

[0041] The drying temperature during the spray drying may 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 conditions that can dry the droplets to the desired moisture content and minimize deterioration in quality (reduction in molecular weight, color tone) or melting. The volume of hot air in the dryer can also be appropriately set depending on, for example, the size of the dryer.

[0042] The method for producing P3HA powder may include a step of further drying the obtained P3HA after the spray drying. The method for producing P3HA may also include other steps (e.g., a step of adding various additives to the P3HA aqueous suspension).

[0043] (2-2. Compression Granulation Step) This production method includes a step of compressing and granulating the powder containing the aliphatic polyester described above (hereinafter also referred to as the "compression granulation step"). By compressing and granulating the powder, it is possible to obtain granules containing the aliphatic polyester that have a high bulk density and excellent fluidity. By improving the fluidity of the granules, it is possible to reduce the occurrence of a phenomenon known as "feed neck," in which raw materials supplied to the device (powder containing the aliphatic polyester in this production method) are pushed back by raw materials already supplied, thereby improving the production efficiency of the product. Furthermore, the compression granulation step makes it possible to granulate the powder even if it does not contain the above-mentioned binder, thereby reducing production costs.

[0044] The inventors believe that the reason why granules containing aliphatic polyesters with high bulk density can be obtained by the compression granulation process is that the heat (frictional heat) generated in the compression granulation process causes the aliphatic polyesters to fuse together and solidify. Thus, according to this production method, it is possible to solidify the powder without heating, thereby eliminating the need to use the binder described above. This also has the advantage of reducing production costs.

[0045] In the compression granulation step, the compression pressure is preferably 10 kN to 60 kN, more preferably 15 kN to 50 kN, and even more preferably 17 kN to 47 kN. If the pressure is 10 kN or more, the powder can be sufficiently fused. On the other hand, if the pressure is 60 kN or less, torque over of the granulator is unlikely to occur and the raw materials can be prevented from completely melting.

[0046] In this 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 carried out at 50°C or less, more preferably 40°C or less, and even more preferably 30°C or less. The lower limit of the temperature is not particularly limited, but may be, for example, 0°C or more. By carrying out the compression granulation step within the above temperature range, thermal decomposition of the aliphatic polyester is less likely to occur, and therefore a decrease in the molecular weight of the aliphatic polyester can be suppressed.

[0047] The temperature of the raw materials in the compression granulation step is not particularly limited. The temperature of the raw materials may be, for example, 0 to 100°C. The raw materials may be heated or unheated. That is, in the present production method, powder granulation can be performed regardless of the temperature of the raw materials. From the viewpoint of making thermal decomposition of the aliphatic polyester less likely to occur, it is preferable that the raw materials are not heated.

[0048] In this production method, the compression granulation method is not particularly limited, and can be carried out using, for example, a known compression granulation device. The type of compression granulation device is not particularly limited, and examples include plate-type, tablet-type, briquette-type, compacting-type, screw extrusion-type, roll-foot extrusion-type, blade extrusion-type, moving die-type, and ram extrusion-type. Among these, a briquette-type granulator is preferred from the viewpoint of achieving both the quality and productivity of the granules containing the aliphatic polyester. Examples of briquette-type granulators that can be used include a briquette machine (manufactured by Hosokawa Micron Corporation), a Briquette (registered trademark) BSS type (manufactured by Shinto Kogyo Co., Ltd.), and a BM-2 type (Keihan).

[0049] The method for supplying the raw material powder to the compression granulation apparatus is not particularly limited. For example, the powder may be stored in a hopper and supplied directly to the granulation apparatus from a transport conveyor attached to the hopper, or it may be supplied to the compression granulation apparatus from a hopper transport conveyor via a belt conveyor, bucket conveyor, or the like.

[0050] In a briquette-type compression granulation device, the supplied powder is pressed vertically by a screw, and the pressed powder is compressed from the left and right using a pair of rollers, such as a ring roll, a segment roll, and a compact roll, to produce granules.

[0051] When using the briquette-type compression granulation device, the roll rotation speed is preferably 5 rpm to 20 rpm, more preferably 7 rpm to 15 rpm, and even more preferably 10 rpm to 14 rpm. The compression force is preferably 10 kN to 60 kN, more preferably 15 kN to 50 kN, and even more 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 even more preferably 4.5 MPa to 9 MPa.

[0052] The compression granulation step may be performed by separately performing a compression step and a crushing (granulation) step. That is, the powder may be compressed and then crushed to perform granulation. Specifically, for example, the powder may be compressed to produce a compressed sheet containing the aliphatic polyester, and then the compressed sheet may be crushed.

[0053] In one embodiment of the present invention, the compression granulation step may include the following steps: (a) a bulk density of 0.30 g / cm ３ ~0.50 g / cm ３ (b) a step of compressing a powder containing an aliphatic polyester to obtain a sheet-like aliphatic polyester, and (b) a step of crushing the sheet-like aliphatic polyester obtained in (a).

[0054] The method for the crushing step is not particularly limited as long as it can crush the obtained compressed granules, and can be carried out using a known crusher. Preferred devices that can be used in the crushing step include various crushers such as jaw crushers, roll crushers, and flake crushers, various mills such as roller mills, cutting mills, and cutter mills, and vibrating sieves with added crushing media. It is also possible to use a combination of these crushers. Examples of flake crushers that can be used include Feather Mill (manufactured by Hosokawa Micron Corporation) and Rotoplex (manufactured by Hosokawa Micron Corporation).

[0055] 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 can be carried out by known methods.

[0056] There is no limitation on the method of transporting the powder and granules in each step, and it is possible to use gravity drop, conveyor transport, air blowing, etc. For example, a method is preferred in which the raw material is transported to a granulator by conveyor transport, and then transported to a crusher, a granulator, and a classifier by gravity drop.

[0057] [3. Granules containing aliphatic polyester] The granules have a bulk density of 0.50 g / cm ３ Super, 0.70g / cm ３ or less, and the content of the aliphatic polyester is 90% by weight or more. The granules have the above-mentioned structure, which improves the flowability, transportability, etc. Note that with regard to "aliphatic polyester," the matters described in [2. Method for producing aliphatic polyester granules] can be appropriately cited.

[0058] The bulk density of the granules is 0.50 g / cm ３ Super, 0.70g / cm ３ or less, preferably 0.51 g / cm ３ ~0.65g / cm ３ and more preferably 0.52 g / cm ３ ~0.60 g / cm ３ and 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 have excellent flowability and transportability.

[0059] 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 even more 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 may be, for example, 100%.

[0060] The median diameter of the present granules is preferably 0.5 mm to 4.0 mm, more preferably 0.7 mm to 3.8 mm, even more preferably 1.0 mm to 3.5 mm, and particularly preferably 1.3 mm to 3.2 mm. If the median diameter of the present granules is 0.5 mm or more, the flowability of the present granules is improved. Furthermore, if the median diameter of the present granules is 4.0 mm or less, clogging in piping and the like is suppressed, and the granules are more likely to be caught in the screw of an extruder or the like during processing, thereby improving productivity. The median diameter of the granules can be measured by the method described in the Examples below.

[0061] The hardness of the present granules is preferably 5 kgf to 35 kgf, more preferably 7 kgf to 30 kgf, and even more preferably 10 kgf to 25 kgf. If the hardness of the present granules is 5 kgf or more, breakage during transportation can be suppressed, thereby improving transportability and flowability. Furthermore, if the hardness is 35 kgf or less, crushing using a screw or the like becomes easy, resulting in excellent processability. The hardness of the granules can be measured by the method described in the Examples below.

[0062] The moisture content of the present granules is preferably 5% or less, more preferably 1% or less, even more preferably 0.5% or less, and particularly preferably 0.3% or less. The lower the moisture content, the better, and it may be, for example, 0%. If the moisture content of the present granules is within the above range, the hardness and flowability of the obtained granules will be improved.

[0063] The yellowness index (YI) of the present granules is, for example, preferably 40 or less, more preferably 35 or less, and even more preferably 30 or less. The lower the YI, the lower the yellowness, and the lower limit is not particularly limited, but may be, for example, 5 or more. If the YI of the present granules is within the above range, it can be evaluated that the amount of impurities mixed in is kept below a certain level, and a certain level of quality can be ensured. The YI can be measured by the method described in the examples below.

[0064] The thermal stability of the present granules is, for example, 70% or more, preferably 73% or more, and more preferably 75% or more. If the thermal stability is within the above range, the granules can be used as a granule raw material with excellent thermal stability. The higher the thermal stability, the better, and it may be, for example, 100%.

[0065] In one embodiment of the present invention, the granules are produced by the production method.

[0066] The granules can be used for a variety of purposes, such as paper, film, sheets, tubes, plates, rods, containers (for example, bottle containers), bags, and parts.

[0067] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0068] That is, one embodiment of the present invention is as follows: <1> Bulk density is 0.30 g / cm ３ ~0.50 g / cm ３<2> A method for producing granules containing an aliphatic polyester, comprising a step of compression-granulating a powder containing an aliphatic polyester, wherein the aliphatic polyester is poly(3-hydroxyalkanoate). <2> A method for producing granules according to <1>, wherein the compression-granulation step is carried out at 50°C or less. <3> A method for producing granules according to <1> or <2>, wherein the compression-granulation step is carried out using a briquette-type granulator. <4> A method for producing granules according to <1> to <3>, wherein the compression pressure in the compression-granulation step is 10 kN to 60 kN. <5> A method for producing granules according to any one of <1> to <4>, wherein the aliphatic polyester is poly(3-hydroxyalkanoate). <6> The method for producing a granule according to any one of <1> to <5>, wherein the aliphatic polyester is one or more selected from the group consisting of 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 method for producing a granule having a bulk density of 0.50 g / cm ３ Super, 0.70g / cm ３ <8> A granule containing an aliphatic polyester, wherein the aliphatic polyester content is 90% by weight or more, and the aliphatic polyester content is 90% by weight or more. <8> The granule according to <7>, wherein the aliphatic polyester is poly(3-hydroxyalkanoate). <9> The granule according to <7> or <8>, wherein the aliphatic polyester is one or more selected from the group consisting of 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 granule according to any one of <7> to <9>, wherein the median diameter is 0.5 mm to 4.0 mm. <11> The granule according to any one of <7> to <10>, wherein the hardness is 5 kgf to 35 kgf. <12> The granule according to any one of <7> to <11>, wherein the moisture content is 5% or less.

[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Measurement Method] (Moisture Content) The moisture contents of the aliphatic polyester powder and granules were measured using a heat-drying moisture meter (product name: MS-70, manufactured by A&D Co., Ltd.).

[0070] [Composition Ratio] The composition ratio of 3HB units to comonomer units in the aliphatic polyester (copolymer) in the aliphatic polyester powder (the above-mentioned (3HB units / comonomer units)) was calculated as follows. 1 ml of a sulfuric acid-methanol mixture (15:85) and 1 ml of chloroform were added to approximately 20 mg of dried cells cultured to produce the aliphatic polyester powder, and the mixture was sealed and heated at 100°C for 140 minutes to obtain a methyl ester of a PHA decomposition product. After cooling, 0.5 ml of deionized water was added to the mixture and mixed well, and then the mixture was allowed to stand until the aqueous and organic layers separated. The monomer unit composition of the PHA decomposition product in the separated organic layer was then analyzed by capillary gas chromatography. A Shimadzu GC-17A gas chromatograph and a GL Sciences NEUTRA BOND-1 capillary column (column length 25 m, column inner diameter 0.25 mm, liquid film thickness 0.4 µm) were used. He was used as the carrier gas, the column inlet pressure was 100 kPa, and 1 μl of sample was injected. The temperature was increased from an initial temperature of 50 to 200°C at a rate of 8°C / min, and then from 200 to 290°C at a rate of 30°C / min.

[0071] (Yellowness Index) The yellowness index (YI) of the aliphatic polyester powder and granules was measured in accordance with JIS K 7373 using a color difference meter (product name: CM-5, manufactured by Konica Minolta, Inc.).

[0072] (Molecular Weight) The weight average molecular weight of the aliphatic polyester in the aliphatic polyester powder and in the granules was determined as the weight average molecular weight in terms of polystyrene by gel permeation chromatography (GPC) (Shodex GPC-101 manufactured by Showa Denko K.K.) using a polystyrene gel (Shodex K-804 manufactured by Showa Denko K.K.) as a column and chloroform as a mobile phase. (Bulk Density) The bulk density of the aliphatic polyester powder and granules was measured using a bulk specific gravity measuring instrument (product name: Standard Type Bulk Specific Gravity Meter, manufactured by Kuratori Scientific Instruments Co., Ltd.) in accordance with JIS K 7365:1999.

[0073] (Hardness) The hardness of the aliphatic polyester granules was measured using a hardness tester (trade name: Kiya hardness tester, manufactured by Fujiwara Seisakusho).

[0074] (Median diameter of aliphatic polyester powder) The median diameter of the aliphatic polyester powder was measured using a laser diffraction / scattering particle size distribution analyzer LA-950 (manufactured by HORIBA). 0.05 g of sodium dodecyl sulfate as a surfactant was added to 20 mL of ion-exchanged water to obtain a surfactant aqueous solution. Next, 0.2 g of the aliphatic polyester powder to be measured was added to the surfactant aqueous solution, 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 analyzer, and measurement was performed.

[0075] (Median diameter of granules) The median diameter of the aliphatic polyester granules was measured using a metal mesh sieve in accordance with JIS Z 8801-1:2000.

[0076] (Thermal Stability) The thermal stability of the aliphatic polyester powder and granules was measured using a small heat press (product name: H300-01, manufactured by AS ONE Corporation). Pressing was performed at 160°C and 13 MPa for 20 minutes, and the rate of change in molecular weight before and after heating was taken as the thermal stability.

[0077] (Fluidity) The fluidity of the aliphatic polyester powder and granules was measured using an extruder, TEM26SS (manufactured by Toshiba Machine Co., Ltd.) A fixed amount of powder or granules was fed into the extruder, the number of screw revolutions until a feed neck occurred was measured, and the throughput per revolution was calculated and compared to evaluate the fluidity.

[0078] [Example 1] (Compression Granulation) A P3HB3HH powder (dry powder) having the 3HH ratio shown in Table 1 was obtained by the method described in Example 1 of WO 2021 / 085534. The obtained powder was fed to a briquette machine (manufactured by Hosokawa Micron Corporation), which is a briquette-type granulator having a vertical screw and two rotating rolls, and compressed to obtain a compressed sheet. The obtained compressed sheet was granulated by crushing with a feather mill (manufactured by Hosokawa Micron Corporation) equipped with a vertical screw and a rotating roll to obtain a granule. The roll rotation speed of the compression granulator was 14 rpm, the compression force was 40 kN, and the roll support pressure was 9 MPa. The production 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 diameter 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.

[0079] Example 2: A P3HB3HH powder (dry powder) having the 3HH (comonomer unit) ratio shown in Table 1 was obtained by the method described in Example 1 of WO 2022 / 091685. The obtained powder was fed to the briquetting machine (manufactured by Hosokawa Micron Corporation) to obtain a compressed sheet. The obtained sheet was crushed using the feather mill (manufactured by Hosokawa Micron Corporation) to obtain granules. The roll rotation speed of the compression granulator was 10 rpm, the compression force was 17 kN, and the roll support pressure was 4.5 MPa. The granules were produced at room temperature (23°C), and the raw material temperature was 22°C. The granules had a moisture content of 0.09%, a molecular weight of 650,000, a bulk density of 0.53, a median diameter of 3.2 mm, a YI of 26, a hardness of 18 kgf, a thermal stability of 77%, and a P3HB3HH content of 99% by weight.

[0080] Example 3: A P3HB3HH powder (dry powder) having the 3HH ratio shown in Table 1 was obtained by the same method as in Example 1, except that the culture method for the fungus was changed to the method described in Example 2 of WO 2019 / 142845. The obtained powder was fed to the briquetting machine (manufactured by Hosokawa Micron Corporation) to obtain a sheet. The obtained sheet was crushed using a feather mill (manufactured by Hosokawa Micron Corporation) equipped with a vertical screw and a rotating roll to obtain granules. The roll rotation speed of the compression granulator was 14 rpm, the compression force was 45 kN, and the roll support pressure was 9 MPa. The production 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 0.20%, a molecular weight of 650,000, a bulk density of 0.53, a median diameter of 3.2 mm, a hardness of 14 kgf, a thermal stability of 55%, and a P3HB3HH content of 99% by weight.

[0081] Example 4: A P3HB3HH powder (dry powder) having the 3HH ratio listed in Table 1 was obtained by the same method as in Example 1, except that the culture method for the fungus was changed to the method described in Example 2 of WO 2019 / 142845. The obtained powder was fed to the briquetting machine (manufactured by Hosokawa Micron Corporation) to obtain a sheet. The obtained sheet was crushed using a Rotoplex (manufactured by Hosokawa Micron Corporation) equipped with fixed and rotating blades to obtain granules. The roll rotation speed of the compression granulator was 10.7 rpm, the compression force was 25 kN, and the roll support pressure was 4.5 MPa. The production 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 diameter 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.

[0082] Example 5 A dispersion slurry was obtained using the same method as in Example 1 (Washing 2) of WO 2022 / 091685. This was dehydrated using a filter cloth and dried using a plate dryer (Andritz) to obtain a P3HB3HH powder (dry powder) having the 3HH ratio listed in Table 1. The obtained powder was fed to the briquetting machine (Hosokawa Micron Corporation) to obtain a sheet. The obtained sheet was crushed using a Rotoplex (Hosokawa Micron Corporation) equipped with a fixed blade and a rotating blade to obtain granules. The roll rotation speed of the compression granulator was 11.5 rpm, the compression force was 36 kN, and the roll support pressure was 9 MPa. The production 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 diameter 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.

[0083] Example 6 A dispersion slurry was obtained using the same method as in Example 1 (Washing 2) of WO 2022 / 091685. This was dehydrated using a filter cloth and dried using a plate dryer (Andritz) to obtain a P3HB3HH powder (dry powder) having the 3HH ratio listed in Table 1. The obtained powder was fed to the briquetting machine (Hosokawa Micron Corporation) to obtain a sheet. The obtained sheet was crushed using a Rotoplex (Hosokawa Micron Corporation) equipped with fixed and rotating blades to obtain granules. The roll rotation speed of the compression granulator was 14.4 rpm, the compression force was 13 kN, and the roll support pressure was 4.1 MPa. The production of 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 diameter 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.

[0084] Comparative Example 1 The powder (dry powder) of Example 1 was used as Comparative Example 1. The powder of Comparative Example 1 contained 3HH as a comonomer, and had a moisture content of 0.21%, a (3HB unit / 3HH unit) ratio of 94.8 / 5.2 (mol% / mol%), a weight-average molecular weight of 420,000, a bulk density of 0.42, a median diameter of 163 μm, a YI of 14, and a thermal stability of 84%.

[0085] Comparative Example 2 The powder (dry powder) of Example 2 was used as Comparative Example 2. The powder of Comparative Example 2 contained 3HH as a comonomer, and had a moisture content of 0.09%, a (3HB unit / 3HH unit) ratio of 82 / 18 (mol% / mol%), a weight-average molecular weight of 650,000, a bulk density of 0.44, a median diameter of 163 μm, a YI of 26, and a thermal stability of 77%.

[0086] [Comparative Example 3] The powder (dry powder) of Example 3 was designated Comparative Example 3. The powder of Comparative Example 3 contained 3HH as a comonomer, had a moisture content of 0.20%, a (3HB unit / 3HH unit) ratio of 96.3 / 3.7 (mol% / mol%), a weight average molecular weight of 330,000, a bulk density of 0.36, a median diameter of 113 μm, and a thermal stability of 55%. [Comparative Example 4] The powder (dry powder) of Example 4 was designated Comparative Example 4. The powder of Comparative Example 4 contained 3HH as a comonomer, had a moisture content of 0.09%, a (3HB unit / 3HH unit) ratio of 82 / 18 (mol% / mol%), a weight average molecular weight of 650,000, a bulk density of 0.44, a median diameter of 163 μm, a YI of 26, and a thermal stability of 77%. [Comparative Example 5] The powder (dry powder) of Example 5 was designated Comparative Example 5. The powder of Comparative Example 5 contained 3HH as a comonomer, had a moisture content of 0.17%, a (3HB unit / 3HH unit) ratio of 94.9 / 5.1 (mol% / mol%), a weight average molecular weight of 450,000, a bulk density of 0.32, a median diameter of 2.9 μm, a YI of 14, and a thermal stability of 83%. [Comparative Example 6] The powder (dry 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%, a (3HB unit / 3HH unit) ratio of 87.5 / 12.5 (mol% / mol%), a weight average molecular weight of 700,000, a bulk density of 0.35, a median diameter of 26.1 μm, a YI of 23, and a thermal stability of 83%.

[0087] 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 soft enough to be crushed by hand, so their hardness was not measured.

[0088]

[0089] The results of the fluidity tests for Examples 1 and 3 and Comparative Examples 1 and 3 are shown in Table 2. In Table 2, "FN" means feed neck.

[0090]

[0091] [Results] From Table 1, the bulk density of the granules of Examples 1 to 6 was 0.50 g / cm ３ The bulk density exceeded 100%, and was higher than that of the powders of Comparative Examples 1 to 6. Furthermore, Table 2 shows that the granules of Examples 1 and 3 have excellent fluidity because the screw rotation speed at which FN occurs is lower and the throughput is improved compared to the powders of Comparative Examples 1 and 3. Furthermore, there were no significant changes in thermal stability and YI between the Examples and Comparative Examples. Therefore, it was demonstrated that the granules of the present invention produced by compression granulation are no different in quality from the dried powder produced by spray drying. From the above, it was demonstrated that the production method according to one embodiment of the present invention can produce granules containing an aliphatic polyester having high bulk density and high fluidity.

[0092] The granules obtained by the production method of the present invention can be suitably used in the fields of agriculture, fisheries, forestry, horticulture, medicine, hygiene products, clothing, non-clothing, packaging, automobiles, building materials, and other fields.

Claims

1. Bulk density is 0.30 g / cm ３ ~0.50g / cm ３ The present invention relates to a method for producing a granule comprising an aliphatic polyester, the method comprising the step of compressing and granulating a powder comprising an aliphatic polyester, the powder comprising the aliphatic polyester being

2. The method for producing granules according to claim 1 , wherein the compression granulation step is carried out at 50° C. or lower.

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

4. The method for producing granules according to claim 1, wherein the compression granulation step is performed with a compression pressure of 10 kN to 60 kN.

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

6. The method for producing a granule according to claim 5, wherein the aliphatic polyester is one or more selected from the group consisting of 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. Bulk density is 0.50 g / cm ３ Super, 0.70g / cm ３ The granules containing an aliphatic polyester have a diameter of 0.5 mm to 4.0 mm and a content of the aliphatic polyester of 90% by weight or more.

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

9. The aliphatic polyester is one or more selected from the group consisting of 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). The granule according to claim 8.

10. The granule according to any one of claims 7 to 9, having a hardness of 5 kgf to 35 kgf.

11. The granule according to any one of claims 7 to 9, having a moisture content of 5% or less.