Producing method for granules, and granules

Abstract

To provide a producing method for granules of aliphatic polyester resin that can reduce melting within a transport line.SOLUTION: A producing method for granules containing an aliphatic polyester resin comprises a granulation step of extrusion-granulating a powder containing an aliphatic polyester resin using a rotary porous die granulator.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing granulated bodies and to granulated bodies.

Background Art

[0002] Since biodegradable resins such as polyhydroxyalkanoic acid (PHA) have biodegradability, their use in various applications has been progressing. For example, Patent Document 1 describes a production method for granulating a poly-3-hydroxybutyrate-based polymer having a crystallization temperature of 120°C or higher and 170°C or lower into pellets.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Granulated bodies of the aliphatic polyester-based resin described in Patent Document 1 as described above may be transported to a feeder for a compounding process by a transportation method such as air transportation after production. The inventors have found that, during such transportation, the transportation line becomes blocked due to foreign matter generated by the melting of the granulated bodies in the pipe, and as a result, the air transportation of the granulated bodies is delayed. As a result of intensive studies by the inventors, it has been found that this foreign matter is generated by melting with the energy when the granulated bodies of the aliphatic polyester-based resin collide with the transportation pipe.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing granulated bodies of an aliphatic polyester-based resin capable of reducing melting in a transportation line and granulated bodies.

Means for Solving the Problems

[0006] The inventors of the present invention have conducted intensive studies to solve the above problems. As a result, they have found that the above problems can be solved by including a step of extrusion granulation of a powder containing an aliphatic polyester using a rotary porous die granulator, and have thus completed the present invention.

[0007] That is, the method for producing a granule and the granule according to an embodiment of the present invention include the following configurations. <1>A method for producing a granule containing an aliphatic polyester resin, the method including a granulation step of extrusion granulating a powder containing an aliphatic polyester resin using a rotary porous die granulator. <2>The granulation step according to <1>, wherein the extrusion granulation temperature when extruding the powder is 30°C to 90°C lower than the melting point of the aliphatic polyester resin. <3>The method for producing a granule according to <1> or <2>, wherein the bulk density of the granule when the bulk density of the powder is 100% is 70 to 95%. <4>The method for producing a granule according to any one of <1> to <3>, wherein the aliphatic polyester resin is a poly(3-hydroxyalkanoate) resin. <5>A granule containing an aliphatic polyester resin, the granule being granular and having a bulk density of 0.30 g / cm 3 ~0.40 g / cm 3 . <6>The granule according to <5>, wherein the major axis diameter is 1 mm to 10 mm. <7>The granule according to <5> or <6>, wherein the granule is placed between two flat plates heated to 160°C and contacted with the two flat plates for 30 seconds, and 50% or more remains without melting. <8>The granule according to any one of <5> to <7>, wherein the aliphatic polyester resin is a poly(3-hydroxyalkanoate) resin.

Advantages of the Invention

[0008] According to one aspect of the present invention, it is possible to provide a method for producing aliphatic polyester resin granules, which can reduce melting in a transportation line, and the granules. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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.

[0010] [1] Overview of the present invention The granules of the aliphatic polyester resin described in Patent Document 1 may be transported to a feeder for a compounding process by a transport method such as pneumatic transport after production. The present inventors have found that during such transport, the granules melt in the piping, causing foreign matter to be generated and causing blockage of the transport line, resulting in a problem of delay in pneumatic transport of the granules.

[0011] Therefore, the inventors conducted extensive research to solve the above problems, and discovered that an aliphatic polyester-based resin that can reduce melting in a transportation line can be obtained by extrusion granulating a powder containing an aliphatic polyester, preferably by extrusion granulating using a rotary multi-hole die granulator, to produce granules having a low bulk density.

[0012] Granules with low bulk density, especially those with a bulk density of 0.30 to 0.40 g / cm 3 The granules in the above formula (1) contain a certain amount of air in addition to the aliphatic polyester resin. The present inventors presume that the reason why a granule having a predetermined bulk density can reduce melting in a transportation line (has excellent melting property) is that the granules contain a certain amount of air as described above, which generates voids within the granules, and the presence of the voids suppresses heat transfer within the granules, and the voids make the granules light, thereby reducing the collision energy with piping during the transportation process.

[0013] In particular, the technical idea of extruding and granulating a powder containing an aliphatic polyester to obtain a granulated product with a bulk density lower than that of the powder is unprecedented, and the present invention is extremely excellent. The granulated product obtained by the manufacturing method according to an embodiment of the present invention (hereinafter sometimes referred to as "the present manufacturing method") can reduce melting in the transport line, and thus can be advantageously used as a granulated product containing an aliphatic polyester. Further, according to the configuration as described above, plastic products can be efficiently manufactured, thereby contributing to the achievement of sustainable development goals (SDGs) such as, for example, Goal 12 "Ensure sustainable consumption and production patterns" and Goal 14 "Conserve and use the oceans and marine resources for sustainable development in a sustainable manner". Hereinafter, the configuration of the present manufacturing method will be described in detail.

[0014] 〔2〕Manufacturing method of granulated product containing aliphatic polyester resin In one embodiment of the present invention, there is provided a manufacturing method of a granulated product containing an aliphatic polyester resin, including a granulation step of extruding and granulating a powder containing an aliphatic polyester resin using a rotary porous die granulator. In the following description, the "powder containing an aliphatic polyester resin" may sometimes be referred to as "powder".

[0015] 〔2-1〕Aliphatic polyester resin Examples of the aliphatic polyester resin used in the present manufacturing method include poly(hydroxyalkanoate) resins. Examples of the poly(hydroxyalkanoate) resins include poly(3-hydroxyalkanoate) resins, poly(4-hydroxyalkanoate) resins, and polyglycolic acid. Further, the aliphatic polyester resin may be other aliphatic polyester resins other than poly(hydroxyalkanoate) resins. PHA may be used alone or in combination of two or more.

[0016] 〔Poly(hydroxyalkanoate) resin〕 Poly(hydroxyalkanoate) resins (hereinafter also referred to as "PHA") are a general term for polymers containing hydroxyalkanoic acids as monomer units (monomer repeating units), and generally have biodegradability. PHA is an aliphatic polyester resin, preferably a polyester containing no aromatic ring. In this specification, "PHA" is intended to mean a resin containing 50 mol% or more of repeating units of hydroxyalkanoic acid among all monomer repeating units (100 mol%).

[0017] PHA preferably contains poly(3-hydroxyalkanoate) resins, and more preferably is a poly(3-hydroxyalkanoate) resin (hereinafter also referred to as "P3HA"). P3HA has the formula: [-CHR-CH 2 -CO-O-] represents a 3-hydroxyalkanoic acid repeating unit (wherein R is C n H 2n+1 is an alkyl group represented by, and n is an integer of 1 or more and 15 or less).) is a polyhydroxyalkanoate containing an essential repeating unit. In this specification, "P3HA" is intended to mean a resin containing 50 mol% or more of 3-hydroxyalkanoic acid repeating units among all monomer repeating units (100 mol%). The P3HA preferably contains 60 mol% or more of the 3-hydroxyalkanoic acid repeating units among all monomer repeating units (100 mol%), and more preferably 70 mol% or more.

[0018] P3HA is preferably a copolymer having 3-hydroxybutyric acid (hereinafter sometimes also referred to as "3HB") repeating units and other hydroxyalkanoic acid repeating units, and the ratio of 3HB repeating units to other hydroxyalkanoic acid repeating 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%).

[0019] By changing the composition ratio of the repeating unit, the melting point and the degree of crystallinity can be changed, and as a result, physical properties such as Young's modulus and heat resistance can be changed, and it is possible to impart physical properties between polypropylene and polyethylene.

[0020] Examples of P3HA include copolymers of 3-hydroxybutyric acid and monomers other than 3-hydroxybutyric acid. Examples of monomers other than 3-hydroxybutyric acid include one or more monomers selected from the group consisting of 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxyundecanoic acid, 3-hydroxydodecanoic acid, 3-hydroxytridecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxyhexadecanoic acid, and 3-hydroxyoctadecanoic acid. Alternatively, as another example of the copolymer, examples of monomers other than 3HB include one or more monomers selected from the group consisting of 4-hydroxybutyric acid, 4-hydroxypentanoic acid, 4-hydroxyhexanoic acid, 4-hydroxyheptanoic acid, 4-hydroxyoctanoic acid, 4-hydroxynonanoic acid, 4-hydroxydecanoic acid, 4-hydroxyundecanoic acid, 4-hydroxydodecanoic acid, 4-hydroxytridecanoic acid, 4-hydroxytetradecanoic acid, 4-hydroxyhexadecanoic acid, and 4-hydroxyoctadecanoic acid.

[0021] More specifically, examples of P3HA include poly(3-hydroxybutyrate) (abbreviation: P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH), and the like. Among them, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially. In this specification, "poly(X-co-Y)" means a copolymer containing X repeating units and Y repeating units, and is intended to be a copolymer formed by copolymerizing a monomer derived from the X repeating unit and a monomer derived from the Y repeating unit.

[0022] 〔Method for Producing P3HA〕 P3HA can be produced by microorganisms. Such microbially produced P3HA is usually P3HA composed only of D-form (R-form) 3-hydroxyalkanoic acid repeating units. During the production of P3HA, a trace amount (about 1 mol% or less) of an unintended monomer may be copolymerized by the microorganism. However, if it does not significantly affect the physical properties of the obtained P3HA, that monomer is regarded as not being copolymerized, and it will be called by a name that does not include that monomer.

[0023] 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 by microorganisms. Among them, a production method by microorganisms is preferred. Regarding the method for producing P3HA powder by microorganisms, known methods can be applied, but it preferably includes a culture step, a purification step, and a drying step.

[0024] The method for culturing microorganisms that produce P3HA in the culture step is not particularly limited, and for example, the method described in International Publication No. 2019 / 142717 can be used.

[0025] The microorganisms that produce P3HA are not particularly limited as long as they are microorganisms capable of producing PHA intracellularly. For example, microorganisms isolated from nature and microorganisms deposited in depository institutions of strains (e.g., IFO, ATCC, etc.), or mutants and transformants that can be prepared from them can be used. For example, as the bacterial cells that produce P3HB, which is an example of PHA, Bacillus megaterium discovered in 1925 was the first, and other natural microorganisms such as Cupriavidus necator (formerly classified: Alcaligenes eutrophus, Ralstonia eutropha), Alcaligenes latus, etc. can be mentioned. It is known that PHA accumulates in the bacterial cells in these microorganisms.

[0026] In addition, examples of the bacterial cells that produce a copolymer of hydroxybutyrate and other hydroxyalkanoates, which is an example of PHA, include Aeromonas caviae, which is a P3HB3HV and P3HB3HH-producing bacterium, and Alcaligenes eutrophus, which is a P3HB4HB-producing bacterium. In particular, regarding P3HB3HH, in order to increase the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (Alcaligenes eutrophus AC32, FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, p4821-4830 (1997)) into which genes of a PHA synthase group have been introduced, etc. are more preferable. In addition to the above, the bacterial cells may also be genetically modified microorganisms into which various PHA synthesis-related genes have been introduced according to the PHA to be produced.

[0027] The method for purifying P3HA obtained by microbial culture in the purification step is not particularly limited, and known physical treatment, and / or chemical treatment, and / or biological treatment can be applied. For example, the purification method described in International Publication No. 2010 / 067543 can be preferably applied.

[0028] 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, pneumatic drying, rotary drying, vibration drying, band drying, etc. can be applied. For example, the drying method described in International Publication 2018 / 070492 can be preferably applied.

[0029] As a spray drying method, for example, there is a method in which an aqueous suspension containing P3HA (hereinafter referred to as "P3HA aqueous suspension") is supplied into a dryer in the state of fine droplets and dried while being brought into contact with hot air in the dryer. The method of supplying the P3HA aqueous suspension into the dryer in the state of fine droplets (atomizer) is not particularly limited, and known methods such as a method using a rotating disk and a method using a nozzle can be mentioned. The contact method between the droplets and the hot air in the dryer is not particularly limited, and examples include a co-current type, a counter-current type, and a method using a combination of these.

[0030] The drying temperature during the spray drying may be a temperature at which most of the aqueous medium can be removed from the droplets of the P3HA aqueous suspension, and it can be dried to the target moisture content, and can be appropriately set under conditions that do not cause quality deterioration (molecular weight decrease, color tone decrease) and melting as much as possible. Also, the air volume of the hot air in the dryer can be appropriately set according to, for example, the size of the dryer.

[0031] The method for producing P3HA powder may include a step of further drying the obtained P3HA after the spray drying. Also, the method for producing P3HA may include other steps (for example, a step of adding various additives to the P3HA aqueous suspension).

[0032] [Polyglycolic acid] PHA may be polyglycolic acid. Polyglycolic acid is intended to be a resin containing 50 mol% or more of repeating units represented by [-CH 2 -CO-O-] among all monomer repeating units (100 mol%). Polyglycolic acid may contain 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more of the repeating units represented by [-CH 2 -CO-O-] among all monomer repeating units (100 mol%).

[0033] Polyglycolic acid may be a homopolymer of glycolic acid or a copolymer of glycolic acid and a monomer other than glycolic acid (for example, a copolymer of glycolic acid and lactic acid, a copolymer of glycolic acid and caprolactone, etc.).

[0034] Polyglycolic acid can be obtained by known methods such as condensation polymerization of glycolic acid and ring-opening polymerization of glycolide. Also, the powder of polyglycolic acid can be obtained by known methods.

[0035] [Weight-average molecular weight of PHA] The weight-average molecular weight of PHA is not particularly limited. The weight-average molecular weight of PHA is preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000, and even more preferably 150,000 to 1,500,000. When the weight-average molecular weight of PHA is 50,000 or more, it has the advantage that the tendency of the PHA powder to be sticky due to low-molecular-weight components can be reduced or avoided, and thereby the melting during transportation of the granulated body produced from the powder can be reduced. On the other hand, PHA having a weight-average molecular weight of 3,000,000 or less may have the advantage that the production of PHA is easy and / or the advantage that it is easy to handle PHA to achieve the object of one embodiment of the present invention.

[0036] The measurement of the weight-average molecular weight can be carried out using gel permeation chromatography (GPC) ("High Performance Liquid Chromatograph 20A System" manufactured by Shimadzu Corporation), using polystyrene gel (such as "K-G 4A", "K-806M" manufactured by Showa Denko KK) for the column, and chloroform as the mobile phase. The weight-average molecular weight can be determined as the molecular weight in terms of polystyrene using a calibration curve obtained by measuring polystyrene with a known molecular weight by the same measurement method. As the column in the GPC, a column suitable for measuring the molecular weight may be used.

[0037] [Other aliphatic polyester resins] Examples of the aliphatic polyester resin other than PHA used in this manufacturing method include (i) polycaprolactone (PCL), (ii) polylactic acid (PLA), and (iii) aliphatic polyesters having a structure formed by polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid. Specific examples of the aliphatic polyester having a structure formed by polycondensation of the aliphatic diol and the aliphatic dicarboxylic acid include polyethylene succinate, polybutylene succinate (hereinafter, may also be referred to as "PBS"), polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene succinate adipate (hereinafter, may also be referred to as "PBSA"), polyethylene sebacate, polybutylene sebacate, and the like. Examples of the aliphatic aromatic polyester include aliphatic aromatic polyesters obtained by using both an aliphatic compound and an aromatic compound as monomers and copolymerizing these monomers (using both an aliphatic compound and an aromatic compound as monomers). Examples of the aliphatic aromatic polyester include polybutylene adipate terephthalate (hereinafter, may also be referred to as "PBAT"), polybutylene sebacate terephthalate (hereinafter, may also be referred to as "PBSeT"), polybutylene azelate terephthalate (hereinafter, may also be referred to as "PBAzT"), polybutylene succinate terephthalate (hereinafter, may also be referred to as "PBST"), polybutylene succinate adipate terephthalate (hereinafter, may also be referred to as "PBSAT"), and the like. These resins other than PHA may be used alone or in combination of two or more.

[0038] Aliphatic polyester resins other than PHA can also be obtained by known methods, and their powders can also be obtained by known methods.

[0039] 〔Melting Point of Aliphatic Polyester Resin〕 The melting point of the aliphatic polyester resin is preferably 50 to 200 °C, more preferably 60 to 180 °C, still more preferably 70 to 170 °C, and particularly preferably 80 to 165 °C. If the melting point of the aliphatic polyester is within the range of 50 to 200 °C, the powder can be fused without excessive heating during extrusion granulation, and granules with low meltability can be produced. The melting point of the aliphatic polyester resin depends on the aliphatic polyester resin and can show the same melting point regardless of whether it is measured for the powder or the granules.

[0040] The melting point of the aliphatic polyester resin is preferably measured by a measurement method conforming to JIS K7122:1987. For details of the melting point measurement, refer to the description in the examples.

[0041] 〔2-2〕Powder containing aliphatic polyester The powder containing the aliphatic polyester used in this production method has a bulk density of 0.30 g / cm 3 ~0.50 g / cm 3 which is preferable. The bulk density of the powder is preferably 0.32 g / cm 3 ~0.48 g / cm 3 and more preferably 0.34 g / cm 3 ~0.46 g / cm 3 and still more preferably 0.36 g / cm 3 ~0.44 g / cm 3 In this production method, by setting the bulk density within the range of 0.30 g / cm 3 ~0.50 g / cm 3 granules with a low bulk density can be suitably produced.

[0042] The median diameter of the powder containing the aliphatic polyester is preferably 60 to 200 μm, more preferably 80 to 180 μm, and still more preferably 100 to 170 μm.

[0043] The median diameter in the powder of the aliphatic polyester resin may be measured using a laser diffraction / scattering particle size distribution analyzer LA-950 (manufactured by HORIBA, Ltd.). As a sample for measuring the particle size distribution, 0.05 g of sodium dodecyl sulfate as a surfactant may be added to 20 mL of ion-exchanged water to prepare an aqueous surfactant solution, and 0.2 g of the dry powder of the aliphatic polyester resin to be measured may be dispersed in the aqueous surfactant solution to obtain a sample for measuring the particle size distribution. The prepared dispersion may be introduced into the above laser diffraction / scattering particle size distribution analyzer for measurement. In this specification, the median diameter (D50) on a volume basis is measured for the laser diffraction / scattering particle size distribution.

[0044] The powder containing the aliphatic polyester resin to be used in this production method preferably contains 90% by weight or more of the aliphatic polyester resin, more preferably 95% by weight or more, still more preferably 97% by weight or more, and most preferably 99% by weight or more. The upper limit of the content of the aliphatic polyester in the powder is not particularly limited, and may be, for example, 100% by weight or less than 100% by weight.

[0045] One of the advantages of this production method is that a granulated body can be produced by extrusion granulating a powder of an aliphatic polyester resin not containing a plasticizer. However, within a range where the effects of the present invention are not impaired, the powder containing the aliphatic polyester resin may contain a plasticizer. The plasticizer may sometimes act as a binder that promotes the formation of the granulated body by binding the particles in the powder of the aliphatic polyester resin. However, if it is contained in excess, the biodegradability of the obtained granulated body tends to decrease.

[0046] Examples of the plasticizer include polyester plasticizers such as polypropylene glycol sebacate; aliphatic dibasic acid ester plasticizers such as di-1-butyl adipate, di-n-butyl sebacate, and di-2-ethylhexyl azelate; glycerin plasticizers such as glycerin diacetomonolaurate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate; polyvalent carboxylic acid ester plasticizers such as tri-2-ethylhexyl acetylcitrate and tributyl acetylcitrate; polyalkylene glycol plasticizers such as polyethylene glycol, polypropylene glycol, poly(ethylene oxide·propylene oxide) block and / or random copolymer, and polytetramethylene glycol; phosphate ester plasticizers such as diphenyl-2-ethylhexyl phosphate and diphenyloctyl phosphate; epoxy plasticizers such as epoxidized soybean oil and butyl ester of epoxidized linseed oil fatty acid; castor oil-based plasticizers such as castor oil fatty acid ester, methyl ricinoleate, ethyl ricinoleate, isopropyl ricinoleate, butyl ricinoleate, ethylene glycol monoricinate, propylene glycol monoricinate, trimethylolpropane monoricinate, sorbitan monoricinate, polyethylene glycol ester of castor oil fatty acid, ethylene oxide adduct of castor oil, castor oil-based polyol, castor oil-based toluol, or castor oil-based diol. These plasticizers may be used alone or in combination of two or more.

[0047] Assuming the powder of the aliphatic polyester resin is 100% by weight, the content of the plasticizer may be, for example, 1% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.01% by weight or less. The lower the content of the binder in the powder of the aliphatic polyester resin, the higher the biodegradability of the granulated product can be obtained, for example.

[0048] Another advantage of this manufacturing method is that granules can be produced by extrusion granulation of a powder of an aliphatic polyester resin that does not contain water. However, within the range where the effects of the present invention are not impaired, the powder containing the aliphatic polyester resin may contain water. Water can promote the formation of granules by binding the particles in the powder of the aliphatic polyester resin. At this time, water acts as a binder for the powder of the aliphatic polyester resin.

[0049] The water content of the powder is preferably 5% or less, more preferably 1% or less, still more preferably 0.5% or less, and particularly preferably 0.3% or less. The lower the water content, the better, and for example, it may be 0%. The water content can be measured using, for example, a heated drying type moisture meter (trade name: MS-70, manufactured by A&D).

[0050] [2-3] Granulation step This manufacturing method includes a granulation step of extrusion granulating the powder containing the above-described aliphatic polyester resin using a rotary porous die granulator. By extrusion granulating the powder using a rotary porous die granulator, it is possible to make the bulk density low and make it difficult to melt the granules containing the aliphatic polyester resin.

[0051] A rotary porous die granulator is a method in which flakes of raw material powder obtained by passing the raw material powder between a cylindrical porous die and a roll disposed inside the porous die and compression molding are extruded onto the outer surface of the cylindrical porous die, and the extruded flakes of the raw material powder are cut into granules by a blade such as a knife. The flakes extruded onto the outer surface of the porous die can be cut by a knife rotating along the outer surface of the porous die.

[0052] Examples of the rotary porous die granulator include Pallman PFV (manufactured by Pallman), CPM pellet mill (manufactured by CPM), MIIKE SPM (manufactured by MIIKE), and the like.

[0053] In the granulation process, the granulation process using a rotary porous die granulator may be designed such that the bulk density of the granulated body is 70 to 95% when the bulk density of the raw material powder is 100%.

[0054] In the granulation process, the temperature for extrusion granulation of the powder containing the aliphatic polyester resin may be set according to the melting point of the aliphatic polyester resin. The extrusion granulation temperature is preferably 30°C to 90°C lower than the melting point of the aliphatic polyester resin, more preferably 35°C to 80°C lower, and even more preferably 35 to 70°C lower. By setting the extrusion granulation temperature in the granulation process to be 30°C to 90°C lower than the melting point of the aliphatic polyester resin, the aliphatic polyester resin can be granulated in a partially molten state. As a result, it is possible to produce a granulated body with a low bulk density without excessively fusing the powder containing the aliphatic polyester resin.

[0055] The resin temperature in the granulation process can be the temperature of the powder containing the aliphatic polyester resin heated by the frictional heat generated by the friction between the rotary porous die granulator and the powder containing the aliphatic polyester resin in the rotary porous die granulator. The resin temperature in the granulation process is the temperature of the raw material powder before extruding the granulated body from the cylindrical porous die, and is also referred to as the extrusion granulation temperature.

[0056] In the granulation process, the roll disposed inside the porous die may be, for example, a rotary blade. By designing the rotational power thereof within the range of 28 kW to 52 kW, the raw material will not be completely melted during production, enabling stable production, and the effect of making the produced granulated body difficult to collapse can be obtained. Also, granulated bodies can be stably produced under the condition of a granulated body discharge rate of 100 kg / hour to 490 kg / hour.

[0057] That is, the extrusion granulation temperature can also be adjusted by adjusting the rotational power of the roll (or rotating blade). When controlling the extrusion granulation temperature with the rotational power of the roll (or rotating blade), the rotational power may be designed according to, for example, the outer surface area of the rotating perforated die (outer diameter × length of the cylindrical die), the number of die holes, the die hole diameter, etc. Thereby, the specific energy, that is, the power of the equipment applied per unit amount of the powder containing the aliphatic polyester resin can be designed, and the granulation process may be carried out so that the bulk density of the granulated product and the bulk density of the powder containing the aliphatic polyester resin are 70 to 95%.

[0058] In addition, the rotating perforated die type granulator does not necessarily need to be equipped with a heating part such as a heater as long as the extrusion granulation temperature can be adjusted within a predetermined range, and it may or may not be equipped with the heating part, and the extrusion granulation temperature may be adjusted by the heating part.

[0059] The major axis diameter of the granulated product produced in the granulation process can be designed by adjusting the rotational speed of the knife rotating along the outer surface of the perforated die in consideration of the specifications of the perforated die (number of holes, hole diameter), the rotational speed of the rotating blade, and the discharge amount of the granulated product produced from the raw material powder.

[0060] The method of supplying the powder as the raw material to the granulation device is not particularly limited. For example, the powder may be stored in a hopper and directly supplied to the granulation device from the conveying conveyor attached to the hopper, or it can be supplied to the extrusion granulation device via a belt conveyor, a bucket conveyor, etc. from the hopper conveying conveyor.

[0061] This manufacturing method may further include a step of sizing and classifying the obtained granulated product as needed. The sizing step using a sizing machine and the classification step using a classifier can be carried out by known methods.

[0062] There is no limitation on the transportation method of the powder and the granulated product in each step, but it is possible to use natural fall, conveyor transportation, pneumatic transportation, etc. For example, a method of transporting the raw material to the granulator by conveyor transportation and then transporting it to the crusher, sizing machine, and classifier by natural fall is preferable.

[0063] 〔3〕Granules containing an aliphatic polyester resin These granules are granules obtained by granulating a powder of an aliphatic polyester resin using a rotary porous die granulator, and have a bulk density of 0.30 g / cm 3 or more and 0.40 g / cm 3 or less. The bulk density of these granules is 0.30 g / cm 3 or more and 0.40 g / cm 3 or less, and preferably has a bulk density of 0.32 g / cm 3 or more and 0.39 g / cm 3 or less, more preferably 0.34 g / cm 3 or more and 0.38 g / cm 3 or less.

[0064] The particle shape of these granules is not particularly limited, but is preferably granular. In this specification, "granular particles" refers to particles formed by shaping a powder (powder-like powder) into relatively large particles (for example, having a major axis diameter of about 1 mm to 10 mm). Granular particles have a large number of voids between the powder particles constituting the granular particles and contain a relatively large amount of air (in other words, have a relatively low bulk density).

[0065] The melting point of the aliphatic polyester resin contained in these granules is preferably 50 to 200 °C, more preferably 60 to 180 °C, still more preferably 70 to 170 °C, and particularly preferably 80 to 165 °C.

[0066] The content of the aliphatic polyester resin in these granules is 90% by weight or more, preferably 95% by weight or more, more preferably 97% by weight or more, and still more preferably 99% by weight or more. If the content of the aliphatic polyester in these granules is within the above range, the processability is excellent. The upper limit of the content of the aliphatic polyester in these granules is not particularly limited, and may be, for example, 100%.

[0067] The major axis diameter of the present granule is preferably 1 mm to 10 mm, more preferably 2.0 mm to 8.5 mm, still more preferably 3.0 mm to 7.5 mm, and particularly preferably 4.0 mm to 6.5 mm. If the major axis diameter of the present granule is 1 mm or more and 10 mm or less, it has the effect of being easily transported by the transport equipment for supplying the present granule to the compounding process.

[0068] The hardness of the present granule is preferably 5 kgf to 35 kgf, more preferably 7 kgf to 30 kgf, and still more preferably 10 kgf to 25 kgf. If the hardness of the present granule is 5 kgf or more, there is an advantage that breakage during transportation can be suppressed. Further, if it is 35 kgf or less, it becomes easy to crush with a screw or the like, and thus the processability is excellent. The hardness of the granule can be measured using a hardness tester (trade name: Kiyaki-type hardness tester, manufactured by Fujiwara Seisakusho).

[0069] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in 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.

Examples

[0070] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0071] 〔1〕Measurement method 〔1-1〕Measurement of the bulk density of the raw material powder (powder containing an aliphatic polyester) The bulk density of the raw material powder was measured using a bulk specific gravity measuring device (trade name: Standard Type Bulk Specific Gravity Measuring Device, manufactured by Kuratsuken Kagaku Kikai Co., Ltd.) based on JIS K 7365:1999. The outline of the bulk specific gravity measuring device is as follows. Metal cylinder (receiver): Internal volume: 100 ml ± 0.5 mL Inner diameter of the metal cylinder: 45 mm ± 5 mm Funnel (with lower damper): Outlet diameter: 20 mm to 30 mm In the measurement of the bulk density of the raw material powder, first, 110 ml to 120 ml of the raw material powder, which was confirmed to have no aggregates in advance, was put into a funnel. Next, the lower damper of the funnel was quickly pulled out, and the raw material powder was allowed to flow down into the receiver. After the receiver was overflowed with the raw material powder, the raw material powder that had risen in the receiver was scraped off with a straight plate. Then, the mass of the contents of the receiver was measured with an electronic balance with a minimum scale of 0.1 g. The bulk density was measured twice for each raw material, and the arithmetic mean value of the two measurement results was adopted as the bulk density (g / cm 3 ).

[0072] [1-2] Measurement of the bulk density of the granule sample The bulk density of the granule sample was measured using a 1 L graduated cylinder. First, the weight of the 1 L graduated cylinder was measured with an electronic balance installed horizontally, and by setting the electronic balance to 0 g, the weight of the graduated cylinder was subtracted. Next, the granule sample was put into the graduated cylinder up to the 1 L weighing line with a dedicated funnel and left standing on the electronic balance from which the weight of the graduated cylinder had been subtracted earlier. Thereby, the weight of the granule sample was measured. From the measured weight and volume of the granule sample, the bulk specific gravity (g / cm 3 ) of the granule sample was calculated.

[0073] [1-3] Measurement of the bulk density ratio The bulk density ratio of the granule sample was calculated from the following formula. Bulk density ratio = D 1 / D × 100 D: Bulk density ratio of the raw material powder D 1 : Bulk density ratio of the granule sample

[0074] [1-4] Melting point measurement The melting point of the aliphatic polyester resin granule was measured by a measurement method conforming to JIS K7122:1987. The melting point measurement was obtained from the DSC curve measured under the following conditions using a differential scanning calorimeter DSC6200 manufactured by Seiko Instruments Inc. Sample (dry powder) amount: 4 to 10 mg Temperature measurement range: 30°C to 200°C Rate of temperature increase · Rate of temperature decrease: 10 °C / min In the obtained DSC curve, the temperature at the point where the endothermic quantity was maximum at one melting peak was defined as the melting point of the aliphatic polyester resin.

[0075] 〔1-5〕Evaluation of major axis diameter The major axis diameters of the granulated bodies were measured according to the following procedure. First, five particles were randomly sampled from the granulated bodies, and then the length of the longest side in each granulated body sample was measured as the major axis diameter of each particle. Thereafter, the major axis diameters measured for the five particles were arithmetically averaged, and the calculated average value was defined as the major axis diameter of the granulated body.

[0076] 〔1-6〕Evaluation of meltability Using a heat press machine (Model: AP190 manufactured by RBAYSALE), the meltability of the granulated bodies was evaluated according to the following procedure. First, an approximately 0.1 g granulated body sample was set on an aluminum sheet, and then another aluminum sheet was placed on top, sandwiching the granulated body sample between two aluminum sheets in total. Next, the aluminum sheet sandwiching the granulated body sample was set between the upper and lower press plates of the heat press machine pre-set to 160 °C, the upper press plate (flat plate; weight 400 g, 133 mm × 60 mm) of the press machine was lowered, and when the upper press plate contacted the set aluminum sheet, the lowering of the upper press plate was stopped and the upper press plate was fixed. Thereby, while the granulated body sample was brought into contact with the two press plates through the aluminum sheet, the aluminum sheet was heated without applying the load of the upper press plate to the granulated body sample. When a predetermined evaluation time had elapsed, the heating by the press machine was terminated, the granulated body sample together with the aluminum sheet was taken out, and the melting state of the granulated body sample was confirmed by visually observing the shape change of the granulated body sample. Note that the evaluation times for the meltability of the granulated bodies were set to 10 seconds and 30 seconds. Thereby, it was evaluated whether 50% or more remained without melting in a state where the granulated bodies were heated to 160 °C and contacted two opposing flat plates for a predetermined time.

[0077] The evaluation of the meltability was carried out based on the melting ratio of the granule samples. The lower the melting ratio, the better the meltability (more difficult to melt) of the granules can be said. Specifically, those in which the granules are hardly melted and deformed and no binding between the granule particles is observed are evaluated as unchanged. Those in which the surface of the granules (especially in the case of granular granules, the powder adhering to the surface) is melted and binding between the granule particles of the granule sample is observed (end melting) are evaluated as 10% - 20% or 20% - 30% melting according to the degree. Those in which the entire outer surface of the granules is melted but the original shape is maintained are evaluated as 30% - 50% or 50% - 70% melting according to the degree. Those in which the granule sample is completely melted and the shape of the granule particles is thermally deformed are evaluated as 70% - 80% or 80% - 90% melting according to the degree. In addition, those in which the granule sample is completely dissolved and the shape of the granule particles is lost are evaluated as complete melting.

[0078] 〔2〕Production Example 1 According to the method described in Example 1 of International Publication No. 2021 / 085534, P3HB3HH dry powder was obtained. The melting point of the P3HB3HH dry powder was 145°C, and the bulk density was 429 g / L.

[0079] 〔Example 1〕 Using a rotary porous die granulator (PFV250 manufactured by PALLMANN; outer diameter of the rotary porous die: 280 mm, number of die holes: 92, die hole diameter: 3.5 mm), the granule sample of Example 1 was produced from the P3HB3HH dry powder of Production Example 1. The P3HB3HH dry powder was supplied into the chamber of the granulator and discharged from the die provided on the chamber wall while being compacted by the frictional force between the rotating blade and the chamber wall. The discharged P3HB3HH dry powder was cut by a rotating blade arranged outside the chamber to produce a granular granule sample. In the production of the granule sample of Example 1, the sample discharge rate, the rotational power of the porous die, and the resin temperature (extrusion granulation temperature) were as shown below. The resin temperature was measured using a contact thermometer. Sample discharge rate: 115 kg / hour Rotating blade power: 31 kW Resin temperature: 105°C

[0080] 〔Example 2〕 A granulated sample of Example 2 was produced under the same conditions as the granulated sample of Example 1, except that the sample discharge rate, the rotational power of the porous die, and the resin temperature were changed to the following conditions. Sample discharge rate: 315 kg / hour Rotational power: 38 kW Resin temperature: 83°C

[0081] 〔Example 3〕 A granulated sample of Example 3 was produced under the same conditions as the granulated sample of Example 1, except that the sample discharge rate, the rotational power of the porous die, and the resin temperature were changed to the following conditions. Sample discharge rate: 490 kg / hour Rotational power: 43 kW Resin temperature: 85°C

[0082] 〔Comparative Example 1〕 Using a twin-screw extruder (TEM-26SX manufactured by Toshiba Machine Co., Ltd.), a granulated sample of Comparative Example 1 was produced from the P3HB3HH dry powder of Production Example 1. More specifically, the P3HB3HH dry powder was melt-kneaded with a twin-screw extruder having a cylinder temperature set at 30 to 170°C, and the resin melted at 160°C was discharged from the nozzle of a die attached to the tip of the extruder. Then, after water cooling at 43°C, the granulated sample of Comparative Example 1 was obtained by cutting with a pelletizer.

[0083] 〔Comparative Example 2〕 As the granulated sample of Comparative Example 2, the P3HB3HH dry powder in powder form of Production Example 1 was adopted.

[0084] 〔Comparative Example 3〕 Using a briquetting machine (manufactured by Hosokawa Micron Corporation), granule samples of Comparative Example 3 were produced from the P3HB3HH dry powder of Production Example 1. More specifically, the P3HB3HH dry powder was supplied to a briquetting granulator having a vertical screw and two rotating rolls and compressed to obtain a compressed sheet. The obtained compressed sheet was granulated by crushing it with a feather mill (manufactured by Hosokawa Micron Corporation) equipped with a vertical screw and a rotating roll to obtain a granular granule sample. 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.

[0085]

Table 1

[0086] 〔Results〕 From Table 1, all of the granule samples of Examples 1 to 3 had a bulk density of 0.4 g / cm 3 or less, which was lower than that of the granule samples of Comparative Examples 1 to 3 produced from the same raw material powder. In the evaluation of meltability, the melting of the granule particles was as low as about 20% to 30% even at 30 seconds, indicating that the granule had excellent meltability. On the other hand, the granule samples of Comparative Examples 1 and 3 had a higher bulk density than the raw material powder, and in the evaluation of meltability, melting was observed even under the evaluation conditions of 10 seconds for the granule samples of Comparative Examples 1 and 3, and the result was that 70% to 80% or more melted under the evaluation conditions of 30 seconds.

[0087] The granule samples of Examples 1 to 3 were all produced as granules with a lower bulk density than the raw material powder with a low bulk density. It is presumed that the melting of the granule samples of Examples 1 to 3 is suppressed by the air contained in the granules because they are produced as granular granules with a low bulk density. In addition, since the granule samples of Examples 1 to 3 are granular while the melting is suppressed, it can be confirmed that their transportability is improved compared to the granule sample (raw material powder) of Comparative Example 2. Further, the granule samples of Examples 1 to 3 were produced as granules with a low bulk density by extrusion granulation using a rotary porous die type extrusion granulation device.

Industrial Applicability

[0088] The granulated product obtained by the production method of the present invention can be suitably used in agriculture, fishery, forestry, horticulture, medicine, hygiene products, clothing, non-clothing, packaging, automobiles, building materials, and other fields.

Claims

1. A method for producing a granule containing an aliphatic polyester resin, comprising a granulation step of extruding and granulating a powder containing the aliphatic polyester resin using a rotary porous die granulator.

2. The method for producing a granule according to claim 1, wherein the temperature at which the powder is extruded and granulated is 30°C to 90°C lower than the melting point of the aliphatic polyester resin.

3. The method for producing a granule according to claim 1, wherein the bulk density of the granule is 70% to 95% when the bulk density of the powder is set to 100%.

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

5. A granule containing an aliphatic polyester resin, The granulated particles are granular and have a bulk density of 0.30 g / cm ３ to 0.40 g / cm ３ and are granulated particles.

6. The granule according to claim 5, wherein the major axis diameter is 1 mm to 10 mm.

7. The granule according to claim 5, wherein the granule is placed between two flat plates heated to 160°C and contacted with the two flat plates for 30 seconds, and 50% or more remains without melting.

8. The granule according to any one of claims 5 to 7, wherein the aliphatic polyester resin is poly(3-hydroxyalkanoate).

Images