Granule of thermoplastic resin powder, powder granule of crystalline polymer, and production method therefor

Abstract

An object of the present disclosure is to provide a thermoplastic resin powder granulate which, without subjecting the thermoplastic resin powder to melt-kneading pelletization, has a stable shape and high bulk density, improves the working environment, and has excellent feedability (stability and flowability) to processing machines, and which can contribute to a reduction in the amount of electricity used for production, and thus in the amount of carbon dioxide generated, compared with melt-kneading pelletization. A powder granulate containing thermoplastic resin powder according to an embodiment comprises an outer wall portion in which at least part of the thermoplastic resin powder located in the outermost region of the powder granulate is fused, and which accommodates compacted thermoplastic resin powder.

Description

Thermoplastic resin powder granules, crystalline polymer powder granules, and manufacturing method thereof

[0001] The present disclosure relates to a granulated product of a thermoplastic resin powder, and also to a granulated product of a crystalline polymer powder and a method for producing the same.

[0002] Some thermoplastic resins are in powder form due to their manufacturing process or because they are recycled pulverized products. Since such thermoplastic resin powders are usually difficult to handle, in order to improve their handleability and further increase productivity, they are generally plasticized and melted in a melt extruder, extruded through a die, cooled and solidified, and formed into pellets (hereinafter also referred to as melt-kneaded pellets), which are then fed into various thermoplastic resin processing machines and commercialized. That is, melt-kneaded pelletization is usually performed on powdered thermoplastic resins.

[0003] On the other hand, crystalline thermoplastic polymers (hereinafter also referred to as "crystalline polymers") are sometimes in powder form due to their manufacturing process or because they are recycled pulverized products. Such thermoplastic resin powders are usually difficult to handle, so in order to improve their handleability and further increase productivity, they are generally plasticized and melted in a melt extruder, extruded through a die, cooled and solidified, and formed into pellets (hereinafter also referred to as melt-kneaded pellets), which are then fed into various thermoplastic resin processing machines and commercialized. That is, melt-kneaded pelletization is usually performed on powdered thermoplastic resins.

[0004] Furthermore, in the molding and processing of crystalline polymers, if the "crystallization rate" is slow when the polymer is cooled and solidified from a plasticized molten state, productivity may be hindered in various molding processes. For example, in injection molding, the polymer cannot be solidified in the mold in a short time, resulting in a long molding cycle. Furthermore, the degree of crystallization in the molded product is insufficient, which can lead to problems such as unstable physical properties such as rigidity, dimensional stability, and transparency of the molded product.

[0005] For this reason, a "nucleating agent" is sometimes used for crystalline polymers. A nucleating agent is an additive that promotes the crystallization of crystalline polymers, and is compounded by melt-kneading.

[0006] The crystallization nucleating agent is preferably one that has the effect of generating uniform and fine crystal nuclei in a short period of time, and can bring about a wide range of physical property modifying effects, such as improved rigidity, improved dimensional stability, improved transparency, and improved molding cycle.

[0007] For example, biopolyester resins such as polyhydroxyalkanoates (PHAs) produced by microorganisms in their bodies generally have a slow crystallization rate, so a crystallization nucleating agent may be added.

[0008] Patent Document 1 discloses a resin composition containing pentaerythritol as a crystallization nucleating agent for polyhydroxyalkanoate (PHA).

[0009] Patent Document 2 discloses a biodegradable polymer composition containing polyhydroxyalkanoate (PHA), another biodegradable polymer, and a nucleating agent (corresponding to a crystallization nucleating agent).

[0010] WO2014 / 020838 Special Publication No. 2023-536152

[0011] Regarding thermoplastic resins, even in the process of melt-kneading and pelletizing, problems such as poor supply to various melt-kneading machines including extruders and low productivity often occur because the powdered thermoplastic resin has a low bulk density.

[0012] Recently, there has been a goal to reduce carbon dioxide, one of the greenhouse gases, and in various processing steps of thermoplastic resins, it has become a major challenge to reduce the amount of energy used in the process and the amount of carbon dioxide generated in the process.

[0013] One object of the present disclosure is to provide a granulated product of thermoplastic resin powder that has a stable shape and a high bulk density, improves the working environment, and has excellent feed characteristics (stability and fluidity) to a processing machine, even without undergoing a melt-kneading pelletization process, and that can contribute to reducing the amount of electricity required for production, i.e., reducing the amount of carbon dioxide generated, compared to melt-kneading pelletization.

[0014] In addition, the types of crystallization nucleating agents that can exert sufficient effects in the molding and processing of crystalline polymers are limited. Furthermore, in medical and food applications, i.e., applications that may come into contact with living bodies or foods, the crystallization nucleating agent may be eluted, so it is desirable to avoid using a crystallization nucleating agent as much as possible. Therefore, if it is possible to increase the crystallization rate during molding and processing without adding a crystallization nucleating agent, it would be an extremely useful technology in industry.

[0015] Therefore, one object of the present disclosure is to provide a granulated product of a crystalline polymer powder that has excellent crystallization properties during molding processing.

[0016] A first aspect of this embodiment can be expressed, for example, as follows. (1) A powder granulation product containing a thermoplastic resin powder, the powder granulation product having an outer wall portion formed by melting at least a portion of the thermoplastic resin powder located at the outer edge of the powder granulation product, and compressed thermoplastic resin powder contained inside the outer wall portion. (2) The powder granulation product according to (1), in which at least a portion of the compressed thermoplastic resin powder inside the outer wall portion has an unmelted compressed powder form. (3) The powder granulation product according to (1) or (2), in which at least a portion of the compressed thermoplastic resin powder inside the outer wall portion has a partially melted form. (4) The powder granulation product according to any one of (1) to (3), in which the shape of the powder granulation product is approximately cylindrical or approximately prismatic. (5) The powder granulation product according to any one of (1) to (4), in which an outer wall portion is provided on a side surface of the powder granulation product. (6) The powder granule according to any one of (1) to (5), having a breaking strength of 2.0 kg or more. (7) The powder granule according to any one of (1) to (6), wherein the powder granule is a compressed granule. (8) The powder granule according to any one of (1) to (7), wherein the thermoplastic resin powder comprises a thermoplastic resin having a softening onset temperature of 50 to 150°C. (9) The powder granule according to any one of (1) to (8), wherein the thermoplastic resin powder comprises a thermoplastic resin having a softening onset temperature of 60 to 90°C. (10) The powder granule according to any one of (1) to (9), wherein the thermoplastic resin powder comprises at least one selected from the group consisting of acrylic resins, methacrylic resins, polyhydroxyalkanoate (PHA) resins, polyolefin resins, polyamide resins, polyacetal resins, polyphenylene ether (PPE) resins, polyphenylene sulfide (PPS) resins, polyether ether ketone (PEEK) resins, polyimide (PI) resins, polyamideimide (PAI) resins, polyester resins, polycarbonate (PC) resins, polystyrene resins, polyketone resins, liquid crystal polymers (LCPs), and core-shell polymers. (11) The powder granule according to any one of (1) to (10), wherein the thermoplastic resin powder comprises a PHA resin.(12) A method for producing the powder granulated product according to any one of (1) to (11), comprising a compression granulation step of granulating thermoplastic resin powder by a compression granulation method in which the thermoplastic resin powder is extruded through a die hole, wherein the compression granulation step is carried out under the condition that the temperature of the granulated product immediately after granulation, Tp (°C), and the softening onset temperature, Ts (°C), of the thermoplastic resin powder satisfy the formula (1): Ts - 30 ≦ Tp ≦ Ts + 10. (13) The method according to (12), wherein the temperature of the die is controlled so that the temperature of the granulated product immediately after granulation, Tp (°C), and the softening onset temperature, Ts (°C), of the thermoplastic resin powder satisfy the formula (1). (14) The method according to (12) or (13), wherein the outer wall portion is formed by melting at least a portion of the thermoplastic resin powder at a contact surface with the wall surface of the die hole by frictional heat with the wall surface or heat transfer from the wall surface. (15) The method according to any one of (12) to (14), wherein the compression granulation is carried out using a disk pelleter type compression granulation device. (16) Use of the powder granulated product according to any one of (1) to (11) as a raw material for a thermoplastic resin compound or a molding material.

[0017] The second aspect of this embodiment can be expressed, for example, as follows: [1] A powder granule of a crystalline polymer powder, wherein the powder granule is heated from room temperature to a first hold temperature T at a temperature increasing rate of 10°C / min. Ｈ１ and then heated to the first hold temperature T Ｈ１ When the first DSC measurement was performed under the conditions of holding the sample at this temperature for 15 minutes and then lowering the temperature at a temperature lowering rate of 10°C / min, the first hold temperature T Ｈ１ There exists a first hold temperature T Ｈ１ is the melting peak temperature T of the crystalline polymer that appears on the highest temperature side during the temperature rise in the first DSC measurement. Ｍ [2] The powder granules are heated from room temperature to a second hold temperature T at a temperature increase rate of 10°C / min. Ｈ２ Then, the temperature is raised to a second hold temperature T Ｈ２After holding the sample at this temperature for 15 minutes, the sample was cooled at a rate of 10°C / min. The second hold temperature T Ｈ２ There exists a second hold temperature T Ｈ２ is the first hold temperature T Ｈ１ [3] The peak temperature Tc of the exothermic peak due to recrystallization that appears during cooling in the first DSC measurement is higher than １５ The powder granules are heated from room temperature to a first hold temperature T at a temperature increase rate of 10°C / min. Ｈ１ and then heated to the first hold temperature T Ｈ１ After holding the sample at this temperature for 2 minutes, the third DSC measurement was performed under the condition of cooling at a rate of 10°C / min. The peak temperature Tc of the exothermic peak due to recrystallization of the crystalline polymer that appeared during the cooling ２ The powder granulation product according to [1] or [2], wherein the following formula (A) is satisfied: Formula (A): 0.95≦Tc １５ / Tc ２ ≦1.05. [4] The powder granule according to any one of [1] to [3], which is substantially free of a crystallization nucleating agent. [5] The powder granule according to any one of [1] to [4], which has a breaking strength of 10.0 kg or more as measured with a Kiya hardness tester. [6] The powder granule according to any one of [1] to [5], which has an apparent density ratio calculated by the following formula (B) of 0.85 to 0.95: Formula (B): "apparent density ratio" = "apparent density of powder granule" / "apparent density of melt-kneaded pellets of the crystalline polymer". [7] The bulk density of the crystalline polymer powder before granulation is expressed as ρ １ , the bulk density of the powder granulation product is ρ ２ When this is the case, ρ ２ / ρ １ [8] The powder granule according to any one of [1] to [7], wherein the weight average molecular weight of the crystalline polymer is 200,000 or more and 3,000,000 or less. [9] The powder granule according to any one of [1] to [8], wherein the shape of the powder granule is approximately cylindrical or approximately prismatic.

[10] The melting peak temperature TＭ The powder granule according to any one of [1] to [9], comprising a crystalline polymer powder having a temperature in the range of 70°C or more and 200°C or less.

[11] The powder granule according to any one of [1] to

[10] , wherein the crystalline polymer powder comprises a biodegradable resin.

[12] The powder granule according to any one of [1] to

[11] , wherein the biodegradable resin comprises an aliphatic polyester resin or an aliphatic-aromatic polyester resin.

[13] The powder granule according to any one of [1] to

[12] , wherein the biodegradable resin comprises an aliphatic polyester resin.

[14] The powder granule according to any one of [1] to

[13] , wherein the aliphatic polyester resin comprises polyhydroxyalkanoate.

[15] The powder granule according to any one of [1] to

[13] , wherein the first hold temperature T Ｈ１ There is 180°C as the first hold temperature T Ｈ２

[16] The powder granule according to any one of [1] to

[14] , wherein when the first DSC measurement is performed under conditions in which the powder granule is heated from room temperature to 180°C at a heating rate of 10°C / min, held at 180°C for 15 minutes, and then cooled at a heating rate of 10°C / min, an exothermic peak due to recrystallization of the crystalline polymer appears during temperature reduction; and when the second DSC measurement is performed under conditions in which the powder granule is heated from room temperature to 200°C at a heating rate of 10°C / min, held at 200°C for 15 minutes, and then cooled at a heating rate of 10°C / min, no exothermic peak due to recrystallization of the crystalline polymer appears during temperature reduction.

[17] The powder granule according to any one of [1] to

[15] , wherein the peak temperature Tc of the exothermic peak due to recrystallization that appears during temperature reduction in the first DSC measurement １５ and when a third DSC measurement is performed under the conditions of heating the powder granules from room temperature to 180°C at a heating rate of 10°C / min, holding the powder granules at 180°C for 2 minutes, and then cooling the powder granules at a heating rate of 10°C / min, the peak temperature Tc of an exothermic peak due to recrystallization of the crystalline polymer that appears during cooling is ２ The powder granule according to any one of [1] to

[16] , wherein the following formula (A) is satisfied: Formula (A): 0.95≦Tc １５ / Tc ２≦1.05.

[18] The powder granule according to any one of [1] to

[17] , which is a compression granule.

[19] A method for producing the powder granule according to any one of [1] to

[18] , comprising a compression granulation step of granulating a crystalline polymer powder by a compression granulation method, wherein the temperature Tp (°C) of the granules immediately after granulation is equal to or lower than the melting peak temperature T of the crystalline polymer. Ｍ The method according to

[19] , wherein the compression granulation step is carried out under the following conditions:

[20] The method according to

[19] , wherein the compression granulation is carried out using a disc pelletizer type compression granulator.

[0018] This specification includes the disclosures of Japanese Patent Application Nos. 2023-080938 and 2023-173896, from which the present application claims priority.

[0019] According to the first aspect of this embodiment, it is possible to provide a granulated product of thermoplastic resin powder that has a stable shape, a high bulk density, an improved working environment, and excellent feed characteristics (stability and fluidity) to a processing machine, even without undergoing a melt-kneading pelletizing process, and that can contribute to reducing the amount of electricity required for production, i.e., reducing the amount of carbon dioxide generated, compared to melt-kneading pelletizing.

[0020] According to the second aspect of this embodiment, it is possible to provide a granulated product of crystalline polymer powder that has excellent crystallization characteristics during molding processing.

[0021] 1 is an external photograph of the powder granulated product obtained in Example A1 (using acrylic resin powder A1). 2 is a cross-sectional photograph of the powder granulated product obtained in Example A1 (using acrylic resin powder A1). 3 is a DSC measurement result of biopolyester powder A2 in Example A4. 4 is an external photograph of the powder granulated product obtained in Example A4 (using biopolyester powder A2). 5 is a cross-sectional photograph of the powder granulated product obtained in Example A4 (using biopolyester powder A2). 6 is a photograph of an injection-molded product obtained from the powder granulated product obtained in Example A1 (using acrylic resin powder A1). 7 is a photograph of a sheet-molded product obtained from the powder granulated product obtained in Example A4 (using biopolyester powder A2). 8 is a cross-sectional photograph of the powder granulated product obtained in Example A7 (using biopolyester powder A3). 9 is a cross-sectional photograph of the powder granulated product obtained in Example A8 (using biopolyester powder A3). 1 is a cross-sectional photograph of the powder granules obtained in Example A9 (using biopolyester powder A4). 2 is a graph showing the results of DSC measurement (temperature decrease) showing the "melt memory effect" of the powder granules of crystalline polymer obtained in Example B1 (PHBH powder granules). 3 is a graph showing the results of DSC measurement (temperature decrease) of melt-kneaded pellets of crystalline polymer obtained in Reference Example B1 (containing a crystallization nucleating agent). 4 is a photograph of a cross section of the powder granules of crystalline polymer obtained in Example B2 (PHBH powder granules). 5 is a graph showing the results of DSC measurement (temperature decrease) of melt-kneaded pellets of crystalline polymer obtained in Reference Example B2 (containing no crystallization nucleating agent). 6 is a graph showing the results of DSC measurement (temperature decrease) of the crystalline polymer powder (biopolyester powder A1) shown in Reference Example B3. 7 is a graph showing the results of DSC measurement (temperature decrease) of the PLA powder granules obtained in Example B4.

[0022] (First Aspect) A. Overview of Thermoplastic Resin Powder Granules The powder granules of this embodiment are powder granules containing thermoplastic resin powder, and have an outer wall formed by melting at least a portion of the thermoplastic resin powder located at the outer edge of the powder granules, and the compressed thermoplastic resin powder is contained inside the outer wall. In the powder granules of this embodiment, the outer wall is located at the outer edge of the granules. In this specification, the outer wall is also referred to as a shell. The compressed thermoplastic resin powder is contained inside the outer wall, and the thermoplastic resin powder may be at least partially melted or at least partially unmelted. The compressed thermoplastic resin powder inside the outer wall may be in an unmelted state. That is, at least a portion of the compressed thermoplastic resin powder inside the outer wall may include an unmelted compressed powder form or a partially melted form. The term "partially molten" refers to a state in which the components of the thermoplastic resin powder are partially molten, but do not form a strong fusion structure that can hold the thermoplastic resin powder like the outer wall portion. In this specification, the inside of the outer wall portion is also referred to as the core portion. The core portion inside the outer wall portion contains compressed thermoplastic resin powder, and in this specification, "compressed" refers to the density of the thermoplastic resin powder located in the core portion being higher than the bulk density of the thermoplastic resin powder before granulation.

[0023] The outer wall (shell) of the thermoplastic resin powder granules of this embodiment has a dense structure containing the molten thermoplastic resin powder, while the inner core, although compressed, has a looser structure compared to the dense structure (welded structure) of the outer wall containing the molten thermoplastic resin powder. The thermoplastic resin powder of this embodiment has the molten thermoplastic resin powder as the outer wall, which holds the compressed thermoplastic resin powder present in the core. Therefore, although it is a powder granule, it has a stable structure, little powder falling, is easy to handle and safe, and can lead to an improved working environment.

[0024] Therefore, when the powder granules of this embodiment are used as a compound raw material in preparing a resin composition, the raw material supply capacity, supply stability, and supply accuracy can be improved, which can contribute to improving productivity. At the same time, since the melt-kneading pelletization process can be omitted, the amount of electric energy required for the process can be reduced, and the amount of carbon dioxide generated in the processing process can be reduced.

[0025] The powder granulated material of this embodiment can be directly supplied to various molding machines, such as injection molding machines and extrusion molding machines for thermoplastic resins, or can be used as a molding material. In this case, the melt-kneading and pelletizing process can be omitted, making it possible to reduce the amount of carbon dioxide generated in the processing step. Furthermore, the powder granulated material of this embodiment can have a small thermal history because it is not heated to the extent required for pelletization.

[0026] The outer wall (shell) has a welded structure in which at least a portion of the thermoplastic resin powder located at the outer edge of the powder granules is melted. The outer wall may be smooth enough to have a glossy appearance. Alternatively, the outer wall may be formed by some of the components of the thermoplastic resin powder melting and partially welding with adjacent components, even if the melting is not smooth enough to form a smooth surface. As will be described in detail later, the outer wall can be formed by, for example, melting at least a portion of the thermoplastic resin powder at the contact surface with the die hole due to frictional heat with the wall surface or heat transfer from the wall surface during compression granulation. The thickness of the outer wall can vary depending on the manufacturing conditions of the thermoplastic resin powder granules.

[0027] The core is a portion located inside the outer wall, containing the compressed thermoplastic resin powder. The thermoplastic resin powder located in the core may be porous, or may have a non-welded structure, in which heat is not transferred to the core during granulation. The core is located far from the die contact surface, and therefore may have a structure in which the powder polymer raw material maintains its powder shape (i.e., a non-welded structure or a powder-like structure), or a structure in which the powder polymer raw material is partially fused but retains its shape.

[0028] Furthermore, in this specification, the terms "outer wall portion (shell portion)" and "core portion" are used for ease of explanation, but as described above, the outer wall portion is formed by melting the thermoplastic resin powder due to the heat during granulation, and therefore in reality, there is no clear boundary between the outer wall portion (shell portion) and the core portion. The outer wall portion (shell portion) includes a fused structure of the thermoplastic resin powder and refers to a portion that is located on the outer edge of the powder granules and contributes to maintaining the constant shape of the powder granules, while the core portion refers to a portion located inside the outer wall portion (shell portion).

[0029] The powder granulation product preferably has a substantially cylindrical or substantially prismatic shape, and the powder granulation product preferably has an outer wall portion on the side surface of the powder granulation product. In this embodiment, the powder granulation product preferably has a substantially cylindrical or substantially prismatic shape, and the outer wall portion is preferably formed on the side surface of the powder granulation product having a substantially cylindrical or substantially prismatic shape.

[0030] The powder granulated product of this embodiment can be preferably obtained by using a powder compression granulation method, and the details of the production method will be described later.

[0031] The powder granules of the present embodiment can be used as a raw material for a thermoplastic resin in the production of a resin composition by melt compounding. Furthermore, the powder granules can be directly fed into various resin molding machines such as injection molding and extrusion molding to obtain various molded products.

[0032] Adding a powder granulation material to the melt compounding of a resin composition can improve productivity. Specifically, because the powder granulation material has excellent stability when fed into equipment such as an extruder, the use of the powder granulation material can dramatically improve the productivity of the resin composition (compound processing speed per hour). Furthermore, it can significantly reduce dust pollution in the work environment, improve the occupational safety and health environment for workers, and significantly reduce the time required for cleaning equipment changeovers.

[0033] When the powder granulated material is directly fed into various resin molding processing machines such as injection molding and extrusion molding, the "melt-kneading pelletization" process can be omitted, making it possible to significantly reduce the total amount of carbon dioxide generated in the process compared to conventional methods (resin product processing methods that include the melt-kneading pelletizing process).

[0034] The powder granules may have any suitable shape. Typically, when the powder is produced by compression granulation and passed through a circular die hole, the basic shape is a cylindrical pellet.

[0035] In this specification, the term "die" is a general term for a tool equivalent to a "mold" for compressing and shaping a powder granulated material.

[0036] When the powder granules are cylindrical, the diameter of the powder granules is, for example, 2 mm to 7 mm, preferably 3 mm to 5 mm. The length (height) of the powder granules is, for example, 1 mm to 10 mm, preferably 2 mm to 7 mm. Such a shape results in a powder granule that is easy to handle. The diameter of the powder granules can be adjusted, for example, by the diameter of the die hole in the disc plate (die plate) during granulation, and the length can be adjusted by the distance between the disc plate and the cutter. This distance can be any appropriate distance. The distance between the disc plate and the cutter is, for example, 1 mm to 30 mm, more preferably 2 mm to 20 mm, and even more preferably 3 mm to 10 mm.

[0037] The bulk density of the powder granulation product can be any appropriate bulk density. The bulk density of the powder granulation product is preferably 0.3 kg / L to 2.0 kg / L, more preferably 0.5 kg / L to 1.0 kg / L. Increasing the bulk density improves the supply speed and supply stability of the powder granulation product to various processing machines. The bulk density is calculated by using a measuring cup, allowing the powder to fall naturally into the cup until it is filled to the brim, weighing out a volume of exactly 1 liter, and measuring the mass (unit: kg / L).

[0038] The breaking strength of the powder granulation product measured with a Kiya hardness tester is preferably 0.5 kg or more, preferably 1.0 kg or more, preferably 2.0 kg or more, preferably 3.0 kg or more, preferably 4.0 kg or more, preferably 5.0 kg or more, preferably 6.0 kg or more, preferably 7.0 kg or more, preferably 8.0 kg or more, preferably 9.0 kg or more, and preferably 10 kg or more. The upper limit may exceed the measurement limit of the Kiya hardness tester (10 kg is the measurement limit for the Shiro Sangyo Co., Ltd. product "WPF1600-B"). Within this range, a powder granulation product with excellent handleability and melt processability can be obtained. Here, breaking strength refers to the average breaking stress (breaking load) measured by crushing 20 or more (preferably 25 or more) particles of powder granulation product in a direction perpendicular to the longitudinal direction (extrusion direction) of the powder granulation product. In the case of powder granulation, since the shell portion is made of molten resin, it is possible to maintain a stable shape as a granulation, despite being a powder granulation. The diameter of the pressure surface of the pressure attachment of the Kiya hardness tester is, for example, 5 mm.

[0039] The moisture content of the powder granulation product can be any appropriate moisture content. In addition to the moisture content originally contained in the raw material powder, water may be added to the powder to facilitate granulation. The amount of water added during granulation will be described later.

[0040] The powder granules may be dried after granulation, but the final moisture content is preferably 10% by mass or less, more preferably 5.0% by mass or less, even more preferably 3.0% by mass or less, particularly preferably 1.0% by mass or less, and most preferably 0.5% by mass or less. The moisture content of the final powder granules can be appropriately selected depending on the intended use.

[0041] It is preferable that the powder granulation product is granulated without adding water. If the moisture content of the powder granulation product is low, a drying step after granulation may not be necessary. If granulation can be performed without using water, the drying step is not necessary, and the amount of carbon dioxide emitted during the powder granulation process can be significantly reduced.

[0042] The moisture content of the powder granulated product granulated "without adding water" is, for example, 1.0 mass% or less, preferably 0.5 mass% or less, more preferably 0.3 mass% or less, and even more preferably 0.2 mass% or less.

[0043] The moisture content of the powder granules is measured using an infrared moisture meter as described below.

[0044] The particle diameter of the thermoplastic resin powder used in this embodiment can be any appropriate particle diameter depending on the form, as long as the effects of this embodiment can be obtained. The maximum diameter of the resin powder particles is preferably 5 mm or less, and the minimum diameter is preferably 0.0001 mm or more.

[0045] The average particle diameter of the thermoplastic resin powder is, for example, 0.001 mm to 1.0 mm. The average particle diameter of the thermoplastic resin powder is preferably 1.0 mm or less, more preferably 0.01 mm to 0.8 mm, and particularly preferably 0.1 mm to 0.5 mm. In this specification, the average particle diameter can be measured by a laser diffraction method. The average particle diameter of the resin powder can be the particle diameter (d50) at 50% cumulative in the cumulative particle size distribution on a volume basis.

[0046] The thermoplastic resin powder may be used alone or in combination of two or more kinds.

[0047] The bulk density of the thermoplastic resin powder may be any appropriate value depending on the form of the powder, as long as the effects of the present embodiment are obtained. The bulk density of the thermoplastic resin powder is preferably 0.01 kg / L to 1 kg / L, more preferably 0.05 kg / L to 0.8 kg / L, more preferably 0.1 kg / L to 0.8 kg / L, even more preferably 0.1 kg / L to 0.6 kg / L, and particularly preferably 0.2 kg / L to 0.5 kg / L.

[0048] The thermoplastic resin powder may be a powdered resin obtained through a manufacturing process, i.e., a powder resulting from the manufacturing process, or may be a powdered resin obtained by pulverizing a non-powdered resin such as a pelletized resin, a lump of resin, or a resin molded body. The pulverized powdered resin can be obtained by cooling a molded product, pellets, or a sprue or runner generated during injection molding at room temperature or, if necessary, with dry ice or liquid nitrogen, and then using a pulverizer (e.g., Dalton products under the trade names "Nea Mill," "Sylphid Mill," "Atomizer," or "Impact Mill").

[0049] The thermoplastic resin powder is composed of any appropriate thermoplastic resin. Specific examples of the thermoplastic resin include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), polyurethane (PUR), fluorine-based resin, general-purpose resins such as ABS resin (acrylonitrile butadiene styrene resin), AS resin, and acrylic resin (PMMA), polyamide (PA), polyacetal (POM), polycarbonate (PC), polyphenylene ether, and modified polyphenylene ether ( Examples of suitable polymers include engineering plastics such as m-PPE, modified PPE, PPO), polyesters (PET, PBT, etc.), and cyclic polyolefin (COP); super engineering plastics such as polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone (PSF), polyethersulfone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyetheretherketone (PEEK), polyimide (PI), and polyamideimide (PAI); and core-shell rubbers obtained by emulsion polymerization or suspension polymerization.

[0050] Furthermore, biodegradable resins may be used as the thermoplastic resin. Examples of biodegradable resins include aliphatic polyester resins (e.g., homopolymers or copolymers of polyhydroxyalkanoate (PHA), polycaprolactone, polylactic acid, polyethylene succinate, polybutylene succinate adipate, polyhydroxyvalerate, etc., and modified products of these homopolymers or copolymers), aliphatic / aromatic polyester resins (e.g., block polymers or random polymers of aliphatic carboxylic acids or hydroxy acids, aromatic dicarboxylic acids, and 1,3-propanediol), and polyvinyl alcohol resins (e.g., polyvinyl alcohol, polyvinyl acetate, polyvinyl butyrate, ethylene-vinyl alcohol copolymers, etc.).

[0051] In this embodiment, particularly preferred thermoplastic resin powders include at least one selected from the group consisting of acrylic resins, methacrylic resins, polyhydroxyalkanoate (PHA) resins, polyolefin resins, polyamide resins, polyacetal resins, polyphenylene ether (PPE) resins, polyphenylene sulfide (PPS) resins, polyether ether ketone (PEEK) resins, polyimide (PI) resins, polyamideimide (PAI) resins, polyester resins, polycarbonate (PC) resins, polystyrene resins, polyketone resins, liquid crystal polymers (LCPs), and core-shell polymers.

[0052] Polyhydroxyalkanoate (PHA) resins can be compounds produced in the bodies of microorganisms that feed on carbohydrates, oils, fats, etc. Such polyhydroxyalkanoates are primarily extracted as powdery polymers.

[0053] Polyhydroxyalkanoate resins contain hydroxyalkanoic acid, a raw material component, as a polymerization component and have at least a repeating unit derived from the hydroxyalkanoic acid. Polyhydroxyalkanoate resins may be artificially synthesized or biosynthesized by microorganisms. Examples of hydroxyalkanoic acids include glycolic acid, 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynanoate, 3-hydroxydecanoate, 3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate, 4-hydroxybutyrate, 4-hydroxyvalerate, 5-hydroxyvalerate, and 6-hydroxyhexanoate. The number of carbon atoms in the hydroxyalkanoic acid may be 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or 8 or more, preferably 3 or more. The number of carbon atoms of the hydroxyalkanoic acid may be 15 or less, 12 or less, 10 or less, 8 or less, 6 or less, or 4 or less, preferably 10 or less, particularly preferably 6 or less. One type of hydroxyalkanoic acid may be used alone, or two or more types may be used in combination.

[0054] Preferred examples of the polyhydroxyalkanoate resin include poly(3-hydroxyalkanoate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0055] The acrylic resin, methacrylic resin, and core-shell polymer are preferably used in the form of a powder obtained by emulsion polymerization or suspension polymerization. The powdered polymer obtained by emulsion polymerization or suspension polymerization can be used as is as a thermoplastic resin powder for granulation.

[0056] In the powder granules of this embodiment, in order to form an outer wall (shell) on the granules, it is necessary to melt a part of the constituent components of the thermoplastic resin powder by frictional heat with the powder on the die wall surface or by heat transfer in the granulation process. For this reason, when the softening onset temperature of the thermoplastic resin powder is higher than the granulation temperature, it is advantageous to granulate the mixture with another thermoplastic resin powder having a softening onset temperature lower than the granulation temperature.

[0057] The powder granules may contain any appropriate additives as needed. The additives may be in powder form or liquid form. Examples of additives include antioxidants, light stabilizers, foaming agents, UV absorbers, antiblocking agents, heat stabilizers, impact modifiers, antibacterial agents, dispersants, compatibilizers, processing aids, lubricants, coupling agents, crystallization nucleating agents, hydrolysis inhibitors, oxygen scavengers, colorants (dyes and pigments), and binders. One type of additive may be used alone, or two or more types may be used in combination.

[0058] The additive may be in the form of a powder or a liquid.

[0059] The content of the additive in the powder granules is, for example, 10% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, and more preferably 1.0% by mass or less.

[0060] The powder granules of this embodiment may contain a binder as an additive. Here, the term "binder" refers to a compound that is present between thermoplastic resin powder particles other than the constituent components of the raw thermoplastic resin powder, and that can bind the powder particles together and increase the breaking strength of the granules. However, various compounds that exhibit a binding effect, preferably water-dispersible or water-soluble polymer compounds, polysaccharides, etc., can be appropriately selected and used as the binder, as needed.

[0061] It is preferable to melt and bind some of the components of the thermoplastic resin powder to form a powder granule, and it is preferable not to blend a binder.

[0062] When a binder is blended in the powder granulation product of this embodiment, the content thereof is typically 10 mass% or less, preferably 5.0 mass% or less, more preferably 3.0 mass% or less, even more preferably 1.0 mass% or less, still more preferably 0.5 mass% or less, particularly preferably 0.1 mass% or less, and most preferably 0 mass% (undetectable), relative to the total mass of the powder granulation product.

[0063] In one embodiment, a dispersant is preferably used as the additive. A surfactant is preferably used as the dispersant. The hydrophilic / hydrophobic balance of the dispersant (surfactant) can be controlled by adjusting the degree of esterification of the dispersant compound, the type of fatty acid (presence or absence of hydroxyl groups, saturated or unsaturated fatty acid, alkyl chain length), the degree of polymerization, etc. The use of a dispersant can sometimes bring about benefits such as "improving the productivity (discharge rate) of powder granules," "reducing frictional heat during granulation," and "enhancing the cleanability of the granulation device."

[0064] Examples of dispersants include fatty acids, fatty acid metal salts, fatty acid sulfonates, fatty acid amides, acrylamides, polyhydric alcohol fatty acid esters, polyglycerin fatty acid esters, etc. One type of dispersant may be used alone, or two or more types may be used in combination.

[0065] In one embodiment, the dispersant is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerin fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids.

[0066] The polyhydric alcohol fatty acid ester is an ester compound composed of a polyhydric alcohol and a fatty acid. Examples of the polyhydric alcohol fatty acid ester include esters of a polyhydric alcohol such as pentaerythritol or glycerin with a fatty acid having 8 or more carbon atoms (preferably 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms).

[0067] Fatty acid amides are compounds having a structure formed by dehydration condensation of a fatty acid with ammonia or a primary or secondary amine. Examples of fatty acid amides include saturated fatty acid monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide.

[0068] Polyglycerol fatty acid esters are ester compounds composed of polyglycerol and fatty acids. Examples of polyglycerol fatty acid esters include diglycerol palmitate, diglycerol stearate, diglycerol oleate, decaglycerol palmitate, decaglycerol stearate, and decaglycerol oleate.

[0069] The content of the dispersant is usually 0.01% by mass to 10% by mass, preferably 0.1% by mass to 7.0% by mass, and more preferably 0.3% by mass to 5.0% by mass, based on the total amount of the powder granules.

[0070] In one embodiment, a crystallization nucleating agent is used as the additive. The crystallization nucleating agent is preferably used when the powder granule is a granule mainly composed of a crystalline thermoplastic resin powder. In particular, the crystallization nucleating agent is preferably added when a biopolyester (e.g., polyhydroxyalkanoates (PHAs)) produced by living organisms is used as the thermoplastic resin powder. The use of the crystallization nucleating agent makes it possible to increase the crystallization rate and degree of crystallization of the crystalline thermoplastic resin powder (e.g., biopolyester), thereby improving not only rigidity and heat resistance but also productivity. Examples of such crystallization nucleating agents include organic metal salt compounds such as metal phosphates, metal benzoates, metal pimelates, metal rosins, metal oxalates, and metal fatty acid salts; organic compounds such as aliphatic organic esters, triallyl phosphate, polyalkylene glycols or their derivatives, aliphatic polyesters, and benzylidene sorbitol; dyes and pigments such as quinacridone, cyanine blue, and carbon black; minerals such as talc, mica, kaolin, clay, carbonate minerals, metal oxides, and metal sulfates; and polymer compounds such as ionomers and high-melting-point polyamides. In one embodiment, talc, mica, kaolin, calcium carbonate, and the like are used as the crystallization nucleating agent. One type of crystallization nucleating agent may be used alone, or two or more types may be used in combination.

[0071] The content of the crystallization nucleating agent is usually 0.01% by mass to 10% by mass, preferably 0.1% by mass to 7.0% by mass, and more preferably 0.3% by mass to 5.0% by mass, based on the total amount of the powder granules.

[0072] B. Method for producing powder granules The powder granules having a core portion and a shell portion of this embodiment can be obtained by compressing the powder granules through a "die" and melting the thermoplastic resin powder in the area in contact with the die, but preferably can be obtained by a compression granulation method in which the thermoplastic resin powder is extruded through a die hole, and the shell portion is formed when the thermoplastic resin powder is extruded through the die hole, i.e., during extrusion granulation, the components of the thermoplastic resin powder melt at the contact surface with the wall surface of the die hole due to frictional heat with the wall surface or heat transfer from the wall surface.

[0073] By forming the shell portion, the powder granules can be maintained in a consistent shape (e.g., cylindrical or prismatic), and powder granules with excellent quality stability (shape stability, uniform hardness), low fineness, high hardness, and ease of handling can be obtained.

[0074] In one embodiment, the powder granulation product can be granulated without using water, eliminating the need for a drying process, thereby reducing the amount of electricity used for granulation and significantly reducing the amount of carbon dioxide emitted during the process.

[0075] During extrusion granulation of powder granules, when the powder passes through a die, frictional heat can be generated between the powder and the wall of the die hole. This frictional heat causes the temperature of the powder granules to rise. However, if the granule temperature (Tp; units: °C) immediately after granulation is too high above the softening onset temperature (Ts, where Ts corresponds to the melting point or glass transition temperature) of the thermoplastic resin powder, the thermoplastic resin powder will melt excessively and stick to the wall of the die hole, causing clogging of the die hole and making continuous granulation impossible. On the other hand, if the granule temperature (Tp) immediately after granulation is too low below the softening onset temperature (Ts) of the resin powder, the raw resin powder will not have cohesive strength and will not form granules in its powder state, or the granules will easily collapse under compression, making it difficult to obtain granules in a stable shape.

[0076] In order to stably obtain a powder granulated product, it is preferable that the granulated product temperature (Tp) immediately after granulation and the softening start temperature (Ts) of the thermoplastic resin powder are within a specific range. That is, the method for producing a powder granulated product according to this embodiment includes a compression granulation step in which the thermoplastic resin powder is granulated by a compression granulation method in which the thermoplastic resin powder is extruded through a die hole, and the compression granulation step is carried out under conditions in which the granulated product temperature Tp (°C) immediately after granulation and the softening start temperature Ts (°C) of the thermoplastic resin powder satisfy formula (1), more preferably formula (2), and even more preferably formula (3). Formula (1): Ts - 30 ≦ Tp ≦ Ts + 10 Formula (2): Ts - 20 ≦ Tp ≦ Ts + 5 Formula (3): Ts - 15 ≦ Tp ≦ Ts

[0077] In formulas (1) to (3), the left and right sides may be arbitrarily combined to create other formulas that define a preferred range of Tp. For example, the compression granulation step can be preferably carried out under conditions that satisfy Ts-20≦Tp≦Ts+10, Ts-15≦Tp≦Ts+10, Ts-30≦Tp≦Ts+5, Ts-15≦Tp≦Ts+5, Ts-30≦Tp≦Ts, and Ts-20≦Tp≦Ts.

[0078] The temperature of the granulated material (Tp) immediately after granulation can be measured using a contact thermocouple. The temperature of the granulated material (Tp) immediately after granulation can be measured by bringing the powder granulation apparatus into a state where granulation can be performed stably, stopping the apparatus during granulation, and inserting a thermocouple directly into the die section or into the powder granulated material inside the die hole to quickly measure the temperature. Measurements are performed at least three times (preferably five times), and the average value is taken as Tp. In this case, even if the powder sticks to the die or becomes clogged, making granulation impossible, a thermocouple is similarly inserted directly into the powder to measure the temperature.

[0079] In order to efficiently obtain the powder granules having the core / shell structure of this embodiment, it is most effective to control the temperature of the die that comes into direct contact with the powder. That is, it is preferable to provide a mechanism for heating the die by providing a heater or a heat medium flow path for temperature control, and further a mechanism for cooling by providing a cooling medium flow path, thereby controlling the temperature of the die so as to satisfy the temperature condition of formula (1).

[0080] In general compression granulation equipment, due to the simplicity of the equipment, it often has a simple structure that does not allow for die temperature control. However, even in this case, the temperature of the granulated material immediately after granulation (Tp) can be changed and controlled by methods such as the number of rotations of the rollers of the granulation equipment, the diameter of the die holes, the effective pressurized length of the die holes, the feed rate of the raw material powder, the contact area and contact time between the raw material powder and the die surface, and insulation or cooling of the granulation equipment.

[0081] When there is no temperature control device for the die, the temperature is controlled by balancing the temperature rise due to frictional heat during granulation and the heat dissipation to the outside. In order to satisfy formula (1) and efficiently obtain a powder granule, the softening onset temperature (Ts) of the thermoplastic resin powder is preferably 50 to 150°C, more preferably 55 to 120°C, and even more preferably 60 to 90°C.

[0082] The thermoplastic resin powder may be a single component or a combination of two or more components. In particular, when the difference between the softening onset temperature (Ts) of the target thermoplastic resin powder and the granule temperature (Tp) is large and it is difficult to set the granule temperature to satisfy any of the conditions of the above formulas (1) to (3), it is advantageous to obtain a granule by blending a thermoplastic resin having a softening onset temperature lower than the granule temperature and granulating the mixture.

[0083] When the thermoplastic resin powder is composed of two or more components, it is preferable to set the condition (e.g., die temperature) such that the granule temperature (Tp) immediately after granulation falls within the range satisfying formula (1), with the Ts of the component of the thermoplastic resin powder having the lowest softening onset temperature (Ts) being the Ts in formula (1). More preferably, it is preferable to set the condition (e.g., die temperature) such that the softening onset temperatures of all the components of the thermoplastic resin powder satisfy formula (1).

[0084] When the thermoplastic resin powder is composed of two or more components, the component of the thermoplastic resin powder having the lowest softening initiation temperature is 50% by mass or less, preferably 30% by mass or less, and more preferably 10% by mass or less, of the total amount of the thermoplastic resin powder.

[0085] In this specification, the softening onset temperature (Ts) of the thermoplastic resin powder means the melting point or glass transition temperature, which can be measured by a differential scanning calorimeter (DSC). In one embodiment, when an endothermic or exothermic peak is observed in the DSC measurement, the softening temperature corresponds to the melting point, and when a discontinuity in the baseline is observed, the softening temperature corresponds to the glass transition temperature.

[0086] In DSC measurement, a sample of thermoplastic resin powder, usually about 5 mg, is weighed onto a sample dish and heated at a rate of 10° C. / min in a nitrogen stream to determine the softening onset temperature (Ts).

[0087] In the case of a crystalline resin, the intersection of the baseline from the low temperature part and the tangent at the inflection point (the point where the upward convex curve changes to a downward convex curve) on the melting start side where the endothermic peak of crystalline melting is observed is considered to be the "melting point," and this is the softening initiation temperature (Ts).

[0088] When a plurality of endothermic peaks of crystalline melting appear, the melting point of the peak that appears on the lowest temperature side is taken as the softening initiation temperature.

[0089] In the case of an amorphous resin, the intersection of the baseline from the low temperature part and the tangent line at the inflection point is regarded as the glass transition temperature (Tg), and this is taken as the softening initiation temperature (Ts).

[0090] Powder granulation products can be produced using a compression granulator, examples of which include a disk pelleting system, a screw extrusion system, a briquetting system, and a tableting system. Of the above examples, the disk pelleting system is preferably used from the viewpoints of granulation productivity and the quality and shape uniformity of the resulting powder granulation products. The disk pelleting system can also employ a "semi-wet granulation method" in which an appropriate amount of moisture is added, but in this embodiment, granulation can be performed without using water, in which case a drying step may be unnecessary. Granulation without using water can reduce the amount of energy required in the drying step and significantly reduce the amount of carbon dioxide emitted during the process.

[0091] When the thermoplastic resin powder is a mixture containing two or more powder raw materials, it is preferable to mix them uniformly using any appropriate mixer. Examples of mixers include a Henschel mixer, a Nauta mixer, a powder kneader (KDH, KDA, CKD, CPM) (Dalton), a Spartan mixer (SPM) (Dalton), and an SP granulator (SPG) (Dalton). To obtain a preferable mixture with excellent granulation properties, it is preferable that the mixing and stirring device has appropriate stirring blades. For example, when using a Henschel mixer, it is preferable to use a combination of upper and lower blades, with the upper blade being a Y1 blade (trade name, manufactured by Nippon Coke Co., Ltd.) and the lower blade being an S0 blade (trade name, manufactured by Nippon Coke Co., Ltd.). It is also preferable to install a deflector in the stirring vessel and perform mixing. In other words, a mixing process that can uniformly disperse each component throughout the mixture is advantageous for improving the productivity and quality stability of the final powder granules.

[0092] A "semi-wet granulation method" can also be employed, but the amount of water blended can be any appropriate amount depending on the properties of the powder (water absorption, etc.). In this case, the amount of water blended is 3 to 30 parts by mass, preferably 5 to 25 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the thermoplastic resin powder. The semi-wet method can be employed when the granulation properties are not stable in the granulation step.

[0093] The basic structure of a disc pelletizer includes one or two discs with numerous 2 mm to 30 mm holes and a roller for pressure-feeding raw materials through the holes in the disc. Thermoplastic resin powder (which may contain moisture) supplied between the disc and roller, or between two discs, is forced into the holes in the disc as the roller rotates, forming a cylindrical extrudate. The extruded granules are cut on the back surface of the disc with a cutter or the like to obtain pellet-shaped powder granules. The length of the granules can be adjusted by the distance between the back surface of the disc and the cutter and the rotation speed of the roller. The distance between the disc plate and the cutter can be any appropriate distance. The distance between the disc plate and the cutter is, for example, 1 mm to 30 mm, more preferably 2 mm to 20 mm, and even more preferably 3 mm to 10 mm.

[0094] More specifically, the disc pelleting method includes a roller disc die method, a roller ring die method, a double die method, a flat die method, etc. An example of a commercially available disc pelleting machine is the Disc Pelletter F Series manufactured by Dalton.

[0095] C. Melt Compounding Using Powder Granules In one embodiment, the powder granules are used as a thermoplastic resin compound raw material or molding material. One embodiment is the use of the powder granules of this embodiment as a thermoplastic resin compound raw material or molding material. For example, a melt compounding of the powder granules with another thermoplastic resin may be provided.

[0096] The melt compounding may be carried out by any suitable method. For example, a kneader, a Banbury mixer, a roll, or a single-screw or multi-screw extruder having two or more screws may be used. A twin-screw extruder is preferably used. The composition obtained by melt kneading is pelletized.

[0097] In one embodiment, the powder granulated product can be directly charged into a resin processing device such as an injection molding machine or an extrusion molding machine to obtain various resin composition molded articles.

[0098] (Second Aspect) This embodiment is a powder granulation product of a crystalline polymer powder, and the powder granulation product is heated from room temperature to a first hold temperature T Ｈ１ and then heated to the first hold temperature T Ｈ１ After holding the temperature at this temperature for 15 minutes, a first differential scanning calorimetry (DSC) measurement was performed under the condition of cooling at a temperature decreasing rate of 10°C / min. The first hold temperature T Ｈ１ exists, and the first hold temperature T Ｈ１ is the melting peak temperature T of the crystalline polymer that appears on the highest temperature side during the temperature rise in the first DSC measurement. Ｍ It is a powder granulation product at a higher temperature.

[0099] In this specification, "recrystallization" refers to the process of recrystallizing a crystalline polymer at a melting peak temperature T Ｍ This refers to the phenomenon or process by which a crystalline polymer recrystallizes during the cooling process after being heated to a higher temperature.

[0100] According to this embodiment, it is possible to provide a granulated product of crystalline polymer powder that has excellent crystallization characteristics in molding processing.

[0101] In this embodiment, the powder granules are produced in a state in which the "melt memory effect" of the crystalline polymer can be effectively utilized, thereby promoting the crystallization of the crystalline polymer (particularly a crystalline polymer with a slow crystallization rate (e.g., the biopolyester resin)). This allows the powder granules of this embodiment to exhibit excellent crystallization characteristics in molding. For example, the powder granules of this embodiment can exhibit excellent crystallization characteristics in molding, even without the use of a crystallization nucleating agent. Furthermore, the powder granules of this embodiment not only exhibit excellent moldability, but can also improve the physical properties of the molded product.

[0102] Furthermore, the powder granulated product of this embodiment has a stable shape and a high bulk density without undergoing the melt-kneading pelletizing process, which improves the working environment and has excellent feed characteristics (stability, fluidity) to processing machines.In addition, compared to pelletizing by melt-kneading, it can contribute to reducing the amount of electricity used in production, i.e., reducing the amount of carbon dioxide generated.

[0103] Many crystallization nucleating agents are artificially synthesized substances or inorganic compounds that can be blended as additives to crystalline polymers, and the powder granules according to this embodiment may also contain a crystallization nucleating agent. However, the powder granules according to this embodiment can achieve a crystallization-promoting effect without using a crystallization nucleating agent. The use of no crystallization nucleating agent can simplify the composition of the resin composition, reduce costs, and streamline production, and is also preferable from the viewpoint of "safety," which must be taken into consideration when using the resin in contact with living organisms.

[0104] This embodiment provides a powder granulated product of a crystalline polymer that has a stable shape, a high bulk density, an improved working environment, and excellent feed characteristics (stability and fluidity) to a processing machine, even without undergoing a melt-kneading pelletization process. It also contributes to reducing the amount of electricity required for production, i.e., reducing the amount of carbon dioxide generated, compared to melt-kneading pelletization. The powder granulated product of this embodiment can promote crystallization through the action of the melt memory effect, making it possible to improve moldability and physical properties without the need for the addition of a crystallization nucleating agent. Those skilled in the art will understand that the powder granulated product of this embodiment can contain a crystallization nucleating agent or can be used in combination with a crystallization nucleating agent. When the powder granulated product of this embodiment contains a crystallization nucleating agent or is used in combination with a crystallization nucleating agent, the crystallization nucleating effect of the crystallization nucleating agent can be obtained in addition to the crystallization nucleating effect of the melt memory effect.

[0105] Furthermore, the powder granulation product according to this embodiment can exhibit an excellent crystallization-promoting effect because the recrystallization temperature (Tc) can be observed in a relatively high temperature range due to the melt memory effect. Furthermore, the powder granulation product according to this embodiment has excellent durability of the effect relative to the melt residence time, so can exhibit an even more excellent crystallization-promoting effect.

[0106] The powder granules according to this embodiment are particularly useful for biopolyester resins such as polyhydroxyalkanoates (PHAs) that crystallize slowly, and can significantly improve molding processability in injection molding, compression molding, thermoforming, casting, blown film (inflation) molding, extrusion coating, injection blow molding, injection stretch blow molding, etc. Furthermore, by performing molding process on the powder granules according to this embodiment in a temperature range where the melt memory effect can be effectively utilized, various molding processes can be advantageously improved without the addition of a crystallization nucleating agent as an additional component.

[0107] A. Overview of Powder Granulation Product The powder granulation product according to this embodiment will be described below in 1) to 12).

[0108] 1) The "melt memory effect" refers to the phenomenon in which structural order in the crystalline phase remains in the melt when a crystalline polymer is heated and melted (thermoplasticized). The "melt memory effect" is a phenomenon specific to crystalline polymers, in which, even when the temperature is above the melting point, there remain regions that do not reach a disordered, random state in a short time because the relaxation time required for the polymer to change into a random aggregated state due to thermal disturbance is long.

[0109] 2) The pseudo-crystalline phase structural order (hereinafter also referred to as "melt memory structure") remaining in the polymer melt due to the "melt memory effect" can exhibit a "crystallization nucleating agent effect." When the "melt memory structure" remains in the molten resin, it acts as a starting point and increases the rate of crystal growth nuclei (also referred to as the generation frequency or nucleation rate). In other words, a large number of crystal nuclei can be generated in a short period of time, which has the advantage of accelerating the crystallization rate and shortening the molding process time. The melt memory effect can be easily confirmed, for example, by the phenomenon in DSC measurement where the recrystallization temperature obtained when the temperature is raised to a temperature above the melting point of the crystalline polymer and then cooled at a constant rate is shifted to a higher temperature than the recrystallization temperature of a comparison object (e.g., a melt-kneaded pellet made of the crystalline polymer itself).

[0110] 3) Granulation of crystalline polymer powder (preferably, compressed powder granulation using a disk pelletizer) is advantageous in terms of exhibiting the "melt memory effect." In particular, granulation of crystalline polymer powder using a compression granulation method (e.g., compressed powder granulation using a disk pelletizer) under specified conditions can effectively exhibit the "melt memory effect." Specifically, by compressing and granulating crystalline polymer powder through a die at a temperature below its melting point, the polymer powder is subjected to strong shear stress from the die wall, causing solid-phase deformation (deformation in the temperature range below the melting point) particularly in the crystalline polymer powder near the die wall. This forced solid-phase deformation is thought to promote partial oriented crystallization. It is generally known that oriented crystallization of crystalline polymers is efficiently promoted by performing a "stretching operation" in the "crystallization relaxation temperature range" between the glass transition temperature and the melting point. This effect is utilized in the stretching strengthening of fibers and films. It is presumed that an effect similar to the stretching orientation effect is caused by the solid-state deformation of the crystalline polymer powder.

[0111] 4) The crystalline phase in which oriented crystallization has progressed due to solid-phase deformation is crystallized in a flow deformation field, and the size of the crystalline phase domain (spatial size of the oriented-ordered region) can have larger structural units than the crystalline phase domain of a melt-kneaded pellet that can be obtained by natural cooling from a molten state.Therefore, even when the pellet is overheated to a temperature slightly higher than the melting point, the oriented-ordered structure of the crystalline phase is relatively likely to be maintained and preserved, and as a result, it is thought that the ``melt memory effect'' is more likely to occur.

[0112] 5) Furthermore, in oriented crystallization due to solid-phase deformation, the molecular weight of the crystalline polymer can affect the occurrence of the "melt memory effect." That is, the melt memory effect is a phenomenon that occurs due to a time delay in the process in which polymer molecular chains transition from a crystalline ordered state to a random state in a molten state. Therefore, the larger the molecular weight, the longer the relaxation time (transition time to random chains), which is advantageous in terms of the duration of the effect. From the viewpoint of being advantageous in terms of the occurrence of the melt memory effect, the weight-average molecular weight of the crystalline polymer is preferably 200,000 or more, preferably 300,000 or more, preferably 500,000 or more, and preferably 700,000 or more. The weight-average molecular weight of the crystalline polymer is, for example, 3,000,000 or less.

[0113] 6) The "melt memory effect" in powder granules of crystalline polymer powder is advantageously exhibited by compression granulation. That is, the crystalline polymer powder can be exhibited by subjecting it to forced deformation through a die or the like. Therefore, the expression of the melt memory effect is affected by the processing temperature and deformation time. For example, in compression granulation using a disk pelletizer, granulation at an appropriate processing temperature (above the glass transition point and below the melting point) and at a slow roller rotation speed can be advantageous in exhibiting the melt memory effect.

[0114] 7) Furthermore, in powder granulation products made of crystalline polymers, the above-mentioned "melt memory effect" can be advantageously exhibited by using a powder raw material obtained by pulverizing an injection-molded product or a stretched product (e.g., fiber, stretched film, blow-molded product) as the powder raw material. That is, a powder raw material obtained by pulverizing a molded product containing an oriented crystal phase in a molding process is advantageous for exhibiting the "melt memory effect." Here, "oriented crystallization" refers to the phenomenon in which crystallization progresses in a flow field caused by external forces such as flow and stretching, resulting in order in a specific direction and improved crystallinity.

[0115] 8) In general, when incorporating a crystallization nucleating agent to maximize its effectiveness, similarity in the crystalline structure of the target crystalline polymer and the crystallization nucleating agent can facilitate the growth of crystal nuclei. From this perspective, a "melt memory structure" can be the starting point for the generation of crystal nuclei made of the crystalline polymer itself, and therefore can be advantageous in functioning as a crystallization nucleating agent. In other words, the "melt memory structure" of the crystalline polymer itself can basically be the most excellent crystallization nucleating agent.

[0116] 9) The powder granules according to this embodiment can be used in molding processes such as injection molding, compression molding, thermoforming, injection molding, blown film (blowing) molding, extrusion coating, injection blow molding, and injection stretch blow molding, just like the melt-kneaded pellets. By using the powder granules according to this embodiment and performing molding processes in a temperature range where the "melt memory effect" can be effectively utilized, various molding processes can be improved without adding a crystallization nucleating agent as an additional component.

[0117] 10) From another perspective, the powder granulated material according to this embodiment is obtained by a manufacturing method different from granulation from a molten state (melt-kneaded pellets), and is a granulation method that may "not require heater heating" or "not require strand cutting," and the total amount of electricity used in the granulation process can be significantly reduced compared to the production of melt-kneaded pellets.

[0118] 11) In the production of melt-kneaded pellets by the melt-kneading granulation method, problems that arise in the process, such as "crystallization is slow and strands do not solidify sufficiently in a short time, making pelletizing difficult" and "crystallization of the melt-kneaded pellets is insufficient, so pellets self-aggregate and form blocks due to residual heat or reheating during drying." can be solved by the powder granulation method according to this embodiment.

[0119] 12) In melt-kneaded pellets containing a small amount of an inorganic substance (e.g., talc) as a crystallization nucleating agent, the contact interface between the inorganic crystallization nucleating agent and the base polymer can become a structural defect, which can become a fracture origin during film or sheet molding, resulting in reduced productivity. This is particularly disadvantageous when obtaining thin-walled molded products such as films. Furthermore, since the contact interface between the crystallization nucleating agent and the base polymer is a heterogeneous interface, poor affinity can lead to a decrease in the physical properties of various molded products. However, the powder granules according to this embodiment can promote crystallization through the crystallization nucleating action based on the "melt memory structure" of the crystalline polymer itself, eliminating the need for a crystallization nucleating agent and eliminating these concerns.

[0120] The powder granulated material according to this embodiment is heated from room temperature to a first hold temperature T Ｈ１ and then heated to the first hold temperature T Ｈ１ When the first DSC measurement was performed under the conditions of holding the sample at this temperature for 15 minutes and then lowering the temperature at a temperature lowering rate of 10°C / min, the first hold temperature T Ｈ１ The first DSC measurement is preferably carried out under a nitrogen stream.

[0121] 11 is a graph showing the results of DSC measurement (temperature decrease) showing the "melt memory effect" of the powder granules of the crystalline polymer (PHBH powder granules) obtained in Example B1. Specifically, FIG. 11 shows the melt memory effect of the powder granules of Example B1 (without the addition of a crystallization nucleating agent) at a temperature increase rate of 10°C / min from room temperature to the melting peak temperature T Ｍ (In Example B1, around 147°C) Ｈ１ (180° C. in FIG. 11) and then the first hold temperature T Ｈ１11 is a graph showing the results (during temperature decrease) of a first DSC measurement performed under conditions in which the powder granulation product of Example 1 was held at 100°C for 2 minutes, 5 minutes, 15 minutes, or 30 minutes, and then cooled at a temperature decrease rate of 10°C / min. As shown in FIG. 11 , in the powder granulation product of Example 1, which corresponds to the powder granulation product of this embodiment, an exothermic peak due to recrystallization of the crystalline polymer appears during temperature decrease in the first DSC measurement. The powder granulation product of this embodiment is a powder granulation product of a crystalline polymer powder. However, a portion of the granulated crystalline polymer powder has a "melt memory structure," which is presumed to have a more pronounced effect as crystallization progresses due to solid-phase deformation. Therefore, in molding, even without blending a crystallization nucleating agent, crystallization is promoted by the crystallization action based on the melt memory structure. Therefore, as shown in FIG. 11 , an exothermic peak due to recrystallization of the crystalline polymer appears during temperature decrease in the first DSC measurement. In this embodiment, the first hold temperature T Ｈ１ The presence of the first hold temperature T indicates the presence of a melt memory structure in the granulated crystalline polymer powder. Ｈ１ is the melting peak temperature T of the crystalline polymer that appears on the highest temperature side during the temperature rise in the first DSC measurement. Ｍ It is a higher temperature.

[0122] The powder granulated material according to this embodiment is heated from room temperature to a second hold temperature T Ｈ２ and then heated to a second hold temperature T Ｈ２ After holding the sample at this temperature for 15 minutes, the sample was cooled at a rate of 10°C / min. The second hold temperature T Ｈ２ Preferably, there is a second hold temperature T Ｈ２ is the first hold temperature T Ｈ１ The second DSC measurement is preferably carried out under a nitrogen stream.

[0123] In addition, the powder granulated product according to this embodiment has a peak temperature Tc of an exothermic peak due to recrystallization that appears during cooling in the first DSC measurement. １５ The powder granules are heated from room temperature to a first hold temperature T at a temperature increase rate of 10°C / min. Ｈ１ and then heated to the first hold temperature T Ｈ１ After holding the sample at this temperature for 2 minutes, the sample was cooled at a rate of 10°C / min. The peak temperature Tc of the exothermic peak due to recrystallization that appeared during the temperature drop was ２ It is preferable that the following formula (A) be satisfied. The third DSC measurement is preferably carried out under a nitrogen gas flow. Formula (A): 0.95≦Tc １５ / Tc ２ ≦1.05

[0124] Formula (A) is the first hold temperature T Ｈ１ The peak temperature of the recrystallization exothermic peak when held at 15 minutes (Tc １５ ) is the first hold temperature T Ｈ１ The peak temperature of the recrystallization exothermic peak when held at 400°C for 2 minutes (Tc ２ ) (preferably without shifting to the lower temperature side), and the melt memory effect is maintained with respect to the melting time. When formula (A) is satisfied, it is recognized that the powder granulated product exhibits excellent recrystallization properties. Ｈ１ For example, there is a first hold temperature T Ｈ１ is the melting peak temperature T Ｍ The second hold temperature T Ｈ２ It is sufficient that there is at least one point in the lower temperature range. １５ / Tc ２ is preferably 0.96 or more and 1.04 or less, preferably 0.97 or more and 1.03 or less, preferably 0.98 or more and 1.02 or less, and preferably 0.99 or more and 1.01 or less.

[0125] The structure of the powder granulated product according to this embodiment will be further described below.

[0126] The powder granules according to this embodiment may have an outer wall formed by melting at least a portion of the crystalline polymer powder located at the outer edge of the powder granules, and the compressed crystalline polymer powder is contained inside the outer wall.

[0127] In the powder granules according to this embodiment, the outer wall portion is located at the outer edge of the granules. In this specification, the outer wall portion is also referred to as a shell portion. The compressed crystalline polymer powder is contained inside the outer wall portion, and the crystalline polymer powder may be at least partially melted or may not be at least partially melted.

[0128] The compressed crystalline polymer powder inside the outer wall portion may be in an unmelted state. That is, at least a portion of the compressed crystalline polymer powder inside the outer wall portion may include an unmelted compressed powder form, or may include a partially melted form. A partially melted form refers to a form in which the constituent components of the crystalline polymer powder are partially melted, but do not form a fused structure strong enough to hold the crystalline polymer powder like the outer wall portion. In this specification, the inside of the outer wall portion is also referred to as a core portion. The core portion inside the outer wall portion contains compressed crystalline polymer powder, and in this specification, "compressed" means that the density of the crystalline polymer powder located in the core portion is higher than the bulk density of the crystalline polymer powder before granulation.

[0129] The outer wall (shell) of the powder granules according to this embodiment has a dense structure containing the melt of the crystalline polymer powder, while the core inside it, although compressed, has a looser structure compared to the dense structure (welded structure) of the outer wall containing the melt. In the granules of crystalline polymer powder according to this embodiment, the melt of the crystalline polymer powder forms the outer wall and holds the compressed crystalline polymer powder present in the core, so that, despite being a powder granule, the structure is stable, there is little powder falling off, and the handling and safety are excellent, and the working environment can be improved.

[0130] The outer wall (shell) has a welded structure in which at least a portion of the crystalline polymer powder located at the outer edge of the powder granules is melted. The outer wall may be smooth enough to have a glossy appearance. Alternatively, the outer wall may be formed by some of the constituent components of the crystalline polymer powder melting and partially welding with adjacent components, although not melted to the extent of forming a smooth surface. As will be described in detail later, the outer wall can be formed, for example, by melting at least a portion of the crystalline polymer powder at the contact surface with the die due to frictional heat with the wall surface or heat transfer from the wall surface during compression granulation. The thickness of the outer wall can vary depending on the production conditions of the crystalline polymer powder granules.

[0131] The core is a portion located inside the outer wall, where the compressed crystalline polymer powder is contained. The crystalline polymer powder located in the core may be porous, or may have a non-welded structure in which heat is not transferred to the core during granulation. Because the core is far from the die contact surface, the core may have a structure in which the crystalline polymer powder raw material maintains its powder shape (i.e., a non-welded structure or a powder-like structure), or a structure in which the powder polymer raw material is partially welded but retains its shape.

[0132] Furthermore, in this specification, the terms "outer wall portion (shell portion)" and "core portion" are used for the sake of simplicity, but as described above, the outer wall portion is formed by melting the crystalline polymer powder due to the heat generated during granulation, and therefore in reality there is no clear boundary between the outer wall portion (shell portion) and the core portion. The outer wall portion (shell portion) refers to a portion that includes a fused structure of the crystalline polymer powder and is located on the outer edge of the powder granules, contributing to maintaining the constant shape of the powder granules, and the core portion refers to a portion located inside the outer wall portion (shell portion).

[0133] The powder granulation product preferably has a substantially cylindrical or substantially prismatic shape, and the powder granulation product preferably has an outer wall portion on the side surface of the powder granulation product. In this embodiment, the powder granulation product preferably has a substantially cylindrical or substantially prismatic shape, and the outer wall portion is preferably formed on the side surface of the powder granulation product having a substantially cylindrical or substantially prismatic shape.

[0134] The crystalline polymer powder granules of this embodiment having the above structure can be directly supplied to various molding machines such as injection molding machines and extrusion molding machines for thermoplastic resins, or can be used as a molding material.

[0135] The powder granulated material according to this embodiment can be used as a raw material for thermoplastic resins in the production of resin compositions by melt compounding. When used as a compounding raw material, it can improve raw material supply capacity, supply stability, and supply accuracy, contributing to improved productivity. Specifically, since the powder granulated material has excellent stability when fed into equipment such as an extruder, its use can dramatically improve the productivity of resin compositions (compound processing speed per hour). Furthermore, it can significantly reduce dust pollution in the work environment, improve the occupational safety and health environment for workers, and significantly reduce the time required for cleaning equipment changeovers.

[0136] The powder granulated product according to this embodiment can be preferably obtained by using a powder compression granulation method, and the details of the production method will be described later.

[0137] The powder granules according to the present embodiment may have any suitable shape. Typically, when the powder granules are produced by compression granulation and passed through circular die holes, the basic shape is a cylindrical pellet.

[0138] In this specification, the term "die" is a general term for a tool equivalent to a "mold" for compressing and shaping a powder granulated material.

[0139] When the powder granules are cylindrical, the diameter of the powder granules is, for example, 2 mm to 7 mm, preferably 3 mm to 5 mm. The length (height) of the powder granules is, for example, 1 mm to 10 mm, preferably 2 mm to 7 mm. Such a shape results in a powder granule that is easy to handle. The diameter of the powder granules can be adjusted, for example, by the diameter of the die hole in the disc plate (die plate) during granulation, and the length can be adjusted by the distance between the disc plate and the cutter. This distance can be any appropriate distance. The distance between the disc plate and the cutter is, for example, 1 mm to 30 mm, preferably 2 mm to 20 mm, and preferably 3 mm to 10 mm.

[0140] The breaking strength of the powder granulation product according to this embodiment, as measured with a Kiya hardness tester, is preferably 1.0 kg or more, preferably 2.0 kg or more, preferably 3.0 kg or more, preferably 4.0 kg or more, preferably 5.0 kg or more, preferably 6.0 kg or more, preferably 7.0 kg or more, preferably 8.0 kg or more, preferably 9.0 kg or more, and preferably 10.0 kg or more. The upper limit may exceed the measurement limit of the Kiya hardness tester (the measurement limit for the Shiro Sangyo Co., Ltd. product "WPF1600-B" is 10 kg). Within this range, a powder granulation product with excellent handleability and melt processability can be obtained. Here, breaking strength refers to the average breaking stress (breaking load) measured by crushing 20 or more (preferably 25 or more) particles of powder granulation product in a direction perpendicular to the longitudinal direction (extrusion direction) of the powder granulation product. In the case of powder granulation, since the shell portion is made of molten resin, it is possible to maintain a stable shape as a granulation, despite being a powder granulation. The diameter of the pressure surface of the pressure attachment of the Kiya hardness tester is, for example, 5 mm.

[0141] The apparent density ratio of the powder granulation product according to this embodiment is, for example, 0.85 or more and 0.95 or less, preferably 0.87 or more and 0.94 or less, preferably 0.89 or more and 0.93 or less, and preferably 0.90 or more and 0.92 or less. The closer the apparent density ratio is to 1, the lower the air bubble content of the powder granulation product. When the apparent density ratio of the powder granulation product is 0.95 or less, the granulation productivity of the powder granulation product can be efficiently increased. Furthermore, when the apparent density ratio is 0.85 or more, it can be advantageous for effectively exhibiting the melt memory effect.

[0142] The apparent density ratio is expressed by the following formula: "Apparent density ratio" = "Apparent density of powder granulated product" / "Apparent density of melt-kneaded pellets"

[0143] The "apparent density of the powder granules" or the "apparent density of the melt-kneaded pellets" can be obtained by measuring the apparent density of 10 or more (preferably 15 or more) particles of the "powder granules" or "melt-kneaded pellets" using a hydrometer (manufactured by A&D Co., Ltd., trade name "ELECTRONIC DENSIMETER MDS-300") and calculating the average value. The "apparent density of the melt-kneaded pellets" is measured by preparing melt-kneaded pellets without air bubbles by heating the composition constituting the powder granules at a temperature equal to or higher than the melting point of the crystalline polymer using a melt-kneading device such as a twin-screw extruder, and then measuring the apparent density of the melt-kneaded pellets.

[0144] Regarding the powder granulation product according to this embodiment, the bulk density of the crystalline polymer powder before granulation is ρ １ , the bulk density of the powder granulation product is ρ ２ When this is the case, the bulk density ratio ρ ２ / ρ １ The value of the bulk specific gravity ratio ρ is, for example, 0.90 or more and 3.00 or less, preferably 1.00 or more and 2.50 or less, preferably 1.10 or more and 2.00 or less, and preferably 1.10 or more and 1.80 or less. ２ / ρ １ When the bulk specific gravity ratio ρ is 0.90 or more, the melt memory effect of the powder granulated product can be effectively exhibited. ２ / ρ １When the value is 3.00 or less, the granulation productivity can be improved, and a powder granulated product having excellent breaking strength can be effectively obtained.

[0145] The bulk density of the powder granulated product may be any appropriate bulk density, but is preferably 0.3 kg / L to 2.0 kg / L, and more preferably 0.5 kg / L to 1.0 kg / L. Increasing the bulk density increases the supply speed and supply stability of the powder granulated product to various processing machines.

[0146] The crystalline polymer powder used as the raw material before granulation may have any bulk density, but the bulk density of the crystalline polymer powder is preferably 0.05 kg / L to 1.0 kg / L, more preferably 0.1 kg / L to 0.8 kg / L, and even more preferably 0.2 kg / L to 0.6 kg / L. When the bulk density of the crystalline polymer powder is within this range, compression granulation is easy to carry out.

[0147] The bulk density is calculated by allowing the "crystalline polymer powder before granulation" or the "powder granules" to fall naturally into a measure until it is filled to the brim, weighing it to a volume of exactly 1 liter, and measuring the mass (unit: kg / L).

[0148] The moisture content of the powder granulation product may be any appropriate moisture content. In addition to the moisture content originally contained in the raw material powder, water may be added to the powder to facilitate granulation. When water is added during granulation, the amount of water to be added will be described later.

[0149] During the granulation process of powder granulation material, localized heat generation can lead to clogging of the die, so it can be advantageous for continuous granulation to add an appropriate amount of moisture to the granulation material and use the heat of vaporization of the water to prevent excessive temperature rise during granulation.

[0150] The powder granules may be dried after granulation, but the final moisture content of the powder granules is preferably 10% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, preferably 1.0% by mass or less, and preferably 0.5% by mass or less. The moisture content of the final powder granules can be appropriately selected depending on the intended use.

[0151] It is preferable that the powder granulation product is granulated without adding water. If the moisture content of the powder granulation product is low, a drying step after granulation may not be necessary. If granulation can be performed without using water, the drying step is not necessary, and the amount of carbon dioxide emitted during the powder granulation process can be significantly reduced.

[0152] The moisture content of the powder granulated product granulated "without adding water" is, for example, 1.0 mass% or less, preferably 0.5 mass% or less, preferably 0.3 mass% or less, and preferably 0.2 mass% or less.

[0153] The moisture content of the powder granules is measured using an infrared moisture meter as described below.

[0154] The crystalline polymer powder used as a raw material can be any suitable crystalline thermoplastic resin.

[0155] Specific examples of crystalline polymers include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), polypropylene (PP), polyurethane (PUR), fluorine-based resin, polyamide (PA), polyacetal (POM), polyester (PET, PBT, aliphatic polyester, aliphatic aromatic polyester, etc.), etc. The crystalline polymers may be used alone or in combination of two or more.

[0156] The weight-average molecular weight (Mw) of the crystalline polymer, which is advantageous for effectively exhibiting the melt memory effect, is 200,000 or more, preferably 300,000 or more, preferably 500,000 or more, and preferably 700,000 or more. The melt memory effect is exhibited by a time delay in the process in which polymer molecular chains transition from a crystalline order state to a random state in a molten state. Therefore, the larger the molecular weight, the longer the relaxation time (transition time to random chains), which is advantageous in terms of the durability of the effect. A weight-average molecular weight of 200,000 or more of the crystalline polymer is preferable because it can effectively suppress the reduction or deactivation of the melt memory effect due to thermal disturbance. On the other hand, if the molecular weight of the crystalline polymer is too large, the viscosity becomes too high, which is unfavorable for causing solid-phase deformation and also tends to make powder granulation itself difficult. Therefore, the weight-average molecular weight of the crystalline polymer is preferably 3,000,000 or less, preferably 2,000,000 or less, preferably 1,500,000 or less, and preferably 1,000,000 or less.

[0157] The weight-average molecular weight (Mw) of a crystalline polymer can be determined as a weight-average molecular weight converted to polystyrene by gel permeation chromatography (GPC). For example, it can be evaluated by GPC using a Showa Denko K.K. "Shodex GPC-101" GPC apparatus, a polystyrene gel (Shodex K-804) column packing material, and an organic solvent mobile phase (e.g., chloroform). The column apparatus, column packing material, and organic solvent mobile phase can be appropriately selected depending on the crystalline polymer.

[0158] The crystalline polymer powder may be a powdered resin obtained through its production process, i.e., a powder resulting from the production process, or may be a powdered resin obtained by pulverizing a non-powdered resin such as a pelletized resin, a lump of resin, or a resin molded body. The pulverized powdered resin can be obtained by cooling a molded product, pellets, or a sprue or runner generated during injection molding at room temperature or, if necessary, with dry ice or liquid nitrogen, and then using a pulverizer (for example, Dalton products under the trade names "Neamil," "Sylphid Mill," "Atomizer," or "Impact Mill").

[0159] Powder raw materials obtained by pulverizing molded products containing oriented crystal phases resulting from molding processes, such as injection molded products or films, fibers, blown containers, etc., which include stretching processes, are advantageous in terms of exhibiting the "melt memory effect." Here, "oriented crystallization" refers to the phenomenon in which crystallization progresses under external influences such as flow and stretching, resulting in orderly crystallization in a specific direction and improved crystallinity.

[0160] The powder granulated product according to this embodiment has a melting peak temperature (T Ｍ It is preferable from the viewpoint of stable continuous production using various powder granulators that the crystalline polymer powder contains at least one crystalline polymer powder having a temperature of from 70°C to 200°C. Ｍ [°C] is preferably 70°C or higher and 200°C or lower, more preferably 75°C or higher and 190°C or lower, more preferably 80°C or higher and 180°C or lower, and even more preferably 90°C or higher and 170°C. Ｍ By using a crystalline polymer powder having a temperature [°C], the melt memory effect can be more effectively exhibited.

[0161] A biodegradable resin may be used as the crystalline polymer. Examples of biodegradable resins include aliphatic polyester resins (e.g., homopolymers or copolymers of polyhydroxyalkanoate (PHA), polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polyhydroxyvalerate, etc., and modified products of these homopolymers or copolymers), aliphatic / aromatic polyester resins (e.g., block polymers or random polymers of aliphatic carboxylic acids or hydroxy acids, aromatic dicarboxylic acids, and 1,3-propanediol, etc.). One type of biodegradable resin may be used alone, or two or more types may be used in combination.

[0162] Polyhydroxyalkanoates (PHAs) can be compounds produced in the bodies of microorganisms that feed on carbohydrates, fats, oils, etc. Such polyhydroxyalkanoates are primarily extracted as powdery polymers.

[0163] Polyhydroxyalkanoates contain hydroxyalkanoic acid, a raw material component, as a polymerization component and have at least a repeating unit derived from the hydroxyalkanoic acid. Polyhydroxyalkanoates may be artificially synthesized or biosynthesized by a microorganism. Examples of hydroxyalkanoic acids include glycolic acid, 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3-hydroxynanoate, 3-hydroxydecanoate, 3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate, 4-hydroxybutyrate, 4-hydroxyvalerate, 5-hydroxyvalerate, and 6-hydroxyhexanoate. The number of carbon atoms in the hydroxyalkanoic acid may be 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, or 8 or more, preferably 3 or more. The number of carbon atoms of the hydroxyalkanoic acid may be 15 or less, 12 or less, 10 or less, 8 or less, 6 or less, or 4 or less, preferably 10 or less, particularly preferably 6 or less. One type of hydroxyalkanoic acid may be used alone, or two or more types may be used in combination.

[0164] Preferred examples of the polyhydroxyalkanoate include poly(3-hydroxyalkanoate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0165] The particle size of the crystalline polymer powder as a raw material may be any appropriate particle size depending on the form of the crystalline polymer powder, as long as the effects of this embodiment can be obtained. The maximum particle size of the crystalline polymer powder particles is preferably 5 mm or less, and the minimum particle size is preferably 0.0001 mm or more.

[0166] The average particle size of the crystalline polymer powder is, for example, 0.001 mm or more and 1.0 mm or less. The average particle size of the crystalline polymer powder is preferably 1.0 mm or less, preferably 0.01 mm or more and 0.8 mm or less, and preferably 0.1 mm or more and 0.5 mm or less. In this specification, the average particle size can be measured by a laser diffraction method. The average particle size of the resin powder can be the particle size (d50) at 50% of the cumulative size in the cumulative particle size distribution on a volume basis. One type of crystalline polymer powder may be used alone, or two or more types may be used in combination.

[0167] The crystalline polymer powder may be a powdered resin obtained through its production process, i.e., a powder due to the production process, or may be a powdered resin obtained by pulverizing a non-powdered resin such as a pelleted resin, a lump resin, or a resin molded body. The pulverized powdered resin can be obtained by cooling a molded product, pellets, or a sprue or runner generated during injection molding at room temperature or, if necessary, using dry ice or liquid nitrogen, and then pulverizing it with a pulverizer (e.g., Dalton products under the trade names "Nea Mill," "Sylphid Mill," "Atomizer," or "Impact Mill").

[0168] The powder granules according to this embodiment may contain any suitable additives as needed. The additives may be in a solid form such as a powder, or may be in a liquid form. Examples of additives include binders, dispersants, crystallization nucleating agents, antioxidants, light stabilizers, foaming agents, UV absorbers, antiblocking agents, heat stabilizers, impact modifiers, antibacterial agents, compatibilizers, processing aids, lubricants, coupling agents, hydrolysis inhibitors, oxygen scavengers, and colorants (dyes and pigments). One type of additive may be used alone, or two or more types may be used in combination.

[0169] The additive may be in the form of a solid such as a powder, or may be in the form of a liquid.

[0170] The content of the additive in the powder granules is, for example, 10.0% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, and more preferably 1.0% by mass or less.

[0171] The powder granules according to the present embodiment may contain a binder as an additive. Here, the term "binder" refers collectively to compounds that are present between the crystalline polymer powder particles other than the constituent components of the raw material crystalline polymer powder, bind the powder particles together, and enhance the breaking strength of the granules. However, various compounds that exhibit a binding effect, preferably water-dispersible or water-soluble polymer compounds, polysaccharides, etc., may be appropriately selected and used as the binder, as needed.

[0172] In one embodiment, it is preferable to melt and bind some of the components of the crystalline polymer powder to form a powder granule, and it is preferable not to blend a binder.

[0173] The content of the binder is usually 10.0% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, preferably 1.0% by mass or less, preferably 0.5% by mass or less, preferably 0.1% by mass or less, and preferably 0% by mass (undetectable), relative to the total mass of the powder granules.

[0174] In one embodiment, a dispersant is preferably used as the additive. A surfactant is preferably used as the dispersant. The hydrophilic / hydrophobic balance of the dispersant (surfactant) can be controlled by adjusting the degree of esterification of the dispersant compound, the type of fatty acid (presence or absence of hydroxyl groups, saturated or unsaturated fatty acid, alkyl chain length), the degree of polymerization, etc. The use of a dispersant can sometimes bring about benefits such as "improving the productivity (discharge rate) of powder granulation products," "reducing frictional heat during granulation," and "enhancing the cleanability of the granulation equipment."

[0175] Examples of dispersants include fatty acids, fatty acid metal salts, fatty acid sulfonates, fatty acid amides, acrylamides, polyhydric alcohol fatty acid esters, polyglycerin fatty acid esters, etc. One type of dispersant may be used alone, or two or more types may be used in combination.

[0176] In one embodiment, the dispersant is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerin fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids.

[0177] The polyhydric alcohol fatty acid ester is an ester compound composed of a polyhydric alcohol and a fatty acid. Examples of the polyhydric alcohol fatty acid ester include esters of a polyhydric alcohol such as pentaerythritol or glycerin with a fatty acid having 8 or more carbon atoms (preferably 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms).

[0178] Fatty acid amides are compounds having a structure formed by dehydration condensation of a fatty acid with ammonia or a primary or secondary amine. Examples of fatty acid amides include saturated fatty acid monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide.

[0179] Polyglycerol fatty acid esters are ester compounds composed of polyglycerol and fatty acids. Examples of polyglycerol fatty acid esters include diglycerol palmitate, diglycerol stearate, diglycerol oleate, decaglycerol palmitate, decaglycerol stearate, and decaglycerol oleate.

[0180] The content of the dispersant is typically 0% by mass to 10.0% by mass, preferably 0.01% by mass to 9.0% by mass, preferably 0.1% by mass to 7.0% by mass, and more preferably 0.3% by mass to 5.0% by mass, based on the total mass of the powder granules. The content of the dispersant is typically 10.0% by mass or less, preferably 5.0% by mass or less, preferably 3.0% by mass or less, preferably 1.0% by mass or less, preferably 0.5% by mass or less, preferably 0.1% by mass or less, and preferably 0% by mass (undetectable), based on the total mass of the powder granules.

[0181] In the powder granulation product of this embodiment, a crystallization nucleating agent can be blended as an additive. Examples of such crystallization nucleating agents include organic metal salt compounds such as metal phosphate esters, metal benzoates, metal pimelate salts, metal rosin salts, metal oxalates, and metal fatty acid salts; organic compounds such as aliphatic organic esters, triallyl phosphate, polyalkylene glycols or their derivatives, aliphatic polyesters, and benzylidene sorbitol; dyes and pigments such as pentaerythritol, quinacridone, cyanine blue, and carbon black; minerals such as talc, mica, kaolin, clay, carbonate minerals, metal oxides, and metal sulfates; and polymer compounds such as ionomers and high-melting-point polyamides. In one embodiment, talc, mica, kaolin, or calcium carbonate is used as the crystallization nucleating agent. One crystallization nucleating agent may be used alone, or two or more may be used in combination.

[0182] The content of the crystallization nucleating agent in the powder granules is, for example, 0.1% by mass or more and 10.0% by mass or less, preferably more than 0.1% by mass and less than 10.0% by mass, preferably 0.2% by mass or more and 7.0% by mass or less, and preferably 0.3% by mass or more and 5.0% by mass or less.

[0183] In one embodiment, the powder granules are substantially free of a crystallization nucleating agent. The powder granules according to this embodiment can exhibit a "melt memory effect," and therefore can exhibit excellent crystallization characteristics in molding processes, even when using a crystalline polymer (especially a crystalline polymer with a slow crystallization rate (e.g., the biodegradable resin)), without using a crystallization nucleating agent.

[0184] "Substantially free of crystallization nucleating agent" means, for example, that the content of crystallization nucleating agent in the powder granule is 0.1% by mass or less, preferably that the content of crystallization nucleating agent in the powder granule is less than 0.1% by mass, preferably that the content of crystallization nucleating agent in the powder granule is 0.01% by mass or less, preferably that the content of crystallization nucleating agent in the powder granule is 0.005% by mass or less, preferably that the content of crystallization nucleating agent in the powder granule is 0.001% by mass or less, preferably that the content of crystallization nucleating agent in the powder granule is 0.001% by mass or less, preferably that the content of crystallization nucleating agent in the powder granule is 0% by mass (undetectable).

[0185] B. Method for Producing Crystalline Polymer Powder Agglomerate The powder agglomerate according to this embodiment can be produced, for example, in a temperature range of not less than the glass transition temperature and not more than the melting point of the crystalline polymer raw material.

[0186] The powder granules of this embodiment can be preferably obtained by compressing the powder granules through a "die" and causing a portion of the crystalline polymer powder to undergo solid-state deformation through the die contact area, but are preferably obtained by a compression granulation method in which the crystalline polymer powder is extruded through a die hole, and the shell portion is formed when the crystalline polymer powder is extruded through the die hole, i.e., during extrusion granulation, the constituent components of the crystalline polymer powder undergo solid-state deformation and partial melting at the contact surface with the wall of the die hole due to frictional heat with the wall or heat transfer from the wall.

[0187] By forming the shell portion, the powder granules can be maintained in a consistent shape (e.g., cylindrical or rectangular), and a powder granule with excellent quality stability (shape stability, uniform hardness), low fineness, high hardness, and ease of handling can be obtained.

[0188] The powder granulated product according to this embodiment is a granulated product obtained by a granulation method different from pelletization by melt kneading (melt kneading pelletization method), and is granulated using machinery different from melt kneading processing equipment, but it is possible to reduce the amount of electricity used in the process and significantly reduce the amount of carbon dioxide generated in the production of the powder granulated product. Furthermore, the powder granulated product according to this embodiment can be granulated in a process that does not reach the high temperatures that enable plasticization and melting, so it has the advantage of having a small thermal history compared to the crystalline polymer.

[0189] In one embodiment, the powder granules can be obtained by granulation without using water, which eliminates the need for a drying step, thereby reducing the amount of electricity used for granulation and further reducing the amount of carbon dioxide emitted during the process.

[0190] When the crystalline polymer powder contacts the die during compression granulation of the powder granules, frictional heat may be generated between the die wall and the powder. At this time, the temperature of the powder granules rises due to the frictional heat, and the temperature of the granules immediately after granulation (Tp; unit ° C) is the melting point Tm [° C] of the crystalline polymer (the melting peak temperature T of the crystalline polymer that appears on the highest temperature side in the DSC measurement of the powder granules as described above). Ｍ If the temperature (Tp) of the granules immediately after granulation is too high (this may differ from the Tm [°C]), the crystalline polymer powder will melt excessively, adhering to the die wall or causing clogging of the die holes, making continuous granulation impossible. On the other hand, if the temperature (Tp) of the granules immediately after granulation is too low below the Tm of the crystalline polymer, the raw resin powder will not have cohesive strength and will not form granules in the powder state, or will form granules that easily collapse under compression, making it difficult to obtain granules in a stable shape.

[0191] In order to stably obtain crystalline polymer powder granules having a melt memory effect, it is preferable that the granule temperature (Tp) immediately after granulation and the melting point (Tm) of the crystalline polymer are within a specific range. In one embodiment, compression granulation is carried out under conditions where the granule temperature (Tp) is in a temperature range from the glass transition temperature (Tg) to the melting point (Tm). Preferably, compression granulation is carried out under conditions where Tp is within the "crystallization relaxation temperature range" which exists in the temperature range from the glass transition temperature (Tg) to the melting point (Tm), where the crystalline phase of the crystalline polymer in a solid state below the melting point can be deformed by external stress.

[0192] Here, the glass transition temperature Tg, the melting point Tm, and the "crystallization relaxation temperature range" can be measured by a measurement method such as dynamic viscoelasticity measurement or DSC measurement.

[0193] A preferred method for producing the powder granulated product according to this embodiment includes a compression granulation step of granulating the crystalline polymer powder by a compression granulation method, and the temperature of the granulated product immediately after granulation, Tp (°C), is equal to or higher than the melting peak temperature T of the crystalline polymer. Ｍ This is a method in which the compression granulation step is carried out under the following conditions. The compression granulation method is preferably a compression granulation method in which a crystalline polymer powder is extruded through die holes. The compression granulation step is preferably carried out under conditions in which the temperature of the granules immediately after granulation, Tp (°C), and the melting point of the crystalline polymer, Tm (°C), satisfy formula (1), preferably formula (2), and more preferably formula (3). Formula (1): Tm - 100 ≦ Tp ≦ Tm Formula (2): Tm - 90 ≦ Tp ≦ Tm Formula (3): Tm - 80 ≦ Tp ≦ Tm

[0194] The temperature of the granules (Tp) immediately after granulation can be measured using a contact thermocouple. The temperature of the granules (Tp) immediately after granulation can be measured by bringing the powder granulation apparatus into a state where granulation can be performed stably, stopping the apparatus during granulation, and inserting a thermocouple directly into the die section or the powder granules inside the die holes to quickly measure the temperature. Measurements are performed at least three times (preferably five times), and the average value is taken as Tp. In this case, even if the powder adheres to the die wall or the die holes become clogged, making granulation impossible, a thermocouple is similarly inserted directly into the powder to measure the temperature.

[0195] In order to efficiently obtain the powder granulation product according to this embodiment, it is most effective to control the temperature of the die that comes into direct contact with the powder. That is, it is preferable to provide a mechanism for heating the die by providing a heater or a heat medium flow path for temperature control, or a mechanism for cooling by providing a cooling medium flow path, etc., to control the temperature of the die so as to satisfy the temperature condition of formula (1).

[0196] In general compression granulation equipment, due to the simplicity of the equipment, it is often a simple structure that does not allow direct temperature control of the die. However, even in such cases, the temperature of the granulated material immediately after granulation (Tp) can be changed and controlled by methods such as the number of rotations of the rollers of the granulation equipment, the diameter of the die holes, the effective pressurized length of the die holes, the feed rate of the raw material powder, the contact area and contact time between the raw material powder and the die surface, and insulation or cooling of the granulation equipment.

[0197] In the absence of a temperature control device for the die, temperature control can be performed by balancing the temperature rise due to frictional heat during granulation with the heat dissipation to the outside. In order to efficiently obtain a powder granule by setting the conditions to satisfy formula (1), the melting point Tm of the crystalline polymer powder is preferably 70°C or higher and 200°C or lower, more preferably 80°C or higher and 180°C or lower, and even more preferably 90°C or higher and 170°C or lower. Ｍ By using a crystalline polymer powder having the above structure, the melt memory effect is more likely to be exhibited advantageously.

[0198] The crystalline polymer powder may be a single component or a combination of two or more components. In particular, when there is a large difference between the melting point Tm of the target crystalline polymer powder and the granulation temperature (Tp) and it is difficult to set the granulation temperature so as to satisfy any one of the conditions of the above formulas (1) to (3), a thermoplastic resin having a melting point lower than the granulation temperature may be blended to obtain a granulation product as a mixture.

[0199] When the crystalline polymer powder is composed of two or more components, or when two or more melting points are observed, it is preferable to set the melting point Tm of the component of the crystalline polymer powder having the lowest melting point Tm as Tm in formula (1), and to perform granulation by setting conditions (e.g., die temperature) such that the temperature of the granules immediately after granulation (Tp) falls within the range satisfying formula (1). Preferably, conditions (e.g., die temperature) are set such that formula (1) is satisfied for all melting points Tm of the components of the crystalline polymer powder.

[0200] The content of the crystalline polymer powder in the powder granules is, for example, 90% by mass or more, preferably 95% by mass or more, preferably 96% by mass or more, preferably 97% by mass or more, preferably 98% by mass or more, preferably 99% by mass or more, preferably 99% by mass or more.

[0201] When the crystalline polymer powder is composed of two or more components, the component having the lowest melting point of the crystalline polymer powder accounts for, for example, 50% by mass or less, preferably 30% by mass or less, and preferably 10% by mass or less of the total amount of the crystalline polymer powder.

[0202] In this specification, the melting point Tm of the crystalline polymer powder can be measured by a differential scanning calorimeter (DSC). In DSC measurement, a sample of the crystalline polymer powder, usually about 5 mg, is weighed into a sample dish and heated at a rate of 10°C / min under a nitrogen gas flow to determine the melting point Tm. In this specification, the melting point Tm of the crystalline polymer powder is defined as the "endothermic peak temperature" of crystalline melting observed when the temperature is raised at a rate of 10°C / min.

[0203] It is acceptable for multiple endothermic peaks of crystalline melting to appear, and multiple endothermic peaks may often appear in biopolyesters.

[0204] Powder granulation products can be produced using various powder granulators, but preferred examples include compression granulators such as disc pelletizers, screw extrusion granulators, briquetting granulators, compaction granulators, and tableting granulators. Among the above examples, the disc pelletizer is preferably used from the viewpoints of granulation productivity and the quality and shape uniformity of the resulting powder granulation products. The disc pelletizer can also be used in a "semi-wet granulation method" that incorporates an appropriate amount of moisture, but in this embodiment, granulation may be performed without using water. In this case, a drying step may be unnecessary. Granulation without using water can reduce the amount of energy required in the drying step and significantly reduce the amount of carbon dioxide emitted during the process.

[0205] When the crystalline polymer powder is a mixture containing two or more powder raw materials, it is preferable to mix them uniformly using any appropriate mixer. Examples of mixers include a Henschel mixer, a Nauta mixer, a powder kneader (KDH, KDA, CKD, CPM) (Dalton), a Spartan mixer (SPM) (Dalton), and an SP granulator (SPG) (Dalton). To obtain a preferable mixture with excellent granulation properties, it is preferable that the mixing and stirring device has appropriate stirring blades. For example, when using a Henschel mixer, it is preferable that the mixer blades be a combination of upper and lower blades, with the upper blade being a Y1 blade (trade name, manufactured by Nippon Coke Co., Ltd.) and the lower blade being an S0 blade (trade name, manufactured by Nippon Coke Co., Ltd.). It is also preferable to install a deflector in the stirring vessel and perform mixing. In other words, a mixing process that can uniformly disperse each component throughout the mixture is advantageous in improving the productivity and quality stability of the final powder granules.

[0206] A "semi-wet granulation method" can also be employed, but the amount of water to be blended can be any appropriate amount depending on the properties of the powder (such as water absorption). In this case, the amount of water to be blended is 3 to 30 parts by mass, preferably 5 to 25 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the crystalline polymer powder. The semi-wet method can be employed when the granulation properties are not stable in the granulation step.

[0207] The basic structure of a disc pelletizer includes one (flat die) or two (cylindrical die) discs with numerous 2 mm to 30 mm holes, and a roller for pressure-feeding raw materials through the holes in the disc. Crystalline polymer powder (which may contain moisture) supplied between the disc and roller, or between the two discs, is forced into the holes in the disc as the rollers rotate, forming a cylindrical extrudate. The extruded granules are cut on the back surface of the disc with a cutter or the like to obtain pellet-shaped powder granules. The length of the granules can be adjusted by the distance between the back surface of the disc and the cutter, the number of rotations of the roller, etc. The distance between the disc plate and the cutter can be any appropriate distance. The distance between the disc plate and the cutter is, for example, 1 mm to 30 mm, more preferably 2 mm to 20 mm, and even more preferably 3 mm to 10 mm.

[0208] More specifically, the disc pelleting method includes a roller disc die method, a roller ring die method, a double die method, a flat die method, etc. An example of a commercially available disc pelleting machine is the Disc Pelletter F Series manufactured by Dalton.

[0209] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to these examples. Note that parts and percentages are based on mass unless otherwise specified.

[0210] (Test Examples Related to the First Aspect: Example A and Comparative Example A) [Evaluation] The powder granules obtained in Example A and Comparative Example A were evaluated by the following method. (1) Granulation properties (whether granulation is possible or not) The obtained powder granules were checked, and the granulation properties were evaluated according to the following criteria. A: A powder granule with a core-shell structure was obtained, and molten polymer was clearly observed in the shell portion. B: A powder granule with a core-shell structure was obtained, and molten polymer was partially observed in the shell portion. C: A powder granule with a core-shell structure was obtained, although it was unstable, and a small amount of molten polymer was observed in the shell portion. D: The granules were unstable and prone to collapse. E: The granules remained in a "powder-like shape" or could not be granulated due to "die clogging".

[0211] (2) Cross-sectional observation photograph of granulated product A slice (thickness: 0.5 mm) was cut out from the obtained powder granulated product using a razor blade perpendicular to the extrusion direction from the die, and the cut cross section was observed under an optical microscope.

[0212] (3) Bulk density The dried powder granules were allowed to fall naturally into a 1-liter measure, filled to the brim, and weighed to a volume of exactly 1 liter. The mass was measured to calculate the bulk density (unit: kg / L) of the powder granules.

[0213] (4) Moisture Content The moisture content (unit: mass%) remaining in the powder granules was measured using an infrared moisture meter (FD-660 manufactured by Kett Electric Laboratory).

[0214] (5) Breaking Strength The breaking stress (unit: kg) of the powder granules was measured using a Kiya hardness tester (manufactured by Shiro Sangyo Co., Ltd., product name "WPF1600-B"). The measured value was the average value of 25 particles of powder granules. That is, the powder granules were set in the hardness tester so that the side of the powder granules was the bottom, and the breaking stress was measured by crushing the side of the powder granules using a cylindrical presser with a diameter of 5 mm. In other words, the breaking stress was measured by crushing the powder granules in a direction perpendicular to the longitudinal direction (extrusion direction). A: Breaking strength of 10 kg (measurement limit) or more B: Breaking strength of 5.0 kg or more but less than 10 kg C: Breaking strength of 2.0 kg or more but less than 5.0 kg D: Breaking strength of 0.5 kg or more but less than 2.0 kg E: Breaking strength less than 0.5 kg, or the obtained powder granules were in a powder state.

[0215] (6) Carbon dioxide emissions (CO ２ ) amount of electricity used in powder granulation is calculated based on the basic emission coefficient of 0.000362 [tons-CO ２ / kWh] to calculate the carbon dioxide emissions (CO ２ ) amount calculated (unit: kg(CO ２ ) / kg) was calculated.

[0216] [Production Example 1] Acrylic Resin Powder Granules (Production of Acrylic Resin Powder) Using a polymerization apparatus equipped with a stirrer, reflux condenser, thermometer, nitrogen gas inlet tube, and feed pump, 140 parts by weight of water, 0.05 parts by weight of sodium dodecylbenzenesulfonate, and 0.1 parts by weight of sodium sulfate were mixed to obtain a mixture. After the mixture was purged with nitrogen at 80°C, 0.1 parts by weight of potassium persulfate was added. Next, while stirring, a monomer mixture consisting of 90 parts by weight of methyl methacrylate (also referred to as MMA) and 10 parts by weight of butyl acrylate (also referred to as BA) was continuously added over 180 minutes to carry out emulsion polymerization. At 45 minutes and 90 minutes after the start of addition of the monomer mixture, 0.3 parts by weight of sodium dodecylbenzenesulfonate was added. After completion of the addition of the monomer mixture, the mixture was stirred for an additional hour to carry out polymerization, and the reaction was terminated to obtain an acrylic copolymer latex.

[0217] The obtained latex was cooled to room temperature, salted out with calcium chloride, coagulated, washed with water, and dried to obtain acrylic resin powder A1.

[0218] The resulting acrylic resin powder A1 was sieved through a 10-mesh wire screen (mesh opening: approximately 2.5 mm) and the powder that completely passed through was collected. The bulk density of the powder was 0.32 kg / L, and the glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC, Hitachi High-Tech Science Corporation, product name "DSC6220") to find that it was 81°C.

[0219] [Example A1] (Production of acrylic resin powder granules) The obtained acrylic resin powder A1 was used as a raw material and fed into a disc pelletizer (manufactured by Dalton, product name "Disc Pelleter F-5 / 11-175"), and pellet-shaped powder granules were produced at a roller rotation speed of 108 rpm. The thickness of the die plate of the disc pelletizer was 15 mm, and the hole diameter was 3 mmφ. The length (referred to as the effective length) within the die plate over which the powder received compressive stress from the die wall surface was 10 mm.

[0220] The temperature of the powder granules immediately after granulation was changed by factors such as the number of rotations of the rollers of the granulator, the effective pressurizing length of the die holes, and heating or cooling of the die plate.

[0221] The temperature of the granules immediately after granulation was measured by stopping the apparatus after granulation had stabilized, inserting a thermocouple directly into the die hole, and quickly measuring the temperature of the compressed powder inside the die. This measurement was performed five times, and the average value was taken as the temperature of the granules immediately after granulation (Tp). When granulation became impossible due to reasons such as the powder sticking to the die or clogging, a thermocouple was similarly inserted directly into the powder to measure its temperature.

[0222] Example A1 is an example in which the temperature of the granules immediately after granulation (Tp) was −5°C (i.e., the temperature of the granules was 76°C) relative to the softening initiation temperature (81°C) of the raw material acrylic resin powder A1, and stable, approximately cylindrical granules were obtained.

[0223] A photograph of the appearance of the powder granules of Example A1 is shown in Figure 1. As shown in Figure 1, compressed granules in a substantially cylindrical shape were stably obtained.

[0224] The side of the powder granules obtained in Example A1 had an outer wall structure (shell structure) containing the melted components of the thermoplastic resin powder, and traces of unmelted powder were confirmed inside the outer wall structure (core portion). Figure 2 shows a cross-sectional photograph of the powder granules obtained in Example A1 taken on a plane perpendicular to the longitudinal direction (extrusion direction).

[0225] The powder granules of Example A1 had a bulk density of 0.58 kg / L, a moisture content of 0.12 mass%, and a granule breaking strength of 6.9 kg, and were therefore excellent in handleability.

[0226] Example A2 Example A2 is an example in which the granule temperature (Tp) immediately after granulation was −15° C. (i.e., the granule temperature was 66° C.) lower than the softening initiation temperature (81° C.) of the raw material acrylic resin powder A1. The granule temperature was controlled by reducing the roller rotation speed. The obtained powder granule had a core-shell structure, similar to Example A1.

[0227] The powder granules of Example A2 had a bulk density of 0.52 kg / L, a moisture content of 0.2 mass%, and a granule breaking strength of 5.1 kg, and were therefore excellent in handleability.

[0228] Example A3 Example A3 is an example in which the granule temperature (Tp) immediately after granulation was −26° C. (i.e., the granule temperature was 55° C.) lower than the softening initiation temperature (81° C.) of the raw material acrylic resin powder A1. The granule temperature was controlled by further reducing the roller rotation speed and forcibly cooling by blowing air onto the disc plate. The obtained powder granule had a core-shell structure, similar to Example A1.

[0229] The powder granules of Example A3 had a bulk density of 0.6 kg / L, a moisture content of 0.15 mass %, and a granule breaking strength of 2.7 kg, and were therefore excellent in handleability.

[0230] Table 1 shows the production conditions for the powder granules obtained in Examples A1 to A3 and the results of various measurements of the powder granules.

[0231] Comparative Example A1 is an example in which the temperature of the granules immediately after granulation (Tp) was −41° C. (i.e., the granule temperature was 40° C.) relative to the softening starting temperature (81° C.) of the raw material acrylic resin powder A1. The granule temperature was controlled by changing the effective length of the die to 5 mm and forcibly cooling the disc plate.

[0232] In Comparative Example A1, the acrylic resin powder A1 passed through the die holes in the powder state, and no granules could be obtained.

[0233] Comparative Example A2 is an example in which the temperature of the granules immediately after granulation was +14°C higher than the softening starting temperature (81°C) of the raw material acrylic resin powder A1 (i.e., the granule temperature was 95°C). The granule temperature was controlled by forcibly heating the disc plate using an external heater.

[0234] In Comparative Example A2, the acrylic resin powder A1 clogged the die holes, and no granules could be obtained.

[0235] The powder granules obtained in Examples A1 to A3 and Comparative Examples A1 and A2 were evaluated and the results are shown in Table 1.

[0236]

[0237] [Example A4] Biopolyester Powder Granules Pellets of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), a type of PHA and a copolymer polyester of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid (manufactured by Kaneka Corporation, trade name "Green planet X131A", hexanoate content 6%) were pulverized and sieved through a 10-mesh wire screen to obtain biopolyester powder A2.

[0238] DSC measurement of biopolyester powder A2 revealed that the softening onset temperature (Ts) was 80° C. As shown in Figure 3, the softening onset temperature (Ts) was determined from the temperature at the intersection of the baseline from the low temperature part and the tangent to the inflection point on the melting onset side of the first observed crystalline melting endothermic peak.

[0239] Biopolyester powder A2 was charged into a disc pelletizer in the same manner as in Example A1 to obtain a powder granulated product.

[0240] In Example A4, the granule temperature (Tp) immediately after granulation was 81°C, which was 1°C different from the softening onset temperature (Ts: 80°C), but a stable, approximately cylindrical granule was obtained. The side of the obtained powder granule had an outer wall structure (shell structure) made of molten polymer formed by melting the components of the thermoplastic resin powder, and an unmelted powder-like appearance was confirmed inside the outer wall structure (core). A photograph of the appearance of the powder granule of Example 4 is shown in Figure 4. A cross-sectional photograph of the powder granule of Example A4 is shown in Figure 5.

[0241] The powder granules of Example A4 had a bulk density of 0.50 kg / L, a moisture content of 0.48 mass%, and a granule breaking strength of 10 kg or more, and were therefore excellent in handleability.

[0242] [Example A5] Injection molding using powder granulation material The powder granulation material made of acrylic resin powder A1 obtained in Example A1 was placed in an injection molding machine (Shibaura Corporation, product name "EX75SX"), and a business card-sized molded product (88 mm x 53 mm, three-stage plate with thicknesses of 1, 2, and 3 mm) was obtained at a resin temperature of 240°C, a mold temperature of 60°C, and a cooling time of 30 seconds. A photograph of the obtained injection-molded product is shown in Figure 6.

[0243] [Example A6] Sheet extrusion molding using powder granules The powder granules made of biopolyester powder A2 (PHBH) obtained in Example A4 were fed into a sheet extruder (manufactured by Technovel Co., Ltd., product name "KTZ15") and extruded through a T-die at an extrusion rate of 2 kg / hr to obtain a single-layer extruded sheet having a thickness of 0.5 mm and a width of 100 mm. The roll temperature was 20°C and the take-up speed was 5 m / min.

[0244] In Example A6, extrusion molding was performed without the "melt-kneading pelletization," but a sheet molding almost equivalent to the case where melt-kneading pelletization was used was obtained. A photograph of the obtained sheet molding is shown in Figure 7.

[0245] Example A7 Pellets of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) (manufactured by Kaneka Corporation, trade name "Green Planet X151A", hexanoate content 11%) were pulverized, and the pulverized material was sieved through a 10-mesh wire screen to obtain biopolyester powder A3.

[0246] For biopolyester powder A3, DSC measurement was carried out in the same manner as in Example A4, and the softening onset temperature (Ts) was measured and found to be 80°C.

[0247] 100 parts by mass of biopolyester powder A3 was placed into an FM mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name "5FM5C / I"; processing volume: 5 L), and while the stirring blades were rotating at a rotation speed of 2,000 rpm, 20 parts by mass of clean water (tap water) was continuously sprayed and injected into the biopolyester powder A3 over a period of 10 minutes to obtain a water-containing powder mixture.

[0248] The FM mixer had a combination of upper and lower blades, with the upper blade being a Y1 blade (trade name, manufactured by Nippon Coke Co., Ltd.) and the lower blade being an S0 blade (trade name, manufactured by Nippon Coke Co., Ltd.). A baffle plate (also called a deflector) was installed inside the mixing vessel.

[0249] This water-containing powder was charged into a disk pelleter in the same manner as in Example A1, to obtain a roughly cylindrical granulated material precursor.

[0250] In Example A7, a semi-wet granulation method was used. The presence of an appropriate amount of moisture increased the bulk density of the powder, improved the powder's ability to fit into the die holes, and also suppressed excessive heat generation during granulation, preventing clogging of the die. As a result of these effects, the granulation speed was improved, and the granulation speed of the granule precursor granules reached 88 kg / Hr.

[0251] In Example A7, the temperature of the granule precursor immediately after granulation was 54°C, which was -26°C lower than the softening onset temperature (80°C) of the raw material biopolyester powder A3 (i.e., the granule temperature was 54°C). In Example A7, cylindrical granules could be stably obtained.

[0252] The obtained granule precursor was dried at 140°C using a hot air circulation type dryer (manufactured by Espec, product name "PH-402") until the moisture content was 0.5 wt% or less, thereby obtaining a powder granule.

[0253] The obtained powder granules had a core-shell structure similar to that of Example A1. A photograph of a cross section of the powder granules of Example A7 is shown in Figure 8.

[0254] The powder granules of Example A7 had a bulk density of 0.49 kg / L, a moisture content of 0.27 mass%, and a granule breaking strength of 10.0 kg or more, and were therefore excellent in handleability.

[0255] [Example A8] The biopolyester powder A3 used in Example A7 was charged into a disk pelleter in the same manner as in Example A1 to obtain a powder granulated product. In Example A8, unlike Example A7, no water was added.

[0256] The obtained powder granules had a core-shell structure similar to that of Example A1. A photograph of a cross section of the powder granules of Example A8 is shown in Figure 9.

[0257] The powder granules of Example A8 had a bulk density of 0.53 kg / L, a moisture content of 0.52 mass%, and a granule breaking strength of 10.0 kg or more, and were therefore easy to handle.

[0258] [Example A9] Polyhydroxyalkanoate (PHA) pellets (manufactured by Danimer Scientific, USA, product name "DAH-04267") were pulverized, and the pulverized material was sieved through a 10-mesh wire screen to obtain biopolyester powder A4.

[0259] Biopolyester powder A4 was subjected to DSC measurement in the same manner as in Example A4, and the softening onset temperature (Ts) was measured to be 85°C.

[0260] Example A9 is an example in which biopolyester powder A4 was used and granulation was carried out by blending 20 parts by mass of tap water in the same manner as in Example A7.

[0261] In Example A9, the granulation rate of the granules was 39 kg / Hr, and the temperature of the granule precursor immediately after granulation was 76°C, which was 9°C lower than the softening onset temperature (85°C) of the raw material biopolyester powder A3 (i.e., the granule temperature was 76°C). In Example A9, a granule precursor having a generally cylindrical shape could be stably obtained.

[0262] The obtained granule precursor was dried in a hot air circulation dryer at 140°C until the moisture content was 0.5 wt% or less, as in Example A7, to obtain a powder granule. The obtained powder granule had a core-shell structure. A cross-sectional photograph of the powder granule of Example A9 is shown in Figure 10.

[0263] The powder granules of Example A9 had a bulk density of 0.35 kg / L, a moisture content of 0.30 mass%, and a granule breaking strength of 10.0 kg or more, and were therefore excellent in handleability.

[0264] The evaluation results of Examples A4 and A7 to A9 are shown in Table 2.

[0265]

[0266] [Comparative Example A3] The biopolyester powder A3 used in Example A7 was continuously fed into a twin-screw extruder (manufactured by Nippon Steel Corporation, trade name "TEX44αII", L / D = 42, cylinder set temperature: 140°C) and melt-kneaded to produce pellets of a thermoplastic resin composition.

[0267] Biopolyester powder A3 was quantitatively added to the extruder via a gravimetric feeder at the hopper position at the most upstream part. The screw rotation speed was set to 81 rpm, and a strand was drawn out from the die at the tip of the extruder. The strand was cooled with water at 60°C and pelletized into pellets of approximately 3 mm length using a pelletizer (manufactured by Isuzu Motors, product name "HSCR-150") to obtain "melt-kneaded pellets" of biopolyester powder A3.

[0268] The biopolyester powder A3 was fed into the extruder by gradually increasing the material feeding rate until the compound processing rate per hour was maximized (i.e., the maximum feed rate at which stable production is possible without causing a feed neck of the raw material powder into the extruder). As a result, the maximum output was only 60 kg / Hr.

[0269] The obtained melt-kneaded pellets were dried at 80° C. using a hot air circulation type dryer until the moisture content was 0.2 wt % or less, in the same manner as in Example A7, to obtain melt-kneaded pellets.

[0270] As in Example A7, the amount of power consumed in each process and the amount of carbon dioxide generated in each process (calculated values) per unit mass (1 kg) of granules were calculated. The results are shown in Table 3.

[0271] In comparison of Examples A7 and A8 with Comparative Example A3, the "powder polymer granules" of this embodiment have a lower CO2 emission rate than the "melt-kneaded pellets" produced using a twin-screw extruder that uses a large heat source heater and power. ２ It has been shown to significantly reduce the amount

[0272]

[0273] (Test Examples Concerning the Second Aspect: Example B and Comparative Example B) [Evaluation] The crystalline polymer powder granules (powder granules) obtained in Example B and Comparative Example B were evaluated by the following method.

[0274] (1) Granulation properties (whether granulation is possible or not) The obtained powder granules were checked and the granulation properties were evaluated according to the following criteria. A: A powder granule with a core-shell structure was obtained, and molten polymer was clearly observed in the shell part. B: A powder granule with a core-shell structure was obtained, and molten polymer was partially observed in the shell part. C: A powder granule with a core-shell structure was obtained, although it was unstable, and a small amount of molten polymer was observed in the shell part. D: The granules were unstable and prone to collapse. E: The granules remained in a "powder-like shape" or could not be granulated due to "die clogging".

[0275] (2) Cross-section observation photograph of granules A slice (thickness: 0.5 mm) was cut out from the obtained crystalline polymer powder granules perpendicular to the extrusion direction from the die using a razor blade, and the cut cross section was observed under an optical microscope.

[0276] (3) Bulk density The dried powder granules were allowed to fall naturally into a 1-liter measure, filled to the brim, and weighed to a volume of exactly 1 liter. The mass was measured to calculate the bulk density (unit: kg / L) of the powder granules.

[0277] (4) Moisture Content The moisture content (unit: mass%) remaining in the powder granules was measured using an infrared moisture meter (FD-660 manufactured by Kett Electric Laboratory).

[0278] (5) Breaking Strength The breaking stress (unit: kg) of the powder granules was measured using a Kiya hardness tester (manufactured by Shiro Sangyo Co., Ltd., product name "WPF1600-B"). The measured value was the average value of 25 particles of powder granules. That is, the powder granules were set in the hardness tester so that the side of the powder granules was the bottom, and the breaking stress was measured by crushing the side of the powder granules using a 5 mmφ cylindrical press. In other words, the breaking stress was measured by crushing the powder granules in a direction perpendicular to the longitudinal direction (extrusion direction).

[0279] (Example B1) Powder Granulation (No Water Added) Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH, hydroxyhexanoate content 6%, 100% passing through a 60-mesh sieve, bulk density 0.40 kg / L), a copolymer polyester of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid, was used as a raw material. Powder A1 (biopolyester powder A1) was used as a raw material. DSC measurement was performed on powder A1 at a temperature increase rate of 10°C / min from room temperature in a nitrogen gas flow. The highest observed melting peak temperature T Ｍ The temperature [°C] was 146.8°C. In the following, unless otherwise specified, the DSC measurement was carried out in a nitrogen gas flow.

[0280] Biopolyester powder A1 was fed into a disc pelleter (manufactured by Dalton, product name "Disc Pelleter F-5 / 11-175") and roughly cylindrical powder granules were produced at a roller rotation speed of 108 rpm. The thickness of the die plate of the disc pelleter was 15 mm and the hole diameter was 3 mmφ. The length (referred to as the effective length) within the die plate over which the powder was subjected to compressive stress from the die wall was 10 mm. The granulation rate in Example B1 was 47 kg / Hr.

[0281] The temperature of the powder granules immediately after granulation was measured by stopping the granulation apparatus after stabilization, inserting a thermocouple directly into the die hole, and quickly measuring the temperature of the compressed powder inside the die. This measurement was performed five times, and the average value was taken as the temperature of the granules immediately after granulation (Tp).

[0282] In Example B1, the temperature (Tp) of the granules immediately after granulation was 81° C., and stably, approximately cylindrical granules were obtained. The side of the obtained powder granules had an outer wall structure (shell structure) made of molten polymer, where the constituent components of the crystalline polymer powder were melted, and an unmelted powder-like appearance was confirmed inside the outer wall structure (core portion).

[0283] The powder granulation product of Example B1 was rated "A" based on the above granulation criteria, had a bulk density of 0.53 kg / L, a moisture content of 0.48% by mass, and a breaking strength of the granulation product of 10 kg or more, making it a powder granulation product with excellent handleability.

[0284] Furthermore, the "apparent density ratio" of the powder granules of Example B1 was 0.92, since the "apparent density of the crystalline polymer powder granules" was 1.106 [kg / L] and the "apparent density of the melt-kneaded pellets" was 1.200 [kg / L].

[0285] The "apparent density of the melt-kneaded pellets" was measured by preparing melt-kneaded pellets without air bubbles using a twin-screw extruder (similar to Reference Example B1 below) set at 140°C from the composition constituting the powder granules of Example B1 (in this case, only A1).

[0286] In addition, the bulk density ρ of the crystalline polymer powder before granulation of the powder granules of Example B1 １ is 0.40 [kg / L], and the bulk density ρ ２ is 0.53 [kg / L], and ρ ２ / ρ １ The value was 1.33.

[0287] 11 shows the results of temperature-reducing DSC (differential scanning calorimetry) of the powder granules obtained in Example B1. Specifically, FIG. 11 shows the results of temperature-reducing DSC (differential scanning calorimetry) of the powder granules of Example B1 (without the addition of a crystallization nucleating agent) when the powder granules are heated from room temperature to a first hold temperature T Ｈ１ (180° C. in FIG. 11) and then the first hold temperature T Ｈ１ 1 is a graph showing the results of a first DSC measurement performed under conditions in which the powder granules were held at RT for 2 minutes, 5 minutes, 15 minutes, or 30 minutes, and then cooled at a temperature decreasing rate of 10° C. / min. The samples for DSC measurement were prepared by cutting out from the powder granules of Example B1.

[0288] To cut out a sample for DSC measurement, a razor blade was inserted into the outer edge (shell portion) of the powder granule from a direction perpendicular to the longitudinal direction (extrusion direction) of the powder granule, and a thin piece weighing approximately 5 mg was cut out as the sample.

[0289] In addition, in the DSC measurement, the melting peak temperature (T Ｍ [°C]) was 146.8°C.

[0290] In FIG. 11, the peak temperature (Tc ２ ) is observed at 91.0°C.

[0291] In FIG. 11, the peak temperature (Tc ５ ) is observed at 92.5°C.

[0292] In FIG. 11, the peak temperature (Tc １５ ) is observed at 92.4°C.

[0293] In FIG. 11, the peak temperature (Tc ３０ ) is observed at 91.9°C.

[0294] As shown in the results of the recrystallization exothermic peak in Example B1, the first hold temperature T Ｈ１ This indicates that 180°C exists.

[0295] The behavior of the DSC measurement shown in FIG. 11 is a typical behavior brought about by the "melt memory effect" of the crystalline polymer, and represents the characteristics of the powder granulated product according to this embodiment.

[0296] As shown in FIG. 11, DSC measurements were performed by setting the holding time at a predetermined hold temperature to 2 minutes, 5 minutes, 15 minutes, and 30 minutes, but the temperature values ​​of the recrystallization exothermic peaks obtained at these holding times did not show any shift to a lower temperature side with increasing holding time. Specifically, the temperature of the recrystallization exothermic peak at a holding time of 15 minutes was 92.4°C, and the temperature of the recrystallization exothermic peak at a holding time of 2 minutes was 91.0°C. The ratio of these ("temperature Tc of the recrystallization exothermic peak at a holding time of 15 minutes") was 92.4°C. １５ " / "Temperature Tc of the recrystallization exothermic peak at a holding time of 2 minutes ２ ") was 1.02, which was in the range of 0.95 to 1.05.

[0297] In this example, DSC measurements were performed with retention times set to 2 minutes, 5 minutes, 15 minutes, and 30 minutes. However, as a retention time condition specifying this embodiment, 15 minutes was selected as a standard time that can adequately correspond to a general melt residence time in various actual molding machines.

[0298] The bottom part of Figure 11 shows the DSC curve obtained when the powder granule obtained in Example B1 was heated from room temperature to 200°C at a rate of 10°C / min, held at 200°C for 5 minutes, and then cooled at a rate of 10°C / min. No exothermic peak due to recrystallization was observed. That is, Figure 11 shows the DSC curve obtained when the powder granule obtained in Example B1 was heated from room temperature to 200°C at a rate of 10°C / min. Ｈ２ It is naturally understood that if no recrystallization exothermic peak is observed after a holding time of 5 minutes, no recrystallization exothermic peak should be observed after a holding time of 15 minutes.

[0299] The peak temperature Tc of the recrystallization exothermic peak in FIG. ２ , Tc ５ , Tc １５ and Tc ３０ These results suggest that the melt memory structure is maintained without thermal disturbance even after the melt temperature is held at 180°C for the residence time required for molding, and that the crystallization nucleating agent effect can be maintained even during actual molding processing.

[0300] (Example B2) Powder granulation product (with water addition) 100 parts by mass of biopolyester powder A1 (same as in Example B1) was added to an FM mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name "5FM5C / I"; processing volume: 5 L), and while rotating the stirring blades at a rotation speed of 2,000 rpm, 20 parts by mass of clean water (tap water) was continuously sprayed and injected into the biopolyester powder A1 in a spray form over a period of 10 minutes to obtain a water-containing powder.

[0301] The FM mixer had a combination of upper and lower blades, with the upper blade being a Y1 blade (trade name, manufactured by Nippon Coke Co., Ltd.) and the lower blade being an S0 blade (trade name, manufactured by Nippon Coke Co., Ltd.). A baffle plate was installed inside the mixing vessel.

[0302] This water-containing powder was charged into a disk pelleter in the same manner as in Example B1 to obtain a cylindrical granule precursor.

[0303] In Example B2, a semi-wet granulation method was used. The presence of an appropriate amount of moisture increased the bulk density of the powder, improved the powder penetration into the die holes, and also suppressed excessive heat generation during granulation, preventing clogging of the die. As a result of these effects, the granulation speed was improved, and the granulation speed of the granule precursor granules reached 88 kg / Hr.

[0304] In Example B2, the temperature (Tp) of the granule precursor immediately after granulation was 54°C, and cylindrical granules could be stably obtained.

[0305] The obtained granule precursor was dried at 140°C using a hot air circulation type dryer (manufactured by Espec, trade name "PH-402") to obtain a powder granule with a moisture content of 0.27 wt%.

[0306] The obtained powder granules had a core-shell structure similar to that of Example B1. A photograph of the appearance of the powder granules of Example B2 is shown in Figure 13.

[0307] The powder granulation product of Example B2 was rated "A" based on the above granulation criteria, had a bulk density of 0.49 kg / L, a moisture content of 0.27% by mass, and a breaking strength of the granulation product of 10.0 kg or more, making it a powder granulation product with excellent handleability.

[0308] Furthermore, the "apparent density ratio" of the powder granules of Example B2 was 0.91, since the "apparent density of the crystalline polymer powder granules" was 1.087 [kg / L] and the "apparent density of the melt-kneaded pellets" was 1.200 [kg / L], the same as in Example B1.

[0309] In addition, the bulk density ρ of the crystalline polymer powder before granulation of the powder granules of Example B2 １ was 0.40 [kg / L], the same as in Example B1, and the bulk density ρ ２ is 0.49 [kg / L], and the bulk density ratio ρ ２ / ρ １ The value was 1.23.

[0310] DSC measurement was carried out in the same manner as in Example B1. The peak temperature Tc ２ , Tc ５ , Tc １５ and Tc ３０ The results were 91.5°C, 92.1°C, 92.5°C, and 92.8°C, respectively.

[0311] Also, Tc １５ / Tc ２ The value of is 1.01, which is within the range of 0.95 to 1.05, and indicates that the stability of the melt memory effect with respect to the melt residence time is high at a melting temperature of 180° C., similar to Example B1.

[0312] Reference Example B1 Melt-Kneaded Pellets (with Addition of Crystallization Nucleating Agent) To 100 parts by mass of biopolyester powder A1, 1 part by mass of pentaerythritol powder (manufactured by Taisei Kayaku Co., Ltd., trade name "Neuriser P", melting point 260°C) as a crystallization nucleating agent and 0.5 parts by mass of behenic acid amide (manufactured by Nippon Fine Chemical Co., Ltd., trade name "BNT-22", melting point 110°C) as a processing aid were added, and the mixture was pre-mixed in powder form. The resulting mixture was then continuously fed into a twin-screw extruder (manufactured by Technovel Co., Ltd., trade name "KTZ15", the T-die in Example B3 below was changed to a 3 mmφ two-hole die, L / D = 42, cylinder set temperature: 140°C), and melt-kneaded with the main screw rotation speed set to 80 rpm. The strand was water-cooled and cut at 60°C to produce melt-kneaded pellets. The granulation rate in Reference Example B1 was 1.0 kg / Hr.

[0313] A flake (about 5 mg) for DSC measurement was cut out from the melt-kneaded pellet obtained in Reference Example B1, and DSC measurement was carried out in the same manner as in Example B1. The DSC measurement results are shown in FIG.

[0314] In the DSC measurement of the melt-kneaded pellets of Reference Example B1, the melting peak temperature (T Ｍ [°C]) was 146.8°C, which was the same as that of the powder granules of Example B1.

[0315] 12 shows a DSC curve obtained when the melt-kneaded pellets (containing a crystallization nucleating agent) of Reference Example B1 were heated from room temperature to 180°C at a rate of 10°C / min, held at 180°C for 2 minutes, 5 minutes, 15 minutes, or 30 minutes, and then cooled at a rate of 10°C / min, as in FIG. 11 (Example B1). ２ , Tc ５ , Tc １５ and Tc ３０ were 93.2°C, 87.3°C, 83.9°C, and 85.1°C, respectively. Compared with Fig. 11 (Example B1) in which DSC measurement was performed under the same conditions, the recrystallization exothermic peak shifted to the lower temperature side, and it was found that the crystallization nucleating agent effect was inferior compared to Fig. 11 (Example B1).

[0316] For the melt-kneaded pellets of FIG. 12 (Reference Example B1), the peak temperature Tc of the recrystallization exothermic peak at a holding time of 15 minutes １５ The peak temperature Tc of the recrystallization exothermic peak at a holding time of 2 minutes was 83.9°C. ２ is 93.2°C, and their ratio (Tc １５ / Tc ２ ) was 0.90, which was outside the range of 0.95 to 1.05.

[0317] 12 shows a DSC curve obtained when the melt-kneaded pellets (containing a crystallization nucleating agent) of Reference Example B1 were heated from room temperature to 200°C at a rate of 10°C / min, held at 200°C for 5 minutes, and then cooled at a rate of 10°C / min. A recrystallization exothermic peak was observed, but the peak temperature had dropped to 72.0°C, indicating that the crystallization nucleating agent effect was significantly weakened.

[0318] Reference Example B2 Melt-kneaded pellets (no addition of crystallization nucleating agent) Melt-kneaded pellets were produced under the same conditions as in Reference Example B1, except that pentaerythritol and behenic acid amide were not added.

[0319] The melt-kneaded pellets of Reference Example B2 were similarly subjected to DSC measurement.

[0320] 14 shows a DSC curve of the melt-kneaded pellets of Reference Example B2, which was obtained by increasing the temperature from room temperature to 180° C. at 10° C. / min, holding the pellets at 180° C. for 2 minutes, 5 minutes, or 15 minutes, and then cooling the pellets at a temperature decreasing rate of 10° C. / min. ２ , Tc ５ , and Tc １５ were 79.5°C, 78.7°C, and 77.8°C, respectively.

[0321] In Reference Example B2, a recrystallization exothermic peak was observed, but it was shifted to a lower temperature side compared to Example B1 (FIG. 11), and it was found that the crystallization nucleating agent effect was significantly weakened compared to Example B1.

[0322] The bottom graph in Fig. 14 shows the DSC curve obtained when the melt-kneaded pellets of Reference Example B2 were heated from room temperature to 200°C at a rate of 10°C / min, held at 200°C for 5 minutes, and then cooled at a rate of 10°C / min. As shown in Fig. 14, no recrystallization exothermic peak was observed under these conditions.

[0323] Reference Example B3 Crystalline Polymer Powder (as it is) The biopolyester powder A1 was subjected to DSC measurement in the same manner as in Example B1, without being granulated.

[0324] 15 shows the DSC curves obtained for the biopolyester powder A1 of Reference Example B3 when the temperature was increased from room temperature to 180°C at 10°C / min, held at 180°C for 2, 5 or 15 minutes, and then cooled at a rate of 10°C / min. ２ , Tc ５ and Tc １５ were 75.3°C, 67.7°C and 67.8°C, respectively.

[0325] In Reference Example B3, a recrystallization exothermic peak was observed, but it was significantly shifted to the lower temperature side compared to Figure 11 (Example B1), and the exothermic peak area was also broadened, indicating that the crystallization nucleating agent effect was significantly weakened compared to Figure 11 (Example B1). Compared with Example B1, it is clear that the crystallization nucleating agent effect is significantly improved by adopting the configuration of the powder granulation product of this embodiment.

[0326] The results of Examples B1 and B2 and Reference Examples B1 to B3 are shown in Table 4.

[0327]

[0328] Example B3: Sheet extrusion molding using powder granules The powder granules obtained in Example B2 were charged into a sheet extruder (manufactured by Technovel Co., Ltd., product name "KTZ15") and extruded through a T-die at a cylinder and T-die temperature of 140°C and an extrusion rate of 2 kg / Hr to obtain a single-layer extruded sheet having a thickness of 0.5 mm and a width of 100 mm. The roll temperature was 20°C and the take-up speed was 5 m / min.

[0329] Example B3 confirmed that extrusion sheet molding can be performed directly from the powder granules.

[0330] (Example B4) PLA powder granules Using polylactic acid (PLA) (product name "L130") manufactured by Total Corbion, an injection molding machine ("SI-80W" manufactured by Toyo Machinery & Metal Co., Ltd., mold clamping capacity 80 tons) was used to mold dumbbell-shaped test specimens (Type 1A multipurpose test specimens) at a cylinder setting temperature of 200°C, a mold temperature of 30°C (both fixed side and moving side), and a cooling time of 30 seconds. The test specimens were obtained in a rapidly cooled state in the mold, and were molded bodies in which crystallization had not progressed sufficiently.

[0331] The dumbbell-shaped test pieces were pulverized and passed through a 60-mesh sieve to prepare a powder raw material of polylactic acid (PLA) (A2, bulk density 0.60 kg / L). The polylactic acid powder was used and charged into a disc pelletizer (manufactured by Dalton, product name "Disc Pelleter F-5 / 11-175") in the same manner as in Example B1, and a pellet-shaped powder granulation product was obtained at a roller rotation speed of 108 rpm.

[0332] The PLA powder granules obtained in Example B4 had a bulk density of 0.58 kg / L, a moisture content of 0.57 mass %, and a breaking strength of 10 kg or more.

[0333] In addition, the bulk density ρ of the crystalline polymer powder A2 before granulation in Example B4 １ is 0.60 [kg / L], and the bulk density ρ ２ is 0.58 [kg / L], and ρ ２ / ρ １ The value was 0.97.

[0334] When the PLA powder granules were subjected to DSC measurement in a nitrogen gas flow at a temperature increase rate of 10°C / min from room temperature, the melting peak temperature T Ｍ [°C] was 175.7°C.

[0335] The second and subsequent rows of the graph in Figure 16 show DSC curves obtained when the PLA powder granules of Example B4 were heated from room temperature to 200°C at a rate of 10°C / min, held at 200°C for 2 minutes, 5 minutes, or 15 minutes, and then cooled at a rate of 10°C / min. ２ , Tc ５ , and Tc １５ were 103.1°C, 98.9°C, and 99.8°C, respectively, indicating the presence of a crystallization nucleating agent function due to the melt memory effect.

[0336] Furthermore, in Example B4, the peak temperature Tc of the recrystallization exothermic peak at a holding time of 15 minutes １５ The peak temperature T of the recrystallization exothermic peak at a holding time of 2 minutes was 99.8°C. ２ is 103.1°C, and their ratio (Tc １５ / Tc ２ ) is 0.97, which is within the range of 0.95 to 1.05, and indicates that the PLA powder granules of Example B4 have excellent retention time durability of the crystallization nucleating agent effect.

[0337] On the other hand, the top line of Figure 16 shows the results of a sample piece for DSC measurement cut out from commercially available PLA melt-kneaded pellets (product name "L130") (Reference Example B4) and similarly subjected to DSC measurement. That is, the top line of Figure 16 shows the DSC curve during temperature reduction obtained for commercially available PLA melt-kneaded pellets when the temperature was increased from room temperature to 200°C at 10°C / min, held at 200°C for 2 minutes, and then cooled at a temperature decrease rate of 10°C / min. No recrystallization exothermic peak was observed in the top line of Figure 16. This result indicates that commercially available PLA melt pellets recrystallize very slowly. Comparing Example B4 and Reference Example B4, it is clear that the crystallization nucleating agent effect is significantly improved by adopting the configuration of the powder granulation product of this embodiment.

[0338] The results of Example B4 and Reference Example B4 are shown in Table 5.

[0339]

[0340] From the results of Example B4, it is presumed that the granulated material made from the pulverized powder of the PLA injection molded product contains oriented crystallized material, which exerts the melt memory effect.

[0341] The upper and / or lower limits of the numerical ranges described herein can be arbitrarily combined to define a preferred range. For example, the upper and lower limits of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limits of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limits of the numerical ranges can be arbitrarily combined to define a preferred range.

[0342] Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope that do not deviate from the gist of this disclosure, they are included in this disclosure.

[0343] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims

1. A powder granulation product containing a thermoplastic resin powder, the powder granulation product having an outer wall portion formed by melting at least a portion of the thermoplastic resin powder located at the outer edge of the powder granulation product, and the compressed thermoplastic resin powder being contained inside the outer wall portion.

2. The powder granulation of claim 1, wherein at least a portion of the compressed thermoplastic resin powder inside the outer wall comprises unmelted compressed powder-like forms.

3. The powder granule according to claim 1, wherein at least a portion of the compressed thermoplastic resin powder inside the outer wall portion is in a partially molten state.

4. The powder granulated material according to claim 1, wherein the shape of the powder granulated material is approximately cylindrical or approximately prismatic.

5. The powder granule according to claim 4, having an outer wall on the side of the powder granule.

6. The powder granulated product according to claim 5, having a breaking strength of 2.0 kg or more.

7. The powder granule according to claim 1, wherein the powder granule is a compressed granule.

8. The powder granule according to claim 1, wherein the thermoplastic resin powder contains a thermoplastic resin having a softening onset temperature of 50 to 150°C.

9. The powder granulated product according to claim 1, wherein the thermoplastic resin powder contains a thermoplastic resin having a softening onset temperature of 60 to 90°C.

10. The powder granule according to claim 1, wherein the thermoplastic resin powder comprises at least one selected from the group consisting of acrylic resins, methacrylic resins, polyhydroxyalkanoate (PHA) resins, polyolefin resins, polyamide resins, polyacetal resins, polyphenylene ether (PPE) resins, polyphenylene sulfide (PPS) resins, polyether ether ketone (PEEK) resins, polyimide (PI) resins, polyamideimide (PAI) resins, polyester resins, polycarbonate (PC) resins, polystyrene resins, polyketone resins, liquid crystal polymers (LCPs), and core-shell polymers.

11. The powder granule according to claim 1, wherein the thermoplastic resin powder comprises a PHA-based resin.

12. A method for producing the powder granulated material according to any one of claims 1 to 11, comprising a compression granulation step of granulating thermoplastic resin powder by a compression granulation method in which the thermoplastic resin powder is extruded through a die hole, wherein the compression granulation step is carried out under conditions in which the temperature of the granulated material immediately after granulation, Tp (°C), and the softening starting temperature of the thermoplastic resin powder, Ts (°C), satisfy formula (1): Ts-30≦Tp≦Ts+10.

13. The method according to claim 12, wherein the die temperature is controlled so that the granule temperature Tp (°C) immediately after granulation and the softening starting temperature Ts (°C) of the thermoplastic resin powder satisfy the condition of formula (1).

14. The method according to claim 12, wherein the outer wall portion is formed by melting at least a portion of the thermoplastic resin powder at the contact surface with the wall surface of the die hole by frictional heat with the wall surface or heat transfer from the wall surface.

15. The method according to claim 14, wherein the compression granulation is carried out using a disk pelleter type compression granulator.

16. Use of the powder granules according to any one of claims 1 to 11 as a raw material for a thermoplastic resin compound or as a molding material.