JP7387950B1 - Thermoplastic resin powder granules - Google Patents

Abstract

[Problem] The purpose of the present invention is to provide thermoplastic resin powder with a stable shape and high bulk density without going through the process of melt-kneading and pelletizing, thereby improving the working environment and making it easier for processing machines. A thermoplastic resin that has excellent feed characteristics (stability, fluidity) and can contribute to reducing the amount of electricity required for production, which in turn reduces the amount of carbon dioxide generated, compared to melt-kneading pelletizing. An object of the present invention is to provide a granulated powder.
[Solution] The present invention provides a powder granule containing thermoplastic resin powder, wherein at least a portion of the thermoplastic resin powder located at the outer edge of the powder granule is melted. This is a powder granule that has an outer wall and compressed thermoplastic resin powder is housed inside the outer wall.
[Selection diagram] Figure 2

Description

The present invention relates to a granulated product of thermoplastic resin powder.

Some thermoplastic resins are in powder form due to their manufacturing method or because they are recycled and pulverized products. Such thermoplastic resin powder is usually difficult to handle, so in order to improve handleability and further increase productivity, it is plasticized and melted in a melt extruder and extruded through a die. Generally, it is cooled and solidified, made into a pellet form (hereinafter also referred to as a melt-kneaded pellet), and subjected to various thermoplastic resin processing machines to be manufactured into a product. That is, powdered thermoplastic resins are usually melt-kneaded and pelletized.

Even in the process of melt-kneading and pelletizing thermoplastic resin powder, powdered thermoplastic resin has a low bulk density, so there are problems with insufficient supply to various melt-kneading machines including extruders. Problems such as lack of productivity often occur.

In addition, recently, the goal has been to reduce carbon dioxide, which is one of the greenhouse gases, and in the various processing of thermoplastic resins, we are reducing the amount of energy used in the process. Reducing the amount of carbon dioxide generated has become a major issue.

The purpose of the present invention is to provide thermoplastic resin powder with stable shape and high bulk density without going through the process of melt-kneading and pelletizing, to improve the working environment, and to improve feed characteristics to processing machines ( It is a thermoplastic resin powder that has excellent stability and fluidity, and can contribute to reducing the amount of electricity required for production, which in turn reduces the amount of carbon dioxide generated, compared to melt-kneading and pelletizing. The object of the present invention is to provide a granulated product.

(1) A powder granule containing thermoplastic resin powder, which has an outer wall portion formed by melting at least a portion of the thermoplastic resin powder located at the outer edge of the powder granule. , a powder granule in which compressed thermoplastic resin powder is contained inside the outer wall.
(2) The powder granule according to (1), wherein at least a portion of the compressed thermoplastic resin powder inside the outer wall portion includes an unmolten compressed powder form.
(3) The powder granule according to (1) or (2), wherein at least a portion of the compressed thermoplastic resin powder inside the outer wall portion is partially melted.
(4) The powder granule according to any one of (1) to (3), wherein the powder granule has a substantially cylindrical or substantially prismatic shape.
(5) The powder granule according to any one of (1) to (4), which has an outer wall portion on the side surface of the powder granule.
(6) The powder granule according to any one of (1) to (5), which has a breaking strength of 2.0 kg or more.
(7) The powder granules according to any one of (1) to (6), wherein the powder granules are compression granules.
(8) The powder granules according to any one of (1) to (7), wherein the thermoplastic resin powder contains a thermoplastic resin having a softening start temperature of 50 to 150°C.
(9) The powder granules according to any one of (1) to (8), wherein the thermoplastic resin powder contains a thermoplastic resin having a softening start temperature of 60 to 90°C.
(10) The thermoplastic resin powder is acrylic resin, methacrylic resin, polyhydroxyalkanoate (PHA) resin, polyolefin resin, polyamide resin, polyacetal resin, polyphenylene ether (PPE) resin, polyphenylene sulfide. (PPS)-based resin, polyetheretherketone (PEEK)-based resin, polyimide (PI)-based resin, polyamide-imide (PAI)-based resin, polyester-based resin, polycarbonate (PC)-based resin, polystyrene-based resin, polyketone-based resin, The powder granule according to any one of (1) to (9), which contains at least one member selected from the group consisting of a liquid crystal polymer (LCP) and a core-shell type polymer.
(11) The powder granules according to any one of (1) to (10), wherein the thermoplastic resin powder contains a PHA-based resin.
(12) A method for producing the powder granules according to any one of (1) to (11), comprising:
It includes a compression granulation process in which thermoplastic resin powder is granulated by a compression granulation method in which the thermoplastic resin powder is extruded through a die hole.
A method in which the compression granulation step is performed under conditions where the granulated material temperature Tp (°C) immediately after granulation and the softening start temperature Ts (°C) of the thermoplastic resin powder satisfy formula (1):
Formula (1): Ts-30≦Tp≦Ts+10.
(13) The temperature of the die is controlled so that the temperature of the granulated product immediately after granulation Tp (°C) and the softening start temperature Ts (°C) of the thermoplastic resin powder satisfy equation (1). , (12).
(14) 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 due to frictional heat with the wall surface or heat transfer from the wall surface, (12) ) or the method described in (13).
(15) The method according to any one of (12) to (14), wherein the compression granulation is performed using a disk pelleter type compression granulation device.
(16) Use of the powder granules according to any one of (1) to (11) as a raw material for a thermoplastic resin compound or as a molding material.

The present invention enables thermoplastic resin powder to have a stable shape and high bulk density without going through the process of melt-kneading and pelletizing, which improves the working environment and improves feed characteristics (stability) to processing machines. , fluidity), and can contribute to reducing the amount of electricity required for production, which means reducing the amount of carbon dioxide generated, compared to melt-kneading pelletizing. can provide things.

1 is a photograph of the appearance of the powder granules obtained in Example 1 (using acrylic resin powder A1). 1 is a cross-sectional photograph of the powder granules obtained in Example 1 (using acrylic resin powder A1). It is a DSC measurement result of biopolyester powder A2 of Example 4. It is a photograph of the appearance of the powder granules (using biopolyester powder A2) obtained in Example 4. It is a cross-sectional photograph of the powder granules (using biopolyester powder A2) obtained in Example 4. In Example 5, it is a photograph of an injection molded article obtained from the powder granules obtained in Example 1 (using acrylic resin powder A1). In Example 6, it is a photograph of a sheet molded product obtained from the powder granules obtained in Example 4 (using biopolyester powder A2). It is a cross-sectional photograph of the powder granules (using biopolyester powder A3) obtained in Example 7. It is a cross-sectional photograph of the powder granules (using biopolyester powder A3) obtained in Example 8. It is a cross-sectional photograph of the powder granules (using biopolyester powder A4) obtained in Example 9.

A. Outline of thermoplastic resin powder granules The powder granules of the present invention are powder granules containing thermoplastic resin powder, and the thermoplastic resin located at the outer edge of the powder granules This is a powder granule having an outer wall formed by melting at least a portion of the powder, and compressed thermoplastic resin powder is housed inside the outer wall. In the powder granules of the present invention, 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. Compressed thermoplastic resin powder is housed inside the outer wall, and the thermoplastic resin powder may be at least partially molten or at least partially unmolten. . The compressed thermoplastic resin powder inside the outer wall may be in an unmolten state. That is, at least a portion of the compressed thermoplastic resin powder inside the outer wall portion may include an unmolten compressed powder form, or may include a partially molten form. You can stay there. A partially melted form means that the constituent components of the thermoplastic resin powder are partially melted, but a welded structure that is strong enough to hold the thermoplastic resin powder, such as the outer wall, does not mean a welded structure that is strong enough to hold the thermoplastic resin powder. It is intended to be in a form that is not. Note that in this specification, the inside of the outer wall portion is also referred to as a core portion. Compressed thermoplastic resin powder is contained in the core part inside the outer wall part, but in this specification, "compressed" refers to the bulk density of the thermoplastic resin powder before granulation. In comparison, this refers to the fact that the density of the thermoplastic resin powder located in the core part is higher.

The outer wall portion (shell portion) of the thermoplastic resin powder granules of the present invention has a dense structure containing the melted thermoplastic resin powder, while the inner core portion is compressed. However, it has a sparse structure compared to the dense structure (welded structure) of the outer wall containing the melt. The thermoplastic resin powder of the present invention has a structure in which the melt of the thermoplastic resin powder becomes the outer wall and retains the compressed thermoplastic resin powder present in the core part. It is stable, has little powder falling, has excellent handling and safety, and can improve the working environment.

Therefore, when the powder granules of the present invention are used as a raw material for a compound when preparing a resin composition, the raw material supply capacity, supply stability, and supply accuracy can be improved, and production It can contribute to sexual improvement. At the same time, since the process of melt-kneading and pelletizing 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.

Further, the powder granules of the present invention can be directly supplied to various molding machines such as injection molding machines and extrusion molding machines for thermoplastic resins, and can also be used as a molding material. In this case, since the process of melt-kneading and pelletizing can be omitted, it is possible to reduce the amount of carbon dioxide generated in the processing process. Further, the powder granules of the present invention may have a small thermal history because heat is not applied to the extent that it becomes pelletized.

The outer wall portion (shell portion) has a welded structure in which at least a portion of the thermoplastic resin powder located at the outer edge of the powder granule is melted. The outer wall portion may be so smooth that it has a glossy appearance. In addition, although it is not melted to the extent that it becomes a smooth surface, the outer wall is formed by partially melting the constituent components of the thermoplastic resin powder and partially welding it to adjacent components. Good too. Although the details will be described later, during compression granulation, at least a portion of the thermoplastic resin powder is melted in the outer wall part due to frictional heat with the wall surface or heat transfer from the wall surface at the contact surface with the die hole, for example. can be formed. The thickness of the outer wall portion can vary depending on the manufacturing conditions of the thermoplastic resin powder granules.

The core portion is a portion located inside the outer wall portion, and is a portion in which compressed thermoplastic resin powder is contained. The thermoplastic resin powder located in the core portion may be porous, or may have a non-welded structure so that heat is not transmitted to the core portion during granulation. Because the core part is far from the die contact surface, the powder polymer raw material has a structure in which it 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 remains powdery. The shape of the body polymer raw material may have a residual structure.

In addition, in this specification, the terms "outer wall part (shell part)" and "core part" are used to simplify the explanation, but as mentioned above, the outer wall part is Since it is formed by melting thermoplastic resin powder, there is actually no clear boundary between the outer wall (shell) and the core. The outer wall part (shell part) refers to the part that includes the welded structure of the thermoplastic resin powder, is located at the outer edge of the powder granule, and contributes to maintaining a certain shape of the powder granule, The part refers to the part located inside the outer wall part (shell part).

The shape of the powder granules is preferably substantially cylindrical or substantially prismatic, and the powder granules preferably have an outer wall portion on the side surface of the powder granules. In the present invention, the powder granules preferably have a substantially cylindrical or substantially prismatic shape, and an outer wall portion is preferably formed on the side surface of the powder granules having the substantially cylindrical or prismatic shape.

The powder granules of the present invention can be preferably obtained by using a powder compression granulation method, and details of the manufacturing method will be described later.

The powder granules of the present invention can be used as a raw material for thermoplastic resins in the production of resin compositions 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.

Adding powder granules to the melt compound of the resin composition can improve productivity. Specifically, powder granules are extremely stable when fed into equipment such as an extruder, so using these powder granules can improve the productivity of resin compositions (compound processing speed per hour). ) can be dramatically improved. In addition, it is possible to significantly reduce the pollution of the working environment due to dust, improve the occupational safety and health environment for workers, and further reduce the time required to change and clean equipment.

When powder granules are directly fed into various resin molding processing machines such as injection molding and extrusion molding, the "melt kneading pelletizing" process can be omitted, so conventional methods (including the melt kneading pelletizing process) Compared to resin product processing methods), it is possible to greatly reduce the amount of carbon dioxide generated in the total process.

Powder granules can be of any suitable shape. Typically, when the powder is produced by compression granulation and the granulation is performed by passing through a circular die hole, the basic shape is a cylindrical pellet shape.

Note that the term "dice" in this specification is a general term for a tool corresponding to a "mold" for compressing powder granules to give them a shape.

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 a die hole in a disk plate (dice plate) during granulation, and the length can be adjusted by the distance between the disk plate and the cutter. The distance may be any suitable 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 still more preferably 3 mm to 10 mm.

The bulk density of the powder granules may be any suitable bulk density. The bulk density of the powder granules is preferably 0.3 kg/L to 2.0 kg/L, more preferably 0.5 kg/L to 1.0 kg/L. By increasing the bulk density, the speed and stability of supplying powder granules to various processing machines increases. Bulk density is calculated by using a square, allowing the powder to fall naturally into the square until the volume is completely filled, weighing the volume to an exact 1 liter, and measuring the mass (unit: kg/L) ).

The breaking strength of the powder granules measured by a Kiya hardness tester is preferably 0.5 kg or more, preferably 1.0 kg or more, preferably 2.0 kg or more, and 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. It is 0 kg or more, preferably 10 kg or more. The upper limit may exceed the measurement limit of the Kiya type hardness tester (10 kg is the measurement limit for Shiro Sangyo Co., Ltd., product name "WPF1600-B"). Within this range, powder granules with excellent handling properties and melt processability can be obtained. Here, breaking strength is measured by crushing 20 or more grains (preferably 25 or more grains) of powder granules in a direction perpendicular to the longitudinal direction (extrusion direction) of the powder granules. It shows the average breaking stress (breaking load). In powder granules, since the shell portion is composed of molten resin, it is possible to maintain a stable shape as a granule even though it is a powder granule. The diameter of the pressurizing surface of the pressurizing attachment of the Kiya type hardness tester is, for example, 5 mm.

The moisture content of the powder granules may be any appropriate moisture content. The moisture content of the powder granules is determined by adding water to the powder in order to facilitate granulation, in addition to the moisture originally contained in the raw material powder. The amount of water added when water is added during granulation will be described later.

Although the powder granules can be dried after granulation, the final moisture content is preferably 10% by mass or less, more preferably 5.0% by mass or less, and still more preferably 3.0% by mass or less. 0% by weight or less, particularly preferably 1.0% by weight or less, and most preferably 0.5% by weight or less. The moisture content of the final powder granules can be appropriately selected depending on the intended use.

The powder granules are preferably granulated without the addition of water. If the moisture content of the powder granules is low, a drying step after granulation may be unnecessary. If granulation can be performed without using water, a drying process becomes unnecessary, and the amount of carbon dioxide emissions generated in the powder granulation process can be greatly reduced.

The moisture content of the powder granules granulated without the addition of water is, for example, 1.0% by mass or less, preferably 0.5% by mass or less, and more preferably 0.3% by mass. It is not more than 0.2% by mass, more preferably not more than 0.2% by mass.

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

The particle size of the thermoplastic resin powder used in the present invention may be any suitable particle size depending on its form as long as the effects of the present invention 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.

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, particularly preferably 0.1 mm to 0.5 mm. In this specification, the average particle size can be measured by laser diffraction method. The average particle diameter of the resin powder may be a particle diameter (d50) that accounts for 50% of cumulative particle size distribution on a volume basis.

The thermoplastic resin powder may be used singly or in combination of two or more.

The bulk density of the thermoplastic resin powder may be any appropriate bulk density depending on its form as long as the effects of the present invention can be obtained. The bulk density of the thermoplastic resin powder is preferably 0.01 kg/L to 1 kg/L, preferably 0.05 kg/L to 0.8 kg/L, and more preferably 0.1 kg/L to 0. .8 kg/L, more preferably 0.1 kg/L to 0.6 kg/L, particularly preferably 0.2 kg/L to 0.5 kg/L.

The thermoplastic resin powder is a powdered resin obtained through its manufacturing process, that is, it may be in a powder form depending on the manufacturing process, and may be a resin in the form of pellets, a lump of resin, a resin molding, etc. It may also be a powdered resin obtained by pulverizing a non-powdered resin. The pulverized powdered resin is processed into molded products, pellets, sprues, runners, etc. generated during injection molding at room temperature, or after cooling using dry ice or liquid nitrogen as necessary, using a pulverizer (e.g. It can be obtained using a product manufactured by Dalton Co., Ltd. under the trade name "Nair Mill, Silfeed Mill, Atomizer, Impact Mill", etc.).

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

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

In the present invention, particularly preferred thermoplastic resin powders include acrylic resin, methacrylic resin, polyhydroxyalkanoate (PHA) resin, polyolefin resin, polyamide resin, polyacetal resin, and polyphenylene ether (PPE) resin. , polyphenylene sulfide (PPS) resin, polyetheretherketone (PEEK) resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyester resin, polycarbonate (PC) resin, polystyrene resin, polyketone At least one member selected from the group consisting of a type resin, a liquid crystal polymer (LCP), and a core-shell type polymer is used.

Polyhydroxyalkanoate (PHA)-based resins can be, for example, compounds produced in the body by microorganisms using carbohydrates, oils, and the like as bait. Such polyhydroxyalkanoate is primarily extracted as a powdered polymer.

The polyhydroxyalkanoate resin contains hydroxyalkanoic acid as a raw material component as a polymerization component, and has at least a repeating unit derived from hydroxyalkanoic acid. The polyhydroxyalkanoate resin may be artificially synthesized or may be biosynthesized by microorganisms. Examples of hydroxyalkanoic acids include glycolic acid, 3-hydroxybutyrate, 3-hydroxypropionate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyheptanoate, 3-hydroxyoctanoate. , 3-hydroxy nanoate, 3-hydroxydecanoate, 3-hydroxytetradecanoate, 3-hydroxyhexadecanoate, 3-hydroxyoctadecanoate, 4-hydroxybutyrate, 4-hydroxyvalerate, Examples include 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 in 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, especially 6 or less. One type of hydroxyalkanoic acid may be used alone, or two or more types may be used in combination.

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

As the acrylic resin, methacrylic resin, and core-shell type polymer, powdery polymers obtained by emulsion polymerization or suspension polymerization are preferably used. A powdered polymer obtained by emulsion polymerization or suspension polymerization can be used as it is as a thermoplastic resin powder for granulation.

In the powder granules of the present invention, in order to form an outer wall part (shell part) in the granules, thermoplastic resin is It is necessary to melt some of the powder components. For this purpose, if the softening start temperature of the thermoplastic resin powder is higher than the granulation temperature, by granulating it as a mixture with another thermoplastic resin powder whose softening start temperature is lower than the granulation temperature, This is advantageous in obtaining granules.

The powder granules may contain any suitable additives, if necessary. The additive may be in powder form or liquid form. Examples of additives include antioxidants, light stabilizers, foaming agents, ultraviolet absorbers, antiblocking agents, heat stabilizers, impact modifiers, antibacterial agents, dispersants, compatibilizers, processing aids, and lubricants. agent, coupling agent, crystallization nucleating agent, hydrolysis inhibitor, oxygen scavenger, coloring agent (dye and pigment), or binder. One type of additive may be used alone, or two or more types may be used in combination.

The above additive may be in the form of powder or liquid.

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. % by mass or less.

The powder granules of this embodiment may include a binder as an additive. Here, the term "binder" refers to, in addition to the constituent components of the raw material thermoplastic resin powder, it exists between the thermoplastic resin powders, binds the powders together, and increases the breaking strength of the granules. This is a general term for compounds that can exhibit enhanced effects, but if necessary, various compounds that have a binding effect, preferably water-dispersed or water-soluble polymer compounds, polysaccharides, etc., may be used to bind. It can be appropriately selected and used as an adhesive.

Preferably, a part of the constituent components of the thermoplastic resin powder is melted and bound to form a powder granule, and it is preferred that no binder is blended.

When a binder is added to the powder granules of this embodiment, the content thereof is usually 10% by mass or less, preferably 5.0% by mass, based on the total mass of the powder granules. % or less, more preferably 3.0% by mass or less, even more preferably 1.0% by mass or less, even more preferably 0.5% by mass or less, particularly preferably 0.1% by mass. or less, most preferably 0% by mass (undetectable).

In one embodiment, dispersants are preferably used as additives. As the dispersant, surfactants are preferably used. The hydrophilic/hydrophobic balance in the dispersant (surfactant) can be adjusted by adjusting the degree of esterification of the compound serving as the dispersant, the type of fatty acid (presence or absence of hydroxyl group, saturated or unsaturated fatty acid, alkyl chain length), degree of polymerization, etc. It can be controlled by By using a dispersant, it is possible to ``improve the productivity (discharge speed) of powder granules,'' ``reduce the frictional heat during granulation,'' and ``improve the cleanability of the granulation equipment.'' It may bring benefits such as

Examples of the dispersant include fatty acids, fatty acid metal salts, fatty acid sulfonates, fatty acid amides, acrylamide, polyhydric alcohol fatty acid esters, polyglycerin fatty acid esters, and the like. One type of dispersant may be used alone, or two or more types may be used in combination.

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

A polyhydric alcohol fatty acid ester is an ester compound composed of a polyhydric alcohol and a fatty acid. Examples of polyhydric alcohol fatty acid esters include esters of polyhydric alcohols such as pentaerythritol and glycerin and fatty acids having 8 or more carbon atoms (preferably 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms). It will be done.

Fatty acid amide is a compound having a structure obtained by dehydration condensation of a fatty acid and 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.

Polyglycerin fatty acid ester is an ester compound composed of polyglycerin and fatty acid. Examples of the polyglycerin fatty acid ester include diglycerin palmitate, diglycerin stearate, diglycerin oleate, decaglycerin palmitate, decaglycerin stearate, and decaglycerin oleate.

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 It is 0.3% by mass to 5.0% by mass.

In one embodiment, a crystallization nucleating agent is used as an additive. The crystallization nucleating agent is preferably used when the powder granules are mainly composed of crystalline thermoplastic resin powder. In particular, the crystallization nucleating agent is preferably added when biopolyester produced by living organisms (for example, polyhydroxyalkanoates (PHA)) is used as the thermoplastic resin powder. By using a crystallization nucleating agent, it is possible to increase the crystallization rate and crystallinity of crystalline thermoplastic resin powder (e.g. biopolyester), which not only improves rigidity and heat resistance but also improves productivity. can be increased. Such crystallization nucleating agents include, for example, organic metal salt compounds such as phosphate metal salts, benzoate metal salts, pimelic acid metal salts, rosin metal salts, oxalate metal salts, fatty acid metal salts, aliphatic metal salts, etc. Organic esters, triallyl phosphate, polyalkylene glycols or their derivatives, aliphatic polyesters, organic compounds such as benzylidene sorbitol, dyes and pigments such as quinacridine, cyanine blue, carbon black, talc, mica, kaolin, clay, carbonate minerals , minerals such as metal oxides and metal sulfates, ionomers, and polymer compounds such as high melting point polyamides. In one embodiment, talc, mica, kaolin, calcium carbonate, etc. 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.

The content ratio 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 it is 0.3% by mass to 5.0% by mass.

B. Method for producing powder granules The powder granules having a core part and a shell part of the present invention are produced by compressing the powder granules through a "dice", and then compressing the powder granules in the die contact area. It can be obtained by melting the thermoplastic resin powder, but preferably by a compression granulation method in which the thermoplastic resin powder is extruded from the die holes, and the shell part is formed by extruding the thermoplastic resin powder from the die holes. That is, during extrusion granulation, the thermoplastic resin powder is formed by melting the constituent components of the thermoplastic resin powder 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.

By forming the shell part, it is possible to maintain a certain shape (for example, cylindrical or prismatic) as a powder granule, and improve quality stability (shape stability, uniformity of hardness), low fineness, Powder granules with high hardness and excellent handling properties can be obtained.

In one embodiment, the powder granules can be granulated without using water, so a drying step is not necessary. Therefore, the amount of electricity used for granulation can be reduced, and the amount of carbon dioxide generated in the process can be significantly reduced.

When the powder passes through a die during extrusion granulation of powder granules, frictional heat may be generated between the wall of the die hole and the powder. At this time, the temperature of the powder granules increases due to frictional heat, but the temperature of the granules immediately after granulation (Tp; unit: °C) is the softening start temperature of the thermoplastic resin powder (Ts, Ts is the melting point If the temperature rises too high (corresponding to the glass transition temperature), the thermoplastic resin powder will melt excessively and stick to the wall of the die hole, or cause the die hole to become clogged. becomes impossible. On the other hand, if the temperature (Tp) of the granulated product immediately after granulation becomes too low than the softening start temperature Ts of the resin powder, the raw resin powder will not have binding strength and will form granules in the powder state. Otherwise, the result will be a granulated product that will easily collapse under compression, making it difficult to obtain a granulated product with a stable shape.

In order to stably obtain a powder granule, it is preferable that the temperature of the granule immediately after granulation (Tp) and the softening start temperature (Ts) of the thermoplastic resin powder are within a specific range. That is, the method for producing a powder granule according to the present invention includes a compression granulation step of granulating thermoplastic resin powder by a compression granulation method in which the thermoplastic resin powder is extruded from a die hole, and immediately after granulation. The granule temperature Tp (°C) and the softening start temperature Ts (°C) of the thermoplastic resin powder satisfy the formula (1), more preferably the formula (2), and even more preferably the formula (2). This is a method in which the compression granulation step is performed under conditions that satisfy (3).
Formula (1): Ts-30≦Tp≦Ts+10
Formula (2): Ts-20≦Tp≦Ts+5
Formula (3): Ts-15≦Tp≦Ts

In equations (1) to (3), other equations defining a preferable range of Tp may be created by arbitrarily combining the left and right sides. For example, Ts-20≦Tp≦Ts+10, Ts-15≦Tp≦Ts+10, Ts-30≦Tp≦Ts+5, Ts-15≦Tp≦Ts+5, Ts-30≦Tp≦Ts, Ts-20≦Tp≦Ts. The compression granulation step can be preferably carried out under the conditions that are satisfied.

The temperature (Tp) of the granulated product immediately after granulation can be measured with a contact thermocouple. To measure the temperature (Tp) of the granulated material immediately after granulation, after setting the powder granulation device in a state where granulation can be performed stably, the device is stopped during granulation, and the temperature (Tp) of the granulated product is measured by This can be done by directly inserting a thermocouple into the powder granules and quickly measuring the temperature. The measurement is performed at least three times (preferably five times), and the average value is defined as Tp. At this time, even if the powder sticks to the die or becomes clogged and granulation becomes impossible, a thermocouple is directly inserted into the powder to measure its temperature.

In order to efficiently obtain the powder granules having the core/shell structure of the present invention, it is most effective to control the temperature of the die that is in direct contact with the powder. That is, by providing a mechanism for heating the die by providing a heater and a heat medium flow path for temperature adjustment, and a mechanism for cooling the die by providing a flow path for a cooling medium, the temperature condition of equation (1) can be achieved. It is preferable to control the temperature of the dice so that

Due to the simplicity of the device, general compression granulation equipment often has a simple structure in which the temperature of the die cannot be controlled. The temperature of the granulated product immediately after granulation is determined by the effective pressurizing length of the die hole, the feed rate of the raw material powder, the contact area and contact time between the raw material powder and the die surface, and methods such as insulation or cooling of the granulation equipment. (Tp) can be changed and controlled.

If there is no temperature control device for the die, the temperature will be controlled by a balance between temperature rise due to frictional heat during granulation and heat dissipation to the outside. In order to obtain good results, the softening start 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. .

The thermoplastic resin powder may be a single component or a combination of two or more components. In particular, the difference between the softening start temperature (Ts) of the target thermoplastic resin powder and the granule temperature (Tp) is large, and the granule temperature satisfies any of the conditions of formulas (1) to (3) above. If it is difficult to set such a temperature, it is advantageous to blend a thermoplastic resin with a softening start temperature lower than the temperature of the granules and granulate the mixture to obtain the granules.

When the thermoplastic resin powder is composed of two or more types of components, immediately after granulation, the Ts of the component of the thermoplastic resin powder with the lowest softening start temperature (Ts) is set as Ts in formula (1). It is preferable to set conditions (for example, die temperature) such that the temperature (Tp) of the granulated material satisfies formula (1). More preferably, conditions (for example, die temperature) are set such that the softening start temperature of any of the constituent components of the thermoplastic resin powder satisfies formula (1).

When the thermoplastic resin powder is composed of two or more types of components, the component of the thermoplastic resin powder with the lowest softening start temperature is 50% by mass or less based on the total amount of the thermoplastic resin powder, Preferably it is 30% by mass or less, more preferably 10% by mass or less.

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

In DSC measurement, a sample of thermoplastic resin powder, usually about 5 mg, is weighed into a sample dish, and the temperature is raised at a rate of 10° C./min under a nitrogen stream to determine the softening start temperature (Ts).

In the case of crystalline resin, the tangent line between the baseline from the low-temperature region and the inflection point (the point where the upwardly convex curve changes to a downwardly convex curve) on the melting start side where the endothermic peak of crystalline melting is observed. The intersection point is regarded as the "melting point", and this is taken as the softening start temperature (Ts).

In addition, when multiple endothermic peaks of crystal melting appear, the melting point of the peak appearing on the lowest temperature side is taken as the softening start temperature.

In the case of an amorphous resin, the intersection of the baseline from the low temperature section and the tangent at the point of inflection is regarded as the glass transition point (Tg), and this is taken as the softening start temperature (Ts).

Powder granules can be produced using a compression granulator, examples of which include a disk pelleter method, screw extrusion method, briquetting method, and tabletting method. Among the above examples, the disk pelleter method is preferably adopted from the viewpoint of granulation productivity and the quality and shape uniformity of the powder granules obtained. In the disk pelleter method, a "semi-wet granulation method" in which an appropriate amount of moisture is contained can also be adopted, but with the present invention, it is possible to perform granulation without using water, and in this case, the drying step is may become unnecessary. If granulation can be performed without using water, the amount of energy required in the drying process can be reduced, and the amount of carbon dioxide generated in the process can be significantly reduced.

When the thermoplastic resin powder is a mixture containing two or more types of powder raw materials, it is preferable to uniformly mix them using any suitable mixer. Examples of mixers include Henschel mixer, Nauta mixer, powder kneader (KDH, KDA, CKD, CPM) (Dalton), Spartan mixer (SPM) (Dalton), SP granulator (SPG) (Dalton) company), etc. In order to obtain a preferable mixture with excellent granulation properties, it is preferable that the stirring blade of the mixing and stirring device is appropriate. For example, when using a Henschel mixer type mixer, the mixer blades are a combination of upper and lower blades, the upper blade is a Y1 blade (trade name, manufactured by Nippon Coke Co., Ltd.), and the lower blade is an S0 blade ( It is preferable to use the product name (trade name, manufactured by Nippon Coke Co., Ltd.). Further, it is preferable to install a deflector in the stirring tank for mixing. That is, by using a mixing step in which each component can be uniformly dispersed throughout the mixture, it is advantageous to improve the productivity and quality stability of the powder granules finally obtained.

Although a "semi-wet granulation method" can also be employed, the amount of water blended can be any appropriate amount depending on the characteristics of the powder (water absorption, etc.). In this case, the amount of water blended is 3 to 30 parts by weight, preferably 5 to 25 parts by weight, and more preferably 5 to 20 parts by weight, based on 100 parts by weight of the thermoplastic resin powder. The semi-wet method can be employed when granulation properties are not stable during the granulation process.

A disk pelleter type granulator has, as a basic structure, one or two disks with a large number of holes of 2 mm to 30 mm, and a roller for force-feeding the raw material into the holes of the disks. As the roller rotates, thermoplastic resin powder (which may contain water) supplied between the disk and the roller or between two disks is press-fitted into the hole in the disk, forming a cylindrical extrudate. molded. The extruded granules are cut with a cutter or the like on the back surface of the disk to obtain pellet-like powder granules. The length of the granules can be adjusted by adjusting the distance between the back surface of the disk and the cutter and the number of rotations of the roller. The distance between the disc plate and the cutter may be any suitable 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 still more preferably 3 mm to 10 mm.

More specifically, the disk pelleter method includes a roller disk die method, a roller ring die method, a double die method, a flat die method, and the like. As a commercially available disc pelleter type granulator, for example, the disc pelleter F series manufactured by Dalton Corporation can be mentioned.

C. Melt Compound Using Powder Granules In one embodiment, the powder granules are used as a thermoplastic resin compound raw material or molding material. One embodiment of the present invention is the use of the powder granules of the present invention as a raw material for a thermoplastic resin compound or as a molding material. For example, a melt compound of powder granules and other thermoplastic resins may be provided.

Any suitable method may be used to form the molten compound. For example, a kneader, a Banbury mixer, a roll, a single screw or a multi-screw extruder with two or more screws can be used. Preferably, a twin screw extruder is used. The composition obtained by melt-kneading is pelletized.

In one embodiment, the powder granules 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 products.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples in any way. Note that parts and percentages are based on mass unless otherwise specified.

[evaluation]
The powder granules obtained in Examples and Comparative Examples were evaluated by the following method.
(1) Granulation property (possibility of granulation)
The obtained powder granules were confirmed, and the granulation properties were evaluated according to the following criteria.
A: Powder granules with a core-shell structure are obtained, and molten polymer is clearly observed in the shell portion.
B: Powder granules with a core-shell structure are obtained, and molten polymer is partially observed in the shell portion.
C: Powder granules with a core-shell structure are obtained although unstable, and a small amount of molten polymer is observed in the shell portion.
D: Granules are unstable and easily disintegrate.
E: Unable to granulate due to ``staying in powder form'' or ``die clogging.''

(2) Photograph of cross-sectional observation of granules From the obtained powder granules, a section was cut out perpendicularly to the direction of extrusion from the die (thickness: 0.5 mm) using a razor blade. Observation was made using an optical microscope.

(3) Bulk density After drying, the powder granules are allowed to fall naturally into a 1-liter square, the volume is completely filled, and the volume is accurately weighed to 1 liter.The mass of the powder granules is measured. The bulk density (unit: kg/L) of the material was calculated.

(4) Moisture content The water content (unit: mass %) remaining in the powder granules was measured using an infrared moisture meter (FD-660 manufactured by Kett Scientific Research Institute).

(5) Breaking Strength The breaking stress (unit: kg) of the powder granules was measured using a Kiya type hardness meter (manufactured by Shiro Sangyo Co., Ltd., trade name "WPF1600-B"). The measured value was the average value of 25 powder granules. That is, the fracture stress was measured by setting the powder granules in a hardness tester so that the side surface was the bottom surface, and crushing the side surface of the powder granules using a 5 mm diameter cylindrical pushing tool. went. In other words, the fracture stress was measured by crushing the powder granules in a direction perpendicular to the longitudinal direction (extrusion direction).
A: Breaking strength is 10 kg or more (measurement limit) B: Breaking strength is 5.0 kg or more and less than 10 kg C: Breaking strength is 2.0 kg or more and less than 5.0 kg D: Breaking strength is 0.5 kg or more and 2.0 kg Less than E: The breaking strength is less than 0.5 kg, or the obtained powder granules are in powder form.

(6) Amount of carbon dioxide (CO ₂ ) emitted For the amount of electricity used for powder granulation, the amount of carbon dioxide (CO 2 ) The unit of powder granules is calculated by multiplying by the value of 0.000362 [ton-CO ₂ /kWh], which is the basic emission coefficient of Kansai Electric Power's 2020 basic emission coefficient actual value (published on January 7, 2022). A calculated value (unit: kg(CO ₂ )/kg) of the amount of carbon dioxide (CO ₂ ) discharged per mass (per 1 kg) was determined.

[Production Example 1] Acrylic resin powder granules (manufacture of acrylic resin powder)
Using a polymerization apparatus equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen gas introduction tube, and a feed pump, 140 parts by mass of water, 0.05 parts by mass of sodium dodecylbenzenesulfonate, and 0.1 parts by mass of sodium sulfate were added. Mixed to obtain a mixture. After the mixture was purged with nitrogen at 80°C, 0.1 part by mass of potassium persulfate was added, and then, with stirring, 90 parts by mass of methyl methacrylate (also referred to as MMA) and 10 parts by mass of butyl acrylate (also referred to as BA) were added. A monomer mixture consisting of parts by mass was continuously added over a period of 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 mass of sodium dodecylbenzenesulfonate was added, respectively. After the addition of the monomer mixture was completed, the mixture was further stirred for 1 hour to carry out polymerization, and the reaction was completed to obtain an acrylic copolymer latex.

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

The obtained acrylic resin powder A1 was sieved through a 10-mesh wire mesh (mesh gap is about 2.5 mm), and the acrylic resin powder A1 that passed completely was collected. The bulk density of the powder is 0.32 kg/L, and the glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC, manufactured by Hitachi High-Tech Science Co., Ltd., trade name "DSC6220"), and it was found to be 81 It was observed as ℃.

[Example 1]
(Manufacture of acrylic resin powder granules)
The obtained acrylic resin powder A1 was put into a disc pelleter (manufactured by Dalton Co., Ltd., trade name "Disc Pelleter F-5/11-175") as a raw material, and the powder was made into pellets at a roller rotation speed of 108 rpm. It was made into a granulated product. The thickness of the die plate of the disk pelleter was 15 mm, and the hole diameter was 3 mmφ. The length (referred to as effective length) where the powder received compressive stress from the die wall surface inside the die plate was 10 mm.

The temperature of the powder granules immediately after granulation was varied depending on factors such as the number of rotations of the roller of the granulator, the effective pressurizing length of the die hole, and the heating or cooling of the die plate.

To measure the temperature of the granulated material immediately after granulation, after the granulation has stabilized, stop the equipment, insert a thermocouple directly into the die hole, and quickly measure the temperature of the compressed powder inside the die. It was measured by The measurement was performed five times, and the average value was taken as the temperature of the granulated material (Tp) immediately after granulation. Even when granulation became impossible due to the powder sticking to the die or clogging, etc., a thermocouple was directly inserted into the powder to measure the temperature.

In Example 1, the temperature of the granules immediately after granulation (Tp) is -5°C (i.e., the temperature of the granules is 76°C) with respect to the softening start temperature (81°C) of the raw material acrylic resin powder A1. In this example, substantially cylindrical granules could be stably obtained.

A photograph showing the appearance of the powder granules of Example 1 is shown in FIG. As shown in FIG. 1, substantially cylindrical compression granules could be stably obtained.

The side surface of the powder granules obtained in Example 1 has an outer wall structure (shell structure) containing a melt of the constituent components of the thermoplastic resin powder, and the inside of the outer wall structure (core part) contains , traces of unmelted powder were confirmed. FIG. 2 shows a cross-sectional photograph of the powder granules obtained in Example 1 in a plane perpendicular to the longitudinal direction (extrusion direction).

The powder granules of Example 1 had a bulk density of 0.58 kg/L, a moisture content of 0.12% by mass, and a breaking strength of 6.9 kg, indicating that the powder granules had excellent handling properties. It was grainy.

[Example 2]
Example 2 is a case where the temperature of the granules immediately after granulation (Tp) is -15°C (i.e., the temperature of the granules is 66°C) with respect to the softening start temperature (81°C) of the raw material acrylic resin powder A1. This is an example. Granule temperature was controlled by lowering the roller rotation speed. The obtained powder granules had a core-shell structure as in Example 1.

The powder granules of Example 2 had a bulk density of 0.52 kg/L, a moisture content of 0.2% by mass, and a breaking strength of 5.1 kg, making it a powder product with excellent handling properties. It was grainy.

[Example 3]
In Example 3, the temperature of the granules immediately after granulation (Tp) is -26°C (i.e., the temperature of the granules is 55°C) with respect to the softening start temperature (81°C) of the raw material acrylic resin powder A1. This is an example. The temperature of the granules was controlled by further lowering the roller rotation speed and by blowing air onto the disk plate for forced cooling. The obtained powder granules had a core-shell structure as in Example 1.

The powder granules of Example 3 had a bulk density of 0.6 kg/L, a water content of 0.15% by mass, and a breaking strength of 2.7 kg, making it a powder product with excellent handling properties. It was grainy.

Table 1 shows the manufacturing conditions of the powder granules obtained in Examples 1 to 3 and various measurement results of the powder granules.

[Comparative example 1]
Comparative Example 1 is a case where the temperature of the granules immediately after granulation (Tp) is -41 °C (i.e., the temperature of the granules is 40 °C) with respect to the softening start temperature (81 °C) of the raw material acrylic resin powder A1. This is an example. The temperature of the granules was controlled by changing the effective length of the die to 5 mm and forcing the disk plate to cool.

In Comparative Example 1, the acrylic resin powder A1 passed through the die hole as a powder, and no granules could be obtained.

[Comparative example 2]
Comparative Example 2 is an example in which the temperature of the granules immediately after granulation is +14°C (that is, the temperature of the granules is 95°C) with respect to the softening start temperature (81°C) of the raw material acrylic resin powder A1. . The temperature of the granules was controlled by forcibly heating the disk plate using an external heater.

In Comparative Example 2, the acrylic resin powder A1 clogged the die holes, making it impossible to obtain granules.

Table 1 shows the results of evaluating the powder granules obtained in Examples 1 to 3 and Comparative Examples 1 to 2.

[Example 4] Biopolyester powder granules Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), which is a type of PHA and is a copolymer polyester of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid. (PHBH) pellets (manufactured by Kaneka Corporation, trade name "Green planet

When biopolyester powder A2 was subjected to DSC measurement, the softening start temperature (Ts) was 80°C. As shown in Figure 3, the softening start temperature (Ts) was determined from the temperature at the intersection of the baseline from the low temperature section and the tangent at the inflection point on the melting start side of the first observed crystal melting endothermic peak. .

In the same manner as in Example 1, biopolyester powder A2 was charged into a disc pelleter to obtain powder granules.

In Example 4, the temperature (Tp) of the granules immediately after granulation was 81°C, and the difference from the softening start temperature (Ts: 80°C) was 1°C, but the granules were stably formed into approximately cylindrical shapes. I was able to obtain some grains. The side surface of the obtained powder granule has an outer wall structure (shell structure) made of a molten polymer obtained by melting the constituent components of the thermoplastic resin powder, and inside the outer wall structure (core part), An unmelted powder-like appearance was confirmed. A photograph showing the appearance of the powder granules of Example 4 is shown in FIG. A cross-sectional photograph of the powder granules of Example 4 is shown in FIG.

The powder granules of Example 4 have a bulk density of 0.50 kg/L, a moisture content of 0.48% by mass, a breaking strength of 10 kg or more, and are powder granules with excellent handling properties. It was a thing.

[Example 5] Injection molding using powder granules The powder granules made of acrylic resin powder A1 obtained in Example 1 were put into an injection molding machine (manufactured by Shibaura Co., Ltd., trade name "EX75SX"). By setting the resin temperature at 240°C, the mold temperature at 60°C, and cooling for 30 seconds, a business card-sized molded product (88 mm x 53 mm, 3-tier plate with thicknesses of 1, 2, and 3 mm) could be obtained. A photograph of the obtained injection molded article is shown in FIG.

[Example 6] Sheet extrusion molding using powder granules The powder granules made of biopolyester powder A2 (PHBH) obtained in Example 4 were processed using a sheet extruder (manufactured by Technovel Co., Ltd., product name: KTZ15'') and passed through a T-shaped die at an extrusion rate of 2 kg/Hr to obtain a single-layer extruded sheet with a thickness of 0.5 mm and a width of 100 mm. The roll temperature was 20° C. and the winding speed was 5 m/min.

In Example 6, extrusion molding was performed without "melt-kneading pelletizing", but it was possible to obtain a sheet molded product almost equivalent to that obtained when melt-kneading pelletizing was used. A photograph of the obtained sheet molded body is shown in FIG.

[Example 7]
Pellets of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) (manufactured by Kaneka Corporation, product name "Green planet X151A", hexanoate content 11%) were pulverized to obtain a pulverized product. was sieved through a 10-mesh wire mesh to obtain biopolyester powder A3.

Biopolyester powder A3 was subjected to DSC measurement in the same manner as in Example 4, and the softening start temperature (Ts) was measured to be 80°C.

100 parts by mass of biopolyester powder A3 was put into an FM mixer (manufactured by Nippon Coke Industry Co., Ltd., trade name "5FM5C/I"; processing volume: 5 L), and the stirring blades were rotated at a rotation speed of 2,000 rpm. Meanwhile, 20 parts by mass of clean water (tap water) was continuously sprayed into the biopolyester powder A3 for 10 minutes to obtain a water-containing powder mixture.

The blades of the FM mixer are a combination of upper and lower blades, the upper blade is a Y1 blade (product name, manufactured by Nippon Coke Co., Ltd.), and the lower blade is an S0 blade (product name, manufactured by Nippon Coke Co., Ltd.). did. Additionally, a baffle plate (also referred to as a deflector) was installed inside the stirring tank.

This water-containing powder was charged into a disk pelleter in the same manner as in Example 1 to obtain a substantially cylindrical granulated precursor.

Example 7 uses a semi-wet granulation method, and the presence of an appropriate amount of moisture increases the bulk density of the powder, improves the penetration of the powder into the die holes, and also improves the granulation process during granulation. It has the effect of suppressing excessive heat generation and die clogging, and as a result of these effects, it can improve the granulation rate, and the granulation rate of the granule precursor granules can be increased to 88 kg/Hr. It's arrived.

In Example 7, the granule precursor temperature immediately after granulation was 54°C, which was -26°C (that is, the granulate temperature was 54°C) compared to the softening start temperature (80°C) of the raw material biopolyester powder A3. ℃). In Example 7, cylindrical granules could be stably obtained.

The obtained granule precursor was dried at 140°C using a hot air circulation dryer (manufactured by ESPEC, trade name "PH-402") until the moisture content became 0.5 wt% or less, A powder granule was obtained.

The obtained powder granules had a core-shell structure as in Example 1. A cross-sectional photograph of the powder granules of Example 7 is shown in FIG.

The powder granules of Example 7 have a bulk density of 0.49 kg/L, a moisture content of 0.27% by mass, a breaking strength of 10.0 kg or more, and are powders with excellent handling properties. It was a granulated product.

[Example 8]
Biopolyester powder A3 used in Example 7 was charged into a disc pelleter in the same manner as in Example 1 to obtain powder granules. In Example 8, unlike Example 7, water was not added.

The obtained powder granules had a core-shell structure as in Example 1. A cross-sectional photograph of the powder granules of Example 8 is shown in FIG.

The powder granules of Example 8 have a bulk density of 0.53 kg/L, a water content of 0.52% by mass, a breaking strength of 10.0 kg or more, and are powders with excellent handling properties. It was a granulated product.

[Example 9]
Polyhydroxyalkanoate (PHA) pellets (manufactured by Danimer Scientific, USA, trade name "DAH-04267") were pulverized, and the pulverized product was sieved through a 10-mesh wire mesh to obtain biopolyester powder A4.

Biopolyester powder A4 was subjected to DSC measurement in the same manner as in Example 4, and the softening start temperature (Ts) was measured to be 85°C.

Example 9 is an example in which biopolyester powder A4 was used and 20 parts by mass of tap water was blended in the same manner as in Example 7 to perform granulation.

In Example 9, the granulation rate of the granulated product was 39 kg/Hr, the temperature of the granulated product precursor immediately after granulation was 76°C, and the softening start temperature (85°C) of the raw material biopolyester powder A3 The temperature of the granules was -9°C (ie, the temperature of the granules was 76°C). In Example 9, a substantially cylindrical granule precursor could be stably obtained.

The obtained granule precursor was dried at 140° C. using a hot air circulation dryer in the same manner as in Example 7 until the moisture content became 0.5 wt% or less to obtain a powder granule. . The obtained powder granules had a core-shell structure. A cross-sectional photograph of the powder granules of Example 9 is shown in FIG.

The powder granules of Example 9 have a bulk density of 0.35 kg/L, a moisture content of 0.30% by mass, a breaking strength of 10.0 kg or more, and are powders with excellent handling properties. It was a granulated product.

The evaluation results of Examples 4 and 7 to 9 are shown in Table 2.

[Comparative example 3]
The biopolyester powder A3 used in Example 7 was continuously charged into a twin-screw extruder (manufactured by Nippon Steel Corporation, trade name "TEX44αII", L/D = 42, cylinder set temperature: 140 ° C.), and melt-kneaded. , produced pellets of a thermoplastic resin composition.

Biopolyester powder A3 was quantitatively fed into the extruder from the most upstream hopper position of the extruder via a gravimetric feeder. The rotation speed of the screw was set to 81 rpm, the strand was pulled out from the die at the tip of the extruder, the strand was cooled with water at a temperature of 60°C, and the pelletizer (manufactured by Isuzu Corporation, product name "HSCR-150") was used to cut the strand into a length of about 3 mm. Pelletization was performed to obtain "melt-kneaded pellets" of biopolyester powder A3.

When charging the biopolyester powder A3 to the extruder, the material charging speed is increased stepwise, and the feeding speed is set at a speed that maximizes the compound processing speed per hour (i.e., a feedneck of raw material powder to the extruder occurs). As a result, the maximum discharge rate remained at 60 kg/Hr.

The obtained melt-kneaded pellets were dried at 80° C. using a hot air circulation dryer in the same manner as in Example 7 until the water content became 0.2 wt % or less to obtain melt-kneaded pellets.

As in Example 7, the amount of power consumed in each process and the amount of carbon dioxide generated in the process (calculated values) were calculated for each unit mass (per kg) of granules. The results are shown in Table 3.

A comparison between Examples 7 and 8 and Comparative Example 3 revealed that the "powder polymer granules" of the present invention were found to be more stable than "melt-kneaded pellets" using a twin-screw extruder that uses a large heat source heater and power. It has been shown that the amount of CO ₂ emitted from the process can be significantly reduced.

Claims (16)

A powder granule containing thermoplastic resin powder, the outer wall having an outer wall formed by melting at least a portion of the thermoplastic resin powder located at the outer edge of the powder granule. Powder granules are compressed granules that contain compressed thermoplastic resin powder inside. The powder granule according to claim 1, wherein at least a portion of the compressed thermoplastic resin powder inside the outer wall portion includes an unmolten compressed powder form. The powder granule according to claim 1, wherein at least a portion of the compressed thermoplastic resin powder inside the outer wall portion includes a partially melted form. The powder granule according to claim 1, wherein the powder granule has a substantially cylindrical or substantially prismatic shape. The powder granule according to claim 4, having an outer wall portion on a side surface of the powder granule. The powder granule according to claim 5, having a breaking strength of 2.0 kg or more. The powder granule according to claim 4, wherein the powder granule has a height of 1 mm or more.. The powder granules according to claim 1, wherein the thermoplastic resin powder contains a thermoplastic resin having a softening onset temperature of 50 to 150°C. The powder granules according to claim 1, wherein the thermoplastic resin powder contains a thermoplastic resin having a softening start temperature of 60 to 90°C. The thermoplastic resin powder is acrylic resin, methacrylic resin, polyhydroxyalkanoate (PHA) resin, polyolefin resin, polyamide resin, polyacetal resin, polyphenylene ether (PPE) resin, polyphenylene sulfide (PPS). resin, polyetheretherketone (PEEK) resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyester resin, polycarbonate (PC) resin, polystyrene resin, polyketone resin, liquid crystal polymer ( The powder granules according to claim 1, comprising at least one selected from the group consisting of LCP) and core-shell type polymers. The powder granule according to claim 1, wherein the thermoplastic resin powder contains a PHA-based resin. A method for producing a powder granule according to any one of claims 1 to 11, comprising:
It includes a compression granulation process in which thermoplastic resin powder is granulated by a compression granulation method in which the thermoplastic resin powder is extruded through a die hole.
A method in which the compression granulation step is performed under conditions where the granulated material temperature Tp (°C) immediately after granulation and the softening start temperature Ts (°C) of the thermoplastic resin powder satisfy formula (1):
Formula (1): Ts-30≦Tp≦Ts+10. A claim in which the temperature of the die is controlled so that the temperature of the granulated material immediately after granulation Tp (°C) and the softening start temperature Ts (°C) of the thermoplastic resin powder satisfy equation (1). 12. The method described in 12. 13. 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 due to frictional heat with the wall surface or heat transfer from the wall surface. the method of. The method according to claim 14, wherein the compression granulation is performed using a disk pelleter type compression granulation device. 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.