JP2023103590A - Injection molding pellet manufacturing equipment and method of manufacturing pellets for injection molding - Google Patents

Abstract

To provide an injection molding pellet manufacturing device that reduces the tact time of pellets for injection molding, and a method for manufacturing pellets for injection molding.SOLUTION: An injection molding pellet manufacturing apparatus 100 has a mixing section 50 that mixes fibers and thermoplastic material in air to make a mixture, a deposition section 60 that deposits the mixture in air to make a web W, a forming section 87 that pressurizes and heats the web W to make a sheet molding product S, and a shredding section 90 that shreds the sheet molding product S to make pellets P for injection molding.SELECTED DRAWING: Figure 2

Description

The present invention relates to an injection molding pellet manufacturing apparatus and a method for manufacturing injection molding pellets.

Conventionally, a technique for producing injection molding pellets containing fibers such as waste paper and a thermoplastic material is known. For example, Patent Document 1 discloses a molding composition produced from waste paper pellets and thermoplastic resin pellets A method for doing so is disclosed.

JP-A-2000-52339

However, the technique described in Patent Document 1 has a problem that it is difficult to shorten the tact time of injection molding pellets. Specifically, in this technique, waste paper pellets and thermoplastic resin pellets are heat-kneaded and then granulated. Therefore, it sometimes takes time to heat and knead. That is, there has been a demand for an injection molding pellet manufacturing apparatus that shortens the tact time.

The injection molding pellet manufacturing apparatus includes a mixing section that mixes fibers and a thermoplastic material in the air to form a mixture, a deposition section that deposits the mixture in the air to form a web, and pressurizes and presses the web. It comprises a molding section that heats and forms a sheet molding, and a chopping section that shreds the sheet molding into pellets for injection molding.

A method for producing injection molding pellets includes a mixing step of mixing fibers and a thermoplastic material in air to form a mixture, a depositing step of depositing the mixture in air to form a web, and pressing the web. and heating to form a sheet molding, and a chopping step of chopping the sheet molding into pellets for injection molding.

FIG. 2 is a flowchart showing a method for manufacturing injection-molding pellets according to the embodiment. The schematic diagram which shows the structure of the pellet manufacturing apparatus for injection molding.

In the embodiments described below, an injection-molding pellet manufacturing apparatus for manufacturing injection-molding pellets in a dry process and a method for manufacturing injection-molding pellets are exemplified and described with reference to the drawings. For convenience of illustration, the size of each member is different from the actual size.

In FIG. 2, the Z-axis, which is the coordinate axis, is attached, the direction indicated by the arrow is the +Z direction, and the direction opposite to the +Z direction is the -Z direction. The Z axis is a virtual axis along the vertical direction, and the -Z direction is the vertical direction. The +Z direction is sometimes called upward, and the −Z direction is sometimes called downward. Further, in the injection molding pellet manufacturing apparatus, the side in which the raw material or the web is conveyed is sometimes referred to as the downstream, and the side in which the conveying direction is reversed is referred to as the upstream.

As shown in FIG. 1, the method for producing injection molding pellets according to the present embodiment includes a raw material supply step, a crushing step, a fibrillating step, a mixing step, a stacking step, a pre-pressurizing step, a molding step, and a shredding step. Including process.

In the method for producing injection-molding pellets, injection-molding pellets are produced through the respective steps in the above order, from the upstream raw material supply step to the downstream shredding step. The method for producing pellets for injection molding of the present invention includes a mixing step, a stacking step, a molding step, and a chopping step, and the other steps are not limited to those described above.

Next, a specific example of a method for manufacturing injection-molded pellets will be described together with an injection-molded pellet manufacturing apparatus. An injection-molding pellet manufacturing apparatus 100 according to the present embodiment manufactures injection-molding pellets. The injection molding pellet manufacturing apparatus 100 described below is an example and is not limited to this. In the following description, the injection molding pellet manufacturing apparatus 100 may be simply referred to as the pellet manufacturing apparatus 100.

As shown in FIG. 2, the pellet manufacturing apparatus 100 includes, from upstream to downstream, a supply section 10, a coarse crushing section 12, a defibrating section 20, a mixing section 50, a deposition section 60, a web conveying section 70, a preliminarily A pressure section 85 , a forming section 87 and a chopping section 90 are provided. In addition, although illustration is omitted, the pellet manufacturing apparatus 100 is also provided with a control section for integrally controlling the operations of the above components.

In the supply section 10, a raw material supply process is performed. The supply unit 10 supplies raw materials to the crushing unit 12 . The supply unit 10 , for example, continuously and automatically feeds raw materials into the crushing unit 12 . The raw material supplied by the supply unit 10 is a material containing fibers.

Fiber is one of the main components of the injection-molding pellets P produced by the pellet production apparatus 100 . The fibers affect properties such as strength of molded articles made from the pellets P for injection molding. It should be noted that the pellet P for injection molding may be simply referred to as the pellet P in the following description.

The fibers may be synthetic fibers containing synthetic resins such as polypropylene, polyester, polyurethane, etc., but from the viewpoint of reducing environmental load, fibers derived from natural products, ie, biomass, are preferable.

Among biomass-derived fibers, the fibers are more preferably cellulose fibers. Cellulose fibers are derived from plants and are relatively abundant natural materials. Therefore, the use of cellulose fibers promotes measures to reduce environmental loads. Cellulose fibers are also advantageous in raw material procurement and cost. In addition, cellulose fibers have theoretically high strength among various fibers, and contribute to improvement in the strength of the pellets P and molded articles produced from the pellets P. Materials containing fibers include, for example, platy pulp such as eucalyptus, waste paper, and the like.

Cellulose fibers are made primarily of cellulose, but may contain components other than cellulose. Examples of components other than cellulose include hemicellulose and lignin. Moreover, the cellulose fibers may be subjected to a treatment such as bleaching.

A coarse crushing process is performed in the coarse crushing unit 12 . The coarse crushing unit 12 chops the raw material supplied from the supply unit 10 into small pieces in an atmosphere such as the atmosphere. The crushing section 12 is a shredder having crushing blades 14 . The raw material is shredded into small pieces by the crushing blades 14 . The form of the strip is, for example, a substantially cubic shape or a substantially rectangular parallelepiped shape of several millimeters square. Raw material strips are collected in hopper 1 .

The hopper 1 is equipped with a weighing device (not shown). The weighing device weighs the small pieces of raw material collected in the hopper 1 and feeds them from the tube 2 through the introduction port 22 to the fibrillation section 20 at a constant rate.

A defibration step is performed in the defibration unit 20 . The disentanglement part 20 disentangles the small piece of the supplied raw material, and makes it a disentanglement thing. The term "fibrillation" as used herein refers to unraveling individual fibers from a state in which a plurality of fibers are integrated.

The length of a single independent fiber in the defibrated product is preferably, for example, 1 μm or more and 5 mm or less, more preferably 2 μm or more and 3 mm or less. When the length is within such a range, the pellets P can be easily manufactured, and when the pellets P are used to manufacture a molded product, the strength of the molded product is improved.

The defibration in the defibration unit 20 is performed dry. As used herein, the term "dry process" means that the process is performed in air such as the atmosphere without being performed in a liquid.

The disentanglement unit 20 generates an air current that sucks the raw material pieces and discharges the disentanglement material. As a result, the disentanglement unit 20 uses the airflow generated by itself to suck small pieces of the raw material from the introduction port 22 on the airflow, apply the disentanglement treatment, and then transfer it to the discharge port 24 as a disentanglement material. . The defibrated material is transferred from the outlet 24 to the pipe 54 . The defibrated material is transported through the tube 54 by the air current generated by the defibrating unit 20 and the air current generated by the blower 56 described below.

A mixing step is performed in the mixing section 50 . The mixing unit 50 mixes the defibrated material, which is the fiber, and the additive containing the thermoplastic material in the air to form a mixture. The mixing section 50 has an additive feed section 52 , a tube 54 and a blower 56 . The interior of the tube 54 is continuous with the upstream outlet 24 . The additive supply part 52 supplies the additive into the pipe 54 via the hopper 9 . For example, a screw feeder or a disk feeder is adopted as the additive supply unit 52 .

Additives include a thermoplastic material as a binder, a colorant, a release agent, an aggregation inhibitor, a flame retardant, and the like. Pigments and dyes are used as coloring agents. The coloring agent colors the pellets P and molded articles made from the pellets P. A metal soap or the like is used as a release agent. The release agent improves releasability when a molded product is produced from the pellets P by injection molding. Aggregation inhibitors suppress aggregation of defibrated materials and additives. The flame retardant imparts flame retardancy to the pellets P and molded articles made from the pellets P. As additives, an antioxidant, an ultraviolet absorber, an antiseptic, an antifungal agent, and the like may be used.

The binding agent binds the fibers contained in the defibrated material to improve physical properties such as the strength of the pellets P and molded articles produced from the pellets P. The binder comprises a thermoplastic material. By containing a thermoplastic material, properties such as physical properties of the pellets P and molded articles made from the pellets P can be improved. Examples of thermoplastic materials include starch, dextrin, and sizing agents such as polyvinyl alcohol, which exhibit binding properties when water is applied. The thermoplastic material is melted by the heating of the molding section 87, which will be described later, to promote mixing with the fibers. Note that the binder may contain a thermosetting material in addition to the thermoplastic material.

The thermoplastic material may be either natural resin or thermoplastic resin, and examples thereof include biodegradable plastics such as thermoplastic resin, thermoplastic starch, polylactic acid, and polybutylene succinate.

Thermoplastic resins include AS resin (acrylonitrile-styrene copolymer), ABS resin (acrylonitrile-butadiene-styrene copolymer), polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylic resin, polyester resin, polyethylene terephthalate, polyphenylene. Ether, polybutylene terephthalate, nylon, polyamide, polycarbonate, polyacetal, polyphenylene sulfide, polyether ether ketone, and the like. These resins may be used singly or as an appropriate mixture. In addition, copolymerization or modification may be performed, and examples of such resin systems include styrene resins, acrylic resins, styrene-acrylic copolymer resins, olefin resins, vinyl chloride resins, and polyester resins. resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, styrene-butadiene resins, and the like.

The shape of the thermoplastic material may be particulate or fibrous. When the thermoplastic material is particulate, the average particle size is preferably 100 μm or less, more preferably 10 μm or less. According to this, the miscibility between the defibrated material and the thermoplastic material is improved, and the dropping of the thermoplastic material from the mixture is suppressed. The average particle size referred to here refers to a volume-based particle size distribution (50%) measured by a dynamic light scattering method.

When the thermoplastic material is fibrous, the fiber length is preferably 50 μm or more and 100 mm or less, more preferably 30 mm or less. In addition, the fiber length here refers to the average fiber length (mm) measured by the staple diagram method.

One or a plurality of additive supply units 52 may be provided. When one additive supply unit 52 is provided, a mixture of a plurality of additives is supplied in advance. Alternatively, a plurality of additive supply units 52 may be provided and the additive may be supplied individually from each additive supply unit 52 .

A blower 56 generates an airflow inside the tube 54 . The airflow mixes the fibrillated material and the additive that have reached the pipe 54 to form a mixture and transports it downstream. The mechanism for mixing the fibrillated material and the additive is not limited to the blower 56, and may be a blade that rotates at high speed, or a V-type mixer that utilizes rotation of a container. The mixture is then transferred from tube 54 to deposition section 60 .

A deposition process is performed in the deposition section 60 . The depositing section 60 deposits a mixture containing fibers into a web W in the air. The deposition section 60 has a drum section 61 and a housing section 63 that houses the drum section 61 . The deposition section 60 takes the mixture from the inlet 62 into the drum section 61 and deposits it on the mesh belt 72 in a dry manner.

A web transport section 70 including a mesh belt 72 and a suction mechanism 76 is arranged below the deposition section 60 . The suction mechanism 76 is arranged to face the drum section 61 with the mesh belt 72 interposed therebetween in the direction along the Z axis.

The drum portion 61 is a cylindrical sieve that is rotationally driven by a motor (not shown). A net having a sieve function is provided on the side surface of the cylindrical drum portion 61 . The drum portion 61 allows fibers and additive particles smaller than the mesh size of the sieve to pass from the inside to the outside. In the mixture, tangled fibers are loosened by the drum portion 61 and dispersed in the air inside the housing portion 63 .

Note that the sieve of the drum section 61 may not have the function of sorting out large fibers or the like in the mixture. That is, the drum portion 61 may loosen the fibers of the mixture and release all of the mixture inside the housing portion 63 . The mixture dispersed in the air inside the housing portion 63 is deposited on the upper surface of the mesh belt 72 by gravity and suction of the suction mechanism 76 .

The web transport section 70 has a mesh belt 72 and a suction mechanism 76 . The web transport section 70 promotes deposition of the mixture onto the mesh belt 72 by means of a suction mechanism 76 . Further, the web conveying section 70 conveys the web W formed from the mixture downstream by rotating the mesh belt 72 .

The suction mechanism 76 is arranged below the drum portion 61 . The suction mechanism 76 sucks the air in the housing portion 63 through multiple holes of the mesh belt 72 . As a result, the mixture discharged to the outside of the drum portion 61 is sucked downward together with the air and deposited on the upper surface of the mesh belt 72 . A known suction device such as a blower is employed for the suction mechanism 76 .

The plurality of holes in the mesh belt 72 allows air to pass through, but does not easily allow the fibers and additives contained in the mixture to pass through. The mesh belt 72 is an endless belt and stretched by four tension rollers 74 .

The upper surface of the mesh belt 72 moves downstream due to the rotation of the tension roller 74 . In other words, the mesh belt 72 rotates clockwise in FIG.

The suction mechanism 76 sucks the air inside the housing portion 63 in which the mixture is dispersed through the plurality of holes of the mesh belt 72 . As a result, the mixture is attracted and deposited on the upper surface of the mesh belt 72 . At this time, the web W is formed by continuously depositing the mixture by rotating the mesh belt 72 by the tension roller 74 . The web W contains a relatively large amount of air and is soft and swollen. As the mesh belt 72 moves, the web W is conveyed toward the downstream prepressing section 85 .

The thickness of the web W is, for example, 800 g/m ² or more and 1200 g/m ² or less. The thickness of the web W is adjusted by the transfer amount of the mixture to the depositing section 60 per unit time, the rotating speed of the mesh belt 72, and the like.

The content of fibers in the web W is, for example, 10% by mass or more and 90% by mass or less, preferably 20% by mass or more and 80% by mass or less, more preferably 40% by mass, relative to the total mass of the web W. It is more than 60 mass % or less.

The content of the thermoplastic material in the web W is, for example, 1% by mass or more and 90% by mass or less, preferably 5% by mass or more and 80% by mass or less, more preferably 40% by mass, relative to the total mass of the web W. It is more than mass % and below 60 mass %.

The content of additives such as thermoplastic materials and fibers in the web W depends on the supply amount of the defibrated material transferred from the defibration unit 20 to the pipe 54 and the supply of the additive supplied from the additive supply unit 52. Adjusted by quantity.

Here, the web W formed on the mesh belt 72 may be humidified. Specifically, for example, a humidifying section 78 is provided above the conveying path of the web W. As shown in FIG. The humidifying section 78 humidifies the web W by spraying water mist onto the web W. FIG. A known spraying device such as a sprayer is adopted for the humidifying section 78 . By moistening the web W, when starch or the like is used as a binding agent, the binding agent absorbs moisture, and the strength of the pellets P and the molded article produced from the pellets P is improved.

A preliminary pressurizing step is performed in the preliminary pressurizing unit 85 . The pre-pressurizing section 85 preliminarily pressurizes the web W on the upstream side of the forming section 87 which will be described later. The pre-pressurizing unit 85 is, for example, a calendar device and has a pair of rollers.

The web W is drawn from the mesh belt 72 into the preliminary pressurizing section 85 and moved downstream while being pressurized between the pair of rollers. As a result, the web W is compressed, and the thickness of the web W in the direction in which the pressure is applied is reduced. Therefore, in the above-described direction of the web W, the heat applied by the downstream molding section 87 is easily propagated, and the web W can be efficiently heated.

The density of the web W that has passed through the pre-pressing section 85 is, for example, 0.6 g/cm ³ or more and 1.2 g/cm ^{3 or} less. The density of the web W is adjusted by the pressurization conditions of the preliminary pressurizer 85 . The web W advances through a pre-pressing section 85 to a shaping section 87 . Note that a preheating section that preliminarily heats the web W may be provided between the prepressurizing section 85 and the forming section 87 depending on the type of material and additives. The preheating section may heat the web W in a non-contact manner.

A molding process is performed in the molding section 87 . The shaping unit 87 presses and heats the web W to shape it into a sheet molding S. As shown in FIG. The forming section 87 is a contact-type heating device and has a pair of heating rollers.

Each of the pair of heating rollers of the molding section 87 incorporates an electric heater and has a function of heating the roller surface. By continuously passing the web W between a pair of heating rollers, the web W is pressed while being heated. As a result, a continuous document-like sheet molding S in which the fibers are bound together by the binding agent is manufactured.

Since the molding section 87 has a pair of heating rollers, the web W is heated and pressed in parallel, and is continuously molded. Therefore, thermal damage to the cellulose fibers contained in the web W is suppressed. In addition, the tact time can be further shortened compared to batch processing using a hot press device or the like.

The heating temperature by the molding unit 87 is preferably within a temperature range of ±20° C. with respect to the melting temperature of the thermoplastic material contained in the web W. This completes the melting of the thermoplastic material contained in the web W and mixes the fibers with the additive containing the thermoplastic material. In this specification, the melting temperature of a thermoplastic material refers to the melting point of the thermoplastic material. The sheet molding S advances from the shaping station 87 to the shredding station 90 .

A shredding process is performed in the shredding section 90 . The shredding unit 90 shreds the continuous form-shaped sheet molding S into pellets P. As shown in FIG. The shredding section 90 includes a shredder consisting of vertical blades 92 and horizontal blades 94 .

The vertical blade 92 shreds the sheet molding S in the direction along which the sheet molding S is conveyed. The horizontal blade 94 shreds the sheet molding S in a direction crossing the direction in which the sheet molding S is conveyed. Since the chopping unit 90 has the vertical blades 92 and the horizontal blades 94, variations in the shape of the pellets P can be suppressed, and the pellets P can be easily mass-produced.

The sheet molding S is shredded into pellets P and the pellets P are accommodated in trays 96 . In the shredding section 90 , the sheet molding S may be cut by the vertical blades 92 and taken out without being shredded by the horizontal blades 94 . Specifically, the sheet molding S may be cut into a thread and wound up.

The shape of the pellet P is, for example, a substantially cubic shape with sides of about 0.5 mm×2.0 mm×2.0 mm to about 3.0 mm×6.0 mm×15.0 mm. As a result, when producing a molded product from the pellets P, it becomes possible to put the pellets P into a twin-screw kneader or the like of an injection molding machine without processing. As described above, the pellets P are manufactured by the pellet manufacturing apparatus 100 .

The injection molding pellet manufacturing apparatus 100 of the present embodiment may be connected to an injection molding machine to operate as an injection molding system. Specifically, the pellets P are supplied from the tray 96 to the twin-screw kneader of the injection molding machine. Alternatively, the manufactured pellets P may be put into a hopper or the like of an injection molding machine without passing through the tray 96 .

Molded articles made from the pellets P include, for example, housings and parts of home electric appliances and office equipment, cutlery, tableware, and toys.

According to this embodiment, the following effects can be obtained.

The tact time of the pellets P for injection molding can be shortened. Specifically, since the fibers and the thermoplastic material are mixed in a dry process, a mixture is produced in a short time. Moreover, since the sheet molding S is shredded to form the pellets P, the time required for water removal is not required as compared with granulation by underwater extrusion. Therefore, an injection molding pellet manufacturing apparatus 100 that shortens the tact time of injection molding pellets P and a method for manufacturing injection molding pellets P can be provided.

50... Mixing section 60... Depositing section 87... Molding section 90... Chopping section 92... Vertical blade 94... Horizontal blade 100... Injection molding pellet manufacturing apparatus, P... Injection molding pellet, S... Sheet molding, W... web.

Claims (4)

a mixing section that mixes the fibers and the thermoplastic material in air to form a mixture;
a deposition unit for depositing the mixture in air into a web;
a molding unit that pressurizes and heats the web to form a sheet molding;
and a chopping unit that cuts the sheet molded product into pellets for injection molding. 2. The injection molding pellet manufacturing apparatus according to claim 1, wherein said shredder includes a shredder having vertical blades and horizontal blades. A mixing step of mixing the fibers and the thermoplastic material in air to form a mixture;
depositing the mixture in air into a web;
a molding step of pressurizing and heating the web to form a sheet molding;
A method for producing pellets for injection molding, comprising: a step of chopping the sheet molded product into pellets for injection molding. 4. The method for producing injection molding pellets according to claim 3, wherein the thermoplastic material is thermoplastic resin particles.

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