JP2000313027A - Injection molding method for resin magnet molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin magnet molded article efficiently and inexpensively by injection molding. SOLUTION: A thermoplastic resin and a magnetic powder are mixed in a predetermined ratio to be directly charged in an injection molding machine, and the binder resin is heated and melted in the cylinder 1 of the injection molding machine to be kneaded with the magnetic powder by the screw 2 in the cylinder 1 to prepare a resin magnet compsn. wherein the magnetic powder is mixed with and dispersed in the binder resin. This resin magnet compsn. is injected in the cavity 6 of a mold 5 from the front end of the cylinder 1 directly or through other injection cylinder to inject-mold a target molded article 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a resin magnet composition in which a magnetic powder is mixed and dispersed in a resin binder by injection molding.
The present invention relates to a method for manufacturing a resin magnet molded product.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus, a magnet roller used for a developing mechanism and a cleaning mechanism of an electrostatic latent image, a rotor and a stator of a motor, and a sensor. As a rotor or the like, a resin magnet molded product obtained by dispersing magnetic powder such as ferrite in a binder made of a thermoplastic resin such as nylon or polypropylene and molding it into a desired shape is used.

[0003] These resin magnet molded products are manufactured by molding a resin magnet composition obtained by dispersing and mixing magnetic powder in a resin binder into a desired shape. For example, a resin magnet composition in a cylinder in which a screw is disposed is provided. A molding material consisting of a resin magnet composition in which a magnetic powder is blended with a resin binder is added to the mixture, and the molding material is melt-plasticized by heating from the outside of the cylinder, and is fed forward in the cylinder by the screw. Then, the molten molding material is injected into the cavity of the mold directly from the front end of the cylinder or through an injection cylinder, and the molding material is cooled and solidified in the mold to obtain a desired shape. It is manufactured by a so-called injection molding method for obtaining a resin magnet molded product.

In this case, before a desired resin magnet molded product is obtained by the injection molding, the raw material thermoplastic resin and the magnetic powder are mixed, melt-kneaded and extruded, and the magnetic powder is first contained in a resin binder. A pellet-shaped molding material made of the dispersed resin magnet composition is obtained, and the pellet-shaped molding material is put into the cylinder of the injection molding machine, melt-kneaded again, and injection-molded to obtain a desired resin magnet molding. Getting it done is done. As described above, by temporarily molding the molding material into a pellet, the binder resin and the magnetic powder are pre-kneaded to form a molding material in which the magnetic powder is dispersed in the resin binder, and the pellet-shaped molding material is randomly taken out. By melting and kneading this again and injection-molding the desired resin magnet molded product, the dispersion uniformity of the magnetic powder can be improved, and the desired resin magnet molded product can be stably obtained without variation. Is being done.

[0005]

However, the conventional method of once extruding the binder resin and the magnetic powder into pellets and injection-molding the pellet-shaped molding material to obtain the desired molded product is a conventional method. Although it is a wise method from the viewpoint of manufacturing without variation, it is obviously not preferable in terms of manufacturing efficiency because it is performed twice, namely, extrusion molding at the time of pellet molding and injection molding at the time of molding the target object. In particular, magnet rollers used in electrophotographic devices such as copiers and printers and electrostatic recording devices are often incorporated in toner cartridges and treated as consumables in recent years.
An increase in manufacturing cost due to a single molding operation is a major problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for injection-molding a resin magnet molded product from which a resin magnet molded product can be obtained efficiently and inexpensively.

[0007]

Means for Solving the Problems According to the present invention, as a result of intensive studies to achieve the above object, a thermoplastic resin as a binder resin and a magnetic powder are mixed at a predetermined ratio, and this is directly mixed with an injection molding machine. The thermoplastic resin of the binder resin is heated and melted in the cylinder of the injection molding machine, and the molten binder resin and the magnetic powder are kneaded by the rotation of a screw disposed in the cylinder, thereby forming a resin binder. A resin magnet composition in which magnetic powder is mixed and dispersed is prepared, and this is injection-injected into the mold cavity directly from the front end of the cylinder or through another injection cylinder to injection-mold a target molded article. Even if the molding material is melted and kneaded in an injection molding machine without undergoing pelletization and the target molded product is directly injection molded, there is no practical problem with good resin magnet molding. It can be obtained and found to be produced efficiently at low cost resin magnet molded product by omitting the pelletizing step.

Further, depending on the type of thermoplastic resin constituting the molding material, the binder resin and the magnetic powder are kneaded without pelletizing to prepare a resin magnet composition, which is directly injection-molded. It has been found that a high-performance resin magnet molded product can be obtained by performing the heat-melting operation twice by the conventional molding method.

That is, in the conventional molding method through pelletization, the molding material is formed into a target molded product through two melt-kneading operations. In this case, the thermoplastic resin of the binder resin constituting the molding material includes: Heating may cause performance degradation due to a decrease in molecular weight and the like, and a plurality of heating and melting operations are not preferable in terms of the performance of the obtained molded product. In particular, magnet rollers used in electrophotographic and electrostatic recording devices such as copiers and printers often require high dimensional stability and magnetic properties, and the performance of molding materials deteriorates due to multiple heating and melting operations. There is also a risk that the performance of the product obtained is reduced. For this reason, the binder resin and the magnetic powder are melted and kneaded without undergoing pelletization, and immediately after the resin magnet composition is prepared, the target molded product is injection-molded to reduce the performance degradation due to thermal degradation of the resin. It has been found that a resin magnet molded product having good performance can be more reliably obtained as compared with the case of passing through.

Accordingly, the present invention provides a method in which a molding material in which a magnetic powder is blended with a thermoplastic resin is charged into a cylinder in which a screw is disposed, and the molding material is melt-plasticized by heating from the outside of the cylinder. The mixture is kneaded by the rotation of the screw and is fed forward through the cylinder, and the molten molding material is injected into the mold cavity directly from the front end of the cylinder or through an injection cylinder. Then, in the injection molding method of a resin magnet molded product that obtains a resin magnet molded product of a desired shape by cooling and solidifying the molding material in a mold, the molding is performed by mixing the thermoplastic resin and the magnetic powder at a predetermined ratio. The material is put directly into the cylinder, the thermoplastic resin is melt-plasticized in the cylinder, and the melt-plasticized thermoplastic resin is turned by the rotation of the screw. A magnetic resin and a magnetic powder are kneaded to prepare a resin magnet composition in which the magnetic powder is mixed and dispersed in a resin binder, and this is injection-injected into the cavity of the mold to directly obtain a target molded product. An object of the present invention is to provide a method of injection molding a resin magnet molded product.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the injection molding method for a molded resin magnet of the present invention will be described more specifically with reference to examples. FIG. 1 shows an example of an injection molding machine used when carrying out the injection molding method of a resin magnet molded product of the present invention, and the method of injection molding a resin magnet molded product of the present invention using the injection molding machine. 1 shows a procedure and an operation for injection molding a magnet roller for supplying toner to the surface of an image forming body such as a photosensitive drum in an electrophotographic apparatus or an electrostatic recording apparatus.

The above injection molding machine has a cylindrical cylinder 1
And a screw 2 disposed in the cylinder 1. The screw 2 is rotated by being driven by a motor m, and is advanced and retracted in the cylinder 1 by a hydraulic cylinder s. . Also, cylinder 1
Is provided with a band heater 3 covering the outer periphery thereof. The inside of the cylinder 1 is heated by the band heater 3 and the base end side (the right side in the figure) of the cylinder 1 A hopper 4 for charging a molding material into the cylinder 1 is provided. Further, a front end (left end in the figure) of the cylinder 2 is connected to a mold 5, and an inner space of the cylinder 1 is a runner (not shown).
It is in a state of communicating with the cavity 6 of the mold 5 via a sprue (not shown) and a gate (not shown).
Further, although not particularly shown, one or a plurality of permanent magnets are provided around the cavity 6 of the mold 5, and a magnetic field is generated in the cavity 6 of the mold 5 by the permanent magnet. Is formed.

The procedure and operation of manufacturing a magnet roller (resin magnet molded product) by this injection molding machine according to the injection molding method of the present invention will be described with reference to FIG.
First, a thermoplastic resin (powder, granule or pellet) serving as a binder resin and a magnetic powder are mixed at a predetermined ratio, and if necessary, other additives are blended and mixed. Hopper 4 in cylinder 1
Is heated in the cylinder 1 by the band heater 3 to heat and melt the thermoplastic resin, and the thermoplastic resin melt-plasticized by the rotation of the screw 2 and the magnetic powder are kneaded to form a resin. A resin magnet composition in which magnetic powder is mixed and dispersed in a binder is prepared in a cylinder 1 (FIG. 1A). After the resin magnet composition is pressure-fed inside the cylinder 1 by rotation of the screw 2, a predetermined amount of the resin magnet composition is prepared.
Once the rotation of the screw 2 is stopped, the screw 2 is advanced by the hydraulic cylinder s,
A molding roller in a molten state is injected and injected into the cavity 6 of the mold 5 from the front end of the mold 5 and the molding material is cooled and solidified in the mold 5 to form a magnet roller (FIG. 1).
(B)). In this case, a magnetic field formed by a permanent magnet provided in the mold 5 is applied to the resin magnet composition injected and injected into the cavity 6 of the mold 5, and the magnetic powder in the resin magnet composition is applied. Are oriented in a desired orientation state, and the molded product is magnetized. Next, the mold 5 is opened, and the molded magnet roller 7 is taken out of the mold 5 (FIG. 1).
(C)), a runner, a sprue and the like are cut off, and a finishing process such as polishing is performed as necessary to obtain a final product.

Thus, in the injection molding method of the present invention,
The thermoplastic resin of the binder resin and the magnetic powder are mixed at a predetermined ratio, and the mixture is directly charged into an injection molding machine, and the thermoplastic resin of the binder resin is heated and melted in the cylinder 1 of the injection molding machine. The melted binder resin and the magnetic powder are kneaded by a screw 2 disposed in a cylinder 1 to prepare a resin magnet composition, which is directly injected and injected into a cavity 6 of a mold 5, This is a method in which a molding material is melt-kneaded in an injection molding machine without undergoing pelletization, and then a resin magnet molded product is directly injection-molded.

Further, according to the injection molding method of the present invention, the raw material thermoplastic resin and the magnetic powder are mixed at a predetermined ratio without directly forming the molding material into pellets, and are directly injected into an injection molding machine.
A resin magnet composition is prepared by melting and kneading in a cylinder 1 of the injection molding machine, and the resin magnet composition is directly injected into a cavity 6 of a mold 5 to form a target molded product.
The magnet roller (resin magnet molded product) can be manufactured efficiently and inexpensively by omitting the pelletizing step.

Further, the desired molded product is injection-molded immediately after the binder magnet and the magnetic powder are melt-kneaded without pelletizing to prepare a resin magnet composition.
According to the injection molding method of the present invention in which a target molded product is obtained by a melting operation of a degree, it is possible to suppress a decrease in performance due to thermal deterioration of a resin as compared with a conventional method of performing a melting operation at least twice through pelletization. Thus, a molded resin magnet having good performance can be obtained more reliably.

Here, the thermoplastic resin used as the binder resin is not particularly limited, and is appropriately selected according to the type and use of the desired resin magnet molded product. Specifically, polyamide resins such as nylon 6 and nylon 12, polystyrene resin, polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), and polyphenylene sulfide resin (P
PS), ethylene-vinyl acetate copolymer resin (EV
A), ethylene-ethyl acrylate resin (EEA),
Epoxy resin, ethylene-vinyl alcohol copolymer resin (EVOH), polypropylene resin, polyethylene,
Examples include polyolefins such as polyethylene copolymers, and modified polyolefins in which a reactive functional group such as a maleic anhydride group, a carboxylic acid, a hydroxyl group, or a glycidyl group is introduced into the structure of these polyolefins. Alternatively, two or more kinds can be used as a mixture.

The magnetic powder is not particularly limited, either, and is appropriately selected according to the type and use of the desired molded product. Specifically, ferrite powders such as Sr ferrite and Br ferrite, Sm-Co alloy, Nd-F-
Rare earth alloy powders such as B alloy and Ce-Co alloy can be exemplified.

The mixing ratio of the magnetic powder is appropriately selected according to the strength of the magnetic force required for the target molded product, and is not particularly limited. It is preferred to be about 80 to 94% by weight.

The molding material used in the injection molding method of the present invention is a mixture of the thermoplastic resin as the binder resin and the magnetic powder.
An appropriate amount of a filler having a large reinforcing effect such as mica, whisker, talc, carbon fiber, or glass fiber or other known additives can be added.

In the injection molding method of the present invention, a molding material in which the above-mentioned thermoplastic resin, magnetic powder, and other optional additives are mixed in a predetermined ratio is charged into an injection molding machine, and directly from the molding material. Since the target molded product is injection molded, the mixed state of the components constituting the molding material greatly affects the uniformity of the obtained molded product. For this reason, it is important to mix the above components as uniformly as possible before putting them into an injection molding machine. It is important to mix the above molding materials as uniformly as possible in advance using a mixer such as a Henschel mixer. is necessary.

The injection molding machine used in the injection molding method of the present invention may be a conventional injection molding machine which is conventionally used, and is not particularly limited. In many cases, molding materials that are not subjected to molding have insufficient fluidity. Therefore, improvements such as increasing the number of revolutions of the screw 2 or increasing the length of the compression / kneading section compared with normal injection molding should be performed. If it is difficult for the molding material to bite into the screw 2, it is preferable to take measures such as adding a forced biting facility.

As described above, the injection molding method of the resin magnet molded article of the present invention has been described with reference to FIG. 1. An injection molding machine for carrying out the injection molding method of the present invention is the one shown in FIG. The present invention is not limited to this, and can be appropriately changed according to the type of the target resin magnet molded product, the production scale, and the like. For example, FIG. 1 shows an example in which a general-purpose in-line screw type injection molding machine in which a rotatable and retractable screw 2 is provided in a cylinder 1 is used, but a screw is inserted as an injection molding machine. Equipped with a screw cylinder for melt-kneading the molding material and an injection cylinder for injecting the molding material with an injection plunger inserted therein, and supplying the molding material melt-kneaded in the screw cylinder to the injection cylinder, An injection molding machine equipped with a pre-plasticizing device configured to inject the molding material melt-kneaded with the screw cylinder into the cavity of the mold with the injection cylinder may be used.

In the above embodiment, a permanent magnet is arranged in the mold 5 to orient the magnetic powder by applying a magnetic field.
Magnetization was performed at the same time as molding.However, a magnetic field may not be applied during molding, and the resin magnet molded product obtained after molding may be magnetized. After forming, the magnet may be demagnetized and magnetized again. Furthermore, the injection molding method of the present invention is particularly suitably employed when manufacturing a magnet roller used in a developing mechanism or a cleaning mechanism of an electrophotographic apparatus or an electrostatic recording apparatus as in the above embodiment. However, it is also suitably employed when obtaining other resin magnet molded products such as a motor rotor and a stator, and a sensor rotor.

[0025]

As explained above, according to the injection molding method of the resin magnet composition of the present invention, the raw material thermoplastic resin and the magnetic powder are mixed at a predetermined ratio and directly injected into an injection molding machine. A resin magnet composition is prepared by melt-kneading in a cylinder of the injection molding machine, and a target molded product is injection-molded as it is. The conventional pelletizing process is omitted, thereby efficiently and inexpensively using a magnet roller or the like. Can be manufactured.

According to the injection molding method of the present invention for obtaining a target molded product by one melting operation, the resin is thermally degraded compared to the conventional method of performing at least two melting operations by pelletizing. It is possible to suppress a decrease in performance and to more reliably obtain a resin magnet molded product having good performance.

[Brief description of the drawings]

FIG. 1 shows an example of an injection molding machine used in carrying out an injection molding method of a resin magnet molded product of the present invention, and using the injection molding machine, an injection molding method of a resin magnet molded product of the present invention. FIG. 4 is a schematic view showing a procedure and an operation when the magnet roller is injection-molded.

[Explanation of symbols]

 1 Cylinder 2 Screw 3 Band heater 4 Hopper 5 Mold 6 Cavity 7 Magnet roller (target molding) m Motor s Hydraulic cylinder

Claims (3)

[Claims] 1. A molding material in which a magnetic powder is blended with a thermoplastic resin is charged into a cylinder in which a screw is disposed, and the molding material is melt-plasticized by heating from the outside of the cylinder. While being kneaded by the rotation of a screw, the inside of the cylinder is pressure-fed forward while being kneaded, and the molding material in a molten state is injected or injected directly into the cavity of the mold from the front end of the cylinder or through an injection cylinder. In a method for injection-molding a resin magnet molded product to obtain a resin magnet molded product having a desired shape by cooling and solidifying the material in a mold, a molding material obtained by mixing the thermoplastic resin and magnetic powder at a predetermined ratio is directly cylinder-formed. Into the cylinder to melt-plasticize the thermoplastic resin in the cylinder and rotate the screw to melt-plasticize the thermoplastic resin and magnetic powder. Resin magnetic composition in which magnetic powder is mixed and dispersed in a resin binder to prepare a resin magnet composition, and this is injected and injected into the cavity of the mold to directly obtain a target molded product. Injection molding method for products. 2. A magnet is placed around the cavity of the mold, and a magnetic field is applied to the resin magnet composition injected and injected into the cavity. The injection molding method of a resin magnet molded product according to claim 1, wherein the magnetic powder in the magnet composition is adjusted to a desired orientation state and magnetized. 3. The image forming apparatus according to claim 1, wherein the molded resin magnet is a magnet roller for supplying toner to the surface of the image forming body to form an image in an electrophotographic apparatus or an electrostatic recording apparatus.
Or an injection molding method of the resin magnet molded product according to 2.