JPH1177751A - Mold of magnet roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent resin deterioration and burr by interposing a heat-resistant/ heat insulating member having heat resistance and heat insulating properties withstanding the melt temp. of a resin magnet material between a hot nozzle and the mold material surrounding the tip part thereof in the close contact state with the hot nozzle and the mold material. SOLUTION: The heat-resistant/heat insulating member 24 holding a hot nozzle 23 while sealing the gap between a mold material 21 and the hot nozzle 23 in the close contact state with the hot nozzle 23 is provided between the mold material 21 and the hot nozzle 23. The material of the heat-resistant and heat insulating member 24 has heat resistance withstanding the melt temp. of a resin magnet material and has heat insulating properties suppressing the conduction of heat from the hot nozzle to the mold material. As a result, the tip part of the hot nozzle does not lose heat locally and, even if the whole temp. of the hot nozzle is not raised, the flowability of the resin magnet material is ensured and, since the heat-resistant and heat insulating member does not lose heat, it can be brought into contact with the hot nozzle over a sufficient area in a gap free state and burr is also eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for forming a magnet roll used for a developing roll, a cleaning roll, a transport roll, and the like incorporated in an electrophotographic developing device such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art A magnet roll using a permanent magnet material is used as a developing roll and a cleaning roll in an electrophotographic developing device such as a copying machine, a facsimile, and a printer. Such a magnet roll
Previously, it was mainly made by bonding metal magnets such as alnico magnets and ferrite magnets and sintered magnets.However, because it has a high degree of freedom in shape, it is suitable for mass production, and it is low cost. In recent years, magnet rolls formed using a resin magnet material in which magnetic powder is mixed with a synthetic resin binder have become mainstream in recent years. Although such a magnet roll made of a resin magnet material is manufactured by an injection molding method or an extrusion molding method, these molding methods have advantages but also have problems.

For example, in the injection molding method, the molded product is taken out with an eject pin perpendicular to the longitudinal direction of the molded product, so that the molded product tends to be warped at the time of taking out the molded product. The problem of not having
Since the melt is injected into the empty cavity (molding space), the flow at the time of injection causes a thin wrinkled solidified film to be generated on the surface of the molded body, resulting in a rough surface.
In turn, this leads to the disorder of the orientation of the magnetic powder in the vicinity of the surface, resulting in variations in the surface magnetic flux density. In addition, the injection molding method requires sufficient fluidity of the resin magnet material, so there is a limit to increasing the magnetic powder content to achieve high magnetic force, etc. There's a problem.

[0004] On the other hand, although the extrusion molding method has higher productivity than the injection molding method, if the extruded material uses a thermosetting resin or a hard thermoplastic resin as a binder, an extrusion wire is used. The problem is that it is difficult to increase the speed and there is a limit to productivity improvement.If the melt viscosity of the extruded product is low, a sizing mold is required, and it is difficult to improve the dimensional accuracy of the outer diameter in the longitudinal direction,
When magnetic powder is magnetically oriented, it is difficult to achieve high orientation due to the disorder of orientation of magnetic particles due to frictional resistance received from the inner wall of the die at the time of extrusion or to solidification outside the die. There is a problem.

The present applicant has already proposed a technique which can solve the problems of the injection molding method and the extrusion molding method and can obtain a magnet roll having a uniform surface magnetic force in the longitudinal direction. This technology has a molding die for forming one end of a magnet roll in a main molding die having a molding space for molding a magnet roll inside and a magnetic field generator such as a permanent magnet disposed around the molding die. Attached slidably in the axial direction of the main mold, the magnet roll is molded in a magnetic field while the slide mold is retracted by the injection pressure of the molten resin magnet material, and when the magnet roll is cured, the resin magnet material is injected After removing the mold plate on the injection side, the slide mold is moved forward and the molded product is extruded in the axial direction of the main mold and taken out. In such a manufacturing method, to prevent resin curing, stabilize injection injection, improve the degree of magnetic powder orientation, uniformity of magnetic powder distribution, fluidity of the resin magnet material in order to improve the appearance and surface properties of molded products Is important, and it is advantageous to use a hot nozzle heated by a heater.

According to this method, since the volume of the molding space is increased in accordance with the injection speed of the molten resin magnet material, the molten resin magnet material is not disturbed in the molding space. Can be oriented
The magnetic properties in the longitudinal direction of the magnet roll are made uniform, and a magnet roll having a more uniform magnetic property in the axial direction than that produced by a conventional injection molding method or extrusion molding method can be obtained.

[0007]

On the other hand, by using a hot nozzle, the fluidity of the resin magnet material was enhanced, and the injection and injection of the resin magnet material should have been performed smoothly. However, a drop (ripple) in the longitudinal magnetic force due to nozzle clogging or insufficient fluidity was observed. The inventor of the present invention has investigated the cause and found that the cause is that the hot nozzle is held in direct contact with the template forming a part of the molding space. That is, as shown in FIG. 4, in the conventional molding die, the hot nozzle 1 is heated by the heater 2 disposed around the same, but the nozzle tip side comes into direct contact with the mold 3 constituting a part of the molding space. Therefore, a phenomenon occurs in which the heat of the hot nozzle 1 is deprived of the mold material 3 and the tip temperature of the nozzle drops locally. As a result, the resin is partially solidified at the tip of the nozzle and the nozzle is clogged, making it impossible to inject.
Alternatively, even if injection is possible, a phenomenon occurs in which the fluidity deteriorates and the magnetic properties in the longitudinal direction become unstable. In particular, the resin magnet material, which is the raw material of the magnet roll, contains magnetic powder and has a higher thermal conductivity than general synthetic resins, and the above tendency is more remarkable.

In order to prevent the solidification of the resin at the tip of the nozzle, as shown in FIG. 5, the contact range d with the mold 3 supporting the tip of the nozzle is narrowed to prevent heat from being taken off. Although it is conceivable to raise the overall temperature of the hot nozzle 1 so that the resin magnet material does not solidify even if there is a temperature drop at the nozzle tip, none of these methods can be adopted. This is because, when the contact area between the hot nozzle 1 and the mold plate 3 is reduced, the sealing performance at the contact portion is reduced, and the injection boundary pressure of the resin magnet material into the molding space causes the contact boundary portion 3a as shown in FIG. Resin leakage occurs on the other hand. On the other hand, if the temperature of the hot nozzle 1 as a whole is raised, the resin deteriorates and the strength of the molded product decreases.

The present invention has been made in view of the above situation, and is a molding method for forming a magnet roll while retreating a slide mold slidably mounted in an axial direction of a main molding die with an injection pressure of a molten resin magnet material. In the molding dies used in the method, it is necessary to provide a molding die in which nozzle clogging does not occur without excessively increasing the entire temperature of the nozzle by preventing a local temperature drop at the tip of the hot nozzle. Is what you do.

[0010] Since the resin magnet material has a higher viscosity than the usual resin and is liable to be clogged at the nozzle tip, the resin flow path is normally open as shown in the figure. However, when the temperature of the entire nozzle is increased, a phenomenon occurs in which the resin magnet material leaks from the injection port of the nozzle to form a solidified material, and the solidified mass remains in the molded product as it is and reduces the degree of magnetic powder orientation, The solidified portion becomes a slag-like lump, which may cause a poor appearance of the magnet roll. The present invention also solves such a problem, and proposes a molding die in which the resin magnet material does not leak from the injection port.

[0011]

Means for Solving the Problems and Action Thereof The present invention, which solves the above problems, has the following features. The invention according to claim 1 includes a main mold having a molding space for molding a magnet roll, a slide mold for forming one end of a magnet roll slidably mounted in the molding space, and A nozzle for injecting and injecting the molten resin magnet material into the molding space, and a magnetic field generator for orienting magnetic powder in the molten resin magnet material filled in the molding space, and slide by the injection pressure of the molten resin magnet material. In a molding die for a magnet roll that forms a magnet roll while retracting the mold, as a nozzle for injecting the molten resin magnet material into the molding space, a nozzle tip including the injection port is heated to a temperature equal to or higher than the melting temperature of the resin magnet material. Between the hot nozzle and the mold material that surrounds the tip of the hot nozzle and forms a part of the molding space. It is characterized in that by interposing a heat-insulating member having a heat insulating property of inhibiting the heat conduction toward the mold material from the heat resistance and the hot nozzle to withstand the melting temperature of the fat-magnetic material in close contact to the hot nozzle and the mold material.

In such a molding die, a molten resin magnet material is injected and injected from a heated hot nozzle into a main molding die to which a magnetic field is applied, and the slide die mounted in the main molding die is retracted. Fill the molten resin magnet material into the expanding molding space. When the slide mold retreats to the predetermined position and stops, the injection and injection of the resin magnet material from the hot nozzle is stopped, and after holding pressure and cooling, the mold plate on the opposite side of the slide mold, that is, the mold plate on the hot nozzle arrangement side is molded. Open the mold, advance the slide mold, and take out the molded product in the main mold.

The tip of the hot nozzle is heated to at least the melting temperature of the resin magnet material, and since the tip is supported by a heat-resistant and heat-insulating member, the heat of the tip is not taken away. The resin magnet material is satisfactorily supplied to the entire molding space without solidification of the material at the front end portion or deterioration of fluidity. Therefore, there is no need to excessively raise the temperature of the hot nozzle, so that the resin is not deteriorated and the strength of the molded product is not lost. In addition, the heat-resistant and heat-insulating member is in close contact with the hot nozzle and the mold material that forms part of the molding space, and is in contact with the outer surface of the hot nozzle over a sufficient area without any gap. The magnet material does not leak, and even in such a close contact state, since it has heat insulation properties, the temperature at the nozzle tip does not drop partially.

In order to prevent the slag-like solidified material from being mixed,
It is preferable to use a hot nozzle provided with a valve pin for opening and closing the inlet. When such a hot nozzle is used, the valve pin moves to the open position to open the injection port during injection and injection, and during pressure holding, while the valve pin moves to the closed position during cooling and removal of the molded product, and the injection port opens. To close. The injection port is closed except during injection injection and pressure-holding time, so that the resin magnet material does not leak out of the injection port to form solidified material during cooling or during removal of molded products .

It is preferable to use a member having a heat resistance of at least 300 ° C. and a thermal conductivity of 10 Kcal / m · h · ° C. or less as a member interposed between the hot nozzle and the mold. Specifically, a heat-resistant and heat-insulating resin such as a polyimide resin, a silicon resin, a melamine resin, and a fluororesin can be used. Since these resins are excellent in processability and adhesiveness, resin leakage at the boundary between the hot nozzle and the mold material is completely prevented.

In place of the heat-resistant and heat-insulating resin, aluminum oxide, silicon nitride, zirconia, silicon carbide, carbon, glass, mica, quartz and the like can also be used. These are slightly inferior in workability as compared with the heat-resistant and heat-insulating resin, but are much more excellent in heat resistance. It is also preferable to make these members porous so as to enhance the heat insulating properties.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will now be described with reference to the illustrated embodiments. FIG. 1 shows the entire molding die of the present invention. The molding die of the present invention is for molding a shaft-integrated magnet roll. The shaft-integrated magnet roll M is formed by projecting and shaping the reduced-diameter shaft portions m2 and m3 at both ends of a cylindrical roll portion m1, and positioning or driving the driving force on the shaft portion 3 as necessary. Are formed, and the whole is integrally formed using a resin magnet material. The roll part m1 may be a polygonal pillar instead of a cylinder. Such a magnet roll M is used as a developing roll or a cleaning roll in an electrophotographic developing device such as a copying machine, a facsimile, a printer, or the like.

The magnetic material constituting the magnet roll M is mainly composed of a magnetic powder and a binder for binding the magnetic powders, and a silane or titanate coupling agent for strengthening the bond, A mixture containing a small amount of a lubricant for improving the fluidity, a stabilizer for preventing the thermal decomposition of the binder, and the like is used. If necessary, a flame retardant and a reinforcing agent can be blended. As the magnetic powder, ferrite, rare earth (SmCo, NdFeB)
System), MnAIC system, alnico system, SmFeN system, etc., and as the binder, a thermoplastic resin or a thermosetting resin can be used. A low melting point metal, which is not a synthetic resin, can also be used in substantially the same manner as the synthetic resin.

In the molding die of the present invention, since the fluidity of the resin magnet material is enhanced by using a hot nozzle, the filling ratio of the magnetic powder in the resin magnet material can be increased to nearly 70% by volume. A high-magnetism magnet roll can be obtained.

The movable mold 10 includes a sleeve-shaped main molding die 12 having a molding space 11 for molding a magnet roll, a slide die 13 mounted in the molding space 11, and the main molding die 12. And a magnetic field generator 14 arranged so as to surround it. The slide die 13 is axially slidably mounted in the molding space 11 of the main molding die 12 with substantially no gap in the radial direction. The right end of the slide die 13 in the drawing includes a magnet roll M including a shaft m2. A molding part 15 for molding the left end is provided. On the other hand, although not shown, actuators such as a hydraulic cylinder, a pneumatic cylinder, a screw screw, a rack and pinion gear, and a linear motor are connected to the left end of the slide die 13 in the drawing. It is configured to be able to reciprocate between the two. The slide die 13 has a configuration in which a protruding pin 13b is slidably inserted into the outer cylinder 13a. At the end of the operation of removing the molded product, the shaft m2 is pushed out by the protruding pin 13b to be fitted to the slide die 13. It is configured so that a certain molded product can be released from the mold.

A fixed mold 20 is provided with a non-magnetic material 21 provided with an end forming portion 25 for forming the right end of the magnet roll M including the shaft m3. A hot nozzle 23 provided with a heater 22 is held and fixed to the mold member 21 via a ring-shaped heat-resistant and heat-insulating member 24. As the heater 22, a heater having an amount of heat capable of heating the nozzle tip to at least the melting temperature of the resin magnet material is used. In addition, the cooling water channel 2 is
8 is provided, and the temperature of the nozzle tip is adjusted by controlling the temperature and flow rate of the cooling water passing therethrough.

As shown in FIG. 2, the hot nozzle 23 has, at its tip, an injection port 26 for injecting and injecting a molten resin magnet material into the molding space. A valve pin 27 that retreats and opens and closes the inlet 26 is provided. The valve pin 27 is driven by an actuator (not shown) using a pneumatic pressure, a hydraulic pressure or the like as a driving force source disposed at a base end side thereof, and retreats to the right side in the drawing to open the inlet 26 at the time of injection and pressure holding. On the other hand, at the time of cooling and removal of the molded product, it operates to advance to the left side in the figure to close the injection port 26. By this operation,
This prevents the resin from leaking out of the injection port 26 at the time of cooling and removing the molded product, and eliminates the possibility that the slag-like solidified product is mixed into the molded product.

FIG. 3 shows a state in which the hot nozzle 23 is located between the mold 21 and the hot nozzle 23 and is in close contact with the hot nozzle 23.
2 shows a heat-resistant and heat-insulating member 24 that holds the hot nozzle 23 while sealing the space between them. Heat-resistant and heat-insulating member 2 in the example
4 is provided with a hole 24a that expands from one side to the other in accordance with the tapered shape of the nozzle tip. Heat resistance
The shape of the heat insulating member 24 is not limited as long as it can be interposed between the mold 21 and the hot nozzle 23 in a state of being in close contact with the tip of the hot nozzle 23.

The material of the heat-resistant and heat-insulating member 24 has a heat resistance to withstand the melting temperature of the resin magnet material because the tip of the hot nozzle 23 for injecting the molten resin magnet material is closely supported. A material having heat insulating properties to suppress heat conduction toward the mold material is used. Specifically, it is preferable to use a material having a heat resistance of at least 300 ° C. and a thermal conductivity of 10 Kcal / m · h · ° C. or less. In order to prevent the resin from leaking, a resin having good adhesion to the outer surface of the hot nozzle 23, an effect of preventing the resin from leaking, and having excellent workability is selected. As a material that meets such conditions, there are a polyimide resin, a silicon resin, a melamine resin, a fluororesin, and the like. Aluminum oxide, silicon nitride, zirconia, silicon carbide, carbon, glass, mica, quartz, and the like, which are slightly inferior in workability and adhesion, can also be used. Although the strength is slightly reduced, these materials may be processed to be porous in order to enhance the heat insulation.

The forming operation of the magnet roll 1 by the main forming die having such a configuration is performed as follows. First, the fixed mold 20 and the movable mold 10 as shown in FIG. 1 are combined, the molding space 11 in the main molding die 12 is closed by the end molding die 25, and the slide die 13 is driven by driving the actuator. Move to the advanced position to minimize the volume of the molding space 11.

Next, an injection cylinder (not shown) is driven to feed the molten resin magnet material into the hot nozzle 23 and inject the molten resin magnet material into the molding space 15 through the injection port 26. At this time, the valve pin 27 is
In the retreat position on the right side in the figure as shown by
6 is open. The molding space 11 is filled with the resin magnet material while the slide mold 13 is retracted to the retreat position on the left side in the figure by the injection pressure of the molten resin magnet material. A magnetic field is applied to the molding space 11 by a magnetic field generator 14, and the resin magnet material is filled and solidified in the magnetic field, so that the directions of the magnetic particles are aligned. After this, the packing pressure,
After cooling, the movable mold 10 is moved to the left in the figure to open the mold, and the slide mold 13 is advanced to the right in the figure to take out the molded product in the main mold 12. To take out the molded product, first, the molded product is pushed out of the molding space by the slide die 13, and then the shaft m 2 is pushed out by the protruding pin 13 b and fitted to the slide die 13.
By separating them. The valve pin 27 is retracted to the right side in the drawing to open the injection port 26 at the time of injection and injection and holding pressure. However, during cooling and removal of the molded product, the valve pin 27 advances to the left side of the drawing to close the injection port 26. In addition, the resin magnet material having high fluidity does not leak from the inlet 26. The above is an embodiment using a hot nozzle provided with a valve pin for opening and closing the injection port.However, if the fluidity of the resin magnet material can be controlled so that no resin leaks from the injection port, the valve pin is It is not necessary to provide it.

In order to confirm the effects of the present invention, the inventor of the present invention attached a ring-shaped heat-resistant and heat-insulating member 24 made of a material having a thermal conductivity of 0.2 Kcal / m · h · ° C. A magnet roll is manufactured using a mold having a valve pin 27 that is interposed between the hydraulic cylinders and moves forward and backward by a hydraulic cylinder, and the hot roll is directly held by the mold 21 without using a heat-resistant and heat-insulating member. In addition, a comparison was made with a magnet roll produced using a conventional molding die having no valve pin and always having an injection port opened. As a result, in the conventional mold, the clogging phenomenon of the nozzle was observed at 320 ° C. or less and stable molding could not be performed, whereas in the molding die of the present invention, the clogging phenomenon of the nozzle was not observed even at a temperature of 300 ° C. It was confirmed that stable molding was possible. The ripple characteristics were also improved by 10%.

[0028]

According to the first aspect of the present invention, a hot nozzle having a valve pin for opening and closing the injection port and having at least a tip portion heated to at least the melting temperature of the resin magnet material is used, and the hot nozzle and a molding space are formed. A heat-resistant and heat-insulating member having heat resistance to withstand the melting temperature of the resin magnet material and heat-insulating property for suppressing heat conduction from the hot nozzle toward the mold material is tightly attached to the hot nozzle and the non-magnetic member between the non-magnetic member and the non-magnetic member. By intervening, the tip of the hot nozzle is not locally deprived of heat, and the fluidity of the resin magnet material is secured without increasing the overall temperature of the hot nozzle as in the conventional case. A high quality magnet roll without resin deterioration can be obtained. Further, since the heat-resistant and heat-insulating member does not deprive the heat, it can be brought into close contact with the hot nozzle over a sufficient area without any gap, and does not generate burrs on the molded product. Therefore, it is possible to obtain a magnet roll in which the orientation of the magnetic powder is good, the magnetic powder distribution is uniform, and the magnetic properties are uniform, and the appearance is free from burrs and other poor appearance.

When a hot nozzle provided with a valve pin for opening and closing the injection port is used, the injection port can be closed by the valve pin at the time of cooling and at the time of taking out a molded product. The resin magnet material does not leak out of the injection port when the injection is unnecessary, while ensuring the property.

As defined in claim 3, at least 300
℃ or more and its thermal conductivity is 10Kca
When a heat-resistant and heat-insulating member having a temperature of 1 / m · h · ° C. or less is used, the above-mentioned effect becomes more remarkable.

When a polyimide resin, a silicon resin, a melamine resin, or a fluororesin is used as a material of the heat-resistant and heat-insulating member as described in claim 4, since these materials are excellent in workability and adhesion, a hot nozzle can be used. Can be reliably prevented from leaking from the boundary of the resin.

In the case where any one of aluminum oxide, silicon nitride, zirconia, silicon carbide, carbon, glass, mica and quartz is used as the material of the heat-resistant and heat-insulating member as described in claim 5, they are workable. Although the adhesion is slightly inferior, the heat resistance is superior to that of the resin material.
Therefore, even if the contact area with the hot nozzle is expanded as compared with the case where the resin heat-resistant and heat-insulating member is used, there is no temperature drop at the nozzle tip, so the resin area on the boundary with the hot nozzle is expanded by expanding the contact area. Intrusion of magnet material can be prevented. In addition, if these materials are made porous, the heat insulating property can be further improved, and the local temperature drop at the nozzle tip can be further prevented, so that the overall temperature of the hot nozzle can be lowered and the resin can be prevented from deteriorating.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing an entire configuration of an embodiment of a molding die of the present invention.

FIG. 2 is an explanatory sectional view showing a structure around a hot nozzle in the embodiment.

FIG. 3 is a perspective view showing a shape of a heat-resistant and heat-insulating member used in the embodiment.

FIG. 4 is an explanatory sectional view showing a structure around a hot nozzle in a conventional molding die.

FIG. 5 is an explanatory cross-sectional view illustrating a contact area between a hot nozzle and a mold material holding the hot nozzle in a conventional molding die.

FIG. 6 is a cross-sectional explanatory view showing a state in which a resin magnet material enters a boundary between a hot nozzle and a mold material holding the hot nozzle in a conventional molding die.

[Explanation of symbols]

 M Magnet roll m1 Roll part m2, m3 Shaft part 1 Hot nozzle 2 Heater 3 Mold plate 3a Contact boundary part 10 Movable mold 11 Molding space 12 Main molding die 13 Slide mold 14 Magnetic field generator 15 Molding part 13a Outer cylinder 13b Projection pin DESCRIPTION OF SYMBOLS 20 Fixed mold 21 Mold 22 Heater 23 Hot nozzle 24 Heat-resistant and heat-insulating member 25 End molding 26 Inlet 27 Valve pin 28 Cooling water channel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 31:32 31:34

Claims (6)

[Claims] A main mold having a molding space for molding a magnet roll; a slide mold for forming one end of a magnet roll slidably mounted in the molding space; A nozzle for injecting and injecting the molten resin magnet material, and a magnetic field generator for orienting the magnetic powder in the molten resin magnet material filled in the molding space, and the slide mold is retracted by the injection pressure of the molten resin magnet material. In a molding die for a magnet roll, which forms a magnet roll while being heated, as a nozzle for injecting a molten resin magnet material into a molding space, a hot nozzle in which a nozzle tip including the injection port is heated to a melting temperature of the resin magnet material or higher. Between the hot nozzle and the mold material surrounding the tip of the hot nozzle and forming a part of the molding space. A heat-resistant and heat-insulating member having heat resistance to withstand the melting temperature of the material and heat insulation to suppress heat conduction from the hot nozzle to the mold material, wherein the heat-insulating member is interposed in close contact with the hot nozzle and the mold material. Molding mold. 2. The molding die for a magnet roll according to claim 1, wherein the hot nozzle is provided with a valve pin for opening and closing an injection port. 3. The heat-resistant and heat-insulating member is at least 300 ° C.
It has the above heat resistance, and its thermal conductivity is 10 Kcal
3. The molding die for a magnet roll according to claim 1, wherein the temperature is not more than / m · h · ° C. 4. The heat-resistant and heat-insulating member interposed between the hot nozzle and the mold member is formed of any one of a polyimide resin, a silicon resin, a melamine resin, and a fluororesin. A molding die for a magnet roll according to item 1. 5. The heat-resistant and heat-insulating member interposed between the hot nozzle and the mold material is any one of aluminum oxide, silicon nitride, zirconia, silicon carbide, carbon, glass, mica, and quartz. A molding die for the magnet roll according to any one of the preceding claims. 6. A molding die for a magnet roll, wherein the material of the heat-resistant and heat-insulating member interposed between the hot nozzle and the mold is made of the material according to claim 5 made porous.