JP4438001B2 - Two-layer tube manufacturing apparatus and two-layer tube manufacturing method - Google Patents

Description

  The present invention relates to an apparatus and a manufacturing method for manufacturing a tube by extrusion molding. More specifically, the present invention relates to an apparatus and a manufacturing method for manufacturing a multi-layer seamless thin-film resin tube for a semiconductive rubber roll used in electrophotography or the like by extrusion molding.

  A method of manufacturing a seamless tube or the like by extrusion molding is such that the seamless tube is first extruded by an extrusion die, and is sequentially composed of a water-cooled sizing process, a tube drawing process, a tube cutting process, and a tube storage process (see Patent Document 1). .

  There are mainly three roles of the mold for molding the resin, and the mold is composed of portions that play respective roles. It introduces resin into the mold (for example, tournament portion), expands in the circumferential direction (for example, spider type, spiral type, etc.), smoothes the developed resin, and controls pressure and resin flow rate It is the tip (see Non-Patent Document 1).

  The design of the above three parts is greatly involved in determining the shape of the mold. And the front-end | tip part which squeezes small to a predetermined diameter after each layer of a tube merges is a part which determines the shape of a tube. Moreover, tubes of various sizes can be manufactured by changing the diameter of the tip. The cross-sectional area reduction rate of the front end extrusion port (the maximum annular cross-sectional area inside the mold / the annular cross-sectional area of the mold extrusion port) is usually designed to fall within the range of 1 to 50.

  When the cross-sectional area reduction rate is 1, the resin is rarely squeezed in the mold and can be molded smoothly. However, since the mold becomes larger or smaller in proportion to the diameter and film thickness of the tube, the cross-sectional area reduction rate is usually set within a range of 15 to 35.

Moreover, as the cross-sectional area reduction rate increases, the pressure drop (pressure loss) in the mold increases, so that the resin pressure increases and the shear stress at the mold extrusion port also increases. Since an increase in shear stress leads to abnormal extrusion such as spiraling and melt fracture, it is common to keep the cross-sectional area reduction rate within 50.
JP 11-123753 A The latest technology of plastic extrusion (Author Keiji Sawada)

As the cross-sectional area reduction rate increases, the shear stress of the annular cross-sectional area increases, so the stress applied to the resin also increases and the pressure drop also increases. For this reason, in high-speed molding with a high viscosity resin and a large amount of extrusion, there are problems such as a very high pressure drop in the mold and a high resin pressure during molding.
If the resin pressure rises too much, the tube cannot be pulled at high speed. In addition, if the shear stress is high, there is a high possibility that extrusion abnormalities such as spiraling and melt fracture will occur.

  Since an extrusion mold takes time to manufacture and is expensive, thin resin tube molding in which only a part at the tip is replaced and the cross-sectional area reduction rate exceeds 50 may be performed. At this time, the above problems were frequently reported. If the tube of any diameter can be formed by improving the tip part, it is possible to shorten the production period of the mold and parts and to share the mold, making tube forming easy. In order to become, further examination was awaited.

  The object of the invention of the present application is to cut off the resin flow part with an extrusion mold for manufacturing a tube of a multi-layer seamless thin film resin using a highly viscous material that is semiconductive and contains a large amount of carbon. This relates to a case where the area reduction rate is large (50 or more). At that time, the pressure drop of the mold increases. The object of the present invention is to form a tube with good shape and excellent conductivity uniformity, which can be molded with an appropriate resin pressure and extrusion amount without causing abnormal extrusion such as spiraling and melt fracture even in such a case. It is to provide a manufacturable device. Moreover, it is also providing the manufacturing method. Another object of the present invention is to provide a semiconductive charging roller using the mold.

The present invention, an extrusion molding die for tubular made of seamless thin resin resin simultaneously extruded second layer, and a cooling device for cooling and solidifying the tube, which is extruded from the molded metal mold, it cooled and solidified A two-layered seamless thin-film resin tube having an inner and outer layer, having a take-up machine for taking out the tube from the cooling device and a cutting machine for cutting the taken-out tube, is manufactured by extrusion molding 2 an apparatus for producing a layer tube, the molding die is for a two-layer tube coextrusion, internal molded metal mold at cross-section perpendicular to the molded-type mold longitudinal direction, each forming the inner layer constitutes a use and two annular space of the resin flow path for the outer layer forming resin flow path for forming the inner layer and for an outer layer formed towards the mold longitudinal direction, a two-layer structure having inner and outer layers Become a tube Joins the upstream side of the by Ru positions extrusion becomes one of the resin flow path cross-section is annular Te, the resin flow path of the one, until conforms to the diameter and the clearance of the extrusion opening of the die tip, It has a tapered shape for narrowing down a circular ring from the inner diameter side and outer diameter side, the cross-sectional area of the circular ring in a tapered shape starting position of the narrowing on the inner diameter side of the ring after the confluence straight is a, circular When the sectional area of the ring at the taper shape end position of the narrowing on the outer diameter side of the ring is C, the sectional area reduction rate (A / C) between the annular sectional area A and the annular sectional area C is 50 or more 80 or less, on a cross section containing the longitudinal central axis of the molded metal mold, the circular ring in the resin flow path after the confluence, the inner diameter Ru tapered starting position near the narrowing of the inner diameter side a straight line connecting a point on the side, and a point of the inner diameter side Ru tapered end position near the narrowing of the inner diameter side And the central axis, made of, narrowing taper angle of the inner diameter side is 45 degrees or less than 10 degrees, and, in the tapered end of the annular cross-sectional area A and the inner diameter side of the tapered starting position of the inner diameter side An apparatus for producing a two-layer tube is provided in which the narrowing taper angle on the inner diameter side is determined so that the annular sectional area inside the mold is equal to the annular sectional area B.

Further, according to the present invention, the first step of simultaneously extruding the resin from the molding die to form a tube formed of two layers of seamless thin film resin , and cooling and solidifying the tube extruded from the molding die by a cooling device. An inner and outer layer having a second step, a third step of taking the cooled and solidified tube from the cooling device by a take-off machine, and a fourth step of cutting the taken-up tube by a cutting machine. seamless thin film resin tube having a two-layer structure meet process for producing a two-layer tube manufactured by extrusion, in the first step, the resin is a molding die for co-extrusion two-layer tube, internal molded metal mold at cross-section perpendicular to the molded-type mold longitudinal direction, constitutes a space of two annular, each formed into the resin flow path for forming the inner layer and for an outer layer formed, the mold Longitudinal Inner forming and resin flow path for the outer layer forming towards the direction, the first resin flow path cross-section is annular and joins the upstream side of the Ru is extruded a tube having a two-layer structure positions having inner and outer layers next, the resin flow path of the one, until conforms to the diameter and the clearance of the extrusion opening of the die tip has a tapered shape for narrowing down a circular ring from the inner diameter side and outer diameter side, joins straight the cross-sectional area of the circular ring in a tapered shape starting position of the narrowing on the inner diameter side of the ring after the a, the cross-sectional area of the circular ring in tapered end of narrowing the outer diameter side of the circular ring by C when, circular ring cross-sectional area a and area reduction rate of the circular ring cross-sectional area C is at (a / C) is 50 to 80. in the cross-sectional plane containing the longitudinal central axis of the molded metal mold , circular rings in the resin flow path after the confluence, is tapered starting position of narrowing of the inner diameter side A point of the inner diameter side that, a straight line connecting the point of the inner diameter side Ru tapered end position near the narrowing of the inner diameter side, and the central axis, made of, narrowing taper angle of the inner diameter side is 10 degrees or more and 45 degrees or less, and the cross-sectional area of the annular cross-sectional area to B, circular annular inner mold in tapered end position of the annular cross-sectional area a and the inner diameter side of the tapered starting position of the inner diameter side is defined a taper angle narrowing of the inner diameter side to be equal, the manufacturing method of two-layer tubes, wherein that you molded into a tube is provided by forming metal mold.

  The present invention has a very high pressure drop when using a high-viscosity molding resin with a high viscosity in an extrusion mold for tube production of a multi-layer seamless thin film resin, or when performing high-speed molding with a large amount of extrusion. It is about the case. Even in such a case, according to the present invention, extrusion abnormalities such as spiraling and melt fracture do not occur, and molding can be performed with an appropriate resin pressure and extrusion amount to obtain a tube having an excellent shape and appearance. I can do it.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  The extrusion mold 1 shown in FIG. 1 is a mold for two-layer tube co-extrusion molding. The outer cylinder has a mandrel for an inner layer tube and a mandrel for an outer layer tube. The connecting part consists of a positioning mating surface and a fixing screw. Further, the mating surfaces of the outer cylinder, the outer layer, and the inner layer are tapered to ensure the relative position accuracy in the mold axis direction.

  The mold is divided into two parts, a mold body that directly contacts the material and a part that holds the mold, and the part that holds the mold is mainly a general metal material capable of hard chrome plating, such as S45C. Etc.

  In order to withstand the high pressure of the molten resin and to be heated from the outside, the mold body is made of ordinary hard steel, and in some cases nickel chrome steel, stainless steel, tool steel, etc. are used. This is finished in an appropriate shape, quenched, surface polished, and hard chrome plated. The height of the material is measured by the Rockwell C hardness measurement method, and the value is about 60 to 62. The surface chromium plating film thickness is about 1/100 to 5/100.

  The tube diameter and wall thickness are almost determined by the diameter and clearance of the extrusion port at the tip of the mold, and are adjusted to be within the allowable range of product dimensions by the take-up speed of the take-up machine. Is made. Therefore, it becomes possible to manufacture tubes of various sizes by exchanging the components at the tip.

  In the die front end portion (FIG. 2) of the apparatus according to the present invention, the inside of the molding die has an annular shape on the surface orthogonal to the longitudinal direction of the molding die. The circular cross-sectional area at the tapered shape start position of the narrowing on the inner diameter side of the annular shape is A, and the circular sectional area of the tapered shape end position of the narrowing on the outer diameter side of the annular shape is C. At that time, in the present invention, the cross-sectional area reduction rate (A / C) between the annular cross-sectional area A and the annular cross-sectional area C is 50 or more and 80 or less. Further, the taper angle for narrowing the inner diameter is not less than 10 degrees and not more than 45 degrees. The inner diameter narrowing taper angle is obtained as follows. On the surface including the central axis in the longitudinal direction of the molding die, a point on the inner diameter side in the mold at the tapered shape start position of the narrowing on the inner diameter side of the annular shape, and the annular inner diameter in the die A point on the inner diameter side in the mold at the taper shape end position of the narrowing of the side is connected. The angle formed by the intersection of the straight line thus formed and the central axis is the inner diameter narrowing taper angle. In addition, both the outer diameter and inner diameter of the resin flow path start from the resin confluence, the inner diameter of the taper taper angle is larger than the outer diameter throttle taper angle, and the resin flow path circles to the point where the inner diameter throttle taper ends. The annular cross-sectional area does not change.

  2, 5 is the position of the inner diameter throttle taper start position and the resin flow path annular cross-sectional area A, 6 is the position of the inner diameter throttle taper end position and the resin flow path annular cross-sectional area B, 7 is These are the outer diameter throttle taper end position and the position of the resin channel annular cross-sectional area C.

  In general, the molding die is designed so that the cross-sectional area reduction rate is 50 or less, but according to the present invention, molding is possible even when the cross-sectional reduction rate is higher than 50. However, if the cross-sectional area reduction rate is too large, the mold itself becomes too large or the extrusion port at the tip becomes too small, so the upper limit was set to 80.

  On the other hand, if the aperture taper angle is smaller than 10 °, the aperture portion of the molding die becomes long and the pressure loss of the molding die becomes high. Further, when the squeezing taper angle is larger than 45 degrees, a large stay in the resin flow occurs in the circular pipe. From experiments, it is more preferable that the squeezing taper angle is not less than 12 ° and not more than 30 °, because the length of the squeezed portion is most appropriate, and thus the resin does not stay in the squeezed portion.

  A seamless tube having a plurality of layers can be formed into a film by various methods, and an extrusion method is preferred. FIG. 1 shows a schematic view of extrusion molding of a seamless tube having two layers. A compound in which a polymer and a conductive material and, if necessary, a crosslinking agent, a stabilizer and other additives are mixed is prepared in advance.

  The compound is heated, kneaded, plasticized and melted by an extruder and injected into the extrusion mold 1. The melted compound is shaped into a tube by a mold and extruded from a die having a slit. The tube coming out of the mold is cooled and solidified by the water-cooled water tank 2, taken up by the take-up machine 3, and carried into the cutting machine 4.

  The resin, elastomer, copolymer and the like used for the functional multilayer film in the present invention may be any thermoplastic resin that can be extruded. Further, a thermoplastic rubber can be used, and it is not particularly limited, and a tube configuration having desired characteristics can be obtained.

  Below, the extrusion die and manufacturing method of the present invention will be explained. For convenience, the surface side of the functional multilayer is expressed as an outer layer and the inner side is expressed as an inner layer. However, the present invention is not limited to the following examples.

Example 1
In the tip part of the present invention (see FIG. 2), the outer diameter and inner diameter of the resin flow path start from the resin junction, and the inner diameter throttle taper angle is larger than the outer diameter throttle taper angle. The annular cross-sectional area of the resin flow path does not change until the taper ends.

  With the longitudinal direction as the central axis, the inner diameter IDa to the resin flow path constituting the annular sectional area A is 43 mm, and the inner diameter IDb constituting the annular sectional area B is 11.5 mm. Further, the narrowing taper angle of the inner diameter of the resin flow path formed by the difference between IDa and IDb is 21 degrees. Moreover, the outer diameter Oda of the annular cross-sectional area A of the resin junction is 56.9 mm, the outer diameter ODb constituting the annular cross-sectional area B is 12.5 mm, and the outer diameter of the resin flow path formed by the difference between them is The aperture taper angle is 14 degrees. After the inner diameter of the resin channel reaches 11.5 mm, it becomes a straight portion. The cross-sectional area reduction rate (A / C) between the annular cross-sectional area A and the annular cross-sectional area C is 57.4.

(Comparative Example 1)
The tip part of this example has a larger cross-sectional area reduction rate by making the tip extrusion port smaller than the shape of the first embodiment. The values of the inner diameter IDa up to the resin flow path constituting the annular cross-sectional area A and the outer diameter Oda of the confluence portion annular cross-sectional area A of the resin are the same as those in the first embodiment. However, the outer diameter ODb constituting the annular sectional area B is 10.0 mm, and the inner diameter IDb constituting the annular sectional area B is 9.2 mm. Moreover, the cross-sectional area reduction rate (A / C) of the annular cross-sectional area A and the annular cross-sectional area C is 90.8.

(Comparative Example 2)
The tip part in this example (Fig. 3) has a difference in the starting position of the outer diameter and the inner diameter of the aperture taper. First, the outer diameter is changed to the aperture taper, and the angle of the outer diameter of the aperture taper is larger. It is narrower. The inner diameter IDa to the resin flow path constituting the annular sectional area A is 43 mm, and the inner diameter IDb constituting the annular sectional area B is 11.5 mm. Further, the narrowing taper angle of the inner diameter of the resin flow path formed by the difference between IDa and IDb is 13 degrees, the outer diameter Oda of the resin confluence portion annular cross-sectional area A is 54.3 mm, and the outer surface constituting the annular cross-sectional area B is formed. The diameter ODb is 12.5 mm, and the aperture taper angle of the outer diameter is 15 degrees. The cross-sectional area reduction rate (A / C) between the annular cross-sectional area A and the annular cross-sectional area C is 39.6.

  The following Table 1 shows details from the joining part of the example and the comparative example to the die extrusion port.

Next, the resin used as the raw material of the tube having the functional multiple layers manufactured by the extrusion molds of the above three examples will be described.

  Examples of the material for the outer layer include the following. The main component of the material is 100 parts by weight of a styrene-based thermoplastic elastomer resin. Finally, 72 to 20 parts by weight of polyethylene, 11 to 14 parts by weight of carbon black 1, 20 to 28 parts by weight of carbon black 2, 10 to 15 parts by weight of magnesium oxide, and 1 to 1.5 parts by weight of calcium stearate. In this way, the materials are mixed together. That is, the styrene elastomer resin, carbon black 1, carbon black 2, magnesium oxide, and calcium stearate are melt-kneaded at 200 to 220 ° C. using a pressure kneader. The styrene-based thermoplastic elastomer resin is a styrene-ethylene / butylene-olefin copolymer resin, and is a product name “Dynalon” manufactured by Nippon Synthetic Rubber Co., Ltd. The carbon black 1 is a trade name “Ketjen Black EC” manufactured by Lion Akzo Corporation. The carbon black 2 is a trade name “Special Black 250”, manufactured by Degussa Japan. Then it is cooled and pulverized with a pulverizer to make a master batch. A styrene resin (styrene-ethylene / butylene-olefin copolymer resin) and polyethylene are further added to the master batch. Kneading, cooling, and pulverization are similarly performed again at 200 ° C. to 220 ° C., and pellets granulated at 180 ° C. to 200 ° C. using a single screw extruder are used.

  Examples of the material for the inner layer include the following. 100 parts by weight of an ether-based urethane elastomer resin, 15 to 18 parts by weight of carbon black (trade name “Ketjen Black EC”), 20 parts of conductive titanium oxide, 10 parts by weight of magnesium oxide, and 1 part by weight of calcium stearate. They are kneaded, cooled and pulverized at 160 to 200 ° C. using a pressure kneader, and pellets granulated at 160 to 210 ° C. using a single screw extruder are used.

  The above-mentioned resins are molded using the molds of the above three examples, and the molding conditions such as the pressure inside the mold during molding, the resin extrusion amount, the tube take-up speed, and the like are compared. In addition, visually observe whether there is an abnormal molding of the resin near the extrusion port of the mold, examine the appearance of the tube after molding, and check the state of the tube during extrusion and the result of the tube after molding Comparative evaluation is made in Table 2 below.

In the molding using the mold of Example 1, the tube take-up speed, the resin pressure at the time of molding, and the items that are particularly problematic in the appearance inspection after molding and the like are not found, and good results are obtained. Yes.

  In the molding using the mold of Comparative Example 1, the tube was pushed out so as to draw a spiral, resulting in a tube having a non-uniform film thickness and outer diameter. This phenomenon seems to be due to the occurrence of spiraling because the shear stress at the extrusion port is too high.

  In molding using the mold of Comparative Example 2, the resin pressure in the mold was higher than the resin extrusion amount, and the resin extrusion amount could not be increased. Therefore, it turns out that a taking-up speed is slow compared with shaping | molding using the metal mold | die of Example 1. FIG. It was also found that wrinkles were generated on the appearance of the tube.

  Example 1 described above is an extrusion mold for producing a tube of a multi-layer seamless thin film resin, and the pressure drop of the mold is very high, such as a high reduction rate of the cross-sectional area of the resin flow part (50 to 80). high. Even in such a case, in the present invention, it was possible to perform molding with an appropriate resin pressure and extrusion amount without causing abnormal extrusion such as spiraling and melt fracture.

Schematic diagram of tube manufacturing equipment Outline of the land portion from the joining portion of the molding die of Example 1, and enlarged view of the land portion Outline of the land portion from the joining portion of the molding die of Comparative Example 2, and enlarged view of the land portion

Explanation of symbols

1 Extrusion mold 2 Cooling device (water-cooled water tank)
3 Take-up machine 4 Cutting machine 5 Inner diameter throttle taper start position and position of resin flow path annular cross-sectional area A 6 Inner diameter throttle taper end position and position of resin flow path annular cross-sectional area B 7 Outer diameter throttle taper end position and resin Position IDa of flow path annular cross-sectional area C Inner diameter IDa to resin flow path constituting annular cross-sectional area A
IDb Inner diameter IDb constituting the annular cross-sectional area B
ODa Outer diameter Oda to the resin flow path constituting the annular cross-sectional area A
ODb Outer diameter ODb constituting the annular cross-sectional area B

Claims (3)

An extrusion mold that simultaneously extrudes resin to form a tube formed of two layers of seamless thin film resin, a cooling device that cools and solidifies the tube extruded from the molding mold, and the cooled and solidified tube Manufacture of a two-layer tube for manufacturing a two-layered seamless thin-film resin tube having an inner and outer layer by extrusion molding, having a take-up machine that takes out from the cooling device and a cutting machine that cuts the taken-out tube A device,
The molding die is for two-layer tube coextrusion molding,
Internal molded metal mold at cross-section perpendicular to the molded-type mold longitudinal direction, constitutes a space of two annular, each formed into the resin flow path for forming the inner layer and for an outer layer formed,
Resin flow path for forming the inner layer and for an outer layer formed towards the mold longitudinal direction, is a circular ring cross-section and joins the upstream side of the position that will be extruded becomes tubes having a two-layer structure having an inner and outer layer 1 resin flow path, and the 1 resin flow path has a tapered shape for narrowing the ring from the inner diameter side and the outer diameter side until it matches the diameter and clearance of the extrusion port at the tip of the mold. Have
The cross-sectional area of the circular ring in a tapered shape starting position of the narrowing on the inner diameter side of the ring after the confluence straight is A, the cross-sectional area of the circular ring in tapered end of narrowing the outer diameter side of the circular ring C When the cross-sectional area reduction ratio (A / C) between the circular cross- sectional area A and the circular cross-sectional area C is 50 or more and 80 or less,
On cross-section including a central longitudinal axis of the molded metal mold, the circular ring in the resin flow path after the confluence, and the point of the inner diameter side Ru tapered starting position near the narrowing of the inner diameter side, the inner diameter a straight line connecting the point of the inner diameter side Ru tapered end position near the side of the narrowing, a central axis, made of, narrowing taper angle of the inner diameter side is 45 degrees or less than 10 degrees, and,
The inner diameter side is such that the annular sectional area inside the mold is equal to the annular sectional area A at the tapered shape start position on the inner diameter side and the annular sectional area B at the tapered shape end position on the inner diameter side. An apparatus for producing a two-layer tube, characterized in that a narrowing taper angle is defined. A first step of simultaneously extruding a resin from a molding die to form a tube formed of two layers of seamless thin film resin , a second step of cooling and solidifying the tube extruded from the molding die by a cooling device, and cooling A seamless two-layer structure having an inner and outer layer , comprising: a third step of taking the solidified tube from the cooling device by a take-off machine; and a fourth step of cutting the taken-up tube by a cutting machine. A method for producing a two-layer tube in which a thin-film resin tube is produced by extrusion molding,
In the first step, the resin is
It is a mold for two-layer tube coextrusion molding,
Internal molded metal mold at cross-section perpendicular to the molded-type mold longitudinal direction, constitutes a space of two annular, each formed into the resin flow path for forming the inner layer and for an outer layer formed,
Resin flow path for forming the inner layer and for an outer layer formed towards the mold longitudinal direction, is a circular ring cross-section and joins the upstream side of the position that will be extruded becomes tubes having a two-layer structure having an inner and outer layer 1 resin flow path, and the 1 resin flow path has a tapered shape for narrowing the ring from the inner diameter side and the outer diameter side until it matches the diameter and clearance of the extrusion port at the tip of the mold. Have
The cross-sectional area of the circular ring in a tapered shape starting position of the narrowing on the inner diameter side of the ring after the confluence straight is A, the cross-sectional area of the circular ring in tapered end of narrowing the outer diameter side of the circular ring C When the cross-sectional area reduction ratio (A / C) between the circular cross- sectional area A and the circular cross-sectional area C is 50 or more and 80 or less,
On cross-section including a central longitudinal axis of the molded metal mold, the circular ring in the resin flow path after the confluence, and the point of the inner diameter side Ru tapered starting position near the narrowing of the inner diameter side, the inner diameter a straight line connecting the point of the inner diameter side Ru tapered end position near the side of the narrowing, a central axis, made of, narrowing taper angle of the inner diameter side is 45 degrees or less than 10 degrees, and,
The inner diameter side is such that the annular sectional area inside the mold is equal to the annular sectional area A at the tapered shape start position on the inner diameter side and the annular sectional area B at the tapered shape end position on the inner diameter side. 2-layer manufacturing method of the tube narrowing defines a taper angle, which is characterized that you molded into a tube by forming metal mold of. In a two-layer manufacturing method of the electrophotographic charging roller for producing coated to electronic photographic charging roller a tube made of seamless thin film resin to the conductive rubber roller structure having inner and outer layers, said tube,
It is a mold for two-layer tube coextrusion molding,
In the cross section perpendicular to the longitudinal direction of the molding die, the inside of the molding die forms two annular spaces each serving as a resin flow path for inner layer formation and outer layer formation,
The resin flow path for forming the inner layer and the outer layer in the longitudinal direction of the molding die merges at the upstream side of the position where the tube is extruded as a two-layered tube having the inner and outer layers, and the section is annular. 1 resin flow path, and the 1 resin flow path has a tapered shape for narrowing the ring from the inner diameter side and the outer diameter side until it matches the diameter and clearance of the extrusion port at the tip of the mold. Have
The cross-sectional area of the circular ring at the narrowing tapered shape start position on the inner diameter side of the circular ring immediately after the merge is A, and the cross-sectional area of the circular ring at the narrowing tapered shape end position on the outer diameter side of the circular ring is C. The cross-sectional area reduction rate (A / C) between the annular cross-sectional area A and the annular cross-sectional area C is 50 or more and 80 or less,
On the cross-section including the central axis in the longitudinal direction of the molding die, the point on the inner diameter side of the annular shape in the resin flow path after merging at the tapered shape starting position of the inner diameter side narrowing and the inner diameter side narrowing The narrowing taper angle on the inner diameter side, which is composed of a straight line connecting the inner diameter side point at the tapered end position and the central axis, is not less than 10 degrees and not more than 45 degrees, and
The inner diameter side is such that the annular sectional area inside the mold is equal to the annular sectional area A at the tapered shape start position on the inner diameter side and the annular sectional area B at the tapered shape end position on the inner diameter side. defines a taper angle narrowing down method of to that electronic photographic charging roller, characterized in that the molding by the molding die.