JP2000141507A - Manufacture of conductive belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a novel conductive belt capable of manufacturing the belt having good moldability, no unevenness of an electric resistance and good elastic moduli in lateral and circumferential directions in a mass production. SOLUTION: The method for manufacturing a conductive belt comprises the steps of (1) extruding a melt thermoplastic elastomer in a cylindrical state by using an extruder to obtain a continuous cylinder, (2) forming a mold cavity corresponding to a profile of a molded product at an inside at the time of closing both mold members split along an axial direction of the cylinder extruded by both the members along the cylinder to seal part of the continuously extruded cylinder by using a mold having a function of sealing it in the cavity in a thermally deformable state, (3) blowing fluid in the cylinder sealed in the cavity to expand the outer periphery of the molded product until the periphery is brought into contact with the inner surface of the mold to obtain the molding and (4) releasing the molded product from the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a conductive belt, and more particularly, to a method for manufacturing a transfer belt for an image forming apparatus such as an electrostatic copying machine, a laser printer, and a plain paper facsimile machine. And a method for producing a seamless annular conductive belt.

[0002]

2. Description of the Related Art In the above-mentioned image forming apparatus, a printing paper is conveyed by electrostatic force, and in the middle of the conveyance, the printing paper is brought into contact with the surface of a photoreceptor on which a toner image is formed, so that the toner image is transferred to the surface of the printing paper. There is known a transfer belt for transferring the image to a transfer belt. By using such a transfer belt, the transfer of the toner image can be performed satisfactorily regardless of the conditions such as the type of the printing paper and the transport speed, and the paper after the transfer is forcibly separated from the photoconductor, and is held and transported. can do.

The transfer belt has a seamless ring shape so that no trace of a seam is formed on a formed image.
A conductive belt made of a thermoplastic elastomer is preferably used. Heretofore, this conductive belt has been prepared by transferring a composition (thermoplastic elastomer composition) obtained by blending a conductivity-imparting agent such as carbon black into a thermoplastic elastomer by a known method such as a transfer molding method, a compression molding method, and an extrusion molding method. It is manufactured by shaping the surface of a molded product after forming it into a seamless annular shape by a molding method.

Above all, in the extrusion molding method, since the pressure and heat history applied to the thermoplastic elastomer composition are always constant by keeping the extrusion speed and the temperature of the extrusion head constant, the variation in resistance value is small. Conductive belts can be manufactured. When the conductive belt manufactured by the extrusion method is used for a transfer belt of an image forming apparatus, it is possible to prevent transfer unevenness of a toner image from occurring.

On the other hand, the extrusion molding method has a drawback in that the surface of the conductive belt is wrinkled and undulated, so that it is difficult to obtain a smooth belt. However, there is a problem that the image quality of the formed image is deteriorated when used in the above. That is, according to the extrusion molding method, the thermoplastic elastomer composition is continuously extruded from a die having a cross-sectional shape corresponding to the circumferential size of the annular conductive belt in a state where the thermoplastic elastomer composition is heated and plasticized. By cutting to a predetermined length according to the width size of the, to produce a conductive belt,
Since the direction in which the thermoplastic elastomer composition is extruded from the die is open without any restrictions, the composition extruded from the die first becomes thicker than the circumference of the conductive belt, the so-called ballast effect. Swelling due to
Thereafter, a so-called sagging phenomenon, which is smaller than the circumference of the conductive belt due to the weight and viscosity of the composition, occurs, and as a result, wrinkles and undulations are generated on the surface of the obtained conductive belt.

In the conductive belt manufactured by the above extrusion molding method, the thermoplastic elastomer molecules are oriented in the width direction of the conductive belt (corresponding to the direction in which the thermoplastic elastomer is extruded from the extruder). However, since the molecules of the thermoplastic elastomer are not oriented in the circumferential direction of the conductive belt orthogonal to the conductive belt, there is a problem that the elastic modulus in the circumferential direction is insufficient.

When such a conductive belt having an insufficient elastic modulus in the circumferential direction is used, for example, as a transfer belt of an image forming apparatus, elongation during running is poor.
A transfer failure of the toner image may occur, which may cause image unevenness. Therefore, a so-called extrusion blow molding method in which air or the like is blown into a thermoplastic elastomer composition extruded from a die to expand the composition is being studied.

In such an extrusion blow molding method, the thermoplastic elastomer composition is heated and plasticized, extruded from a die having a cross-sectional shape smaller than the circumference of the annular conductive belt, and then provided on the die. This is a method of manufacturing a conductive belt by blowing air from a fluid inlet to expand the conductive belt to the circumferential size, cooling, solidifying, and cutting into a desired width.

In this extrusion blow molding method, the thermoplastic elastomer molecules can be oriented in the circumferential direction by a blowing operation in which the extruded thermoplastic elastomer composition is expanded to the circumferential size of the conductive belt. As a result, the elastic modulus in the circumferential direction of the manufactured conductive belt becomes as good as the elastic modulus in the width direction,
It was also considered that wrinkles and undulations on the surface of the thermoplastic elastomer composition generated during extrusion could be removed by this blowing operation.

In practice, however, although the elastic modulus in the circumferential direction is improved, wrinkles and undulations still occur on the surface of the conductive belt because the direction of the thermoplastic elastomer extruded from the die is open. It became clear to do. In Japanese Patent Publication No. 7-120061, a preform 41 or 42 made of a thermoplastic elastomer as shown in FIGS. 4 (a) and 4 (b) is once prepared by an injection molding method or an extrusion molding method. An integrated mold 43 shown in FIG.
After placing it in the (mold) and heating it to a state where it can be thermally deformed,
A fluid is introduced into the heated preform, thereby expanding both the width and the circumferential direction until it contacts the inner surface of the mold 43 to obtain an expanded preform, and the expanded preform is removed from the mold 43. A method for producing a conductive belt using a so-called biaxial stretch blow molding method for producing a belt having a seamless shape by taking it out is disclosed.

According to the biaxial stretch blow molding method, the preform 41 or 42 made of a thermoplastic elastomer is used.
Is manufactured once, and these preforms are expanded in both the width direction and the circumferential direction in the integrated mold 43, whereby the ballast effect seen in the conventional extrusion molding method, extrusion blow molding method, and the like is obtained. In addition to preventing the occurrence of swelling and sagging, the thermoplastic elastomer molecules can be oriented in the circumferential direction by expansion in the circumferential direction. As a result, the moldability is excellent, the unevenness of electric resistance is small, and It is possible to manufacture a conductive belt whose elastic modulus in the direction is as good as the elastic modulus in the width direction.

[0012]

However, the above-mentioned 2)
In the axial stretch blow molding method, the following operations are required in order to achieve such an effect, a great deal of time and labor is required, and an extra facility investment is required. However, there is a problem that it is not suitable for mass production (it leads to an increase in cost). It is necessary to once produce a preform to be installed in the integrated mold 43 (mold) by using an injection molding method or an extrusion molding method.

For example, the preform 4 is formed by an injection molding method.
In the case of fabricating No. 1, a molten polymer material is introduced into a mold (a mold for the preform 41) corresponding to the shape of the preform 41 having a desired shape, and the polymer material is cooled and solidified. It is necessary to perform an operation of removing the solid product from the preform 41 mold. Therefore, it is necessary to prepare a mold for the preform 41, and since the mold for the preform 41 affects the formability of the conductive belt, high precision is required for the design of the mold. (Ie, it takes a lot of time and money).

On the other hand, the preform 42 is formed by extrusion molding.
First, a molten polymer material is extruded from a die corresponding to the cross-sectional shape of a seamless annular belt, then cooled and solidified, cut into a desired size, and then cut into a cylindrical polymer material. Collect. Although the operation itself up to this point does not seem complicated, in order to produce a preform 42 that can be installed in the integrated mold 43 from this cylindrical polymer material, the cylindrical polymer material is threaded, Each end must be sealed by means of bonding, welding, or the like, and one end of the end must be provided with an opening 44 which allows the preform 42 to introduce a fluid under pressure. Become. Each of the preforms 41 and 42 is cooled (solidified) due to the necessity of performing the above-described demolding and processing operations, and therefore must be reheated to a state in which it can be thermally deformed. For this reason, problems such as power cost and time required occur, and the productivity of the conductive belt decreases,
Moreover, there is a possibility that the cost will increase. Further, in the above-described biaxial stretch blow molding method, since it is necessary to expand the conductive belt in the width direction as well as in the circumferential direction, the conductive belt is easily torn in the expansion direction, or the degree of expansion is partially different, and the belt surface has unevenness. In some cases, wrinkles occur and the thickness becomes uneven.

When the conductive belt manufactured by the biaxial stretch blow molding method is used as a transfer belt of an image forming apparatus which is stretched between a pair of rollers, a belt portion in a width direction during traveling runs. The quality of the formed image may be reduced due to problems such as shrinking and rolling up. In addition, instead of manufacturing the preform 41 by the injection molding method, a conductive belt corresponding to the outer shape of the belt is directly manufactured. Even so, there is a problem that variations in electric resistance occur, as is apparent from the examples described later.

An object of the present invention is to solve the above-mentioned problems,
Provided is a method for producing a conductive belt, which has good moldability of the obtained conductive belt, has no electric resistance unevenness, has a good elastic modulus in the width direction and the circumferential direction, and can improve productivity and cost. That is.

[0017]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, extruded a melt of a thermoplastic elastomer using an extruder to obtain a thermoplastic elastomer cylinder. Then, as shown in FIG.
A part of the cylinder is sealed in the mold 2 in a state capable of being thermally deformed by a mold 2 composed of two mold members 21, and a fluid is blown into the interior of the cylinder so that only the circumferential direction is achieved. Is expanded, the steps (1) to (4) are not required (that is, the productivity and cost can be improved), the moldability is good, the electric resistance is not uneven, and the elastic modulus in the circumferential and width directions is high. The present inventors have found a new fact that a good conductive belt can be obtained, and have completed the present invention.

The method for producing a conductive belt of the present invention comprises the steps of (1)
A step of extruding a melt of the thermoplastic elastomer into a cylinder using an extruder to obtain a continuous cylinder, and (2) including a mold member divided into two along the axial direction of the cylinder, and When the extruded cylinder is sandwiched between the two mold members and closed, a mold cavity corresponding to the outer shape of the molded product is formed inside, and a part of the continuously extruded cylinder is cut to form the cavity. Using a mold having the function of sealing in, a step of sealing a part of the cylindrical body in a mold cavity of the mold in a thermally deformable state,
(3) Blow fluid into the cylinder sealed in the mold cavity,
By the pressure of the fluid, a step of obtaining a molded product by expanding the outer peripheral surface of the cylindrical body until it contacts the inner surface of the mold, and (4) a step of removing the molded product from the mold. In the present invention, when the mold member is divided into two along the axial direction of the tubular body of the thermoplastic elastomer, and when the tubular body that is continuously extruded by both mold members is closed, A mold having a function of forming a mold cavity corresponding to the outer shape of the molded product inside and cutting a part of a continuously extruded cylindrical body and sealing the inside of the mold cavity (hereinafter, a mold divided into two parts) Is used for the following reason.

According to the above-mentioned step (1), similarly to the conventional extrusion blow molding method, the thermoplastic elastomer melt is formed into a cylindrical shape from a die having a sectional shape smaller than the circumferential size of the seamless annular conductive belt. To obtain a thermoplastic elastomer cylinder having a desired length in the axial direction. Then, in the step (2), by closing both mold members constituting the two-part mold, the length of the conductive belt in the width direction of the conductive belt or longer than that is obtained from the thermoplastic elastomer cylinder. A part of the cylindrical body having the length is cut off and can be sealed in the two-part mold. Therefore, there is no need to expand in the axial direction, and the thickness of the conductive belt in the width direction is uniform.

Since the cylindrical body sealed in the mold is thermally deformable (soft) in the step (3), a temperature at which heat deformation is possible (hereinafter referred to as a stretching temperature).
It is not necessary to reheat the cylinder and the fluid can be blown into the cylinder to expand in the circumferential direction. Since only the circumferential direction where the elastic modulus is insufficient is expanded, it is possible to prevent tearing in the expanding direction, unevenness and wrinkles on the belt surface, which are observed in the biaxial stretch blow molding method in which both the width and the circumferential direction are expanded. . In addition, the steps (1) to (3) and the work requiring human intervention can be performed continuously without intervening.

Therefore, according to the production method of the present invention, the moldability is good, there is no unevenness in electric resistance, and the circumferential and axial directions are eliminated without performing the above-mentioned steps and the operation of expanding the belt in the axial direction. In addition to providing a conductive belt having a good elastic modulus, the productivity can be improved and the cost can be improved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
First, various members used in the present invention will be described.
The thermoplastic elastomer composition used in the present invention is obtained by blending a conductivity-imparting agent and other additives (such as an antistatic agent and a reinforcing agent) in a thermoplastic elastomer.

As the above-mentioned thermoplastic elastomer, for example, resins of polyester type, polyamide type, polyether type, polyurethane type, polyurethane type or polyolefin type can be used. Considering characteristics such as temperature characteristics, it is preferable to use a polyester resin. Examples of the conductivity-imparting agent include carbon black, tin oxide, metal oxides such as titanium oxide, conductive silica, copper,
Metal powder such as iron, nickel, and aluminum may be used. These can be used alone or in combination of two or more.

The compounding amount of the conductivity-imparting agent is generally in the range of 5 to 60 parts by weight, preferably in the range of 20 to 40 parts by weight, based on 100 parts by weight of the thermoplastic elastomer. The thermoplastic elastomer composition is manufactured by kneading the above components using, for example, an open roll, a closed kneader, or the like.

As a die of an extruder for extruding a melt of a thermoplastic elastomer into a cylinder to form a continuous cylinder, a die having a shape of a thermoplastic elastomer cylinder smaller than the shape of a conductive belt is used. There is no particular limitation as long as the section is provided, and either a straight head or a cross head may be used. Explaining the above die in detail, for example, as shown in FIG. 3 (a), an extrusion flow path R and a base D were communicated in this order from upstream to downstream in the extrusion direction of the thermoplastic elastomer. There are things.

As shown in FIG. 3 (b), the die portion D of the die is inserted into a die body D1 having a circular cross section corresponding to the outer shape of a seamless annular thermoplastic elastomer cylinder by a spider (not shown). It supports a cone D2 having a circular cross section corresponding to the inner shape of the conductive belt. Note that FIG.
The symbol D11 in (b) is a through hole through which a melt of the thermoplastic elastomer is extruded, and the symbol E is a melt of the thermoplastic elastomer extruded into a cylinder from a die, that is, a continuous thermoplastic elastomer cylinder. is there. Arrows indicate the direction of extrusion of the melt of the thermoplastic elastomer.

The gap between the through holes D11 is appropriately set according to the thickness of the conductive belt. However, in the shaping step of blowing and expanding a fluid into the thermoplastic elastomer cylinder, the gap between the through holes D11 is 0.2 to 5 so that the thermoplastic elastomer cylinder does not break.
mm. The cross-section circles D1 and D2
In consideration of the effect of stretching the conductive belt in the circumferential direction in the shaping process, the diameter of the conductive belt is usually 0.3 to 0.9 times, preferably 0.3 to 0.9 times the outer and inner diameters of the conductive belt. It is preferable to set the size to 5 to 0.8 times.

The ratio (D1) between the gap of the base D (that is, calculated by the gap of the through hole D11) and the gap R1 of the extrusion flow path R
1) / (R1) is preferably 1 or less in order to obtain an effect of stretching the conductive belt in the width direction. The extruder used in the present invention is not particularly limited as long as it is provided with a die having a die D having a predetermined shape as described above.
Either a single-axis type or a two-axis type can be used.

The melt of the thermoplastic elastomer used in the present invention can be obtained by supplying the above thermoplastic elastomer composition to a hopper of an extruder and heating it to the melting temperature of the thermoplastic elastomer to be used. As the two-part mold used in the present invention, for example, a mold 2 shown in FIG. 2 is exemplified. The mold 2 includes the following (i) to (iii)
It satisfies the requirements of (i) As shown in FIG. 2 (a), it is composed of a mold member 21 divided into two along the axial direction (the direction of the arrow in FIG. 2 (a)) of the thermoplastic elastomer cylinder extruded from the extruder. Is done. (ii) As shown in FIG. 2 (b), when both the mold members 21 are closed with the thermoplastic elastomer cylinder continuously extruded from the extruder sandwiched therebetween, the inside corresponds to the outer shape of the molded product. And upper portion 22 of the surface where both mold members 21 contact each other (side surface of mold 2 on the upstream side in the extrusion direction of the thermoplastic elastomer, hereinafter referred to as upper portion of mold 2) and / or Alternatively, a part of the extruded cylinder is cut at a lower portion 23 (a side surface of the mold 2 on the downstream side with respect to the extrusion direction of the thermoplastic elastomer, hereinafter referred to as a lower portion of the mold 2),
A part of the cut cylindrical body can be sealed in the mold cavity A of the mold 2 in a state capable of being thermally deformed. (iii) It has a fluid blow-in port P through which fluid can be blown into the cylinder enclosed in the mold cavity A of the mold 2.

In the above (i), the length X of the mold member 21 corresponding to the axial direction of the cylindrical body may be set to be at least the width W of at least one conductive belt in the width direction. (Ii) above
In order to cut a part of the continuously extruded thermoplastic elastomer cylindrical body, the two mold members 21 are closed (mold closed) or in addition to the mold 2.
Alternatively, a cutting device (parison cutter) C may be installed so as to be in contact with the upper part 22 and / or the lower part 23 of the above, and it may be moved in the direction of the double arrow.

A part of the thermoplastic elastomer cylinder sealed in the mold cavity A of the mold 2 is cooled from the melting temperature to a lower stretching temperature in order to perform a stable shaping operation. Good to be. Therefore, it is preferable that both mold members 21 constituting the mold 2 are provided with a cooling facility F such as a cooling pipe. The width Y of the mold cavity A corresponding to the outer shape of the molded product is appropriately set according to the size of the circumference of the conductive belt.

As shown in FIG. 2C, when the two mold members 21 constituting the mold 2 are closed, the fluid injection port P is located on either the upper part 22 or the lower part 23 of the mold 2. It is near one central part. It is preferable that the shape of the blowing port P corresponds to the shape of the nozzle that blows the fluid so that the fluid can be blown under pressure into the cylinder of the thermoplastic elastomer.

Particularly, the mold having the blow port P in the lower part 23 of the mold 2 cuts a part of the extruded cylinder in the above (ii) and cuts a part of the cylinder in the above (iii). Can be performed at the same time, and the time required for the manufacturing process can be reduced. In the above (iii), the fluid blown from the fluid blowing port P is
There is no particular limitation as long as it does not adversely affect the thermoplastic elastomer, for example, air, nitrogen, oxygen, argon,
Examples include gas such as carbon dioxide, and liquid such as water. Among them, easily available air is preferably used.

Next, a method for manufacturing the conductive belt of the present invention will be described with reference to FIG. According to the production method of the present invention, the conductive belt (1) continuously extrudes a melt of the thermoplastic elastomer into a tubular shape using an extruder 11 to form a continuous thermoplastic elastomer tubular body 13. Obtaining step (extrusion step, FIG. 1 (a)); and (2) a part of the thermoplastic elastomer cylinder 13 in the above-mentioned two-part mold 2 in a state capable of being thermally deformed. (Parison molding step, FIGS. 1 (b), (c)) and (3) a fluid is blown into the cylinder sealed in the mold cavity A, and the cylinder is compressed by the pressure of the fluid. Of forming the molded product 16 by expanding the outer peripheral surface of the mold until it comes into contact with the inner surface of the mold 2 (shaping process, FIG. 1 (d))
And (4) a step of removing the molded article 16 from the mold (a removing step, FIG. 1 (e)).

In the step (1) of obtaining the continuous cylindrical body 13 (extrusion step), the thermoplastic elastomer composition 10 is supplied to the hopper 12 of the extruder 11. Next, the extruder 1
1, a thermoplastic elastomer composition was melted and kneaded to obtain a thermoplastic elastomer melt (not shown), which was formed between a die body D1 and a cone D2 (not shown) of a die D of a crosshead type die. It is performed by extrusion molding from the through-hole D11 between them.

The conditions for extruding the thermoplastic elastomer melt vary depending on the type of thermoplastic elastomer used and the like. Usually, the extrusion speed is 1 to 10 m / min, and the temperature of the thermoplastic elastomer at the time of extrusion is 160 to 100 m / min. The pressure at the die D of the die at 240 ° C. is preferably in the range of 5 to 30 kg / cm ² . Next, the step (1) of sealing a part of the thermoplastic elastomer cylindrical body 13 into the mold cavity A of the divided mold 2 (parison molding step) is shown in FIG.
As shown in (c), the operation of closing both the mold members 21 constituting the mold 2 in the direction of the arrow (mold closing) with the thermoplastic elastomer cylindrical body 13 extruded from the die portion D of the die is performed. The cutting is performed by a parison cutter C installed on the upper portion 23 of the mold 2.

That is, when the mold members 21 are closed, the extra thermoplastic elastomer cylinder 14 formed in the lower portion 23 of the mold 2 naturally falls due to the weight of the cylinder 14 and falls from the mold 2. break away. Further, a parison cutter C may be provided in the lower portion 23 of the mold 2 as needed. In order to further reduce the cost, a desired amount of the thermoplastic elastomer melt is extruded by appropriately adjusting the extrusion speed of the extruder 11 and the like, and the continuous cylindrical body 13 is extruded.
When the mold closing operation of both mold members 21 is performed, the extra thermoplastic elastomer cylinder 14 is placed on the lower portion 23 of the mold 2.
Should not be formed.

Then, the extra thermoplastic elastomer cylinder 15 formed on the upper part of the mold 2 is cut off by the mold closing and the parison cutter C, and detached from the mold 2.
In the step (2), the thermoplastic elastomer cylinder 13 sealed in the mold 2 is maintained in a thermally deformable state. Therefore, in the present invention using the mold 2 including the mold member 21 divided into two, the cylindrical body 13 made of the thermoplastic elastomer can be sealed in the mold 2 in a thermally deformable state. It is not necessary to manufacture the cooled and solidified preform 41 or 42 as in the conventional biaxial stretch blow molding method using, and the work of reheating the preform to a heat deformable state can be omitted.

In the present invention, the heat-deformable state is a temperature at which the thermoplastic elastomer can expand in the circumferential direction of the conductive belt in the operation performed in the next step (3). State. However, the temperature is
Preferably, it is cooled to a thermoplastic elastomer stretching temperature below the melting temperature. If the cooling here is not sufficient, there is a possibility that a stable fluid blowing operation cannot be performed. For example, in the case of polyethylene terephthalate,
It is preferable to cool to about 90 to 120 ° C.

By closing the two mold members 21 in the above step (2), the mold 2 forms a mold cavity A corresponding to the outer shape of the molded product 16 inside the mold 2, Either the upper part 22 or the lower part 23 of the mold 2 has a fluid inlet P, and the other part is sealed so that the fluid can be blown under pressure into the thermoplastic elastomer cylinder. On the other hand, each end of the thermoplastic elastomer cylindrical body 13 sealed in the mold cavity A of the mold 2 is sealed by the inner surfaces of the upper part 22 and the lower part 23 of the mold 2 except for the fluid inlet P. .

Then, as shown in FIG. 1D, a nozzle N is inserted into a blowing port P provided in an upper portion 22 of the mold 2, and
A fluid is blown in the direction of the arrow into the cylindrical body 13 of the thermoplastic elastomer which can be thermally deformed, and by the pressure of the fluid,
The outer peripheral surface of the cylindrical body 13 is expanded until it contacts the mold cavity A corresponding to the outer shape of the molded product 16 on the inner surface of the mold. The pressure of the fluid blown from the nozzle N is equal to the thermoplastic elastomer cylinder 13.
There is no particular limitation as long as it is larger than the pressure inside, but about 1.2 to
The range of 10 atm (atm) is preferable from the viewpoint of moldability.

In the present invention, it is preferable that the fluid inlet P is formed not in the upper portion 22 of the mold 2 but in the lower portion 23 of the mold 2. In such a case, the cutting operation of the excess thermoplastic elastomer 15 in the above (2) can be performed at the upper portion 22 of the mold 2 (at this time, the excess thermoplastic elastomer 14 existing at the lower portion 23 of the mold 2). Is naturally dropped by its own weight), and at the same time, the nozzle N can be inserted into the thermoplastic elastomer cylindrical body 13 from the lower part 23 of the mold 2 in the above (3).
And (3) the working time can be further reduced.

Further, in the present invention, the number of the extruders 11 and the number of the dies 2 do not necessarily have to be 1: 1. For example, a plurality of dies 2 are used for one extruder 11. You may. Also in such a case, the operation time of the above (2) to (3) can be reduced. As shown in FIG. 1 (e), in the above (4), the mold member 21 constituting the mold 2 is moved in the direction of the arrow to open and the molded product (which is an expanded thermoplastic elastomer cylinder) 16 is released from the mold. If the molded article 16 is heated and cured beforehand, there is no risk of crushing and shrinking, and the dimensional stability of the molded article to be produced can be improved. For example, when polyethylene terephthalate is used as the thermoplastic elastomer, it is preferable to heat at a temperature in the range of about 180 to 250 ° C.

After removing the molded product 16 from the mold 2, the surface is polished to a predetermined thickness, and if necessary, the width direction of the conductive belt is cut to form an annular seam. No conductive belt is obtained. The polishing operation is performed to adjust the thickness of the conductive belt and the surface roughness thereof. For polishing, a normal polishing method such as buff polishing is employed.

The thickness of the conductive belt is not particularly limited, but is preferably about 0.2 to 2.0 mm. When the conductive belt is used as a transfer belt of an image forming apparatus, if the thickness of the conductive belt is less than 0.2 mm, the tension of the belt is insufficient, and the conveyance force of the recording paper may be insufficient. . Conversely, if the thickness of the conductive belt exceeds 2.0 mm, the flexibility of the belt may be reduced, or the surface of the photoconductor may be damaged.

The conductive belt manufactured through the above steps may be used as it is as a transfer belt of an image forming apparatus or the like, or may be wound around a drum or the like.
In addition, to improve the chemical stability of the belt surface, stabilize the surface resistivity, and prevent contamination due to toner adhesion, the surface is coated with a fluororesin or silicone resin-based resin layer. May be used.

[0047]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Example 1 A base D having the shape shown in FIG. 3B (the outer diameter of the die body D1 is 150 mm, the outer diameter of the cone D2 is 50 mm, the through-hole D1
A die having a gap of 2 mm) was mounted on an extrusion head of an extruder (Model JB105 manufactured by Nippon Steel Works), and an inner diameter (φ) of 250 mm and a length of 30 as shown in FIG.
A 0 mm mold 2 was mounted below the die.

Next, as shown in FIG. 1A, 30 parts by weight of a thermoplastic elastomer 40 (polyester, "Hytrel 4047X08" manufactured by Toray DuPont) was blended with 30 parts by weight of a heat imparting agent. The plastic elastomer composition 10 was supplied to a hopper 12 of an extruder, and was heated and kneaded in the extruder 11. The obtained thermoplastic elastomer melt is extruded from the die D of the die at an extrusion speed of 80 mm / sec and an extrusion head temperature of 200 ° C. to form a continuous cylindrical body 13 (length 300 mm). After forming the above, as shown in FIGS. 1 (b) and (c), the cylindrical body 13 is sandwiched between the two mold members 21 constituting the mold 2, and then the upper part 22 of the mold 2 The surplus thermoplastic elastomer cylinder 15 was cut by a parison cutter C.

Next, as shown in FIGS. 1 (d) and 1 (e),
The nozzle N is inserted into the fluid injection port P of the upper part 22 of the mold 2, and air is blown into the thermoplastic elastomer cylindrical body 13 sealed in the mold 2 for 5 seconds.
It was inflated until it touched the mold cavity A formed on the inner surface. Then, the molded product 16 is taken out from the mold, taken out, covered with a polishing core and polished, and the width direction of the belt is cut to obtain an outer diameter of 249.5 mm, a width of 300 mm, and a thickness of 0.5 mm.
A seamless annular conductive belt was produced. Comparative Example 1 The above thermoplastic elastomer composition was supplied to a resin extruder manufactured by Nissei Resin Co., Ltd. to obtain a thermoplastic elastomer melt,
The extrusion speed was 50 mm / sec, and the extrusion head temperature was 20
Under the condition of 0 ° C., the die part D ′ (the outer diameter of the die body
(0 mm, outer diameter of cone D2: 250 mm, through-hole: 1 mm), and extruded from a die to form a continuous cylinder.

Then, the obtained molded product was polished by covering it over a polishing core, and a seamless annular conductive belt having the same dimensions as in Example 1 was produced. Comparative Example 2 A gate was provided at two points 180 ° apart from the center of the circle on one end face of the above-mentioned ring, having a mold cavity for obtaining an annular molded product having an outer diameter of 250 mm, a width of 300 mm, and a thickness of 1 mm. The provided injection mold was set on an injection molding machine (manufactured by Sumitomo Heavy Industries). Next, the above-mentioned mold was injection-molded into the mold cavity through the above-mentioned two points of gates while heating and melting the thermoplastic elastomer composition from a nozzle of an injection molding machine.

Next, the obtained molded product was polished by covering it over a polishing core, and a seamless annular conductive belt having the same dimensions as in Example 1 was produced. The following tests were performed on the conductive belts manufactured in the above-described example and comparative examples 1 and 2, and their characteristics were evaluated. (Electrical Resistance Unevenness) Volume resistivity (lo) at a total of 12 points a-α to d-γ shown in FIG.
gΩ · cm) was measured according to the measuring method of the Japan Rubber Association Standard 2304.

Then, a-α, a-β,
3 points of a-γ, 3 points of b-α, b-β, b-γ, c-
α, c-β, c-γ, and d-α, d-β, d
3 points -γ as one set, respectively, and a maximum value R _{ma x} and the minimum value R _min of the volume resistivity in each set (log Ω · cm), wherein: a difference by ΔR ₁ = logR _max -logR _min ΔR ₁ was determined. Then, the value of the difference ΔR ₁ of the group having the largest difference ΔR ₁ was recorded as the unevenness of the electric resistance. (Measurement of elastic modulus in circumferential direction) The elastic modulus (kg / cm ² ) of each conductive belt in the circumferential direction was measured in accordance with the measuring method of JIS K7198. (Surface Appearance) The surface of the conductive belt was visually observed for waviness and wrinkles.

Table 1 shows the measurement results.

[0054]

[Table 1] As is clear from Table 1, the conductive belt of Comparative Example 1 has wrinkles and undulations on the belt surface, causing a problem in appearance and having a low elastic modulus in the circumferential direction. Further, the conductive belt of Comparative Example 2 had good external appearance, but had a low elastic modulus in the circumferential direction, and had a large variation in electric resistance.

On the other hand, it can be seen that the conductive belt of the example has no problem in any of the appearance, the electric resistance, and the elastic modulus in the circumferential direction, and is satisfactory.

[0056]

According to the method for producing a conductive belt of the present invention, a melt of a thermoplastic elastomer is extruded using an extruder to obtain a continuous thermoplastic elastomer cylinder, and then a two-part mold member is obtained. A part of this cylindrical body is sealed in the mold in a state capable of being thermally deformed,
And, since a conductive belt is manufactured by blowing a fluid into the cylinder enclosed in the mold and expanding only in the circumferential direction, the production of a preform performed in the conventional biaxial stretch blow molding method, It is possible to omit a preform processing operation required for installing the preform in an integrated mold. That is, the productivity of the conductive belt is increased, and the cost is reduced.

The conductive belt obtained by the production method of the present invention has good moldability, has no uneven electric resistance,
In addition, since the elastic modulus in the circumferential direction and the width direction is good, there is an effect that, when used for a transfer belt of an image forming apparatus, for example, transfer defects such as transfer unevenness of a toner image hardly occur.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a method for producing a conductive belt of the present invention.

FIG. 2 is a view showing an example of a mold used to obtain a molded product by sealing a thermoplastic elastomer cylinder, blowing a fluid into the cylinder and expanding the cylinder in the production method of the present invention.

FIG. 3 shows a die used for extruding a thermoplastic elastomer into a seamless annular shape in the production method of the present invention, and a thermoplastic elastomer cylindrical body continuously extruded from the die into a cylindrical shape. FIG.

FIG. 4 is a diagram showing a preform used for a biaxial stretch blow molding method and a mold on which the preform is installed.

FIG. 5 is a perspective view showing a measurement position of a volume resistivity in the conductive belts manufactured in Examples and Comparative Examples.

[Explanation of symbols]

 2 Mold A Mold cavity E Melt of thermoplastic elastomer 11 Extruder 13 Cylindrical body of thermoplastic elastomer 16 Molded product

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 15/16 G03G 15/16 5G301 H01B 1/20 H01B 1/20 Z // B29K 101: 12 B29L 29:00 F term (Ref.)

Claims (1)

[Claims] (1) a step of extruding a melt of a thermoplastic elastomer into a cylinder using an extruder to obtain a continuous cylinder; and (2) a step of dividing the melt into two along the axial direction of the cylinder. When the molded body is closed by sandwiching the extruded cylinder with both mold members, a mold cavity corresponding to the outer shape of the molded product is formed inside, and the continuously extruded cylinder is formed. Using a mold that has the function of cutting part and sealing it in the mold cavity,
(3) a step of sealing a part of the cylindrical body in a mold cavity of the mold in a state capable of being thermally deformed, and (3) blowing a fluid into the cylindrical body sealed in the mold cavity, and the pressure of the fluid causes the cylindrical body to be sealed. A method for producing a conductive belt, comprising: a step of obtaining a molded product by expanding the outer peripheral surface until it comes into contact with the inner surface of the mold; and (4) a step of removing the molded product from the mold.