JP2006142516A - Extrusion molding device and extrusion molding method of resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a extrusion molding method of a resin which suppresses the streak on the surface of an extruded resin efficiently without using a large-scaled apparatus and enables the uniformization of thickness, and to provide an extrusion molding device. <P>SOLUTION: In the extrusion molding device equipped with an extruder 1 for extruding a heated resin and an extrusion die 3 for molding the resin supplied from the extruder 1 into a predetermined shape to extrude the same, the die 3 is equipped with a resin flow channel 7 for permitting the resin supplied from the extruder 1 to pass and provided with a heating means 8 for locally heating the mouth edge part 5a of the outlet 7d of the resin flow channel 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin extrusion molding method and an extrusion molding apparatus suitable for manufacturing electronic materials, in particular, belt members such as intermediate transfer belts and transfer conveyance belts of image forming apparatuses that require smoothness. It is.

  In the image forming apparatus, after a toner image formed on a photoconductor is once transferred, an intermediate transfer belt used to transfer the transfer image to a transfer material and a toner image formed on the photoconductor are also transferred. A transfer belt such as a transfer conveyance belt used for direct transfer to a transfer material is used.

  The resin transfer belt used in these image forming apparatuses is required to have a uniform and smooth thickness in order to form a highly accurate image. As a method of manufacturing such a smooth belt, a method of manufacturing a seamless belt by extruding a resin into a cylindrical shape using an extrusion molding apparatus and then cutting the resin is known.

However, the above method may cause streaks on the belt surface due to the influence of the resin characteristics, the structure of the extrusion molding apparatus, and the like. It is known that the unevenness of the belt surface, in other words, the variation in the belt thickness causes color shift as shown in Patent Document 1, and an accurate image cannot be obtained.
JP 2003-206046 A

  As a method for preventing the occurrence of streaks in the belt member and making it uniform, Patent Document 1 discloses that the tubular melt is taken up at a take-up speed faster than the discharge speed of the tubular melt extruded from the extrusion molding apparatus. And a method for making the tube thin and uniform.

  However, in this method, no matter how fast the resin coming out from the resin flow path outlet is taken and thinned, the thickness of the molded product is reduced, but the thickness variation rate in the circumferential direction does not change. In order to reduce the thickness variation of the molded product, it is necessary to reduce the thickness variation at the resin flow path outlet.

  Therefore, in the present invention, there is provided a resin extrusion molding method and an extrusion molding apparatus capable of efficiently suppressing streaks on the extruded resin surface and uniforming the thickness without using a large-scale apparatus. With the goal.

  As a result of various studies by the present inventors in order to solve the above-mentioned problems, extrusion molding including an extruder for extruding heated resin, and a die for extruding the resin supplied from the extruder into a predetermined shape. In the apparatus, it was found that the main cause of the thickness variation in the finally obtained resin product is as follows.

  That is, when the resin supplied from the extruder passes through the resin flow path in the die, if the temperature of the resin is high, the resin viscosity decreases and the internal pressure of the die decreases, and the influence of the shape of the resin flow path affects the resin product. appear. The influence becomes large particularly when a spiral die is used, and the influence of the spiral appears in the resin product, and the thickness variation increases in the circumferential direction.

  On the other hand, if the temperature of the resin that passes through the resin flow path is lowered, the resin viscosity increases and the internal pressure of the die rises, and the influence of the shape of the resin flow path decreases, but the resin partially solidifies by lowering the resin temperature. As a result, a so-called eye-sag phenomenon occurs at the edge of the outlet of the resin flow path, which causes streaks.

  The present inventors have further studied based on the above findings and have completed the present invention. That is, in the present invention, in an extrusion molding apparatus comprising an extruder for extruding heated resin and a die for forming and extruding the resin supplied from the extruder into a predetermined shape, the die uses the resin supplied from the extruder. A resin flow path is provided, and heating means for locally heating the mouth edge of the outlet of the resin flow path is provided.

  According to the above configuration, the high-temperature resin supplied from the extruder to the die is allowed to cool while passing through the resin flow path in the die, thereby increasing the resin viscosity and ensuring the die internal pressure. . In addition, since the heating means for locally heating the lip portion of the resin flow path outlet is provided, there is no possibility of eye-cracking, and it becomes possible to obtain a resin product having a smooth surface and a uniform thickness. .

  Furthermore, a major feature of the present invention is that the edge portion of the resin flow channel outlet is locally heated, whereby only the surface of the resin product can be heated and softened. The resin product whose surface has been softened is squeegeeed at the edge of the die when discharged to the outside, thereby further improving the smoothness of the surface.

  There is no particular limitation on the type of heating means, and for example, an electric heater can be installed on the outer portion of the die surface where the resin flow channel outlet is formed. However, in this case, heat transmitted from the heating means to the die may be transmitted not only to the edge portion but also to the resin flow path on the upstream side of the die.

  Therefore, in the present invention, it is preferable to provide a heat transfer suppressing means for suppressing the heat of the heating means for heating the mouth edge portion from being transmitted to the resin flow channel upstream of the mouth edge portion. Thereby, it is possible to prevent the resin passing through the resin flow path from being excessively heated and to soften only the surface of the resin product as described above.

  The heat transfer suppression means is not particularly limited. For example, a heat insulation made of a material having low thermal conductivity between a die portion outside the mouth edge portion and a die portion adjacent to the die portion on the upstream side in the resin flow direction. A layer may be interposed, and a space may be formed. In particular, the space portion is preferable because it is easy to form and has a high heat insulating effect. Furthermore, heat may be positively removed using a coolant such as water.

  In the die, the high-temperature resin extruded from the extruder is gradually cooled while passing through the resin flow path to lower the temperature, thereby increasing the internal pressure of the die. The temperature of the resin in the resin flow path varies depending on the room temperature and the like, and as a result, the thickness of the resin product may vary. Therefore, in the present invention, the resin flow channel upstream of the edge of the resin flow channel outlet is divided into a plurality of regions in the resin flow direction, and heating means capable of adjusting the temperature for each region can be installed.

  According to the above configuration, the resin temperature in the resin flow path, and hence the resin viscosity, can be accurately managed, thereby making it possible to properly maintain the internal pressure of the die, and the resin product finally obtained Variation in thickness can be suppressed.

  There is no restriction | limiting in particular about the kind of die | dye, Both a circular die | dye and T dice | dies can be used. When a circular die is used, a seamless transfer belt can be obtained by cutting a cylindrical body extruded from the die. Moreover, when using T dice | dies, a sheet | seat with a smooth surface can be obtained, for example, can be used suitably as a liquid crystal substrate.

  There are no particular limitations on the number of regions in which the resin flow path of the die is divided, but it may be divided into at least two regions on the upstream side and the downstream side in addition to the mouth edge of the outlet. In the resin flow path divided in this way, as the temperature of each region, the temperature of the upstream region is maintained equal to the resin temperature extruded from the extruder, and the temperature of the downstream region is lowered. What is necessary is just to control the heating of each heating means. When the resin flow path of the die is divided into three or more regions, the region adjacent to the mouth edge of the resin flow channel outlet may be the lowest temperature region.

  Thus, if the temperature of the upstream region of the resin flow path is kept high and the temperature of the downstream region (region adjacent to the mouth edge) is lowered, the resin viscosity in the upstream region does not increase. Since the resin viscosity can be increased only in the downstream region, an appropriate internal pressure can be ensured without the die internal pressure becoming too high. The resin channel length in each region may be adjusted as appropriate, but the resin channel length in the downstream region that is the lowest temperature region or the region adjacent to the mouth edge is at least lowered to the set temperature. What is necessary is just to set so that required length can be ensured.

  After controlling the temperature as described above, controlling the heating of the heating means so that the outlet opening edge of the resin flow path becomes the highest temperature region, softens only the surface of the resin product without reducing the die internal pressure. Finally, a resin product having a smooth surface and a uniform thickness can be obtained. That is, the temperature of the mouth edge may be set to be equal to or higher than the temperature of the most upstream region.

  The temperature of the upstream region and the downstream region, and the temperature of the mouth edge portion may be appropriately set because they vary depending on the type of resin used as a raw material, etc., but in general, while maintaining an appropriate die internal pressure, In order to soften only the surface of the resin product at the edge, the heating of each heating means is controlled so that the temperature difference between the mouth edge and the lowest temperature region adjacent to the mouth edge is 20 to 30 ° C. It is preferable. In particular, when using polyethersulfone as the resin, if the temperature difference between the mouth edge and the lowest temperature region is set within the above range, a product with a smoother surface and a uniform thickness can be obtained. At the same time, a product having a glossy surface can be obtained.

  In the present invention, since the heating means for locally heating the edge portion of the resin flow path outlet of the die is provided, the internal pressure of the die can be secured, there is no possibility that the eyes will be sprinkled, the surface is smooth and has a thickness. It becomes possible to obtain a uniform resin product.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an extrusion molding apparatus according to the present invention, and FIG. 2 is a cross-sectional view showing a die used in the extrusion molding apparatus of FIG. In the present embodiment, polyether sulfone (PES), which is a thermoplastic resin, is used as the resin, and the transfer belt is manufactured by forming this into a cylindrical shape and cutting it.

  As shown in FIG. 1, the extrusion molding apparatus according to this embodiment includes an extruder 1, a gear pump 2 that pumps the resin discharged from the extruder 1, and a resin that is supplied from the extruder 1 via the gear pump 2. A die 3 for extruding into a predetermined shape is provided. The resin cylindrical body extruded from the die 3 is taken up by the take-up machine 4 and cut into a predetermined size to form a transfer belt.

  Although the single screw extruder is used as the extruder 1, it is not restricted to this, For example, you may use a twin screw extruder. Polyether sulfone, which is a resin, is charged into the extruder 1 and supplied to the die 3 in a heated and kneaded state.

  The die 3 is a circular die (spiral die), and includes an outer cylinder portion 5, an inner cylinder portion 6, and a resin flow path 7 through which resin passes, as shown in FIG. A spiral groove (not shown) is formed on the outer peripheral surface. The resin flow path 7 includes a tubular path 7 a penetrating the outer cylinder part 5 and an annular path 7 b formed between the outer cylinder part 5 and the inner cylinder part 6.

  In the resin flow path 7 having such a configuration, the resin extruded from the extruder 1 is introduced into the annular path 7b from the inlet 7c of the resin flow path 7 through the tubular path 7a in the direction indicated by the arrow X, and It is discharged to the outside from the outlet 7d at the end of the annular path 7b while being evenly developed on the circumference of the inner cylinder portion 6 along the spiral groove. The outlet 7d of the resin flow path is formed as an annular slit in which the width of the annular path 7 is narrowed, and the resin is molded into a cylindrical shape and extruded therefrom.

  In the die 3, a heater 8 is provided outside the outlet 7d on the surface where the outlet 7d of the resin flow path 7 is formed as a heating means for heating the rim 5a (outer cylinder side) of the outlet 7d. Yes. Further, as heat transfer suppressing means for suppressing the heat of the heater 8 from being transmitted to the resin flow path 7 on the upstream side of the rim portion 5a, a die portion 3a outside the rim portion 5a and adjacent to the die portion 3a. An annular groove portion 9 is formed as a space portion between the die portion to be formed.

  The annular groove portion 9 is formed so as to be carved from the outer periphery of the outer cylinder portion 5 to the vicinity of the resin flow path 7, whereby the die portion 3 a outside the mouth edge portion 5 a is formed in a flange shape. Therefore, when the heater 8 is heated, the heat is transmitted through the die portion 3a, and the mouth edge 5a can be locally heated.

  The resin flow path 7 is divided into three regions A, B, and C in the resin flow direction on the upstream side of the mouth edge portion 5a, and heaters 10, 11, and 12 are provided in the regions A to C, respectively. . Thus, the temperature of the resin flow path 7 can be controlled in each of the four regions including the mouth edge 5a. The temperatures of the heaters 8, 10, 11, and 12 can be adjusted by a temperature controller (not shown).

  In the regions A to C, a temperature measurement hole having a depth from the surface of the outer cylinder portion 5 to the vicinity of the resin flow path is formed, and a thermocouple (not shown) is inserted into the hole to insert the resin flow path 7. The temperature is measured. A thermocouple is also attached to the mouth edge 5a. The electric signal detected by each thermocouple is input to the above-described temperature controller, the temperature is detected, and the outputs of the heaters 8, 10, 11 and 12 are controlled according to the temperature.

  In order to extrude the resin using the extrusion molding apparatus having the above-described configuration, the heating of the heaters 8 to 11 may be controlled so that the region C adjacent to the rim portion 5a is the lowest temperature region. Specifically, the temperature may be lowered stepwise from the upstream region so that the region adjacent to the mouth edge 5a becomes the lowest temperature region. Thus, if the temperature is lowered stepwise, stable temperature control of the resin becomes possible.

  Actual temperature control can be performed by inputting the set temperature of each heater 8, 10, 11 and 12 to the temperature controller, and then automatically based on the thermocouple signal so that the temperature controller maintains the set temperature. In addition, the outputs of the heaters 8, 10, 11 and 12 are controlled.

[Manufacture of transfer belt]
Using the extrusion apparatus described in the above embodiment, the temperature of the heaters 8 and 10 to 12 is changed to actually produce 10 types of transfer sheets (Examples 1 and 2 and Comparative Examples 1 to 8). The evaluation was performed. Specifically, PES was put into the extrusion molding machine 1, kneaded at 350 ° C. and extruded, and then supplied to the die 3 through the gear pump 2 heated to 350 ° C.

  The diameter of the die was 150 mm in diameter, the product thickness was 150 μm, and the extrusion speed was 1 m / min. Table 1 shows the temperatures of the areas A to C and the edge portion 5a and the die internal pressure when each transfer sheet was manufactured.

[Characteristic test]
As the characteristics of the transfer belt, three items were evaluated: streak generation, transfer belt surface gloss and circumferential thickness variation. The details of each characteristic test are described below.

(1) Situation of generation of streaks In this case, the streaks mean a portion having a width of 2 mm or less and a thickness that is thicker or thinner than the surroundings, and was visually determined. The evaluation criteria were as follows.
○… A level where there is no problem in using the product △… A state in which several streaks are entered ×… A state in which an infinite number of streaks have entered the entire belt

(2) Gloss of the belt surface The gloss of the belt surface was judged visually. The evaluation criteria were as follows. In addition, the bubbles were mixed with bubbles and clearly marked as “bubbles”.
○… Glossy state △… Intermediate state between ○ and × ×… Dull state

(3) Circumferential thickness variation The thickness at 100 arbitrary points on the circumference was measured with a thickness meter, and the maximum and minimum values were determined to be ±% of the average value.
The results of each characteristic test are shown in Table 1.

[Evaluation results]
From Table 1, the rim portion 5a is set to the highest temperature region, the region C adjacent to the lip portion 5a is set to the lowest temperature region, and the rim portion 5a and the lowest temperature region (region C) are set. In Examples 1 and 2 which were set so that the temperature difference was 20 to 30 ° C., both of the streaks were at a level with no problem in use. Further, it can be seen that both the transfer belts have gloss on the surface and the variation in circumferential thickness is suppressed to ± 5% or less.

  On the other hand, no streaks occurred in Comparative Examples 4 to 7 in which the heater 8 was not provided in the die portion 3a outside the rim portion 5a and the rim portion 5a was not locally heated. Moreover, when the temperature of the area | region C was reduced too much like the comparative example 8, die internal pressure became high too much and it became impossible to extrude PES.

  Even in the case where the rim portion 5a is heated by the heater 8, Comparative Examples 1 and 2 which did not provide an appropriate temperature difference between the lip portion 5a and the lowest temperature region both have low die internal pressure, The variation in circumferential thickness has increased.

  In addition, when the temperature of the rim portion 5a was too high as in Comparative Example 3, although the variation in circumferential thickness was small, bubbles were generated on the belt surface and the gloss was not glossy.

Schematic showing the extrusion molding apparatus of the present invention Sectional drawing which shows the circular die | dye used with the extrusion molding apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Gear pump 3 Dies 3a Die part outside a mouth edge part 4 Take-out machine 5 Outer cylinder part 5a Mouth part 6 Inner cylinder part 7 Resin flow path 7a Tubular path 7b Annular path 7c Resin flow path inlet 7d Resin flow path Outlet 8 Heater 9 Annular groove 10, 11, 12 Heater

Claims (9)

In an extrusion molding apparatus comprising an extruder for extruding heated resin and a die for extruding the resin supplied from the extruder into a predetermined shape, the die passes through the resin supplied from the extruder An extrusion molding apparatus comprising a flow path, and provided with a heating means for locally heating the rim portion at the outlet of the resin flow path. 2. The extrusion molding apparatus according to claim 1, wherein a heating means for heating the edge portion is provided on an outer portion of the outlet on the outlet forming surface of the die. The heat transfer suppression means for suppressing the heat of the heating means for heating the mouth edge portion from being transmitted to the resin flow channel upstream of the mouth edge portion is provided. Extrusion equipment. 4. The extrusion molding apparatus according to claim 3, wherein the heat transfer suppression means is a space portion formed between a die portion outside the mouth edge portion and a die portion adjacent to the die portion. . The resin flow path on the upstream side of the edge portion is divided into a plurality of regions in the resin flow direction, and heating means capable of adjusting the temperature for each region is provided. The extrusion molding apparatus described in 1. 6. The extrusion molding apparatus according to claim 1, wherein a circular die is used as the die, and a transfer belt is formed by cutting a cylindrical body extruded from the die. 7. A resin extrusion method using the extrusion apparatus according to claim 5 or 6, wherein each heating is performed so that the temperature of the lip portion becomes the highest in the entire region of the resin flow path including the lip portion. A method for extruding a resin, characterized by controlling heating of the means. 8. The resin extrusion molding method according to claim 7, wherein heating of each heating means is controlled so that a region adjacent to the mouth edge portion is a lowest temperature region. 9. The heating of each heating means is controlled so that the resin is polyether sulfone and the temperature difference between the mouth edge and the lowest temperature region is 20 to 30 ° C. Extrusion method.

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