JP2007118500A - Mold for extrusion molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for extrusion molding capable of controlling the occurrence of streaks in extrusion molding of cylindrical tubes made of a synthetic resin. <P>SOLUTION: A cylindrical resin passage 13 is secured by an inside mold 11 and an outside mold 12. A spiral area 14, a communicating area 15 and a parallel area 16 are demarcated in the resin passage 13, and the mold 1B for extrusion molding is constituted so that a molten resin is supplied and extruded to mold cylindrical tubes continuously. The shear rate γ<SB>w</SB>of the molten resin, expressed by an equation (1), is ≤300 s<SP>-1</SP>on the inner peripheral surface 12a of the outside mold 12a and the outer peripheral surface 11a of the inside mold 11a in the parallel area 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an extrusion mold used for extrusion molding of a synthetic resin. In particular, it relates to an improvement of an extrusion mold for forming a cylindrical tube.

  Conventionally, extrusion molding has been performed to mold a cylindrical tube of synthetic resin, and this extrusion molding is generally performed as follows using an extruder, a die, and a take-up device.

  First, a resin material is supplied to an extruder, and the resin material is heated to be in a uniform fluid state by the extruder, and is pressurized and continuously sent out to a mold. Next, the molten resin sent out from the extruder is formed into a cylindrical shape by a mold and pushed out from the discharge port at the tip. Finally, a cylindrical tube of a predetermined shape is obtained by pulling out the cylindrical tube pushed out from the discharge port of the mold while cooling the shape and size while regulating the shape and size.

  Examples of molds used for such extrusion molding include spiral dies, spider dies, and crosshead dies. Among these, synthetic resin can be used because the thickness of the cylindrical tube can be uniformly and accurately formed. A spiral die as shown in FIG. 3 is often used for extrusion molding of a cylindrical tube (for example, Patent Document 1).

In the spiral die, a cylindrical resin flow path 13 is secured by the inner mold 11 and the outer mold 12, and the resin flow path 13 is configured by a spiral groove 14 a formed on the outer peripheral surface 11 a of the inner mold 11. The most upstream spiral region 14, the most downstream parallel region 16 parallel to the central axis 18 of the inner mold 11, and the communication region 15 that connects the spiral region 14 and the parallel region 16. ing. The molten resin is supplied from the extruder (not shown) to the uppermost stream portion of the resin flow path 13 at a predetermined extrusion amount, and sequentially passes through the spiral area 14, the communication area 15, and the parallel area 16 of the resin flow path 13. The cylindrical tube is continuously formed by being pushed out from.
JP-A-10-29237

  By the way, since the molten resin is supplied to the spiral die while being pressurized from the extruder, the synthetic resin in the mold is in a state where pressure is applied. Friction was generated between the mold outer peripheral surface 11a and the outer mold inner peripheral surface 12a and the molten resin. At this time, if the shear rate of the molten resin on the inner mold outer peripheral surface 11a and the outer mold inner peripheral surface 12a of the parallel region 16 is high, the molten resin rubs against the inner mold outer peripheral surface 11a and the outer mold inner peripheral surface 12a, thereby causing residue. This debris is pushed out from the discharge port 17 at the same time as the cylindrical tube. The debris adheres to the discharge port 17 and accumulates, and the accumulated debris may detach from the mold and adhere to the extruded cylindrical tube. When such debris adheres, the cylindrical tube is cooled in a state where the debris is adhered and hardens while the debris is adhered, resulting in poor appearance or poor thickness. It was discarded as a defective product.

  Further, if extrusion molding is continued with the residue attached to the discharge port 17, there is a risk that the residue will scratch the cylindrical tube being pushed out. It was discarded as a good product.

  Further, the molten resin supplied from the extruder passes through the plurality of spiral grooves 14 a and joins at the base end portion of the communication region 15 to form a cylindrical shape. At that time, if the back pressure at the boundary between the spiral region 14 and the communication region 15 is small, the molten resin that has been divided into a plurality of pieces by the spiral groove 14a has insufficient force to press each other and merges sufficiently. In other words, streaks occur at the boundaries between the molten resins. When the cylindrical tube in which streaks are generated in this way is connected to a pipe joint, a gap is formed between the two at the streaks of the cylindrical tube, which causes a fluid leak. Accordingly, the cylindrical tube in which streaks are generated has been discarded as a defective product due to an appearance defect or a wall thickness defect similarly to the cylindrical tube to which debris is attached.

  SUMMARY OF THE INVENTION The present invention has been made in view of the actual situation, and the object thereof is to join a molten resin at a base end portion of a communication region and a residue attached to a mold discharge port in extrusion molding of a synthetic resin cylindrical tube. Another object of the present invention is to provide an extrusion mold capable of smooth fusion and suppressing generation of streaks.

In order to solve the above problems, the extrusion molding die of the present invention has a cylindrical resin flow path secured by the inner mold and the outer mold, and the outermost portion of the inner mold is provided at the most upstream portion of the resin flow path. A spiral region constituted by spiral grooves carved on the surface is set, while a parallel region parallel to the central axis of the inner mold is set in the most downstream portion connected to the discharge port that is the end of the resin flow path. In addition, a communication region for communicating these two regions is set between the spiral region and the parallel region, and the uppermost stream of the resin flow path from the extruder connected to the proximal end side of the inner mold A molten resin is supplied to the part at a predetermined extrusion amount, and the molten resin is sequentially passed through the spiral region, the communication region, and the parallel region of the resin flow path, and is extruded from the discharge port to continuously form a cylindrical tube. In the extrusion mold configured as described above, outside the parallel region Shear rate gamma _w represented by the following formula of the molten resin in the inner circumferential surface and the inner mold the outer peripheral surface (1) is characterized in that it is a 300 s ^-1 or less.

このような本発明によると、平行領域の外型内周面および内型外周面における溶融樹脂の上記式（１）で表される剪断速度γ_wが３００ｓ^-1以下とされたものであるから、溶融樹脂が平行領域の外型内周面および内型外周面から受ける摩擦が小さくなり、吐出口でのカスの発生が抑制される。従って、カスが押し出された円筒管に付着することがなく、また、カスによって押し出されている円筒管を傷つけることがなくなるため、カスに起因する不良品の発生が減少する。

According to the present invention as described above, the shear rate γ _w represented by the above formula (1) of the molten resin on the outer peripheral surface of the outer mold and the outer peripheral surface of the inner mold in the parallel region is 300 s ⁻¹ or less. Further, the friction that the molten resin receives from the outer peripheral surface of the outer mold and the outer peripheral surface of the inner mold in the parallel region is reduced, and the generation of waste at the discharge port is suppressed. Therefore, the residue does not adhere to the extruded cylindrical tube, and the cylindrical tube extruded by the residue is not damaged, so that the occurrence of defective products due to the residue is reduced.

  In the extrusion mold of the present invention, a cylindrical resin flow path is secured by the inner mold and the outer mold, and the most upstream portion of the resin flow path is engraved on the outer peripheral surface of the inner mold. While a spiral region constituted by a spiral groove is set, a parallel region parallel to the central axis of the inner mold is set in the most downstream part connected to the discharge port that is the end of the resin flow path, and the spiral A communication region for communicating these two regions is set between the region and the parallel region, and a predetermined amount of extrusion from the extruder connected to the proximal end side of the inner mold to the most upstream portion of the resin flow path. The cylindrical resin is continuously formed by supplying the molten resin with the above, and sequentially passing the molten resin through the spiral region, the communication region, and the parallel region of the resin flow path and extruding from the discharge port. In an extrusion mold, the boundary between the spiral region and the communication region Back pressure P represented by the following formula (2) and (3) of the definitive molten resin is characterized in that it is a more 15 MPa.

このような本発明によると、螺旋領域と連通領域との境界における溶融樹脂の上記式（２）および（３）で表される背圧Ｐが１５ＭＰａ以上とされたものであるから、螺旋溝によって複数本に分割されていた溶融樹脂が連通領域の基端部で合流する際に、互いに十分な圧力で押しつけ合って良好に融合される。従って、押し出された円筒管におけるスジの発生がないため、スジに起因する不良品の発生が減少する。

According to the present invention, the back pressure P expressed by the above formulas (2) and (3) of the molten resin at the boundary between the spiral region and the communication region is set to 15 MPa or more. When the molten resin that has been divided into a plurality of pieces merges at the base end portion of the communication region, the molten resins are pressed against each other with sufficient pressure and are fused well. Therefore, since no streak is generated in the extruded cylindrical tube, the generation of defective products due to the streak is reduced.

  Furthermore, the extrusion mold according to the present invention may satisfy both of the above two conditions.

That is, a cylindrical resin flow path is secured by the inner mold and the outer mold, and a spiral region constituted by a spiral groove carved on the outer peripheral surface of the inner mold is set in the uppermost stream portion of the resin flow path. On the other hand, a parallel region parallel to the central axis of the inner mold is set in the most downstream portion connected to the discharge port that is the end of the resin flow path, and between the spiral region and the parallel region. A communication region is set to connect these two regions, and the molten resin is supplied to the most upstream portion of the resin flow path from the extruder connected to the proximal end side of the inner mold at a predetermined extrusion amount. In an extrusion mold configured to continuously form a cylindrical tube by sequentially passing resin through a spiral region, a communication region, and a parallel region of the resin flow path and extruding the resin from the discharge port, Molten resin on outer peripheral surface of outer mold and outer peripheral surface of inner mold With the shear rate gamma _w represented by the above formula (1) is a 300 s ^-1 or less, represented by the above formula of the molten resin at the boundary between the helical region and the communicating area (2) and (3) The back pressure P is set to 15 MPa or more.

According to the present invention as described above, the shear rate γ _w represented by the above formula (1) of the molten resin on the outer peripheral surface of the outer mold and the outer peripheral surface of the inner mold in the parallel region is 300 s ⁻¹ or less. Further, the friction that the molten resin receives from the outer peripheral surface of the outer mold and the outer peripheral surface of the inner mold in the parallel region is reduced, and the generation of waste at the discharge port is suppressed. Therefore, since the residue does not adhere to the extruded cylindrical tube and the cylindrical tube from which the residue is extruded is not damaged, the occurrence of defective products due to the residue is reduced.

  At the same time, the back pressure P expressed by the above equations (2) and (3) of the molten resin at the boundary between the spiral region and the communication region is set to 15 MPa or more. When the divided molten resin joins at the base end portion of the communication region, they are pressed against each other with sufficient pressure and are fused well. Accordingly, no streaks are formed in the extruded cylindrical tube, and the occurrence of defective products due to the streaks is reduced.

  In the extrusion molding die of the present invention, in the extrusion molding of a synthetic resin cylindrical tube, no debris adheres to the mold discharge port, and the molten resin joins and fuses at the base end of the communication region. Since the process is carried out smoothly, it is possible to suppress the generation of defective products due to scum and streaks. As a result, the amount of discarded cylindrical tubes due to defective molding can be significantly reduced as compared with the conventional case.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a partial cross-sectional view showing an extrusion mold 1A according to the present embodiment.

  In the extrusion mold 1A of the present embodiment, a cylindrical resin flow path 13 is secured by the inner mold 11 and the outer mold 12, and the resin flow path 13 is formed in the spiral region 14 in the most upstream area, It is composed of a parallel region 16 at the most downstream portion and a communication region 15 that allows the spiral region 14 and the parallel region 16 to communicate with each other.

  The spiral region 14 is a region for uniformly spreading the molten resin supplied from an unillustrated extruder on the circumference of the communication region 15 described later. Further, the spiral region 14 is a region corresponding to the most upstream portion of the resin flow path 13 and is configured by a plurality of spiral grooves 14a carved on the inner peripheral surface 11a.

  The spiral groove 14a is formed so as to gradually become shallower from the proximal end side connected to the extruder toward the distal end side (downstream side of the resin flow path 13), and at the proximal end of the spiral groove 14a, A pressurized molten resin is supplied from an extruder not shown.

  The parallel region 16 is a region for adjusting the molten resin merged and fused in the communication region 15 to a predetermined inner diameter and outer diameter and extruding the molten resin out of the extrusion mold 1A. The parallel region 16 is located in the most downstream part connected to the discharge port 17 that is the end of the resin flow path 13, and is formed in parallel with the central axis of the inner mold 11. The parallel region 16 has a predetermined length in order to stabilize the shape of the molded product.

  The communication region 15 is smoothly fused by the back pressure applied at the boundary between the spiral region 14 and the communication region 15 while the molten resin extruded from the plurality of spiral grooves 14a in the spiral region 14 merges. It is an area formed in a uniform cylindrical shape.

In the extrusion mold 1A of the present embodiment, the shear rate γ _w represented by the following equation (1) of the molten resin on the outer mold inner peripheral surface 12a and the inner mold outer peripheral surface 11a of the parallel region 16 is 300 s ^−1. In addition to the following, a mold design is performed in which the back pressure P expressed by the following equations (2) and (3) of the molten resin at the boundary between the spiral region 14 and the communication region 15 is 15 MPa or more. .

＜実施例と比較例＞
上記の本実施の形態１の押出成形用金型１Ａを用いてポリエチレン樹脂を押出成形した際の実施例および従来の押出成形用金型１Ｃを用いた比較例について表１を用いて説明する。

<Examples and comparative examples>
An example when a polyethylene resin is extruded using the above-described extrusion mold 1A according to the first embodiment and a comparative example using a conventional extrusion mold 1C will be described with reference to Table 1.

（実施例１〜３）
実施例１、２および３における押出成形用金型１Ａの連通領域１５は、図１に示すように、内型１１の中心軸１８と平行とされた第１区間１５ａと、内型１１の中心軸１８と平行とされるとともに内型１１の外径が第１区間１５ａよりも大きくされた第２区間１５ｂと、第２区間１５ｂからテーパ状に縮径された第３区間１５ｃの３つの区間で構成した。各区間における外型１２の内径、内型１１の外径および軸方向の長さを表１に記載の通りとした。また、平行領域１６を第４区間とし、この平行領域（第４区間）１６における外型１２の内径、内型１１の外径および軸方向の長さを表１に記載の通りとした。

(Examples 1-3)
As shown in FIG. 1, the communication region 15 of the extrusion mold 1 </ b> A in Examples 1, 2, and 3 includes a first section 15 a parallel to the central axis 18 of the inner mold 11, and the center of the inner mold 11. Three sections, a second section 15b that is parallel to the shaft 18 and whose outer diameter of the inner mold 11 is larger than the first section 15a, and a third section 15c that is tapered from the second section 15b in a tapered shape. Consists of. Table 1 shows the inner diameter of the outer mold 12, the outer diameter of the inner mold 11, and the axial length in each section. The parallel region 16 is defined as a fourth section, and the inner diameter of the outer mold 12, the outer diameter of the inner mold 11, and the length in the axial direction in the parallel region (fourth section) 16 are set as shown in Table 1.

(Comparative Examples 1-3)
As shown in FIG. 3, the communication region 15 of the extrusion mold 1 </ b> C in Comparative Examples 1, 2, and 3 has a configuration in which a section corresponding to the second section 15 b of Examples 1 to 3 is omitted. That is, the first section 15a is made parallel to the central axis 18 of the inner mold 11, and the third section 15c is reduced in diameter from the first section 15a in a tapered shape.

  In these comparative examples 1 to 3, the second section does not exist as described above, and the axial length of the third section 15c is short as compared with the first to third embodiments. In the section) 16, the inner diameter of the outer mold 12 and the outer diameter of the inner mold 11 are set small and the axial length is set short.

  In addition, since the same polyethylene resin is used in all Examples and Comparative Examples, the viscosity coefficients η all have the same value. Further, Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 are set so that the extrusion amount Q and the dimension of the cylindrical tube after molding are the same. Yes. Here, the dimension of the cylindrical tube after molding is not the dimension immediately after being extruded from the discharge port 17 of the extrusion molding die 1A, but is the dimension when the final shape is obtained while being taken out by a take-off device (not shown). is there.

As shown in Table 1, in all the examples, by increasing the inner diameter of the outer mold 12 and the outer diameter of the inner mold 11 in the parallel region (fourth section) 16 than the respective comparative examples, The shear rate represented by the formula (1) of the molten resin on the outer peripheral surface 12a and the outer peripheral surface 11a of the inner mold was 300 s ⁻¹ or less, and as a result, the generation of debris at the discharge port 17 was suppressed.

  Further, in the embodiment, in contrast to the comparative example, the second section 15b having a narrow flow path is provided, the length of the third section 15c and the parallel region (fourth section) 16 in the axial direction is increased, and the outer mold 12 is provided. By increasing the inner diameter of the inner mold 11 and the outer diameter of the inner mold 11, the back pressure expressed by the equations (2) and (3) of the molten resin at the boundary between the spiral region 14 and the communication region 15 becomes 15 MPa or more, As a result, it was possible to suppress the generation of streaks in the formed cylindrical tube.

[Embodiment 2]
FIG. 2 is a partial cross-sectional view showing an extrusion mold 1B according to the present embodiment.

  In the extrusion molding die 1B of the present embodiment, a cylindrical resin flow path 13 is secured by the inner mold 11 and the outer mold 12, and the resin flow path 13 is formed in the spiral region 14 in the most upstream area, It is composed of a parallel region 16 at the most downstream portion and a communication region 15 that allows the spiral region 14 and the parallel region 16 to communicate with each other.

  The extrusion mold 1B according to the present embodiment has basically the same configuration as the extrusion mold 1A according to the first embodiment, and therefore, the same members are denoted by the same reference numerals and the description thereof is omitted. Will be omitted and only the differences will be described.

In the extrusion mold 1B of the present embodiment, the shear rate γ _w represented by the following equation (1) of the molten resin on the outer mold inner peripheral surface 12a and the inner mold outer peripheral surface 11a of the parallel region 16 is 300 s ^−1. The following mold design is performed.

＜実施例と比較例＞
上記の本実施の形態２の押出成形用金型１Ｂを用いてポリエチレン樹脂を押出成形した際の実施例および従来の押出成形用金型１Ｃを用いた比較例について表２を用いて説明する。

<Examples and comparative examples>
An example when a polyethylene resin is extruded using the above-described extrusion mold 1B of the second embodiment and a comparative example using the conventional extrusion mold 1C will be described with reference to Table 2.

（実施例４〜６）
実施例４、５および６における押出成形用金型１Ｂは、図２に示すように、平行領域１６における外型１２の内径および内型１１の外径を表２に記載の通りとした。

(Examples 4 to 6)
As shown in FIG. 2, the extrusion mold 1B in Examples 4, 5 and 6 had the inner diameter of the outer mold 12 and the outer diameter of the inner mold 11 in the parallel region 16 as shown in Table 2.

(Comparative Examples 4-6)
In these comparative examples 4-6, compared with Examples 4-6, the internal diameter of the outer mold | type 12 in the parallel area | region 16 and the outer diameter of the inner mold | type 11 are small, and these space | intervals are set narrowly.

  In addition, since the same polyethylene resin is used in all Examples and Comparative Examples, the viscosity coefficients η all have the same value. Further, Example 4 and Comparative Example 4, Example 5 and Comparative Example 5, and Example 6 and Comparative Example 6 are set such that the extrusion amount Q and the dimension of the formed cylindrical tube are the same. Yes. Here, the dimension of the cylindrical tube after molding is not a dimension immediately after being extruded from the discharge port 17 of the extrusion molding die 1B, but is a dimension when the final shape is obtained while being taken out by a take-off device (not shown). is there.

As shown in Table 2, in all of the examples, the parallel region 16 has an inner diameter of the outer mold 12 and an outer diameter of the inner mold 11 that are larger than those of the comparative examples and wider than each other. The shear rate represented by the above formula (1) of the molten resin on the outer peripheral surface 12a and the outer peripheral surface 11a of the inner mold was 300 s ⁻¹ or less, and as a result, generation of debris at the discharge port 17 was suppressed. .

[Embodiment 3]
FIG. 1 is a partial cross-sectional view showing an extrusion mold 1A according to the present embodiment.

  In the extrusion mold 1A of the present embodiment, a cylindrical resin flow path 13 is secured by the inner mold 11 and the outer mold 12, and the resin flow path 13 is formed in the spiral region 14 in the most upstream area, It is composed of a parallel region 16 at the most downstream portion and a communication region 15 that allows the spiral region 14 and the parallel region 16 to communicate with each other.

  The extrusion mold 1A of the present embodiment has basically the same configuration as that of the above-described first embodiment. Therefore, the same members are denoted by the same reference numerals, and the description thereof is omitted. Only the point will be described.

  The extrusion mold 1A of the present embodiment is a mold in which the back pressure P expressed by the following equations (2) and (3) of the molten resin at the boundary between the spiral region 14 and the communication region 15 is 15 MPa or more. Mold design is in progress.

＜実施例と比較例＞
上記の本実施の形態３の押出成形用金型１Ａを用いてポリエチレン樹脂を押出成形した際の実施例および従来の押出成形用金型１Ｃを用いた比較例について表３を用いて説明する。

<Examples and comparative examples>
An example when the polyethylene resin is extruded using the extrusion mold 1A of the third embodiment and a comparative example using the conventional extrusion mold 1C will be described with reference to Table 3.

（実施例７〜９）
実施例７、８および９における押出成形用金型１Ａの連通領域１５は、図１に示すように、内型１１の中心軸１８と平行とされた第１区間１５ａと、内型１１の中心軸１８と平行とされるとともに内型１１の外径が第１区間１５ａよりも大きくされた第２区間１５ｂと、第２区間１５ｂからテーパ状に縮径された第３区間１５ｃの３つの区間で構成した。各区間における外型１２の内径、内型１１の外径および軸方向の長さを表３に記載の通りとした。また、平行領域１６を第４区間とし、この平行領域（第４区間）１６における外型１２の内径、内型１１の外径および軸方向の長さを表３に記載の通りとした。

(Examples 7 to 9)
As shown in FIG. 1, the communication region 15 of the extrusion mold 1 </ b> A in Examples 7, 8 and 9 includes a first section 15 a parallel to the central axis 18 of the inner mold 11, and the center of the inner mold 11. Three sections, a second section 15b that is parallel to the shaft 18 and whose outer diameter of the inner mold 11 is larger than the first section 15a, and a third section 15c that is tapered from the second section 15b in a tapered shape. Consists of. Table 3 shows the inner diameter of the outer mold 12, the outer diameter of the inner mold 11, and the axial length in each section. Further, the parallel region 16 is defined as a fourth section, and the inner diameter of the outer mold 12, the outer diameter of the inner mold 11 and the length in the axial direction in the parallel region (fourth section) 16 are as shown in Table 3.

(Comparative Examples 7-9)
As shown in FIG. 3, the communication region 15 of the extrusion molding die 1 </ b> C in Comparative Examples 7, 8 and 9 has a configuration in which a section corresponding to the second section 15 b of Examples 7 to 9 is omitted. That is, the first section 15a is made parallel to the central axis 18 of the inner mold 11, and the third section 15c is reduced in diameter from the first section 15a in a tapered shape.

  In these comparative examples 7 to 9, as compared with the examples 7 to 9, the second section does not exist as described above, and the axial length of the third section 15c and the parallel region (fourth section) 16 is longer. The length is set short.

  In addition, since the same polyethylene resin is used in all Examples and Comparative Examples, the viscosity coefficients η all have the same value. Further, Example 7 and Comparative Example 7, Example 8 and Comparative Example 8, and Example 9 and Comparative Example 9 are set such that the extrusion amount Q and the dimension of the cylindrical tube after molding are the same. Yes. Here, the dimension of the cylindrical tube after molding is not the dimension immediately after being extruded from the discharge port 17 of the extrusion molding die 1A, but is the dimension when the final shape is obtained while being taken out by a take-off device (not shown). is there.

  As shown in Table 3, with respect to the comparative example, in the embodiment, the second section 15b having a narrow flow path is provided, and the axial length of the third section 15c and the parallel region (fourth section) 16 is set. By increasing the length, the back pressure expressed by the equations (2) and (3) of the molten resin at the boundary between the spiral region 14 and the communication region 15 becomes 15 MPa or more. As a result, streaks are formed in the cylindrical tube after molding. It was possible to suppress the occurrence.

It is a fragmentary sectional view which shows the metal mold | die for extrusion molding of Embodiment 1 and 3 of this invention. It is a fragmentary sectional view which shows the metal mold | die for extrusion molding of Embodiment 2 of this invention. It is a fragmentary sectional view which shows the conventional metal mold | die for extrusion molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold for extrusion 11 Inner mold 11a Inner outer peripheral surface 12 Outer mold 12a Outer inner peripheral surface 13 Resin flow path 14 Spiral area 14a Spiral groove 15 Communication area 15a First section 15b Second section 15c Third section 16 Parallel Area (4th section)
17 Discharge port 18 Central axis of inner mold

Claims (3)

A cylindrical resin flow path is secured by the inner mold and the outer mold, and a spiral region constituted by a spiral groove carved on the outer peripheral surface of the inner mold is set in the uppermost stream portion of the resin flow path. On the other hand, a parallel region parallel to the central axis of the inner mold is set in the most downstream part connected to the discharge port that is the end of the resin flow path, and between these two regions between the spiral region and the parallel region. A communication region that connects the two regions is set, and a molten resin is supplied to the uppermost stream portion of the resin flow path from the extruder connected to the proximal end side of the inner mold with a predetermined extrusion amount. In an extrusion mold configured so that a cylindrical tube is continuously formed by sequentially passing through a spiral region, a communication region and a parallel region of the resin flow path and extruding from the discharge port,
An extrusion mold, wherein the shear rate γ _w represented by the following formula (1) of the molten resin on the inner peripheral surface and the outer peripheral surface of the inner mold in the parallel region is 300 s ⁻¹ or less.

A cylindrical resin flow path is secured by the inner mold and the outer mold, and a spiral region constituted by a spiral groove carved on the outer peripheral surface of the inner mold is set in the uppermost stream portion of the resin flow path. On the other hand, a parallel region parallel to the central axis of the inner mold is set in the most downstream part connected to the discharge port that is the end of the resin flow path, and between these two regions between the spiral region and the parallel region. A communication region that connects the two regions is set, and a molten resin is supplied to the uppermost stream portion of the resin flow path from the extruder connected to the proximal end side of the inner mold with a predetermined extrusion amount. In an extrusion mold configured so that a cylindrical tube is continuously formed by sequentially passing through a spiral region, a communication region and a parallel region of the resin flow path and extruding from the discharge port,
An extrusion mold, wherein a back pressure P expressed by the following equations (2) and (3) of the molten resin at a boundary between the spiral region and the communication region is 15 MPa or more.

A cylindrical resin flow path is secured by the inner mold and the outer mold, and a spiral region constituted by a spiral groove carved on the outer peripheral surface of the inner mold is set in the uppermost stream portion of the resin flow path. On the other hand, a parallel region parallel to the central axis of the inner mold is set in the most downstream part connected to the discharge port that is the end of the resin flow path, and between these two regions between the spiral region and the parallel region. A communication region that connects the two regions is set, and a molten resin is supplied to the uppermost stream portion of the resin flow path from the extruder connected to the proximal end side of the inner mold with a predetermined extrusion amount. In an extrusion mold configured so that a cylindrical tube is continuously formed by sequentially passing through a spiral region, a communication region and a parallel region of the resin flow path and extruding from the discharge port,
The shear rate γ _w represented by the following formula (1) of the molten resin on the outer peripheral surface of the outer mold and the outer peripheral surface of the inner mold in the parallel region is set to 300 s ⁻¹ or less,
An extrusion mold, wherein a back pressure P expressed by the following equations (2) and (3) of the molten resin at a boundary between the spiral region and the communication region is 15 MPa or more.

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