JP4955612B2 - Kneading screw - Google Patents

Description

  The present invention relates to a kneading screw that mainly kneads a resin material in an extruder.

  Generally, a synthetic resin raw material is made of a screw-type biaxial shaft as shown in FIG. 4 in order to homogenize and modify physical properties or characteristics as a synthetic resin, or to add new functional characteristics by adding an additive material or the like. Processing by a kneading extruder is performed.

  A screw-type kneading extruder 100 includes a long cylindrical cylinder 101, one or two screws 102 inserted into an inner hole of the cylinder 101 so as to be rotationally driven, and a kneading unit 103 for melting and kneading a resin raw material. The material supply port 104 through which the raw material is supplied into the cylinder 101 and the vent 105 for removing unnecessary volatile components generated from the raw material are provided.

  The two screws 102 and the kneading unit 103 are configured by combining screw pieces having shapes corresponding to the functions of the respective units. As a kneading screw piece constituting the kneading part 103 which is the main part, a screw piece constituted by KD (Kneading disc) having an excellent kneading function is incorporated as needed (for example, patent Reference 1).

  FIG. 5 shows a partially enlarged view of an example of a conventional kneading unit 103.

  The kneading part 103 is composed of three screw pieces 120a, 120b, 120c. The screw piece 120 a is disposed on the upstream side of the kneading unit 103 and is disposed adjacent to the screw 102. That is, the most upstream KD of the screw piece 120a is disposed adjacent to the most downstream end face of the screw 102, which is a full flight screw. The screw piece 120c is disposed on the downstream side of the kneading unit 103, and the screw piece 120b is disposed between the screw piece 120a and the screw piece 120c. Each of the screw pieces 120a, 120b, 120c is made of KD composed of five disks. The deviation angle between the disks around the axis of the screw 102 is 45 °.

  The most downstream KD of the screw piece 120a and the most upstream KD of the screw piece 120b, and the most downstream KD of the screw piece 120b and the most upstream KD of the screw piece 120c are combined at the end surfaces of the same phase.

  In the kneading unit 103, an example in which the screw piece is made of KD has been shown. However, there is a case in which the screw piece is made of TKD (twist kneading disc) (for example, Patent Documents 2 and 3). ).

A screw piece composed of KD has an ability to give a higher shearing force to the raw material than TKD. On the other hand, TKD has a characteristic that the feed ability of the raw material is higher than that of KD.
JP 2001-260208 A JP 2005-035212 A JP 2007-237679 A

  Although the screw piece comprised by the conventional KD has the capability to give sufficient shear with respect to a raw material, there existed a case where an internal pressure will become high locally depending on a raw material. When the internal pressure increases, there is a risk of adversely affecting product quality due to an increase in mechanical load, partial physical property change (deterioration) of the raw material resin, or aggregation of added substances.

  On the other hand, in the conventional screw piece constituted by TKD, although the internal pressure at the time of melting can be reduced, the degree of kneading is different from that of the conventional screw piece constituted by KD, and the necessary degree of kneading cannot be maintained and is sufficient. In some cases, the quality could not be obtained.

  Usually, the internal pressure is highest at the boundary between a transport screw such as a full flight screw and KD (position indicated by α in FIG. 5). This is because there is a difference between the screw arranged on the upstream side of KD and the feeding ability of KD. That is, the raw material that has been transported by the screw has its transporting ability rapidly reduced at the transition to the KD section on the downstream side, so that the internal pressure at that part increases.

  On the other hand, since the top of the TKD (tip portion) is twisted and each disk itself has a feeding ability, the feeding ability is higher than that of a normal KD, and the difference in feeding ability from the upstream screw is reduced. Therefore, it is easy to avoid a sudden increase in pressure. However, on the contrary, when the feeding ability is high, sufficient shearing is not given, which causes a reduction (change) in the degree of kneading.

  The higher the degree of kneading, the better the quality can not be said, but there are some raw materials that require a high degree of kneading. Conventionally, such a configuration has not been regarded as a problem, but in recent years, the raw material configuration has become complicated, and high quality requirements and high mechanical stability (reliability) due to high discharge force are required. .

  Therefore, in view of the above problems, the first object of the present invention is to provide a kneading screw capable of suppressing a local increase in internal pressure that occurs during plasticization of a resin. Furthermore, a second object of the present invention is to provide a kneading screw that does not reduce kneading characteristics.

In order to achieve the above object, the kneading screw of the present invention has a phase angle E, which is a deviation angle between the screw and the disc around the axis of the screw, arranged on the downstream side of the screw, when 0 ° <E <90 °. and a kneading section having a screw piece comprising a plurality of disks are arranged, a plurality in the kneading screw to plasticize by kneading the resin material, which constitutes the screw piece (20a) adjacent to the screw at the downstream end of the screw The disk (30a ₁ ) located on the uppermost stream side of the screw piece (20a) is between the top on the front side of the disk and the top on the rear side of the disk at the tip part which is the tip of the disk. Is a range of 0 ° <θ <90 ° in the counter-rotating direction of the screw when the cross section of the disc with the axis of the screw as a normal is viewed in the direction of the shaft tip. Twist kneading disks der in is, the disk (30a ₅₎ located on the most downstream side among a plurality of disks constituting a screw piece (20a), and the screw piece (20a in the downstream side of the screw piece (20a) The disk (30b ₁ ) located on the most upstream side among the plurality of disks constituting the screw piece (20b) adjacent to the screw piece (20b) is a twist kneading disk, and among the plurality of disks constituting the screw piece (20a) The disc sandwiched between the disc (30a ₁ ) and the disc (30a ₅ ) is a kneading disc having a spiral angle θ of 0 °.

  The internal pressure is usually the highest at the boundary between the screw and the kneading disk disposed downstream thereof, but as described above, the kneading screw of the present invention is fed more than the kneading disk at this boundary. High-performance twist kneading is placed. For this reason, according to this invention, it becomes possible to suppress the local internal pressure raise which generate | occur | produces at the time of the plasticization of the resin in the said boundary part.

Further, the kneading screw of the present invention may be a kneading disc whose helical angle θ is 0 ° when the disc disposed downstream of the disc (30b ₁ ) located on the most upstream side of the screw piece (20b). Good.

  As described above, according to the present invention, it is possible to provide a kneading screw capable of suppressing a local internal pressure increase that occurs during plasticization of a resin. In addition, the present invention can provide a kneading screw that does not reduce kneading characteristics.

  FIG. 1 shows an example of a plastic plasticizing kneading extruder according to this embodiment.

  Two screws 2 are provided in a heat-coolable cylinder 1. The screw 2 is connected to the speed reducer 4 and is driven to rotate in the same direction by a motor 3 connected to the speed reducer 4. The two screws 2 are engaged with each other. The cylinder 1 is provided with a supply port 5, a vent 6a, and a discharge port 7 from upstream. The screw 2 includes a solid transport unit 8, a kneading unit 9, and a melt transport unit 10 from upstream.

  The solid plastic raw material supplied from the supply port 5 is transported to the kneading unit 9 by the screw 2. The kneading unit 9 is composed of the screw piece shown in FIG. 2, and melts and kneads the solid plastic raw material in a short time. The plastic raw material melted in the kneading section 9 is transported to the discharge port 7 while removing unnecessary volatile components contained in the plastic raw material at the vent 6a of the melt transporting section 10, and is formed in a strand shape outside the cylinder 1 through the discharge port 7. It is discharged at. The molten plastic raw material discharged in a strand form is formed into a pellet shape by a cutter (not shown). The cutter is installed directly or at an interval at the outlet of the discharge port 7. The melted plastic raw material may be filtered for unnecessary solid impurities contained in the plastic raw material by the screen 19 provided in front of the discharge port 7.

  The screw piece which comprises the kneading part of this embodiment in FIG. 2 is shown. FIG. 3A is a side view of the screw piece, and FIG. 3B is a view of a cross section of the disk with the axis of the screw 2 as a normal line when viewed in the axial tip direction. In addition, the screw piece shown in FIG. 3 is the screw piece 20a in FIG.

  The kneading part 9 is composed of three screw pieces 20a, 20b, 20c. The screw piece 20 a is arranged on the most upstream side of these screw pieces 20 a, 20 b, and 20 c, and is arranged after the screw 2. The screw piece 20c is disposed on the most downstream side, and the screw piece 20b is disposed between the screw piece 20a and the screw piece 20c.

  First, the structure of each screw piece 20a, 20b, 20c is demonstrated. Each of the screw pieces 20a, 20b, and 20c is the same in that each of the screw pieces 20a, 20b, and 20c is composed of five disks, but the disks used and the arrangement thereof are different. In the following description, the suffixes of the disk 30 indicate that “a”, “b”, and “c” are the disks of the screw pieces 20a, 20b, and 20c, respectively. In addition, the subscripts “1” to “5” mean that “1” is the most upstream side and “5” is the most downstream side.

The screw piece 20a is a screw piece adjacent to the screw 2 at the downstream end of the screw 2, and has TKD and KD. Screw piece 20a is a disk 30a ₅ of the disc 30a ₁ and the most downstream side of the most upstream side TKD, these disks 30a _1, 3 discs 30a ₂ ~30a ₄ sandwiched between the discs 30a ₅ is KD It is.

  Here, the configuration of the TKD will be described with reference to FIG. In the TKD, the tip 32 of the disk 30 has a spiral angle θ, which is an angle between the top part a on the front surface side and the top part b on the rear surface side, and the axis of the screw 2 is normal. The section AA is inclined at about 11 ° in the counter-rotating direction of the screw 2 when viewed in the axial tip direction. The spiral angle θ can be appropriately selected within a range of 0 ° <θ <90 ° in the counter-rotating direction of the screw 2 when the section of the disk 30 having the axis of the screw 2 as a normal is viewed in the axial tip direction. . On the other hand, KD has a spiral angle θ of 0 °.

  Further, the phase angle E, which is a deviation angle between the disks 30 around the axis of the screw 2, is 45 °. The phase angle E can also be selected as appropriate within the range of 0 ° <E <90 °, and the number of disks 30 may be, for example, 6 or more and 15 or less. The number of disks 30 is not limited to these. Moreover, although the example which the kneading part 9 consists of three screw pieces was shown here, you may consist of four or more screw pieces.

The screw piece 20b is a screw piece adjacent to the screw piece 20a on the downstream side of the screw piece 20a. The screw piece 20b, only the disk 30b ₁ on the most upstream side is TKD, disc 30b ₂ ~ disk 30b ₅ of this downstream side are all KD.

In the screw piece 20c, all of the disks 30c ₁ to 30c ₅ are KD.

  Next, the arrangement and operation of the screw 2 and the three screw pieces 20a, 20b, 20c will be described.

As shown in FIG. 2, the screw 2 and the screw piece 20a are disposed adjacent to each other. In the case of the prior art in which the KD is arranged adjacent to the full flight screw, the boundary α is a portion where a large difference occurs in the feeding capacity and the internal pressure is usually the largest. However, in the case of the present embodiment, at the boundary α, the full flight screw having a high material transport capability is connected to a TKD having a transport capability higher than that of KD. For this reason, the increase in the internal pressure at the boundary α can be reduced as compared with the conventional configuration. Then, the screw piece 20a is a three discs 30a ₂ ~30a ₄ high kneading capacity than TKD followed disk 30a ₁ is disposed is TKD. That is, the screw piece 20a can knead the raw material without increasing the local internal pressure at the boundary α.

Between the screw piece 20a and the screw piece 20b, the disk 30a ₅ and the disk 30b ₁ which are TKD are continuously arranged (before and after the boundary β in FIG. 2). Further, the disk 30a ₅ and the disk 30b ₁ are combined at the end faces of the same phase as shown in FIG.

Usually, the mating surfaces of the screw pieces are combined on the same phase plane. The same phase planes are combined with each other even in a screw piece composed of ordinary KD (see, for example, FIG. 5). This is because if the screw pieces are not matched with each other on the same phase plane, there is a possibility that a screw piece assembly error occurs. For this reason, in order to facilitate the work at the time of assembly and to avoid mistakes, the mating surfaces of the screw pieces are usually combined with the same phase surface. However, as can be seen from FIG. 5 , disks having the same phase overlap before and after the boundary β, and disks having an apparent thickness of two sheets are arranged. That is, the part with weak feeding ability exists twice as much as the usual distance, and it has become a part where a large internal pressure is generated locally.

In contrast, in the present embodiment, the disk 30a ₅ located downstream of the screw piece 20a as described above and TKD, and further the disk disk 30b ₁ of the most upstream side of the screw piece 20b and TKD. As a result, even if the disks are combined with the same phase plane and apparently have a thickness of two sheets, it has a feeding ability, so the local internal pressure rises at the boundary β. Can be suppressed.

Screw piece 20b are all KD disk 30b ₂ ~30b _5, are all KD disk 30c ₁ ~30c ₅ of the screw piece 20c. That is, the disk 30b ₂ can give a sufficient shearing force to the raw material.

  As described above, according to the present invention, the TKD is disposed in a portion of the screw piece where the internal pressure is increased, and the conventional KD is disposed in the other portion.

  TKD acts to lower the internal pressure, and KD maintains the conventional degree of kneading. That is, since the disk itself has a feeding capability, the TKD has a feeding capability higher than that of a normal KD, and the feeding capability difference is reduced, so that a rapid increase in internal pressure can be suppressed. At the same time, KD increases the residence time of the raw material by the low feeding capacity, increases the number of times of shearing with the screw tip, and increases the degree of kneading, so that the degree of kneading can be maintained.

  As mentioned above, according to the extruder of this embodiment, it becomes possible to suppress the local internal pressure raise which generate | occur | produces at the time of plasticization of resin, without reducing a kneading | mixing characteristic.

  Table 1 shows the results of measuring the pressure in the cylinder in the extruder of the present invention having the screw piece shown in FIG. 2 and the conventional extruder having the screw piece shown in FIG.

  Both the extruder of the present invention and the conventional extruder have a processing capacity of 700 kg / h. However, when the conventional screw piece was used, the internal pressure rose to 40 MPa, whereas when the screw piece of the present invention was used, it could be reduced to 32 MPa.

It is the schematic which shows the structure of the screw type twin-screw kneading extruder of this invention. It is a partially expanded view which shows the structure of the screw piece in the kneading part of this invention. It is the figure which looked at the cross section of the disk which made the normal line the screw shaft of the example of the screw piece of this invention, and the axis of the screw in the shaft tip direction. It is the schematic which shows the structure of the conventional screw type twin-screw kneading extruder. It is a partially expanded view which shows the structure of an example of the screw piece in the conventional kneading part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Screw 3 Motor 4 Reducer 5 Supply port 6a Vent 7 Discharge port 8 Solid transport part 9 Kneading part 10 Melt transport part 19 Screen 20a-20c Screw piece 30 Disc 32 Chip part a, b Top part E Phase angle α, β boundary θ helix angle

Claims (2)

Screw (2),
A plurality of disks (30) arranged at a downstream side of the screw (2) and having a phase angle E, which is a deviation angle between disks around the axis of the screw (2), 0 ° <E <90 ° In a kneading screw for plasticizing a resin raw material by kneading, a kneading part (9) provided with a screw piece (20) consisting of
Among the plurality of disks (30) constituting the screw piece (20a) adjacent to the screw (2) at the downstream end of the screw (2), the screw piece (20a) is positioned on the most upstream side. The disk (30a ₁ ) includes a top part (a) on the front surface side of the disk (30) and a top part (b) on the rear surface side of the disk (30) in the tip part (32) which is the tip part of the disk (30). Is 0 ° in the counter-rotating direction of the screw (2) when the section of the disk (30) with the axis of the screw (2) as a normal is viewed in the axial tip direction. <theta <Ri twist kneading disk der which is within the range of 90 °,
The disk (30a ₅ ) located on the most downstream side of the plurality of disks (30) constituting the screw piece (20a) adjacent to the screw (2) at the downstream end of the screw (2 ); and The disk (30b ₁ ) located on the most upstream side of the plurality of disks (30) constituting the screw piece (20b) adjacent to the screw piece (20a) on the downstream side of the screw piece (20a ) is: The twist kneading disc,
Of the plurality of disks (30) constituting the screw piece (20a) adjacent to the screw (2) at the downstream end of the screw (2), the disk (30a ₁ ) and the disk (30a ₅ ) disc sandwiched Doo _{(30a 2, 30a 3, 30a} 4) is characterized in that the helix angle θ is kneading disks of 0 °, the kneading screw. Wherein said disc located on the most upstream side of the screw piece (20b) (30b ₁₎ the disc (30) which is disposed downstream from, the helix angle θ is claim 1 which is kneading disks of 0 ° The kneading screw described in 1.

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