Screw, extruder and extrusion process

Abstract

A screw, extruder, and extrusion method are provided to improve the application range of elastomers that can balance quality and productivity. A screw (2) has helical blades (5) for extruding a highly silica-based, plastic elastomer (G) containing 100 phr or more of silica while mixing. It has a first region (6) disposed on the downstream side of the extrusion direction (A). In the first region (6), a barrier (9) extending obliquely relative to the screw axis is formed between adjacent helical blades (5) in the extrusion direction (A). The length (w) of the long side of the barrier (9) is 1.5 to 3.0 times the lead length (L1) of the helical blades (5) in the first region (6). The height (h) of the barrier (9) is less than the height (H) of the helical blades (5), and the difference (H-h) between the height (H) of the helical blades (5) and the height (h) of the barrier (9) is 2 to 10 mm. The thickness (t) of the barrier (9) is 0.9 to 3.0 times the difference (H-h) between the height (H) of the spiral blade 5 and the height (h) of the barrier 9.

Description

Technical Field

[0001] The present invention relates to a screw having helical blades for extruding a plastic elastomer while mixing, an extruder comprising the screw, and an extrusion method. Background Technology

[0002] Previously, various screws with helical blades for simultaneously mixing and extruding plastic elastomers were known. For example, Patent Document 1 below discloses a screw that, by providing a mixing-promoting zone, can maintain good quality of the plastic elastomer and improve its productivity.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-043043 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the screw of Patent Document 1, the barrier runs along the screw axis, and depending on the type of elastomer used in the compounding, such as the one containing silica, productivity sometimes decreases. Therefore, further improvements are desired in the screw of Patent Document 1 to balance quality and productivity.

[0008] The present invention was made in view of the above-mentioned actual situation, and its main objective is to provide a screw, extruder and extrusion method that can improve the application range of elastomers that can balance quality and productivity.

[0009] Methods for solving problems

[0010] This invention relates to a screw having helical blades for simultaneously mixing and extruding a highly silica-based, plastic elastomer containing more than 100 phr of silica. The screw is characterized by having a first region disposed on the downstream side in the extrusion direction. In this first region, a barrier extending obliquely relative to the screw axis is formed between adjacent helical blades in the extrusion direction. The length of the barrier in the long side direction is 1.5 to 3.0 times the lead length of the helical blades in the first region. The height of the barrier is less than the height of the helical blades, and the difference between the height of the helical blades and the height of the barrier is 2 to 10 mm. The thickness of the barrier is 0.9 to 3.0 times the difference between the height of the helical blades and the height of the barrier.

[0011] In the screw of the present invention, preferably, 1 to 4 of the barriers are formed in the first region.

[0012] In the screw of the present invention, it is preferable to have a second region disposed on the upstream side of the extrusion direction of the first region, wherein a notch for pin passage is formed on the helical blade in the second region.

[0013] In the screw of the present invention, it is preferable that a third region is continuously disposed on the upstream side of the extrusion direction of the second region, wherein at least a portion of the helical blades are formed by a single thread in the third region.

[0014] In the screw of the present invention, preferably, a portion of the upstream side of the third region in the extrusion direction is formed by multiple threads.

[0015] The present invention is an extruder comprising the above-described screw and a barrel in which the screw is disposed internally, characterized in that the barrel comprises a plurality of pins inserted into the notch formed by the helical blade in the second region.

[0016] The present invention is an extruder, characterized in that it includes the aforementioned screw and a barrel in which the screw is disposed internally.

[0017] The present invention is an extrusion method for extruding the elastomer using the above-described extruder, characterized in that it includes: an input step of inputting the elastomer into the interior of the barrel; and an extrusion step of extruding the elastomer while mixing it, the extrusion step including a deformation step of deforming the elastomer into a film shape through the barrier.

[0018] Invention Effects

[0019] In the screw of the present invention, in a first region, a barrier extending obliquely relative to the screw axis is formed between adjacent helical blades in the extrusion direction. The length of the barrier in the long side direction is 1.5 to 3.0 times the lead length of the helical blade in the first region. The height of the barrier is less than the height of the helical blade, and the difference between the height of the helical blade and the height of the barrier is 2 to 10 mm. The thickness of the barrier is 0.9 to 3.0 times the difference between the height of the helical blade and the height of the barrier.

[0020] Such a screw can sequentially deform the elastomer into a thin film shape through a barrier inclined at a specific length, while ensuring the amount of elastomer passing through. Therefore, the screw of the present invention can suppress excessive heating of the elastomer and ensure the amount of elastomer discharged.

[0021] Furthermore, this barrier enables efficient transport and deformation of even high-silica-blended elastomers without the formation of internal air bubbles, thus improving the surface condition of the elastomer. Therefore, the screw of this invention expands the application range of elastomers that balance quality and productivity. Attached Figure Description

[0022] Figure 1 This is a side view illustrating one embodiment of the extruder of the present invention.

[0023] Figure 2 This is a partial side view of the first region.

[0024] Figure 3 yes Figure 2 A partial sectional view of line A-A.

[0025] Figure 4 This is a flowchart of the extrusion method.

[0026] Figure 5 This is a flowchart of the extrusion process.

[0027] Figure 6 This is a side view of an extruder according to another embodiment. Detailed Implementation

[0028] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0029] Figure 1 This is a side view showing the extruder 1 of this embodiment. Figure 1 As shown, the extruder 1 of this embodiment includes: a screw 2 for extruding a plastic elastomer G in the extrusion direction A while mixing it; and a barrel 3, in which the screw 2 is disposed.

[0030] Examples of plastic elastomers G include uncured rubber and thermoplastic elastomers. While there are no particular limitations on elastomer G, for example, if it is rubber for tires, then in accordance with the recent demand for low fuel consumption, it is ideal to have a high silica blend, preferably with a silica content of 50 phr or more, and more preferably 100 phr or more.

[0031] The screw 2 of this embodiment includes: a screw shaft 4; and a helical blade 5, which protrudes radially outward from the screw shaft 4. The helical blade 5 of this embodiment is used to extrude a plastic elastomer G while it is being mixed.

[0032] The screw 2 of this embodiment has: a first region 6 disposed downstream of the extrusion direction A; a second region 7 disposed upstream of the first region 6 in the extrusion direction A; and a third region 8 disposed upstream of the second region 7 in the extrusion direction A. The first region 6, the second region 7, and the third region 8 are provided, for example, continuously in the extrusion direction A.

[0033] Figure 2 This is a partial side view of region 6 in the first area. (Example) Figure 1 as well as Figure 2 As shown, in the first region 6 of this embodiment, a barrier 9 extending obliquely relative to the screw axis is formed between adjacent spiral blades 5 in the extrusion direction A. The length w of the barrier 9 in the long side direction is preferably 1.5 to 3.0 times the lead length L1 of the spiral blades 5 in the first region 6. Here, "obliquely extending relative to the screw axis" means that the long side direction of the barrier 9 has an angle θ greater than 0° and less than 90° relative to the screw axis.

[0034] Such a barrier 9 is inclined at a specific length, thus enabling the elastomer G to be deformed sequentially into a thin film shape and ensuring the throughput of the elastomer G. Therefore, the screw 2 of this embodiment can suppress excessive heating of the elastomer G and ensure the discharge volume of the elastomer G. Furthermore, such a barrier 9 can efficiently transport and deform even elastomer G with a high silica blend without generating air bubbles inside, thus improving the surface condition of the elastomer G. Therefore, the screw 2 of this embodiment can expand the application range of elastomer G that balances quality and productivity.

[0035] The length w of the long side of the barrier 9 is more preferably at least 2.0 times the lead length L1 of the helical blade 5 in the first region 6. Furthermore, the length w of the long side of the barrier 9 is more preferably at least 2.5 times the lead length L1 of the helical blade 5 in the first region 6. Such a barrier 9 is suitable for the efficient transport and deformation of the high silica-blended elastomer G, helping to balance the quality and productivity of the elastomer G.

[0036] The angle θ of the barrier 9 relative to the screw axis is preferably 10° or more, more preferably 20° or more, and preferably 80° or less, more preferably 70° or less. Such a barrier 9 is suitable for the efficient delivery and deformation of the high silica-blended elastomer G, which helps to balance the quality and productivity of the elastomer G.

[0037] In this embodiment, the helical blade 5 in the first region 6 is formed by two threads. The helical blade 5 in the first region 6 is not limited to two threads; for example, it may have one thread, or even three or more threads. Furthermore, the first region 6 may, for example, be partially formed by different numbers of threads.

[0038] Here, "one thread" refers to a configuration where one helical blade 5 is present in the same axial portion of the screw shaft 4. Furthermore, "two threads" refers to a configuration where two helical blades 5 are present in the same axial portion of the screw shaft 4. Moreover, "multiple threads" refers to a configuration where two or more helical blades 5 are present in the same axial portion of the screw shaft 4. Two threads are a type of multiple threads.

[0039] In the first region 6, preferably one to four barriers 9 are formed. In this embodiment, an example is shown where one barrier 9 is formed in the first region 6. Such a first region 6 allows the elastomer G to deform into a thin film shape and flow downstream in the extrusion direction A through the barrier 9, thus enabling the molecules of the elastomer G to be uniformly and finely broken down. Therefore, the extruder 1 of this embodiment can reduce the expansion rate of the extruded elastomer G and improve the surface condition of the elastomer G. Therefore, the extruder 1 of this embodiment can stabilize the shape of the extruded elastomer G and improve the surface condition of the elastomer G, thus enabling the extrusion of high-quality elastomer G.

[0040] Figure 3 yes Figure 2 A partial sectional view of line AA. (e.g.) Figure 3 As shown, in this embodiment, the height h of the barrier 9 is less than the height H of the helical blade 5. The difference (H-h) between the height H of the helical blade 5 and the height h of the barrier 9 is preferably 2 to 10 mm. When the difference (H-h) is 2 mm or more, excessive heating of the elastomer G can be suppressed, and the discharge rate of the elastomer G can be ensured, thus balancing quality and productivity. When the difference (H-h) is 10 mm or less, deformation of the elastomer G can be promoted, and quality can be improved.

[0041] The thickness t of the barrier 9 is preferably 0.9 to 3.0 times the difference (H-h) between the height H of the helical blade 5 and the height h of the barrier 9. When the thickness t is 0.9 times or more of the difference (H-h), the deformation of the elastomer G can be promoted, and the quality can be improved. When the thickness t is less than 3.0 times the difference (H-h), excessive heating of the elastomer G can be suppressed, and the discharge rate of the elastomer G can be ensured, thus balancing quality and productivity.

[0042] like Figure 1 As shown, the helical blade 5 in the second region 7 of this embodiment is formed by two threads. The helical blade 5 in the second region 7 is not limited to two threads; for example, it may have one thread, or even three or more threads. Furthermore, the second region 7 may, for example, be partially formed by different numbers of threads.

[0043] In the second region 7 of this embodiment, a notch 10 for pin passage is formed in the helical blade 5. The barrel 3 preferably includes a plurality of pins 11 inserted into the notch 10 formed in the helical blade 5 in the second region 7. Such a second region 7 can improve the mixing and dispersion effect of the elastomer G by shearing the elastomer G mixed between the screw 2 and the barrel 3 through the pins 11, thereby improving the quality of the elastomer G.

[0044] Multiple rows of pins 11 are arranged in the axial direction of the screw shaft 4, for example, 2 to 5 rows. In this embodiment, an example is shown where 3 rows of pins 11 are arranged in the axial direction of the screw shaft 4. Multiple pins 11 are arranged in the same part relative to the axial direction of the screw shaft 4, for example, 4 to 8. Such pins 11 can improve the mixing and dispersion effect of the elastomer G, thereby helping to improve the quality of the elastomer G.

[0045] The multiple pins 11 are preferably configured to vary the amount of protrusion into the barrel 3. Such pins 11 can be individually adjusted in terms of the amount of protrusion according to the elastomer G being compounded.

[0046] In this embodiment, at least a portion of the helical blade 5 in the third region 8 is formed by a single thread. The elastomer G inserted into such a third region 8 exhibits excellent transportability, enabling efficient delivery of the elastomer G to the second region 7, thereby improving productivity.

[0047] The third region 8 is preferably in the range of 20% to 40% of the total thread length L0. When the third region 8 is more than 20% of the total thread length L0, the elastomer G can be transported efficiently, and productivity can be improved. When the third region 8 is less than 40% of the total thread length L0, the range of the first region 6 and the second region 7 can be relatively expanded, which helps to improve the quality of the elastomer G.

[0048] The barrel 3 of this embodiment includes: an inlet 12 for feeding elastomer G; and an outlet 13 for discharging the compounded elastomer G. The inlet 12 is preferably located in a portion corresponding to the third region 8 of the screw 2. The outlet 13 is preferably located downstream of the first region 6 of the screw 2 in the extrusion direction A. Such a barrel 3 increases the distance from the inlet 12 to the outlet 13, which helps to improve the quality of the elastomer G.

[0049] The screw 2 is preferably rotated in one direction via a drive unit 14 disposed upstream of the extrusion direction A of the barrel 3. The rotational speed of the screw 2 can be appropriately adjusted via the drive unit 14. Such a screw 2 can easily change its rotational speed according to the operating conditions of the extruder 1.

[0050] Next, refer to Figures 1 to 3 The extrusion method of this embodiment will be described.

[0051] Figure 4 This is a flowchart of the extrusion method according to this embodiment. Figure 4 As shown, the extrusion method of this embodiment is suitable for use with an extruder 1, and for extruding an elastomer G that is preferably a high silica blend with silica of 50 phr or more, more preferably 100 phr or more.

[0052] In the extrusion method of this embodiment, firstly, an input step S1 is performed to input elastomer G into the interior of the barrel 3. Input step S1 is, for example, a continuous input of elastomer G. The input speed of elastomer G is preferably adjustable according to the operating conditions of the extruder 1. This input step S1 ensures that even elastomer G with a high silica content can be input into the interior of the barrel 3 in an appropriate amount.

[0053] In this embodiment, after the input step S1, an extrusion step S2 is performed where the elastomer G is extruded while being mixed. The extrusion step S2 preferably involves rotating the screw 2 to sequentially extrude the elastomer G in the extrusion direction A. This extrusion step S2 allows for extrusion in a manner that balances the quality of the high-silica-blended elastomer G with productivity.

[0054] Figure 5 This is a flowchart of extrusion process S2. (Example) Figure 5 As shown, in the extrusion step S2 of this embodiment, a conveying step S21 is first performed to transport the input elastomer G downstream in the extrusion direction A. The conveying step S21 is preferably performed in the third region 8 of the screw 2. This conveying step S21 can efficiently transport the high silica-blended elastomer G and improve productivity.

[0055] In this embodiment, the extrusion step S2 follows the conveying step S21, and then undergoes a shearing step S22 in which the elastomer G, compounded between the screw 2 and the barrel 3, is sheared by the pin 11. The shearing step S22 is preferably performed in the second region 7 of the screw 2. This shearing step S22 improves the mixing and dispersion effect of the high-silica compounded elastomer G, thereby improving its quality.

[0056] In this embodiment, the extrusion step S2 follows the shearing step S22, and then undergoes a deformation step S23 in which the elastomer G is deformed into a thin film by passing through the barrier 9. The deformation step S23 is preferably performed in the first region 6 of the screw 2. This deformation step S23 can suppress excessive heating of the elastomer G, ensure the discharge volume of the elastomer G, and balance quality and productivity.

[0057] Figure 6 This is a side view of an extruder 20 according to another embodiment. Elements having the same function as in the above embodiment are labeled with the same symbols, and their descriptions are omitted. Figure 6 As shown, the extruder 20 of this embodiment includes: a screw 21 for extruding a plastic elastomer G in the extrusion direction A while mixing it; and a barrel 22 in which the screw 21 is disposed inside.

[0058] The screw 21 of this embodiment includes: a screw shaft 4; and a helical blade 23, which protrudes radially outward from the screw shaft 4. Preferably, the screw 21, like the screw 2 described above, includes: a first region 6 disposed downstream of the extrusion direction A; a second region 7 disposed upstream of the first region 6 in the extrusion direction A; and a third region 8 disposed upstream of the second region 7 in the extrusion direction A.

[0059] In this embodiment, an example is shown where three barriers 9 are formed in the first region 6. Such a first region 6 can break down the molecules of the elastomer G into finer fragments through the barriers 9, thereby further improving the quality of the elastomer G.

[0060] In this embodiment, an example is shown in which four rows of pins 11 are provided axially on the screw shaft 4 in the second region 7. Such pins 11 can further improve the mixing and dispersion effect of the elastomer G, thereby further improving the quality of the elastomer G.

[0061] In this embodiment, a portion of the upstream side of the third region 8 in the extrusion direction A is formed by multiple threads. Examples of this embodiment, where a portion of the upstream side of the third region 8 in the extrusion direction A is formed by 2 threads and 6 threads, are illustrated. Such a third region 8 promotes mixing and dispersion while maintaining the bite-in properties of the elastomer G fed from the inlet 12, thus helping to balance the quality and productivity of the elastomer G.

[0062] The above describes in detail the particularly preferred embodiments of the present invention, but the present invention is not limited to the above embodiments and can be implemented in various ways.

[0063] Example

[0064] Based on the specifications in Table 1 and Table 2, a trial production was carried out. Figures 1 to 3 as well as Figure 6 The screw of the embodiment shown. As comparative examples, a screw of Comparative Example 1, in which the third region is formed by two threads and no barrier is provided, and a screw of Comparative Example 2, in which the third region is formed by one thread and the barrier extends axially along the screw shaft, were prototyped. Using an extruder containing the prototype screws, utilization was carried out. Figure 4 as well as Figure 5 The extrusion method shown was used to extrude elastomers, and the quality and productivity of the extruded elastomers were evaluated. Common aspects of the test and the test methods are as follows.

[0065] <Common Matters>

[0066] Elastomer: Uncured rubber blended with 100 phr of silica

[0067] First zone: 2 threads

[0068] Second zone: 2 threads

[0069] <Quality Testing>

[0070] The surface condition of the extruded elastomer was measured as the surface roughness calculated using the arithmetic mean height. The results were expressed as the reciprocal of the surface roughness, with Comparative Example 1 as the exponent of 100. The larger the value, the better the surface condition and the superior quality.

[0071] <Productivity Trial>

[0072] The discharge rate of the extruded elastomer was measured. The results are shown using Comparative Example 1 as the index of 100; the larger the value, the greater the discharge rate and the better the productivity.

[0073] The results of the experiment are shown in Table 1 and Table 2.

[0074] [Table 1]

[0075]

[0076] [Table 2]

[0077]

[0078] The test results confirmed that the extruder of the embodiment improved the combined evaluation values ​​of quality and productivity tests compared to the extruder of the comparative example, achieving a balance between quality and productivity even for uncured rubber with high silica blends.

[0079] Symbol Explanation

[0080] 2 screws

[0081] 5. Spiral blades

[0082] 6. First District

[0083] 9. Barrier.

Claims

1. A screw having helical blades for simultaneously compounding and extruding a highly silica-based, plastic elastomer containing more than 100 phr of silica. The screw has a first region located on the downstream side in the extrusion direction, and the spiral blades are defined as being formed by two threads. In the first region, a barrier extending obliquely relative to the screw axis is formed between adjacent helical blades in the extrusion direction. The length of the barrier along its long side is 1.5 to 3.0 times the lead length of one of the two threads of the helical blade in the first region. The height of the barrier is less than the height of the helical blade, and the difference between the height of the helical blade and the height of the barrier is 2–10 mm. The thickness of the barrier is 0.9 to 3.0 times the difference between the height of the helical blade and the height of the barrier.

2. The screw according to claim 1, wherein, In the first region, 1 to 4 of the barriers are formed.

3. The screw according to claim 1 or 2, wherein, The screw has a second region disposed on the upstream side of the extrusion direction of the first region. In the second region, a notch for pin passage is formed on the helical blade.

4. The screw according to claim 3, wherein, The screw has a third region continuously disposed in conjunction with the second region on the upstream side of the extrusion direction of the second region. In the third region, at least a portion of the helical blade is formed by a single thread.

5. The screw according to claim 4, wherein, The upstream part of the third region in the extrusion direction is formed by multiple threads.

6. An extruder comprising a screw according to any one of claims 3 to 5, and a barrel having the screw disposed internally therein, wherein, The barrel includes a plurality of pins inserted into the notch formed by the helical blades in the second region.

7. An extruder comprising a screw according to any one of claims 1 to 5, and a barrel disposed therein with respect to the screw.

8. An extrusion method for extruding the elastomer using the extruder of claim 6 or 7, comprising: In the input process, the elastomer is fed into the interior of the barrel; as well as In the extrusion process, the elastomer is compounded and extruded simultaneously. The extrusion process includes a deformation process in which the elastomer is deformed into a thin film shape by passing through the barrier.

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