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JP-2026514238-A - Screw elements having improved mixing effect and improved heat transfer capacity, and their use

JP2026514238AJP 2026514238 AJP2026514238 AJP 2026514238AJP-2026514238-A

Abstract

The present invention relates to a pair of three lead screw elements for a multi-screw machine having screw shafts rotating in the same direction and at the same speed. Two screw elements of the pair of screw elements according to the present invention, which are directly adjacent and facing each other on two directly adjacent screw shafts, are practically cleaned from each other. The present invention also relates to the use of the pair of screw elements according to the present invention in a multi-screw machine, a multi-screw machine equipped with the pair of screw elements according to the present invention, and a method for extruding plastics or viscoelastic compounds using the pair of screw elements according to the present invention.

Inventors

  • ケーニッヒ トーマス
  • ビーアデル ミヒャエル

Assignees

  • コベストロ、ドイチュラント、アクチエンゲゼルシャフト

Dates

Publication Date
20260507
Application Date
20240422
Priority Date
20230504

Claims (15)

  1. A pair of three flight screw elements, The aforementioned pair of screw elements consists of screw element SE and screw element SE', The pair of screw element SE and screw element SE' is, m screw shafts SW1 to SWm that rotate in the same direction and at the same speed, wherein each adjacent rotation axis X1 to Xm has a center distance A in a cross section perpendicular to the rotation axis, m circular housing bores that penetrate each other, each having the same internal housing radius R, with bore centers M1 to Mm at a distance equal to the center distance A, and the bore centers M1 to Mm coinciding with the respective associated rotation axes X1 to Xm of the screw shafts SW1 to SWm, Suitable for multi-screw machines, The screw element SE has a screw profile SP, and the screw element SE' has a screw profile SP'. (1) Each of the two screw profiles SP and SP' is a closed convex curve, This closed convex curve is composed only of curve sections whose radius of curvature is less than or equal to the center distance A. (2) Neither of the two screw profiles SP and SP' has mirror symmetry, or the screw profiles SP and SP' are not congruent to each other. (3) Each of the two screw profiles SP and SP' has three precisely spaced grooves. (4) Each of the two screw profiles SP and SP' has exactly three peaks, and the screw profile SP is labeled K1, K2, and K3 around its periphery, and the screw profile SP' is labeled K1', K2', and K3'. (6) The two screw elements of the pair of screw elements of the multi-screw machine, which are positioned opposite each other in pairs on the two screw shafts, directly adjacent to each other, and rotating in the same direction at the same speed, practically clean each other as a pair. (7) The groove is separated by the flank from the nearest point of the adjacent apex. (8) Frank, having exactly six curves, This is true, (9) r(Ki) is the vertex radius of vertex Ki, and r(Ki') is the vertex radius of vertex Ki', where, r(K1) > r(K2) and r(K1) > r(K3) and r(K1') >r(K2') and r(K1') >r(K3') and r(K2) ≥ r(K3) and r(K2') ≥ r(K3'), and at least one of condition a) or b) is true, where, a) r(K2) > r(K3) and r(K2') >r(K3') b) r(K2) is not equal to r(K2'), and r(K3) is not equal to r(K3'), Here, r(K1) is the top radius of screw crown K1, r(K2) is the top radius of screw crown K2, r(K3) is the top radius of screw crown K3, r(K1') is the top radius of screw crown K1', r(K2') is the top radius of screw crown K2', and r(K3') is the top radius of screw crown K3'. (10) The screw top K1 has a vertex angle KW1, the screw top K2 has a vertex angle KW2, the screw top K3 has a vertex angle KW3, the screw top K1' has a vertex angle KW1', the screw top K2 has a vertex angle KW2', the screw top K3 has a vertex angle KW3', (10.1) (10.1.a) If KW1 > 0, then KW1 < KW2 and KW1 < KW3, and, (10.1.b) If KW1'> 0, then KW1'< KW2 and KW1 < KW3. Or, (10.2) (10.2.a) If KW1 > 0, then KW1 < KW2 and KW1 < KW3, and, (10.2.c) When KW1' = 0, KW2 ≥ 0 and KW3 ≥ 0. Or, (10.3) (10.3.b) If KW1'> 0, then KW1'< KW2 and KW1 < KW3, and, (10.3.d) When KW1 = 0, KW2 ≥ 0 and KW3 ≥ 0. Or, (10.4) (10.4.d) When KW1 = 0, KW2 ≥ 0 and KW3 ≥ 0, and, (10.4.c) If KW1' = 0, then KW2 ≥ 0 and KW3 ≥ 0. Here, r(K1) is equal to r(K1'), and is equal to the outer radius RA or RA' of the screw element. m is an integer greater than 1, preferably 2 to 16, and particularly preferably 2, 3, 4, 6, 8, 10, 12, and 16. i can take the value 1, 2, or 3. A pair of three-flight screw elements, characterized in that the outer radius RA is the radius of a circle enclosing the entire screw profile, the center point of the circle is the rotation center associated with this screw profile, and the apex K1 is a segment of this circle.
  2. Each of the three vertices K1, K2, and K3 of the screw element SE is formed from only one curved section that is an arc, having a center that is a common rotation center DP for the vertices K1, K2, and K3 in each case, and each of the three vertices K1', K2', and K3' of the screw element SE' is similarly formed from only one curved section that is having a center that is a common rotation center DP' for the vertices K1', K2', and K3' in each case, and, The screw element according to claim 1, characterized in that each of the three grooves of the screw element SE is formed from only one curved section that is an arc, having a center which is the rotation center DP of the screw element SE common to the three grooves, and there is exactly one groove whose distance from the rotation center DP is smaller than the distance from the rotation center DP of the other grooves, and each of the three grooves of the screw element SE' is formed from only one curved section that is an arc, having a center which is the rotation center DP' of the screw element SE' common to the three grooves.
  3. In the case of screw profile SP, the screw apex having the largest apex radius r(Ki), i.e., apex K1, has the smallest apex angle among apex K1, K2, and K3; and in the case of screw profile SP', the screw apex having the largest apex radius r(Ki)', i.e., apex K1', has the smallest apex angle among apex K1', K2', and K3', characterized by the screw element pair according to claim 1 or 2.
  4. The screw element pair according to any one of claims 1 to 3, characterized in that the screw profile SP is continuously differentiable at all of the apex portions K1, K2, and K3, and the screw profile SP' is also continuously differentiable at all of the apex portions K1', K2', and K3'.
  5. A pair of screw elements according to any one of claims 1, 2, or 4, characterized in that each of the three vertices K1, K2, and K3 of the screw element SE is formed from exactly one point, and similarly, each of the three vertices K1', K2', and K3' of the screw element SE' is formed from exactly one point.
  6. A pair of screw elements according to any one of claims 1 to 4, characterized in that the vertices K1 and K1' are formed from exactly one point, the vertices K2 and K3 are each formed from exactly one arc whose respective center coincides with the rotation center DP, and the vertices K2' and K3' are each formed from exactly one arc whose respective center coincides with the rotation center DP'.
  7. A pair of screw elements according to any one of claims 1 to 4, characterized in that all vertices of the screw profile SP and all vertices of the screw profile SP' have vertex angles greater than zero.
  8. Given a given center distance A and a given housing inner radius R with respect to a given housing inner diameter D = 2R, the distance r(K1) from the rotation center to the top K1 is within the following range for r(K1) or r(K1'), i.e., r(K1) is less than or equal to R - 0.002D, r(K1) is R-0.05D or higher. r(K1') is less than or equal to R - 0.002D, r(K1') is R-0.05D or higher. A pair of screw elements according to any one of claims 1 to 7, characterized in that they are selected so that the following can be applied.
  9. Given a given center distance A and a given housing inner radius R relative to a given housing inner diameter D = 2R, the distance r(K1) of the apex K1 from the center of rotation is within the following range for the apex K2 and K2', i.e., r(K2) is less than or equal to r(K1) - 0.002D, r(K2) is greater than or equal to r(K1) - 0.08D. r(K2') is less than or equal to r(K1') - 0.002D, r(K2') is greater than or equal to r(K1') - 0.08D, Here, it is also true that r(K2) is greater than (r(K1) + r(N1))/2 and r(K2') is greater than (r(K1') + r(N1'))/2. A pair of screw elements according to any one of claims 1 to 8, characterized in that they are selected so as to apply.
  10. Given a given center distance A and a given housing inner radius R relative to a given housing inner diameter D = 2R, the distance r(K1) of the apex K1 from the center of rotation is within the following range for the apex K3 and K3', i.e., r(K3) is greater than or equal to r(K1) - 0.09D. r(K3) is less than or equal to r(K2), r(K3) is greater than or equal to r(K2) - 0.05D. r(K3') is greater than or equal to r(K1') - 0.09D, r(K3') is less than or equal to r(K2'), r(K3') is greater than or equal to r(K2') - 0.05D, Also, (r(K1) + r(N1))/2, and r(K3') is greater than (r(K3') + r(N1'))/2. A pair of screw elements according to any one of claims 1 to 9, characterized in that they are selected so that the following is preferably applied.
  11. Regarding the screw profiles SP and SP', independently of each other, A pair of screw elements according to any one of claims 1 to 10, characterized in that the vertex angle KW1 is true to be 0 degrees < KW1 < 10 degrees, preferably 2 degrees < KW1 < 8 degrees, and the vertex angle KW1' is true to be 0 degrees <KW1'< 10 degrees, preferably 2 degrees <KW1'< 8 degrees.
  12. A pair of screw elements according to any one of claims 1 to 11, characterized in that the screw profiles of the two screw elements SE and SE' are congruent without rotation, or the screw profiles SP and SP' of the two screw elements SE and SE' are congruent in opposite directions.
  13. Use of a pair of screw elements according to any one of claims 1 to 12 in a multi-screw machine.
  14. A multi-screw machine comprising a pair of screw elements according to any one of claims 1 to 12.
  15. A method for extruding a plastic or viscoelastic mass using a pair of screw elements as described in claim 1, or using a screw machine as described in claim 14.

Description

This invention relates to a pair of three-flight screw elements for a multi-screw machine having screw shafts rotating in the same direction and at the same speed. The two screw elements of the pair of screw elements according to the present invention, positioned directly adjacent and facing each other on two directly adjacent screw shafts, practically clean each other. This invention also relates to the use of the pair of screw elements according to the present invention in a multi-screw machine, a multi-screw machine equipped with the pair of screw elements according to the present invention, and a method for extruding plastic or viscoelastic lumps using the pair of screw elements according to the present invention. In the context of this invention, a multi-screw machine is understood to mean a screw machine having two or more screw shafts, for example, a screw machine having two, three, or four screw shafts, or a screw machine having eight to sixteen, particularly twelve, screw shafts in an annular arrangement. In the case of three or more screw shafts, the axes of rotation of the screw shafts may be arranged adjacent to each other, or they may be annular in shape, as in the case of what is called a ring extruder. In a multi-screw extruder, the axes of rotation of the screw shafts are generally arranged parallel to each other. This parallel arrangement of the axes of rotation is also preferred according to this invention. The screw elements according to this invention are preferably arranged opposite each other on the screw shafts, in a number corresponding to the number of screw shafts in each extruder. Such a screw machine having two or more screw shafts is hereinafter also referred to as a multi-screw machine, multi-screw machine, or multi-screw extruder. A twin-screw machine is hereinafter also referred to as a twin-screw extruder. In the context of this invention, the term "screw machine" is used synonymously with the term "extruder." Current extruders have a modular system in which various screw elements can be mounted on a core shaft to form a screw shaft, and therefore such a screw shaft is segmented. This allows those skilled in the art to adapt the extruder to various processing tasks. However, a screw shaft can also be made as a single unit, that is, having only one screw element extending substantially along the entire length of the screw shaft, or it can be segmented only partially. This invention relates to both screw elements that can be mounted on a core shaft and screw shafts made from the single parts described above. Co-rotating twin-screw machines, in which the screw shafts precisely clean each other, have long been known, for example from Patent Document 1. In polymer production and processing, screw machines having screw shafts based on the principle that the screw elements precisely clean the screw cross-sectional profile have been used in various ways. This is mainly because, at normal processing temperatures, molten polymer adheres to the surface and deteriorates over time, but this is prevented by the self-cleaning effect of the screw elements in a multi-screw machine that precisely clean each other in pairs. Rules for generating the cross-sectional screw profile of screw elements that precisely clean each other are shown, for example, in [1] ([1] = Non-Patent Document 1). According to the description therein, in the case of screw elements that precisely clean each other, a predetermined cross-sectional screw profile on the first shaft of a twin-screw extruder determines the cross-sectional screw profile on the second shaft of the twin-screw extruder ([1], p. 108). In the context of the present invention, the screw cross-sectional profile, also abbreviated as screw profile, is understood to mean the outer contour of the screw element in a planar cross-section perpendicular to the axis of rotation of the screw element, according to the axis of rotation of the associated screw shaft. The screw profile of the screw element on the first shaft is called the generated screw profile. The screw profile of the screw element on the second shaft follows the screw profile of the first shaft in a twin-screw extruder, and is therefore called the generated screw profile. In a multi-screw extruder, screw elements with generated screw profiles and screw elements with generated screw profiles are always used alternately on adjacent shafts. Those skilled in the art of screw elements will understand that a single screw element or screw profile alone cannot precisely or practically rub against each other, and that a pair of such elements is always necessary. Here, two distinctions must be made: namely, a precisely rubbing screw profile, that is, a mathematical configuration in which two screw elements, located immediately adjacent to each other on two screw shafts, clean each other without any gaps; and a screw profile for a screw element designed with a material entity for its intended application,