Wear-resistant rotor

Abstract

The present invention relates to a rotor for a stirred mill having a substantially cylindrical rotor body, the outer wall of which defines the inner surface of a grinding chamber through which the feed material to be processed flows during operation of the stirred mill. A ceramic ring is arranged at the rotor end of the rotor body, the rotor end being arranged opposite the product inlet of the stirred mill. The present invention also relates to a stirred mill comprising a rotor according to the invention, to the use of the rotor according to the invention in a stirred mill for producing a dispersion, and to a method for producing the rotor.

Description

[Technical field]

[0001] The present invention relates to rotors for agitator mills, and more particularly to wear-resistant, dimensionally stable plastic rotors. [Background technology]

[0002] Stirrer mills have a wide range of applications involving the grinding and dispersion of solids in liquids. Stirrer mills are used, for example, in the production of adhesives, printing inks, cosmetics, pharmaceuticals and also in the production of raw materials for battery pastes (particularly silicon). Typically, a grinding chamber is formed in a vertical stirrer mill by a rotor rotating about a vertically oriented longitudinal central axis and a stator, in which chamber, if applicable, a dispersion is produced using auxiliary grinding bodies, for example ceramic balls. For this purpose, grinding tools, for example in the form of circular pins, can be attached to the rotor and / or the stator. The feed material is led into the grinding chamber via a product feed, is ground there and is discharged via a product discharge. Such a stirrer mill is known, for example, from EP 1992412 (A1).

[0003] Especially in the production of raw materials for battery pastes, a fineness of x50 = 100-200 nm has to be achieved, which requires long grinding times. Due to the abrasive nature of the solids to be processed, a considerable wear of the process areas in the grinding chamber can be expected. In addition, metal contamination of the final product should be avoided, so the use of metal-free rotors for the agitator mills is preferred instead of the otherwise typical steel rotors.

[0004] The use of ceramic and plastic rotors is known in the prior art. However, the production of ceramic rotors is very expensive and complex to design. For example, SSiC or SiSiC are highly wear-resistant due to their hardness, but are therefore prone to fracture. These two ceramics have very good thermal conductivity, much higher than steel. However, the production of large components involves great problems.

[0005] Metal contamination can also be avoided by using plastic rotors. However, depending on the feed material, this type of rotor can be subject to rapid mechanical wear. In particular, in the area of ​​crushing body compression (high energy density range), the plastic material is highly affected. Furthermore, the compatibility of the plastic used in the rotor with the feed material must be checked at all times to ensure chemical resistance. The generally low thermal conductivity of plastics is a major disadvantage. Summary of the Invention

[0006] The object of the present invention is to provide a rotor for an agitator mill that is dimensionally stable, in particular resistant to common solvents, and can be used in particular for the production of battery pastes, in a cost-effective manner. It must allow wet grinding of the abrasive grains without destructive wear of the final product.

[0007] The basic concept of the present invention is to use a rotor body of the rotor of the agitator mill, which has wear elements made of ceramic in the area of ​​high energy density, specifically in the lower area of ​​the process area, i.e. at the lower end of the rotor. In particular, in the case of an agitator mill arranged vertically at the bottom of the process area, i.e. in the lower area of ​​the rotor, gravity and the deflection of the grinding bodies by the product solids and grinding bodies combined with high rotor speeds lead to high wear on the rotor. Generally, the highest wear in the agitator mill occurs at the rotor end, i.e. opposite the product inlet.

[0008] Thus, according to the invention, a rotor is provided having a substantially cylindrical rotor body, the outer wall of which defines the inner surface of a grinding chamber through which the feed material to be processed flows during operation of the stirred mill. The ceramic ring is arranged in a region of the rotor with high energy input. This region is the side of the rotor opposite the inlet of the product to the stirred mill. In a vertical stirred mill, this is the lower part of the rotor body. The surface of the ceramic ring in particular forms a part of the outer wall of the rotor which forms the inner surface of the grinding chamber. This part preferably extends to a grinding tool arranged on the outer wall of the rotor. The grinding tool can thus fix the ceramic ring against twisting and / or dropping.

[0009] The ceramic ring is preferably joined to the rotor body, in particular by screwing, gluing or connecting with a positive interlock. According to a preferred embodiment, if the rotor body is made of plastic, the ceramic ring can also be cast into the rotor body.

[0010] The ceramic ring may have a substantially L-shaped cross section with the longer sides or legs of the L-shaped ceramic ring disposed on the outer surface of the rotor, or alternatively, the ceramic ring may have a substantially U-shaped cross section with the legs disposed on the outer and inner surfaces of the rotor.

[0011] Preferably, the ratio L / D of the length L of a portion of the rotor outer wall formed by the ceramic ring to the outer diameter D of the rotor is 0.05 to 0.5. The ratio S1 / S2 of the thickness S1 of the portion of the ceramic ring forming the rotor outer wall to the total thickness S2 of the rotor wall is preferably 0.1 to 0.9.

[0012] The plastic rotor may include at least one of PA, PET, PEEK, PVDF, and POM. The ceramic ring may include at least one of ZrO2, SSiC, SiSiC, and Si3N4.

[0013] The invention further provides an agitator mill with a rotor according to the invention. According to known mills, the agitator mill according to the invention further comprises a stator with an inner stator wall, the rotor being arranged in the stator. Furthermore, a product supply and a product discharge are provided, the grinding chamber being formed between the inner stator wall and the outer wall of the rotor. The feed material can be led into the grinding chamber via the product supply and out of the grinding chamber via the product discharge.

[0014] The ratio of the rotor outer diameter D to the stator inner diameter D2 is preferably 0.6≦D / D2≦0.95. Furthermore, the stirring mill can have an inner stator arranged in a portion of the rotor, and the product discharge is formed between the rotor and the outer wall of the inner stator. The ratio of the inner stator outer diameter d22 to the rotor inner diameter d1 is preferably 0.8≦d22 / d1≦0.98.

[0015] The invention further relates to the use of a rotor according to the invention in a stirring mill for producing a dispersion, in particular a battery paste, and to a method for producing a rotor, comprising the step of joining - in particular by gluing, screwing or a positive interlocking connection - a ceramic ring with the rotor body. [Brief description of the drawings]

[0016] The invention is explained in more detail below with reference to the figures. [Figure 1] FIG. 1 is a cross-sectional view of a prior art vertical agitator mill. [Diagram 2] FIG. 2 is a cross-sectional view of a rotor for a vertical agitator mill according to one embodiment of the present invention. [Diagram 3] FIG. 13 is a cross-sectional view of a rotor for a vertical agitator mill rotor according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 shows, by way of example, details of a vertically arranged agitator mill according to the prior art. The agitator mill shown in FIG. 1 has a mill vessel or stator 2 with an internal grinding chamber 8 in a conventional manner. The grinding chamber 8 is at least partially filled with grinding elements 43. The agitator mill further comprises an inner stator 22 and a rotor 35 which can rotate about a central longitudinal axis 19. A first tool 38 is attached to the rotor 35, which projects into the grinding chamber 8. A second tool 74 is attached to the inner wall 9 of the vessel or stator, which projects into the grinding chamber 8. The treated feed material is led through the gap between the rotor 35 and the inner stator 22, forming a protective screen 30 which holds the grinding bodies 43, and flows out via a discharge line 31.

[0018] Figure 2 shows a cross-sectional view of a rotor for the vertical stirred mill shown in Figure 1. The rotor according to the shown embodiment of the invention has a substantially cylindrical rotor body 351 with an outer wall 32. The rotor body 351, having an outer diameter D, can be made of plastic or steel, with plastic being preferred here. The rotor together with the stator shown in Figure 1 forms a grinding chamber through which the feed material to be processed flows during operation of the stirred mill.

[0019] The greatest wear in the rotor of a vertical agitator mill generally occurs in the lower area of ​​the rotor, i.e. in the area where the high energy density is due to gravity and the deflection of the feed material and the grinding bodies in combination with the high rotor speed. In general, in agitator mills, both vertical and horizontal, the area where the greatest wear occurs during operation is the area opposite the product inlet. According to the invention, an annular wear ring is provided precisely in this area and is made from a hard and therefore highly wear-resistant ceramic material. In this case, for example, the materials are ZrO2, SSiC, SiSiC and Si3N4. Thus, most of the rotor 35 can be manufactured from a cost-effective rotor base, while the parts that are prone to wear are replaced with wear-resistant ceramic materials.

[0020] As represented by Y in Fig. 2 and shown in a further enlarged detailed view, the ceramic ring 352 can have a substantially L-shaped profile. The short side of the L forms the lower side, and the long side of the L, i.e., the leg, forms the lower part of the outer side 32 where the most wear occurs. Thus, the lower part of the length L of the outer side 32 and the lower side of the rotor having the total wall thickness S2 are formed by the ceramic ring 352.

[0021] The ceramic ring 352 is joined to the rotor body, for example, screwed, glued, or in the case of a plastic rotor body, also cast into the plastic. As shown in the section of Fig. 2 represented by X, on the outer side 32 of the rotor, the ceramic ring 352 preferably extends to the lowermost row of the grinding tool 38. Thus, the ceramic ring 352 can be additionally fixed by the tool 38, specifically against torsion or dropping.

[0022] Regarding the wall thickness S1 of the ceramic ring with respect to the total wall thickness S2 of the rotor, it is preferable that 0.1 < S1 / S2 < 0.9.

[0023] Fig. 3 shows a cross-sectional view of a rotor according to another embodiment of the present invention. As in Fig. 2, the wear element made of ceramic is attached to the lower part of the rotor body 351. According to the embodiment shown in Fig. 3, this is also realized in the form of a ceramic ring 352. However, different from Fig. 2, it has a substantially U-shaped profile. Thus, in addition to the lower side and a part of the outer side 32, a part of the inner surface of the rotor, i.e., a part of the product discharge part, is also reinforced by the wear element via the second leg of the U. This is also more precisely shown in the detailed view represented by Y in Fig. 3. As shown in the section of Fig. 3 represented by X, here too, on the outer side 32, the ceramic ring 352 can extend at least to the lowermost row of the grinding tool 38.

[0024] The invention further provides an agitator mill using a rotor according to the invention. For this purpose, only the rotor 35 shown by way of example in Fig. 1 is replaced by a rotor according to the invention, for example as shown in Fig. 2 or 3. A typical extension of such an agitator mill results in values ​​for the ratio of the outer diameter of the rotor 35 to the inner diameter of the stator 2 of between 0.6 and 0.95. The ratio of the outer diameter of the inner stator 22 to the inner diameter of the rotor 35 is, for example, between 0.8 and 0.98.

[0025] The rotor according to the invention can in particular be produced by joining the ceramic ring 352 to the rotor body 351. This can in particular be done by gluing, screwing or a positive interlocking connection. If the rotor body 352 is made of plastic, the ceramic ring 352 can also be cast in the plastic body 351.

[0026] The rotor according to the invention and the stirring mill using this rotor are particularly suitable for the production of dispersions which require a high fineness, for example x50=100-200 nm, and therefore long grinding times, and which must be kept as free as possible from metal contamination. This applies, for example, to the production of raw materials for battery pastes.

Claims

1. A rotor (35) for an agitation mill, a substantially cylindrical rotor body (351), the outer wall (32) of the rotor defining the inner surface of a grinding chamber through which the feed material to be processed flows during operation of the agitator mill; a ceramic ring (352) disposed at a rotor end of the rotor body (351), the rotor end being disposed opposite a product inlet of the agitator mill; a surface of the ceramic ring (352) forming a portion of the outer wall (32) of the rotor which forms the inner surface of the grinding chamber; A rotor (35), wherein the portion extends to a grinding tool (38) arranged on the outer wall (32) of the rotor, and the ceramic ring (352) is secured against twisting and / or dropping by the grinding tool (38).

2. The rotor (35) of claim 1, wherein the rotor (35) is configured for use in a vertical agitator mill.

3. The rotor (35) according to claim 1 or 2, wherein the ceramic ring (352) is joined to the rotor body (351), in particular by screwing or joining with a positive interlock connection.

4. A rotor (35) according to any one of claims 1 to 3, wherein the ceramic ring (352) has a substantially L-shaped cross-section, and legs of the L-shaped ceramic ring (352) are disposed on an outer surface (32) of the rotor (35).

5. A rotor (35) according to any one of claims 1 to 3, wherein the ceramic ring (352) has a substantially U-shaped cross-section, legs of the U-shaped ceramic ring (352) being disposed on the outer surface (32) and the inner surface of the rotor (35).

6. A rotor (35) according to any one of claims 1 to 5, wherein a ratio L / D between a length L of a portion of the outer wall (32) of the rotor (35) formed by the ceramic ring (352) and an outer diameter D of the rotor (35) is 0.05 to 0.

5.

7. A rotor (35) according to any one of claims 1 to 6, wherein a ratio S1 / S2 of a wall thickness S1 of the ceramic ring (352) to a total wall thickness S2 of the rotor (35) is between 0.1 and 0.

9.

8. The rotor (35) of any one of claims 1 to 7, wherein the rotor body (351) comprises at least one of PA, PET, PEEK, PVDF, and POM.

9. The ceramic ring (352) is made of ZrO ２ , SSiC, SiSiC, and Si ３ N ４ The rotor (35) according to any one of claims 1 to 8, comprising at least one of:

10. An agitation mill comprising: A rotor (35) according to any one of claims 1 to 9; a stator (2) having a stator inner wall (9), the rotor (35) being disposed within the stator (2); A product supply department; A product discharge section, A grinding chamber (8) is formed between the stator inner wall (9) and the outer wall (32) of the rotor (35), and the feed material can be led into the grinding chamber (8) via the product supply section and out of the grinding chamber (8) via the product discharge section.

11. Use of a rotor (35) according to any one of claims 1 to 9 in an agitator mill for producing a dispersion, in particular a battery paste.

12. A method for manufacturing a rotor (35) according to any one of claims 1 to 9, characterized by a step of joining a ceramic ring (352) to said rotor body (351), in particular by gluing, screwing or a positive interlocking connection.

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