WO2015089528A1

WO2015089528A1 - Method for the production of abrasive

Info

Publication number: WO2015089528A1
Application number: PCT/AT2014/000214
Authority: WO
Inventors: Klaus SIGWART; Martin Hirschmann
Original assignee: Tyrolit - Schleifmittelwerke Swarovski K.G.
Priority date: 2013-12-18
Filing date: 2014-12-02
Publication date: 2015-06-25
Also published as: AT515229A1; EP3083026A1; AT515229B1

Abstract

Method (1) for producing abrasive (2, 3), comprising the following steps: i. providing a burnable net-shaped or grating-shaped structure (4, 5), which is preferably made of plastic and includes a plurality of openings (6, 7), on a carrier (10), preferably an endless carrier band; ii. providing a feedstock mixture (8) which preferably contains aluminum hydroxide, can be converted at least to alumina, and is preferably pourable; iii. filling the openings (6, 7) with the feedstock mixture (8); and iv. sintering the net-shaped or grating-shaped structure (4, 5) that is filled with the feedstock mixture (8).

Description

The invention relates to a process for the production of abrasives.

Such abrasives are incorporated, for example, in abrasive coatings, in solid abrasive or in abrasive papers. In this case, all known ceramic bonds and synthetic resin bonds come into consideration as a bond for the abrasive. The field of application of these grinding tools is the grinding of steels, metals and alloys, plastics and wood.

Different methods for the production of abrasives are known from the prior art. For example, WO 201 1/087649 discloses a method in which a rotary shadow mask in combination with vacuum is used to make shaped ceramic material sections which are subsequently sintered. It is a technically very complex and maintenance-intensive process.

The present invention is based on the object of specifying a simplified process for the production of abrasives.

This task is solved by the following process steps:

i. Providing a combustible reticulated or grid-shaped structure, preferably made of plastic, with a plurality of openings on a carrier, preferably an endless carrier belt,

Ii. Providing a, preferably aluminum hydroxide-containing, starting mixture, which is convertible by sintering at least in alumina, wherein the starting mixture is preferably flowable,

iii. Filling the openings with the starting mixture, and

iv. Sintering the net or latticed structure filled with the starting mixture.

One of the fundamental ideas of the method according to the invention is therefore that during the process step of sintering, the starting mixture is converted at least into alumina and, secondly, the reticulated or grid-shaped structure is burned, which results in automatic separation of the abrasive particles, so that the Abrasive particles after sintering - at least for the most part - be present separately. A significant advantage of the method according to the invention over the prior art is that the geometry and dimension of the abrasive particles can be determined in a simple manner by the choice of the shape of the mesh or lattice-shaped structure. In addition, it is possible to quickly and easily change the geometry and size of the manufactured abrasive particles by changing the mesh or lattice-shaped structure.

It should be noted that the technique of converting a starting mixture containing preferably aluminum hydroxide by sintering, at least in aluminum oxide, has been known for some time. In this connection, reference should be made to the so-called "sol-gel process." If the starting mixture contains aluminum hydroxide, various modifications, such as boehmite, may be used Depending on the starting mixture, it may also occur in addition to aluminum oxide (typically as alpha-alumina). Secondary phases, such as spinel, are formed, which is accounted for by the expression "at least in aluminum oxide".

In an advantageous embodiment of the method, the net or latticed structure filled with the starting mixture is predried before sintering, preferably at a temperature between 50 ° C and 500 ° C, more preferably at a temperature between 150 ° C and 400 ° C. In this way, the network or lattice-shaped structure filled with the starting mixture can be converted into a state which, for example, allows the division into sections which are preferably plate-shaped. These sections can then be fed subsequently to the method step of the sinter.

Alternatively or additionally, however, it is also possible that the net or lattice-shaped structure filled with the starting mixture remains on the support and the sintering is carried out in a continuous furnace.

The sintering is preferably carried out at a temperature between 1200 ° Celsius and 1800 ° Celsius, more preferably at a temperature between 1200 ° Celsius and 1500 ° Celsius.

It is useful for the mesh or lattice structure to use a material which will burn completely at the sintering temperature, but at lower temperatures - e.g. in a possible pre-drying process - is heat resistant.

Preferably, the net or grid-shaped structure (one-ply) provided on the support has a height less than or equal to 1.5 millimeters viewed from the side. This height essentially corresponds to the thickness of the threads or webs from which the network or lattice-shaped structure is advantageously constructed. In addition, this height determines the thickness of the abrasive particles present at the end of the manufacturing process since the starting mixture, when it is flowable, flows beyond the confines of an aperture in the form of the strands and into an adjacent aperture as the apertures are filled. However, it must also be taken into account that the thickness in the course of the sintering process - mainly due to the reduction of the liquid content - still decreases. In general, it should be pointed out that reticulated and grid-shaped structures differ in that reticulated structures have nodes in contrast to grid-shaped structures.

If it is a somewhat more viscous starting mixture, it can be provided as an alternative or supplementary measure to ensure a certain thickness of the abrasive particles that the net or lattice-like structure filled with the starting mixture passes a gap having a predetermined height prior to sintering. This height is advantageously adjusted to the height of the mesh or latticed structure provided on the support or the thickness of the threads or webs of the net or latticed structure or slightly above, so that the starting mixture is evenly spread in the openings. Polygons, preferably diamonds, squares or triangles, are suitable as geometries for the openings of the mesh or latticed structure.

Depending on the choice of concrete process parameters, it may happen that the sintered products or abrasive particles obtained by sintering are still occasionally connected to one another via webs or the like. In these cases, it is advantageous to supply the sintered products obtained by sintering to a separating device, preferably a vibrating device.

Further advantages and details of the invention will become apparent from the figures and the associated description of the figures. Showing:

Fig. 1 is a schematic representation of the invention

Method in the form of a flowchart,

2a and 2b, two advantageous embodiments of the invention with reference to

Schematic drawings,

FIGS. 3a and 3b show two possible network or latticed structures used in the method, and FIGS Fig. 4a and 4b two possible producible by the method according to the invention

Abrasive particles.

FIG. 1 shows, with reference to a flowchart, the four basic method steps of the method 1 according to the invention for the production of abrasives, namely

i. the provision of a combustible reticulated or grid-shaped structure, preferably of plastic, with a plurality of openings on a support, preferably an endless carrier fire,

ii. the provision of a starting mixture, preferably containing aluminum hydroxide, which is convertible by sintering at least in aluminum oxide, the starting mixture preferably being flowable,

iii. filling the openings with the starting mixture, and

iv. the sintering of the filled with the starting mixture net or lattice-shaped structure.

The technical implementation of this method can take place in different ways, wherein two particularly preferred embodiments are shown in FIGS. 2a and 2b:

In the case of FIG. 2a, the combustible reticulated or grid-shaped structure 4 is provided on a carrier in the form of an endless carrier belt 10 by unwinding the net or lattice-like structure 4 from a roller 15. The angular velocity of this roller 15 and the speed of the endless carrier belt 10 become coordinated with each other to ensure a uniform unwinding of the net or lattice-shaped structure 4. The Endlosträgerband 10 is guided over the rolling elements 16 and 17.

After providing the combustible reticulated or grid-shaped structure 4, which in this case consists of plastic, the openings 6 thereof (see Fig. 3a) with a flowable starting mixture 8, which by sintering at least in alumina (and as stated above in possible secondary phases) can be converted, and which in this case contains predominantly aluminum hydroxide, filled. For this purpose, the starting mixture 8 is poured onto the mesh or grid-shaped structure 4. The net or grid-shaped structure 4 filled with the starting mixture 8 then passes through a gap 13, the height of which substantially corresponds to the height 18 of the net or grid-shaped structure 4 provided in one layer on the carrier 10.

The filled with the starting mixture 8 mesh or lattice-shaped structure 4 is finally transported by means of Endlosträgerbands 10 through a continuous furnace 14, in which the Dry process or sintering takes place. In this case, on the one hand the portions of the starting mixture 8, which are located in the openings of the mesh or lattice-shaped structure 4 are sintered to alumina particles. At the same time, the mesh or grid-shaped structure 4 burns. That is, after the sintering process step, the abrasive particles 2 are present on the endless carrier belt 10 in accordance with the predetermined geometry of the mesh or grid-shaped structure 4. Finally, the abrasive particles 2 are collected in a collecting container.

In the case of the exemplary embodiment of the method according to the invention diagrammatically shown in FIG. 2b, the two method steps "providing a combustible reticulate or grid-shaped structure" and "filling the openings thereof" are carried out in the same way as in the embodiment shown in FIG. 2a. However, the network or grid-shaped structure 5 filled with the starting mixture 8 is subsequently predried by means of a heating device 19 before sintering, specifically at a temperature between 150 ° Celsius and 400 ° Celsius. At this temperature, the mesh or lattice-shaped structure 5 is heat-resistant. Predrying removes liquid from the starting mixture so that it is less flexible and adheres to the net or latticed structure. Therefore, the net or grid-shaped structure 5 filled with the starting mixture 8 can be subdivided into plate-shaped sections 9 by means of a suitable device, which are subsequently supplied to a sintering furnace 20.

In the sintering furnace 20, the sintering process is again carried out, wherein the starting mixture 8 is converted at least into aluminum oxide and any secondary phases and at the same time the mesh or lattice-shaped structure 5 is burnt, so that a separation of the abrasive particles 3 occurs during sintering.

As already stated, the geometry of the mesh or lattice-shaped structure can be used to determine the geometry of the abrasive particles produced by the process. FIGS. 3a and 3b show two exemplary network geometries, namely, in the case of FIG. 3a, a net or lattice-shaped structure 4 whose openings are diamond-shaped and, in the case of FIG. 3b, a net or lattice-shaped structure 5, whose openings square are formed. The threads or webs 1 1 and 12 of the mesh or lattice-like structure 4 and 5 have a thickness of less than or equal to 1, 5 millimeters. The mesh or latticed structures 4 and 5 can be used both in the embodiment according to FIG. 2a and in the embodiment according to FIG. 2b. It is also conceivable to use a network or lattice-shaped structure, the openings with has different geometries, and in this way to produce a mixture of abrasive particles with correspondingly different geometries.

FIGS. 4a and 4b show two examples of abrasive particles which can be produced by the process, wherein the particle 2 in FIG. 4a has a diamond shape with a predetermined edge length 22 and the particle 3 in FIG. 4b has a square shape with a predetermined edge length 24. These geometries The abrasive particles 2 and 3 correspond to the grid or grid geometries shown in FIGS. 3a and 3b. The thickness 25 or 26 of the abrasive particles is - due to the liquid removal during the sintering process - smaller than the thickness of the threads or webs of the mesh or lattice-shaped structure.

Claims

Patent claims

Process (1) for producing abrasives (2, 3), characterized by the following process steps:

i. Providing a combustible net or grid-shaped structure (4, 5), preferably made of plastic, with a plurality of openings (6, 7) on a carrier (10), preferably an endless carrier belt,

ii. Providing a starting mixture (8), preferably containing aluminum hydroxide, which can be converted at least into aluminum oxide by sintering, the starting mixture (8) preferably being flowable, iii. Filling the openings (6, 7) with the starting mixture (8), and

iv. Sintering the net or grid-shaped structure (4, 5) filled with the starting mixture (8).

Method (1) according to claim 1, characterized in that the net or grid-shaped structure (4, 5) filled with the starting mixture (8) is pre-dried before sintering, preferably at a temperature between 50 ° C and 500 ° C, especially preferably at a temperature between 150°C and 400°C.

Method (1) according to claim 1 or 2, characterized in that the net or grid-shaped structure (4, 5) filled with the starting mixture (8) is divided into, preferably plate-shaped, sections (9) before sintering.

Method (1) according to one of claims 1 to 3, characterized in that the sintering is carried out in a continuous furnace (14).

Method (1) according to one of claims 1 to 4, characterized in that the sintering is carried out at a temperature between 1200°C and 1800°C, preferably at a temperature between 1200°C and 1500°C.

Method (1) according to one of claims 1 to 5, characterized in that the openings (6, 7) of the net or grid-shaped structure (4, 5) are filled essentially by casting.

7. Method (1) according to one of claims 1 to 6, characterized in that the net or grid-shaped structure (4, 5) provided on the carrier has a height (18) less than or equal to 1.5 mm when viewed from the side.

8. Method (1) according to one of claims 1 to 7, characterized in that the net or grid-shaped structure (4, 5) filled with the starting mixture (8) passes through a gap (13) with a predetermined height before sintering.

9. Method (1) according to one of claims 1 to 8, characterized in that the openings (6, 7) of the net or grid-shaped structure (4, 5) are polygonal, preferably diamond-shaped, square or triangular.

10. Method (1) according to one of claims 1 to 9, characterized in that the sintered products obtained by sintering are fed to a separating device, preferably a shaking device.