Abstract
The disclosure relates to a method for producing an abrasive article, in which method a granular substance is scattered onto an abrasive article substrate that is coated with a binder, wherein the granular substance is deagglomerated by gas pulses and the deagglomerated granular substance is scattered onto the abrasive article substrate. The disclosure further relates to a correspondingly produced abrasive article.
Claims
1. A process for producing an abrasive article, comprising: deagglomerating a particulate substance using gas pressure pulses; and sprinkling an abrasive article substrate coated with binder with the deagglomerated particulate substance.
2. The process as claimed in claim 1, further comprising: providing the particulate substance is through a sieve, with the gas pressure pulses being directed by a gas pressure nozzle against the sieve.
3. The process as claimed in claim 2, wherein the gas pressure pulses are directed against the sieve essentially in a direction opposite to a direction of passage of the particulate substance through the sieve.
4. The process as claimed in claim 2, wherein the gas pressure pulses are directed against the sieve by the gas pressure nozzle at an angle between the gas pressure nozzle and the sieve which is in the range from 0° to 90°.
5. The process as claimed in claim 2, wherein the mesh opening of the sieve is greater than an the average diameter of the particulate substance.
6. The process as claimed in claim 2, wherein: the abrasive article substrate is an abrasive article substrate web; the particulate substance is provided through the sieve over an entire width of the abrasive article substrate web; and the gas pressure nozzle is one of a plurality of gas pressure nozzles delivering gas pressure pulses against the sieve.
7. The process as claimed in claim 1, wherein the particulate substance comprises at least one of abrasive grains and abrasive additives, or consists of at least one of abrasive grains and abrasive additives.
8. The process as claimed in claim 1, wherein the particulate substance has an average particle size of less than 300 microns.
9. The process as claimed in claim 1, wherein the gas pressure pulses are produced at a frequency of from 1 Hz to 500 Hz.
10. The process as claimed in claim 1, wherein the gas pressure pulses have an average duration in the range from 0.5 to 30 milliseconds.
11. The process as claimed in claim 1, wherein the gas pressure pulses have a pressure of more than 0.5 bar.
12. The process as claimed in claim 1, wherein the deagglomerated particulate substance is sprinkled electrostatically onto the abrasive article substrate.
13. The process as claimed in claim 12, wherein the sieve is made of metal and is operated as a high-voltage electrode during electrostatic sprinkling.
14. The process as claimed in claim 1, wherein the deagglomerated particulate substance is sprinkled mechanically or gravimetrically onto the abrasive article substrate.
15. An abrasive article, in particular abrasive article web, produced as claimed in claim 1.
16. The process as claimed in claim 2 wherein the gas pressure pulses are directed against the sieve by the gas pressure nozzle at an angle between the gas pressure nozzle and the sieve which is in the range from 35° to 55°.
17. The process as claimed in claim 2, wherein the mesh opening of the sieve is 400% greater than an average diameter of the particulate substance.
18. The process as claimed in claim 1, wherein the particulate substance has an average particle size of less than 50 microns.
19. The process as claimed in claim 1, wherein the gas pressure pulses are produced at a frequency of from 10 Hz to 40 Hz.
20. The process as claimed in claim 1, wherein the gas pressure pulses have an average duration in the range from 1 to 5 milliseconds.
Description
DRAWINGS
[0020] The invention will be illustrated by working examples depicted in the drawings in the following description. The drawings, the description and the claims contain numerous features in combination. A person skilled in the art will advantageously also look at the features individually and combine them to give purposeful further combinations. Identical reference numerals in the figures denote identical elements.
[0021] The drawings show:
[0022] FIG. 1 a schematic side view of an illustrative embodiment of a sprinkling machine for carrying out the process of the invention;
[0023] FIG. 2 a schematic side view of an alternative illustrative embodiment of a sprinkling machine for carrying out the process of the invention;
[0024] FIG. 3 a schematic side view of an alternative illustrative embodiment of a sprinkling machine for carrying out the process of the invention;
[0025] FIG. 4a a schematic plan view onto an illustrative abrasive article produced by a process of the prior art;
[0026] FIG. 4b a schematic plan view onto an illustrative abrasive article produced by the process of the invention;
[0027] FIG. 5 a schematic sectional view of an abrasive article produced by the process of the invention.
[0028] FIGS. 1, 2 and 3 each show a schematic side view of an illustrative embodiment of a sprinkling machine 10 (roll-to-roll machine) for carrying out the process of the invention for producing an abrasive article 100. The sprinkling machine 10 serves to sprinkle abrasive grains 102 as particulate substance onto an abrasive article substrate 104, here, in particular, in the form of an abrasive article substrate web 14.
[0029] In particular, the abrasive grains can have an average particle size of less than 50 microns, for example abrasive grains of the FEPA type #2000, which have an average diameter of about 10 microns. Such abrasive grains are typically present in the form of an at least partially agglomerated powder 106 because of their small size.
[0030] The sprinkling machine 10 has two transport rollers 12 which serve to rollably support the abrasive article substrate web 14. In FIGS. 1-3, the abrasive article substrate web 14 is conveyed counterclockwise by means of the transport rollers 12 in the direction of extension 16 of the abrasive article substrate web 14. A roll carrier for continuously rolling off the input material, i.e. the abrasive article substrate web 14, is not shown in each of the FIGS. 1-3. The abrasive article 100 produced by the process of the invention, i.e. the sprinkled abrasive article substrate web 14, is rolled up onto roll carriers which are likewise not shown in FIGS. 1-3. The incoming abrasive article substrate web 14 is, in all embodiments of the sprinkling machine shown, already coated with a binder (not shown in more detail here). The features of the sprinkling machine 10 for coating the abrasive article substrate web 14 with the binder, for example a spray apparatus or the like, are not shown in more detail in each of the FIGS. 1-3.
[0031] The sprinkling machine 10 in FIGS. 1-3 further comprises, in each case, a vessel 18, in particular a funnel, for provision of abrasive grains 102. The container 18 is open at the bottom (in a downward direction 30), with the opening being covered by means of a sieve 20. Abrasive grains 102 supplied by the vessel 18 can thus get out of the vessel 18 only through the sieve 20, and leave the sieve 20 in the direction of passage 22. The sieve 20 has a mesh opening which is about four times the average diameter of the abrasive grains. In one working example, abrasive grains of the FEPA type #2000, having an average diameter of about 10 microns, are sprinkled onto the substrate, with the sieve 20 having a mesh opening of about 42 microns.
[0032] The sieve 20 is subjected from below to gas pressure pulses 26, i.e. to a pulsed gas stream, using at least one gas pressure nozzle 24. In particular, the gas pressure pulses 26 are directed in the form of pulsed air pressure pulses against the sieve 20 from below in a direction essentially opposite to the direction of passage 22. The gas pressure nozzle 24 is oriented at an angle of 45° relative to the plane of the sieve 20, so that the gas pressure pulses 26 are directed against the sieve 20 with a grazing incidence relative to the sieve 20. The gas pressure pulses 26 are produced at a frequency of 30 Hz with an average duration of 5 milliseconds and with a pressure of 7 bar and directed against the sieve 20.
[0033] The at least partially agglomerated abrasive grains 102 which are provided in the vessel 18 and are present directly on the sieve 20 are deagglomerated by the gas pressure pulses 26. This forms an abrasive grain cloud 28 which exits from the sieve 20 in the direction of passage 22 and is subsequently sprinkled on the abrasive article substrate web 14.
[0034] In FIG. 1, sprinkling of the deagglomerated abrasive grains 102 is effected electrostatically. Here, the sieve 20 is made of metal and is operated as high-voltage electrode during electrostatic sprinkling. Behind, viewed from the sieve 20, the abrasive article substrate web 14, there is a counterelectrode 36 in the direction of which the abrasive grains 102 are accelerated in the electric field and are thus accelerated against the abrasive article substrate web 14. Electrostatic sprinkling is known to a person skilled in the art. The advantage of arranging the abrasive article substrate web 14 at the side of the vessel 18 is that it reduces the probability of agglomerates of abrasive grains 102 reformed after deagglomeration, for example as a result of collisions between abrasive grains 102, subsequently being sprinkled onto the abrasive article substrate web 14, since these drop down before reaching the abrasive article substrate web 14 because of their greater weight. A collection pan for agglomerates 106 which fall down can optionally be provided under the vessel 18.
[0035] In FIG. 2, sprinkling of the deagglomerated abrasive grains 102 occurs gravimetrically. The abrasive grains 102 are accelerated from the abrasive grain cloud 28 essentially in the downward direction 30 under the action of gravity due to their intrinsic weight and are thus accelerated against the abrasive article substrate web 14 which is conveyed horizontally underneath. Gravimetric sprinkling is known to a person skilled in the art.
[0036] FIG. 3 depicts a further alternative working example in which the deagglomerated abrasive grains 102 firstly trickle gravimetrically onto an inclined plane 32 on which they likewise slide under the action of gravity. The inclined plane 32 is made of metal and is operated as a high-voltage electrode so that the abrasive grains 102 become electrostatically charged as they move over the inclined plane 32. The electrostatic charging results in the abrasive grains 102 being repelled by one another and thus becoming distributed uniformly spaced over the inclined plane 32, especially in the direction of their sliding movement and also in the lateral direction (i.e. in the direction into the plane of the image, cf. direction of the width 34). When the abrasive grains 102 have arrived at the end of the inclined plane 32, they are electrostatically sprinkled onto the abrasive article substrate web 14 which, in a manner similar to FIG. 1, is oriented vertically and is moved along the inclined plane 32. The uniform distribution of the abrasive grains 102 using the inclined plane 32 operated as high-voltage electrode has an advantageous effect on the uniform arrangement of the sprinkled abrasive grains 102 on the abrasive article.
[0037] Furthermore, it can be seen in FIG. 3 that the abrasive grains 102 are provided by the sieve 20 over the entire width 34 of the abrasive article substrate web 14, with gas pressure pulses 26 being directed against the sieve 20 by means of a plurality of gas pressure nozzles 24. In this way, the abrasive article substrate web 14 can be sprinkled with abrasive grains 102 over the entire width 34. It may be pointed out that the use of a plurality of gas pressure nozzles 24 to produce gas pressure pulses 26 can likewise be realized in the arrangements of FIGS. 1 and 2.
[0038] FIG. 4a shows a schematic plan view onto an abrasive article 200 which has been produced by a process of the prior art. Difficulties are typically encountered here, since the abrasive grains 202 are agglomerated or “clumped” and are accordingly likewise sprinkled in the form of clumped agglomerates 206 onto the abrasive article substrate 204 in an electrostatic or gravimetric sprinkling process. Irregularly applied, clumped abrasive grain agglomerates 206 are formed on the surface of the abrasive article substrate 204. In order for the abrasive grain agglomerates 206 not to produce scratch marks on the surface of the abrasive article substrate 204 in a later grinding process, the abrasive grain agglomerates 206 subsequently have to be blown off, knocked off, brushed off or washed off, and excess abrasive grains 202 become distributed over the free areas 210 between the abrasive grain agglomerates 206 so as to clog the entire surface area of the abrasive article 200 produced (not shown in more detail here). For this reason, an abrasive article 200 having a surface closed by abrasive grains 202 is typically formed in processes of the prior art.
[0039] The process of the invention, on the other hand, makes it possible firstly to deagglomerate abrasive grain powders which have become clumped and agglomerated by attractive forces between individual abrasive grains 102 into individual abrasive grains 102 and then subsequently to sprinkle the deagglomerated abrasive grains 102. This makes it possible to produce an open surface of the abrasive article 100, in which the abrasive grains 102 are distributed uniformly and with a spacing on the surface of the abrasive article 100. FIG. 4b shows a schematic plan view onto an abrasive article 100 which has been produced in this way. It can be seen that the abrasive grains 102 are uniformly distributed over the surface of the abrasive article substrate 104, in particular over the surface of the abrasive article substrate web 14. Free areas 110 between neighboring abrasive grains 102 are likewise present and are relatively uniform.
[0040] FIG. 5 finally shows a section of an illustrative embodiment of an abrasive article 100 according to the invention with abrasive grains 102 in a schematic sectional view. In the embodiment depicted, the abrasive article 100 is a coated abrasive article 100 having an abrasive article substrate 104. The abrasive article substrate 104 serves as flexible substrate for the abrasive grains 102. The abrasive grains 102 are fastened by means of a binder 112, in particular a base binder 114, which is, for example, in the form of phenolic resin, onto the abrasive article substrate 104. The layer of base binder 114 and abrasive grains 102 is additionally coated with a covering binder 116, in particular likewise composed of phenolic resin. The abrasive grains 102 have been sprinkled on using the process of the invention. This results in regular free areas 110 between neighboring abrasive grains 102 and thus an open surface of the abrasive article 100.
