DE102020209521A1 - Method of making a structured abrasive article and abrasive article - Google Patents

Abstract

The invention relates to a method for producing an abrasive article (10) with structured abrasive areas (22). According to the invention, the method comprises the steps of providing an abrasive article backing (14), coating the abrasive article backing (14) with a binder (16), spatially resolved activation or deactivation of the binder (16) and sprinkling the abrasive article backing (14) with abrasive grains (12). a correspondingly manufactured abrasive article (10) is proposed.

Description

The invention relates to a method of making an abrasive article having structured abrasive areas. The invention also relates to a corresponding abrasive article.

State of the art

Methods for manufacturing abrasive articles having structured abrasive areas are already known. Typically, a binder is already applied to an abrasive article backing in a structured manner in such a way that it defines structured grinding areas. If abrasive grains are then scattered all over the backing of the abrasive article, the abrasive grains will only adhere to those places on the backing of the abrasive article that were previously coated with binder. Stamps, stamp rollers or roll-to-roll processes such as relief printing or gravure printing processes are used in particular for the structured application of the binder.

Another known method for structuring grinding areas is the use of abrasive article backings already structured with elevations and/or depressions. The abrasive article backing is coated with binder at the elevations using a roller.

Disclosure of Invention

A method of making an abrasive article having structured abrasive areas is proposed. According to the invention, the method comprises the steps of providing an abrasive article backing, coating the abrasive article backing with a binder, in particular a base binder, locally resolved activation or deactivation of the binder and sprinkling the abrasive article backing with abrasive grains.

An "abrasive article" is used for grinding or abrasive processing of a workpiece, in which material from the workpiece is mechanically removed from the surface of the workpiece in the form of chips. In particular, the abrasive article is a coated abrasive article or a composite abrasive article comprising foam and a facestock or a foam abrasive article. Furthermore, in principle, alternative grinding articles are also conceivable, such as bonded grinding articles, which in particular are typically synthetic resin-bonded cutting and grinding wheels. In one embodiment, the abrasive article is implemented as sandpaper.

The abrasive article comprises an abrasive article backing, in particular a flexible one, with at least one layer. The abrasive article backing, which is particularly flexible, gives the abrasive article specific properties in terms of adhesion, elongation, tear and tensile strength, flexibility and stability. The backing for the abrasive article can include, in particular, paper, cardboard, vulcanized fiber, foam, a plastic, a textile structure, in particular a woven fabric, knitted fabric, knitted fabric, mesh, fleece, or a combination of these materials, in particular paper and fabric, in one or more layers.

"Structured grinding areas" are areas on the surface of the abrasive article that are provided with abrasive grains, whereby these areas differ from a full-surface design - as is usually realized in the prior art - and are "structured" in this sense. A structured abrasive area is therefore distinguished from an abrasive grain-free area on the surface of the abrasive article (ignoring apertures, as these are not part of the surface of the abrasive article). In particular, the structured grinding areas that can be generated in a controlled (and in particular also reproducible) manner - especially in combination with the areas not provided with abrasive grains (omitted or free of abrasive grain) - can be viewed as a controlled (and in particular also reproducible) pattern on the surface of an abrasive article. The areas of the abrasive article that are not provided with abrasive grains have no abrasive effect when the abrasive article is used during a grinding operation.

In one embodiment of the method, a continuously changing pattern of textured abrasive areas is applied to the abrasive article. According to the invention, disadvantages of the prior art can be overcome in this way. In known methods of the prior art, a pattern of structured areas applied to abrasive articles is always uniform, since changing the pattern requires an exchange of an applicator roller, a die or a stamp and the respective template for each pattern has to be produced separately. Consequently, these known methods of the prior art also do not allow continuously changing patterns of the structured areas. The proposed invention, on the other hand, makes it possible to produce continuously changing patterns of the sanding areas without making templates or negatives for the pattern—similar to a conventional printer as is known from the office. In this way, rapidly changing patterns or "grain patterns" can be applied to the abrasive article backing and thus to the abrasive article surface be generated. Such patterns can in particular be images such as manufacturer logos or the like. As an alternative or in addition, the patterns can specifically implement abrasive grain-free areas that serve to advantageously remove abrasive dust generated during a grinding process. The abrasive article can also be structured so that the abrasive article can be easily folded in areas free of abrasive grain.

In one embodiment of the method, the structured abrasive areas encode information, in particular information relating to the abrasive article. Such information may, for example, relate to the manufacturer (e.g. in the form of a logo, a name), a grit of the abrasive article, a material of the abrasive article, a serial number of the abrasive article, or the like. It should be noted that the encoded information can also be applied to different areas of the abrasive article backing in a continuously altered manner by the method according to the invention. For example, in the case of an implementation of the method according to the invention implemented as a roll-to-roll method, running meters of the web of abrasive articles can be provided with a running indication of meters. It is also conceivable to produce consecutively numbered abrasive article blanks on the web of abrasive articles, depending on the position, which result in individual, consecutively numbered abrasive articles after the web of abrasive articles has been manufactured. It is also conceivable to deliberately release areas that will later be cut out by punching or laser cutting, so that no abrasive grains bind here.

In one process step, the abrasive article backing is coated with a binder. In a coated abrasive article, abrasive grits are generally held in place on the abrasive article backing by a bonding agent (often referred to as a make coat). With the binder, the abrasive grains are at least prefixed, in particular fixed, in a desired position and/or distribution on the abrasive backing. The binder may be applied to the surface of the abrasive article backing by means of a knife, roller, imprint, brush, or the like. In one embodiment of the method, the binder is a hardening plastic, in particular a non-crosslinked thermoplastic, for example a thermoplastic polyurethane, or a free-radically crosslinkable resin. Such a binder allows a particularly simple realization of the process step of locally resolved activation or deactivation of the binder.

In one embodiment of the method, the binder has a viscosity greater than 10,000 mPa.s, in particular greater than 40,000 mPa.s, very particularly greater than 70,000 mPa.s at 100.degree. Binders with a high viscosity can be used with the proposed method. This effectively prevents abrasive grains from tipping over during a scattering process. It is also possible to combine the method according to the invention with an electrostatic scattering method for applying the abrasive grains to the coated abrasive article backing in order to achieve an orientation of the abrasive grains which is predominantly orthogonal to the web of abrasive articles.

By "activating the binder" is meant that the binder applied to the abrasive article backing - typically a more or less solid, non-wetting and therefore not particularly adhesive layer - is modified in such a way that it has its wetting or adhesive properties, i.e. a adhesive effect, unfolds. Consequently, in this embodiment, the binder initially does not exhibit (extraordinarily) adhesive properties when coated onto the abrasive article backing. When the binder is activated, a property that binds the abrasive grains is first created, by means of which the abrasive grains can be fixed mechanically. The activation goes well beyond the state of a slightly adhesive property of the binder (comparable to a post-it glue), which can cause, for example, a temporary, not particularly stable adhesion of dust (or abrasive grains). “No (particularly) adhesive properties” is to be understood, for example, as the mentioned slightly adhesive property of the binder in the non-activated state.

By "deactivating the binder" is meant that the binder applied to the abrasive article backing is modified in such a way that it substantially loses its binding or adhesive properties, i.e., an adhesive effect. Consequently, in this embodiment, the binder initially exhibits tacky and optionally wetting properties upon coating the abrasive article backing. With the deactivation of the binder, the binder is modified in such a way that it cannot bind abrasive grains and thus fix them on the abrasive article backing. As a result, the binder cannot form a mechanical bond with the abrasive grains. “Substantially” means that the deactivated binder can still retain slightly adhesive properties (comparable to a post-it), which, however, can only cause dust (or abrasive grains) to adhere temporarily and not particularly stable.

It should be noted that the process steps of activating or deactivating the binder and sprinkling with abrasive grains can in principle be carried out in any order. However, sprinkling is preferably carried out after activation or deactivation.

"Locally resolved" means that the binder applied - for example over the entire surface - to the abrasive article backing can be activated or deactivated in any way at different points, with correspondingly binding (adhesive) or non-binding (non-adhesive) areas being produced on the coated abrasive article backing will. If these areas on the abrasive article backing are then sprinkled with abrasive grits, abrasive grits will only adhere to the tacky areas, while they will not bond to non-tacky areas. The structured grinding areas according to the invention can be realized in this way. The spatial resolution therefore relates to an at least two-dimensional position on the abrasive article backing.

In one embodiment of the method, the binder is activated in a locally resolved manner by irradiation with light, in particular with laser light or UV light. For example, it is conceivable to illuminate a binder made of non-crosslinked thermoplastic material, in particular thermoplastic polyurethane, in a targeted, spatially resolved manner by means of laser light and consequently to heat it locally and activate it in this way. Alternatively or additionally, in this exemplary embodiment, it can be a binder based on polyethylene, polystyrene, polypropylene, ethylene-vinyl acetate copolymer or the like. UV light activation can take place, for example, by spatially resolved exposure of the applied binder if the binder is selected as a UV light-curable binder, for example a free-radically crosslinkable resin. It should be mentioned that activation can be achieved in principle by chemically activating and/or by heating, in particular by melting or softening, the binder.

In one embodiment of the method, the activation is carried out immediately after the coating step, so that residual heat of the abrasive article, in particular of the binder coated thereon, is utilized. As a result, the energy input required to activate the binding agent (i.e. to be irradiated) can be lower, so that energy is saved.

In an alternative or additional embodiment of the method, the binder is deactivated in a locally resolved manner by irradiation with light, in particular with laser light or UV light. A plastic that hardens at elevated temperature can, for example, be illuminated in a targeted, spatially resolved manner using laser light, and thus heated and hardened so that its binding properties are destroyed and it can no longer be used as a binding agent. Furthermore, the binder can also be thermally destroyed and deactivated in this way. UV light deactivation can take place, for example, by spatially resolved exposure of the applied binder if the binder is selected as a UV light-curable binder, for example a free-radically crosslinkable resin. The binder is already hardened at the points where UV light is irradiated for deactivation, so that it loses its sticky properties. In principle, deactivation can be achieved by burning it away, i.e. destroying it, or by curing the binder.

Activation or deactivation by means of light is a particularly efficient way of activating or deactivating the binder in a highly spatially resolved manner. A spatially resolved exposure of the binder by means of directed light can be implemented, for example, using an x-y laser scanner, as is known, for example, from applications such as laser printing, lidar, etc. Alternatively, a DLP chip (known from applications such as light projectors) or a shading mask can be used to achieve spatially resolved light irradiation. A solid-state laser or a CO2 laser, for example, or the use of infrared laser diodes is suitable as a laser.

In one embodiment of the method, the abrasive article is also finished by irradiating the light and/or a hole pattern is produced in the abrasive article. In this way, the components required to produce the abrasive article, in particular a light source for activating or deactivating and for assembling or perforating the abrasive article, can be reduced. No additional equipment is required to shape the abrasive article into its target shape, such as a grinding wheel containing holes.

In an alternative or additional embodiment of the method, the binder is locally activated by applying a liquid agent, in particular a coolant or a reactant. For example, it is conceivable to wet or print the binder in inkjet printing using a reactive component in such a spatially resolved manner that the combination of the binder with the reactive component brings about the binding properties of the binder. A binder based on polyol can be printed with an isocyanate solution and thus crosslinked and exhibit a tacky property at the printed areas. The areas not activated with isocyanate, on the other hand, do not develop any sticky properties. If the abrasive article backing prepared in this way is then sprinkled with abrasive grains, these only adhere to the areas of the abrasive article backing previously activated with the liquid agent, which consequently represent the structured grinding areas.

In an alternative or additional embodiment of the method, the binder is deactivated locally by applying a liquid agent, in particular a coolant or a reactant. An embodiment of this embodiment may be provided, for example, by cooling a thermally activated binder (e.g., thermoplastic polyurethane) applied to the abrasive article backing as a result of application of a cooling liquid. In this way, a binder that has already been melted is consequently cooled in a locally resolved manner and consequently artificially solidified and thus deactivated. In one embodiment of the method, the liquid agent comprises water and/or a wetting agent and/or an anti-adhesive agent, in particular stearate, and/or a solvent, in particular glycol, and/or a polymer which hardens rapidly when heated. Each of these liquid agents represents a particularly suitable agent. In particular, a wetting agent and/or an anti-stick agent are advantageously suitable since these substances are often subsequently applied to the abrasive article in order to achieve further advantageous effects. A heat-curable polymer can be specified, for example, in the form of a dissolved adhesive such as epoxy resin, the adhesive drying and thereby hardening as a result of evaporation of the solvent.

In one embodiment of the method, the liquid agent is applied in a spatially resolved manner using an inkjet printing method or by means of at least one directional spray nozzle. In principle, any inkjet printing process that is compatible with the liquid used, for example water, is suitable for this. A so-called "long-distance inkjet printing process" is also conceivable, in which the liquid agent can be printed over a comparatively large distance of a few centimeters. Any pattern or image of the liquid agent, such as water, can be printed onto the make coated abrasive article backing using an ink jet printing process.

For example, it is conceivable to coat a foam block as a backing for abrasive articles with a hot-melt binder, with any pattern (or image) then being “printed” with water onto the foam block using an inkjet printing process. The water evaporates on the still hot hotmelt binder surface (e.g. at 220 °C), with the hotmelt binder cooling below the melting point at the printed areas and allowing it to solidify locally. Abrasive grains can then be sprinkled on, with abrasive grains adhering to the areas that are still melted, while they do not adhere to the areas of the foam block surface that have been previously imprinted with water and are therefore already solidified. The abrasive grain still adhering to the non-adhesive areas due to surface effects is then removed again by blowing away. The surface structured with grinding areas remains on the abrasive article backing.

In one embodiment of the method, the method is implemented as a roll-to-roll method, the activation or deactivation step being carried out after, in particular immediately after, the coating step. In this way, the method according to the invention can be integrated into an existing process chain of the manufacturing method and a corresponding process landscape, for example in an existing production plant, without the need for additional, particularly complex machines or restructuring in the process chain and/or process landscape. “Immediately after” is to be understood as meaning that no further process or processing steps are carried out between the coating step and the activation or deactivation step.

In one embodiment of the method, the abrasive grains are scattered onto the abrasive backing by means of electrostatic scattering. The abrasive grains adhere to the activated or non-deactivated areas, the structured abrasive areas according to the invention being formed. In one embodiment of the method, the abrasive grains that are not bonded to the abrasive article backing by means of a binder are removed mechanically after the binder has been spread and cured, for example by brushing off, shaking off, blowing away or vacuuming away. In this way, excess abrasive grain can be recycled, which is particularly advantageous in the case of expensive abrasive grains such as diamond, ceramic or tungsten carbide.

It should be noted that, in addition to the binder, a further so-called top binder can be used as a base binder, which is applied in particular in layers over the abrasive grains fixed to the abrasive backing by means of the base binder. The top binder connects the abrasive grains firmly to each other and firmly with the abrasive pad. The person skilled in the art is in principle familiar with suitable top coats from the prior art. Furthermore, the abrasive article can be further processed conventionally after the scattering process, for example by applying stearate, making it up or the like.

The invention also relates to an abrasive article made by the method of the invention.

character list

The invention is explained in more detail in the following description on the basis of exemplary embodiments illustrated in the drawings. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into further meaningful combinations. The same reference symbols in the figures designate the same elements.

• 1 eine schematische Schnittdarstellung eines erfindungsgemäßen Schleifartikels mit Schleifkörnern;
• 2 eine Aufsicht auf ein Ausführungsbeispiel eines erfindungsgemäßen Schleifartikels;
• 3 ein Verfahrensdiagramm zur Darstellung des erfindungsgemäßen Verfahrens zur Herstellung eines Schleifartikels;
• 4 einen beispielhaften Fertigungsaufbau zur Durchführung des erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic sectional representation of an abrasive article according to the invention with abrasive grains;
• 2 a top view of an embodiment of an abrasive article according to the invention;
• 3 Figure 12 is a process diagram showing the method of making an abrasive article of the present invention;
• 4 an exemplary production setup for carrying out the method according to the invention.

1 shows a detail of an exemplary embodiment of an abrasive article 10 according to the invention with abrasive grains 12 in a schematic sectional view. The abrasive article 10 in the illustrated embodiment is a coated abrasive article 10 having an abrasive article backing 14 made of paper. The abrasive article backing 14 made of paper serves as a flexible substrate for the abrasive grains 12. The abrasive grains 12 are attached to the abrasive article backing 14 by means of a binding agent 16, in particular a base binder 18, which is implemented here as thermoplastic polyurethane (TPU), for example. The layer of base binder 18 and abrasive grains 12 is additionally coated with a top binder 20, in particular made of phenolic resin. Abrasive article 10 includes structured abrasive areas 22 separated by areas 24 that do not include abrasive grains.

2 shows a plan view of an abrasive article 10 according to the invention, as produced by the method according to the invention (cf. 3 ) to produce an abrasive article 10 having structured abrasive areas 22 . As already to 1 As discussed above, abrasive article 10 includes structured abrasive areas 22 separated by areas 24 that do not include abrasive grits 12 . The structured abrasive areas 22 reproduce—in combination with the abrasive grain-free areas 24—a pattern 26 or image. The structured abrasive areas 22 in combination with the abrasive grain-free areas 24 also encode information about the abrasive article 10, shown as the company logo (“Sia Abrasives” above) and the grit (“80” below) of the abrasive article 10. Encode in this sense the structured abrasive areas 22 - or, analogously, the abrasive grain-free areas 24 - information about the abrasive article 10.

In 3 1 is a process diagram illustrating one embodiment of the method 100 of the present invention for making an abrasive article 10 having structured abrasive regions 22. FIG. 4 FIG. 12 shows a production structure 30 that matches this. In a first method step 102, an abrasive article backing 14 is provided. in the in 4 In the exemplary roll-to-roll method illustrated, this is realized by unwinding and threading a web of paper material 32 into the production structure 30 so that the web of paper material 32 runs over the deflection rollers 40 . In process step 104, the abrasive article backing 14 is coated with a binder 16, here chosen to be a thermoplastic polyurethane binder. The binder 16 is applied to the web of paper goods 32 as the abrasive article backing 14 by means of a doctor blade 34 . In method step 106, the previously applied binding agent 16 is immediately chemically activated in a spatially resolved manner, here by irradiation with light 36. In 4 the light 36 is generated as laser light by a laser 38 . In method step 108, the abrasive article 10 is also finished using the light 36 - here laser radiation - by irradiation with the light 36 (ie in circular discs as in 2 shown cut) and a hole pattern 28 is created in the abrasive article 10. However, the abrasive article 10 that has been cut out initially remains in the paper web 32 (for example, because the abrasive article 10 was not cut out all around, but instead a few thin backing webs holding the abrasive article 10 remained).

Finally, in method step 110, abrasive article backing 14 is sprinkled electrostatically with abrasive grains 12 (by generating an electric field between two electrodes 42) and cured (not shown in detail here).

Instead of activating a binding agent 16 with light 36, it is alternatively conceivable to deactivate an already liquid and adhesive binding agent 16 in a spatially resolved manner by applying a liquid agent, for example water. It is conceivable to use the laser 38 in 4 to be replaced by an inkjet printhead (not shown separately here), by means of which the liquid agent--here water--is applied to the abrasive article base 14 coated with binder 16 in an inkjet printing process.

Claims (11)

A method of making an abrasive article (10) having structured abrasive areas (22) comprising the steps of the method - providing an abrasive article pad (14), - coating the abrasive article backing (14) with a binder (16), - spatially resolved activation or deactivation of the binding agent (16), - Sprinkle the grinding article support (14) with abrasive grains (12). procedure after claim 1 , wherein the binder (16) is locally activated or deactivated by irradiation with light (36), in particular laser light or UV light. Method according to one of the preceding claims, in which the binding agent (16) is locally activated or deactivated by applying a liquid agent, in particular a coolant or a reactant. procedure after claim 3 wherein the liquid agent comprises water and/or a wetting agent and/or an anti-stick agent, in particular stearate, and/or a solvent, in particular glycol, and/or a heat-curing polymer. Procedure according to one of claims 3 - 4 , The liquid agent being applied in a spatially resolved manner using an inkjet printing process or by means of at least one directional spray nozzle. Method according to one of the preceding claims, in which the structured grinding areas (22) encode information. Method according to one of the preceding claims, in which the binder (16) is a hardening plastic, e.g. Method according to one of the preceding claims, wherein the method is implemented as a roll-to-roll method, the activation or deactivation step being carried out after, in particular immediately after, the coating step. procedure after claim 2 , wherein the abrasive article (10) is made up by means of irradiation of the light (36) and/or a hole pattern (28) is produced in the abrasive article (10). Method according to one of the preceding claims, wherein the abrasive article backing (14) comprises paper, cardboard, foam, vulcanized fiber, plastic, a textile structure, in particular a woven fabric, knitted fabric, crocheted fabric, mesh, fleece, or a combination of these materials. Abrasive article (10) made by a method of the preceding claims.

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