Flexible grinding product with flattened surface and method for manufacturing the same

Abstract

A method of manufacturing a flexible grinding product comprises the steps: a) preparing an open cloth of knitted or woven fabric; b) applying a coating to one surface of the cloth, wherein the coated surface of the cloth has one or more flat portions; c) applying a grinding agent to the coated surface of the cloth. Further, a flexible grinding product has an open cloth, wherein a surface of the cloth is provided with a coating such that the coated surface has one or more flat areas which are at least partially provided with a grinding agent.

Claims

1. A method of manufacturing a flexible grinding product, the method comprising the following steps: a) preparing an open cloth of knitted or woven fabric, the cloth having an open structure; b) applying a coating to one surface of the cloth, wherein the coating is applied discontinuously in a shape of separated small islands, wherein the coated surface of the cloth has one or more flat plateaus, and the coated cloth maintains the open structure after applying the coating to facilitate removing grinding dust through the coated cloth during use of the grinding product; c) applying a grinding agent to the coated surface of the cloth after step b), wherein step b) includes: b1) applying the coating to one surface of the cloth; b2) flattening the coated surface to produce the one or more flat plateaus before applying the grinding agent to the coated surface of the cloth in step c).

2. The method according to claim 1, wherein step b2) includes flattening the coated surface by pressing the surface against a working surface of a smoothing element.

3. The method according to claim 2, characterized in that the working surface of the smoothing element is provided with a structural pattern for producing a pattern of plateaus in the coated surface.

4. The method according to claim 1, characterized in that the coating is cured after step b), with UV-radiation or heat.

5. The method according to claim 1, characterized in that, step b) comprises sanding the coated surface to produce the one or more flat plateaus.

6. The method according to claim 1, characterized in that the cloth is impregnated between steps a) and b).

7. The method according to claim 1, characterized in that the cloth is provided with projecting loops and/or threads situated on an opposite surface of the surface to be coated, the loops and/or threads originating from threads of the cloth, wherein the coating is applied and cured such that the projecting loops and/or threads are substantially free of the coating.

8. The method according to claim 1, characterized in that the coating includes a polymer.

9. The method according to claim 2, characterized in that the smoothing element is a smoothing drum.

10. The method according to claim 1, characterized in that the grinding agent is a slurry deposited into sanding formations on the flat portions of the cloth.

11. The method according to claim 1, characterized in that the flexible grinding product is laminated with a foam onto a respective surface of a grinding tool.

12. The method according to claim 1, characterized in that the flexible grinding product is laminated with a velour onto a respective surface of a grinding tool.

13. A flexible grinding product made according to the method of claim 1, the flexible grinding product having an open cloth, wherein a surface of the cloth is provided with a coating such that the coated surface has one or more flat plateaus which have been obtained by flattening the coated surface and which are at least partially provided with a grinding agent after flattening the coated surface, the cloth having an open structure and maintaining the open structure after applying the coating.

14. The flexible grinding product according to claim 13, characterized in that the coated surface of the cloth has a pattern of grooves or an engraved structure including protruding flat plateaus.

15. The flexible grinding product according to claim 13, characterized in that the coated surface is sanded for producing the one or more flat plateaus.

16. The flexible grinding product according to claim 13, characterized in that the cloth is impregnated.

17. The flexible grinding product according to claim 13, characterized in that the cloth is provided with projecting loops and/or threads situated on an opposite surface of the surface to be coated, the projecting loops and/or threads originating from threads of the cloth, wherein the projecting loops and/or threads are substantially free of the coating.

18. The flexible grinding product according to claim 13, characterized in that the grinding agent is a slurry that is deposited as sanding formations on the flattened surfaces of the cloth.

19. The flexible grinding product according to claim 13, characterized in that the flexible grinding product is laminated with a foam onto a respective surface of a grinding tool.

20. The flexible grinding product according to claim 13, characterized in that the flexible grinding product is laminated with a velour onto a respective surface of a grinding tool.

21. A method of manufacturing a flexible grinding product, the method comprising the following steps: a) preparing an open cloth of knitted or woven fabric, the cloth having an open structure; b) applying a coating to one surface of the cloth, wherein the coated surface of the cloth has one or more flat plateaus, wherein 1) the coating is applied to the one surface of the cloth, the coated cloth maintaining the open structure after applying the coating, the coating being applied discontinuously in shapes of separated small islands; and 2) the coated surface is flattened by pressing the surface against a working surface of a smoothing element to produce the one or more flat plateaus, the working surface of the smoothing element having a structural pattern for producing a pattern of plateaus in the coated surface; and c) applying a grinding agent to the coated surface of the cloth after flattening the coated surface.

22. A method of manufacturing a flexible grinding product, the method comprising the following steps: a) preparing an open cloth of knitted or woven fabric, the clothing having an open structure; b) applying a coating to one surface of the cloth, wherein the coated surface of the cloth has one or more flat plateaus, wherein 1) the coating is applied to the one surface of the cloth, the coated cloth maintaining the open structure after applying the coating, the coating being applied discontinuously in shapes of separated small islands; and 2) the coated surface is sanded for producing the one or more flat plateaus; and c) applying a grinding agent to the coated surface of the cloth after producing the one or more flat plateaus.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a plan view of a cloth of knitted fabric.

(2) FIG. 2 is a plan view of the cloth according to FIG. 1, which has been coated and flattened.

(3) FIG. 3 is a plan view of a knitted fabric different to the fabric shown in FIG. 1.

(4) FIG. 4 is a plan view of the fabric shown in FIG. 3, which has been coated and flattened.

(5) FIGS. 5A to 5H show cross sections of exemplary raw, coated and modified threads of a cloth.

(6) FIG. 6 is a plan view of an impregnated, coated and sanded cloth.

(7) FIG. 7 shows the cross section through line C-C in FIG. 6.

(8) FIGS. 8A to 8D show cross sections through line D-D of FIG. 6.

(9) FIGS. 9 to 15 schematically illustrate tools and processes for coating and flattening a cloth of fabric.

(10) FIG. 16 shows a cross section of a grinding product including loops on the surface opposite to the grinding surface.

PREFERRED EMBODIMENT

(11) FIG. 1 is a plan view of a warp-knitted jersey according to ISO 8388 3.5.1. The fabric can be used as the basis for producing a flexible grinding product.

(12) The cloth is provided with a coating and it is flattened such that a sine-type plateau-structure 100 is generated as shown in FIG. 2.

(13) FIGS. 9 and 10 schematically illustrate a tool and process for applying a coating to the grinding surface of the cloth and for flattening the surface. FIG. 9 shows a processing line having a number of drums 10, 20, 21, 30, 31, some of them are optional, for transporting and processing a flexible grinding product and one or more UV-radiation sources 40. Drum 30 is for unwinding the pre-processed flexible grinding product, and drum 31 is for winding the prepared product.

(14) Smoothing drum 10 is illustrated in FIG. 10 in more detail. The smoothing drum 10 is arranged such that it gets into contact with a piece or sheet of cloth C such as illustrated in FIGS. 1 and 3. Press plates 11 press the cloth C against a working surface of the smoothing drum 10. Application of the coating is for instance performed either via the smoothing drum 10 itself or, as illustrated in FIG. 9, via a coating drum 20 which is directly or indirectly in contact with a reservoir of coating agent 22. In FIG. 9, coating drum 20 is in contact with another drum 21 dipped into the reservoir coating agent 22. Transporting drums 30, 31 and/or other devices for transporting the sheet of cloth C are provided as required.

(15) The smoothing drum 10 serves for flattening the coated cloth C. The result is a coated but still open cloth C having flat portions as for instance illustrated in FIGS. 2 and 4.

(16) Thereafter or at the time of pressing the cloth C against the working surface of the smoothing drum 10, the coating is cured via UV-radiation originating from the UV-light source 40. Optionally, a second UV-light source 41 can be provided, or more, in case curing in more than one stages is required or desired. Depending on the coating agent, curing via heat or cooling is as well conceivable. It is as well possible to place one or more UV-light sources on the smoothed side of the cloth.

(17) In order to achieve a zig-zag-pattern or sine-pattern as shown in FIG. 2, the smoothing drum 10 or optionally drum 20 or one or more additional drums may be provided with a structured pattern. The surface of the cloth is pressed against the working surface of the drum with a desired surface structure, thereby generating a regular or irregular structure of plateaus or islands of flat surfaces.

(18) Alternative tools and processes for applying a coating to the grinding surface of the cloth and for flattening the surface are shown in FIGS. 11 to 15.

(19) FIG. 11 shows a process with a drying- or pre cure unite 50 used for resins that are water- or solvent based. Alternatively, unite 50 may be an pre cure unite when the smoothing and resin need to be pre cured or thickened before the smoothing.

(20) FIG. 12 shows a process where a heat set, water or solvent based resin is used for the smoothing. Drum 10 is heated and the coated cloth and its surface is heat set against the surface of the drum having the desired pattern or smoothness.

(21) FIG. 13 shows a process including a curing unit 60 which is located between smoothing drum 10 and drum 31 for winding the flexible grinding product.

(22) For simplicity, FIG. 14 illustrates a sub-process concentrating on an optional sanding process which can be included in one or more of the above described processes. Unwinding and winding rollers 130 and 131 are optional and may be omitted when incorporating the sanding process in one of the above described processes. Support rollers 132 to 135 serve for adjusting the flexible grinding product relative to the sanding unit which includes a sanding belt 139, an idle roller 138, a drive roller 136 and a pressure roller 137. For instance, two 134 and 135 of the support rollers may be movable as illustrated in order to adjust the angle of enlacement of the grinding product C. Other rollers may as well be movable, for instance for adjusting the enlacement pressure. As an example, the described grinding process may be included immediately after the curing unit illustrated in FIG. 13.

(23) For simplicity, FIG. 15 illustrates a sub-process concentrating on a possible mineral coating process which may fully or partially be included in one or more of the above described processes. Unwinding and winding rollers 230 and 231 are optional and may be omitted when incorporating the mineral coating process in one of the above described processes. FIG. 15 schematically illustrates a kiss roller coating unit 131 for make coat, an electrostatic mineral coating unit 132, a first drying or curing chamber 233, another kiss roller coating unit 134 for size coat and a second drying or curing chamber 235.

(24) In another example, the basic cloth is based on a warp-knitted mesh fabric according to ISO 8388 3.5.46 as shown in FIG. 3. In FIG. 4, the open cloth is regularly flattened. The plateaus follow the shape of the filet openings of the cloth.

(25) FIG. 5A shows a cross section of a loop bundle in a wale included in the cloth, such as a wale bundle or a double warp thread. In FIG. 5B, the thread is provided with a coating 102 partially or completely filling the thread. In FIG. 5C, the thread is filled and overcoated with coating agent 102, thereby supporting manipulation of the shape of the thread in view of generating flattened portions. Reference sign 102 denotes the overcoated portion of the coating 102. For example, the overcoated portions 102 are flattened or smoothed in FIGS. 5D, 5E and 5F. Wherein in FIG. 5D the flattened portion is narrowed, a flattened and broadened example is shown in FIG. 5E. A smoothed and sanded coated thread is shown in FIG. 5F. Overcoating of the thread is not necessarily required for flattening. Instead, the filled thread as shown in FIG. 5B may as well be flattened via a smoothing drum or sanded as shown in FIGS. 5G and 5H. The small and big circles in the illustrated loop bundles schematically indicate that it is possible to have fibers of different cross section. As an example, four monofilaments of larger cross section are included, which can be used to form projecting loops and/or threads situated on the surface opposite to the grinding surface. The projecting loops and/or threads may serve as fastening means for mounting and holding the grinding product to a grinding tool. The loops and/or threads may serve as one part of a hook-and-loop fastener.

(26) An embodiment illustrating the above mentioned projecting loops is shown in FIG. 16. Here, the flexible grinding product has loops 105 on the surface opposite to the grinding surface carrying the coating 102 and the plateaus 100. The grinding product and a supporting surface of a grinding tool, which is not shown, are attached to each other by means of the loops 105 and corresponding means of the supporting surface, such as hooks. The loops and/or hooks provide for a distance between the grinding product and the supporting surface of the tool. Grinding dust which is first transported through the open areas/meshes of the cloth is, thus, easily removed from the grinding product via the open attachment structure utilizing loops 105. Alternatively or additionally, the flexible grinding product is laminated with foam and/or velour onto a respective surface of the tool, and, alternatively, the foam may further be laminated with a velour on the opposite side for fastening.

(27) For sanding the product, a belt sander can be used, a drum sander, an oscillating sanding beam, combinations thereof or one or more other suitable sanding units. There may be used a calibrating roller or flat pad nip or the cloth can be pressed against the sanding unit by the actual web tension and certain angle of enlacement. There may as well be used combinations thereof.

(28) FIG. 6 is a plan view of a knitted fabric which was impregnated, overcoated, sanded and thereafter selectively provided with horizontal stripes of polymer, thereby a pattern of plateaus or protruding flat areas 100 was generated. These plateaus 100 are provided with grinding particles after curing the product such that wale-portions 101 remain free of grinding particles. Thus, islands of flattened portions carrying grinding particles are achieved. The grinding islands will naturally be arbitrarily or randomly positioned on the wales as the separation of the islands do not necessarily coincide with the pattern of the fabric. This effect can be enhanced by optimizing the pitch of the smoothing pattern in relation to the pattern of the cloth.

(29) The pattern of plateaus can be achieved via different methods. For instance, the smoothing drum may carry a corresponding pattern, which then is transferred onto the surface of the fabric. Alternatively, after sanding or flattening the grinding surface of the cloth, the surface can be coated in an additional step with an engraved drum or roller, for instance with grooves in horizontal directions. As a third alternative, the illustrated plateaus 100 may as well be created with a screen-print-device. According to a fourth alternative, the coated, flattened and/or sanded surface of the cloth may be provided with an adhesive agent or make coat. The applied make coat may be structured via an engraved drum. Alternatively, a screen-print-device may be used for applying the make coat. Typically, the difference of level between the plateaus and the depressions when applying the fourth alternative is smaller than what is achievable via the first, second or third alternative because the amount of make coat is limited by abrasive coating demands.

(30) The coating of the grinding particles can be made in different ways, the coating can comprise a separate make coat that bonds the separately coated grinding particles. The coating can alternatively comprise a slurry of bonding agent and grinding particles and this slurry can be coated into a layer as such, but the layer may subsequently be formed to sanding formations on the flattened surfaces in a desired pattern and shape of formations. The slurry may also be transferred by a roller, belt or film with the engraved desired pattern and may further be formed and cured while in contact with the transferring element.

(31) A cross section through line C-C in FIG. 6 is shown in FIG. 7. Engraved stripes separating the plateaus 100 are cut roughly horizontally. A sloped cutting or other cuttings may as well be possible. Further, a zig-zag-shape or sine-shape as illustrated in FIG. 6 is not necessarily required. The shape of the flattened areas and/or the engraved pattern is adjustable in view of the used fabric, the intended grinding result or other requirements.

(32) FIGS. 8A to 8D are cross sections including the plateaus 100 of FIGS. 6 and 7 as well as an underlying coated thread or wale part. The wale part is provided with a coating 102.

(33) Overcoated portions 102 are flattened or smoothed. In FIG. 8B, plateau 100 is provided with an abrasive mineral serving as a grinding agent 103. Abrasive mineral 103 is applied utilizing an adhesive layer 102. In FIGS. 8C and 8D, the grinding agent 103 is a slurry deposited in even or structured formations on the flat portion 100.

(34) Turning to the composition of the coating, polymers are preferred. The coating may be based on standard Oligomer and monomer-based acrylic formulations, water-dilutable acrylates, dual cure formulations, as well as Polyurethane-dispersions or similar materials. Further, also UV-curable epoxides and vinylmonomers are suitable materials. However acrylic oligomer/monomer-based formulations are preferred.

(35) As an example, a formulation can consist of 20 wt % Bisphenol A Epoxy diacrylate, 5 wt % (1,6)-Hexanedioldiacrylate, 15 wt % Tricyclodecanedimethanol Diacrylate, 60 wt % Trimethylolpropane Triacrylate.

(36) As alternatives also other combinations may be used which include other types of Epoxy acrylates, Polyester, Melamin, Polyurethane or Polyether acrylates.

(37) To achieve suitable viscosity ranges some of the reactive thinners or monomers may as well partially be substituted by low viscous oligomer types such as aliphatic epoxy acrylates, e.g. CN152 from Sartomer.

(38) Alternative monomers may include materials such as 2(2-ethoxyethoxy)ethyl acrylate, Isobornyl acrylate, Tetrahydrofurfuryl acrylate, 2-Phenoxyethyl acrylate, (1,6)-Hexanedioldiacrylate, Tripropylene glycol diacrylate, Dipropylene glycol diacrylate, Pentaerythritol Tetraacrylate, Di-Pentaerythritol Pentaacrylate, as well as other acrylate or methacrylate monomers. Suitable materials can also be for example other radically polymerizable vinylmonomers, like N-vinylcaprolactam.

(39) The amount and type of filler that is used in the coating strongly influences on the final performance of the cured material. In order to modify the properties of the coating different kind of fillers can be used whereas also various combinations of filler materials may be applied. In case of UV-curable coating formulations one needs to assure that the filler is sufficiently penetrable for UV-light in order to ensure curing of the formulation. If, however, EB post-curing is applied during or after the coating step, the filler may also be impenetrable to UV-light. In this case UV-curing is applied in order to preliminary cure the material and fix surface shape and structure whereas the full mechanical properties are reached after EB-post-curing.

(40) For fillers powders having small particle sizes below 10 m are preferred. However coarser particles may be used as well, if applicable. Fillers may as well be used as blends in order to fine-tune the mechanical parameters of the coating. Examples for suitable fillers are Talc which is the preferred filler for this coating or Aluminumtrihydroxide as an example of an UV-penetrable filler material. Further on Kaolin, Calcium sulfate or fillers which are similar or identical to abrasive particles based on aluminumoxide, siliconcarbide and the like may be used. With increasing hardness of the filler material the coating will typically show a more brittle behavior towards tear and strain.

(41) The initiator system used in the formulation is dependent on the resin system that is used. For a typical radically curing acrylic formulation mixtures of several initiators may be used, depending on the type of UV-lamp, line speed and if EB-postcuring is applied.

(42) For a typical formulation with UV pre-curing and EB post-curing e.g. 5 wt % Benzophenone 1-hydroxy-cyclohexylphenyl-ketone mixture (Additol BCPK from Cytec) in combination with an amine acrylate (7 wt %) (Ebecryl 7100) or an amine synergist for instance a tertiary amine (Ebecryl P116) may be used. Other initiators and combinations e.g. MAPO, BAPO, thioxanthones and combinations thereof may be more suitable in some cases, for example when good through cure is required, typically in combination with only UV-curing hardening.

(43) Other initiator types and combinations such as Iodonium-, Sulphonium and other derivates and e.g. anthracence-based derivates of sensitizers or the like may be applicable in case of acid-catalyzed hardening systems or if e.g. UV-LED curing is applied.

(44) Blending of the resins requires no special attention except to assure that all components are homogenously blended within the mixture. Depending on the mixing equipment, the UV-resin may be blended first and the filler is added to the resin, though also the opposite order can be applied.

(45) The choice of the type of monomer, oligomer and filler combination as well as their ratios strongly depend on the mechanical properties which are required or desired during the further process, e.g. as to the treatment the material such as winding or cutting. Mechanically, the coating needs to be capable of achieving sufficient tension and tear resistance as well as a sufficient flexibility for handling the material during the process.

(46) In terms of applying the coating to a cloth, the UV-curing resin formulation with filler is blended as previously described. Initiators are required in case UV-curing is applied as a curing method.

(47) According to one embodiment, it has shown to be practical to spread the resin/filler mixture by using a doctor roller on an even plastic film substrate, e.g. a PET film. Coating thickness of the resin blend hereby depends on the thickness of the cloth that shall be coated. Preferably coating thicknesses for the coating on the film substrate are between 50 and 800 m, more preferably a thicknesses of approximately 300 m is provided. Subsequently, the film which is coated with the uncured resin mixture is bent around a roller of suitable size and pressed against the cloth. The coated cloth is then moved under a UV-radiation source and cured, preferably from the backside of the cloth. It is possible to provide an even or calendered film with a surface pattern to be transferred into the grinding surface of the product.