ABRASIVE PRODUCT AND METHOD FOR MANUFACTURING ABRASIVE PRODUCT

Abstract

An abrasive product has a flexible abrasive area for abrading surfaces to be abraded and comprises: a fabric; a plurality of flexible loops protruding from the fabric towards the flexible abrasive area, wherein each loop is formed by a pair of bottom-half arcs, a pair of legs and a head, wherein the pair of legs connects the pair of bottom-half arcs with the head, the bottom-half arcs of the loops are interlaced in rows in the fabric and form rows of interlaced bottom-half arcs, wherein the legs and heads protrude from the fabric, the heads of the loops are interconnected with one another at a distance to the fabric such that the flexible abrasive area is at a distance to the fabric, and the heads of the loops are at least partially provided with abrasive particles and form the flexible abrasive area.

Claims

1. Abrasive product having a flexible abrasive area for abrading surfaces to be abraded, the abrasive product comprising: a fabric; a plurality of flexible loops, wherein each loop is formed by a pair of bottom-half arcs, a pair of legs and a head, wherein the pair of legs connects the pair of bottom-half arcs with the head, the bottom-half arcs of the loops are interlaced in rows in the fabric and form rows of interlaced bottom-half arcs, wherein the legs and heads protrude from the fabric, the heads of the loops are at least partially provided with abrasive particles and form the flexible abrasive area, the plurality of flexible loops protrude from the fabric towards the flexible abrasive area and the heads of the loops are interconnected with one another at a distance to the fabric such that the flexible abrasive area is at a distance to the fabric.

2. Abrasive product of claim 1, wherein the abrasive product is obtained by interconnecting the heads of the loops so to form rows of interconnected heads, wherein optionally, in the abrasive product, the rows of interconnected heads extend in the same direction as the rows of interlaced bottom-half arcs.

3. Abrasive product of claim 1, wherein the rows of the interlaced bottom-half arcs extend in the wale direction of the fabric.

4. Abrasive product of claim 1, wherein the fabric is impregnated and/or coated and/or flattened.

5. Abrasive product of claim 1, wherein the distance between the flexible abrasive area and the fabric is between 1 mm to 100 mm, preferably between 2 mm to 50 mm, and most preferably between 2 mm and 12 mm.

6. Abrasive product of claim 1, wherein the heads of the loops and/or the fabric are/is coated with a coating based on latex, epoxy acrylates, polyester, melamine, polyurethane, phenolic resins, urea resins, acrylic resins and/or polyether acrylates.

7. Abrasive product of claim 1, wherein the abrasive particles have an average grit size between 1 μm and 1000 μm, preferably between 5 and 200 more preferably between 10 μm and 100 μm.

8. Abrasive product of claim 1, wherein the yarn count for the fabric is between 30 to 2000 dtex and/or the yarn count for the loops is between 5 to 200 dtex, preferably between 10 to 100 dtex, and more preferably between 20 to 50 dtex.

9. Abrasive product of claim 1, wherein the fabric is laminated to a further layer, in particular a pliable layer, preferably a foam layer, an attachment layer for attachment to an abrading machine, preferably a grip velour, and/or a backing, preferably a Polyethersulfon woven textile or film.

10. Abrasive product of claim 1, wherein the abrasive particles comprise soft abrasive particles, preferably cerium oxide, bound by a coating comprising nano cellulose.

11. Method of manufacturing an abrasive product having a flexible abrasive area for abrading surfaces to be abraded, the method comprising: Preparing a fabric comprising a plurality of flexible loops protruding from the fabric towards the flexible abrasive area, wherein each flexible loop is formed by a pair of bottom-half arcs, a pair of legs and a head, wherein the pair of legs connects the pair of bottom-half arcs with the head, preparing the fabric including: interlacing the bottom-half arcs of the loops in the fabric in rows to form rows of interlaced bottom-half arcs, wherein the legs and heads protrude from the fabric, and interconnecting the heads of the loops with one another at a distance to the fabric to form rows of interconnected heads, and Providing at least partially to the interconnected heads abrasive particles so as to form the flexible abrasive area at a distance to the fabric.

12. The method of claim 11, wherein the rows of interlaced bottom-half arcs and/or the rows of interconnected heads extend in the wale direction of the fabric and/or the rows of interlaced bottom-half arcs and the rows of interconnected heads extend in the same direction.

13. The method of claim 11 wherein a double needle bar knitting machine is used in preparing the fabric.

14. The method of claim 11, further comprising impregnating, coating and/or flattening the fabric.

15. The method of claim 11, further comprising coating the heads and/or the fabric with a coating based on latex, epoxy acrylates, polyester, melamine, polyurethane, phenolic resins, urea resins, acrylic resins and/or polyether acrylates.

16. The method of claim 11, further comprising laminating the fabric to a further layer, in particular to a pliable layer, preferably a foam layer, an attachment layer for attachment to an abrading machine, preferably a grip velour, and/or a backing, in particular for increasing the tensile strength and/or lowering the elongation properties of the fabric, preferably a PES woven textile or film.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0079] The invention may be better understood by reference to the following and taken in conjunction with the accompanying figures.

[0080] FIGS. 1A to 1D are schematic illustrations of an abrasive product of the invention.

[0081] FIG. 2 is a schematic illustration of fabric yarns and loops yarns of an abrasive product of the invention.

[0082] FIGS. 3A and 3B show microscopic pictures of coated loops of an abrasive product of the invention.

[0083] FIGS. 4A and 4B show an example for a knitting pattern for an abrasive product of the invention.

[0084] FIGS. 5A and 5B show another example for a knitting pattern for an abrasive product of the invention.

[0085] The description and the accompanying drawings are to be construed by way of example and not of limitation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0086] In the following, the invention is described in detail with reference to the drawings and specific examples of the invention.

[0087] FIGS. 1A and 1B are schematic representations of an abrasive product 1 according to the invention. The abrasive product 1 comprises a (base) fabric or cloth 2 which constitutes the base layer of the abrasive product 1. The fabric 2 is a knitted textile fabric which is formed of knitted yarns 20 and can be produced on a textile producing machine by warp-knitting or weft-knitting, for instance.

[0088] The fabric 2 has a first side directed towards an abrasive area or surface 60 of the abrasive product, which is the upper side of the fabric 2 in FIG. 1A. On the first side of the fabric 2, a plurality of loops 71 which protrude from the knitted fabric 2 are formed. The loops 71 are formed of loop yarns 70.

[0089] To the loops 71, abrasive agents or abrasive particles 50 are applied so as to form the abrasive area 60. The fixation of the abrasive particles 50 can be promoted by a coating 40. This is shown in FIG. 1A, but has been omitted from FIG. 1B.

[0090] As indicated in the cross section of FIG. 1A, the abrasive area 60 in this example is coherent throughout the product 1, wherein the abrasive particles 50 are evenly distributed over the abrasive area 60. However, the abrasive area may also be incoherent, e.g., in the form of isolated spots or islands of abrasive particles.

[0091] The average grit size of the abrasive particles may be between 1 μm and 1000 μm, preferably between 5 μm and 200 μm, more preferably between 10 μm and 100 μm. Depending on the type of application, mixtures of different particle sizes can be used. In grinding applications, the grit size is defined according to desired grinding results, while the grit size may span over the whole range in cleaning or polishing applications.

[0092] Referring to FIG. 1C, the relevant parts of the loops 71 are defined as follows: Each loop comprises a pair of bottom-half arcs 76 connected to a protruding head 77 by way of a pair of legs 75. With the bottom-half arcs 76, the loops are connected to the fabric 2 in the sense that these portions of the loops 71 are interlaced in the fabric 2. The protruding head 77 and the legs 75 are the portions of the loop 71 which actually protrude from the fabric 2, i.e., are arranged outside of the fabric 2. The protruding head 77 as well as the legs protrude from the fabric 2 towards the abrasive area 60.

[0093] In the example according to FIGS. 1A and 1B, the interconnection of the loops 71 is achieved by chaining the protruding heads 77 of the loops 71, which loops succeed one another in the wale direction W of the fabric 2 by threading the protruding head 77 of one loop 71 through the protruding head 77 of the preceding loop 71. However, other techniques—in particular, knitting techniques—may also be used for interconnecting the heads of the loops 71.

[0094] The loops 71 are arranged in rows, optionally in the wale direction W of the fabric 2, as the bottom-half arcs 76 of the loops are interlaced in rows in the fabric 2. This means that the bottom-half arcs 76 of the loops which succeed one another in a direction of the fabric (preferably the wale direction W of the fabric 2) form a row.

[0095] Further, as can be seen in the Figures, the heads 77 of the loops 71 are interconnected with one another in a plane essentially parallel to and spaced apart from the fabric 2. In other words, the protruding loops 71 are interconnected outside the fabric 2 and at a distance to the fabric 2. The interconnected loops form the abrasive area 60 which is positioned parallel and at a distance d to the plane of the fabric 2, see FIG. 1A.

[0096] Accordingly, the interconnected heads 77 may form rows 73 of interconnected loops, which rows 73 of interconnected heads may extend in the same direction as the rows formed by the bottom half arcs, preferably in the wale direction W of the fabric 2.

[0097] As can be seen from FIG. 1D, the bottom-half arcs 76 of each loop 71 are spaced apart from one another in the course direction of the fabric (which is perpendicular to the wale direction W). This has the effect that the loops are held “open”, with the leg portions 75 being inclined against one another as they extend from the surface of the fabric 2. Hence, if the product is regarded in the wale direction W, the loops 71 have a V-shape or U-shape like configuration which narrows towards the heads 77. The inclination or tilting of the leg portions 75 (with respect to a normal line onto the fabric) can be adjusted by varying the spacing between the bottom-half arcs 76 and the contour length of protruding heads 77.

[0098] Due to the tilting of the leg portions 75 in counter directions, the product 1 becomes more resistant against shear forces.

[0099] Another effect is that the loops 71 can be kept relatively open which to some extent prevents that upon chaining the loops to one another the head or noose of one loop “slides down” the leg portions of the loop it is chained to. By consequence, this further promotes the dimensional stability of the loops 71 because they are less likely to collapse under mechanical impact and pressure. Moreover, the heads 77 are arranged essentially horizontally with respect to the fabric 2.

[0100] Preferably, the bottom-half arcs 76 of each loop are at least spaced by one stitch-row 22 of the fabric 2 and more preferably by two stitch-rows 22 of the fabric (c.f. FIG. 1D). The latter, in other words, means that the loop 71 spans over one stitch row 22 (c.f. FIG. 1D). In that case, it is particularly preferable if the loops 71 (or their protruding heads 77) alternatingly span one stitch-row 22 in the course direction (c.f. FIG. 1D).

[0101] In this regard, a stitch row 22 or wale is a stitch wale of stitches which proceeds over the length of the knitted fabric (c.f. ISO 4921:2000, 3.3.1). Exemplarily, the product 1 as described in FIG. 1 can be manufactured by using a double needle bar knitting machine for forming the abrasive product. This means, in other words, that the loops are held in a predominantly open configuration in a shape which resembles a V- or U-shape. Moreover, the loops are less prone to lay down and the resulting structure is more resistant.

[0102] The properties of the ensuing product can be adjusted by increasing the number of loop yarns, the number/thickness of filaments constituting a yarn and, correspondingly, the number of stitches with which the loops 71 are connected.

[0103] FIG. 2 shows a schematic illustration of the yarns of the loops 71 and the yarns 20 of the fabric. The heads 77 are interconnected or chained with one another and form a plane (the abrasive area) which is basically parallel to the plane of the fabric. The distance between these two planes is referred to as distance d. The distance d may basically correspond to the length of the legs of the loops. The protruding legs 75 have a length of 1 mm to 500 mm, preferably 2 mm to 80 mm and most preferably between 2 mm and 20 mm. The distance d in the abrasive product between the abrasive area and the fabric is preferably between 1 mm to 100 mm, more preferably between 2 mm to 50 mm, and most preferably between 2 mm and 12 mm.

[0104] Each head of a chained loop may have a (contour) width w and a (contour) length 1. The length 1 may be in the wale direction W of the fabric, wherein the width w may be perpendicular to the wale direction W. Preferred dimensions for the heads of the loops are as follows: w:0.01 to 30 mm, preferably 0.1 to 20 mm, more preferably 0.2 to 10 mm; 1: 0.05 mm to 30 mm, preferably 0.1 to 20 mm, more preferably 0.2 to 10 mm.

[0105] FIGS. 3A and 3B show microscopic pictures of an abrasive product of the invention, seen from above. These top views of the abrasive products show the interconnected heads 77 comprising abrasive particles 50 which are evenly distributed over the entire abrasive area. The heads 77 include coating 40 and abrasives 50.

[0106] An example for such a textile structure according to the invention is shown in FIG. 4A and the corresponding yarn path notation in FIG. 4B in which black dots represent one needle bar of a double needle bar knitting machine and grey dots represent the other needle bar. As can be seen from the thread courses, the yarns 20 forming the fabric 2 are worked on one needle bar, while the loop yarns 70 are worked on both needle bars. The actual loops 71 of the loop yarns 70 are formed on the second needle bar (grey dots), however. In the example shown in FIG. 4B, the loops 71 are only connected in the wale direction W. There is no interconnection between the individual rows 73.

[0107] The fabric 2 is based on an (open) atlas binding and the interlacing of the loop yarns 70 is done by means of a pillar stitch—with the exception that a stitch is made on the second needle bar when the loops pass over the needles. Unlike the example which is shown in FIG. 1, the bottom-half arcs 76 of the individual loops are not spaced apart from one another in the course direction of the fabric, meaning that they are arranged in one and the same stitch row 22.

[0108] However, the loops 71 may also be knitted in the wale direction W of the fabric 2 so as to form rows 73 of interconnected loops 71 which extend in the wale direction W. Accordingly, the geometric stability of the loops 71 is enhanced and the loops 71 are less prone to lay down on the fabric. During subsequent process steps and/or storing, the interconnected loops might become irregular to some extent, so that the rows 73 might appear to be less easily discernible in the final product.

[0109] A further example for a concrete knitting pattern is shown in FIGS. 5A and 5B. As can best be seen from the yarn path notation of FIG. 5B, also the loop yarns 70 are interlaced in the form of an atlas binding. FIGS. 5A and 5B reflect that the loops do not only extend in the wale direction W of the fabric, but that the protruding heads alternatingly span one stitch row in the course direction of the fabric. This is clearly shown in FIG. 5B, where the pattern for the loop yarns 70 indicates a movement not only in the wale direction W, but also in the direction perpendicular to the wale direction W, namely the course direction (which is the left-right direction in FIG. 5B). By that, the loops which are arranged in the course direction may overlap one another in the sense that a bottom-half arc of one loop is arranged between the bottom-half arcs of the neighboring loops.

[0110] The fabrics 2 that are shown in the Figures are based on structures which are highly permeable due to a number of regularly arranged through holes in the base fabric 2. The open structure enables an optimal dust removal. When dust is created during sanding, the dust can easily be removed by air streams which penetrate through fabric 2 and the loops 71.

[0111] As illustrated in the Figures, it is possible to use different kinds of yarns for the loop yarns 70 and the yarns 20 of the fabric 2. This enables to use thinner yarns for the loop yarns 70 as compared to the yarns 20 of the fabric 2, for instance. The product as a whole can still be kept substantially open which is beneficial for dust removal and cooling. In addition, using thinner yarns for the loop yarns 70 ensures that the overall product is still soft and flexible. Moreover, this guarantees that no pronounced elevations in the fabric 2 result when the loop yarns 70 are worked on the same needle bar as the fabric 2.

[0112] In this regard, the loop yarns 70 preferably have a yarn count between 5 to 200 dtex and more preferably between 10 to 100 dtex, and even more preferably between 20 to 50 dtex.

[0113] Moreover, the loop yarns 70 may be formed of mono- or multifilament yarns while the yarns 20 forming the fabric 2 may be multifilament yarns. Also combinations of monofilaments and multifilaments can be used for each of the base fabric and the loops. Particularly for forming the geometrical shape of the loops, monofilaments are suitable, as they are usually stiffer and therefore create better geometrical stiffness, but multifilament yarns are conceivable for the loops for at least some applications.

[0114] An impregnation or coating 30 may be used for the fabric 2. Such coating may level any existing unevenness. Moreover, such coating also leads to a fixation of the loop yarns 70 in the fabric 2 which renders it difficult to pull out individual loops 71 from the fabric 2. The coating 30 may be applied from the side of the fabric 2, where the loops do not protrude (i.e. the backside of the fabric and of the abrasive product, i.e. the lower side of the fabric 2 in FIG. 1A).

[0115] In addition, the fabric and/or the loop yarns may comprise an impregnation for further enhancing the mechanical stability of the product.

[0116] The base fabric 2 including the loops 71 may be manufactured as described above in connection with FIGS. 4 and 5. A preferred direction for the rows of the bottom-half arcs and/or the rows of the interconnected heads is the wale direction of the fabric. However, any direction is conceivable. Afterwards, the fabric 2 may be impregnated and/or coated with the coating 30, to make it stiffer. Optionally, the coating 30 is flattened (from the backside) by one of the measures described above, such a using a roller and/or sanding.

[0117] Abrasive particles 50 are then applied to the heads 77 of the loops, by way of slurry coating (the abrasive particles 50 are in the coating 40) or a coating 40 is applied and afterwards abrasive particles 50 are provided, as described above. The coating 40 may serve as a primer for applying the abrasive particles 50.

[0118] In general, resin coating can be applied to the base fabric as an impregnation layer to achieve the desired stiffness in the base fabric. Resin coating to the loops is usually applied either as a make coat-strewing-size coat or as a slurry coating that is a combination of resin and abrasives.

[0119] When manufacturing the abrasive product according to the invention, in particular when proving the coating 40 and/or the abrasive particles 50 to the interconnected loops, rows formed by the interconnected heads may be affected and the order and regularity of the interconnected heads may be reduced. Due to such effects, the rows of interconnected heads may be harder to discern in the (final) abrasive product.

[0120] The fabric 2 may be worked further at its backside. For example, it may be laminated to a pliable layer (foam) , a tape, backing or grip system. The backing is preferable for increasing the tensile strength and/or lowering the elongation properties, such as a PES woven textile or film.

[0121] As explained above, the “backside” or second side of the fabric may alternatively also comprise loops, for engagement with a hook-and-loop fastener for attachment to a machine, or coated with abrasive particles so as to obtain a two-sided abrasive product, as described above.

[0122] For the examples shown in the Figures and the below examples, the desired flexibility/movability of the loops is achieved, wherein at the same time, the interconnection of the heads provides for the desired coherence of the abrasive area. Hence, the abrasive products as described allow for improved quality and efficiency in abrading processes.

[0123] The abrasive product may in particular be an abrasive belt, an abrasive disc or a hand sanding article (abrasive cleansing sponge). The below examples 1 to 3 are only exemplary for these applications and do not limit the conceived abrasive belt, abrasive disc and hand sanding article to these specific examples.

Example 1

[0124] According to a first example, the invention is applied to a hand sanding product, such as an abrasive cleansing sponge. The fabric of an abrasive product in this form of the invention is optionally laminated to a foam, for example, a 3.5 mm polyurethane foam, with a polyurethane hot melt resin. The foam is provided on the side of the fabric which is free from loops, i.e. the opposite side of the side on which the loops forming the abrasive area are provided. Hence, the pad may be laminated to such foam layer.

[0125] SiC slurry coating has been provided to the heads of the loops. The grit size of the abrasive particles is P800 (FEPA). Preferably, the coating has a soft base coating, such as a latex coating.

[0126] An application for such hand sanding product can be the rectification of a stainless steel surface, for example. Typically, such hand sanding product is used for a wet abrasive process.

Example 1a

[0127] Another application within Example 1 is a cleaning sponge for removing stains or corrosion from a glass surface. The abrasive used here is a mineral comprising a mixture of hard and soft abrasive particles, such as (preferably recycled) crushed glass (such as with an average grit size below 25 μm and/or glass of recycled bottles, cans etc. or window glass), and cerium oxide (such as with an average grit range in the range 1.5-2.5 μm). The mixing ratio of hard abrasives (e.g. glass) and soft abrasives (e.g. cerium oxide) (in weight-%) may be between 0 and 100% (meaning 0% hard abrasives (glass) and 100% soft abrasives (cerium oxide); or 100% hard abrasives (glass) and 0% soft abrasives (cerium oxide)), but is preferably between 80 to 90% hard abrasives (glass) and 20 to 10%, respectively, soft abrasives (cerium oxide). The crushed glass removes the stains mechanically, while the cerium oxide polishes the glass surface. The binder for the mineral can be a polymeric binder or a nano cellulose or a combination thereof. The hard abrasives (crushed glass or mineral mixture) may be bound with a polymer binder while the soft abrasives (cerium oxide) may be bound with nano cellulose.

Example 2

[0128] According to a second example, the invention is applied to an abrasive belt (for belt sanding). For an abrasive belt, the fabric has (optionally) been impregnated with a resin formulation (for example based on SBR latex). Phenolic, acrylates or latex dispersions are conceivable. Optionally, the coated fabric has been sanded, in order to provide a well-defined structure.

[0129] The loops have been coated with a PF resin slurry with SiC or AlOx particles. The yarn count for the loops is 2×33 dtex, and for the base 2×78 dtex.

[0130] The back side of the belt was flattened by a flattening process (such as disclosed in WO 2014/037034 A1) and the ends of the belt were taped together from the back side with a thin polyester reinforced tape. This formed an endless belt for sanding. The technology disclosed in WO 2018/069574 A1 could be used for joining the ends of the belt. For belt sanding applications, usually dry sanding is performed.

Example 3

[0131] In a third example, the invention is used in an abrasive disc for an (random) orbital sander. Usually, a fastening aid, e.g. a grip velour, is laminated to the fabric with a hot-melt resin to allow for attachment to the sander. Such grip velour is laminated to the backside (i.e. the side of the fabric without loops) of the fabric (the pad). A disc is punched out from the laminated combination of the pad and the grip velour.

[0132] The abrasive particles may be SiC, grit size SiC P800 (FEPA). Dry sanding is carried out.