Technical field

This specification relates to a cleaning product for dry dust cleaning of a sanded surface as well as to a method for treating a surface prior to painting or coating the surface. The specification also relates to a method of obtaining the cleaning product as well as to an apparatus comprising the cleaning product.

Background

After a sanding step, before subsequent painting or coating, the sanded surface has to be cleaned as the remaining dust on the surface affects the properties and appearance of the painted or coated surface. Traditionally this cleaning is performed by manually wiping the surface with a dry or wet rag. This manual wiping is time consuming and it is particularly difficult to conduct in an automated working process.

Thus, there is a need for a product for dust cleaning, which product is utilizable also in automated working process including sanding and subsequent painting or coating.

Summary

Solutions for dry dust cleaning of a sanded surface are provided. Treatment of a sanded surface with a cleaning product disclosed herein provides a sanded and thereafter cleaned surface with close to similar properties, such as surface tension and topography, when compared to the neighbouring unsanded surface. This has the effect that sanded surface and the unsanded surface after subsequent painting and coating appear similar.

The cleaning product disclosed herein enables automatization of the entire process starting from sanding and ending with painting or coating. The traditional manual wiping step after sanding and prior to painting or coating can now be automated using the cleaning product according to this disclosure. This also expedites the surface treatment process, and thus enables a more costefficient process.

According to an embodiment, a cleaning product for dry dust cleaning of a sanded surface is provided. The cleaning product comprises a substrate having a first surface and a second surface. The substrate has an open structure configured to allow penetration of air and dust through the substrate, and the second surface of the substrate is suitable for attachment with fasteners. The cleaning product is configured to be mountable to a backing pad of a sander arranged with a dust extraction system.

According to another embodiment, a method of obtaining a cleaning product for dry dust cleaning of a sanded surface is provided. The method comprises providing a substrate having a first surface and a second surface, and cutting the substrate in order to provide the cleaning product. The substrate has an open structure configured to allow penetration of air and dust through the substrate. The second surface of the substrate is suitable for attachment with fasteners, and the cleaning product is configured to be mountable to a backing pad of a sander arranged with a dust extraction system.

According to yet another embodiment, a method for treating a surface prior to painting or coating the surface is provided. The method comprises sanding the surface by an abrasive product for providing a sanded surface, and dry cleaning the sanded surface by a cleaning product in order to provide a dry cleaned surface. The cleaning product comprises a substrate having a first surface and a second surface, the substrate having an open structure configured to allow penetration of air and dust through the substrate, and the second surface of the substrate being suitable for attachment with fasteners. The cleaning product is configured to be mountable to a backing pad of a sander arranged with a dust extraction system.

According to still another embodiment, an apparatus for dry dust cleaning of a sanded surface is provided. The apparatus comprises a cleaning product as disclosed above. Brief description of the drawings

Fig. 1 illustrates, by way of an example, a cross section of a cleaning product,

Fig. 2 illustrates, by way of an example, a cross section of another cleaning product,

Fig. 3 illustrates, by way of an example, a cross section of a cleaning product and a backing pad, and

Fig. 4 shows SEM images of sanded surfaces after cleaning with varying cleaning products/methods.

The figures 1 -3 are schematic. The figures are not in any particular scale.

Detailed description

The solution is described in the following in more detail with reference to some embodiments, which shall not be regarded as limiting.

The following reference numbers are used in this specification:

100, 200, 300 cleaning product 101 , 201 substrate 101 a, 201 a first surface 101 b, 201 b second surface

202 loop

303 backing pad

304 fastener h thickness d diameter of a cleaning product db diameter of a backing pad

Sanding refers to surface treatment that prepares a surface to subsequent painting or coating. Sanding aims at smoothing the surface and ensures that paint, varnish or any other coating is received by a smooth surface. Sanding is one of the most important steps in determining the end finish and quality of a product.

Sanding finds use in different fields of technology, such as automotive industry, ships and boats, airplane industry, railway industry and furniture industry, to name a few. Sanding may be performed to various materials, such as wood, metal, putties, composites, plastics, minerals or different coatings such as primers, paints or varnishes. Sanding is performed by an article which comprises abrasive material for sanding. The article may be called an abrasive product. The article may be for example a sanding paper. The abrasive product, such as a sanding paper, may be configured to be mountable to a backing pad of an abrading apparatus, which may be called a sanding machine, i.e. a sander.

In all sanding processes, whether sanding a discrete work piece or larger surface such as a wall or ceiling, sanding dust is formed. This dust may comprise sanded material from the sanded surface as well as abrasive particles detached from the abrasive material of the abrasive product. After the sanding step, before subsequent painting or coating, the sanded surface has to be cleaned from the dust as efficiently as possible, since the remaining dust on the surface affects the properties and appearance of the painted or coated surface.

This specification aims to provide solutions for dry dust cleaning of a sanded surface.

A cleaning product for dry dust cleaning of a sanded surface is provided. The cleaning product refers to an article which may be used for cleaning. The cleaning product may be shaped from a cleaning web by cutting. Multiple cleaning products may be shaped from a cleaning web by cutting. The cleaning product may have any suitable shape, such as circular, triangular, polygonal, quadrangular, rectangular, hexagonal or oval. A circular cleaning product may be called a cleaning disc. A quadrangular or rectangular cleaning product may be called a cleaning sheet. The shape of the cleaning product corresponds to the shape of a sanding machine, or a support such as a (hand held) pad or a grip surface thereof. The cleaning product may also be a cleaning belt. The cleaning belt refers to a product that may be mountable for example on rotating wheels or axles.

Figure 1 illustrates a cross section in S _x ,S _z -plane of a cleaning product. The cleaning product 100 comprises a substrate 101 having a first surface 101 a and a second surface 101 b. The substrate 101 has an open structure which is configured to allow penetration of air and dust through the substrate. The first surface 101 a of the substrate is for cleaning the sanded surface. The first surface 101 a of the substrate is responsible for rubbing the dust particles from the surface to be cleaned.

The second surface 101 b of the substrate is suitable for attachment with fasteners. For example, the second surface 101 b of the substrate may be suitable for attachment with hook type fasteners. The cleaning product 100 is configured to be mountable to a backing pad of a sander arranged with a dust extraction system. In other words, the cleaning product is suitable for mounting to a backing pad of a sander arranged with a dust extraction system. The sander may be a manual sander or an automated sander.

A lower surface of the backing pad is equipped with a plurality of suction openings. The lower surface of the backing pad refers to the surface that is configured to receive the cleaning product. Preferably the backing pad is so- called backing pad net. The backing pad net is suitable for net abrasive products. The backing pad is a multipurpose backing pad having a plurality of suction openings and being suitable for attachment with variable abrasive products differing in number and/or location of the openings provided therein. The backing pad comprises fasteners with which the second surface 101 b of the substrate is configured to be attached to the lower surface of the backing pad. The fasteners preferably are hook type fasteners. The hook type fasteners may be J-hooks or mushroom-type hooks.

The backing pad is configured to be attachable to a sander. The backing pad may be attached to the sander via a spindle. By this arrangement the backing pad may move in random circles, which refers to oscillating movement. In use the backing pad attached to the sander is arranged to move, the cleaning product attached to the sander is arranged to clean the surface to be cleaned, and the dust extraction system of the sander is arranged to extract the dust from the surface to be cleaned through the cleaning product, i.e. from the first surface 101 a of the substrate through the body of the substrate 101 to the second surface 101 b of the substrate, through the backing pad and eventually to the dust collector of the dust extraction system of the sander.

According to an embodiment, the cleaning product is a cleaning disc having a circular shape. Also, the backing pad and the sander have a circular shape.

According to an embodiment, the substrate 101 of the cleaning product comprises or consists of reticulated foam. Reticulated foam is very porous, low density solid foam. Reticulated foams are extremely open foams, i.e. there are few, if any, intact bubbles or cell windows. Reticulated foam only comprises the lineal boundaries where the bubbles meet. Such an open structure enables penetration of air and dust through the substrate. Within context of this specification, a solid component of the reticulated foam comprises or consists of at least one organic polymer. Thus, the substrate comprises or consists of one or more organic polymer(s), such as polyurethane (PU). Polyurethane may be polyester-based. The reticulated foam may have a porosity of at least 95 %, even of 98 %.

The substrate comprising or consisting of reticulated foam preferably does not comprise loops on the second surface of the substrate, but the reticulated foam itself is directly attachable with fasteners, preferably hook type fasteners, of a backing pad of a sander. In an example, the hook type fasteners may be of a mushroom style, such as Binder Pressogrip® mushroom D soft finish 19, item 18195-19. Alternatively the hook type fasteners may be so called J-hooks. Cost efficiency is gained as it is not necessary to provide the substrate with a separate textile layer, such as a velour layer, with loops. Further, risk of getting contamination on the sanded surface from the textile fibers is thus lowered. Moreover, penetration of air and dust through the cleaning product is not endangered or hindered by incorporation of an additional layer.

The cleaning product having a substrate comprising reticulated foam may have a thickness h of from 5 to 50 mm, or from 5 to 40 mm, or from 5 to 30 mm. Bigger thickness enables the cleaning product to better follow irregularities of the surface to be cleaned. In an example, the substrate comprising reticulated foam has a thickness h of from 20 to 30 mm. However, especially for flat surfaces a thinner substrate may be used. Different applications may require varying thicknesses.

The polymer type and hardness of the reticulated foam can be adjusted in order to provide optimal properties for different surfaces to be cleaned. In certain applications, particularly when the surface to be cleaned has varying shapes and contours, good surface following properties are important. Better surface following properties are achieved with softer foam when compared to a harder one.

The reticulated foam as the substrate has a cell diameter that efficiently enables penetration of air and dust through the substrate. Further, the cell diameter must be chosen in such a way that the attachment with the fasteners of the backing pad is enabled. Too small cell diameter may hinder the attachment. Therefore, the reticulated foam preferably has a cell diameter of from 1000 to 5000 pm.

Further, the reticulated foam as the substrate typically shows a certain compression resistance (compression strength). Compression resistance refers to the load-bearing properties of the foam. Preferably the reticulated foam has a compression resistance (40 %) of from 1 .5 to 6.0 kPa, when measured according to standard ISO 3386/1 .

The substrate of the cleaning product comprising or consisting of reticulated foam typically shows certain pressure drop. The pressure drop is mainly influenced by the cell diameter and the density of the foam. Pressure drop can be evaluated at different thickness of the foam and with variable air velocity on a surface of 25 cm ² . The density of the reticulated foam as the substrate may be from 15 to 40 kg/m ³ , when measured according to standard ISO 845. Preferably the pressure drop of the reticulated foam is below 10 hPa / 25 cm ² , even more preferably below 6 hPa / 25 cm ² with air velocity of from 1 to 6 m/s.

Cell diameter, permeability (openness) and compression resistance are the main features that are responsible for the desired effect achieved by the reticulated foam as the substrate of the cleaning product. Further, the reticulated foam as the substrate material may show ultimate elongation of up to 400 % and tensile strength of from 50 to 250 kPa, when both measured according to standard ISO 1789.

In an example, the substrate of the cleaning product consists of reticulated foam and has a thickness of 25 mm. The reticulated foam is a polyester-based polyurethane foam. The foam has a density of from 23 to 27 kg/m ³ , when measured according to standard ISO 845. The foam has a compression resistance (40 %) of from 2.0 to 4.0 kPa, when measured according to standard ISO 3386/1 . Cell diameter of the foam is from 1500 to 2500 pm. The foam shows a typical ultimate elongation value of 300 % and a typical tensile strength value of 150 kPa, when both measured according to standard ISO 1789. Pressure drop of the foam may range from 0.1 to 2 hPa / 25 cm ² for a foam having a thickness of 10 mm (air velocity 1 -6 m/s). For a foam having a thickness of 50 mm the pressure drop may range from 0.2 to 5 hPa / 25 cm ² (air velocity 1 -6 m/s).

According to another embodiment, illustrated by Figure 2, the substrate 202 of the cleaning product 200 comprises or consists of spacer fabrics. The spacer fabrics is a textile wherein yarns are fused, looped or knotted at their intersections, resulting in a fabric with open spaces between the yarns. The open spaces provide through holes. Open spaces are necessary for enabling penetration of air and dust through the substrate. The second surface 201 b of the substrate may comprise loops for attachment with hook type fasteners. Alternatively, the second surface 201 b of the substrate may itself be suitable for attachment with hook type fasteners.

In an embodiment, the second surface 201 b of the substrate comprises loops 202 that are configured for attachment with hook type fasteners. The second surface 201 b of the substrate comprises an arrangement of interlaced loops 200 protruding from the substrate in a direction away from the first surface of the substrate. The loops 202 have protruding heads. The protruding heads may have contour lengths of from 2 mm to 50 mm, for example from 2 mm to 10 mm. The loops 202 may be formed by loop yarns which are interlaced in a textile. Alternatively the loops 202 may be formed by pulling under or overlapping out from a textile. The loops 202 may be comprised by the substrate 201 as integrated part of the substrate. Alternatively, the loops 202 may be comprised by a textile laminated onto the second surface 201 b of the substrate.

The loops may be comprised by a textile comprising loops that has been laminated onto the second surface of the substrate. The textile comprising loops may be laminated via an adhesive layer on the second surface of the substrate. The textile comprising loops may be a loop knitted textile.

Alternatively, the loops may be comprised by the substrate itself. Thus the loops are provided as integrated part of the substrate. In that case the cleaning product does not comprise a separate laminated textile comprising loops.

The second surface 201 b of the substrate comprising or consisting of spacer fabrics may comprise a melted and/or burnt area next to the edge of the cleaning product, the melted and/or burnt area having a width of at least 1 mm. Purpose of such melted and/or burnt area is to avoid formation of partial loops or loop parts that, as a result of cutting the cleaning product, are no longer permanently attached to the cleaning product. Such so-called loose loops may be responsible for contaminating the cleaning product and may eventually cause problems by contaminating the surface to be cleaned. Alternatively, in order to avoid the contamination by the loose loops, the edge of the sealing product can be sealed by sewing the layers, i.e. the substrate and the textile comprising loops, together.

The cleaning product having a substrate comprising or consisting of spacer fabrics may have a thickness h of from 1 to 5 mm, for example 3 mm.

The substrate comprising or consisting of spacer fabrics shows pressure drop comparable to that of the reticulated foam. The cleaning product disclosed herein distinctly differs for example from polishing products. Polishing products aim at creating a smooth and shiny surface, and require only partly open substrate. For cleaning, a fully open substrate capable of penetrating air as much as possible is required. Foam-based polishing products typically are non-reticulated, have a cell diameter well below 1000 pm and densities higher than the cleaning products according to this disclosure. Thus, the polishing products show higher pressure drop when compared to the cleaning product disclosed here. Therefore, the polishing products are not as effective in dust removal as the cleaning products disclosed herein and would not be suitable for cleaning purposes.

A diameter d of the cleaning product may be larger than a diameter db of the backing pad. For a cleaning product having a shape on the S _x , Sy-plane other than circular, the diameter d refers to longest possible distance between the edges of the cleaning product. In other words, the edges of the cleaning product may extend farther than edges of the backing pad. Larger diameter of the cleaning product enables good adaptation to the contours on the surface. Further, the larger diameter prevents the direct contact between the backing pad and the surface to be cleaned. However, the diameter of the cleaning product must be chosen such that efficient suction by the dust extraction system can still be effectuated. In an example, the diameter d of the cleaning product is from 2 to 10 mm larger than the diameter db of the backing pad. In that case, the edges of the cleaning product extend from 1 to 5 mm farther than edges of the backing pad.

Figure 3 illustrates a cleaning product 300 and a backing pad 303, the cleaning product 300 being configured to be mountable to the backing pad 303. The cleaning product 300 consists of a reticulated foam. A lower surface of the backing pad 303 comprises fasteners 304, particularly hook type fasteners, for attachment with the reticulated foam of the cleaning product. The diameter d of the cleaning product 300 is larger than the diameter db of the backing pad, in other words d > db.

In an embodiment, an apparatus for dry dust cleaning of a sanded surface is provided. The apparatus comprises a cleaning product as disclosed above. Preferably the apparatus comprises a backing pad comprising fasteners for attachment with a second surface of the substrate of the cleaning product. Further, the apparatus may comprise a sander arranged with a dust extraction system. Preferably the apparatus is part of an automated sander.

The machine cleaning of the surface with the cleaning product provided herein provides not only efficiently cleaned surface free of dust but also a homogenized surface. Differences in the surface tension and the surface geometry of the sanded (and cleaned) and unsanded surfaces may be visible for example in that that the respective surfaces may have a slightly different luster after painting, caused for example by different organization of the metal particles in the paint between the sanded and unsanded areas. Treatment with the cleaning product disclosed herein provides a sanded and thereafter cleaned surface with close to similar properties, such as surface tension and topography, when compared to the neighbouring unsanded surface. This has the effect that sanded surface and the unsanded surface after subsequent painting and coating appear similar. Preferably, the visual appearance of the sanded surface corresponds to that of the unsanded surface, and the human eye or even an automated vision system is not able to differentiate between the respective surfaces.

In order to provide even more homogenized surface, it is possible to provide the substrate of the cleaning product with grinding particles. The grinding particles may be mineral fillers, such as calcium carbonate or clay. Alternatively, the grinding particles may be abrasive grits, such as aluminium oxide or silicon carbide. For example, such grinding particles may have a diameter of from 0.5 to 10 pm, such as from 1 to 5 pm. For softer particles a bigger size when compared to harder particles may be needed for achieving a similar effect. Clay and TiO2 may be mentioned as examples of soft particles. Silicon carbide, for one, is a hard particle. Calcium carbonate has an average hardness. The grinding particles, when present, are arranged as part of the substrate. When the substrate comprises or consists of reticulated foam, the grinding particles are arranged as part of the foam material. In spacer fabrics the grinding materials are arranged as part of the yarn material. The grinding particles are part of the substrate material, and not being arranged for example as a separate coating. This has effect in enabling maintaining the open structure configured to allow penetration of air and dust through the substrate.

The cleaning product disclosed herein is useable in a method for treating a surface prior to painting or coating the surface. The method comprises sanding the surface by an abrasive product for providing a sanded surface and dry cleaning the sanded surface by the cleaning product disclosed above in order to provide a dry cleaned surface. The method may be implemented manually or automatically.

The cleaning product disclosed herein enables automatization of the entire process starting from sanding and ending with painting or coating. The traditional manual wiping step after sanding and prior to painting or coating can now be automated using the cleaning product according to this disclosure. This also expedites the surface treatment process, and thus enables a more costefficient process. Thus, according to an embodiment, the method is part of an automated working process. Moreover, use of the cleaning product according to this disclosure may enable the process containing sanding and subsequent painting or coating to be performed at one go, such that no re-sanding or repainting is required. This brings out savings, as the post-treatment is highly expensive.

For example in automotive industry, a finished painting job typically is subsequently scanned with an automated vision system in order to inspect the painting quality. If even small faults in the painting are found, such fault areas are sanded with a robot sanding device that is capable of responding to the information given by the vision system. After sanding, cleaning of such sanded areas before being re-painted must be carried out, preferably automatically. In any case, the cleaning product disclosed herein improves also this process by enabling automatization of the cleaning step.

Surface properties of sanded surfaces after cleaning with varying cleaning products/methods have been investigated by scanning electron microscopy (SEM) and 3D surface measurement. Figure 4 illustrates the SEM images with a magnification of 1000x. Samples 1 -5 differ in the cleaning method used. Surface of sample 1 has been cleaned by using a flow of pressurized air. Sample 2 has been cleaned by a cleaning product disclosed herein, comprising reticulated foam as the substrate. Sample 3 has been cleaned by wiping with a wet rag. In samples 4 and 5 cleaning products disclosed herein, comprising spacer fabrics as the substrate have been utilized. The images clearly show that the cleaning product is capable of evening the surface after sanding more efficiently when compared to air flow or wet rag. In the images of samples 1 and 3 sharper profiles when compared to samples 2, 4 and 5 are visible. Thus, the cleaning product disclosed herein is capable of rounding the sharp unevennesses of the sanded surface.

3D surface measurements conducted by an optical profilometer have been performed to study the surface roughness after cleaning. Surface roughness, often shortened to roughness, is a component of surface finish (surface texture).

Roughness values for the surfaces treated with varying cleaning products/methods were determined as areal roughness parameters according to standard series ISO 25178. According to the measurements with the cleaning product comprising reticulated foam as the substrate cleaned surface with lowest maximum peak height Sp (height of the highest peak within the definition area), lowest maximum height Sz (sum of the largest peak height value and the largest pit depth value within the definition area) and lowest five point peak height S5p is obtainable.

Air flow through different cleaning products with varying substrate materials was determined and only very small differences were observed. Air flow of 29.5 l/s was used for the tests. With the backing pad alone (no cleaning product attached) the determined air flow was 28.4 l/s (with vacuum behind the backing pad 0.84 kPa). For backing pad with cleaning products having reticulated foam as the substrate, the flow was shown to vary from 28.1 to 28.3 l/s (vacuum from 1 .09 to 0.92 kPa, respectively). The combination of backing pad and spacer fabrics as the substrate showed the flow of from 28.0 to 28.1 l/s (vacuum 1.10 kPa). The experiments show that the performance of the cleaning products with varying substrate materials disclosed herein is comparable in terms of penetration of air flow.

For comparison, similar experiments were conducted for two different polishing products having a non-reticulated foam as a substrate and a velour grip cloth laminated on the second surface of the substrate for attachment to the backing pad. Also here, air flow of 29.5 l/s was used. For backing pad with such polishing products the air flow was shown to be strangled a lot compared to the cleaning products. The flow was shown to vary from 23.8 to 24.5 l/s (vacuum from 5.20 to 4.62 kPa, respectively).

The solution disclosed herein provides a product and a method for dry dust cleaning purposes, the product and the method being separate from those directed to sanding purposes. The cleaning product and the surface treating method disclosed herein enable complete dust removal from the surface as well as from the cleaning product due to the open structure of the substrate of the product. Dust removed from the surface being cleaned is not even temporarily retained or stored within the cleaning product, but the product enables direct removal of dust both from the surface being cleaned as well as the cleaning product. Direct removal, i.e. negligible residence time, of the dust enables maintaining the cleaning product clean. Cleanliness of the cleaning product enables its use for varying surfaces, alternating for example in terms of color of the surface, without the possibility of contaminating the surface to be cleaned by the cleaning product.