WO2007097970A1

WO2007097970A1 - An abrasive article for hand-held, or similar, use and preparation thereof

Info

Publication number: WO2007097970A1
Application number: PCT/US2007/003925
Authority: WO
Inventors: Jean Le Normand
Original assignee: 3M Innovative Properties Company
Priority date: 2006-02-17
Filing date: 2007-02-15
Publication date: 2007-08-30
Also published as: GB0603275D0; EP1986820A1; EP1986820A4

Abstract

An abrasive article comprises an abrasive part (1) having a first surface and an opposing second surface, and a backing (2) suitable for hand-held use or for attachment to the pad of a machine that provides a similar action, wherein the backing (2) is formed of injection-moulded polymeric material, the first surface of the abrasive part being fixed directly to the backing by the polymeric material and the second surface defining a working surface of the abrasive article. A method of making the abrasive article comprises: providing the abrasive part (1); injecting molten polymeric material in contact with the first surface thereof; and allowing the polymeric material to cool while remaining in contact with the first surface to form the backing.

Description

AN ABRASIVE ARTICLE FOR HAND-HELD, OR SIMILAR, USE AND PREPARATION THEREOF

FIELD

The present invention relates to an abrasive article comprising an abrasive part fixed to a backing, and to its preparation. The invention is particularly concerned with abrasive articles for hand-held use, or for attachment to the pad of a machine that provides a similar action.

BACKGROUND

Abrasive articles for hand-held use are available in many different grades, from coarse grades suitable for sanding or grinding, to very fine grades suitable for polishing or cleaning. Sheets and pads of abrasive material are the simplest forms of such articles and are widely used. It is also known to provide holders for sheets and pads of abrasive material, to facilitate their use. One example of such a holder is the Twist-Lok™ Pad Holder available from 3M Company of St. Paul, Minnesota, USA, which is intended for use with pads of 3M Scotch-Brite™ non-woven abrasive material: the holder enables the manual pressure applied by the user to be distributed evenly over the pad surface for efficient cleaning action and improved pad life

Although consumers who are faced with carrying out a hand-sanding operation appreciate the advantages provided by holders for abrasive sheets or pads, there are situations in which they decide that the cost of a suitable holder is not justified by the amount of use that it will receive, or they feel that its use (i.e. fitting the abrasive sheet or pad in the holder and then replacing it as necessary) will be too time consuming. As an alternative to hand-held use, it is also known to attach abrasive parts (especially abrasive sheets and pads) to machines that provide a similar action, such as flat bed or orbital sanders.

However, some abrasive parts have a configuration that is not suitable for attachment to such machines.

The invention has been made with these points in mind. SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a method of making an abrasive article comprising an abrasive part and a backing, fixed to the abrasive part, suitable for hand-held use or for attachment to the pad of a machine that provides a similar action, which method comprises: providing an abrasive part having a first surface and an opposing second surface;

and injecting molten polymeric material in contact with the first surface and allowing the polymeric material to cool while remaining in contact with the first surface to form the backing.

Advantageously, a predetermined amount only of polymeric material is injected in contact with the first surface.

In a second aspect of the invention, an abrasive article comprises an abrasive part having a first surface and an opposing second surface, and a backing suitable for hand-held use or for attachment to the pad of a machine that provides a similar action, wherein the backing is formed of injection-moulded polymeric material, the first surface of the abrasive part being fixed directly to the backing by the polymeric material and the second surface defining a working surface of the abrasive article.

In the invention, the backing is fixed directly to the abrasive part by the polymeric material. This is achieved by contacting the abrasive part with the polymeric material while the polymeric material is molten, and allowing the polymeric material to cool. The polymeric material of the backing therefore becomes integrally formed with the abrasive part. The invention does not require the use of a separate adhesive to fix the backing to the abrasive part. The backing may be shaped to provide a handle, or for attachment to the pad of an abrading machine such as a flat bed sander or an orbital sander.

The abrasive part may comprise a plurality of abrasive flaps having a first edge and an opposing second edge, the flaps being arranged adjacent one another so that the first edges define the said first surface and the second edges define the said second surface. In that case, the invention has the advantage that the working surface is formed from the edges of a plurality of abrasive flaps, rather than a single layer of material. As the end of the flaps wears down, new material is exposed, prolonging the useful life of the article.

The backing, when in the form of a handle, can act as a part which can be safely gripped by a user, with reduced risk of injury from stiff abrasive material. The backing can also provide the abrasive article with increased rigidity. The backing can further provide a means of attaching, to the pad of an abrading machine, an abrasive part in a form not usually used for that purpose, for example an abrasive part comprising a plurality of flaps. Few raw materials are needed to make the abrasive article of this invention, and the possibility exists of using materials that are readily and cheaply available. Thus the invention can provide an article which lasts longer, is easier and safer to use, and is more economical to produce.

Preferably, the backing extends beyond, and forms a flange around, the abrasive part. However, the backing may be co-extensive with, or slightly smaller than, the abrasive part, depending on its intended use.

The abrasive part can be made of non-woven fibres, in which case the molten polymeric material may penetrate into interstices between the fibres, fixing the backing to the abrasive part. Non-woven abrasive materials typically include a three-dimensional, open, lofty web formed often of a network of autogenously-bonded filaments which provide surfaces upon which abrasive particles may be adhesively attached. The thickness, length and composition of the filaments and the type of adhesive binders and abrasive particles may be selected depending upon the intended application of the abrasive web. Examples of non-woven abrasive web materials are disclosed in US 2,958,593, US 4,227,350, US 5,928,070 and US 6,302,930. Suitable non-woven abrasive materials for use in the present invention are commercially known as Scotch-Brite™ abrasive material, available from 3M Company of St. Paul, Minnesota, USA. The abrasive part can alternatively be made of a material that is not porous to the injected polymeric material, for example a coated abrasive material. In this case, the molten polymeric material may adhere to the backing of the abrasive material. Coated abrasive materials generally comprise a substrate to which a plurality of abrasive particles are bonded by suitable bond systems. Various coated abrasives are known to the person skilled in the art. As a further alternative, an article according to this invention may be made of a combination of non-woven abrasive material and abrasive material that is not porous to the injected polymeric material. When the abrasive part comprises flaps, the two kinds of flaps can be arranged to alternate.

Optionally, a restricting layer can be placed adjacent the first surface of the abrasive part such that the molten polymeric material is injected onto the restricting layer. The restricting layer is permeable to the molten polymeric material. It causes the polymeric material to spread over the abrasive part while allowing molten polymeric material to contact the abrasive part. This is particularly preferred when the abrasive part comprises non-woven fibres.

In the absence of a restricting layer, polymeric material may not spread evenly to form the backing as intended. This is because the polymeric material may preferentially penetrate into the non-woven material, particularly in the region where the polymeric material is injected, rather than build up to form the backing. In embodiments having non-porous abrasive material, it can also be beneficial to use a restricting layer. With non-porous abrasive material, polymeric material may preferentially stick to the non-porous material in the region where polymeric is injected, thus hindering or possibly preventing even spreading of the polymeric material over the abrasive part.

The restricting layer therefore ensures that polymeric material spreads substantially evenly over the surface of the abrasive part before the polymeric material penetrates into or adheres to the abrasive part, and limits the penetration of polymeric material into the abrasive part.

The restricting layer is preferably a mesh, also known as a scrim. The mesh may have a mesh opening of up to 1000 micrometers, and the filaments of the mesh may be composed of a plastic material such as polyamide or polypropylene, an organic material such as cotton or linen, or a metal such as steel.

In one embodiment in which the abrasive apart comprises flaps, the flaps extend substantially perpendicularly away from the backing. The flaps may alternatively extend obliquely away from the backing. The abrasive flaps can be substantially parallel. In this case, and in other embodiments of the invention, the second surface of the abrasive part may have a square or rectangular shape, or it may be curved.

The abrasive flaps may be arranged under compression. A greater amount of compression provides a stiffer brush, whereas little or no compression provides a softer brush. The degree of compression will also affect the extent to which the polymeric material of the backing permeates into, or between, the flaps.

The method of making the abrasive article may further comprise the steps of providing a mould having first and second mould plates which together define a mould cavity, placing said abrasive part in the mould cavity, and injecting molten polymeric material into the mould cavity to form the backing.

When using a restricting layer, there can be a further step of placing the restricting layer on the first surface of the abrasive part.

Preferably, one of the mould plates is formed with a channel through which the molten polymeric material is injected.

Advantageously, the polymeric material of the backing is a thermoplastic material. A range of thermoplastic materials can be used, and the selection of one suitable for a given use will be apparent to those skilled in the art. The material is selected so that it will have a suitable viscosity at the injection temperature, generally 200 to 28O⁰C. Exemplary thermoplastic materials include thermoplastic polyether ester elastomer block copolymers comprising hard (crystalline) segments of polybutylene terephthalate and soft (amorphous) segments based on long-chain polymether glycols commercially available from DuPont under the trade name HYTREL; polyamides such as nylon 66 e.g. commercially available from LATI Industria Termoplastic S.p.A. under the trade name LATAMID and polyolefins, such as polyethylene and polypropylene. The thermoplastic material may optionally contain filler and/or reinforcing fibres.

The polymeric material of the backing need not, however, be a thermoplastic material: other polymeric materials suitable for injection moulding could be used including thermoset materials (for example, a blocked epoxy resin). Suitable injection moulding machines for use in the invention are well known and may have vertical or horizontal orientations. A vertical orientation moulding machine provides an advantage since it facilitates controlling of the spread of the molten polymeric material. Suitable injection moulding machines are commercially available from Arburg GmbH under the trade name ALLROUNDER. Horizontal injection moulding machines are widely available and may also be used. As described below, the machine selected should be capable (following adaptation if necessary), of injecting only a specific, predetermined, amount of molten polymeric material.

Embodiments of the invention will now be described, by way of example only, with reference to the following drawings in which:

Figure 1 is a diagrammatic perspective view of an abrasive article according to one embodiment of the invention;

Figure 2 is a diagrammatic section through a mould used to make the article of Figure 1;

Figure 3 is a diagrammatic section through a mould used to make an article according to another embodiment of the inventi on .

The abrasive article shown in Figure 1 has a backing (2) fixed to a plurality of abrasive flaps (1). The backing is made of injection moulded plastic. The abrasive flaps are substantially planar, rectangular flaps of a non-woven abrasive material, more specifically an abrasive material of the type comprising a three-dimensional lofty, open, non-woven web of autogenously-bonded fibres. Suitable abrasive material is the above-mentioned Scotch-Brite™ abrasive material, but could instead be flaps of coated abrasive or a mixture of both. The thickness of the flaps (1) has been exaggerated in the drawings: typically, there would be a greater number of thinner flaps used in the abrasive article.

The flaps have a first edge (4) (not visible in, Figure 1) and a second, opposing, edge (5), the first edges defining a first surface (also not visible in Figure 1) and the second edges defining a second surface which is the working surface of the article. The flaps (1) extend perpendicularly away from the backing (2), the first edge (4) of each flap being fixed to the backing (2). The flaps are generally parallel and are linearly arranged so as to form a longitudinal flap brush, the second, working, surface of which has a rectangular shape. The backing (2) has a thickness which ensures that it can be easily gripped by a user. It extends beyond the abrasive flaps (1) forming a flange (3) around the flaps, which again helps a user to grip the article. The, backing (2) is rectangular, but it could have other shapes suitable for being gripped. The backing (2) facilitates the use of the abrasive material to treat a surface but, as described below, can be provided in a cost-effective manner.

This hand-held brush is made by placing a plurality of abrasive flaps (1) in a mould cavity (9) defined by first (10) and second (11) mould plates, as shown in Figure 2. The first mould plate (10) has a rectangular recess (12), into which the flaps (1) are placed. The flaps are arranged in the recess (12) so that their planes are perpendicular to a base (6) of the recess. A shoulder (7) surrounds the recess (6). The depth of the recess (6) is less than the height of the flaps (1) so that part of the flaps protrude from the recess (6) beyond the shoulder (7).

The mould is closed and molten thermoplastic material is injected through the channel (8) into the mould cavity (9). Some of the plastic material penetrates into some of the interstices of the web material from which the flaps (1) are formed. The rest of the cavity (9) is filled with the plastic material to form the backing (2). Due to the presence of the shoulder (7), the resultant backing is wider than the width of the flaps and longer than the plurality of flaps together, thus providing the flange (3) around the flaps (1).

In this embodiment, the extent to which the thermoplastic material of the backing (2) penetrates into the flaps (1) can be controlled by injecting only a limited amount (i.e. a shot) of molten thermoplastic material into the mould cavity through the channel (8). If the flaps (1) are compressed together when they are placed in the recess (12) in the mould plate (10), the extent of penetration of the molten thermoplastic material may also be limited by the degree of the compression.

In another embodiment, shown in Figure 3, a scrim (13) is used to improve the distribution of the thermoplastic material. The method' is the same as that described above with reference to Figure 2, except that the scrim (13) is placed in the mould cavity (9) on the first edges (4) of the flaps (1) before the thermoplastic material is injected. The scrim (13) is a mesh of Sefar™ Nitex™ 06-850/53 monofilament open mesh fabric composed of polyamide 6. The mesh opening is 850 micrometers, the filament has a diameter of 305 micrometers, and the fabric has a thickness of 555 micrometers. The fabric is available from Sefar AG, Filtration Division, Moosstrasse 2, CH-8803, Rueschlikon, Switzerland.

As an alternative, or additional, aid to improving the distribution of the thermoplastic material, several injection channels may be provided in the mould rather than the single channel (8) as illustrated.

In a moulding process as described above with reference to Figs. 2 or 3, the amount of thermoplastic material that is injected into the mould cavity 9 can be controlled by means of a suitable valve (not shown) located in the channel 8. The channel 8 is connected to a suitable supply of molten thermoplastic material under pressure so that, if the valve is opened for a predetermined interval of time, a predetermined amount of the thermoplastic material will be injected into the mould cavity 9, sufficient to form the backing 2 and to penetrate, to the desired extent, into the abrasive material of the flaps 1. The process thus differs from a conventional injection moulding process in which the injection of molten thermoplastic material into the mould would continue until the mould cavity has been filled. The process may, nevertheless, be carried out using a conventional injection moulding machine suitably-adapted for the purpose although, because the mould cavity is never filled with the injected thermoplastic material, it is not actually essential for the mould to be closed. Through the use of such a process, it can be ensured that the injected thermoplastic material does not permeate throughout the abrasive material of the flaps 1 and, because the abrasive material is not subjected to the high pressures normally generated in the mould cavity of an injection moulding machine, the risk of structural damage to the abrasive material is minimized.

Suitable injection moulding machines for carrying out the method described above may have vertical or horizontal moulding orientations, provided that they permit the injection repeatedly of predetermined amounts of molten material into the mould cavity with reasonable accuracy. A vertical orientation moulding machine provides an advantage, as already mentioned, since it facilitates regulation of the spread of the injected molten thermoplastic material. The valve used to control the amount of thermoplastic material injected into the mould cavity may be of any suitable type, one being an electromagnetically-controlled needle valve known for use in sprueless injection moulding. A suitable valve is an electromagnetic needle valve available, under the trade name "Z 1081" from HASCO Hasenclever GmbH + Co KG of Lϋdenscheid, Germany. The opening of the valve can be controlled by the injection machine itself.

The invention can cover various alternatives not described here. For example, the abrasive part and/or backing can have various different shapes and sizes, and can be made of other suitable materials. More specifically, in the abrasive article of Figure 1, it is possible for the planes of the flaps (1) to extend from the backing (2) at an angle of other than 90° and/or for the planes of the flaps to be inclined to one another, subject to the requirement that the completed article can be removed from the mould in which it is formed. The flaps (1) could also be selected and arranged so that the working surface formed by the edges (5) is non-rectangular and/or non-planar. As a further alternative, the flaps (1) of the abrasive article could be formed from a length of Z-folded material as described in our co- pending PCT application claiming priority from UK patent application No. 0603280.9 of 17 February 2006, and entitled "SURFACE TREATMENT ARTICLE COMPRISING A PLURALITY OF FLAPS, AND PREPARATION THEREOF".

In other embodiments, the abrasive flaps 1 of Figure 1 are replaced by a block of abrasive material, for example a block of a non- woven abrasive material.

As a further alternative, the backing 2 of the abrasive article is formed so that it can be attached to the pad of a sanding machine, typically a machine that provides an abrasive action similar to hand sanding. For that purpose, the backing could for example be provided with a mechanical fastener (such as one part of a hook-and-loop attachment system) enabling it to be attached to the pad of a sanding machine. The mechanical fastener could be attached to the abrasive article during, or after, the moulding process in which the backing is formed.

Claims

1. A method of making an abrasive article comprising an abrasive part and a backing, fixed to the abrasive part, suitable for hand-held use or for attachment to the pad of a machine that provides a similar action, the method comprising: providing an abrasive part having a first surface and an opposing second surface; and injecting molten polymeric material in contact with the first surface and allowing the polymeric material to cool while remaining in contact with the first surface to form the backing.

2. A method as claimed in claim 1, in which a predetermined amount only of polymeric material is injected in contact with the first surface.

3. A method a claimed in claim 1 or claim 2, wherein the backing extends beyond, and forms a flange around, the abrasive part.

4. A method as claimed in any one of the preceding claims, wherein the abrasive part comprises fibrous non-woven abrasive material.

5. A method as claimed in any one of the preceding claims, comprising the step of placing a restricting layer adjacent the first surface of the abrasive part such that the molten polymeric material is injected onto the restricting layer, the restricting layer causing the polymeric material to spread over the first surface.

6. A method as claimed in any one of the preceding claims, wherein the abrasive part comprises a plurality of abrasive flaps having a first edge and an opposing second edge, the flaps being arranged adjacent one another so that the first edges define the said first surface and the second edges define the said second surface.

7. A method as claimed in any one of the preceding claims, further comprising the steps of: providing a mould having first and second mould plates which together define a mould cavity;

placing the abrasive part in the mould cavity; and

injecting molten polymeric material into the mould cavity to form the backing.

8. An abrasive article comprising an abrasive part having a first surface and an opposing second surface, and a backing suitable for hand-held use or for attachment to the pad of a machine that provides a similar action, wherein the backing is formed of injection-moulded polymeric material, the first surface of the abrasive part being fixed directly to the backing by the polymeric material and the second surface defining a working surface of the abrasive article.

9. An article as claimed in claim 8, made in accordance with the method of any one of claims 1 to 7.