BACKGROUND TO THE JNVEMTIOM

THIS invention relates to a method of producing a polymer product.

Furniture slides are used to assist persons in moving heavy furniture or objects across floors. Typically a furniture slide comprises a sliding portion, which is produced from a material exhibiting a very low coefficient of friction, and a holding portion in which a foot of an article of furniture which is to be moved can be supported. In order to move an article of furniture across a floor, for example a large table, a furniture slide is placed between the floor and each foot of the table. The feet are supported in the holding portions of the slides while the sliding portions face the floor. Due to the fact that the sliding portions are made of a material having a low coefficient of friction, the table can be slid across the floor with more ease than would have been the case had the feet of the table been in direct contact with the floor.

Various types of furniture slides are known. One existing type of furniture slide comprises a sliding portion, produced from polytetrafluoroethylene (PTFE), and a holding portion produced from rubber. It has however been found that an article of furniture may slide relative to the furniture slide, often bending securing edges of the rubber holding portion such that the slide becomes dislodged from underneath the article of furniture. This causes inconvenience due to the fact that the dislodged furniture slide first has to be relocated in position before further movement can take place. In instances where an article of furniture is to be slid across a large distance or during regular intervals, such dislodgements could cause severe inconvenience as well as a substantial waste of time.

One possible solution to address the problems associated with furniture slides having rubber holding portions would be to replace the rubber with alternative materials. Unfortunately the non-stick physical properties of PTFE, the only known material having a static coefficient of friction which is lower than its dynamic coefficient of friction, also leads to the disadvantage that it is difficult and expensive to cause PTFE to bond to other materials. A further solution to address the problems associated with rubber holding portions would be to produce the entire furniture slide of PTFE. This would however lead to a substantial increase in the production cost of a furniture slide, making it extremely difficult to compete in the marketplace with existing furniture slides which are produced and sold at substantial lower costs.

It is an object of the present invention to address the above problems.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method of producing a polymer product comprising the steps of:

providing a fluoropolymer body;

preparing a bonding surface on the fluoropolymer body;

adding a bonding agent to the bonding surface of the fluoropolymer body; and

moulding or extruding either a thermoplastic polymer or a thermoset polymer onto the bonding agent on the bonding surface of the fluoropolymer body. Advantageously moulding of the polymer takes place by way of injection moulding or compression moulding.

Preferably the thermoset polymer is chosen from the group consisting of urethane formaldehyde, phenol formaldehyde, melamine formaldehyde, unsaturated polyesters and epoxy based polyesters.

Advantageously the step of preparing a bonding surface is achieved by etching, filling the fluoropolymer or plasma treatment.

According to a second aspect of the invention there is provided a method of producing a slide comprising the steps of:

providing a fluoropolymer body for forming a sliding portion of the slide;

preparing a bonding surface on the fluoropolymer body;

adding a bonding agent to the bonding surface of the fluoropolymer body; and

moulding either a thermoplastic polymer or a thermoset polymer onto the bonding agent on the bonding surface of the . fluoropolymer body for forming a holding portion of the slide.

Typically the fluoropolymer body comprises polytetrafluoroethylene (PTFE).

According to a third aspect of the invention there is provided a polymer product comprising a fluoropolymer body having a bonding surface, the bonding surface having undergone a process to prepare it for bonding, a bonding agent that is applied to the bonding surface and either a thermoplastic polymer or a thermoset portion moulded or extruded onto the bonding agent on the bonding surface. -A-

According to a fourth aspect of the invention there is provided a slide comprising a polytetrafluoroethylene sliding portion having a sliding surface and a bonding surface, the bonding surface having undergone a process to prepare it for bonding, a bonding agent that is applied to the bonding surface and a holding portion of either a thermoplastic polymer or a thermoset polymer moulded onto the bonding agent on the bonding surface of the sliding portion.

Typically the holding portion is moulded by way of injection moulding.

According to a fifth aspect of the invention there is provided a method of producing a composite polymer product:

providing a first and a second fluoropolymer body;

preparing a bonding surface on each fluoropolymer body;

adding a bonding agent to the bonding surface of both the first and second fluoropolymer body;

moulding or extruding either a thermoplastic polymer or a thermoset polymer onto the bonding agent on the bonding surface of the first and second fluoropolymer body respectively thereby forming a first and a second polymer product; and

moulding or extruding a connector for connecting the first polymer product with the second polymer product.

According to a sixth embodiment of the invention there is provided a composite polymer product comprising a first and a second polymer product, each polymer product comprising a fluoropolymer body having a bonding surface which has undergone a process to prepare it for bonding, a bonding agent that is applied to the bonding surface and either a thermoplastic polymer or a thermoset portion, moulded or extruded onto the respective bonding agents on the bonding surfaces, and wherein the polymer products are attached to each other with a connector.

BRIEF DESCRIPTtON OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings wherein:

Figure 1 shows a diagrammatic representation of steps in a method of producing a polymer product in accordance with the invention;

Figure 2 shows a perspective view of a first embodiment of a slide produced by the method of the invention;

Figure 3 shows a perspective view of a second embodiment of a slide produced by the method of the invention;

Figure 4 shows a side view of a chair being slid along a floor on slides produced in accordance with the invention, the slides being shown in cross-section;

Figure 5 shows a side view of a third embodiment of a slide produced in accordance with the invention as well as an enlarged cross-sectional view of a portion of the slide;

Figure 6 shows a top view of a composite slide made in accordance with the invention;

Figure 7 shows a cross-sectional side view of the composite slide of Figure 6 at the line 7-7; and Figure 8 shows a perspective view of a composite slide which is to be secured to an article of furniture.

DESCRIPTION OF THE ILLUSTRATED EiWBODItVlENTS

Figure 1 shows a diagrammatic representation of steps followed in a method of producing a polymer product in accordance with the present invention, specifically a moulded product including a fluoropolymer. The steps of the method are generally indicated with the reference numeral 10. In the present embodiment the method of the invention is employed to produce a slide, typically a furniture slide, incorporating the polymer product.

In the described embodiments the fluoropolymer is polytetrafluoroethylene (hereinafter referred to as PTFE), it will however be appreciated that the invention is not limited to PTFE but that other types of fluoropolymers could also be used.

PTFE is normally produced in large sheets. The first step in the invention, indicated with the reference numeral 12, is to provide a PTFE body, here for use as a sliding portion of a slide. The sliding portion, indicated with the reference numeral 14, is provided by pressing a disc from a PTFE sheet 16 by means of a suitable press, not shown in the drawings. The sliding portion 14 hereafter undergoes a process for preparing a bonding surface, in this case an etching process, indicated by the reference numeral 18.

During the etching process a surface of the sliding portion is prepared for bonding to another material. As stated in the background portion of the specification, PTFE exhibits a very low coefficient of friction which is the result of its non-stick properties. The non-stick properties of PTFE can be attributed to the fact that PTFE exhibits no surface charges. Persons skilled in the field of PTFE will be familiar with the chemistry involved in bonding materials together and that surface charges are required to effect bonding. Persons skilled in the field of PTFE will further also be familiar with the process of etching which is used to create a surface charge on a PTFE. For the sake of completeness the process of etching is however briefly discussed below.

Etching involves the use of radicals to remove fluorine atoms from a PTFE surface thereby leaving a carbon backbone which partially oxidises to form ketones and alcohols. This surface, referred to as the bonding surface, is capable of bonding to other polymers due to intermolecular attraction forces, typically Van der Waals forces. The most common methods of producing radicals are to either dissolve a sodium metal into ammonia or a sodium metal in a naphthalene solution. Persons skilled in the art will however appreciate that there are further methods of producing radicals for use in preparing a bonding surface.

After etching, the sliding portion 14 comprises a bonding surface 20 and a sliding surface 22 as shown. A primer or bonding agent 21 is now added to the bonding surface 20 of the sliding portion 14. This step is indicated with the reference numeral 23. In this embodiment the bonding agent is a polychloroprene/neoprene based glue.

The sliding portion 14 is now placed in an injection moulding machine, not shown, such that the fourth step of the invention, generally indicated with the reference numeral 24, can take place. During the injection moulding process a holding portion 26 of a thermoplastic polymer is injection moulded onto the sliding portion 14. A bond is now allowed to form between the bonding surface 20, the bonding agent 21 and the thermoplastic polymer 14.

It is pointed out that in this embodiment of the invention the thermoplastic polymer is acrylonitrile butadiene styrene, commonly referred to as ABS. It will however be appreciated that a range of thermoplastic polymers could be used. Figure 2 and Figure 3 show two embodiments of completed furniture slides, generally indicated with the reference numerals 28 and 30 respectively, produced in accordance with the method of the invention. Each furniture slide comprises a sliding portion 14 and a cup-shaped holding portion 26. It will however be noticed that the proportions of the respective sliding portions and holding portions differ. It will be appreciated that a wide range of slides having various shapes and proportions could be produced by the method of the invention.

Figure 4 shows a chair 32 having legs 34. The feet of the legs 34 are located inside holding portions 38 of furniture slides 40 of the invention. Sliding portions 42 of the furniture slides 40 are in contact with a floor 44 which is covered with a carpet, not shown. In order to move the chair 32 across the carpet in the direction of the arrow 46, a user exerts a pulling force in the direction of the arrow. Due to the fact that the coefficient of friction between the carpet and the furniture slides 40 is lower than the coefficient of friction between the feet of the chair and the carpet, less force will be required to move the chair than is the case without furniture slides.

It is pointed out that the step of preparing a bonding surface on the polytetrafluoroethylene body can be achieved through a number of methods. One such method is through the use of filling. In this method the polytetrafluoroethylene body is provided in a powder form which is mixed with a suitable filler. Examples of filler materials are fibres, molybdenum, bronze and carbon. When sufficient filler is mixed with the PTFE, an active surface may be created for bonding without requiring an etching process. One example of a sufficient filling is a PTFE having a carbon fill of 25%.

The step of preparing a bonding surface can also be achieved by way of plasma treatment. As persons skilled in the art will know, plasma treatment comprises treating a polymer surface with a highly ionized flame thereby to ionize the treated surface. Figure 5 shows a third embodiment of a slide produced in accordance with the present invention, generally indicated with the reference numeral 50. The slide 50 comprises a PTFE sliding portion 52, a holding portion 54 produced from a thermoplastic polymer and a bonding agent 56 which comprises multi-layered bonding substances. In this embodiment the bonding agent 56 comprises a layer of a first bonding substance 58 which is located between two layers 60 and 62 of another bonding substance.

During trials it was found that by providing a bonding agent which comprised multi-layered bonding substances, effective bonds between the holding portion and sliding portion of a slide could be created. An example of this alternative configuration is described with reference to Figure 5 of the drawings.

In the embodiment of Figure 5 the second and third layers 60 and 62 of the bonding agent 56 is provided by a chlorosulphonated polyethylene glue. The first layer 58 on the other hand is provided by a glue comprising polychloroprene and synthetic resins in a solvent blend.

Although the bonding agent 56 of the slide 50 comprises a layer of one bonding substance which is located between two layers of a second substance it will be appreciated that the bonding agent could comprise a layer of a first bonding substance which is located between layers of a second and a third bonding substance.

Figure 6 and Figure 7 show a composite slide made in accordance with the present invention, generally indicated with the reference numeral 70. The composite slide 70 comprises four slides 72.1 , 72.2, 72.3 and 72.4 which are connected to each other via connectors 74. The connectors 74 provide pre-marked cut lines such that the slides 72.1, 72.2, 72.3 and 72.4 of the composite slide 70 can be cut and separated from each other. This feature has the advantage that a supplier need only stock a single sized composite slide which a user may then cut to a suitably sized section for his specific application. This is illustrated in Figure 8 of the drawings where the user has removed slides 72.3 and 72.4 from the composite slide 70 so that only slides 72.1 and 72.2 can be secured to an item of furniture 76.

In the embodiment of Figures 6 to 8 each slide 72.1, 72.2, 72.3 and 72.4 includes a hole 78.1, 78.2, 78.3 and 78.4 which can receive attachment means 80, typically a screw, for securing the composite slide to, for example, an article of furniture. It will be appreciated that the slides 72.1, 72.2, 72.3 and 72.4 need not include a hole but could also include adhesive layers by which the slides could be secured to the article of furniture.

The composite slide will typically be manufactured in a manner as described above but with the exception that when moulding takes place connectors will also be moulded which connect a number of slides to each other.

Although specific mention has been made of thermoplastic polymers the invention extends to the use of moulding or extrusion to adhere a thermoset polymer to a fluoropolymer. In particular the thermoset polymer is chosen from the group consisting of urethane formaldehyde, phenol formaldehyde, melamine formaldehyde, unsaturated polyesters, epoxy based polyesters and elastomers, typically rubber.

It will be appreciated that the method of the invention could be employed to produce a range of products where low friction or other fluoropolymer characteristics, such as good electrical and chemical resistance, are required and that the method of the invention is not restricted to the production of furniture slides. It is for example envisaged that as a result of the hydrophobic characteristics displayed by PTFE, the method of the invention could be used to produce coasters for glasses. A disadvantage of existing coasters is that they tend to stick to the bottom of a glass when a user lifts the glass to take a sip. By using PTFE as a base for the coaster this problem can be addressed. It is also envisaged that that polymer product of the invention can be utilised as wear strips in various applications, for example in tumble dryers. A wear strip for use in a tumble dryer will comprise a strip of filled PTFE with a supporting plastic backing. In such applications the polymer product will reduce friction and improve wear life.

By using the method of the invention the beneficial characteristics of PTFE can be employed in a large number of applications. In particular by providing a furniture slide having a holding portion of a polymer which is injection moulded onto a PTFE sliding portion, the problems with existing furniture slides are addressed.