TECHNICAL FIELD

The disclosure relates to a laminates comprising a metal support, a transition layer comprising a non-fluorinated thermoplastic applied directly thereto and a fluorinated polymer, which can serve as a sliding layer applied to the transition layer.

BACKGROUND ART

Laminates which comprise a layer structure having a metallic support material, an intermediate layer and a sliding layer applied thereto have been known for a long time in a variety of forms from the prior art and are used in a wide variety of technical fields, for example in the field of automotive engineering.

For slide bearings, especially conventional DU ^® bearing material, a sliding layer composed of a PTFE compound material is in turn applied to the intermediate layer. In this slide bearing material, the intermediate layer, which has the function of establishing firm adhesion of the sliding layer to the support material, is just a bronze layer sintered from bronze particles. However, this process is problematic for a variety of reasons, including performance limitations of the laminate product and failure in ensuring the combination between PTFE and the support material. As such, there is a continued need for improved laminates for applications such as slide bearings.

Therefore, it would be advantageous if a laminate could be produced that has strong adhesion to the metal support and the sliding layer.

SUMMARY OF THE INVENTION

In one aspect, a bearing article can include a metal substrate. The metal substrate can include a bronze layer. The bearing article can further include a polyether-ether-ketone (PEEK) layer. A polytetrafluoroethylene (PTFE) composition layer can overlie and penetrate the PEEK layer.

In another aspect, a method of forming a laminate includes providing a metal substrate. The method can include preheating the metal substrate. The method can include electrostatic spraying the metal substrate with a thermoplastic powder to form a transition layer. The thermosplastic powder can include a non-fluorinated thermoplastic powder. The method can include spraying the transition layer with a second thermoplastic powder. The second thermoplastic powder can include a fluorinated thermoplastic powder.

In yet one further aspect, a method of forming a bearing article can include providing a metal substrate. The method can include sintering the metal substrate with a bronze layer. The method can further include preheating the metal substrate. The method can include electrostatic spraying the metal substrate with a polyether-ether-ketone to form a transition layer. The method can include spraying the transition layer with a thermoplastic powder. The thermoplastic powder can include a fluorinated thermoplastic powder.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.

FIG. 1 shows an exemplary slide bearing in sectional view; and FIG. 2 shows a process for forming a laminate.

The use of the same reference symbols in different drawings indicates similar or identical items.

DETAILED DESCRIPTION OF THE PREFERRED EMB ODIMENT(S)

In an embodiment, a bearing article can include a metal substrate, a bronze layer, and a polyether-ether-ketone (PEEK) layer. A polytetrafluoroethylene (PTFE) composition layer can overlie and penetrate the PEEK layer.

In one embodiment, the metal substrate including the bronze layer can have a surface roughness of at least about 1 micron, such as at least about 2 microns, or about 5 microns, at least about 10 microns, or even at least about 100 microns. The surface roughness of the metal substrate can be no greater than about 200 microns, such as no greater than about 150 microns, not greater than about 100 microns, or even no greater than about 80 microns.

In one embodiment, the bronze layer can be sintered with bronze particles. In another embodiment, the bearing article includes a PEEK layer with a thickness of at least about 10 microns, such as at least about 20 microns, at least about 30 microns, at least about 50 microns, or at least about 70 microns. In another embodiment, the bearing article includes a PEEK layer with a thickness of not greater than about 500 microns, such as not greater than about 400 microns, not greater than about 300 microns, not greater than about 200 microns, not greater than 180 microns, or not greater than about 150 microns.

In another embodiment, the bearing article includes a PEEK layer, wherein the PEEK layer is porous. The porosity, which is the ratio of void volume over total volume of the PEEK layer, can be at least about 0.05, such as at least about 0.1, or at least about 0.2. The porosity can be no greater than about 0.8, such as no greater than about 0.7, or not greater than about 0.5.

In one embodiment, the bearing article includes a PTFE composition layer with a thickness of at least about 10 microns, such as at least about 20 microns, at least about 30 microns, at least about 50 microns, or at least about 70 microns. In another embodiment, the bearing article includes a PTFE composition layer with a thickness of not greater than about 500 microns, such as not greater than about 400 microns, not greater than about 300 microns, not greater than about 200 microns, not greater than 180 microns, or not greater than about 150 microns.

In one embodiment, the bearing article includes a PEEK in an amount of at least about 10 vol , such as at least about 20 vol , at least about 40 vol , or at least about 50 vol of the combined polymer layers, i.e. the combination of the PEEK layer and the PTFE composition layer. In another embodiment, the bearing article includes a PEEK layer in an amount of not greater than about 80 vol , such as not greater than about 70 vol , not greater than about 60 vol , or not greater than about 50 vol of the combined layers, i.e. the combination of the PEEK layer and the PTFE composition layer.

In yet another embodiment, the bearing article has PTFE composition layer which further includes a filler. The filler can include fibers, glass fibers, carbon fibers, aramids, inorganic materials, ceramic materials, carbon, glass, graphite, aluminum oxide, molybdenum sulfide, bronze, silicon carbide, woven fabric, powder, sphere, thermoplastic material, polyimide (PI), polyamidimide (PAI), polyphenylene sulfide (PPS), polyethersulofone (PES), polyphenylene sulfone (PPS02), liquid crystal polymers (LCP), polyetherketone (PEK), poly ether ether ketones (PEEK), aromatic polyesters (Ekonol), mineral materials, wollastonite, barium sulfate, or any combinations thereof.

In one embodiment, a method of forming a laminate can include providing a metal substrate; preheating the metal substrate; electrostatic spraying the metal substrate with a non-fluorinated thermoplastic powder to form a transition layer. The method can further include spraying the transition layer with a fluorinated thermoplastic powder to form a compound layer.

In another embodiment, the method can further include heat rolling the transition layer. In another embodiment, the method can include heat pressing the transition layer.

In one embodiment, the metal substrate includes a sintered layer. In another embodiment, the metal substrate includes a bronze layer. In one particular embodiment, the metal substrate includes a sintered bronze layer.

In one embodiment, preheating the metal substrate includes preheating at a temperature of at least about 25 °C, such as at least about 30 °C, at least about 40°C, or at least about 60 °C. In another embodiment, preheating the metal substrate includes preheating at a temperature of not greater than about 125 °C, such as not greater than about 100 °C, not greater than about 90 °C, or not greater than about 80 °C. In a particular embodiment, preheating the metal substrate includes preheating at a temperature between 25 °C and 100 °C.

In one embodiment, the method includes electrostatic spraying the metal substrate with a non-fluorinated thermoplastic powder to form the transition layer to a thickness of at least about 10 microns, such as at least about 20 microns, at least about 30 microns, at least about 50 microns, or at least about 70 microns.

The non-fluorinated powder can have an average particle size of at least about 1 micron, such as at least about 2 microns, at least about 5 microns, or even about 10 microns. In another embodiment, the non-fluorinated powder can have an average particle size of not greater than about 100 microns, such as not greater than about 80 microns, not greater than about 60 microns, or even not greater than about 40 microns. In another embodiment, the method includes electrostatic spraying the metal substrate with a non-fluorinated thermoplastic powder to form the transition layer to a thickness of not greater than about 500 microns, such as not greater than about 400 microns, not greater than about 300 microns, not greater than about 200 microns, not greater than 180 microns, or not greater than about 150 microns.

In one embodiment, electrostatic spraying of the metal substrate with a non- fluorinated thermoplastic powder can include a thermoplastic powder selected from a poly- ether-ether-ketone (PEEK), an ultra-high-molecular-weight polyethylene (UHMWPE), a polyimide (PI), a polyamide (PA), a polyamideimide (PAI), or any combination thereof.

In one embodiment, spraying of the transition layer includes spraying the transition layer with a fluorinated thermoplastic powder. The fluorinated thermoplastic powder can include a polytetrafluoroethylene (PTFE), a perfluoroalkoxy polymer (PFA), fluorinated ehylene-propylene (FEP), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), a polyethylenetetrafluoroethylene (ETFE), a polyethylenechlorotrifluoroethylene (ECTFE), or any combination thereof.

In one further embodiment, spraying of the transition layer includes electrostatic spraying the transition layer with a fluorinated thermoplastic powder.

In another embodiment, the method can further include heat rolling the compound layer. In another embodiment, the method can include heat pressing the compound layer.

In one embodiment, a method of forming a bearing article includes providing a metal substrate, sintering the metal substrate with a bronze layer, preheating the metal substrate, electrostatic spraying the metal substrate with a polyether-ether-ketone to form a transition layer. The method can further include spraying the transition layer with a fluorinated thermoplastic powder to form a compound layer.

In one embodiment, the method includes heat rolling the compound layer.

As discussed above regarding the method of forming a laminate, preheating the metal substrate in this method includes preheating at a temperature of at least about 25 °C, such as at least about 30 °C, at least about 40°C, or at least about 60 °C. In another embodiment, preheating the metal substrate includes preheating at a temperature of not greater than about 125 °C, such as not greater than about 100 °C, not greater than about 90 °C, or not greater than about 80 °C. In a particular embodiment, preheating the metal substrate includes preheating at a temperature between 25 °C and 100 °C.

In one embodiment, the transition layer has a thickness of thickness of at least about 10 microns, such as at least about 20 microns, at least about 30 microns, at least about 50 microns, or at least about 70 microns. In another embodiment, the transition layer has a thickness of not greater than about 500 microns, such as not greater than about 400 microns, not greater than about 300 microns, not greater than about 200 microns, not greater than 180 microns, or not greater than about 150 microns.

The fluorinated thermoplastic powder includes a polytetrafluoroethylene (PTFE), a perfluoroalkoxy polymer (PFA), fluorinated ehylene-propylene (FEP), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), a polyethylenetetrafluoroethylene (ETFE), a polyethylenechlorotrifluoroethylene (ECTFE), or any combination thereof.

In one embodiment, the transition layer and the compound layer have a combined thickness of at least about 20 microns, such as at least about 40 microns, at least about 80 microns, or at least about 100 microns. In another embodiment, the combined thickness is not greater than about 1 millimeter, such as not greater than about 500 microns, or at not greater than about 300 microns.

Examples

High performance non-fluorinated polymers, such as PEEK have favorable properties such as chemical resistance, electric insulation, self-lubrication, or durability against stress. Fluorinated polymers such as PTFE have favorable properties such as chemical resistance, heat resistance, and low friction.

FIG. 1 shows an exemplary laminate in sectional view. Layer 102 depicts PTFE overlying and penetrating layer 104. Layer 104 consists of PEEK, surrounding and overlying elements 106 and backing 108. Elements 106 are bronze particles sintered onto metal backing 108. FIG. 2 shows an exemplary process for forming a laminate. A metal substrate202 including a roughened surface through bronze particles sintered onto the surface of the metal surface is sprayed with PEEK powder 204. The spraying is conducted through device 206 capable of electrostatic spraying. Electrostatic spraying creates a porous PEEK layer 214. The porous PEEK layer 214 can be applied to any desired thickness. The amount of PEEK applied can be made dependent from properties such as desired adhesion strength to the metal backing or other properties, e.g., electrical insulation, which may require a thicker layer. After the spraying of the PEEK layer, the PEEK layer is smoothened by skimming board 208. Next, PTFE compound powder 212 from applicator 210 is applied onto the porous PEEK layer 214. The PTFE compound can include a single PTFE polymer or a mixture of PTFE with another polymer, filler, surface agent, softening agent, plasticizer, or any other beneficial agent.

The PTFE compound layer can be applied to any desired thickness depending from its commercial purpose. The PTFE compound layer can be sprayed onto the porous PEEK layer. For example, the PTFE can also be electrosprayed. It is also contemplated that PEEK and PTFE can be sprayed subsequently as shown in FIG. 2, concurrent (not shown in FIG. 2) or partially concurrent (not shown in FIG. 2), i.e. there is a phase when PEEK is sprayed, a phase when PEEK and PTFE is applied, and a phase when PTFE is applied.

Upon application of the PTFE compound powder, the assembly undergoes pressure and/or heat treatment. As shown in FIG. 2, the assembly can be pressed through rolls 216. In another embodiment, rolls 216 can also be heated, thereby calendering the assembly. Heat 220 can be applied with heater 218. Optionally, after heat treatment, the assembly can be pressed or calendered by rolls 220 to form compound layer 224. In other embodiments and not shown in FIG. 2, the assembly can undergo cold rolling followed by polymer or plastic sintering.

Example 1

PEEK with an average particle size of about 20 microns was electrosprayed onto a bronze sintered steel substrate. After that a PTFE compound material was applied. The PTFE compound material includes PTFE powder, graphite, and molybdenum disulfide. The PTFE powder had an average particle size of 40 microns, the graphite had an particle size ranging from 1 micron to 7 microns. Molybdenum disulfide had an average particle size of about 3 microns.

The laminate was rolled to achieve a laminate thickness of 1 mm, then the laminate was sintered at 370 °C for 2 hrs followed by heating at 200 °C for

Tribological testing was conducted according to China Standard GB3960-83 using Instrument Tribometer MA2000. The testing condition included a load of 200N, rotating speed: 200 rpm. Table 1 summarizes the result of laminates with and without a PEEK layer. The metal backing became visible on laminates without PEEK layer after 2hrs of tribological testing while laminate with PEEK layer still have plastics on the surface.

Table 1

As shown in Table 1 , the laminate containing an electrosprayed PEEK layer have lower coefficient of friction during the testing and a lower weight loss than samples that contain no PEEK layer. Furthermore, the wear width of samples with PEEK is less than without PEEK.

Laminates or slide bearings can be prepared in a vast number of very different shapes and sizes. The smallest bearing, also called a pico bearing, is only a few μιη in height compared to bearings for other applications that could be up to 500 mm.

Slide Bearings made from the laminates discussed herein can include plane bearings, annular bearings, bushings, balljoint bearings (half spheres), plain bearings, axial bearings, thrust bearings, linear bearings, bearing shells, bearing cups and combinations thereof.

It is advantageous that the bearing is maintenance free. The term "maintenance-free" describes bearings that do not need to be greased as was the case for bearings in early car doors. Yet, the life time of maintenance-free bearings exceeds the average life time of the product these bearings are incorporated or the life time of conventional bearings applied for the same purpose. Slide bearings are applied in a broad spectrum of commercial industry ranging from the heavy metal industry to the automotive and bike industry, laptop / mobile phone hinges, bearings for solar applications and more.

Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed are not necessarily the order in which they are performed.

In the foregoing specification, the concepts have been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of features is not necessarily limited only to those features but may include other features not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, "or" refers to an inclusive-or and not to an exclusive-or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Also, the use of "a" or "an" are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims. After reading the specification, skilled artisans will appreciate that certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, references to values stated in ranges include each and every value within that range.