EP0214970A1 - A high frictional coefficient coating for rubber tires of vehicles - Google Patents

Abstract

A coating with a high coefficient of friction intended to be applied to vehicle tires and rolling bodies in general with the aim of making them non-slip on wet, snowy or icy road surfaces, comprises an elastic substrate for adhesion to the ground and support in which are incorporated several hard bodies or "granules" having a hardness of at least 7 Mohs and distributed randomly on this substrate and partially projecting from the surface of the substrate; this support substrate is formed from at least one rubber and at least one synthetic resin, the granules comprising an inorganic substance and having the shape of irregular polyhedra which can be enveloped by ideal spheres with a diameter of order of 1 to 9 mm, preferably 1 to 3 mm.

Description

"A HIGH FRICTIONAL COEFFICIENT COATING FOR RUBBER TIRES OF VEHICLES"

This invention relates to a high frictional coefficient coating for application to the rubber tires of vehicles and generic rolling bodies to enhance their non-skid properties on wet, snow and/or ice covered road surfaces. It is known that in order to improve the traction of vehicle, in particular passenger car, tires on ice or snow covered surfaces, spikes or chains can he applied. Chains have some well-known disadvantages, resulting in particular from the slow and uncomfortable ride of the vehicle even when, on removal of the ice or snow layer from the road surface, the vehicle is to run over the normal wearing course of the road; in that case, chains must be taken off or speed of travel is to he drastically reduced, while the vehicle and passengers are subjected to objectionable vibration. Spikes have instead the disadvantage that while they can provide good traction on an ice covered road, quite a different situation is experienced in deep snow. Further, the spikes may come loose from the tire tread on an asphalt surface, to make the road condition dangerous and the wheel traction unevenly distributed.

It is, therefore, an object of this invention to provide a high frictional coefficient anti-skid coating for application to the rubber tires of vehicle wheels and rolling bodies in general, wherehy they can be made particularly well skid-resisting on wet, snow and/or ice covered road surfaces.

Another object of this invention is to provide ice and snow wheels for motor vehicles, that is, to improve the traction power of such wheels as a motor vehicle is driven over wet and/or snow and/or ice covered road surfaces.

These and other objects, such as will be apparent from the description that follows, are achieved by a coating comprising, according to the invention, a supporting, elastic grip substrate incorporating a plurality of hard bodies or "granules" distributed randomly thereon and protruding part-way out of the surface of the supporting substrate and having a hardness-preferably no lower than 7 Mohs, said supporting substrate including at least one, synthetic or natural rubber, and at least one synthetic resin, advantageously of the epoxy kind, said granules being granules of an inorganic material having a hardness preferably no lower than 7 Mohs and being in the shape of irregular polyhedrons envelopable by ideal spheres having a diameter on the order of 1 to 9 mm, preferably 1-3 mm. Said rubber or said resin (which would contain, of course, known conventional additives and adjuvants, such as stabilizers, curing agents, plasticisers, reinforcing fillers, anti-oxidants, and the like) hold said granules anchored therein being bonded to the same by bonds of a physical, and/or physico-chemical nature. Said granules (hereinafter referred to also as "hard granules") preferably comprise, according to the invention, a substance selected from a group including natural or synthetic corundum, boron carbide, tungsten carbide, silicon carbide, titanium carbide, widia, metal-ceramic and ceramic materials. The invention may be variously embodied, based upon the above-specified inventive concept, without departing from the protection scope of the invention. As an example, one embodiment of the invention consists of providing four already worn motor car rubber tired wheels, removing with conventional methods the tire worn tread down to the "ply", then regenerating on the ply itself, and using known methods, a new tread employing a blend of vulcanisable rubber, known in the art, to which blend there are incorporated (prior to its forming and vulcanisation) hard granules of the type described above in conformity with the invention (e.g. corundum) in an amount varying in the 30% to 50% by weight of the blend range.

Prior to being incorporated to the rubber blend, said hard granules may be coated with a thin layer of an adhesive having a high compatibility and affinity for both rubber and the hard granules, and this for the purpose of making the adhesion-incorporation of said granules to the end rubber strong and stable once it is formed and vulcanised to provide the new snow and ice tread for the four wheels, which wheels are thus ready for use on wet and/or snow and/or ice covered road surfaces.

Of course, the foregoing method may be implemented (rather than on rebuilding used tires) during the standard process of tire making (or making of pneumatic tires for motor vehicles and the like), by incorporating at a suitable stage of the manufacturing process the hard granules to the blend wherefrom the tire tread is to be formed.

Another embodiment of the invention will be described with reference to the following illustrative and not limitative Example. Example

100 parts (by weight) of the component "Chem-Res 200" and 120 parts of the component "BJF 50" (curing agent), respectively, of an epoxy resin produced by

Ditta Chemplast of Buccinasco, Milan, Italy, are heated separately to a temperature in the 30° to 40°C range, and said two components are then mixed together. The resulting resinous syrup is applied evenly to form a layer of about 3-8 mm over the tread of four motor car tires (still in a usable condition) as previously degreased with trichloroethylene; thereafter, said syrup is allowed to cure at room temperature until it achieves a "soft" consistency. Prior to spreading said resinous syrup over the tread, sections of 10 mm wide adhesive tape are laid onto the latter in crisscrossing configuration to form a plurality of lozenges with the sides of the lozenges measuring approximately 10 to 14 cm. It may be appreciated that during the application no resin will adhere on the tread areas occupied by the tape sections (thus enabling the later formation of draining flutes and leading edges).

In the meantime, a further epoxy resin syrup similar to the former syrup is prepared, except that incorporated to and homogeneously dispersed through the syrup are irregular polyhedral granules of corundum, of the red-brown type having a hardness of 9 Mohs and an average size of about 2.5 mm (in terms of the diameter of an ideal sphere enveloping said granules), said granules amounting to about 75% by weight with respect to the resinous syrup.

This composition, forming a "dispersion" of corundum granules through an epoxy resin, is evenly spread to a depth of about 3-6 mm over the treads of the-previously coated four wheels --as described hereinabove --with an epoxy resin in the "soft" state.

The four wheels are then allowed to stand, in a suitable containing molds, for about 10 hours, thereby the resinous syrup of the aforesaid dispersion is brought to cure to a consistency which permits of its handling, thereafter, on removal of the aforementioned tape sections, the four wheels are subjected to treatment in a kiln to a temperature of 60-70°C so as to complete curing of the syrups previously applied in two successive steps as described above, which will form, therefore, a unitary body incorporating in the outer layer the corundum granules, said granules being at least part-way embedded in said outer layer from which they stand proud, at least partially. Road tests on both snow and ice covered road surfaces, carried out with a Volkswagen "Golf" front drive car, both with the driver alone and in full load conditions (driver plus three passengers), have revealed unexpected good traction or adherence of the vehicle to the ground, both on level and mountain roads, at speeds in the range of 60 to 90 km/kour. Of course, besides epoxy resins, it would be possible to use other types of synthetic resins, so long as these are effective to "glue" and hold elastically fast the hard granules (corundum and the like, as indicated above) dispersed therethrough, and of such a nature as to adhere on the rubber and follow any expansion-compression and flexing thereof. Suitable resins may be polyurethane resins and polyester resins, for example.

Another embodiment of the invention consists of preparing a fluted rubber band which is preferably at least partly pre-shaped to conform with the rolling cross-section of a motor car wheel, said band having a length which is substantially equal to the circumferential length of said wheel and incorporating hard granules (such as corundum ones), said granules protruding at least part-way outwards once said band has been applied to the wheel. Assembling of the band, as provided by the invention, to the wheel is carried out by either by bonding, as by adhesive means, the inward surface of the band to the outward surface of the wheel tread, or by detachably anchoring the band to the wheel via securing means of some known type. A further embodiment of the invention consists of applying (by brush, spray, and the like) a syrup of a resin (such as an epoxy resin) over the entire surface (including any recesses) of the tread of a motor car wheel tire, and then "dusting" it with granules (e.g. of corundum), thereafter the resin is thoroughly cured preferably at 50-60°C in a kiln.

Yet another embodiment of the invention consists of preparing (with suitable molds and known techniques) blocks comprised of a supporting and elastic grip substrate of rubber or resin incorporating a plurality of hard bodies or granules distributed randomly therethrough and projecting part-way from the outward block. surface. Such blocks would have a substantially parallelepipedal or truncated pyramid shape, or the like, with a base whose dimensions are orientatively in the range of 1x1 cm to 6x6 cm, with a depth orientatively in the 4 to 10 mm range.

For applying such blocks to vehicle wheel tires, there would be provided suitable recesses distributed over the tire tread of such tires, whereinto the blocks can be inserted and secured using means conventional per se.

In a modified embodiment, said blocks could be fonned directly into recesses formed in the tire tread, by pouring directly into the recesses a blend according to the invention, i.e. either rubber or resin including the cited hard granules.

In practicing the invention, it is, of course, possible to utilise other methods of forming the coating according to the invention, such methods being easily borrowed by a skilled person in the art from similar methods and related apparata (such as molds, jigs, curing means, heaters, spreading means, and the like) as employed in the coating art in general, and in particular in the technologies of forming coatings, bands, and the like from either rubber or synthetic resins, preferably by combining said methods and said apparata together so as to provide the coating of this invention in a continuous or semi-continuous automated process.

Also the selection of the synthetic resin and/or rubber may be made from a wide choice of homopolymers, copolymers, and elastomers, there being well defined, as previously explained, the applicational characteristics (of both the product and process) for said synthetic resin and said rubber, in particular their ability to elastically retain the hard bodies or "granules" therein. Of the various possible variations in the method and product which may be adopted to practice the invention, worth mentioning herein, by way of example only, is a method consisting of preparing the coating according to the invention, forming the same in several resin layers, wherein each of said layers comprises a different type of resin, each of said resin types having different hardness, elasticity and adhesion characteristics so as to provide for optimum elastic securement of the granules therein. The formation of the aforesaid layers (which form accordingly a "composite" coating) is accomplished through one or more of the various known methods, such as by applying (by dip coating, spraying, brushing and the like) the resin in the polycondensation phase or a polymer dissolved in an organic solvent (which is then removed during the drying step).

Claims

1. A high frictional coefficient coating, characterised in that it comprises a supporting, elastic grip substrate incorporating a plurality of hard bodies or granules distributed randomly thereon and protruding part-way out of the surface of the supporting substrate, and is adapted for application to vehicle wheel rubber tires and generic rolling bodies to make them particularly well skid-resisting on wet, snow and/or ice covered road surfaces.

2. A high frictional coefficient coating according to Claim 1, characterised in that it is provided as a blend for application as a tread to vehicle wheel tires using methods, known per se, of rebuilding or fabricating tires.

3. A high frictional coefficient coating according to Claim 1, characterised in that it has a band structure or block structure applicable to the outer surfaces of vehicle rubber tires using anchoring devices known per se.

4. A high frictional coefficient coating, according to Claims 1 to 3, characterised in that the supporting substrate is comprised of at least one synthetic or natural rubber or at least one synthetic resin, advantageously of the epoxy kind, including additives-adjuvants known per se, such as antioxidants, stabilizers, reinforcing fillers, plasticisers, and the like.

5. A high frictional coefficient coating, according to the preceding claims, characterised in that the granules comprise inorganic substances of irregular polyhedral shape, advantageously natural or synthetic corundum, boron carbide, tungsten carbide, silicon carbide, titanium carbide, widia, metal ceramic and ceramic materials.

6. A high frictional coefficient coating according to Claim 5, characterised in that the granules have a hardness no lower than 7 Mohs and a size which envelopable by an ideal sphere with a diameter on the order of 1 to 9 mm, preferably 1 to 3 mm.